Research On Traction Control System Of Four-wheel Drive Electric Vehicle

Due to the environmental pollution and energy depletion problem Electric Vehicle withits advantages of low pollution, low noise, high efficiency has quickly became the researchhot spot. The power sources and control systems of electric cars are significantly differentfrom traditional cars. The traditional active safety technology such as ABS, TCS, ESP has todevelop new control algorithm and implementation way in order to apply to EV. This paperfocus on the traction control of the double motor drive EV by reference to the domestic andforeign advanced research results and taking advantage of the rich resources of the projectgroup.Firstly, this paper expounds the current development situation of the electric vehiclesand some advanced traction control research methods and results in domestic and foreign.On the basis of analysing the structural characteristics of double drive EV, this paperdeveloped the vehicle dynamic model with simulink and veDYNA. With the15degrees offreedom vehicle dynamic model in veDYNA, we can add to the motor model,driver modeland power coupling model in order to turn the traditional vehicle model into the doublemotor drive vehicle.Secondly, this paper carried out the research on traction torque control of4WD EV. Thecontent mainly includes two aspects:driving force distribution and TCS. The forcedistribution between front axle and rear axle is on the basis of two degrees of freedomvehicle model, combining with the friction ellipse theory. We can get the distributioncoefficient in the condition of both axles arriving the operation limit. Distributing the drivingforce according to this coefficient can ensure the vehicle acceleration performance andimprove the vehicle’s lateral stability margin at the same time. Comparing with front-drive, rear-drive,and distribution according to load, this method can effectively improve the abilityof resistance to lateral interference. TCS control based on the theory of logic thresholdcontrol method, the tire slip rate are controlled within the specific scale. Firstly, the motorrotate speed has already been kown,we can use these datas to estimate the vehicle speed withthe method of dynamic slope. Secondly determine the target wheel speed by the target slipratio and target differential of wheel speed and finally set the wheel speed and wheelacceleration to be the threshold to make the control logic. By controlling the motor torque tochange the wheel slip state, preventing excessive wheel slip, improving vehicle accelerateperformance and the ability of resistance to the interference. At the same time, according tothe structural characteristic of the multity motor drive vehicle and the vehicle stabilityneeded, this paper determined the required torque of each motor and the driving mode of thevehicle.The key factors that influence the result are that motor driving ability, driving shaftslip state, the driving shaft torque demand.The vehicle can be adaptively four wheel drivethrough the power coupling device.Finally, this paper carried out off-line simulation and hardware in the loop experimentto verify the effectiveness of the proposed control strategy. By analysing those typicalparameters such as speed of the vehicle, longitudinal displacement, lateral displacement,acceleration, and the parameters of the motor parameters under the typical workingconditions (such as high and low adhesion road linear acceleration condition, high and lowadhesion under side wind disturbance condition, climbing conditions, etc), this paper hasverified the effectiveness of the proposed control strategy.