A hierarchical-orthogonal-space approach to collision-free path planning

We present a methodology for 3-D collision-free path planning in which planning is done in the 3-orthogonal 2-D projections of a 3-D environment. Suboptimal path searching is done in each of the 3 orthogonal 2-D subspaces using primitive path segments. A hierarchical path searching method is introduced to speed up the search process. This approach lends applications to spatial planning in environments where no a priori knowledge is assumed. The three orthogonal 2-D projections can be readily obtained from 3 orthogonal cameras in simple environments.