Two DegreeofFreedom Myoelectric Prosthetic Arm

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Two Degree-of-Freedom Myoelectric Prosthetic Arm

• Andrea Ho Aimee Schultz
• ME 433 Advanced Mechatronics
• Fall 2005

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Prostheses
Myoelectric
Body - Powered

• Users movements
• Cables
• 1 DOF at a time

• EMG
• Motors Batteries
• 1 DOF

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Neuromuscular Junction
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EMG (Electromyogram)
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Myoelectric Control Strategies

• Autonomous (everything done by prosthesis)
• Voluntary
• Digital (based on thresholds or detection of
  soft or hard contractions)
• Analog
• Proportional (velocity in proportion to EMG)
• Compliant (user specifies joint angles and
  compliance)

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OVERVIEW
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Analog Filters

• Active band-pass with corner frequencies 20 Hz
  250 Hz
• Notch filter
• Remove signals at 60 Hz

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Frequency Response Basic Bandpass Filter
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Frequency Response Butterworth LPF
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Frequency Response Butterworth HPF
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Frequency Response High Q Notch Filter
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Amplifiers

• Instrumental amplifier
• Analog Devices AD 620
• Low cost, low power, high accuracy
• Requires one external resistor for gains from 1
  to 10 000
• Second-stage amplifier
• Total gain 2000

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Timeline

• October 11-21 EMG signal filtering,
  amplification, rectification and smoothing
• October 21-28 EMG output analysis (Matlab)
• October 28-? Mechanical Design and Construction