Prototype 2: Tank controllers . A distributed application that interconnects
the simulator with the colour tank controllers. The controllers regulate the
level of paint in the tanks.
Prototype 3: The supervisory station . The fully distributed system which
interconnect the mixture tank controller with the colour tank controllers
and the remote supervisory station.
Prototype 1: Work cell simulation
This section identifies the functional requirements of the car painting work
cell, defines the architecture of the work cell simulator and implements its
basic components. The result is a standalone application that animates the
behaviour of the physical devices (tanks and pumps) under the control of
the responsible technician.
The main entities found in the problem specification are colour tank,
mixture tank, input pump, output pump and pipes. The colour tanks and the
mixture tank differ only in their functionality: the colour tanks behave such
as buffers that can guarante a continuous output flow. The mixture tank
receives paint quantities of different tonalities and mixes them in order to
obtain a homogeneous paint tonality. The problem specification does not
indicate any detail about the mixing process. Thus, the simulator can
abstract from the real mixing process; the new tonality is obtained from the
sum of the fundamental colours' tonality weighted by their corresponding
paint volumes. Some functional requirements should be taken into account:
The simulator architecture should promote a seamless transition from the
prototype to the real system in such a way that the rest of the SCADA
system will not be affected by the transition.
Consistency of physical constraints must be enforced: the pumps and the
pipes guarantee that the same volume of paint is pulled from an upstream
tank and pushed into the downstream tank.
The responsible technician should be allowed to monitor the variations of
pump flow and tank level in real time and can operate the pump manually
from a local console.
According to the SCADA model described in Section 13.2.1 physical devices
such as tanks and pumps are equipped with sensors and actuators that are
connected to the PLCs through dedicated communication links such as
serial cables. We can assume that the communication protocol and the data
format are standard, i.e. every physical device is a blackbox component that