Many quadrupedal robots can handle uneven or sloping terrain well, but only if the ground beneath them is relatively stable. When you factor in a slippery or muddy environment, four-legged machines can quickly malfunction or fail completely. But one engineering team believes they have found a solution by simulating animals often found in swampy habitats. According to a study published in Bio-inspiration and biomimetics by researchers at Estonia’s Tallinn University of Technology (TalTech), dog bots could soon take over the signals of giant moose.
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“[M]Most robots do not have access to a wide range of very important terrestrial environments, including wetlands, marshes, coastal marshes, estuaries and fields, which are abundant in nature,” explains TalTech professor and biorobotics team leader Maarja Kruusmaa. in an accompanying statement on January 2.
However, ungulates (animals with cloven hooves such as cattle and elk) are evolutionarily equipped to deal with these often difficult situations. After conducting physical experiments observing real elk feet, researchers discovered that cloven hooves are the key to maneuvering through mud and similarly boggy terrain. This is due to the ability of cloven hooves to both spread and contract with each footstep. The exposed contact area of each toe increases and decreases as it steps in and out of muddy ground, helping a moose avoid sinking too far into the mud. But more important are the suction properties of the cloven hoof.
“We discovered that a moose’s hoof behaves much like a suction cup, like how you manage to stick your fingernail under the surface and break the suction,” says Simon Godon, PhD candidate in biorobotics and co-author of the research.
Godon also compared the physical properties of mud to wet bathroom tiles, because they stick to your feet after you step out of the shower. But unlike humans, a moose’s moving hooves can better break surface tension and prevent it from getting stuck in the mud.
Following their moose tests, researchers then designed silicone slippers for a four-legged robot. According to the results of their lab analysis, the ungulate-inspired booties reduced sinking depth by about 46 percent and reduced suction by about the same amount. The accessories also reduced the machine’s running energy costs by as much as 70 percent.
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From there, engineers took one of their own moose dog bots for a walk through the Estonian forests. Further measurements indicated a reduction of more than 38 percent in mechanical transport costs, as well as a speed improvement of 55 percent. Furthermore, the team wrote in their study that they found “no downside to the cloven-hoof-inspired design on hard surfaces.”
“[This] suggests that redesigning the feet of quadrupedal robots improves their overall versatility and efficiency on natural terrains,” they concluded.
These simple silicone modifications could potentially allow future four-legged robots to access previously impossible environments to aid in land surveys, security and rescue efforts.
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