摘要:

This paper investigates the response model approach for the dynamic robust design problem. We derive relationships between the effect estimates of the loss model approach and those of the response model approach. We show that the bias problem for the static case solely exists in the estimation of process variance and does not exist in the estimation of the slope and intercept parameters. The two analysis approaches are compared by use of a real example.

ISSN:0740-817X    

DOI:10.1080/07408179908969912

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

This paper presents an on-line Statistical Process Control (SPC) technique, based on a Generalized Likelihood Ratio Test (GLRT), for detecting and estimating mean shifts in autocorrelated processes that follow a normally distributed Autoregressive Integrated Moving Average (ARIMA) model. The GLRT is applied to the uncorrelated residuals of the appropriate time-series model. The performance of the GLRT is compared to two other commonly applied residual-based tests - a Shewhart individuals chart and a CUSUM test. A wide range of ARIMA models are considered, with the conclusion that the best residual-based test to use depends on the particular ARIMA model used to describe the autocorrelation. For many models, the GLRT performance is far superior to either a CUSUM or Shewhart test, while for others the difference is negligible or the CUSUM test performs slightly better. Simple, intuitive guidelines are provided for determining which residual-based test to use. Additional advantages of the GLRT are that it directly provides estimates of the magnitude and time of occurrence of the mean shift, and can be used to distinguish different types of faults, e.g., a sustained mean shift versus a temporary spike.

ISSN:0740-817X    

DOI:10.1080/07408179908969913

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

As short run manufacturing becomes more prevalent, run-to-run components of variation, such as that contributed by set-up error, have greater potential to crucially affect product quality. While efforts should be made to eliminate such between-run variance contributing factors, some will always be present. Here, we assume there is one such factor which we envisage as set-up error that, unless the process is adjusted, remains fixed throughout a run. We develop a single adjustment strategy based on taking a sample of fixed size from the process. If a significant set-up error is indicated, a single compensatory adjustment, equal to the predicted process offset, is executed. The actual procedure depends on process parameters, including adjustment error, run size, and adjustment and sampling costs. The procedure not only specifies the adjustment amount, if any, but the time during the run at which to adjust. The procedure is, optimal among all fixed sample size procedures for the chosen cost function. Besides incorporating adjustment and sampling costs, the cost function is based on a 0–1 loss criterion, where the loss is 0 (1) units per item produced if the process offset caused by set-up error is less than or equal to (greater than) a specified amount. Tables are provided, with examples, illustrating the procedure for representative values of process parameters, costs, and run sizes.

ISSN:0740-817X    

DOI:10.1080/07408179908969914

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Accelerated testing is the attempt to accelerate the degradation processes that occur in a material system by applying a high stress. Typically accelerated testing requires extrapolating results from a feasible regime for laboratory or factory experimentation to a natural setting of interest. Usually the models used for this extrapolation either arise from assuming a single rate limiting step in the physical or chemical degradation process or as purely empirical relations. This paper presents a general theory for the design and interpretation of accelerated testing derived by considering a simple theory of how processes may trade off as stress decreases and time increases. Some of the main results of the theory are counter to current accepted practice. In particular, careful step stress experiments (experiments in which stress is perturbed during the accelerated aging) are shown to be necessary for identifying acceleration functions, and the possibility of predicting how long experiments need to be run prior to beginning the experiments is indicated.

ISSN:0740-817X    

DOI:10.1080/07408179908969915

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The “predictor-corrector” feedback controller is a popular adjustment scheme proposed for the quality control of certain semiconductor manufacturing process steps. This controller is based on a double Exponentially-Weighted Moving Average (EWMA) scheme; thus the performance of the closed-loop system depends on the two weight parameters of the EWM A equations. In this paper, the conditions the weights must satisfy to ensure closed-loop stability are discussed. The optimal determination of the controller weights depends on a trade-off between long-run process variance and transient bias performance. It is shown that small weights, although they can guarantee stability, may result in severe, long transients, an important concern if fabrication is in small batches. An optimization model for finding the controller weights is given and numerically solved. An extension of this type of controllers to the multiple controllable factor case is described. The performance of the controller is illustrated with an application to Chemical Mechanical Polishing, a critical semiconductor manufacturing step.

ISSN:0740-817X    

DOI:10.1080/07408179908969916

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

In this paper we examine a variety of customer-centered reliability measures, generalized to multistate and continuum contexts. A classification scheme is proposed for these measures, and a new measure based on customer-usage patterns is defined. In each case, reliability measures are defined such that they are equally valid for binary, multistate, continuum, and mixed systems. Techniques which facilitate the use of continuum models are discussed, and time-dynamic, infinite-time, and partial-information modeling considerations are also addressed.

ISSN:0740-817X    

DOI:10.1080/07408179908969917

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The rapid evolution of sensor technology, using techniques such as lasers, machine vision and pattern recognition, provides the potential to greatly improve the Statistical Process Control (SPC) method for monitoring manufacturing processes. This paper studies the method of using on-line sensors to monitor manufacturing processes and compares that method with the control chart method, a widely used SPC tool. Two separate economic models are formulated for using either a sensor or a control chart to monitor a manufacturing process. Then, the two models are compared in a sensitivity analysis with lespect to several process parameters.

ISSN:0740-817X    

DOI:10.1080/07408179908969918

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

ISSN:0740-817X    

DOI:10.1080/07408179908969921

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

ISSN:0740-817X    

DOI:10.1080/07408179908969922

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor