Monday, September 25, 2023

This fingertip for robots uses magnets to ‘feel’ things

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Imagine, if you will, the domestic robot of the future. He picks up clutter from the floor, sweeps and does the dishes. And he has to do it Perfectly: If the robot has an error rate of only 1 percent, it will drop one in a hundred dishes. Totally unacceptable. In no time at all, your floor would be covered in shards and the robot would get stuck in a sad and vicious feedback loop, dropping dishes and sweeping them and dropping more dishes, endlessly.

To avoid this domestic nightmare, engineers will need to give robots a keen sense of touch. And for that, the machines will need the fingertips, maybe like this one recently described in the newspaper Scientific robotics. It feels in a decidedly unhuman way, feeling the subtle changes in the magnetic field of the finger, and it could one day make super-sensitive prosthetics and robots that don’t mutilate dishes (or people) because ‘they can’t control their hold.

You, a human being, can feel pressures and textures at your fingertips, thanks to specialized sensory cells in the skin called mechanoreceptors. These, along with the nervous system as a whole, translate mechanical information from the environment into signals your brain can understand such as the perception of “touch”. Combined with thermoreceptors (which sense temperature) and nociceptors (which sense pain), you are able to manipulate the world around you without harming yourself.

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We need robots to do the same, only we want them to avoid hurting themselves and we. A robot can, for example, be put to work to help the elderly, lifting them and lifting them out of bed. “With tactile feedback, it would be much safer for the home robot to interact with people,” says computer scientist Youcan Yan of the University of Hong Kong and the City University of Hong Kong, lead author of the new article. describing the system. “And the robot can do much more difficult tasks than it could before, like skillful gripping and handling.”

It is simply not possible, however, to try to replicate the extremely complicated human system of touch – so Yan’s team sort of replica. The “skin” of their robotic finger is made of a flexible magnetic film, which generates a magnetic field inside the device. The supporting “bone” of the finger is a printed circuit board, which is studded with sensors that monitor the magnetic field. If you poke, for example, a pencil eraser in the tip of your finger, the magnetic skin depresses and the magnetic field of the finger subtly changes, which the sensors analyze to determine where the eraser makes contact. If you hit those fingers on a humanoid robot, the machine would be able to locate where its fingers came in contact with an object, improving its grip.

Video: Yan et al., Sci. Robot. 6, eabc8801 (2021)

In the GIF above you can see how sensitive the team design is: when the object is dragged on the fingertip, the system not only detects where it is touching, but also shape of the rounded object. It can even read the smallest details of braille, as you can see below.

Video: Yan et al., Sci. Robot. 6, eabc8801 (2021)

The robotic fingertip also picks up the sliding – known to nerds as shear force – of the object it is holding. Imagine lightly grabbing a water bottle while filling it. As the bottle gets heavier, gravity tries to push it out of your hand. When you feel that happening, you tighten your grip, obviously. But it’s not so obvious to robots that they should do the same.


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