Adaptive Switching Control Strategy and Structural Optimization of a Pump-Valve Compound Hydraulic Circuit

For a hydraulic ship lifting system, heavy load systems, such as the multi-degree-freedom test platform, hydraulic cylinder control systems with long-stroke, etc., not only need high control performance requirements but also require high efficiency in energy conservation. According to the high performance of the valve control circuit and the high efficiency characteristics of the pump control circuit, this paper proposes a new circuit design that drives the valve control open circuit and pump control closed circuit in a parallel way, and the corresponding three-stage adaptive control strategy is given. The feasibility of the proposed control method is verified through simulations. The simulation results demonstrate that the new circuit system has the abilities of fast responding, high precision, and high efficiency. The problem that only one chamber of the hydraulic cylinder is preloaded in the direct pump-controlled working process can be resolved using the new proposed circuit. The natural frequency and load rigidity of the circuit system are enhanced, and the problem of circuit coupling is also greatly improved. Compared with different control strategies, the performance of the proposed method is superior under load disturbance.