基于变转速控制的负载敏感系统研究

传统的纯电驱动工程机械利用电机来模拟发动机的功能，没有燃油消耗和污染排放，符合目前节能减排的趋势，但电机调速性能和过载能力未得到充分利用；另外，动力总成发生了变化，但相应的控制策略没有充分考虑液压系统的工作特点而进行有效的优化和完善，因此，整机的动力性、节能性、操控性和安全性等均有待提高。为进一步降低能耗，提高纯电驱动工程机械的效率，提出一种基于变转速控制的定量泵负载敏感系统，并针对定压差不能满足工程机械在复杂工况下的高效性问题，提出一种变压差控制策略，使系统在不同工况下进一步满足对动态响应或节能性的需求。建立了该负载敏感系统变压差控制的仿真模型，并在某8 t纯电驱动挖掘机上对所提出的控制策略进行测试。结果表明：系统压差与先导压力变化一致，仅与操纵阀杆的位移有关，而与负载压力的变化无关。在复合运动需要大流量时可通过操作手柄使先导压力增大，实现大范围无流量饱和功能，且在整个过程中流量变化曲线平滑，整机运行无抖动现象，具有较好的操控性；在压差为1 MPa时消耗的能量仅为压差3 MPa时的2/3；在低速需要小流量时，通过操作手柄保证系统压差处于较低水平，从而降低了系统的压力损耗，提高了系统的节能性。所提出的变转速控制负载敏感系统变压差控制策略能有效降低能耗，提高系统的操控性。

Load Sensitive System Based on Variable Speed Control

Traditional pure electric drive construction machinery uses a motor to simulate the engine function. There is no fuel consumption or emissions, that is in line with the current trend of energy conservation and emissions reduction. However, this system does not make full use of the motor's speed regulation performance and strong overload capacity. In addition, although the powertrain in these designs has been changed, the control strategy has not been optimized and improved effectively considering the working characteristics of the hydraulic system. Therefore, the whole machine performance, including power, energy-saving, controllability, and safety still requires improvement. To reduce the energy consumption and improve the efficiency of pure electric drive construction machinery, a load-sensitive system, which uses a quantitative pump controlled by variable speed, is proposed. To solve the inability of the constant pressure differential to satisfy the high-efficiency requirements of construction machinery under complex working conditions, a variable-pressure differential control strategy is proposed. This system can achieve a higher dynamic response and energy-saving effects under different working conditions. A simulation model of the proposed load-sensitive system based on variable speed control was established and the proposed control strategy was tested on an 8 t pure electric drive excavator. The results show that the pressure differential of the system is consistent with the change of the pilot pressure. This is because it relates to the displacement of the joystick and has nothing to do with the load-pressure change. When compound movements require large flow, operating the joystick increases the pilot pressure to achieve a wide range of non-flow saturation functions. Furthermore, the flow change curve was smooth during the whole process and the entire machine ran without vibration. The proposed control system can achieve good control performance. Also, the energy consumption at a differential pressure of 1 MPa is only 2/3 of that at a differential pressure of 3 MPa. At low-speed conditions, which require a low flow rate, reducing the pressure difference of the system can effectively reduce the pressure loss and improve the energy conservation of the system. The proposed variable pressure-differential control strategy of the load-sensitive system with variable speed control can effectively reduce the energy consumption and improve the control performance of the system.