Towards a Collaborative Function-to-Form Mapping

The technological advances carried out these last years in the field of products development led the researchers to elaborate approaches that reduce the cost and time of product development, enhance the quality of product and help the designers to be more creative. Currently, computer aided systems have concentrated on the capture and representation of geometrical shape and technical information as opposed to provide supports for product design in the earlier stages of design process. The aim of this paper is to present a methodology to aid designers during the first stages of design. The standard models using the STEP standard are proposed in order to ensure co-operative and collaborative works during the first stages of design. Then, we apply our methodology in the case of a bottle design by considering multiple designers’ viewpoints. as earlier as possible. In a non–routine design, it is delicate and extremely complex to obtain the best products answering customer’s specifications. Indeed, a great number of different experts of different disciplines participate in product design. The difficulty lies in the fact that those persons have to collaborate. Shape is today the main representation of a product, even though the current trend is to remove geometry from its central position in order to add high-level information (Gorti et al. 1996, Szykman et al. 2000, Szykman et al. 2001). Therefore, the function to form mapping appears to be one of the most important activities of the design process and up till now happened manually. This activity is very important both for choices that are made and for the amount of work that it represents. That is why we have the desire to assist designers in the first stages of product design. The objective is not to construct automatically the shape but both to automate a certain number of heavy and tiresome tasks, and assist designers during the first stages of design. In best case, this assistance makes the designers’ stimulation possible by presenting them solutions that they had not thought before. We suppose that the first information we have at our disposal are included in the customer’s specifications, which are expressed in natural language (Figure 1a). Due to the functional decomposition (Figure 1b) eventually using functions of making, maintaining, prevention, control (Keuneke 1991) and allowing (McDowell et al. 1996), behaviors of the product could be identified (Figure 1c) in order to respect the philosophy of FBS (Ranta et al. 1996, Tomiyama et al. 1993, Umeda et al. 1996). Next, with the help of the same philosophy, the structure of the product can be obtained. This previous model can be identified as a set of product’s components linked by assembly relation (Figure 1d). Actions achieved by designers in the traditional FBS methodology (represented by Figure 1a to Figure 1d) are currently manual. Assisting designers during those phases is difficult due to the fact that manipulated information are mainly expressed in natural language. That is why we attempt to formalize some design information in order to partially automate the shape mapping (Figure 1e to Figure 1g). In some cases, we have noticed that a function can also be decomposed into a set of constraints on physical parameters, called intermediate specifications (Figure 1e). Only such design cases will be considered in next sections. Decomposition that consists in translating functions into constraints on physical parameters can correspond to the “function → structure” reasoning techniques identified in (Hsu et al. 1998). Physical parameters are defined as quantifiable and measurable entities referring to the physical world. For instance, in the case of a box design, aesthetics functions may be converted as the following: the ratio of length to height of the box approaches the gold number ( ) ( 5 +1)/2 . The corresponding constraints would be length = ( ) ( 5 +1)/2 /height. In a larger extent, the handling of a water bottle by a human being, which is a function, may be converted into constraints on the weight, the compactness and so on, which are parameters. Physical parameters used in the intermediate specifications are called intermediate parameters (Gardan et al. 1999a, Gardan et al. 1999b). They are of a rather high level and are not necessarily related to geometry. Like parameters and specifications, constraints established in the intermediate specifications are called intermediate constraints. In (Gardan et al. 1999b), we have defined an intermediate constraint by a quadruple where IP is an intermediate parameter, R is a relation among {<, >, =, ≠} that must be considered as fuzzy relation, Exp is an arithmetic expression and W is the relative weight of the intermediate constraint in comparison with the other constraints of the intermediate specifications. For the moment, only one designer gives the weight for all the intermediate constraints. Once a great number of intermediate constraints are manually deduced from the functional decomposition obtained by the FBS methodology, we propose The will to capitalize the knowhow of firms and to reduce times of production make that one now truly approaches the CAD/CAM systems in the optics of a functional modeling. The goal is to assist the designers during the earlier stages of the product realization. However the current systems are still based on geometry and in order to achieve the wished goal, it is necessary to delay computations and to introduce higher semantic level concepts [JTF 93]. A first effort was carried out by introducing form features [SAL 94]. They assemble elements of geometry of very low level (as Product’s Specifications Functional