Modeling and dynamic characteristics analysis on a three-stage fast-response and large-flow directional valve

The large transient power hydraulic systems, characterized by high pressure, large transient flow and high output power, have widespread industrial applications in converting powerful hydraulic energy to kinetic energy in a transient period. A conventional large flow rate directional valve is unable to be used in these applications due to the slow response. A directional control valve with fast response and high flow capacity simultaneously is presented for the large transient power hydraulic system in this paper. The valve utilizes a three-stage structure with two high-speed on/off solenoid valves as the pilot stage and two cartridge poppet valves as the secondary stage to overcome the fundamental trade off between valve response and flow capacity. A precise mathematical model of this valve considering both turbulent flow and laminar flow is developed. A test apparatus which has the ability to provide and measure transient large flow is built. The flow rate is estimated based on the pressure dynamics. The property parameters in the simulation model are optimized against measured data. According to the dynamic characteristics analysis, the valve response is split into the starting delay and opening time. The step response is rapid enough to provide a large transient flow, while the high flow capacity is not reduced due to the fast response. The main control pressure is characterized by its change time and critical open pressure and these two parameters determine the main-stage response. Some key structural factors concerning with these two parameters are discussed in detail and optimize to further reduce the response time.