Adaptive output feedback for uncertain nonlinear systems in output feedback form using fuzzy logic systems

In this paper, we consider the tracking control problem of a class of SISO nonlinear systems transformable into uncertain nonlinear systems in output-feedback form using output feedback control. The unknown output functions are approximated by fuzzy logic systems. The unmeasured states are estimated by K-filters. Based on these filters, observer backstepping method is used to design the controller. Nonlinear damping terms are used to counteract the destabilizing effect of the parameter estimation errors and observation estimation errors. The overall closed-loop system can be guaranteed all the signals involved semi-globally uniformly bounded and the tracking errors are proved to converge to a small residual set around the origin.