| Direct drive volume control(DDVC)electro-hydraulic servo system is a highly integrated electro-hydraulic servo closed pump control unit,which is controlled by servo motor,quantitative pump and servo hydraulic cylinder.Compared with traditional electro-hydraulic servo valve control,the system has the advantages of simple structure,high efficiency,low cost,and easy maintenance.Especially in the occasion of large load and low dynamic response requirements,the system can be used to replace the electro-hydraulic servo valve control system,which has high efficiency,energy saving and high power.Than and environmentally friendly and other advantages.However,due to the high integration of the DDVC electro-hydraulic servo system and the poor cooling capacity of the system,the system thermal equilibrium temperature is high.Once the system thermal equilibrium temperature exceeds the normal value,it will lead to a decrease in the output performance of the servo motor,a decrease in the viscosity of the system oil,oxidation failure,and impurities,etc.,which seriously affect the system performance and service life.The research of the DDVC electro-hydraulic servo system in the United States,Japan and other countries has been relatively mature,and has obtained certain applications,and has achieved considerable economic benefits.However,China 's theoretical research work on the system heat balance started late,and the theoretical depth is still far from the developed countries.Therefore,in-depth research on the thermal balance of DDVC electro-hydraulic servo system has important academic significance and application value.First,this chapter briefly describes the structure and working principle of the DDVC electro-hydraulic servo system,and analyzes the heat source of the system.The thermal power of DDVC electro-hydraulic servo system is solved and analyzed from two parts: permanent magnet synchronous servo motor and closed pump control hydraulic system.The thermal power calculation model is established for the two parts respectively,and the heat generation power of each part of the two parts and the change rule of the heat generation power of each part with the load under typical working conditions are calculated and solved.The proportion of the total loss of the system components under different loads in the system is given,and the largest heat-producing component of the system is analyzed.Secondly,the thermal balance analysis of the temperature field of the DDVC electro-hydraulic servo system.According to the related knowledge of fluid mechanics and heat transfer,the temperature field solution model of DDVC electro-hydraulic servo system is established,the initial conditions and boundary conditions of the solution domain are set,and the thermal equilibrium parameters of the temperature field are solved.Then,with the help of Ansys and Amesim temperature field thermal balance analysis software,calculate the thermal equilibrium point of the temperature of each component of the DDVC electro-hydraulic servo system under different working conditions.The influence law of load torque on the thermal equilibrium temperature field of DDVC electro-hydraulic servo system under natural cooling and forced air cooling is analyzed.At the same time,the influence law of the thermal equilibrium temperature field of the wind speed under forced air cooling is analyzed,and finally the maximum torque under normal system operation is obtained.Finally,an experimental platform was built for experimental research,and the thermal equilibrium temperature field of the permanent magnet synchronous servo motor under natural cooling and forced air cooling was experimentally analyzed.The experimental temperatures of the system under different loads and different wind speeds were measured respectively.The experimental results show the rationality and feasibility of the thermal equilibrium theoretical analysis method. |
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