Adaptive Fuzzy Tracking Control for a Class of Uncertain Switched Nonlinear Systems with Multiple Constraints: A Small-Gain Approach

This paper deals with the problem of adaptive fuzzy tracking control for a class of uncertain switched nonlinear systems. The considered issues include arbitrary switchings, unmodeled dynamics, input saturation, unknown dead-zone output, dynamic disturbances, and unmeasurable states, which makes the results more applicable. A Nussbaum-type function is exploited in the paper to overcome the difficulty existing in tracking the dead-zone output with unknown control direction. Furthermore, fuzzy logic systems are utilized to approximate the uncertain nonlinear system functions. Also, the state observer is constructed to approximate the unmeasurable states. Then, the adaptive fuzzy tracking controller with only three adaptive laws is presented on the basis of backstepping technique, common Lyapunov function, and small-gain approach. Under the designed controller, all the signals of the switched closed-loop systems are semi-globally, uniformly and ultimately bounded, and the tracking error is driven to a small area of the origin. Finally, simulation results are provided to demonstrate the effectiveness of the proposed control scheme.