Sushant M. DuttaGraduate student |
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Research
Inverse Problems in Nondestructive Evaluation. Nondestructive evaluation (NDE) involves the inspection of samples for corrosion and physical damage without altering them in any way. Two widely used methods for nondestructive evaluation of ferromagnetic pipes and tubes are: (1) Ultrasonic testing (UT), and (2) Magnetic flux leakage testing (MFLT). Broadly speaking, these methods pervade the sample with known physical fields (elastic wave field and magnetic field, respectively), and subsequently use suitable sensors to measure the fields altered by the sample. The measured sensor data is expected to contain information about material grain size, boundaries, and defects. However, acquiring this information involves solving inverse problems. Inverse problems involve the estimation of desired parameters (defects, grain size, material properties) from inadequate data (measured sensor data). The inadequacy of this data stems from the limitations of the measurement procedure/device. Consequently, inverse problems usually are ill-posed. Existing practices in the NDE industry rely on the experience of human operators to interpret sensor data. In contrast, forward problems involve the acquisition of sensor data, given the material properties and parameters of the sample and the defects. This research addresses the inverse problem of detection and characterization of defects in ferromagnetic pipes and tubes.
Dynamic Hysteresis Modeling and Applications. Hysteresis is a phenomenon which is widely observed in a variety of physical systems. It introduces a nonlinear and multivalued behavior in systems, making their modeling and control problematic. This research underlines the significance of dynamic hysteresis modeling (dynamic meaning that the model is in the form of differential equations) from the perspectives of analysis and control. Toward that end, a widely accepted definition of hysteresis is adopted and some important properties of hysteresis are presented. Five general hysteresis models are discussed, along with some damping and friction models. Their properties are compared and contrasted. The Duhem model is shown to be a versatile dynamic hysteresis model, and it is adapted to two distinct physical systems. First, the evolution of dynamic hysteresis modeling of harmonic drive is studied, and a new dynamic model, based on Duhem model, is developed. It is more accurate than previous models and is used to prove, via the method of describing functions, that PID regulation control of harmonic drive can cause a limit cycle due to hysteresis. Second, a dynamic hysteresis model, based on Duhem model, is proposed for a shape memory alloy actuator, which yields a complete dynamic model of the actuator, linking its temperature, strain and electrical resistance together. Therefore, this research provides a foundation for dynamic hysteresis modeling in engineering systems and brings out the salient features of dynamic hysteresis modeling from the perspectives of analysis and control.
Publications & Presentations
Dutta, S.M., Ghorbel, F.H., and Stanley, R.K., "Dipole Modeling of Magnetic Flux Leakage," submitted to IEEE Transactions on Magnetics, October 2007.
Dutta, S.M., Ghorbel, F.H., and Stanley, R.K., "Simulation and Analysis of Magnetic Flux Leakage," submitted to IEEE Transactions on Magnetics, October 2007.
Dutta, S.M. and Ghorbel, F.H., "Magnetic Flux Leakage Sensing: Current Practices and Mathematical Analysis," Proceedings of the ASME International Mechanical Engineering Congress, Seattle, Washington, November 2007.
Dutta, S.M., "Modeling and Control of a Shape Memory Alloy Actuator," Seminar, Mechanical Engineering Department, IIT Bombay, January 16, 2006.
Dutta, S.M., Ghorbel, F.H., and Dabney, J.B.,"Modeling and Control of a Shape Memory Alloy Actuator", Proceedings of the 2005 IEEE International Symposium on Intelligent Control, Limassol, Cyprus, pp. 1007-1012, June 2005.
Dutta, S.M. and Ghorbel, F.H.,"Differential Hysteresis Modeling of a Shape Memory Alloy Wire Actuator", IEEE/ASME Transactions on Mechatronics, Vol. 10, No. 2, pp. 189-197, April 2005.
Dutta, S.M., Ghorbel, F.H., and Dabney, J.B.,"Dynamic Modeling and Control of Hysteresis in a Shape Memory Alloy Actuator", Proceedings of the ASME International Mechanical Engineering Congress, Anaheim, California, November 2004.
Dutta, S.M.,"Dynamic Hysteresis Modeling and Applications", Masters Thesis, Rice University, April 2004.
Dutta, S.M., Dabney, J.B., and Ghorbel, F.H.,"Hysteresis and its Modeling", Presented at Innovations 2002, University of Houston-Clear Lake, May 2002.