Actuation: Ottobock Communications and Proof of Concept
When we started our project, we were given a donated Ottobock prosthetic arm. It was unclear whether or not the prosthesis would work, and after many troubleshooting attempts, we found that the arm was not functional. Upon mechanical isolation between the motor and gears, it was found that no jamming was occurring. We also increased the gain (sensitivity) of the electrodes, yet we did not observe any motor actuation. However, we did hear “twitching” noises coming from the motor, so it is possible that the electrodes were working fine but the motor was damaged.
We found out that this product was donated to our sponsor’s lab and is a slightly older prosthesis, the Ottobock Transcarpal Hand 8E44. Despite personally making some connections at Ottobock, we were unable to successfully troubleshoot the device. Ottobock was reluctant to disseminate information as to how we could troubleshoot further and recommended that we send the arm in for an assessment. One caveat was that we would need a prosthetist to approve the inquiry, which we did not want to do.
After reaching out to our sponsors once again, we made a few more connections at Ottobock who were more willing to help (without the need of a prosthetist). However, they are currently asking for a serial number which we cannot locate—perhaps it is under the base of the hand, which has been laminated to the socket.
While figuring out details as to how to get the arm serviced, we began looking into other options which would provide a “proof of concept.” We decided to purchase a few servo motors which operate similarly to the Ottobock motor (pulse width modulation). We currently plan to map electromyogram data to certain pulse widths, which would correlate to specific positions that hand (servo) should assume. Our assertion is that this system should be analogous to if we were to interface with the Ottobock prosthesis.