Fascination with technology Intelligent skin makes human-robot interaction safer

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Fraunhofer-Institut für Hochfrequenzphysik und Radartechnik FHR

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In our "Fascination with Technology" section, we present impressive research and development projects to designers every week. Today: intelligent skin for more precise communication and near-field scanning in robotics.

Especially in industrial manufacturing, robots are playing an increasingly important role. Accordingly, the physical interaction between humans and robots has developed into a key technology that helps to make production processes more efficient.

In all developments of human-machine interaction, the safety of the workforce is paramount. This is where the EU project FITNESS (Flexible IntelligenT NEarfield Sensing Skins) comes in, which aims to optimize communication and interaction between humans and machines using intelligent antenna solutions in the form of novel electromagnetic meta-material surfaces with integrated electronics. The flexible and stretchable metasurface antennas, which are suitable for emitting surface waves, should be able to sample the immediate surroundings much better than conventional antennas, thereby increasing human safety and robot performance.

In addition to the Fraunhofer FHR, six other partners from industry and research are involved in the project: Centre National de la Recherche Scientifique CNRS, eV Technologies, Technische Universität Hamburg, Université Catholique de Louvain, University of Zagreb Faculty of Electrical Engineering and Computing and L-up. The Belgian university UCLouvain is coordinating the project, which is funded by the European Union.

Our antenna solution is characterized by the fact that it can both scan the closer environment and detect movement, and at the same time control a radio-based communication with the base station in the industrial hall. The market does not currently offer such a solution.

Andrej Konforta, Fraunhofer FHR

Antenna skin with sensory and communicative functionality

The metasurface antennas are flat antennas integrated into film-like substrates that adapt to the contour of the robot. Due to their flat structure, these antennas can be bent and stretched and laid around the robot like a skin. Alternatively, and depending on the application, they can also be attached only to the robot arm. They are therefore also referred to as "smart skins" or intelligent skin. "Our future antenna solution is characterized by the fact that it can both scan the immediate environment and detect movement, and at the same time master radio-based communication with the base station in the industrial hall," says Andrej Konforta, Group Leader 3D Printing HF Systems at Fraunhofer FHR. "Such a solution is not yet available on the market."

Small geometries with a high degree of freedom

The novel antenna solution is supposed to enable beamforming—a method for locating sound sources in wave fields—so that the adjustable electromagnetic beam always looks at the base station, guaranteeing a stronger, more stable signal and resulting in increased range. So far, so-called phased arrays support beamforming. "In this process, many antennas are interconnected in a group. The phase of each individual antenna element is variable, which allows the viewing direction of the group antenna to be influenced," the researcher explains the technology, which so far has been used predominantly in a military context.

In conventional group antennas, the antenna elements and their electronics are closely placed. The result: high costs, a lot of heat dissipation and high susceptibility to errors. Metasurface antennas, on the other hand, could be built with far less electronics—without losing the properties of the conventional construction method. The new concept allows cost savings and smaller, more compact structures to be realized. "With the meta-material surfaces, we are pursuing a new construction concept that enables very small geometries that allow a high degree of freedom in the design of the radiated fields, as well as the best possible extraction of the gesture signals," says the researcher.

Development of new antenna substrates

Usually, antennas are integrated into rigid microwave substrates. Alternatively, there are materials that can also be stretched and thus have high flexibility. However, these flexible substrates have too high losses, they do not achieve optimal performance in the high-frequency range, as the measurement technology developed by Fraunhofer FHR researchers revealed. Therefore, the conventional substrates available on the market are not optimal for the transmission of high-frequency signals.

Based on the results obtained by Fraunhofer FHR, new substrates are being developed at the project partner Technische Universität Hamburg (TUHH) as part of FITNESS—the Institute for Applied Polymer Physics (IAPP) there synthesizes stretchable and potentially high-frequency suitable materials, relying on a mix of polymers and polymers with ceramic foreign particles. These are tested by Fraunhofer FHR during the course of the project. Also, based on the first results, an existing measurement setup is currently being optimized, expanded for other frequency bands and the software for the final setup is being developed. In parallel, the project partners are investigating how the deformations of the stretchable surfaces affect the properties in the near and far field. In the long term, self-calibrating metasurface antennas are planned, which independently recognize their curvature and shaping in order to ensure optimal signal reception and avoid communication problems.

Medical technology as another field of application

In addition to robotics in the production environment, the project partners also see medical technology and robotics as potential fields of application: Here, metasurface antennas as intelligent skin could help devices such as assistant robots better recognize gestures and interact more with humans. The technology could also be used in the protective equipment of firefighters or in space suits.