直动式机载2D电液压力伺服阀特性

设计了一种直动式二维(Two Dimensional,2D)电液压力伺服阀,采用2D伺服活塞机构产生液压力来驱动主阀芯运动,输出需要的负载压力。设计的2D伺服活塞机构采用直线位移传感器(Linear Variable Differential Transformer,LVDT)进行检测从而形成闭环位置反馈,精确控制2D活塞位移;主阀芯与2D伺服活塞通过弹簧连接,2D活塞在两侧压力差作用下运动,通过弹簧来对主阀芯施加作用,控制主阀阀口的开度,来精确控制输出的负载压力;为提高压力伺服阀的稳定性和可靠性,主阀阀芯根据挤压油膜缓冲理论进行了圆盘结构设计,以增大系统黏性阻尼。在建立该阀的数学模型的基础上,仿真分析了该阀的静动态特性,并通过设计样阀及实验研究,验证了该阀设计的可行性,实验结果表明:在系统压力28 MPa下,该阀的阶跃响应时间在30ms,其滞环3%,线性度2%,压力跟随特性和输出稳定性好;相较于传统直动式比例伺服压力阀,该阀的结构特点决定了其抗污染能力强,可靠性高,且质量和体积分别仅为同类伺服阀的1/5和1/7左右,非常适用于机载液压刹车系统。

Characteristics of direct-acting airborne 2D electro-hydraulic pressure servo valve

A direct-acting Two Dimensional (2D) electro-hydraulic servo valve is designed ,in which the main spool is driv-en by the 2D servo piston mechanism to get the load pressure as required .Linear Variable Differential Transformer (LVDT) is used for testing and forming closed loop position feedback .The displacement of piston can be controlled precisely using closed-loop feedback .The opening degree of the main spool connecting to the piston with a spring is changed by the force of the spring produced by the movement of the piston under the pressure difference on both sides to control the load pressure as accurately as possible .Based on the theory of squeeze oil film ,a disc structure is applied to the main spool to increase the damping ratio and to improve the stability and reliability of the system .Static and dynamic characteristics are analyzed by simulating the mathematical model of the valve ,and the feasibility of the prototype is verified in the experiment .The results demonstrate good characteristics of voltage follower and stable output ,with the step response time being 30 ms ,the hyster-esis less than 3% ,and the linearity less than 2% ,when the system pressure is 28 MPa .Compared with traditional direct-acting proportional servo valve ,the valve has the advantages of strong anti-pollution ,high reliability ,light weight and small volume (about 1/5 in mass and 1/7 in volume of the same kind of servo valve) ,and is very suitable for the airborne hydrau-lic braking system .