Hybrid transmission promises extremely precise movement of robot arms

System could be used for applications such as remote surgery or the handling of nuclear materials

A hybrid hydrostatic transmission that combines hydraulic and pneumatic lines promises to provide “unparalleled” precision of movement for robot arms.

The system could be used for applications such as remote surgery or the handling of nuclear materials.

A robot joint traditionally has two hydraulic cylinders, balanced against each other. Instead, John P Whitney, lead author of the research and assistant professor of mechanical and industrial engineering at Northeastern University in Boston, paired each water-filled cylinder with an air-filled cylinder. The pneumatic cylinder serves as a constant force air-spring, providing the necessary preload force to move a joint in both directions, while halving the number of bulky hydraulic lines. Robot limbs can be made lighter and smaller as a result, said Whitney.

The transmission has “almost no friction”, meaning robot arms can undertake extremely delicate tasks such as threading a needle.

To test the system, the researchers used the transmission to build a simple humanoid robot with two arms and stereo cameras mounted in the head, streaming their video signal to an operator wearing a head-mounted display. The arms were coupled to an identical control figure behind a wall connected via the hydrostatic transmission. This operator used the control figure to move the robot arms, and feel interaction forces between the robot and the external environment.

Jessica Hodgins, vice-president at Disney Research, which collaborated on the project, said: “The transmission provides our robot with incredibly smooth and fast motion, while also allowing the handling of delicate objects.”

Whitney is now working to develop an MRI-compatible remote manipulation system using the transmission.