A measure for design coupling

The degree of coupling between design modules affects design quality: designs with high coupling are generally more complex and difficult to adapt, while uncoupled designs are simpler and their adaptation requires fewer iterations or even a single pass. The design process of products involving a high degree of coupling is consequently inefficient and often many iterations are required to complete it. In order to assess and compare the level (degree) of design coupling it is necessary to specify a general quantitative measure. Two such measures – Reangularity and Semangularity [Rinderle, 1982 (9)] – are already being used for this task [Suh, 1990 (12)]. This paper proposes a new method based on measuring the direct consequences of coupling. The analysis is based on the Axiomatic Design framework which assumes that a design can be described formally as a matrix representing the relationship between functional requirements and adjustable design parameters. This paper also intends to demonstrate that the degree of coupling approach to the choice of a possible design solution is faster than the classical method based on the information content. We will analyse and optimise the design of a water pump to show how coupling functions are to be used