OUTPUT-FEEDBACK STABILIZING CONTROL WITH AN H-INFINITY BOUND ON DISTURBANCE ATTENUATION

This paper considers the design of direct output static and dynamic st abilizing controllers for linear systems. Here, the controllers that s tabilize the closed-loop system must satisfy an H(infinity) disturbanc e attenuation constraint. Sufficient conditions for the existence of s uch controllers are presented in the form of two coupled nonlinear mat rix equations. These conditions are derived by solving a mixed-norm H- 2/H(infinity) optimal control problem. The solution of these equations via a continuation method is also presented. Using the solution algor ithm, a fixed order stabilizing controller gain matrix that minimizes the H(infinity) norm of the closed-loop transfer function can be compu ted. The controller design technique is applied to the vertical dynami cs of an aircraft. It is shown that the performance of the reduced ord er controllers designed using the technique proposed in this paper is superior to that of full order controllers obtained using th standard LQG approach.