Adaptive fuzzy backstepping control for a class of strict-feedback nonlinear systems with unknown time-delay

In this paper, a new fuzzy adaptive control approach is developed for a class of strict-feedback nonlinear systems with unknown time-delay. Using fuzzy logic systems to approximate the unknown nonlinear functions, a fuzzy adaptive observer is introduced for state estimation. Under the backstepping design, fuzzy adaptive output feedback control is constructed recursively. In addition, the number of on-line adaptive parameters is not more than the order of the considered systems. It is proved that the proposed backstepping design approach guarantees the semi-global boundedness property for all the signals. Finally, Simulation results are provided to show the effectiveness of the proposed approach.