week 1 - intro to control systems

8/10/2019 Week 1 - Intro to Control Systems

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INTRODUCTION TO CONTROL

SYSTEM ENGINEERINGEDDIE G. SANTILLAN, JR., ECE

Reference: Control System Engineering 6E Norm n Nise


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Denition

A control system consists of s!"systems n# $rocesses%or $l nts& ssem"le# for t'e $!r$ose of o"t ining #esire# o!t$!t (it' #esire# $erform nce, gi)en s$eci*e# in$!t.

A control system ' s n in$!t, $rocess, n# n o!t$!t.


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An elevator as

+'en t'e fo!rt' -oor "!tton is $resse# on t'e*rst -oor, t'e ele) tor rises to t'e fo!rt' -oor(it' s$ee# n# -oor le)eling cc!r cy #esigne#for $ ssenger comfort.

T(o m or me s!res of $erform nce re $$ rent:/. t'e tr nsient res$onse0. t'e ste #y st te error


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An elevator as

Ele) tor res$onse


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Advantages of Control Systems

+e "!il# control systems for fo!r $rim ryre sons:/. 1o(er m$li*c tion

2or e3 m$le, r # r ntenn , $ositione# "y t'e lo(

$o(er rot tion of 4no" t t'e in$!t, re5!ires l rgemo!nt of $o(er for its o!t$!t rot tion.

0. Remote control2or e3 m$le, remote controlle# ro"ot rm c n "e!se# to $ic4 !$ m teri l in r #io cti)e en)ironment.


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Advantages of Control Systems

. Con)enience of in$!t form2or e3 m$le, in tem$er t!re control system, t'ein$!t is position on t'ermost t. T'e o!t$!t is heat.

T'!s, con)enient $osition in$!t yiel#s #esire#t'erm l o!t$!t.

7. Com$ens tion for #ist!r" nces2or e3 m$le, $osition controlle# ntenn system is#is$l ce# "y (in# forces %or #!e to noise orinterference& from its comm n#e# $osition, t'e system

m!st "e "le to #etect t'e #ist!r" nce n# correct t'entenn 8s $osition comm n#e# "y t'e in$!t.


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A History of Control s

Liquid-Level ControlKtesibios in)ente# ( ter cloc4 in 99 .C.o$er te# "y ' )ing ( ter tric4le into me s!ring cont iner t const nt r te. T'e

le)el of ( ter in t'e me s!ring cont iner co!l#"e !se# to tell time.Soon fter ;tesi"ios, t'e i#e of liquid-levelcontrol ( s $$lie# to n oil l m$ "y P ilon o!"#$%ntiu& .


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Ste%& Pressure %nd Te&'er%tureControlsReg!l tion of ste m $ress!re "eg n ro!n#/6


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S'eed ControlIn />7?, s$ee# control ( s $$lie# to (in#mill"y Ed&und Lee( Incre sing (in#s $itc'e# t'e"l #es f rt'er " c4, so t' t less re ( s

) il "le. As t'e (in# #ecre se#, more "l #ere ( s ) il "le.

)illi%& Cubitt im$ro)e# on t'e i#e in /


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St%bilit#+ St%bili$%tion+ %nd Steerin,In /


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T/entiet -Centur# Develo'&entsIn /@00, t'e S'err# G#ros1o'e Co&'%n# inst lle#n !tom tic steering system t' t !se# t'e elements

of com$ens tion n# # $ti)e control to im$ro)e$erform nce.

Ni1 ol%s Minors # concei)e# t'e $$lic tion of$ro$ortion l $l!s integr l $l!s #eri) ti)e %1ID&controllers to t'e !tom tic steering of s'i$s.In t'e l te /@09s n# e rly /@ 9s, 2( )( "ode n#

2( N#quist t ell Tele$'one L "or tories #e)elo$e#t'e n lysis of fee#" c4 m$li*ers ('ic' e)ol)e# intosin!soi# l fre5!ency n lysis n# #esign tec'ni5!esc!rrently !se# for fee#" c4 control system.


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T/entiet -Centur# Develo'&entsIn /@7


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System Congurations

Two major con gurations of controlsystems:o'en loo'

#o not correct for #ist!r" nces n# re sim$lycomm n#e# "y t'e in$!t.

1losed loo' or !eedb%1 1ontrol s#ste&com$ens tes for #ist!r" nces "y me s!ring t'eo!t$!t res$onse, fee#ing t' t me s!rement " c4t'ro!g' fee#" c4 $ t', n# com$ ring t' tres$onse to t'e in$!t t t'e s!mming !nction


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3un1tions o! E%1 Co&'onentIt st rts (it' s!"system c lle# n in$!ttr ns#!cer, ('ic' con)erts t'e form of t'e in$!tto t' t !se# "y t'e controller.

T'e controller #ri)es $rocess or $l nt. T'e in$!t is sometimes c lle# t'e reference, ('ilet'e o!t$!t c n "e c lle# t'e controlle# ) ri "le.Ft'er sign ls, s!c' s #ist!r" nces, re s'o(n

##e# to t'e controller n# $rocess o!t$!ts )is!mming !nctions, ('ic' yiel# t'e lge"r ic s!mof t'eir in$!t sign ls !sing ssoci te# signs.


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Block Diagram of an Closed Loop System


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3un1tions o! E%1 Co&'onent

T'e in'ut tr%nsdu1er con)erts t'e form of t'ein$!t to t'e form !se# "y t'e controller.An out'ut tr%nsdu1er , or sensor , me s!res t'eo!t$!t res$onse n# con)erts it into t'e form

!se# "y t'e controller. 2or e3 m$le, if t'econtroller !ses electric l sign ls to o$er te t'e) l)es of tem$er t!re control system, t'e in$!t$osition n# t'e o!t$!t tem$er t!re recon)erte# to electric l sign ls. T'e in$!t $osition c n "e con)erte# to )olt ge "y

$otentiometer. T'e o!t$!t tem$er t!re c n "e con)erte# to

)olt ge "y t'ermistor, #e)ice ('ose electric l

resist nce c' nges (it' tem$er t!re.


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T'e 4rst su&&in, 5un1tion lge"r ic lly ##st'e sign l from t'e in$!t to t'e sign l from t'eo!t$!t, ('ic' rri)es )i t'e fee#" c4 $ t', t'eret!rn $ t' from t'e o!t$!t to t'e s!mming

!nction.The output signal is subtracted from the inputsignal.The result is generally called the actuatingsignal .In systems where both the input and outputtransducers have unity gain (that is, thetransducer ampli es its input by 1 , theactuating signal!s value is equal to the actual

di"erence between the input and the output


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Advantages and Trade-offClose# loo$ systems ' )e gre ter cc!r cy t' no$en loo$ systems. T'ey re less sensiti)e to noise,#ist!r" nces, n# c' nges in t'e en)ironment.

Tr nsient res$onse n# ste #y st te error c n "econtrolle# con)eniently n# (it' gre ter -e3i"ilityin close# loo$ systems "y sim$le # !stment ofg in % m$li*c tion& in t'e loo$ n# sometimes "yre#esigning t'e controller or com$ens ting t'esystem n# t'e res!lting ' r#( re s

1o&'ens%tor(Close# loo$ systems re more com$le3 n#e3$ensi)e ('ile o$en loo$ systems re sim$le n#lo( cost.


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Analysis and Design

0n%l#sis is t'e $rocess "y ('ic' system8s$erform nce is #etermine#.2or e3 m$le, (e e) l! te its tr nsient res$onse n#ste #y st te error to #etermine if t'ey meet t'e#esire# s$eci*c tions.

Desi,n is t'e $rocess "y ('ic' system8s$erform nce is cre te# or c' nge#.

2or e3 m$le, if system8s tr nsient res$onse n#ste #y st te error re n ly e# n# fo!n# not to

meet t'e s$eci*c tions, t'en (e c' nge $ r metersor ## ##ition l com$onents to meet t'es$eci*c tions.


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0 1ontrol s#ste& is d#n%&i1 : It res$on#s ton in$!t "y !n#ergoing tr nsient res$onse"efore re c'ing ste #y st te res$onse t' tgener lly resem"les t'e in$!t.

T'ree m or o" ecti)es of systems n lysis n##esign:$ro#!cing t'e #esire# tr nsient res$onsere#!cing ste #y st te error

c'ie)ing st "ility


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Steady-State ResponseSte #y st te res$onse #etermines t'e cc!r cy oft'e control system it go)erns 'o( closely t'eo!t$!t m tc'es t'e #esire# res$onse.

2or e3 m$le, t'is res$onse m y "e n ele) torsto$$e# ne r t'e fo!rt' -oor or t'e 'e # of #is4 #ri)e *n lly sto$$e# t t'e correct tr c4.

Ste$s in n lysis n# #esign of ste #y st teerrors:

/. De*ne ste #y st te errors 5! ntit ti)ely.0. n ly e system8s ste #y st te error.

. Design correcti)e ction to re#!ce t'e ste #yst te error.


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Stability T'e tot l res$onse of system is t'e s!m of t en%tur%l res'onse n# t e !or1ed res'onse .

Natural res onse #escri"es t'e ( y t'esystem #issi$ tes or c5!ires energy n# is#e$en#ent only on t'e system, not t'e in$!t.

2or control system to "e !sef!l, t'e n t!r lres$onse m!st %/& e)ent! lly $$ro c' ero, t'!sle )ing only t'e force# res$onse, or %0& oscill te.

T'e force! res onse is #e$en#ent on t'e in$!t.

A st%ble control systems m!st ' )e t'eir n t!r lres$onse #ec y to ero s time $$ro c'es in*nity,or oscill te.


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StabilityIf t'e n t!r l res$onse gro(s (it'o!t "o!n#r t'er t' n #iminis' to ero or oscill te n#"ecomes gre ter t' n t'e force# res$onse in('ic' t'e system is no longer controlle# le #ingto #estr!ction or # m ge of t'e system itself. T'iscon#ition is c lle# instability .

t'e ele) tor (o!l# cr s' t'ro!g' t'e -oor or e3itt'ro!g' t'e ceiling

n ircr ft (o!l# go into n !ncontroll "le roll

An !nst "le system (o!l# s'o( tr nsientres$onse t' t gro(s (it'o!t "o!n# n# (it'o!t

ny e)i#ence of ste #y st te res$onse.


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Other Considerations3%1tors %6e1tin, %rd/%re sele1tion

motor si ing to f!l*ll $o(er re5!irementsc'oice of sensors for cc!r cy

3in%n1es 7 bud,et %llo1%tions %nd

1o&'etitive 'ri1in, &ust be 1onsideredRobust desi,n

T'e system (ill not "e sensiti)e to $ r meterc' nges ('en !se# in n ct! l en)ironment.


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The Design Process


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Test waveforms used in control s


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Test waveforms used in control s


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Computer-Aided DesignHATLA n# t'e HATLA Control System Tool"o3

n ltern te met'o# of sol)ing control system$ro"lems

NI L " IE+ N tion l Instr!ments L "or tory irt! lInstr!ment tion for Electronic +or4"enc'

T'is gr $'ic l $rogr mming tool $ro#!ces front$ nels of )irt! l instr!ments on yo!r com$!ter t' t

re $ictori l re$ro#!ctions of ' r#( re instr!ments,

s!c' s ( )eform gener tors or oscillosco$es.Also incl!#es "loc4s ('ic' cont in !n#erlying co#efor t'e controls n# in#ic tors on t'e front $ nel.

ItdtitPitiCtl


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Introduction to Position ControlSystems

A $osition control systemcon)erts $osition in$!tcomm n# to $osition o!t$!tres$onse (it' (i#es$re #

$$lic tions in ntenn s, ro"otrms, n# com$!ter #is4 #ri)es. T'e r #io telesco$e ntenn isone e3 m$le of system t' t!ses $osition control systems.An ntenn im!t' $ositioncontrol system is !se# to $osition

r #io telesco$e ntenn .


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Step 1: Transform Requirements Into aPhysical System


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Step 2: Draw a Functional Block Diagram


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The Operation

T'e in$!t comm n# is n ng!l r #is$l cement. T'e $otentiometer con)erts t'e ng!l r#is$l cement into )olt ge.Simil rly, t'e o!t$!t ng!l r #is$l cement is

con)erte# to )olt ge "y t'e $otentiometer int'e fee#" c4 $ t'.

T'e sign l n# $o(er m$li*ers "oost t'e#iBerence "et(een t'e in$!t n# o!t$!t )olt ges.

T'is m$li*e# ct! ting sign l #ri)es t'e $l nt. T'e motor is #ri)en only ('en t'e o!t$!t n# t'ein$!t #o not m tc'. T'e gre ter t'e #iBerence"et(een t'e in$!t n# t'e o!t$!t, t'e l rger t'emotor in$!t )olt ge, n# t'e f ster t'e motor (illt!rn.


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Step 3: Create a S chematic


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Step 3: Create a Schematic (Detailed)

Ste$ 7: De)elo$ H t'em tic l


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Ste$ 7: De)elo$ H t em tic lHo#el % loc4 Di gr m&


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Ste$ ?: Re#!ce t'e loc4 Di gr m%"& 1!s'ing in$!t $otentiometer to t'e rig't $ st

t'e s!mming !nction

%c& s'o(ing e5!i) lentfor( r# tr nsfer f!nction

%#& 2in l close# loo$tr nsfer f!nction


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Step 6: Analyze and DesignRes$onse of $osition control system, s'o(ingeBect of 'ig' n# lo( controller g in on t'eo!t$!t res$onse.


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AnalysisIf (e incre se t'e g in of t'e sign l m$li*er, (illt'ere "e n incre se in t'e ste #y st te ) l!e oft'e o!t$!tIf t'e g in is incre se#, t'en for gi)en ct! tingsign l, t'e motor (ill "e #ri)en ' r#er "!t (ill stillsto$ ('en t'e ct! ting sign l re c'es ero, t' tis, ('en t'e o!t$!t m tc'es t'e in$!t.


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Transient ResponseIf t'e motor is #ri)en ' r#er, it t!rns f ster to( r#its *n l $osition. Also, "ec !se of t'e incre se#s$ee#, incre se# moment!m co!l# c !se t'emotor to o)ers'oot t'e *n l ) l!e n# "e force#"y t'e system to ret!rn to t'e comm n#e#

$osition. T'!s, t'e $ossi"ility e3ists for tr nsientres$onse t' t consists of damped oscillations(that is, a sinusoidal res$onse ('ose m$lit!#e

#iminis'es (it' time& "o!t t'e ste #y st te) l!e if t'e g in is 'ig'.


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Steady-State Response Ty$ic lly, t'e ste #y st te error #ecre ses (it' nincre se in g in n# incre ses (it' #ecre se ing in.

T'e res$onse s'o(s ero error in t'e ste #y st teres$onse t' t is, fter t'e tr nsients ' )e#is $$e re#, t'e o!t$!t $osition e5! ls t'ecomm n#e# in$!t $osition.In some systems, t'e ste #y st te error (ill not "e

ero for t'ese systems, sim$le g in # !stment

to reg!l te t'e tr nsient res$onse is eit'er noteBecti)e or le #s to tr #e oB "et(een t'e#esire# tr nsient res$onse n# t'e #esire#ste #y st te cc!r cy.


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Stability To sol)e t'is $ro"lem, controller (it' #yn micres$onse, s!c' s n electric l *lter, is !se# long(it' n m$li*er. +it' t'is ty$e of controller, it is$ossi"le to #esign "ot' t'e re5!ire# tr nsientres$onse n# t'e re5!ire# ste #y st te cc!r cy

(it'o!t t'e tr #e oB re5!ire# "y sim$le settingof g in. =o(e)er, t'e controller is no( morecom$le3. T'e *lter in t'is c se is c lle# com$ens tor.

H ny systems lso !se #yn mic elements in t'efee#" c4 $ t' long (it' t'e o!t$!t tr ns#!cer toim$ro)e system $erform nce.


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Summary T'e #esign o" ecti)es n# t'e system8s$erform nce re)ol)e ro!n# t'e tr nsientres$onse, t'e ste #y st te error, n# st "ility.G in # !stments c n Bect $erform nce n#sometimes le # to tr #e oBs "et(een t'e$erform nce criteri . Com$ens tors c n often "e#esigne# to c'ie)e $erform nce s$eci*c tions(it'o!t t'e nee# for tr #e oBs.


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Assignment:Re)ie( L $l ce tr nsform n# In)er L $l cetr nsform for t'e ne3t lect!re.

week 1 - intro to control systems

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