Improved perturbation bounds for the continuous-time [H.sub.[infinity]]-control problem

New local perturbation bounds for the continuous-time [H.sub.[infinity]]-control problem are obtained, which are nonlinear functions of the data perturbations and are tighter than the existing condition number-based local bounds. These nonlinear local bounds are then incorporated into nonlocal perturbation bounds which are less conservative than the existing nonlocal perturbation estimates for the [H.sub.[infinity]]-control problem. Key words. [H.sub.[infinity]]-control, perturbation analysis, Riccati equations