Soon, robots that move gracefully like humans

Disney researchers have developed a new system that will help robotic arms to be light enough to move swiftly and gracefully, yet with precise control.
The transmission consists of antagonist pairs of rolling diaphragm cylinders - similar to traditional hydraulic cylinders, but sealed with a rubber diaphragm instead of sliding seals and valves.
The result is a system that can efficiently transmit power with little friction. Yet it is also "backdriveable," capable of absorbing energy, as well as transmitting it.
The latter characteristic allows engineers to design limbs with "give," an important feature as designers contemplate new applications in the home, at work, or in entertainment venues that enable soft interactions between people and robots.

"We've combined the best elements of a hydraulic system with the best elements of an electric motor system," said Peter Whitney, an associate research scientist at Disney Research Pittsburgh.
The transmission allows robot limbs to be light, strong and graceful, he said, while driving them with easily controlled, low-friction motors.

The motors, which normally would add significant weight to the limbs, can be mounted on the robot body instead.
The system transmits force so efficiently that Whitney and a Disney Research Pittsburgh lab associate, Tianyao Chen, found they could build an entirely passive "puppet" system, moving one robot arm by manipulating a second robot arm linked to it with the transmission.

The system is notably sensitive to tactile feedback from the puppet arm. One possible application of a system made of non-ferrous material would be as a surgical robot compatible with use in a magnetic resonance imaging (MRI) device, Whitney said.
Hydraulic systems often are used to actuate robots whose limbs need to be light and to move fluidly.
But conventional hydraulics use a system of valves, which only transmit power and are unable to absorb power from the environment.
The passive fluid transmission developed at Disney uses pairs of rolling diaphragm cylinders - so named because the rubber diaphragm rolls back upon itself between the piston and the cylinder walls - connected by fluid-filled lines.

Each drive line is completely sealed, with a rolling diaphragm cylinder at each end, much like the master cylinder and slave cylinder of the brakes on a car.