2023-2024
Wearable Lifting-ASSISTIVE Device MK II
DEsign review FALL '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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Zephyr linux found to be 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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elbow: frictionless extension/retraction of forearm
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wrist: 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
DEsign review spring '24
THE FUNCTIONAL PROTOTYPE
With the spring Engineering Expo on the horizon, the team set out to finish the school year with a functioning prototype. With an overhaul in the assembly design, the type of motor used, the devices included on the circuit board, as well the software for the prototype, each sub-team had a lot to get done before their respective parts were put together to meet the semester's goal.