Study On Suspension Vertical Mechanical-Electrical Coupled Vibration Of In-Wheel Motor Electrical Vehicle

Due to the removing of fuel engine, transmission and driving axle, in-wheel motor driving vehicle (IWMDV) can disperse power source to each cartwheel to alleviate vehicle mass and enhance transmission efficiency. By tracking and comparing the development of domestic and foreign related fields, the suspension vertical mechanical-electrical coupled vibration of in-wheel motor electrical vehicle was studied.Firstly, a 1/4 vehicle dynamics model of in-wheel motor vehicle was established. The sprung mass vibration input, the body vertical vibratory acceleration and the tire dynamic load were defined to evaluate the suspension vertical mechanical-electrical coupled vibration. The model was established and analysed by using the solfware MATLAB/SMULINK.Secondly, compared with the original suspension, the influence of the under spring mass and the in-wheel motor torque ripple were studied under the action of road random vibration. The simulation results show that the power spectral densities of the sprung mass vibration input, the body vertical vibratory acceleration and the tire dynamic load increase obviously. Under the influence of the in-wheel motor torque ripple, the body vertical vibratory acceleration increases obviously in the range of 9Hz to 18Hz. The peak value increases to 61m2/s3 from 49m2/s3, increase of about 24.5% at 9Hz or so.Thirdly, the motor was incorporated to the wheel by the spring-damper shock absorber. Than the suspension parameters were optimized and the suspension structure of in-wheel motor was improved. The optimization results show that the improved suspension system makes the vertical vibration features of in-motor-wheel superior to the original suspension which motor and cartwheel are in rigid connection. And compared with the common vehicle suspension of non-motor, the vertical vibration amplitude of the improved suspension system can be reduced in the frequency range of over 7Hz. The vehicle ride comfort is improved noticeably.Finally, a 1/2 vehicle dynamics model was established and simulated. The model was analysed and compared with 1/4 vehicle dynamics model. The results show that the vertical vibration features can be accurately responsed by both dynamics models. The vehicle suspension deflection and the tire dynamic load can be appropriately appraised by the 1/4 vehicle model, while the motor suspension deflection and body vertical vibratory acceleration can be appropriately appraised by the 1/2 vehicle model.