Assembly stability as a constraint for assembly sequence planning

In this paper we discuss assembly stability as a constraint for assembly sequence planning. An assembly sequence plan is a high-level plan for constructing a mechanical product from its component parts. Assembly stability is a very important constraint for assembly sequence generation and evaluation. The analysis of (sub)assembly stability avoids mating parts which tend to disassemble under the influence of gravity. Further more, the number of reorientations which gives a, good idea on the value of an assembly sequence depends on the stability of the parts to be assembled. We give algorithms to calculate the set of potentially stable orientations of an (sub)assembly considering static friction under uniform gravity. This set is applied for the evaluation of assembly sequences and the minimization of the number of reorientations during plan execution. Therefore, a new evaluation function based on the set of potentially stable assembly orientations is proposed and integrated into the assembly cost evaluation of a high level assembly planning system.