Motion planning with six degrees of freedom by multistrategic bidirectional heuristic free-space enumeration

This paper presents a general and efficient method that uses a configuration space for planning a collision-free path among known stationary obstacles for an arbitrarily moving object with six degrees of freedom. The basic approach taken in this method is to restrict the free space concerning path planning and to avoid executing unnecessary collision detections. The six-dimensional configuration space is equally quantized into cells by placing a regular grid, and the cells concerning path planning are enumerated by simultaneously executing multiple search strategies. Search strategies of different characteristics are defined by assigning different values to the coefficients of heuristic functions. The efficiency of each search strategy is evaluated during free-space enumeration, and a more promising one is automatically selected and is preferentially executed. The total number of necessary collision detections for free-space enumeration mainly depends on the most efficient search strategy among the evaluated strategies. Therefore, the free-space cells are efficiently enumerated for an arbitrary moving object in all kinds of working environments. This method has been implemented and has been applied to several examples that have different characteristics.