16 Mar 2018

"New finger design~
This version uses a different pulley system compared to the previous that's more commonly used in other prosthetic hands. Changes have also been made to the choice of motor as well as the aesthetics of the finger.

Improvements in design:
- Simplified assembly with the use of a single actuation cord.
- Increased load bearing capabilities. The finger should be able to hold more than 1kg with no power draw due to locking actuator.
- Reduced power consumption to less than 100mA at 5V during actuation (including boost converter running the motor at 7.2V.
- Increased actuation speed.
- Improved asthetics to match more closely to a human finger.
- The motor can be ran straight off of a 2 cell li-ion battery pack (7.2V - 8.4V) without the need of a high power converter circuit.
- The driver is now more compatible with the power requirements of the motor.
- Still has a non rigid finger when forced closed to prevent damage to the mechanism.
- The different pulley system allows for the finger to dynamically conform around any given object.
- Still low cost.
- Still 3D printed.

Downsides of the design:
- The choice of motor stalls quite a lot easier than previous motor, so the gripping force is a bit weaker but still usable. 
- The required actuation length has increased to 25mm which will limit how small the actuator can be.
- Has a lot of sliding friction so lubrication is a must.

Changes to be made:
- Reduce actuator length
- Improve release mechanism for non rigid motion.
- Improve Arduino code.
- Make changes to design files for reliability and consistency when 3D printing.
- May make changes to mechanism to reduce actuation length.
- Ball bearings may be added to improve reliability.
- Figure out a way to add rubber grip.

The design is still far from a perfect solution and isn't the best design, however, it certainly offers a low cost, low power and high load bearing prosthetic but with the downside of having a weak gripping force."

Jason Lee