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21 measured their maximum speed at 64.3 mph (103 kph) That was a two- direction average measured using a stopwatch, the Radio Kenya time signal, a Land Rover, a piece of meat and a cheetah. “It was classic derring-do,” Wilson says. “And that was just a pet cheetah, so they must go much faster in the wild when they are really trying, we thought.” Cheetah hunting speeds With more advanced technology, the opportunity came in 2012 to get a better picture of cheetah performance in the wild. “At that point, we were building small GPS trackers and putting them on birds to look at aerodynamic interactions in flocks,” Wilson says. “So we took some bird trackers, built them into more substantial boxes and put them on some wild cheetahs. “We captured 500 hunts in the end, and found that cheetahs hunt at about half maximum speed. We never saw them go as fast as Craig did because – it’s obvious when you think about it – manoeuvrability is highest at low speed,” he notes. “A cheetah at its top speed is generating a lateral acceleration of 13 m/s 2 – which is massive – and it has a turn radius of 65 m. In other words, it could not turn around on a football pitch. Velocity squared hurts, be it a fighter jet or a running animal.” Wilson’s team also looked at the escape space for an impala being chased by a cheetah, which is a maximum-rate turn because it is where the two animals are most evenly matched. “It comes down to the equivalent of a performance envelope in fighter aircraft: the velocity/acceleration envelope it can operate in and hence where it can get to in a given time. In an aircraft it would be measured in seconds, but with a cheetah you break it up by strides, because a stride is an actual break for a running animal in which it can make a manoeuvring decision.” Legged robots Wilson’s first contact with robotics came in the late 1990s with a visit to the MIT Leg Laboratory, where he met Marc Raibert, author of the seminal 1986 book Legged Robots That Balance and founder of Boston Dynamics. Preoccupied with sensors and instrumentation, particularly accelerometers, at a time when an accelerometer cost around £1000, he was impressed by the new technology in use. “I remember visiting MIT and seeing a little Murata MEMS gyroscope and thinking, ‘Wow, what could you do with a gyroscope like that?’ Such things didn’t exist in our realm.” Professor Alan Wilson | In conversation capture Uncrewed Systems Technology | October/November 2022 The Cheetah robot built for DARPA did not equal the speed of the flesh-and-blood animal, and needed an external power source (Courtesy of Boston Dynamics)