Prescribed-Time Tracking Control of Electro-Hydraulic Servo Systems with Non-Vanishing Uncertainties

Most of the existing nonlinear control methods for electro-hydraulic servo systems can only ensure the output tracking error to asymptotically converge to zero or an adjustable compact set around zero, which will result in not good enough transient tracking performance. In this paper, a prescribed-time tracking control strategy is proposed for electro-hydraulic servo systems subjected to non-vanishing uncertainties. The nonlinear mathematical model of electrohydraulic servo system with both matched and mismatched uncertainties is firstly established. Then, a prescribed-time controller is designed by introducing a novel finite-time function based on backstepping framework. The closed-loop system stability analysis reveals that the proposed controller guarantees the output tracking error to converge to zero in finite time. Furthermore, the convergence time can be explicitly pre-determined and is independent of initial condition. Comparative simulation results are obtained to verify the high-performance nature of the proposed control method.