Scientists at ETH Zurich and the Max Planck Institute for Intelligent Systems (MPI-IS) have created a robotic leg that uses artificial muscles instead of conventional motors. This innovation, detailed in a study published in Nature Communications, marks a departure from traditional robotic designs and brings machines one step closer to mimicking the mobility and adaptability of living creatures.
The research team, led by Robert Katzschmann at ETH Zurich and Christoph Keplinger at MPI-IS, developed the leg as part of the Max Planck ETH Center for Learning Systems (CLS) partnership. Thomas Buchner and Toshihiko Fukushima, doctoral students on the project, are co-first authors of the publication.
The robotic leg employs electro-hydraulic actuators, dubbed HASELs, which function similarly to human muscles. These actuators consist of oil-filled plastic bags with electrodes on either side. When voltage is applied, the electrodes attract each other due to static electricity, pushing the oil to one side and shortening the bag. This mechanism allows for paired muscle movements, mimicking the extensor and flexor muscles in living organisms.
One of the key advantages of this design is its energy efficiency. Compared to conventional motor-driven legs, the muscle-powered leg consumes significantly less energy, especially when maintaining a static position. "On the infrared image, it's easy to see that the motorised leg consumes much more energy if, say, it has to hold a bent position," Buchner explains.
The leg's design also allows for agile movement and adaptability to different terrains. It can perform high jumps and react to obstacles without complex sensors. Fukushima notes, "Adapting to the terrain is a key aspect. When a person lands after jumping into the air, they don't have to think in advance about whether they should bend their knees at a 90-degree or a 70-degree angle."
While the technology is still in its early stages, the researchers see great potential for its application in various fields. Katzschmann suggests that while it may not be suitable for heavy machinery, it could excel in applications requiring highly customised movements, such as grippers for delicate objects.
Looking to the future, Katzschmann envisions combining this technology to create more complex robots. "If we combine the robotic leg in a quadruped robot or a humanoid robot with two legs, maybe one day, when it is battery-powered, we can deploy it as a rescue robot," he says.