一种可重构Stewart型并联机器人的静刚度分析

一种可重构Stewart型并联机器人的静刚度分析

Abstract:

ReconfigurableStewart-typeparallelrobots(SPRs)arebecomingincreasinglypopularduetotheirflexibility,highaccuracy,anddynamicperformance.Inthispaper,wepresentastaticstiffnessanalysisforareconfigurableStewart-typeparallelrobot.Theanalysisisbasedonthekinematicsandstaticsequationsoftherobot,andthederivedstiffnessmatrixrepresentstheresistanceoftherobottoexternalforcesandtorques.Theresultsshowthatthestaticstiffnessoftherobotisaffectedbythetopologyoftherobotandcanbeimprovedbyadjustingtheactuationparametersoftherobot.ThisanalysisprovidesatoolforoptimizingthedesignofreconfigurableSPRs.

Introduction:

Stewart-typeparallelrobots(SPRs)havebeenwidelyusedinvariousapplications,suchasaviation,aerospace,medical,andautomotiveindustriesduetotheirhighaccuracy,high-speedperformance,androbustness.TheSPRisasix-degree-of-freedom(DOF)parallelrobot,wheretheend-effectorismountedonaplatformthatisinterconnectedwithsixlinearactuators.Theplatformmovesrelatively

tothebase,thusenablinghighlyaccurateandhigh-speedpositioningandmanipulationoftheendeffector.SPRsarealsoabletocarryheavyloadswithoutdeflection.Therefore,theyarepreferredoverserialrobotsforpreciseandrobustapplications.

ReconfigurableSPRshaveamodularstructurethatallowsresearchersanddesignerstochangetherobot'stopologyandconfigurationbyaddingorremovingmodulesorchangingtheactuationparameters.Stochasticreconfigurationisacharacteristicfeatureoftheserobots,whichmakesthemflexibleandadaptabletodifferenttasksandenvironments.

StaticstiffnessanalysisisessentialforunderstandingthemechanismsofreconfigurableSPRs.Thestaticstiffnessoftherobotrepresentstheabilityoftherobottoresistdeformationunderexternalforcesandtorques.Thisanalysiscanaidintheoptimizationoftherobotdesignandthecontrolstrategy.

Inthispaper,wepresentastaticstiffnessanalysisforareconfigurableSPR.Theanalysisisbasedonthekinematicsandstaticsequationsoftherobot,andthederivedstiffnessmatrixrepresentsthe

resistanceoftherobottoexternalforcesandtorques.WeuseMATLABasanumericaltooltosimulateandanalyzetherobot'sperformance.

ModelingofReconfigurableSPR:

ThereconfigurableSPRconsistsoffivemodules,includingonebasemodule,onemobileplatform,andthreeintermediatemodules.Thebasemoduleisfixedtotheground,andtheplatformisattachedtotheintermediatemodules.Therobothassixlinearactuators,whicharemountedbetweenthebaseandintermediatemodulesortheintermediateandplatformmodules.

ThekinematicsequationsoftherobotarederivedfromtheinversekinematicsequationsofthegeneralSPR.Theinversekinematicsequationsexpresstheactuationparametersoftherobotasfunctionsofthepositionandorientationoftheend-effector,assumingthattherobotisinmotion.Bysolvingtheseequations,wecanobtaintheactuationparametersatanydesiredpositionandorientationoftheendeffector.

Thestaticsequationsoftherobotrelatestheexternalforcesandtorquesactingontherobottotheactuationforcesandtorques.ThestaticsequationsaresolvedusingtheNewton-Raphson'smethodfornonlinearequations.

StaticStiffnessAnalysis:

Thestaticstiffnessoftherobotisdefinedasthechangeintheendeffectorpositionandorientationresultingfromanexternalforceortorqueappliedtotherobot.Thestaticstiffnessmatrixrepresentstherelationshipbetweentheexternalforcesandtorquesandtheresultingdisplacementoftheendeffector.

Thestaticstiffnessmatrixisderivedbyperturbingtheactuationforcesandtorquesandcomputingtheresultingdisplacementoftheendeffector.Thestiffnessmatrixisa6x6matrixthatrelatestheexternalforcesandtorquestothepositionandorientationoftheend-effector.

ThestiffnessmatrixelementscanbecalculatednumericallyusingMATLAB.

Results:

ThestaticstiffnessanalysisofthereconfigurableSPRshowsthattherobot'sstaticstiffnessisdependentonthetopologyoftherobotandtheactuationparameters.Thestaticstiffnessishigherwhenallsixactuatorsareusedtocontroltherobot.However,whenonlythreeactuatorsareused,thestiffnessdecreasesduetothedependencyontheremainingthreeactuators.

Inaddition,thestaticstiffnesscanbeimprovedbyadjustingtheactuationparameters.Byincreasingtheforceortorqueoftheactuators,thestiffnessincreases.However,themaximumforce/torquethatcan

beappliedtotheactuatorsislimitedbytheactuator'sspecifications.

Conclusion:

Inthispaper,wepresentedastaticstiffnessanalysisforareconfigurableStewart-typeparallelrobot.Theanalysiswasbasedonthekinematicsandstaticsequationsoftherobot,andthederivedstiffnessmatrixrepresentedtheresistanceoftherobottoexternalforcesandtorques.Theresultsshowedthatthestaticstiffnessoftherobotwasaffectedbythetopologyoftherobotandcouldbeimprovedby