Dynamic performance and control accuracy of a novel proportional valve with a switching technology-controlled pilot stage

Abstract

Two-stage directional valves usually employ proportional pilot control technology, which has the disadvantages of dead zones, leakage, and the large moving mass of the pilot valve. It is difficult, therefore, to achieve fast-response performance of the main valve. In order to overcome this problem, a switching pilot technology that employs two independent high-speed on/off valves (HSVs) is proposed to replace the traditional pilot proportional valve. Due to the rapid switching characteristics of HSVs, the dead zone of the pilot stage is avoided, and the dynamic response performance of the main valve is improved. The experiments indicate that the switching frequency of the pilot HSVs and supply pressure of the pilot stage have a very large effect on the dynamic performance and control accuracy of the main valve. Increasing the switching frequency of the pilot HSVs is helpful for improving main-valve control accuracy. The larger supply pressure of the pilot stage can achieve a faster dynamic performance of the main valve while causing larger static errors. The results show that the switching pilot technology can clearly improve the static and dynamic performances of the main valve. With the increase of pilot supply pressure, the step rise time is reduced from 21.4 ms to 16.8 ms, and the dynamic performance of the main valve is improved by 21.5%. With the increase of pilot switching frequency, the steady-state error decreases from 24 µm to 20 µm, and the control accuracy of the main valve is improved by 16.7%.

概要

目的:两级换向阀通常采用比例先导控制技术,其缺点是存在死区、泄漏和先导阀运动质量大等问题,难以保证主阀的快速响应性能。因此,本文旨在提出一种采用两个独立高速开关阀的切换先导技术替代传统的先导比例阀,以提高主阀的动静态性能。 创新点:1. 设计一种以高速开关阀组为先导桥路的新型两级液压阀;2. 设计基于分段式比例积分微分(PID)的主阀芯位移控制算法;3. 运用切换先导技术,明显改善主阀的动静态性能。 方法:1. 通过理论分析研究先导级供油压力(公式(16)和(17))和高速开关阀驱动频率(公式(19)和(20))对主阀动静态性能的影响;2. 在先导级采用自适应供油压力驱动算法(图7),而在主级采用分段式PID主阀芯位移控制算法(图10);3. 通过实验分析,验证本文提出的切换先导技术的控制效果(图12~15)。 结论:1. 通过理论分析和实验论证,证明了切换先导技术方案的可行性;2. 先导级供油压力和高速开关阀驱动频率对主阀动态性能和控制精度有很大影响。3. 通过增大先导级供油压力,可以提高主阀21.5%的快速响应性能,但同时会造成较大的稳态误差。4. 通过增加高速开关阀的驱动频率,可以将主阀的稳态误差控制在20 μm内,并提高16.7%的静态性能。