To solve the problem of the control accuracy in electrohydraulic loading systems caused by load increment, this paper proposes a multi-cylinder electrohydraulic digital loading (MEDL) technology for accurate reproduction of large load. A traditionally used single cylinder loading (SCL) is replaced by a new hydraulic cylinders group that includes N hydraulic cylinders at each point, in which one is controlled by the electrohydraulic servo valve and the others (N-1) are controlled by the on-off valve. The areas of the on-off valve controlled (OVC) cylinders form an increasing geometric sequence with a common ratio of 2. In addition, the force of the servo valve controlled (SVC) cylinder can be regulated continuously, and the OVC cylinders have only two states of no force or maximum force. There should be no force tracking error caused by nonlinear factors for the OVC cylinders. Thus, a continuous accurate large loading can be achieved by changing the working area of the cylinders group. Moreover, an improved full closed-loop (FCL) control strategy is proposed to solve the load reverse sudden change caused by the asynchronous opening and closing of the servo valve and on-off valve. With a case of N = 4 for MEDL, AMESim simulation results illustrated that the tracking error of the 4-cylinder group was about 1/6 of the single cylinder under a case of 40 kN. Furthermore, extensive experiments conducted on a real full loading bench under the FCL control method indicated that compared with SCL, the tracking error of the 4-cylinder group with a multi-step signal and various-frequency sinusoidal signals were reduced by 73% and 46%, respectively. Both simulation and experimental results proved that the proposed MEDL technology improved the loading accuracy and optimized the dynamic performance of the system.

为解决由于负荷增加而引起的电液加载系统控制精度问题，提出了一种多缸电液数字加载技术，用于大载荷的精确再现。传统上使用的单缸负载（SCL）被新的液压缸组所取代，该组在每个点上都包含N个液压缸，其中一个由电液伺服阀控制，其他（N-1）由接通液压缸控制。关闭阀门。开关阀控制（OVC）气缸的面积形成一个递增的几何序列，且公共比率为2。此外，伺服阀控制（SVC）气缸的力可以连续调节，并且OVC气缸仅具有无力或最大力的两种状态。对于OVC气缸，不应存在由非线性因素引起的力跟踪误差。因此，可以通过改变气缸组的工作面积来实现连续准确的大负载。此外，提出了一种改进的全闭环（FCL）控制策略，以解决由于伺服阀和开关阀的异步打开和关闭而引起的负载反向突然变化。对于MEDL，在N = 4的情况下，AMESim仿真结果表明，在40 kN的情况下，四缸组的跟踪误差约为单缸的1/6。此外，在FCL控制方法下在实际满载工作台上进行的大量实验表明，与SCL相比，具有多步信号和各种频率正弦信号的4缸组的跟踪误差分别降低了73％和46 ％，分别。仿真和实验结果均表明，所提出的MEDL技术提高了加载精度并优化了系统的动态性能。