State Estimation Of Electric Vehicle With4In-wheel Motors

As people’s living standards and economic conditions improve, number of carsincreased year by year. At the same time, environment, resources and security issues growobviously. In recent years, people pay more and more attention to the development ofelectric vehicles, with the strong support of government, electric vehicles will gainpopularity. Due to the increasing number of vehicles equipped with ABS/ASR and ESP,traffic accidents decreases. We have to know the accurate sideslip angle and yaw rate totake control of the car by ESP.The longitudinal velocity is an important parameter of vehicle, playing an importantrole in ABS/ASR and ESP. We have to estimate the longitudinal velocity by the signal ofwheel speed sensor and verify the accuracy of our estimation method by HIL.Estimation of accurate longitudinal speed is the basis for estimation of sideslip angle.Based on the electric vehicle’s driving and braking torque is easy to obtain, this paperestimate the sideslip angle by using vehicle dynamics method. Through two degree offreedom four wheel vehicle dynamics model and HSRI tire model, getting the formula toestimate sideslip angle by KF. Then carry on the simulation in veDYNA in differentworking conditions. The simulation results show that the method used in this paper isreal-time and has good estimation accuracy.Sideslip angle estimation is based on the already known road friction coefficient andthe actual road friction coefficient is difficult to measure directly. Also it needs to beestimated. Selection of three degree of freedom four wheel vehicle dynamics model and theHSRI tire model are for the estimation of road friction coefficient. Longitudinal, lateralacceleration and yaw rate as the measured variable of extended Kalman filter. Jointestimation is necessary, analyzing the influences and the final estimation effect of them. Theresults show that: the joint estimation will influence each other, the final results of theestimated separately and the effects of some deviation, but the overall effect is basically the same. As long as we can ensure the road friction coefficient and the sideslip angleestimation are in a certain range of error, joint estimation effect can be guaranteed.Relatively speaking, the sideslip angle estimation has little influence on the road frictioncoefficient estimation, and the road friction coefficient affects the sideslip angle estimationresult more.