Abstract:  The positioning control of hydraulic support pushing system in fully mechanized mining face is the key technical support to realize intelligent mining. The opening and closing of the existing support switch reversing valve will cause sudden change of system pressure and flow under the condition of high pressure and large flow, which will affect the life of components, the precision and stability of the actuator movement. To solve the problem, the structure of two-speed buffer valve for hydraulic support pushing circuit was designed. Firstly, through theoretical research on the pushing system and the two-speed buffer valve, the pressure characteristics during the start-up and operation of the system after adding the two-speed buffer valve were analyzed. Then, the valve and hydraulic circuit were modeled by SimulationX to analyze the influence of key parameters on valve pressure drop and speed of hydraulic execution system. Finally, an experimental platform was built to study the pressure characteristics of double valve series pushing system under different pressure flow of liquid supply. The research results show that when the two-speed buffer valve is used, the pressure and velocity change thresholds of the system are reduced, which reduces the pressure fluctuation in front of the valve and its effect on the system pressure. At the same time, under different system pressure and flow, the downstream pressure characteristics of the valve are improved, the steady-state pressure anti-interference is enhanced. Therefore, the effectiveness of the scheme is verified, and the basis is provided for the optimization of the downhole valve control cylinder scheme and the subsequent valve.
Key words:  on-off reversing valve; hydraulic support pushing system; double valves in series; two-speed buffer valve; buffer performance; pressure response characteristics; SimulationX