| Along with the continuous progress and development of science and technology,intelligent vehicles as the main participants of intelligent transportation,is an important carrier to achieve the vehicle active obstacle avoidance function,so the study for the intelligent vehicle-based vehicle active safety field collision avoidance trajectory planning as well as tracking control is an effective solution to improve vehicle driving safety.Among them,trajectory planning is the basis to achieve vehicle safety collision avoidance.Since the longitudinal and horizontal direction control in tracking control has a complex coupling relationship,this paper takes the vehicle speed as the coupling point and adopts the longitudinal and horizontal direction joint control scheme to study the collision avoidance strategy of intelligent vehicle.Firstly,the longitudinal and transverse motion and yaw motion of the vehicle were taken as the research entry point,the tire magic formula was used to simplify the dynamics model,and the vehicle model in CarSim software was selected as the reference model to verify the validity of the model established in this paper,which laid the foundation for the following tracking controller research.Secondly,according to the abstraction and simplification of the driving scenario,the minimum safe distance model under three working conditions is defined,and the fuzzy logic-based lane change decision strategy is established by combining the difference between the actual distance of two vehicles and the minimum safe distance and the relative speed of vehicles.The decision time is used as the reference point for collision avoidance trajectory planning,and the quintic polynomial is used as the reference trajectory for collision avoidance.By establishing the objective function,the optimal collision avoidance trajectory with constraints is solved.Then,based on the model predictive control algorithm,the lateral trajectory tracker in this paper is built,and the objective function of the control algorithm is designed with the control objective as the model optimization purpose.In order to get a good tracking control effect,and at the same time,to maintain good dynamic characteristics of the vehicle in motion,it is necessary to control the amount,control increment and dynamic constraints,The tracking effect of the lateral controller is verified by using the common double lane shift trajectory of vehicle driving stability evaluation.To make the vehicle travel as close as possible to the given desired speed.The fuzzy PID algorithm is used as the theoretical basis to build the longitudinal speed controller in this paper.The control quantity is selected as the throttle opening and braking pressure of the vehicle,and two conditions of acceleration and deceleration are adopted.Compared with the traditional PID control algorithm,the good control effect of the longitudinal speed tracking controller is verified.Finally,the joint control of the longitudinal and transverse controllers is realized with the vehicle speed as the coupling point,and the maximum driving speed of the vehicle under the planned reference trajectory is designed,and the simulation is analyzed and verified by the real collision cases extracted from the NAIS database and a kind of dangerous working condition in which the target lane is disturbed by an obstacle vehicle.The results show that the proposed The results show that the collision avoidance control method proposed in this paper can effectively avoid collisions while ensuring the driving stability of the vehicle. |
