USING BALANCE VARIABLES TO DESCRIBE SYSTEM INTERFACES AND ASSESS IN-PROGRESS DESIGNS
Editor: Christian Weber, Stephan Husung, Gaetano Cascini, Marco Cantamessa, Dorian Marjanovic, Frederico Rotini
Author: Salustri, Filippo Arnaldo; Rogers, Damian
Institution: 1: Ryerson University, Canada; 2: Ionada Incorporated, Canada
Section: Design Methods and Tools - part 1
To balance effectiveness and efficiency in design, a method is needed that can capture the range of expected behaviours (effectiveness) as well as their quality (efficiency) of artefacts existing in specific situations. The authors introduce "balance variables" for this purpose. A balance variable (BV) is a pair of triplets, each of the form (minimum, nominal, maximum) that represent the range of values that a flow between two system interfaces can reasonably obtain. One triplet quantifies a flow from outside the object system and represents a requirement on the object system; the other triplet represents the flow handled by the object system and represents a measure of performance. BVs can capture cases of over- and under-design. A BV that is neither over- nor under-designed is said to be balanced. Measures of balance are normalized and non-dimensional, thereby permitting (a) balance measures for difference system flows to be reasonably compared, and (b) overall design balance measures to be trivially calculated. Using the example of an electric kettle, all these characteristics are shown.