full Paper - Nguyen Dang Binh

EUROGRAPHICS 2005 Tutorial
A novel fingertip haptic device
G. Cini, A. Frisoli, S. Marcheschi, F. Salsedo, M. Bergamasco
PERCRO Scuola Superiore S. Anna, Italy
Abstract
This paper presents a new concept of fingertip haptic device for the display of local contact geometry on the
user’s fingerpad. We propose an extension of the encountered haptic interface concept [YY04], in order to build
an active haptic thimble, that is portable and can be fixed to the user’s finger. The device is endowed with an
actuation system that controls the motion of a platform, that can come in contact with the fingerpad with different
orientations and at different fingerpad locations, simulating the contact with a virtual surface. A prototype of the
device has been built and tested and is presented throughout the paper.
1. Introduction
Haptic interaction with virtual environments is ideally meant
to provide an intuitive method of exploration. In [KLM85],
it was shown that haptic perception by free exploration with
hands can be accurate and fast. This type of performance,
however, has not been duplicated in experiments with constrains
on the number and natural movement of fingers. In
[Ka93], it was found that free hand exploration is more efficient
than outstretched five-finger exploration, which was
subsequently more efficient than one outstretched finger. G.
Jansson [Jan00] in discovered a significant detriment in performance
when only one finger was available for exploration
of common objects. In an earlier experiment, also reported in
[JM03], he found that numbers of fingers had a great effect
on the efficiency in identification of real objects, the largest
difference appearing between the One finger and the Two
fingers conditions.
A further experiment conducted by the G. Jansson involved
an haptic display condition with not differentiated
information within the contact region, simulated by a hard
sheath attached to the finger(s) in contact with the objects,
similar to the one used by [KL99] when studying some other
haptic functions. A personal communication from the same
author, supported by experimental data reported in an internal
report [Jan04], confirmed that in the Sheath conditions
there was no difference in Exploration time at all between
the One finger and the Two fingers conditions, according
to the experimental findings. This suggested that the effect
of restrictions on the fingerpad contact region can limit the
added value of having multiple contact points on more fin-
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gers. In [AF04], Frisoli et al. performed an experiment to
explore the difference in performance for object recognition
as the number of contact points of an haptic interface
is increased using either the right hand or both. The conditions
with two fingers did not show up any substantial improvement
in the recognition task, and on average the one
finger condition results performed better than the two conditions,
contrary to the expectations that performance, in terms
of exploration time and response error, should improved as
more contact points were provided to the participant. Further
analysis suggested that some specific factors can account for
lack of haptic information observed in these experiments,
and they are the following:
• Absence of physical location of the contact on the fingerpad;
• Inhomogenous perception of dynamic properties at the
fingertip level, due to differences of reflected inertias
among different haptic interfaces;
• Absence of any geometrical information related to the orientation
of the contact area.
These points suggested new criteria and guidelines for the
design of multipoint haptic interfaces.
Recently several new conceptual schemes have been proposed
to solve some of the problems arising during the direct
exploration of virtual environments. In particular two
new approaches have been proposed for the exploration of
shapes. The first one hypothesizes [KJK04] that the shape
recognition is due either to the perception of slipping of the
fingerpad over the object surface or to the displacement of
the contact area over the fingerpad. In [MAS02] preliminary