Ph.D. Dissertation Defense by Philip A. Voglewede
Friday, March 19, 2004
( Dr. Imme Ebert-Uphoff, Chair)
"Design of Redundant Actuation for Parallel Manipulators"
Parallel manipulators are not prevalent in industry and academia due in part to their complexity a swell as singularities. At one type of these singularities, commonly known as platform singularities, the manipulator loses constraint. These singularities can be eliminated by redundant actuation - the process of adding an extra actuator in an existing leg or a new leg. Several researchers have designed redundant manipulators for a small class of parallel manipulators. However, most of these manipulators have not used frame invariant techniques in their design. Thus, there exists a need for a new framework to understand singularities.
This dissertation develops measures for closeness to singularities that can be used as objective functions for designing redundant actuation. First, the effects of the singularities must be studied and understood - a process that has not been fully completed to this date. These effects will be used to create physically meaningful measures. Second, two frameworks to measure closeness to singularities will be developed. The first framework is done by formulating the measure as a constrained optimization problem. This optimization framework will allow several existing seemingly unrelated measures to be put under one foundation as well as demonstrating avenues for new measures. The second framework is a clearance propagation technique that is based on workspace generation.
These singularity measures can easily be expanded to encompass redundancy and
are used in an optimization routine to create a three degree of freedom redundant
parallel manipulator. A manipulator was built and tested to verify the results
from the theoretical analysis.