Approximation-Free Control for Unknown Systems With Performance and Input Constraints

This article addresses the problem of tracking control for an unknown nonlinear system with time-varying bounded disturbance subjected to prescribed performance and input constraints (PIC). Since the simultaneous prescription of PIC involves a tradeoff, we propose an analytical feasibility condition to prescribe a feasible PIC, which also results in a feasible initial state set as a corollary. In addition, we propose an approximation-free controller to ensure the tracking performance meets the prescribed PIC. The effectiveness of the proposed approach is demonstrated through numerical examples.