四象限工况单双泵控差动缸控制性与效率对比

Performance Comparison between Single and Double Pump Controlled Asymmetric Cylinder under Four-quadrant Operation

针对单泵控差动缸闭式系统需要补油单元及在负载方向频繁变化下运行速度波动的问题,提出了一种以液压蓄能器为低压油箱、单伺服电机驱动双定量泵的变转速双泵控差动缸闭式系统及其控制方法。分析了变转速单泵和双泵控差动缸闭式系统在四象限工况下的运行原理。在Matlab/Simulink中建立了液压挖掘机工作装置机构模型、单泵和双泵控差动缸闭式系统模型、速度开环和速度前馈加闭环的控制系统,并对所构建的双泵控差动缸模型进行了局部试验验证。以斗杆速度和铲斗空载为输入,通过仿真对单泵和双泵控缸闭式系统在挖掘机斗杆液压缸四象限工况下的控制性和效率进行了对比分析。结果表明,所提出的采用速度前馈加闭环控制的双泵控差动缸闭式系统,虽然总效率较单泵控差动缸闭式系统降低了4个百分点,但实现了差动缸流量的平衡,解决了由四象限工况造成的速度波动问题,且最大位移误差仅为4 mm,系统及其控制方法对于差动缸的四象限工况运行是切实可行的。

Since the single pump controlled asymmetric cylinder closed circuit demands extra flow compensating unit and its velocity fluctuates during the changes of load directions, an innovative double pump controlled asymmetric cylinder closed circuit system and its control strategy were proposed. The cylinder was directly controlled by double variable speed pumps driven by a servo motor and a low-pressure hydraulic accumulator was adopted as the tank. The operating principles of the single pump and double pump controlled cylinder closed circuit under a four-quadrant operation were analyzed. The mechanical model of the front attachment of a micro-excavator was built, as well as the pump controlled cylinder closed circuit system and the velocity feed-forward open loop and closed loop control strategies. Furthermore, the built hydraulic system of the double pump controlled cylinder was partially validated. The simulation was performed by using this partially validated model, a velocity reference for the stick cylinder and a zero load for the bucket of the front attachment. After the analyses and comparisons of the operating behavior and energy consumption, the results magnified that compared with the single pump controlled cylinder system, although the energy efficiency of the proposed double pump controlled cylinder system was decreased by 4 percentage points, the velocity fluctuation problem caused by the four-quadrant operation was eliminated and the maximum position error of running 0.8 m was only 4 mm. Therefore, the proposed system and its control strategies were effective and feasible for the four-quadrant operation of the asymmetric cylinder.