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Montanari M.
"Sensorless Control of Induction Motors: Nonlinear and Adaptive Techniques"
Type PhD Thesis
Author(s) Montanari M.
Title Sensorless Control of Induction Motors: Nonlinear and Adaptive Techniques
Editor University of Bologna
Keywords induction motor, sensorless control, field orientation, adaptive control, singular perturbation, stability analysis

Speed controlled induction motor drives are wide-spread electromechanical systems suitable for a large spectrum of industrial applications. When high dynamic performance and high precision control in a wide speed range are required, induction motor vector control based on the availability of the speed sensor is used. However, the speed sensor reduces the robustness and reliability of the IM drive and increases its cost. Hence, for medium and low performance applications, sensorless control of induction motor is becoming an industrial standard. In recent years, a large variety of different solutions has been applied in commercial products; at the same time, the problem of IM sensorless control has been greatly treated in scientific literature, becoming an attractive task for different nonlinear control techniques. Sensorless control represents a challenging theoretical problem, since the IM is represented by a 5th order, highly coupled nonlinear model, with unknown state variables and external inputs and demanding control objective.

The present Ph.D. Thesis deals with the design of different sensorless control algorithms for induction motor. Main aim of this work is to design sensorless controllers with theoretically proved stability properties, suitable for industrial applications. All the controllers are defined in the common framework of indirect field oriented control. Theoretical tools utilized for the design are in the framework of nonlinear control methods, in particular Lyapunov-like technique, adaptive control theory, singular perturbation technique, linearization method, etc. Combined with the decomposition of the nonlinear full-order system in simpler interconnected subsystems, on the basis of "natural" properties (e.g. related to energy conversion and to the physics of the induction machine) or time-scale separation, nonlinear control theory is applied in order to prove the stability properties of the controlled induction motor. Common and general theoretical and practical problems introduced by the sensorless specification in the IM control are enlightened and discussed and different solutions are proposed. Intensive simulation and experimental results, combined with attention to implementation problems, have been carried out in order to verify the suitability of the proposed sensorless controllers.

The experiments have been performed at the Laboratory of Automation and Robotics (L.A.R.) of the Department of Electronics, Computer Science and Systems (D.E.I.S.), University of Bologna.

The Ph.D. Thesis is organized as follows. An introduction on sensorless control, with a brief survey on most important works present in literature, is made. Then, each of the successive chapters refers to a novel IM sensorless controller presented during the Ph.D. period by the author and should be considered independent by the other ones. Working hypothesis, control objective, detailed design procedure and stability analysis are reported for each controller, while simulation and/or experimental results verify the performance of the controller. At last, final discussion and concluding remarks on sensorless control are provided.

Dottorato di Ricerca in Automatica e Ricerca Operativa
Universitą degli Studi di Bologna
XV ciclo

Coordinatore: Prof. Alberto Tonielli
Tutor: Prof. Alberto Tonielli
Year 2003

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