Research On Characteristics Of Variable Displacement Asymmetric Axial Piston Pump

The pump controlled system has the advantages of high energy efficiency,simple hydraulic system and small installation space compared with the valve controlled system.Therefore,it has been widely used.After years of development,pump controlled technology is very mature.However,for the pump-controlled asymmetric cylinder,the existing solution needs to add an auxiliary pump or valve to balance the asymmetric flow of the two chambers,and has problems such as high system cost,complicated circuit,and low energy efficiency.In order to solve this problem,the team of Professor Quan long from Taiyuan University of Technology designed a variable displacement asymmetric axial piston pump based on the three-distribution window(Ports A,B,T).The problem of pump-controlled asymmetric cylinder flow matching is well solved,but the research content mainly focuses on the positive inclination angle of the swash plate,that is,the static and dynamic characteristics of the plunger pump when Port A sucks oil,Port B and T drain oil.There is a lack of analysis of the variable displacement control strategy and the static and dynamic characteristics of the plunger pump when the swashplate is negatively inclined.In response to this problem,based on the previous research,this topic determines the corresponding variable displacement control scheme based on mathematical analysis.Based on the joint simulation model of variable displacement asymmetric axial piston pump,the dynamic and static performance of the variable displacement asymmetric axial piston pump with positive/negative inclination is analyzed,and the key parameters of the mechanism are determined by simulation.,as well as the variable resistance torque acting on the swash plate of the asymmetric axial piston pump,were analyzed in detail.Firstly,the kinematics and dynamics analysis of the asymmetric axial piston pump are carried out by means of coordinate transformation,and the motion relationship between the components is obtained.The transfer function of the piston pump is established.The transfer function is simplified by the approximate linearization method,and the appropriate control strategy is determined according to the simplified transfer function.Secondly,a joint simulation model of variable displacement asymmetric axial piston pump is established by AMESim and ADAMS.The effects of the oil discharge port pressure,the swash plate inclination angle and the piston pump speed on the static characteristics of the piston pump drain port are analyzed.The main parameters of the variable mechanism such as proportional coefficient,variable piston area,servo proportional valve flow gain and servo proportional valve frequency response are determined by simulation.At the same time,the action torque of the piston slipper assembly on the swash plate is studied,and the influence of the swash plate variable resistance torque on the dynamic performance of the asymmetric axial piston pump is verified by simulation.Finally,a prototype of a variable displacement asymmetric axial piston pump was prototyped.According to the characteristics of the suction and discharge of the asymmetric axial piston pump,the test platform of the pump was designed and built.The feasibility of the displacement control scheme was verified.The research results show that when Port A sucks oil,Port B,T drains oil,the flow unevenness coefficient of Port B is always smaller than the flow unevenness coefficient of Port T.Meanwhile,with the pump speed,the swash plate inclination angle and the pressure of Port B rises,the flow pulsation of the Ports B and T increases.The dynamic response of the pump is mainly affected by the variable piston area,the variable cylinder force arm,the servo proportional valve flow gain and the proportionality coefficient.When Ports B,T suck oil and Port A drains oil,the variable displacement torque of the swash plate of the pump is similar to that of the ordinary axial piston pump,and has little effect on the performance of the variable displacement;when Port A sucks oil,Port B,T are drain oil,the variable resistance torque evolves into a large one-way torque,which will reduce the dynamic response of the pump during the swashplate inclination reduction process.The test results show that when the proportionality coefficient k_p=3,the pump has a higher response speed.