Robust Adaptive Fuzzy Controller for Sisoaffine Nonlinear Systems without State Observer

This paper proposes a new output-feedback adaptive fuzzy controller for SISO affine nonlinear systems. The previous output-feed-back control algorithms are all based on the state observer (e.g., higher-order-observer) or additional low-pass filter to make the estimation error dynamics SPR, which makes the stability analysis of the closed-loop system and real implementation very complicated. The distinguished aspect of the proposed output-feedback control algorithm is that no state observer or low-pass filter is employed. Only the output error is used to generate control input and update laws for unknown fuzzy parameters. The stability analysis depends heavily on the universal function approximation property of the fuzzy system to estimate unknown function of the desired control input. It is shown that, combining this simple output feedback control algorithm with fuzzy system, the Lyapunov stability of the closed-loop system is globally guaranteed.