Intelligent antenna skin for more precise communication in robotics

Especially in the manufacturing industry, cobots are playing an increasingly important role. When developing human-machine interactions, worker safety is of paramount importance. This is where the EU project FITNESS (Flexible IntelligenT NEarfield Sensing Skins) comes in. The project aims to optimise communication and interaction between humans and machines. Researchers want to achieve this with intelligent antenna solutions in the form of innovative electromagnetic metamaterial surfaces with integrated electronics (an intelligent antenna skin).

Flexible, stretchable antennas made of flexible metamaterials, capable of emitting surface waves, are expected to be able to scan their near-surface environment much more effectively than conventional antennas. As a result, they can improve both human safety and the robots' own performance. Six other partners from industry and research are collaborating with Fraunhofer FHR on the project. The French National Centre for Scientific Research (CNRS), eV-Technologies, the Technical University Hamburg (TUHH), the Katholieke Universiteit Leuven (UCLouvain), the Faculty of Electrical Engineering and Computer Science at the University of Zagreb and L-up. The project is coordinated by UCLouvain, in Belgium, and funded by the European Union.

Metasurface antennas are flat antennas integrated into film-like substrates that conform to the contours of the robot. Their flat structure allows these antennas to bend and stretch and wrap around the robot like a skin. Alternatively, and depending on the application, they can be placed on the robot arm alone, for example. Thus, they were called "smart skins" (intelligent antenna skin). "What makes our future smart antenna skin special is that it can scan the nearby environment and detect motion, while also being adept at radio-based communication with the base station on the shop floor," says Andrej Konforta, 3D-Print HF Systems group manager at Fraunhofer FHR. "So far, no other solution like this exists on the market."

The researchers' goal is for the new, innovative intelligent antenna skin to enable beamforming . That is a process used to electronically control the radiation properties of an antenna. As a result, the adjustable electromagnetic beam is always directed in the direction of the base station. This provides a stronger and more stable signal and a longer range of the robot. Until now, beamforming has mostly been supported by so-called "phased arrays". "In a phased array, many antennas are connected as a group. The phase of each individual antenna element is variable. This makes it possible to influence the direction of the array," Konforta explains.

The technology has so far been used mainly in military contexts. In conventional antenna arrays, the antenna elements and their electronics are densely packed together. This results in high costs, a lot of waste heat and high susceptibility to errors. In contrast, an intelligent antenna skin can be designed with significantly streamlined electronics. And this without losing the properties of the conventional configuration. The new concept can help save costs and achieve smaller, more compact structures. "With the metamaterial surfaces, we are pursuing a new design concept that enables very small geometries. Geometries with a high degree of freedom in the design of the emitted fields. But also for the best possible extraction of signalling signals," says Konforta.

Antennas are usually integrated into rigid microwave substrates. There are also materials that can stretch and thus offer a high degree of flexibility. However, losses are too high with these flexible substrates. They do not perform optimally in the high frequency range. This means that the conventional substrates available on the market are not optimally suited for the transmission of high-frequency signals. Based on the findings of Fraunhofer FHR, TUHH is developing new substrates as part of the FITNESS project.

The Institute of Applied Polymer Physics (IAPP) uses a polymer blend and polymers with integrated ceramic particles to synthesise stretchable materials that may be suitable for high frequencies. These materials will then be tested by Fraunhofer FHR as the project progresses. An existing measurement setup will also be optimised based on the initial results and extended for other frequency bands. Researchers are also developing software for the setup. At the same time, the project partners are investigating how deformations in the stretchable surfaces affect their properties in the near and far field. Long-term plans call for self-calibrating antennas for meta-surfaces. The aim is for them to autonomously recognise their curvature and shape to ensure optimal signal reception and avoid communication problems.

Besides robotics in manufacturing environments, the project partners also believe that medical engineering and robotics are potential application areas. Metasurface antennas in the form of an intelligent antenna housing could help devices such as assistant robots recognise gestures more accurately and communicate better with humans. There are also potential applications for this technology in personal protective equipment for firefighting and in spacesuits.

Source: Fraunhofer FHR

Photo: Investigation of a polymer (Photo: Fraunhofer FHR / Alexander Balas)

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