Adaptive robust L2-gain hybrid controller design for a class of uncertain nonlinear systems

In order to deal with the mismatched unknown disturbance and nonparametric uncertainties in nonlinear systems, we propose an adaptive robust L-2-gain hybrid controller for a class of nonlinear systems with uncertainties. Our controller employs a robust L-2-gain control strategy to deal with the unknown disturbance, and a state reference adaptive control algorithm with the nonlinear damp term to eliminate the nouparametric uncertainties in the nonlinear systems. Our new hybrid controller can guarantee robust stability of the close loop control system, and make it have less than or equal to gamma for L-2-gain performance index. Compared with the classical adaptive control procedure, it allows the mismatched unknown disturbance and bounded nonparametric uncertainties in the systems. The robustness of the closed loop system is enhanced. Finally, simulation results are provided to illustrate the correctness and flexibility of the controller.