ROBUST STABILIZATION IN THE BIBO GAP TOPOLOGY

We consider robust stabilization of both linear causal discrete-time s ystems in an l(1)-setting and linear causal continuous-time systems in an L-1-setting. We introduce a new metric in the space of l(1)(L-1)-s tabilizable systems in terms of their coprime factorizations. This met ric is easily computed and induces the gap topology. We show how robus tness optimization in this metric is related to robustness optimizatio n for normalized factor perturbations, In each case, the optimal contr oller determined by Clover and McFarlane (and studied by Georgiou and Smith) in the l(2) (L-2)-setting plays an important role. Finally we s how that this metric is easily linked to approximation and identificat ion. (C) 1997 by John Wiley & Sons, Ltd.