Hybrid Hydrostatic Transmission Enables Robots with Human-Like Grace and Precision

Hydrostatic Transmission Combines Hydraulic/Pneumatic Lines

A new kind of hydrostatic transmission which combines hydraulic as well as pneumatic lines can precisely as well as safely drive robot arms, providing them with the delicacy essential to pick an egg without breaking it. This communication does not have any friction or play providing great precision for jobs like threading a sewing needle. The hybrid transmission had made it possible to split the number of bulky hydraulic lines which a complete hydraulic system requires. Robotic limbs could thus be lighter and smaller according to John P. Whitney, assistant professor of mechanical and industrial engineering at North-eastern University, who is leading the development of the transmission and also an associate research scientist at Disney Research.

Whitney together with his colleagues from Disney Research, the Catholic University of America and Carnegie Mellon University would be reporting on the new transmission as well as the upper body humanoid robot, built with it at the IEEE Conference on Robotics and Automation, ICRA 2016, on May 17 in Stockholm, Sweden. Co-author Jessica Hodgins, vice-president at Disney Research and a professor of robotics at the Carnegie Mellon had stated that `the communication provides the robot with incredibly smooth and fast motion as well as enabling life-like interaction with people and the handling of delicate objects.

Robot Remotely Controlled by Human Operator

She adds that presently, the robot is remotely controlled by human operator though the same level of mechanical performance, once the motions are automated would be expected. Whitney states that the robot joint would normally have two hydraulic cylinders, which are balanced against each other. However in the new design, the researchers have paired each water-filled cylinder instead with air-filled cylinder.

The pneumatic cylinder tends to assist as a constant force air-spring offering the required preload force enabling the joint to move in both directions with half the number of bulky hydraulic lines. The new transmission was used by the researchers to build a simple humanoid robot having two arms with stereo cameras placed in the head, streaming their video signal to an operator wearing a head mounted display. The arms have been coupled to a similar control figure, which is hidden behind a wall to permit the robot to be used for human-robot communication study.

Combination of Small Mass/High Speed/Accurate Motion

Whitney has mentioned that this technology has enabled them to build robot arms which are light, fast and dexterous and that they have an incredible life-like nature, providing a combination of small mass, high speed together with accurate motion not envisage earlier.

Together with Whitney and Hodgins, the research team had also included John Mars of Disney Research, who had developed the camera and head-mounted display system as well as Tianyao Chen, research assistant at The Catholic University of America, who had designed the robot arms at intern at Disney Research.

Robots utilising this technology are suitable for naturally accommodating and life-like interaction with people. On tele-operation, the low friction and the lack of play enables the transmission to devotedly transmit contact forces to the operator, offering a high reliability remote sense of touch.