Electromyography, Myoelectric signals and their use in Controlling Prosthetic Limbs

1
Electromyography, Myoelectric signals and their
use in Controlling Prosthetic Limbs

• Brian Kennedy

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What Is Electromyography?

• Electromyography is a procedure to test for
  electrical activity
• Needles!
• Solid, not hollow, so less pain
• Contracting muscles

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Why is EMG so Important?

• Used for a vast number of applications
• Diagnose Diseases
• Gives better insight into the human body
• Helps develop new prosthetic technologies

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A Particular EMG Setup
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How Muscles Work

• Myosin and Actin are the main contributors to
  muscle contraction
• Myosin grabs the actin and pulls to shorten the
  sarcomere
• This shortening is the act of muscle contraction

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Myoelectric Signals

• Electric signals that make muscles contract
• Much less electrical current in muscles than in
  your house
• EMG is able to detect these signals
• Signals are decoded and used for research

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The Phantom Limb

• Patients who have lost limb still Feel
• Myoelectric signals still being produced
• Research found that these signals could be tapped
  into

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Progression of Traditional Prosthetics

• Originating from the peg leg
• Growing to a simple mechanical bend
• Electricity added
• Grasping of simple objects with four fingers
• Individual finger control

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Picture History of Prosthetics
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Electric Switch Prosthetics

• Require cables or straps to control
• Body movement required to operate prostheses
• For Example..
• Protraction pushed a switch to extend the arm
• Retraction of the shoulder would hit another
  switch to flex the arm
• Elevation opened up a hook-hand

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Problems of Electric Switch Prosthetics

• Can be cumbersome to operate
• Simple grasping ability
• Normally not enough grip strength
• Simple motions do not mimic normal fluid human
  motion

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Benefits of Myoelectric Control Schemes
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Why Use Myoelectric Controls?

• Myoelectric controls give feedback to the
  prosthetic purely based on signals from your
  muscles
• Does not require extra movement
• More precise than electric switch

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Disadvantages of a Myoelectric Control Scheme

• Difficulty in determining strength
• Non-invasive receiving methods dont create
  accurate enough signals
• Other muscle functions determine movement. Grip
  etc. . Not just Myoelectric signals

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A Successful Myoelectric Prosthetic

• The i-LIMB by Touch Bionics
• Uses Myoelectric controls to manipulate
  individual digits
• Rotating thumb

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But Wait, Theres More!

• i-LIMB solves the issue of grip strength
• Individual Sensors for each finger
• Knows when object has enough pressure applied for
  grip
• Fingers lock into position

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Fitting Into Society

• Many owners of prosthetics feel like they dont
  fit into society
• Bulky prostheses and unnatural movement
• Dont act like actual human body parts
• Anatomically out of place

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Solution to the Problem

• The i-LIMB rests in an anatomically natural
  position
• Looks like the real finger structure of a human
• Acts in very similar manner to a real human hand
• Add LIVINGSKIN to make it look just like real

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Can You Tell the Difference?
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LIVINGSKIN

• Makes Prosthetic look amazingly realistic
• Touch Bionics developed the product to be
  applied to i-LIMB but other prosthetics can have
  the technology applied
• Skin is painted to match your own body, not just
  a cookie cutter hand

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LIVINGSKIN

• The Hand to the right has the LIVINGSKIN applied
• All skin types and colors are made to purely
  personal specifications
• Hair is even painted on to maximize detail

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Resources

• "Electric Power in Upper Limb Prosthetics The
  Michigan Experience ICIB Online Library, 1983
  ." ACPOC - Association of Children's
  Prosthetic-Orthotic Clinics. Web. 10 Feb. 2010.
  lthttp//www.acpoc.org/library/1983_04_001.aspgt.
• "Electromyography (EMG)." Web. 08 Feb. 2010.
  lthttp//www.emedicinehealth.com/electromyography_e
  mg/article_em.htmgt.
• "HowStuffWorks "Contracting a Muscle""
  Howstuffworks "Health" Web. 10 Feb. 2010.
  lthttp//health.howstuffworks.com/muscle2.htmgt.
• "Myoelectric prosthesis -." Wikipedia, the free
  encyclopedia. Web. 08 Feb. 2010.
  lthttp//en.wikipedia.org/wiki/Myoelectricgt.
• "Quantifying Pattern RecognitionBased
  Myoelectric ... IEEE Trans Neural Syst Rehabil
  Eng. 2010 - PubMed result." National Center for
  Biotechnology Information. Web. 08 Feb. 2010.
  lthttp//www.ncbi.nlm.nih.gov/pubmed/20071269?itool
  EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.
  Pubmed_RVDocSumordinalpos2gt.
• "Simulated neuroprosthesis state activation and
  hand-position control using myoelectric signals
  from wrist muscles." Rehabilitation Research and
  Development Service Home Page. Web. 09 Feb. 2010.
  lthttp//www.rehab.research.va.gov/jour/04/41/3b/kn
  utson.htmlgt.
• "Surface electromyography and muscle force
  limits ... Clin Biomech (Bristol, Avon). 2009 -
  PubMed result." National Center for Biotechnology
  Information. Web. 08 Feb. 2010.
  lthttp//www.ncbi.nlm.nih.gov/pubmed/18849097?ordin
  alpos1itoolEntrezSystem2.PEntrez.Pubmed.Pubmed_
  ResultsPanel.Pubmed_SingleItemSupl.Pubmed_Discover
  y_RAlinkpos5logrelatedreviewslogdbfrompubme
  dgt.
• Touch Bionics. Web. 08 Feb. 2010.
  lthttp//www.touchbionics.com/i-LIMB/controlsgt.
• Touch Bionics. Web. 08 Feb. 2010.
  lthttp//www.touchbionics.com/LIVINGSKINgt.
• "Welcome to IEEE Xplore 2.0 Physiology and
  Mathematics of Myoelectric Signals." IEEE Xplore
  Guest Home Page. Web. 08 Feb. 2010.
  lthttp//ieeexplore.ieee.org/xpl/freeabs_all.jsp?ar
  numbe