Decentralized Routing Algorithm with Physical Time Windows for Modular Conveyors

Sohrt, Simon; Overmeyer, Ludger

doi:10.31224/osf.io/f4eq6

Cited by 3 publications

(3 citation statements)

References 9 publications

(13 reference statements)

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“…We answer: eliminating the need for a central clock reduces the communication load on the system because the system can react flexibly to delayed or early transports without renegotiation of reservations. Unlike decentralized methods that rely on time windows with safety margins [15], execution with logical clocks introduces delays only in response to existing delays and then only as long as necessary. Liveness is guaranteed as long as the order of events is respected on each resource.…”

Section: Discussionmentioning

confidence: 99%

Using Logical Time to Ensure Liveness in Material Handling Systems With Decentralized Control

Seibold

Furmans

Kevin

2022

IEEE Trans. Automat. Sci. Eng.

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We describe a method for decentralized control of route-based material handling systems in which devices have no central controller (by definition), no common source of information, and no synchronized or common clocks with which to plan and execute their activities. The control scheme is based on the concept of logical time, which is a means of partially ordering events in computer operating systems. We modify the concept to the domain of material handling systems and prove system liveness. We conclude by describing GridSorter, a conveyance-based sorter that uses decentralized control and logical time to sort packages. A prototype has been successfully built and tested at the Institute for Material Handling and Logistics, Karlsruhe Institute of Technology.Note to Practitioners-Decentralized control is a means of distributing the control of a complex system away from a central computing source toward individual devices and subsystems. In material handling, complex systems can malfunction due to deadlock, livelock, or starvation. This article presents a new method for controlling decentralized material handling systems based on logical time, a method from computer operating systems describing a sequence of activities at each resource. We modify logical time for material handling and show that the system is deadlock-free, thus giving engineers an easy-to-implement method of controlling route-based material handling systems such as automated guided vehicles (AGVs) or conveyors. Index Terms-Decentralized control, logical time, material handling. I. DECENTRALIZED CONTROL IN MATERIAL HANDLINGA N IMPORTANT feature of the Industry 4.0 concept in material handling systems is autonomy, the ability of devices to make independent decisions. When autonomous devices must cooperate to get things done without a central controller, we say that the system has decentralized control.

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Section: Discussionmentioning

confidence: 99%

Using Logical Time to Ensure Liveness in Material Handling Systems With Decentralized Control

Seibold

Furmans

Kevin

2022

IEEE Trans. Automat. Sci. Eng.

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“…Thus, preventing deadlocks or ensuring system liveliness in general under these conditions remains unresolved as well. Apart from [11], complexity aspects of the presented decentralized algorithms are not studied.…”

Section: A Conveyor Systems With Decentralized Controlmentioning

confidence: 99%

Sequencing With Decentralized Control Using Modular Highest-Density Conveyor Systems

Fleischmann

Furmans

2024

IEEE Trans. Automat. Sci. Eng.

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We present a decentralized sequencing algorithm applicable to modular high(est)-density conveyor systems that enables items to enter the system randomly from multiple input points. They are rearranged within the system to be retrieved at an assigned output point observing a predefined sequence. A variety of applications benefits from this, such as storing and retrieving, order picking, packing and shipping operations as well as Just-in-Sequence (JiS) applications of production systems. We prove that our decentralized algorithm -based on the concept of logical time -is able to prevent deadlocks, livelocks, and starvation. It guarantees a complexity of order O(n 2 ) at module level depending on system size n. Using throughput evaluations, we show how to parameterize the decentralized sequencing algorithm to optimize its performance. Furthermore, we deduce that small batch sizes, high conveying speeds, a high number of output points, or non-perforated network structures increase system throughput. A simulative demonstration of the developed algorithm can be found at our institute channel.Note to Practitioners-The need for flexibility, scalability, and robustness has led to decentralized control concepts becoming more and more popular in practice. In the field of material handling systems, transportation, storage, sortation, and picking functionality is already being realized based on decentralized control. In this paper, we present a decentralized control algorithm which dispatches randomly introduced items to match a specified sequence at their assigned destination. It applies to systems including multiple input and output points ((m : n) setting) and thus allows for parallel order processing and customizable system configurations of various application scenarios. As sequencing combines routing, buffering and relocation functionality, additionally, an overall logic for implementing transport, storage and retrieval, sortation and picking systems is provided as well.

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“…Similar to other decentralized structures, the sensor provides feedback to its own module and neighboring modules. Therefore, the control algorithm for DCS is challenging, because the algorithm needs to perform appropriate action merely based on the feedbacked logic states without having a complete and precise view on the whole conveyor system [3,21,22]. The DCS also does not have vision on the exact location of the carton.…”

Section: Existing Control Systemmentioning

confidence: 99%

Design and Control System Setup of an E-Pattern Omniwheeled Cellular Conveyor

2021

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The addition of omnidirectional capability and modularization to conveyor systems is an exciting and trending topic in current conveyor research. The implementation of omnidirectional modular conveyors is foreseen as mandatory in the future of conveyor technologies due to their flexibility and efficiency. In this paper, an E-pattern omniwheeled cellular conveyor (EOCC) is first introduced. Camera and image processing techniques are utilized to achieve a centralized system, which is more robust than conventional decentralized systems. In order for cartons to maneuver across the EOCC, a unique method for activation of the actuators is subsequently designed. Next, the nominal characteristic of the EOCC is analyzed based on the step responses, which then inspire the proposal of four simple controllers, namely the P–P–P–P controller, tTS + P–P–P–P controller, P–P–PD–PD controller, and tTS + P–P–PD–PD controller (P for proportional, D for derivative and tTS for time-shifting), which are used to evaluate the tracking performance of the EOCC in diagonal-shaped, ∞-shaped (horizontal lemniscus), and 8-shaped (vertical lemniscus) trajectories. The results show that there is no clear winner among the controllers, with each having its own advantages and disadvantages. Nevertheless, such findings provide clearer insight into the EOCC, which is vital for future works. After all, the introduction of the EOCC system in this paper is also anticipated to elevate the benchmarks and competitiveness in the current field of modern conveyor technologies.

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Decentralized Routing Algorithm with Physical Time Windows for Modular Conveyors

Cited by 3 publications

References 9 publications

Using Logical Time to Ensure Liveness in Material Handling Systems With Decentralized Control

Using Logical Time to Ensure Liveness in Material Handling Systems With Decentralized Control

Sequencing With Decentralized Control Using Modular Highest-Density Conveyor Systems

Design and Control System Setup of an E-Pattern Omniwheeled Cellular Conveyor

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