Abstract:In order to fully grasp the inherent characteristics of torsional vibration of pure electric vehicle powertrain and improve the ride comfort of the system, it is necessary to conduct in-depth research on the torsional vibration characteristics of the system. Taking a new type of all-electric direct-drive integrated power transmission system as the research object, a modeling method considering the coupling of electromagnetic stiffness of the motor and time-varying meshing stiffness of the gear was proposed, and the 8-DOF mechanical branching model was established and verified. The natural frequency and mode shape of the system were calculated and analyzed, and the validity of the analysis results was verified by Adams. Based on the direct derivation method, the sensitivity analysis of the natural frequency was carried out, the characteristic parameters of the integrated system were improved, and the dynamic changes of the system before and after the parameter optimization were analyzed by co-simulation. The results showed that the "zero order" natural frequency was obtained by considering the electromagnetic stiffness, which presented abundant dynamic phenomena. Low-order vibration was shown in the position of wheel and body, and high-order vibration was shown in the transmission part. Based on the sensitivity analysis results, the critical speed of the system was 5097 r/min, which exceeded the common speed range. The maximum fluctuation amplitude of motor shaft angular acceleration response in frequency domain was reduced by 25.9%, and the overall fluctuation amplitude was obviously reduced, the maximum fluctuation speed of transmission output shaft was reduced by 0.26%. The research results can provide theoretical reference for the inherent characteristics and sensitivity analysis of electromechanical coupling system.