Japanese Kengoro Robot Sweats During Exercise
Humanoid robots are very much like humans. Not only externally, but also according to the principle of work. For example, when our muscles work actively under physical stress, 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, releasing a liquid that evaporates from the surface (sweat).
Exactly by this principle, the cooling of mechanical systems occurs in the new humanoid robot Kengoro , which was developed in the JSK robotics laboratory of the University of Tokyo.
As you know, in the process of the phase transition of a substance from a liquid state to a gaseous state, some liquid molecules detach from neighboring molecules and fly away. The escaped molecules have a higher kinetic energy, and the average energy of the remaining molecules becomes less. In other words, the liquid on the surface cools - and thereby cools the surface.
This is how the cooling system of the human body and the Kengoro robot works.
In a robot, the release of cooling fluid is simpler 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 electric motors (in the photo, the engine with the wires connected is located in the lower part of the structure). Mechanical glands of the robot release fluid through the frame to the surface, cooling the metal directly next to the engine.
A two-layer porous frame allows fluid to pass through to the surface. It is made of aluminum using laser sintering technology. Probably, direct laser sintering (DMLS) technology is used, and not selective. The process uses fiber optic lasers with a power of about 200 watts or more. The powder material is fed into the working chamber in an amount necessary for applying one layer. A special roller aligns the supplied material in an even layer and removes excess material, after which the laser head sinteres the particles of fresh powder between each other and with the previous layer according to the contours defined by the digital model in STL format. Print resolution is about 20 microns. After the first layer, sintering of the next begins and so on.
Porous aluminum for Kengoro frame
In a report at a scientific conference, the authors described the production process of aluminum parts and a porous structure that does not allow fluid leakage, as well as cited the test results of the material for the strength 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 effective than conventional air cooling, and significantly better than water cooling, in which water circulates in a closed loop. True, the “perspiration” is still inferior in effectiveness to traditional radiators with active cooling.
A special cooling system can significantly increase the performance of robots in some conditions. For example, with intensive work in the heat. You can recall how well the water-cooled SCHAFT performed at the DARPA Robotics Challenge Trials in hot desert conditions, when some other robots suffered from glitches in and crashes.
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 gear. For example, it can push up from the floor for 11 consecutive minutes without engine failure due to overheating.
Kengoro robot with a height of 1.7 meters and a weight of 56 kg is designed on the basis of the musculoskeletal system, also mimicking the structure of the human body. To do this, as many as 108 motors had to be included in the design of the machine. Plus numerous gears and circuit boards with electronics. There is no way to do without cooling.
Kengoro's presentation took place at the IEEE / RSJ International Conference on Intelligent Robots and Systems ( IROS 2016 ), which takes place on October 9-14 in South Korea.
The invented cooling system, mimicking the human body, the authors described in several scientific articles and reports at conferences. For example, "Human Mimetic Musculoskeletal Humanoid Kengoro for Real World Physically Interactive Actions" (2016 JSME Conference on Robotics and Mechatronics, 2A1-13a2, 2016), "Skeletal Structure with Artificial Perspiration for Cooling by Latent Heat for Musculoskeletal Humanoid Kengoro" (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 frame for rigidity, but also for auxiliary tasks: fluid transportation and thermoregulation. At the same time, it also performs its main function well.
On the JSK website, you can find information about several more interesting humanoid robots designed in the laboratory. For example, a Keshiro robot with an even more advanced musculoskeletal system than Kengoro.
It seems that if somewhere humanoid robots appear, almost indistinguishable from humans, it will be Japan.