4.Acceleration and Deceleration

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1、Chapter4AccelerationandDecelerationInordertosmooththemovementofamachine,theaccelerationanddecelerationforthemovementofthemachineaxesshouldbecontrolled.ForCNCsystems,twokindsofAccelerationandDeceleration(Acc/Dec)controlmethodshavebeendeveloped;Acc/DecControlB

2、eforeInterpolation(ADCBI)andAcc/DecControlAfterInterpo-lation(ADCAI).TheseareclassifiedbasedontheorderinwhichtheAcc/Deccontrolisexecuted.Inthischapter,firstwewillintroducetheAcc/Deccontrolafterinter-polationthatwasoriginallyusedforNCsystems.Followingthis,wewil

3、lintroducetheAcc/Deccontrolbeforeinterpolationwhichissuitableforhigh-speedandhigh-accuracymachining.Inaddition,aLookAheadAlgorithmwillbeaddressedthatisusedwiththeAcc/DeccontrolbeforeinterpolationforDieandMoldmachining.4.1IntroductionTheAcc/Deccontrolmethodca

4、nbeclassifiedwithanAcc/Deccontrolbeforein-terpolationandanAcc/Deccontrolafterinterpolationwithrespecttotheprocessingorderofaccelerationanddecelerationcontrol.TheAcc/Deccontrolbeforeinterpolation(ADCBI)isconstructeddifferentlyac-cordingtotheinterpolationtypesu

5、chaslinear-,exponential-andS-curve-typein-terpolation.BecausetheADCBIneedstoholdalotofinformation,relatedtoalltheinterpolatedpoints,alargeamountofmemoryisrequiredforexecutingthistypeofAcc/Deccontrol.However,becauseofthelargeamountofinformationtheAcc/Deccontr

6、oldoesnotresultinmachiningerrorbecauseoftheincreasedaccuracy.Ontheotherhand,Acc/Deccontrolafterinterpolationisappliedinanidenticalmannerforallinterpolationmethods.Therefore,theimplementationissimplebutmachiningerrorsoccurbecauseeachaxismovementisdeterminedse

7、parately.SinceAcc/DeccontrolinADCAIisindividuallyappliedforeachaxis,accelerationanddecelerationformovementsofeachaxisarecarriedoutregardlessoftheinterpolatedposition.Accordingly,theinterpolatedpointsdeviatefromthedesiredpath.Atypical1071084AccelerationandDec

8、elerationexampleofthisdeviationoccursduringthecornermachiningprocessandthelongertheAcc/Dectime,thelargerthemachiningerror.Incontrast,machiningerrorsduetoADCBIdonotoccurbecausethecommandpathiside