An exoskeleton is a powered external framework that attaches to a person to boost their strength and endurance. While early attempts in 1965 were unsuccessful, current exoskeletons use hydraulics or electric motors to help lift heavy loads. They are used militarily but also have applications in industries like construction, healthcare for moving patients, and rehabilitation. Technological challenges include developing lightweight yet powerful actuators, joint flexibility, and precise computer controls to move in sync with the wearer.

2. POWERED EXOSKELETON
i-What is exoskeleton and how it works?
ii-History and application
iii-Practical examples
iv-Limitations and design issues

3. What is exoskeleton?
• An exoskeleton is a hard, protective outer-body
covering of an animal. Although exoskeletons
provide support they are not comprised of
bones.

4. Powered exoskeleton
A powered exoskeleton is a mobile machine
consisting primarily of an outer framework worn
by a person, and a powered
system of motors or
hydraulics that delivers at
least part of the energy for
limb movement.

5. Powered exoskeleton
The main function of a
powered exoskeleton is to
assist the wearer by boosting
their strength and endurance.

6. Application
Powered exoskeletons are commonly designed for military use,
also in civilian areas, similar exoskeletons could be used to help
firefighters and other rescue workers survive dangerous
environments.
The medical field is another prime area for exoskeleton
technology, where it can be used for enhanced precision
during surgery, or as an assist to allow nurses to move heavy
patients. Exoskeletons could also be applied in the area of
rehabilitation of stroke or Spinal cord injury patients.

7. History
The first attempt to build a practical
powered exoskeleton, by general
electric in 1965.The suit was made
lifting 110Kg feel like lifting4.5Kg,it
weighs 680Kg, powered by both
hydraulics an electricity the suit
allowed the wearer to amplify their
strength by a factor of 25.the project
was not successful.

8. HULC
(Human Universal Load
Carrier), The HULC is a battery
powered, lower extremity
exoskeleton. The innovative
hydraulic architecture is highly
efficient enabling the system to
run on batteries, It carries up
to 90 kg, An onboard micro-
computer ensures the
exoskeleton moves in concert
with the individual.
Powered by Four lithium ion batteries, 48-
hour operation

9. HAL-5
The Hybrid Assistive Limb It
has been designed to support
and expand the physical
capabilities of its users,
particularly people with
physical disabilities. Double-
leg model/approximately 12kg,
hip joint: extension 20˚/flexion
120˚ | knee joint: extension
6˚/flexion 120,made of nickel
molybdenum and ammonium
alloy. Powered by 100-volt battery pack

10. Ekso bionics
Ekso provides functional based
rehabilitation, over ground
gait training, and upright,
weight bearing exercise unlike
any other. Provides a means for
people with as much as
complete paralysis, and minimal
forearm strength, to stand and
walk

11. Raytheon XOS 2
The XOS is similar to the
HULC in that it allows the
wearer to lift upwards of 90kg
without feeling any strain,
thanks to hydraulic assistance
and sensors attached to the
hands and feet, Powered
by External power supply via
cable.

12. Limitations and design issues
Engineers of powered exoskeletons face a number of large
technological challenges to build a suit that is capable of
quick and agile movements, yet is also safe to operate
without extensive training.

13. Power supply
One of the largest problems facing
designers of powered exoskeletons
is the power supply. Power supplies
being used:
1-Li-ion or Li-Po rechargeable cells
2-Alkaline or silver-oxide non-
rechargeable cells
3-Internal combustion engine
4-solid oxide fuel cells
5-Direct external power(cable)
Future trend: wireless energy
transfer

14. Skeleton material
Initial exoskeleton experiments are
commonly done using inexpensive and easy
to mold materials such as steel and
Aluminum. As the design moves past the
initial exploratory steps, the engineers move
to progressively more expensive and
strong but lightweight materials such as
titanium, and use more complex component
construction methods, such as
molded carbon-fiber plates.

15. Actuators
The powerful but
lightweight design issues
are also true of the joint
actuators, actuators being
used:
1-pneumatic cylinders
2-hydraulic cylinders
3-electronic servomotors
Future trend: elastic
actuators like SMP

16. Joint flexibility
Several human joints such as the hips and shoulders
are ball and socket joints, with the center of rotation
inside the body. It is difficult for an exoskeleton to
exactly match the motions of this ball joint using a
series of external single-axis hinge points, limiting
flexibility of the wearer. Possible solutions:
1-Separate exterior ball joint alongside the shoulder
or hip
2-Hollow spherical ball joint that encloses the human
joint
3-Spinal flexibility

17. Power control and modulation
It is not enough to build a simple single-speed assist motor, with
forward/hold/reverse position controls and no on-board computer
control. Such a mechanism can be too fast for the user's desired
motion, with the assisted motion overshooting the desired position.
Sudden unexpected movements such as tripping or being pushed over
requires fast precise movements to recover and prevent falling over,
Fast and accurate assistive positioning is typically done using a range
of speeds controlled using computer position sensing of both the
exoskeleton and the wearer, so that the assistive motion only moves as
fast or as far as the motion of the wearer and does not overshoot or
undershoot.

18. Other possible problems
• Detection of unsafe/invalid motions
• Pinching and joint fouling
• Adaptation to user size variations