NONLINEAR VERSUS LINEAR-CONTROL IN THE ROBUST STABILIZABILITY OF LINEAR UNCERTAIN SYSTEMS VIA FIXED-ORDER OUTPUT-FEEDBACK

This paper considers the problem of robustly stabilizing an uncertain system via fixed-order output feedback control. This problem is consid ered by defining a notion of robust stabilizability with a quadratic s torage function. This notion is closely related to the notion of quadr atic stabilizability. The main result of the paper shows that if an un certain system is robustly stabilizable with a quadratic storage funct ion via a nonlinear time-varying controller, then it will also be robu stly stabilizable with a quadratic storage function via a linear time- invariant controller of the same order.