THP Semifinalist: Autonomous Recharging For Multirotors

September 2, 2014 by Brian Benchoff 20 Comments

Even with visions of quadcopters buzzing around metropolitan areas delivering everything from pizzas to toilet paper fresh in the minds of tech blogospherites, There’s been a comparatively small amount of research into how to support squadrons of quadcopters and other unmanned aerial vehicles. The most likely cause of this is the FAA’s reactionary position towards UAVs. Good thing [Giovanni] is performing all his research for autonomous recharging and docking for multirotors in Australia, then.

The biggest obstacle of autonomous charging of a quadcopter is landing a quad exactly where the charging station is; run of the mill GPS units only have a resolution of about half a meter, and using a GPS solution would require putting GPS on the charging station as well. The solution comes from powerful ARM single board computers – in this case, an Odroid u3 – along with a USB webcam, OpenCV and a Pixhawk autopilot.

Right now [Giovanni] is still working out the kinks on his software system, but he has all the parts and the right tools to get this project up in the air, down, and back up again.

The project featured in this post is a semifinalist in The Hackaday Prize.

Extrinsic Motivation: Smart Antenna Tracker For R/C Aircraft

September 1, 2014 by Adam Fabio 20 Comments

Long distance FPV (First Person View) flying can be a handful. Keeping a video feed alive generally requires a high gain directional antenna. Going directional creates the chore of keeping the antenna pointed at the aircraft. [Brandon’s] smart antenna tracker is designed to do all that automatically. What witchcraft is this, you ask? The answer is actually quite simple: Telemetry! Many flight control systems have an optional telemetry transmitter. [Brandon] is using the 3DRobotics APM or PixHawk systems, which use 3DR’s 915 MHz radios.

The airborne radio sends telemetry data, including aircraft latitude and longitude down to a ground station. Equipped with a receiver for this data and a GPS of its own, the smart antenna tracker knows the exact position, heading and velocity of the aircraft. Using a pan and tilt mount, the smart antenna tracker can then point the antenna directly at the airborne system. Since the FPV antenna is co-located on the pan tilt mount, it will also point at the aircraft and maintain a good video link.

One of the gotchas with a system like this is dealing with an aircraft that is flying directly overhead. The plane or rotorcraft can fly by faster than the antenna system can move. There are a few commercial systems out there that handle this by switching to a lower gain omnidirectional whip antenna when the aircraft is close in. This would be a great addition to [Brandon’s] design.

Droning On: Maiden Flights

August 28, 2014 by Adam Fabio 4 Comments

When we last left off, the Hackaday Drone Testbed was just a box of parts on workbench. Things have changed quite a bit since then! Let’s get straight to the build.

With the arms built and the speed controls soldered up, it was simply a matter of bolting the frame itself together. The HobbyKing frame is designed to fold, with nylon washers sliding on the fiberglass sheets. I don’t really need the folding feature, so I locked down the nylock nuts and they’ve stayed that way ever since. With the arms mounted, it was finally starting to look like a quadcopter.

Using the correct screws, the motors easily screwed into the frames. I did have to do a bit of filing on each motor plate to get the motor’s screw pattern to fit. The speed controls didn’t have a specific mount, so I attached them to the sides of the arms with double-sided tape and used some zip ties to ensure nothing moved. In hindsight I should have mounted them on the top of the arms, as I’m planning to put LED light strips on the outside of edges of the quad. The LEDs will help with orientation and ensure a few UFO sightings during night flights.

Power distribution is a major issue with multicopters. Somehow you have to get the main battery power out to four speed controls, a flight controller, a voltage regulator, and any accessories. There are PCBs for this, which have worked for me in the past. For the Hackaday Testbed, I decided to go with a wiring harness. The harness really turned out to be more trouble than it was worth. I had to strip down the wires at the solder joint to add connections for the voltage regulator. The entire harness was a bit longer than necessary. There is plenty of room for the excess wire between the main body plates of the quad, but all that copper is excess weight the ‘bench’ doesn’t need to be carrying. The setup does work though. If I need to shed a bit of weight, I’ll switch over to a PCB.

Click past the break to read the rest of the story.

Continue reading “Droning On: Maiden Flights” →

Aerodynamics? Super Honey Badger Don’t Give A @#*^@!

July 30, 2014 by Adam Fabio 50 Comments

honeybadger-rcplane

[Arron Bates] is a pro R/C Pilot from Australia. He’s spent the last few years chasing the dream of a fixed wing plane which could perform unlimited spins. After some promising starts with independently controlled wing spoilers, [Arron] went all in and created The Super Honey Badger. Super Honey Badger is a giant scale R/C plane with the tail of a helicopter and a soul of pure awesome.

Starting with a standard 87″ wingspan Extra 300 designed for 3D flight, [Arron] began hacking. The entire rear fuselage was removed and replaced with carbon fiber tubes. The standard Extra 300 tail assembly fit perfectly on the tubes. Between the abbreviated fuselage and the tail, [Arron] installed a tail rotor from an 800 size helicopter. A 1.25 kW brushless motor drives the tail rotor while a high-speed servo controls the pitch.

[Arron] debuted the plane at HuckFest 2013, and pulled off some amazing aerobatics. The tail rotor made 540 stall turn an easy trick to do – even with an airplane. Flat spins were a snap to enter, even from fast forward flight! Most of [Arron’s] maneuvers defy any attempt at naming them – just watch the videos after the break.

Sadly, Super Honey Badger was destroyed in May of 2014 due to a structural failure in the carbon tubes. [Arron] walked away without injury and isn’t giving up., He’s already dropping major hints about a new plane (facebook link).

Continue reading “Aerodynamics? Super Honey Badger Don’t Give A @#*^@!” →

Flight For Your Right (And Do It By Friday)

July 23, 2014 by Brian Benchoff 65 Comments

About a month ago, the FAA – the governing body for nearly everything that flies in US airspace – proposed an interpretation of their rules governing model aircraft. The world hasn’t ended quite yet, but if the proposed rules go into effect, an entire hobby will be destroyed in the United States. While congress has given the FAA authority over nearly everything that flies, there are specific laws saying what the FAA has no jurisdiction over – model aircraft being one of the major exceptions.

Congress, however, is working on a definition of model aircraft that is at least 10 years out of date and doesn’t have any leeway for the huge advances in technology that have happened since then. Specifically, all FPV flight with video goggles would be banned under the proposed FAA rules. Also, because model aircraft are defined as being for, ‘hobby or recreational purposes,’ anyone who flies a model aircraft for money – a manufacturer conducting flight tests on a new piece of equipment, or even anyone who records a video of their flight, uploads it to YouTube, and hits the ‘monetize’ button – would be breaking the law.

The proposed FAA rules for model aircraft are not in effect yet, and you can still make a public comment on the proposal until 11:59 PM EDT Friday. If you leave a comment, please make a well-reasoned statement on why the FAA’s interpretation of the rules governing model aircraft are overly broad, do not take into account technological advances made since the drafting of Congress’ working definition of ‘model aircraft,’ and the effects of a complete ban flying model aircraft for any type of compensation.

Of course, if the proposed rules for model aircraft go through, the only option will be to turn to the courts. Historically, the FAA simply does not lose court cases. Recently, cases involving drones have come up with successful defenses and judges deciding in favor of drone operators. The legal services for the eventual court case challenging the proposed FAA rules will most likely be funded by the Academy of Model Aeronautics, who just so happen to be offering membership at 50% off.

Below is a video of some RC people we really respect – [Josh] from Flite Test and [Trappy] of Team BlackSheep – talking about what the proposed rule change would do to the hobby. There’s also a great podcast featuring the first lawyer to successfully defend drone use in federal court that’s worth a listen.

Continue reading “Flight For Your Right (And Do It By Friday)” →

Droning On: PID Controllers And Bullet Connectors

July 7, 2014 by Adam Fabio 30 Comments

Not all drones are multirotors – Posing in our title photo are Maynard Hill and Cyrus Abdollahi. Maynard’s plane, TAM5 aka The Spirit of Butts Farm, is the smallest aircraft to make a transatlantic flight (YouTube link). Retracing the path of Alcock and Brown from Newfoundland to Ireland, the 6 pound (dry weight) model made the trip in just under 39 hours. All this happened in 2003, and was the cap on a lifetime of achievements for Hill. These are the types of pursuits that will be banned in the USA if the FAA restrictions go into effect.

Flight Controllers

Quite a few of you thought the Naze32 was left out of last column’s flight controller roundup. I hear you loud and clear! I’ll add the Naze to the controllers which will be tested on The Hackaday Testbed. The hard part is finding the darn things! I currently have an Acro Naze32 on its way to Droning On HQ. If I can find a full version, I’ll add that.

PID Controllers Deep Dive

I’ve gotten a few questions on Proportional Integral Derivative (PID) controllers, so it is worth diving in a bit deeper to explain what a PID controller is. PID controllers are often found in process controls managing parameters like temperature, humidity, or product flow rate. The algorithm was initially designed in the late 1800’s as a method of controlling the helm of large naval ships. In fixed wing drones, PID keeps the plane’s wings level and on course. In multicopters, PID loops control heading, but they also provide the stable flight which allows the quadcopter to fly in the first place. A full explanation of PID loops would be beyond the scope of a single article, but let’s try a 10,000 foot explanation.

P: This is the “Present” parameter. P Has the most influence on the behavior of the aircraft. If the wind blows your quadcopter from level flight into a 30 degree right bank, P is the term which will immediately take action to level the quad out. If the P value is too high, The quadcopter will overshoot level flight and start banking the other way. In fact, way too high a P value can cause a quadcopter to shake as it oscillates or “hunts” for level. Too Low a P value? the quadcopter will be very slow to react, and may never quite reach level flight again.

I: This the “Past” parameter. The I term dampens the overshoot and oscillations of the P term, and avoids the tendency of P to settle above or below the set point. Just like with P, too high an I term can lead to oscillation.

D: This is the “Future” parameter, and has the smallest impact on the behavior of the aircraft. In fact, some flight controllers leave it out entirely. If P and I are approaching a set point too quickly, overshoot is likely to occur. D slows things down before the overshoot happens.

So why do multicopter pilots dread PID tuning? Quite simply, it’s a tedious process. Couple a new pilot and an unproven aircraft with un-tuned PID values, and you have a recipe for frustration – and broken propellers. Things get even more complex when you consider the fact that there are at least 3 sets of PID variables to be tuned – Pitch, Roll, and Yaw. Some flight controllers now support multiple PID values depending on the style of flight. Want your plane or multicopter to fly around like a hotrod? You need a totally different set of PID values than a docile trainer craft. Rolf Bakke (KapteinKUK himself) made a video illustrating how multicopters behave when tuning PID values. You can easily see how a quad can go from “drunk” to “angry bee” with just a few value tweaks. All this is coming together with The Hackaday Testbed, which will help me in posting a few PID tuning videos of my own.

Hackaday Testbed Update

As for the testbed itself, it’s nearly complete! You can follow the progress on my Hackaday Projects Page. Most of the assembly has been relatively straightforward. though of course there are always a few snags. It seems I always forget something when ordering up parts for a build. In this case it was 2.5mm banana plugs and motor mounting screws.

The Hobbyking motors attach to the frame with 3mm screws. The problem is that there really is no way to know how long the screws should be until you have the motors, mounting plates and drone frame on hand. I have a bunch of 3mm screws of various lengths, and thankfully there were enough screws of the correct length to mount the motors. Murphy is always at my side, as I accidentally grabbed a screw that was 1mm too long and, you guessed it, screwed right into the windings of the motor. Doh! Thankfully I had spares.

Bullet connectors can be a real pain to solder. There are some jigs out there which help, but I’ve always found myself going back to the old “helping hands” alligator clips. Bullets tend to use lower gauge wire than we’re used to with regular electronics. 14, 12, even 8 gauge wires are used on R/C aircraft. A low power soldering iron with a surface mount tip just won’t cut it. Those irons just doesn’t have the thermal mass to get the connectors up to soldering temperature. This is one of those places where a decent 40 watt or better Weller iron (yes, the kind that plugs right in the wall) can be a godsend. I’m using an Metcal iron here, with a wide flat tip.

Bare bullet connectors and alligator clips can also create a problem – the metal clips create even more thermal mass. Years back an old-timer showed me a trick to handle this. Slip a piece of silicone R/C plane fuel tubing on the bullet, and then clip the helping hands onto the tube. The tube will act as insulation between the bullet and the clip. Silicone can easily withstand the temperatures of soldering. I’ve also used the silicone tube on the jaws themselves – though eventually the jaws will cut the soft tubing.

That’s about it for this edition Droning on! Until next time, keep ’em flying!

Title photo credit Cyrus Abdollahi.

Congress Destroys A Hobby, FAA Gets The Blame

June 26, 2014 by Brian Benchoff 177 Comments

As ordered by the US Congress, the FAA is gearing up to set forth a standard for commercial UAVs, Unmanned Aerial Systems, and commercial drones operating in America’s airspace. While they’ve been dragging their feet, and the laws and rules for these commercial drones probably won’t be ready by 2015, that doesn’t mean the FAA can’t figure out what the rules are for model aircraft in the meantime.

This week, the FAA released its interpretation (PDF) of what model aircraft operators can and can’t do, and the news isn’t good: FPV flights with quadcopters and model airplanes are now effectively banned, an entire industry centered around manufacturing and selling FPV equipment and autopilots will be highly regulated, and a great YouTube channel could soon be breaking the law.

The FAA’s interpretation of what model aircraft can and cannot do, and to a larger extent, what model aircraft are comes from the FAA Modernization And Reform Act Of 2012 (PDF). While this law states the, “…Federal Aviation Administration may
not promulgate any rule or regulation regarding a model aircraft…” it defines model aircraft as, “an unmanned aircraft that is capable of sustained flight in the atmosphere; flown within visual line of sight of the person operating the aircraft; and flown for hobby or recreational purposes.” The FAA has concluded that anything not meeting this definition, for example, a remote controlled airplane with an FPV setup, or a camera, video Tx and Rx, and video goggles, is therefore not a model aircraft, and falls under the regulatory authority of the FAA.

In addition, the FAA spent a great deal of verbiage defining what, “hobby or recreational purposes” in regards to model aircraft are. A cited example of a realtor using a model aircraft to take videos of a property they are selling is listed as not a hobby or recreation, as is a farmer using a model aircraft to see if crops need water. Interestingly, receiving money for demonstrating aerobatics with a model aircraft is also not allowed under the proposed FAA guidelines, a rule that when broadly interpreted could mean uploading a video of yourself flying a model plane, uploading that to YouTube, and clicking the ‘monetize’ button could soon be against the law. This means the awesome folks at Flite Test could soon be out of a job.

The AMA, the Academy Of Model Aeronautics, and traditionally the organization that sets the ‘community-based set of safety guidelines’ referred to in every law dealing with model aircraft, are not happy with the FAA’s proposed rules (PDF). However, their objection is a breathless emotional appeal calls the proposed rules a, “a strict regulatory approach to the operation of model aircraft in the hands of our youth and elderly members.” Other than offering comments per the FAA rulemaking process there are, unfortunately, no possible legal objections to the proposed FAA rules, simply because the FAA is doing exactly what congress told them to do.

The FAA is simply interpreting the Modernization And Reform Act Of 2012 as any person would: FPV goggles interfere with the line of sight of an aircraft, thus anyone flying something via FPV goggles falls under the regulatory authority of the FAA. Flying over the horizon is obviously not line of sight, and therefore not a model aircraft. Flying a model aircraft for money is not a hobby or recreation, and if you’re surprised about this, you simply aren’t familiar with FAA rules about money, work, and person-sized aircraft.

While the proposed FAA rules are not yet in effect, and the FAA is seeking public comment on these rules, if passed there will, unfortunately, exactly two ways to fix this. The first is with a change in federal law to redefine what a model aircraft is. Here’s how to find your congresscritter, with the usual rules applying: campaign donations are better than in-person visits which are better than letters which are better than phone calls which are better than emails. They’ll also look up if you have voted in the last few elections.

If passed, the only other way these rules will align with the privileges model aircraft enthusiasts have enjoyed for decades is through a court ruling. The lawsuit objecting to these rules will most likely be filed by the AMA, and if these rules pass, a donation or membership wouldn’t be a bad idea.