Robust control of linear systems with real parametric uncertainty

We discuss the problem of robust controller synthesis to provide quadratic stability and a desirable disturbance attenuation level (through an appropriately small L-2 gain) for systems with time-varying, real parametric uncertainty. Through the use of skew-symmetric matrices, the conservatism of standard scaled H-infinity approach is reduced. While the full stale 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 concerning the 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. (C) 1999 Elsevier Science Ltd. All rights reserved.