| Electric drive system is the key component in pure electric vehicle.High speed,high efficiency,high density,and low vibration & noise are its key development directions.With the development trend of high-speed and integration of electric drive system,compared with traditional powertrain,due to the lack of masking effect of engine noise,medium and high frequency noise such as motor noise and gear meshing order noise become increasingly prominent.At the same time,high speed makes system natural frequency more dense,local modes increase,and more potential resonance points;Integration makes system more highly coupled and its dynamic response more complex.Therefore,a series of new NVH problems appear in electric drive system,which forms a more severe challenge.In view of the above NVH problems of electric drive system,this paper carry out gear load tooth contact analysis modeling,gear micro-modification analysis and its multi-objective optimization,rigid-flexible coupling modeling and dynamic characteristics analysis of high-speed electric drive system,vibration & noise analysis and optimization of electric drive system.Complete the vibration and noise modeling,simulation,analysis and optimization of electric drive system in pure electric vehicle.This paper rely on the National Key Research and Development Program of China "Development of high-performance precision integrated drive motor system",the main research content includes the following five aspects:1)In view of the cumbersome modeling and slow solution of finite element method,poor adaptation range and low solution accuracy of analytical method,a fast analysis model of helical gear load tooth contact based on hybrid FE-analytical method is proposed.The model can consider the factors such as lightweight gear blank,gear micro-modification,meshing misalignment,gear backlash,assembly and manufacturing errors,meanwhile taking into account the calculation accuracy and solution efficiency.The model adopts parametric modeling method,based on finite element method and Hertz contact theory to achieve accurate calculation of tooth surface compliance.It does not need to separate the Hertz deformation and does not rely on finite element analysis software.It can quickly solve the NVH key performance indicators such as time-varying meshing stiffness,static transmission error and tooth surface load distribution of helical gear pair.2)Taking the reducer gear pair of electric drive system in a pure electric vehicle as the research carrier,based on the established helical gear load contact analysis model,the influence factors such as torque,gear meshing misalignment,manufacturing and assembly errors,lightweight gear blank and gear geometric parameters on gear transmission error and time-varying meshing stiffness are analyzed.In addition,the change mechanism of gear NVH performance index under the above-mentioned parameter is analyzed and studied in depth.3)In view of the multi-objective optimization design problem of gear micro-modification of electric drive system reducer,firstly,based on gear micro-modification analysis,the change rule of gear NVH,strength and durability in the micro-modification space and the synergy characteristics of gear modification parameters are obtained;Secondly,a stepwise optimization strategy of gear modification parameters is carried out based on gear micro-modification analysis to obtain the approximate optimal design;Thirdly,based on NSGA-II algorithm,multi-objective optimization of gear micro-parameters is carried out for peak-to-peak value of transmission error and its first-order harmonics,and peak value of tooth surface contact stress.Finally,based on Monte Carlo simulation,random manufacturing error excitations are introduced to discuss the impact of manufacturing errors on the robustness of gear NVH,strength and durability,and robustness analysis and optimization for multi-objective optimization candidates are carried out.4)Aiming at the NVH problems of high-speed and integrated electric drive system,such as high speed resulting in dense system natural frequencies and increased local modes,complex system dynamic response under the action of multiple NVH excitation sources such as motor torque ripple,radial electromagnetic force and gear transmission error.strong coupling of overall load deformation of electric drive system.Considering the motor structure,gear-shaft-bearing rotor system,differential and electric drive system housing,as well as electromagnetic excitation and transmission error excitation,a rigid-flexible coupling dynamic model of electric drive system is established,and the calculation method of system dynamic response is studied.Finally,dynamic response of electric drive system under the excitation of motor radial force,torque ripple and gear transmission error is compared and analyzed,and the change rules of system dynamic characteristics under each excitation are obtained.5)Based on the NVH bench test of electric drive system,vibration & noise performance of electric drive system under four NVH conditions such as accelerating and sliding are analyzed using the order tracking theorem,and NVH problem location and identification of vibration & noise source of electric drive system are carried out.Secondly,in order to locate the resonant frequency of the system dynamic response and provide a basis for the analysis of system vibration characteristics and structural dynamic optimization,a simulation modal analysis and test verification of key components of electric drive system are carried out.Finally,in order to solve the calculation efficiency problem caused by a large number of iterative optimization,a fast simulation analysis method of noise radiation of electric drive system based on surface vibration method is introduced.Aiming at the NVH problem of electric drive system of a pure electric vehicle,NVH optimization is carried out based on gear micro-modification.The comparative analysis of the dynamic response at suspensions and the root-mean-square velocity on the housing surface shows that the optimization method is effective. |
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