Measures center of pressure (CoP) during walking using photo-reflective sensors embedded in shoe soles. Estimates CoP through regression analysis of sensor values with 11.4mm average error. Identifies gait patterns like normal walking, toe contact, etc. with 78% average accuracy using support vector machine on images of sensor values over time. Aims to provide durable, measurable gait analysis without environment limitations of existing systems.

1. Center of Pressure Estimation and
Gait Pattern Recognition Using Shoes
with Photo-reflective Sensors
K o n o m i I n a b a †1
A k i h i k o M u r a i †2
Y u t a S u g i u r a †1
†1 K e i o U n i v e r s i t y
†2 A I S T

2. • Having a good walking posture will promote health.
• Center of Pressure
2
[1] http://www.kao.co.jp/rd/eiyo/about-hoco/hoco02.html
Gait Analysis
Gait measurement system using
camera [1]
Difference in CoP trajectory depending
on subject group [2]
• Measure pressure and its center position during walking
[2] The initiation of gait in young, elderly, and Parkinson's disease subjects Suzanne E Halliday, David A Winter, James S Frank, Aftab E Patla, François Prince
GAIT&POSTURE 1998

3. • The measurable environment
is limited.
3
[3] A Mobile Force Plate System and Its Application to Quantitative Evaluation of Normal and Pathological Gait, T. Liu, Y, Inoue, K. Shibata, Y. Hirota, K. Shiojima,
IEEE/ASME International Conference on Advanced Intelligent Mechatronics, 2010
Measurement of CoP
Measurement by force plate
and motion capture [3]
by Force Plate by Using Insole
• Durability may be an issue.
[4] Gait Analysis Using a Shoe-Integrated Wireless Sensor System. Stacy J. Morris Bamberg, Ari Y.Benbasat, Donna Moxley Scarborough, David E. Krebs, and Joseph
A. Paradiso, Senior. IEEE TRANSACTIONS ON INFORMATION TECHNOLOGY IN BIOMEDICINE. 2008
Insole with built-in sensor [4]

4. 4
Our Purpose and Methods
Purpose
• Highly durable devices
• CoP estimation and gait pattern identification using it
Methods
• Embed photo-reflective sensor (PRS)
in outsole of shoes
• Estimate CoP by regression analysis
• Recognize gait pattern using Support
Vector Machine(SVM)

5. • Measures the deformation of the sole by photo sensor.
5
Shoe Hardware Device

6. 6
Method of CoP Estimation

7. 7
Experiment for accuracy evaluation of CoP estimation
Conditions
Participant 2 (Male)
Estimation Y-axis only
Ground truth
CoP coordinates calculated from
the force plate
Data set per
participant
450frame (35fps, 0.43s/step,
30step)
Learning Random forest regression
Ground truth and estimation CoP when the decision
coefficients is the highest (left) and lowest (right)
(mm)
(mm)
Estimation result
Ground truth
Max Ave
Coefficient 0.94 0.69
Error(mm) 32.7 11.4
• A lag occurs from movement
to detection of deformation.
• Accuracy may increase
by including the lag into
the preprocessing of
learning and estimation.
Result

8. 8
Method of Gait Pattern Identification
Learn

9. • Generate an image by converting sensor values to
pixel values
9
Conversion of Sensor Values to Image Data
1
2
3
・
・
・
1 2 3
Sensor value
max
min
Heel contactNormal Toe contact
…
n
frame
sensor

10. 10
Experiment for Accuracy Evaluation of Gait Pattern Identification
Participants 5 (Male)
Gait pattern 9
Data set per class 15 step
Learning SVM
Evaluation 5-fold cross validation
Condition
Normal Heel contactToe contact
Inner locus Outer locus
Pigeon-toedBowlegged
Left turn Right turn

11. 11
Result and Discussion 2
Normal
Toe
contact
Heel
contact
Bowlegg
ed
Pigeon-
toed
Inner
locus
Outer
locus
Left
turn
Right
turn
Normal 87% 0% 3% 3% 3% 1% 1% 1% 1%
Toe
contact 1% 97% 0% 0% 1% 0% 1% 0% 0%
Heel
contact 3% 1% 79% 2% 3% 2% 3% 2% 4%
Bowlegg
ed 1% 0% 1% 75% 7% 4% 1% 5% 6%
Pigeon-
toed 4% 1% 5% 12% 55% 9% 3% 5% 7%
Inner
locus 3% 0% 2% 7% 8% 74% 2% 1% 3%
Outer
locus 0% 0% 4% 2% 1% 3% 87% 3% 1%
Left
turn 3% 0% 1% 5% 5% 4% 3% 71% 7%
Right
turn 2% 0% 1% 3% 7% 3% 2% 7% 76%
• The identification
accuracy was 78% on
average.
• The accuracy of pigeon-
toed was 55%.
• It is still challenging to
differentiate walking
above the shoes.

12. 12
Conclusion
Background • CoP estimation is important in medical field.
Purpose
• CoP estimation and Gait recognition
using shoes with photo-reflective sensors.
Experiment
• CoP estimation error is 11.4mm.
• Accuracy of Gait pattern recognition is 78%.