PLUG-AND-WORK MATERIAL HANDLING SYSTEMS and INCREASE IN FLEXIBILITY

PLUG-AND-WORK MATERIAL HANDLING SYSTEMS

Kai Furmans and Frank Schonung
Karlsruhe Institute of Technology, Germany
Kevin R. Gue
Auburn University, USA


Abstract - One disadvantage of automated material handling systems is their
relative inflexibility: once racks are installed and conveyors are laid, making even
minor changes to a system can be cumbersome and expensive. However, recent
progress in the capabilities and cost of basic system components, such as
controllers, drives, and sensors, has made possible a new class of material handling
systems having a much higher degree of flexibility.

The paper provides underlying design principles for such systems and describes some  prototype "plug-and work" systems, which provide ease of reconfiguration.



Smart Rack


The SmartRack is a rack with HF-RFID sensors in each channel or slot. Bins in each channel are equipped with the matching RFID-tags, which contain all necessary information about the parts as well as their origin and their destination. Bins in the rack have a unique ID, and the current status is transferred to a webservice, which allows the supplier to get current inventory and to control
production and resupply accordingly.  The design is simple, but effective:

The SmartRack is made modular because and more channels can easily be added if more part numbers must be stored. SmartRack integrates all functions necessary to create the decentralized, physical material flow via a micro-controller in each rack which allows information to be exchanged on a higher level between the user and the system.


Flexconveyor

The Flexconveyor is a modular, unit-sized conveyor, which can be combined with other modules to create a conveyor network. Each module is able to convey in the four cardinal directions (north, south, east, west). The modules are connected by a serial connection, which is used to exchange all necessary information between adjacent modules. Each module uses light beams to detect any bins present and has an RFID reader, which identifies the bins and determines the destination.

The modules exchange information with each other on several levels. The first is topological—when each module is connected, modules pass messages to discover or update the existing topology. Next is routing information: During the message passing, each module executes an algorithm to update connections of its neighbors (and their neighbors, and so on), as well as the the distance (measured in modules) to each reachable module. This information is exchanged continuously between adjacent neighbors, leading quickly to complete routing information, which shows which direction an individual module should convey in order to send its bin to its destination most efficiently. When material from a bin is to be moved, a module reads its RFID tag and determines the target module. Based on the routing matrix, the appropriate port is selected, which is the link with the shortest distance to the destination. Then a “telegram” is sent to the respective port, asking whether the route towards the destination is available. The next module forwards this telegram to its neighbor, and so on, until the destination module is  reached. The destination then sends back a positive or negative answer to the origin module, which then takes the appropriate action (convey or not). The system is completely decentralized, and may be reconfigured in a matter of minutes. The Flexconveyor uses all the design principles described in the paper.