Conceptual Design 416
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Pairwise Testing
An efficient way to come up with a conceptual design is the Pairwise Testing method. In Pairwise, you are able to compare the importance of each individual criterion to one another. A list of criteria can include, but is not limited to:
• Cost • Design Time • Build Time • Controllability • Accuracy • Reliability • Maintainability • Lifetime
After one criterion is compared to the rest of the criteria, the number of times that specific criterion is considered more important than the others will determine the “total importance” number. When two criteria are equal in importance, they cancel one another out and do not contribute to the total importance. When the comparison of the criteria is complete, 100 divided by the total importance sum gives you the approximate percentage value for each criterion.
For example, if the sum of the total importance was 34, 100/34 = 2.94. Rounding up to 3, this means that if cost beat out other criteria 5 times, it would have 3*5 or 15% total importance.
Using this method provides your group with a very simple way to compare individual criterion and provide a weighting system that can assist with concept selection.
Component Comparison
Now that the criteria has been established and weighted, your group can compare specific components that could potentially be used in your design. For example, if you needed something that produced linear motion, a linear actuator could be compared with a hydraulic cylinder. A scale is created from 0 to 4, 0 being the worst and 4 being the best. For both components, the design criteria are ranked using this scale, and the scale number is multiplied by the total percentage number. For cost (15% importance), if the linear actuator was ranked 2 and the hydraulic cylinder was ranked a 4, the points received would be 30 and 60, respectively. Once the ranking is complete, the total number of points is summed up and the component with a higher number of points would be used for that part of the design. Since this method incorporates the importance of each design criterion customized to your specific project, it is a highly effective way in selecting major components for your design.
Link to Example
Reference: http://www.pairwise.org/