Three-Legged Dogs: The EU’s Lokomorph project aims to design and develop efficient robots that can adapt to unpredictable situations – and even keep moving when they lose a leg. Martin Grubb and his colleagues looked to both humans and monkeys for ideas, but Grubb’s ultimate motivation came from a question from his brother.
The dog, which had only three legs (and only one eye), was significantly faster than the other square puppies. “He leaves the other dogs behind with four legs,” says Grubb. “I wanted to measure with three-legged dogs because we thought there should be a difference in the work of the legs. There should be a difference when the front or hind leg is missing.”
Grab a reflective marker on the back, knees, and elbow joints of German Shepherd-sized dogs that have lost a limb. The dogs ran on a treadmill with 10 high-speed infrared cameras that emitted light at 240 Hz. The markers reflected the light, and the cameras captured it. “We recorded them, and we got a 3D speed for each marker, and from that data, we calculated different things,” says Grubb. “I started calculating the joint and segment kinematics between the amputations of the front and hind legs, finding the difference between the two, as well as the difference compared to quadruple dogs.”
Researchers have found that dogs use the front or forelegs to support themselves – about 60 percent of their body weight – as well as to balance and break and move their hind legs forward. Depending on which organ is missing, they have to be compensated in different ways. If the dog’s hind leg was missing, “they run as if there is no problem,” says Grubb. “The front legs rotate left, right, left, right. But the rest of the hind legs keep jumping all the time.” But running like this is easier than running with a missing forehead. In this case, the rest of the limbs have to coordinate with each other in order to move properly in a process called gate compensation. Dogs also have to reach a certain speed to move. “They can’t really walk slowly,” says Grubb. “They need a certain speed to move. It’s like a motorcycle – you push the bike forward without a driver and it falls when it’s too slow and when it’s too fast. So it can go many meters without a rider and it’s still stable. ” The owners of the dogs interviewed by the researchers confirmed that it was more difficult for dogs with missing front limbs to walk than for dogs with missing front limbs.
Grob and his team unveiled their findings at the annual meeting of the Society for Experimental Biology in Prague. For now, this information is for research purposes only. Scientists will create four-shaped robots with removable legs and adjustable gait. But it’s not hard to imagine how the research could be applied in the real world – robots equipped with IEDs that can shuttle supplies on roads and still deliver them to their destination, even if none of them Don’t be a member. “We still need some time to measure something else to validate our results; right now it’s just to implement and test different things,” says Grubb. “But I think it’s moving in that direction.”