Autonomous paddy field puddling and leveling operations based on full-coverage path generation and tracking

In planning the path for a puddling and leveling tractor in a paddy field, achieving multiple leveling across the whole area with minimal traversal while synchronously utilizing a rotary cultivator and a paddy-drive harrow is a key design requirement. This study describes the development of an autonomous puddling and leveling tractor equipped with an optimal coverage path planner (CPP) designed to enable the tractor to level the entire field more than twice using the paddy-drive harrow with foldable wings after prior tilling by the rotary cultivator in fields with irregular shapes. The genetic algorithm was employed to determine the optimal sequence of inner tracks by minimizing the headland turning distance and traversal throughout the field. The feasibility of the developed planner was investigated through simulation studies involving three different shapes of paddy fields, followed by a field test comparing autonomous and manually driven tractors. The simulation results confirmed that the developed CPP effectively achieved the proposed implement strategy and significantly improved efficiency by reducing headland turning distances by 28.5% (pentagon), 33.9% (trapezoid) and 45.0% (rectangle) compared to those obtained from the CPP with gathering track pattern used in a previous study. In the field test, the autonomous tractor demonstrated superior performance in distance and fuel efficiency over the manually operated tractor with comparable leveling capability. Although the operation time was increased by 30.3% because of the lower speed during headland turning, the autonomous tractor reduced travel distance and fuel consumption by 36.1% and 4.7%, respectively, reducing multiple or non-worked areas while resulting in similar altitude variability of 0.24 m (autonomous) compared to 0.19 m (manual).