

Ask HN: Why did multicopters suddenly take off? - J-dawg

Drones &#x2F; UAVs are developing incredibly quickly, and being used for all kinds of things.<p>One thing they have in common is that they&#x27;re all the quadcopter &#x2F; multicopter type. (I&#x27;m talking specifically about the small to medium sized kind used for filming etc, not big military drones)<p>Given that model helicopters existed for many years before &quot;drones&quot; came along, I&#x27;m curious as to why the multicopter became the dominant design, seemingly over a very short time period. Presumably some technical hurdle was overcome to make this possible? What was stopping it from being invented sooner? And what makes the design superior to a scaled-down version of a full-size helicopter?
======
ChuckMcM
I was looking for the previous discussion on this topic and could not find it,
but to recap my contribution to it;

Multi-copters became possible when several technologies got light enough and
cheap enough.

The first was perhaps 6 and later 9 degrees of freedom MEMS (silicon) sensors
(gyro, acceleration, magnetics). Early helicopter models required too much
work to fly, but these sensors combined with cpus made multicopters 'fly by
wire'

The second was a rechargable and _light_ battery chemistry (Lithium Polymer
batteries) which allow a multicopter to fly for a useful amount of time.

The third was brushless motor controllers which allowed for the creation of
high power, but _light_ , motors that were also efficient.

Some will also add high power SoCs (embedded 32 bit computers of 'cell phone
class') but early multicopters were powered by 8bit controllers so I'm not
sure that this is as important as the other three.

The things that are common to all of them, lightness and energy efficiency,
these made the multicopter _possible_ and as the price has been driven down
with mass production for these parts it has made them easy to obtain for a big
enough market. (and that is a positive feedback loop, the market grows, the
quantity increases, the price goes down, the market grows ...)

~~~
Phlarp
The MEMS sensors, high power SoCs and sophisticated battery chemistry in a
light/cheap form were all (arguably) enabled by the mass production of
smartphones.

Now that multicopters are beginning to ramp up the mass adoption curve and
drive innovations of their own will we see this same kind of technological
cross pollination happen to other fields with what's being created for multis?

The pace of innovation in brushless speed controllers has been exciting to
watch, but I can't think of what other applications there are for brushless
motors that accelerate quicker or can change direction nearly instantly. Lots
of work seems to be happening in the position tracking arena, with everything
from cameras to sonar arrays to lidar being considered and used both
professionally and on the hobbyist scene.

I really want to see one of Googles project tango boxes used as a sensor to do
real time object avoidance on a quad.

~~~
gurkwart
Adressing object avoidance. Intel and AscTec are ahead in the game ;) [1]. But
I agree that this indeed will become more and more prominent and really
interesting in the coming years!

"[...] Someday obstacle avoidance technology in UAVs will be like seatbelts in
cars: You simply don’t start going without it!” [2]

\- Daniel Gurdan, CEO Ascending Technologies GmbH.

[1]
[https://www.youtube.com/watch?v=Us0BqJvsF9k](https://www.youtube.com/watch?v=Us0BqJvsF9k)

[2] [http://www.asctec.de/en/ascending-technologies-and-intel-
col...](http://www.asctec.de/en/ascending-technologies-and-intel-collaborate/)

------
gurkwart
Around 2002 two german guys set the path for today's quadcopters. They built
the X-UFO and developed the X-3D and X-3D-BL sensors [1], which for the first
time enabled amazing control capabilities for the still rather unknown
quadcopters [2]. This led to the first success stories and the market kind of
jumped on the train. Media did it's job and here we are. Technology has
advanced a lot since then [3, 4]. Better and smaller sensors and
microprocessors. More sophisticated materials and design, production and
marketing processes. This surely played a big role as well, now that consumer
market UAVs and flying toys can be produced quite cheaply. Also various open
source projects popped up and nowadays even beginners can build and program
their own quadcopter and PID controller.

As for helicopter vs. quadcopter - The latter is much simpler to fly,
especially with autopilots and control units such as the X-3D or today's
AscTec Trinity. Also safety for consumer products is an issue, where
quadcopters with their embedded propellers have the bonus. And its omni-
directional nature of movement yields more freedom and fun, especially as a
toy.

[1] [http://www.asctec.de/en/ascending-
technologies/company/](http://www.asctec.de/en/ascending-
technologies/company/)

[2]
[https://www.youtube.com/watch?v=Csti6mHZNF4](https://www.youtube.com/watch?v=Csti6mHZNF4)

[3]
[https://www.youtube.com/watch?v=Us0BqJvsF9k](https://www.youtube.com/watch?v=Us0BqJvsF9k)

[4] see ChuckMcM's comment

~~~
weinzierl
One of the AsTec founders (Daniel Gurdan) has an interesting back story.

Playing with explosives in his basement he lost part of his hand. Being an
avid juggler he was sad that he could not juggle clubs anymore.

He built himself an robotic hand which won the first price at the German youth
science competition [1]. He was 16 at the time.

The quadcopter was his follow up project and a main component of that project
was that the copter was controlled with a glove[2].

Referenced articles are in German, but the images are worth a click.

[1] [http://www.jugend-
forscht.de/projektdatenbank/jonglierhandsc...](http://www.jugend-
forscht.de/projektdatenbank/jonglierhandschuh-servotechnische-
fingerprothese/1999/1/7.html)

[2] [http://www.jugend-forscht.de/projektdatenbank/die-ufos-
komme...](http://www.jugend-forscht.de/projektdatenbank/die-ufos-kommen-
selbstregelnde-fliegende-robotikplattform/6/rotor.html)

------
Roboprog
Have you ever flown a (toy) helicopter? They are very non-intuitive. The
torque of the main rotor causes every course change to have side effects that
have to be compensated for.

Change the engine speed (lift), and the tail rotor needs to be adjusted so the
copter does not yaw.

Change the tilt of the rotor blades to lean fore/after or drift to the side,
and the engine needs to be sped up just a little to avoid slight loss of lift,
and the tail rotor needs an ajustment to avoid yaw for the increased torque.

With multiple lifting, fixed, rotors, the electronics adjust the motor speeds
for you to DWIM when you manipulate the sticks.

~~~
abandonliberty
My friend with a helicopter license felt cheated the first time he flew a
plane and discovered how easy it was.

~~~
chubot
I once took a helicopter lesson, and I watched some videos about flying before
hand.

One of the guys said: "A plane wants to fly. A helicopter wants to crash".
This seems true to me: flying a helicopter is a continual act of not crashing.

It makes complete sense to me that a quadcopter is 100x easier to write
software to autonomously fly vs a helicopter design.

~~~
TeMPOraL
There's a popular quote in the pilot community:

"The thing is, helicopters are different from planes. An airplane by it's
nature wants to fly, and if not interfered with too strongly by unusual events
or by a deliberately incompetent pilot, it will fly. A helicopter does not
want to fly. It is maintained in the air by a variety of forces and controls
working in opposition to each other, and if there is any disturbance in this
delicate balance the helicopter stops flying; immediately and disastrously.
There is no such thing as a gliding helicopter.

This is why being a helicopter pilot is so different from being an airplane
pilot, and why in generality, airplane pilots are open, clear-eyed, buoyant
extroverts and helicopter pilots are brooding introspective anticipators of
trouble. They know if something bad has not happened it is about to."

Harry Reasoner, Approach magazine, November 1973

~~~
Phlarp
The pedant in me feels obligated to point out that helicopters can accomplish
unpowered landings using autorotation.

If I had to make a choice about which unpowered craft to be in though-- I'll
take the plane!

~~~
TeMPOraL
Autorotation requires action from a skilled pilot, it doesn't happen
automatically. It's also one-shot maneuver - if you fail it, you're done, and
you can't abort it like you could abort an unpowered plane landing.

~~~
tzs
How do you abort an unpowered plane landing?

~~~
TeMPOraL
You basically answered it yourself upthread - the plane has lots of forward
velocity on approach, which gives the pilot a pretty big window to abort by
gliding away, turning some of this forward velocity into lift.

------
Phlarp
I've been into the hobby (building, flying and racing multicopters) for about
10 months now-- I personally think it was a combination of factors with the
biggest one being the advent of the tiny / cheap gyro and accel sensors mostly
used in smartphones. The catalyzing event for the hobbyist side of things was
the release of the Nintendo Wii-- since the wiimote controllers were a readily
available and relatively cheap source of these components the hobbyist "scene"
really converged around an open source project to hack together active flight
controllers from wii controllers and arduino boards. These flight controllers
are what allows multicopters to hover so effortlessly-- the computer does all
the hard work of balancing motor speeds on the millisecond timescale. (If you
could go back and give one of these boards to the guys at NASA in the 60's
they would have called it cheating.)

Obviously I've painted that with a very broad brush and people with different
opinions will show up to tell me about how I'm wrong and a noob-- but this is
how I see the history in a nutshell. Traditional model RC electric airplane
components were also getting better and cheaper in conjunction with the birth
of $20 flight computers. Faster and more efficient motors running on smaller
better speed controllers, all powered by lithium polymer batteries that not
only have great energy density and discharge capability but have become almost
a commodity product thanks to modern consumer electronics.

------
bingaling
MEMS sensor (gyros/accelerometers) technology developed for smartphones made
cheap multicopter control systems possible.

------
glup
I think small and mid-sized quads have dropped in price / increased in quality
because of the fall in the price for gyroscopes, accelerometers, and ICs that
can do decent sensor fusion. If you have ever broken these parts, you know
that quadcopters are effectively impossible to fly. As for the preference over
helicopters, multicopters all have fixed pitch rotors, which are cheaper.

I think they also benefit from increased mindshare given UAVs in the news.

------
jrsmith1279
I can't speak to why it wasn't invented sooner, but I do think that the
biggest reason that they've taken off (pun?) is that they are much easier to
fly and much more stable than a helicopter. The fact that many of them now
have cameras attached to them that offer professional-quality photos and
videos, along with the ability to get a live feed while in-flight, is
definitely making them more and more popular every day.

~~~
davismwfl
I'd agree with the ability to get images and post them is a huge draw.

But I just spent a few minutes reading some about quadcopters vs even
helicopters and from what I have read everyone so far seems in agreement that
the quadcopters are less stable and less efficient then a helicopter design.
It is the software stabilization that makes flight even possible, but even
then they aren't very stable.

I had always wondered about this, as I have seen model helicopters (and full
sized) maintain a level hover for significant time periods, but I can't ever
recall a nearly still level hover from a quadcopter. From reading it sounds
like that is tough to achieve given that they are constantly adjusting power
to each of 4 motors to maintain flight and without the ability to change pitch
of the blades that is the only option. So while mechanically easier to build
they aren't necessarily more stable.

~~~
Phlarp
>but I can't ever recall a nearly still level hover from a quadcopter.

Seriously? Every one of the DJI products can do this out of the box using just
GPS/accel/gyro/barometer. Newer ones can do it even better by adding in a
camera pointing at the ground that works like an optical mouse. Some really
insane stuff can be done if you throw an active positioning system into the
mix:
[http://www.ted.com/talks/raffaello_d_andrea_the_astounding_a...](http://www.ted.com/talks/raffaello_d_andrea_the_astounding_athletic_power_of_quadcopters?language=en)

~~~
davismwfl
Just saw that, thanks for the link. I stand corrected, I hadn't personally
seen them stay very still in a hover before, maybe it was operator
inexperience.

~~~
Phlarp
If the quad has only an accel and gyro sensor onboard then yes, the stability
will be based primarily on the skill of the pilot and how well the machine is
tuned.

With a GPS and barometer thrown in, position hold should be pretty close to a
still hover unless there is significant wind or unresolved problems with the
power train

~~~
TeMPOraL
I'm surprised that GPS has enough accuracy to do a position hold. Why, then,
my cellphone GPS is accurate only to 5-10 meters?

~~~
Someone
The copter doesn't need to know where it is, just whether it is moving and if
so, how far and in what direction. Because the error in GPS measurements
doesn't vary much in small time frames, that can be done more accurately than
absolute position measurements. See
[http://en.m.wikipedia.org/wiki/Differential_GPS](http://en.m.wikipedia.org/wiki/Differential_GPS).

------
Riegerb
From an aerodynamic efficiency and maneuverability standpoint, a traditional
single rotor helicopter is far superior. However, the operational benefits,
safety, and mechanical simplicity (way less expensive when they crash) of the
multirotor configuration make it a very popular choice. The confluence of
better battery technology and cheap/lightweight controllers has allowed for
increased viabiliity. As the commercial drone industry matures and payload
carrying missions become viable, I expect there to be a shift in popularity
back to the single rotor configuration. For example, more than 30% of Japan's
rice paddy fields are sprayed with Yamaha's single rotor drone
[[http://textually.org/drones/2013/06/032493.htm](http://textually.org/drones/2013/06/032493.htm)].
There is an exception here; the multirotor configuration is a more stable
platform for shooting video.

------
kenrikm
Being able to do this: [1] [https://www.youtube.com/watch?v=NsxyV-
kgfio](https://www.youtube.com/watch?v=NsxyV-kgfio)

Using these: [2]
[http://www.fatshark.com/product/1757.html](http://www.fatshark.com/product/1757.html)

Is also a contributing factor to the popularity ;-)

~~~
Phlarp
You can watch this happen in real time too-- every once and a while a video
like this will bubble up through social media, hitting the reddit frontpage
and making the rounds on facebook. Then TC or pando will run an article
featuring the video and suddenly all the domestic part shops are out of stock
for a week!

------
mattgibson
I think cheap rare earth magnets was a factor, although I suspect only a part
of the reason. The motors are now far smaller, lighter and more powerful, as
well as cheap to produce. Given you need four of them, they are now light
enough that a small (therefore also cheap) battery can give a useful range to
them, so you can have a very effective device at mass-market prices.

------
shepardrtc
Controller boards and multi-axis sensors became cheap, powerful, and easy to
work with. Companies then sprang up with pre-made kits that weren't too
expensive.

If you're interested in seeing the start of this craze, check out the Wii
Copter. The sensors in the Wii controllers, and also cheap boards like the
Arduino, made it so any hobbyist could build one.

------
arsey
Pun intended?

Anyways, a university experiment video that went viral [0] is the first I
recall seeing a quadcopter in action. Maybe the tipping point if you care to
investigate further.

[0]:
[https://www.youtube.com/watch?v=YQIMGV5vtd4](https://www.youtube.com/watch?v=YQIMGV5vtd4)

~~~
soylentcola
Yep, same here. May have seen another article or video that same year but that
was the one that stuck in my head. Kind of sad that I didn't even get a "toy"
quad until this year but I ought to be building my own sometime this summer.

------
dionidium
I was going to reference the software that makes it possible for complete
amateurs to fly these things, but there's no reason that the software couldn't
have been developed 30 years ago. So the answer is probably battery technology
(driven by cell phones).

~~~
Roboprog
Lithium-polymer batteries are much better than the old Nickel-Cadmium
batteries we had when I was a kid. Also, brushless motors (with electronic
controllers) are much more efficient than brushed motors. The power to weight
ratio of electric propulsion in the last 10 years is incredible.

------
kenrikm
Simplicity and cost. At its most basic form a quadcopter is just two sticks, 4
motors with four speed controllers a flight controller and a battery. [1] if
crashed they are easily repaired. a single rotor helicopter on the other had
is more mechanically complex, more fragile and more expensive to repair. The
reason they became popular was that different technologies (battery, ESCs,
flight controllers) all aligned and some very good work was put into open
source software to control them lowering the barrier to entry.

[1]
[http://undcon.com/rc/quadcopter/img_20101002_011858.jpg](http://undcon.com/rc/quadcopter/img_20101002_011858.jpg)

------
benjohnson
Legal observation:

The tip of a single blade helicopter has much more energy than the tip of a
roughly 1/4 radius of a quad-copter blade.

Despite the complexity, if the copter is large, I would think there's much
less liability baked into a quad-copter.

~~~
Phlarp
Reality backs this up, a stunt pilot more or less decapitated himself with a
heli a while back and while I've seen plenty of rough multicopter injuries
ranging from bruises to lacerations I'm not aware of anyone who has managed to
kill themselves with one... yet.

------
kocsenc
I think its mostly the fact that technology caught up and became cheap enough.
Battery technology, motor technology (brushless), electronics (ESC's which
control the motors, and the onboard boards with gyros and accelerometers) and
many other things.

I'd attribute it the most to battery technology. As part of the hobby myself,
Ni-Cad batteries were the go-to's. But they were crappy. Li-Pos have existed
before, but the thing about multi-rotors and flying in general is it doesn't
need a high capacity, but a high output rate, which we can get now.

------
swalsh
The two new biggest upcoming industries (VR and Drones) seem to have their
origins with smartphones. Cheap screens and cheap/accurate gyros. Which all 3
got their start from cheap/fast computing.

------
lambda
The reason that you see so many multicopters for the smaller ones is that they
are much mechanically simpler, and thus cheaper to manufacture. All you need
mechanically for a multicopter is a number of independent rotors that you can
vary the speed on.

A traditional helicopter has a very complicated assembly to allow powering a
rotor that can tilt forward, backwards, and to the sides, as well as change
the angle of the blades. This is a lot more expensive to produce.

It is more efficient, in a power to weight ratio sense, to have only a single
motor, which is why you see this design on full-sized helicopters. But for
smaller, cheaper drones, you don't need as good of a power to weight ratio to
make it worthwhile, and the cheaper simpler design makes them easier to mass-
produce and sell to amateurs or professionals on a budget.

The things that probably have led to an explosion of them recently include
electronics getting cheaper, and control systems getting better. Regular
helicopters can be piloted by a skilled operator with some training. A
mutlicopter needs a automated control system to keep it balanced. As
electronics for the control systems have gotten cheaper, as well as MEMS
sensors (accelerometers and gyroscopes built into ICs), these control systems
have become cheap and easy to integrate into mass produced products.

In addition, battery technology has been improving, as has electric motor
technology. While previously only the single big fossil fuel engine was the
only viable power source, as battery capacity has increased and electric
motors have gotten more efficient, it's more viable to have small electric
copters.

Another thing that makes these more accessible to casual amateurs, and again
makes mass production more viable, is that most people now carry around a
flexible input device with wireless control capabilities. That means that you
can sell devices without a dedicated controller, can do things like streaming
video back from the drone, and so on, increasing the range of things that you
can do with one.

Other technological improvements also help feed into this. Having widely
available, small, light HD and 4K cameras means that you can actually do
something useful with these drones; back when to do any real filming you
needed a big, bulky camera, they weren't as efficient for getting aerial
shots, but once there are small, light, high quality cameras, it becomes
feasible.

------
lazyjones
The quadcopter design is much simpler and cheaper but less stable (before
electronic stabilization) and efficient than a helicopter. The popularity is
probably due to a combination of easy handling (with modern
gyros/electronics), robustness, low cost and the trend to film everything.
Helicopters are difficult to control and more suited to serious applications
(carrying weight, long flight times...).

------
davismwfl
I really don't know, but a quick search popped up this article.

[http://www.forbes.com/sites/quora/2013/12/23/what-makes-
the-...](http://www.forbes.com/sites/quora/2013/12/23/what-makes-the-
quadcopter-design-so-great-for-small-drones/)

------
neel8986
Those who are interested edx is featuring a course on quadcopter
[https://www.edx.org/course/autonomous-navigation-flying-
robo...](https://www.edx.org/course/autonomous-navigation-flying-robots-tumx-
autonavx-0)

------
thearn4
My understanding is that the quad rotor configuration is more stable at low
reynolds numbers, but I'm not a rotary wing expert.

------
nailer
Part of the reason is the JavaScript community, specifically
[http://nodebots.io/](http://nodebots.io/).

A few Felix G made a module to control Quadcopters using JavaScript. There
have been robotics hackathons at every major JS event worldwide since.

~~~
emddudley
This sounds rather far-fetched to me.

~~~
nailer
Original presentation in 2012:
[https://www.youtube.com/watch?v=jl5v3bsMH_E](https://www.youtube.com/watch?v=jl5v3bsMH_E)

Past events:

Oct 5, 2012 - Berlin by Core Team & JSConf.eu

Oct 20, 2012 - Dublin by Paul Campbell

Oct 31, 2012 - San Francisco by Christian Sanz

Nov 8-9, 2012 - Seattle, WA by Chris Williams

Nov 10, 2012 - Brighton by Remy Sharp

Dec 1, 2012 - San Francisco by Christian Sanz & Jyri Engeström

Jan 23, 2013 - Zurich by Jordi Boggiano

Mar 2, 2013 - Oslo by Trygve Lie & Gregers Gram Rygg

Mar 16, 2013 - London by Andrew Nesbitt

Mar 23, 2013 - Bath by Andrew Nesbitt

Apr 20, 2013 - Helsinki by Janne Aukia and Team

May 11, 2013 - Scotland by Andrew Nesbitt & Julian Cheal & Scotland.js

May 30, 2013 - Amelia Island by Core Team & JSConf.us

Jul 27, 2013 - Manchester by Andrew Nesbitt

Aug 10, 2013 - Southampton by Andrew Nesbitt & Julian Cheal

Aug 18, 2013 - London by Andrew Nesbitt

Sep 7, 2013 - Cincinnati by Jim Weirich & Carin Meier

Sep 13, 2013 - Berlin by Core Team

Sep 21, 2013 - Bristol by Andrew Nesbitt

Sep 28, 2013 - Berlin by Henri Bergius (NoFlo Edition!)

Oct 4, 2013 - Lisbon by A few Portuguese guys

Oct 13, 2013 - New York City by Core Team

Nov 23, 2013 - Sheffield by Julian Cheal & Caolan McMahon

Dec 6-7, 2013 - Amelia Island by Chris & Laura (RobotsConf!)

Jan 23, 2014 - Istanbul by Kod Mutfağı

Feb 12, 2014 - London by Andrew Nesbitt

Mar 17, 2014 - Warsaw, Poland by Core Team & Makerland

May 29, 2014 - JSConf, Florida by Core Team & JSConf

(and there's a year of other events since then - they need to update the
website)

See [http://www.nodecopter.com/](http://www.nodecopter.com/)

