os, T.
anning
)botics
1720—
-Based
mputer
fed '95
m, C.
| H.-P.
rungen
rurgie,
edings,
aft für
itza, I.
und
riffen*,
71.101,
orn, C.
M.W.
in der
und
Aedizin
'hmann
S, “The
Reality
edicine
, 1998,
ANALYSIS OF TIME-SPACE EFFECT OF WALKING
USING ACCELEROMETERS AND GYRO SENSOR SYSTEM
Masako Tsuruoka®*, Yuriko Tsuruoka®, Ryosuke Shibasaki’, Yoshifumi Yasuoka*, Shunji Murai*
^ Institute of Industrial Science, University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo, Japan -
(*masako, yyasuoka) @iis.u-tokyo.ac.jp, shibasaki@skl.iis.u-tokyo.ac.jp, shmurai@nifty.ne.jp
^ Institute of Statistical Mathematics,4-6-7, Minamiazabu, Minato-ku, Tokyo, Japan -
tsuruoka@ism.ac.jp
Commission V, WG V/3
KEY WORDS: Accelerometer, AR Modelling, Gyro Sensor, Measurement System, Movement, Spectral Analysis
ABSTRACT:
The walking sequence becomes less stable under the influence of
analysed on the basis of two new approaches. The first approac
a problematic part of the lower limb or back. This problem was
h is a newly developed measurement system, consisting of two
accelerometers for walking analysis (MSA). It was a small, wearable, personal computer-assisted system (WPC). The WPC was
worn on a subject’s wrist, and the sensors were fixed to a subject’s knees. However, it was difficult to analyse directly the
characteristics of movement stability using the raw measurement data. The second approach was an analysis of impulse response
using AR modelling. In the case of a normal right knee, the response value of left knee was small, because the impulse seemed to be
absorbed and wasn’t transmitted to the left knee, and vice versa. The value and duration of the impulse response curves have
showed which knee is stronger and to what degree. It was observed that the movement of center body gravity (COG) was also
influenced by physical and mental stress. The 1/f (f frequency) fluctuation, i.e., an index to stable walking was disappeared while
the subjects had a high pulse rate or strong breathing as a result of stress.
1. INTRODUCTION
The fluctuation of movement, i.., the feedback control
movement of left and right legs in the walking sequence
becomes less stable under the influence of a problematic part of
the lower limb or back. The CCD video cameras are used for
the 3-D measurement of human movement. However, there are
some problems: the measured distance is not enough for the
walking analysis because cameras are fixed at place, and it is
necessary to process many images. Also sometimes markers on
joints seem to disappear suddenly against camera angles in
walking Also sometimes markers on joints seem to disappear
suddenly against camera angles while walking.
For medical evaluation in rehabilitation, it is expected to
measure without cords and to secure some extent of the walking
distance and the ascending and descending of stairs in daily
movement. This problem was analysed on the basis of two new
approaches. The first approach is newly developed
measurement system of human movement. They are small
wearable personal computer (WPC)-assisted systems consisting
of two accelerometers (Figure 1) or a gyro sensor. While
walking or standing, the WPC is worn on a subject's wrist, the
sensors are fixed to a subject's left and right knees or back, and
batteries are inserted into a subject's waist pouch. | While
walking, the time series data of accelerations in two axes of
both of the subject’s knees or three angles of back are recorded
into the WPC.
However, it is difficult to analyse directly the characteristics of
movement stability using the raw serial measurement data,
because of their complex fluctuations in feedback control
movement among their variables. The second approach is an
analysis of impulse response or power spectrum using
autoregressive (AR) modelling. AR modelling defines the best
prediction. Giving the power spectral density, which expresses
the characteristics of a sequential system concisely,
decomposing it into periodic components. An analysis of
impulse response was done with a particular focus on the
feedback control movement: the movement of left and right
knees in walking balance. Another analysis of power spectral
was done a particular focus on the feedback control movement:
the movement of center body gravity in standing balance after
given physical and metal stress.
5 Batteries
WPC
Right & Left Aaccelerometers
Figure 1. Measurement of Walking Balance
using two Accelerometers
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