Observer-Based Adaptive Fuzzy Control for Nonstrict-Feedback Systems with Output Constraint

This paper presents an adaptive fuzzy output-feedback control method for a category of nonstrict-feedback systems appearing output constraint. An observer and a barrier Lyapunov function are used to address the problem of un-measurable state variables and output constraint, respectively. For the considered nonlinear system with nonstrict-feedback form, a variable separation technology is introduced. The unknown nonlinear functions in the system are approximated by fuzzy logic systems. Moreover, in the framework of adaptive backstepping control, an adaptive fuzzy control scheme is developed to guarantee all the signals of the resulting closed-loop system to be bounded. Finally, an example is given to validate the effectiveness of the methodology proposed.