Unlike most helicopters, hovering drones use multiple rotors. Many drones are based on a design called a quadcopter, which employs four rotors on arms set 90 degrees to each other. Each rotor is directly driven by an electric motor. By turning two of the rotors clockwise and two anticlockwise it counters the twisting effects of torque produced by a single-rotor helicopter (without a tailrotor to push against the torque, a helicopter would spin hopelessly round and round). Moreover, whereas a helicopter needs to vary the pitch of its blades (the angle at which they attack the air) in order to manoeuvre, the multiple rotors on a drone have a fixed pitch. The drone instead manoeuvres by independently changing the speed of one or more of its rotors under computer control. As this set-up requires fewer and less complex moving parts than a helicopter, it makes drones simpler, cheaper to build and maintain, and potentially more reliable.
Ascending Technologies, a German dronemaker bought earlier this year by Intel, a giant chipmaker, gave e-volo a hand with the electronic systems that control them (the craft contains more than 100 microcontrollers). The greater number of rotors provides both more efficiency in lift and higher levels of redundancy in the event of a failure. And, just in case of a big emergency, there is also a parachute—one that will gently carry to the ground the entire drone with its passengers remaining in their seats.
The VC200 gained permission to fly from German authorities earlier this year. It has an all-in weight of 450kg and, in its present form, a flight duration of 30 minutes. After completing a series of flight tests the VC200 should be fully certified by 2017 in a category of aircraft known as an “ultralight”. The company have taken this route because it will get the VC200 into the air sooner and allow valuable flight experience to be built up while discussions continue about creating a possible new class of aircraft for passenger drones.
A rather different approach is being taken by Malloy Aeronautics, a British company. It is developing a drone you can sit on like a motorbike. The Hoverbike is now in its third incarnation, having begun with two rotors, one at the front and another at the rear, but progressing to four. However, it does not look like a typical quadcopter. Instead, it has a pair of rotors at the front and another pair at the back. Each is slightly offset and partially overlapping. So far, the company is carrying out test flights of the craft as an unmanned drone in order to develop its software and systems fully before fitting a seat and handlebars to produce a passenger version. Malloy has, though, flown a one-third scale remote-controlled prototype with a dummy pilot (see picture below).
The idea behind the Hoverbike is to produce a rugged and simple air vehicle which, because it is oblong rather than square, would be more easily transportable in vehicles or other aircraft, and would be able to operate and land in difficult surroundings, such as on the side of a mountain, says Grant Stapleton, a Malloy director. The company is also working with America’s Army Research Laboratory on the Hoverbike concept. It would have basic controls, such as a throttle grip for the right hand—as on a motorbike—with the handlebars used to provide other commands.
The above is from an article in The Economist magazine. Read the full article here.