Influence Of Road Excitation On Fatigue Life Of Electric Vehicle Reducer

As a key component of the transmission system of electric vehicles,the reducer not only bears the rotation excitation from the motor,but also the excitation from the road surface generated by the road roughness is transmitted to the reducer through the suspension system,and its fatigue reliability has attracted more and more attention from manufacturers and consumers.At present,the relevant standards have not been issued,and most studies ignore the road surface excitation.Research on the influence of road excitation on fatigue life of electric vehicle reducer is very limited.Based on the system multi-body dynamics,this paper takes an electric vehicle reducer as the research object,combines the load extraction method and finite element technology,establishes the rigid-flexible coupling multi-body dynamics model of the whole vehicle equipped with the reducer,extracts and analyzes the gear meshing force and gear shaft torque load of the reducer under the synchronous application of rotational excitation and road excitation,explores the influence of road excitation on the critical fatigue life of the reducer,and lays a theoretical foundation for accurate analysis and verification of the fatigue life of the electric vehicle reducer.Firstly,the existing load extraction methods are summarized.Based on the analysis of the working principle,main failure forms,key load types affecting fatigue life and the influence mechanism of road excitation on the reducer,the load extraction method of the reducer based on virtual simulation method and its realization idea are put forward.Secondly,the finite element model of reducer shell is established and free mode analysis is carried out.The correctness of the model is verified by free mode experiment.The flexible body model of the shell is extracted,and the dynamic model of rigid-flexible coupling system of reducer is established with gear transmission system.On this basis,the dynamic model of rigid-flexible coupling system of reducer is simulated,tested and verified by typical working conditions.Then,the model of each subsystem of the whole vehicle is established,and the whole vehicle model is built by combining the rigid-flexible coupling multi-body dynamics system of the reducer,and the constraints and boundary conditions of the whole vehicle and its subsystems are defined.Thus,establishing the virtual prototype model of the whole vehicle with both rotational excitation and road excitation.At last,the standard road roughness program based on filtered white noise method is compiled by Matlab/Simulink,and the road roughness under three working conditions of120km/h,60km/h and 20km/h is generated.In the virtual prototype model of the whole vehicle,the rotation excitation is applied separately and the rotation excitation and road excitation are applied simultaneously,and the fatigue load spectrum of the reducer is extracted by simulation analysis.Through the difference analysis of fatigue loads extracted with or without road excitation,the influence of road excitation on fatigue life of reducer is studied.