Stability Monitoring Algorithm with a Combined Slip Tire Model for Maximized Cornering Speed of High-Speed Autonomous Driving

This paper presents a stability monitoring algorithm with a combined slip tire model for maximized cornering speed of high-speed autonomous driving. It is crucial to utilize the maximum tire force with maintaining a grip driving condition in cornering situations. The model-free cruise controller has been designed to track the desired acceleration. The lateral motion has been regulated by the sliding mode controller formulated with the center of percussion. The controllers are suitable for minimizing the behavior errors. However, the high-level algorithm is necessary to check whether the intended motion is inside of the limit boundaries. In extreme diving conditions, the maximum tire force is limited by physical constraints. A combined slip tire model has been applied to monitor vehicle stability. In previous studies, vehicle stability was evaluated only by vehicle acceleration. The proposed algorithm improves vehicle stability by independently monitoring the saturation point and tire slip angle of four wheels in real-time. The monitoring algorithm and coordinated motion controller have been successfully implemented. The performance has been investigated via both computer simulations and vehicle tests. The vehicle stability is verified by implementing high-speed autonomous driving on a racing track. The results show that the proposed algorithm prevents vehicle instability in advance. In the simulation, the front wheel slip angle decreased from a maximum of 11.5 deg to -5.0 deg, maintaining the vehicle stability. In the vehicle test, the tire slip angle did not exceed the saturation point and showed stable high-speed autonomous driving.