Experimental Verfication of Fall Simulation and Wearable Protect
Airbag
Youngho Lee, Beomguen Jo, Jeoungwoo Lee, Jaemin Kim, Soonmoon Jung, Taekyung Lee
and Junghwa Hong
Department of Control and Instrument Engineering, Korea University, Seoul, Republic of Korea
Keywords: Fall Injury, Protective Device, Fall Simulation, Reducing Injury, Elderly Fall.
Abstract: Falling of the elderly becomes an important issue in the aging society. Falls could cause fractures which is
significant cause of morbidity and mortality. As a result, active protecting devices are being developed to
protect fallers’ body from severe injuries. In this study, as boundary condition and injury parameter are figured
out by experiments and simulation of falls situation, the wearable airbag for protecting from falls is designed
and make prototype of airbag. After that, compare contact force between fall simulation and experiments with
prototype airbag. It will be possible to establish the reliability of the development of the fall prevention system
for the elderly and to be the basis for the future development.
1 INTRODUCTION
Most people experiment fall accident by losing a
balance. Especially, more than 30% of the elderly
over the age of 65 years have experiences at least one
fall per year, which significantly deteriorates quality
of life. Based on movements, the elderly falls during
the level walking (43 %), going in-and-out of a
bathroom (30 %), during sitting down and standing
up from a seat (13 %), and in ascending and
descending stairs (15 %), which are the activities of
daily living (ADL) (W. L. Watson et al., 2011).
Particularly, it was found that a slip was a main cause
of falling injury. For the elderly, it was reported that
more than 66 % of the slip fallers have the hip injuries
in pelvis (Ambrose et al., 2013). However, it is still
unknown why the slip fallers in the old age have the
high injury value at the pelvic region. Many of these
falls may be avoided if fall risk assessment and
prevention tools where available as an integral part of
ADL. However, the fall risk assessment is still not
completed at this moment. Currently, active
protecting devices for fallers are developing to protect
fallers’ body from severe injuries as an alternative or
for a practical purpose. Developed equipment is
divided into passive and active type to protect the
body from falling. Research on active equipment is
divided into research on fall detection algorithms and
research on wearable airbags. In the case of wearable
airbags, there are studies to confirm the performance
of the airbag using a dummy. However, most studies
have designed the airbag only as a shock absorber
between the ground and the human body without
going through ergonomic design. In this study, the
wearable protect airbag is designed and is confirmed
through simulation of fall injury situation, and also,
compare with the fall experiments by using an
accelerometer and a gyro-sensor for an active
protecting device from the falling injuries.
2 MATERIALS AND METHODS
2.1 Design of Wearable Protect Airbag
and Simulation of Falls
2.1.1 Design of the Wearable Protect Airbag
For falls simulations, human models, environments
and algorithms must be applied to simulations.
Pedestrian facet model (mathematical dynamic
model) provided by the MADYMO program (Release
7.6, TASS international, Netherlands). Wearable
protective equipment has high protection
performance when it is made of hard material, but
users prefer the soft material because they don’t want
to wear it (Honkanen et al., 2006). Also, since there
is a difference in the protection performance
according to the wearing method of the wearer or the
Lee, Y., Jo, B., Lee, J., Kim, J., Jung, S., Lee, T. and Hong, J.
Experimental Verification of Fall Simulation and Wearable Protect Airbag.
DOI: 10.5220/0006785202150218
In Proceedings of the 4th International Conference on Information and Communication Technologies for Ageing Well and e-Health (ICT4AWE 2018), pages 215-218
ISBN: 978-989-758-299-8
Copyright
c
2019 by SCITEPRESS – Science and Technology Publications, Lda. All rights reserved
215
fall method, it is possible to fix the body to the
maximum to overcome it (Forsen et al., 2004). The
shape of the wearable airbag is designed to cover
body and to protect pelvic by considering the average
body size of the elderly over 65 years old.
(a)
(b)
Figure 1: (a) Designed wearable protect airbag and (b)
Human model with wearing airbag.
2.1.2 Simulation of Falls Situation and
Reduce the Fall Injury by Airbag
The falling simulation of the human model is
designed on a condition of concrete properties
(Density:
, Elastic modulus: 
, Poisson’s ratio:  ). and the angle of 70°
between the lower limb and the ground is set, where
the elderly person cannot maintain and regain the
balance (Hsiao, 2008) (Figure 2). Thereafter, gravity
is applied to allow the human body to fall back on the
ground.
To determine how much the human body model
was injured by the falls, Impact force and acceleration
is measured in simulation. Acceleration is important
parameter to calculate injury, such as HIC (Head
Injury Criterion), CTI (Combined Thoracic index)
and etc. At the beginning of the simulation, the human
body model is tilted toward the ground by gravity. As
the angle of the joint cannot be maintained due to the
characteristics of the human body model, the joint
collapses due to the gravity, and the human body
model impacts to the ground in the order of the hips,
thorax and head.
(a)
(b)
Figure 2: Initial position of human model in falling
simulation (a) without wearable airbag (b) with wearable
airbag.
2.2 Fall Experiments
2.2.1 Falling Experiments Toward
Backward
21 male subjects participated in the experiment for
falling data. The 3D accelerometer (L3G4200D, ±
2000 Deg/sec, 70 mdps/digit), and compass
(HMC5883L, ± 8 Gauss, 5 milli-gauss) put on the
sacrum, Thoracic and neck of the subjects for the
falling experiments. The data from the sensors were
wirelessly transmitted by using RF (nRF2401+,
2.4GHz). Fig. 3 (a) shows the experimental setups
and an example of the falling experiments, which was
using a slider to induce a backward falling. The
falling postures were determined based on the
resultant pelvic acceleration and angular velocity, and
pelvic tilt and obliquity angles. Based on the resultant
acceleration as depicted in Fig. 3 (b), a falling event
could be classified as the Fall 1; the period from the
start of fall to the lowest peak, and the Fall 2 + Impact
period; the period from the lowest peak to the highest
peak. Using the measured results, the falling posture
of the people was analyzed.
(a)
(b)
Figure 3: (a) Falling experiments and (b) Definitions of fall.
2.2.2 Falling Experiments by using Dummy
Model
60kg-dummy is used in the experiment for falling
data. Prototype of wearable pelvic airbag (Figure 4
(a)) is designed by simulation. Wearable protect
airbag is manufactured in the form of a belt and can
accommodate the airbag. And sensor module (3D
accelerometer, gyro-sensor and compass sensor) is
used to measure and calculate z-axis acceleration,
sum acceleration, angular velocity, tilt angle,
obliquity angle, resultant angle. These values is used
in double threshold algorithm to determine fall event.
If fall event is found, the inside airbag (thermoplastic
poly urethane) is unfolded by the gas. Force plate
(OR6-7 force platform, ADVANCED
MECHANICAL TECHNOLOGY INC, USA) is used
to measure contact force between dummy and
ground. Dummy is set on 100cm-height from ground.
ICT4AWE 2018 - 4th International Conference on Information and Communication Technologies for Ageing Well and e-Health
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As the angle of the joint cannot be maintained due to
the characteristics of the human body model, the joint
collapses due to the gravity, and the human body
model impacts to the ground in the order of the hips
(Figure 4 (b)).
(a)
(b)
Figure 4: (a) Prototype of wearable pelvic airbag and
(b)Falling experiments by using dummy.
3 RESULTS AND DISCUSSION
After analysing the data collected from movements in
fall situation, the summation of acceleration at the
neck, thoracic, pelvic could detect almost all
movements of the fall. For perfect protection of the
falling person’s body, the detection should be
accomplished within the period from the start of the
fall to the lowest peak. And highest peak value can
calculate maximum impact force which indicates
numerically that the injury occurred to the human
body. First, compare the acceleration of each position
(neck, thoracic, pelvic) (Figure 1(a)). All of position
show similar tendency and lowest peak, but they have
different level of highest peak value. The reason for
this result is that the sequence of the impact of the
human body model with the ground changes in order
of hip, head and thoracic.
(b)
Figure 5: (a) Sum of acceleration on neck, thoracic and
pelvic and (b) Comparison between simulation and
experiments of acceleration.
Figure 5(b) show comparison between simulation
and experiments. As a result, the simulation is set
similarly with experiments. Based on the results of
the simulation, the wearable pelvic airbag was
developed.
The graph of Figure 6(a) shows the impact force
applied to the hips of the human model at the time of
the falls in case 1 (before wearing airbag) and case 2
(after wearing airbag) in simulation.
In case 1, maximum impact force is 4694N, and
in case 2, maximum impact force is 2240N,
respectively. Case 1 (4694N) exceed the reference hip
fracture point of the elderly people (3100N) and case
2 (2240N) not exceed (Kennedy, 1987).
(a)
(b)
Figure 6: Impact force of before and after wearing pelvic
airbag (a) simulation and (b) dummy experiments.
The graph of Figure 6(b) shows the impact force
applied to the hips of the dummy at the time of the
falls in case 1 (before wearing airbag) and case 2
(after wearing airbag) in simulation.
In case 1, maximum impact force is 5733N, and
in case 2, maximum impact force is 2911N,
respectively.
4 CONCLUSIONS
In this study, the simulation of the fall and wearable
airbag is verified by fall experiments. All condition of
simulation is set similarly with real fall situation. It
can be simulation method that can be used as a basis
of safety research for the elderly.
Based on simulation and experiment results, the
effectiveness of the airbag is proved by showing the
injury value in the simulation and prototype. This
airbag is expected to prevent fractures and reduce cost
of treatment. In addition, through this study, it is
possible to develop wearable airbags in other parts to
prevent injuries caused by falls.
ACKNOWLEDGEMENTS
This work was supported by the Korea Health
Technology R&D Project (HI15C1025) funded by
the Korean Ministry of Health & Welfare.
Experimental Verification of Fall Simulation and Wearable Protect Airbag
217
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