ECE 504 Linear System Theory and Design 3th.pdf

《ECE 504 Linear System Theory and Design 3th.pdf》由会员上传分享，免费在线阅读，更多相关内容在教育资源-天天文库。

1、Chapter1Introduction1.1IntroductionThestudyanddesignofphysicalsystemscanbecarriedoutusingempiricalmethods.Wecanapplyvarioussignalstoaphysicalsystemandmeasureitsresponses.Iftheperformanceisnotsatisfactory,wecanadjustsomeofitsparametersorconnecttoitaco

2、mpensatortoimproveitsperformance.Thisapproachreliesheavilyonpastexperienceandiscarriedoutbytrialanderrorandhassucceededindesigningmanyphysicalsystems.Empiricalmethodsmaybecomeunworkableifphysicalsystemsarecomplexortooexpensiveortoodangeroustobeexperi

3、mentedon.Inthesecases,analyticalmethodsbecomeindispensable.Theanalyticalstudyofphysicalsystemsconsistsoffourparts:modeling,developmentofmathematicaldescriptions,analysis,anddesign.Webrieflyintroduceeachofthesetasks.Thedistinctionbetweenphysicalsystems

4、andmodelsisbasicinengineering.Forexample,circuitsorcontrolsystemsstudiedinanytextbookaremodelsofphysicalsystems.Aresistorwithaconstantresistanceisamodel;itwillburnoutiftheappliedvoltageisoveralimit.Thispowerlimitationisoftendisregardedinitsanalytical

5、study.Aninductorwithaconstantinductanceisagainamodel;inreality,theinductancemayvarywiththeamountofcurrentflowingthroughit.Modelingisaveryimportantproblem,forthesuccessofthedesigndependsonwhetherthephysicalsystemismodeledproperly.Aphysicalsystemmayhave

6、differentmodelsdependingonthequestionsasked.Itmayalsobemodeleddifferentlyindifferentoperationalranges.Forexample,anelectronicamplifierismodeleddifferentlyathighandlowfrequencies.Aspaceshipcanbemodeledasaparticleininvestigatingitstrajectory;however,itm

7、ustbemodeledasarigidbodyinmaneuvering.Aspaceshipmayevenbemodeledasaflexiblebodywhenitisconnectedtoaspacestation.Inordertodevelopasuitablemodelforaphysicalsystem,athoroughunderstandingofthephysicalsystemanditsoperationalrangeisessential.Inthistext,wewi

8、llcallamodelofaphysicalsystemsimplyasystem.Thusaphysicalsystemisadeviceoracollectionofdevicesexistingintherealworld;asystemisamodelofaphysicalsystem.Onceasystem(ormodel)isselectedforaphysicalsystem,thenextstepistoapplyvariousphysicallawstodevelopmath