Research On Torque Distribution Control Strategy Of In-wheel Motors Electric Vehicle Considering Intense Driving Behavior

In recent years,as the problems of fossil energy consumption and environmental pollution have become increasingly prominent,new energy vehicles represented by electric vehicles have become the mainstream of future industry development.In-wheel Motors Electric Vehicle(IEV)is a wheel hub motor installed in the wheel hub to drive the wheels directly,so it is also called electric wheel vehicle.It can eliminate the traditional transmission mechanism,and each wheel can be driven by the motor alone,so it has the characteristics of strong power,high transmission efficiency,and more rapid response,etc.,thus becoming a research hotspot for universities,research institutions and car companies.However,due to the influence of power battery quality,the overall mass of electric vehicles is generally high,and the handling stability is highly dependent on stability control.In the traditional stability control of electric vehicles,there is a lack of consideration of driving behavior and subjective feelings of the sporty type,when the driver cannot give full play to the advantages of strong power and high limits of handling stability of electric wheel vehicles during intense driving.In this paper,we analyze the characteristics of intense driving style by taking a wheel motor distributed drive electric vehicle as an example,and use them to design a traction control strategy for high acceleration and a transverse sway stability control strategy that considers driving behavior.The contents are as follows.Firstly,the whole vehicle dynamics model and real vehicle verification platform were built.It includes the seven degrees of freedom model of the body,the motor model,and the magic formula tire model.The parameters of the real vehicle verification platform and the sensors carried were introduced in detail.The accuracy of the wholevehicle dynamics model was verified by real-vehicle tests.Next,the analysis of the intense driving behavior based on the driver-in-the-loop simulation platform was conducted.The software part of the driver-in-the-loop simulation platform is Vi-Car Real Time real-time vehicle simulation environment,and the hardware part is Fanatec professional driving simulator.The driver-in-the-loop data were used to conduct a comprehensive analysis of the aggressive driving style in both longitudinal and lateral directions.Then a traction control strategy for high acceleration is designed.A road state observer and a fused longitudinal speed observer are built.Based on the longitudinal driving behavior obtained from the analysis of the aggressive driving style,a "feedforward + feedback" traction control strategy is proposed.The feedforward is to predict the longitudinal acceleration based on the observed road surface adhesion and the driver’s accelerator pedal request,and to introduce the axle load transfer from the longitudinal acceleration into the drive force control.The feedback is a PID control based on the difference between the actual slip rate and the target slip rate,while the target slip rate is corrected to ensure lateral stability at higher speeds.A real-world linear acceleration comparison was performed to validate this traction control strategy.Finally,a transverse pendulum stability control strategy considering the driver’s behavior is designed.A linear two-degree-of-freedom reference model and a center-ofmass lateral eccentricity observer are constructed.The lateral driving behavior is obtained based on the analysis of the aggressive driving style,i.e.,the driver expects to adjust the vehicle attitude through the steering wheel and acceleration/brake pedal coordination.A two-tier transverse sway stability controller is designed,with a model prediction controller for additional transverse sway moments in the upper layer and a quadratic programming effective set method torque distribution controller considering driving behavior in the lower layer,introducing driving behavior constraints in addition to physical constraints.The above control strategy is verified by real vehicle tests.The research in this paper has a certain significance to the comprehensive performance improvement of wheel hub motor distributed drive electric vehicles,taking the driving behavior into account in the vehicle control,ensuring the best power and transverse stability of the vehicle under the driver’s intense driving condition,and achieving the best coordination of "driver + vehicle".