A stability robustness analysis and design method for linear discrete-time systems with structured uncertainty

The lineal discrete-time systems to be discussed are described by state-space models with structured uncertainties. First, a new sufficient condition is presented to measure the quadratic stability robustness of the closed-loop system with prescribed ranges of parameter variations. An iterative scheme is also presented to obtain the maximal tolerable perturbation bound. Then a robust design method is proposed for the output feedback system. The proposed robust design method uses an iteratine minimax optimization program to find a linear constant output feedback law which maximizes the perturbation bound to retain quadratic stability. Examples are utilized to show the improvements and advantages of the proposed methods over previous ones.