Outboard body effects on flexible branch body dynamics in articulated multibody systems

Abstract

Investigations addressing modeling of component flexible bodies in articulated multibody systems have typically been concerned only with the boundary conditions at the inboard end of a body. It is shown here that the boundary conditions at the end (or joint) leading to the outboard bodies of a branch body play an important role as well, especially in nonplanar multibody systems. An example for such a system is a uniform flexible beam fixed at one end and with a rotating end mass attached at the other. The end mass is offset from, and rotates in a plane perpendicular to, the beam axis. This results in a time-varying boundary condition on the beam bending moment. Shape functions that account for this time-varying boundary condition are presented in this paper, and using these, the associated dynamic equations are derived. The performance of these shape functions is compared to that of three traditional mode sets, using numerical simulations. These results demonstrate the limitation of the latter mode sets.