An autonomous drone with wheels can roll along the ground, only flying when needed to clear obstacles, which helps its battery last seven times longer, according to its developers.
Rolling robots are efficient and can travel long distances, but cannot traverse big obstacles, while flying drones can get past large obstructions, but have limited range. Now, and his colleagues at Zhejiang University in Hangzhou, China, have attempted to combine the benefits of both types of machine in what they call terrestrial-aerial bimodal vehicles.
Their drone, which weighs just under a kilogram, has four rotors like a traditional drone along with two large, unpowered wheels. It can use thrust from the rotors to fly or drive along the ground. An onboard stereo camera and tiny computer running control software allow it to autonomously navigate complex courses.
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In tests, the researchers found the drone鈥檚 energy consumption in driving mode was one-seventh that of flying mode. Driving most of the time and only hopping over objects with short flights when needed can hugely increase its range, they say.
Other researchers have attempted similar designs in the past, but Zhang says these were over-complicated machines that incorporated the hardware of a rolling robot and a flying drone, unlike the new design, which simply attaches passive wheels. The former adds cost and weight and makes it more complex to make and control.
鈥淔ancy design means complex structure and dynamics, and it poses challenges to autonomous navigation,鈥� says Zhang. 鈥淔or example, driving a car or even driving a spacecraft is far more complicated than riding a bike.鈥�
But Zhang says controlling a rolling drone remains a tricky proposition because it has different characteristics when rolling or flying, which software needs to understand and plan ahead for. 鈥淚t鈥檚 like you need to drive a car and fly a quadrotor simultaneously,鈥� says Zhang. 鈥淲hen do you fly? When do you drive?鈥� Nevertheless, the drone could be useful in cluttered or dangerous environments, he says.
The team has also experimented with a two-wheeled and two-rotor drone, which is narrower and can fit through smaller gaps, as well as a four-rotor drone that balances on a single castor wheel like those on shopping trolleys, which Zhang says can change direction faster than the original device at the cost of just a slight efficiency drop.
arXiv
