Modeling and analysis of the electro-hydraulic proportional valve controlled motor system supplied by variable pressure accumulator

In recent years, the electro-hydraulic control system, which takes accumulator as the energy storage and oil supplying component, has been preliminary applied in hybrid electric vehicles, energy collection and power systems. Different from traditional electro-hydraulic control systems, the imported oil pressure of electro-hydraulic control system which is supplied by accumulator will decline over time. So it is not a constant value. This phenomenon has additional interference with the load control, especially for electro-hydraulic control systems which has a requirement for a constant speed. So firstly an electro-hydraulic valve controlled motor system with variable pressure accumulators for supply hydraulic oil is designed, in which the electro-hydraulic proportional valve control hydraulic motor is needed to drive an AC or DC generator with constant speed rotation and power. Secondly the mathematic model of this system supplied by variable pressure accumulator is built. Then the corresponding system transfer function is deduced. And the static and dynamic characteristics of system are analyzed in theory. Thirdly, based on a combination of Matlab / Simulink and AMESim, the simulation models of the studied system are built, which are focused on the simulation analysis. Fourthly, a method with a combination of real time feedback of output pressure of accumulators and PID control is presented in this paper. Its corresponding control system simulation is completed. Finally, the experiment prototype is made. The theoretical analysis, simulation and the experimental results show that the mathematic model and the transfer function of the system are correct and effective. The performance of the new control method is better than that of the traditional PID control method.