The initial CAD for this project was borrowed from the research paper "An open-source anthropomorphic robot hand system: HRI hand" by Hyeonjun Park and Donghan Kim as a jumping-off point to test how the mechanism behaved before the kinematic analysis was complete. Notably, the authors of this paper chose to actuate each digit individually, while we aim to actuate them all at the same time.
| Link | Length |
|---|---|
| L1 | 6.286 mm |
| L2 | 9.5 mm |
| L3 | 27.05 mm |
| L4 | 27.3 mm |
| Loffset | 3.693 mm |
| L5 | 19.56 mm |
| L6 | 6 mm |
Table 1: Link Lengths
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The next steps for our project will be to design a more comprehensive ground link that will incorporate five of these fingers into a hand. A special case is the thumb; we will simply reduce it's DOF from that of an actual thumb to 1, and treat it as a shorter finger. We plan on approximating a thumb We plan on using springs in parallel to connect each finger to the linear actuator located on the back of the palm. The fingers will be extended when the actuator is unextended, keeping the springs in tension. When the actuator extends, it will allow the spring to compress, thus releasing the force on the actuation joint on L2 allowing the fingers to close. We will select springs with sufficient stiffness such that there will still be force on the fingers when they are fully flexed, which will provide the force needed to grasp whatever object is in the palm. Due to the natural compliance of the springs, the fingers will be able to grasp objects of differing widths.
| BOM | Qt. | Cost | Link |
|---|---|---|---|
| PLA Filament | ~ 1 lb | Free from TIW | |
| Arduino | 1 | Free from parts box | |
| Extension Springs with Loop Ends | 5 | $14.05 | Link |
| Linear Actuator | 1 | $19.99 | Link |
| Electrical Connectors | 1 | Free from parts box |
Table 2: Projected Bill of Materials for Final Project