(Dr. Wayne Book, advisor)

"Active Vibration Control of a Flexible Base Manipulator"

Abstract
 

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 macro manipulator can interfere with positioning accuracy.  A rigid manipulator attached to a flexible but unactuated base will be used to study a scheme to achieve accurate positioning of the micro manipulator combined with enhanced vibration damping of the macro manipulator.  Inertial interaction forces and torques acting between the robot and its base will be determined and used to damp the vibration.   Six degree-of-freedom base vibration is assumed, making this work applicable to a wide variety of macro/micro manipulators.

The use of the rigid manipulator to damp vibrations in a flexible macro manipulator has proven to be a promising area of research.  Advantages include the fact that the damping forces can be applied directly to the tip of the macromanipulator, and the actuators can respond quickly and efficiently to provide large inertial forces.  On the other hand, the ability of the robot to create forces and torques at its base varies widely throughout the workspace and there are locations where coupling effects between the macro and micromanipulator are unsuited to vibration damping.  This work will include an investigation of the dynamic coupling effects between a six degree-of-freedom robot and flexible base and how to best use these effects to damp the vibration.

First, a complete derivation of the coupled equations of motion will be developed and analyzed for two typical six degree-of-freedom robot manipulators mounted on flexible bases.  A performance index will be developed to predict the ability of the robot to damp vibrations throughout its usable workspace and will be implemented in parallel with a position control scheme.   The ability of the method to provide combined position and base vibration control will be demonstrated via Matlab simulations using the two sample robots.  Finally, the control scheme will be demonstrated experimentally.