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外文翻译CNC加工加减速平稳变化的方法.doc

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外文翻译CNC加工加减速平稳变化的方法.doc

南京工程学院自动化学院本科毕业设计(论文)1附录A英文资料AGeneralizedApproachfortheAccelerationandDecelerationofCNCMachineToolsJaeWookJeonDepartmentofControlandInstrumentationEngineeringSungkyunkwanUniversity300ChunchunDong,JanganGu,SuwonCity,KoreaAbstractManytechniquesfortheaccelerationanddecelerationofCNCmachinetoolshavebeenproposedinordertomakeCNCmachinetoolsperformgivenmachiningtasksefficiently.Sincetheyshouldbecalculatedinalimitedtime,mostofthemarenotcomputationallyintensive.However,theseprevioustechniquescannotgeneratevelocityprofileshavingsomekindsofaccelerationanddecelerationcharacteristicsthoughtheycangeneratevelocityprofileshavingvariousaccelerationanddecelerationcharacteristics.Thispaperproposesageneralizedapproachforgeneratingvelocityprofileswhichcannotbegeneratedbyprevioustechniquesaswellasvelocityprofilesgeneratedbythem.Accordingtothedesiredcharacteristicsofaccelerationanddeceleration,eachsetofcoefficientsiscalculatedandisstored.Givenamovingdistance,anaccelerationinterval,andadecelerationintervalforCNCmachinetools,avelocityprofilehavingthedesiredcharacteristicsofaccelerationanddecelerationcanbeefficientlygeneratedbyusingthesecoefficients.Itwillbeshownhowtogeneratetypicalvelocityprofilesbytheproposedtechnique.I.INTRODUCTIONThedemandforbetteraccuracyinthemanufacturingofcomplicatedpartsandthedesiretoincreaseproductivityhavedevelopedCNCsystemssothatCNCmachinetoolsmovemoreaccuratelyandmorequickly.SincethecombinedcharacteristicsofthecontrolandthemachinetooldeterminethefinalaccuracyandproductivityoftheCNCsystem,therearemanyfactorstoconsiderforimprovingthesequantities.Oneoftheimportantfactorsisefficientlygeneratingvelocityprofileswhichhavethedesiredaccelerationanddecelerationcharacteristicswhichinturnaredeterminedaccordingtogivenmachiningtasks.ManyresearchershaveproposedtechniquesforgeneratingvelocityprofilesofCNC南京工程学院自动化学院本科毕业设计(论文)2machinetools.Oneofthemisgeneratingvelocityprofilesbytheselectionofpolynomialfunctions1.Thistechniquecangeneratesomanykindsofvelocityprofilesandfurthermorecanmakethecharacteristicsofdecelerationbeindependentfromthatofacceleration.Themajorproblemofthistechniqueiscomputationalloadtoincreasealmostexponentiallywiththeorderofpolynomialintheaccelerationorthatinthedeceleration.Duetotimeconstraints,itisverydifficulttoapplythesetechniquestocontrollingCNCsystems.Otherprevioustechniquesforgeneratingvelocityprofilesisbasedonadigitalconvolution26.Thesetechniquesaremuchmoreefficientthanthetechniquesselectingpolynomialfunctionsandareeasilyimplementedbyahardware.But,invelocityprofilesgeneratedbythesetechniques,theaccelerationintervalisalwayssameasthedecelerationintervalandthecharacteristicsofdecelerationaredependentonthatoftheacceleration.Thus,somevelocityprofilescannotbegeneratedbythesetechniques.Inthispaper,ageneralizedapproachfortheaccelerationanddecelerationofCNCmachinetoolsisproposed.Theproposedtechniqueisassimpleandefficientasthetechniquesbasedonadigitalconvolutionandcangeneratevelocityprofileswhichhavemorevariouscharacteristicsofaccelerationanddecelerationthanthetechniquesbasedonadigitalconvolutioncan.Thatis,theproposedtechniquecangeneratevelocityprofilesofwhichthedecelerationcharacteristicsareindependentfromtheaccelerationcharacteristics.First,somecoefficientsarecalculatedandarestoredaccordingtotheaccelerationcharacteristic,thedecelerationcharacteristic,andtheaccelerationinterval,andthedecelerationinterval.Thengivenadesiredmovingdistance,avelocityprofilewhichhasthedesiredcharacteristicsisgeneratedbycalculatingthepositionincrementduringeachsamplingtime.Thepositionincrementduringeachsamplingiscalculatedbymultiplyingthestoredcoefficientswiththeproductofonesamplingtimeandthevelocityafteracceleration.InsectionII,existingtechniquesforgeneratingvelocityprofilesofCNCmachinetoolswillbeexplained.InsectionIII,itwillbeexplainedhowtogenerateadesiredvelocityprofilebytheproposedtechnique.Theproposedtechniqueandotherexistingtechniqueswillbecompared.InsectionIV,itwillbeshownthattheproposedtechniquecangeneratesomeusefulvelocityprofilesforCNCmachinetools.II.PREVIOUSTECHNIQUES南京工程学院自动化学院本科毕业设计(论文)3Fortheillustrationoftheprevioustechniques,letusconsideronesingleaxiscontrolsystemofwhichthemaximumvelocity,themaximumacceleration,andthesamplingtimeareVmax,Amax,andTsrespectively.IfthissystemmovesthegivendistanceSatthemaximumvelocityVmax,thenthemovementtimeT1intherectangularvelocityprofilewillbeT1S/VmaxpTs,1Selectinganintegernwhichisthesmallestintegeramongintegerswhichareequaltoorgreaterthanp,theresultingrectangularvelocityprofileisconstructedasinFig.1.ThevelocityandpositionequationsforthisprofileareThepositionincrementduringeachsamplingtimeis0001/,14sssPkTPkTPkTSnknwhere0sPkTand01sPkTarethepositioncommandsatthekthandthe1kthsamplingtimesrespectively.Thatis,thepositionincrementduringeverysamplingtimeisthesame.However,sincenophysicalsystemcanachievetheaboverectangularvelocityprofileduetoimpulseacceleration,theaccelerationintervaltoincreasevelocityfromtheresttoaspecifiedvalueandthedecelerationintervaltodecreasevelocityfromthespecifiedvaluetotherestareneeded.IIA.SelectionofPolynomialFunctionsGivenanaccelerationintervalTsnaTs,adecelerationintervalTdndTswherenand,andadistanceS,atrapezoidalvelocityprofilewhichhasthelinearaccelerationanddecelerationcharacteristicscanbeconstructedasinFig.2.Ifthisprofilehastheconstantvelocityinterval,thennS/VmaxTsislargerthanna.ThevelocityandpositionequationsforthisprofileareAnd1asaassssasaasSttTnTTSVtTtnTnTStnSnTtnTTnTTnnT500/0,2/0,3ssVtSnTtnTPtSnTtnT南京工程学院自动化学院本科毕业设计(论文)4Fig.1.ArectangularvelocityprofileformovingadistanceSFig.2.AtrapezoidalvelocityprofileformovingadistanceSIntheabovederivation,itisassumedthattheaccelerationintervalisthesameasthedecelerationintervalandtheconstantvelocityintervalispresent.Inthecasethattheaccelerationintervalisdifferentfromthedecelerationintervalortheconstantvelocityintervalisnotpresent,similarequationsarepossibletoderive.Thistrapezoidalvelocityprofilewhichhasthelinearaccelerationanddecelerationcharacteristicsisparticularlyeffectiveforcontrollingamachinetoolhavingahighdegreeofrigidity.However,largejerkquantityatthestoppointinthetrapezoidalvelocityprofilemaywearoutaleadscrewassemblyveryquicklyandbelikelytomakemachinetoolshavinglittlerigidityvibrate.Sincesmoothvelocityprofileswhichhaveparabolicsecondorderorhigherorderaccelerationanddecelerationcharacteristicsdonothavelargejerkquantityatthestoppoint,thesevelocityprofilesareveryoftenusedforCNCmachinetools16.Severaltechniqueswhichselectapolynomialfunctionforgeneratingvelocityprofileswithsmall2120222222asaaasssassasaaaSttTnTTSPttTTtnTnTStnntTTnTtnTTnTTnn6

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