Research On Vehicle State Parameter Estimation Algorithms For Automotive Active Safety System

The automotive active safety system can greatly improve the vehicle's hedging ability and effectively reduce the accident rate.The premise of its function is to accurately and timely obtain the current vehicle operating state,such as the centroid deflection angle,the yaw rate and the road friction.The situation,etc.,by judging the current vehicle state information,and then controlling the vehicle to play a driving safety role.With the development of sensor technology,although these vehicle status information can be obtained by adding corresponding sensors,the same will increase the manufacturing cost of the automobile,which is not conducive to mass production of automobiles.Aiming at the above problems,based on the vehicle dynamics characteristics,this paper designs a vehicle state parameter estimation algorithm for the automotive active safety system based on the sensor information of the existing vehicle configuration.The specific work content is as follows:Firstly,aiming at the fact that the traditional vehicle driving state estimation algorithm based on three-degree-of-freedom dynamic model usually neglects the influence of wheel dynamic load on the lateral stiffness in the dynamic model,a vehicle driving state estimation algorithm considering the influence of wheel dynamic load under roll effect is proposed.The algorithm flow can be summarized as follows: Based on the Four-Degree-of-Freedom coupled non-linear vehicle dynamic analysis model considering roll effect,the mapping relationship between wheel vertical load and tire lateral stiffness is established by using BP neural network,and the real-time updating of tire lateral stiffness in the model is realized,and square-root cubature Kalman filter(SCKF)is used to construct the vehicle state parameter estimation algorithm.The algorithm can effectively estimate the vehicle longitudinal speed,the yaw rate,center of mass deflection angle and roll angle.The algorithm is validated on CarSim/Simulink simulation platform.Secondly,according to the performance results of the new algorithm and the traditional vehicle driving state estimation algorithm on the simulation platform,two kinds of vehicle driving state estimation algorithms are designed for real vehicle verification test,that is,the real vehicle test under right-angle bending condition where the wheel dynamic load changes greatly and the real vehicle test under off-track condition where the wheel dynamic load changes little.Comparing and analyzing the estimation results of the new algorithm and the traditional algorithm under the two validation conditions,the influence of wheel dynamic load changes on the vehicle driving state estimation algorithm is investigated.At the same time,the two algorithms are integrated into software.Finally,based on the single-wheel dynamic model,an algorithm for estimating the road friction is designed on the basis of vehicle driving state estimation.Specific algorithm flow can be summarized as follows: based on the driving wheel model,the longitudinal tire force observer is designed by using Lyapunuov stability theorem;based on the above-mentioned vehicle driving state estimation algorithm,the wheel load and slip rate are estimated;with the longitudinal tire force,slip rate and wheel load as input,and based on the PAC2002 tire longitudinal force model,the recursive least squares algorithm(RLS)was used to estimate the road friction.The validity of the algorithm is verified on CarSim/Simulink joint simulation platform and bench test platform respectively.The results show that the accuracy of the vehicle traveling state estimation algorithm considering the effect of wheel dynamic loads under roll effect is higher than that of the traditional algorithm when the wheel dynamic loads change greatly,and the accuracy of the two algorithms is equal when the wheel dynamic loads change slowly.On the whole,the new algorithm has better robustness and higher accuracy.The algorithm of estimating the peak adhesion coefficient of road based on single-wheel dynamic model is real.It has good timing and high precision,and can meet the requirements of active safety system of automobile.