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Chapter 5INDUSTRIAL CONTROLS

REVIEW QUESTIONS

5.1 What is industrial control?

Answer : s de!ined in the te"t, industrial control is the auto#atic re$ulation o! unit o%erations and their

associated e&ui%#ent as 'ell as the inte$ration and coordination o! the unit o%erations into a lar$er %roduction s(ste#.

5.) What is the di!!erence *et'een a continuous +aria*le and a discrete +aria*le?

Answer : continuous +aria*le or %ara#eter is one that is uninterru%ted as ti#e %roceeds, and it is$enerall( considered to *e analo$, 'hich #eans it can ta e on an( +alue 'ithin a certain ran$e. discrete+aria*le or %ara#eter is one that can ta e on onl( certain +alues 'ithin a $i+en ran$e, such as on or o!!.

5.3 a#e and *rie!l( de!ine each o! the three di!!erent t(%es o! discrete +aria*les.

Answer : he three di!!erent t(%es o! discrete +aria*les are 1 *inar(, ) discrete other than *inar(, and 3 %ulse data. inar( #eans the +aria*le can ta e on either o! t'o %ossi*le +alues, 2 or 2 , o%en or closed,and so on. iscrete +aria*les other than *inar( are +aria*les that can ta e on #ore than t'o %ossi*le +alues

*ut less than an in!inite nu#*er. ulse data consist o! a train o! %ulses and each %ulse can *e counted.

5.4 What is the di!!erence *et'een a continuous control s(ste# and a discrete control s(ste#?Answer : continuous control s(ste# is one in 'hich the +aria*les and %ara#eters are continuous andanalo$. discrete control s(ste# is one in 'hich the +aria*les and %ara#eters are discrete, #ostl( *inar(discrete.

5.5 What is !eed!or'ard control?

Answer : eed!or'ard control is a #eans o! control that antici%ates the e!!ect o! distur*ances that 'ill u%setthe %rocess *( sensin$ the# and co#%ensatin$ !or the# *e!ore the( can a!!ect the %rocess. he !eed!or'ardcontrol ele#ents sense the %resence o! a distur*ance and ta e correcti+e action *( ad ustin$ a %rocess

%ara#eter that co#%ensates !or an( e!!ect the distur*ance 'ill ha+e on the %rocess.

5.6 What is ada%ti+e control?

Answer : da%ti+e control co#*ines !eed*ac control and o%ti#al control *( #easurin$ the rele+ant %rocess+aria*les durin$ o%eration as in !eed*ac control and usin$ a control al$orith# that atte#%ts to o%ti#i eso#e inde" o! %er!or#ance as in o%ti#al control . da%ti+e control is distin$uished !ro# !eed*ac controland stead(-state o%ti#al control *( its uni&ue ca%a*ilit( to co%e 'ith a ti#e-+ar(in$ en+iron#ent.

5.7 What are the three !unctions o! ada%ti+e control?

Answer : he three !unctions o! ada%ti+e control are the !ollo'in$: 1 Identi!ication !unction, in 'hich thecurrent +alue o! the inde" o! %er!or#ance o! the s(ste# is deter#ined, *ased on #easure#ents collected!ro# the %rocess. ) ecision !unction, 'hich consists o! decidin$ 'hat chan$es should *e #ade toi#%ro+e s(ste# %er!or#ance. ossi*le decisions include chan$in$ one or #ore in%ut %ara#eters to the

%rocess, alterin$ so#e o! the internal %ara#eters o! the controller, or #a in$ other chan$es. 38odi!ication !unction, 'hich #eans i#%le#entin$ the decision. Whereas decision is a lo$ic !unction,#odi!ication is concerned 'ith %h(sical chan$es in the s(ste#, such as chan$in$ the s(ste# %ara#eters or

%rocess in%uts to dri+e the s(ste# to'ard a #ore o%ti#al state.

5.9 What is the di!!erence *et'een an e+ent-dri+en chan$e and a ti#e-dri+en chan$e in discrete control?

Answer : n e+ent-dri+en chan$e #eans that so#e e+ent has occurred to cause the state o! the s(ste# to *ealtered. ti#e-dri+en chan$e re!ers to a chan$e that occurs at a s%eci!ic %oint in ti#e or a!ter a certain ti#ela%se has occurred.

5. What are the t'o *asic re&uire#ents that #ust *e #ana$ed *( the controller to achie+e real-ti#e control?

Answer : he t'o *asic re&uire#ents are: 1 it #ust *e a*ale to res%ond to %rocess-initiated interru%ts and) it #ust *e a*le to e"ecute certain actions at s%eci!ied %oints in ti#e. hese t'o re&uire#ents corres%ond

to the t'o t(%es o! chan$es encountered in discrete control s(ste#s: 1 e+ent-dri+en chan$es and ) ti#e-dri+en chan$es.

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5.10 What is %ollin$ in co#%uter %rocess control?

Answer : In co#%uter %rocess control, %ollin$ re!ers to the %eriodic sa#%lin$ o! data that indicates the statuso! the %rocess.

5.11 What is an interloc ? What are the t'o t(%es o! interloc s in industrial control?

Answer : n interloc is a ca%a*ilit( *( 'hich the controller is a*le to se&uence the acti+ities in a 'or cell,ensurin$ that the actions o! one %iece o! e&ui%#ent are co#%leted *e!ore the ne"t %iece o! e&ui%#ent *e$ins

its acti+it(. he t'o t(%es o! interloc s are 1 in%ut interloc s, 'hich are si$nals ori$inatin$ !ro# e"ternalde+ices and ) out%ut interloc s, 'hich are si$nals sent *( the controller to e"ternal de+ices.

5.1) What is an interru%t s(ste# in co#%uter %rocess control?

Answer : ccordin$ to the te"t, an interru%t s(ste# is a co#%uter control !eature that %er#its the e"ecutiono! the current %ro$ra# to *e sus%ended in order to e"ecute another %ro$ra# or su*routine in res%onse to aninco#in$ si$nal indicatin$ a hi$her %riorit( e+ent. ;%on recei%t o! an interru%t si$nal, the co#%uter s(ste#trans!ers to a %redeter#ined su*routine desi$ned to deal 'ith the s%eci!ic interru%t.

5.13 What is co#%uter %rocess #onitorin$?

Answer : Co#%uter %rocess #onitorin$ in+ol+es the use o! the co#%uter to o*ser+e the %rocess andassociated e&ui%#ent and to collect and record data !ro# the o%eration, *ut the co#%uter is not used todirectl( control the %rocess.

5.14 What is direct di$ital control C , and 'h( is it no lon$er used in industrial %rocess control a%%lications?

Answer : C is a co#%uter %rocess control s(ste# in 'hich certain co#%onents in a con+entional analo$control s(ste# are re%laced *( the di$ital co#%uter, and the re$ulation o! the %rocess is acco#%lished *( thedi$ital co#%uter on a ti#e-shared, sa#%led-data *asis rather than *( the #an( indi+idual analo$co#%onents 'or in$ in a dedicated continuous #anner. he reason 'h( C is no lon$er used in industrial

%rocess control a%%lications is that toda(