After seeing my work on the robotic hand, my professor asked if I would intern for him over the summer. My project was to take over a previous group's senior design project that they had started but couldn't finish.
When I started, I inherited a CAD model as well as a physical prototype. Some parts were ready, but it soon became clear that there were structural issues that meant each part needed a redesign.
First, I changed the pulley wheel. A colleague reworked the Matlab scripts for sizing the pulleys and discovered that they could be reduced from 4 inches to 3 inches in diameter. Next, we selected the Bowden cables. The channels in the pulley could be significantly scaled-down for a much thinner pulley. I changed what had previously been several washers to a spacer integrated with the pulley. Then I added a bracket extending from the pulley to the arm brace, eliminating slippage and allowing repairs to be conducted without solvents.
My next task was fixing the original Bowden cable attachments. The attachment bracket was flimsy. To rectify this, I increased the thickness of the top plate. I attached the bracket to the arm brace at more than one point and added screws to the front and the back so that it would not wobble. To finish, I added threaded holes for fittings attaching to the Bowden cable sheath.
For angle tracking, there is a mounting plate for a potentiometer. This was originally adhered with glue and a small cover piece that broke during installation. After taking charge of the project, I researched an alternative potentiometer as the original was just found in a lab scrap bin and had no accompanying specifications. I spec'd out a new one and made a cover to protect the whole assembly. This was screwed on so that it could be removed if needed. Next, I added another attachment point for the whole cantilever arm to prevent unwanted rotation.
Lastly, I decided to also add a SEA (series elastic actuator) system to the drive motor pulley for a purely assistive control mode that is still currently in the works.