As the product design progresses to the prototype phase

Each attribute and function should perform according to the technical specifications and their target values that resulted from the House of Quality, HoQ. Robust product design is a concept from the teachings of Dr. Genichi Taguchi, a Japanese quality guru. It is defined as reducing variation in a product without eliminating the causes of the variation. In other words, making the product or process insensitive to variation. This variation (sometimes called noise) can come from a variety of factors and can be classified into three main types: internal variation, external variation, and unit to unit variation. Internal variation is due to deterioration1 such as the wear of a machine（机器的磨损） and aging of materials（物料的老化）. External variation is from factors relating to environmental conditions such as temperature, humidity, and dust. Application of Taguchi methods focuses on the product concept selection and design parameters optimization and searches to minimize the effects of sources of variability.


Taguchi developed a quality loss function (QFL) which has a quadratic form.

This equation relates the deviation of any design parameter from its target value to the loss in dollars connecting quality with its related cost. A measure of robustness is the signal to noise ratio (S/N) which is used to determine the optimal levels of the design parameters through a design of experiment optimization process.

  1. deterioration，n.恶化
  2. Taguchi，田口玄一，[日本]，质量大师
  3. QFL，质量损失函数