Composite fuzzy control of a class of uncertain nonlinear systems with disturbance observer

In this paper, a novel composite control, using fuzzy logic system (FLS) and disturbance observer, is proposed for a class of uncertain nonlinear systems with actuator saturation and external disturbances. FLS is employed to approximate the unknown nonlinearities and a serial–parallel identification model is introduced to construct the composite updating law. The disturbance observer is developed to estimate the unknown compounded disturbance composed of the unknown external disturbance, the unknown fuzzy approximation error and the effect of actuator saturation. The uniformly ultimate boundedness of the closed-loop tracking error can be guaranteed rigorously via Lyapunov stability analysis. Simulation results are presented to demonstrate the effectiveness of the proposed method.