Research Of Vehicle Active Collision Avoidance Based On Cooperative Control Of Braking And Steering

With the rapid development of intelligent transportation system and automatic driving technology,the research on active collision avoidance system has drawn wide attention.Aiming at the limitations of single braking and steering collision avoidance modes in terms of braking distance and lane changing stability,it is of great importance to research on the active collision avoidance based on cooperative control of braking and steering.In the paper,combined with Changzhou technology plan and application of basic research project "research on automobile emergency collision avoidance system based on coordinated control of active steering and braking",a collision avoidance strategy based on cooperative control of braking and steering,which used function allocation and multiobjective fuzzy decision,was proposed.Active collision avoidance control of the vehicle was achieved,and the simulation tests under different conditions were carried out.Aiming at the important influence of the change of road adhesion coefficient on the safety distance of collision avoidance,the road adhesion coefficient was estimated by recursive least square method with limited memory,and the typical pavement type was identified.Aiming at the collision avoidance mode of braking,a braking safety distance model was established to adapt to different road surface.Aiming at the collision avoidance mode of steering,a model of lane changing trajectory and lane changing safety distance was designed to improve the adaptability of safety distance model.In order to overcome the limitation of a single collision avoidance method and solve the problems of vehicle collision avoidance under complicated working conditions,a collision avoidance selective strategy based on functional allocation and multi-objective fuzzy decision was proposed.Based on the constraint of attachment and domain of distribution coefficient,the vague set theory was used to determine the stability region of brake and steering distribution coefficient based on the typical road surface to ensure the safety and stability of the collision avoidance process.In order to realize the cooperative optimization distribution of braking and steering,an optimal method of functional distribution coefficients based on genetic algorithm was proposed.The fitness function,which was about normalized sum of values of braking deceleration,braking safety distance,lane change time and lateral acceleration,was designed,and the more optimal distribution coefficients were selected.In order to track the expected value well,the braking and steering controllers were set up to achieve the closed-loop control.In order to establish the functional relationship between the control variables of brake deceleration and lateral acceleration and the input variables of brake pressure and steering wheel angle,the inverse dynamics model of braking and steering was established.The stability threshold was established to evaluate the stability of collision avoidance process.Based on the CarSim and Simulink co-simulation platform,the estimation tests of road adhesion coefficient in the linear and saturation regions of the tire and the collision avoidance tests under different typical road conditions were carried out.The simulation results show that the recursive least squares algorithm can effectively identify typical mutant pavement;It can effectively shorten the collision avoidance distance through cooperative control,and the vehicle has better handling stability in the process of collision avoidance,which improves the driving safety.