RRT*-GSQ: A hybrid sampling path planning algorithm for complex orchard scenarios

Traditional sampling-based path planning algorithms, such as the rapidly-exploring random tree star (RRT*), encounter critical limitations in unstructured orchard environments, including low sampling efficiency in narrow passages, slow convergence, and high computational costs. To address these challenges, this paper proposes a novel hybrid global path planning algorithm integrating gaussian sampling and quadtree optimization(RRT*-GSQ). This methodology aims to enhance path planning by synergistically combining a Gaussian mixture sampling strategy to improve node generation in critical regions, an adaptive step-size and direction optimization mechanism for enhanced obstacle avoidance, a Quadtree-AABB(quadtree - axis-aligned bounding box) collision detection framework to lower computational complexity, and a dynamic iteration control strategy for more efficient convergence. In obstacle-free and obstructed scenarios,compared with the conventional RRT*, the proposed algorithm reduced the number of node evaluations by 67.57% and 62.72%, and decreased the search time by 79.72% and 78.52%, respectively. In path tracking tests, the proposed algorithm achieved substantial reductions in the root mean square error(RMSE) of the final path compared to the conventional RRT*. Specifically, the lateral RMSE was reduced by 41.5% in obstacle-free environments and 59.3% in obstructed environments, while the longitudinal RMSE was reduced by 57.2% and 58.5%, respectively. Furthermore, the maximum absolute errors in both lateral and longitudinal directions were effectively constrained within 0.75 m. Field validation experiments in an operational orchard confirmed the algorithm's practical effectiveness, showing reductions in the mean tracking error of 47.6% (obstacle-free) and 58.3% (with obstructed), alongside a 5.1% and 7.2% shortening of the path length compared to the baseline method. The proposed RRT*-GSQ algorithm effectively enhances path planning efficiency and navigation accuracy for robots, presenting a superior solution for high-precision autonomous navigation of agricultural robots in orchard environments and holding significant value for engineering applications.