Research Papers

A Recursive Algorithm for Solving the Generalized Velocities From the Momenta of Flexible Multibody Systems

[+] Author and Article Information
Martin M. Tong

 The Aerospace Corporation, El Segundo, CA 90245

J. Comput. Nonlinear Dynam 5(4), 041002 (Jun 29, 2010) (7 pages) doi:10.1115/1.4001819 History: Received September 16, 2008; Revised March 02, 2010; Published June 29, 2010; Online June 29, 2010

Hamilton’s equations can be used to define the dynamics of a tree configured flexible multibody system. Their states are the generalized coordinates and momenta (p,q). Numerical solution of these equations requires the time derivatives of the states be defined. Hamilton’s equations have the benefit that the time derivative of the system momenta are easy to compute. However, the generalized velocities q̇ need be solved from the system momenta as defined by p=J(q)q̇ to support the computation of ṗ and the propagation of q. Because of the size of J, the determination of q̇ by linear equation solution schemes requires order ([N+i=1Nni]3) arithmetic operations, where N is the number of bodies and ni is the number of mode shape functions used to model the ith body deformations. It has been shown that q̇ can be solved recursively from the momentum equations for rigid multibody systems (Naudet, Lefeber, and Terze, 2003, “Forward Dynamics of Open-Loop Multibody Mechanisms Using An Efficient Recursive Algorithm Based On Canonical Momenta,” Multibody Syst. Dyn., 10, pp. 45–59). This paper extends that result to flexible multibody systems. The overall arithmetic operations to solve for q̇ in this case is proportional to N if the effort to solve for the flexible coordinate rates for each body is weighted the same as that for the joint rate. However, each time the flexible coordinates rate of a body is solved an order (ni3) operations is incurred. Thus, the total computational effort for flexible multibody systems includes an additional order (i=1Nni3) operations.

Copyright © 2010 by American Society of Mechanical Engineers
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Grahic Jump Location
Figure 1

A ten-body system

Grahic Jump Location
Figure 2

Two connected bodies in a multibody system



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