MBD analysis of flexible multibody system with mass loss

Abstract

In this paper, we propose a formulation method for flexible multi-body systems with mass loss. The method derives the equation of motion using the velocity transformation method, in consideration of the shift of center-of-mass. There are three research purposes in this paper. The first purpose is to extend the velocity transformation method for describing flexible bodies. Conventional velocity transformation method has only focused on the dynamics of rigid bodies. The restoring force due to flexibility is introduced to the equation of motion as generalized external force. Our proposed method can deal with rigid, elastic, or geometric connections, such as hinge and sliding joints. The second purpose is to formulate flexible multi-body systems with mass loss. Conventional Kane's technique only deals with the dynamics of particles. On the other hand, the proposed method can express the dynamics for the mixed model of particles and rigid bodies, where particle elements express the mass change of the system. The third purpose is to verify the high usefulness of our method for the dynamics simulation of a flying rocket. The rocket is a representative multi-body system whose mass varies. We analyze the flight characteristics, such as pitch angle, for rocket models associated with the variation in stiffness. The simulation indicates that the mass loss greatly affects the dynamics of rockets. The calculation demonstrates a large difference in the flight dynamics between rigid and flexible models.