Hierarchical object models for efficient anti-collision algorithms

The author presents an offline programming system specially designed for complex robotic applications (e.g., intervention of redundant manipulators in a nuclear plant). It uses hierarchical CAD models of solids and manipulators. These models are derived from constructive solid geometry trees and combine simple volume primitives with union or difference set operations. They offer different levels of description of the objects and enable an efficient computation of local minima of the distance between points of the objects. By setting constraints on the variation of the distance at these points, it is possible to produce collision-free trajectories achieving complex tasks with Cartesian and/or joint parameter goals