Inertial Vibration Damping Control of a Flexible Base Manipulator

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George, Lynnane E.
Book, Wayne J.
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A rigid (micro) robot mounted serially to the tip of a long, flexible (macro) manipulator is often used to increase reach capability, but flexibility in the macromanipulator can interfere with positioning accuracy. A rigid manipulator attached to a flexible but un actuated base was used to study a scheme to achieve positioning of the micromanipulator combined with enhanced vibration damping of the base. Ineltial interaction forces and torques acting between the robot and its base were modeled and studied to determine how to use them to damp the vibration. One issue is that there are locations in the workspace where the rigid robot loses its ability to create interactions in one or more degrees of freedom. These "ineltial singularities" are functions of the rigid robot's joint variables. A performance index was developed to predict the ability of the rigid robot to damp vibrations and will help ensure the robot is operating in joint space configurations favorable for inertial damping. It is shown that when the performance index is used along with the appropriate choice of feedback gains, the inertia effects, or those directly due to accelerating the robot's links, have the greatest influence on the interactions. By commanding the robot link's accelerations propOitional to the base velocity, vibration energy will be removed from the system. This signal is then added to the rigid robot's position control signal. Simulations of a three-degree of freedom anthropomorphic rigid robot mounted on a flexible base were developed and show the effectiveness of the control scheme. In addition, results from two degree of freedom vibration damping are included.
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