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[Th016] Citation: Abstract
Throughout this thesis we have, theoretically and experimentally,
analyzed various properties of pen grasp interaction. We showed that
to experimentally measure the mechanical impedance of the human hand we
need a haptic device with specific characteristics, such as low
inertia, almost zero friction and very high stiffness. Part of the
research activity was devoted into designing a haptic device that would
satisfy these stringent requirements. Using a theoretical model and
experimental data we found that pen grasp manipulation is superior to
single finger manipulation, both in terms of mechanical impedance and
accuracy of motion control. Moreover, because of its parallel
structure, the pen grasp stiffness ellipse is not very sensitive to
changes in the kinematic configuration.
The haptic display can be tuned to a specific user and task introducing
an additional term in the device controller. The stiffness and damping
ellipses can be enlarged, rotated, and their shape altered, so that
better rejection to disturbance while executing precise motion control
can be achieved. However we discovered that the potential benefits are
limited by the natural performance of the device itself, since
simulating dynamic elements, such as springs and dampers, introduces
noise into the system. Our analysis was just a preliminary test and
much more remains to be done.
We analyzed four different types of grasp, with particular attention to
four-fingered grasps, and found similar stiffness ellipses for all of
them. Some of these grasps were chosen observing different people
interacting with a pen, others by trying different configuration on a
custom computer animated model.
["I would like a hard copy of this report"]
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Updated: Tue Jul 15 23:54:51 2008
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