~First Prototype

Figure 1 shows the first prototype that we built with plywood, 3D printed ABS parts and acrylic. We first decided to use a four bar mechanism to drive our robot. We adjusted the link lengths in the simulation in Figure 2 to obtain the output that we desired. Then, we used laser cutter to cut out acrylic links which are shown in Figure 3. The orange parts in Figure 1 are the sliders and finger tip attachment. The brown part is the attachment for proximal phalanx. After that, we used screws and nuts to put all the linkages together. Finally, we cut out wood pieces and built a platform to fit everything. It is powered manually by cranking the longest screw on the mechanism.

There were a lot of problems with our first prototype which would be improved later on with our final product. Firstly, the 3D printer track and sliders were not smooth enough. Too much friction is not good for rehabilitation exercise machines.  Secondly, there were no guidance for the slider. We designed the machine to be passive so the slider should have predicted movement. Thirdly, the links were loose. Repetitive motion should not make the machine dissemble. Fourthly, the platform was too low. It is not comfortable for hand exercise. Last but not least, it should be powered by motor as we are making a passive exercising machine.

Figure 1: First Prototype

Figure 2: Four Bar Mechanism Simulation

Figure 3: Links