The fastest land animal on Earth, the cheetah, has inspired a number of swift-footed robots. The latest has cropped up at the University of Twente, where doctoral candidate Geert Folkertsma has spent four years developing a scale robotic cheetah that is not only capable of replicating many of the real animal's movements, but in doing so uses only 15 percent more energy than the real thing.

According to Folkertsma, the design of his 30 cm (1 ft)-long robot is based on an extensive study of cheetah videos and digital analysis of their movement. The purpose of this was to produce a robot that is a simulation of the cheetah's skeleton, models, and joints. However, the finished product was not a precise reproduction, but only an approximation that can move like a real cheetah in many ways, but isn't capable of, for example, climbing trees, and uses a simple, lightweight spring mechanism instead of a mechanical paw for greater efficiency.


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A key element in the design is the spine of the robot. In a cheetah, the backbone acts as a spring that stores and releases energy as it bends and extends, allowing the cat to run at 97 km/h (60 mph) with great efficiency and perform prodigious leaps.

"The main difference between existing walking robots and my cheetah robot is therefore the backbone," says Folkertsma. "The trick was to imitate it without complicating matters unnecessarily: instead of vertebrae and intervertebral discs, we worked with a cleverly placed spring which delivers approximately the same effect. Cheetahs are also able to store a lot of energy in their muscles for later use. This, too, is something we have imitated by fitting carefully selected springs in our robot's legs."

The robotic cheetah weighs only 2.5 kg (5.5 lb), which is 20 times lighter than a live cheetah. It's also four times smaller, and Folkertsma says that when the difference is taken into account, the robot uses only 15 percent more energy than the animal version as it moves at about 1 km/h (0.6 mph). This is fast for a small robot and improvements, like more advanced legs, could get it to run at 20 km/h (12 km/h) – a speed equal to that of the cheetah on a quarter-size scale.

But speed isn't the only application of the robotic technology. Folkertsma believes that imitating the cheetah will lead to lighter, less cumbersome walking robots that can move with elegance and efficiency. Such robots would be useful in housekeeping and healthcare, as well as in helping with physical rehabilitation and the development of advanced prostheses.

"As you might expect of the fastest land animal in the world, the cheetah makes very efficient use of its energy," says Folkertsma. "I wanted to create a robot that runs the same way, with the aim of applying this knowledge to the development of new robots. Robots are bound to play an increasingly important part in our daily lives and we therefore have to ensure that they can move effectively in our environment. My robot vacuum cleaner, for example, cannot climb stairs or even cope with thresholds. We therefore need to develop robots that can walk and when it comes to moving around efficiently, there's a lot we can learn from the cheetah."

Folkertsma will present a PhD defense of his work at the University of Twente campus on April 21.

Source: University of Twente