Long Actuator Delays - Extending the Smith Predictor to Nonl





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Uploaded on Oct 21, 2008

Long Actuator Delays - Extending the Smith Predictor to Nonlinear

Miroslav Krstic
Mechanical and Aerospace Engineering
University of California, San Diego
One would be hard pressed to find "long actuator delays, "unknown delays," or "nonlinear control" co-existing in the same sentence in the control literature. This is due to the potential for finite escape in the presence of nonlinearity, and due to the uncertainty in the size of the infinite-dimensional part of the system's state in the case of unknown delay. It has been half a century since Otto Smith, a professor of Mechanical Engineering at UC Berkeley, invented the "predictor" feedback for compensating long but known actuator delays for linear systems. This method has since become one of the favorite tools in chemical process control and many other applications. I will show an extension of predictor feedback to nonlinear (possibly unstable) systems, which is enabled by "infinite dimensional/continuum backstepping." Backstepping yields the construction of Lyapunov-Krasovskii functional with which I have been able to prove robustness of predictor feedbacks to both underestimating and overestimating the length of the actuator delay, as well as to develop the first delay-adaptive controllers.

Miroslav Krstic is the Sorenson Professor of Mechanical and Aerospace Engineering and the Director of the newly formed Center for Control Systems and Dynamics (CCSD) at the University of California at San Diego. He is a coauthor of the books Nonlinear and Adaptive Control Design, Stabilization of Nonlinear Uncertain Systems, Flow Control by Feedback, Real Time Optimization by Extremum Seeking Control, and Control of Turbulent and Magnetohydrodynamic Channel Flows. Dr. Krstic received the National Science Foundation Career, ONR YI, and PECASE Awards, as well as the Axelby and the Schuck paper prizes. In 2005, he was the first engineering professor to receive the UCSD Award for Research. He is a Fellow of IEEE, a Distinguished Lecturer of the Control Systems Society, and a former CSS VP for Technical Activities.


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