Internal model principle and robust control of nonlinear systems

A dynamic compensator is constructed to achieve asymptotic tracking and disturbance rejection for a class of nonlinear systems in the presence of certain plant uncertainties. The key component of this compensator is the k^th-order robust control law introduced by the authors (1994), which features what is called the internal model principle in the linear literature. The result extends the robust linear servomechanism or structurally stable output regulation theory to nonlinear setting