Abstract: Because traditional CAD system can not support the design of mechanic motion scheme very well a hierarchical scheme model which is composed of three levels motion function mechanism mapping and mechanism combination is put forward. The level of motion function realizes the abstraction expression of design process and complex relationship of motion by function symbols. The level of mechanism mapping realizes the evolution of function symbols to mechanism symbols and mechanism symbols to assembly symbols by the mapping of motion function to mechanism and the mapping of motion relationship to mechanism combination. The level of mechanism combination realizes the visualization of motion scheme by the combination of assembly symbols.

Key words: Symbols Motion scheme Hierarchical model