WORD OF WARNING: OUTSIDE FLYING

[nimble]

Ok - I've had my Crazyflie 2.0 for 3 days, and sadly, it is gone.
He was such a wonderful flyer. This post is in hopes of saving someone else the pain. Please write your phone number on your crazyflie people - unfortunately I didn't think of that until afterwards.

Setup:
Macbook Pro running Windows 8.1
CrazyRadio PA
Playstation DusalShock 4 connected Bluetooth

I was flying him at the park, within a 40m radius. I had been doing this for about 3-4 minutes with no problems, doing plenty of laps.
I was standing about 2 meters from my laptop, flying the quad towards me, and I reduced throttle and moved the joystick to turn 180 degrees. The quad did not turn, it continued towards me, passing me about 10m over my head. I throttled down 100% and it continued full pitch (about 30 degrees), full throttle - increasing altitude and distance. Now I realise there is a major problem, but he very quickly disappears over trees, probably about 200m in the air, at least 200m away.

What went wrong? I don't know - I quickly pulled the USB transmitter and ran after it to look for it, but amongst the suburbs, there will be no chance without someone reporting it, and from that height it will likely be destroyed anyway.

I still had a bluetooth connection to the laptop, but I don't know if there was a connection to the crazy from the crazyradio because I pulled the transmitted out in hopes of bringing it down (but after it was out of sight).

Question 1: Assuming a data connection failed somewhere - why would the crazyflie CONTINUE to follow its flightpath? I assume there are no failsafes in the software, but I must admit, I had yet to try things like pulling out the crazyradio. I do know, however, when the playstaion controller loses connection to the laptop, crazyflie just throttles down.

[marcus]

Hi,

Sorry to hear about your Crazyflie! The Crazyflie will throttle down and cut the motors if it looses connection with the host (1s with Crazyradio and 4s with Bluetooth). But when using the Crazyradio PA the signal is pretty strong so that will probably not happen unless you far away or behind a building when you are outside. There might be an issue if the computer looses connection with the controller. This is even driven, so the input device layer will send events when changes occur in the input device. If you push full thrust and then disconnect the input device there's a risk that the last event you will get is full thrust and this will then keep being sent to the Crazyflie. With the previous version of the Crazyflie python client we used PyGame where it wasn't possible to detect the disconnection of an input device. But since SDL2 is now used there might be a chance to detecting this. I've added an issue for it and we will investigate.

If you loose control of a Crazyflie it's best to pull the Crazyradio from the computer, this will trigger the internal watchdog of the Crazyflie and cut the motors. The automatic power-down feature is not compiled in yet, so it might be possible to move around and scan for the Crazyflie to find it. It's probably best to use your phone since the range is not as long.

[mighty_falcon]

That sucks I would recommend mapping a button as a killswitch. I just did this after reading your story.

[chad]

That sucks I would recommend mapping a button as a killswitch. I just did this after reading your story.

I think all of the default controller configs (in crazyflie-clients-python/conf/input) have this implemented. Just search for the key "estop" or the name "killswitch" (though I think the Generic_OS_X config has the name misspelled as "Killswtich" but the key "estop" is the important part).

Trust me, I have used this emergency stop functionality many, many (many, many, many) times...

[nimble]

But the killswitch couldn't work if the laptop software is stuck in a loop, or the controller has become disconnected somehow... or am I misunderstanding how the Killswitch works?

[nimble]

I've been looking at the GPS solutions - and at around 10g and 25-55mA - its not really viable - You'd ruin your agility - and it would consume around as much power as the quad when active, so would probably just run out of power and fall out of the sky.

I was thinking about a completely passive optical system - what about putting some IR receivers on the quad, tuned to a carrier frequency?
If the quad losses connectivity, you grab your high powered infrared beacon, the quad does a 360 to search for infrared signal, and using the difference in signal strength between multiple receivers, flies toward the infrared beacon.
Hopefully by the time it's gotten back to you, you've restored radio connectivity and you can bring it down.

Something like that would use significantly less power, and be lighter weight - for the sacrifice of line of sight.

Thoughts?

[chad]

But the killswitch couldn't work if the laptop software is stuck in a loop, or the controller has become disconnected somehow... or am I misunderstanding how the Killswitch works?

No you're exactly right. If you've got a connectivity break, the kill won't be sent from the controller. It's more of a "nice to have" when you're about to run into your dog, or the lamp, or your wife...

[marcus]

After almost loosing one in in a large field with high grass we thought about making an expansion board with a small piezo speaker on it, when you loose connection it starts beeping. This is a low tech solution that we think will help.

[chad]

After almost loosing one in in a large field with high grass we thought about making an expansion board with a small piezo speaker on it, when you loose connection it starts beeping. This is a low tech solution that we think will help.

Good idea!! We used to do this when I was (a lot) younger and flying model rockets. We put piezo buzzers in nose cones instead of clay weights to help us find them after they touched back down. Helped a lot.

[dbrgn]

Yesterday I also tried outside flying, on a big parking lot next to our house. It was 01:30 in the morning so cars were around.

Flying in the dark is great with the LED ring on, it looks fantastic. Keeping the orientation is hard though. I think text time I'll invert front/back controls and turn on the headlight. This way when I see the light I know that the orientation is correct.

Unfortunately after 2 minutes I accidentally set it down on a roof that had ~50cm of snow on it (due to losing track of the orientation), where it immediately sunk in... :/ We managed to get on the roof and get the CF down after a few minutes though. It still seems to work properly.