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
PROBLEMS FROM MKI
​ASSEMBLY
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Uncomfortable, more space needed for components, poor force orientation
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Excessive friction at joint
PCB
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Electrically Unsafe, Non Battery powered
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Currently powered by PSU, not isolated from user
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“Lithium Polymer” LiPo can be dangerous additional things needed
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SOFTWARE
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Software is messy, built on complex architecture
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Built on Zephyr linux, overkill for application
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Depending on battery voltage monitoring must be added
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NEW CUFF MATERIAL
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Formlabs Flexible 80A -> TPU
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Advantages:
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Cost effective: ~10% cost reduction for both cuffs
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Greater rigidity -> firm fit to bars
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NEW PULLEY DESIGN
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goal: maximize efficiency of rotational moment provided by motor
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move spool closer to bar -> parallelism b/t thread and bar
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LINKAGE SYSTEM OVERHAUL
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change Al bars to PLA -> quick production of design changes
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cheap, $0.10-$0.12 per gram
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multiple iterations t/o semester
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indentations needed for cuffs, bearings, motor
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removed motor enclosure, now fastened to assembly via screws
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addition of bearings
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allows for seamless rotation
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limits friction (past issue)
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allows for constant line of force b/t pulley and point of lift​
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THE MICROCONTROLLER
Goal: establish communication between the firmware and the motor w/out setting the device on fire
Components:
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Microcontroller (U1)
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3.3V
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H-Bridge (U2)
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Motor spins both directions
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5V
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Power supply
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Lithium ion battery
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Battery Protection (IC1)
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Buck Converter (U3, U4)
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Steps down supply voltage
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Coupling Capacitors (C)
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Protects from surges
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LED Test Points
THE ROADMAP
End of Next Semester
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integrate firmware, electrical, mechanical components
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fix battery and PCB to bar
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determine solution for wrist rotation w/out having to refasten cuff
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maximize efficiency of motor output via electrical and assembly design
Future Semesters
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enclose electrical components
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test on real patients/get feedback to refine design