A robot with human-like grace and precision

Teleoperated system can thread a needle, pick up an egg
May 11, 2016

A hybrid hydrostatic transmission and human-safe haptic telepresence robot (credit: Disney Research)

A human-safe lifelike telepresence robot with the delicacy and precision needed to pick up an egg without breaking it or thread a sewing needle has been developed by researchers at Disney Research, the Catholic University of America, and Carnegie Mellon University.

The secret: a hydrostatic transmission that precisely drives robot arms, offering extreme precision with almost no friction or play.

The hybrid transmission design also makes it possible to halve the number of bulky hydraulic lines that a fully hydraulic system would require and allows for making its robotic limbs lighter and smaller, said John P. Whitney, an assistant professor of mechanical and industrial engineering at Northeastern University, who led the development of the transmission while an associate research scientist at Disney Research.

Whitney said a robot joint normally would have two hydraulic cylinders, balanced against each other. But in this latest design, the researchers paired each water-filled cylinder with an air-filled cylinder instead. The pneumatic cylinder serves as a constant force air-spring, providing the necessary preload force and allowing the joint to move in both directions with only half the number of bulky hydraulic lines.

Lifelike interaction with people

The researchers used the new transmission to build a simple humanoid robot with two arms, with stereo cameras mounted in the head, streaming their video signal to an operator wearing a head-mounted display. The arms are coupled to an identical control figure to enable the robot to be used for human-robot interaction research.

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

Robots using this technology are ideally suited for naturally compliant and lifelike interaction with people. When tele-operated, the low friction and lack of play allow the transmission to faithfully transmit contact forces to the operator, providing a high-fidelity remote sense of touch.

Whitney and colleagues will report on the new transmission and the upper body humanoid robot they built with it at the IEEE Conference on Robotics and Automation, ICRA 2016, May 17 in Stockholm, Sweden.

Disney Research | A Hybrid Hydrostatic Transmission and Human Safe Haptic Telepresence Robot

Abstract of A Hybrid Hydrostatic Transmission and Human-Safe Haptic Telepresence Robot

We present a new type of hydrostatic transmission that uses a hybrid air-water configuration, analogous to N+1 cable-tendon transmissions, using N hydraulic lines and 1 pneumatic line for a system with N degrees of freedom (DOFs). The common air-filled line preloads all DOFs in the system, allowing bidirectional operation of every joint. This configuration achieves the high stiffness of a water-filled transmission with half the number of bulky hydraulic lines. We implemented this transmission using pairs of rolling-diaphragm cylinders to form rotary hydraulic actuators, with a new design achieving a 600-percent increase in specific work density per cycle. These actuators were used to build a humanoid robot with two 4-DOF arms, connected via the hydrostatic transmission to an identical master. Stereo cameras mounted on a 2-DOF servo-controlled neck stream live video to the operator’s head-mounted display, which in turn sends the real-time attitude of the operator’s head to the neck servos in the robot. The operator is visually immersed in the robot’s physical workspace, and through the bilateral coupling of the low-impedance hydrostatic transmission, directly feels interaction forces between the robot and external environment. We qualitatively assessed the performance of this system for remote object manipulation and use as a platform to safely study physical human-robot interaction.