Planning Robot Motions in the SHARP System

Automating the programming of assembly robots necessitates to develop methods for planning robot motions. In this paper we describe the geometric models and the reasoning techniques we have implemented as part of the SHARP system (SHARP is an automatic robot programming system currently under development at the LIFIA laboratory). We first present which modelling facilities are required for constructing a suitable representation of the robot world. Then, we show how this representation has been used for implementing two classes of reasoning functions: functions aimed at computing collision free trajectories for the robot and its payload, and functions allowing to automatically generate contact based motions under uncertainty constraints (i.e motions involved in grasping and in part-mating operations). Our method for solving the first motion planning problem operates in the configuration space. It is based on two types of techniques aimed at computing the valid ranges of values associated with some selected motion directions, and at constructing and searching a graph representation of the free space. Solving the second planning problem makes it necessary to construct an explicit representation of the involved contacts along with their associated moving constraints. It leads to reason on the morphological properties of the manipulated objects.