• Haptic interface
• variable friction

This work focuses on the extension to new geometries of the Tactile Pattern
Display (TPaD) developed at Northwestern University.
The TPaD is a haptic device which allows to simulate texture sensations
by means of friction modulation. The underlying assumption is that shear
forces play a signicant role in the perception of the surface characteristics.
Previous work allows to be condent on the plausibility of this assumption.
To modulate friction, which is the principal factor in the generation of shear
forces, a squeeze lm of air between the ngertip and the device, is conveniently
used. A "thick" squeeze lm of air will reduce the friction between
the skin and the surface of the device, while a "thin" or nonexistent lm will
cause the friction to be at its maximum. Knowing the position and eventually
the velocity of the nger, it is possible to generate a great variety of
spatial texture sensations.
In order to apply this technology to a wide number of devices for everyday
use, it is necessary to explore the possibility of increasing the dimensions of
the active surface of the device. This work addresses this challenge.
The document is arranged as follows: After a brief description of the TPaD
an analytical approach to the problem is presented. Afterwards a Finite Element
analysis is carried out, and the results of both, the analytical and the
numerical analysis are compared. The realization of several prototypes and
the evaluation of their performances is described next. Finally, the driving electronics is presented.