Proceedings of the 3nd International Conference on Engineering & Emerging Technologies (ICEET), Superior
University, Lahore, PK, 7-8 April, 2016
Design of an Anthromorphic Upper Extremity Exoskeleton for
Rehabilitation*
Faizan Ahmed, Ali Yar Khan, Syed Hammad Ullah Alqadry , and Yasar Ayaz

Abstract— Robotics exoskeletons or active orthosis is one of
the areas of great activity in contemporary study in robotics.
Significant evolution in these systems has taken place for them to
be used in human power augmentation, reducing fatigue in
repetitive tasks via power assist, rehabilitation of stroke patients
and haptic interaction in virtual world. Since exoskeletons have
a direct interaction with human joints their designs must be
prepared with special consideration keeping in mind the
difference in application from industrial robotics. Some special
considerations for the mechanical design are that: (1) flexible
length of joints (for adaptability), (2) safety considerations and
(3) lightweight for low inertia. Since the system is to be used on a
daily basis, the design should also be easy to wear and store. The
controller of the exoskeleton should have high responsiveness, as
well as smooth and flexible motion generation. At the same time,
the motion generated by the controller should be in agreement
with the intention of motion of the human user. The proposed
design used 4Degree of Freedoms (DoF), 3DoF for the shoulder
joint and a 1DoF for Elbow flexion/extension. The paper gives a
brief review of key technologies used in current exoskeleton
systems with a new proposed design and future development in
said design.
I. INTRODUCTION
The functional movement such as walking, extending and
other actions by the Upper and Lower extremity limbs are the
principle motions of living humans today. Due to poor physical
and muscular abilities, Aged human beings are ached with
many forms of locomotive handicaps such as strokes, paralysis,
hemiplegic cases and spinal cord damage [1]. In today's
everyday life, there are numerous reasons from which humans
are deprived of their functional movements such as geriatric
disorders, trauma, strokes and spinal cord damage. If the
human body were to be looked upon as a mechanical device,
then its complexity marks on such a high level that every other
human being would have a different disability. For such
disabilities, Rehabilitation therapies stand as the prime
solution. Generally, these treatments lean on the dysfunctional
motions, which are setup by the means of manipulative
physical therapy strategies [1]. Sadly, there are some group of
patients that are not able to regain all functions of their bodies.
Additional aid of exoskeletons or prosthesis have the ability to
support and help in the recovery of the lossy function.
Physiotherapy and Functional Electrical simulation (FES) are
vastly used techniques for the healing of paralysis and states of
lost movement but they have limitations. Exoskeleton of
mobile orthosis is a wearable external device that amplifies the
*The work is supported by the research and partial funding of RISE Lab.
(Dept. Robotics and AI, SMME, NUST, Pakistan)
F. Ahmed , A.Y. Khan , S.H.U. Alqadri , Y. Ayaz are with the Robotics
and Intelligent Systems Engineering (RISE) Laboratory, Department of
Robotics and Artificial Intelligence, School of Mechanical and Manufacturing
performance of motions. Artificial aid and rehabilitation has
lately in recent times have become readily available. Since
artificial aid and rehabilitation is preferred, the inventions in
commercial robotics and orthosis are readily available and
extensively required to aid and speed up the rehabilitation and
therapy of patients.
As explained earlier The Robotic exoskeleton is a wearable
external device with actuation on specific joints to induce
movements in otherwise paralyzed joints. Orthosis is a device
that is replaced or assisted people who have limb pathology,
while prosthesis is a device that replaces and acts as same as
the damaged organ. However, the exoskeletons and assisted
devices have designed and developed to improve the losing
function of the upper or lower extremity. [1]
A robotic exoskeleton is not just a device to use for helping
in physical therapic procedures. It can also be used as an
assistive device to amplify human joints, or cause less fatigue
to limbs in repetitive tasks. Another use of an exoskeleton
system is for haptic interactions in virtual reality systems.
There are many exoskeleton systems commercial available
for rental purposes, most famous example is cyberdyne japan's
HAL, which is available in three options full body/ lower
extremity/upper extremity. Some full body exoskeletons are
still in research and development as Body Extender from
PERCRO Lab of Scuola Superiore S. Anna, Pisa, Italy.[2]
Raytheon XOS 2 by SARCOS funded by DARPA and HULC
by Lockheed Martin all three are for military use for the
purpose of increasing endurance of soldiers on battlefield. A
brief list of previous systems are mentioned in later sections of
this paper.
II. BRIEF HISTORY OF EXOSKELETONS
HARDIMAN by General Electric was the first practical
full body exoskeleton suit attempted in 1965. The system was
actuated by Hydraulic Actuators. [3] Robotic exoskeleton
systems were studied for the purposes of industry or medical
applications in the 1960s and 1970s [3]-[7]. Table I, shows a
few recent full body and upper extremity exoskeletons that
became source of inspiration for the current project.
Engineering (SMME), National University of Sciences and Technology
(NUST), Main Campus, Sector H-12, Islamabad, 44000, Pakistan. Email:
[email protected],[email protected],[email protected],yasar@
smme.edu.pk
Proceedings of the 3nd International Conference on Engineering & Emerging Technologies (ICEET), Superior
University, Lahore, PK, 7-8 April, 2016
Table 1 : Comparision of previous Exoskeletons
Research
Application
D.O.Fs
Miranda[8]
passive therapy
exercises
01 Elbow
Prasertsakul[1] Physiotherapy as well 02 Elbow
as to support & fulfill 03 Shoulder
the lost functions of
the limb.
Body
Extender[2]
Tsai [9]
To enhance human
strength in handling
heavy materials in
unstructured
environment.
Assistance to
rehabilitation patients
so that they can
perform daily
activities later.
In this paper basically
exoskeleton has 6
DOF. It is mainly
targeted for disabled
patients.
Future Ideas of
Amelioration
Training of user, increasing
level of complexity and
comfort, Use of EMG
(electromyography)
05 DC
Maturity of the technology
motors, pulley
and research regarding
system & driving controllers and EMG signals.
wire system
22DoFs; All
Electrical motors, Better control strategies in
actuated; in
gears, pulleys & order to reduce the resistant
four
wire systems.
forces while tracking
anthropomorph
movement of limbs.
ic limbs
06DoFsof
04 force sensors To design the controller
Shoulderwith strain gauges, which can guide the patient
complex
potentiometer,
to trace the circular path and
(additionalDoF motor
train the patient’s motor
sto replicate the (FAULHABER control strategy for moderate
motion without series) actuators paresis.
conflicts)
and encoders.
01DoFof
Elbow &
02DoFfor
wrist.
GARREC[10] Used for teleoperation 02DoFsfor
(nuclear) and haptics Shoulder,
(automotive
01-Elbow
industry).
SUEFUL7[11]
Power Source &
Transmission
Mechanism
DC brushed
motor
The Screw-Cable Future work comprises of
System, Dc
adjustable segments and
motors, pulleys. optimization of the shoulder.
6 DOF:
Cable drive, gear
2 DOF of
and motors.
shoulder,
2 DOF of
elbow,
2 DOF of wrist
Bringing internal / external
rotation in shoulder. We can
even try to balance weight of
motors for avoid using wheel
chair for weight
compensation.
Proceedings of the 3nd International Conference on Engineering & Emerging Technologies (ICEET), Superior
University, Lahore, PK, 7-8 April, 2016
CADEN-7
[12]
(CADEN)-7 were
targeted for
Physiotherapy of
disabled people.
7 DOF :
Cable drive,
3 DOF of
motors.
shoulders,
2DOF of elbow
and 2 DOF of
elbows
Moubarak[13] Robotic assistance for 4 DOF :
motors
handicaps and
3 DOF of
rehabilitative training shoulder and 1
DOF of elbow
I. MECHANICAL DESIGN
A. Conceptual Design
The shoulder and elbow gather 5 bones of the upper limb:
the clavicle, the scapula, the humerus, the ulna and the radius.
[14]
The human arm has three complex articulations; the
shoulder, the elbow and the wrist. Our prototype, being
dedicated to the shoulder and elbow rehabilitation training,
covers three shoulder degrees of freedom (DoFs) (abduction /
adduction, flexion / extension and internal / external rotation)
and one elbow DoF (flexion / extension). [1]
The proposed exoskeleton arm focuses on the upper arm,
current design only features shoulder and elbow. The human
shoulder features 3 degree-of-freedom, i.e. flexion/extension,
horizontal flexion/extension, internal/external rotation. Elbow
has only one Degree-of-freedom i.e. flexion/extension. Figure
1-3 give an overview on these Degrees-of-freedom.
Figure 2: Shoulder rotation
Figure 1: Shoulder degrees of freedom
Figure 3 : Elbow degrees of freedom
B. Joint Design
The proposed joint design uses a system of pulleys and
cables to keep the motors away from the joint. This system
helps keep the weight reduced on the joints. The motors/
actuators are kept on the back plate where the weight is
distributed. Figure 4 shows a complete 3d model our
exoskeleton RobEX.
Proceedings of the 3nd International Conference on Engineering & Emerging Technologies (ICEET), Superior
University, Lahore, PK, 7-8 April, 2016
Figure 6 : Back plate view
III. CONCLUSION AND FUTURE ENHANCEMENTS
Figure 4 : 3D model of RobEX
C. Actuation
Simple worm geared DC motors were used in the
actuation. Currently the actuation is done using simple relay
based controller that gives bidirectional control of individual
motors. An Electromyography based system is under
development for RobEX.
II. MECHANICAL FABRICATION
RobEX was fabricated using Aluminum 7060 alloy, to keep
the weight as minimum as possible for the prototype. The final
prototype weighed about 10kg with more than 7 kg distributed
on the back like a normal backpack. Simulations were done for
alternate materials to reduce further weight and a suitable
strength to weight ratio was found is carbon fiber reinforced
ABS was used, this could reduce the weight by more than 50
percent. Figure 5-7 shows a team member wearing the
fabricated prototype.
The RobEX exoskeleton system is a new type to
exoskeleton design for rehabilitation of which uses modular
structure for different needs of different patients. A motor
control system based on raspberry pi board using
electromyography (EMG) and machine learning algorithms is
under development for RobEX, of which EMG signal filter
circuit prototypes are completed as of 8th march 2016 , and are
under testing for various test subjects , which can make it
compete with current commercially available systems. This
paper gives a brief review of previous upper extremity
exoskeleton systems. As well as a brief review of new
proposed design RobEX. The EMG based motor control will
make RobEX suitable for not just rehabilitation of stroke
patients but then it can also be used in industry and hospitals
or anywhere repetitive load bearing task is done.
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Proceedings of the 3nd International Conference on Engineering & Emerging Technologies (ICEET), Superior
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