Andrew Chapman's Posts

A Pixhawk powered job for Fox Sports

Posted by Andrew Chapman on June 14, 2015 at 10:29am

Hi everyone,

The question comes up from time to time as to whether the Pixhawk is a good alternative to DJI, Mikrokopter, etc for professional use in heavy-lift cinematography. So I wanted to mention this high profile and *very* high risk job we recently completed for Fox Sports as part of their coverage for the FIFA 2015 Women’s World Cup here in Vancouver.

We flew quite a lot over two days, racking up 4 hours of flight time in 19 flights, mostly over water, and much of it not only within controlled airspace but literally adjacent to one of the world’s busiest floatplane ports, right under the nose of the control tower. They had 396 landings/departures and 242 transits through the zone over the two days we were flying there!

You can see our flight paths at the main location in the front here, and two additional locations in the background:

The Pixhawk performed flawlessly, the only things getting in the way were pre-arm issues which although frustrating at the time are reassuring in that you know it is doing a good job of checking everything is 100% good to go before taking off.

One constant issue I have with the larger octocopters is that it needs to be perfectly still during startup or you get sensor calibration failures. This is easy to do on a small rigid quad, but on a large one sitting atop a 3-axis tripod gimbal with multiple layers of dampening, it tends to sway around a bit after connecting the power. I’ve mostly solved this by having some hard foam wedges to jam in between the gimbal and frame during startup, but it would be nice if this issue went away. I also frequently turn down jobs that would require launching from a boat because I know it couldn’t arm in that scenario. My suggestion is to have the sensor calibration converge over a period of time, so it would happen quickly in the normal case of a small rigid quad on solid ground, but take a lot longer to average out to a solution when there’s movement.

The other minor issue was compass failures during startup when launching near to metal. This is a minor one, and once you know about it it’s not a big deal but it caught me completely unaware and the failure message isn’t reported by the Tower app (reported) so I needed to get the laptop out and diagnose what was going on (while the Producers stood there tapping their feet!). In my case it was a concrete surface but there must have been a metal beam right underneath. It failed a half-dozen times before seeing the error on the laptop, but after moving to a slightly different location it armed right away.

Here’s some more info if you’re interested, I wrote a little puff-piece for a less technical audience on LinkedIn:

https://www.linkedin.com/pulse/skymount-drone-aerial-shoot-fox-sports-fifa-womens-world-chapman

Thanks to all the devs (especially Randy) who make this such a great platform, keep it up!

It’s Okay to Call Them Drones. Seriously, That’s What They’re Called

Posted by Andrew Chapman on June 13, 2014 at 2:05pm

Hi everyone,

Although it is less of an issue for the DIY/hobby end of things (we all seem able to use the word 'drone' without thinking of hellfire missiles), but I've been getting pretty tired of the argument in wider circles and dancing around trying not to use the 'D-word' when dealing with the media.

So... I wanted to write my thoughts down in one place so I can refer back to them whenever this comes up, and I thought I'd share it here in case you guys find yourself repeatedly having the same debate too:

http://www.skymount.com/its-okay-to-call-them-drones/

Keen to hear if you agree or disagree!

Flip and spiral death from 100m, solved

Posted by Andrew Chapman on April 19, 2013 at 4:00pm

I recently had my 4th in-flight motor shutdown on my old 3DR Quad - I think I've finally figured it out so I thought I'd share the story so others can check for the same problem as well as show some logfile diagnosis.

My earlier flip deaths were from quite low so I didn't have a chance to see what was going on, and I didn't have the motor logging on to see which one shut down. I also suspected I could have been having brownouts in the past as I was powering my gimbal servos from the signal pins for a while until I discovered that was *BAD*.

This one was from high enough that I could observe and try a couple of things on the way down. It definitely still had power to the APM and some of the motors as you could hear it trying to correct itself, I switched out of auto mode into stabilize, pulled the throttle back to idle then up again in the hope it would restart the 4th motor, but it didn't. I heard the other three spin up again and whine dramatically but it never corrected. It thumped into the ground, broke all the props, bent the arms, but all the electronics survived (even the S100 camera). Reinforcing the message: NEVER FLY OVER PEOPLE! For sure that would have caused more than a bruise if someone was below it.

From the logs it looks like it was the #4 engine that quit (rear-right on a quad), as you can see it suddenly pitches up and rolls right, commanding more power for the #4 and less power to the opposing #3 engine (to no avail, as there's no RPM feedback in our current hardware so it doesn't know the motor is out).

The frustrating thing was that after this crash when I tested the motors they all ran fine, just like the previous flip crashes, so I was at a bit of a loss to diagnose the problem. I thought it could be low power and bad ESC programming that would cause the #4 ESC to cut out early, so I ran an old pack right down and all 4 motors slowed down in sync together as the voltage dropped off.

So I knew it was something with the #4 motor and it was unlikely to be the ESC as I'd replaced that before after one of the crashes. I removed the props, ran the motors and pulled and jiggled all the wires around to check the connections and...

BINGO!

The motor glitched then restarted. I pulled the cable some more and it stopped altogether. Here's a vid showing the problem:

https://www.youtube.com/watch?v=_iB5r6-AE-o

Turns out a bad wire connection to this motor had caused me 4 crashes and lots of headscratching. One more for the 3DR Quality Assurance department I think (well, 4 more...)

So a lesson for all: when you're finished a new build and periodically thereafter, remove your props, run your motors and jiggle all the wires around to check you have solid connections!

AC.