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1、毕业设计(论文)外文资料翻译系别:电气工程系专业:电气化与自动化班级:姓名:学号:外文出处:SpecializedEnglishForArchitecturalElectricEngineeringandAutomation附件:1、外文原文;2、外文资料翻译译文。指导教师评语:签字:年月日注:请将该封面与附件装订成册。1、外文原文IntroductionstotemperaturecontrolandPIDcontrollersProcesscontrolsystem.Automaticprocesscontrolisconcernedwithmaintainingprocessvariab
2、lestemperaturespressuresflowscompositions,andthelikeatsomedesiredoperationvalue.Processesaredynamicinnature.Changesarealwaysoccurring,andifactionsarenottaken,theimportantprocessvariables-thoserelatedtosafety,productquality,andproductionrates-willnotachievedesignconditions.Inordertofixideas,letuscons
3、ideraheatexchangerinwhichaprocessstreamisheatedbycondensingsteam.TheprocessissketchedinFig.1Fig.1HeatexchangerThepurposeofthisunitistoheattheprocessfluidfromsomeinlettemperature,Ti(t),uptoacertaindesiredoutlettemperature,T(t).Asmentioned,theheatingmediumiscondensingsteam.Theenergygainedbytheprocessf
4、luidisequaltotheheatreleasedbythesteam,providedtherearenoheatlossestosurroundings,iiithatis,theheatexchangerandpipingarewellinsulated.Inthisprocesstherearemanyvariablesthatcanchange,causingtheoutlettemperaturetodeviatefromitsdesiredvalue.[21Ifthishappens,someactionmustbetakentocorrectforthisdeviatio
5、n.Thatis,theobjectiveistocontroltheoutletprocesstemperaturetomaintainitsdesiredvalue.OnewaytoaccomplishthisobjectiveisbyfirstmeasuringthetemperatureT(t),thencomparingittoitsdesiredvalue,and,basedonthiscomparison,decidingwhattodotocorrectforanydeviation.Theflowofsteamcanbeusedtocorrectforthedeviation
6、.Thisis,ifthetemperatureisaboveitsdesiredvalue,thenthesteamvalvecanbethrottledbacktocutthestearrflow(energy)totheheatexchanger.Ifthetemperatureisbelowitsdesiredvalue,thenthesteamvalvecouldbeopenedsomemoretoincreasethesteamflow(energy)totheexchanger.Allofthesecanbedonemanuallybytheoperator,andsinceth
7、eprocedureisfairlystraightforward,itshouldpresentnoproblem.However,sinceinmostprocessplantstherearehundredsofvariablesthatmustbemaintainedatsomedesiredvalue,thiscorrectionprocedurewouldrequiredatremen