Researchers at the University of Tokyo are
taking bio-inspired robots to new heights with
Kenshiro — their new human-like musculoskeletal
robot. They have added more muscles and more
motors to their Kojiro robot from 2010, making
Kenshiro’s underlying structure the closest to a
human's form so far.
Kenshiro mimics the body of the average
Japanese 12 year old male, standing at 158
centimeters tall and weighing 50 kilograms.
Kenshiro’s body mirrors almost all the major
muscles in a human, with 160 pulley-like "muscles"
— 50 in the legs, 76 in the trunk, 12 in the shoulder,
and 22 in the neck. It has the most muscles of any
other bio-inspired humanoid out there.
Why try and mimic the human body? It turns
out that getting a robot’s weight right is a tricky
problem. Yuto Nakanishi, the head of the project,
spoke about the weight problems of Kenzoh,
Kenshiro's tendon-driven upper-body robot
ancestor. Kenzoh was a hearty 45 kg — just for the
upper body. Scaling up, they projected that a full-body Kenzoh could weigh as much as 100 kg.
That was a lot of weight for a relatively small
robot. So, they decided to design a robot with the
same weight ratios of a human. For example, a 55 kg
boy would have about a 5 kg thigh and 2. 5 kg calf.
Kenshiro copies that ratio, with a 4 kg thigh and
2. 76 kg calf. Balance is key.
Weight was one thing, but the researchers also
tried to mimic the muscle torque and joint speeds.
Kenshiro’s total power output is five times greater
than Kojiro’s. Kenshiro can get almost the same
amount of joint torque as a human, with joint
angular speed not quite at human level — at 70-100
degrees per second. It’s a trade-off in weight and
power; bigger and stronger motors are often
Like Kojiro, Kenshiro is actuated by a system of
pulley-like muscles. This time, instead of single point-to-point muscles, they decided to make planar
These flat and wide muscles use only one
motor and are much more stable. All in all, these
motors give Kenshiro 64 degrees of freedom
(except for the hands): 13 in the neck, 13 in each
arm, seven in each leg, and 11 in the spine.
Kenshiro's bone structure is also quite amazing.
Its aluminum bones — including an impressive rib
cage — are sturdier than previous 3D printed
bones (breakage tended to be a problem), and its
knee-joints include imitations of cruciate ligaments
and a floating patella.
Cool tidbits herein provided by www.botjunkie.com, www.robotsnob.com,
www.plasticpals.com, http://www.robots-dreams.com, and other places.
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