Robots are hailed for their intelligence and work efficiency, but excessive heating from prolonged hours of work often affects their performance. To address the heating problem faced by humanoid robots, Japanese researchers have devised an out-of-the-box solution.

Using the analogy of sweating that happens in the human body as a result of continuous activity that cools the heated muscles, researchers at the University of Tokyo's JSK Lab presented a novel method at the IEEE/RSJ International Conference on Intelligent Robots and Systems held in South Korea.

Their cooling solution addresses the heating problem of a musculoskeletal humanoid robot called Kengoro, which stands at 1.7 meters (5.6 feet) tall and weighs 56 kilograms (123.5 pounds). The Japanese researchers' cooling solution involves tinkering to make the robot "sweat" water straight out of its frame.

This sweating technique also solves the dilemma of space. There is little space to add more cooling systems such as water cooling tubes, radiator and fans to the already loaded robot, which carries components such as circuit boards, gears and 108 motors.

The sweating mechanism also gets easy thanks to Kengoro's laser sintered frame made of aluminum powder that offers low and high permeability areas embedded with micro channels that allow water to pass through.

Thanks to the "aluminum bones," water is transported across the robot with laser sintering serving to hasten the ejection of water through an inner porous layer to the porous regions close to the surface of the frame.

The techniques are explained in the paper "Skeletal Structure with Artificial Perspiration for Cooling by Latent Heat for Musculoskeletal Humanoid Kengoro," presented at IROS 2016.

The lead author is Toyotaka Kozuki and the co-authors included Hirose Toshinori, Kei Okada, Takuma Shirai, Shinsuke Nakashima, Yohei Kakiuchi, Masayuki Inaba and Yuki Asano from the University of Tokyo.

Cost-effective Cooling Solution

The JSK Lab's innovative cooling technique basically involves perspiration that allows deionized water to drip into Kengoro's 108 motors to cool them off through evaporation.

The sweating mechanism also lets the humanoid robot do push-ups for 11 minutes without any overheating. The beauty is that a cup of deionized water is enough for the robot to run efficiently for half a day.

According to experts, the cooling technique is three times better than air cooling and highly efficient than the method of running water through an internal channel. Throwing insight into the innovation, the lead author explained how it works at the frame level of the humanoid robot.

"Usually the frame of a robot is only used to support forces," Kozuki told IEEE Spectrum. "Our concept was adding more functions to the frame, using it to transfer water, release heat, and at the same time support forces."

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