Eye Controlled Operation for Disabled People Using EMG

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Eye Controlled Operation for Disabled People
Using EMG
A Project Presentation by

• Fahim Ibn Karim (052437)
• Rashedul Amin Tuhin (052439)
• Tasnim Manzar (052441)
• Project webpage
• http//eyecontrolled.wordpress.com

Supervised By Prof. Dr. Ashraful Haque EEE
Department, IUT
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Project Overview

• EMG signal acquisition from Extraocular Muscles
  (Eye movement Muscles)
• Processing the signals
• Simulation and Implementation

Objective
Helping disabled people to perform several
operations (i.e. simple on/off, speed control etc)
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EMG Overview

• EMG Electromyography
• Electromyography measures the electrical impulses
  of muscles at rest and during contraction.
• Amplitudes of EMG signal range between 0 to 10 mV
  (peak-to-peak) or 0 to 1.5 mV (rms).
• Frequency of EMG signal is between 0 to 500 Hz.
• The usable energy of EMG signal is dominant
  between 50-150 Hz.

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The Human Eye Movement Muscles
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Extraocular Muscles

• Notations
• Superior Rectus (SR)
• Superior Oblique (SO)
• Lateral Rectus (LR)
• Inferior Rectus (IR)
• Inferior Oblique (IO)
• Media Rectus (MR)

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muscle movements

• A given extraocular muscle moves the pupil, at
  the front of the eye, in a specific direction or
  directions, as follows
• medial rectus (MR) inward, toward the nose
  (adduction)
• lateral rectus (LR) outward, away from the nose
  (abduction)
• superior rectus (SR) upward (elevation)
• rotates the top of the eye toward the nose
  (intorsion)
• inward (adduction)
• inferior rectus (IR) downward (depression)
• rotates the top of the eye away from the nose
  (extorsion)
• inward (adduction)
• superior oblique (SO)
• primarily rotates the top of the eye toward the
  nose (intorsion)
• secondarily moves the eye downward (depression)
• tertiarily moves the eye outward (abduction)
• inferior oblique (IO)
• primarily rotates the top of the eye away from
  the nose (extorsion)
• secondarily moves the eye upward (elevation)
• tertiarily moves the eye outward (abduction)

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cardinal positions of gaze

• Conjugate eye movements
• Vergence eye movements
• saccadic eye movements
• Smooth pursuit movements
• These movements are simplified
• up/right (1.3.5)
• up/left (1.6)
• Up (1)
• Down (4)
• right (3)
• left (6)
• down/right (3,4)
• down/left (6,4,2)

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Electrodes

• Plastic piece and snap on for holding electrode
  elements
• Dimension of 1 inch between electrode contacts
• 4 electrode extensions and 1 body reference
  extension

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Electrodes

• EL1 (TDE23) 4mm silver / silver chloride
  electrodes
• plugged into the white and black differential
  measurement sockets
• A third positioned anywhere to make Isolated
  Ground

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Positions of the Electrodes
Positions shown in the diagram above are (right
and left) A) Medial frontalis, B) Lateral
frontalis, C) Levator labii superioris, D)
Zygomaticus major.
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EMG Amplifier Preamplifier

• Industry standard instrumentation amplifier
  op-amp (INA2128)
• Accuracy providing high bandwidth at high gain
  and output offset current
• Differential amplifier circuit with 2 inputs
• High gain to boost the EMG signals
• Body Reference Circuit or Feed Back (OPA2604)

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EMG Amplifier Preamplifier

• Factors to be considered
• Boost signal to TTL standard level ( 5 V.)
• Enough gain
• Noise/Artifact problem
• Filter, stability of electrodes attached to skin,
  proper grounding
• DC offset or bias problem
• Bias adjustment

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EMG Amplifier Preamplifier
Industry standard instrumentation amplifier
op-amp (INA2128)
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EMG Amplifier Preamplifier
BURR-BROWN INA2128 Application Information
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EMG Amplifier Preamplifier (cont.)
Gain Equation
Find RG at Gain 1,000
Find Gain at RG 22 ohm
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EMG Amplifier Preamplifier (cont.)
Common Mode Rejection Ratio (CMRR) calculation
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Averaging Body Reference Circuit

• Common body reference circuit for 4 channels
• Using summing amplifier circuit and sign changing
  circuit

For independent R1, R2, R3, and R4
For independent R1, and R2
For R1 R2 R3 R4
For R1 R2
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Averaging Body Reference Circuit
Average Body Reference Circuit
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Averaging Body Reference Circuit
Common Body Reference Output
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EMG Amplifier Filter

• Suppress noise that has been amplified by the
  preamplifier
• Help to sink any DC current that cause bias to
  the output
• Select particular signal frequency range
• Use RC High Pass Filter of 12 Hz

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EMG Amplifier Filter (cont.)
1st order RC High Pass Filter with Cutoff
Frequency of 12Hz
1st order RC High Pass Filter
Cutoff Frequency
Cutoff Frequency of 12 Hz
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Amplifier and Bias Adjustment

• Provide abilities to amplify and adjust reference
  level of output signals
• Individual amplifier and bias adjustment unit for
  each channel
• Use Non-Inverting circuit for amplifier unit
• Use Voltage Follower Offset Adjustment circuit
  for bias adjustment unit
• Provide Gain of 21 times
• Provide Offset of 9 volts

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Amplifier and Bias Adjustment
Ideal Non-Inverting Amplifier Circuit
Non-Inverting Output
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Amplifier and Bias Adjustment
Amplifier Circuit with Gain Adjustment
Amplifier Circuit with Gain Adjustment
Amplifier Gain
Computing the value of R34
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Amplifier and Bias Adjustment
Output of the circuit
Offset Adjustment for Voltage Follower
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Amplifier and Bias Adjustment
Output of the circuit
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Amplifier and Bias Adjustment
Output of the circuit
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Limitations of gain and bias adjustment

• The output can not exceed 9V or -9V (power
  supply voltage).
• If 2 volts fed and gain is 3 and offset is 2
  volts, then the output is (2x3)28 volts, and
  we are ok with it.
• But If 2 volts fed and gain is 10 and offset
  is -9 volts, then it gives (2x10)-911 volts,
  but opamp will still produce 9 volts.

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Future work (Brainstorming )

• A/D conversion, Normalizing and processing the
  EMG signals
• Simulation and Modification (if needed)
• Logic Design for performing different actions
• Simulation with MATLAB and Documentation
• Code, Code and Code for PIC microcontroller
• Implementation to perform several operations
• (i.e. simple on/off, speed control etc)

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Project Block Diagram
input
ADC
EMG capture prog.
Simulation
EMG capture software
ADC
Computer
MCU/Control circuit
output
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Sources

• S. Siriprayoonsak "Real-Time Measurement of
  Prehensile EMG Signals," thesis defense, August
  24, 2005, SDSU
• Gianluca De Luca Fundamental Concepts in EMG
  Signal Acquisition, 2001 Rev.2.1, March 2003,
  DelSys Inc
• Sylvia Ounpuu Electromyography (EMG)
  Fundamentals Interpretation 6/14/1999 Chaoyang
  University of Technology
• "Cursor Control Using Voice and Facial EMG
  Signals", by Grant Connell

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Q A
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Thank you for patient hearing.