Research On Traction Control For In-wheel-motor Electric Vehicle

The change in chassis structure and the driving mode of in-wheel-motorelectric vehicle push forward the reform of the VSC and TCS in internalcombustion engine vehicles and also bring more challenging problems. Theresearch in this paper is doing under this background and has theory and practicalsignificance.Firstly, this paper analyzes the TCS problem for in-wheel-motor electricvehicle on basis of that for internal combustion engine vehicles. This chapterpresents the traction control strategy and the way to calculate the desired slipratio.Secondly, this paper proposed the slip ratio control model according to thedefinition of slip ratio and the dynamic equation of wheel and vehicle. Thismodel is related with wheel speed, acceleration, drive torque and slip ratio. It canbe used to control the slip ratio in every wheel independently. The parameter inthe model can be got by calculating or estimating. This model solves the coupleof the four wheel slip ratio in the slip ratio equation. A LPV controller withdisturbance rejection is designed based on Hinf method. The system with thiscontroller has good robust performance. In order to verify the performance of theslip ratio control, this chapter shows the simulation results under different testconditions by using the high precision vehicle dynamic simulation software. Theresults of the simulation show that the slip ratio control method proposed in thischapter is effective.The former slip ratio model does not take consider of the road adhesioncoefficient. The essence of it is to control the slip ratio by adjusting the vehicleacceleration. The slip ratio appears oscillation because of the big inertia of thevehicle. In order to solve the oscillation, the slip ratio control approach isimproved by using Dugoff tire model and treating the nonlinear term in theDugoff model as variable under the condition of the known road adhesioncoefficient. Then A new LPV slip ratio model has been derived. The parametervertices is determined by analysis and a different slip ratio control methodcomparing to the former one is presented. The simulation results show that thiscontrol method is more effective than the former one.Different with the straight driving condition, when the vehicle is steering, the yaw rate and the sideslip angle maybe exceed the stability limitation. So thata research of traction control in steering condition is done through slip ratioscheduling at last. The bicycle model in most research is changed by consideringthe nonlinear part of the driving force and side force and derives a novel yaw rateand sideslip angle model. When the vehicle is driving on low friction coefficientroad and has a big steering angle, the yaw rate and the sideslip angle maybeexceed the limitation which will lead to uncontrollable of the vehicle. A modelpredictive control method is presented to scheduling slip ratio according to theproposed sideslip angle and yaw rate control model. In order to limit the yaw rateand side slip angle, this paper derived the control model which can reflect theconstraint of sideslip angle and yaw rate and the dynamic character of sideslipangle and yaw rate.A slip ratio scheduling approach is given using modelpredictive control method. And simulations are done combining with the slipratio control method while the road adhesion coefficient is unknown. Thesimulation results show that the yaw rate controller is effective when the vehicleis driving on low friction coefficient road.