Vehicle Active Collision Avoidance Control Strategy Based On Horizontal And Longitudinal Coupling

With the continuous increase in the number of cars,various traffic accidents,especially collisions,and other safety issues have become more and more prominent.How to better avoid obstacles in front without driver intervention is of great significance to the development of active vehicle collision avoidance systems.However,most of the current active collision avoidance control systems decouple the horizontal and vertical collision avoidance research.Although the collision avoidance can be achieved to a certain extent,the stability of the vehicle during the collision avoidance process is not considered sufficiently.In order to make up for the limitation of single collision avoidance control,this research proposes to couple the horizontal and longitudinal collision avoidance control of the vehicle to better realize the collision avoidance effect against the obstacle in front and the driving stability of the vehicle.This study considers the dynamic coupling relationship between the vehicle’s horizontal and vertical directions,takes the actual longitudinal speed as the coupling point of the horizontal and vertical collision avoidance,and establishes the horizontal and vertical coupling collision avoidance controller.First,based on the traditional time-to-collision model t_ttc,a risk classification based on the longitudinal driving safety factor and the reciprocal of the time-to-collisiont^-1_ttcis proposed to determine the horizontal and vertical collision avoidance plan,and analyze the collision avoidance logic through the horizontal and vertical collision avoidance plan.Secondly,establish a laterally layered collision avoidance control method based on the linear time-varying model predictive control algorithm（LTV MPC）.The upper trajectory planning controller is based on a low-precision point quality model and plans to avoid obstacles based on obstacles and reference path information.The desired path.The lower-level trajectory tracking controller is based on a high-precision three-degree-of-freedom nonlinear dynamics model.According to the actual state of the vehicle and the collision avoidance trajectory input by the upper layer,it controls the front wheel angle of the vehicle,and realizes collision avoidance through active steering of the steering wheel.Tracking of collision avoidance trajectory.Thirdly,real-time control of the longitudinal speed is achieved through longitudinal collision avoidance.The upper controller obtains the braking deceleration of the vehicle based on the collision time safety model and the relative speed and relative displacement with the obstacle ahead.The lower-level controller is based on fuzzy PID,according to the braking deceleration of the upper-level vehicle,and realizes the control of the vehicle speed by controlling the pressure of the vehicle brake master cylinder.Considering the dynamic coupling,the real-time longitudinal velocity of the longitudinal collision avoidance output is used as the input parameter of the lateral collision avoidance to realize the establishment of the horizontal and longitudinal coupling controller.Finally,based on the Car Sim software,a vehicle dynamics model was established,including 7 major systems such as the car body,transmission system,braking system,steering system,suspension system,and tire model.Under different working conditions,the lateral collision avoidance control system.The horizontal and vertical collision avoidance control system is compared and analyzed,which further verifies the effectiveness of the horizontal and vertical coupling control strategy.