![[Picture of testbed]](newtb1_bk.jpg)
Description of Testbed
The testbed was designed for the purpose of investigating the
implementation of Discrete Event Systems (DES) supervisors on Programmable
Logic Controllers (PLC). It is designed to simulate a manufacturing workcell,
in particular, problems of routing and collision. It is composed
primarily of model railroad components, featuring Märklin Digital trains.
The testbed tracks are laid out to resemble a set of three interacting
work units. The two trains simulate Automated Guided Vehicles (AGV)
that provide and remove material to/from each manufacturing unit. Each
unit has a small electric crane to simulate robots loading and
unloading the AGV. Finally, the system contains several remote track
switches (10) to control the paths of the trains, plus sensors (28)
that detect the presence and identity of each train.
The testbed is controlled by two embedded MC68332 processors and an
Allen-Bradley
Programmable Logic Controller (PLC).
The microprocessors control the trains and cranes
directly, plus they have a discrete interface for communication with the
PLC. The PLC actually implements the DES supervisors and is responsible for
the control of the overall system.
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