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The accuracy of the measurement system is vital for reliable process monitoring using statistical process control charts. The applied chart’s effectiveness depends on the measurement system's performance. Measurement uncertainty can lead to incorrect decisions like unnecessary stops or failure to intervene. In this paper, we investigated the effect of measurement errors on the performance of four well-established combined charts for monitoring the mean of normally distributed processes: Shewhart-CUSUM, Shewhart-Crosier’s CUSUM, Shewhart-EWMA and Shewhart-GWMA charts. To deal with measurement errors we considered the additive measurement error model. Detailed run length profiles of these charts are studied in terms of average run length (ARL), extra quadratic loss, relative ARL, and performance comparison index through Monte Carlo simulations under different sizes of measurement errors. It was found that measurement errors significantly reduce the power of the combined charts. Thus, multiple measurements scheme is incorporated as a remedy to this effect. The Shewhart-Crosier’s CUSUM performed best of four charts, while the Shewhart-EWMA chart did worst. To demonstrate the effect of measurement uncertainty and highlight implications further, a simulated dataset with a shift in the process mean is considered. Validerad;2023;Nivå 2;2023-01-01 (joosat);Licens full text: CC BY License;Funder: Foundation of Nanjing University of Posts and Telecommunications (NY222176); The Excellent Innovation Teams of Philosophy and Social Science in Jiangsu Province (2017ZSTD022); Key Research Base of Philosophy and Social Sciences in Jiangsu

Traditional practice within railway maintenance is based on engineering knowledge and practical experience, which are documented in regulations. This practice is often time-based, but can also be condition-based by combining time-based inspections with condition-based actions depending on the inspection results. However, the logic behind the resulting regulation is seldom well documented, which makes it challenging to optimise maintenance based on factors such as operational conditions or new technologies, methodologies and best practices. One way to deal with this challenge is to use statistical analysis and build models that support fault diagnostics and failure prognostics. This analysis approach will increase in importance as automated inspections replace manual inspections. Specific measurement equipment and trains are not the only ones producing automated measurements; regular traffic is increasingly often producing measurements. Hence, there will not be any lack of condition data, but the challenge will be to use this data in a correct way and to extract reliable information as decision support. In this context, it is crucial to balance the risks of false alarms and unrecognised faults, but also to estimate the quality of both data and information. The purpose of this work is to use statistics in order to support improved asset management, by building statistical models as a complement to physical models and engineering knowledge. The resulting models combine theories from the field of time-series analysis, statistical process control (SPC) and measurement system analysis. Charts and plots present results and have prognostic capabilities that allow necessary track possession times to be included in the timetable. Fortsättningsprojekt: Förbättrad tillståndsbedömning genom statistisk analys

The maintenance of railway infrastructure has in several instances been changed from government-based to being based on public procurement, with varying degrees of flexibility for the contractor to design their maintenance work. The purpose of-giving contractors a larger freedom of choice of how to perform maintenance is to stimulate them to innovate and develop their maintenance processes. Since the contracts differ in between and there are changes in government policies over time that affects both existing and new contracts, a comparison between different contracts becomes challenging. A literature review has been conducted to understand the change in procurement strategy and how to encourage contractors to innovate. The research questions include: What procurement strategies are there? How is maintenance evaluated? How does procurement affect the innovation opportunities for entrepreneurs? The literature review focuses on railway maintenance and contract design between client and contractor. In total, 17 articles matched the search criteria and were selected for the review. To have successful maintenance service, five articles suggested partnering as a strategy with common goals in combination with good communication during the entirety of the contract. When selecting incentive plan, four articles mentions that a focus on performance-based incentives in combination with riskmanagement is better rather than actual payment schemes. The reason being that payment is often themain cause of conflicts between client and contractor. The scientific literature suggests that improvement in incentives improves quality of maintenance, decreases delays and technical failures. The conclusion from the literature review is that partnering in railway maintenance is considered successful. With accurate knowledge about railway assets the incentive plan becomes accurate which reduces costs. The literature review is a part of a research project with an overall goal to develop a model to guide the selection of appropriate type of procurement strategy, contract and control of maintenance for a moresustainable railway system.

Godkänd; 2013; 20130910 (bjarne)

Godkänd; 2012; 20121214 (andbra) Förbättrad tillståndsbedömning genom statistisk analys

Godkänd; 2011; 20110816 (ysko)

Traceability is important for quality control and process improvements, but it is often difficult to track or trace products in continuous process production, since products and product lots are difficult to separate. In the past, engineers have had to rely on coarse calculations for tracing products, but new possibilities emerge as new technology and models are being used. In this paper, we present experiences from applying chemical and RFID tracers to achieve traceability in continuous flows, with examples taken from the minerals processing sector. Godkänd; 2011; 20110309 (bjarne_b)

Godkänd; 2010; Bibliografisk uppgift: Værtspublikationsredaktører: Göran Bäckblom Sider: 33-35; 20100615 (biem)

At the beginning of 2008 three SMEs in a small town in Sweden started a network project inspired by the Six Sigma programme, and hired a full-time Black Belt to lead the improvement activities. Three months into the project, we interviewed the top management of the participating companies and the Black Belt, to pinpoint success factors as well as risks of the cooperation project. Results show that statistical methods were unused in favour of methods associated with lean manufacturing such as 5S. Accordingly, the expectations of the CEOs were related to production improvements and flow rather than quality. Both the Black Belt and the CEOs stated that management commitment was vital for the success of the partnership, but also that the visibility of this commitment could be improved. Despite this, all interviewees agreed that the project had gotten a good start and the managers had high expectations for its progress. Godkänd; 2008; 20081106 (bjarne_b)

In continuous process industries, large investments in automated process control systems are made to reduce variance, but the variance in key process parameters often remain unchanged. One reason is that the operators often lack tools to assess the impact of process changes on the final product properties. Dynamic simulation could be used to estimate effects of attempted changes, on models with current process information and dynamics. However, the use of dynamic simulation for such purposes is infrequent in process industry. Therefore, the purpose of this paper is to outline a simulation model for mineral processing using existing process knowledge. An iron ore pelletizing process was studied, and process knowledge was collected through interviews and research reports. The material flow mechanisms of a critical process section were also determined experimentally. A simulation model of the process was constructed in SIMULINK, and the effects of various variations were tested. The statistical properties of the output distribution of particle residence times were compared for various settings. Finally, various applications field in a mineral process for the simulation model is discussed, for example, predicting or explaining effect of corrective actions. Godkänd; 2008; Bibliografisk uppgift: The CD contains an electronic version of the proceedings printed in two volumes that are identified as follows: Printed in Sweden by Runit AB, Skövde “June 30th – July 2nd 2008, University of Skövde, Sweden”. “FAIM2008” ISBN: 978-91-633-2757-5; 20080904 (ysko)

Godkänd; 2008; 20081024 (rick_g)

Godkänd; 2007; Bibliografisk uppgift: Proceedings från konferensen distrubuerades elektroniskt (USB-minne) under konferensen; 20070927 (evan)

Godkänd; 2007; 20070917 (ysko)

CD-ROM Godkänd; 2002; Bibliografisk uppgift: CD-ROM; 20070211 (ysko)