Direct Adaptive Control for a Class of Nonlinear Systems

Although sliding mode control is simple and insensitive to uncertainties and disturbances, control input chattering is the main problem in the sliding mode controller (SMC). In the paper, the fuzzy neural networks sliding mode controller (FNNSMC) is presented firstly for a class of nonlinear systems. The FNNSMC can eliminate the chattering indeed and has more robustness than the SMC. However the tracking error of the FNNSMC is larger than that of the SMC. Since in some cases small tracking error is very important, based on the FNNSMC, a direct adaptive control scheme is presented where the FNNSMC and the sliding mode controller with dead zone (SMCDZ) are incorporated by the smooth transformation. This methodology can eliminate the high frequency chattering efficiently and obtain good tracking behavior. The simulation results demonstrate the advantages of the adaptive scheme