Research On Ride Comfort Analysis And Control Of Wheel Motor Driven By Electric Vehicle

With problems such as insufficient energy supply and serious environmental pollution,the development of electric vehicles has become an effective way to alleviate energy and environmental pressures.As a newer driving form applied to electric vehicles,the hub motor drive has many advantages such as zero exhaust emission,simple and efficient transmission structure,and controllable power output.It is considered to be the most ideal drive for electric vehicles in the future.form.However,due to the introduction of the hub motor,the unsprung mass of the whole vehicle becomes larger and the motor excitation generated during the operation of the hub motor greatly interferes with the ride comfort of the vehicle.This article will focus on the above issues:First,the in-wheel motor-driven vehicle model is simplified into a vibration system that establishes an input model of the vibration system.(1)Typical speed bump road input model;(2)Continuous random road single wheel input model,and four-wheel random road input model based on the correlation between the left and right wheels and the delay of the front and rear wheels.(3)According to the electromagnetic theory,the tangential force and radial force of the motor are obtained.Through the decomposition and synthesis of the force,the motor excitation input model in the vertical direction is obtained.Secondly,based on the 1/4 vehicle two-degree-of-freedom model,the in-vivo motor drive and the concentrated drive amplitude-frequency characteristics are compared and analyzed.The in-wheel motor-driven vehicle has a lower natural frequency than the concentrated-motor-driven vehicle,and the amplitude becomes larger.The effects of the unsprung mass increase on the vertical vibration of the vehicle are studied by using continuous random road input and deceleration belt input.The results show that the unsprung mass increases and the ride is deteriorated.Comparing the road input with the “road + motor” double input,the influence of motor excitation on the vertical vibration of the vehicle is analyzed.The results show that the motor excitation has a great influence on the ride comfort.Then,in order to reflect the actual situation of the vehicle as comprehensively as possible,this paper establishes a seven-degree-of-freedom vehicle model driven by the hub motor,and analyzes the ride comfort of different mass ratio,stiffness ratio and damping ratio.The results show that the weight reduction of the wheel,that is,the weight of the wheel,can effectively improve the ride comfort of the vehicle.Selecting an electric wheel with a relatively soft tire is beneficial to improve the driving safety of the vehicle.An increase in the damping ratio,that is,an increase in the damping coefficient of the suspension,is advantageous in reducing the acceleration of the vehicle body,but the acceleration of the roll and pitch angle of the vehicle body is significantly deteriorated.Finally,in order to improve the vertical vibration of the vehicle driven by the hub motor,the active suspension is used to suppress the vibration from the transmission path.According to the optimal control principle,the optimal feedback gain matrix is obtained,and the seven-degree-of-freedom active suspension LQG vehicle model is established and simulated.Compared with the passive suspension,three indicators and suspensions reflecting the attitude of the vehicle body can be obtained.The moving stroke can be effectively controlled,and the tire stroke is slightly deteriorated.