Dr.-Ing. Marc Schleyer
- Ehemaliger
- FB Logistiksysteme
Karlsruher Institut für Technologie
Institut für Fördertechnik und Logistiksysteme
Geb. 50.38 Gotthard-Franz-Str. 8
76131 Karlsruhe
| Titel | Bild | Quelle | Kurzbeschreibung |
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| A Framework of Stochastic Finite Elements for Models of Material Handling Systems | Submitted for publication to IIE Transactions (In Revision) |
The aim of this paper is to introduce a framework of model elements and associated computation methods which are well suited to model information flow and physical processes in warehouses and distribution centers. The proposed elements, the so called stochastic finite elements, are based on a discrete representation of time, in order to render distribution assumptions unnecessary. We extend available discrete time queueing models by adding models for batch processes, which are very common in material handling systems, when goods are transported or processed in some steps in batches or in some other steps piecewise. |
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| Leistungsbewertung logistischer Systeme mit zeitdiskretem Logistikbaukasten | Simulation in Produktion und Logistik 2006, Tagungsband zur 12. Fachtagung, Hrsg. Sigrig Wenzel | Es wird ein Baukasten vorgestellt, mit dessen Hilfe Logistiksysteme abgebildet und mit Leistungskennzahlen bewertet werden können. Den hierbei eingesetzten einzelnen Analysebausteinen liegen zeitdiskrete bedientheoretische Verfahren zu Grunde, welche kurz vorgestellt werden. Um zeitdiskrete bedientheoretische Verfahren der Anwendung in der Praxis zugänglich zu machen, wurde ein objektorientiertes Analysetool geschaffen, das eine einfache Modellierung und eine schnelle Analyse von Logistiksystemen ermöglicht. Vor- und Nachteile der entwickelten Lösung gegenüber simulativen Verfahren werden erläutert. |
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| System analysis of the discrete time G/G/1-queue with batch arrivals | Proceedings of the 21th IAR Annual Meeting, Nancy |
Considering material flow and production systems, there is a limited space close to a machine or a group of machines for buffering unfinished goods. Therefore, for the dimensioning of material ow bu ers it is of vital importance to analyze the number of customers in the queue at the arrival instant. It is crucial that there is enough free bu er capacity to receive the arriving customers. In our paper we consider a G/G/1-queueing system with batch arrivals in the discrete time domain. On the basis of the waiting time distribution we present an analytical approach for the calculation of the number of customers at the arrival instant. Given a confidence level the required buffer capacity can be calculated. |
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| Analysis of Batch Building Processes | Proceedings of the 20th IAR Annual Meeting, Mulhouse | Batch building processes are common in many areas of material flow and production systems and of communication networks. This paper presents an analytic method to calculate the inter-departure time distribution and the waiting time distribution for batch building processes using discrete time analysis. The batch building process happens at so called collecting stations in the considered queueing network, at which the arriving customers are collected up to a defined capacity. The arrival is a batch arrival of stochastic size and is described by a generally identically distributed inter-arrival time. The presented method enables a performance evaluation of batch building processes in a stochastic environment. | |
| An Analytical Method for the Calculation of the Waiting Time Distribution of a Discrete Time G/G/1-Queueing System with Batch Arrivals | OR Spectrum, 2006. (Online first) | This paper presents an analytical method to calculate the waiting time distribution for the G/G/1-queueing system with batch arrivals. Using the discrete time scale, it is possible to calculate the distribution of the waiting times and the idle times of a G/G/1-queueing system based on the Wiener-Hopf factorization. The influence of batch arrivals on the waiting time distribution is analyzed. The waiting time distribution is calculated for batch arrivals with both constant and stochastic batch sizes. The effect of stochastic batch sizes on the waiting process is highlighted. With the developed methods it is possible to obtain congestion measures of high precision for logistic systems. The analytical results are evaluated by simulation. Several numerical examples are presented to emphasize the quality of the introduced methods. | |
| An analytical method for the calculation of the number of units at the arrival instant in a discrete time G/G/1-queueing system with batch arrivals | OR Spectrum Online |
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| An Extension of the Framework of Stochastic Finite Elements for Models of Material Handling Systems | International Material Handling Research Colloquium, Salt Lake City, 2006 | In our earlier work we proposed a framework of model elements and associated computation methods which are well suited to model information flow and physical processes in warehouses and distribution centers. The proposed elements, the so called stochastic finite elements, are based on a discrete representation of time. In this paper we extend the available elements by elements for batch processes, which are very common in material handling systems, when goods are transported or processed in some steps in batches and some other steps piecewise. |
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| Simulative Untersuchung der Auswirkung von stochastischen Verkehrssystemen auf logistische Prozesse | Experiences from the Future, Hrsg. Kai Mertins und Markus Rabe, Fraunhofer IRB-Verlag, 2004, S.65-75 | Das Verkehrsaufkommen in Deutschland wächst stetig. Gleichzeitig wächst die damit verbundene Stochastik bezüglich der realisierbaren Transportzeiten. Herkömmliche Planungsverfahren erfassen diese Schwankungen nicht. Diese Vereinfachung verhindert einen kostenoptimalen Ablauf logistischer Prozesse. Im Rahmen des Verbundprojektes OVID wird ein Verkehrsmodell zur kurz- und mittelfristigen Verkehrsaufkommensprognose erstellt. Um den Nachteil der Nichtbeachtung kurzfristiger Verkehrsänderungen zu quantifizieren wurde eine Simulationsstudie eines bestandslosen Warenumschlagsterminals (Crossdocking Point) durchgeführt. Die Ergebnisse zeigen, dass es, besonders in Anbetracht der für das 2015 prognostizierten Verkehrsaufkommenssteigerung, zwingend nötig ist, neue Planungs und Steuerungsverfahren zu entwickeln. Das vorgestellte Simulationsmodell wird dabei als erster Schritt für ein vorrausschauendes simulationsbasiertes Planungstool angesehen. | |
| Simulation für die Bewertung zeitdiskreter Modelle zur Analyse logistischer Prozesse | Experiences from the Future, Hrsg. Kai Mertins und Markus Rabe, Fraunhofer IRB-Verlag, 2004, S.397-407 | ||
| A Framework of Stochastic Finite Elements for Models of Manufacturing Systems | 6. International Conference on Analysis of Manufacturing Systems, Lunteren, The Netherlands, 193 – 198 |
The purpose of this paper is to introduce a framework of model elements and associated computation methods which are well suited to model information flow and physical processes in manufacturing systems. The proposed elements, the so called stochastic finite elements, are based on a discrete representation of time, in order to render distribution assumptions unnecessary. In our research, we extend available discrete time queueing models by models for batch processes, which are very common in manufacturing systems, when goods are transported or processed in some steps in batches and in some other steps piecewise. We give a short review of these models. |
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| Analysis of a Batch Server Operating according the Minimum Batch Size Rule | 6. International Conference on Analysis of Manufacturing Systems, Lunteren, The Netherlands, 187 – 192 |
Due to the improvement of efficiency, batch servers are very common in manufacturing systems. This paper presents an analytical method to calculate the distribution of the number of customers at the departure instant for the G/G[L,K]/1 batch server system operating according the minimum batch size rule. Under this rule, when the batch service ends and there are less than L (L<= K) customers waiting, the server remains idle until L customers are accumulated in the queue. We present an approximative approach and our analysis is done in the discrete time domain. |
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| Performance evaluation of material flow systems in discrete time | 3. Fachkolloquium der WGTL, Tagungsbeiträge, Hamburg, 155 – 164 |
Im folgenden Beitrag werden zeitdiskrete analytische Methoden vorgestellt mit Hilfe deren Informations- und Materialflüsse in logistischen Systemen analysiert und bewertet werden können. Bestehende zeitdiskrete Verfahren sind jedoch auf die Bearbeitung und Weitergabe in immer gleichen Mengen („One Piece Flow“) beschränkt. Vor allem in Materialflusssystemen kommt es bedingt durch die Zusammenfassung von Aufträgen, durch Transporte und durch Sortiervorgänge zur Bildung von Batches. Daher wurden analytische Methoden entwickelt, die es ermöglichen verschiedene Sammelprozesse, Batchankünfte an Ressourcen, Batchbearbeitung und Sortieren von Batches analytisch abzubilden und Leistungskenngrößen zu deren Bewertung zu bestimmen. Die im Rahmen der Entwicklungsarbeiten entstandene Software-Lösung „Logistic Analyzer“ ermöglicht eine einfache Modellierung und Analyse von praktischen Problemen. Der Beitrag schließt mit einem numerischen Beispiel. |