UCI study finds why birds do it better

Irvine, Calif., March 17, 2022 – An international team of researchers has demonstrated a novel approach to bipedal robotic locomotion using birds as inspiration. While many robots utilize human-inspired mechanisms for bipedal locomotion, the bipedal locomotion of birds — with a track record going back hundreds of millions of years by way of evolving from dinosaurs — might prove to be a better, more effective form of locomotion for robotics.

The study, titled “BirdBot achieves energy-efficient gait with minimal control using avian-inspired leg clutching,” appears in the journal Science Robotics.

One of the big challenges in robotics is navigating complex environments and moving across unstructured terrain, as it requires a lot of sensing and information. Based on the anatomy and their studies of biomechanics of avian locomotion, the team built a prototype to test a hypothesis that birds do not require active sensory feedback control to run with economical and stable gaits, which could prove beneficial in robotics design.

“We realized there are some anatomical features of bird legs that differ substantially from what you find in humans and appear to allow for what we call intrinsic mechanical stability,” said Monica Daley, Ph.D., senior author and associate professor in UCI’s Department of Ecology and Evolutionary Biology. “The ligaments and tendons of a bird’s lower leg allow passive absorption of impact loads during gait and allow the system to respond to changes in the foot-substrate interaction automatically without active neural control.”

The prototype’s bird-inspired leg mechanisms demonstrated that robots designed in this fashion could achieve economical locomotion with significantly less sensory information when compared to other legged robotics designs.

“We now have a robot that uses gaits that are similar in body motions and energetics as walking and running in birds and humans, with only four actuators in total. Compare that to the many dozens of muscles that are required for human locomotion,” said Daley. “What’s interesting about this device is that it involves a multi-joint tendon linkage, inspired by the anatomy of birds, with a similar spring and multi-articular tendon. The leg can support bodyweight during stance, and as soon as the foot lever is released, there’s an automatic transition into the swing phase, which helps propel the leg forward. In the swing phase, the spring is totally slack so that the bird can swing the leg forward without resistance.”

While the current robot is a prototype, it demonstrates principles that could improve the capabilities of bipedal robots and prosthetics.

The team includes Alexander Badri-Spröwitz, Ph.D., Alborz Aghamaleki Sarvestani, and Metin Sitti, Ph.D., from the Max Planck Institute for Intelligent Systems.

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