The art of compliant robotics

The art of compliant robotics
by Robert Schreiber
Berlin, Germany (SPX) Feb 28, 2025

As human-robot interaction becomes increasingly common, ensuring robots can flexibly adapt to their environment is essential for both efficiency and safety. The German Aerospace Center (DLR) has emerged as a leader in the development of collaborative robots (cobots) that work closely with humans. Traditionally, cobots have been designed to behave like mechanical springs, returning to their original position after being displaced. However, researchers at DLR have now introduced a novel elasto-plastic approach that allows robots to remain in their new position rather than reverting, enhancing their ability to work dynamically with humans.

Michael Panzirsch, a researcher at the DLR Institute of Robotics and Mechatronics, explains, "The new elasto-plastic approach makes human-robot collaboration much easier, as the robot can now clearly distinguish between its own programmed movements and external influences from the environment. The robot should only react plastically to the influence of the environment, meaning it should move out of the way and remain in that spot."

This innovation also simplifies the way robots interact with objects that have defined movement constraints. For example, opening a hinged door requires a specific rotational motion. With the new controller, a robot can intuitively follow this movement without requiring an explicit model, much like a person instinctively adjusting their grip when opening a door with their eyes closed.

Applications in Space and Caregiving

DLR has long been at the forefront of developing sensitive robotic systems. The elasto-plastic controller was successfully tested in space in January 2024 as part of the Surface Avatar project. This initiative explores how multiple robotic avatars can collaborate effectively on planetary surfaces. "For the first time, our controller enabled cooperation between a rover from the European Space Agency's Human Robot Interaction Laboratory and a humanoid DLR robot controlled by an astronaut on the International Space Station," explains Neal Y. Lii, Scientific Director of the Surface Avatar programme.

Beyond space applications, this advanced technology is proving beneficial in the caregiving sector. Within the SMiLE project (Services for People with Living Conditions and Restrictions), DLR researchers, including Jorn Vogel, are working on robotic assistance systems to support individuals with physical limitations. The elasto-plastic controller facilitates human-robot cooperation without requiring complex sensor systems, allowing robots to seamlessly assume assistive roles in everyday life.

Advancements in compliant robotics are shaping a future where robots integrate more naturally into human environments, improving safety and functionality. By enhancing their ability to interpret and adapt to human needs, these technologies pave the way for more intuitive and effective robotic assistance.

Research Report:Virtual elasto-plastic robot compliance to active environments