Image: Movement Control Laboratory/University of Washington
(February 18, 2016) There are two generalized schools of thought when it comes to robot hand design. You have robot hands that are simple and straightforward and get the job done, like two- or three-finger grippers that can reliably do many (if not most) things well without any fuss. And then you have very complex hands with four fingers and a thumb that are designed to closely mimic human hands, on the theory that human hands were intelligently designed by millions of years of evolution, and we’ve designed all of our stuff around them anyway, so if you want your robot to be able to do as many things as possible as well as possible you want a hand that’s as humanlike as possible.
Because of the inherent complexity of a real human hand, biomimetic anthropomorphic hands inevitably involve lots of compromises to get them to work properly while maintaining a human-ish form factor. Zhe Xu and Emanuel Todorov from the University of Washington, in Seattle, have gone crazy and built the most detailed and kinematically accurate biomimetic anthropomorphic robotic hand that we’ve ever seen, with the ultimate goal of replacing human hands completely.
Here’s why it was important for them to design a new kind of robotic hand, according to Xu:
“The conventional approach to designing anthropomorphic robotic hands often involves mechanizing biological parts with hinges, linkages, and gimbals in order to simplify the seemingly complicated human counterparts. This approach is helpful for understanding and approximating the kinematics of the human hand in general, but inevitably introduces undesirable discrepancies between the human and robotic hands since most of those salient biomechanical features of the human hand are discarded in the mechanizing process. The inherent mismatch between mechanisms of these robotic hands and biomechanics of human hands essentially prevents us from using natural hand motion to directly control them. Thus none of the existing anthropomorphic robotic hands can achieve the human-level dexterity yet.”
With their hand, Xu and Todorov decided to start from scratch, duplicating the human hand mechanically in as accurate a way as possible. First, they laser scanned a human skeleton hand, and then 3D-printed artificial bones to match, which allowed them to duplicate the unfixed joint axes that we have, as Xu explains:
“For example, the motion of our opposable thumb is relying the complicated shape of the trapezium bone located at the carpometacarpal (CMC) joint. Due to the irregular shape of the trapezium bone, the exact locations of CMC joint axes are not fixed. Thus, none of the existing anthropomorphic robotic hands can restore the natural thumb motions with conventional mechanical joints that require fixed rotation axes. We 3D print artificial bones from the laser-scanned model of a cadaver skeleton hand and connect them with artificial finger joints whose range of motion, stiffness, and dynamic behaviors are very close to their human counterparts. Our robotic hand design uniquely preserves the important biomechanical information of the human hand on anatomical level.”
read also (cs.washington.edu):
Design of a Highly Biomimetic Anthropomorphic Robotic Hand towards Artificial Limb Regeneration >>
Optimal Control with Learned Local Models: Applicationto Dexterous Manipulation >>
Design of an Anthropomorphic Robotic Finger Systemwith Biomimetic Artificial Joints >>
The UW Hand: A Low-cost, 20-DOF Tendon-driven Hand with Fast and Compliant Actuation >>
A Low-cost and Modular, 20-DOF Anthropomorphic Robotic Hand: Design, Actuation and Modeling >>