Robust Design

The underlying principles, techniques & methodology of robust design are discussed in detail in this report with a case study presented to appreciate the effectiveness of robust design. The importance of Parameter design & Tolerance design as the major elements in Quality engineering are described. The Quadratic loss functions for different quality characteristics are narrated, highlighting the fraction defective fallacy. The aim of the robust design technique is to minimize the variance of the response and orthogonal arrays are an effective simulation aid to evaluate the relative effects of variation in different parameters on the response with the minimum number of experiments. Statistical techniques like ANOM (analysis of means) and ANOVA (analysis of variance) are the tools for analyzing the data obtained from the orthogonal array based experiments. Using this technique of robust design the quality of a product or process can be improved through minimizing the effect of the causes of variation without eliminating the causes. Fundamental ways of improving the reliability of a product are discussed highlighting the importance of robust design on this. Based on the classification of uncertainties in design, the role of robust design optimization & reliability based design optimization are discussed. The mathematical formulations for these types of optimization strategies are explained. Based on this study, it can be concluded that the robust design methodology based on Taguchi's principles will take care of the entirety of the noise factors which can cause underperformance and failures, but it will be advantageous to do a robust & reliability based design optimization because apart from making the design insensitive to noises, it will enable the designer to predict the reliability of the product. The current research activities in the application of robust design techniques in the aerospace systems are also discussed, one with respect to relaxing manufacturing tolerances on an aircraft nacelle to reduce cost and the other, tackling uncertainties in Mach number in the design optimization of an airfoil for a transport aircraft.