Fraunhofer FHR-Newsletter 12/2024

In the manufacturing industry, the professional services sector, and healthcare, the demand for specific physical human-robot interactions is continuously increasing. This requires improvements in comfort and communication between humans and machines. Robots need to be able to anticipate human actions and recognize their intentions. Flexible metamaterials and planar metasurface antennas with highly integrated electronics offer an attractive solution, as they enable precise sensing of the immediate environment. The Fraunhofer Institute for High-Frequency Physics and Radar Technology FHR is developing such surfaces, which will surround a robot like adaptive, intelligent skin, in collaboration with six partners in the EU project FITNESS. Equipped with metasurface antennas, robots are expected to be able to specifically sense their surroundings in the near field and communicate more efficiently with their base station in the far field.

Robots are playing an increasingly significant role in industrial manufacturing. As a result, physical interaction between humans and robots has become a key technology that enhances the efficiency of production processes.

At the heart of all developments in human-machine interaction is the safety of the workforce. The EU project FITNESS (Flexible Intelligently Nearfield Sensing Skins) aims to optimize communication and interaction between humans and machines through intelligent antenna solutions. These are based on novel electromagnetic meta-material surfaces with integrated electronics. The flexible and stretchable metasurface antennas can emit surface waves and are expected to capture the immediate environment significantly better than conventional antennas. This enhances both human safety and the performance of robots. In addition to Fraunhofer FHR, six other partners from industry and research are involved in the project: Centre National de la Recherche Scientifique CNRS, eV-Technologies, Technical University of Hamburg, Université Catholique de Louvain, University of Zagreb Faculty of Electrical Engineering and Computing, and L-up. The Belgian university UCLouvain coordinates the project, which is funded by the European Union under contract number 101098996.

The metasurface antennas are planar, film-integrated antennas that conform to the contour of the robot. Due to their flat design, they can be bent and stretched, functioning like a skin around the robot. Alternatively, depending on the application, they can also be mounted only on the robot arm. These antennas are therefore referred to as "smart skins." “Our future antenna solution is intended to sense both near environments and detect movements while simultaneously enabling wireless communication with the base station in the industrial hall,” explains Andrej Konforta, group leader for 3D Printing HF Systems at Fraunhofer FHR. “Such a solution does not currently exist on the market.”

The innovative antenna solution is expected to enable beamforming – a method for locating sound sources in wave fields – so that the electromagnetic beam is always directed towards the base station, ensuring a stronger and more stable signal and increasing range. Currently, so-called phased arrays support beamforming, where many antennas are grouped together, and the phase of each antenna element is variable, affecting the direction of the grouped antenna. “This technology is predominantly used in the military sector. In conventional grouped antennas, the antenna elements and their electronics are closely arranged, leading to high costs, excessive heat, and high susceptibility to failure. In contrast, the metasurface antennas developed in the project can be realized with significantly less electronics, without losing the advantages of conventional designs. This new concept allows for cost reduction and the development of more compact structures. “The FITNESS meta-material surfaces enable very small geometries with high design flexibility for the emitted fields and the best possible extraction of gesture signals,” says the researcher.

Typically, antennas are integrated into rigid microwave substrates. However, there are also materials that are stretchable and therefore exhibit high flexibility. These flexible substrates, however, have too high losses and do not achieve optimal performance in the high-frequency range, as demonstrated by the measurement technology of Fraunhofer FHR. Therefore, the conventionally available stretchable substrates on the market are not ideal for transmitting high-frequency signals. Based on the results from Fraunhofer FHR, the project partner Technical University of Hamburg (TUHH) is developing new substrates as part of FITNESS. The Institute for Applied Polymer Physics (IAPP) synthesizes stretchable, potentially high-frequency-capable materials by using a mix of polymers and polymer materials with ceramic foreign particles. These will be tested by Fraunhofer FHR throughout the project. Additionally, an existing measurement setup will be optimized to support other frequency bands, and the software for the final setup will be developed. Concurrently, the project partners are investigating how the deformations of the stretchable surfaces affect properties in the near and far fields. In the long term, self-calibrating metasurface antennas are planned, which will autonomously recognize their shape and curvature to ensure optimal signal reception and avoid communication problems.

In addition to robotics in production environments, the project partners also see applications in medical technology and robotics: Here, metasurface antennas as intelligent skin could help devices like assistive robots better recognize gestures and interact more strongly with humans. These technologies could also be applied in firefighters' protective gear or in space suits.