Advances in chip fabrication have made it possible to put accelerometers and gyroscopes directly on silicon chips, so you can have an entire inertial sensing platform on a single chip. It used to be that an IMU cost thousands of dollars and was a huge piece of machinery with many moving parts, now it’s under $100 and the size of a credit card.
Advances in miniature low-power high-speed microcontrollers have made it possible to embed a computer capable of taking the data from the IMU, GPS, and other sensors and make minute changes to the speed of the propellers many times a second, with a micro controller that costs $10 and is the size of a postage stamp.
Advances in lithium-polymer batteries that make it possible for a battery powered helicopter to have a flight time of more than a few minutes. This is huge - a drone powered by lead-acid or nicad batteries would be too heavy and/or have too short of a flying time to be useful, and the modern multi-propeller drone really needs to be electric powered to be able to control the speed of each propeller precisely enough. You could theoretically do it with a gas engine and a complex system of clutches, variable speed drives, or variable-pitch propellers, but then you’re adding a lot of mechanical complexity and cost.
And everyone has a smart phone now (except me). So anyone who is interested can see where they are flying; unlike back in the '70s when you had to have eye contact with your camera-equipped radio controlled airplane.
Without putting a specific date on it, helicopter drones work much, much better than they did say 15 years ago, because the technology (sensors, small computers, more easily controlled motors and the software to tie it together) to make self-stabilizing small helicopters has been developed and gotten to consumer type products.
20 years ago, you could buy a radio-controlled helicopter, but you basically needed to be a trained helicopter pilot with freakish reflexes to keep it from crashing immediately.
Now, a quad-copter that you buy from Radio Shack has sensors and computers that keep it upright and balanced all by itself. You just need to tell it which way to go and it figures out itself how to run its rotors and flight controls.
[ETA: Curse you AndrewL and your freakish quick-typing skills!]
Another thing on the technology side is that small cheap HD cameras that can be carried by them (and stream back live footage sometimes) are widely available. With old RC aircraft, you’d usually just fly them around a model airstrip out in the boonies somewhere, but with the cameras a big part of the appeal is flying around getting footage of cool stuff which includes places where there’s a lot of people.
I do also think the switch from calling them RC aircraft to calling them “drones” has heightened some of the concern about them in people’s minds by causing people to draw parallels between them and their larger military brethren.
There’s more to your comment than you might realize: most of the technologies mentioned by AndrewL were pioneered as compact consumer electronic components for use in smartphones. GPS, accelerometers, micro cameras, powerful computer-on-a-chip systems, super-energy-dense batteries.
A modern drone has much the same electronics as a smartphone, just distributed and programmed differently in a different kind of device.
A consumer [del]R/C quadcopter[/del] drone might have a GoPro camera on it that sends live video to a smart phone mounted on the control box the pilot is using, so you have a pilot’s eye view.
In the '70s (and probably earlier), flying [del]drones[/del] radio-controlled airplanes equipped with a camera was a popular hobby for more advanced R/C flyers. But there was no provision for ‘seeing out of the cockpit’. You stood on the ground and directed the airplane by looking from outside of it. You’d have to estimate when to trigger the (still) camera.
It really is astonishing how much cost-driving power there is from popular consumer products. Drones aren’t the only beneficiaries of low-cost sensors, displays etc. from the cell phone industry–VR is another example.
I don’t think that’s what made drones popular though. Most hobbyist/consumer drones don’t even have this capability.
Anyway, am I correct in thinking that modern drones have not just gyros, but also downward-looking cameras or accelerometers that allow it to hover in one spot without constant correction from the operator? This seems to be the biggest difference between old-fashioned RC helicopters (which required a lot of training just to hover) and modern drones.
The SO frequently tells me she can’t read my mind.
Back in the '80s I wanted an R/C helicopter that I could put a super-8 camera on. But helicopters were extremely expensive, and good super-8 cameras were too heavy. (I had – still have, in fact – an Elmo 1000S. Great lens, but pretty darned heavy for super-8.) If I had a smart phone, I’d be very tempted to get a GoPro-equipped quadcopter.
I think the FAA has made some rulings, but I haven’t looked them up. As far as I’m concerned, ‘What is a drone?’ is an open question. I don’t think the ability to hover is a criterion.
Are radio-controlled airplanes drones? Or do they have to have cameras? If so, does that make the camera-equipped R/C airplanes from 30 or 40 years ago ‘drones’? Is a ‘drone’ equipped with a transmitting camera so that the flyer can have a pilot’s eye view? What’s the difference between a ‘drone’ and a regular R/C airplane that just happens to have a transmitting camera? Is the difference in how it’s used? Whether a recording is made? What a third party thinks? ISTM that the definition is a bit fuzzy, and that people deciding the definition are a bit reactionary instead of objective.
Gyroscopes and accelerometers for stability, magnetometers for true direction reference (because gyros drift), GPS for coarse position and waypoint following, and some of them have optical flow cameras which look downward and detect motion relative to the ground.
You can, of course, now buy true helicopters that are self-stabilized and much easier to learn to fly than those of 20 years ago.
But a helicopter is fundamentally a very complex mechanism, whereas a quadcopter is really dead simple (4 moving parts). Yes, it needs a sophisticated control system, but that’s just software (well, firmware) on a microcontroller that can be had for under a dollar.
Barometers, too. It might be surprising but a barometer gives much better relative accuracy for altitude than a GPS (combining the two together gives even better results). Some units also use ultrasonic sensors for near-ground-level maneuvering.
The flight controller in one of my “drones” was developed from the IMU used on a Wii controller, my first tricopter used a home made flight controller that I put together using a microcontroller and three of-the-shelf gyroscopes normally used on R/C airplanes.
The main impetus now, IMO, is progress in software and/or firmware, rather than the electronics themselves. Now one doesn’t need to actually program and calibrate the flight controller, it comes as is from the factory and it is advanced enough that even an idiot can fly one of this things… of course that introduces a small problem.
When I first started hearing the word, it referred to a semi-autonomous unmanned aircraft. That is, an aircraft where an onboard computer would do most of the flying, and on-the-ground operators would just give it high-level commands.
It’s only within the last year or two I’ve noticed the usage has drifted to any sort of unmanned aircraft, including that require constant control (i.e. RC helicopters).