Our first week for the Winter quarter centered around continuing to work with the electromyography(EMG) capabilities to control a whole prosthetic hand, as well as testing the structural integrity of our current finger design.

There may be a limiting factor in the way that basic EMG sensors allow us to control multiple sensors. To pick up a variety of signals for different functions that an amputee might use in their day to day use of the prosthesis, more than one set of EMG sensors would be needed for each muscle group, which could lead to an overcrowding of sensors on the existing segments of an amputee’s arm. We’re currently still leaning towards EMG over any other type of control system for the amputee, as we think that it still is one of the most effective ways for a prosthesis to be controlled by an amputee by non-invasive means, but this is arguably the biggest challenge that we face.

Our structural test results had a better outcome. Though we have yet to run a tensile test, which we plan to run in either week two or three of this quarter, we ran a 3-point bending test (Pictured above) of our most up to date finger design for the Krobohand, and were thoroughly impressed with the force it could withstand.

We tested two different tolerances in the build of our design – 0.5mm and 0.4mm. After running the tests using the Instron machine in the Engineering tower, with the help of Steve Weinstock, the results were as follows:

0.5mm – 0.55kN of force before failure.
0.4mm – 0.83kN of force before failure.

A video of one of the test runs can be found here:

These results were averaged off of three different tests for each tolerance respectively. The 0.4mm tolerance was able to withstand significantly more than the 0.5mm, but it is much more difficult to 3D print accurately. To capture that strength, but maintain ease of manufacturing, we will attempt printing at a 0.45mm tolerance.

Our next courses of action are to continue working with EMG connectivity viability and integration, as well as running a tensile test on the current design of our finger. Further, we will soon have a finalized lateral joint design. Once this has been completed, we plan on constructing a single finger structure that we can use to demonstrate the capabilities of our designs.

Thank you,

Krobohand Group