What do robots feel?

Today you tell us what robots feel like.

Yes, and since we humans get a lot of inspiration from making robots, we can first ask ourselves the question about our senses. And there, it’s easy!

Yes, we have 5 senses, sight, hearing, smell, taste and touch

Yes, these are the five historical senses, but we must at least add the sense of balance, which allows us, among other things, to stand still, which is nothing. And there is also this whole thing called proprioception, how we feel about our bodies, hunger, thirst, the condition of muscles, joints, etc. Obviously, all these signals are very useful, and if they are useful to us, then also to robots. However, with nuances: for example, it is not very useful to give a sense of taste to a robot that cannot eat!

Effective way ! And suddenly, how do you give these sensations to a robot?

It’s the same principle for living things, you have to equip it with sensors. For example, the sensation of temperature that we feel when we touch something is provided by thermoreceptors distributed over the skin. These are neurons that convert changes in temperature into a nerve impulse that is transmitted to the brain. Well, in order for the robot to have the same sensations, we will equip it with temperature sensors that will convert the temperature measurement into an electrical signal, which will then be processed by the robot’s processor.

And what are these temperature sensors?

Well, we make use of a property of some materials to obtain a temperature-dependent electrical resistivity. Electrical resistivity is the property that characterizes the ease with which an electric current can flow through a material. If it changes due to temperature, as in rust, then the current changes, so the temperature can be inferred directly.

Did I say in rust? Are temperature sensors made of rust?

Yes, with iron oxide, but it could be from other materials, such as chromium oxide or manganese oxide. So if we continue with the sense of touch, another important sense is the sense of grip, which means when you take an egg, you don’t crush it. Finally, usually!

Ah, this is a pressure story, right?

exactly. And so it’s important for the robot to feel the pressure it’s putting on the body. Another physical property of certain materials can be exploited for this purpose, which is the piezoelectric effect. When you press on these materials, they generate an electric current, so, again, the electric current received by the robot’s processor makes it possible to know what pressure is being exerted on the sensor.

The piezoelectric effect, that means something to me. Not used in gas lighters?

Yes, the little batteryless gas lighters that spark when the handle is depressed, it’s the exact same principle, except you have to push hard enough to create a spark of about 1,000 volts.

What kind of material has this property?

Oh, there are many. The most widely used are PZT, lead titano-zirconite, and therefore oxides containing titanium, zirconium and lead. There are of course dozens of other sensors, and if you’re interested, Thursday and Friday I’ll be on stage at the Science in Books Festival, in Villeneuve-D’Ascq, to ​​show some of them. Admission is free, and I will post the details on ramenetascience.fr as usual.