Inclusive & Assistive Products
ISDN2001/2002: Second Year Design Project
Independent Technical Study
Chloe Yuen
Adjustable resistance for eversion/inversion of ankle, Sensors
Target:
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Have different levels of resistance for eversion/inversion exercise
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Sensors to achieve accurate resistance execution
Eversion
Inversion
Eversion/Inversion
Rotation of the axis of the ankle
Rotation -> Motor control
Resistance -> Torque of motor
Adjustable resistance -> Different Torque
Motor to achieve adjustable resistance
Motors
Testing different motors to find the suitable one to provide adjustable resistance
Gearbox
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Change speed/pulse frequency to achieve different torque (Nema17: 0.3Nm)
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Use gearbox to magnify the torque to be able to be felt by humans (~50Nm)
Nema17
Nema17 Torque to Pulse Frequency Graph
1:189 Gearbox
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Change speed/pulse frequency to achieve different torque (Nema17: 0.3Nm)
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Use gearbox to magnify the torque to be able to be felt by humans (~50Nm)
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Torque after gearbox
=0.3 * 189 * 0.9 (efficiency)
=51.03Nm
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3 levels achieved by arduino (delay -> slower speed)
Assembly finished
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3 levels achieved by arduino (delay -> slower speed)
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Resistance controller to control speed
Sensors
Sensors we tested during the design journey
Ending up only using IMU for the simplicity of data processing
1 / IMU
Provide current location of foot
3D representation on software
Adjust direction of the resistance
2 / Load Cell
Stress on the foot by resistance to dorsiflexion
Not useful in application, just for reference for physiotherapist
3 / Encoder
On motor for direction adjustment for resistance
Not available on motor used to achieve adjustable resistance
IMU
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Motor rotate counter-clockwise during inversion
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Motor rotate clockwise during eversion
