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Samadani M, Kwuimy CK and Nataraj C (2015), "Model-based fault diagnostics of nonlinear systems using the features of the phase space response", Communications in Nonlinear Science and Numerical Simulation . Vol. 20(2), pp. 583 - 593.
Abstract: Abstract A novel algorithm is presented in this paper for the diagnostics of nonlinear systems based on the idea of estimating the parameters of the system using features of the nonlinear response. The method combines statistical features of the nonlinear response and capabilities of artificial neural networks in data fitting with the objective of estimating the parameters of a defective nonlinear system. New features extracted from the density distribution of position and velocity signals are introduced to characterize the complex topologies of the phase plane response in periodic and multi-periodic domains. A nonlinear pendulum is used for experimental validation of the procedure. The results show that, with appropriately selected features of the response, the parameters of the nonlinear system can be estimated with an acceptable accuracy.
BibTeX:
@article{Samadani2015,
  author = {M. Samadani and C.A. Kitio Kwuimy and C. Nataraj},
  title = {Model-based fault diagnostics of nonlinear systems using the features of the phase space response},
  journal = {Communications in Nonlinear Science and Numerical Simulation },
  year = {2015},
  volume = {20},
  number = {2},
  pages = {583 - 593},
  url = {http://www.sciencedirect.com/science/article/pii/S1007570414002731},
  doi = {10.1016/j.cnsns.2014.06.010}
}
Anderson JW, Lebbad A, Nataraj C and Clayton GM (2014), "An Integrated LIDAR/Video Vision System for Autonomous Surface Vehicles", Naval Engineers Journal.
BibTeX:
@article{Anderson2014,
  author = {J. Wesley Anderson and Anderson Lebbad and C. Nataraj and Garrett M. Clayton},
  title = {An Integrated LIDAR/Video Vision System for Autonomous Surface Vehicles},
  journal = {Naval Engineers Journal},
  year = {2014}
}
Bender D, Jalali A, Licht DJ and Nataraj C (2014), "Prediction of periventricular leukomalacia occurrence in neonates using a novel unsupervised learning method", In Conference Proceedings Dynamic Systems and Control Conference.
Abstract: Prior work has documented that Support Vector Machine (SVM) classifiers can be powerful tools in predicting clinical outcomes of complex diseases such as Periventricular Leukomalacia (PVL). A preceding study indicated that SVM performance can be improved significantly by optimizing the supervised training set used during the learning stage of the overall SVM algorithm. This preliminary work, as well as the complex nature of the PVL data suggested integration of the active learning algorithm into the overall SVM framework. The present study supports this initial hypothesis and shows that active learning SVM type classifier performs considerably well and outperforms normal SVM type classifiers when dealing with clinical data of high dimensionality.
BibTeX:
@inproceedings{Bender2014,
  author = {Dieter Bender and Ali Jalali and Daniel J Licht and C. Nataraj},
  title = {Prediction of periventricular leukomalacia occurrence in neonates using a novel unsupervised learning method},
  booktitle = {Conference Proceedings Dynamic Systems and Control Conference},
  year = {2014},
  doi = {10.1115/DSCC2014-6304}
}
Jalali A, Nadkarni VM and Nataraj C (2014), "Modeling Mechanical Properties of the Chest During the Cardiopulmonary Resuscitation Procedure", In Conference Proceedings Computing in Cardiology. Vol. 41, pp. 13-16.
Abstract: The first step in improving the cardiopulmonary resuscitation (CPR) procedure is to understand how the force applied on the chest relates to the resulting blood pressure. In order to capture the mechanical properties of the chest and abdomen accurately, in this paper we proposed a nonlinear mass spring and damper model which consists of nonlinear spring up to 5th order, a combination of viscous and hysteresis damper. We then nondimensionalized the proposed model in order to enhance parametric study of the model for future use. In the next step we used gradient decent optimization method to identify the model parameters for force-compression data of 10273 CPR cycles collected from different pigs at the Children's Hospital of Philadelphia (CHOP). We used the mean square error (RMSE) between the estimated force and actual force for each cycle as an objective function to be minimized. Using the above method we were able to estimate the model parameters for each cycle seperately. In order to find a best set of estimated parameters we used K-nearest neighbor (K-NN) method. K-NN is an unsupervised learning technique which clusters the data into different groups based on the distance metric. The cluster center with lowest RMSE is selected as the estimated parameters for the entire cycles. The resulted MSE of testing entire cycles with the estimated parameters are 0.12 mean and 0.04 SD. Results show that the proposed model is the most accurate model of pig chest during the CPR.
BibTeX:
@inproceedings{Jalali2014,
  author = {Ali Jalali and Vinay M Nadkarni and C Nataraj},
  title = {Modeling Mechanical Properties of the Chest During the Cardiopulmonary Resuscitation Procedure},
  booktitle = {Conference Proceedings Computing in Cardiology},
  year = {2014},
  volume = {41},
  pages = {13-16}
}
Jalali A, Buckley EM, Lynch JM, Schwab PJ, Licht DJ and Nataraj C (2014), "Prediction of periventricular leukomalacia occurrence in neonates after heart surgery.", IEEE Journal of Biomedical and Health Informatics., Jul, 2014. Vol. 18(4), pp. 1453-1460.
Abstract: This paper is concerned with predicting the occurrence of periventricular leukomalacia (PVL) using vital and blood gas data which are collected over a period of 12 h after the neonatal cardiac surgery. A data mining approach has been employed to generate a set of rules for classification of subjects as healthy or PVL affected. In view of the fact that blood gas and vital data have different sampling rates, in this study we have divided the data into two categories: 1) high resolution (vital), and 2) low resolution (blood gas), and designed a separate classifier based on each data category. The developed algorithm is composed of several stages; first, a feature pool has been extracted from each data category and the extracted features have been ranked based on the data reliability and their mutual information content with the output. An optimal feature subset with the highest discriminative capability has been formed using simultaneous maximization of the class separability measure and mutual information of a set. Two separate decision trees (DTs) have been developed for the classification purpose and more importantly to discover hidden relationships that exist among the data to help us better understand PVL pathophysiology. The DT result shows that high amplitude 20 min variations and low sample entropy in the vital data and the defined out of range index as well as maximum rate of change in blood gas data are important factors for PVL prediction. Low sample entropy represents lack of variability in hemodynamic measurement, and constant blood pressure with small fluctuations is an important indicator of PVL occurrence. Finally, using the different time frames of data collection, we show that the first 6 h of data contain sufficient information for PVL occurrence prediction.
BibTeX:
@article{Jalali2014b,
  author = {Ali Jalali and Erin M Buckley and Jennifer M Lynch and Peter J Schwab and Daniel J Licht and C. Nataraj},
  title = {Prediction of periventricular leukomalacia occurrence in neonates after heart surgery.},
  journal = {IEEE Journal of Biomedical and Health Informatics},
  year = {2014},
  volume = {18},
  number = {4},
  pages = {1453--1460}
}
Kwuimy CAK, Samadani M and Nataraj C (2014), "Bifurcation analysis of a nonlinear pendulum using recurrence and statistical methods: Applications to fault diagnostics", Nonlinear Dynamics. Vol. 76 (4), pp. 1963-1975.
Abstract: The problem of maintenance of expensive and heavy systems has increased the need for powerful tools to analyze their performance. The methods of recurrence plots (RPs) and statistical measurement have been used as data-driven tools for diagnostics with no possibility of classifying the nature of defect and poor ability to localize it. In order to enhance the efficiency of the forecast, innovative approaches consist of using physics-based features to train a data-based assessment methods. This requires proper analysis of the physical system using appropriate methods. For this purpose, this paper focusses on the bifurcation dynamics of nonlinear systems using the recurrence and statistical methods. Considering the nonlinear pendulum as a model, the qualitative behavior of the system is discussed through the bifurcation diagram of some recurrence quantification analysis (RQA) parameters, namely the recurrence rate, determinism, and laminarity. These parameters are used to measure the level of complexity and transition from regular to chaotic motion and vice versa. Statistical parameters such as crest factor, skewness, and kurtosis are used to identify various bifurcation and amplitudes in the system, and to measure the orientation and the level of asymmetry. Plots of recurrence diagrams and histograms are presented to support our observations. Examples of detection of dynamic changes using these two methods are provided. The interesting results obtained in this paper show that statistical methods complement results obtained from RPs. In addition, the paper demonstrates how the RPs can be employed in conjunction with the physics-based model. © 2014 Springer Science+Business Media Dordrecht.
BibTeX:
@article{Kwuimy2014,
  author = {Kwuimy, C A. Kitio and Samadani, M. and Nataraj, C},
  title = {Bifurcation analysis of a nonlinear pendulum using recurrence and statistical methods: Applications to fault diagnostics},
  journal = {Nonlinear Dynamics},
  year = {2014},
  volume = {76 (4)},
  pages = {1963-1975},
  doi = {10.1007/s11071-014-1261-0}
}
Kwuimy CK, Samadani M, Kappaganthu K and Nataraj C (2014), "10th International Conference on Vibration Engineering and Technology of Machinery", In 10th International Conference on Vibration Engineering and Technology of Machinery. , pp. 683. Springer.
BibTeX:
@inbook{Kwuimy2014,
  author = {C.A. Kitio Kwuimy and M. Samadani and K. Kappaganthu and
C. Nataraj}, editor = {Jyoti K. Sinha}, title = {10th International Conference on Vibration Engineering and Technology of Machinery}, booktitle = {10th International Conference on Vibration Engineering and Technology of Machinery}, publisher = {Springer}, year = {2014}, pages = {683} }
Kwuimy CAK, Samadani M and Nataraj C (2014), "Preliminary diagnostics of dynamic systems from time series", In Proceedings of the ASME 2014 International Design Engineering Technical Conferences &
Computers and Information in Engineering Conference.
Abstract: The state space reconstruction technique was recognized by Edward N. Lorenz as “one of the most surprising developments in nonlinear dynamics” [1]. Nowadays, the technique is applied in various scientific areas for prediction, analysis and diagnostics. This paper aims to discuss the possibility of using the embedding dimension of a reconstructed state space of time series as a tool for preliminary diagnostics. After a short description and illustration of the method, the paper considers two case studies: a single degree of freedom (DOF) and a 2 DOF system. The results of the analysis help detect a class of structural defects, including defects connected to a coupling mechanism. There is clearly a huge potential of such an approach for diagnostics of complex machinery.
BibTeX:
@inproceedings{Kwuimy2014a,
  author = {C. A. Kitio Kwuimy and M. Samadani and C. Nataraj},
  title = {Preliminary diagnostics of dynamic systems from time series},
  booktitle = {Proceedings of the ASME 2014 International Design Engineering Technical Conferences &
Computers and Information in Engineering Conference}, year = {2014}, doi = {10.1115/DETC2014-35425} }
Lebbad A and Nataraj C (2014), "Probabilistic Vision Based Guidance & SLAM for Autonomous Surface Vehicles", Naval Engineers Journal.
Abstract: This article presents an overview of the systems developed and equipped on a WAM-V USV16 (16 foot Wave Adaptive Modular Vehicle), and pioneered by a team of students from both Villanova University and Florida Atlantic University. The vessel uses an extensive sensor suite including a RGB-D vision system robust to lighting variations, an underwater USBL (Ultra Short Base Line) localization system, and a GPS aided MEMS-based Inertial Measurement Unit. Many innovative technologies, which have been developed for the first time ever, have been implemented on the vehicle. For example, the developed controller is robust to various environmental disturbances, including wind force, current, lighting variations, and rain, and the vision system implements a novel data fusion algorithm and integrates an innovative Bayesian color recognition. Team WORX’s WAM-V USV16 carries out three degree of freedom state estimation, mapping, path planning, obstacle avoidance and navigation. Missionlevel control is provided by a hierarchical structure and programmed using a finite state machine, allowing for the development of modular routines that can be rapidly implemented.
BibTeX:
@article{Lebbad2014,
  author = {Anderson Lebbad and C. Nataraj},
  title = {Probabilistic Vision Based Guidance & SLAM for Autonomous Surface Vehicles},
  journal = {Naval Engineers Journal},
  year = {2014}
}
Zhu E, DeGaetano D, Cheng G, Shah P, Benson M, Jenkins G, Ferrese F and Nataraj C (2014), "An Experimental Autonomous Surface Vehicle With Vision-Based Navigation, Obstacle Avoidance & SLAM", Naval Engineers Journal.
BibTeX:
@article{Zhu2014,
  author = {Edward Zhu and Dylan DeGaetano and GinSiu Cheng and Priya Shah and Michael Benson and Gus Jenkins and Frank Ferrese and C. Nataraj},
  title = {An Experimental Autonomous Surface Vehicle With Vision-Based Navigation, Obstacle Avoidance & SLAM},
  journal = {Naval Engineers Journal},
  year = {2014}
}
Maraini D and Nataraj C (2014), "10th International Conference on Vibration Engineering and Technology of Machinery" , pp. 663. Springer.
BibTeX:
@inbook{,
  author = {Daniel Maraini and C. Nataraj},
  editor = {Jyoti K. Sinha},
  title = {10th International Conference on Vibration Engineering and Technology of Machinery},
  publisher = {Springer},
  year = {2014},
  pages = {663}
}
Jalali A, Berg R, Nadkarni V and Nataraj C (2013), "Improving Cardiopulmonary Resuscitation (CPR) by Dynamic Variation of CPR Parameters", In Conference Proceedings Dynamic Systems and Control Conference. ASME.
Abstract: Cardiopulmonary resuscitation (CPR) is a commonly used procedure and plays a critical role in saving the lives of patients suffering from cardiac arrest. This paper is concerned with the design of a dynamic technique to optimize the performance of CPR and to consequently improve its outcome, the survival rate. Current American Heart Association (AHA) guidelines treat CPR as a static procedure with fixed parameters. These guidelines set fixed values for CPR parameters such as compression to ventilation ratio, chest compression depth, etc., with an implicit assumption that they are somehow “optimal,” which has not been really substantiated. In this study, in a quest to improve this oft-used procedure, an interactive technique has been developed for dynamically changing the CPR parameters. Total blood gas delivery which is combination of systemic oxygen delivery and carbon dioxide delivery to the lungs has been defined as the objective function, and a sequential optimization procedure has been explored to optimize the objective function by dynamically adjusting the CPR parameters. The results of comparison between the sequential optimization procedure and the global optimization procedure show that the sequential optimization procedure could significantly enhance the effectiveness of CPR.
BibTeX:
@inproceedings{Jalali2013,
  author = {A. Jalali and R.A. Berg and V.M. Nadkarni and C. Nataraj},
  title = {Improving Cardiopulmonary Resuscitation (CPR) by Dynamic Variation of CPR Parameters},
  booktitle = {Conference Proceedings Dynamic Systems and Control Conference},
  publisher = {ASME},
  year = {2013},
  doi = {10.1115/DSCC2013-3879}
}
Jalali A, Licht DJ and Nataraj C (2013), "Discovering hidden relationships in physiological signals for prediction of Periventricular Leukomalacia.", Conf Proc IEEE Eng Med Biol Soc., In Conference Proceedings IEEE Engineering in Medicine and Biology Society. Vol. 2013, pp. 7080-7083.
Abstract: This paper is concerned with predicting the occurrence of Periventricular Leukomalacia (PVL) using vital data which are collected over a period of twelve hours after neonatal cardiac surgery. The vital data contain heart rate (HR), mean arterial pressure (MAP), right atrium pressure (RAP), and oxygen saturation (SpO2). Various features are extracted from the data and are then ranked so that an optimal subset of features that have the highest discriminative capabilities can be selected. A decision tree (DT) is then developed for the vital data in order to identify the most important vital measurements. The DT result shows that high amplitude 20 minutes variations and low sample entropy in the data is an important factor for prediction of PVL. Low sample entropy represents lack of variability in hemodynamic measurement, and constant blood pressure with small fluctuations is an important indicator of PVL occurrence. Finally, using the different time frames of the collected data, we show that the first six hours of data contain sufficient information for PVL occurrence prediction.
BibTeX:
@inproceedings{Jalali2013a,
  author = {Ali Jalali and Daniel J Licht and C. Nataraj},
  title = {Discovering hidden relationships in physiological signals for prediction of Periventricular Leukomalacia.},
  booktitle = {Conference Proceedings IEEE Engineering in Medicine and Biology Society},
  journal = {Conf Proc IEEE Eng Med Biol Soc},
  year = {2013},
  volume = {2013},
  pages = {7080--7083},
  doi = {10.1109/EMBC.2013.6611189}
}
Kwuimy CAK and Nataraj C (2013), "Bistability and Bursting Oscillations in Electromechanical Butterfly Valves", Journal of Applied Nonlinear Dynamics. Vol. 2(3), pp. 303-313.
BibTeX:
@article{Kwuimy2013,
  author = {Kwuimy, C A. Kitio and Nataraj, C},
  title = {Bistability and Bursting Oscillations in Electromechanical Butterfly Valves},
  journal = {Journal of Applied Nonlinear Dynamics},
  year = {2013},
  volume = {2},
  number = {3},
  pages = {303-313}
}
Kwuimy CAK, Ramakrishnan S and Nataraj C (2013), "On the nonlinear on-off dynamics of an electromechanically actuated butterfly valve", Journal of Sound and Vibration. Vol. 332(24), pp. 6488-6504.
BibTeX:
@article{Kwuimy2013a,
  author = {C. A. Kitio Kwuimy and S. Ramakrishnan and C. Nataraj},
  title = {On the nonlinear on-off dynamics of an electromechanically actuated butterfly valve},
  journal = {Journal of Sound and Vibration},
  year = {2013},
  volume = {332},
  number = {24},
  pages = {6488-6504}
}
Naseradinmousavi P and Nataraj C (2013), "Optimal design of solenoid actuators driving butterfly valves", ASME Journal of Mechanical Design. Vol. 135(9), pp. 094501.
Abstract: Smart valves are used in cooling applications and are responsible for regulating and supplying the coolant, which is critical for safe and effective operation of many components on naval and commercial ships. In order to be operated under local power (for various mission-critical reasons) they need to consume as little energy as possible in order to ensure continued operability. This paper focuses on optimized design of a typical system using high fidelity nonlinear dynamic models for all the subsystems with full consideration of stability constraints. A simulated annealing algorithm is applied to explore optimal design using two sets of design variables. The results indicate that substantial amount of energy can be saved by an intelligent design that helps select parameters carefully, but also uses hydrodynamic loads to augment the closing effort. Copyright © 2013 by ASME.
BibTeX:
@article{Naseradinmousavi2013,
  author = {P. Naseradinmousavi and C. Nataraj},
  title = {Optimal design of solenoid actuators driving butterfly valves},
  journal = {ASME Journal of Mechanical Design},
  year = {2013},
  volume = {135(9)},
  pages = {094501},
  note = {I was the project director and principal author working with my student. Impact factor: 1.893.},
  doi = {10.1115/1.4024720}
}
Samadani M, Behbahani S and Nataraj C (2013), "A reliability-based manufacturing process planning method for the components of a complex mechatronic system", Applied Mathematical Modelling . Vol. 37(24), pp. 9829 - 9845.
Abstract: Abstract Uncertainties in the values of the parameters of a system can originate from the manufacturing tolerances of the system components, which can produce a degree of unreliability in the performance of the system. A systematic framework for realistic reliability assessment of an electro-hydraulic servo system has been presented in this paper with the objective of providing adequate information for the selection of the best manufacturing process for each of the servo valve components. Monte Carlo simulation has been employed to evaluate the effect of these uncertainties of the servo valve parameters on the statistical performance of the system. Possible manufacturing processes have been introduced for each component and the justifiability of using each one has been discussed based on the estimated reliability of the system.
BibTeX:
@article{Samadani2013,
  author = {Mohsen Samadani and Saeed Behbahani and C. Nataraj},
  title = {A reliability-based manufacturing process planning method for the components of a complex mechatronic system},
  journal = {Applied Mathematical Modelling },
  year = {2013},
  volume = {37},
  number = {24},
  pages = {9829 - 9845},
  url = {http://www.sciencedirect.com/science/article/pii/S0307904X1300351X},
  doi = {10.1016/j.apm.2013.05.030}
}
Ghorbanian P, Jalali A, Ghaffari A and Nataraj C (2012), "An improved procedure for detection of heart arrhythmias with novel pre-processing techniques", Expert Systems. Vol. 29(5), pp. 478-491.
Abstract: The objective of this study is to develop an algorithm to detect and classify six types of electrocardiogram (ECG) signal beats including normal beats (N), atrial pre-mature beats (A), right bundle branch block beats (R), left bundle branch block beats (L), paced beats (P), and pre-mature ventricular contraction beats (PVC or V) using a neural network classifier. In order to prepare an appropriate input vector for the neural classifier several pre-processing stages have been applied. Initially, a signal filtering method is used to remove the ECG signal baseline wandering. Continuous wavelet transform is then applied in order to extract features of the ECG signal. Next, principal component analysis is used to reduce the size of the data. A well-known neural network architecture called the multi-layered perceptron neural network is then utilized as the final classifier to classify each ECG beat as one of six groups of signals under study. Finally, the MIT-BIH database is used to evaluate the proposed algorithm, resulting in 99.5% sensitivity, 99.66% positive predictive accuracy and 99.17% total accuracy. © 2011 Wiley Publishing Ltd.
BibTeX:
@article{Ghorbanian2012a,
  author = {Parham Ghorbanian and Ali Jalali and Ali Ghaffari and C. Nataraj},
  title = {An improved procedure for detection of heart arrhythmias with novel pre-processing techniques},
  journal = {Expert Systems},
  year = {2012},
  volume = {29},
  number = {5},
  pages = {478-491},
  doi = {10.1111/j.1468-0394.2011.00606.x}
}
Jalali A, Berg RA, Nadkarni V and Nataraj C (2012), "Model based optimization of the cardiopulmonary resuscitation (CPR) procedure", Conference Proceedings of IEEE Engineering in Medicine and Biology., In Conference Proceedings IEEE Engineering in Medicine and Biology Society. Vol. 2012, pp. 715-718.
Abstract: This paper is concerned with the optimization of the cardiopulmonary resuscitation (CPR) procedure, which plays a critical rule in saving the life of patients suffering from cardiac arrest. In this paper, we define the performance index for optimization using the oxygen delivery. A model developed earlier is used to calculate the oxygen delivery through CPR. The free parameters of this model which depend on the rescuer performance are ventilation time, compression speed, tidal volume, and fraction of oxygen in the inspired air. Two different optimization problems are carried out. First, a global optimization is implemented to discover the best values of the free parameters which maximize the oxygen delivery. In addition to this, a sequential optimization scheme is explored which uses a two step optimization in each CPR sequence to maximize the oxygen delivery. Results show that the sequential optimization procedure will enhance the performance of the CPR significantly.
BibTeX:
@inproceedings{Jalali2012,
  author = {Jalali, Ali and Berg, Robert A. and Nadkarni, Vinay and Nataraj, C.},
  title = {Model based optimization of the cardiopulmonary resuscitation (CPR) procedure},
  booktitle = {Conference Proceedings IEEE Engineering in Medicine and Biology Society},
  journal = {Conference Proceedings of IEEE Engineering in Medicine and Biology},
  year = {2012},
  volume = {2012},
  pages = {715--718},
  doi = {10.1109/EMBC.2012.6346031}
}
Jalali A, Ghorbanian P, Ghaffari A and Nataraj C (2012), "A novel technique for identifying patients with ICU needs using hemodynamic features", Advances in Fuzzy Systems. Vol. 696194(3), pp. 1-9.
Abstract: Identification of patients requiring intensive care is a critical issue in clinical treatment. The objective of this study is to develop a novel methodology using hemodynamic features for distinguishing such patients requiring intensive care from a group of healthy subjects. In this study, based on the hemodynamic features, subjects are divided into three groups: healthy, risky and patient. For each of the healthy and patient subjects, the evaluated features are based on the analysis of existing differences between hemodynamic variables: Blood Pressure and Heart Rate. Further, four criteria from the hemodynamic variables are introduced: circle criterion, estimation error criterion, Poincare plot deviation, and autonomic response delay criterion. For each of these criteria, three fuzzy membership functions are defined to distinguish patients from healthy subjects. Furthermore, based on the evaluated criteria, a scoring method is developed. In this scoring method membership degree of each subject is evaluated for the three classifying groups. Then, for each subject, the cumulative sum of membership degree of all four criteria is calculated. Finally, a given subject is classified with the group which has the largest cumulative sum. In summary, the scoring method results in 86% sensitivity, 94.8% positive predictive accuracy and 82.2% total accuracy.
BibTeX:
@article{Jalali2012,
  author = {Ali Jalali and Parham Ghorbanian and Ali Ghaffari and C. Nataraj},
  title = {A novel technique for identifying patients with ICU needs using hemodynamic features},
  journal = {Advances in Fuzzy Systems},
  year = {2012},
  volume = {696194},
  number = {3},
  pages = {1-9},
  doi = {10.1155/2012/696194}
}
Jalali A, Licht DJ and Nataraj C (2012), "Application of decision tree in the prediction of periventricular leukomalacia (PVL) occurrence in neonates after heart surgery.", Conference Proceedings IEEE Engineering in Medicine and Biology Society., In Conference Proceedings IEEE Engineering in Medicine and Biology Society. Vol. 2012, pp. 5931-5934.
Abstract: This paper is concerned with the prediction of the occurrence of periventricular leukomalacia (PVL) that occurs in neonates after heart surgery. The data which is collected over a period of 12 hours after cardiac surgery contains vital measurements as well as blood gas measurements with different resolutions. Vital data measured using near-inferred spectroscopy (NIRS) at the sampling rate of 0.25 Hz and blood gas measurement up to 12 times with irregular time intervals for 35 patients collected at Children's Hospital of Philadelphia (CHOP) are used for this study. Features derived from the data include statistical moments (mean, variance, skewness and kurtosis), trend and minimum and maximum values of the vital data and rate of change, time weighted mean and a custom defined out of range index (ORI) for the blood gas data. A decision tree is developed for the vital data in order to identify the most important vital measurements. In addition, a decision tree is developed for blood gas data to find important factors for the prediction of PVL occurrence. Results show that in the blood gas data, maximum rate of change of concentration of bicarbonate ions in blood (HCO(3)) and minimum rate of change of partial pressure of dissolved CO(2) in the blood (PaCO(2)) are the two most important factors for prediction of the PVL. Also important are the kurtosis of heart rate and hemoglobin values.
BibTeX:
@inproceedings{Jalali2012,
  author = {Ali Jalali and Daniel J Licht and C. Nataraj},
  title = {Application of decision tree in the prediction of periventricular leukomalacia (PVL) occurrence in neonates after heart surgery.},
  booktitle = {Conference Proceedings IEEE Engineering in Medicine and Biology Society},
  journal = {Conference Proceedings IEEE Engineering in Medicine and Biology Society},
  year = {2012},
  volume = {2012},
  pages = {5931--5934},
  doi = {10.1109/EMBC.2012.6347344}
}
Jalali A, Licht DJ and Nataraj C (2012), "Time-Frequency Analysis of Hemodynamic Waveforms to Predict the Occurrence and Severity of Periventricular Leukomalacia", In Conference Proceedings Dynamic Systems and Control Conference. , pp. 561-566.
Abstract: This paper is concerned with the prediction of the occur-rence and severity of Periventricular Leukomalacia (PVL), a form of white-matter brain injury that occurs often in neonates after heart surgery. The data which is collected over a period of twelve hours after the cardiac surgery contains vital measure-ments. The fact that the exact cause of the PVL have still not been clearly understood renders a mathematical modeling ap-proach for fault diagnosis impractical, if not impossible. Hence, the decision tree classification technique has been selected for its capacity for discovering rules and novel associations in the data. It classifies groups based on reducing uncertainty in the classi-fied data. From a physiological point of view we know that there are several regulatory mechanisms responsible for fluctuation of the hemodynamic variables at different time scales. To discover the most important active physiological components which might lead to the occurrence of PVL and possibly affect its severity, we focus on the variation in the data in one minute, twenty minute and two hour periods. We calculate the energy of continuous wavelet transform coefficients of vital data at these time scales as a measure of variation in the different time frames. The re-sults obtained from developing decision tree classifiers show that among all variations in all the variables, 2 hour and 20 minute variations in the heart rate, 1 minute and 20 minute variations in Oxygen saturation, and 2 hour variations in the mean arterial pressure are the most important parameters to be able to predict PVL occurrence.
BibTeX:
@inproceedings{Jalali2012a,
  author = {Ali Jalali and Daniel J. Licht and C. Nataraj},
  title = {Time-Frequency Analysis of Hemodynamic Waveforms to Predict the Occurrence and Severity of Periventricular Leukomalacia},
  booktitle = {Conference Proceedings Dynamic Systems and Control Conference},
  year = {2012},
  pages = {561-566},
  doi = {10.1115/DSCC2012-MOVIC2012-8601}
}
Jalali A and Nataraj C (2012), "Prediction of Occurrence of Periventricular Leukomalacia in Neonates After Heart Surgery Using a Decision Tree Algorithm", In Conference Proceedings ASME International Design Engineering Technical Conferences and Computers and Information in Engineering. , pp. 217-222.
Abstract: This paper is concerned with the prediction of the occurrence of Periventricular Leukomalacia (PVL), a form of white-matter brain injury, in neonates after heart surgery. The data which is collected over a period of 12 hours after the cardiac surgery contains measurements with different resolutions. The fact that data is collected at different time scales makes the modeling approach impractical, if not impossible. Hence, the decision tree classification technique has been selected for its capacity for discovering rules and novel associations in the data. It classifies groups based on reducing uncertainty in the classified data. From a physiological point of view we know that there are several regulatory mechanisms responsible for fluctuation of the hemodynamic variables at different time scales. To discover the most important active physiological components which might lead to the occurrence of PVL, we focus on the variation in the data in 1 min, 20 min and 2 hour periods. We calculate the energy of continuous wavelet transform coefficients of vital data at these time scales as a measure of variation in the different time frames. Results obtained from developing decision tree classifiers show that among all variations in all the variables, 2 hour and 20 minute variations in the heart rate and also 1 minute and 20 minute variation in Oxygen saturation are the most important parameters to predict PVL occurrence.
BibTeX:
@inproceedings{Jalali2012b,
  author = {Ali Jalali and C. Nataraj},
  title = {Prediction of Occurrence of Periventricular Leukomalacia in Neonates After Heart Surgery Using a Decision Tree Algorithm},
  booktitle = {Conference Proceedings ASME International Design Engineering Technical Conferences and Computers and Information in Engineering},
  year = {2012},
  pages = {217-222},
  doi = {10.1115/DETC2012-71301}
}
Kwuimy CK and Nataraj C (2012), "Modeling and nonlinear dynamics analysis of a magnetically actuated butterfly valve", Nonlinear Dynamics. Vol. 70, pp. 435-451.
Abstract: Recent progress in the analysis of butterfly valve presented accurate information for mathematical modeling and analysis. In this work, a magnetically actuated butterfly valve is considered and an innovative and accurate mathematical model is derived. Static analysis of the system is investigated and the effects of the inlet velocity and direct current voltage (DC) on the stable tilt angle of the valve are presented. Considering a time periodic perturbation, the effects of operating angle, inlet velocity and driving parameters on the periodic and chaotic dynamics of the system are highlighted. It is observed that, for an opening angle less than the cut-off angle, there exists a unique DC voltage for a stable equilibrium. The stability of this equilibrium nonlinearly depends on the inlet velocity and seating torque. The expression of the threshold bound for the stability of the valve is derived. Under periodic perturbation, the inlet velocity and stable angle induced backward shift on the resonant frequency; jump phenomena and sub-harmonic are observed for some values of the driving amplitude. The highest amplitudes of vibration are detected for a full open valve or large rotational valve, and large inlet velocity. Using the bifurcation diagram and Lyapunov exponent, the system shows a route to chaos with windows of period doubling and unbounded motion. Some guidance for design of future magnetically actuated butterfly valves is proposed as well as recommendations for future work.
BibTeX:
@article{Kwuimy2012a,
  author = {C.A. Kitio Kwuimy and C. Nataraj},
  title = {Modeling and nonlinear dynamics analysis of a magnetically actuated butterfly valve},
  journal = {Nonlinear Dynamics},
  year = {2012},
  volume = {70},
  pages = {435-451},
  note = {I was the project director and principal author. This is one of the leading journals in the field of nonlinear dynamics. Impact factor: 1.923.},
  doi = {10.1007/s11071-012-0466-3}
}
Kwuimy CAK, Litak G, Borowiec M and Nataraj C (2012), "Performance of a piezoelectric energy harvester driven by air flow", Applied Physics Letters., January 9, 2012. Vol. 100(2), pp. 024103.
Abstract: A turbulent wind source for possible energy harvesting is considered. To increase the amplitude of vibration we apply a magnetopiezoelastic oscillator having a double well Duffing potential. The output voltage response of the system for different level of wind excitations is analyzed. The energy harvesting appeared to be the most efficient for the conditions close to the stochastic resonance region where the potential well was overcame.
BibTeX:
@article{Kwuimy2012b,
  author = {C. A. Kitio Kwuimy and G. Litak and M. Borowiec and C. Nataraj},
  title = {Performance of a piezoelectric energy harvester driven by air flow},
  journal = {Applied Physics Letters},
  year = {2012},
  volume = {100},
  number = {2},
  pages = {024103},
  note = {I was a secondary author working with a colleague and a postdoc. Impact factor: 3.685.},
  doi = {10.1063/1.3676272}
}
Lee D, Nataraj C and Naseradinmousavi P (2012), "Nonlinear Dynamic Model-based Adaptive Control of a Solenoid-Valve System", Journal of Control Science and Engineering. Vol. 17(11), pp. 4336–4345.
Abstract: In this paper, a nonlinear model-based adaptive control approach is proposed for a solenoid-valve system. The challenge is that solenoids and butterfly valves have uncertainties in multiple parameters in the nonlinear model; various kinds of physical appearance such as size and stroke, dynamic parameters including inertia, damping, and torque coefficients, and operational parameters especially, pipe diameters and flow velocities. These uncertainties are making the system not only difficult to adjust to the environment, but also further complicated to develop the appropriate control approach for meeting the system objectives. The main contribution of this research is the application of adaptive control theory and Lyapunov-type stability approach to design a controller for a dynamic model of the solenoid-valve system in the presence of those uncertainties. The control objectives such as set-point regulation, parameter compensation, and stability are supposed to be simultaneously accomplished. The error signals are first formulated based on the nonlinear dynamicmodels and then the control input is developed using the Lyapunov stability-type analysis to obtain the error bounded while overcoming the uncertainties. The parameter groups are updated by adaptation laws using a projection algorithm.Numerical simulation results are shown to demonstrate good performance of the proposed nonlinear model based adaptive approach and to compare the performance of the same solenoid-valve system with a non-adaptive method as well.
BibTeX:
@article{Lee2012,
  author = {Lee, D. and Nataraj, C. and Naseradinmousavi, P.},
  title = {Nonlinear Dynamic Model-based Adaptive Control of a Solenoid-Valve System},
  journal = {Journal of Control Science and Engineering},
  year = {2012},
  volume = {17},
  number = {11},
  pages = {4336–4345},
  note = {I was the project director and co-principal author working with my postdoc. Impact factor: 0.862.},
  doi = {10.1155/2012/846458}
}
Lee D and Nataraj C (2012), "Linear Time-varying Control of Adaptive Model-Based System", In Proceedings of the American Control Conference.
BibTeX:
@inproceedings{Lee2012,
  author = {DongBin Lee and C. Nataraj},
  title = {Linear Time-varying Control of Adaptive Model-Based System},
  booktitle = {Proceedings of the American Control Conference},
  year = {2012}
}
Lee D and Nataraj C (2012), "Model-based Adaptive Tracking Control of Linear Time-varying System with Uncertainties (in press)", In Numerical Simulation - From Theory to Industry., September 19, 2012. , pp. 35-48. InTech.
BibTeX:
@inbook{Lee2012c,
  author = {DongBin Lee and C. Nataraj},
  editor = {Mykhaylo Andriychuk},
  title = {Model-based Adaptive Tracking Control of Linear Time-varying System with Uncertainties (in press)},
  booktitle = {Numerical Simulation - From Theory to Industry},
  publisher = {InTech},
  year = {2012},
  pages = {35-48},
  doi = {10.5772/51625}
}
Naseradinmousavi P and Nataraj C (2012), "Transient chaos and crisis phenomena in butterfly valves driven by solenoid actuators", Communications in Nonlinear Science and Numerical Simulation . Vol. 17(11), pp. 4336 - 4345.
Abstract: Chilled water systems used in the industry and on board ships are critical for safe and reliable operation. It is hence important to understand the fundamental physics of these systems. This paper focuses in particular on a critical part of the automation system, namely, actuators and valves that are used in so-called “smart valve� systems. The system is strongly nonlinear, and necessitates a nonlinear dynamic analysis to be able to predict all critical phenomena that affect effective operation and efficient design. The derived mathematical model includes electromagnetics, fluid mechanics, and mechanical dynamics. Nondimensionalization has been carried out in order to reduce the large number of parameters to a few critical independent sets to help carry out a broad parametric analysis. The system stability analysis is then carried out with the aid of the tools from nonlinear dynamic analysis. This reveals that the system is unstable in a certain region of the parameter space. The system is also shown to exhibit crisis and transient chaotic responses; this is characterized using Lyapunov exponents and power spectra. Knowledge and avoidance of these dangerous regimes is necessary for successful and safe operation.
BibTeX:
@article{Naseradinmousavi2012,
  author = {Peiman Naseradinmousavi and C. Nataraj},
  title = {Transient chaos and crisis phenomena in butterfly valves driven by solenoid actuators},
  journal = {Communications in Nonlinear Science and Numerical Simulation },
  year = {2012},
  volume = {17},
  number = {11},
  pages = {4336 - 4345},
  url = {http://www.sciencedirect.com/science/article/pii/S1007570412000585},
  doi = {10.1016/j.cnsns.2012.01.034}
}
Nataraj C, Jalali A and Ghorbanian P (2012), "The Cardiovascular System - Physiology, Diagnostics and Clinical Implications" , pp. 211-240. INTECH.
BibTeX:
@inbook{Nataraj2012,
  author = {C. Nataraj and A. Jalali and P. Ghorbanian},
  editor = {David C. Gaze},
  title = {The Cardiovascular System - Physiology, Diagnostics and Clinical Implications},
  publisher = {INTECH},
  year = {2012},
  pages = {211-240}
}
Nataraj C, Jalali A and Ghorbanian P (2012), "The Cardiovascular System - Physiology, Diagnostics and Clinical Implications", In Application of Computational Intelligence Techniques for Cardiovascular Diagnostics. , pp. 211-241. InTech.
BibTeX:
@inbook{Nataraj2012a,
  author = {C. Nataraj and Ali Jalali and Parham Ghorbanian},
  editor = {David Gaze},
  title = {The Cardiovascular System - Physiology, Diagnostics and Clinical Implications},
  booktitle = {Application of Computational Intelligence Techniques for Cardiovascular Diagnostics},
  publisher = {InTech},
  year = {2012},
  pages = {211-241},
  note = {I was the project director and principal author working with my students.},
  doi = {10.5772/38032}
}
Ferrese F, Dong Q, Nataraj C and Biswas S (2011), "Optimal Feedback Control of Power Systems Using Eigenstructure Assignment and Particle Swarm Optimization", Naval Engineers Journal., March, 2011. Vol. 123(1), pp. 67–75.
Abstract: The US Navy has a continuing interest and investment in basic and applied research in the area of automation and control. The potential naval applications for this research are numerous and wide ranging. The need for advances in control and automation systems exists from missile defense, to shipboard auxiliary systems, to naval aircraft, and virtually everywhere in between. This research is performed in industry, academia, and in naval laboratories across the nation. This paper will detail particular research in control theory being performed in the area of automation and controls in the naval laboratories. A particle swarm optimization algorithm is used to manipulate the state and control weighting matrices of a linear quadratic regulator to achieve an optimal control for a desired eigenstructure. The algorithm is demonstrated on a nonlinear power system model, and is found to be highly effective in the stabilization of the system output performance, showing both rapid convergence and a closed loop eigenstructure very close to the specified eigenstructure.
BibTeX:
@article{Ferrese2011,
  author = {Frank Ferrese and Qing Dong and C. Nataraj and Saroj Biswas},
  title = {Optimal Feedback Control of Power Systems Using Eigenstructure Assignment and Particle Swarm Optimization},
  journal = {Naval Engineers Journal},
  year = {2011},
  volume = {123},
  number = {1},
  pages = {67–75},
  note = {I was a secondary author working with my student and colleagues at Temple University. This is a journal read widely by the Navy engineers. Impact factor: 0.138.},
  doi = {10.1111/j.1559-3584.2010.00300.x}
}
Jalali A, Jones GF, Licht DJ and Nataraj C (2011), "Computational Modeling of Hypoplastic Left Heart Syndrome (HLHS) in Newborn Babies", In Conference Proceedings ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. , pp. 191-197.
Abstract: Hypoplastic left heart syndrome (HLHS) is a congenital heart defect (CHD) in which left side of the heart is severely underdeveloped. To better understand this unique physiology, a computational model of the hypoplastic heart was constructed on the basis of compartmental analysis. Lumped parameter model of HLHS is developed based on the electrical circuit analogy. Model is made up of three parts: hypoplastic heart, pulmonary circulation and systemic circulation. Plots of blood pressure and flow for various parts of body show great match between predicted values and what we expected for the case of HLHS babies. Influence of patent ductus arteriosus (PDA) and ASD resistances on cardiac output and pulmonary to systemic flow was also studied. Results show that by increasing the PDA resistance causes more flow to pulmonary compartments and so the ratio increases. Blood flow increases by decreasing of pulmonary artery resistant. Increasing the PDA resistance causes decrease the cardiac output because of more resistance against blood occurs. Saturation increases by decreasing of pulmonary artery resistant.
BibTeX:
@inproceedings{Jalali2011,
  author = {Ali Jalali and Gerard F. Jones and Daniel J. Licht and C. Nataraj},
  title = {Computational Modeling of Hypoplastic Left Heart Syndrome (HLHS) in Newborn Babies},
  booktitle = {Conference Proceedings ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference},
  year = {2011},
  pages = {191-197},
  doi = {10.1115/DETC2011-48825}
}
Jalali A, Ghaffari A, Ghorbanian P and Nataraj C (2011), "Identification of sympathetic and parasympathetic nerves function in cardiovascular regulation using ANFIS approximation", Artificial Intelligence in Medicine., Nov, 2011. Vol. 52(1), pp. 27-32.
Abstract: In this paper a new nonlinear system identification approach is developed for dynamical quantification of cardiovascular regulation. This approach is specifically focused on the identification of the heart rate (HR) baroreflex mechanism. The principal objective of this paper is to improve the model accuracy in the estimation of HR by proposing a modified nonlinear model.The proposed HR baroreflex model is based on inherent features of the autonomic nervous system for which we develop an adaptive neuro-fuzzy inference system (ANFIS) structure. This method allows incorporation of physiological understandings about the sympathetic and parasympathetic nerves through the selection of appropriate membership functions in the ANFIS structure. The required data for system modeling are collected from the publicly available PhysioNet database.The results agree with the natural characteristics and physiological understanding of the cardiovascular regulatory system, such as delay in the parasympathetic function, durability in the function of sympathetic nerves and the correlation between the HR and the ABP signals. They also show significant improvements in HR prediction in terms of the normalized root mean square error (NRMSE) in comparison with other reported methods. We achieved to 0.191 in mean NRMSE in prediction of HR in this paper which is about 20% better than the best reported result in other researches.We have shown that for cardiovascular system regulation, our proposed nonlinear model is more accurate than other recently developed methods. Accurate HR baroreflex modeling enables clinicians to have more reliable information for their patients.
BibTeX:
@article{Jalali2011,
  author = {Ali Jalali and Ali Ghaffari and Parham Ghorbanian and Chandrasekhar Nataraj},
  title = {Identification of sympathetic and parasympathetic nerves function in cardiovascular regulation using ANFIS approximation},
  journal = {Artificial Intelligence in Medicine},
  year = {2011},
  volume = {52},
  number = {1},
  pages = {27--32},
  doi = {10.1016/j.artmed.2011.01.002}
}
Jalali A and Nataraj C (2011), "A cycle-averaged model of hypoplastic left heart syndrome (HLHS).", Conference Proceedings IEEE Engineering in Medicine and Biology Society., In Conference Proceedings IEEE Engineering in Medicine and Biology Society. Vol. 2011, pp. 190-194.
Abstract: This paper is concerned with computational modeling of a severe congenital defect called Hypoplastic left heart syndrome (HLHS) that is the most common cardiac malformation with the highest likelihood of deaths in newborns. A lumped parameter model of the HLHS circulation has been developed to study the hemodynamic variables in the various sections of the cardio-pulmonary circulation system. We applied a short-term, cycle-averaging operation to the differential equations of the HLHS model to obtain the cycle-averaged model. Study has been carried out to analyze the variation of blood flow rate in different parts due to parameter changes. Results show that the developed model, could bring a good insight into understanding of the HLHS disease.
BibTeX:
@inproceedings{Jalali2011a,
  author = {Ali Jalali and C. Nataraj},
  title = {A cycle-averaged model of hypoplastic left heart syndrome (HLHS).},
  booktitle = {Conference Proceedings IEEE Engineering in Medicine and Biology Society},
  journal = {Conference Proceedings IEEE Engineering in Medicine and Biology Society},
  year = {2011},
  volume = {2011},
  pages = {190--194},
  doi = {10.1109/IEMBS.2011.6090030}
}
Jalali A, Nataraj C, Butchy M and Ghaffari A (2011), "Feature Extraction and Abnormality Detection in Autonomic Regulation of Cardiovascular System", In Conference Proceedings ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. , pp. 185-189.
Abstract: The objective of this study is to develop an efficient methodology for classifying patients suffering any type of blood pressure dysregulation from healthy subjects. Four features of malfunctions in blood pressure regulation are introduced, and a criterion is proposed for each feature to evaluate and distinguish patients from healthy subjects. The evaluated features are based on the analysis of difference between data related to healthy subjects and those collected from patients. The proposed criteria are implemented on a group of healthy and patient subjects by collecting their systolic blood pressure (SBP) and their heart rate (HR) time series. The proposed method is applied on three different groups of subjects each containing four healthy and eleven patients. It is shown that the algorithm properly detects the status of all fifteen subjects in one group and fourteen subjects in two groups. The results obtained indicate that the selected features have remarkable capability in detection of blood pressure dysregulation.
BibTeX:
@inproceedings{Jalali2011b,
  author = {Ali Jalali and C. Nataraj and Margaret Butchy and Ali Ghaffari},
  title = {Feature Extraction and Abnormality Detection in Autonomic Regulation of Cardiovascular System},
  booktitle = {Conference Proceedings ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference},
  year = {2011},
  pages = {185-189},
  doi = {10.1115/DETC2011-48617}
}
Jalali A, Ghorbanian P and Nataraj C (2011), "Cardiovascular System" InTech (invited, under review).
BibTeX:
@inbook{Jalali2011c,
  author = {Ali Jalali and Parham Ghorbanian and C. Nataraj},
  editor = {David Gaze},
  title = {Cardiovascular System},
  publisher = {InTech (invited, under review)},
  year = {2011}
}
Kappaganthu K. and Nataraj C (2011), "Modeling and Severity Estimation of Outer Race Defects in Rolling Element Bearings", Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science., In Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science. (under review)
BibTeX:
@inproceedings{Kappaganthu2011,
  author = {Kappaganthu, K., and Nataraj, C.},
  title = {Modeling and Severity Estimation of Outer Race Defects in Rolling Element Bearings},
  booktitle = {Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science},
  journal = {Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science},
  year = {2011},
  number = {under review}
}
Kappaganthu K and Nataraj C (2011), "Modeling and analysis of outer race defects in rolling element bearings", Advances in Vibration Engineering. Vol. 11(4)(4), pp. 371-384.
BibTeX:
@article{Kappaganthu2011a,
  author = {Karthik Kappaganthu and C. Nataraj},
  title = {Modeling and analysis of outer race defects in rolling element bearings},
  journal = {Advances in Vibration Engineering},
  year = {2011},
  volume = {11(4)},
  number = {4},
  pages = {371-384},
  note = {I was the project director and principal author working with my student.}
}
Kappaganthu K and Nataraj C (2011), "Mutual Information Based Feature Selection From Data Driven And Model Based Techniques For Fault Detection In Rolling Element Bearings", In Proceedings of the ASME IDETC/CIE.
Abstract: This paper proposes a novel technique combining data-driven and model-based techniques to significantly improve the performance in bearing fault diagnostics. Features that provide best classification performance for the given data are selected from a combined set of data driven and model based features. Some of the common data driven techniques from time, frequency and time-frequency domain are considered. For model based feature extraction, recently developed cross-sample entropy is used. The ranking and performance of each of these feature sets are studied, when used independently and when used together. Mutual information based technique is used for ranking and selection of the optimal feature set. Using this method, the contribution to performance and redundancy of each of the data driven features and model based features can be studied. This method can be used to design an effective diagnostic system for bearing fault detection.
BibTeX:
@inproceedings{Kappaganthu2011b,
  author = {Karthik Kappaganthu and C. Nataraj},
  title = {Mutual Information Based Feature Selection From Data Driven And Model Based Techniques For Fault Detection In Rolling Element Bearings},
  booktitle = {Proceedings of the ASME IDETC/CIE},
  year = {2011},
  doi = {10.1115/DETC2011-47822}
}
Kappaganthu K. and Nataraj C (2011), "Nonlinear modeling and analysis of rolling element bearing with clearance", Communications in Nonlinear Science and Numerical Simulation. Vol. 16(10), pp. 4134–4145.
Abstract: Rolling element bearings are the key components in many rotating machinery. For efficient performance of the machine it is necessary to accurately predict the effect of various parameters and operating conditions on the machine's behavior. This paper deals with the development of a nonlinear model of the rotor-bearing system on rolling element bearings with clearance. Clearance is an important nonlinearity which can cause bifurcations and chaos as has been shown in this paper. In this paper a detailed model for clearance is developed. In this model the inner race center and the outer race center are not assumed to be collinear when relations for deflections in the rolling element are developed. The model is non-dimensionalized and then analyzed to reveal rich nonlinear phenomena. Further, for better performance of any machine it is necessary to identify and stay out of chaotic regimes of operation. Hence, Lyapunov exponents and Poincare´ mappings are used to analyze the system and determine the regions of chaotic response.
BibTeX:
@article{Kappaganthu2011d,
  author = {Kappaganthu, K., and Nataraj, C.},
  title = {Nonlinear modeling and analysis of rolling element bearing with clearance},
  journal = {Communications in Nonlinear Science and Numerical Simulation},
  year = {2011},
  volume = {16(10)},
  pages = {4134–4145},
  doi = {10.1016/j.cnsns.2011.02.001}
}
Kappaganthu K and Nataraj C (2011), "Optimal Biped Design Using a Moving Torso: Theory and Experiments", In Biped Robots. , pp. 35-54. Intech International.
Abstract: This research has explored a novel aspect of biped robots with torsos. It has shown the importance and utility of the torso in the dynamics of the biped. The torso has been used efficiently to make the biped walk with the specified step length and velocity. The use of the torso has reduced the number of actuators required; further, the use of optimal torque has greatly reduced the external energy required for walking. The biped we analyzed, designed and constucted effectively uses the natural dynamics of the system; at the same time, the external excitation at torso has increased the practicability of the biped.
BibTeX:
@inbook{Kappaganthu2011g,
  author = {Karthik Kappaganthu and Nataraj, C.},
  editor = {Armando Carlos Pina Filho},
  title = {Optimal Biped Design Using a Moving Torso: Theory and Experiments},
  booktitle = {Biped Robots},
  publisher = {Intech International},
  year = {2011},
  pages = {35-54},
  note = {I was the project director and co-principal author working with my student.},
  doi = {10.5772/13791}
}
Kwuimy CK and Nataraj C (2011), "Prediction of horseshoes chaos in active magnetic bearings with time-varying stiffness", In Proceedings of ASME 2011 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference IDETC/CIE 2011. Washington, DC, USA, August 29-31, 2011, 2011. Vol. DETC2011-48317
Abstract: The paper considers a model of an active magnetic bearing with time-varying stiffness and investigates the effects of the control gain parameters on the appearance of horseshoes chaos. The Melnikov method is used to derive the critical conditions for chaos and numerical simulations are performed to determine the basins of attraction. It is shown that the domain of chaotic mo- tion strongly depends on the gain parameters and that this do- main increases with the magnetic force and decrease with the static current. The controller frequency w is found to be a key parameter and has a critical effect on the enlargement of the chaotic domain.
BibTeX:
@inproceedings{Kwuimy2011c,
  author = {C.A. Kitio Kwuimy and C. Nataraj},
  editor = {ASME},
  title = {Prediction of horseshoes chaos in active magnetic bearings with time-varying stiffness},
  booktitle = {Proceedings of ASME 2011 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference IDETC/CIE 2011},
  year = {2011},
  volume = {DETC2011-48317},
  doi = {10.1115/DETC2011-48317}
}
Kwuimy CK, Litak G, Borowiec M and Nataraj C (2011), "On the performance of piezoelectric energy harvesting driven by air fow", In 11th conference on dynamical systems theory and applications. Loodoz, Poland, December 5-8, 2011.
Abstract: A wind source for possible energy harvesting is proposed. To increase the amplitude of vibration we apply a magnetopiezoelastic oscillator possessing a double well Dung potential. We show the output voltage response of the system for di erent choice of wind excitations including the combination of harmonic and noisy components. The energy harvesting appeared to be the most ecient for the conditions close to the stochastic resonance region where the potential well was overcame.
BibTeX:
@inproceedings{Kwuimy2011d,
  author = {C.A. Kitio Kwuimy and G. Litak and M. Borowiec and C. Nataraj},
  title = {On the performance of piezoelectric energy harvesting driven by air fow},
  booktitle = {11th conference on dynamical systems theory and applications},
  year = {2011}
}
Lee D, Sullivan R and Nataraj C (2011), "Design and Control of a Surface Vehicle Demonstrator", In 2nd IEEE Workshop on Model-based Engineering for Real-Time Embedded Systems (MoBE-RTES 2011).
BibTeX:
@inproceedings{Lee2011,
  author = {DongBin Lee and Ralph Sullivan and Nataraj, C},
  title = {Design and Control of a Surface Vehicle Demonstrator},
  booktitle = {2nd IEEE Workshop on Model-based Engineering for Real-Time Embedded Systems (MoBE-RTES 2011)},
  year = {2011}
}
Lee D, Burg TC, Xu P and Nataraj C (2011), "Modeling and Coordinated Control of Flying Robotic Arm", In American Control Conference.
Abstract: In this paper, a flying vehicle with a robotic arm is addressed. The flying robotic arm, called UAVARM, is modeled as an integrated system comprising a small-scale unmanned, underactuated aerial vehicle (UAV) and a revolute robotic manipulator which can have a fast and flexible maneuverability in space. The main concern for the combined system is to control the position and orientation of the end-effector of the UAVARM while collaboratively stabilizing the UAV body so that it can follow and track a desired trajectory. Success in solving the control design problem will allow the system to be used in remote dextrous applications such as replacing bulbs on a radio tower. Many control challenges exist due to the complexity of the system including that the UAV is underactuated, inherently unstable, and the interaction of the arm and the UAV. The novelty of this system is that UAVARM is the complete integration of the subsystem to function as a single entity -the subsystems are cooperatively controlled in the sense that spatial states such as position, attitude, and orientation are transferred or cumulated in an automated manner using homogeneous matrices to the end-effector in order to exactly control the flying arm. The closed-loop controller will control the trajectory-tracking of the end-effector while satisfying a Lyapunov-type stability of the integrated system, which yields an asymptotically stable tracking result in a given angle condition.
BibTeX:
@inproceedings{Lee2011a,
  author = {DongBin Lee and Timothy C. Burg and Peng Xu and C. Nataraj},
  title = {Modeling and Coordinated Control of Flying Robotic Arm},
  booktitle = {American Control Conference},
  year = {2011},
  doi = {10.1115/DSCC2012-MOVIC2012-8770}
}
Lee D and Nataraj C (2011), "Design and Control of an Autonomous Surface Vehicle Demonstrator", In American Control Conference.
BibTeX:
@inproceedings{Lee2011c,
  author = {DongBin Lee and Nataraj, C},
  title = {Design and Control of an Autonomous Surface Vehicle Demonstrator},
  booktitle = {American Control Conference},
  year = {2011}
}
Lee D and Nataraj C (2011), "Adaptive Control of a Nonlinear Model-based Solenoid-Valve System with Uncertainties", In Intelligent Ships Symposium IX.
Abstract: In this paper, a nonlinear model-based adaptive control approach is proposed for a solenoid-valve system. The challenge is that solenoids and butterfly valves have uncertainties in multiple parameters in the nonlinear model; various kinds of physical appearance such as size and stroke, dynamic parameters including inertia, damping, and torque coefficients, and operational parameters especially, pipe diameters and flow velocities. These uncertainties are making the system not only difficult to adjust to the environment, but also further complicated to develop the appropriate control approach for meeting the system objectives. The main contribution of this research is the application of adaptive control theory and Lyapunov-type stability approach to design a controller for a dynamic model of the solenoid-valve system in the presence of those uncertainties. The control objectives such as set-point regulation, parameter compensation, and stability are supposed to be simultaneously accomplished. The error signals are first formulated based on the nonlinear dynamic models and then the control input is developed using the Lyapunov stability-type analysis to obtain the error bounded while overcoming the uncertainties. The parameter groups are updated by adaptation laws using a projection algorithm. Numerical simulation results are shown to demonstrate good performance of the proposed nonlinear model-based adaptive approach and to compare the performance of the same solenoid-valve system with a non-adaptive method as well.
BibTeX:
@inproceedings{Lee2011d,
  author = {DongBin Lee and C. Nataraj},
  title = {Adaptive Control of a Nonlinear Model-based Solenoid-Valve System with Uncertainties},
  booktitle = {Intelligent Ships Symposium IX},
  year = {2011},
  url = {https://admin.navalengineers.org/SiteCollectionDocuments/2011%20Proceedings%20Documents/ISSIX/Abstracts/1Track1_Nataraj.pdf},
  doi = {10.1155/2012/846458}
}
Lee D, Sullivan R, Nataraj C and Loeb H (2011), "Model-based Control Systems For an Autonomous Surface Vehicle", In ASNE Intelligent Ship Symposium IX., May, 2011.
BibTeX:
@inproceedings{Lee2011f,
  author = {D. Lee and R. Sullivan and C. Nataraj and H. Loeb},
  title = {Model-based Control Systems For an Autonomous Surface Vehicle},
  booktitle = {ASNE Intelligent Ship Symposium IX},
  year = {2011}
}
Lee D and Nataraj C (2011), "Adaptive Tracking Control of Linear Time-varying Unmanned Surface Vehicles with Disturbances", In ASNE Intelligent Ship Symposium IX., May, 2011.
BibTeX:
@inproceedings{Lee2011g,
  author = {Don Lee and C. Nataraj},
  title = {Adaptive Tracking Control of Linear Time-varying Unmanned Surface Vehicles with Disturbances},
  booktitle = {ASNE Intelligent Ship Symposium IX},
  year = {2011}
}
Lee D, C. Nataraj and Burg TC (2011), "Robust Control Of A Surface Vehicle With Disturbances", In Proceedings of the ASME Dynamic Systems and Control Conference.
Abstract: In this paper, a new approach for robust control of a surface vehicle is presented. This approach uses a sliding mode controller with an additional robust term. A nonlinear dynamic model which is complicated by environmental disturbances is presented for a surface vehicle, dividing the model into the rigid-body portion, and a portion containing disturbance terms that the robust controller will reject. Following that, a robust approach based on sliding mode controller is developed for tracking desired trajectories in finite time while compensating for disturbances such as hydrodynamics, wind, wave, and currents based on Lyapunov-type stability analysis. Finally numerical simulation results are shown to demonstrate the validity of the proposed controllers.
BibTeX:
@inproceedings{Lee2011i,
  author = {DongBin Lee and C. Nataraj, and Timothy C. Burg},
  title = {Robust Control Of A Surface Vehicle With Disturbances},
  booktitle = {Proceedings of the ASME Dynamic Systems and Control Conference},
  year = {2011},
  doi = {10.1115/DSCC2011-6201}
}
Lee D, C. Nataraj, Burg TC and Dawson DM (2011), "Adaptive Tracking Control of an Underactuated Aerial Vehicle", In American Control Conference.
Abstract: In this paper, adaptive tracking control of an underactuated quadrotor is addressed. Position and yaw trajectory tracking is designed using state feedback control system and an integrator backstepping approach is applied to this coupled and cascaded dynamic system. The control design is further complicated by considering the parametric uncertainty of the dynamic modeling of the quadrotor aerial-robot vehicle. Projection-based adaptive control schemes are then designed to estimate the unknown parameters. Lyapunov-type stability analysis and numerical simulation results which yields a bounded tracking result are shown to demonstrate the initial validity of the proposed controllers.
BibTeX:
@inproceedings{Lee2011k,
  author = {DongBin Lee and C. Nataraj, and Timothy C. Burg and Darren M. Dawson},
  title = {Adaptive Tracking Control of an Underactuated Aerial Vehicle},
  booktitle = {American Control Conference},
  year = {2011}
}
Loeb H, Holihan R and Nataraj C (2011), "Design of an Intelligent Collision Avoidance System based on a Scanning Range Finder", In Intelligent Ships Symposium IX.
BibTeX:
@inproceedings{Loeb2011,
  author = {Helen Loeb and Ryan Holihan and C. Nataraj},
  title = {Design of an Intelligent Collision Avoidance System based on a Scanning Range Finder},
  booktitle = {Intelligent Ships Symposium IX},
  year = {2011}
}
Naseradinmousavi P and Nataraj C (2011), "Nonlinear mathematical modeling of butterfly valves driven by solenoid actuators", Journal of Applied Mathematical Modelling. Vol. 35(5), pp. 2324-2335.
Abstract: This paper describes high fidelity modeling and analysis of the opening and closing processes of butterfly valves driven by solenoid actuators using multiphysics models. The equations are derived and solved numerically. The variable of primary interest is the butterfly valve rotation angle. The coupled model for electromagnetics, fluid dynamics and mechanical dynamics are derived by making some simplifying assumptions. It is shown that the behavior of hydrodynamic torque plays an important role in the closing and opening processes. A discussion is presented with an explanation of the results and a comparison has been made for both the processes.
BibTeX:
@article{Naseradinmousavi2011,
  author = {Peiman Naseradinmousavi and C. Nataraj},
  title = {Nonlinear mathematical modeling of butterfly valves driven by solenoid actuators},
  journal = {Journal of Applied Mathematical Modelling},
  year = {2011},
  volume = {35},
  number = {5},
  pages = {2324-2335},
  url = {http://www.sciencedirect.com/science/article/pii/S0307904X10004464}
}
Naseradinmousavi P and Nataraj C (2011), "A chaotic blue sky catastrophe of butterfly valves driven by solenoid actuators", In Proceedings of the ASME 2011 International Mechanical Engineering Congress & Exposition. (IMECE2011/62608)
Abstract: Chilled water systems used in the industry and on board ships are critical for safe and reliable operation. It is hence important to understand the fundamental physics of these systems. This paper focuses in particular on a critical part of the automation system, namely, actuators and valves that are used in so-called "smart valve" systems. The system is strongly nonlinear, and necessitates a nonlinear dynamic analysis to be able to predict all critical phenomena that affect effective operation and efficient design. The derived mathematical model includes electromagnetics, fluid mechanics, and mechanical dynamics. Nondi-mensionalization has been carried out in order to reduce the large number of parameters to a few critical independent sets to help carry out a broad parametric analysis. The system stability analysis is then carried out by the aid of the tools from nonlinear dynamic analysis. This reveals that the system is unstable in a certain region of the parameter space. The system is also shown to exhibit crisis and chaotic responses; this is characterized using Lyapunov exponents and power spectra. Knowledge and avoidance of these dangerous regimes is necessary for successful and safe operation. Copyright © 2011 by ASME.
BibTeX:
@inproceedings{Naseradinmousavi2011b,
  author = {Peiman Naseradinmousavi and C. Nataraj},
  title = {A chaotic blue sky catastrophe of butterfly valves driven by solenoid actuators},
  booktitle = {Proceedings of the ASME 2011 International Mechanical Engineering Congress & Exposition},
  year = {2011},
  number = {IMECE2011/62608},
  url = {http://www.asmeconferences.org/Congress2011/TechnicalProgramOverview.cfm#696}
}
Nataraj C and Kappaganthu K (2011), "Vibration-based diagnostics of rolling element bearings: state of the art and challenges", In 13th World Congress in Mechanism and Machine Science, Guanajuato, Mexico., June 19-25, 2011.
Abstract: Fault identification and estimation is an important and necessary step in Condition Based Maintenance. In general, there are two prevalent methods that are used for this purpose, data driven techniques and model based techniques. Data driven techniques use data collected from experiments, learn about the system and then use this knowledge to infer the system's current state of health; these tend to be more in the applied arena and are favored for implementation in the industry. Model based techniques use models to derive the knowledge that can be used to determine the machine's condition; these tend to be more fundamental and are pursued often as a research topic to gain insights into the physics underlying the observed phenomena. Each of these methods has its own strengths and limitations. This paper reviews the state of the art in this area focusing on defects in rolling element bearings, and identifies the challenges to be tackled. Finally, a new paradigm is proposed using an illustrative example.
BibTeX:
@inproceedings{Nataraj2011a,
  author = {C. Nataraj and Karthik Kappaganthu},
  title = {Vibration-based diagnostics of rolling element bearings: state of the art and challenges},
  booktitle = {13th World Congress in Mechanism and Machine Science, Guanajuato, Mexico},
  year = {2011}
}
O’Brien JC, Stein RA, Clayton GM, Wemhoff AP and Nataraj C (2011), "Exchange Sea Perch/Mate Science Learning Modules", In American Society for Engineering Education Annual Conference.
BibTeX:
@inproceedings{O’Brien2011,
  author = {James C. O’Brien and Rebecca A Stein and Garrett M. Clayton and Aaron P. Wemhoff and C. Nataraj},
  title = {Exchange Sea Perch/Mate Science Learning Modules},
  booktitle = {American Society for Engineering Education Annual Conference},
  year = {2011}
}
Ghorbanian P, Ghaffari A, Jalali A and Nataraj C (2010), "Heart arrhythmia detection using continuous wavelet transform and principal component analysis with neural network classifier", In Conference Proceedings Computing in Cardiology. Vol. 37, pp. 669 - 672.
BibTeX:
@inproceedings{Ghorbanian2010,
  author = {Parham Ghorbanian and Ali Ghaffari and Ali Jalali and C. Nataraj},
  title = {Heart arrhythmia detection using continuous wavelet transform and principal component analysis with neural network classifier},
  booktitle = {Conference Proceedings Computing in Cardiology},
  year = {2010},
  volume = {37},
  pages = {669 - 672}
}
Jalali A, Ghaffari A, Ghorbanian P, Jalali F and Nataraj C (2010), "Quantitative Analysis of Heart Rate Baroreflex in Healthy Subjects Using Adaptive Neuro Fuzzy Inference System Approximation", In Computing in Cardiology 2010.
BibTeX:
@inproceedings{Jalali2010,
  author = {Ali Jalali and Ali Ghaffari and Parham Ghorbanian and Fatemeh Jalali and C Nataraj},
  title = {Quantitative Analysis of Heart Rate Baroreflex in Healthy Subjects Using Adaptive Neuro Fuzzy Inference System Approximation},
  booktitle = {Computing in Cardiology 2010},
  year = {2010}
}
Kappaganthu K and Nataraj C (2010), "Feature Selection for Outer Race Bearing Fault Detection Based on Mutual Information", In Emerging Trends in Rotor Dynamics. Springer Verlag.
BibTeX:
@inbook{Kappaganthu2010b,
  author = {Karthik Kappaganthu and Nataraj, C},
  editor = {K. Gupta},
  title = {Feature Selection for Outer Race Bearing Fault Detection Based on Mutual Information},
  booktitle = {Emerging Trends in Rotor Dynamics},
  publisher = {Springer Verlag},
  year = {2010}
}
Kappaganthu K and C. N (2010), "Optimal Biped Design Using a Moving Torso: Theory and Experiments", In Biped Robots. , pp. 1-20. Intech International.
Abstract: This research has explored a novel aspect of biped robots with torsos. It has shown the importance and utility of the torso in the dynamics of the biped. The torso has been used efficiently to make the biped walk with the specified step length and velocity. The use of the torso has reduced the number of actuators required; further, the use of optimal torque has greatly reduced the external energy required for walking. The biped we analyzed, designed and constucted effectively uses the natural dynamics of the system; at the same time, the external excitation at torso has increased the practicability of the biped.
BibTeX:
@inbook{Kappaganthu2010d,
  author = {Karthik Kappaganthu and Nataraj. C.},
  title = {Optimal Biped Design Using a Moving Torso: Theory and Experiments},
  booktitle = {Biped Robots},
  publisher = {Intech International},
  year = {2010},
  pages = {1--20}
}
Kappaganthu K and Nataraj C (2010), "Feature Selection for Bearing Fault Detection Based on Mutual Information", In Emerging Trends in Rotor Dynamics. Springer Verlag.
Abstract: This paper deals with the important task of feature selection for the detection of faulty bearings in a rotor-bearing system. Various time, frequency and time-frequency based features are obtained from signals measured from bearings with and without outer race defect. The features are divided into a training set, a validation set and a test set. The task is to develop an optimal subset of features for a pattern classification algorithm which can efficiently and accurately classify the state of the machine as healthy or faulty. The features are ranked based on the mutual information content between the feature subset and the state of the machine. A validation set from the measured data is then used to obtain the optimal subset for classification. The performance of the method is evaluated using the test set.
BibTeX:
@inbook{Kappaganthu2010f,
  author = {Karthik Kappaganthu and Nataraj, C},
  editor = {K. Gupta},
  title = {Feature Selection for Bearing Fault Detection Based on Mutual Information},
  booktitle = {Emerging Trends in Rotor Dynamics},
  publisher = {Springer Verlag},
  year = {2010},
  note = {I was the project director and co-principal author working with my student.},
  doi = {10.1007/978-94-007-0020-8__44}
}
Kappaganthu K and Nataraj C (2010), "Nonlinear modeling of a rigid rotor supported on rolling element bearings with localized defects", In Proceedings of the ASME IDETC/CIE 2009.
Abstract: In this paper a nonlinearmodel for defects in rolling element bearings is developed. Detailed nonlinear models are useful to detect, estimate and predict failure in rotating machines. Also, accurate modeling of the defect provides parameters that can be estimated to determine the health of the machine. In this paper the rotor-bearing system is modeled as a rigid rotor and the defects are modeled as pits in the bearing race. Unlike the previous models, the motion of the rolling element thorough the defect is not modeled as a predetermined function; instead, it is dynamically determined since it depends on the clearance and the position of the shaft. Using this nonlinear model, the motion of the shaft is simulated and the effect of the rolling element passing through the defect is studied. The effect of shaft parameters and the defect parameters on the precision of the shaft and the overall performance of the system is studied. Finally, suitable measures for health monitoring and defect tracking are suggested.
BibTeX:
@inproceedings{Kappaganthu2010h,
  author = {Karthik Kappaganthu and C. Nataraj},
  title = {Nonlinear modeling of a rigid rotor supported on rolling element bearings with localized defects},
  booktitle = {Proceedings of the ASME IDETC/CIE 2009},
  year = {2010},
  doi = {10.1115/DETC2010-29041}
}
Lee D, Nataraj C, Burg TC and Dawson DM (2010), "Robust and Adaptive Tracking Control of a Surface Vessel", In American Control Conference.
BibTeX:
@inproceedings{Lee2010,
  author = {DongBin Lee and C. Nataraj and Timothy C. Burg and Darren M. Dawson},
  title = {Robust and Adaptive Tracking Control of a Surface Vessel},
  booktitle = {American Control Conference},
  year = {2010}
}
Lee D, Nataraj C and Naseradinmousavi P (2010), "Nonlinear Model-based Adaptive Control Of A Solenoid-Valve System", In Proceedings of the ASME Dynamic Systems and Control Conference.
BibTeX:
@inproceedings{Lee2010b,
  author = {Lee, D. and Nataraj, C. and Naseradinmousavi, P.},
  title = {Nonlinear Model-based Adaptive Control Of A Solenoid-Valve System},
  booktitle = {Proceedings of the ASME Dynamic Systems and Control Conference},
  year = {2010},
  url = {https://asme-dscd.papercept.net/conferences/scripts/abstract.pl?ConfID=4&Number=4283}
}
Nataraj C, Reddy S, Woods M and Nataraj C (2010), "Swarm robotics: a research project with high school students as active participants", In ASEE Annual Conference. (AC 2010-1655)
Abstract: This paper is concerned with an educational project to provide a rich research experience on swarm robotics to high school students. A group of three mobile robots (the popular Lego NXT) was used to implement a 'search and rescue' operation. A bio-inspired global optimization technique called particle swarm optimization (PSO) was used as the principal algorithm. Each robot was placed in pre-defined positions with a target position corresponding to a single target. The robots were programmed to search in spirals until the target was found by any one of the robots. Once the target was detected the robots attempted to reach the target using the PSO algorithm. Results were encouraging. The high school students were wholly responsible for all programming and experimental tasks and got an immersive experience of a real-time cutting-edge engineering research application.
BibTeX:
@inproceedings{Nataraj_Chiraag2010,
  author = {Chiraag Nataraj and Sanjeev Reddy and Mark Woods and C. Nataraj},
  title = {Swarm robotics: a research project with high school students as active participants},
  booktitle = {ASEE Annual Conference},
  year = {2010},
  number = {AC 2010-1655}
}
Nataraj C and Thimmaraya R (2010), "Tracking control of unmanned surface vehicles with Abkowitz steering model", In ASME Dynamic Systems & Control Conference.
Abstract: This paper is concerned with the tracking control of unmanned surface vehicles. Steering dynamics is modeled using nonlinear equations with three degrees of freedom following Abkowitz. Tracking control of this nonlinear system leads to the need to derive a control algorithm for linear error equations which have time-varying coefficients. Next, a control algorithm has been derived for this set of linear time-varying equations. Lyapunov transformations have been applied to transform the error equation into a canonical form. A desired closed-loop PD-spectrum and the desired right PD-modal matrix have been chosen and the resulting Sylvester equation has been solved to obtain a matrix of time-varying controller gains. This leads to the closed loop equations for controlling the ship steering of an unmanned ship. The controller algorithm is applied to the motion control of ships with parametric values from published reports. Several tracking trajectories have been generated with and without obstacles, and time-varying control has been investigated and presented. The control algorithm is shown to be quite effective for tracking of unmanned surface vehicles. Stability conditions are derived to ensure convergence. Present work in experimental verification is outlined.
BibTeX:
@inproceedings{Nataraj2010,
  author = {C. Nataraj and Ramesh Thimmaraya},
  title = {Tracking control of unmanned surface vehicles with Abkowitz steering model},
  booktitle = {ASME Dynamic Systems & Control Conference},
  year = {2010},
  doi = {10.1115/DSCC2010-4293}
}
Nataraj C and Lee D (2010), "Model-based Adaptive Control of A Solenoid-Valve System", In ASME Intl Mechanical Engineering Congress and Exposition (IMECE-39371).
Abstract: In this paper, a model-based control algorithm is developed for a solenoid-valve system. Solenoids and butterfly valves have uncertainties in multiple parameters in the model, which make the system difficult to adjust to the environment. These are further complicated by combining the solenoid and butterfly dynamic models. The control objective of a solenoid-valve system is to position the angle of the butterfly valve through the electric-driven actuator in spite of the complexity presented by uncertainties. The novelty of the controller design is that the current source of the solenoid valve from the model of the electromagnetic force is substituted for the control input in order to reach the set-point of the butterfly disk based on the error signals, overcoming the uncertainties represented by lumped parameters groups, and a stable controller is designed via the Lyapunov-based approach for the stability of the system and obtaining the control objective. The parameter groups are updated by adaptation laws using a projection algorithm. Numerical simulation is shown to demonstrate good performance of the proposed approach.
BibTeX:
@inproceedings{Nataraj2010a,
  author = {Nataraj, C. and Lee, D.},
  title = {Model-based Adaptive Control of A Solenoid-Valve System},
  booktitle = {ASME Intl Mechanical Engineering Congress and Exposition (IMECE-39371)},
  year = {2010},
  doi = {10.1115/DSCC2010-4283}
}
Nataraj C and Kappaganthu K (2010), "Nonlinear Response in a Rotor System with a Coulomb Spline", In Dynamical Systems: Discontinuity, Stochasticity and Time-Delay. Springer Verlag.
BibTeX:
@inbook{Nataraj2010b,
  author = {Nataraj, C and Karthik Kappaganthu},
  editor = {Albert Luo},
  title = {Nonlinear Response in a Rotor System with a Coulomb Spline},
  booktitle = {Dynamical Systems: Discontinuity, Stochasticity and Time-Delay},
  publisher = {Springer Verlag},
  year = {2010}
}
Thimmaraya R, Nataraj C and Lee D (2010), "Linear Time-Varying Tracking Control With Application to Unmanned Aerial Vehicles", In American Control Conference.
Abstract: This paper presents a novel control algorithm for tracking of nonlinear dynamic systems. The tracking problem leads to linearized time-varying error equations. Hence new eigenvalue notions are introduced for linear time varying systems, and a PD eigenstructure assignment scheme is proposed for linear time-varying structure via a differential Sylvester equation. Also shown is that closed-loop systems could be stabilized by assigning PD-eigenvalues appropriately, and a desired performance could be obtained by assigning the PD-eigenvectors according to the design specifications. The present control algorithm has an internal framework for testing the controllability of the time varying system via Lyapunov transform. The algorithm proposed is very general, and in principle applicable to systems of any order of complexity with any degree or kind of nonlinearity. An Unmanned Aerial Vehicle flight control application for a real aircraft is presented to validate the proposed algorithm.
BibTeX:
@inproceedings{Thimmaraya2010,
  author = {Ramesh Thimmaraya and C. Nataraj and DongBin Lee},
  title = {Linear Time-Varying Tracking Control With Application to Unmanned Aerial Vehicles},
  booktitle = {American Control Conference},
  year = {2010}
}
Feresse F, Kappaganthu K and Nataraj C (2009), "Eigenstructure assignment using a linear quadratic regulator and particle swarm optimization", In 7th IEEE International Conference on Control & Automation, IEEE.
BibTeX:
@inproceedings{Feresse2009,
  author = {F. Feresse and Karthik Kappaganthu and C. Nataraj},
  title = {Eigenstructure assignment using a linear quadratic regulator and particle swarm optimization},
  booktitle = {7th IEEE International Conference on Control & Automation, IEEE},
  year = {2009}
}
Ferrese F, Dong Q, Nataraj C and Biswas S (2009), "Optimal Feedback Control of Power Systems Using Eigenstructure Assignment and Particle Swarm Optimization", Naval Engineers Journal. Vol. 123(1)(Under Review), pp. 1559-3584.
BibTeX:
@article{Ferrese2009,
  author = {Frank Ferrese and Qing Dong and C. Nataraj and Saroj Biswas},
  title = {Optimal Feedback Control of Power Systems Using Eigenstructure Assignment and Particle Swarm Optimization},
  journal = {Naval Engineers Journal},
  year = {2009},
  volume = {123(1)},
  number = {Under Review},
  pages = {1559-3584}
}
Harsha SP and Nataraj C (2009), "Intermittent chaotic dynamics of rail axle supported by roller bearings", In Proceedings of the International Design Engineering Technical Conferences (IDETC2009)., August 30 - September 2, 2009. (DETC2009-87183)
BibTeX:
@inproceedings{Harsha2009,
  author = {S. P. Harsha and C. Nataraj},
  title = {Intermittent chaotic dynamics of rail axle supported by roller bearings},
  booktitle = {Proceedings of the International Design Engineering Technical Conferences (IDETC2009)},
  year = {2009},
  number = {DETC2009-87183}
}
Kappaganthu K and Nataraj C (2009), "A Biped with a Moving Torso", International Journal of Humanoid Robotics., December, 2009. Vol. 6(4), pp. 657-674.
Abstract: The moving torso plays an important role in the dynamics of bipeds like human beings, the exploitation of which is the essential focus of this paper. A design is presented where the torso is actuated to make the biped walk with the required step-length while allowing the legs to move passively. A periodic response excitation is achieved and the motion of the torso is optimized with respect to the external energy input. A working model of the biped is designed and built in which only the torso is actuated and the legs are passive. This laboratory model is used to test and validate the analytical solutions.
BibTeX:
@article{Kappaganthu2009,
  author = {Karthik Kappaganthu and C. Nataraj},
  title = {A Biped with a Moving Torso},
  journal = {International Journal of Humanoid Robotics},
  year = {2009},
  volume = {6},
  number = {4},
  pages = {657-674},
  note = {I was the project director and principal author working with my student. Impact factor: 1.885.},
  doi = {10.1142/S0219843609001887}
}
Kappaganthu K, Nataraj C and Samanta B (2009), "Fault parameter identification for model based prognostics of a ball bearing with an outer race defect", In Proceedings of IDETC/CIE 2009., August 30 - September 2, 2009. (DETC2009-87599)
Abstract: This paper deals with identifying the fault parameters of a rotor-bearing system with an outer race defect. The fault parameters can then be used for prognostics. The faults in the bearing are modeled as pits in the outer race of a bearing in a rotor- bearing system with four degrees of freedom. Discrete wavelet transforms are used to obtain the energy and entropy features of the rotor-bearing system. The relationship between the features and the fault parameter is studied. Particle swarm optimization is used to generate an optimal set offeatures. This optimal feature set is used to train an artificial neural network to determine the amount of fault in the system. Copyright © 2009 by ASME.
BibTeX:
@inproceedings{Kappaganthu2009c,
  author = {Karthik Kappaganthu and C. Nataraj and B. Samanta},
  title = {Fault parameter identification for model based prognostics of a ball bearing with an outer race defect},
  booktitle = {Proceedings of IDETC/CIE 2009},
  year = {2009},
  number = {DETC2009-87599},
  doi = {10.1115/DETC2009-87599}
}
Kappaganthu K, Nataraj C and Samanta B (2009), "Optimal Feature Set for Detection of Inner Race Defect in Rolling Element Bearings", In Annual Conference of the Prognostics and Health Management Society.
Abstract: Rolling element bearings are the key components in many rotating machinery. It is necessary to determine the condition of the bearing with reasonable degree of confidence. Many techniques have been developed for bearing fault detection. Each of these techniques have their own strengths and weaknesses. In this paper various features are compared for detecting inner race defects in rolling element bearings. Mutual information between the feature and defect is used as a quantitative measure of quality and the features are ranked appropriately. Often, a combination of different features is used for bearing fault detection. Hence it is important to understand the interaction of features for classification purposes. This paper addresses this issue and determines the optimal feature set for best detection performance.
BibTeX:
@inproceedings{Kappaganthu2009h,
  author = {Karthik Kappaganthu and C. Nataraj and B. Samanta},
  title = {Optimal Feature Set for Detection of Inner Race Defect in Rolling Element Bearings},
  booktitle = {Annual Conference of the Prognostics and Health Management Society},
  year = {2009}
}
Kappaganthu K, Nataraj C and Samanta B (2009), "Model Based Bearing Fault Detection Using Support Vector Machines", In Annual Conference of the Prognostics and Health Management Society.
Abstract: This paper deals with the development of a model based method for bearing fault diagnostics. This method effectively combines the information available in the data and the model for efficient classification of the bearing and the type of defect. A four degrees of freedom nonlinear rigid rotor model is used to simulate the rotor bearing system. Precession of the shaft is measured using proximity probes. The deviation of the measurement from the model is used to classify the system. Typically proximity probe data by itself does not contain enough information for accurate classification. However, when the information from the model is incorporated the combined features provide excellent classification performance. Further the use of a model also enables better classification over varying parameters. A support vector machine is used for classification.
BibTeX:
@inproceedings{Kappaganthu2009i,
  author = {Karthik Kappaganthu and C. Nataraj and B. Samanta},
  title = {Model Based Bearing Fault Detection Using Support Vector Machines},
  booktitle = {Annual Conference of the Prognostics and Health Management Society},
  year = {2009}
}
Naseradinmousavi P and Nataraj C (2009), "Nonlinear Analysis of Solenoid Actuators and Butterfly Valve Systems", In Intelligent Ships Symposium VIII.
BibTeX:
@inproceedings{Naseradinmousavi2009,
  author = {Peiman Naseradinmousavi and C. Nataraj},
  title = {Nonlinear Analysis of Solenoid Actuators and Butterfly Valve Systems},
  booktitle = {Intelligent Ships Symposium VIII},
  year = {2009}
}
Nataraj C and Ehrich F (2009), "Nonlinear Vibration", In Shock and Vibration Handbook. McGraw Hill.
BibTeX:
@inbook{Nataraj2009,
  author = {C. Nataraj and F. Ehrich},
  editor = {Alan G. Piersol and Thomas L. Paez},
  title = {Nonlinear Vibration},
  booktitle = {Shock and Vibration Handbook},
  publisher = {McGraw Hill},
  year = {2009},
  edition = {Sixth},
  note = {[Standard handbook on vibrations.]}
}
Nataraj C (2009), "Accurate Analytical Determination Of Electromagnetic Bearing Coefficients", In Emerging Trends in Rotor Dynamics. Springer Verlag.
Abstract: Electromagnetic contactless bearings have unique advantages over conventional bearings including no wear, reduced pollution and maintenance, and active control prospects. Their existing mathematical models are however very simplistic, and not very accurate leading to inferior (and, sometimes, catastrophic) performance under demanding conditions. This paper seeks to derive a better model from a basic consideration of the fundamental physics of the problem. It also intends to provide a family of curves suitable for use by an engineering designer. First, the fundamental electromagnetic equations are presented for a typical radial magnetic bearing configuration. The bearing is divided into four subdomains and the resulting partial differential equations and the boundary conditions are formulated over the different subdomains. The rotor is placed into a circular orbit, which leads to a moving boundary problem. The equations are then solved in closed form using an approximate asymptotic technique. The resulting magnetic fields and forces are computed, and the results are presented in a form suitable for use by a bearing designer. The results are also in a form that is decoupled from the active control strategy which greatly enhances their applicability.
BibTeX:
@inbook{Nataraj2009a,
  author = {C. Nataraj},
  editor = {K. Gupta},
  title = {Accurate Analytical Determination Of Electromagnetic Bearing Coefficients},
  booktitle = {Emerging Trends in Rotor Dynamics},
  publisher = {Springer Verlag},
  year = {2009},
  note = {[Was also the subject of a keynote speech at IUTAM Conference, March 2009.]},
  doi = {10.1007/978-94-007-0020-8__24}
}
Nataraj C, Bolla S and Samanta B (2009), "Analysis & Design Of An Adaptive Autopilot: Theory & Experiments", In International Ship Symposium 7., May, 2009.
BibTeX:
@inproceedings{Nataraj2009c,
  author = {C. Nataraj and Sreekanth Bolla and B. Samanta},
  title = {Analysis & Design Of An Adaptive Autopilot: Theory & Experiments},
  booktitle = {International Ship Symposium 7},
  year = {2009},
  note = {[abstract reviewed]}
}
Nersesov S, Nataraj C and Avis J (2009), "Design of finite-time stabilizing controllers for nonlinear dynamical systems", International Journal of Robust and Nonlinear Control. UK Vol. 19(8), pp. 900-918.
Abstract: Finite-time stability involves dynamical systems whose trajectories converge to an equilibrium state in finite time. Since finite-time convergence implies nonuniqueness of system solutions in reverse time, such systems possess non-Lipschitzian dynamics. Sufficient conditions for finite-time stability have been developed in the literature using Holder continuous Lyapunov functions. In this paper, we extend the finite-time stability theory to revisit time-invariant dynamical systems and to address time-varying dynamical systems. Specifically, we develop a Lyapunov-based stability and control design framework for finite-time stability as well as finite-time tracking for time-varying nonlinear dynamical systems. Furthermore, we use the vector Lyapunov function approach to study finite-time stabilization of compact sets for large-scale dynamical systems. Copyright © 2008 John Wiley & Sons, Ltd.
BibTeX:
@article{Nersesov2009,
  author = {Nersesov, S.G. and Nataraj, C. and Avis, J.M.},
  title = {Design of finite-time stabilizing controllers for nonlinear dynamical systems},
  journal = {International Journal of Robust and Nonlinear Control},
  year = {2009},
  volume = {19},
  number = {8},
  pages = {900-918},
  url = {http://dx.doi.org/10.1002/rnc.1359}
}
Samanta B and Nataraj C (2009), "Application of particle swarm optimization and proximal support vector machines for fault detection", Swarm Intelligence. Vol. 3(4), pp. 303–325.
Abstract: This paper presents a novel application of particle swarm optimization (PSO) in combination with another computational intelligence (CI) technique, namely, proximal support vector machine (PSVM) for machinery fault detection. Both real-valued and binary PSO algorithms have been considered along with linear and nonlinear versions of PSVM. The time domain vibration signals of a rotating machine with normal and defective bearings are processed for feature extraction. The features extracted from original and preprocessed signals are used as inputs to the classifiers (PSVM) for detection of machine condition. Input features are selected using a PSO algorithm. The classifiers are trained with a subset of experimental data for known machine conditions and are tested using the remaining data. The procedure is illustrated using the experimental vibration data of a rotating machine. The influences of the number of features, PSO algorithms and type of classifiers (linear or nonlinear PSVM) on the detection success are investigated. Results are compared with a genetic algorithm (GA) and principal component analysis (PCA). The PSO based approach gave test classification success above 90% which were comparable with the GA and much better than PCA. The results show the effectiveness of the selected features and classifiers in detection of machine condition.
BibTeX:
@article{Samanta2009,
  author = {B. Samanta and C. Nataraj},
  title = {Application of particle swarm optimization and proximal support vector machines for fault detection},
  journal = {Swarm Intelligence},
  year = {2009},
  volume = {3},
  number = {4},
  pages = {303–325},
  note = {I was the project director and co-principal author working with my postdoc. Leading journal in swarm intelligence. Impact factor: 3.054.},
  doi = {10.1007/s11721-009-0028-6}
}
Samanta B and Nataraj C (2009), "Morphological signal processing and computational intelligence for engineering system prognostics", Proceedings of the Institution of Mechanical Engineers. Part I: Journal of Systems and Control Engineering. Vol. 223(8), pp. 1095-1109.
Abstract: A computational intelligence (CI)-based approach is presented for prognostics of machine conditions using morphological signal processing (MSP). The machine vibration signals are processed using MSP to extract a novel entropy-based health index (HI) characterizing the signal shape-size complexity for system prognostics. The progression of HI is predicted using CI techniques, namely, recursive neural network (RNN), adaptive neurofuzzy inference system (ANFIS), and support vector regression (SVR). Both single- and multistep ahead predictions were evaluated through benchmark datasets of non-linear, nonstationary, and chaotic time series solutions of Mackey-Glass and Lorenz equations. The prognostic effectiveness of the CI techniques was illustrated using a vibration dataset of a helicopter drive-train system gearbox. For each CI predictor, both training datasets gave almost similar prediction performance. In training, the performance of ANFIS was the best, followed by SVR and RNN. In test, the best performance was obtained with SVR for both single- and multi-step ahead predictions. The results are helpful in understanding the relationship between the system conditions, the corresponding indicating feature, the level of degradation, and their progression.
BibTeX:
@article{Samanta2009a,
  author = {B. Samanta and C. Nataraj},
  title = {Morphological signal processing and computational intelligence for engineering system prognostics},
  journal = {Proceedings of the Institution of Mechanical Engineers. Part I: Journal of Systems and Control Engineering},
  year = {2009},
  volume = {223},
  number = {8},
  pages = {1095-1109},
  note = {I was the project director and co-principal author working with my postdoc. Impact factor: 0.907.},
  doi = {10.1243/09596518JSCE722}
}
Samanta B, Bird G, Kuijpers M, Zimmerman R, Jarvik G, Wernovsky G, Clancy R, Licht D, Gaynor J and Nataraj C (2009), "Prediction of periventricular leukomalacia. Part II. Selection of hemodynamic features using computational intelligence", Artificial Intelligence in Medicine. Netherlands Vol. 46(3), pp. 217-231.
Abstract: For pt. I see ibid.,p. 201-15 (2009). Objective: The objective of Part II is to analyze the dataset of extracted hemodynamic features (Case 3 of Part I) through computational intelligence (CI) techniques for identification of potential prognostic factors for periventricular leukomalacia (PVL) occurrence in neonates with congenital heart disease. Methods: The extracted features (Case 3 dataset of Part I) were used as inputs to CI based classifiers, namely, multi-layer perceptron (MLP) and probabilistic neural network (PNN) in combination with genetic algorithms (GA) for selection of the most suitable features predicting the occurrence of PVL. The selected features were next used as inputs to a decision tree (DT) algorithm for generating easily interpretable rules of PVL prediction. Results: Prediction performance for two CI based classifiers, MLP and PNN coupled with GA are presented for different number of selected features. The best prediction performances were achieved with 6 and 7 selected features. The prediction success was 100% in training and the best ranges of sensitivity (SN), specificity (SP) and accuracy (AC) in test were 60-73%, 74-84% and 71-74%, respectively. The identified features when used with the DT algorithm gave best SN, SP and AC in the ranges of 87-90% in training and 80-87%, 74-79% and 79-82% in test. Among the variables selected in CI, systolic and diastolic blood pressures, and pCO2 figured prominently similar to Part I. Decision tree based rules for prediction of PVL occurrence were obtained using the CI selected features. Conclusions: The proposed approach combines the generalization capability of CI based feature selection approach and generation of easily interpretable classification rules of the decision tree. The combination of CI techniques with DT gave substantially better test prediction performance than using CI and DT separately. [All rights reserved Elsevier].
BibTeX:
@article{Samanta2009b,
  author = {Samanta, B. and Bird, G.L. and Kuijpers, M. and Zimmerman, R.A. and Jarvik, G.P. and Wernovsky, G. and Clancy, R.R. and Licht, D.J. and Gaynor, J.W. and Nataraj, C.},
  title = {Prediction of periventricular leukomalacia. Part II. Selection of hemodynamic features using computational intelligence},
  journal = {Artificial Intelligence in Medicine},
  year = {2009},
  volume = {46},
  number = {3},
  pages = {217-231},
  note = {I was the project director and principal author working with my postdoc and medical colleagues. Leading journal for AI techniques applied to medicine. Impact Factor: 2.374.},
  url = {http://dx.doi.org/10.1016/j.artmed.2008.12.004},
  doi = {10.1016/j.artmed.2008.12.004}
}
Samanta B and Nataraj C (2009), "Use of Particle swarm optimization for machinery fault detection", Engineering Applications of Artificial Intelligence. Vol. 22(2), pp. 308-316.
Abstract: A study is presented on the application of particle swarm optimization (PSO) combined with other computational intelligence (CI) techniques for bearing fault detection in machines. The performance of two CI based classifiers, namely, artificial neural networks (ANNs) and support vector machines (SVMs) are compared. The time domain vibration signals of a rotating machine with normal and defective bearings are processed for feature extraction. The extracted features from original and preprocessed signals are used as inputs to the classifiers for detection of machine condition. The classifier parameters, e.g., the number of nodes in the hidden layer for ANNs and the kernel parameters for SVMs are selected along with input features using PSO algorithms. The classifiers are trained with a subset of the experimental data for known machine conditions and are tested using the remaining set of data. The procedure is illustrated using the experimental vibration data of a rotating machine. The roles of the number of features, PSO parameters and CI classifiers on the detection success are investigated. Results are compared with other techniques such as genetic algorithm (GA) and principal component analysis (PCA). The PSO based approach gave a test classification success rate of 98.6–100% which were comparable with GA and much better than with PCA. The results show the effectiveness of the selected features and the classifiers in the detection of the machine condition.
BibTeX:
@article{Samanta2009d,
  author = {Samanta, B. and Nataraj, C},
  title = {Use of Particle swarm optimization for machinery fault detection},
  journal = {Engineering Applications of Artificial Intelligence},
  year = {2009},
  volume = {22},
  number = {2},
  pages = {308-316},
  note = {I was the project director and co-principal author working with my postdoc. Impact factor: 2.498.},
  url = {http://dx.doi.org/10.1016/j.engappai.2008.07.006},
  doi = {10.1016/j.engappai.2008.07.006}
}
Samanta B, Nataraj C, Reddy S, Woods M and Nataraj C (2009), "Swarm robotics: research experience for high school students", In ASEE Midatlantic Conference., October, 2009.
Abstract: This paper is concerned with an educational project to provide a rich research experience on swarm robotics to high school students. A group of three mobile robots (the popular Lego NXT) was used to implement a 'search and rescue' operation. A bio-inspired global optimization technique called particle swarm optimization (PSO) was used as the principal algorithm. Each robot was placed in pre-defined positions with a target position corresponding to a single target. The robots were programmed to search in spirals until the target was found by any one of the robots. Once the target was detected the robots attempted to reach the target using the PSO algorithm. Results were encouraging. The high school students were wholly responsible for all programming and experimental tasks and got an immersive experience of a real-time cutting-edge engineering research application.
BibTeX:
@inproceedings{Samanta2009g,
  author = {B. Samanta and Chiraag Nataraj and Sanjeev Reddy and Mark Woods and C. Nataraj},
  title = {Swarm robotics: research experience for high school students},
  booktitle = {ASEE Midatlantic Conference},
  year = {2009}
}
Samanta B and Nataraj C (2009), "Intrinsic mode decompostion of physiological signals for feature extraction", In Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, DETC2007. San Diego, CA, August 30 - September 2, 2009. (DETC2009-86806)
BibTeX:
@inproceedings{Samanta2009i,
  author = {B. Samanta and C. Nataraj},
  title = {Intrinsic mode decompostion of physiological signals for feature extraction},
  booktitle = {Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, DETC2007},
  year = {2009},
  number = {DETC2009-86806}
}
Samanta B and Nataraj C (2009), "Health Indices Based on Morphology and Complexity Measures of Vibration Signals for Machine Condition Monitoring and Prognostics", In Annual Conference of the Prognostics and Health Management Society., October, 2009.
Abstract: The paper presents health indices (HI) for monitoring and prognostics of machine condition. HI are developed using morphology and entropy based complexity measures of machine vibration signals. The indices are compared with a recently introduced energy based feature and the commonly used statistical measure of signal kurtosis. The procedure of extracting HI is illustrated first using the simulated response of a simple gear model with tooth crack. Next the HI extraction process is applied to the experimental vibration data of a helicopter drivetrain gearbox with a seeded tooth fault. The effectiveness of the extracted HI is compared for gear condition monitoring and prognostics.
BibTeX:
@inproceedings{Samanta2009j,
  author = {B. Samanta and C. Nataraj},
  title = {Health Indices Based on Morphology and Complexity Measures of Vibration Signals for Machine Condition Monitoring and Prognostics},
  booktitle = {Annual Conference of the Prognostics and Health Management Society},
  year = {2009}
}
Samanta B and Nataraj C (2009), "Particle swarm optimization for chaotic system parameter estimation", In 2009 IEEE Swarm Intelligence Symposium., March 30 - April 2, 2009.
Abstract: A study is presented on the application of particle swarm optimization (PSO) for estimation of parameters in chaotic systems. The parameter estimation is formulated as a nonlinear optimization problem using PSO to minimize the synchronization error for the observable states of the actual system and its mathematical model. The procedure is illustrated using a typical chaotic system of Lorenz equations. The effectiveness of different variants of PSO on parameter estimation is studied with a wide search range of parameters. The results show the capability of the proposed PSO based approach in estimating the chaotic system parameters even in the presence of observation noise.
BibTeX:
@inproceedings{Samanta2009k,
  author = {B. Samanta and C. Nataraj},
  title = {Particle swarm optimization for chaotic system parameter estimation},
  booktitle = {2009 IEEE Swarm Intelligence Symposium},
  year = {2009},
  doi = {10.1109/SIS.2009.4937847}
}
Samanta B and Nataraj C (2009), "Estimation Of States And Parameters In Chaotic Systems Using Particle Swarm Optimization", In Proceedings of the ASME IDETC/CIE 2009.
Abstract: A study is presented on the application of particle swarm optimization (PSO) for estimation of states and parameters in chaotic systems. The parameter estimation is formulated as a nonlinear optimization problem using PSO to minimize the synchronization error for the observable states of the actual system and its mathematical model. The procedure is illustrated using a typical chaotic system of Lorenz equations. Results are presented to study the effects of different observable system states and observation noise on parameter estimation. The effectiveness of different variants of PSO on parameter estimation is also studied. The results show the capability of the proposed PSO based approach in estimating the chaotic system parameters with wide search range (50-200%) and in the presence of observation noise.
BibTeX:
@inproceedings{Samanta2009r,
  author = {B. Samanta and C. Nataraj},
  title = {Estimation Of States And Parameters In Chaotic Systems Using Particle Swarm Optimization},
  booktitle = {Proceedings of the ASME IDETC/CIE 2009},
  year = {2009},
  doi = {10.1115/DETC2009-87535}
}
Fahimi F, Rineesh S and Nataraj C (2008), "Formation controllers for underactuated surface vessels and zero dynamics stability", Control and Intelligent Systems. Calgary, AB, T3E 7J9, Canada Vol. 36(3), pp. 277-287.
Abstract: Nonlinear feedback control laws for controlling multiple robotic vessels in arbitrary formations are proposed. The presented leader-follower formation control approach uses only the inertial information obtained from the immediate neighbours of each vehicle via communication for control calculations. A three-degree-of-freedom (3DOF) surface vessel dynamic model and the method of Lyapunov has been used to derive the nonlinear control laws that stabilize the relative distance and orientation of neighboring vessels. It is shown that the internal dynamics of the 3DOF vessel as an underactuated system is also stable. The performance of these control laws is demonstrated in the presence of sea disturbances by computer simulations using a 6DOF dynamic model of the surface vessel. These controllers can be utilized to control an arbitrary number of robotic vessels moving in very general formations.
BibTeX:
@article{Fahimi2008,
  author = {Fahimi, F. and Rineesh, S.V.S. and Nataraj, C.},
  title = {Formation controllers for underactuated surface vessels and zero dynamics stability},
  journal = {Control and Intelligent Systems},
  year = {2008},
  volume = {36},
  number = {3},
  pages = {277-287}
}
Fahimi F, Nataraj C and Ashrafiuon H (2008), "Real-time obstacle avoidance for multiple mobile robots", Robotica., In Press, 2008. Vol. 27, pp. 189-198.
Abstract: An efficient, simple, and practical real time path planning method for multiple mobile robots in dynamic environments is introduced. Harmonic potential functions are utilized along with the panel method known in fluid mechanics. First, a complement to the traditional panel method is introduced to generate a more effective harmonic potential field for obstacle avoidance in dynamically changing environments. Second, a group of mobile robots working in an environment containing stationary and moving obstacles is considered. Each robot is assigned to move from its current position to a goal position. The group is not forced to maintain a formation during the motion. Every robot considers the other robots of the group as moving obstacles and hence the physical dimensions of the robots are also taken into account. The path of each robot is planned based on the changing position of the other robots and the position of stationary and moving obstacles. Finally, the effectiveness of the scheme is shown by modeling an arbitrary number of mobile robots and the theory is validated by several computer simulations and hardware experiments.
BibTeX:
@article{Fahimi2008a,
  author = {Farbod Fahimi and C. Nataraj and Hashem Ashrafiuon},
  title = {Real-time obstacle avoidance for multiple mobile robots},
  journal = {Robotica},
  year = {2008},
  volume = {27},
  pages = {189-198},
  url = {http://dx.doi.org/10.1017/S0263574708004438},
  doi = {10.1017/S0263574708004438}
}
Mousavi PN, Nataraj C, Bagheri A and Entezari MA (2008), "Mathematical simulation of combined trajectory paths of a seven link biped robot", Applied Mathematical Modelling. New York, NY 10010, United States Vol. 32( 7), pp. 1445-1462.
Abstract: The following article focuses on biped robot simulation and control over combined trajectory paths with the aid of mathematical modeling methods focusing on the effects of hip height over torso's modified motion. The mathematical simulation has been exploited to interpolate the combined trajectory of the robot path with the given breakpoints using inverse kinematic and dynamic methods to determine ZMP and stability treatments. After the robot's combined path determination, a third-order spline is utilized because of its high precision and ability to calculate the kinematic, dynamic and control parameters. With the aid of this software, common parameters such as joint angles and inertial forces for the given specifications and nominal conditions are calculated and simulated. © 2007 Elsevier Inc. All rights reserved.
BibTeX:
@article{Mousavi2008,
  author = {Mousavi, Peiman Naseradin and Nataraj, C. and Bagheri, Ahmad and Entezari, Mahdi Alizadeh},
  title = {Mathematical simulation of combined trajectory paths of a seven link biped robot},
  journal = {Applied Mathematical Modelling},
  year = {2008},
  volume = {32},
  number = { 7},
  pages = {1445-1462},
  url = {http://dx.doi.org/10.1016/j.apm.2007.11.026}
}
Nataraj C and Marx S (2008), "Bifurcation analysis of a one dof rotor on electromagnetic bearings", 2007 Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, DETC2007., In Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, DETC2007. New York, NY 10016-5990, United States Vol. 1 PART C, pp. 1775 - 1782.
Abstract: This paper considers a one degree of freedom rotor supported on an electromagnetic bearing in a feedback control loop. A nonlinear model of an electromagnetic bearing is developed and a nondimensional model is derived for the system with two distinct parameters corresponding to the controller gain and the static load. Nonlinear analysis is carried out as a function of these two parameters and bifurcation diagrams are derived. The results reveal a very interesting panoply of fixed points with varying stability conditions. Numerical simulations are carried out to confirm the results of nonlinear analysis. Practical implications of the nonlinear analysis results are discussed. Copyright © 2007 by ASME.
BibTeX:
@inproceedings{Nataraj2007b,
  author = {Nataraj, C. and Marx, Steven},
  title = {Bifurcation analysis of a one dof rotor on electromagnetic bearings},
  booktitle = {Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, DETC2007},
  journal = {2007 Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, DETC2007},
  year = {2008},
  volume = { 1 PART C},
  pages = {1775 - 1782},
  doi = {10.1115/DETC2007-35721}
}
Nataraj C and Harsha S (2008), "The effect of bearing cage run-out on the nonlinear dynamics of a rotating shaft", Communications in Nonlinear Science and Numerical Simulation. Amsterdam, 1000 AE, Netherlands Vol. 13( 4), pp. 822-838.
Abstract: This paper presents an analytical model to investigate the nonlinear dynamic behavior of an unbalanced rotor-bearing system due to cage run-out. Due to run-out of the cage, the rolling elements no longer stay equally spaced. The mathematical model takes into account the sources of nonlinearity such as Hertzian contact forces and cage run-out, and the resulting transition from a state of no contact to contact between the rolling elements and the races. The contact between the rolling elements and races is treated as nonlinear springs and the system is analyzed for varying numbers of balls. The results are presented in the form of fast Fourier transformations and Poincare maps. The results show that the ball passage frequency is modulated with the rotational frequency. The response falls into three regimes: periodic motion, quasi-periodic oscillations, and chaotic response. © 2006 Elsevier B.V. All rights reserved.
BibTeX:
@article{Nataraj2008,
  author = {Nataraj, C. and Harsha, S.P.},
  title = {The effect of bearing cage run-out on the nonlinear dynamics of a rotating shaft},
  journal = {Communications in Nonlinear Science and Numerical Simulation},
  year = {2008},
  volume = {13},
  number = { 4},
  pages = {822-838},
  url = {http://dx.doi.org/10.1016/j.cnsns.2006.07.010}
}
Nataraj C and Marx S (2008), "Optimal Control of a Nonlinear Magnetic Bearing System Using the Trigonometric Collocation Method", In Proceedings of ASME 2008 Conference on Smart Materials, Adaptive Structures and Intelligent Systems (SMASIS2008). Ellicott City, MD, October 28-30, 2008.
Abstract: Magnetic bearings are non-contacting, with the rotor being suspended between electromagnets, and therefore they can eliminate the need for lube oil and reduce machinery wear. The magnetic bearing is naturally unstable, and very nonlinear. This paper proposes a method designed to suppress the motion of a nonlinear magnetic bearing system rotor due to base excitation. The method combines PD feedback with feedforward optimal control, where a measured base motion is used to select a control signal designed to suppress the rotor response. The signal is generated from a combination of subharmonic frequencies and optimized coefficients stored in a lookup table. The trigonometric collocation method (TCM) is used to generate solutions for the four degree-of-freedom system made up of a shaft suspended at each end by a magnetic bearing. The TCM method uses a trigonometric series to simulate the multiharmonic behavior of each degree-of-freedom of strongly nonlinear systems. The method is easy to use and its advantage over numerical methods is that it demands less computation, particularly with higher numbers of degrees-of-freedom.
BibTeX:
@inproceedings{Nataraj2008a,
  author = {C. Nataraj and Steven Marx},
  title = {Optimal Control of a Nonlinear Magnetic Bearing System Using the Trigonometric Collocation Method},
  booktitle = {Proceedings of ASME 2008 Conference on Smart Materials, Adaptive Structures and Intelligent Systems (SMASIS2008)},
  year = {2008},
  doi = {10.1115/SMASIS2008-600}
}
Nersesov SG, Nataraj C and Avis JM (2008), "Design of finite-time stabilizing controllers for nonlinear dynamical systems", Proceedings of the IEEE Conference on Decision and Control., In Proceedings of the IEEE Conference on Decision and Control. Piscataway, NJ 08855-1331, United States , pp. 1740 - 1745.
Abstract: Finite-time stability involves dynamical systems whose trajectories converge to an equilibrium state in finite time. Since finite-time convergence implies nonuniqueness of system solutions in reverse time, such systems possess nonLipschitzian dynamics. Sufficient conditions for finite-time stability have been developed in the literature using Holder continuous Lyapunov functions. In this paper, we extend the finite-time stability theory to revisit time-invariant dynamical systems and to address time-varying systems. Specifically, we develop a Lyapunov based stability and control design framework for finite-time stability as well as finite-time tracking for time-varying nonlinear dynamical systems. Furthermore, we use vector Lyapunov function approach to study finite-time stabilization of sets for large-scale dynamical systems which is essential in formation control of multiple agents. © 2007 IEEE.
BibTeX:
@inproceedings{Nersesov2008,
  author = {Nersesov, Sergey G. and Nataraj, C. and Avis, Jevon M.},
  title = {Design of finite-time stabilizing controllers for nonlinear dynamical systems},
  booktitle = {Proceedings of the IEEE Conference on Decision and Control},
  journal = {Proceedings of the IEEE Conference on Decision and Control},
  year = {2008},
  pages = {1740 - 1745},
  url = {http://dx.doi.org/10.1109/CDC.2007.4434736}
}
Samanta B and Nataraj C (2008), "Automated diagnosis of cardiac state in healthcare systems using computational intelligence", International Journal of Services Operations and Informatics. Geneve 15, CH-1215, Switzerland Vol. 3(2), pp. 162-177.
Abstract: A study is presented for the diagnosis of a patient's heart conditions using recorded heart sounds and Computational Intelligence (CI) techniques. The digitally recorded heart sound signals are processed through Continuous Wavelet Transform (CWT) to extract time frequency features for normal and abnormal heart conditions. The wavelet energy distributions are used as inputs to classifiers based on soft computing techniques such as Adaptive Neuro-Fuzzy Inference Systems (ANFIS) and Genetic Algorithms (GAs) for diagnosis of heart conditions. The number and the parameters of Membership Functions (MFs) used in ANFIS along with the features from wavelet energy distribution are selected using GAs, maximising the diagnosis success. ANFIS with GAs (GA-ANFIS) are trained with a subset of data with known heart conditions. The trained GA-ANFIS are tested using the other set of data (testing data), not used in training. The results are compared with Artificial Neural Network (ANN) and GA (GA-ANN). The results show the effectiveness of the proposed approach in automated diagnosis of cardiac state in healthcare systems. Copyright © 2008, Inderscience Publishers.
BibTeX:
@article{Samanta2008,
  author = {Samanta, Biswanath and Nataraj, C.},
  title = {Automated diagnosis of cardiac state in healthcare systems using computational intelligence},
  journal = {International Journal of Services Operations and Informatics},
  year = {2008},
  volume = { 3},
  number = {2},
  pages = {162-177},
  note = {[I was the project director and co-principal author working with my postdoc. Impact factor: 0.543.},
  doi = {10.1504/IJSOI.2008.019331}
}
Samanta B and Nataraj C (2008), "Design of Intelligent Ship Autopilots using Particle Swarm Optimization", 2008 IEEE Swarm Intelligence Symposium, SIS 2008., In IEEE Swarm Intelligence Symposium (SIS2008). Piscataway, NJ 08855-1331, United States , pp. 4668327 - .
Abstract: A study is presented on the application of particle swarm optimization (PSO) to design intelligent autopilots for ship steering. Two versions of PSO - conventional and anti-predatory (APSO)- have been used. The autopilot consists of a fuzzy logic controller (FLC) emulating the characteristics of manual ship steering. The parameters for the FLC are optimized using PSO and APSO. The robustness of the autopilot based on the optimized FLC is illustrated through the simulation of a realistic nonlinear ship model. The steering performance of the optimal FLC is compared with a PID type autopilot designed with and without PSO. © 2008 IEEE.
BibTeX:
@inproceedings{Samanta2008,
  author = {Samanta, B. and Nataraj, C.},
  title = {Design of Intelligent Ship Autopilots using Particle Swarm Optimization},
  booktitle = {IEEE Swarm Intelligence Symposium (SIS2008)},
  journal = {2008 IEEE Swarm Intelligence Symposium, SIS 2008},
  year = {2008},
  pages = {4668327 - },
  url = {http://dx.doi.org/10.1109/SIS.2008.4668327}
}
Samanta B and Nataraj C (2008), "Prognostics of machine condition using soft computing", Robotics and Computer-Integrated Manufacturing. Oxford, OX5 1GB, United Kingdom Vol. 24(6), pp. 816-823.
Abstract: This paper presents a system for monitoring and prognostics of machine conditions using soft computing (SC) techniques. The machine condition is assessed through a suitable 'monitoring index' extracted from the vibration signals. The progression of the monitoring index is predicted using an SC technique, namely adaptive neuro-fuzzy inference system (ANFIS). Comparison with a machine learning method, namely support vector regression (SVR), is also presented. The proposed prediction procedures have been evaluated through benchmark data sets. The prognostic effectiveness of the techniques has been illustrated through previously published data on several types of faults in machines. The performance of SVR was found to be better than ANFIS for the data sets used. The results are helpful in understanding the relationship of machine conditions, the corresponding indicating features, the level of damage/degradation and their progression. © 2008 Elsevier Ltd. All rights reserved.
BibTeX:
@article{Samanta2008a,
  author = {Samanta, B. and Nataraj, C.},
  title = {Prognostics of machine condition using soft computing},
  journal = {Robotics and Computer-Integrated Manufacturing},
  year = {2008},
  volume = { 24},
  number = {6},
  pages = {816-823},
  note = {I was the project director and co-principal author working with my postdoc. Impact factor: 2.712.},
  doi = {10.1016/j.rcim.2008.03.011}
}
Samanta B and Nataraj C (2008), "Cracked rotor diagnostics using soft computing", 2007 Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, DETC2007., In Proceedings of the ASME International Design Engineering Technical Conference (IDETC2008). New York, NY 10016-5990, United States Vol. 1 PART C, pp. 1731 - 1740.
Abstract: A study is presented for detection and diagnostics of cracked rotors using soft computing techniques like adaptive neuro-fuzzy inference system (ANFIS), artificial neural networks (ANN) and genetic algorithms (GA). A simple model for a cracked rotor is used to simulate its transient response during startup for different levels of cracks. The transient response is processed through continuous wavelet transform (CWT) to extract time-frequency features for the normal and cracked conditions of the rotor. Several features including the wavelet energy distributions and the grey moment vectors (GMV) of the CWT scalograms are used as inputs for diagnosis of crack level. The parameters of the classifiers, ANFIS and ANN, along with the features from wavelet energy distribution and grey moment vectors are selected using GA maximizing the diagnostic success. The classifiers are trained with a subset of the data with known crack levels and tested using the other set of data (testing data), not used in training. The procedure is illustrated using the simulation data of a simple de Laval rotor with a 'breathing' crack for different crack levels during run-up through its critical speed. A comparison of diagnostic performance for the classifiers is presented. Results show the effectiveness of the proposed approach in detection and diagnosis of cracked rotors. Copyright © 2007 by ASME.
BibTeX:
@inproceedings{Samanta2008b,
  author = {Samanta, B. and Nataraj, C.},
  title = {Cracked rotor diagnostics using soft computing},
  booktitle = {Proceedings of the ASME International Design Engineering Technical Conference (IDETC2008)},
  journal = {2007 Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, DETC2007},
  year = {2008},
  volume = {1 PART C},
  pages = {1731 - 1740},
  doi = {10.1115/DETC2007-35181}
}
Samanta B and Nataraj C (2008), "Surface roughness prediction in machining using computational intelligence", International Journal of Manufacturing Research. Olney, Bucks, MK46 5WB, United Kingdom Vol. 3(4), pp. 379-392.
Abstract: A study is presented to model surface roughness in turning using Genetic Programming (GP). The machining parameters, namely, the spindle speed, feed rate, depth of cut and the workpiece tool vibration amplitudes in three orthogonal directions have been used as inputs to model the workpiece surface roughness. The input parameters and the corresponding functional relationship are automatically selected using GP and maximising the modelling accuracy. The effects of different GP parameters on the prediction accuracy and training time are studied. The results of the GP-based approach are compared with other Computational Intelligence (CI) techniques like Artificial Neural Networks (ANN). © 2008, Inderscience Publishers.
BibTeX:
@article{Samanta2008b,
  author = {Samanta, Biswanath and Nataraj, C.},
  title = {Surface roughness prediction in machining using computational intelligence},
  journal = {International Journal of Manufacturing Research},
  year = {2008},
  volume = { 3},
  number = {4},
  pages = {379-392},
  note = {I was the project director and secondary author working with my postdoc. Impact factor: 0.654.},
  doi = {10.1504/IJMR.2008.020900}
}
Samanta B and Nataraj C (2008), "Prognostics using morphological signal processing and computational intelligence", Proceedings of the 1st IEEE International Conference on Prognostics and Health Management (PHM2008)., In Proceedings of the 1st IEEE International Conference on Prognostics and Health Management (PHM2008). Denver, CO, October 6-9, 2008.
Abstract: A procedure is presented for monitoring and prognostics of machine conditions using computational intelligence (CI) techniques. The machine vibration signals are processed using morphological operations to extract an entropy based feature characterizing the signal shape-size complexity for assessment of machine conditions. An evolutionary average entropy of the system is introduced as the 'monitoring index' for prognostics of the system condition. The progression of the 'monitoring index' is predicted using CI techniques, namely, recursive neural network (RNN), adaptive neuro-fuzzy inference system (ANFIS) and support vector regression (SVR). The proposed prediction procedures have been evaluated through benchmark datasets. The prognostic effectiveness of the CI techniques has been illustrated through vibration dataset of a helicopter drivetrain system gearbox. The performances of ANFIS and SVR have been found to be better than RNN for the dataset used. The results are helpful in understanding the relationship of machine conditions, the corresponding indicating feature, the level of damage/degradation and their progression.
BibTeX:
@inproceedings{Samanta2008e,
  author = {Samanta, B. and Nataraj, C.},
  title = {Prognostics using morphological signal processing and computational intelligence},
  booktitle = {Proceedings of the 1st IEEE International Conference on Prognostics and Health Management (PHM2008)},
  journal = {Proceedings of the 1st IEEE International Conference on Prognostics and Health Management (PHM2008)},
  year = {2008},
  url = {http://dx.doi.org/10.1109/PHM.2008.4711461},
  doi = {10.1109/PHM.2008.4711461}
}
Samanta B and Nataraj C (2008), "Prognostics of machine condition using energy based monitoring index and computational intelligence", In Proceedings of ASME 2008 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference (IDETC/CIE 2008). Brooklyn, NY, Aug. 3-6, 2008.
Abstract: A study is presented on applications of computational intelligence (CI) techniques for monitoring and prognostics of machinery conditions. The machine condition is assessed through an energy-based feature, termed as “energy index,” extracted from the vibration signals. The progression of the “monitoring index” is predicted using the CI techniques, namely, recursive neural network (RNN), adaptive neurofuzzy inference system (ANFIS), and support vector regression (SVR). The proposed procedures have been evaluated through benchmark data sets for one-step-ahead prediction. The prognostic effectiveness of the techniques has been illustrated through vibration data set of a helicopter drivetrain system gearbox. The prediction performance of SVR was better than RNN and ANFIS. The improved performance of SVR can be attributed to its inherently better generalization capability. The training time of SVR was substantially higher than RNN and ANFIS. The results are helpful in understanding the relationship of machine conditions, the corresponding indicating feature, the level of damage or degradation, and their progression.
BibTeX:
@inproceedings{Samanta2008f,
  author = {Samanta, B. and Nataraj, C},
  title = {Prognostics of machine condition using energy based monitoring index and computational intelligence},
  booktitle = {Proceedings of ASME 2008 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference (IDETC/CIE 2008)},
  year = {2008},
  doi = {10.1115/1.3249574}
}
Harsha S and Nataraj C (2007), "Nonlinear dynamic analysis of a rotor bearing system due to distributed defects using factorial design of experiments", International Journal of Applied Mechanics and Engineering. Poland Vol. 12(2), pp. 379-399.
Abstract: This paper focuses on accurate performance prediction which is essential to the design of high performance rotor bearing system. It considers distributed defects such as internal radial clearance and surface waviness of the bearing components. In the analytical formulation the contacts between the rolling elements and the races are considered as nonlinear springs, whose stiffnesses are obtained by using Hertzian elastic contact deformation theory. The governing differential equations of motion are obtained by using Lagrange's equations. In terms of the feature that the nonlinear bearing forces act on the system, a reduction method and corresponding integration technique is used to increase the numerical stability and decrease computer time for system analysis. Poincard maps are used to elucidate and to illustrate the diversity of the system behavior. For investigating the nonlinear behavior of a rotor bearing system, effects of distributed defects are considered simultaneously. It is shown that the system dynamic behavior is sensitive to small variations of distributed defects.
BibTeX:
@article{Harsha2007,
  author = {Harsha, S.P. and Nataraj, C.},
  title = {Nonlinear dynamic analysis of a rotor bearing system due to distributed defects using factorial design of experiments},
  journal = {International Journal of Applied Mechanics and Engineering},
  year = {2007},
  volume = { 12},
  number = {2},
  pages = {379-399}
}
Harsha SP and Nataraj C (2007), "Dynamic Analysis of High-Speed Ball Bearings Due to Geometrical Imperfections", In Arctic Summer Conference on Dynamics, Vibrations and Control. Saariselka, Finland, August 6-10, 2007.
BibTeX:
@inproceedings{Harsha2007,
  author = {S. P. Harsha and C. Nataraj},
  title = {Dynamic Analysis of High-Speed Ball Bearings Due to Geometrical Imperfections},
  booktitle = {Arctic Summer Conference on Dynamics, Vibrations and Control},
  year = {2007}
}
Harsha S and Nataraj C (2007), "The effect of surface waviness and number of rolling elements on the dynamic behavior of a rotor-bearing system", 2007 Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, DETC2007., In Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, DETC2007. New York, NY 10016-5990, United States Vol. 1 PART C, pp. 1755-1762.
Abstract: In the paper, the effects of the number of rolling elements and wave number of surface waviness on the nonlinear dynamic analysis of a rotor-bearing system has been studied. In the analytical formulation, the contacts between rolling elements and races are considered as nonlinear springs, whose stiffnesses are obtained by using Hertzian elastic contact deformation theory. The results are presented in the form of Fast Fourier Transformations (FFT) and Poincare maps, which show that the vibration characteristics of the rotor and its bearings change when the bearings operate in different regions of their nonlinear load deflection characteristics. The appearance of regions of periodic, sub-harmonic and chaotic behavior has been observed to be strongly dependent on number of rolling elements. Copyright © 2007 by ASME.
BibTeX:
@inproceedings{Harsha2007b,
  author = {Harsha, S.P. and Nataraj, C.},
  title = {The effect of surface waviness and number of rolling elements on the dynamic behavior of a rotor-bearing system},
  booktitle = {Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, DETC2007},
  journal = {2007 Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, DETC2007},
  year = {2007},
  volume = {1 PART C},
  pages = {1755-1762}
}
Nataraj C and Harsha SP (2007), "Intermittent Chaos in Steering Dynamics of Ships", In Arctic Summer Conference on Dynamics, Vibrations and Control. Saariselka Finland, August 6-10, 2007.
BibTeX:
@inproceedings{Nataraj2007,
  author = {C. Nataraj and S. P. Harsha},
  title = {Intermittent Chaos in Steering Dynamics of Ships},
  booktitle = {Arctic Summer Conference on Dynamics, Vibrations and Control},
  year = {2007}
}
Samanta B and Nataraj C (2007), "Automated Diagnosis of Cardiac State in Healthcare Systems", In The 17th International Conference on Flexible Automation and Intelligent Manufacturing. Philadelphia, PA, June 18-20, 2007.
Abstract: A study is presented for the diagnosis of a patient's heart conditions using recorded heart sounds and computational intelligence (CI) techniques. The digitally recorded heart sound signals are processed through continuous wavelet transform (CWT) to extract time-frequency features for normal and abnormal heart conditions. The wavelet energy distributions are used as inputs to classifiers based on soft computing techniques such as adaptive neuro-fuzzy inference systems (ANFIS) and genetic algorithms (GAs) for diagnosis of heart conditions. The number and the parameters of membership functions (MFs) used in ANFIS along with the features from wavelet energy distribution are selected using GAs, maximising the diagnosis success. ANFIS with GAs (GA-ANFIS) are trained with a subset of data with known heart conditions. The trained GA-ANFIS are tested using the other set of data (testing data), not used in training. The results are compared with artificial neural network (ANN) and GA (GA-ANN). The results show the effectiveness of the proposed approach in automated diagnosis of cardiac state in healthcare systems.
BibTeX:
@inproceedings{Samanta2007,
  author = {B. Samanta and C. Nataraj},
  title = {Automated Diagnosis of Cardiac State in Healthcare Systems},
  booktitle = {The 17th International Conference on Flexible Automation and Intelligent Manufacturing},
  year = {2007},
  doi = {10.1504/IJSOI.2008.019331}
}
Samanta B and Nataraj C (2007), "Machinery Prognostics Using Soft Computing", In The 17th International Conference on Flexible Automation and Intelligent Manufacturing. Philadelphia, PA, June 18-20, 2007.
BibTeX:
@inproceedings{Samanta2007a,
  author = {B. Samanta and C. Nataraj},
  title = {Machinery Prognostics Using Soft Computing},
  booktitle = {The 17th International Conference on Flexible Automation and Intelligent Manufacturing},
  year = {2007}
}
Harsha SP and Nataraj C (2006), "Nonlinear Dynamic Analysis of High-Speed Ball Bearings Due torsion Surface Waviness and Unbalanced Rotor", International Journal of Nonlinear Sciences and Numerical Simulation. Vol. 7(2), pp. 163-167.
BibTeX:
@article{Harsha2006,
  author = {Harsha, S. P. and Nataraj, C.},
  title = {Nonlinear Dynamic Analysis of High-Speed Ball Bearings Due torsion Surface Waviness and Unbalanced Rotor},
  journal = {International Journal of Nonlinear Sciences and Numerical Simulation},
  year = {2006},
  volume = {7},
  number = {2},
  pages = {163-167},
  note = {I was the project director and co-principal author working with my postdoc. A leading journal in nonlinear dynamics. Impact factor: 7.123.}
}
Harsha S, Nataraj C and Kankar P (2006), "The effect of ball waviness on nonlinear vibration associated with rolling element bearings", International Journal of Acoustics and Vibrations. Auburn, AL 36849-3501, United States Vol. 11(2), pp. 56-66.
Abstract: An analytical model was developed to investigate the nonlinear vibrations of a rotor bearing system due to ball waviness. In the analytical formulation the contacts between the balls and the races are modelled as nonlinear springs, whose stiffnesses are obtained by using Hertzian elastic contact deformation theory. The governing differential equations of motion are obtained by using Lagrange's equations. The implicit type of numerical integration technique Newmark-β with Newton-Raphson method is used to solve the nonlinear differential equations iteratively. A computer program was developed to simulate the effect of ball waviness. The formulation predicts the discrete spectra with specific frequency components for each order of ball waviness. Numerical results obtained from the simulation are compared with those of prior researchers.
BibTeX:
@article{Harsha2006a,
  author = {Harsha, S.P. and Nataraj, C. and Kankar, P.K.},
  title = {The effect of ball waviness on nonlinear vibration associated with rolling element bearings},
  journal = {International Journal of Acoustics and Vibrations},
  year = {2006},
  volume = {11},
  number = {2},
  pages = {56-66}
}
Harsha SP and Nataraj C (2006), "Nonlinear Vibration Analysis Of A Balanced Rotor Supported By Roller Bearings", In 2nd Annual AIAA-ASME Symposium. Philadelphia, PA
BibTeX:
@inproceedings{Harsha2006a,
  author = {S. P. Harsha and C. Nataraj},
  title = {Nonlinear Vibration Analysis Of A Balanced Rotor Supported By Roller Bearings},
  booktitle = {2nd Annual AIAA-ASME Symposium},
  year = {2006}
}
Harsha SP and Nataraj C (2006), "Intermittent Chaotic Behavior of an Unbalanced Rotor Supported by Rolling Element Bearings with to Race Waviness", In Eleventh conference on Nonlinear vibrations, stability and dynamics of structures., August 13-17, 2006.
BibTeX:
@inproceedings{Harsha2006c,
  author = {S. P. Harsha and C. Nataraj},
  title = {Intermittent Chaotic Behavior of an Unbalanced Rotor Supported by Rolling Element Bearings with to Race Waviness},
  booktitle = {Eleventh conference on Nonlinear vibrations, stability and dynamics of structures},
  year = {2006},
  note = {[abstract reviewed]}
}
Nataraj C and Harsha SP (2006), "Nonlinear Vibration Analysis of an Unbalanced Rotor on Rolling Element Bearing Due to Cage Run-out", In Transaction of Nonlinear Science and Complexity (NSC). , pp. 213-221. World Scientific.
BibTeX:
@inbook{Nataraj2006,
  author = {C. Nataraj and Harsha, S. P.},
  editor = {Albert C J Luo and Liming Dai and Hamid R Hamidzadeh},
  title = {Nonlinear Vibration Analysis of an Unbalanced Rotor on Rolling Element Bearing Due to Cage Run-out},
  booktitle = {Transaction of Nonlinear Science and Complexity (NSC)},
  publisher = {World Scientific},
  year = {2006},
  pages = {213--221}
}
Nataraj C and Muske KR (2006), "Nonlinear Dynamics in Chemical Processes" Taylor & Francis.
BibTeX:
@inbook{Nataraj2006a,
  author = {C. Nataraj and Kenneth R. Muske},
  title = {Nonlinear Dynamics in Chemical Processes},
  publisher = {Taylor & Francis},
  year = {2006},
  doi = {10.1081/E-ECHP-120039236}
}
Samanta B and Nataraj C (2006), "Detection and diagnostics of cracked rotors using soft computing", In Proc. 10th Mechatronics Forum Biennial International Conference - Mechatronics 2006 (MX2006). Penn State Great Valley, Malvern, PA, June 19-21, 2006.
BibTeX:
@inproceedings{Samanta2006,
  author = {B. Samanta and C. Nataraj},
  title = {Detection and diagnostics of cracked rotors using soft computing},
  booktitle = {Proc. 10th Mechatronics Forum Biennial International Conference - Mechatronics 2006 (MX2006)},
  year = {2006}
}
Cartes D, Nataraj C, Metzer J and Castelin S (2005), "Path Planning and Nonlinear Model Selective Control Using Neural Networks: Precision Maneuvering of Unmanned Surface Vehicles", In Intelligent Ships Symposium VI. Villanova, PA
BibTeX:
@inproceedings{Cartes2005,
  author = {David Cartes and C. Nataraj and John Metzer and Steve Castelin},
  title = {Path Planning and Nonlinear Model Selective Control Using Neural Networks: Precision Maneuvering of Unmanned Surface Vehicles},
  booktitle = {Intelligent Ships Symposium VI},
  year = {2005},
  note = {[abstract reviewed]}
}
Fahimi F, Rineesh SVS and Nataraj C (2005), "Formation control of under-actuated robotic boats", American Society of Mechanical Engineers, Dynamic Systems and Control Division (Publication) DSC., In Proceedings of International Mechanical Engineering Congress and Exposition (IMECE2005). New York, NY 10016-5990, United States, November 5-11, 2005. (IMECE2005-81561), pp. 1607-1615.
Abstract: Feedback control laws for controlling multiple robotic boats in arbitrary formations are proposed. The presented formation control method uses only local sensor-based information. The method of input-output linearization has been used to exponentially stabilize the relative distance and orientation of neighboring boats with a three-degree-of-freedom dynamic model. It is shown that the internal dynamics of the system is also stable. The use of these control laws is demonstrated by computer simulations. These controllers can be utilized to control an arbitrarily large number of robotic boats moving in very general formations. Copyright © 2005 by ASME.
BibTeX:
@inproceedings{Fahimi2005,
  author = {Fahimi, Farbod and Rineesh, S. V. Sudhil and Nataraj, C.},
  title = {Formation control of under-actuated robotic boats},
  booktitle = {Proceedings of International Mechanical Engineering Congress and Exposition (IMECE2005)},
  journal = {American Society of Mechanical Engineers, Dynamic Systems and Control Division (Publication) DSC},
  year = {2005},
  number = {IMECE2005-81561},
  pages = {1607-1615}
}
Fahimi F, SiddaReddy R and Nataraj C (2005), "Controlling Formation of Unmanned Surface Vehicles", In Intelligent Ships Symposium VI. Villanova, PA
BibTeX:
@inproceedings{Fahimi2005a,
  author = {Farbod Fahimi and Rineesh SiddaReddy and C. Nataraj},
  title = {Controlling Formation of Unmanned Surface Vehicles},
  booktitle = {Intelligent Ships Symposium VI},
  year = {2005},
  note = {[abstract reviewed.]}
}
Harsha SP and Nataraj C (2005), "Nonlinear Dynamic Analysis of a Unbalanced Rotor Supported by High-Speed Rolling Element Bearings with Effect of Surface Waviness", In International Symposium on Nonlinear Dynamics. Shanghai, China, December 20-21, 2005.
BibTeX:
@inproceedings{Harsha2005,
  author = {Harsha, S. P. and Nataraj, C.},
  title = {Nonlinear Dynamic Analysis of a Unbalanced Rotor Supported by High-Speed Rolling Element Bearings with Effect of Surface Waviness},
  booktitle = {International Symposium on Nonlinear Dynamics},
  year = {2005}
}
Marx S and Nataraj C (2005), "An optimal control algorithm for suppression of harmonic base excitation in nonlinear magnetic bearings", Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference - DETC2005., In Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, DETC2005. New York, NY 10016-5990, United States Vol. 1 B, pp. 1239 - 1248.
Abstract: The paper deals with rotor systems that suffer harmonic base excitation when supported on magnetic bearings. Magnetic bearings using conventional control techniques perform poorly in such situations mainly due to their highly nonlinear characteristics. The compensation method presented here is a novel optimal control procedure with a combination of conventional, proportional and differential feedback control. A four degree of freedom model is used for the rotor system, and the bearings are modeled by nonlinear expressions. Each disturbance frequency is exprcted to produce a multi-harmonic system response, a characteristic of nonlinear systems. We apply optimal control choosing to minimize a performance index, which leads to the optimization of the trigonometric coefficients in the correction current function. Results show that the control technique suppresses rotor vibration to amplitudes that were significantly smaller than the disturbance amplitudes for the entire range of disturbance frequencies applied. The control technique explored in this paper is a promising step towards the successful application of magnetic bearings to systems mounted on moving platforms.
BibTeX:
@inproceedings{Marx2005,
  author = {Marx, Steven and Nataraj, C.},
  title = {An optimal control algorithm for suppression of harmonic base excitation in nonlinear magnetic bearings},
  booktitle = {Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, DETC2005},
  journal = {Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference - DETC2005},
  year = {2005},
  volume = { 1 B},
  pages = {1239 - 1248}
}
Marx S and Nataraj C (2005), "A Combined PD and Optimal Control of a Nonlinear Magnetic Bearing Rotor Subject to Harmonic Base Motion", In Intelligent Ships Symposium VI. Villanova, PA
BibTeX:
@inproceedings{Marx2005a,
  author = {Steven Marx and C. Nataraj},
  title = {A Combined PD and Optimal Control of a Nonlinear Magnetic Bearing Rotor Subject to Harmonic Base Motion},
  booktitle = {Intelligent Ships Symposium VI},
  year = {2005},
  note = {[abstract reviewed]}
}
Nataraj C and Kasliwal P (2005), "Comparison of ship models for nonlinear dynamic steering response", In Intelligent Ships Symposium VI. Villanova, PA
Abstract: This paper considers the path planning control of an unmanned surface vehicle. The nonlinear equations have been derived assuming one control input (rudder). The equations have been written assuming that the ship is moving with a large forward velocity. A steering input has been provided and then the error equations have been derived. The error equations have been linearized assuming small errors; this leads to time varying equations, the control of which is a nontrivial problem. Lyapunov transformations have been applied to change the error equation into a canonical form. A desired closed-loop PD-spectrum and the desired right PD-modal matrix have been chosen and the resulting Sylvester equation has been solved to obtain the parameter matrix. This leads to the closed loop equations for controlling the ship steering of an unmanned ship. Using the kinematic equations and the closed loop control equations the steering motion of the ship has been simulated. An example circular trajectory has been investigated and presented. The control algorithm is shown to be quite effective for tracking of unmanned surface vehicles.
BibTeX:
@inproceedings{Nataraj2005,
  author = {Nataraj, C. and Kasliwal, Pritesh},
  title = {Comparison of ship models for nonlinear dynamic steering response},
  booktitle = {Intelligent Ships Symposium VI},
  year = {2005},
  note = {[abstract reviewed]}
}
Nataraj C and Pietrusko RG (2005), "Dynamic response of rigid rotors supported on rolling element bearings with an outer raceway defect", Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference - DETC2005., In Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, DETC2005. New York, NY 10016-5990, United States Vol. 1 B, pp. 1249 - 1261.
Abstract: This paper is concerned with the nonlinear dynamical response of a rigid rotor supported on rolling element bearings with defects in the outer raceway. The rotor is modeled with five degrees of freedom, and the bearings are modeled with nonlinear forces arising from Hertzian contact stresses. Then we introduce a defect into the roller bearings with a controllable parameter, and analyze the effect of the growth of this defect on the dynamic response of the system using serveral signal processing tools such as spectrum, cepstrum and envelope methods. Numerical results are obtained for a screw compressor rotor. We examine these results with the idea a potential application towards the development of automated condition assessment tools for machinery diagnostics and prognostics. It appears from the results that no single tool is ideal, and that a combination of existing tools could possibly lead to a good strategy.
BibTeX:
@inproceedings{Nataraj2005a,
  author = {Nataraj, C. and Pietrusko, Robert Gerard},
  title = {Dynamic response of rigid rotors supported on rolling element bearings with an outer raceway defect},
  booktitle = {Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, DETC2005},
  journal = {Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference - DETC2005},
  year = {2005},
  volume = { 1 B},
  pages = {1249 - 1261}
}
Nataraj C and Kasliwal P (2005), "Linear Time Varying Control of Unmanned Surface Vehicles", In Intelligent Ships Symposium VI. Villanova, PA
Abstract: This paper considers the path planning control of an unmanned surface vehicle. The nonlinear equations have been derived assuming one control input (rudder). The equations have been written assuming that the ship is moving with a large forward velocity. A steering input has been provided and then the error equations have been derived. The error equations have been linearized assuming small errors; this leads to time varying equations, the control of which is a nontrivial problem. Lyapunov transformations have been applied to change the error equation into a canonical form. A desired closed-loop PD-spectrum and the desired right PD-modal matrix have been chosen and the resulting Sylvester equation has been solved to obtain the parameter matrix. This leads to the closed loop equations for controlling the ship steering of an unmanned ship. Using the kinematic equations and the closed loop control equations the steering motion of the ship has been simulated. An example circular trajectory has been investigated and presented. The control algorithm is shown to be quite effective for tracking of unmanned surface vehicles.
BibTeX:
@inproceedings{Nataraj2005b,
  author = {Nataraj, C. and Kasliwal, Pritesh},
  title = {Linear Time Varying Control of Unmanned Surface Vehicles},
  booktitle = {Intelligent Ships Symposium VI},
  year = {2005},
  note = {[abstract reviewed]}
}
Fahimi F, Nataraj C and Ashrafiuon H (2004), "Obstacle avoidance for groups of mobile robots using potential field technique", American Society of Mechanical Engineers, Dynamic Systems and Control Division (Publication) DSC. New York, NY 10016-5990, United States Vol. 73( 2 PART B), pp. 1179 - 1186.
Abstract: An efficient real time path planning method for groups of mobile robots in dynamic environments is introduced. Harmonic potential functions are utilized along with the panel method known in fluid mechanics. First, a complement to the traditional panel method is introduced to generate a more effective harmonic potential field for obstacle avoidance in dynamically changing environments. Second, a group of mobile robots working in an environment containing stationary and moving obstacles is considered. Each robot is assigned to move from its current position to a goal position. The group is not forced to maintain a formation during the motion. Every robot considers the other robots of the group as moving obstacles and hence the physical dimensions of the robots are also taken into account. The path of each robot is planned based on the changing position of the other robots and the position of stationary and moving obstacles. Finally, the effectiveness of the scheme is shown by modeling groups of an arbitrary number of mobile robots and the theory is validated by several computer simulations and hardware experiments. Copyright © 2004 by ASME.
BibTeX:
@inproceedings{Fahimi2004,
  author = {Fahimi, F. and Nataraj, C. and Ashrafiuon, H.},
  title = {Obstacle avoidance for groups of mobile robots using potential field technique},
  journal = {American Society of Mechanical Engineers, Dynamic Systems and Control Division (Publication) DSC},
  year = {2004},
  volume = { 73},
  number = { 2 PART B},
  pages = {1179 - 1186}
}
Marx S and Nataraj C (2004), "A Control Technique used to Compensate for Magnetic Bearing Responses to Base Motion", In ASNE EMTS 2004 Symposium. Philadelphia, PA, January 27-29, 2004.
BibTeX:
@inproceedings{Marx2004,
  author = {Steven Marx and C. Nataraj},
  title = {A Control Technique used to Compensate for Magnetic Bearing Responses to Base Motion},
  booktitle = {ASNE EMTS 2004 Symposium},
  year = {2004},
  note = {[abstract reviewed]}
}
Fahimi F, Ashrafiuon H and Nataraj C (2003), "Obstacle avoidance for spatial hyper-redundant manipulators using harmonic potential functions and the mode shape technique", Journal of Robotic Systems. Vol. 20( 1), pp. 23-33.
Abstract: This paper deals with the obstacle avoidance problem for spatial hyper-redundant manipulators in known environments. The manipulators is divided into two sections, a proximal section that has not entered the space among the obstacles and a distal section among the obstacles. Harmonic potential functions are employed to achieve obstacle avoidance for the distal section in three-dimensional space in order to avoid local minima in cluttered environments. A modified panel method is used to generate the potential of any arbitrary shaped obstacle in three-dimensional space. An alternative backbone curve concept and an efficient fitting method are introduced to control the trajectory of proximal links. The fitting method is recursive and avoids the complications involved with solving large systems of nonlinear algebraic equations. The combination of a three-dimensional safe path derived from the harmonic potential field and the backbone curve concept leads to an elegant kinematic control strategy that guarantees obstacle avoidance.
BibTeX:
@article{Fahimi2003,
  author = {Fahimi, F. and Ashrafiuon, H. and Nataraj, C.},
  title = {Obstacle avoidance for spatial hyper-redundant manipulators using harmonic potential functions and the mode shape technique},
  journal = {Journal of Robotic Systems},
  year = {2003},
  volume = { 20},
  number = { 1},
  pages = {23-33},
  url = {http://dx.doi.org/10.1002/rob.10067}
}
Nataraj C and Calvert TE (2003), "Compensation of base motion in magnetic-bearing supported rotors for Navy applications", In Intelligent Ships Symposium V., May, 2003.
BibTeX:
@inproceedings{Nataraj2003,
  author = {C. Nataraj and Thomas E. Calvert},
  title = {Compensation of base motion in magnetic-bearing supported rotors for Navy applications},
  booktitle = {Intelligent Ships Symposium V},
  year = {2003},
  note = {[abstract reviewed]}
}
Wenzel B and Nataraj C (2003), "Effect of dynamics on path planning of mobile robots", Proceedings of the ASME Design Engineering Technical Conference., In Proceedings of the ASME International Design Engineering Technical Conference (IDETC2003). New York, NY 10016-5990, United States Vol. 5 B, pp. 1705 - 1713.
Abstract: This paper deals with accurate path planning of two kinds of mobile robots: conventionally steered and differentially steered. In particular, we are concerned with the effect of dynamics. Dynamic models are derived, and numerical and experimental results are presented. The effects of varying mass, velocity and manipulator arms on the mobile robots are presented.
BibTeX:
@inproceedings{Wenzel2003,
  author = {Wenzel, Bryan and Nataraj, C.},
  title = {Effect of dynamics on path planning of mobile robots},
  booktitle = {Proceedings of the ASME International Design Engineering Technical Conference (IDETC2003)},
  journal = {Proceedings of the ASME Design Engineering Technical Conference},
  year = {2003},
  volume = { 5 B},
  pages = {1705 - 1713}
}
Asl F, Ashrafiuon H and Nataraj C (2002), "A general solution for the position, velocity, and acceleration of hyperredundant planar manipulators", Journal of Robotic Systems. Vol. 19( 1), pp. 1-12.
Abstract: A new approach for the solution of the position, velocity, and acceleration of hyperredundant planar manipulators following any twice-differentiable desired path is presented. The method is singularity free, and provides a robust solution even in the event of mechanical failure of some of the robot actuators. The approach is based on defining virtual layers, and dividing them into virtual/real three-link or four-link subrobots. It starts by solving the inverse kinematic problem for the subrobot located in the lowest virtual layer, which is then used to solve the inverse kinematic equations for the subrobots located in the upper virtual layers. An algorithm is developed that provides a singularity-free solution up to the full extension through a configuration index. The configuration index can be interpreted as the average of the determinants of the Jacobians of the subrobots. The equations for the velocities and accelerations of the manipulator are solved by extending the same approach, and it is shown that the value of the configuration index is critical in maintaining joint velocity continuity. The inverse dynamic problem of the robot is also solved to obtain the torques required for the robot actuators to accomplish their tasks. Computer simulations of several hyperredundant manipulators using the proposed method are presented as numerical examples. © 2002 John Wiley and Sons, Inc.
BibTeX:
@article{Asl2002,
  author = {Asl, F.M. and Ashrafiuon, H. and Nataraj, C.},
  title = {A general solution for the position, velocity, and acceleration of hyperredundant planar manipulators},
  journal = {Journal of Robotic Systems},
  year = {2002},
  volume = { 19},
  number = { 1},
  pages = {1-12},
  url = {http://dx.doi.org/10.1002/rob.8117}
}
Fahimi F, Ashrafiuon H and Nataraj C (2002), "An improved inverse kinematic and velocity solution for spatial hyper-redundant robots", IEEE Transactions on Robotics and Automation. Vol. 18( 1), pp. 103-107.
Abstract: A new and efficient kinematic position and velocity solution scheme for spatial hypers-redundant manipulators is presented. The manipulator's arm has discrete links and universal joints. Backbone curve concepts and a modal approach are used to resolve the manipulator's redundancy. The effects of the mode shapes and the slope of the backbone curve at the starting point on the workspace are studied. It is shown that the usage of conventional mode shapes limits the workspace of the hyper-redundant arm. By introducing new mode shapes, an improved workspace is obtained. A simple and efficient recursive fitting method is introduced to avoid complications involved with solving systems of nonlinear algebraic equations. This method also guarantees the existence of solution for the inverse kinematic problem at the velocity level. Velocity properties of the backbone curve are investigated and the inverse velocity propagation is solved for the spatial hyper-redundant arm. The velocity propagation scheme is recursive and is efficiently applicable to any number of links.
BibTeX:
@article{Fahimi2002,
  author = {Fahimi, Farbod and Ashrafiuon, Hashem and Nataraj, C.},
  title = {An improved inverse kinematic and velocity solution for spatial hyper-redundant robots},
  journal = {IEEE Transactions on Robotics and Automation},
  year = {2002},
  volume = { 18},
  number = { 1},
  pages = {103-107},
  url = {http://dx.doi.org/10.1109/70.988980}
}
Fahimi F, Ashrafiuon H and Nataraj C (2002), "Inverse kinematic solution for universal-jointed hyper-redundant robots", Proceedings of the ASME Design Engineering Technical Conference., In Proceedings of the ASME International Design Engineering Technical Conference. Vol. 5 B, pp. 1447 - 1454.
Abstract: A new and efficient kinematic position and velocity solution scheme for spatial hyper-redundant manipulators is presented. The manipulator's arm has discrete links and universal joints. Backbone curve concepts and a modal approach are used to resolve the manipulator's redundancy. The effects of the mode shapes and the slope of backbone curve at the starting point on the workspace are studied. It is shown that the usage of conventional mode shapes limits the workspace of the hyper-redundant arm. By introducing new mode shapes, an improved workspace is obtained. A simple and efficient recursive fitting method is introduced to avoid complications involved with solving systems of nonlinear algebraic equations. This method also guarantees the existence of solutions for the inverse kinematic problem at the velocity level. Velocity properties of the backbone curve are investigated and the inverse velocity propagation is solved for the spatial hyper-redundant arm. The velocity propagation scheme is recursive and is efficiently applicable to any number of links.
BibTeX:
@inproceedings{Fahimi2002a,
  author = {Fahimi, Farbod and Ashrafiuon, Hashem and Nataraj, C.},
  title = {Inverse kinematic solution for universal-jointed hyper-redundant robots},
  booktitle = {Proceedings of the ASME International Design Engineering Technical Conference},
  journal = {Proceedings of the ASME Design Engineering Technical Conference},
  year = {2002},
  volume = { 5 B},
  pages = {1447 - 1454}
}
Fahimi F, Ashrafiuon H and Nataraj C (2001), "Obstacle avoidance for 2D hyper-redundant manipulators using harmonic potential functions and the mode shape technique", Proceedings of the ASME Design Engineering Technical Conference., In Proceedings of the ASME International Design Engineering Technical Conference. Vol. 6 B, pp. 1919 - 1925.
Abstract: Obstacle avoidance for discrete-link two-dimensional (2D) hyper-redundant manipulators in known environments is considered. The manipulator is divided into two sections, a proximal section that has not entered the space among obstacles and a distal section among the obstacles. Harmonic potential functions were used, in order to avoid local minima in cluttered environments. A modified panel method is used to generate the potential of any arbitrary shaped obstacle in two-dimensional space. An alternative backbone curve concept and an efficient fitting method are introduced to control the trajectory of proximal links. The fitting method is recursive and avoids the complications involved with solving large systems of nonlinear algebraic equations. Combination of the safe path derived from the harmonic potential field and the backbone curve concept leads to an elegant kinematic control strategy that guarantees obstacle avoidance for planar hyper-redundant robotic manipulators.
BibTeX:
@inproceedings{Fahimi2001,
  author = {Fahimi, F. and Ashrafiuon, H. and Nataraj, C.},
  title = {Obstacle avoidance for 2D hyper-redundant manipulators using harmonic potential functions and the mode shape technique},
  booktitle = {Proceedings of the ASME International Design Engineering Technical Conference},
  journal = {Proceedings of the ASME Design Engineering Technical Conference},
  year = {2001},
  volume = { 6 B},
  pages = {1919 - 1925}
}
Hailu G, Nataraj C and Ashrafiuon H (2001), "Is reduction in task space a condition for accelerated learning?", Proceedings of the IEEE International Conference on Systems, Man and Cybernetics., In Proceedings of the IEEE International Conference on Systems, Man and Cybernetics. Vol. 1, pp. 628 - 633.
Abstract: The effect of two different biases on the learning time of a reinforcement learning agent was studied. Generally, results indicate that different biases affect learning differently. It was concluded that learning speed is not a mere function of search size and large state space should be viewed only as a potential indication of slow learning.
BibTeX:
@inproceedings{Hailu2001,
  author = {Hailu, G. and Nataraj, C. and Ashrafiuon, H.},
  title = {Is reduction in task space a condition for accelerated learning?},
  booktitle = {Proceedings of the IEEE International Conference on Systems, Man and Cybernetics},
  journal = {Proceedings of the IEEE International Conference on Systems, Man and Cybernetics},
  year = {2001},
  volume = { 1},
  pages = {628 - 633},
  url = {http://dx.doi.org/10.1109/ICSMC.2001.969922}
}
Arakere NK and Nataraj C (1999), "Numerical simulation of nonlinear spur gear dynamics", In Proceedings of DETC99 Deisgn Engineering Technical Conferences. Las Vegass, Nevada, September 12-15, 1999.
BibTeX:
@inproceedings{Arakere1999,
  author = {Nagaraj K. Arakere and C. Nataraj},
  title = {Numerical simulation of nonlinear spur gear dynamics},
  booktitle = {Proceedings of DETC99 Deisgn Engineering Technical Conferences},
  year = {1999}
}
Asl F, Ashrafiuon H and Nataraj C (1999), "Analysis of Hyper-redundant manipulators", In 17th ASME Biennial Conference on Mechanical Vibration and Noise., September, 1999.
BibTeX:
@inproceedings{Asl1999,
  author = {Farshid Asl and Hashem Ashrafiuon and C. Nataraj},
  title = {Analysis of Hyper-redundant manipulators},
  booktitle = {17th ASME Biennial Conference on Mechanical Vibration and Noise},
  year = {1999}
}
Nataraj C and Arakere NK (1999), "Dynamic response and stability of a spur gear pair", In 17th ASME Biennial Conference on Mechanical Vibration and Noise., September, 1999.
BibTeX:
@inproceedings{Nataraj1999,
  author = {C. Nataraj and N. K. Arakere},
  title = {Dynamic response and stability of a spur gear pair},
  booktitle = {17th ASME Biennial Conference on Mechanical Vibration and Noise},
  year = {1999}
}
Arakere N and Nataraj C (1998), "Vibration of high-speed spur gear webs", Journal of Vibration and Acoustics, Transactions of the ASME. Fairfield, NJ, USA Vol. 120( 3), pp. 791-800.
Abstract: This paper presents an analytical treatment of the in-plane vibration of high-speed gear webs resulting from rotational effects and periodic excitation from dynamic tooth loading. Dynamic tooth loads result from the combined effect of inertia forces of gear wheels which are significant at high speeds, the periodic variation of gear mesh stiffness, and involute tooth profile errors. The in-plane vibration equations are solved by an approximate method of weighted residuals.
BibTeX:
@article{Arakere1998,
  author = {Arakere, N.K. and Nataraj, C.},
  title = {Vibration of high-speed spur gear webs},
  journal = {Journal of Vibration and Acoustics, Transactions of the ASME},
  year = {1998},
  volume = { 120},
  number = { 3},
  pages = {791-800}
}
Nataraj C and Calvert TE (1998), "Optimal Design of Radial Magnetic Bearings", In Proceedings of the Sixth International Symposium on Magnetic Bearings. , pp. 296-305.
BibTeX:
@inproceedings{Nataraj1998,
  author = {C. Nataraj and T. E. Calvert},
  title = {Optimal Design of Radial Magnetic Bearings},
  booktitle = {Proceedings of the Sixth International Symposium on Magnetic Bearings},
  year = {1998},
  pages = {296-305}
}
Jones G and Nataraj C (1997), "Heat transfer in an electromagnetic bearing", Journal of Heat Transfer, Transactions ASME. New York, NY, USA Vol. 119( 3), pp. 611-616.
Abstract: An exact solution for two-dimensional, full transient, and steady periodic heat conduction in an electromagnetic bearing is obtained. Classical methods are used to obtain an analytical expression for the temperature distribution that arises from power dissipated in the pole windings. Among the key findings is the need for cooling in the immediate neighborhood of the bearing support due to the relatively large thermal resistance of the supporting structure. The results presented prove the existence of large temperature gradients in the bearing in both the radial and circumferential directions. This demands the need for a fine mesh when performing the commonly used nodal-network thermal analysis. Conditions are described under which the temperature distribution is independent of the frequency of the time-dependent current supplied to the poles. For these cases the problem reduces to steady state, and the solution is given. A peak circumferential temperature difference of about 55 °C in the bearing is possible under certain conditions that are discussed. Attention to proper thermal design is critical to reduce the dimensional distortion of the bearing caused by thermal expansion. The effects of thermal expansion can range from catastrophic, should the shaft come in contact with the bearing, to an undesirable change in the force and dynamic control characteristics caused by a variation in the critical shaft-to-bearing clearance, which is of the order of a fraction of a millimeter.
BibTeX:
@article{Jones1997,
  author = {Jones, G.F. and Nataraj, C.},
  title = {Heat transfer in an electromagnetic bearing},
  journal = {Journal of Heat Transfer, Transactions ASME},
  year = {1997},
  volume = { 119},
  number = { 3},
  pages = {611-616},
  note = {I was a secondary author working with a colleague. ASME's flagship journal in heat transfer. Impact factor: 1.7.},
  doi = {10.1115/1.2824149}
}
Nataraj C and Whitman AM (1997), "Parameter Excitation Effects in Gear Dynamics", In 16th ASME Biennial Conference on Vibration and Noise. Sacramento, CA
BibTeX:
@inproceedings{Nataraj1997,
  author = {C. Nataraj and Alan M. Whitman},
  title = {Parameter Excitation Effects in Gear Dynamics},
  booktitle = {16th ASME Biennial Conference on Vibration and Noise},
  year = {1997}
}
Arakere N and Nataraj C (1995), "In-plane vibration of high-speed spur gear webs", American Society of Mechanical Engineers, Design Engineering Division (Publication) DE., In Proceedings of the ASME International Design Engineering Technical Conference. Vol. 84( 3 Pt A/1), pp. 259 - 275.
Abstract: This paper presents an analytical treatment of the in-plane vibration of high-speed gear webs resulting from rotational effects and excitation from dynamic tooth loading. The gear web is modeled as a thin rotating disc and the governing differential equations of motion and the associated boundary conditions are derived from first principles. A comprehensive tooth stiffness model for spur gear is used that accounts for periodic variation of mesh stiffness.
BibTeX:
@inproceedings{Arakere1995,
  author = {Arakere, N.K. and Nataraj, C.},
  title = {In-plane vibration of high-speed spur gear webs},
  booktitle = {Proceedings of the ASME International Design Engineering Technical Conference},
  journal = {American Society of Mechanical Engineers, Design Engineering Division (Publication) DE},
  year = {1995},
  volume = { 84},
  number = { 3 Pt A/1},
  pages = {259 - 275}
}
Nataraj C (1995), "Nonlinear analysis of a rigid rotor on magnetic bearings", American Society of Mechanical Engineers (Paper)., In Proceedings of the ASME International Design Engineering Technical Conference. New York, NY, USA , pp. 7 - .
Abstract: A simple model of a rigid rotor supported on magnetic bearings is considered. A proportional control architecture is assumed, the nonlinear equations of motion are derived and some essential nondimensional parameters are identified. The free and forced response of the system is analyzed using techniques of nonlinear analysis. Both qualitative and quantitative results are obtained and stability criteria are derived for safe operation of the system.
BibTeX:
@inproceedings{Nataraj1995,
  author = {Nataraj, C.},
  title = {Nonlinear analysis of a rigid rotor on magnetic bearings},
  booktitle = {Proceedings of the ASME International Design Engineering Technical Conference},
  journal = {American Society of Mechanical Engineers (Paper)},
  year = {1995},
  pages = {7 - }
}
Sampath AM, Nataraj C and Ashrafiuon H (1995), "Optimal design of coupled structures subjected to random excitation", American Society of Mechanical Engineers, Design Engineering Division (Publication) DE., In Proceedings of the ASME International Design Engineering Technical Conference (IDETC1995). Vol. 82( 1), pp. 323 - 330.
Abstract: This paper presents optimization of the response of coupled structures subjected to random excitation. The dynamic system involves discrete and continuous models of coupled structures. The structures are assumed to be subjected to white noise excitation of known power spectral density. The mean square response of the structure is taken as the objective function. The physical properties such as length, thickness, stiffness and damping are taken as the design variables. The discrete system is assumed to be subjected to two kinds of excitation; band-limited white noise excitation and ideal white noise excitation. Coupling stiffness and damping characteristics are used as design variables. For the case of continuous coupled beam model, band-limited white noise excitation is considered and the root mean square response of the structure is minimized for a range of excitation frequency. Geometric properties of the structure are used as design variables.
BibTeX:
@inproceedings{Sampath1995,
  author = {Sampath, Arun M. and Nataraj, C. and Ashrafiuon, H.},
  title = {Optimal design of coupled structures subjected to random excitation},
  booktitle = {Proceedings of the ASME International Design Engineering Technical Conference (IDETC1995)},
  journal = {American Society of Mechanical Engineers, Design Engineering Division (Publication) DE},
  year = {1995},
  volume = { 82},
  number = { 1},
  pages = {323 - 330}
}
Nataraj C, Ashrafiuon H and Arakere NK (1994), "Effect of fluid inertia on journal bearing parameters", Tribology Transactions. Park Ridge, IL, USA Vol. 37( 4), pp. 784-792.
Abstract: In the modeling and analysis of rotordynamic systems with journal bearings, the stiffness and damping parameters are usually obtained from the Reynolds equation of hydrodynamic lubrication. The Reynolds equation is derived from the continuity and momentum equations with several assumptions; the principal one among them being that the inertia terms are negligible since the lubricant flow is viscosity-dominated. Some previous work has shown, however, that the effect of fluid inertia on the static and dynamic properties of a bearing is not negligible in many circumstances. This paper uses a perturbation approach to present a rigorous derivation of the correction terms to be added to account for the effect of inertia in the case of a journal on a short bearing. The governing equation for pressure correction is derived and the corrected stiffness, damping, and inertia coefficients to the first order are displayed as a function of the equilibrium position.
BibTeX:
@article{Nataraj1994,
  author = {Nataraj, C. and Ashrafiuon, Hashem and Arakere, Nagaraj K.},
  title = {Effect of fluid inertia on journal bearing parameters},
  journal = {Tribology Transactions},
  year = {1994},
  volume = { 37},
  number = { 4},
  pages = {784-792}
}
Nataraj C (1993), "Flexibility effects in a single link robotic manipulator", American Society of Mechanical Engineers, Design Engineering Division (Publication) DE., In Proceedings of the ASME International Design Engineering Technical Conference. New York, NY, USA Vol. 57, pp. 115 - 122.
Abstract: A single link robotic manipulator is modeled as a rotating flexible beam with a rigid mass at the tip and accurate energy expressions are derived. The resulting partial differential equations are solved using an approximate method of weighted residuals. From the solutions, coupling between axial and flexural deformations and the interactions with rigid body motions are rigorously analyzed. The emphasis in the current paper is not on a exhaustive analysis of existing systems but it is rather intended to compare and highlight the various flexibility effects in a relatively simple system. Hence, a nondimensional parametric analysis is performed to determine the effect of several parameters ( including the rotating speed) on the errors and the individual interaction effects are discussed. Comparison with previous work in the field shows important phenomena often ignored or buried in large scale numerical analyses. Future work including application to multi-link robots is outlined.
BibTeX:
@inproceedings{Nataraj1993,
  author = {Nataraj, C.},
  title = {Flexibility effects in a single link robotic manipulator},
  booktitle = {Proceedings of the ASME International Design Engineering Technical Conference},
  journal = {American Society of Mechanical Engineers, Design Engineering Division (Publication) DE},
  year = {1993},
  volume = { 57},
  pages = {115 - 122}
}
Nataraj C (1993), "On the interaction of torsion and bending in rotating shafts", Journal of Applied Mechanics, Transactions ASME. Vol. 60( 1), pp. 239-241.
Abstract: The problem of torsional and transverse deformations of a shaft rotating at a constant speed is considered. The displacements are expressed in a perturbation series in terms of a small parameter. Energy expressions are derived to each order and Hamilton's principle is applied to obtain the equations of motion and the boundary conditions governing the displacement functions of different orders. It is clearly shown that the interaction of torsion and transverse vibration occurs at second order. Previous work reporting results of torsional vibration caused at a frequency equal to twice the rotational speed due to this interaction is confirmed.
BibTeX:
@article{Nataraj1993,
  author = {Nataraj, C.},
  title = {On the interaction of torsion and bending in rotating shafts},
  journal = {Journal of Applied Mechanics, Transactions ASME},
  year = {1993},
  volume = { 60},
  number = { 1},
  pages = {239-241}
}
Nataraj C and Ashrafiuon H (1993), "Optimal design of centered squeeze film dampers", Journal of Vibration, Acoustics, Stress, and Reliability in Design. Vol. 115( 2), pp. 210-214.
Abstract: A two degree-of-freedom model, consisting of a rigid rotor supported on rigid bearings which are in turn supported on squeeze film dampers, is considered. Isotropic centering springs are assumed resulting in a steady synchronous centered circular response for the rotor. The resulting nonlinear system is modeled in nondimensional form. The transmissibility ratio of the system as well as the power dissipated are minimized for various values of unbalance and at several speeds, with the squeeze film bearing parameter as the primary design variable. Expressions are derived for linear variational stability of the circular orbit, and are imposed as constraints in the optimization process. The dependence of the optimal configuration on speed and unbalance is discussed.
BibTeX:
@article{Nataraj1993a,
  author = {Nataraj, C. and Ashrafiuon, H.},
  title = {Optimal design of centered squeeze film dampers},
  journal = {Journal of Vibration, Acoustics, Stress, and Reliability in Design},
  year = {1993},
  volume = { 115},
  number = { 2},
  pages = {210-214},
  doi = {10.1115/1.2930332}
}
Ashrafiuon H and Nataraj C (1992), "Dynamic analysis of engine-mount systems", Journal of Vibration, Acoustics, Stress, and Reliability in Design. Vol. 114( 1), pp. 79-83.
Abstract: This paper examines the forced response of an airplane engine supported by an elastic foundation. It is assumed that the vibrations of the engine and the foundation are small enough such that the equations of motion are linear. The engine is modeled as a rigid body connected to the foundation by standard industrial rubber mounts which act as three-dimensional springs with a significant amount of hysteresis damping. There fundamental models of the foundation are considered: rigid, stutically flexible, and dynamically flexible. In the flexible cases, the foundation is modeled as a clamped circular plate, infinite plate, or any structure identified by a finite element stiffness matrix. In all cases, the mass, stiffness, and damping matrices of the engine-mount system are constructed and the frequency response to the rotating unbalance is determined. For the infinite and clamped circular plate cases, analytical methods are used to determine the real and imaginary parts of the flexibility matrix at different frequencies in responses to the harmonic forces transmitted to the plate through the rubber mounts. It is shown here that the foundation elasticity may have a significant effect on the engine vibration and the mounting forces transmitted from the engine to the structure. It is also shown that only the dynamic model of the foundation is able to capture the correct response of the system at frequencies close to the foundation's natural frequencies.
BibTeX:
@article{Ashrafiuon1992,
  author = {Ashrafiuon, H. and Nataraj, C.},
  title = {Dynamic analysis of engine-mount systems},
  journal = {Journal of Vibration, Acoustics, Stress, and Reliability in Design},
  year = {1992},
  volume = { 114},
  number = { 1},
  pages = {79-83},
  note = {I was a secondary author working with a colleague. ASME's flaghsip journal in vibrations. Impact Factor: 1.200.}
}
Nataraj C, Arakere NK and Ashrafiuon H (1992), "Effect of Fluid Inertia on Journal Bearing Parameters", In STLE Annual Tribology Meeting. Philadelphia, PA
Abstract: In the modeling and analysis of rotordynamic systems with journal bearings, the stiffness and damping parameters are usually obtained from the Reynolds equation of hydrodynamic lubrication. The Reynolds equation is derived from the continuity and momentum equations with several assumptions; the principal one among them being that the inertia terms are negligible since the lubricant flow is viscosity-dominated. Some previous work has shown, however, that the effect of fluid inertia on the static and dynamic properties of a bearing is not negligible in many circumstances. This paper uses a perturbation approach to present a rigorous derivation of the correction terms to be added to account for the effect of inertia in the case of a journal on a short bearing. The governing equation for pressure correction is derived and the corrected stiffness, damping, and inertia coefficients to the first order are displayed as a function of the equilibrium position.
BibTeX:
@inproceedings{Nataraj1992,
  author = {C. Nataraj and N. K. Arakere and H. Ashrafiuon},
  title = {Effect of Fluid Inertia on Journal Bearing Parameters},
  booktitle = {STLE Annual Tribology Meeting},
  year = {1992}
}
Nataraj C and Raju PK (1992), "The Vibrational Response of Coupled Composite Beams", In Proceedings of the Second International Congress on Recent Developments in Air and Structure Borne Sound and Vibration. Auburn, AL
BibTeX:
@inproceedings{Nataraj1992a,
  author = {C. Nataraj and P. K. Raju},
  title = {The Vibrational Response of Coupled Composite Beams},
  booktitle = {Proceedings of the Second International Congress on Recent Developments in Air and Structure Borne Sound and Vibration},
  year = {1992}
}
Ashrafiuon H and Nataraj C (1991), "Dynamic analysis of engine-mount systems", American Society of Mechanical Engineers, Design Engineering Division (Publication) DE., In Proceedings of the ASME International Design Engineering Technical Conference. New York, NY, USA Vol. 34, pp. 191 - 196.
Abstract: This paper examines the forced response of an airplane engine supported by an elastic foundation. It is assumed that the vibrations of the engine and the foundation are small enough such that the equations of motion are linear. The engine is modeled as a rigid body connected to the foundation by standard industrial rubber mounts which act as three dimensional springs with a significant amount of hysteresis damping. Three fundamental models of the foundation are considered: rigid, statically flexible, and dynamically flexible. In the flexible cases, the foundation is modeled as a clamped circular plate, infinite plate, or any structure identified by a finite element stiffness matrix. In all cases, the mass, stiffness, and damping matrices of the engine-mount system are constructed and the frequency response to the rotating unbalance is determined. For the infinite and clamped circular plate cases, analytical methods are used to determine the real and imaginary parts of the flexibility matrix at different frequencies in response to the harmonic forces transmitted to the plate through the rubber mounts. It is shown here that the foundation elasticity may have a significant effect on the engine vibration and the mounting forces transmitted from the engine to the structure. It is also shown that only the dynamic model of the foundation is able to capture the correct response of the system at frequencies close to the foundation's natural frequencies.
BibTeX:
@inproceedings{Ashrafiuon1991,
  author = {Ashrafiuon, Hashem and Nataraj, C.},
  title = {Dynamic analysis of engine-mount systems},
  booktitle = {Proceedings of the ASME International Design Engineering Technical Conference},
  journal = {American Society of Mechanical Engineers, Design Engineering Division (Publication) DE},
  year = {1991},
  volume = { 34},
  pages = {191 - 196}
}
Ashrafiuon H and Nataraj C (1991), "Effect on flexibility on manipulator dynamics", Proceedings of the International Conference on CAD/CAM, Robotics, and Factories of the Future., In Proceedings of the ASME International Design Engineering Technical Conference. Secaucus, NJ, US , pp. 565 - .
BibTeX:
@inproceedings{Ashrafiuon1991a,
  author = {Ashrafiuon, H. and Nataraj, C.},
  title = {Effect on flexibility on manipulator dynamics},
  booktitle = {Proceedings of the ASME International Design Engineering Technical Conference},
  journal = {Proceedings of the International Conference on CAD/CAM, Robotics, and Factories of the Future},
  year = {1991},
  pages = {565 - },
  note = {[abstract reviewed]}
}
Ashrafiuon H and Nataraj C (1991), "Dynamic Analysis of Serial Rotary Manipulators With Flexible Links", In Proceedings of the Second National Applied Mechanisms and Robotics Conference. Cincinnati, OH (91 AMR-IIB-2)
BibTeX:
@inproceedings{Ashrafiuon1991b,
  author = {H. Ashrafiuon and C. Nataraj},
  title = {Dynamic Analysis of Serial Rotary Manipulators With Flexible Links},
  booktitle = {Proceedings of the Second National Applied Mechanisms and Robotics Conference},
  year = {1991},
  number = {91 AMR-IIB-2},
  note = {[abstract reviewed]}
}
Nataraj C and Wallace CE (1990), "Analysis of transverse vibration of coupled beams using SEA", In Proceedings of the International Congress on Recent Developments in Air and Structure Borne Sound and Vibration. Auburn, AL
BibTeX:
@inproceedings{Nataraj1990,
  author = {C. Nataraj and C. E. Wallace},
  title = {Analysis of transverse vibration of coupled beams using SEA},
  booktitle = {Proceedings of the International Congress on Recent Developments in Air and Structure Borne Sound and Vibration},
  year = {1990}
}
Nataraj C and Nelson H (1989), "Collocation method for the investigation of periodic solutions in nonlinear systems", American Society of Mechanical Engineers, Design Engineering Division (Publication) DE., In Proceedings of the ASME International Design Engineering Technical Conference. New York, NY, USA Vol. 18( pt 5), pp. 325 - 330.
Abstract: The problem of periodic solution of non-autonomous and autonomous ordinary differential equations is considered. A trigonometric collocation method (TCM), recently developed by Ronto (Samoilenko and Ronto, 1979), is extended and implemented for the analysis of engineering systems. The procedure developed is applied to the problem of forced response of a journal on a hydrodynamic bearing. The self-excited galloping vibration of a single degree-of-freedom oscillator is also discussed and the results by the present method are compared to previously published works. A typical nonlinear control system with an on-off relay is analyzed and the results obtained by the Describing Function method and the TCM are compared. The TCM is thus shown to be a viable procedure for engineering analysis and design.
BibTeX:
@inproceedings{Nataraj1989,
  author = {Nataraj, C. and Nelson, H.D.},
  title = {Collocation method for the investigation of periodic solutions in nonlinear systems},
  booktitle = {Proceedings of the ASME International Design Engineering Technical Conference},
  journal = {American Society of Mechanical Engineers, Design Engineering Division (Publication) DE},
  year = {1989},
  volume = { 18},
  number = { pt 5},
  pages = {325 - 330},
  note = {[Published before Villanova.]}
}
Nataraj C and Nelson H (1989), "Periodic solutions in rotor dynamic systems with nonlinear supports: A general approach", Journal of Vibration, Acoustics, Stress, and Reliability in Design. Vol. 111(2), pp. 187-193.
Abstract: A new quantitative method of estimating steady state periodic behavior in nonlinear systems, based on the trigonometric collocation method, is outlined. A procedure is developed to analyze large rotor dynamic systems with nonlinear supports by the use of the above method in conjunction with Component Mode Synthesis. The algorithm discussed is seen to reduce the original problem to solving nonlinear algebraic equations in terms of only the coordinates associated with the nonlinear supports and is a big improvement over commonly used integration methods. The feasibility and advantages of the procedure so developed are illustrated with the help of an example of a typical rotor dynamic system with an uncentered squeeze film damper. Future work on the investigation of the stability of the periodic response so obtained is outlined.
BibTeX:
@article{Nataraj1989,
  author = {Nataraj, C. and Nelson, H.D.},
  title = {Periodic solutions in rotor dynamic systems with nonlinear supports: A general approach},
  journal = {Journal of Vibration, Acoustics, Stress, and Reliability in Design},
  year = {1989},
  volume = { 111},
  number = {2},
  pages = {187-193},
  note = {[Published before Villanova.]}
}
Nataraj C and Nelson HD (1987), "Periodic solutions in rotor dynamic systems with nonlinear supports: a general approach", American Society of Mechanical Engineers, Design Engineering Division (Publication) DE., In Proceedings of the ASME International Design Engineering Technical Conference. New York, NY, USA Vol. 3, pp. 51 - 58.
Abstract: A new quantitative method of estimating steady state periodic behavior in nonlinear systems, based on the trigonometric collocation method, is outlined. A procedure is developed to analyze large rotor dynamic systems with nonlinear supports by the use of the above method in conjunction with Component Mode Synthesis. The algorithm discussed is seen to reduce the original problem to solving nonlinear algebraic equations in terms of only the coordinates associated with nonlinear supports and is a big improvement over commonly used integration methods. The feasibility and advantages of the procedure so developed are illustrated with the help of an example of a typical rotor dynamic system with an uncentered squeeze film damper. Future work on the investigation of the stability of the periodic response so obtained is outlined.
BibTeX:
@inproceedings{Nataraj1987,
  author = {Nataraj, C. and Nelson, H. D.},
  title = {Periodic solutions in rotor dynamic systems with nonlinear supports: a general approach},
  booktitle = {Proceedings of the ASME International Design Engineering Technical Conference},
  journal = {American Society of Mechanical Engineers, Design Engineering Division (Publication) DE},
  year = {1987},
  volume = { 3},
  pages = {51 - 58},
  note = {[Published before Villanova.]}
}
Nelson HD and Nataraj C (1986), "Dynamics of a rotor system with a cracked shaft", Journal of Vibration, Acoustics, Stress, and Reliability in Design. Vol. 108(2), pp. 189-196.
Abstract: A theoretical analysis of the dynamics of a rotor-bearing system with a transversely cracked rotor is presented. The rotating assembly is modeled using finite rotating shaft elements and the presence of a crack is taken into account by a rotating stiffness variation. This stiffness variation is a function of the rotor's bending curvature at the crack location and is represented by a Fourier series expansion. The resulting parametrically excited system is nonlinear and is analyzed using a perturbation method coupled with an iteration procedure. The system equations are written in terms of complex variables and an associated computer code has been developed for simulation studies. Results obtained by this analysis procedure are compared with previous analytical and experimental work presented by Grabowski.
BibTeX:
@article{Nelson1986,
  author = {Nelson, H. D. and Nataraj, C.},
  title = {Dynamics of a rotor system with a cracked shaft},
  journal = {Journal of Vibration, Acoustics, Stress, and Reliability in Design},
  year = {1986},
  volume = { 108},
  number = {2},
  pages = {189-196},
  note = {[Published before Villanova.]}
}
Nataraj C, Nelson HD and Arakere N (1985), "Effect of coulomb spline on rotor dynamic response", NASA Conference Publication. Washington, DC, USA , pp. 225 - 233.
Abstract: A rigid rotor system coupled by a coulomb spline is modelled and analyzed by approximate analytical and numerical-analytical methods. Expressions are derived for the variables of the resulting limit cycle and are shown to be quite accurate for a small departure from isotropy.
BibTeX:
@inproceedings{Nataraj1985,
  author = {Nataraj, C. and Nelson, H. D. and Arakere, N.},
  title = {Effect of coulomb spline on rotor dynamic response},
  journal = {NASA Conference Publication},
  year = {1985},
  pages = {225 - 233},
  note = {[Published before Villanova.]}
}
Nelson HD and Nataraj C (1985), "Dynamics of a rotor system with a cracked shaft", American Society of Mechanical Engineers (Paper)., In Proceedings of the ASME International Design Engineering Technical Conference. New York, NY, USA , pp. 8 - .
Abstract: A theoretical analysis of the dynamics of a rotor-bearing system with a transversely cracked rotor is presented. The rotating assembly is modeled using finite rotating shaft elements and the presence of a crack is taken into account by a rotating stiffness variation. This stiffness variation is a function of the rotor's bending curvature at the crack location and is represented by a Fourier series expansion. The resulting parametrically excited system is nonlinear and is analyzed using a perturbation method coupled with an iteration procedure. The system equations are written in terms of complex variables and an associated computer code has been developed for simulation studies. Results obtained by this analysis procedure are compared with previous analytical and experimental work presented by Grabowski.
BibTeX:
@inproceedings{Nelson1985,
  author = {Nelson, H. D. and Nataraj, C.},
  title = {Dynamics of a rotor system with a cracked shaft},
  booktitle = {Proceedings of the ASME International Design Engineering Technical Conference},
  journal = {American Society of Mechanical Engineers (Paper)},
  year = {1985},
  pages = {8 - },
  note = {[Published before Villanova.]}
}
Kamath M, Narasimhan R, Nataraj C and Ramamurti V (1982), "Dynamic response of multicylinder engines with a viscous or hysteretic crankshaft damper", Journal of Sound and Vibration., April, 1982. Vol. 81(3), pp. 448-452.
BibTeX:
@article{Kamath1982,
  author = {M. Kamath and R. Narasimhan and C. Nataraj and V. Ramamurti},
  title = {Dynamic response of multicylinder engines with a viscous or hysteretic crankshaft damper},
  journal = {Journal of Sound and Vibration},
  year = {1982},
  volume = {81},
  number = {3},
  pages = {448-452},
  note = {Co-principal author. Paper published as an undergraduate student.},
  doi = {10.1016/0022-460X(82)90255-3}
}