Research On Active Obstacle Avoidance Control Strategy Based On Braking And Steering Intervention

Automobile active obstacle avoidance technology through the controller to change the movement of the vehicle to reduce the probability of collision risk has become an important guarantee for vehicle driving safety.In this paper,front-wheel drive vehicles are the research object,and the control of the distance through braking intervention and steering control are studied.There are three active obstacle avoidance methods for lane change and the joint action of braking intervention and steering control.The main research contents of the paper are as follows:(1)Aiming at the longitudinal obstacle avoidance method that controls the longitudinal distance between vehicles through braking intervention,the longitudinal braking control system is divided into an upper controller that generates the desired acceleration and a lower controller that reduces real-time errors by using a layered control strategy.The upper controller uses linear The quadratic regulator,in order to maintain a suitable safety distance from the vehicle in front,simulates several representative safety distance models under the three working conditions of the vehicle in front of stationary,constant speed and deceleration,and selects the best performance as the Safety distance model under working conditions,the lower layer reduces control error through PID control theory.(2)Aiming at the steering obstacle avoidance method of changing lanes through automatic steering intervention,analyze the force and motion state of the vehicle during the driving process,build a tire model and a three-degree-of-freedom vehicle dynamics model,and verify the above models in the Carsim simulation software to ensure When the vehicle is moving,the curvature is continuous and the acceleration does not change suddenly.The fifth-order polynomial is used as the lane-changing path.Aiming at the traditional control method that cannot constrain multiple targets during the lane-changing process of the vehicle,a lane-changing path tracking controller based on model prediction is designed.(3)When a single brake intervention and steering intervention cannot effectively avoid obstacles,a brake-steer coordinated obstacle avoidance method with both braking and steering interventions is proposed.Set the longitudinal acceleration to remain constant during the lane change,and establish a fifth-order polynomial lane change path with constant longitudinal acceleration based on the relationship between the longitudinal and lateral displacement changes with time and the safety conditions of not colliding with the preceding vehicle during the lane change.(4)In order to verify the effectiveness of obstacle avoidance,three obstacle avoidance strategies,namely longitudinal obstacle avoidance,steering obstacle avoidance,and brake-steering coordinated obstacle avoidance,are set in the Carsim software to determine the feasibility of the strategy by setting different vehicle speeds and the initial distance between the two vehicles.verification.The simulation results of the longitudinal obstacle avoidance strategy in the three working conditions of the front vehicle at a standstill,constant speed and deceleration show that the upper controller of the longitudinal obstacle avoidance controller can give the desired deceleration according to different working conditions within the braking force range of the brake.The controller can reduce the real-time error of deceleration.Steering obstacle avoidance and braking steering coordinated obstacle avoidance can complete obstacle avoidance in a small distance between vehicles,and the critical safety distance required for coordinated obstacle avoidance is shorter.It can complete obstacle avoidance under extreme conditions,and the trajectory during lane change The tracking is accurate,the error between the expected trajectory and the actual trajectory is small,and the obstacle avoidance strategy is safe and reliable.