Sensitive artificial skin allows robots to feel their bodies and their surroundings, which is particularly important for close contact with humans. The artificial skin developed by Prof. Gordon Cheng and his team at the Technical University of Munich (TUM) is made up of hexagonal cells about the size of a two-euro coin. Each is equipped with a microprocessor and sensors that measure touch, acceleration, proximity and temperature. Such artificial skin enables robots to perceive their environment in much more detail and with greater sensitivity, which not only helps them to move safely, but also ensures that the machines are safer when interacting with people and can actively avoid accidents.

The biggest obstacle to the development of robotic skin has so far been computing capacity. Human skin has around five million receptors. If you want to permanently evaluate the data from sensors in artificial skin, the limits quickly become clear. Previous systems were already working at full capacity with data from a few hundred sensors. To solve this problem, Gordon Cheng and his team have chosen a neuroengineering approach. Instead of permanently monitoring skin cells, they use what is known as an event-based system, which reduces the computing effort by up to 90 %. The trick: individual cells only pass on information from their sensors when measured values change. Our nervous system works in a similar way. For example, we feel a hat the moment we put it on, but we quickly get used to it. As there is no need to constantly pay attention to the hat, we only become aware of it again when it blows off our head. This allows our nervous system to concentrate on new impressions to which the body has to react.

Safety even with close physical contact

The event-based approach has made it possible for the first time to equip a human-sized autonomous robot that is not dependent on external calculations with artificial skin. The H-1 robot is equipped with a total of 1,260 cells and accordingly more than 13,000 sensors on its upper body, arms, legs and even on the soles of its feet, which provide a new 'body feeling'. For example, the skin on the soles of the feet helps H-1 to react to unevenness in the ground and even balance on one leg.

Through the skin, H-1 is able to hug a person safely. This is less trivial than it sounds: robots can exert forces that would seriously injure humans. When hugging, a robot has contact with a person at many different points and must very quickly calculate the correct movements and the appropriate amount of force from this complex information. "This may be less important in industry, but in areas such as care, robots need to be designed for very close contact with people," explains Gordon Cheng.

The robotic skin system is also robust and variable. As the skin is made up of cells rather than a single piece, it is still functional even if individual cells fail. "Our system is designed to work smoothly and quickly with all types of robots," says Gordon Cheng. "We are now working on designing smaller skin cells that can be produced in larger quantities in the future."