DYNAMICS OF AN ARBITRARY FLEXIBLE BODY IN LARGE ROTATION AND TRANSLATION

Conventional theories underlying many multibody codes used for simulating the behavior of elastic structures undergoing large rotation and translation with small vibrations fail to predict dynamic stiffening of the structures. This can lead to significantly incorrect simulations in many practical situations. A theory that does not suffer from this defect and is valid for an arbitrary structure is given here. The formulation is based on Kane's equations and consists of two steps: First, generalized inertia forces are written for an arbitrary structure for which one is forced to linearize prematurely in the modal coordinates; next, this defect in linearization is compensated for by the introduction of contributions to the generalized active forces from the "motion stiffness" of the structure. The stress associated with the motion stiffness is identified as due to 12 sets of inertia forces and 9 sets of inertia couples distributed throughout the body during the most general motion of its flying reference frame. An algorithm is set for a reader wishing to implement the theory* and illustrative examples are given to demonstrate the validity and generality of the formulation. © 1990 American Institute of Aeronautics and Astronautics, Inc., All rights reserved.