Thursday 31 October 2013

The Art of Flying Your Very Own Drone

Drones are coming to American skies—not just for surveillance or security work, but also for hobbyists. If you want to pilot your own drone, learn the ABCs of UAVs.


Drones have gained a reputation for hunting terrorists and spying on both foreigners and Americans alike. So it's easy to overlook the fact that these hovering, loitering aircraft have quite a following in the hobbyist world as well. To the people who build and fly them recreationally, modern unmanned aerial vehicles (the terms drone and UAV are pretty much interchangeable) are just a technological advancement of the radio-controlled planes and helicopters that amateurs have been flying for years. The Federal Aviation Administration is still struggling to work out the rules for operating UAVs commercially, but for private use, the agency's regulations are remarkably lenient ("Drone Skies," September)—no license is required, and so long as you keep your drone below 400 feet and don't do anything dangerous over densely populated areas, you're free to fly around as you please.

The ABCs of UAVs
 

The ABCs of UAVs


Like many hobbyist toys, drones have a sliding scale of sophistication and cost. The more you spend, the more a drone can do, and the more a drone can do, the harder it is to learn to fly reliably. Drones come in two flavors: fixed-wing aircraft that operate like airplanes, and multicopters that take off vertically and can hover like helicopters. You can build a drone yourself with kit parts from online merchants such as HobbyKing, 3D Robotics, DJI, or Team BlackSheep, or you can do as I did, and pay a little extra to have one of these manufacturers build it for you. There are also several open-source movements designing flight-control and autonomous-flight software for UAVs, including OpenPilot, APM:Copter, and APM:Plane—although not all software works on all hardware.

Large RC planes and helicopters are typically powered by combustion engines and can be difficult and (as the death of an RC hobbiest in Brooklyn, N.Y., this August demonstrates) sometimes dangerous to fly. But a new breed of small and accessible aircraft uses digitally controlled electric motors and high-discharge, rechargeable, lithium-polymer batteries. These are not your average cellphone batteries. Li-Po batteries are powerful and highly volatile, have specialized connectors, must be charged carefully, and have a vocabulary all their own (see "Anatomy of a Battery"). Most importantly, many hobbyist drone aircraft don't come with a battery—which can throw your weekend plans in the ice bath when you excitedly open the box of your first drone, only to find you've got another online order to place before the fun times begin.

Rotary ClubOver a four-month period I learned how to fly three multicopters: a super-simple $300 Parrot AR.Drone 2.0, a $680 DJI Phantom, and a tricked-out, six-rotor $1300 3D Robotics Y6. Multicopters have anywhere from three to eight rotors, are highly maneuverable, and can hover and fly in virtually any direction. These are good starter drones, because they are generally quite controllable and won't disappear over the horizon in a hurry, the way fixed-wing craft tend to do.

But as I found out, multicopter flying is not without its challenges. Things can sometimes go haywire faster than you can react. Plus, piloting one can be a mind-bending exercise in relative positioning. Multicopters are symmetrical, so it's not always obvious which way your drone is "facing." Remote control usually involves either a radio-control unit with dual analog sticks and a dizzying array of switches and buttons (many of which do nothing), or, in the case of the Parrot AR.Drone, an iOS or Android smartphone or tablet with onscreen virtual controls. Regardless, operation can get a little complicated. When your drone flies behind you and you turn around to face it, the directional controls are now the reverse of what they were when it was in front of you—likewise, if you swivel your drone to face a new direction without reorienting your own body, the drone moves sideways relative to you. For this reason, I suggest keeping your first flights low and close by, and that you find a wide, open area to practice in—I used a local dog park. Also, purchase a few extra propellers, because you're going to crash your drone. And that's okay, because repairing your drone is part of the hobby.

In terms of accessibility, the Parrot AR.Drone 2.0 is the newbie's top choice. It is affordable, durable, comes with a battery and an onboard camera, and is controlled via a smartphone. You can even fly it indoors—it comes with a removable hull that protects the rotors from bumps into walls, pets, and people. Takeoff and landing are accomplished with a single button. The AR.Drone has a sonar sensor that keeps it a fixed distance from the ground, and its 720p camera records a video to your tablet or phone as it flies.

I had fun flying it, and my nerdy little toy impressed my nerdy friends. But the limitations surfaced quickly. The standard battery for the model I tested was rated for 1000 milliampere-hours—good for a paltry 12 minutes of air time. The company now sells a 1500-mAhr battery for longer flight times. Also, since the AR.Drone is controlled via Wi-Fi, it is constrained in its range to about 165 feet from the controller. There's plenty of fun to be had within that range, but more sophisticated choppers put it to shame.

Lithium-polymer batteries for radio-controlled vehicles are chemically similar to the batteries in cellphones, but the voltage, power density, and discharge rates are considerably higher. Read the specs of your aircraft to match the cable connector and voltage of your battery and find the minimum milliamp-hour and discharge rates. Also, to prevent fire or battery damage, you'll need to use a balance charger to maintain voltage across the battery's cells.

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