An Implementation Method for Constrained Flexible Multibody Dynamics Using a Virtual Body and Joint

Abstract

A convenient implementation method for constrained flexiblemultibody dynamics is presented by introducing a virtual rigid body andjoint. The general purpose program for rigid and flexible multibodydynamics consists of three major parts of a set of inertia modules, aset of force modules, and a set of joint modules. Whenever a new forceor joint module is added to the general purpose program, the modules forthe rigid body dynamics are not reusable for the flexible body dynamics.Consequently, the corresponding modules for the flexible body dynamicsmust be formulated and programmed again. Since the flexible bodydynamics handles more degrees of freedom than the rigid body dynamicsdoes, implementation of the module is generally complicated and prone tocoding mistakes. In order to overcome these difficulties, a virtualrigid body is introduced at every joint and force reference frames. Newkinematic admissibility conditions are imposed on two-body referenceframes of virtual and original bodies by introducing a virtual flexiblebody joint. There are some computational overheads due to the additionalbodies and joints. However, since computation time is mainly dependenton the frequency of flexible body dynamics, the computational overheadof the presented method is not a critical problem, while implementationconvenience is dramatically improved.