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Detection of Gait Phases with Piezoelectric Gyroscope under
Different Walking Speed Conditions
Norio Furuse1 and Takashi Watanabe2
1
2
Miyagi National College of Technology, Japan
Graduate School of Biomedical Engineering, Tohoku University, Japan
Abstract
Functional electrical stimulation (FES) training of paralyzed muscles has been suggested to be effective for incomplete spinal cord injured patients in the early period of the rehabilitation process. Information of gait phases
is very important to assist walking and to restore motor function with FES. It is considered that a small and inexpensive gyroscope is useful to construct a sensor system in clinical. In this paper, to examine the detection methods of the gait phases, we performed the walking measurement that attached a gyroscope on the leg in normal
and slow speed with normal subjects. From the result, it was indicated that the sensor could detect the swing
phase and the stance phase without mistake. However, it was indicated that the detection algorithm detected the
gait phase change in the slow walking earlier than one in the normal speed walking.
1
Introduction
Functional electrical stimulation (FES) training of
paralyzed muscles was found to be effective for the
great majority of incomplete spinal cord injured patients in the early period of the rehabilitation process
[1]. Information of gait phases is very important to
assist walking with appropriate timing and to restore
motor function with FES. Moreover, they are important information for evaluating ability and stability of
the patient’s walking [1-2]. Acceleration sensors and
gyroscopes are used in the field of mechatronics etc.
in recent years. They are suitable for clinical use because they are small and inexpensive and are easy to
be attached on the body. As examples using those sensors, many methods of the recognizing the gait phases
are reported [2-3].
We have also shown the possibility of measuring with
appropriate accuracy the joint angles of the hip, the
knee and the ankle during walking with piezoelectric
gyroscopes [4-5]. In addition, we showed the possibility of detection of swing phase and stance phase without mistake by using output of the gyroscope that was
attached to the dorsum of foot for the measurement of
the ankle joint angle [6]. However, it was an examination concerning the detection of the gait phases in
normal speed walking. In this paper, we performed
the walking measurement that attached the gyroscope
on the leg in the normal and the slow speed with normal subjects. From the result, the detection of the gait
phases was examined under different walking speeds.
2
Method
2.1
System
A piezoelectric gyroscope (Murata, ENC-03J) was
attached to the dorsum of foot as shown in Fig. 1. The
attached position of the sensor was decided based on
our previous examinations [4-6]. The positive direction of angular velocity measured by gyroscope is
shown by arrow in Fig.1. The sensor signals were
amplified, low-pass filtered (2nd, 22.6Hz, Q=0.71)
and sampled at 120 Hz.
To validate the gait phases detected based on the output signal of the gyroscope, the gait phases during the
walking were detected with two aluminum electrodes
and an aluminum plate simultaneously. The foil form
aluminum electrodes were attached to the forefoot and
the heel of a shoe. The aluminum plate put on the
floor was the length of 8 m with the width of 1 m.
Four gait phases (mid stance, heel-off, swing and
heel-strike) were detected by electric contact condition between the electrodes and the plate [4-6].
Three healthy subjects participated in the experiments.
Their tasks were to walk 10 times in the normal and
slow speed respectively on the aluminum plate. The
subjects were able to do 6 steps by the right leg in one
trial of the walking in normal speed. The subjects
were able to do 7 steps or to do rarely 8 steps in the
slow speed walking. The measured data were analyzed offline using a personal computer.
Gyroscope
G5(foot)
[deg/sec]
500
0
Gait Phase
-500
Gyroscope
Aluminum
Plate
Electrode
(heel)
Electrode
(forefoot)
Fig. 1 Attachment position of the sensor for the
measurement. The positive direction of angular velocity measured by the gyroscope is shown by arrow.
2.2
Detection methods of gait phases
The stance phase is the phase that consists of mid
stance, heel-off and heel-strike. The output of gyroscope attached to the dorsum of foot was considered
to be effective in detecting the gait phases because the
output during the gait varied in relation to the phase
clearly [6].
The swing phase is detected by the gyroscope if the
second negative peak value is detected after the stance
phase is detected. However, the swing phase of the
first step is detected if the first negative peak value is
detected. The stance phase is detected by the gyroscope if its output becomes the negative value after
the output reaches the positive peak value in the
swing phase.
3
Results
An example of the result of detecting the swing phase
and the stance phase by using the above-mentioned
method is shown in Fig. 2. All the swing and stance
phases could be detected without mistake in the all
subject's walking experiments. The method using the
output of the gyroscope detected the beginning of the
swing phase earlier than the method using the
aluminum electrode.
The delay times of the gait phases detected by using
the output of the gyroscope to the gait phases
measured with the electrode are shown in Table 1. It
was indicated that the detection algorithm used in this
paper detected the stance phase more exactly than the
swing phase. In addition, it was indicated that the
detection algorithms detected the gait phases in the
slow walking earlier than the gait phases in the
normal speed walking.
0
1
2
3
4
0
1
2
3
4
5
6
7
8
9
10
5
6
Time [sec]
7
8
9
10
1
0.5
0
Fig. 2 The swing and stance phases detected by
the output of gyroscope (subject A, normal speed).
Gait phase: 0) stance phase and 1) swing phase.
Solid line: gait phases detected by the aluminum
electrode, broken line: gait phases detected by the
gyroscope.
Table 1 The delay times of the gait phases detected by using the output of the gyroscope to the
gait phases measured with the aluminum electrode.
The numerical value of the minus means that the
method using the outputs of the gyroscope detected
the gait phase earlier than the method using the
electrode.
Detect phase Subject A
(speed)
[msec]
Subject B
[msec]
Swing (nor.)
Swing (slow)
Stance (nor.)
Stance (slow)
-50.0±13.1 -55.7±10.1 -47.9±14.6
-61.4±24.4 -96.8±13.2 -74.9±26.3
1.4±17.0 - 1.9±20.8 - 1.9±16.7
-27.6±31.4 -26.6±25.6 -31.3±30.5
4
-38.1±14.3
-66.7±24.1
- 5.0±10.2
-39.9±32.8
Subject C
[msec]
Average
[msec]
Discussion
The gait phases in the slow walking were detected by
the method using the gyroscope about 30 msec earlier
then the gait phases in the normal speed walking. It
was thought that the slow joint movement depended
on slow walking was the reason why the time
difference with the gait phases detected by the
aluminum electrode increased. An increase in the
standard deviation of the delay time in slow walking
indicated that the error of the timing increased. It was
thought that walking tended to have large variablity in
a slow walking as the above-mentioned reason.
5
Conclusion
In this paper, the detection of the gait phases was examined under different walking speed. The walking
measurements that attached the gyroscope on the leg
were performed in the normal and the slow speed with
the normal subjects. From the result, it was indicated
that the sensor could detect the swing phase and the
stance phase without mistake. Therefore, the sensor of
gait phase detection with appropriate accuracy that
can be used in clinical can be constructed compactly
at a low price by using the gyroscopes. However, it
was indicated that the detection algorithm detected the
gait phases change in the slow walking earlier than
the gait phases in the normal speed walking.
Acknowledgments
This study was partly supported by the Ministry of
Education, Culture, Sports, Science and Technology
of Japan under a Grant-in-Aid for Scientific Research,
and the Sendai Advanced Preventive Health Care
Services Cluster.
References
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Use of Functional Electrical Stimulation in the
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Detection for FES Using Accelerometers and
Supervised Machine Learning, IEEE Trans.
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[3] I P I Pappas, M R Popovic, T Keller, V Dietz and
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IEEE Trans. Neural Syst. Rehab. Eng., 9-2,
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Simplified Measure-ment Method of Lower
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[6] N Furuse and T Watanabe: A Study on Sensing
System of Lower Limb Condition with Piezoelectric Gyroscopes: Measurements of Joint Angles and Gait Phases, Mediterranean Conference
on Medical and Biological Engineering and
Computing, pp.689-692, 2007