Simulation Study Of Vehicle Active Collision Avoidance System

With the development of the automobile industry,traffic safety issues have increasingly become the focus of people’s attention,and the resulting active safety of automobiles has also become a hot spot for the majority of scientific researchers.This article aims to improve the driving safety of vehicles.Aiming at the problem of insufficient collision avoidance ability of a single longitudinal braking collision avoidance system on low-attachment roads,a vehicle combining longitudinal braking collision avoidance and lane-changing collision avoidance is designed.Active collision avoidance system.The system can autonomously decide the collision avoidance mode and control the steering or braking of the vehicle to avoid a rear-end collision when a straight-running vehicle is about to have a rear-end collision with the preceding vehicle and the driver does not respond in time.According to the components of the system,this article mainly conducts research from three aspects: longitudinal braking and collision avoidance control,steering and lane-changing collision avoidance trajectory tracking control,and active collision avoidance decision-making design.1.This article first established the vehicle longitudinal dynamics model,designed the longitudinal acceleration controller,and carried out a joint simulation with Car Sim software to verify the effect of the controller on the acceleration control of the vehicle.In order to take into account the comfort and safety of the collision avoidance process,a safety model based on collision time was built,and a longitudinal braking collision avoidance system with a two-stage braking intensity control strategy was adopted.The co-simulation verifies the collision avoidance performance of the system under high-adhesion road conditions.2.Through theoretical calculations,the characteristics of the two collision avoidance methods are compared and analyzed,and the model predictive control method is adopted to realize the trajectory tracking control of the steering-changing collision avoidance.In view of the poor road adhesion conditions,the model predictive trajectory tracking control is prone to problems such as poor vehicle stability,longer control adjustment time,and excessive adjustment of the control amount.A method of combined control of model predictive trajectory tracking and yaw moment is proposed.improve.Then,the yaw rate parameter and the reference value of the center of mass side slip angle output by the linear two-degree-of-freedom vehicle model when the vehicle is driving in a steady state are used as the control target,and the vehicle is designed using the method of linear quadratic optimal control and optimal tire force distribution.Yaw moment controller.3.Aiming at the problem that the longitudinal braking and collision avoidance method has greater limitations in collision avoidance under low adhesion road conditions,the peak road adhesion coefficient identification method is used to identify the road surface,and the road surface recognition results are used to evaluate the low adhesion road conditions.The safety distance model of the vehicle’s longitudinal braking and collision avoidance effectiveness.Then the decision logic of the active collision avoidance system was built,and the parameters of the latest braking distance and the latest steering distance required in the collision avoidance decision process were calculated.The limitation of longitudinal braking and collision avoidance under low adhesion road conditions is compensated by combining the way of steering and changing lanes to avoid collision.Finally,through the Matlab/Simulink and Car Sim co-simulation method,several working conditions are selected to simulate the active collision avoidance system designed in this paper.The simulation results show that when the road adhesion coefficient is low,the longitudinal braking collision avoidance cannot be avoided.In a collision,the vehicle of the active collision avoidance system can recognize the road surface,realize collision avoidance by autonomously switching the collision avoidance mode,and the vehicle can shorten the collision avoidance tracking adjustment time and reduce the front wheels through the joint control of model prediction and vehicle yaw moment The amount of corner adjustment can effectively improve the stability during steering and collision avoidance.