Energy Saving Motion Control of Independent Metering Valves and Pump Combined Hydraulic System

The independent meter-in and meter-out valves control approach makes the two chamber pressures of the hydraulic actuator completely controllable, and offers possibilities for energy conservation. However, the entire flow rate is throttling controlled by the metering valves, which leads to the essential difficulty to realize the high level of energy efficiency further. On the other hand, although the direct pump controlled system might be an option with high energy efficiency, the poor dynamic response, and complicated controller design restrict its applications in precise motion occasions. To further improve the energy efficiency as well as guarantee the high precision position tracking performance, a novel hardware configuration that combines the independent metering valves and the direct pump control method is proposed in this paper, which is essentially different from our previous works and other independent metering research works. The motion control of the single-DOF cylinder actuator is studied to verify the effectiveness and advantages of the proposed system. During the tracking process, the pump is controlled by the reference velocity feedforward method and provides the majority amount of the flow rate without throttling losses, while the rest amount is accurately controlled by the independent metering valves in the closed loop for high precision tracking. Since the hydraulic system is highly nonlinear with uncertainties and disturbances, the high-performance adaptive robust control approach is applied in the closed-loop controller. Besides, the mode selection method and the flow distribution law are involved to deal with the enhanced flexibilities brought by the proposed configuration.Comparative experiments are carried out and the results show the proposed combined hydraulic system achieves the same level of position tracking precision as the independent metering system with less than a half of total energy consumption.