2 Legged – High-Power Robot Legs Can Jump – 11018

University of Tokyo’s JSK Lab researchers have developed a high-torque, high-speed robotic leg for based on a novel electrical actuation system.

For some reason, roboticists seem to enjoy testing their creations by kicking them, punching them,shoving them, and even striking them with baseball bats and heavy pendulums. All in the name of science, of course. It wasn’t different with this Japanese pair of robot legs, which as you can see from the photo above, is about to get kicked in the gut.

If we want robots that can do chores around the house, care for the elderly, or (if you’re a DARPA program manager) drive trucks and crash through walls, then we need robots with actuators that are both fast and strong. The problem is actuators based on electrical motors can only deliver a limited amount of power, and the alternative, hydraulics, requires bulky pumps and can be difficult to control.

Junichi Urata and his colleagues at the University of Tokyo’s JSK Lab, led by Professor Masayuki Inaba, are working on a possible solution. They’ve developed a high-torque, high-speed robotic leg based on a novel electrical actuation system. Their robot uses high-voltage and high-current liquid-cooled motor drivers that get their power from a 13.5-farad capacitor system. Why a capacitor? Because it can supply lots of current very fast and reliably, something that batteries are not good at. The researchers modified an existing HRP3L, developed by Kawada Industries, to create their robot, which they call HRP3L-JSK

Thanks to the capacitor-powered motor drivers, the robot’s Maxon 200-watt brushless motors (modified to be liquid-cooled) can achieve instantaneous speeds of over 1000 degrees per second and 350 Nm of torque on the robot’s knee joint. This capability allows the 53-kg robot to react to disturbances (in its case, kicks, knee strikes, and other abuse from researchers) and even jump 44 centimeters off the ground (though the landing part will need work).

The robot relies on a new balance control system that detects disturbances and computes 170 foot placement possibilities in 1 millisecond, choosing the best candidate to keep the robot from falling. The new method is a collaboration between the JSK team and researchers from Japan’s National Institute of Advanced Industrial Science and Technology (AIST).

Urata, who recently received a PhD degree for his HRP3L-JSK work, now has his eyes on the DARPA Robotics Challenge. He’s starting to organize a team to add manipulation arms and more sensors to the HRP3L-JSK lower-body. Will their fully electrical robot be able to perform all the tasks DARPA has conceived for the challenge? DARPA, for its part, has chosen a Boston Dynamics humanoid powered by hydraulic systems as the official hardware platform (to be used by teams that don’t want, or can’t afford, to develop their own robot). As more teams join the competition, it will be interesting to see what kind of actuation system they choose. Electrical or hydraulics: which will prevail?





Prof. Dr. Masayuki Inaba

Masayuki Inaba is a Professor in the Information Science and Technology, Graduate School at the University of Tokyo. He graduated from the department of Mechanical Engineering at the University of Tokyo in 1981, and received M.S. and Ph.D. degrees from the graduate school of Information Engineering at The University of Tokyo in 1983 and 1986 respectively. He was appointed as a lecturer in the Department of Mechanical Engineering at The University of Tokyo in 1986, an associate professor in 1989, and a professor in the Department of Mechano-Informatics in 2000, and also a professor in new Department of Creative Informatics from 2005. He is directing the Robotics Lab, JSK at The University of Tokyo.

His research interests include key technologies of robotic systems and software architectures to advance robotics research. His research projects have included hand-eye coordination in rope handling, vision-based robotic server system, remote-brained robot approach, whole-body behaviors in humanoids, robot sensor suit with electrically conductive fabric, flexible spined humanoid and developmental JSK mother projects with the remote-brained system environment, life-size assistive humanoids, musculoskeletal spined humanoid series, whole-body soft sensor tissues, IRT home assitance with personal mobility, open-source robotics middlewares, high speed-and-powered legs for the next generation, on the budget from MEXT and MITI, such as ongoing Grant-in-Aid Scientific Research(S) entitled “Developmental Approach in Configuring Body and Behavior of Life-size Humanoids with Whole-body Passivity and Attention Inductivity”.

He received several awards including outstanding

-Paper Awards in 1987, 1998 and 1999 from the Robotics Society of Japan, JIRA Awards in 1994,
-ROBOMECH Awards in 1994 and 1996 from the division of Robotics and Mechatronics of Japan Society of Mechanical Engineers,
-and Best Paper Awards of International Conference on Humanoids in 2000 and 2006 with JSK Robotics Lab members.

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