Output feedback robust H∞ control for a class of nonlinear systems with input unmodeled dynamics

The problem of output feedback robust H_∞ control is considered for a family of nonlinear systems with dynamic uncertainties at the input of the plant. By introducing a high-gain observer with tow design parameters, a robust output feedback controller is explicitly constructed. The proposed controllers attenuate the disturbance´s effect on the output of the closed-loop system to an arbitrary degree of accuracy in the L₂-gain sense, and achieve global asymptotic stability in the absence of disturbance.