Tools Developed:
To
aid my research in the area of Haptic Icons and Perception, I've
developed several tools to aid in the creation, editing and displaying
of Haptic Icons. I've also developed tools to aid in the user
testing of the perception of these Hapticons.
Hapticon
Designer, Editor and Displayer. (HDED)
This Software allows you to Create, Edit and Display Hapticons
in a simple understandable manner using a graphic display.
The icons are stored in CSV (comma separated value) files, which
can be read and edited using excel or any other text editor. These
files contain a single column of numbers, specifying the position
of the knob. Each row is a millisecond of time when played back.
Software
Explained:
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| Figure
1. The Hapticon Displayer-Editor Main Screen. |
The
main screen of the Hapticon Displayer-Editor shows the existing
hapticon files on the left of the screen. By selecting a file
from the list, it's graphically displayed as shown in Figure 1.
Play
In Time Button. - The Play buttons allow you to haptically
display the icon files previously selected in the haptic device,
for our studies, a knob. Play in Time displays the information
in the file through time, generating motions on the knob following
the graph displayed from left to right.
Play
In Space Button. - The Play In Space button displays the file
in a position-force manner. This is that you can move the knob
to "explore" the file. The forces displayed represent
the 1st derivative of the function in the position specified by
the knob.
Record
New Button. - This button allows you to create a new file
by storing the motions in the haptic display (the knob). When
pressed, it asks the user for a recording time and starts recording
the motions specified by the user. The file recorded is stored
with the name "Recorded.csv" and is displayed in the
file list on the left of the screen. (Figure 1)
Edit
Button. - This button displays an additional screen that allows
the user to graphically edit the Hapticon using the mouse. The
points displayed on the function can be dragged to a different
position allowing the user to modify the file for a different
feel. (Figure 2)
Create
New Button. - This button allows the user to create a new
Haptic Icon from scratch, by using simple waveforms added together
to form a file. When pressed, the New Icon Screen is displayed.
(Figure 3)
Speed
Selector. - This slider allows the user to determine the playback
speed used to display the Haptic Icon. (When using the play in
time button)
 |
| Figure
2. The Haptic Icon Graphic Editor Screen. |
 |
Figure
3. The Haptic Icon Creator.
This screen allows the user to create a new Hapticon by selecting
from simple waveforms to be added to the icon. |
Haptic
Icon MDS Tester.
This program was developed to aid in the user testing of the previously
designed Hapticons. It allows the user to gather basic information
about the subject and displays selected icon pairs in random order,
storing dissimilarity information taken from the subject. This
information is stored in both a CSV file (to view in excel) and
a special format text file to be used by ALSCAL. [4,5] (A simple
Multidimensional Scaling Program)
The
Icons to be displayed for the testing are specified in a text
file "c:\iconlist.txt".
The file contains the names of the hapticon files to be displayed
for the test on a single column.
The
program first presents a simple questionnaire of subject information;
this is stored with the results of the test for further studies.
1.
Subject Info Gathering
This screen allows the user to capture basic information about
the subject to be tested. (Figure 4)
 |
| Figure
4. Subject Information Capture Screen. |
2.
Hapticon Test Screen. (Figure 5)
Here the subject is presented with pairs of hapticons and is
asked to specify the dissimilarity between them. All possible
pairs of hapticons are presented to the subject and their relative
"dissimilarity" is stored in a dissimilarity matrix.
The results of the test are the measures between all possible
pairs of hapticons.
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| Figure
5. Hapticon Test Screen, dissimilarity input slider. |
MDS
Analysis Information.
The
information gathered with the tools previously described, will
be analyzed using a statistical method known as Multidimensional
Scaling (MDS).
MDS
allows you to analyze objects (in this case hapticons) according
to their measured dissimilarity. It takes as input a dissimilarity
matrix containing the perceived distances between these objects
and outputs a multidimensional representation of positions of
these objects that meets the distance criterion specified by the
matrix. MDS outputs several representations ranging form one to
N dimensions. According to the literature reviewed [3] most object
sets can be satisfactorily represented with 2 to 3 dimensions.
The
representation obtained from MDS is a set of points in an N dimensional
space that represent each object tested (hapticons). MDS generates
outputs for several numbers of dimensions (usually 1 to 3) and
generates a "fit to data" value for each of these outputs.
This fitness value is called stress. This stress value is derived
from Kruskal's stress formula. (Figure 6)
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| Figure
6. Kruskal's stress formula. |
This
measure of fitness is used to determine the number of dimensions
appropriate for representing the analyzed data. A greater number
of dimensions in the representation generally gives a lower stress
value. When graphing these stress values you select the number
of dimensions for your representation where the graph bends. For
the example graph in figure 7, the correct number of dimensions
to use for the representation is 2.
This
representation is axis independent and can be rotated while maintaining
the distances between the objects in order to match the axes to
some known perceivable axes in the object set.
Figure
8 shows the output from an initial preliminary test run with some
simple haptic icons on a set of 10 subjects. For this output,
a 2 dimensional representation was chosen. This graph will be
further analyzed in following sections.
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| Figure
8. Two-dimensional MDS representation of simple haptic icons. |
REFERENCES:
[1] Enriquez, M. (2001). MSc. Thesis Proposal. Computer Science.
Vancouver, B.C., University of British Columbia.
(attached)
[2] Mario Enriquez, Karon MacLean, Oleg Afonin, Brent Yager (2001).
A Pneumatic Tactile Alerting System for the Driving Environment.
PUI 2001, Orlando, Fl.
[3] Trevor F. Cox, M. A. C. (1988). Multidimensional Scaling,
Chapman & Hall.
[4] FORREST W. YOUNG, Y. T. R. J. L. (1990). ALSCAL, ALTERNATING
LEAST SQUARES SCALING.
[5] Lewyckyj, F. W. Y. R. (1996). Alscal User's Guide, Chapel
Hill.
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