Research On The Energy-Saving Control Strategy Of Four-Wheel-Independent-Drive Electric Vehicle

At this period, the transportation energy is transforming, and electric vehicle is againwining the favor of many enterprises and governments as its low pollution, high efficiencyand multiple sources of energy. But one of the major issues is its short Max range percharge. Therefore this article mainly focuses on the control strategy to study how to makethe electric vehicle with four motorized wheels that are controlled individually becomemore efficient.Firstly, the current situation, key technology and driving technology of electric vehicleare introduced in brief, and the influence factors of electric vehicle energy consumption areindicated, and the electric wheel drive technology is presented, mainly on its classificationsand advantages, in addition the corresponding energy-saving ways are approached.Secondly, the driving conditions are classified, and the appropriate drive mode is selectedunder the corresponding driving condition, moreover the corresponding types of torquedistribution are formulated, which are all based on the control strategy. Finally, using theco-simulation of AVL CRUISE and AMESim to create the vehicle mode, and usingMATLAB/Simulink to establish energy saving control strategy of the vehicle, then theco-simulation is presented, the correctness of the control strategies under the differentdriving conditions is verified, moreover the energy-saving data are concluded under thecondition of cycle run.The control strategy mainly includes the launch control, linear driving control, slipcontrol of driving wheel, brake control and steering control. Among them, the launchcontrol makes the starting torque increase in a slope mode, which reduces the initial gridcurrent, and lowers the impact and interference between the motor and the load. Duringstraight driving, it will choose what kind of driving mode, single axle drive or double shaftdrive, according to demand torque. If double shaft drive mode is selected, the front and rearshaft torque will be distributed to maximize the combined efficiency of motors. If the slip rate of driving wheel exceeds the threshold, the slip control will be performed, and thetorque of driving wheel will be regulated to make the actual slip rate of driving wheel tendto the optimal one, which is contributed to reducing energy consumption. The electricbraking proportion is determined by using fuzzy control technology, in addition theanterior-posterior axis torque is distributed on the basis of piecewise constant proportion,which would recycle braking energy maximally as well as ensure the braking stability. Thetorque distributions of anterior-posterior axis and inside and outside wheels are determinedaccording to the deviations of yaw velocity and lateral acceleration individually, and thiscan achieve the optimized torque distribution.Finally, through co-simulation, this paper concludes that the control strategy can savemore energy than the method of average distribution and single motor drive. Furthermorein NEDC condition, the energy saving ratio of this control strategy may be0.14%,6.46%,13.07%if the launch control, linear driving control and brake control areutilized, the corresponding value are0.35%,3.4%,22.61%in FTP75condition. Thereforethe control strategy can optimize the torque distribution and efficiency of the motors, andextend the endurance mileage of electric vehicle.