Advisors: Eric Chang, Matei Ciocarlie
During this project, I made hardware and control updates to an existing robotic hand to introduce tactile sensing capabilities. The underactuated, single-DOF, tendon-driven hand was originally designed for use on the Astrobee platform aboard the ISS, but has since become a research platform in the lab. It features three fingers, each with two flexion/extension joints. Two of the fingers also have abduction/adduction capabilities, totaling eight joints controlled by a single motor. The whole hand is actuated by a system of tendons and pulleys that run througout.
Diagram
Credit: T. Chen, L. Wang, M. Haas Heger, M. Ciocarlie
My first task was to assemble the hand, evaluate how it moved, and make needed improvements. Here, I focused on ensuring the proximal and distal flexion/extension joints in each finger moved together in sync. In other words: the outer finger joints tended to bend before the inner ones, resulting in a dysfunctional grasp. To fix this, I changed the pulley design to reduce friction, re-calibrated the pulley sizes, and redesigned the finger housing to accomodate the changes.
Original Motion
Improved Motion
Using the improved design, I then worked on integrating tactile sensing into the hand. In doing so, we hoped to create a hand that could grasp an object lightly, attempt to lift it, determine if it was slipping through the fingers, and adjust the grasp accordingly. This would make the hand functional for a variety of objects, from fragile items like oragami or balloons (which require a gentle grasp!) to robust, heavy pieces like ceramic cups and soup cans.
Finally, we conducted a variety of tests with the hand, demonstrating some success in adaptive grasping!
Empty Cup
Heavy Cup
Pouring Beads