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Molecular lib

on-going project 2023-2024

Wearable Lifting-ASSISTIVE Device MK II 
Design REVIEW 12/12/23

The team has agreed to a refresh of the PCB, the firmware, as well as the linkage assembly used for the device

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PROBLEMS FROM MKI

ASSEMBLY

  • Uncomfortable, more space needed for components, poor force orientation

  • Excessive friction at joint

PCB

  • Electrically Unsafe, Non Battery powered

    • Currently powered by PSU, not isolated from user

    • “Lithium Polymer” LiPo can be dangerous additional things needed

SOFTWARE

  • Software is messy, built on complex architecture

    • Built on Zephyr linux, overkill for application

    • Depending on battery voltage monitoring must be added

assmMK2.jpg
Screenshot 2024-01-08 132423_edited.png
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NEW CUFF MATERIAL

  • Formlabs Flexible 80A -> TPU

    • Advantages:

      • Cost effective: ~10% cost reduction for both cuffs

      • Greater rigidity -> firm fit to bars

NEW PULLEY DESIGN

  • goal: maximize efficiency of rotational moment provided by motor

    • move spool closer to bar -> parallelism b/t thread and bar

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LINKAGE SYSTEM OVERHAUL

  • change Al bars to PLA -> quick production of design changes

    • cheap, $0.10-$0.12 per gram

  • multiple iterations t/o semester

    • indentations needed for cuffs, bearings, motor

      • removed motor enclosure, now fastened to assembly via screws

  • addition of bearings

    • allows for seamless rotation 

      • limits friction (past issue)

    • allows for constant line of force b/t pulley and point of lift​

Screenshot 2024-01-08 154330_edited.png
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THE MICROCONTROLLER

Goal: establish communication between the firmware and the motor w/out setting the device on fire

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Components:

  • Microcontroller (U1)

    • 3.3V

  • H-Bridge (U2)

    • Motor spins both directions

    • 5V

  • Power supply

    • Lithium ion battery

  • Battery Protection (IC1)

  • Buck Converter (U3, U4)

    • Steps down supply voltage

  • Coupling Capacitors (C)

    • Protects from surges

  • LED Test Points

microContSchem_edited.jpg
hBridgeSchem_edited.jpg
battProtSchem_edited.jpg
buckConvSchem_edited.jpg

THE ROADMAP

End of Next Semester

  • integrate firmware, electrical, mechanical components

  • fix battery and PCB to bar

  • determine solution for wrist rotation w/out having to refasten cuff

  • maximize efficiency of motor output via electrical and assembly design

Future Semesters

  • enclose electrical components

  • test on real patients/get feedback to refine design

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