Robust Tracking Control of Unknown Nonlinear Systems With Discontinuous References Under Output Constraints

This article is concerned with the problem of tracking control with discontinuous references for the strict-feedback systems with both multiplicative and additive nonlinearities as well as unmatched disturbances. In contrast with the existing studies, it is focused on the cases where the system nonlinearities are radially unbounded; the system dynamics or its bounding functions are unknown; and the reference derivatives are unavailable. They significantly challenge the existing control solutions under discontinuous references which are based on filtering, guidance, or impulsive systems. To conquer this obstruction, a novel hybrid control scheme is devised in this article, which consists of a robust constraint-handling controller and a proportional controller. It steers the system output to track the discontinuous reference with tunable setting time and accuracy, without violation of the prescribed constraint. Moreover, the controller exhibits a significant simplicity. While it is independent of the specific model information of the plant or the derivatives of the intermediate control signals, no effort is paid for parameter identification, function approximation, command filtering, or disturbance estimation. Finally, three simulation studies are conducted to substantiate the theoretical result.