Valve-pump parallel control of hydraulic motor speed servos with large power

This study proposes both replenishing type and leaking type valve-pump parallel controlled systems, and then establishes their mathematical principle models and simulated numerical models. Comparative analysis of performances and parameters of the pump controlled system and valve-pump parallel controlled system indicate that the proposed systems can respond faster with high efficiency than the pump controlled systems, just because the valve responds more rapidly than the variable pump and works at low flow status; total leakage coefficients and damping ratios of the proposed system are large and vary widely with the valve opening and load pressure. When suffering disturbance of variable loads, the replenishing type system has more stable damping ratios and speed stiffness compared with the leaking type system. In addition, it can further improve response and speed stiffness by raising the supply pressure of the controlled valve, while the leaking type system does not have this flexibility. Therefore, the replenishing type valve-pump parallel control is more suitable for hydraulic speed servo systems with large power to achieve rapid response and good speed stiffness with high efficiency.