Research On The Characteristc Of Proportional Flow Amplifying Valve Based On Pilot Digital Control

Digital hydraulic system is believed to be a development direction which is different from the existing analog hydraulic system, because it has advantages of high reliability, strong robustness, good repeatability, strong ability to resist pollution, convenient interface with computer, and it can also realize high precision control without sensors. As a key element, the application range of digital hydraulic valve is limited because of the small control flow and the discontinuous output. To solve the problem, this paper present a two-stage digital proportional flow valve, whose pilot stage is small flow digital valve and main stage is cartridge valve based on flow amplifying principle. The pilot digital control and continuous flow can be realized, and the problem of small flow can be effectively solved.Firstly, the performance of pilot digital valve- high-speed switching valve is studied. The dynamic equation is set up when the high-speed on-off valve is opening and closing, and the driving characteristics is analyzed. Furthermore, the single power supply and double voltage driving control circuit are designed based on MCU. And performance test platform is set up based on HSV high-speed on-off valve, then the dynamic and static characteristics are studied, and the influence of control parameters on the performance is analyzed. The results show that: 1.dynamic performance: In the opening phase, for the effect of high voltage, the response time have little difference when pressure difference is different; In the maintenance phase, the valve power consumption significantly reduced under the action of low driving voltage; In the closing stage, the residual magnetism in coil is reduced by the low voltage of the maintenance phase, and the voltage-regulator tube unloading circuits make it unload rapid ly, so the closing time is also shorten, but response time is more sensitive to change of differential pressure. 2. Static performance: with the increase of the pressure difference and the decrease of control frequency, the dead zone and saturated zone is decreased, and the linear control region is increased gradually.Secondly, the proportional flow amplifying valve based on pilot digital control is studied. The theoretical derivation and simulation model in SimulationX is set up about proportional throttle valve and compensated flow control valve. Then the influence of structure and control parameters on static and wave characteristics is analyzed. The results show that the proportional control of the flow valve can be implemented through the duty ratio of pilot digital valve control s ignal, but when the duty ratio is different, flow magnification of the main valve to pilot flow is different, and the greater the duty ratio, the larger the magnification; Flow fluctuation caused by the pilot digital switching valve can be reduced by increasing control cavity volume and the control signal frequency, and flow rate fluctuation is maximum when the duty ratio is 50%; For the compensated flow valve, the pre-opening has a great influence on the accuracy of the valve for the limitation of its structure, and the precision will be lower when opening displacement is bigger.Finally, the experimental platform of proportional throttle valve based on pilot digital control is set up, and the dynamic and static characteristics is studied through experiment, and the feas ibility of the valve results is verified; the proportional control for the flow of main valve can be achieved by changing the duty ratio of the control signal.