PORTLAND, Ore. A robotic hand called the Robotic Air-Powered Hand with Elastic Ligaments (Raphael) uses compressed air to combine improved dexterity with low cost, according to engineers at Virginia Tech's Robotics and Mechanisms Laboratory.
The team recently won the Innovation Award Contest at the Compressed Air and Gas Institute in Cleveland.
"Our hand [has] many joints controlled by a single corrugated tube actuator in each finger, which makes our implementations very reliable, very low cost and very light weight compared to other robotic hands," claimed professor Dennis Hong, director of the robotics lab.
|Virginia Tech's fully articulated robotic hand is said to be able to hold objects as heavy as a can or as delicate as an egg.|
Raphael has three articulated joints just like human fingers. Instead of a complex mesh of artificial muscles and tendons, it uses a single inflatable tube in each finger. Inflating the tube with compressed air causes the finger to curl toward the object to be grasped. Once it contacts an object, more air pressure is applied until enough friction is generated to pick up the object.
"Our compliance changes as we add air pressure," said Hong. "Allowing Raphael's single actuator-per-finger architecture to pick up a very very delicate object like an egg or lightbulb, or heavy objects like a grapefruit or can of food."
The inflatable actuators use 60 psi of compressed air to work against an elastic band on the backside of each finger that uncurls the fingers when at rest. By adjusting the air pressure in each finger separately with a microcontroller, a wide variety of hand positions can be realized, according to Hong.
Raphael is part of a larger project called CHARLI (Cognitive Humanoid Robot with Learning Intelligences), which Hong claims will implement the first full-sized bipedal walking humanoid robot entirely based on U.S. designs. The 5-foot-tall robot will compete in the RoboCup soccer competition next year in Singapore.
Funding for the robotics research was provided by the National Science Foundation and the Virginia Tech Student Engineering Council.