Optimization of the Control Performance of a Novel 3/2 Water Proportional Directional Valve With a Special Position Following Servo Mechanism

The 3/2 water proportional directional valve (PDV) is an important hydraulic component to ensure a precise, low impact, and safety control of hydraulic powered roof support, which has been a technical challenge facing to coal mining industry for many years. To address this issue, a new 3/2 water PDV is developed. The valve includes a novel three-core follow-up servo mechanism consisting of three key components: the pilot inlet valve, the pilot outlet valve, and the main inlet spool. This mechanism enables precise and reliable opening, and closing capacity of the valve. The prototype is manufactured and the performance test is conducted to improve the control performance of the new water PDV. During the test, two significant discoveries are made. First, it is determined that the control chamber of the main inlet spool must be in the predischarge state at the initial time to ensure adequate closing capacity of the new valve during the returning process. Second, it is found that the continuous small-step control mode can better cope with the friction and is more effective in achieving quick and smooth following characteristics of the three valve cores in the opening process, compared with the ramp control mode.