A structure model is presented which can represent not only the simplified geometry of an individual part but also the whole structure of a machine. The model is derived from observation of the general features of a machine, ie the hierarchy and the topology (connectivity) among parts. The model plays an important role in developing a CAD system to aid designers in the primary design stage, because a general method for representing the whole structure of a machine is needed at that stage. An interactive machine design system named HIMA DES-I has been developed. The data structure of the system is based on the above structure model. The system has some original features, the most distinctive of which is the unified algorithm for dimension matching and motion analysis which reduces design labour in the primary stages of machine design.
structure model, hierarchy, topology, dimension matching, motion analysis
In the field of CADCAM, development of solid modelling systems has taken place in many countries. I n a machine design system, a solid model can play an important role at the stage of detail design. However, it cannot play such an effective role at the stage of primary design. The reason is that most existing solid modelling systems aim at a general representation of the geometry of a single solid (part), but not at helping designers at the whole-machine design stage where many parts have to be dealt with simultaneously. In this stage, one should consider the relations between parts and the whole structure or mechanism rather than the detailed geometry of each part. In order to realize a machine design system which helps to design a whole machine, it is essential to set up a more global model that can represent a whole machine systematically in a computer.This paper presents such a model, which the authors call a structure model. It can represent the general features of machine structure, ie the hierarchy and the connectivity