高压阀口液动力补偿控制策略仿真分析

Simulation Analysis of Fluid Force Compensation Control Strategy for High Pressure Valve Port

直动式比例伺服阀是一种新型的单级伺服阀,采用比例电磁铁或线性力马达直接驱动滑阀运动,具有成本低、频响高、抗污染能力强等优点,广泛应用于注塑机进给控制、轧机板厚控制系统等高速高精度液压控制系统中。传统的直动式比例伺服阀采用PID控制策略实现阀芯的精确位置控制,在高压大流量工况下(供油压力达到20 MPa、流量大于100 L/min),阀芯受到液动力扰动变得更加剧烈,易出现响应速度慢、阀芯抖动的现象,影响了比例伺服阀的控制精度。为了解决大液动力扰动的问题,提出了一种基于指数收敛干扰观测器的滑模控制器。通过建立阀芯动力学模型来设计滑模控制器,保证阀芯位置的高动态跟踪性能;使用基于指数收敛的干扰观测器,估计阀芯动力学模型中液动力的不确定性扰动,解决高压大流量工况下的阀芯液动力扰动补偿问题。搭建了比例伺服阀系统的联合仿真模型进行仿真验证,结果表明,提出的控制器可以解决高压大流量工况下阀芯液动力扰动对阀芯位置控制的干扰问题。

Direct proportional servo valve is a new type of single-stage servo valve,which uses proportional solenoid or linear force motor to drive the spool valve directly.Because it has the advantages of low cost,high frequency response and strong anti-pollution ability,it is widely used in high-speed and high-precision hydraulic control systems,such as feed control of injection molding machine and plate thickness control system of rolling mill.Traditional direct proportional servo valve adopts PID control strategy to achieve precise spool position control.However,under the condition of high pressure(20 MPa)and large flow(100 L/min),the flow force disturbance of the valve spool becomes more and more serious,which leads to slow response speed,spool dither and it cannot meet the high-precision control requirements of the proportional servo valve.In order to solve the problem of worsening flow force disturbance,a sliding mode controller based on exponential convergent disturbance observer is proposed in this paper.The sliding mode controller is designed by establishing spool dynamic model to ensure high dynamic tracking performance of the spool position.The disturbance observer based on exponential convergence is used to estimate the uncertain disturbance of flow force in the spool dynamic model and to compensate spool flow force disturbance under high pressure and large flow conditions.A co-simulation model of direct proportional servo valve system is built for simulation verification.The simulation results show that the proposed controller can solve the interference problem of spool flow force disturbance on spool position control under high pressure and large flow conditions.