Study On The Estimation Of Vehicle Dynamic State And Road Adhesion Coefficient

Recent years people need more high-level demands for vehicle active safety.Electronic Stability System,which can maintain the stability of the vehicle under extreme driving conditions,has a rapid development.In order to improve the reliability of the system,the vehicle state parameters should be obtained accurately in real time.At present,it is not suitable for large scale application in the actual application of vehicles because the method of direct measure vehicle state is immature and costly.In order to obtain the parameters of the vehicle state variable accurately,the estimator based on extended Kalman filter is designed in the paper.It has great significance for improving the reliability of vehicle stability control system to obtain the vehicle motion state and road adhesion coefficient.The specific work is as follows:Firstly,the nonlinear seven degrees freedom vehicle model,which can reflect the vehicle longitudinal movement,lateral movement and yaw rate,is established in the software of MATLAB/Simulink.And the calculating model correspondingly is given.Its kinematic state and dynamic state are analyzed,and the validity of the vehicle model is verified by the real vehicle,which provide research foundation for the following estimate methods.Secondly,by researching Kalman filter principle and characters the vehicle state parameters estimation model is established combined with vehicle dynamic model.The estimator model can estimate the longitudinal velocity,lateral velocity and yaw rate.According to the verification results,revise and adjust the estimation algorithm to improve the estimation accuracy.Finally,by studying the influence of the road adhesive characteristics on the vehicle dynamics,the calculation formula of tire force and adhesion coefficient are obtained through deforming the “magic formula” tire model.The road friction coefficient estimation model,which can estimated the road friction coefficient,is established based on the theory of extended Kalman filter.The reliability of the estimation method is verified by compared with the set value of the road adhesion coefficient.The estimation model of vehicle state parameters and road adhesion coefficient is designed based on the extended Kalman filter in the paper.The accuracy of the estimation algorithm is verified,the result shows that the estimator has good reliability.