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Control System Design - Index | Book Contents |
Chapter 1
| Section 1.5
1. The Excitement of Control Engineering
1.5.5 Communications
Interconnecting sensors to actuators involves the use of
communication systems. A typical plant can have many thousands of
separate signals to be sent over long distances. Thus, the design
of communication systems and their associated protocols is an
increasingly important aspect of modern control engineering.
There are special issues and requirements for communication
systems with real-time data. For example, in voice communication,
small delays and imperfections in transmission are often
unimportant by virtue of being transparent to the recipient.
However, in high-speed real-time control systems, these issues
could be of major importance. For example, there is an increasing
tendency to use Ethernet-type connections for data transmission in
control. However, as is well known by those familiar with this
technology, if a delay occurs on the transmission line, then the
transmitter simply tries again at some later random time.
This obviously introduces a non-deterministic delay into the
transmission of the data. All control systems depend upon precise
knowledge of, not only what has happened, but when
it happened, so attention to such delays is very important for the
performance of the overall system.
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