Theobjectiveofthisinvestigationistoexaminethecorrectnessandefficiencyofthechoiceofboundaryconditionswhenusingassumedmodeapproachtosimulateflexiblemulti-bodysystems.ThedisplacementfieldduetodeformationisapproximatedbytheRayleigh-Ritzassumedmodesinfloatingframeofreference(FFR)formulation.Thedeformationsobtainedbytheabsolutenodalcoordinate(ANC)formulationwhicharetransformedbytwosetsofreferencecoordinatesareintroducedasacriteriontoverifytheaccuracyofthesimulationresultsbyusingtheFFRformulation.Therelationshipbetweenthedeformationsobtainedfromdifferentboundaryconditionsisrevealed.Numericalsimulationexamplesdemonstratethattheassumedmodeswithcantilevered-free,simply-supportedandfreefreeboundaryconditionswithoutinclusionofrigidbodymodesaresuitableforsimulationofflexiblemulti-bodysystemwithlargeoverallmotion,andthesamephysicaldeformationcanbeobtainedusingthosemodefunctions,differonlybyacoordinatetransformation.Itisalsoshownthatwhenusingmodeshapeswithstaticallyindeterminateboundaryconditions,significanterrormayoccur.Furthermore,theslidercrankmechanismwithrigidcrankisaccurateenoughforinvestigatingboundaryconditionproblemofflexiblemulti-bodysystem,whichcostsignificantlesssimulatingtime.
