Researches On The Longitudinal And Lateral Control Of Intelligent Vehicle In Evasion Maneuvers

The development of automotive intelligence provides solutions to the traffic safety problems faced by automotive industry and provides a powerful impetus for industrial upgrading.Active collision avoidance is one of the representative technologies in automotive intelligence,which avoids or mitigates collision damage by changing the vehicle’s motion state actively.Considering the collision avoidance method,the vehicle can avoid more collision accidents by lateral steering collision avoidance under the conditions of high speed,low adhesion,and low overlap rate.Therefore,from the perspective of further improving the safety of vehicles,the research on the longitudinal and lateral active collision avoidance control strategy of vehicles is particularly important.Relying on the national key R&D project ‘Test and Evaluation Technology of AutoDriving Electric Vehicle’(No.2018YFB0105103)and the school-enterprise cooperation project ‘Development of ADAS Simulation Platform and Scene Verification’,this paper studies longitudinal and lateral active collision avoidance control methods of intelligent vehicles,and analyzes the collision risk assessment,collision avoidance mode decision,longitudinal active collision avoidance control and lateral active collision avoidance control.(i).Design of collision risk assessment and collision avoidance mode decisionFor the motion characteristics of the main vehicle and the target vehicle in the scene with potential collision hazard,the trajectory prediction method for the main vehicle and the target vehicle is designed based on the kinematics model.On this basis,the collision danger of the main vehicle and the vehicle in its driving area is analyzed from the perspective of the risk of collision,and the TTC/ETTC hybrid index which can reflect the driver’s hazard perception characteristics is used as the basis for judging.At the same time,according to the various safety of the lateral collision avoidance process,combined with the planning method of polynomial fitting,the latest turning point calculated by numerical algorithm is used as a judgment,and the TTC-1 is used to evaluate whether there is enough longitudinal space in the target area.Finally,the latest braking point obtained from the analysis of braking process is used as the decision-making basis combined with TTC/ETTC index.From driver characteristics and collision avoidance safety point of view,the decision-making logic of collision avoidance mode for longitudinal and lateral active collision avoidance control is designed.(ii).Study on Longitudinal Active Collision Avoidance Control StrategyFor the need of longitudinal active collision avoidance control,the longitudinal active collision avoidance control method with longitudinal acceleration as interface is designed.The combined control scheme of driving and braking is adopted.The idle sliding curve of the vehicle is used as the switching basis and the error compensation method.At the same time,according to the characteristics of the driving and braking systems,PD and PI feedback controllers are designed respectively to improve the stability of the system.Based on the active mechanism of i Booster and ESP,this paper designs a feedforward and feedback control scheme for active boost control.By using a rapid prototype controller,the characteristics of increasing pressure are analyzed,and the longitudinal dynamics control method is combined to verify the acceleration tracking effect.At the same time,for the increasing test scenario of longitudinal active collision avoidance control,the characteristics of the scene are analyzed from the Euro NCAP test standard.The multi-scene automatic simulation test platform for longitudinal active collision avoidance is set up by using the hierarchical structure of logical scene and concrete scene.(iii).Research on Lateral Active Collision Avoidance Control Strategy.For the requirements of path tracking accuracy and vehicle stability in the lateral active collision avoidance control,a simplified four-wheel vehicle lateral dynamics model with steering wheel angle and four-wheel braking force as input is established.Combined with approximate linearization and error feedback correction,a model predictive controller structure based on linear time-varying vehicle model is designed.By means of the model predictive controller structure,the objective function which comprehensively considers the lateral control precision and the dynamic characteristics of the actuator is designed.Vehicle stability constraints including rear wheel yaw angle and yaw rate,and the safety constraints consist of road boundaries are also designed.The simulation is carried out under typical conditions,and the results show that the controller can achieve better control effect than the optimal preview controller.(iv).System test and verification of longitudinal and lateral active collision avoidance control.Based on the active brake system prototype controller,a multi-scene real-time brake evaluation platform is build combined with d SPACE hardware and software tools.The realtime test of vertical active collision avoidance is carried out according to the Euro NCAP test standard.The results show that the TTC and ETTC mixed time indicators can achieve higher test results,and the active braking fast-running system can meet the requirements of active collision avoidance control.At the same time,this paper simulates and analyses the characteristic working conditions of collision avoidance.The results show that the intelligent vehicle active collision avoidance control system designed in this paper can accurately complete the assessment of collision risk,decision-making and control of collision avoidance process,and can further reduce the probability of collision accidents.