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Inverse control and stabilization of free-flying flexible robots

Published online by Cambridge University Press:  01 May 1999

G. de Rivals-Mazères
Affiliation:
Ecole Nationale de l'Aviation Civile, 7 rue E. Belin, 31055 Toulouse (France)
W. Yim
Affiliation:
University of Navada Las Vegas, College of Engineering, Las Vegas, NV 89154 (USA)
F. Mora-Camino
Affiliation:
Ecole Nationale de l'Aviation Civile, 7 rue E. Belin, 31055 Toulouse (France)
S.N. Singh
Affiliation:
University of Navada Las Vegas, College of Engineering, Las Vegas, NV 89154 (USA)

Abstract

The question of control and stabilization of flexible space robots is considered. Although, this approach is applicable to space robots of other configurations, for simplicity, a flexible planar two-link robot, mounted on a rigid floating platform, is considered. The robotic arm has two revolute joints and its links undergo elastic deformation in the plane of rotation. Based on nonlinear inversion technique, a control law is derived for controlling output variables describing the position and orientation of the platform and the joint angles of the robot. Although, the inverse controller accomplishes reference trajectory tracking, it excites the elastic modes of the arm. For the vibration suppression, three different stabilizers are designed. Using linear quadratic optimal control theory, a composite stabilizer for stabilization of the rigid and flexible modes and a decoupled flexible mode stabilizer are designed for regulating the end point of the robot to the target point and vibration suppression. Stabilization using only elastic mode velocity feedback is also considered. For large maneuvers, first the inverse controller is active, and the stabilizer is switched for regulation when the motion of the robot lies in the neighborhood of the terminal equilibrium state. Simulation results are presented to show that in the closed-loop system including the inverse controller and each of the stabilizers, trajectory tracking and stabilization of elastic modes are accomplished.

Type
Research Article
Copyright
© 1999 Cambridge University Press

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