Disturbance attenuation for systems with real parametric uncertainty

We discuss the problem of parameter independent controller synthesis to provide quadratic stability and a desirable disturbance attenuation level (through an appropriately small L/sub 2/ gain) for systems with time varying, real parametric uncertainty. Through the use of skew symmetric matrices, the conservatism of standard scaled H/sub /spl infin// approach is reduced. While the full state feedback problem is convex, the output feedback problem is not. A set of conditions under which the design of output feedback controllers can be broken into two sequential convex problems is presented. The results are compared with recent results in design of parameter-varying controllers and a simple result regarding the mixed problem (where some of the unknown parameters can be measured on line) is discussed. An example is presented to illustrate the proposed approach.