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Abstract: An Experimental Investigation of the Cobot Wheel Contact Patch
An Experimental Investigation of the Cobot Wheel Contact Patch
Gregory W. Bachman
Master's thesis, Department of Mechanical Engineering, Northwestern University, December, 1997.
© 1997 NWU.
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Abstract:
Current research at the Laboratory for Intelligent Mechanical Systems
is focused on developing a new class of passive robots called cobots,
which use nonholonomic joints rather than actuated joints. The
nonholonomic joint takes advantage of the nonholonomic velocity
constraint imposed by a wheel to relate both linear and angular
velocities. As a result, the performance of the cobot is in part
dependent on how well the wheels function. This paper looks at what
effect varying different wheel parameters has on the performance of
the cobots. Using Taguchi methods we were able to examine how the
compression of the wheel, the contact patch size, and coefficient of
friction, were affected by the diameter, durometer, and profile of the
urethane wheels used on many cobots. Additionally, by modifying Hertz
theory for the contact of elastic bodies using an elastic foundation
simplification it was possible to develop an equation for the load
which was a function of measured parameters. By comparing the
theoretical results with the actual results, it was then possible to
determine the validity of modeling the contact using the assumptions
found in Hertz theory.
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