Japanese robot Kengoro "sweats" during exercise

Humanoid robots are a lot like humans. Not only externally, but also on the principle of work. For example, when our muscles are actively working under physical exertion, they heat up. Therefore, the body urgently needs to cool them. How to do it? Mammals traditionally use a passive cooling system for the surface of the body, emitting a liquid that evaporates from the surface (sweat).

Exactly according to this principle, mechanical systems are cooled in the new humanoid robot Kengoro , which was developed in the laboratory of robotics JSK at the University of Tokyo.

As is well known, during the phase transition of a substance from a liquid to a gaseous state, some liquid molecules break away from neighboring molecules and fly away. The molecules that fly away have a higher kinetic energy, and the average energy of the remaining molecules becomes smaller. In other words, the liquid on the surface cools - and thereby cools the surface.
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This is how the cooling system of the human body and the Kengoro robot works.

In a robot, the release of coolant is easier than in humans. In mammals, this is a complex system of skin glands.


The type and location of the sweat gland in humans

And the Kengoro robot has mechanical devices located on the frame next to the electric motors (in the photo, the engine with the wires connected is located at the bottom of the structure). Mechanical glands of the robot release fluid through the frame to the surface, cooling the metal directly next to the engine.



The two-layer porous frame passes liquid to a surface. It is made of aluminum by laser sintering technology. Probably, the technology of direct laser sintering (DMLS), rather than selective, is used. The process uses fiber lasers with a power of about 200 watts or more. Powder material is fed into the working chamber in an amount necessary for applying one layer. A special roller aligns the fed material into an even layer and removes excess material, after which the laser head sintering fresh powder particles between themselves and with the previous layer according to the contours defined by the digital model in the STL format. Print resolution is about 20 microns. After the first layer, the next sintering begins, and so on.


Porous Aluminum for Kengoro Frame

In a report at a scientific conference, the authors described the process of manufacturing parts from aluminum and a porous structure that prevents liquid leakage, and also gave the results of material testing for durability and efficiency of the cooling system (unfortunately, the report has not yet been published in the public domain).

Japanese engineers found this method of thermoregulation quite acceptable. Tests have shown that it is three times more efficient than conventional air cooling, and significantly better than water cooling, in which water circulates in a closed loop. True, the "sweating" is still inferior in efficiency to traditional radiators with active cooling.

A special cooling system can significantly improve the performance of robots in some conditions. For example, during intensive work in the heat. You can recall how well water-cooled SCHAFT performed at the DARPA Robotics Challenge Trials robot competition in a hot desert when some other robots suffered glitches and falls.

Thanks to the cooling of the motors, the Kengoro robot is capable of vigorous movements in a configuration with a low gear ratio of the drive reducer. For example, it can be wrung out from the floor for 11 minutes in a row without failure of the motors due to overheating.



The Kengoro robot, 1.7 meters tall and weighing 56 kg, is designed on the basis of the musculoskeletal system, which also mimics the structure of the human body. To do this, the design of the car had to include as many as 108 engines. Plus numerous gears and printed circuit boards with electronics. Without cooling here is not enough.

The Kengoro presentation was held at the IEEE / RSJ International Conference on Intelligent Robots and Systems Robotic Conference ( IROS 2016 ), which takes place October 9-14 in South Korea.

The authors invented the cooling system, which mimics the human body, in several scientific articles and conference reports. For example, "Human Mimetic Musculoskeletal Humanoid Kengoro for Real World Physical Interactive Actions" (2016 JSME Conference on Robotics and Mechatronics, 2A1-13a2, 2016), "2016 IEEE / RSJ International Conference on Intelligent Robots and Systems, paper WeH2.5 ).

Kengoro is the first robot in the world, the frame of which is used not only as a supporting framework for rigidity, but also for auxiliary tasks: transportation of fluid and thermoregulation. At the same time it performs well and its main function.

On the JSK website, you can find information about several interesting humanoid robots designed in the laboratory. For example, the robot Keshiro with an even more advanced musculoskeletal system than the Kengoro.


Robot keshiro

It seems that if there appear humanoid robots somewhere, practically indistinguishable from people, then it will be Japan.