Robust Indirect Adaptive Control of Time-Varying Plants with Unmodeled Dynamics and Disturbances

Abstract

It is shown that indirect pole-zero placement adaptive controllers are robust for systems with time-varying parameters as well as unmodeled dynamics and disturbances. A parameter estimator with projection is used. No special signal normalization is employed to ensure robustness. The nominal system parameters need only be bounded, and their variations need only be small in an average sense. This allows them to vary slowly with time, as well as to take large jumps occasionally. The adaptive controllers can also simultaneously tolerate small unmodeled dynamics, as well as bounded disturbances, with no restriction on the magnitude of the bound.