Advanced Path Tracking Controller for Follow Trails-Of-Tractor Guidance Objective Without GNSS

Automatic guidance systems are crucial in modern agriculture, enabling precise field operations such as planting, spraying, and harvesting. Current methods often rely on Global Navigation Satellite System (GNSS) technology, which can be limited by signal loss or inaccuracies. While GNSS-based tractor guidance is standard, combined tractor and trailer navigation is not widely adopted, and dependency on centimeter-level GNSS is a limitation. This paper introduces a novel guidance method that eliminates the need for GNSS, utilizing a limited set of sensors for state estimation including, trailer steer angle, tractor velocity and tractor curvature feedback. The proposed approach calculates the tractor path based on past states, allowing the trailed implement to follow the tractor tracks with high accuracy. A feedback controller adjusts the implement steering based on computed lateral and angular deviation errors, using proportional gains. Additionally, a feedforward component from the tractor curvature enhances system responsiveness. This paper presents the concept, controller design, simulation results, and real field experiments with full-size machinery.