Dynamic Simulation Analysis Of Hub Motor Under Compound Excitation

The world environment problem and the energy problem are increasingly serious,the automobile as a large energy consumer,has to face the transformation,and the electric vehicle will become one of the important directions of the future automobile industry development.However,there are still many disadvantages to be overcome for hub-motor driven cars.In addition to the hub motor arranged in the wheels,by the influence of the layout space,the hub motor directly ACTS on the wheels,the vehicle's unsprung mass significantly increases,the ratio of the unsprung mass to the unsprung mass decreases,the wheel dynamic load changes greatly,which affects the tire grounding,thus bringing a negative impact on the vehicle's smoothness and handling stability.On the other hand,the power output of the motor itself will also have an impact on the dynamic performance of the vehicle.Firstly,the motor is subject to the inverter nonlinearity,and torque fluctuations exist.To a certain extent,the torque fluctuations will affect the longitudinal grounding force and vertical deformation of the tire.At the same time,when stimulated by uneven road surface and motor production and assembly,the rotor and stator in the hub motor will be eccentric,resulting in the motor air gap magnetic field distortion,which will lead to the increase of the radial electromagnetic excitation force of the motor and further torque fluctuations,further resulting in the vehicle system dynamics deterioration.This paper set up the road surface model and as compound excitation motor electromagnetic exciting force model,vehicle seven degrees of freedom vehicle vertical vibration model is established,considering the interaction of the electric magnetic force problem,separately considering the motor stator and rotor,11 degrees of freedom vehicle vertical vibration model is established,under the environment of simulink simulation,analysis of wheel hub motor brings the increase of the unsprung mass effect on vehicle ride comfort;The influence of different speeds on vehicle smoothness and motor rotor eccentricity was analyzed.The influence of composite excitation on vehicle smoothness and rotor eccentricity of motor was analyzed.The results show that the increase of unsprung mass has the greatest effect on the dynamic load of the vehicle,followed by the acceleration of the vehicle body,which has less effect on the dynamic deflection of the suspension.With the increase of the vehicle speed,the road surface excitation,the indexes of smoothness and the eccentricity of the fixed rotor of the motor all increase.The addition of electromagnetic excitation force further deteriorates vehicle smoothness,the effect on each index is consistent with the effect of the unsprung mass increase,and will aggravate the motor rotor eccentricity.Considering the deterioration of vehicle dynamics caused by composite excitation,the motor is converted into the mass module of the dynamic vibration absorber by applying the principle of dynamic vibration absorber,and the spring damping system is added to serve as the motor suspension.In order to simplify the calculation,the establishment of belt wheel motor three free 1/4 vehicle model of suspension,body vertical vibration acceleration and the wheel dynamic load,motor vertical vibration acceleration with the optimization target of minimizing the sum of the three root mean square value of the maximum vertical displacement of the motor as constraint conditions,the application of particle swarm algorithm to optimize the motor suspension parameters,the optimization effect is validated by computer simulation.The results show that the motor suspension can effectively improve the vehicle comfort index and the motor vertical vibration acceleration.