Designing products that are robust to the environment

Professor Genichi Taguchi has emphasized the use of designed experiments in several novel and important applications. In this paper, we focus on the use of statistical experimental designs in designing products to be robust to environmental conditions. The engineering concept of robust product design is very important since it is frequently impossible or prohibitively expensive to control or eliminate sources of variation due to environmental conditions. Robust product design enables the experimenter to discover how to modify the design of the product to minimize the effect due to variation from environmental sources. In experiments of this kind, Professor Taguchi's total experimental arrangement consists of a cross-product of two experimental designs, an inner array containing the design factors and an outer array containing the environmental factors. Except in situations where both of these arrays are small, this arrangement may involve a prohibitively large amount of experimental work. One of the objectives of this paper is to show how this amount of work can be reduced. In this paper, we develop a robustness measure for this particular experimental situation. Consideration of this robustness measure leads to classes of experimental designs that generally require significantly fewer runs than the designs proposed by Professor Taguchi.