The Trials Of Quadcopter Graffiti

Last April, graffiti artist [KATSU] strapped a can of red spray paint to a Phantom quadcopter, flew it up against one of the largest billboards in New York City, and pressed a button. Now, [KATSU], [Dan Moore], and Adafruit’s [Becky Stern] are trying to perfect a flying can of spraypaint, and they’ve met with some success and surely many broken props.

The team used an Iris+ for this project instead of the Phantom used by [KATSU] earlier this year, but the principle of the entire endeavor remains the same: fly up against a wall, flick a switch, and watch paint come out of a spray gun. To get the can spraying paint, they modified a can gun to accept a micro servo. This servo is connected to the trigger mechanism of the can gun, and the entire unit is slung under the quad.

Getting a quadcopter to put paint exactly where you want it is hard, even indoors. Luckily, the Pixhawk inside the Iris has sensor inputs and an ‘altitude hold’ mode that can accept a sonar sensor and can be programmed to stay a set distance away from a wall. These sensors are susceptible to interference, and a proper, shielded cable had to be made, but the sensor did work.

Flying the quad did not go as smoothly. The swinging can of paint changes the center of gravity of the quad, and even flying indoors proved difficult. Still, if you’d like to give it a go, [Becky] put up the instructions for their build. You can see the hover attempts in the video below.

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Quadrotor Control Systems And Kerbal Harriers

Kerbal Space Program, the game that teaches engineers at JPL and SpaceX the basics of rocket design and orbital mechanics, recently had a giant update. There are now science contracts that require you to fly Kerbals all over their tiny globe, collect data, and transmit it back to the Kerbal Space Center. As would be expected, this is a grind for XP, and the contracts sometimes don’t make sense – you need to collect data from cliff faces and mountain tops. Landing a Kerbal jet at these places is hard.

[Matt Thiffault] wanted to do these science contracts more efficiently. The best way to get to a remote location without a landing strip would be a helicopter, but a harrier jump jet would do just as well. This isn’t supported in the stock game, so [Matt] wrote a complete control system for four engines to control a hovering Kerbal jet.

[Matt]’s work is built on kOS, a scriptable autopilot mod for Kerbal that was originally intended to be something like the Apollo Guidance Computer. People have been using it to make computerized skycranes and automated rendezvous and docking programs, but these are actually relatively simple examples; there’s far more math involved in flying a quadcopter than there is getting into orbit.

To build his automated hovering harrier, [Matt] needed an aircraft. His Kerrier has parts from the Kerbal Aircraft Expansion, B9, and Infernal Robotics mods for KSP, but this is only half the problem. Anyone can put four tilt jets on an airplane, and it takes a real wizard to force a control system to hover. Hover control of the Kerbal harrier is accomplished with a complete control system for a four-engined aircraft, with proper PID control loops and code updating at 20Hz.

With kOS, the proper plane, and the right software running on this emulated guidance computer, [Matt] is able to park his plane in mid-air, have a Kerbal descend the ladder, perform some science, and return to base. It’s an impressive amount of work for a video game. A good thing, too: [Matt] is looking to get into controls engineering professionally. Whether this will go on his resume is another question entirely.

Hackaday Prize Entry: A 3D Mapping Drone

Quadcopters show a world of promise, and not just in the mediums of advertising and flying Phantoms over very large crowds. They can also be used for useful things, and [Sagar]’s entry for The Hackaday Prize does just that. He’s developing a 3D mapping drone for farmers, miners, students, and anyone else who would like high-resolution 3D maps of their local terrain.

Most high-end mapping and photography work done with quadcopters these days uses heavy DSLRs to record the images that are brought back to the base station to be stitched into a 3D image. While this works, those GoPros are getting really, really good these days, and with 4k resolution, too. [Sagar] is mounting one of these to a custom quad and flying around an area to get images of an area from every angle.

To stitch the images together [Sagar] will be using the Pix4D mapping software, an impressive bit of software that will convert a multitude of still images to a 3D scene. It’s an expensive piece of software – $8500 for a perpetual license, but the software can be rented for $350/month until a FOSS alternative can be developed.

The 2015 Hackaday Prize is sponsored by:

Foldable Quadrotor is Origamilicious

A team at the École Polytechnique Fédéral de Lausanne has developed and built a quadcopter with arms that unfold just before takeoff. The idea is that you can fold the device back up when you’re done with it, making it possible to store a bunch more of the quads in your backpack for instance.

The unfolding mechanism relies on the torque of the rotors spinning up to swing the arms into place. Once fully extended, a spring-loaded flap folds up, catches on some magnets, and forms an L-shaped structure that won’t re-fold without human intervention.

quadcopter_animUnder normal flying conditions, quads have a two left-handed propellers and two right-handed ones and the motors spin in opposite directions. In order to do the unfolding, two of the motors need to run essentially in reverse until the frame has clicked into place. They use a sensor (Hall effect?) to detect the arm locking, and then the rotors quickly switch back to their normal rotation before the quad hits the floor. In the video, they demonstrate that they’ve got this so well tuned that they can throw it up into the air to launch. Wow.

Everything’s still in prototype phase, and one of the next goals is “strengthening the arms so they can withstand crashes”, so don’t expect to see these in your local hobby store too soon. In the mean time, you’ll be able to see them in the flesh if you head up to the IEEE International Conference on Robotics and Automation in Seattle that started today and runs through Friday. If anyone goes, take more video and post in the comments?

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Hackaday Prize Entry: Density Altitude Gauge

Despite what extraordinarily overpowered quadcopters suggest, the air pressure of whatever a flying machine flys at is extremely important. Pressure is dependent on altitude and temperature, and there are hundreds of NTSB investigations that have concluded density altitude – pressure altitude corrected for nonstandard temperature variations – was the reason for a crash. Normally density altitude is computed through a slide rule or a flight computer, with the pilot entering in altitude and temperature, but somehow accidents still happen. For his entry to The Hackaday Prize, [Neil McNeight] is building an automated density altitude calculator to automate the process entirely.

Instead of having a pilot enter the altitude and temperature into a flight computer manually, [Neil]’s device grabs the current altitude from a GPS unit, and reads the temperature with a tiny sensor acquired from SparkFun. With just a little bit of math, this device will spit out the altitude an airplane or ‘copter thinks it’s at.

While the FAA won’t allow instruments that are cobbled together on a breadboard, this does have a few applications in the RC world. There are extremely high performance racing quadcopters out there now, and knowing how the craft will perform before flying it will save a few props.

The 2015 Hackaday Prize is sponsored by:

Hackaday Links: March 29, 2015

Every once in a while, the Hackaday Overlords have a Hardware Developers Didactic Galactic in San Francisco. Last week was #06 featuring [Mike Estee] from Othermill and Hackaday writer [Joshua Vasquez] talking about synthesizing an SPI slave in an FPGA. Video here.

It’s no secret that [Fran] is building a DSKY – the part of the Apollo guidance computer that was on-screen in Apollo 13. It’s time for a project update, and here’s where she stands: if anyone has a source of JAN-spec Teledyne 420 or 422-series magnetic latching relays (they’re in a TO-5 package), contact [Fran]. The backplane connector has been identified; it’s a Teradyne I/O 100 series connector with a 120mil spacing. Contact [Fran] if you know where to get them.

Let’s say you want a carbon fiber quadcopter frame. What’s the most reasonable thing you can do? 3D print a CNC machine, obviously. That’s a 200mm FPV racer cut from 1mm and 3mm carbon fiber sheets, but the real story here is the CNC machine. It’s a PortalCyclone, and even the cable chains are 3D printed.

What does an AMOLED display look like up close? Pretty cool, actually. That’s 20x magnification, and it’s not a Bayer filter. Can anyone fill us in on the reason for that?

Laser cutters are tricky if you want to do grayscale or half tones. [oni305] made an Inkscape extension to generate better GCode for engraving with a laser cutter.

19″ racks have no dimensions that are actually 19″. Also 2x4s aren’t 2 inches by four inches. Somehow, a 2×4 server rack works.

1-Hour Quadcopter Build

[marhar] was pretty confident in his quadcopter building skills when he made a bet to build and fly a quadcopter in just one hour! This is a big task but he saved valuable time by using some unlikely parts that were hanging around his parts bin. And to make the task a little more difficult, this build wasn’t done in a nice shop, either. It was built outside on a patio floor with the only power tools available being a hand drill, miter saw and small drill press!

The frame is made from cheap, sturdy and available scrap wood. The center plates are 1/4″ plywood and the arms are 3/4″ square fir strips. Notice the landing gear, yes, those are mini wiffle balls zip-tied to the wooden arms. Although an unlikely candidate for landing gear, they are surprisingly effective.

The flight controller board is an Ardupilot. [marhar] did use a flight controller that he previously had in another quadcopter. He used it as-is, and it worked, but no programming or configuration time is included in the 1-hour limit. Even so, it doesn’t take away from the impressiveness of the build time.  The motors, ESC’s and battery are just standard types used for most multirotors.

[marhar] doesn’t say what he won for completing the ‘copter but we hope it was something good, he deserves it. If you’d like to make something similar, [marhar] gives very detailed instructions and provides templates for the wood parts on his Instructables page. Check out the time-lapse build video after the break…

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