Research On Optimal Torque Vectoring Control For Minimum Cornering Energy Consumption Of Four-wheel-independent-drive Electric Vehicle

Compared with the traditional vehicle powered by inner combustion engine,electric vehicle exhibits its comparative merits of energy conservation and environmental friendliness fully.Among the various layouts of the electric vehicles,four-wheel-independent-drive electric vehicles whose wheels are driven by motors respectively are increasingly attracting attention from scholars for their flexible layout,torque decoupling,and diversification of driving modes.Besides the spatial arrangement merit,this architecture offers the interesting opportunity of easily and efficiently distributing the driving torque to generate a yaw moment(torque vectoring).While this characteristic is usually exploited able to increase lateral stability and to improve the handling of the car in most of previous research.This paper tries to investigate the effect of torque vectoring on traction energy conservation during cornering for four-wheelindependent-drive electric vehicle.Firstly,using the simulation software,which is MATLAB/Simulink,a four-wheelindependent-drive electric vehicle dynamic model,an in-wheel motor model,a driver model,etc.were built.In addition,vehicle dynamic commercial software,which is Car Sim,was used to test the veracity of the self-built model.The self-built model supported the following theory analysis and simulation experiment.In order to explain the mechanics of the vehicle’s turning in principle,this paper theoretically deduces the 3-DOF vehicle dynamic model.Based on the phenomenon of turning speed-reduction,it explains the mechanism and influencing factors of the turning 7resistance and proposes the control method suppressing the turning resistance according to the adoption of torque vectoring control.This paper indicated that torque-vectoring control would prevent the influence of turning resistance.By analyzing how the turning resistance affected the vehicle dynamic property and energy consumption,the vehicle speed and wheel sideslip angle were found as the two main factors,which affect the turning resistance mostly.Through the simulation,the torque vectoring control can adjust the inner side and the outer side wheel torque actively.The turning resistance can be reduced without change the vehicle transport condition,while the traction power can be reduced for energy conservation.According to this simulation,it indicated that torque-vectoring control could also change the vehicle turning performance,which can change the understeer,and improving the turning maneuverability.For purpose of conforming the optimal torque distribution coefficients for energy conservation,which are the axis torque distribution coefficient,the front axis torque distribution coefficient and the rear axis torque distribution coefficient,the GA-PSO hybrid optimization algorithm was used.Considered both the economy and stability of turning condition,an optimal torque vectoring control strategy was made to optimize the torque distribution coefficients offline,and a table of optimizing torque distribution coefficients for energy conservation was made.In this paper,a map of best contribution to energy efficiency with different turning conditions of torque vectoring control was made.In order to indicate the practical value of torque vectoring control,the influence of motor operation points for torque distribution coefficients was taken into account.Moreover,a new table of torque distribution coefficients with the consideration of motor operation points was made by offline optimization.In this paper,while optimizing the torque distribution for the purpose of energy conservation for vehicle cornering conditions,the stability effects caused by longitudinal and lateral disturbances in the vehicle curve conditions are also taken into consideration.Based on the estimation of vehicle speed,the self-adaption acceleration slip regulation control was formulated.Meanwhile,to prevent vehicle side slippage instability a torque coordination control strategy is designed through the yaw rate control for vehicle instability situations,which may be caused by efficiency allocation.This article has comprehensively considered the demand including vehicle turning energy-saving and stable operation of the torque,and achieves online correction of the offline optimization table to achieve coordination control of energy saving and stability torque.Consisting of d SPACE and driving simulation,a HIL test platform was adopted at the end of this paper.Employed driver-in-line,the normal turning condition and comprehensive condition were tested.In order to verify the feasibility and practical value of the torque coordination control,the condition of toque distribution and economy performance is analyzed emphatically.