The robust nonlinear servomechanism problem

We study the asymptotic tracking and disturbance rejection property of a general nonlinear multi-input multi-output distributed servomechanism which consists of input as well as output channel nonlinearity. We also explore the robustness of this property of such nonlinear servomechanism. Our result shows that the design principle of the robust linear servomechanism (i.e. replicating the dynamics of the reference and disturbance signals) works well for a large class of nonlinear servos provided that certain stability conditions are satisfied.