Fottner, Johannes

Lieberoth-Leden, Christian

English

Georgia Southern University: Digital Commons@Georgia Southern

2018 International Material Handling Research ColloquiumSavannah, Georgia USA, July 23-26, 2018Deployment of an Distributed Strategic Material Flow Control for Automated Material Flow Systems Consisting of Autonomous ModulesChristian Lieberoth-Leden and Johannes FottnerTechnical University of MunichSource2Sink2Source1Sink1Source2Sink2Source1Sink1Source2Sink2Source1Source2Source2Sink2Source1Sink1TU TU TU TU TU TU TU 1TU TU TU 1TU TU TU 1 TU TU TU TU TU TU 1TU TU TU TU TU TU 1TU TU TU with buffer demand Buffer spaces for TUBuffers close to source Buffers close to sinkBuffers close to current position Buffers with best quality indicatorSource2Sink2Source1Sink1TU 2TU 1 TU 2TU 1 TU 3TU 3Source2Sink2Source1Sink1TU 2TU 1 TU 1TU 2TU 2TU 2TU 2Modularized Automated Material Flow Systems (aMFSs)Conventional aMFSs• There are no standardized components or modules for aMFSs, so there is a great variety of heterogeneous modules on the market.• aMFSs are mostly operated by a specialized control software and changes due to new demands require a high manual effort• New demands arise from:• Changed manufacturing or logistics processes caused by new products• Fluctuating production volume• Modification of the layout in the production process due to new machineryDistributed Strategic Material Flow Control Buffer Selection StrategiesConvertible aMFSs• Convertible aMFSs are characterized by providing flexibility beyond predefined limits• Convertible aMFSs can be realized by dividing the monolithic software usually implemented on a single PLC in independent automated material flow modules (aMFMs)• An aMFMs is defined as an encapsulated unit that performs predefined logistical functions, such as transporting or buffering• An aMFM possesses all the necessary knowledge and software to control its hardware and to communicate with other aMFMs or superior systems.System Architecture• The knowledge of the layout is generated automatically during the self-configuration process of an aMFM, when an aMFM detects its neighbourhood and establishes the material flow interfaces to neighbouring aMFMs.• The central coordinator aggregates data and provides consistent information for all aMFMs and is dynamically allocated• Utilization of semi-static routes in aMFSs, based on the multi-label protocol switching concept used in communication networksStrategic Material Flow ControlWorkflow management:• Superior systems send transport tasks to the coordinator• The coordinator processes the transport task for aTU and generates workflows through the aMFSThere are three material flow roles for an aMFM:1. Destination aMFM: The material flow control incorporates the logistical pull principle.• Destinations decide whether a TU is released for transport• Destinations cyclical check the state of the workflows and apply release criteria (e.g. sequence)• In the case of waiting time until the workflow may be released, the destination is responsible for selecting a suitable aMFM to buffer the TU.2. Start aMFM: Start aMFMs update destinations about the current state of a workflow or request a transport.• The start aMFM searches for an existing semi-static route to the destination or establishes a new route.• For the routing a constraint-based routing algorithm is applied.3. Intermediate aMFM: Intermediate destinations act as start and destination at the same time.Source2Sink2Source1Sink1TU 2TU 1 TU 2TU 1 TU 3TU 3 TU 2TU 3Workflow ManagementTransport RequestBuffer WorkflowsCancelled BuffersBuffer Selection• Every aMFM can act as buffer• The maximum and available buffer capacity are communicated to the coordinator• The destination aMFM strategically selects a buffer set with one or more buffer aMFMs and requests an update for the set of buffers from the coordinatorBuffer Selection Strategy1. Select the buffer which is closest to the start:The TU arrives within a short transport time at the buffer and the majority of the transport is not accomplished yet.2. Select a buffer which is closest to the destination:The TU already accomplishes the majority of the transport to the destination.3. Select the buffer which is close to the current position:The TU only has a short transport to the next buffer.4. Select a buffer in dependence of the system layout and utilisation of the aMFMs:In order to evaluate the qualification of an aMFM to act as a buffer, an indicator is introduced which favours the scenarios shown on the right.TU1TU1TU2TU1TU2TU3TU2TU3TU3Direction of conveyorResults of the Simulation Study• The strategy to select buffers with the introduced indicator showed the best results.• Combination of the quality indicator with the buffer position• The strategy solely selecting buffers after the quality indicator showed the best resultsBuffer QualityQuality SinksQuality SourcesQuality PositionAll StrategiesMax. Size 5, Sequence 84% 72% 50% 35% -6%Max. Size 3, Sequence 152% 53% 157% 205% 68%Max. Size 5, No Sequence 112% 93% -42% -39% -8%Max. Size 3, No Sequence 29% 29% 2% 59% -2%All scenarios 83% 59% 30% 55%ScenarioBuffer Strategy

Deployment of an Distributed Strategic Material Flow Control for Automated Material Flow Systems Consisting of Autonomous Modules

The modularisation of hardware and software is one approach to handle the demand for increasing flexibility and changeability of automated material flow systems that are, for example, utilised in flexible production systems. In such automated material flow systems, autonomous modules communicate with each other to coordinate and execute transport tasks. In this paper a strategic material flow control is introduced, which is distributed on several modules realised with a multi-agent system. The strategic material flow control agent coordinates transport tasks with advanced logistical requirements, such as sequencing. A transport task states for a transport unit the system source and sink together with arrival criteria at the sink, e.g. sequence In order to fulfil the arrival criteria the strategic material flow agent selects additional destinations within the automated material flow system to buffer a transport unit. For the selection of suitable buffer modules, several strategies are proposed and evaluated in a simulation study

https://digitalcommons.georgiasouthern.edu/cgi/viewcontent.cgi?article=1010&context=pmhr_2018

Deployment of an Distributed Strategic Material Flow Control for Automated Material Flow Systems Consisting of Autonomous Modules

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Georgia Southern University: Digital Commons@Georgia Southern

Georgia Southern University: Digital Commons@Georgia Southern