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Tag: flight

  • Flying robot leaps upwards and then takes to the air like a bird

    Flying robot leaps upwards and then takes to the air like a bird

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    A robot that can jump into flight like a bird could eliminate the need for runways for small fixed-winged drones.

    Birds use the powerful explosive force generated by their legs to leap into the air and start flying, but building a robot that can withstand the strong acceleration and forces involved in doing that has proved difficult.

    Now, Won Dong Shin at the Swiss Federal Technology Institute of Lausanne (EPFL) and his colleagues have built a flying propellered robot called RAVEN that can walk, hop and jump into the air to start flying, with legs that work like a bird’s.

    “Fixed-wing vehicles, like airplanes, always require a runway or a launcher, which is not found everywhere. It really requires designated infrastructure to make an airplane take off,” says Shin. “But if you see a bird, they just walk around, jump and take off. For them, it’s quite easy. They don’t need any external assistance.”

    Unlike real birds’ legs, which have joints at the hip, knee and ankle, RAVEN’s legs have just two joints, at the hip and knee, that are powered by motors. There is also a spring in each foot that can store and release elastic energy. Using fewer components meant that Shin and his team could keep RAVEN to a weight of around 600 grams, similar to that of a crow.

    In indoor tests, RAVEN could jump almost half a metre into the air and at 2.4 metres per second – which is a similar speed to birds of the same size – at which point a propeller takes over. Being able to launch upwards from anywhere could make RAVEN useful in disaster relief missions where regular fixed-wing drones can’t land or take off, says Shin. First, however, the team will need to develop RAVEN’s ability to land safely, he says.

    “We have seen quite a lot of work on flying robots that land on perches, but not a lot of people have focused on take off with legs,” says Raphael Zufferey, also at EPFL, who wasn’t involved with the work. “I think we’ll see the two fields – landing, or perching, and take off – come together in single platforms, where we’re able to have these robots fly, detect a branch, land on it, recover, do a mission and then take off.”

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  • Robotic pigeon reveals how birds fly without a vertical tail fin

    Robotic pigeon reveals how birds fly without a vertical tail fin

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    A pigeon-inspired robot has solved the mystery of how birds fly without the vertical tail fins that human-designed aircraft rely on. Its makers say the prototype could eventually lead to passenger aircraft with less drag, reducing fuel consumption.

    Tail fins, also known as vertical stabilisers, allow aircraft to turn from side to side and help avoid changing direction unintentionally. Some military planes, such as the Northrop B-2 Spirit, are designed without a tail fin because it makes them less visible to radar. Instead, they use flaps that create extra drag on just one side when needed, but this is an inefficient solution.

    Birds have no vertical fin and also don’t seem to deliberately create asymmetric drag. David Lentink at the University of Groningen in the Netherlands and colleagues designed PigeonBot II (pictured below) to investigate how birds stay in control without such a stabiliser.

    PigeonBot II, a robot designed to mimic the flying techniques of birds

    Eric Chang

    The team’s previous model, built in 2020, flew by flapping its wings and changing their shape like a bird, but it still had a traditional aircraft tail. The latest design, which includes 52 real pigeon feathers, has been updated to include a bird-like tail – and test flights have been successful.

    Lentink says the secret to PigeonBot II’s success is in the reflexive tail movements programmed into it, designed to mimic those known to exist in birds. If you hold a pigeon and tilt it from side to side or back and forward, its tail automatically reacts and moves in complex ways, as if to stabilise the animal in flight. This has long been thought to be the key to birds’ stability, but now it has been proven by the robotic replica.

    The researchers programmed a computer to control the nine servomotors in Pigeonbot II to steer the craft using propellers on each wing, but also to automatically twist and fan the tail in response, to create the stability that would normally come from a vertical fin. Lentink says these reflexive movements are so complex that no human could directly fly Pigeonbot II. Instead, the operator issues high level commands to an autopilot, telling it to turn left or right, and a computer on board determines the appropriate control signals.

    After many unsuccessful tests during which the control systems were refined, it was finally able to take off, cruise and land safely.

    “Now we know the recipe of how to fly without a vertical tail. Vertical tails, even for a passenger aircraft, are just a nuisance. It costs weight, which means fuel consumption, but also drag – it’s just unnecessary drag,” says Lentink. “If you just copy our solution [for a large scale aircraft] it will work, for sure. [But] if you want to translate this into something that’s a little bit easier to manufacture, then there needs to be an additional layer of research.”

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