Experimental investigation on the spool displacement response of the PWM driven electro-hydraulic proportional valve

The digital direct drive circuit controlled by PWM signal is a key control component for the electro-hydraulic proportional valve, the driving performance of which is a significant factor of proportional/servo hydraulic system. In order to clarify the displacement response characteristic of proportional directional valve spool, PWM driving test experiments for electro-hydraulic proportional valve spool were carried out. Firstly, a PWM drive test platform of proportional directional valve is developed based on the traditional diode natural continuous flow drive circuit, which can realize programmable output of PWM drive voltage, real-time data acquisition, data display and data preservation. Secondly, the displacement response tests of proportional-valve spool under step PWM signal, various-frequencies PWM signals, various-duty-cycles PWM signals and various PWM voltages were carried out. The influence of PWM parameters on the spool displacement response was analyzed. Experiment results show that the spool displacement of proportional valve can quickly respond under step PWM signal; the flutter phenomenon of spool is more serve under lower frequency PWM signal; as the frequency of PWM signal increases, the stability of spool in-creases but the response hysteresis become serve; the spool displacement of proportional valve can be continuously controlled by adjusting the duty cycle of the PWM signals; the spool displacement-duty cycle factor is larger under larger PWM voltage. The research results of this paper will provide theoretical and data basis for the design, control and application of proportional valve PWM drive circuit.