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Quasilinear Control: Performance Analysis and Design of Feedback Systems with Nonlinear Actuators and Sensors

Quasilinear control (QLC) is a set of methods for performance analysis and design of linear plant/nonlinear instrumentation (LPNI) systems. The approach of QLC is based on the method of stochastic linearization, which reduces the nonlinearities of actuators and sensors to quasilinear gains. Unlike the usual, Jacobian linearization, stochastic linearization is global. The price to pay is that the quasilinear gains depend not on the operating point but on all functional blocks and exogenous signals of the system (i.e., the plant and controller, reference and disturbance, etc.). Using this approximation, QLC extends most of the linear control theory techniques to LPNI systems. These include system type, error coefficients, root locus, , LQR/LQG, H∞, LMI, etc. The resulting equations consist of the usual linear control relationships (e.g., Lyapunov and Ricatti equations) coupled with transcendental equations, which account for quasilinear gains. A bisection algorithm for solving these equations is provided. In addition, QLC includes new problems, specific for the LPNI scenario. Examples are Instrumented LQR/LQG, where the controller is designed simultaneously with the actuator and sensor, and partial and complete performance recovery, where the degradation of linear performance is either contained by selecting the right instrumentation or completely eliminated by the controller boosting. In this talk, the theory of QLC will be overviewed and several of problems, namely, saturated root locus, Instrumented LQR/LQG, and performance recovery, will be discussed in some details.

Type of Seminar:
IfA Seminar
Prof. Semyon M. Meerkov
Department of Electrical Engineering and Computer Science, University of Michigan
May 25, 2010   16:15

ETZ E9, Gloriastrasse 35
Contact Person:

Prof. M. Morari
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Biographical Sketch:
Semyon M. Meerkov received his MSEE degree from the Polytechnic of Kharkov, Ukraine, in 1962 and Ph.D. in Systems Science from the Institute of Control Sciences, Moscow, Russia, in 1966. He was with the Institute of Control Sciences until 1977. From 1979 to 1984 he was with the Department of Electrical and Computer Engineering, Illinois Institute of Technology, Chicago, IL. Since 1984 he has been a Professor at the Department of Electrical Engineering and Computer Science of the University of Michigan, Ann Arbor, MI. He has held visiting positions at UCLA (1978-1979), Stanford (1991), Technion, Israel (1997-1998 and 2008) and Tsinghua,China (2008). He was the Editor-in-Chief of Mathematical Problems in Engineering, Department Editor for Manufacturing Systems of IIE Transactions and Associate Editor of several other journals. His research interests are in Systems and Control with applications to Production Systems, Communication Networks, and Theory of Rational Behavior.