In The Name Of God

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In The Name Of God

• Exoskeletal Assistive Devices

• Dr. Parnianpour
• Mohammad Ali Sanjari
• Damoon Soudbakhsh
• Elham Sahraei
• Fatemeh Malekipour

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Table of Contents

• Muscles
• Natural Artificial Muscles
• EAD
• Steps for designing EAD
• Conclusion
• Future works

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Natural Muscle

• What does a natural muscle do?
• Its a contractile organ.
• Fibers actuate force and motion in response to
  nervous stimulation.
• How does it work?
• 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.

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Natural vs. Artificial Muscle

• How can we develop replacements for the natural
  muscle?
• Develop biomimetic actuators.
• Emphasis on implantable technologies (not on the
  forefront now).
• What do we have to work with?
• Electrical/pneumatic servos (robotic limbs, late
  1940s-present).
• New materials.
• Synthetic polymers
• Carbon

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What constitutes a muscle?

• Any system or combination of sub-systems can be
  considered a muscle
• 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
• motion, acceleration (dv/dt or d2x/dt2).
• force application (Fm.a).

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Three types

• Skeletal voluntary and striated
• Cardiac involuntary, striated, and branched
• Smooth involuntary and unstriated
• Skeletal muscle

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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

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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

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The McKibben Artificial Muscle
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How its made

• Consists of an internal bladder
• Bladder is covered by a braided mesh shell
• Attached at either end to tendon-like structures

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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

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Disadvantages of McKibben Muscles

• Odd Force-velocity behavior
• a hydraulic damper operates in parallel with the
  McKibben muscles

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Series Elastic Actuator

• Position tolerance
• Interaction with humans
• Backlash free joints are not required
• Damage/force tolerant

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Whats the purpose ?

• Importance of Construction of motion assistive
  devices
• Approaching to other countries in such cases
• Advantageous of EAD such as
• 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.

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Design Steps

1. Imaging Link Segment( LS ) Modeling
2. Selection of Ballscrew
3. Motor selection

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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.
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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

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Ballscrew Selection

• Criteria
• Permissible Rational Speed
• Dangerous Screw-Shaft Speed
• DN Value
• Permissible Axial Load
• Screw shaft Buckling Load
• Static Safety Factor

• Output Data
• Screw Shaft OD
• Lead
• Length

• Input Data
• Axial Load
• Linear Speed

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Motor Selection

• Criteria
• Effective Torque (Trms)
• Iterate with Mass Dimensions of Motor

• Inputs
• Lead Linear Speed
• Motor Rotational Speed
• Ballscrew Specifications

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Future Works

• Test the device on a human subject
• Improve conformability
• Enhance Control system
• Custom made devices
• Use in more activities
• Wearable Robots

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Thanks For Your Time Attention