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Showing papers by "Hassan K. Khalil published in 2003"


Proceedings ArticleDOI
09 Dec 2003
TL;DR: In this paper, a nonlinear single-input-single-output (SISO) minimum phase system with large parametric uncertainty is considered and a switching rule using an estimate of the derivative of a Lyapunov function is used to choose the appropriate control law.
Abstract: We consider a nonlinear single-input-single-output minimum phase system with large parametric uncertainty. The system can be represented globally in the normal form and our goal is to find an output dynamic feedback control law to ensure that the output (practically) asymptotically tracks a bounded smooth reference signal. Earlier work used high-gain observers with saturation to derive adaptive as well as robust control laws for this problem. The adaptive control law requires the nonlinear functions to be linearly parameterized in the unknown parameters and could have unsatisfactory transient performance for a large parameter set. The robust control law is based on a worst-case design and could be overly conservative for a large parameter set. In this paper we propose a new approach based on partitioning the set of uncertain parameters into smaller subsets. Robust control laws are designed for each subset and logic based switching is used to choose the appropriate control law. The switching rule uses an estimate of the derivative of a Lyapunov function, which is estimated using a high-gain observer.

9 citations


Proceedings ArticleDOI
04 Jun 2003
TL;DR: Simulation results show that nonlinear gains can be designed to improve overshoot and settling time and proves regional as well as semiglobal asymptotic regulation.
Abstract: For an SISO minimum-phase nonlinear system with relative degree one or two, a universal integral controller with nonlinear proportional, integral and derivative gains is proposed. Our analysis proves regional as well as semiglobal asymptotic regulation. Simulation results show that nonlinear gains can be designed to improve overshoot and settling time.

6 citations


Proceedings ArticleDOI
04 Jun 2003
TL;DR: The design of a robust continuous sliding mode controller that achieves asymptotic tracking and disturbance rejection for a class of nonlinear systems is considered, and both regional as well as semi-global results for error convergence are given.
Abstract: We consider the design of a robust continuous sliding mode controller (CSMC) that achieves asymptotic tracking and disturbance rejection for a class of nonlinear systems. Previous work has shown how to do this by incorporating a linear servo-compensator in the sliding mode design, but the asymptotic tracking is usually achieved at the cost of poor transient performance (compared to ideal SMC). Extending previous ideas from the design of "conditional integrators" for the restricted regulation problem in the presence of constant disturbances, we design the servo-compensator as a conditional one that provides servo-compensation only inside the boundary layer; achieving asymptotic tracking, but with improved transient performance. We give both regional as well as semi-global results for error convergence, and show that the controller can be tuned to recover the performance of an ideal SMC.

1 citations