Study On The Characteristics Of Electro-Hydraulic Proportional Control Valve Based On The Flow Feedback Principle

Poppet type metering valves have the advantages of low leakage,big flow capacities and simple structure.It has been widely used in all fields of construction machinery.In the last century,Professor Andersson put forward the Valvistor valve,which is widely used in hydraulic systems.Its characteristic is that the displacement of the main valve is a linear amplification of the displacement of pilot valve and the main valve flow is a linear amplification of pilot valve flow.There is a large dead zone and hysteresis in the opening of the valve.Therefore,the control principle of the valve and the design of the controller has important theoretical significance to improve the performance of the valve.According to the real-time design requirement of spool displacement in hydraulic system,a new sensor detecting circuit based on discrete component is designed.Then the paper makes a concrete analysis of sine signal generator and demodulation module and compare it with circuit based on AD698 chip in linearity,hysteresis,step response of output voltage,the characteristic of sine wave and stability aspects.At the same time,in order to control pilot valve,the proportion of the electromagnet drive circuit is designed,the paper make a detailed analysis of the power amplifier circuit and program control strategy.And then proportional amplifier is used in the VT-DFP valve on the experiment,the experiment shows that the amplifier can drive the electromagnet better,while the control accuracy is high,the displacement hysteresis is small,and the working bandwidth is 14 Hz.In the research,the complete mathematical model is established based on the working principle.With the reasonable hypothesis,the model is simplified as a first order linear system.Then the multi-domain model is set up in SimulationX.Experiment platform of Valvistor valve has been set up,and main spool displacement electronic closed-loop control scheme is achieved by the NI controller.The static and dynamic characteristics of the main valve have been studied by using the experiment platform.The steady-state flow and displacement control characteristics of the valve,the steady-state flow and displacement load characteristic curve,the displacement step and the frequency response characteristic curve are obtained.The results show that the closed-loop control of the Valvistor valve can improve the control accuracy and eliminate the dead zone of the valve.The shortcomings of existing pressure-compensated control valve is low accuracy and the instantaneous flow overshoot when load mutation.The motion detection of flow rate is not easy to achieve.In this paper,the principle of neural network compensation is applied to the Valvistor valve,which constitutes the closed-loop proportional velocity regulating valve to realize the precise control of the flow.The Experiment and simulation results show that the new principle flow valve control has high precision.At present,in the electro-hydraulic proportional control technology,the internal feedback valve has complex structure,low control accuracy and difficulties in Processing and manufacturing.To solve these problem,the paper designed the new principle proportional directional valve,and the core idea of the valve is to apply the displacement-flow feedback principle to the three-position four-way valve,which drives the movement of the main stage spool through the drive stage spool to achieve a smaller pressure control main spool movement and the hydraulic system model of the valve is established,then the dynamic and static characteristics of the valve are analyzed.Finally,the influence of the area gradient of the pilot valve and the throttle area gradient on the performance of the main valve is studied.The research shows that the new principle valve has better dynamic and static characteristics.