Design and Dynamic Characteristics Measurement of a Water Hydraulic Proportional Flow Valve With a Discrete Pilot Stage

The accurate control of hydraulic support movement in coal mining remains a significant technical challenge due to the limitations of the existing electrohydraulic directional valves, which are typically on/off valves without proportional control function. To address this issue, a high-pressure, large-flow water hydraulic proportional flow valve piloted by two high-speed on/off valves (HSVs) is proposed. The main valve spool employs a symmetrical cylinder-type cone structure, featuring a nonfull-circle U-shaped valve port. The transfer function of the flow valve is derived based on Laplace transformation, and the impact of discrete pulse flow output from the HSVs on main valve displacement fluctuations is theoretically calculated. The influence of the key structural parameters and control parameters on the main valve dynamic characteristics is also simulated. Finally, a prototype of the flow valve is developed, and a semi-physical simulation testing rig using MATLAB/xPC Target is constructed. The experimental results demonstrate that the flow valve exhibits favorable dynamic and static characteristics, with the step rise time of 0.3 s and the steady-state error of 0.18 mm. The amplitude-frequency experiments reveal that the proposed flow valve achieves a frequency response of no less than 2 Hz at 100% full scale. The proposed flow valve is not limited to coal mining applications, and it is suitable for use in high-temperature and high-pressure heavy machinery equipment operating.