Research Papers

Maneuvering and Vibrations Control of a Free-Floating Space Robot with Flexible Arms

[+] Author and Article Information
Ramin Masoudi

Department of Systems Design Engineering,  University of Waterloo, Waterloo, ON N2L 3G1 Canadarmasoudi@engmail.uwaterloo.ca

Mojtaba Mahzoon

Associate Professor Department of Mechanical Engineering,  Shiraz University, Shiraz, Fars 71348-51156, Iranmahzoon@shirazu.ac.ir

J. Dyn. Sys., Meas., Control 133(5), 051001 (Jul 19, 2011) (8 pages) doi:10.1115/1.4004042 History: Received January 29, 2009; Revised February 23, 2011; Published July 19, 2011; Online July 19, 2011

A free-floating space robot with four linkages, two flexible arms and a rigid end-effector that are mounted on a rigid spacecraft; is studied in this paper. The governing equations are derived using Kane’s method. The powerful tools of Kane’s approach in incorporating motion constraints have been applied in the dynamic model. By including the motion constraints in the kinematic and dynamic equations, a two way coupling between the spacecraft motion and manipulator motion is achieved. The assumed mode method is employed to express elastic displacements, except that the associated admissible functions are supplanted by quasicomparison functions. By a perturbation approach, the resulting nonlinear problem is separated into two sets of equations: one for rigid-body maneuvering of the robot and the other for elastic vibrations suppression and rigid-body perturbation control. The kinematic redundancy of the manipulator system is removed by exploiting the conservation of angular momentum law that makes the rigid manipulator system nonholonimic. Nonholonomic constraints, resulted from the nonintegrability of angular momentum, in association with equations obtained from conservation of linear momentum and direct differential kinematics generate a set of ordinary differential equations that govern the motion tracking of the robot. The digitalized linear quadratic regulator (LQR) with prescribed degree of stability is used as the feedback control scheme to suppress vibrations. A numerical example is presented to show the numerical preferences of using Kane’s method in deriving the equations of motion and also the efficacy of the control scheme. Acquiring a zero magnitude for spacecraft attitude control moment approves the free-floating behavior of the space robot in which considerable amount of energy is saved.

Copyright © 2011 by American Society of Mechanical Engineers
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Figure 4

Uncontrolled (a) and controlled (b) end-effector position error in X-direction

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Figure 5

Uncontrolled (a) and controlled (b) end-effector position error in Y-direction

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Figure 6

Uncontrolled (a) and controlled (b) end-effector angular position error about Z-direction

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Figure 7

Time history of uncontrolled (a) and controlled (b) perturbations in rigid-body rotations of the first (top) and second (bottom) bodies

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Figure 8

Time history of uncontrolled (a) and controlled (b) perturbations in rigid-body rotations of the third (top) and fourth (bottom) bodies

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Figure 9

Spatial configurations including rotational and translational movement of various components of the space robot during the maneuvering of the manipulator

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Figure 1

Free-floating flexible space robot

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Figure 2

Elastic deformation of the flexible arms

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Figure 3

Zero-order actuator torques




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