机械毕业设计英文外文翻译244基于制动试验台的虚拟仪器与变频技术 副本.docx

机械毕业设计英文外文翻译244基于制动试验台的虚拟仪器与变频技术 副本.docx

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机械毕业设计英文外文翻译244基于制动试验台的虚拟仪器与变频技术副本

附录

VIRTUALINSTRUMENTANDFREQUENCYCONVERSION

TECHNOLOGY-BASEDBRAKETESTSYSTEM

Brakeiswidelyusefulandveryimportantsafetyassuringequipment.TheaimofBraketestsystem，whichisbasedonvisualinstrumentandfrequencychangingtechnology，istointegrativemeasureandanalyzetheperformanceandqualityofthebrake.Thispapermainlyintroducestheprinciple，composing，functionandfeaturesofthebraketestsystem.AndfromthepointofviewoftheprincipleofVisualInstrument（VI）technology，atestsystem，basedontheVIandfrequencychangingtechnologiesandconsistoffrequencychangingdriveandcontrolsub-systemandmeasuringsub-one，isconstructed.Withthetestsystemtheperformancesandbrakingcoursecouldbeautocontrolledandmeasuredtothebrakeswhichincludesdiscanddrumones.AndthemeasuringandcontrolsoftwareisprogrammedwiththeLabVIEWpublishedbyAmericanNICorporation，USA.Thendatarealtimeacquisition，processing，displayingandrecordingwillberealized.Thetestsystemalsohasthefunctionsofvoltageadjusting，rotatingspeedcontrol，loadregulating，JCvaluesetting，temperaturemeasuring，andbrakingrouteandtimememorizingandanalyzing.Itwillbeveryimportantformeaningandexcitingboostingeffecttoadvancequalityandcapabilitiesofthebrakesandthesecurityofequipmentsandsystemwhichhaveadoptthebrakes.

1Operatingprinciples

Accordingtotheprincipleofworkandpower，thechangeofkineticenergyinthemovingofobjectsequalstothefullpoweroftheforceactontheobjectinthatprocess.Theenergyobtainedbybraketobetested：

Therefore，itisfeasibletousecombinedinertialflywheelstosimulaterotatinginertiaofcranehoistanditstransmissioncomponentstotesttheperformanceandqualityofthebrake.

Accordingtothemomentofmomentumtheorem：

Tb·t=Ji·ω

（1）

WhenTbisfixed，tbcanbecontrolledthroughcombinationsbetweenJiandωdifferently.Brakedrumorplate，whichwillbemeasured，andcombinedinertialflywheelsforloadingonaredriventorotatebyACfrequencyconversionmotor（orDCone，whichwillnotbe

dealtwithinthisarticlecarefully）.Accordingtotheprinciplesshownintheformula

（1），wecansimulateactualprocessesofbrakesfittedonliftingandtransportmachineries，engineeringones，miningonesandconstructiononesbychangingthetechnicalspecificationdutyJC，theflywheel'sinertialmomentJiandmotor'srotationalspeedni.Whendetectedbrakesworkinsimulationcycleandbrakerepeated，infraredthermoscopesandtorquesensors，andothersensorswillrecordbrakingshownintheheat，brakingtorque，brakingtimeandbrakespeedparameters.

2Thecompositionandstructureofthebraketestsystem

Thistestsystemisintendedtoachievetheperformancesofdrumanddiscbrakesandhasfollowingfunctions：

（1）Brakereplacement

Accordingtodifferenttypeofbrakesthecorrespondingbasewillbechosenandbrakepositioncouldbeadjustedusingelectricslidetest-bed；

（2）Multi-levelloading

Wecansimulatetheactualloadingonbrakesinacranewithdifferentcombinedflywheels.Thetestsystemadoptsmanualhydraulicsystemcomposedbyathree-positionfour-wayhand-operateddirectionvalve，areliefoneandtheiraccessories，anditisoperationsavingandconvenienttoreplaceflywheels.

（3）Regulationtherotationalspeedn（orω）

ItcanberealizedbychangingfrequencysuppliedtotheACmotor.Whenbrakingtorqueisverylarge，suchas10000Nm，itshouldbeappropriateforregulatinginitialbrakespeedupward1000r/mintominimizerotatinginertiapossibly.

（4）Brakingfrequencyadjustment

Basedonactualneedsbrakingfrequencycanbeconfinedinarangeof1~4timesperminute.

（5）Brakingtorquemeasurement

Therearethreemethods：

a）Directmeasurementviatorquesensors：

Rotationalspeedandtorquesensorwillbeinstalledbetweenthedetectedbrakedrumorplateandinertialflywheelplates.Dynamicbrakingtorqueofdetectedbrakewillbedirectlymeasured，showninFig.1andFig.2.Accordingtothescopeofbrakingtorqueofdetectedbrakes，twoorthreerotationalspeedandtorquesensorsshouldbepreparedfortestingtorquetomeettheaccuracyrequirements；

b）Indirectparametermeasurement：

Basedontherotatinginertiaandbrakingtimewecangetbraketorqueusingmathematicalrelationshipbetweentheseparameters，asshowninFig.2.

c）Indirectmeasurementbypedestal-force：

Thepressuresensorsareinstalledunderthebasewheredetectedbrakearefixedtofeeltheforcesgivenbybrake，andthentoobtainbraketorque.

Thesecondapproachhassmallinvestment，simplestructureandnotorquesensorswhichmeannotconsideringrelatedtroublesofchangingtorquesensors.Buttheprocedureto

calculatetorqueiscomplex，andaccumulatingtotalerrorswouldbelargerandthentheresultaccuracywillbelow.

Thethirdwayhastheadvantageofthereplacementofsensorsiseasierandnospecialrequirementsforsensorsinstallingprecision.Itisstillanindirectmeasurementbuttheprocedureislessthanthatinthesecondmethodandthatmeansthecumulativeerrorsrelativelyissmaller.Andvisibleshortcomingispoordynamicresponse.

（6）Automaticcontrol

Excepttomanualoperationtestsystemisalsoprogrammedcontrol.

（7）Monitoring

Brakingfrequency，initialbrakingspeed，theaggregatebrakingnumber，moment，timeandsoonwillbeshownautomatically.

（8）Automaticallydataacquisitionandprocessing

Thecurvedescribingbrakingtorque，timeandspeedcouldbedrawnautomaticallybymeansofcomputersoftwarewhiledetectedbrakeismeasuredindutycycleoperation.Therefore，inresponsetothewaytotestbrakingtorquethesystemcanbedividedintothreeonesofthatwithtorquesensorsuchasFig.1and2above，thatwithouttorquesensorsuchasshowninFig.3andthatofpedestal-powermeasurementwithouttorquesensor，asshowninFig.4.ThetestsystemismainlycomposedofACfrequencyconversiontransmissionsystem，flywheelsloadingsystem，rotationalspeedandtorquesensors，basewhichtofixdrumorplatebrakes，adjustableDCpowersupply，detectedbrakesandtestandcontrolsystem.

Inadditiontotheabovefunctions，thesystemcouldtestfollowingperformancesofthebrakes：

a）Releaseperformance：

Thisistestedundertheconditionsof85%Veandratedload，adjustingvoltageviaboosterdevices；

b）Closeperformance：

ThisistestedundertheconditionsofratedvoltageVeand50%ofratedloading；

Otherwise，thefollowingperformancescouldalsobetested：

1）Structuralperformances：

a）Abilityofbrakeshoe'spositionfollowingdrum；

b）Assemblyforkeepinggapsbetweendrumandshoesequalling；

c）Lubricating.

2）Otheritems：

a）Contactarea；

b）Springtesting；

c）Brakingliningsandshoesgap；

d）Pin'shardness.

3ACfrequencyconversionadjustingspeedsystem

ComparedwithDCmotor，theACmotorhassimpleandcompactstructure，littlemaintenanceworkload，highefficiency，smallrotatinginertiaandquickdynamicresponse，anditcouldbemadeofhigh-voltage，largecapacityandhighspeed.Currently，ACmotorhastrendtoreplaceDConeinthefieldofadjustingspeedtransmission.Generallyspeaking，therearemanykindsofmotorswhichcouldbeappliedtodiversetypesofconverter-driven，andwhichareroughlydividedintoordinaryACmotor，specialoneanddedicatedone.Thefrequencyconversionadjustingspeedingsystemiscomposedoffrequencyconverterand

dedicatedliftmotor.

Totheordinaryasynchronousmotor，thefollowingfactorsshouldbeconsideredwhiletodeterminetheircapacity：

（1）Chosenmotorcapabilityshouldbegreaterthanthepowerloadneeded；

（2）Comparedwithneededloadpull-intorquethegreatesttorquethatmotorexportsshouldhavesufficientlysurplusvolume；

（3）Evensupplyvoltageislower10%thanratedvalue，motorscanexportneededtorquealso；

（4）Consideringthelifelengthofmotoritshouldrunninginthespecifiedtemperaturescope；

（5）Becauseoftransmissionrateofthetransmissionsystem，efficiencyandloadfluctuation，themotorpowershouldhaveenoughsurplusvolume；

（6）Againstloadnature，itisnecessarytochoiceasuitable

motorsoperatingmodessuchascontinuousservicesystem，short-termoperationandduplicationsystem.

IntheACadjustingspeedcontrolsystemwithfrequencyconvertermotor'sslowdownisachievedbyreducingtheoutputfrequencyoftheconverter.Whenmotorsneedslowdownfasterthantherateoffreedeceleration，underspeedofconverteroutputfrequencymightberan-upandthespeedwhichiscorrespondingtothatfrequencyislowerthantheactualrotationalspeedofmotor，andmotorwillberegenerativebraking.Insuchcases，asynchronousmotorwillbeanasynchronousgenerator，andloadmechanicalenergywillbeconvertedtoelectricalenergyandthenfeedbacktotheconverter.However，whenthebackfeedisoverload，overvoltageprotectioncircuitofconverterwillworktocutconverter'soutputandmotorswillbefreelyslowdowninsteadarapidspeed-down.Toavoidabovephenomenon，thatis，toconsumetheenergyinotherpartsoftheDCcircuitwithoutcausingvoltageriseinthevoltage-fedconverter，regeneratingbrakingcircuits（brakingresistors）arenormallyusedandtheenergyfedbacktotheDCcircuitwillconsumedintheformofheat.Forthetestsystem，itisapparentlythatbrakingresistancesarenotnecessarybecauseoftheusageofbrakeforbrakingdeceleration.Itisnecessarytodefinesurpluscapacityofmotororconverteronthebasisofpracticalsituation.Andonthecaseofensuringtomeetrequirementsofdrivingsystemperformance，energyconsumptionoreconomicfactorsshouldbeconsidered，andoveral