• Title/Summary/Keyword: EWMA Control

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An Integrated System of EWMA and EPC Using Second-order Autoregressed Model in the Process with Trend (추세가 있는 공정에서 이계자기회귀 모형을 이용한 EPC와 EWMA의 통합시스템)

  • Jung Hae Woon
    • Journal of the Korea Safety Management & Science
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    • v.7 no.2
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    • pp.141-151
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    • 2005
  • EPC seeks to minimize variability by transferring the output variable to a related process input(controllable) variable, while SPC seeks to reduce variability by detecting and eliminating assignable causes of variation. In the case of product control, a very reasonable objective is to try to minimize the variance of the output deviations from the target or set point. We consider an alternative EPC model with second-order autoregressive disturbance. We compare three control systems; EPC, EPC combined with EWMA. This paper shows through simulation that tlhe performance of the integrated model of EPC and EWMA is more preferable than that of EPC.

A Study of Demerit-DEWMA Control Chart (Demerit-DEWMA 관리도)

  • Kang, Hae-Woon;Baik, Jae-Won;Kang, Chang-Wook
    • Journal of Korean Society of Industrial and Systems Engineering
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    • v.33 no.2
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    • pp.9-17
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    • 2010
  • Complex products may present more than one type of defects and these defects are not always of equal severity. These defects are classified according to their seriousness and effect on product quality and performance. So, demerit systems are very effective systems to monitor the different types of defects. Recently, Kang et al.(2009) proposed the revised Demerit-CUSUM for the evaluation of the Demerit-CUSUM control chart performance exactly. In this paper, we present an advanced Demerit control chart using the double EWMA technique. The double EWMA technique is very efficient and strong method for process control where defects and nonconformities occur with various defect types. Moreover, we compare exact performance of Demerit-CUSUM, Demerit-EWMA and Demerit-DEWMA control chart according to changing sample size or mean shifts magnitude. By the result, we confirm that the performance of Demerit-DEWMA control chart is more than the performance of the Demerit-CUSUM and Demerit-EWMA control chart.

Multivariate Exponentially Weighted Moving Average(EWMA) Process Control and Statistical Process Monitoring in the Process Industry (장치산업에서 다변량 EWMA 공정제어와 통계적 공정감시)

  • 김복만;최성운
    • Journal of Korean Society of Industrial and Systems Engineering
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    • v.15 no.26
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    • pp.119-124
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    • 1992
  • 본 논문은 장치산업에서 적용되는 다변량 EWMA 공정제어와 통계적 공정감시 통합시스템을 제안한다. 본 논문에서 제안한 통합시스템은 자동공정제어(APC)의 예측, 조정기능과 통계적 정정감시(SPM)의 이상점 발견 및 제거등의 각각의 장점을 이용하였다. 기존의 다변량 EWMA연구는 데이타간의 독립성을 가정하였으나 본 논문은 데이타간의 종속적인 형태인 IMA(1,1)모델을 대상으로 하였다.

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Research Results and Trends Analysis for EWMA Control Chart of Manufacturing Processes (제조공정에서 EWMA 관리도의 적용에 관한 연구동향 분석)

  • Kim, Jong-Gurl;Um, Sang-Jun;Choi, Sung-Won;Kim, Dong-Nyuk
    • Proceedings of the Safety Management and Science Conference
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    • 2013.04a
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    • pp.581-591
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    • 2013
  • 제조공정에서 사용되어 지는 SPC(Statistical Process Control)관리 기법은 가피원인을 탐지하여 변동을 감소시키는 통계적 공정관리 시스템이다. SPC의 대표적인 관리 기법으로는 Shewhart관리도, Cusum관리도, EWMA관리도가 있으며 이러한 관리 기법들은 공정을 보다 안정적으로 관리 할 수 있도록 유지 및 예측하는데 사용 되어 진다. 하지만 제조 공정의 유형에 따라 샘플링 방법, 관리한계선 등을 다양하게 설정하여 보다 효율적인 관리를 모색하고 있다. 공정 형태에 따라 다양한 관리 방법과 분석 결과가 나타난다. 일반적으로 Xbar-R 관리도와 같은 Shewhart 관리도를 사용하지만 Batch 단위의 공정, 연속 공정의 라인에서 사용되기에는 부분적인 한계를 보이고 있다. 본 논문에서는 일반적인 관리도와 공정 변화에 민감하게 반응 할 수 있는 누적합 관리도와 지수가중치이동평균 관리도를 비교해 보고 작은 변동에 대한 탐지 능력이 우수한 지수가중치이동평균 관리도에 대한 연구동향과 사례를 분석하여 제조 공정에 적합한 관리 방법을 모색하고자 한다.

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Exponentially Weighted Moving Average Control Charts for Dispersion Matrix

  • Chang, Duk-Joon;Shin, Jae-Kyoung
    • Journal of the Korean Data and Information Science Society
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    • v.15 no.3
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    • pp.633-644
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    • 2004
  • Exponentially Weighted Moving Average(EWMA) control chart for variance-covariance matrix of several quality characteristics based on accumulate-combine approach has proposed. Numerical computations show that multivariate EWMA chart based on accumulate-combine approach is more efficient than corresponding multivariate EWMA chart based on combine-accumulate approach.

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Comparison of control charts for individual observations (개별 관측치에 대한 관리도 비교)

  • Lee, Sungim
    • The Korean Journal of Applied Statistics
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    • v.35 no.2
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    • pp.203-215
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    • 2022
  • In this paper, we consider the control charts applicable to monitoring the change of the population mean for sequentially observed individual data. The most representative control charts are Shewhart's individual control chart, the exponential weighted moving average (EWMA) control chart, and their combined control chart. We compare their performance based on a simulation study, and also, through real data analysis, we present how to apply control charts in practical application and investigate the problems of each control chart.

Evaluating the ANSS and ATS Values of the Multivariate EWMA Control Charts with Markov Chain Method

  • Chang, Duk-Joon
    • Journal of Integrative Natural Science
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    • v.7 no.3
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    • pp.200-207
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    • 2014
  • Average number of samples to signal (ANSS) and average time to signal (ATS) are the most widely used criterion for comparing the efficiencies of the quality control charts. In this study the method of evaluating ANSS and ATS values of the multivariate exponentially weighted moving average (EWMA) control charts with Markov chain approach was presented when the production process is in control state or out of control state. Through numerical results, it is found that when the number of transient state r is less than 50, the calculated ANSS and ATS values are unstable; and ATS(r) tends to be stabilized when r is greater than 100; in addition, when the properties of multivariate EWMA control chart is evaluated using Markov chain method, the number of transient state r requires bigger values when the smoothing constatnt ${\lambda}$ becomes smaller.

EWMA control charts for monitoring three parameter regions (3개의 모수영역을 모니터링하는 EWMA 관리도)

  • Yukyung, Kim;Jaeheon, Lee
    • The Korean Journal of Applied Statistics
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    • v.35 no.6
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    • pp.725-737
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    • 2022
  • In the standard assumption of statistical process monitoring (SPM) under consideration, the in-control region of the control parameter of quality characteristic consists of a single point. However, if small deviations from the ideal situation may not be of practical importance, the parametric space can consist of three regions: In-control, indifference, and out-of-control. In this paper, we propose two exponentially weighted moving average (EWMA) charting procedures applicable to the situation with three parameter regions, and compare the efficiency of the proposed procedures with the Shewhart chart and the cumulative sum (CUSUM) chart.

Comparisons of Multivariate Quality Control Charts by the Use of Various Correlation Structures

  • Choi, Sung-Woon;Lee, Sang-Hoon
    • Journal of the Korean Operations Research and Management Science Society
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    • v.20 no.3
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    • pp.123-146
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    • 1995
  • Several quality control schemes have been extensively compared using multivariate normal data sets simulated with various correlation structures. They include multiple univariate CUSUM charts, multivariate EWMA charts, multivariate CUSUM charts and Shewhart T$^{3}$ chart. This paper considers a new approach of the multivariate EWMA chart, in which the smoothing matrix has full elements instead of only diagonal elements. Performance of the schemes is measured by avaerage run length (ARL), coefficient of variation of run length (CVRL) and rank in order of signaling of off-target shifts in the process mean vector. The schemes are also compared by noncentrality parameter. The multiple univariate CUSUM charts are generally affected by the correlation structure. The multivariate EWMA charts provide better ARL performance. Especially, the new EWMA chart shows remarkable results in small shifts.

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An Effective Hybrid UPC Algorithm for the Traffic Control of ATM Networks (ATM 망의 트래픽 제어를 위한 효율적인 하이브리드 UPC 알고리즘)

  • 윤석현
    • Journal of the Korea Society of Computer and Information
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    • v.5 no.3
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    • pp.112-118
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    • 2000
  • In this paper, a hybrid UPC algorithm is proposed, which combines the representative Leaky Bucket UPC algorithm with the EWMA window algorithm in the ATM network and then its performance Is evaluated. The hybrid UPC algorithm is made up of Leaky Bucket and EWMA, which control the Peak bit rate and the mean bit rate, respectively. According to the result of the simulation using BONeS with the On/off traffic source model. it is revealed that the proposed UPC algorithm has superior performance to the existing Leaky Bucket UPC algorithm with regard to both the cell loss rate and the buffer size.

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