Development of a Path Tracker Based on a 4WS Vehicle for Low-Speed Automated Driving Systems

With the increasing demand for various autonomous driving services in urban environments, low-speed autonomous vehicles, such as autonomous shuttles and purpose-built vehicles, equipped with enhanced driving characteristics suitable for urban roads featuring narrow streets, intersections, congested traffic, and small radii, are emerging. In particular, the 4WS (four-wheel steering) system, which is being integrated into these vehicles, is designed to steer both the front and rear wheels. This system improves steering responsiveness and stability, providing maneuverability under various driving conditions and making it highly suitable for urban environments. However, the 4WS system involves complex dynamic modeling and poses challenges in designing a path tracker, especially if factors such as the vehicle’s turning radius and road curvature are not properly considered. To address these challenges, this paper proposes a path tracker for a low-speed autonomous driving system based on a 4WS system, optimized for the characteristics of urban roads to minimize the vehicle’s turning radius and enhance driving performance. The proposed path tracker independently controls the front and rear wheels and incorporates road curvature and vehicle turning radius as feedforward terms to improve the response performance of the path tracker. The performance of the proposed path tracker was evaluated through simulations and real-car experiments.