Robustness of high-gain observer-based nonlinear controllers to unmodeled actuators and sensors

Abstract

We investigate the robust stabilization of a class of nonlinear systems in the presence of unmodeled actuator and sensor dynamics. We show that, given any globally bounded stabilizing state-feedback control, the closed-loop system performance can be recovered by a sufficiently fast high-gain observer in the presence of sufficiently fast actuator and sensor dynamics. The performance recovery includes recovery of exponential stability of the origin, the region of attraction and state trajectories. Moreover, it is shown that the sensor dynamics should be sufficiently faster than the observer dynamics; a restriction that does not apply to the actuator dynamics. � 2001 Elsevier Science Ltd. All rights reserved.