EFFICIENT SIMULATION OF TREE-STRUCTURED, FREE-FLOATING MULTIBODY SYSTEMS USING MOMENTUM INTEGRALS

The kinematic simulation of a free-floating multibody system, with joi nt motion commands as inputs and inertial description of the motion as outputs, can be performed by the following methods: (1)joint commands are treated as rheo-nomic inputs to a multibody dynamics code and the motion of the free-floating base is computed by integrating the resul ting dynamic differential equations of motion; (2) the kinematics is c oupled with momentum integrals of equations of motion of the system to result in a map between the inertial velocities and joint velocities, which on integration results in inertial description of the system. T he first method requires the full simulation tools of multibody dynami cs, while the second method constructs the same information starting a t the velocity level. The second viewpoint results in a compact mappin g between the joint velocities and inertial velocities of the system, which is useful for motion planning. The objective of this paper is to develop the equations for kinematic simulation of a general tree-stru ctured, free-floating system using the second method. Some important c ontributions are (1) explicit description of the momentum integrals, ( 2) explicit mapping between inertial velocities and the joint velociti es of the system, and (3) an efficient computational procedure for for mulation of the necessary equations. Copyright (C) 1996 by Marcel Dekk er, Inc.