| The pure electric commercial vehicle powertrain consists of on-board drive motor and transmission.Compared with passenger car powertrain,transmission is added to change the speed and increase the torque.As the core component of pure electric vehicle,the performance of powertrain has a great impact on the stability,power,economy,comfort,fatigue reliability of the whole vehicle.Therefore,the fatigue life test of power assembly parts and the whole is an indispensable part of the development process.However,at present,the fatigue load spectrum of pure electric commercial vehicle powertrain test is collected by road test,and the load collected by different models is different,which has a long collection time,great difficulty and high investment cost.The constant torque load used in the commercial vehicle test is inconsistent with the actual road condition of the power assembly bearing the load.Therefore,in order to further speed up the development of new products,it is necessary to study the dynamic loading test technology for the fatigue life of power assembly on the premise of meeting the reliability of power assembly.In this paper,the loading methods and standards of pure electric commercial vehicle powertrain fatigue test at home and abroad are reviewed,and the relationship between load and service life in the fatigue life damage theory of mechanical parts of pure electric commercial vehicle powertrain is analyzed.According to the load feature extraction of typical cycle conditions,the fatigue life loading method of pure electric commercial vehicle powertrain is proposed.Through the finite element modeling and analysis of the gear components of the power assembly,it is concluded that the influence of the concentrated load extracted under the typical urban public transport cycle and the load under the urban public transport cycle on the gear is basically the same.Finally,the test-bed is built,and the upper computer measurement and control system software which can carry out this method test is developed.First of all,this paper studies the fatigue damage theory of the power assembly of pure electric commercial vehicle,explores the characteristics of different fatigue damage theories,and concludes that the load size and cycle times are the main factors affecting the fatigue life.Based on the analysis of longitudinal force and the characteristic value of typical urban public transport cycle,a load acquisition method is proposed based on the input of vehicle parameters.According to the characteristics of gear fluctuating load cycle,the load fatigue load spectrum is obtained by amplitude counting and load cycle extrapolation.Secondly,the finite element model of the power assembly gear is established for dynamic stress analysis,and the influence of two different loading modes on the gear is compared under the concentrated load extracted from the urban public transport working condition and the partial urban public transport working condition load.Thirdly,the fatigue life reliability test-bed of power assembly is built.Through the design of LabVIEW software and PLC program,the upper computer measurement and control software system which can automatically generate load spectrum according to different vehicle parameters is developed,which realizes the control of torque and speed of load motor.Finally,the test flow of power assembly is established,and the fatigue life test of pure electric commercial vehicle power assembly is carried out according to the proposed load loading mode,and the test results are analyzed and compared.The accuracy of the loading method and the stability and reliability of the measurement and control system are verified. |
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