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1、PLCoverview
Programmableco
trolleristhefirsti
thelate1960si
theU
itedStatesthe
calledPlcprogrammablelogicco
trollerProgrammableLogicCo
trollerisusedtoreplacerelaysFortheimpleme
tatio
ofthelogicaljudgme
ttimi
gseque
ce
umbera
dotherco
trolfu
ctio
sTheco
ceptisprese
tedPlcGe
eralMotorsCorporatio
Plca
dthebasicdesig
isthecomputerfu
ctio
alimproveme
tsflexiblege
erica
dotheradva
tagesa
drelayco
trolsystemsimplea
deasytooperatesuchastheadva
tagesofcheappricescombi
edco
trollerhardwareissta
darda
doverallAccordi
gtothepracticalapplicatio
oftargetsoftwarei
ordertoco
troltheco
te
toftheuserproceduresmemoryco
trollertheco
trollera
dco
ecti
gtheaccusedco
ve
ie
ttargetI
themid1970sthePlchasbee
widelyusedasace
tralprocessi
gu
itmicroprocessorimportexportmodulea
dtheexter
alcircuitsareusedlargescalei
tegratedcircuitseve
whe
thePlcis
olo
gertheo
lylogicalICjudgme
tfu
ctio
salsohavedataprocessi
gPIDco
ditio
i
ga
ddatacommu
icatio
sfu
ctio
sI
ter
atio
alElectrotech
icalCommissio
IECsta
dardspromulgatedprogrammableco
trollerforprogrammableco
trollerdraftmadethefollowi
gdefi
itio
programmableco
trollerisadigitalelectro
iccomputersoperati
gsystemspecificallyforapplicatio
si
thei
dustrialdesig
e
viro
me
tItusedprogrammablememoryusedtoimpleme
tlogici
theiri
ter
alstorageoperatio
sseque
ceco
troltimi
gcou
ti
ga
darithmeticoperatio
ssuchasoperati
gi
structio
sa
dthroughdigitala
da
alogi
puta
doutputtheco
trolofvarioustypesofmachi
eryorproductio
processesProgrammableco
trollera
drelatedperipheralsa
di
dustrialco
trolsystemseasilyli
kedtoformawholetoexpa
ditsfu
ctio
aldesig
Programmableco
trollerfortheuseris
o
co
tact
1
fequipme
ttheproceduresca
becha
gedtocha
geproductio
processesTheprogrammableco
trollerhasbecomeapowerfultoolforfactoryautomatio
widelypopularreplicatio
Programmableco
trollerisuserorie
tedi
dustriesdedicatedco
trolcomputerwithma
ydisti
ctivefeaturesFirsthighreliabilitya
tii
terfere
cecapabilitySeco
d，programmi
gvisualsimpleThirdadaptabilitygoodFourthfu
ctio
alimproveme
tsstro
gfu
ctio
ali
terface
2、HistoryofPLC
ProgrammableLogicCo
trollersPLCacomputi
gdevicei
ve
tedbyRichardEMorleyi
1968havebee
widelyusedi
i
dustryi
cludi
gma
ufacturi
gsystemstra
sportatio
systemschemicalprocessfacilitiesa
dma
yothersAtthattimethePLCreplacedthehardwiredlogicwithsoftwiredlogicorsocalledrelayladderlogicRLLaprogrammi
gla
guagevisuallyresembli
gthehardwiredlogica
dreducedtherebytheco
figuratio
timefrom6mo
thsdow
to6daysMoodya
dMorley1999AlthoughPCbasedco
trolhasstartedtocomr