Research On In-wheel Motor Vibration Control Of Distributed Drive Vehicle

The in-wheel motor driven vehicles by placing the hub motor directly inside the wheel,eliminating the drive shaft and greatly optimizing the drive efficiency of electric vehicles.Because the in-wheel motor is placed in the wheel,road excitation and motor electromagnetic excitation make the vibration characteristics of the electric wheel complicated,which affects the reliability of the hub motor and reduces the service life of the hub.In recent years,the vibration control of electric drive wheel has attracted extensive attention of scholars at home and abroad.On the one hand,vibration can be suppressed from the "source" to reduce the transmission of unsprung vibration to the car body;On the other hand,the working environment of the wheel motor can be improved to enhance the reliability and service life of the wheel motor.Through the investigation,it is found that there are still some practical problems in the research on vibration control of electric wheel,such as complex vibration control device(structure),further increase of unsprung mass and unsatisfactory vibration control effect.With the development of Magnetorheological Elastomer(MRE),a new intelligent material,combined with the summary and analysis of previous studies on MRE,this paper proposes the method of introducing MRE mount to realize vibration control of electric wheel,and carries out an in-depth study on the feasibility of the method in theory and application.Based on theoretical derivation and multi-body dynamics analysis,the vibration characteristics of hub-motor driven vehicles are analyzed in depth.It is found that the hub-motor driven vehicles have the characteristics of broadband vibration except the low-frequency vibration problem,and the peak value occurs around 200 Hz,indicating that the hub-driven vehicles have the characteristics of broadband vibration.Through the combination of theory and experiment,the controllable stiffness of MRE in magnetic field environment was analyzed,and a MRE mounting structure was designed between the supporting shaft and stator to suppress vibration.Based on the analysis of the vibration characteristics of the electric wheel after the introduction of MRE mounting,the optimization of the in-wheel vibration characteristics of the hub-driven vehicle was proposed by using LQR optimal control algorithm.The effectiveness of LQR optimal control on vibration suppression of support shaft is verified by LMS Virtual.Lab Motion and Simulink co-simulation.The main research work of this paper is as follows:(1)Based on the theory of multi-body system dynamics and with the help of the multi-body dynamics software LMS Virtual.Lab Motion,the multi-body dynamics models of hub-motor driven vehicles and traditional centralized motor driven vehicles were established.Simulation tests under various working conditions were carried out,and the vibration characteristics of electric wheels of hub-driven vehicles were systematically analyzed and mastered.The analysis shows that there is an obvious vibration peak near 200 Hz at the hub motor support shaft of the hub-driven vehicle,which is easy to cause the resonance of the electric wheel system of the hubdriven vehicle and the internal noise.Therefore,effective vibration suppression is required.(2)Aiming at the problem of hub-driven wideband vibration,MRE mounting is proposed to suppress the vibration.The magneto dynamic characteristics of MRE were investigated by means of theoretical analysis and experiment.It was found that the static stiffness had a good linear relationship with the magnetic field strength,and the dynamic stiffness had a negative correlation with the magnetic field strength in the wide frequency range.Based on this,the MRE mount scheme of hub-driven vehicle wheel vibration reduction was proposed,and the electromagnetic analysis software Maxwell was used to analyze the magnetic field and predict the adjustable range of its stiffness.(3)Based on the actual constraints in the electric wheel,the vibration characteristics of the hub-driven electric wheel after the introduction of MRE mounting were analyzed based on the multi-body system dynamics theory,and the initial stiffness of MRE mounting was matched.Preliminary study shows that MRE mount has a good suppression effect on vibration peak near200Hz(audio segment)without MRE mount control,but the control effect does not appear in the low frequency band below 50 Hz,so MRE mount control strategy needs to be further studied.(4)Based on the analysis and comparison of PID control algorithm and LQR optimal control algorithm,LQR algorithm is more suitable for in-wheel vibration control of hub-driven electric wheel.LMS Virtual.Lab Motion and Simulink co-simulation method were used to explore the vibration suppression effect of LQR optimal control on the support shaft acceleration.The simulation results show that the optimal LQR control achieves the maximum drop of the vertical vibration acceleration at the hub motor support shaft of 36.4% in low frequency band(4-12.5Hz)and 98.6% in audio band(180-220Hz)without worsening the ride comfort of the vehicle and increasing the unbalanced electromagnetic force of the motor.The multi-source wideband vibration of hub motor is suppressed effectively.