Improved Robotic Hand Works on Compressed Air

An innovative robotic hand can hold objects as heavy as a can of food or as delicate as a raw egg, while being dexterous enough to gesture for sign language, and could one day serve as a prosthetic replacement.

Developed by students at the Virginia Tech College of Engineering (Virginia Tech, Blacksburg, VA, USA), the Robotic Air Powered Hand with Elastic Ligaments (RAPHaEL) 2 is a second-generation version of a robotic hand that is powered by compressed air and a novel, accordion-type tube actuator. Because the hand's grasping force and compliance is adjusted by changing the air pressure, it does not require the use of motors or other expensive and bulky actuators. The most significant changes between the RAPHaEL 2 and its predecessor are a closed loop control mechanism and sensors that are used for automatic position and force feedback of the fingers using data acquisition hardware; also, while the first version of RAPHaEL relied on solenoids with a microcontroller to operate, the current actuators are mechanical; finally, the material that comprises the hand was changed to a durable polycarbonate, replacing a fragile acrylic-based material that was prone to breakage. Additional future developments will include the ability to grasp small moving objects, as well as the use of silicone, carbon fiber, and other materials to make the hand lighter, simpler in structure, and more human-like in appearance.


"This gives us a lot more control over the kinds of things we can do with the hand,” said codeveloper junior year student Kyle Cothern, one of the five undergraduate mechanical engineering students that comprise the development team. "Eventually, we might be able to tell how soft an object you're grabbing is just by touching it.”

RAPHaEL 2 is part of a larger project of the Virginia Tech Robotics and Mechanisms Laboratory (RoMeLa) - The humanoid robot CHARLI (Cognitive Humanoid Robot with Learning Intelligence), a 152 cm tall robot that will be used as a general humanoid research platform. Once the hand is connected to the larger body, it will be able to pick up - not just grasp and hold - objects, as would a person. RAPHaEL2 recently won first place in the American Society of Mechanical Engineers (ASME) Student Mechanism and Robot Design Competition, held during august-September 2009 in San Diego (CA, USA).

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