INTRODUCTION to walk in an unfamiliar way. This difficulty

INTRODUCTION

                  
Technology has been advanced from swords to bows and arrows through the
discovery of riffles and the invention of the aircraft and now to the presence
of unmanned laser guided aerial drones and various robots. The military is now
hoping for the new class of warrior –Exoskeleton envisions dreams to come into
reality and procreates a dismounted soldier into a faster robust and empowered
exoskeleton suits such as “iron man”. 

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                   Exoskeletons
are external skeleton structures that are used to protect animal’s body.
 Military Exoskeletons or exo-suits have been in development since early
1960’s, often known as wearable robotics for military designed to boost
soldier’s strength and endurance. These are devices which are put on a human
and are intended for humans’ augmentation in particular to increase the efforts
that a person may apply.

                  
Exoskeletons help soldiers to carry heavy loads both in and out of
combat, run at faster speeds and defend themselves from enemy attacks. These
systems are anthromorphic (ascribing human characteristics to nonhuman
things)   devices that work in
conjunction with our body’s natural architecture. There are several factors
driving the demand for these exoskeletons globally. The most basic exoskeleton is more or
less a pair of legs taking the weight of an equipment rack.

EXISTING SYSTEMS:

·        
Raytheon’s XOS
exoskeleton

·        
Lockheed Martin’s
human universal load carrier (HULC) ,etc.,

have demonstrated greatly improved strength, allowing soldier to
carry loads of up to 200lbs for extended periods of time. But they are
hydraulic-powered, anthropomorphic exoskeleton designed specifically to fit
around the body of a dismounted soldier. There is no control mechanism, instead sensors detect
movement and, using a micro-computer, make the suit to move in time with the
body.

 

PROBLEM
STATEMENT

                   Robotic exoskeletons are
used for various purposes in different sizes. Exoskeletons can be classified
into full body, upper extremity (torso and hands) and lower extremity (for
legs) exoskeletons. One big problem was that these initial exoskeletons forced
wearers to walk in an unfamiliar way. This difficulty was compounded by a lack
of coordination between human and machine. A wearable exoskeleton solution is
to be conceived to aid the soldier and enhance his capabilities.

 

SOLUTION

                  We propose a further
invention involved in eliminating the main reason of former failures through
the uses of different approaches. Latest exoskeletons has been developed to
reduce the weight that impact on the wearer and also various exo-frames were
introduced in both military and medical fields for rehabilitation purposes such
as restoring lost limb functions.

Our Exoskeleton is specifically designed for
soldiers and acts as coalescence of technologies. We have proposed an
exoskeleton which helps to carry load without causing an effect for wearer.
Former powered exoskeletons uses some mechanical movement as a single power
source and batteries or fuel cells as power storage which acted as a main
reason for weight of the exoskeleton.

Our exo suit consists of distributed power sources
of three types:

(1) Power generated from backpack movement.

 (2) Power
generated from the wearers knee and

 (3) Power
generated from the wearers shoe.

These sources produce power enough to allow the
exoskeleton produce the wearer strength and endurance to move along with a load
of approximated weight. Light weight actuators have been used to create more
compact design with better characteristics.

 

HYPOTHESIS:

                      The main reason behind
exoskeleton development is the augmentation of the physical abilities of a
human being, specifically strength and endurance for the current state of the art.
Human walking carries a lot of energy, although this has been realized by many
current robotic devices, producing better rehabilitation outcomes with robotic
devices is still a developing area of research.

To design better robotic devices, it is
important to understand:

·        
the
principles governing how humans learn to interact with the robotic assistance
and

·        
How
to identify the gait parameters humans prioritize as objectives for their gait
pattern. 

Considering the above, the kinematic
relationship has been understood to be robust both in forward and backward
locomotion and its nature is not altered by perturbing gait patterns and
changing gait speed.

In order to apply human biomechanical
data to design guidance for an exoskeleton, six assumptions were made:

1. The size, mass, and inertial
properties of the exoskeleton will be equivalent to those of a human.

2. The exoskeleton will carry itself
(including power supply) and the soldier’s load.

3. The joint torques and joint powers
scale linearly with mass.

4. The exoskeleton’s gait will be the
same as a human’s gait.

5. The exoskeleton will carry a load on
its back in the same way those humans carry loads on

 their
backs.

6. The exoskeleton will move at the same
speed, cover the same distance, and carry the same load as a soldier who does
not have an exoskeleton.

 

 

DESCRIPTION:

                      Previous
exoskeleton development has largely been part of major research 

Endeavors and has yielded solutions exhibiting high inertia
limbs which are burdensome to the wearer. Now let us have a study on the
principal behind our proposal.

 

 

 

POWER GENERATION FROM BACKPACK MOVEMENT:

 

                            When
we walk, we naturally optimize coordination patterns for energy efficiency. In
order to achieve maximum optimization, we have designed a fully portable
hip-assistance exosuit that uses a backpack frame to attach to the torso, onto
which is mounted a spooled-webbing actuator that connects to the back of the
users thigh. The actuators, powered by a geared brushless motor connected to a
spool via a timing belt, wind up seat-belt webbing onto the spool so that a
large travel is possible with a simple, compact mechanism.

 

                         The linkages were
attached to the back frame and were located on either side of the body. They
acted as a first class lever with the pivot at the center.The load and the
actuating force were on either ends of the link. The lengths of the links and
the forces acting on them can be calculated.The law of moments was applied to
obtain the force that the actuator must provide in order to lift the weight.

               
         The back frame consists of
two vertical structures with two cross links in order to set them apart. L
links projecting backwards were used to attach the actuator.They were welded to
the back frame.The actuators were fixed rigidly at the end to the back frame.
Hence the stress induced in the L link and the strength of the welds must to be
determined.

                        The material used was cold
rolled steel. The axial stress, maximum normal stress was calculated for each
link and they were within the yield strength of the material chosen. As shown
in the figure a load is attached to a load plate which is placed on the L
links. Due to the walking movement of the wearer, a force is applied on the
linear actuators placed on the hip section which makes the spring attached to
the back frame move which instead provides vertical movement to the load plate.
This in turn generates power which is stored in the battery situated beneath
the L linkages. The power stored in the battery used by the exoskeleton for the
mechanical movements.

POWER
GENERATED FROM KNEE

                         Scientists have proved
that every movement we do with our legs generate some amount of force which in
turn can be used to charge some devices. Power can be generated from these ankle
movements. This power generated can be collected and stored in a battery.Every time that you take a step, your
leg both accelerates and decelerates. For a walking movement, due to swinging
action a braking action happens at the knee joint. And it is this braking
mechanism generates energy, a generator that was able to absorb that
wasted energy and turn it into electricity is designed.

We have analyzed two
types of robotic exoskeletons movements to examine rapid locomotors adaptation
to mechanical assistance.

·        
Power absorption at heel strike
and 

·        
Power generation at toe-off.

In other words, the tibialis
anterior has two main bursts of activity during gait:

·        
One at heel strike to slowly lower
the foot to the ground and

·        
One at toe-off to help provide
toe clearance during swing.

The
former provides mechanical power absorption at the ankle joint and
the latter provides mechanical power generation at the ankle joint.

                      The proposed controller captures the user’s intent to
generate task-related assistive torques by means of the exoskeleton in
different phases of the subject’s normal activity. Three dominant antagonistic
muscle pairs are used in our model, in which electromyography (EMG) signals (technique
for evaluating and recording the electrical activity produced by skeletal
muscles)are acquired, processed and used for the estimation of the

·        
knee
joint torque,

·        
trajectory
and

·        
the
stiffness trend,

 in real
time. In addition, experiments can be conducted of standing-up and sitting-down
tasks are demonstrated to further investigate the capabilities of the
controller. Knee exoskeleton, can effectively generate assistive actions that are
volitionally and intuitively controlled by the user’s muscle activity.

 

POWER GENERATION THROUGH SHOE

                              Piezoelectric
materials generate electricity when pressure is applied to it. A piezoelectric
generator in the sole of a shoe could produce electricity with every step .This
regenerative footstep is based on the principle of piezoelectric effect in
which pressure or strain applied to the piezoelectric material placed in the
insole of the wearers shoe  is converted into electricity. The generated
power can be used to power the exoskeleton. Generation of electrical
polarization of the material of the shoe in response to the mechanical strain
is practiced here.

 

Walking With Loads

In 2000, Harman, Hoon, Frykman and Pandorf reported
about the effects of load carriage on lower extremity biomechanics during
walking. Joint angle data were collected and joint moments were calculated for
carried backpack loads of 6, 20, 33, and 47 kg while subjects walked at a speed
of approximately 1.33 m/s. In contrast to change in walking speed, the instant
when toe-off occurs in the gait cycle was affected by change in carried load.
As carried load increased from 6 to 47 kg, the duration of the stance phase was
observed to increase from approximately 63.4% to 65.2% of the gait cycle.
Timing of transitions from flexion to extension and extension to flexion also
appears to be affected by change in carried load. The effect of change in
carried load on hip joint angles was not reported, but slight changes in knee
and ankle joint angles were. Peak knee flexion during mid-stance (? 10%
to30% gait cycle) was found to increase from approximately 22.5 to 27.5
degrees, while peak knee flexion at the transition from initial to mid-swing
(? 72% gait cycle) was found to decrease from approximately 68 to 64
degrees with an increase in carried load. At the ankle, peak dorsi flexion during
terminal stance (? 30% to 50% gait cycle) was found to decrease from
approximately11.5 to 10 degrees, and peak plantar flexion at the transition
from mid- to terminal swing (? 90%gait cycle) was found to decrease from
approximately 5 to 3.5 degrees with an increase in carried load. As with the
joint angles, timing of transitions from extensor to flexor and flexor to
extensor moments, as well as peak values obtained at each joint, appears to be
affected by change in carried load. At the hip, peak extensor moment values
during loading response, as well as peak flexor moment values during terminal
stance, were found to increase with an increase in carried load. Peak knee
extensor moment values during mid-stance and peak ankle plantar flexor moment values
during terminal stance were also found to increase with an increase in carried
load, while peak knee flexor and ankle dorsi flexor moments did not follow a
monotonically increasing trend.

The
peak extensor and flexor moment values obtained at each joint under each of the
four

different
backpack loads are summarized in Table .

 

MINE DETECTION

                   As an advancement of sole
power generator we have attached an additional feature for our exoskeleton. The
insole of this made up of a conductive material and has a planar coil printed
in the form of ultra thin layer. This insole consists of an ultra thin
microprocessor. This mine detection works on the principle of metal detector.
These metal detectors consist of inductor coil which is used to interact with
the mine inside the ground. This insole produces electromagnetic frequency
waves and detects the mine within 6.5ft (2m) radius. When the electromagnetic
field is disrupted as there is a mine in the ground it the
radio transmitter transmits signal to the wristwatch and produces an alarm
signal to the watch cinched on the wearer’s wrist and thus the location of the
mine is manifested on the watch screen

ADVANTAGES

Exoskeleton is a technology developed not only to
improve soldier work but also to change lives. Exoskeletons were beyond human
ability and will be lighter than current versions so that it can be worn for
longer periods of time. These exoskeletons were fully integrated so that you can sustain the most capability
at the lowest impact to the soldier. Battery usage augments the exoskeleton
even at the idle state of the wearer though it stores less amount of
electricity. This exo suit compensate well on combat even when one of the power
sources gets damaged due to external factors. Our exo suit works mainly on
feedback principle were the output achieved during walking is given as the
input to the actuators and the exoskeleton.

LIMITATIONS

All the systems generally have limitations, since this
is in the conceptual stage total power generation and the cost for creating the
prototype will be estimated at the time of implementation only.

At initial stage, the battery must be fully charged
before the wearer uses suit.

May be due to vertical oscillations the wearer gets
uncomfortable with the backpack.

Since these suits acts in parallel with the wearer’s
muscles and tendons it could mimic their function

 

 

CONCLUSION

                 
The ability to assist humans through an exoskeleton is what researchers
have been thriving for. Many different exoskeletons for various body parts have
been developed to try and assist human movements efficiently. This research
proposes the development of a power generating exoskeleton to assist the human
through ambulation while carrying a substantial payload. Even though
Exoskeletons are been into existence for more than a 5 decades, they are still
facing many challenges related to power supply, weight, battery existence etc.
These Limitations have been tried to overcome in this proposal. We being the budding
engineers, have come up with a solution to solve some exiting problems faced by
former exo skeletons to assist our troops in war field.