The early development process of products imposes to fulfill numerous types of requirements simultaneously. Those requirements are often qualitative and imprecise. The main tasks of a development team consist of grasping and understanding customer needs, refining these needs, synthesizing concepts of solutions, evaluating and selecting appropriate solutions. Evaluating and selecting solutions is a critical stage because various types of metrics are used to measure performances of concepts. This paper presents both theoretical contributions and practical implementations. This article presents a theoretical analysis of resource consumption and environmental impact from the viewpoint of exergy. In addition, this article provides a theoretical answer to the issue of qualitative modeling of early design concepts of solutions. This article opens a fruitful perspective for combining heterogeneous requirements in a coherent and systematic manner by using dimensional analysis calculus.
Comparison and ranking of solutions are central tasks of the design process. Designers have to deal with decisions simultaneously involving multiple criteria. Those criteria are often inconsistent in the sense that they are expressed according to different types of metrics. This means that usual engineering performance indicators are expressed according to physical quantities (i.e. SI system) and indicators such as preference functions can be “measured” by using other type of qualitative metrics. This aspect limits the scientific consistency of design because a coherent scientific framework will at first require the creation of a unified list of fundamental properties. A combined analysis of the measurement theory, the General Design Theory (GDT) and the dimensional analysis theory give an interesting insight in order to create guidelines for establishing a coherent measurement system. This article establishes a list of fundamental requirements. We expect that these guidelines can help engineers and designers to be more aware of the drawbacks linked with the use of wrong comparison procedures and limitations associated with the use of weak measurement scales. This article makes an analysis of the fundamental aspects available in major scientific publications related to comparison, provides a synthesis of these basic concepts and unifies those concepts together from a designing perspective. A practical design methodology using the fundamental results of this article as prerequisites has been implemented by the authors.
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