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Overall Course Objectives

Develop the skills necessary to function as anindustrial process control enineer!

" #kills

Tuning loops

Control loop desin

Control loop troubleshootin

Command of the terminoloy

" $undamental understandin

Process dynamics

Feedback control

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P-only Control

$or an open loop overdamped process as %cis

increased the process dynamics oes throuh the

follo&in se'uence of behavior

"overdamped"critically damped

"oscillatory

"rinin

"sustained oscillations

"unstable oscillations

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Dynamic Chanes as Kcis

Increased for a $OPD( Process

Time Time Time

Time Time Time

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ffect of Kcon Closed-*oop

-0.5

0

0.5

1

1.5

0 2 4 6 8

K c

Dam

ing!ac"#

r$%& #'erdamed

(nderdamed

(ns"able

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P-only Controller .pplied to $irst-

Order Process &ithout Deadtime

/ithout deadtime, the system &ill not become

unstable reardless of ho& lare %cis!

$irst-order process model does not consider

combined actuator0process0sensor system!

(herefore, first-order process model &ithout

deadtime is not a realistic model of a process

under feedback control!

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PI Control

.s %cis increased or Iis decreased +i!e!,

more aressive control, the closed loop

dynamics oes throuh the same se'uenceof chanes as the P-only controller1

overdamped, critically damped, oscillatory,

rinin, sustained oscillations, and unstableoscillations!

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ffect of 2ariations in Kc

Time Time Time

ffect of 2ariations in I

Time Time Time

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.nalysis of the ffect of Kcand

I

/hen there is too little proportional action

or too little interal action, it is easy toidentify!

3ut it is difficult to differentiate bet&een

too much proportional action and too muchinteral action because both lead to rinin!

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)esponse of a Properly (uned PI

Controller

Time

*ag

c

ys

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)esponse of a PI Controller &ith

(oo 4uch Proportional .ction

Time

*ag

c

ys

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)esponse of a PI Controller &ith

(oo 4uch Interal .ction

Time

*ag

ys

c

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PID Control

Kcand Ihave the same eneral effect as

observed for PI control!

Derivative action tends to reduce the

oscillatory nature of the response and

results in faster settlin for systems &ith

larer deadtime to time constant ratios!

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Comparison bet&een PI and PID

for a *o& p0p)atio

Time

+I

+ID

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Comparison bet&een PI and PID

for a 5iher p0p)atio

Time

+ID

+I

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ffect of Don Closed-*oop

0

0.5

1

1.5

0 0.25 0.5 0.,5D

Daming!ac"#r$&

#'erdamed

(nderdamed

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Demonstration1 2isual 3asic

#imulator

ffect of Kc,

I, and

D

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Overvie&

.s the controller aressiveness is increased+i!e!, Kcis increased or Iis decreased, theresponse oes from overdamped to criticallydamped to oscillatory to rinin to sustained

oscillations to unstable! (oo little proportional or interal action are

easy to identify &hile too much proportional

or interal results in rinin! Differentiatinbet&een too much interal or proportionalaction re'uires comparin the la bet&eenthe controller output and the C2!