Copters

What’s a multicopter? It’s like 2 (or more) or orthogonal Segways, in the air. It’s a more complicated controls problem than a single-axis stabilized vehicle, and even worse, you’re not riding on it to close the feedback loop. I first became interested in these in 2011, and have since spawned a few different designs. Unless otherwise noted, the control software for all of these was custom-written – they are not kits or based on commercial UAV controllers. The newest things are at the bottom in the usual lazy style.


Deathcopter

Go big, or go home. That was the inspiration for my *first* quadrotor build, and it was retroactively named “Deathcopter” for very good reason. I had recently gotten ahold of some large inexpensive Chinese ducted fans and wanted to make something take off with it. After all, that was the whole purpose of Fankart’s existence. Sadly, Fankart’s thrust to weight ratio was just too poor. With all four fans spinning in the same direction, I needed to think of a way to vector the thrust such that I could control the yaw motion (spinning about vertical axis), and the solution was to pivot the four fans on servo-controlled trunnions. Deathcopter was a really, really ambitious first flying thing build, and unfortunately it ended sadly.

Frame Size 30″ x 18″
Propeller Size
5″ (ducted fan)
Power Source
37v 10Ah (10S lithium polymer)
Motor
Hobbyking T600 880 kv
Motor Controller
Turnigy Sentilon 100A HV
Flight Controller
Custom Arduino-Based
Sensors
Razor 6DOF IMU
Weight
8.1 kg

Tinycopter


Tinycopter 1.0

Tinycopter 2.0

Tinycopter 3.0

Born of the wreckage of the Deathcopter, Tinycopter is… well, much smaller, easier managed, and significantly less a hazard to life forms in general. It went through three different builds, mostly because I kept crashing it. Outside of those times when it has been completely out of service, it’s generally been reliable and easy to fly, allowing me to test different controller gains. The latest build features attitude-or-rate mode switching as well as dynamic (on-the-fly, literally) gain variability using the last 2 analog channels on my 6 channel radio.

Tinycopter has an extensive and often tragic build thread.

Frame Size 200mm across motors (8″)
Propeller Size
5″ x 3″ (5030)
Power Source
7.4v 460mAh Lithium polymer
Motor
Hobbyking HXT 1811 10-gram
Motor Controller
Turnigy 18A Plush (v1)
Hobbyking 10A (v2)
Hobbyking 6A (v3)
Flight Controller
Custom Arduino-Based
Sensors
Razor 6DOF IMU from Deahtcopter
Weight
Around 140g

Chibicopter!

Can I build a quadrotor even smaller than Tinycopter? Sure, quite a few people have done it already. As the copter size shrinks, the system mechanical time constant (which is proportionally to the frame inertia, itself proportional to mass and arm length, and inversely proportional to the thrust of the props) becomes smaller and smaller – in other words, it gets faster, and therefore more difficult to control. Chibicopter 1 also features a fully 3d printed frame made of white laser-sintered nylon, which turned out to be a bit more flexible than intended. Coupled with poor board design, insufficient control bandwidth (my motor controllers could only be refreshed at 100hz) and IMU mounting, and it just sort of, barely flies, demonstrating slowly diverging oscillation. There are many things I want to change if it gets a rebuild…

Like everything, Chibicopter has a build thread.

Frame Size 75mm across motors (3″)
Propeller Size
2.5″ x 1.0″ (2510)
Power Source
3.7v 160mAh lithium polymer
Motor
Hobbyking HXT 2 gram outrunner
Motor Controller
Hobbyking 1S 3A controller
Flight Controller
Custom Arduino-Based
Sensors
Pololu MinIMU9
Weight
39g

Ballcopter


Ballcopter 1.0

Ballcopter 2

I saw this video of A Certain Ball-Shaped Drone and was hooked pretty much instantly. After alot of Google Images and forum hunting yielding no detailed engineering results, I decided to just freelance one (always fun and educational). My first attempt ended in disappointing failure as I discovered that it was both too heavy and my servo linkages were poorly designed – small angle approximations really only work if you’re not starting at 45 degrees already. Furthermore, I discovered after the fact that it had 8 independently actuated flaps (video). So Ballcopter 2 was assembled – but once again, more research and reading showed me that I had wrongly chosen which flaps were in charge of maintaining the vehicle attitude (hint: it’s the bottom set). Perhaps it’s time for Ballcopter 3…

The trials and tribulations of Ballcopter are found in its build thread.

Frame Size 16″ sphere
Propeller Size
10″ x 4.5″ SF
Power Source
11.1v 1000mAh lithium polymer battery (v1)
11.1v 500mAh lithium polymer battery (v2)
Motor
300 class outrunner
Motor Controller
Exceed-RC 18A
Flight Controller
Custom Arduino-Based
Sensors
Razor 6DOF IMU
Weight
700+g (v1)
550g (v2)

TinyStar 8


it’s tiny!

Another exercise in my aversion to large copters, TinyStar was built for two reasons. First, to one two-up the multicopter ….arm’s race? at MIT by adding 2 more arms; and second, to imitate the preposterously awesome Cinestar 8, as a little scale model. In lieu of making a custom 8 channel flight controller, I’m actually using two stock Hobbyking i86 boards, based off the KKMulticopter controller, one configured as a + type quadrotor, other an X-type, on the same frame.  This initially facetious idea ended up working extremely well. Of course, a week after I ordered the non-8-channel boards, Hobbyking came out with an 8-channel one.

Tinystar’s frame is mostly carbon fiber rod with 3D printed clamping elements. The landing legs are made of 2mm plywood, painted black to look vaguely badass.

Here’s some Tinystar test videos (outside, inside) and its one-post-long build thread.

Frame Size 13″
Propeller Size
4 x 2.5 (4025)
Power Source
11.1v 460mAh LiPoly
Motor
Hobbyking HXM1400 5 gram outrunner
Motor Controller
Hobbyking 6A
Flight Controller
2x i86; one in “+” mode, other in “X” mode
Sensors
Onboard (gyros only)
Weight
270g

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