Industrial Communication Systems

20-1

20.1 Introduction

Industrial control applications use controllers, sensors, and actuators to close control loops. Sensors

and

actuators

are

usually

distributed

topologically

through

the

controlled

plant.

As

ubiquitous

embed-

ded

controllers,

sensors,

and

actuators

are

more

and

more

common,

while

inexpensive

and

reliable

communication

systems

are

ready

for

use

in

the

industry,

many

of

the

control

loops

are

closed

using

industrial

communication

systems.

A

large

part

of

the

industry

control

loops

are

discrete

in

nature,

where

a

sequence

of

discrete

actions

are

done

aer

a

sequence

of

sensings,

e.g.,

aer

a

displacement

has

been

completed,