Wassim M. Haddad

Fixed-structure controller design for systems with actuator amplitude and rate nonlinearities

In this paper we develop fixed-order (i.e., full- and reduced-order) dynamic output feedback compensators for systems with actuator amplitude and rate saturation constraints. The proposed design methodology employs a rate limiter as part of the controller architecture. The problem of simultaneous control amplitude and rate saturation is embedded within an optimization problem by constructing a Riccati equation whose solution guarantees closed-loop global asymptotic stability in the face of sector bounded actuator amplitude and rate nonlinearities. Application of the proposed framework is demonstrated via a numerical example.

Guaranteed Domains of Attraction for Multivariable Luré Systems Via Open Lyapunov Surfaces 1

Abstract In this paper we provide guaranteed stability regions for multivariable Lure systems, Specifically, using the Lure-Postnikov Lyapunov function a guaranteed subset of the domain of attraction for a feedback system whose forward path contains a dynamic linear time-invariant system and whose feedback path contains multiple sector-bounded time-invariant memoryless nonlinearities is constructed via open Lyapunov surfaces, It is shown that the use of open Lyapunov surfaces yields a considerable improvement over closed Lyapunov surfaces in estimating the domain of attraction of the zero solution of the nonlinear system

Robust controller synthesis via shifted parameter-dependent and quadratic cost bounds

Parametrized Lyapunov bounds and shifted quadratic guaranteed cost bounds are merged to develop shifted parameter-dependent quadratic cost bounds for robust stability and robust performance. Robust fixed-order (i.e., full- and reduced-order) controllers are developed based on new shifted parameter-dependent bounding functions. A numerical example is presented to demonstrate the effectiveness of the proposed approach.

Stable H/sub 2/-optimal controller synthesis

This paper considers fixed-structure stable H/sub 2/-optimal controller synthesis using a multiobjective optimization technique. The problem is presented in a decentralized static output feedback framework developed for fixed-structure dynamic controller synthesis. A quasi-Newton/continuation algorithm is used to compute solutions to the necessary conditions. To demonstrate the approach, a numerical example is considered, which consists of a second-order spring-mass-damper system pulled from the stable stabilization literature. The results are then compared with other methods of stable compensator synthesis.