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

Abstract

A convenient implementation method for constrained flexible multibody dynamics is presented by introducing a virtual rigid body and joint. The general purpose program for rigid and flexible multibody dynamics consists of three major parts of a set of inertia modules, a set of force modules, and a set of joint modules. Whenever a new force or joint module is added to the general purpose program, the modules for the rigid body dynamics are not reusable for the flexible body dynamics. Consequently, the corresponding modules for the flexible body dynamics must be formulated and programmed again. Since the flexible body dynamics handles more degrees of freedom than the rigid body dynamics does, implementation of the module is generally complicated and prone to coding mistakes. In order to overcome these difficulties, a virtual rigid body is introduced at every joint and force reference frames. New kinematic admissibility conditions are imposed on two-body reference frames of virtual and original bodies by introducing a virtual flexible body joint. There are some computational overheads due to the additional bodies and joints. However, since computation time is mainly dependent on the frequency of flexible body dynamics, the computational overhead of the presented method is not a critical problem, while implementation convenience is dramatically improved.