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When we use our muscles, they produce heat as a byproduct. When we use them a lot, we need to actively cool them, which is why we sweat. By sweating, we pump water out of our bodies, and as that water evaporates, it cools us down. Robots, especially dynamic robots like humanoids that place near-constant high torque demands on their motors, generate enough heat that it regularly becomes a major constraint on their performance. One of the reasons that SCHAFT did so well at the DRC Trials, for example, was their fancy liquid-cooled motors that could put out lots of torque over an extended period of time without overheating.

Engineers solve this heat-generating problem in most mechanical systems by using fans, heat sinks, and radiators, which means that you’ve got all of this dedicated cooling infrastructure that takes up space and adds mass. At the IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS) this week, Japanese researchers presented a novel idea of how to cool humanoid robots in a much more efficient way: Design them to be able to sweat water straight out of their bones.

The researchers, from the University of Tokyo’s JSK Lab led by Professor Masayuki Inaba, were trying to figure out how to add a cooling system to their 1.7-meter tall, 56-kilogram musculoskeletal humanoid named Kengoro (who joins Kojiro and Kenshiro as part of the JSK robot family). Kengoro is already stuffed to the brim with structural components, circuit boards, gears, and 108 motors (!), and there was simply no room to add active water cooling with tubes and a radiator and fans. The researchers started looking at how they could make better use of Kengoro’s existing components, and they came up with the idea of using the robot’s skeletal structure (its metal frame) as a coolant-delivery system.

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