Adaptive Fuzzy Control With Prescribed Performance for Block-Triangular-Structured Nonlinear Systems

In this paper, an adaptive fuzzy control method with prescribed performance is proposed for multi-input and multioutput block-triangular-structured nonlinear systems with immeasurable states. Fuzzy logic systems are adopted to identify the unknown nonlinear system functions. Adaptive fuzzy state observers are designed to solve the problem of unmeasured states, and a new observer-based output-feedback control scheme is developed based on adaptive fuzzy control principle and bacsktepping design technique. The proposed control method not only overcomes the problem of "explosion of complexity" existing in the backstepping design, but also removes the restrictive assumption that unknown nonlinear functions must satisfy global Lipschitz condition. The proposed scheme can ensure that all variables of the control systems are semiglobally uniformly ultimately bounded and the tracking errors converge to a small residual set with the prescribed performance bound. Simulation results of chemical process control system are presented to further demonstrate the effectiveness of the proposed control strategy.