Internal Models for Output Regulation of Nonlinear Systems: History and Applications

This article begins with a brief account of how the notion of the internal model has evolved. It then formalizes an enhanced view of the internal model as a dynamic compenby means of which the output regulation problem is converted into the robust stabilization problem of an invarimanifold of an augmented system composed of the plant and the internal model. This enhanced view enables the adof the output regulation problem for some classes of uncertain nonlinear systems and uncertain exosystems. The article also examines the pivotal role of the internal model in dealing with the cooperative output regulation and the output synchronization for multiagent systems.