Hello everyone and welcome to this talk about our paper
Vibromap Understanding the Spacing of Vibrotactile Actuators across the Body
Vibrotactile displays have been commonly used in situations where interacting with an audio
or a visual display is not possible or recommended for example while driving or holding conversations
or while riding a bike. Prior work has also investigated the use of vibrotactical
displays for physical activities, for coding tactile symbols for phonemic communication,
and as a means of information transmission using 2d stationary phantom sensations.
A phantom sensation refers to the illusion where vibrotactile actuators that are placed in close
proximity can generate continuous phantom sensations between them.
However there is a lack of systematic understanding of the required spacing of
vibrotactile actuators. A single vibration motor offers a low information transmission capacity.
Groups of vibration motors that are placed far apart lose the
ability to generate continuous phantom sensations between them
and vibration motors that are placed too close together cannot be properly distinguished.
This information is critical in order to construct grids to be worn on the body.
Our contribution is VibroMap it is a map of the minimum and maximum distances possible across
body parts and orientations. We included seven body locations in our experiments:
the wrist, forearm, upper arm, back stomach, thigh, and leg. In each of these body locations we
tested two orientations: a transverse orientation which is around the body part and a longitudinal
orientation which is along the body part. Our two controlled experiments investigated the
maximum distance between vibration motors where continuous haptic feedback is still possible
that's experiment one, and the minimum distance between vibration motors where vibration motors
can still be discriminated, that's experiment two. I'll go into details on the experiments now.
For the experiments we had shared participants and apparatus. We recruited 24 voluntary
participants between 21 and 34 years old. 12 of them were female 12 of them were male.
The standardized clothing used in our experiments was to avoid that the clothing has an influence
of the on the perception of the participants. We used ERM vibration motors fixed on a piece
of cloth for vibration output. The motors were placed with two centimeters distance.
We used a digital pen and paper for input. Our experiments followed a
within subject study design with body location and orientation as our independent variables.
In the first experiment we wanted to figure out what the maximum distance was between
vibration motors where continuous haptic feedback is still possible.
The user's task was in in this case that he or she felt two simultaneous
vibrations and was required to indicate if they felt a single vibration or multiple vibrations. We
then calculated the threshold distance using a one up one down adaptive staircase procedure. We also
asked participants to answer our questionnaire at the end. The questionnaire evaluated how
important the users rated the location for haptic feedback, how comfortable was the feedback on the
body location, and how confident they were in the accuracy of their answers.
Our results indicate that body location significantly affects the maximum distance
possible between vibration motors. The wrist had a lower threshold distance in comparison to all
other body locations. Back was significantly higher than the forearm thigh and leg.
With regard to orientation, we found out that the transverse orientation resulted
in a significantly lower threshold distance in comparison to a longitudinal orientation.
In experiment 2 we wanted to investigate what the minimum distance between vibration motors
where they can still be discriminated. Here the participant's task was to indicate using the
digital pen and paper where he or she felt the vibration. The difference between the
location perceived and the actual location was then calculated to be the localization error.
Similarly our findings here show that body location has a significant effect on localization
error. We found a lower localization error on the wrist in comparison to the upper arm,
thigh, stomach, and leg. We also found a higher localization error
on the stomach in comparison to the forearm, upper arm, thigh, and leg.
With regard to orientation we found a significant difference between longitudinal and transverse.
A transverse orientation resulted in a lower localization error
in comparison to a longitudinal orientation.
To sum up, we conducted two controlled experiments. VibroMap combines the results
of these experiments to to figure out the maximum and the minimum distance required
between vibration motors. You can see here in the plot the minimum and maximum distance for
the body parts as well as orientations. For more information please refer to our paper.
Thank you very much for your attention and feel free to ask any questions.