Trajectory Tracking and Differential Steering Coordinated Control of Active Collision Avoidance Under Extreme Conditions

This paper proposes a novel active collision avoidance (ACA) control structure, in order to improve the performance of vehicles under extreme steering driving conditions. Firstly, the critical safety distance models of the two emergency modes are optimized by considering the road adhesion coefficient (RAC), driving state of the preceding vehicle, ultimate capacity of the braking system and lateral acceleration constraints comprehensively. According to the change curves of these two models with vehicle speed and intersection point, the decision space is divided into four regions, and the car-following mode is added. An improved ACA decision-making mechanism with three modes of car-following / emergency braking / emergency steering is proposed. Then, an ACA cooperative control framework utilizing longitudinal and lateral cooperative trajectory tracking control (LLC-TTC) integrated with differential steering control (DSC) based on model-free adaptive control (MFAC) theory is proposed. Finally, an improved phase plane delineation method based on the bilinear method is proposed considering the three constraints of yaw rate, maneuverability and stability. The co-simulation results show that the ACA control method proposed in this paper maximally improves the trajectory tracking accuracy and lateral stability performance by 23.18% and 33.47%, respectively, compared with the traditional integrated control with DYC (IC-DYC) under the three typical extreme driving conditions. This bears significance for the effectiveness of ACA control system to improve vehicle safety under extreme driving conditions.