Detc 2001/dtm-21702

RedesignIT is a computer program that uses model-based reasoning to generate and evaluate proposals of redesign plans for engineered devices. These proposals describe how the design parameters could be changed to achieve a specified performance goal. Equally important, the program proposes complementary modifications that may be necessary to counteract the undesirable side effects of the primary changes. RedesignIT is intended for use during the first stages of a redesign project, when engineers need to make a quick, yet accurate assessment of the overall effects of a particular design change. The program uses qualitative device models, which allow it to compute redesign plans efficiently. With its ability to predict the collateral, and probably undesirable, effects of a design change, the program is well suited to aid product designers in deciding on the feasibility of introducing design changes to a product. RedesignIT employs methods of artificial intelligence, especially qualitative reasoning, causal reasoning, and heuristic search. INTRODUCTION Customers have ever increasing expectations about the quality and performance of the products that they buy. In order to keep pace with this demand for value, companies in practically every business field have to come up with frequent upgrades of their products. One of the main difficulties in redesigning a product is that a proposed design change can have many undesirable side effects besides the intended ones. In complex engineered devices such as automobiles, these side effects are often hard to predict, especially when they cross the boundaries between the device's subsystems. Clearly, a manufacturer could save considerable amounts of resources and effort if it were possible to make a quick, yet accurate assessment about the overall effects of a design change, before making a commitment to implementing the change. As a response to this need we are currently developing RedesignIT, a model-based computational tool that generates and evaluates proposals of redesign plans for engineered devices. RedesignIT is designed for use at the beginning of a redesign task. Its purpose is to aid the designer in answering the following questions: What is the complete set of possible changes —within the scope of the model—that can be made in order to achieve the design goal? For each of these possibilities, what is the complete list of both certain and probable side effects? How can each of the side effects be remedied? Which design change has (1) the greatest influence on the design goal and (2) the least cost in terms of implementation and undesirable side effects? RedesignIT receives as input a model of the device under study. Because the purpose of the project is to help the designer understand how a change to one part of a device generates changes elsewhere in the device, the model we use consists mainly of the relevant physical quantities, and the causal relationships between them. In general, these relationships can be expressed in qualitative, quantitative or semi-quantitative terms. We have found a semi-quantitative representation, based on orders of magnitude, to be especially effective. Such a representation allows comparisons between the effects that different design changes have on the design constraints, without incurring the expense of building a mathematically exact model. The program’s task is to use this model to generate several combinations of changes to the quantities, by which the redesign goals, as intended by the designer, can be accomplished. Redesign goals are expressed as a desired