Assembly modelling by geometric constraint satisfaction

A new approach for representing and reasoning about assemblies of mechanical parts has been developed. The approach combines a formalism for representing relationships among features with a new method for geometric constraint satisfaction. The method employs symbolic reasoning about the geometric structure of parts to solve spatial constraints between the parts, in contrast to other approaches that reduce the geometric relationships to a set of non-linear equations to be solved. The system characterizes over-, under-, and fully-constrained assemblies. For under-constrained assemblies, the remaining degrees of freedom are automatically coalesced into a set of kinematic joints that capture some of the functionality of the assembly. For over-constrained situations, redundant constraints are identified and checked for consistency, and degenerate cases are handled; this allows multiple feature relationships between two parts to be handled. A computer implementation in a limited feature domain is described and used to illustrate the approach with an example. Copyright (C) 1996 Elsevier Science Ltd