基于双线性插值控制策略的比例流量阀特性研究

Characteristics of Proportional Flow Valve Based on Bilinear Interpolation Control Strategy

当前液压调速阀通常采用机械式压差补偿器或动态流量器等方式实现输出流量的精确控制,但存在机械结构复杂、通流量小,以及输出流量受负载影响大等不足。提出一种基于双线性插值的流量补偿策略,并将该策略应用到以Valvistor阀为主阀的比例流量阀中,形成具有数字流量补偿功能的比例流量阀,其包括主阀、先导阀、压力传感器和流量补偿器,压力传感器的作用是检测反馈主阀进、出口压力;流量补偿器以主阀进、出口压力和设定流量为输入变量,经双线性插值计算后,流量补偿器输出流量校正控制信号,调节先导阀开口以补偿主阀口压差变化对输出流量的影响,从而实现流量的精确控制。建立该比例流量阀的简化数学模型(不考虑流量补偿器),研究发现输出流量、先导阀输入电压与主阀压差平方根之间存在着线性关系,基于此特征,设计基于双线性插值算法的流量补偿器,并利用仿真和试验对该流量阀的动、静态特性进行研究;结果表明该流量阀输出流量具有良好的静态控制精度且受主阀压差变化的影响较小;若主阀口压差越大,则主阀芯动态响应会越快;对于由负载压力阶跃变化产生的主阀压差而言,若主阀压差越大,则系统流量抗干扰能力随之减弱。

Nowadays, in order to make the outlet flow stable, flow control valves usually adopts mechanical pressure difference compensator or dynamic flow meter to compensate the variations of pressure difference. Its disadvantages are low control precision, complex mechanical structure, small flow capacity and so on. To tackle some of the problems, a two-stage proportional flow control valve based on bilinear interpolation control strategy is presented. The proposed valve is composed of a Valvistor poppet(main stage), a proportional directional valve(pilot stage), a flow compensation controller and two pressure sensors. The pressure drop across the poppet metering orifice are measured by two pressure sensors and fed back into the flow compensation controller. With the help of the bilinear interpolation algorithm, a compensation voltage is calculated from the given flow rate and the measured pressure drop. Then, the compensation voltage is delivered into the pilot stage to regulate the pilot spool. In order to verify the feasibility of the proposed valve, a simulation model is established by means of SimulationX, and a test research is also carried out. Its dynamic and static characteristics are analyzed. Results show that the proposed valve has a good static control performance, and the output flow keeps approximately constant under variable load conditions; in addition, the greater pressure drop across the poppet metering orifice is, the faster the dynamic response of the poppet becomes. Under step response of the load pressure conditions, it indicates that the ability to resist load interference is reduced with the increase of pressure difference.