Quadruped Robots Can Reproduce the Gait of Walking Cats

Researchers from Osaka University have developed a quadruped robot capable of reproducing the neuromuscular dynamics of animals, including the gait of walking cats using a reflex circuit. The steady gaits of four-legged animals were thought to be controlled by the nervous systems in their brains and spinal marrow, but it turns out that a steady reflex circuit enables our furry friends to walk without issue. The team began investigating the locomotion of cats by reproducing their motor control using simulations with quadruped robots.

Most academic institutions prohibit experimentation on animals, so the engineers were decided to utilize quadruped robots, which were outfitted with back-drivable legs to reproduce the flexibility of felines and a series of torque-controllable motors to mimic their muscle characteristics. Along with those simulations, the robots allowed researchers to zero in on a reflex circuit that produced nearly the same leg trajectories and gaits used by cats.

The circuit pattern, termed reciprocal excitatory reflex between hip and knee extensors, let the robots generate steady walking motions via reproducing the reciprocal circuit in each leg. When the circuit was turned off, the robot's gait became unstable and no longer functioned correctly.

During the experimentation phase, the team noticed that when the mutual excitatory circuit was stimulated, it generated a phenomenon known as "prolongation of the stance phase," which suggests that the circuit is a critical component of a cat's gait while walking in a steady motion. Not only will their findings serve to design quadruped robots that can walk in a steady motion, it will also help serve as a robotic replacements' biologists can use as a tool over real cats to study motion.