Adaptive Fuzzy Dynamic Surface Control for a Class of Nonlinear Systems with Unknown Time-delays

In this paper,adaptive fuzzy dynamic surface control(DSC) is presented for a class of strict-feedback nonlinear systems with unknown time-delays and control directions.By incorporating DSC design technique and a novel Lyapunov-Krasovskii function into adaptive fuzzy control design framework,the proposed control system can overcome not only the problem of "explosion of complexity" inherent in the backstepping design methods but also the unknown time-delays.The control singularity problem and unknown signs of the virtual control coefficients are well solved by using Nussbaum gain function(NGF).The proposed controller guarantees the semiglobal boundedness of all states and signals in the closed-loop system,with an arbitrary small tracking error by appropriately choosing design constants.Simulation results are given to demonstrate the effectiveness of the proposed scheme.