Output-Feedback Proportional-Integral Fuzzy Control of Unknown Nonlinear Systems With Prescribed Performance

The problem of high-performance tracking control for the nonlinear systems with nonparametric uncertainties as well as time-varying disturbances is investigated in this paper. In place of the methods of sliding-mode control, variable structure control, and robust integral of the sign of the error control, an output- feedback fuzzy prescribed performance control approach is put forward. It consists of a fuzzy state observer, a proportional- integral (PI) constraint-handling scheme, and an adaptive fuzzy backstepping PI control unit. The developed approach achieves output tracking with the predefined settling time and accuracy. Moreover, it actively restrains the oscillations of both the tracking error and the intermediate errors. On the other hand, the compact set condition for fuzzy approximation is rigorously warranted. Besides, the chattering phenomenon and the requirement for differentiable disturbances by the existing methods are excluded. A pair of comparative simulations is performed to demonstrate the efficacy and advantage of our approach.