Time-optimal guidance control for an agricultural robot with orientation constraints

This paper deals with time-optimal control for the row guidance system of an autonomous field robot with differential drive. The movement of the robot is concretely constrained by the plant cultivation environment. A time-optimal differential velocity profile is generated based on optimal control theory to eliminate any initial error or tracking deviation. To allow for an efficient implementation on a micro-processor, a substitute controller is suggested to perform the minimum-time guidance task. The substitute with a cascade structure is proposed using PID algorithms. The computational efficiency is consequently improved and the system is more convenient to be carried out on a micro-processor. The performance of the proposed substitute system is investigated through numerical studies by comparison with the time-optimal controller. Experiments are comprehensively conducted indoors and outdoors to evaluate the proposed row guidance regime. The results show the satisfactory performance and efficiency with a high precision of ±3cm in the field.