A Research on Autonomous Vehicle Control in Track Beyond Its Limits of Handling 2021-01-0977

This paper presents the research related to the self-driving system that has been actively carried out recently. Previous studies have been limited to ensure the path following performance in linear and steady state-alike handling region with small lateral acceleration. However, in the high speed driving, the vehicle cornering response is extended to nonlinear region where tire grips are saturated. This requires a technology to create the driving path for minimum time maneuvering while grasping the tire grip limits of the vehicle in real time. The entire controller consists of three stages-hierarchy: The target motion is determined in the supervisor phase, and the target force to follow the target behavior is calculated in the upper stage controller. Finally, the lower stage controller calculates the actuator phase control input corresponding to the target force. Considering driving on a racing track, the best performance here is to drive the whole track course with the shortest lap time. The racing track consists of a series of straight and curved course section. In particular, there are two ways in which the vehicle can travel through the course the fastest in curved sections. The first is to reduce the racing path distance by driving inside of the cornering course, while the other is to escape at a high speed while maintaining a large turning radius and less centrifugal force. The first method is called “the shortest path driving”, and the second method is called “the least curvature driving”. In the end, the best driving in the racing track with straight and curved courses result from a balance in the form of a mixture of the least curvature and the shortest path distance driving techniques. That is why a tire grip, vehicle weight (specifications as entire mass, inertia moments of yaw, roll and pitch), powertrain output and braking capacity are different according to vehicles. This study covered vehicle control technology that creates and follows optimal driving paths while maintaining maximum lateral acceleration within high speed driving tracks.