Applied Bionics and Biomechanics 11 (2014) 119–134
DOI 10.3233/ABB-140099
IOS Press
119
Design considerations of a lower limb
exoskeleton system to assist walking and
load-carrying of infantry soldiers
Seungnam Yu
a,∗
, Changsoo Han
b
and Ilje Cho
a
a
Remote System Technology Development Section, Korea Atomic Energy Research Institute, Deajeon, South Korea
b
Department of Robot Engineering, Hanyang University, Ansan, South Korea
Abstract. This paper describes the development of a wearable exoskeleton system for the lower extremities of infantry soldiers
and proposes appropriate design criteria based on existing case studies. Because infantry soldiers carry a variety of equipment,
the interference with existing equipment and additional burden of the exoskeleton support system should be minimized. Recent
studies have shownthatauseronlyneedstobesupportedinthegravitational direction when walking on flat terrain; however, active
joints are necessary to support walking over rough and sloped terrain such as mountains. Thus, an underactuated exoskeleton
system was considered: passive joints are applied to the hip and ankle joints, and active joints are applied to the knee joints to
exploit the dynamic coupling effect of the link structure and muscular activation patterns when the user is going up and down
stairs. A prototype of the exoskeleton system was developed and validated through a simple stair-climbing experiment.
Keywords: Exoskeleton, wearable robot, infantry soldier, underactuated system, weight suppot mechanism (WSM)
1. Introduction
According to records from the past 10 years, heavy
personal belongings on soldiers have increased [1,
2]. This inevitably increases the possibility of mus-
culoskeletal diseases; likewise, injuries to soldiers
in circumstances other than battles, i.e., nonbattle
injuries, have emerged as problems that critically affect
the physical condition of soldiers [3–6]. The increase
in these heavy personal belongings results from indi-
vidual soldiers’ requests to be sufficiently equipped
to ensure personal safety in any circumstance as well
as the increase in additional equipment used during
field operations. For example, the maximum weight of
personal belongings recommended for a U.S. infantry
soldier is known to be approximately 23 kgf, whereas
∗
Corresponding author: Seungnam Yu, Remote System Technol-
ogy Development Section, Korea Atomic Energy Research Institute,
Deajeon, South Korea. E-mail: hymecer@gmail.com.
the practical weight of personal belongings is known
to reach no less than 45–60 kgf [1]. This tendency is
true for other countries’ infantry systems as well; thus,
it is necessary to improve transportation equipment
for heavy personal belongings, to minimize nonbat-
tle injuries such as musculoskeletal diseases and to
enhance the fighting power and mobility of infantry
soldiers. In particular, in the field of national defense,
many wearable lower extremity exoskeleton systems
have been proposed, focusing on relieving the weight
of the backpack, which is one of the major heavy per-
sonal belongings of individual wearers [7–11]; some
of these systems emphasize their effectiveness by mea-
suring the metabolic rate changes of wearers [12, 13].
However, as proposed in some studies, these systems
tend to hinder the natural gaits of wearers owing to
the excessive application of actuators or the kinematic
problems of exoskeletons, and this tendency is a pri-
mary cause of the additional metabolic consumption
of wearers [14]. Considering the nature of infantry
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