Lesson-16-开环与闭环控制.ppt

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1、SpecializedEnglishforMechatronicsLecturer:LiuJianjunUnite16Open-loopandClosed-loopControlOpen-loopControlSystems(Nonfeedbacksystems)开环控制系统（无反馈系统）Thewordautomaticimpliesthatthereisacertainamountofsophisticationinthecontrolsystem.Byautomatic,itgenerallymeansthatthesystemisusuallycapableo

2、fadaptiontoavarietyofoperationconditionsandisabletorespondtoaclassofinputssatisfactorily.自动化这个单词暗含着在控制系统中采用一定的先进技术。通过自动化技术，系统一般能适应不同工作条件的变化并且能够对输入满意度做出反应。Unite16Open-loopandClosed-loopControlUnite16Open-loopandClosed-loopControlHowever,notanytypeofcontrolsystemhastheautomaticfeature.Us

3、ually,theautomaticfeatureisachievedbyfeedingtheoutputvariablebackandcomparingitwiththecommandsignal.然而，不是任何的控制系统都具有自动化的特色的。一般说来，自动化就意味着把输出变量反馈回来并且和命令信号加以对比。Unite16Open-loopandClosed-loopControlUnite16Open-loopandClosed-loopControlWhenasystemdoesnothavethefeedbackstructure,itiscalledano

4、pen-loopsystem,whichisthesimplestandmosteconomicaltypeofcontrolsystem.Unfortunately,open-loopcontrolsystemslackaccuracyandversatilityandcanbeusedinnonebutthesimplesttypesofapplications.当一个系统没有反馈结构时，我们称之为开环系统，这是最简单也是最经济的控制系统。但是，开环控制系统缺少精确度和多方面适应性因此只能在最简单的环境中使用。Unite16Open-loopandClosed-

5、loopControlUnite16Open-loopandClosed-loopControlConsider,forexample,controlofthefurnaceforhomeheating.Letusassumethatthefurnaceisequippedonlywithatimingdevice,whichcontrolstheonandoffperiodsofthefurnace.Toregulatethetemperaturetotheproperlever,thehumanoperatormustestimatetheamountoftim

6、erequiredforthefurnacetostayonandthensetthetimeraccordingly.Whenthepresettimeisup,thefurnaceisturnedoff.就以控制家里加热的火炉为例，让我们设想一下火炉仅仅依靠定时器来控制它的开闭周期。为了把温度调节到一个舒适的温度，操作者必须估算一下火炉需要加热持续的时间然后设置号定时器。当预设的时间到的时候，火炉就被断电了。Unite16Open-loopandClosed-loopControlUnite16Open-loopandClosed-loopControlHowe

7、ver,itisquitelikelythatthehousetemperatureiseitheraboveorbelowthedesiredvalue,owingtoinaccuracyintheestimate.Withoutfurtherdeliberation,itisquiteapparentthatthistypeofcontrolisinaccurateandunreliable.Onereasonfortheinaccuracyliesinthefactthatonemaynotknowtheexactcharacteristicsofthef