Abstract: In order to solve the hyper pressure problem in the proportional valve controlled asymmetric cylinder system, nonlinear state equations model and bond graph model are built to analyze the system performance influenced by the nonlinear factor of the different valve port overlap value, which is caused by the machining error. These two models are used to analyze the pressure properties of a practical asymmetric valve controlled asymmetric cylinder system. The comparison of the outcomes between simulation and experiment proves the correctness of these two models. The simulation and experiment indicate that the valve port error in the proportional valve controlled asymmetric cylinder system, which is the prime reason of the pressure on the rod side exceeding the pressure of hydraulic power supply, has great influence on the system performance. The relation between the valve port error and hyper pressure in the system, which is derived from lots of simula-tions, indicates that improving the valve port machining preci-sion of the proportional valve is favorable to avoid the hyper pressure and improve the system performance. It’s suggested that the valve port error of proportional valve should be within 0.5 percent of the maximum valve displacement. The two non-linear mathematic models presented are universal, which can be used on various valve controlled cylinder systems to simulate, design and research the control strategy.

Key words: Bond graph model, Hyper pressure, Nonlinear state equations model, Valve controlled cylinder system, Valve port error