Fuzzy dynamic surface control for uncertain nonlinear systems under input saturation via truncated adaptation approach

In this paper, a fuzzy control scheme is presented for uncertain nonlinear systems with input saturation and external disturbance using truncated adaptation and dynamic surface control technique. Fuzzy logic systems are used in the online approximating of uncertain system dynamics, and adaptation laws used to online adjust weights of fuzzy logic system are designed. Auxiliary system is constructed and used to truncate the adaptation laws of fuzzy logic system and disturbance attenuator to prevent aggressive action when input saturation happens. Dynamic surface control technique is incorporated into traditional backstepping design to circumvent the problem of “explosion of complexity” caused by differentiating the so-called virtual controllers during the recursive procedures. It is proved that the proposed controller guarantees the uniformly ultimately boundedness of all signals in the closed-loop system. The steady tracking error and transient tracking error can be adjusted to arbitrarily small by choosing proper design parameters in spite of uncertain dynamics, external disturbance and input saturation. Numerical simulations are presented to demonstrate the effectiveness of the proposed controller.