Output tracking control of nonlinear nonminimum phase systems

This paper investigates an extremely important and challenging problem in nonlinear control: output tracking control of nonminimum phase nonlinear systems. Not only does the controller provide stable asymptotic tracking, it also ensures that the transient error will be within a prespecified bound. This is achieved by using a novel approach of stable inversion. In this approach, the nonminimum phase system is first stably inverted off-line to obtain desired (and stable) state and input trajectories that map exactly into the desired output trajectory. Then a feedback controller is designed to stabilize the closed-loop system and to ensure robustness to certain types of uncertainties. The procedures developed may be applied to many important engineering problems, such as aircraft control, rocket control, medical equipment, nondestructive evaluation, and so on