An interpreter for a language for describing assemblies

This paper makes explicit the relation between relative part position and kinematic freedom of the parts which is implicitly available in the literature. An extensive set of representative papers in the areas of assembly and kinematic modelling is reviewed to specifically identify how the ideas in the two areas are related and influencing the development of each other. The papers are categorised by the approaches followed in the specification, representation, and solution of the part relations. It is observed that the extent of the part geometry is not respected in modelling schemes and as a result, the causal flow of events (proximity–contact–mobility) during the assembling process is not realised in the existing modelling paradigms, which are focusing on either the relative positioning problem or the relative motion problem. Though an assembly is a static description of part configuration, achievement of this configuration requires availability of relative motion for bringing parts together during the assembly process. On the other hand, the kinematic freedom of a part depends on the nature of contacting regions with other parts in its static configuration. These two problems are thus related through the contact geometry. The chronology of the approaches that significantly contributed to the development of the subject is also included in the paper.

This paper presents a feature-based method to obtain assembly mating relations between a set of polyhedral components. Previous research in assembly planning has assumed that these assembly mating relations, or equivalent information such as the final assembled configuration of the components, is provided as part of the problem input. This paper addresses the case where only the component geometry is provided, which can arise in product maintenance or emergency repair applications where the originally designed assembly mating relations are no longer valid, and in robotic autonomous construction applications. The basis of the method is to represent components in terms of form features using a feature recognition method based on Alternating Sum of Volumes with Partitioning (ASVP) decomposition. Feature recognition is applied to each component to obtain its Form Feature Decomposition (FFD), which is a hierarchy of positive and/or negative form features. Positive form features of each component are compared with negative form features of other components to obtain mating relations between pairs of features. Multiple feature matings between the same pair of components are merged into component matings, which comprise the assembly mating relations. A backtracking search generates all feasible assembly configurations from the component matings.

We present a new and convenient method for automatically positioning parts in an assembly. High-level entities of mating features and mating relations are used to describe the composed state of parts in an assembly. The characteristics of volume, reference origin, and boundary face of mating features and parts are used to determine automatic part-positioning operations. Using the proposed approach, a hierarchical model of the assembly can be constructed more easily with fewer input data. This approach thus makes computer-aided assembly design systems more user-friendly and greatly reduces the amount of input data required. An example is presented to demonstrate the simplicity and effectiveness of the proposed approach.