Three-Legged Dogs Teach Robots New Tricks

Charles Q. Choi

Date: 30 June 2010 Time: 12:10 PM ET

Analyzing how three-legged dogs run could help inventors design and develop robots that can adapt to "injuries," researchers now report.

Scientists have made great strides in walking robots over the decades, but significant questions remain about how they would perform in the real world. To help prepare droids for life outside the lab where the unexpected might happen, biologist Martin Gross at the University of Jena in Germany and his colleagues wanted to see how nature solved problems in locomotion, such as the loss of limbs.

Gross chose man's best friend to study largely because they are relatively easy to handle. In addition, he noted that "my brother has four dogs, and one of them is a three-legged dog that had a hind leg amputated because of cancer, and he's still the fastest of the four."

The scientists used a set of 10 high-speed infrared cameras to analyze how dogs that lost either a front or back leg ran on treadmills for two minutes. Reflective markers placed on their skins allowed the researchers to follow the movements of separate parts of the body. They next compared these motions with those of normal four-legged dogs.

"Sometimes dogs jumped from the treadmill, but mostly there was no problem," Gross said.

The investigators found the canines adopted different coping strategies depending on which limb was lost. Specifically, the loss of a front leg proved harder for dogs to deal with.

If a front leg was missing, the remaining limbs apparently had to go through careful adaptations to coordinate with each other. In contrast, with missing hind-limbs, the scientists discovered the front legs continued to act as they would normally in a four-legged dog, showing little or no compensation strategies. The researchers suspect the reason for this difference is due to the greater amount of weight dogs place on their front legs, as well as the fact that the front legs are used for braking, while the hind limbs are used for propulsion.

"Once you know how walking with a missing limb works in dogs, this could help in the programming of robots when it happens to them," Gross said.

The researchers only worked with two dogs who each lost a front leg and two dogs who each lost a back leg, which they found by asking dog lovers on the Internet — three-legged dogs proved hard to find in Germany, Gross explained. They next hope to recruit more three-legged dogs for study to confirm their findings, perhaps by looking at veterinary schools.

In the future, the scientists will also examine how locomotion responds to changes in a wide variety of animals, including humans.

The scientists detailed their findings on July 1 at the Society for Experimental Biology Annual Meeting in Prague.