Abstract: A generic function and an effect feature model are proposed in the research of conceptual design based on the mapping process of function-effect-solution. A derivative function and physical parameters are then introduced, which disclose that the derivative function is a bridge in the functional space expansion. To realize the one-to-more mapping process of product function, functional field expanses layer by layer. The strategy expansion of functional space based on the variation of original aim function, the strategy of expansion from derivative functions to effects, and the strategy of functional space expansion based on physical quantities reasoning from effects are put forward respectively. The process of functional space expansion with three phases is then discussed in detail, which includes four layers: original function layer, derivative function layer, effect layer and physical parameter layer. The process of functional space expansion is treated as a three-step process, first transforming original function to derivative functions, and then mapping these derivative functions into effects, and at last expansion from these effects to physical quantities space. A computer aided functional design software platform is then developed. The functional design of new devices for decreasing resistance of amphibious vehicles is given as an example, which demonstrates that the methodology is obviously helpful to realizing the methodology expansion and system innovation of product functions and concepts, thus increasing opportunities for product innovation in conceptual design.

Key words: Conceptual design, Effect, Function, Functional space expansion, Physical parameter