Coverage Path Planning Algorithm for Autonomous Two-Pass Diagonal Harrowing: Geometry-Aware Swath Connection

Efficient tractor coverage planning requires suitable swath orientations and kinematically feasible connections. In two-pass diagonal harrowing, sequential boustrophedon planning treats the two swath families independently and may introduce avoidable connection travel. This study proposes a Field-Geometry-Aware Bidirectional Coverage and Connection Path Co-Optimization algorithm (FG-BCO) for a single tractor operating in convex, obstacle-free polygonal fields. FG-BCO clips two parallel swath families to the field boundary, constructs feasible cross-pass links between oriented endpoints, assembles alternating route paths, and applies subset dynamic programming to optimize their visiting order and traversal orientation. The resulting route is converted into a forward-only trajectory and checked against boundary-containment and minimum-turning-radius constraints. FG-BCO was compared with Sequential Boustrophedon Coverage Path Planning (SB-CPP) in rectangular, regular pentagonal, regular hexagonal, and irregular fields using 648 matched angle pairs per field. When the minimum path length of each algorithm was selected independently from the tested angle pairs, FG-BCO achieved reductions of 18.65%, 9.65%, 15.20%, and 17.11% in the four fields, respectively. However, FG-BCO produced shorter routes in only 57.87%, 41.82%, 40.43%, and 40.59% of the matched cases. The corresponding mean paired saving rates were 0.646%, −0.484%, −0.144%, and −0.833%, with medians of 0.939%, −1.060%, −0.923%, and −1.094%. These results distinguish the potential reduction obtainable through angle selection from performance under an arbitrary prescribed angle pair. FG-BCO is advantageous when the two swath families produce favorable endpoint proximity, heading compatibility, and turning space, but its improvement is not universal. Preliminary evaluation of the working-angle pair in relation to the target field geometry is therefore recommended before application.