process dynamics and control seborg(2ed)

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1、12345678981.1a)Trueb)Truec)Trued)Falsee)True1.2QLQTTCON/OFFSWITCHControlledvariable-T(houseinteriortemperature)Manipulatedvariable-Q(heatfromthefurnace)ndSolutionManualforProcessDynamicsandControl,2edition,Copyright©2004byDaleE.Seborg,ThomasF.EdgarandDuncanA.Mellichamp.1-1Disturbancevariabl

2、e-QL(heatlosttosurroundings);otherpossiblesourcesofdisturbancesarethelossofgaspressureandtheoutsidedooropening.Specificdisturbancesincludechangeinoutsidetemperature,changeinoutsidewindvelocity(externalheattransfercoefficient),theopeningofdoorsorwindowsintothehouse,thenumberofpeopleinside(ea

3、chonegeneratingandtransmittingenergyintothesurroundingair),andwhatotherelectriclightsandappliancesofanynaturearebeingused.1.3Theordinarykitchenoven(eitherelectricorgas),thewaterheater,andthefurnace(Ex.1.2)allworksimilarly,generallyusingafeedbackcontrolmechanismandanelectronicon-offcontrolle

4、r.Forexample,theovenusesathermalelementsimilartoathermocoupletosensetemperature;thesensor'soutputiscomparedtothedesiredcookingtemperature(inputviadialorelectronicset-point/displayunit);andthegasorelectriccurrentisthenturnedonoroffdependingonwhetherthetemperatureisbeloworabovethedesiredvalue

5、.Disturbancesincludetheintroductionorremovaloffoodfromtheoven,etc.Anon-electronichouseholdappliancethatutilizesbuilt-infeedbackcontrolisthewatertankinatoilet.Here,afloat(ball)onaleverarmclosesoropensavalveasthewaterlevelrisesandfallsabovethedesiredmaximumlevel.Thefloatheightrepresentsthesen

6、sor;theleverarmactingonthevalvestemprovidesactuation;andtheon-offcontrolleranditssetpointarebuiltintothemechanicalassembly.1.4No,amicrowaveoventypicallyusesonlyatimertooperatetheovenforaset(desired)periodoftimeandapowerlevelsettingthatturnsthepoweronatitsmaximumlevelforafixedfractionoftheso

7、-calleddutycycle,generallyseveralseconds.ThussettingthePowerLevelat6(60%offullpower)andtheCookTimeto1:30wouldresultintheovenrunningforatotalofoneandone-halfminuteswiththepowerproportionedat60%(i.e.,turnedon100%for6secondsandofffor4seconds,ifthefixeddutyc