Research On Vehicle Active Collision Avoidance Control System Based On Longitudinal Braking/Steering Lane-changing

Vehicle active collision avoidance control system has been a hot research topic in the field of automotive safety.When encountered danger situation, vehicle could solve the problem of collision vehicle through braking or lane-changing, which could effectively improve vehicle active safety. The object of study is the research on two kinds of collision avoidance—longitudinal braking and steering.Firstly, Paper has been determined the overall designed project of vehicle active collision avoidance control system. And defined the functions of respective parts as well as designed related specific structure. According to the different requirements of vehicle collision avoidance, decision-making mechanism of collision avoidance was presented, which to decide the optimal way of collision avoidance based on specific driving conditions. The following contents are mainly researched on three aspects: vehicle dynamics system modeling, safety distance model and controller design.In this paper, longitudinal dynamic system was established by Carsim — the dynamics simulation software. Then based on Matlab/Simulink software, vehicle inverse engine/ longitudinal braking kinetics model are set up. According to the analysis of the process of longitudinal braking,longitudinal braking safety distance model was researched on the analysis of braking process, and three kinds of safe distance expressions were obtained,which was discussed from the leading vehicle's status,such as typical static condition, uniform motion condition and emergency braking condition, as well as driver characteristics and road adhesion coefficient. On the basis of safety distance model, Paper was adopted a hierarchical control method to establish longitudinal braking controller by optimal control theory. Then through controlling vehicle dynamics system, the desired deceleration has been achieved and safe distance has been maintained.Through longitudinal braking merely on highway, vehicles are difficult to avoid ahead obstacles.And the typical control method could not satisfy lane-change problem constrained multi-objective optimization.Therefore, combined with the 3-DOF vehicle model and tire dynamics model, lateral movement characteristics of the vehicle has been analyzed. Based on the theory of Model Predictive Control(MPC), the emergent lane-change control system has designed. To combine with minimum longitudinal safety distance keeping model, lateral safety distance model based on five order polynomial reference path was proposed.Finally, considered about various constraints under the high speed steering condition, vehicle was controlled to change lane by controlling front wheel steering angle input and ensure the vehicle steering stability.Finally, according to the vehicles driving conditions, Paper was used Matlab/Simulink to design different simulation conditions. According to the decision-making mechanism, the collision avoidance control system selected the different way of collision avoidance, which could realize the expected function. And through the vehicle dynamics parameters constraints, the stability of the system and passenger comfort could be enhanced.