A Disassembly Path Planning Method for Mechanical Products in Narrow Passages Based on Improved RRT-connect Algorithm

The narrow installation space and complex assembly relationships of mechanical products bring difficulties to disassembly and maintenance. However, during product design process, it is difficult for designers to intuitively judge whether there is a product disassembly path in virtual environment. For such high-dimensional configuration space path planning problems, sampling-based algorithms such as Rapidly-exploring Random Tree (RRT) and its variants are widely used. However, due to the uniform sampling strategy of these algorithms, there are two problems: the planning performance is significantly reduced because of the low sampling probability in narrow passages, and the direction of products are random. Therefore, we improve the RRT-connect algorithm for disassembly path planning in narrow passages. First, we propose a narrow-biased sampling strategy to improve the sampling density in narrow passages. We use the bridge test to identify narrow passages, and modify the extend function of RRT-connect algorithm to make the tree extend to narrow passages with higher probability. We also propose a rotation constraint method to facilitate the disassembly and carrying of products. The rotation parameters are represented by unit quaternions and are changed only when necessary. When the sampling point is in wide space, the rotation parameters of the point are not changed. And when the sampling point is in narrow passage, the rotation parameters are changed to the direction perpendicular to the bridge (which means parallel to the narrow passage). Our method improves the efficiency of path planning in three-dimensional narrow space, and reduces unnecessary rotation of the product during random sampling.