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The anatomy of a (hobby) drone

You've seen them in the media (relentlessly) and you've probably also seen them advertised in print or online.

I'm talking about those little radio controlled "drones" which have three or more propellers and can carry cameras to the most otherwise inaccessible places with ease.

No area of miniature aviation has advanced at the rate these craft have in recent times and it's all down to some clever electronics and software.

They have anywhere between three and eight small brushless (AC) motors made using very powerful rare-earth magnets for maximum efficiency and smallest size/weight and are powered by lithium polymer batteries capable of energy densities that were only dreamed of a few short years ago.

However, the real magic lies under the covers.

Deep within the bowels of these craft is a magnificent piece of computing hardware called the flight controller (FC).

This board (and it usually is just a single printed circuit board) contains a raft of sensors and a microcontroller. Some of the simpler FCs have 8-bit processors such as those made by Atmel while the more sophisticated units are more likely to sport 32 bit ARM-based processors with in-built hardware math processors.

Of course all this processing power is useless without some kind of sensor input -- and that's where the MEMs gyros and accelerometers come in.

No doubt you have marveled at how these drones can sit, motionless, suspended in the air as if by an invisible wire. That's all down to the tiny solid-state gyroscopes and accelerometers that detect even the smallest deviation from the chosen position.

The gyros report on any angular (rotation) movement and feed that information to the FC which responds by calculating and outputting a corrective signal to the motors.

Of course gyros, even today's modern solid state devices, have a tendency to drift over time. In the days of the old mechanical gyros, with their spinning disks, bearing friction was a primary contributor to this drift but today it's temperature and other factors.

To help compensate for the drift and to provide an "auto leveling" capability, the accelerometers report the exact angle of the craft. If the craft is tipped to the right, once again the sensors will report this fact to the CPU which will output corrective signals.

Of course all of this happens in the blink of an eye -- far faster than any human pilot could respond -- and that's pretty important because trying to fly one of these craft without all this hi-tech assistance would be nigh on impossible.

The more advanced hobby drones also have a GPS receiver and an electronic compass onboard.

The addition of these devices allows the drone to accurately establish its actual position in space and "hold" that position if required, even in the face of a modest wind that would otherwise blow it far away. Similarly, by recording the start position at the beginning of every flight, the GPS-enabled FC can automatically return the craft to that point (and land it) if something goes wrong with the radio control link or the pilot loses sight of it and doesn't know which way to fly it back.

The fact that you can now buy all this hi-techery for a three figure sum beggars belief -- when you consider that just a decade or two ago it was the stuff of science fiction and beyond the reach of even the military forces of the richest nations.

Of course now that all this power and sophistication is available "off the shelf" to anyone who cares to purchase it, it's only natural that the law-makers, regulators and fun-police are rapidly grasping for ways to "control" its use.

I love it when the pace of technological advancement outstrips the ability of the bureaucrats to keep up.

So if you're considering getting yourself a bit of real hi-tech for Christmas, drop me a line and I'll gladly help out with the selection process.

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