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Precision hydraulic-pneumatic drive ‘can thread a needle’

13 May, 2016

US engineers have developed a new type of hydrostatic transmission system that combines hydraulic and pneumatic technologies and can be used, for example, to drive robot arms safely and precisely, giving them the delicacy to pick up an egg without breaking it. The transmission system has almost no friction or play, resulting in high enough precision for tasks such as threading a sewing needle.

According to the developers, whose work was backed by Disney Research, the hybrid transmission system needs only half as many bulky hydraulic lines as a fully hydraulic system. It could also result in smaller and lighter robotic limbs.

The researchers have used the new transmission system to power a two-armed humanoid robot with stereo cameras mounted in its head, which can stream video signals to a remotely-located operator wearing a head-mounted display.

“The transmission provides our robot with incredibly smooth and fast motion, while also allowing life-like interaction with people and the handling of delicate objects,” says Jessica Hodgins, vice-president of Disney Research and a professor of robotics at Carnegie Mellon, who has co-authored a paper describing the development. “For now, the robot is remotely controlled by a human operator, but we would expect the same level of mechanical performance once the motions are automated.”

John Whitney, an assistant professor of mechanical and industrial engineering at Northeastern University, who led the development of the transmission technology while an associate research scientist at Disney Research, explains that hydraulically-powered robot joints normally need two hydraulic cylinders, balanced against one another. In the new design, a water-filled cylinder is paired instead with an air-filled cylinder that acts as a constant-force air-spring, providing the necessary preload force and allowing the joint to move in both directions with only half as many bulky hydraulic lines.

The robot built to demonstrate the hydrostatic drive system has two arms, each with four degrees of freedom

“The technology has enabled us to build robot arms that are light, fast, and dexterous,” says Whitney. “They have an incredible life-like nature, offering a combination of small mass, high speed, and precise motion not seen before.”

Robots powered using the hybrid technology are ideal for interacting with people in a life-like way. When operated remotely, the low friction and lack of play allow the drive system to transmit forces accurately to the operator, providing them with a remote sense of touch.

The US researchers are presenting a paper on on the new transmission system, and the humanoid robot they built with it, at an IEEE Conference on Robotics and Automation in Sweden this month.

Disney Research is a network of research laboratories that support the Walt Disney Company. Its aim is to pursue scientific and technological innovation to advance the company’s media and entertainment activities.

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