Graph-Based Cooperative Robot Path Planning in Agricultural Environments

This paper describes a method of using dual robot arms to cooperatively pick apples in an unstructured orchard environment. Each arm is equipped with an RGB-D (color- plus-depth) camera in an eye-in-hand configuration. The first robot arm, termed the Grasp arm, is positioned relatively close to the tree and designated with picking apples. It uses its camera to locate apples that are within view and also within reach. The second Search arm, is located nearby and is used to detect apples that are hidden from the grasp arm and to plan a clear path for it to those fruits using a method based on rapidly-exploring random trees. Fruit location and clear path information is encoded into a graph representation that is expressive enough to encode memory and lends itself to various decision-making algorithms. It embodies the idea of using clear paths for planning, as opposed to mapping obstacles, hence maintaining a lower-dimensional representation. Computer simulation and experimental results are presented based on a preliminary implementation.