It was a tasty little concept introduced last year at CES2017. While not actually called a “Dronut”, the donut-shaped Cleo drone prototype was basically a ducted fan with propellors completely encased inside a duct, making it safe to fly inside and near people. You can even grab it out of the air with your hand, with no concerns for injury, and put it straight into your pocket – while the simple, elegant design also boasts a camera and battery, it is less than 10cm in diameter.
Developed by Omar Eleryan and Simon Czarnota of Cleo Robotics and first gaining attention in late 2016, the motivation behind the donut-like design was safety. As Eleryan told Metro News, “Drones need to be safer, smaller, and easier to use.” So they set to making what is essentially a “point and shoot” drone without a lot of the features that most consumers aren’t concerned with.
But that’s not all that is special about this little drone. It makes a departure from the traditional quadcopter propellor design, instead stacking two blades, one on top of the other. A smartphone app acts as the drone’s controller – but how does it steer it? It’s a question originally asked by Evan Ackerman at the IEEE Robotics and Automation Society. Back at CES2017, Eleryan wasn’t going to give the game away.
Other drones that focus on the aspect of propellor safety, such as the Flyability Elios or the Hover Camera Passport, do not come in such a compact size, nor do they excel in battery life (the Cleo by the way can fly around 12-15 minutes – not bad for such a little drone). Ducted fan drones commonly use four fans in a quad formation, and there is a lot of discussion about the efficiency of ducted fans vs propellors. Paul Gelhausen at Avid Aerospace makes the case for ducted fan UAVs, stating, “The design and flight control is more involved than the multi rotor platform, but the noise, safety, payload, precision hover, footprint, robustness, and control advantages make it worth the extra effort.”
A quad fan formation is steered differently to a single stack like the Cleo. A paper published by Osgar John Ohanian of the Virginia Polytechnic Institute in 2011 looked at methods of jet flow control for a single fan UAV. One such configuration described control vanes in addition to the propulsion blades which would create control forces to stabilize and steer the drone.
Cleo however boasts only one twin-blade stack. The technology that allows the Cleo to be steered is still under wraps though. Eleryan told IEEE, “We introduce control surfaces into the airstream to change the direction of the airflow and create a thrust vectoring effect.” Their recently released video shows how maneouverable Cleo is, but exactly how this is done is still not entirely apparent.
While currently still in prototype stage, Cleo expects to be able to take their “dronut” design to the security market within 12 months or so. Consumers however can expect a competitively priced drone by mid next year.
“Initially, we’re going to launch a camera drone,” Eleryan says. “But we think the possibilities for the technology itself go far beyond personal photography.”