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In The Name Of God
Exoskeletal Assistive Devices
Dr. Parnianpour
Mohammad Ali Sanjari
Damoon Soudbakhsh
Elham Sahraei
Fatemeh Malekipour
Table of Contents
Muscles
Natural & Artificial Muscles
EAD
Steps for designing EAD
Conclusion
Future works
Natural Muscle
What does a natural muscle do?
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It’s a contractile organ.
Fibers “actuate” force and motion in response to
nervous stimulation.
How does it work?
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Contract by the chemo-mechanical action of the
proteins actin and myosin.
Joints of the body are arrayed such that they comprise
muscles which oppose each other.
Natural vs. Artificial Muscle
How can we develop replacements for the
natural muscle?
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Develop biomimetic actuators.
Emphasis on implantable technologies (not on the
forefront now).
What do we have to work with?
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Electrical/pneumatic servos (robotic limbs, late
1940’s-present).
New materials.
Synthetic polymers
Carbon
What constitutes a muscle?
Any system or combination of sub-systems
can be considered a “muscle”:
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hydraulic/pneumatic cylinder.
electromagnetic servo.
biological muscle tissue.
In short, anything which accomplishes
actuation under the command of a stimulus.
Muscles primarily exert energy (ATP) to bring
about:
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motion, acceleration (dv/dt or d2x/dt2).
force application (F=m.a).
Three types
Skeletal – voluntary and striated
Cardiac – involuntary, striated, and branched
Smooth – involuntary and unstriated
Skeletal muscle
The Design of Natural Muscle
Muscles are simply transducers

They change the chemo-electric signal from
nerves to mechanical energy.
Artificial muscles should be similar in
resilience and in the ability to produce
large actuation strains
Artificial Muscle: An Overview
Many types of artificial “muscle”:
McKibbin muscle actuators

Inflatable air tubes, delivering large force at a low
frequency.
PAN-chemically stimulated by pH change.
Electrically Stimulated “Tissues”

IPMC, Solenoids, Piezo-active polymers and
ceramics
Series Elastic Actuators
The McKibben Artificial
Muscle
How it’s made
Consists of an internal bladder
Bladder is covered by a braided mesh shell
Attached at either end to tendon-like structures
How it works
Internal bladder pressurized
Bladder expands in a
balloon-like manner against
the braided shell
Shell maintain a cylindrical
shape
As the volume of the
bladder increases, the
actuator shortens and
produces tension
Disadvantages of McKibben
Muscles
Odd Force-velocity behavior:
 a hydraulic damper operates in parallel
with the McKibben muscles
Series Elastic Actuator
Position tolerance
Interaction with humans
Backlash free joints are not required
Damage/force tolerant
What’s the purpose ?
Importance of Construction of
motion assistive devices
Approaching to other countries in
such cases
Advantageous of EAD such as:
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Good interaction with human
almost no disturbance
In needed times, it applies forces to
ease movement of knee joint
Help disable people for rising up
stairs and walking.
Results have Applications in
Rehabilitation and Robotic
sciences.
Design Steps
1) Imaging & Link Segment( LS ) Modeling
2) Selection of Ballscrew
3) Motor selection
Imaging
1. Inserting markers on
specific locations
2. Imaging
3. Capturing data
4. Detecting markers
5. Output data (position
of markers in each
frame)
Sharif Univ. of Tech.
Biomechanics Lab.
Computation of Forces
Construct LS Model
Mass & center of
mass of the Limbs
from Anthropometric
Tables
Torque require at
knee joint
Estimated Maximum
Force at a Supposed
Position
Ballscrew Selection
Input Data
Axial Load
Linear Speed
Criteria
Output Data
Permissible Rational
Speed
a) Dangerous
Screw-Shaft Speed
b) DN Value
Permissible Axial Load

Screw shaft Buckling
Load
Static Safety Factor
Screw Shaft OD
Lead
Length
Motor Selection
Inputs
Lead & Linear Speed
Motor Rotational
Speed
Ballscrew
Specifications
Criteria
Effective Torque (Trms)
Iterate with Mass &
Dimensions of Motor
Future Works
Test the device on a human subject
Improve conformability
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Enhance Control system
Custom made devices
Use in more activities
Wearable Robots
Thanks For Your Time & Attention