Design and validation testing of a complete paddy field-coverage path planner for a fully autonomous tillage tractor

Successful use of an auto-guided agricultural machine in paddy fields depends on the ability to generate a full-coverage path consisting of inner and outer-work paths adapted to various field shapes in the presence of an enclosing field boundary. To enhance the performance of a coverage path planner (CPP) developed in our previous study, this article describes the development of a complete CPP for a fully autonomous tillage tractor that provides automatic generation of both inner and outer-work paths, and boundary corner turning methods applicable to polygonal-shaped paddy fields with various corner angles. Computer simulation of the developed turning manoeuvres was conducted using a 3D tractor-driving simulator by analysing the trajectories of a virtual tractor on ground under varying corner angle conditions. A field evaluation was performed with a 60-kW auto-guided tillage tractor equipped with the developed CPP in three different shapes of paddy fields. The results of the computer simulation confirmed that the designed boundary corner turning methods could provide an acceptable level of tracking performance with lateral deviations <70 mm when following boundary corner turning paths. In the field tests, the autonomous tillage tractor successfully followed the whole paths with lateral and heading root-mean-squared errors ranging from 32 to 101 mm and 0.6°–2.2°, respectively, and demonstrated superior tillage performance by reducing the skipped areas of 1.7% (triangle), 0.9% (quadrilateral), and 1.0% (pentagon) of the total area as compared with that of 8.5% obtained with the previously developed system.