design control system

7/25/2019 Design Control System

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CONTROL SYSTEM

DESIGNGraham C. Goodwin

Stefan F. Graebe

Mario E. Salgado


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Goodwin Graebe Salgado !renti"e #all $%%%Chapter 1

Cha&ter '

The Excitement of ControlEngineering


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Moti(ation for Control Engineering

Feedba") "ontrol ha* a long hi*tor+ whi"h began

with the earl+ de*ire of h,man* to harne** the

material* and for"e* of nat,re to their ad(antage.Earl+ e-am&le* of "ontrol de(i"e* in"l,de "lo")

reg,lating *+*tem* and me"hani*m* for )ee&ing

windmill* &ointed into the wind.

Modern ind,*trial &lant* ha(e *o&hi*ti"ated "ontrol*+*tem* whi"h are "r,"ial to their *,""e**f,l

o&eration.


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/ modern ind,*trial &lant0 / *e"tion of

the OM1 Oil Refiner+ in /,*tria


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Control Engineering ha* had a ma2or im&a"t on

*o"iet+. For e-am&le 3att4* Fl+ 5all Go(ernor had a

ma2or im&a"t on the ind,*trial re(ol,tion. Indeedmo*t modern *+*tem* 6air"raft high *&eed train* CD

&la+er* 7 8 "o,ld not o&erate witho,t the aid of

*o&hi*ti"ated "ontrol *+*tem*.


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Fig,re '.'0 Watts fly ball governor


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Thi* &hotogra&h *how* a fl+ball

go(ernor ,*ed on a *team engine

in a "otton fa"tor+ near Man"he*terin the 9nited :ingdom. Of "o,r*e

Man"he*ter wa* at the "entre of the

ind,*trial re(ol,tion. /"t,all+ thi*

"otton fa"tor+ i* *till r,nning toda+.


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Thi* fl+ball go(ernor i* in the

*ame "otton fa"tor+ in Man"he*ter.

#owe(er thi* &arti",lar go(ernor

wa* ,*ed to reg,late the *&eed ofa water wheel dri(en b+ the flow of

the ri(er. The go(ernor i* ;,ite

large a* "an be ga,ged b+ the o,tline

of the door frame behind the

go(ernor.


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Im&ro(ed "ontrol i* a )e+ enabling te"hnolog+

,nder&inning0

enhan"ed &rod,"t ;,alit+wa*te minimi


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Fig,re '.$0Process schematic of a Kellogg ammonia plant

/ll of the abo(e i**,e* are rele(ant to the "ontrol of an

integrated &lant *,"h a* that *hown below.


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T+&e* of Control S+*tem De*ign

Control *+*tem de*ign al*o ta)e* *e(eral different

form* and ea"h re;,ire* a *lightl+ different

a&&roa"h.The "ontrol engineer i* f,rther affe"ted b+ where

the "ontrol *+*tem i* in it* life"+"le e.g.0

Initial =gra** root*= de*ignCommi**ioning and T,ning

Refinement and 9&grade*

Foren*i" *t,die*


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S+*tem Integration

S,""e** in "ontrol engineering de&end* on ta)ing a

holi*ti" (iew&oint. Some of the i**,e* are0

&lant i.e. the &ro"e** to be "ontrolledob2e"ti(e*

*en*or*

a"t,ator*

"omm,ni"ation*"om&,ting

ar"hite"t,re* and interfa"ing

algorithm*

a""o,nting for di*t,rban"e* and ,n"ertaint+

G d i G b S l d i ll $%%%


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!lant

The &h+*i"al la+o,t of a &lant i* an intrin*i" &art of

"ontrol &roblem*. Th,* a "ontrol engineer need* to

be familiar with the =&h+*i"*= of the &ro"e** ,nder*t,d+. Thi* in"l,de* a r,dimentar+ )nowledge of the

ba*i" energ+ balan"e ma** balan"e and material

flow* in the *+*tem.

G d i G b S l d ! i # ll $%%%C 1


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Ob2e"ti(e*

5efore de*igning *en*or* a"t,ator* or "ontrol

ar"hite"t,re* it i* im&ortant to )now the goal that i*

to form,late the "ontrol ob2e"ti(e*. Thi* in"l,de* what doe* one want to a"hie(e 6energ+ red,"tion +ield

in"rea*e...8

what (ariable* need to be "ontrolled to a"hie(ethe*e ob2e"ti(e*

what le(el of &erforman"e i* ne"e**ar+ 6a"",ra"+ *&eed...8

G d i G b S l d ! ti # ll $%%%Ch t 1


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Sen*or*

Sen*or* are the eyesof "ontrol enabling one tosee

what i* going on. Indeed one *tatement that i*

*ometime* made abo,t "ontrol i*0

If you can measure it, you can control it.

G d i G ebe S l d ! e ti e # ll $%%%Ch t 1


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/"t,ator*

On"e *en*or* are in &la"e to re&ort on thestateof a

&ro"e** then the ne-t i**,e i* the abilit+ to affe"t or

a"t,ate the *+*tem in order to mo(e the &ro"e**from the ",rrent *tate to a de*ired *tate

Goodwin Graebe Salgado !renti"e #all $%%%Ch t 1


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/ t+&i"al ind,*trial "ontrol &roblem will ,*,all+

in(ol(e man+ different a"t,ator* *ee below0

Fig,re '.>0 Typical flatness control set-up for rolling mill



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/ modern rolling mill



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Comm,ni"ation*

Inter"onne"ting *en*or* to a"t,ator* in(ol(e* the ,*e

of "omm,ni"ation *+*tem*. / t+&i"al &lant "an ha(e

man+ tho,*and* of *e&arate *ignal* to be *ent o(erlong di*tan"e*. Th,* the de*ign of "omm,ni"ation

*+*tem* and their a**o"iated &roto"ol* i* an

in"rea*ingl+ im&ortant a*&e"t of modern "ontrol

engineering.



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Com&,ting

In modern "ontrol *+*tem* the "onne"tion between

*en*or* and a"t,ator* i* in(ariabl+ made (ia a

"om&,ter of *ome *ort. Th,* "om&,ter i**,e* arene"e**aril+ &art of the o(erall de*ign. C,rrent

"ontrol *+*tem* ,*e a (ariet+ of "om&,tational

de(i"e* in"l,ding DCS?* 6Di*trib,ted Control

S+*tem*8 !LC?* 6!rogrammable Logi" Controller*8!C?* 6!er*onal Com&,ter*8 et".



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A modern computer based rapid prototyping system



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/r"hite"t,re* and interfa"ing

The i**,e of what to "onne"t to what i* a nontri(ial

one in "ontrol *+*tem de*ign. One ma+ feel that the be*t

*ol,tion wo,ld alwa+* be to bring all *ignal* to a"entral &oint *o that ea"h "ontrol a"tion wo,ld be ba*ed

on "om&lete information 6leading to *o "alled

"entrali


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Goodw G ebe S g do e "e %%%Chapter 1

Table '.': T+&i"al "ontrol heirar"h+



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g Chapter 1

/lgorithm*

Finall+ we "ome to the real heartof "ontrol engineering

i.e. the algorithm* that "onne"t the *en*or* to the a"t,ator*.

It i* all to ea*+ to ,ndere*timate thi* final a*&e"t of the

&roblem.

/* a *im&le e-am&le from o,r e(er+da+ e-&erien"e

"on*ider the &roblem of &la+ing tenni* at to& international

le(el. One "an readil+ a""e&t that one need* good e+e *ight6*en*or*8 and *trong m,*"le* 6a"t,ator*8 to &la+ tenni* at

thi* le(el b,t the*e attrib,te* are not *,ffi"ient. Indeed

e+ehand "oordination 6i.e. "ontrol8 i* al*o "r,"ial to

*,""e**.



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g Chapter 1

In *,mmar+0

ensors provide the eyes and actuators the musclebut control science provides the finesse!



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gC p e

Better Control!ro(ide* more fine**e b+ "ombiningsensorsandactuatorsin more intelligent wa+*

Better Actuators!ro(ide more"uscle

Better Sensors

!ro(ide better #ision



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p

Di*t,rban"e* and 9n"ertaint+

One of the thing* that ma)e* "ontrol *"ien"e

intere*ting i* that all real life *+*tem* are a"ted on b+

noi*e and e-ternal di*t,rban"e*. The*e fa"tor* "anha(e a *ignifi"ant im&a"t on the &erforman"e of the

*+*tem. /* a *im&le e-am&le air"raft are *,b2e"t to

di*t,rban"e* in the form of windg,*t* and "r,i*e

"ontroller* in "ar* ha(e to "o&e with different roadgradient* and different "ar loading*.



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p

#omogeneit+

/ final &oint i* that all inter"onne"ted *+*tem*

in"l,ding "ontrol *+*tem* are onl+ a* good a* their

wea)e*t element. The im&li"ation* of thi* in "ontrol*+*tem de*ign are that one *ho,ld aim to ha(e all

"om&onent* 6&lant *en*or* a"t,ator* "omm,ni"ation*

"om&,ting interfa"e* algorithm* et"8 of ro,ghl+

"om&arable a"",ra"+ and &erforman"e.



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p

In order to ma)e &rogre** in "ontrol engineering 6a*

in an+ field8 it i* im&ortant to be able to 2,*tif+ the

a**o"iated e-&endit,re. Thi* ,*,all+ ta)e* the formof a "o*t benefit anal+*i*.



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Co*t benefit anal+*i*

T+&i"al *te&* in"l,de0

/**e**ment of a range of "ontrol o&&ort,nitie*@

De(elo&ing a *hort li*t for "lo*er e-amination@ De"iding on a &ro2e"t with high e"onomi" or

en(ironmental im&a"t@

Con*,lting a&&ro&riate &er*onnel 6management o&erator*

&rod,"tion *taff maintenan"e *taff et".8@ Identif+ing the )e+ a"tion &oint*@

Colle"ting ba*e "a*e data for later "om&ari*on@

De"iding on re(i*ed &erforman"e *&e"ifi"ation*@

9&dating a"t,ator* *en*or* et".@



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De(elo&ment of algorithm*@

Te*ting the algorithm* (ia *im,lation@

Te*ting the algorithm* on the &lant ,*ing a ra&id

&rotot+&ing *+*tem@

Colle"ting &reliminar+ &erforman"e data for "om&ari*on

with the ba*e "a*e@

Final im&lementation@

Colle"tion of final &erforman"e data@

Final re&orting on &ro2e"t.

Co*t benefit anal+*i* 6$ontd.8



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Signal* and *+*tem* terminolog+

design control system

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