1
Haptic Characteristics of some Activities of
Daily Living
Brittany Redmond, Rachel Aina, Tejaswi Gorti and Blake Hannaford
Biorobotics Laboratory, Department of Electrical Engineering
The University of Washington
I. A BSTRACT
Activities of daily living (ADLs) are of interest in
rehabilitation, independent living for the elderly and
infirm, and to the designers of everyday objects. This
paper reports measurements of forces and torques at
the interaction point between users and some everyday
objects in ADLs. We report force and torque recordings
of several writing tasks with pen and pencil, opening
and closing a jar, and dialing and texting with a cell
phone. Besides average measurements, we measured
some statistically significant differences between some
very similar activities. For example, RMS forces in
writing tasks were lower with pencil than ball-point pen,
dialing a number showed lower forces than texting, and
texting forces differed between “ABC” and “T9” texting
methods.
II. I NTRODUCTION
The vast majority of the activities in our daily lives
involve the hands in haptic interaction with tools, objects,
or the enviornment. These “Activities of Daily Living,”
(ADLs) are of interest to designers of consumer artifacts
and tools, as well as medical and gerontological researchers concerned with self sufficiency of rehabilitation
patients and older persons.
However little data exists on the physical nature of
these interactions. Much of the literature on ADLs relates
to locomotion (level and stairs), getting in and out of
seating, extent of reach, etc. For example, Hortobagyi et
al. show that older people use a greater percentage of
maximal voluntary joint moments than young adults[1]
in these tasks.
Other related work emphasizes computation of joint
torques in the human limb. For example, [2] and [3]
measured arm motions in ADLs to compute joint torques
in the arm using a biomechanical model. Fowler et
al. designed a 6-axis sensor for the index finger[4],
and instrumented a jar opening-closing task in order to
estimate forces and joint torques in the index finger[5].
Hooke et al.[6] designed a pen containing three 6-axis
force/torque sensors which could measure contact forces
and moments, including internal forces, for the individual
The authors would like to acknowledge National Science Foundation
grant IIS-0303750 and support for undergraduate researchers from Boeing Company, and Intel Research, Seattle. The authors also thank Diana
Friedman and members of the Biorobotics Lab for their invaluable
assistance.
fingers. However this instrument clearly adds significant
weight beyond the 5-15 g of a normal pen.
Computer scientists have emphasized recognition of
ADLs through multisensory measurements which could
be used for real-time data collection. For example, Philipose et al.[7] uses RFID tags on the environment and
a reader on the hand to record interactions. This paper
also contains a literature review of ADL recognition. In
specialized fields, our group has characterized forces and
torques characteristic of surgery[8], [9] and conservation
of rare documents[10].
The present paper reports measurements of force
and torque characteristics of a few ADLs involving
manipulation. The overall aim is to begin to create a
database researchers can access containing measurements
of physical variables characteristic of manipulation tasks
in the everyday environment. Selection of the taskss was
somewhat arbitrary. Our analysis goals were exploratory
and opportunistic. It is not intended to generalize these
results to other tasks, but instead to provide data and
methodology for comparison between ADLs, and to seed
a future comprehensive database of ADLs.
III. M ETHODS
A. Tasks
Four different ADL tasks were selected from the wide
variety of activities performed by people daily. In total,
nine different tasks were performed, each with 3 axes
of force and torque recorded to data files. The data files
were analyzed using the R statistical software package
which compared root-mean-squared (RMS) force and
torque for each task and subject.
B. Instrumentation
To collect data, different instrumentation was designed
for each activity. A task holding platform was attached
to the top of a 6-axis force/torque sensor (Nano 17 from
ATI Industrial Automation). The design of the task holder
varied with each activity (Figure 1).
Writing Activity: The writing activity included a
bubble-fill-in task, check-box task, number task and
signature task. The tool holder for the writing activity
was designed by securely fixing the sensor to a metal
plate with a hard rubber surface. The plate was then
mounted flush with a wooden platform. The tasks were
attached to the metal plate with double faced tape.
2
Fig. 2. Cell phone body modified for button force sensing. Six-axis
force/torque sensor is mounted between masonite plates mounted to
back of cell phone.
C. Data Recording and Analysis
Force and torque data around three orthogonal axes
was collected at 100Hz with a LabViewTM application described previously[10]. Video was synchronously
recorded at 25 frames per second. The application saves
data into a tab delimited text file. Subsequent analysis
with MATLABTM thresholds the data and tags intervals
of activity above the sensor’s noise level (about 0.2
N). We also computed RMS forces (FRMS) and RMS
torques (TRMS) for data collected from each subject for
each subtask. Where
s
1 X X 2
FRMS =
fkj
m j
k=xyz
s
TRMS =
1 X X 2
τkj
m j
k=xyz
Fig. 1. Instrumentation used to capture force/torque information from
activities of daily living including jar lid opening/closing (force/torque
sensor at base of jar), instrumented writing surface (6-axis sensor is
fixed to center of black rectangular surface), and toothbrushing (sensor
inserted between handle and brush).
Jar Activity: This activity included opening and closing a jar. The tool holder for this activity was designed
by drilling holes in the bottom of a platic (PET) jar with
a screw-top lid. The 6-axis force/torque sensor was then
attached to the bottom of the jar and to a metal base plate
for stability.
Tooth Brushing Activity: Traditional toothbrushes
were cut and attached to a special handle designed to
accommodate the sensor and the modified toothbrush.
A shield was installed to keep the sensor from getting
damaged by water during tooth brushing.
Cell phone Activity: The tool holder for the cell phone
activity was designed by removing the backplate and
battery of a traditional cell phone and designing two
wooden plates with the same dimension as the back
plate of the original cell phone. The sensor was mounted
between the plates directly below the “5” button. The top
plate was attached to the back of the cell phone battery
compartment.
and j is the sample number and m is the number of
samples.
D. Protocols
A total of ten subjects were studied for each task.
Subjects ages ranged from 18-54 and were approximately
50% male. The experimental protocol was approved by
the University of Washington Human Subjects Division.
Each subject was asked to perform all or some of the
following tasks.
Writing tasks: All subjects performed the specific
writing tasks in the same order, but it was randomized
whether they used a pen or pencil first. The bubble
task was completed first, followed by the checkbox and
number task, and ending with the signature task.
Bubble-In Task: Samples for this task were prepared
on plain sheet of paper, with three bubble ovals per sheet.
The subjects were asked to completely fill in the bubble
without falling outside the lines. This task was performed
with both pen and pencil.
Checkbox Task: Samples for this task were prepared
on plain sheet of paper, with three check boxes per sheet.
Subjects were asked to fill out the check box by marking
an X without going outside the lines. This task was
performed with both pen and pencil.
3
Number Task: Samples for this task were prepared
on a plain sheet of paper. A random seven digit number
was printed on the sheet with little boxes beneath each
digit. The subjects were required to transcribe the number
above into the boxes below. This task was conducted in
both pen and pencil and was repeated three times.
Signature Task: Samples for this task were prepared
on a plain sheet of paper. For this task, subjects were
required to sign their name on a specified line inside of
a box. The subjects were required to sign their names
directly on the printed line without going outside of the
box. This task was conducted in both pen and pencil and
was repeated three times.
Jar Task: Subjectes performed the jar tasks in the
same order for all the trials. Subjects were asked to close
the jar and then open the jar. When closing, they were
instructed to match a line on the lid with one on the
body that indicated when the jar was at a complete close.
Subjects used their non-dominant hand to hold the base
plate to the table top to resist the imposed forces and
torques. Since this is different than the usual way of
holding the oustide of the jar, these measurements should
be considered representative only for the hand twisting
the lid, although forces and torques relevant to the jarholding hand could be computed from our measurements
if the grasping posture is known. The opening and closing
tasks were repeated three times.
Tooth Brushing Task: Subjects were asked to brush
their teeth as they would every day. This task was
completed three times, and subjects brushed their teeth
for 20 seconds.
Cell Phone Task: The cell phone activity included
four distinct tasks: dialing a familiar 10-digit phone
number (the subject’s own phone number), dialing an
unknown 10-digit phone number, and texting with two
texting methods: “T9” predictive texting[11], in which
there is one keystroke per character, and “ABC mode”,
which requires the user to press the key n times where
n = {1, 2, 3} is the position of the desired letter among
three letters assigned to the touchpad key.
All subjects performed the cell phone tasks in the
same order. Dialing a known number was performed first,
followed by dialing an unknown number, then T9 texting
and ABC texting.
T9 Texting: Subjects were asked to text the 14 keystroke phrase “meet me there” using the T9 method. This
task was repeated three times.
ABC Texting: Subjects were asked to text the phrase
“call me” using the ABC method. Using the ABC
method, the phrase “call me” takes 14 key strokes. This
task was also repeated three times.
E. Statistics
An analysis of variance (ANOVA) was performed
on a 2x4 (tool vs task) matrix of averages over the
subjects collected during the writing task. The two tools
(Pen and Pencil) were compared along with each of
the four writing tasks to identify statistically significant
differences.
Fig. 3. Typical force trace for filling in an answer bubble with a pencil
and frequency of forces during pencil writing (all tasks)
IV. R ESULTS
A. Writing
A typical applied force for a bubble task when performed with a pencil is shown in Figure 3. The three
larger peak sections (t=1-4.5, t=5-8, t=8.5-11.5) correspond to the time when the pencil was in contact
with the paper for the three bubbles. The small forces
in between the larger peaks correspond to noise. A
histogram showing relative frequency of contact forces
for all subjects and all tasks in writing with a pencil
shows most of the forces less than 3 N but peaks up to
8N (Figure 3).
Results from the writing tasks showed that a greater
force is applied when a pen was used as a writing utensil
compared to when a pencil was used (Figure 4). The
box represents the middle 50% of data points and the
lines above and below the box, known as the whiskers,
represent the most extreme points within 1.5 interquartile
range (IQR). The circles above the whiskers represents
outliers above the 1.5 IQR. The line through the middle
shows the median for the two sets of data. An analysis
of variance confirmed that the difference between a pen
and pencil is statistically significant with less than a 5%
chance of these results being random (Table I).
A similar analysis can be performed for the different
writing tasks (Figure 5), but ANOVA revealed no significant difference between the tasks in terms of average
force level.
B. Jar
Figure 6 represents a typical applied force and torque
when a test subject opened a jar. The force RMS for all
4
Fig. 4. Average force levels for the writing tasks using ball-point pen
vs. pencil.
Fig. 6. Typical forces and torques for jar opening and histogram of
forces during jar opening.
jar tasks was 5.318 N. The torque RMS value was 434 Nmm. An analysis of variance was performed on the data
and showed that there was not a statistically significant
difference between opening versus closing the jar.
C. Tooth Brushing
Figure 7 shows the typical force and torque response
when a person bushes their teeth. The force RMS for all
tooth brushing tasks was 6.32 N. The torque RMS for
tooth brushing was 79.7 N-mm.
Fig. 5. Average force levels for the subjects during the different writing
tasks.
Tool
Task
Tool:Task
DF
1
3
3
F Value
4.39
1.59
0.30
Pr(> F )
0.038
0.192
0.824
TABLE I
ANOVA RESULTS FOR PEN VS . PENCIL AND FOUR WRITING TASKS
D. Dialing and Texting
Typical Forces A typical applied force recording for a
phone number dialing task is shown in Figure 8. Typical
forces did not exceed 6 N. We do not report torque values
because the dialing and texting tasks result from a single
finger contact. Figure 9 shows typical force values for
the T9 texting technique.
Relative Forces Subjects used greater forces when
dialing a phone number compared to texting, using any
method (Figure 10). ANOVA confirmed this result was
statistically significant at the 5% level.
A greater force was measured when texting using the
T9 method compared to the ABC method (Figure 11).
ANOVA confirmed the significance of this difference.
The same analysis method compared dialing the known
5
Fig. 8. Typical force recordings for dialing a phone number on the
cell phone.
Fig. 7. Typical forces and torques recorded for 20 seconds of tooth
brushing. Histogram showing relative frequency of force values for all
toothbrushing data.
Task
Writing - Pencil
Writing - Pen
Jar Open-Close
Tooth Brushing
Dialing Phone Number
Texting — T9
Texting — ABC
FRMS (N)
0.95
1.03
5.31
6.37
1.70
1.40
1.03
TRMS (Nmm)
N/A
N/A
434
79.7
N/A
N/A
N/A
Fig. 9. Typical force recording during sending a 14 character text
message with the T9 texting method.
TABLE II
AVERAGE VALUES OF FORCE AND TORQUE RECORDED IN EACH
TASK .
versus unknown number (Figure 12), but there was no
significant difference.
E. Overall Averages
The average force and torque RMS for each task is
shown in Table II. Force RMS range from .954 to 6.37
N and torque RMS range from 79.7 N-mm to 434 Nmm. There is no significant torque RMS associated with
the writing and phone tasks because they are considered
a point contact with no torque values.
V. D ISCUSSION
The statistical analysis showed interesting, statistically
significant differences in RMS forces between variations
Fig. 10. Comparison of average forces for dialing a number vs. texting
by either method.
6
1.0-1.5 N, with most of the force peaks below 2.5 N.
There were statistically significant differences in force
between dialing numbers and text messaging and a
difference of about 0.5 N in dialing force between the
two texting methods. T9 style predictive testing had
about 50% higher mean force than ABC texting. One
possibility is that ABC texting more frequently hits the
same button multiple times in succession and that there
are lower forces on secondary hits. However we have not
yet tested this theory.
We are currently packaging this data for
an on-line archive which will be available to
all researchers by the time of the conference
(http://brl.ee.washington.edu).
R EFERENCES
Fig. 11. Comparison of average forces for texting by the ABC vs. T9
texting methods.
of some of the tasks. For example, the difference in
mean RMS force of the tasks performed with a pen verse
a pencil was statistically significant (Figure 4). Yet the
difference in writing force among the different tasks was
not significant. This means that the force RMS values
for writing was only dependent on the utensil used and
not the specific task being performed.
Our jar opening torque measurement of 0.434 Nm
RMS is comparable to the torque values that Fowler
et al. [5] obtained, although their measurements were
referenced to the interphalangeal joints of the index
finger and ours were referenced to the center of the lid.
Dialing forces for various cell phone tasks averaged
Fig. 12. Comparison of dialing a new 10-digit number (’unknown’)
vs. the subject’s own (’known’) 10 digit number.
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