Page 278 - Mechatronics for Safety, Security and Dependability in a New Era

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proprietary robot language. However it is hard to integrate all functions required in a real factory,
because the real factory is composed of many kinds of devices. This approach is confronted with a lot
of problems. To cope with the problem, we made conceptual change from INTEGRATION to
DISTRIBUTION.

In this paper, we propose a simulation environment which is integrating the real devices into the
manufacturing simulation systems on the network. This environment is realized as a distributed real
simulation system. The system is composed of ORiN system, soft-wiring system, production cell
simulator, ORiN-HLA gateway and so on. By using this system, manufacturing system developers are
able to use the same simulation model consistently from the design stage to the implementation stage.

BASIC CONCEPT

The procedure for developing a manufacturing system is commonly based on the waterfall model to
reduce a waste of loop-back and re-doing. But still there are many loop-backs on each process. It is
difficult to shorten the manufacturing system development time without reducing the loop-backs.
Therefore, it is necessary for development time reduction to reduce the "loop frequency" and/or to
shorten the "loop time".
To reduce the loop frequency, the upper-layer design process should be highly accurate. To achieve
this goal, the FA programming task in the simulation environment is indispensable. However, this
causes increase in modelling cost and deterioration of cost-effectiveness. The simulation is not usually
used at the implementation stage for these reasons.

As a solution of this problem, we propose an architecture that enables diverting the simulation
program to the real device in the implementation stage. The point is to use the same model throughout
the manufacturing system life cycle. This means that an implementation task is to embody the exactly
same model as the real devices. And this leads to the wide-use of the simulator at the implementation
stage. As a result, this also leads to shorter average loop time because of the easier loop back in the
simulation.
However, it is easy to imagine the difficulty of creating the simulation environment which is usable in
all stages of the manufacturing system construction. The difficulty originates from the fact that the
production system is composed of quite a lot of FA devices. Moreover the user programs of those
devices are described not in a simulation language but in a ladder language or a robot language, etc.
Therefore, we propose architecture of using a real FA device in one simulation environment. By using
actual ladder programs or robot programs in the simulation, the simulation accuracy can be improved,
and those programs can be reused at the implementation stage.

To achieve this simulation environment, it is necessary to realize the following four functions.
1) Function to abstract a wide variety of FA devices.
2) Function to absorb the differences between the abstracted devices and the real devices.
3) Function to connect the abstracted devices logically.
4) Function to simulate the mechanical motion by the signal from the abstracted device.
In addition, to execute a manufacturing cell simulation in the real production environment such as the
production order patterns, it is necessary to make an interaction with the upper-layer simulators such
as a production line simulator. Therefore the following two functions are also required.
5) Function to exchange data between the cell simulator and the upper-layer production simulators.
6) Function to manage the logical time and the synchronization between simulators.