Physiological control of a computer mouse
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Physiological Control of a Computer Mouse. Presented by Danielle Smith, Shawn Purnell, & Chris Hawk. Outline of Presentation. Project Introduction Background/Theory Block Diagram Hardware Circuit Implementation Software Implementation Results/Discussion Future Developments Conclusion.

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Physiological control of a computer mouse

Physiological Control of a Computer Mouse

Presented by

Danielle Smith, Shawn Purnell, & Chris Hawk


Outline of presentation
Outline of Presentation

  • Project Introduction

  • Background/Theory

  • Block Diagram

  • Hardware Circuit Implementation

  • Software Implementation

  • Results/Discussion

  • Future Developments

  • Conclusion


Introduction
Introduction

  • Project Purpose

    • Acts as a proof of concept project

    • Simulate low resolution physiological directional control of an automated computer cursor

      • for paraplegic empowerment

      • for military strategic targeting systems


Background on electrodes
Background on Electrodes

  • Silver/Silver-Chloride Electrodes

    • Contact/ Capacitive electrodes

    • Serve as a transducers to change an ionic current into an electronic current

  • Ag/AgCl Electrodes used for measurements

    • Electrodes used for EOG

      • Small with solid gel

      • Prevent motion artifact and contact with eye

    • Electrodes used for EMG

      • Large with liquid gel


Emg and eog signals
EMG and EOG Signals

  • EMG measurements - lie within muscle movement

    • Skeletal muscle organized on basis of motor unit

    • Motor unit - smallest unit that can be activated by volitional effort

    • Fibers of a given motor unit are interspersed with fibers of other motor units

    • At high levels of effort and contraction, many motor unit responses are superimposed

    • Gives Rise to the complicated interference pattern taken as the signal

  • EOG signal - based on dipole within the eye

    • There is a steady corneal-retinal potential from the back of the eye to the front of the eye

    • This steady dipole may be used to measure eye potential by placing surface electrodes around the eyes




Biopotential differential amplifier
Biopotential Differential Amplifier

  • Three stage gain

  • High input impedance

  • Variable resistor to minimize common mode gain

  • Low gain in dc-coupled stages to minimize offset potentials produced by electrodes

  • Bandpass filter in third stage


Eog circuit design
EOG Circuit Design

  • EOG parameters

    • frequency range: 0 - 10 Hz

    • voltage amplitude: 50 - 3500 µVolt

  • EOG Amplifier theoretical values

    • Frequency response: .048 - 5.3 Hz

    • Gain of approximately 21 for dc-coupled stages

    • Overall gain: 14,000


Eog hardware schematic
EOG Hardware Schematic

  • High Cutoff Frequency: 4.5 Hz

  • Low Cutoff Frequency: 0.05 Hz

  • Midband Frequency Range: 0.25 - 1.5 Hz

  • Midband Gain: 16,090


Emg circuit design
EMG Circuit Design

  • EMG parameters

    • frequency range: dc - 10,000 Hz

    • voltage amplitude: 0.1 - 5 mVolt

  • EMG Amplifier theoretical values

    • Frequency response: 241 Hz - 5.3 kHz

    • Gain of approximately 21 for dc-coupled stages

    • EMG signal processed by diode and LPF

    • Overall gain: 15,000


Emg hardware schematic
EMG Hardware Schematic

  • High Cutoff Frequency: 4.7 kHz

  • Low Cutoff Frequency: 250 Hz

  • Midband Frequency Range: 2.1 - 2.5 kHz

  • Midband Gain: 15,828


Specification testing
Specification Testing

  • Common Mode Tests

    • Common mode output voltages less than 10% the signal

    • Minimize common mode gain

  • dc-Coupled Stage Gain Tests

    • dc-coupled stage gain of less than 25

    • to prevent saturation of amplifiers


Results and discussion
Results and Discussion

  • Frequency Response Tests

    • Frequency responses were as predicted theoretically

  • Common Mode Tests

    • Common mode output voltage fall within 10% of their signals

  • dc-Coupled Stage Gain Tests

    • dc-coupled stage gain for all three amplifiers were approximately 25


Goals of software
Goals of Software

  • Goals of Software

    • Acquire continuous analog signals

    • Create logic to process signals

      • click for EMG jaw clench

      • grid for EOG eye movement


Data acquisition
Data Acquisition

  • Scales analog signals into a one-dimensional array

  • Indexes the data by channel

  • Separates individual data within specified channel




Design complications and alterations
Design Complications and Alterations

  • Complications

    • Improper installation of LabVIEW

  • Alterations

    • EOG amplifier high cutoff frequency reduced from 10 Hz to 4 Hz to minimize high frequency components in the signal

    • Summer circuits were found to be unnecessary

    • Comparator implemented into LabVIEW


Future development
Future Development

  • Project acts as proof of concept

  • Software Development

    • Create more resolution in software implementation by creating a counter-based system

  • Apply to actual computer mouse connector

  • Hardware Development

    • Replace electrodes with high sensitivity magnetic sensors

    • Replace bioamplifiers with amplifiers designed for the magnetic sensor outputs

  • Develop marketable product


Conclusion
Conclusion

  • Successful Overall Results in obtaining project goals

  • Project proves that directional control and clicking simulation can be achieved through facial physiological manipulation

  • Questions ???


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