Research on backstepping adaptive sliding mode control of digital piezoelectric two-stage proportional valve

Adapting to the development trend of the integration of digitalization, intelligence and electrification technologies in engineering vehicles, a high-frequency response and highly reliable digital piezoelectric two-stage proportional valve (DPPV) is proposed and verified. The structure and working principle of the DPPV are described, and its nonlinear dynamic mathematical model is established. Aiming at the influence of serious nonlinearity, time-varying and unmodeled factors on the displacement control performance of DPPV, A backstepping adaptive sliding mode control strategy is proposed. The simulation model of the DPPV and its controller is constructed by Simulink, and the spool displacement tracking effect of the valve under step and sinusoidal input signals is analyzed. A DPPV test bench is built, and the tracking performance under three sinusoidal conditions (covering different displacement amplitudes and frequencies) is investigated experimentally. The experimental results show that, compared with the traditional PWM control strategy, so the control method reduces at least 12.3%, 40.8% and 37.7% in terms of the maximum, average and standard deviation of the tracking error, respectively. In addition, the control effect of the digital electromagnetic two-stage proportional valve is compared and analyzed. The results show that the maximum error, average error and mean square error of the proposed structure power main spool displacement tracking (racking curve: x = 4.5sin (3πt)) are improved by 64.1 %, 40.35 % and 70 %, respectively, which further verifies its superiority under complex working conditions. This research not only provides a new theoretical basis and design ideas for the development of large flow digital proportional valves, but also expands new direction for the application of digital hydraulic components in wider range of fields.