Contact formations and design constraints: a new basis for the automatic generation of robot programs

In order to achieve an ultimate goal of automatically generating assembly programs for robots from design information, it is necessary that one be able to devise part-mating strategies that will work in spite of sensor, control and manufacturing errors. In general, this is almost certainly unachievable. However, if appropriate design and motion constraints relating nominal and error parameters (of the system) are enforced, significant progress can be made. As the first step in our approach, we introduce a concept of contact formations to describe contacts among parts in a system, aiming at reducing the dimensionality of assembly verification. We also describe a technique for identifying contact formations in spite of system errors. Next, we develop a replanning strategy together with design and motion constraints sufficient to guarantee the success of the strategy for certain insertion tasks. The constraints are reasonable in the sense that they do not impose unrealistic conditions on typical designs. Simulation results uphold the theoretical derivations and show empirically that the theoretical constraints can be relaxed somewhat with excellent results still obtained.