High Precision Motion Control for High-Speed on/off Valves-Controlled System

The high-frequency discrete pressure pulses generated by the high-speed onloff valve (HSV) exacerbate the parameter uncertainty and uncertain nonlinearity of the HSV s-controlled system, resulting in poor tracking performance and robustness of the system. To improve the control accuracy of the HSV s-controlled system, the nonlinear mathematical model is established in this paper. Based on the backstepping method, a nonlinear adaptive robust controller is designed to reduce the parameter uncertainty in the model, and to suppress the effects of parameter estimation error and uncertain nonlinear terms. Furthermore, the online parameter estimation is guaranteed to be bounded by discontinuous projection mapping. The stability of the closed-loop system is analyzed by Lyapunov theory, and the compound control of velocity and pressure is realized on hydraulic cylinder. Results show that when tracking a sinusoidal signal with an amplitude of 20mm/s and a frequency of 0.5Hz, the average tracking error and its standard deviation are 1.1 mm/s and 0.9 mm/s, respectively. Compared with the traditional PID algorithm, the average tracking errors of the sinusoidal trajectory and smooth square trajectory are decreased by 61.45% and 73.15% respectively, while the steady tracking accuracy is enhanced by 63.49%, thus achieving higher precision motion control for HSV s-controlled system.