Research On Control Strategy Of Vehicle Active Collision Avoidance System

The rapid development of the automobile industry has brought great convenience to human life,and it has also brought severe traffic safety problems to human beings.With the continuous development and progress of the society,countries have paid more and more attention to traffic safety issues.Research on the field of active safety technology for avoiding accidents has become a hot topic in research in various countries.Among them,the research on active collision avoidance system of automobiles is gradually becoming one of the research hotspots in the field of active safety of automobiles at home and abroad.Through in-depth study of the car’s active collision avoidance system,it can effectively reduce the traffic accident rate,reduce the property losses of the people and society,and promote the rapid development of the intelligent transportation system.Based on the research results of the active collision avoidance system at home and abroad,the overall scheme of the vehicle active collision avoidance system is planned.Then,it points out the key technologies needed to realize the overall scheme,and proposes the functional modules of the system.According to the functions of the system,the overall plan technical requirements and implementation approaches of the vehicle active collision avoidance system are planned.With the powerful modeling function of CarSim software,the vehicle system dynamics model,radar model and C-NCAP（China-New Car Assessment Program）test scene are established,and the vehicle inverse longitudinal dynamics model for calculating the desired throttle opening and the desired brake pressure is established.The safe time scale TTC（Time to Collision）model of the vehicle active collision avoidance system is studied.In order to accurately and intuitively judge the danger degree of the current working condition,based on the full use of the known vehicle motion information and the safe time scale model,a new collision time TTC modeling methodis adopted,and the safe time scale model is used as the system’s risk judgment indicator.Based on the risk determination index TTC,an active collision avoidance system conforming to the driver’s collision avoidance characteristics is developed.The brake response time of the driver under typical dangerous conditions,the average and maximum deceleration of the driver’s braking during collision avoidance are analyzed.The active collision avoidance grading braking strategy is designed according to the driver’s braking characteristics,and the parameters of the TTC and the host vehicle speed are taken as the determination conditions.The key parameters are based on the driver’s characteristics and the actual vehicle test results.At the same time,an early warning threshold T_warningarning is introduced.According to the C-NCAP test requirements for early warning in the automatic emergency braking system,the relative speed,the deceleration during the driver’s braking and the driver collision avoidance reaction time are considered,and the active collision avoidance warning strategy is designed.The system uses early warning of sound and light to help the driver achieve effective collision avoidance.The TTC model,control strategy and inverse longitudinal dynamics model are all built in Simulink.Based on the software environment of Simulink and CarSim,co-simulation is carried out.According to the test conditions of the automatic emergency braking system in C-NCAP,verifying the validity of the safe time scale model,braking strategy and early warning strategy of the active collision avoidance system.Then the control algorithm is integrated into the real vehicle test platform of the active collision avoidance system.The overall function and various key technologies of the active collision avoidance system under the C-NCAP condition is tested.Simulated and real vehicle test results show that the grading braking strategy and collision warning strategy of the system are in line with the driver’s collision avoidance characteristics,reflecting the priority and coordination of driver control,which can effectively avoid collisions,and the results of simulation and real vehicle test are consistent in the trend.It verifies the effectiveness of the vehicle’s active collision avoidance system collision warning strategy and the grading braking strategy meet the requirements of the car active collision avoidance system.