Adaptive Asymptotic Tracking Control of Valve-Controlled Hydraulic Servo Systems with Input Constraint

Valve-controlled hydraulic servo systems have been broadly utilized in applications requiring fast response and high power, where input constraints represent one of the major limitations on control performance. To tackle this problem, this study proposes an adaptive asymptotic tracking control method considering input constraints. First, a nonlinear mathematical model of the valve-controlled hydraulic servo system is established and transformed into an integrator form to facilitate controller derivation. Second, a tracking controller is designed based on the robust integral of the sign of the error (RISE) method, and an adaptive law for the robust gain is developed. This method not only realizes asymptotic tracking but also guarantees that the control input magnitude remains within the prescribed bounds. The controller stability is rigorously analyzed via Lyapunov theory. Finally, the validity of the proposed control method is confirmed by comparative simulations. The results show that the amplitude of the control input can be effectively limited, and the tracking accuracy is further improved.