The Pneupard is a creation of researchers Andre Rosendo and Shogo Nakatsu, under the supervision of Kenichi Narioka and Professor Koh Hosoda at Osaka University's Graduate School of Information Science and Technology. The team has worked extensively with pneumatic artificial muscles in the past. We've previously covered their biped Athlete, and shared a video of their adorable infant robot Pneuborn.
Pneumatic artificial muscles may be made from a rubber tube sheathed in nylon, but they contract much like the real thing when filled with air. They can pack a lot of power in short bursts and are also highly flexible and impact-resistant, giving them a lifelike quality that is often missing in robots powered by electric motors. The muscle contractions, when combined with limbs that accurately replicate the length, forces, and range of motion of a real cat, naturally generate a lifelike movement.
Rosendo, the project leader, explains that, in the current prototype, each hind limb has eight active muscles, and the fore limbs, which are still under construction, will have six muscles. "The spine will also have muscles, performing flexion and extension," he says. "The main idea of this project is to create a biomimetic platform, where we can replicate feline structure to better understand how they can excel in so many different areas in locomotion. After grasping their secret, it would be possible to apply that knowledge to future robots."
You can see the Pneupard's hind legs walking on a treadmill in the video below. Rosendo notes that the researchers haven't pre-programmed the muscles by hand; the muscles actually activate based on EMG signals recorded from a cat walking on a treadmill.
The only sensors used by the robot are force sensors in each foot. "The walking is robust enough to withstand random disturbances, including asymmetry between the right and left caused by the artificial muscle construction method," Rosendo says. "We are compelled to believe that the musculoskeletal structure found in animals is 'intelligent' enough to compensate for disturbances without requiring a sophisticated control method."
For the time being the robot walks with a stilted nervousness, but in the future the team will attach the spine and attempt other gait patterns. They're optimistic, but they're not trying to compete with Boston Dynamics' Cheetah for the world's fastest legged robot—at least, not yet—but their work could pave the way to lighter, less costly robots in the coming years.