Study on Structure Optimization of a Load Port-independent Double-spool Electro-hydraulic Valve

To improve the dynamic characteristics of an electro-hydraulic valve system with an independent double-valve core at the load port, this study derives the system state space equation of the main stage closed-loop system, including the structural characteristics of a pressure-reducing valve, a relief valve, a system pipeline, and a cavity based on the power bond diagram theory. The influence of the listed structural parameters on the dynamic characteristics of the main valve’s position is analyzed by the first-order sensitivity method. Since the pilot stage structural parameters of a feedback control system are crucial to the main valve’s motion characteristics, the influence of a different pilot valve’s port structural characteristics on the electro-hydraulic valve system’s characteristics is also studied. The matching performance, linearity, and control sensitivity are used as optimization objectives, the no-self-excited oscillation is set as a constraint condition, and a pilot valve’s structural parameters are self-optimized. The representative structural parameters are used for sensitivity analysis and test verification. Based on the PIV test, similar tests are conducted for different pilot valve port forms, and the pilot valve’s port structural parameters are tested both before and after parameter optimization. The theoretical and experimental results show that the factors that have a significant influence on the main valve's fretting characteristics include the closed-loop proportional gain, the main valve core friction, the spring preload force, and the liquid capacity of the non-spring control chamber. When the pilot valve’s port is U-shaped, the linearity of the flow gain, control sensitivity, and the fretting characteristics of the main valve are significantly improved.