Research On Characteristics Of The Hydraulic Power System With Inverter-driven Induction Motor And Variable Displacement Piston Pump

Variable speed hydraulic technology has the advantages of wide speed range and high efficiency, so it is widely used in injection molding machine, hydraulic lifts and other fields, but variable speed hydraulic system have some faults, including respond slow and poor stability, which restrict the application of variable speed hydraulic technology. In view of the above problems, this paper combines the advantages of variable speed and variable displacement volume speed control, presents a hydraulic power system variable-frequency asynchronous motor drag based on variable-displacement pump.it elaborates the speed variable volumetric speed control system stability at low speed, slow speed of response difference reason based on hydraulic power system performance effected asynchronous motor speed and variable pump displacement. Simulation model of variable-spend variable-displacement pump hydraulic system is established using the AMESim simulation platform, the performance of hydraulic power system effected control method under different load working conditions. Finally the control strategy of variable-spend variable-displacement pump hydraulic power system is given. The paper provides a new method and train of thought to improve the low speed stability and response speed. The main research work done in this paper:(1) According to the motor theory and fluid mechanics theory, a theoretical model is established to calculate the asynchronous motor and the plunger pump efficiency, the efficiency of variable displacement pump and mechanical characteristics of asynchronous motor at low speed running state are analyzed.it expounds the influence of asynchronous motor speed and variable pump displacement on the low speed performance of the hydraulic power system, provides the theoretical basis for the study on the characteristics of the hydraulic power system.(2) the simulation model of variable-spend variable-displacement pump hydraulic system is established by using the method of power bond graph, the correctness of the simulation model is proved by the analysis of the simulation results with the theoretical results. It provides support for the characteristics of hydraulic power system.(3)In order to improve the low speed stability and response speed of hydraulic power system, the influence of control mode on characteristics of hydraulic power system is analyzed. Finally the control strategy of variable-spend variable-displacement pump hydraulic power system is given.