Robot programmed to walk, run and gallop


A four-legged robot has been programmed to walk, trot and gallop based on special motion-capture data of horse movement.

The robot, known as Cheetah-Cub, is under development at the Biorobotics Lab at the Swiss Federal Institute of Technology in Lausanne, Switzerland.

The robot, named "cheetah cub".
The robot, named “cheetah cub”.

The robot was programmed to walk based on horse data gathered by researchers at the Italian Institute of Technology (IIT). The IIT team used motion-capture technology which enabled them to break down and analyse the movement of a horse.

The movement pattern was then programmed into the Cheetah-Cub, giving it three gaits – the walk, trot, and gallop.

Movements were also developed to help the robot transition between each gait smoothly.

The work of the researchers has been published in the March 2013 issue of Biological Cybernetics.

The Cheetah-Cub weighs just over 1 kilogram and is about the size of a domestic cat.

Developing walking patterns for robots with legs is usually accomplished using what is known as a Central Pattern Generator, or CPG, which generates a rhythmic leg motion.

Researchers have broken down the CPG into what are known as kinematic Motion Primitives (kMPs), which can also be identified in animal gaits.

The researchers in Italy used data from the motion-capture of a horse to extract kMPs data which could then be used to program the Cheetah-Cub.

Effectively, the kMPs data is programmed as a loop to generate ongoing movement.

Interestingly, the researchers discovered that the differences in the kMPs between the walk, trot and gallop amounted to only 3 per cent.

“A possible interpretation is that the kMPs extracted from walk, trot, and gallop are in fact the same set of kMPs, that together are sufficient to describe the three different gaits,” the researchers said.

The Cheetah-Cub managed to walk at about 1mph and trot at 1.3 mph.

The gallop was not so successful. The researchers put this down to the fact that horses flexed their spine at a gallop – a feat that is currently beyond the Cheetah-Cub.

Because of the Cheetah-Cub’s inability to flex, its robotic feet slipped at a gallop.

The Cheetah-Cub was originally built to move like a cheetah, hence its name.

F.L. Moro, A. Spröwitz, A. Tuleu, M. Vespignani, N.G. Tsagarakis, A.J. Ijspeert, D.G. Caldwell.
Horse-Like Walking, Trotting, and Galloping derived from Kinematic Motion Primitives (kMPs) and their Application to Walk/Trot Transitions in a Compliant Quadruped Robot.
Published in the March 2013 issue of Biological Cybernetics. DOI 10.1007/s00422-013-0551-9

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