Reliability modelling of automated guided vehicles using Petri nets

This is an Accepted Manuscript of a book chapter published by Routledge in Risk, Reliability and Safety: Innovating Theory and Practice: Proceedings of ESREL 2016 on September 13 2016, available online: http://www.routledge.com/9781138029972.Automated guided vehicles (AGVs) are being extensively used due to their attributions of high efficiency and low costs. To assure their added value, taking a typical AGV transport system as an example, the reliability issues in AGVs are investigated in this paper. First of all, the AGV transport system was mod-elled as a phased mission that comprises a few key phases. Then, the Petri net (PN) method is applied to describe the logic of the whole phase mission and based on this, the reliability of the mission is assessed via Monte-Carlo simulation. In order to validate the reliability assessment result by the PN method, the theoretical reliability of the AGV system is also assessed through performing fault tree analysis (FTA). The comparison indicates that both methods give very similar results. Thus, it can be concluded that apart from FTA, the PNs method is also a reliable tool for AGV system reliability assessment

Autonomous mobile robots in manufacturing : Highway Code development, simulation and testing

A dynamic and flexible manufacturing environment presents many challenges in the movement of Autonomous Mobile Robots (AMRs), leading to delays due to the complexity of operations while negotiating even a simple route. Therefore, an understanding of rules related to AMR movement is important both from a utility perspective as well as a safety perspective. Our survey from literature and industry has revealed a gap in methodology to test rules related to AMR movement in a factory environment. Testing purely through simulations would not able to capture the nuances of shop floor interactions whereas physical testing alone would be incredibly time-consuming and potentially hazardous. This work presents a new methodology that can make use of observations of AMR behaviour on selected cases on the shop floor and build up the fidelity of those simulations based on observations. This paper presents the development of a Highway Code for AMRs, development of simulation models for an ideal-AMR (based on the rules from the Highway Code) and physical testing of real-AMR in an industrial environment. Finally, a behavioural comparison of an ideal-AMR and a real-AMR in five scenarios (taken from the shop floor of an industrial partner) is presented. This work could enable informed decisions regarding the implementation of AMRs through identification of any adverse behaviours which could then be mitigated either through improvements on the AMR or through establishing shop floor protocols that reduce the potential impact of these behaviours

Zastosowanie logiki rozmytej i metody Taguchiego w optymalizacji parametrów procesu produkcyjnego

Given the importance of quality and responsiveness of manufacturing companies to customers, the most important principle can be considered reducing the cycle time of the production process. Since preserving the quality standards in a disposable necessities manufacturer is important, the Fuzzy Taguchi method as a powerful design optimization tool is used to determine the quality and design of optimal control parameters. Because in the real world due to measurement errors and inaccuracies in information and uncertainty in processes, fuzzy concepts have been used. Therefore, in this study, the parameters for controlling the process of disposable essentials are optimized to reduce the time cycle. Also, S/N and ANOVA methods have been used to study the characteristics of process performance. The four control parameters affecting the feed rate of the sheet, the machine wind pressure, and the mold temperature and sheet thickness affect the quality of the process. And Taguchi Fuzzy is a systematic and efficient method that reduces the cycle time. Experimental results have been reviewed and presented to evaluate the effectiveness of this approach in the Kach Company.Czas trwania cyklu procesu produkcyjnego jest jednym z podstawowych czynników zarówno zapewnienia wysokiej jakości produkcji jak również zmniejszenia czasu reakcji producentów na wymagania klienta. W pracy prowadzono optymalizację parametrów sterujących stosowanych w procesie produkcji wyrobów jednorazowego użytku dla skrócenia czasu cyklu produkcyjnego. Do badań przyjęto metodę Taguchiego z elementami logiki rozmytej. Uwzględniono w procesie optymalizacji wpływ błędów pomiarowych, niedokładność danych wejściowych oraz niepewność w ustaleniu prawidłowych wartości parametrów procesu. Stosowano w badaniach cztery parametry sterujące procesu: grubość arkusza tworzywa, prędkość podawania arkusza, ciśnienie robocze maszyny i temperaturę matrycy. Stosowano metodę S/N i analizę wariancji (ANOVA) dla oceny przebiegu procesu produkcyjnego. Wyniki analizy danych doświadczalnych były podstawą oceny efektywności optymalizacji procesu produkcyjnego w firmie Kach Company

Decomposition versus Minimal Path and Cuts Methods for Reliability Evaluation of an Advanced Robotic Production System

As complex systems have become global and essential in today’s society, their reliable design and the determination of their availability have turned into a very important task for managers and engineers. Industrial robots are examples of these complex systems that are being increasingly used for intelligent transportation, production and distribution of materials in warehouses and automated production lines. In this paper, two techniques of reliability evaluation are developed for a complex system of robots. Decomposition method and minimal path and cuts method are adapted for the proposed complex system. For practical implementation, a particular robot system is first modeled. Then, reliability block diagram is adopted to model the complex system for reliability evaluation purpose. Finally, the methods are implemented and their properties are discussed