C.B. Soh

On regularizing singular systems by decentralized output feedback

This paper considers linear time-invariant decentralized singular systems which are either nonregular or, if they are regular, they have impulsive modes. It derives algebraic necessary and sufficient conditions for making a singular system both regular and impulse-free by decentralized output feedback control laws and decentralized proportional-plus-derivative output feedback control laws.

Reliable nonlinear control system design by using strictly redundant control elements

This paper is concerned with the single-contingency reliable controller design problem for nonlinear systems. A procedure for designing reliable nonlinear controllers is presented for nonlinear systems with strictly redundant sensors and strictly redundant actuators. The resulting closed-loop nonlinear systems are reliable in the sense that they provide guaranteed local internal stability and H performance not only when all sensors and actuators are operational but also when any one, but only one, sensor or actuator experiences an outage. An example is given to illustrate the design procedure and the effectiveness of the proposed methods.

Necessary and sufficient conditions for the controllability of linear interval descriptor systems

Abstract In this paper, we investigate a class of uncertain linear descriptor systems with interval plants, and give necessary and//or sufficient conditions for controllability. Examples are also given to illustrate the results. The corresponding results for the dual observability robustness problems are straightforward extensions.

Maximum bounds for robust stability of linear uncertain descriptor systems with structured perturbations

This paper considers the robust stability of descriptor systems with structured perturbations. It presents a maximum perturbation bound for keeping a system regular, impulse-free and stable, by using the technique of Kronecker product and the structured singular value μ.

Robust controllability and robust closed-loop stability with static output feedback for a class of uncertain descriptor systems

Abstract This paper considers robust controllability for uncertain linear descriptor systems with structured perturbations. Necessary and sufficient conditions based on the μ -analysis are obtained by transforming the problem into checking the nonsingularity of a class of uncertain matrices. Also a tight bound is obtained in terms of μ for keeping the closed-loop system regular, impulse-free and stable under a preconstructed static output feedback. An example is given to illustrate the results.

Reliable nonlinear control system design using duplicated control elements

Reliable L2 gain bounding (i.e., H∞) controllers for nonlinear systems are designed by using redundant control elements. One sensor and one actuator are duplicated, and the resulting closed-loop system is reliable with respect to both the single contingency case and the primary contingency case. The design procedures for reliable controllers are developed by using the Hamilton–Jacobi inequalities from nonlinear H∞ control theory. Linear reliable controller design methods are also obtained by restricting the proposed nonlinear methods to the linear case, and the linear methods are found to be less conservative than existing methods for linear reliable controller design. Examples are given to illustrate the design procedures for both linear and nonlinear reliable controllers and the advantages of the proposed linear method over existing ones.

On a root distribution criterion for interval polynomials

H. Kokame and T. Mori (1991) and C.B. Soh (1990) derived conditions under which an interval polynomial has a given number of roots in the open left-half plane and the other roots in the open right-half plane. However, the one-shot-test approach using Sylvesters resultant matrices and Bezoutian matrices implies that the implemented conditions are only sufficient (not necessary) for an interval polynomial to have at least one root in the open left-half plane and open right-half plane. Alternative necessary and sufficient conditions, which only require the root locations of four polynomials to check the root distribution of an interval polynomial, are presented. >

Reliable nonlinear control system design using redundant control elements

This paper considers the single contingency reliable controller design problem for nonlinear systems. A procedure for designing reliable nonlinear controllers is presented for nonlinear systems with redundant sensors and redundant actuators. The resulting closed-loop nonlinear systems are reliable in the sense that they provide guaranteed local internal stability and H/sub /spl infin// performance not only when all sensors and actuators are operational but also when any one, but only one, sensor or actuator experiences an outage.

Decentralized H/sub /spl infin//-controller design for nonlinear systems

Considers the decentralized H/sub /spl infin//-controller design problem for nonlinear systems. Sufficient conditions for the solution of the problem are presented in terms of solutions of Hamilton-Jacobi inequalities. The resulting design guarantees local asymptotic stability and ensures a predetermined L/sub 2/-gain bound on the closed-loop system.

Robustness of uncertain descriptor systems

This paper considers a class of descriptor systems with perturbations. It derives sufficient conditions for the uncertain systems to be impulse-free (regular) and asymptotically stable. The problems of the impulse controllability and impulse observability, and the robust impulsive controller (RIG) of the uncertain system are considered.