Using analytic hierarchy process to determine process economics in multivariate loss functions

The Taguchi robust design method traditionally deals with single-characteristic problems. Various methods have been developed for extending the Taguchi single-characteristic robust design method to the case of multi-characteristic robust design problems. However, most of those methods have shortcomings in that they do not properly consider the variance-covariance structures among performance characteristics and/or do not preserve the original properties of the Taguchi signal-to-noise ratio for single-characteristic robust design problems. To overcome these shortcomings, this paper develops a multivariate loss function approach to multi-characteristic robust design problems with an appropriately defined signal-to-noise ratio. Its performance is evaluated using simulated examples, and the results indicate that it generally outperforms existing representative methods for correlated as well as uncorrelated experimental data. IntroductionO ne of the most important goals for engineers is to design high-quality products and processes at low cost and within an affordable amount of time. The robust design (or parameter design) method proposed by Taguchi has been widely used as an efficient way of achieving this goal. The purpose of Taguchi robust design is to determine optimal settings of product or process design parameters while making performance characteristics (PCs) robust to uncontrollable noise variables. In the Taguchi robust design method, orthogonal arrays are used for experimental design, and a performance measure (PM) called the signal-tonoise (SN) ratio is calculated at each experimental run. Then, optimal settings of design parameters are determined such that the SN ratio is maximized.The Taguchi robust design method has mainly focused on the case of a single PC although the case of multiple PCs appears more commonly in practice. For example, in the literature, in order to find the optimal settings of the injection-molding parameters to minimize the imbalance of a plastic wheel cover component, two correlated characteristics of the wheel cover component were considered: total weight and the balance of the component. In another example to improve a plasma-enhanced chemical vapor deposition process in the fabrication of integrated circuits, two correlated characteristics of the deposition thickness and a refractive index were considered. Refer to Chiao and Hamada 1 for more details on these examples. A difficulty involved in multi-characteristic robust design (MCRD) is that optimal settings of design parameters may be different from characteristic to characteristic. An important issue in MCRD is how to resolve such conflicts to provide a compromised design condition.Many authors have extended the Taguchi robust design method to the case of MCRD problems. One popular approach is to combine the PMs of PCs into a single aggregated PM and, thereby, re-formulate the MCRD problem as a single-characteristic robust design (SCRD) problem to be solved. For example, the SN ratio for each PC is calculated independently of...

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“…For some other methods for determining the cost matrix, refer to Vining, Khorramshahgol and Djavanshir, and Özler et al , among others.…”

Section: Signal‐to‐noise Ratio For Multiple Performance Characteristicsmentioning

confidence: 99%