Direct adaptive fuzzy control with compressors and limiters for a class of uncertain nonlinear systems

This paper proposes a novel direct robust adaptive fuzzy output tracking control schemes for a class of uncertain nonlinear systems with external disturbance. The adaptive fuzzy controller is based on the definition of compressor and limiter with adjustable parameters, then a controller with updated laws of the parameters of the compressor and estimate values of the fuzzy approximation accuracies is designed to track a given reference signal. The main contribution of the proposed method is that the logic structure of the fuzzy logic system can be neglected, which only focus on the parameters of the compressor, limiter and the fuzzy approximation accuracies. The adaptive fuzzy control method in this paper has no relation to the number of on-line updated parameters, so this design method suited to various types of fuzzy logic systems with fuzzy rules or without any rules. So that convergence to zero of tracking errors and uniformly ultimately bounded (UUB) of all the signals in the closed-loop system can be guaranteed. Finally, the simulation result demonstrates the fuzzy control can guarantee the system stability and also maintain a good tracking performance.