An Extended Functional Design Approach Based on Working Principle and Property and Its Application

(1) Background: Functional design is an activity that is part of conceptual design; it aims to clarify customer needs and develop the functional architecture and solution concepts for a product or system under development. The existing functional design approaches mainly focus on assisting designers in searching for design solutions to desired functions, which rely too much on established design knowledge. This type of approach is usually characterized by the relevant design analogy, especially case analogy, or structure analogy. However, this cannot help to generate new design solutions if there is little established design knowledge. (2) Methods: To overcome this limitation, working principle and property are designated as intermediate transformation variables. The corresponding mapping relationships, from function to working principle, and from working principle to property, are comprehensively discussed. Then, an extended functional design approach is proposed, which is characterized by the function (F)–working principle (WP)–property (P)–structure (S) mapping process. The conceptual design of a self-adaptive luggage transfer device is taken as an example to illustrate the proposed approach. (3) Conclusions: Based on the working principle and the desired property, how to generate a possible structure solution according to an expected function is clarified explicitly. The proposed approach could be regarded as a complement to the existing functional design approach