Study On SUV Safety Driving On Highway Based On Unscented Kalman Filter State Estimation

The safety driving of automobile on highway has always been one of the most important parts of traffic safety.Because of higher center of mass and faster speed,rearend collision and rollover accidents of SUV are a frequent occurrence on highway.Therefore,the car-following safety and handling stability of SUV attract researchers’interest.Compared with the passive safety technology to reduce the loss of life and property after car accidents,The active safety technology aimed at improving vehicle driving safety and handling stability is more forward-looking and preventive.In this paper,the sport utility vehicle(SUV)driving on highway is chosen as the research target.Considering the types of traffic accidents and the characteristics of SUV itself,through the analysis of the state of SUV driving on the highway,modeling plane motion dynamics and rollover dynamics of automobile based on plane motion,and the plane motion dynamics model includes the three degrees of freedom considering linear tire force and the seven degrees of freedom considering magic formula.According to the established plane motion dynamics model,Kalman Filter(KF)would be used to estimate the state parameters,such as longitudinal vehicle speed,yaw rate,sideslip angle and wheel rotation speed respectively.Two method including self-building filter modules and Simulink’s toolbox modules,which are composed of various dynamics models and filter algorithms,were tested in conditions as follows:double-lane change,straight-line braking and step condition with SUV parameters in the Carsim/Simulink co-simulation.Then,Unscented Kalman Filter(UKF)filter based on the nonlinear seven degrees of freedom model is selected,because of its accurate estimation of the state parameters.Considering the main motion form of SUV on highway and the characteristics of the higher centre of mass of the SUV itself,the car-following process and handling stability would be analysed:a safety distance analysis based on the braking process consist of a variety of factors is proposed,and the parameters previously estimated are applied to the SUV on highway car-following safety.The roll stability about steady-state response under time domain is analysed in a dynamics model based on the previous study of the plane motion.Besides,the influence of the yaw rate,sideslip angle and slip ratio on the handling stability were also considered.Then select different parameter evaluation index for the research:safe distance is chosen as the index to judge the process of car-following safety,the lateral load transfer rate is selected as the index to judge the roll stability,thresholds of yaw rate,sideslip angle and slip ratio were picked to indicate the lateral and longitunal stability.Compared with above thresholds based on SUV’s driving parameter estimation under different conditions,it was verified that following driving safety and handling stability evaluation index as SUV highway safety driving theory and practice is reliable.Based on the types of highway accidents and the unfavorable factors of SUV structure,this paper calculates and deduces the evaluation index and threshold value of SUV’s car-following driving safety and handling stability by using the Unscented Kalman filter state estimation method based on vehicle dynamics model,which has the best estimation effect.Through the joint simulation of CarSim/Simulink,the carfollowing safety and handling stability of SUV driving on highway are evaluated.It’s shown that the results can provide a theoretical and practical basis for the development of early warning system of SUV safety driving on highway.