Students from the Tech Foundry worked to build a pair of robotic hands for Salvius at this weekends workshop. While working, students learned that the length of each digit in a finger follows the pattern of a Fibonacci sequence. The Fibonacci sequence occurs quite commonly in nature, however the significance of this pattern in the human hand is that it allow the fingers to curl into a fist shape which is why human hands are good at using a wide variety of tools. In addition, it was shown that the sum of the length of the distal, intermediate and proximal phalanges in the little finger equal the length of those in the thumb. This creates symmetry between these two fingers and improves the hand's ability to pick up small objects. By design, each finger has four degrees of freedom, except for the thumb which has five due to the added complexity of its saddle joint. Normally each finger has an additional three degrees of freedom, two for extension and flexion and one for abduction and adduction.
Salvius has been built using readily available materials and the design for the hands is no exception. Pens donated from +Western New England University were repurposed to construct the structural components of each finger. The hands are designed to compliantly grip objects by changing shape to match a surface instead of requiring each finger digit to be positioned individually. As a result, the hands use fewer servos and less processing power to control.
