Java Reference
In-Depth Information
13
Supervisory control and
data acquisition system
Synthesis
A typical distributed subsystem that integrates data and functionalities
within a factory work cell is represented by the SCADA (supervisory control
and data acquisition) system. It collects process data from hardware devices
(e.g. temperatures, speeds, forces, etc.), stores relevant data in a central
database, processes data in order to identify anomalous situations, generates
reports and alarms, and allows the operator to send commands to the hard-
ware devices in order to control the manufacturing process. This case study
exemplifies the development of a very simple SCADA system for car surface
painting.
Focus: the emphasis is on the system architecture and the mechanisms
used to interconnect distributed components such as the work cell
simulator, the colour tank controllers and the supervisory station.
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OO techniques: distributed components.
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Java features: Remote Method Invocation (RMI).
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Background: Chapters 9, 10 and 11 presented three simulation models
that are taken into consideration in this case study as a starting point for
analysis and design.
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13.1
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Specifications
Increasingly, automotive manufacturers recognize that vehicle paint appear-
ance is strongly representative of the quality of the product as a whole and
makes an important contribution to customer product satisfaction. The
main problem the measurement of paint appearance. Since there has been
no point so far in attempting to automatically correlate process data with
customer perception coherently, feedback process control is based on
online adjustments of process parameters performed by responsible tech-
nicians. Currently, there are SCADA systems available for measuring
process parameters such as pressure, flow and spray booth data that are
plotted on attribute charts.
We want to develop a SCADA system for the remote control of a car paint-
ing work cell. The work cell is made up of three paint tanks (one for each
fundamental colour) and a mixture tank that receives paint flows from them
(see Figure 13.1). The colour tanks behave as finite capacity buffers that
