Observer-based fuzzy adaptive robust control of nonlinear systems with time delays and unmodeled dynamics

In this paper, an adaptive fuzzy output feedback backstepping control approach is developed for a class of nonlinear time-delay systems with unmeasured states and unmodeled dynamics. Using fuzzy logic systems to approximate unknown nonlinear functions, a fuzzy state observer is designed for estimating the unmeasured states. By combining adaptive backstepping technique with adaptive fuzzy control design and using changing supplying function idea, an observer-based adaptive fuzzy backstepping control approach is developed. It is proved that the proposed adaptive fuzzy control approach is able to guarantee that all the signals in the closed-loop system are semiglobally uniformly ultimately bounded (SUUB) and the output of the controlled system converges to a small neighborhood of the origin. Simulation results are provided to show the effectiveness of the proposed approach.