Robust Optimal Output Regulation for Nonlinear Systems With Unknown Parameters

In this article, a robust optimal output regulation framework for nonlinear systems with unknown parameters is proposed, in which a suboptimal feedforward–feedback controller is designed. Specifically, a novel internal model principle-based feedforward controller is designed to cope with the adverse effects of unknown parameters. Considering the system performance and control cost, an optimal-feedback controller is then designed via the adaptive dynamic programming method. It is proved that under the proposed suboptimal controller, all the signals of the closed-loop systems remain bounded and the tracking error is arbitrarily small. Furthermore, the predefined performance index is minimized. Finally, two simulation examples are given to verify the effectiveness of the proposed framework.