Hi all,

I need some help interpreting the attached log file.

Scenario :

I was flying my Arducopter Y-6, (What a machine, by the way!)
APM 2.6

AC3.xx

Stock hardware, no mods or changes.

5300mah 3S Lipo

Took off, flew around for about 30 secs, hit LOITER at about 3m Height. Held perfectly.
Throttled up, climb out to about 30 meteres, still in LOITER.

Hang around at this altitide for around 2 minutes, slowly yawing left and right to get some nice camera shots.

SUDDENLY, no power, ALL the motors stop, and the copter falls to the ground tumbling from about 20 meters up. During the fall I changed to STABILISE, and applied full throttle, nothing.

Amazingly only damage is one broken prop, this is one tough bird!

Now I have tried to decipher the logs. I have checked the following graphs:

VOLTS - battery was 12.4 at full , dropped quite quickly, but never below 11V

Satts - 7 satellites all the time, HDOP 1.8VCC - 5.0 to 5.5 V all the time, so no brownout on the APM

the only funny I can see is the graph of Throttle in vs throttle out, As the motors quit, the throttle out goes haywire, but no indication WHY.



I think perhaps I just dont know where to look..

Any Ideas? Any help will be greatly appreciated.

Wessie

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So here is the Latest in the post Crash investigation. If you watch this video, (start from 02:20), you will see that my initial assumptions that ALL the motors stopped dead were incorrect. Indeed the copter even tried to correct on the way down.  It sounds as if possibly one or more motors quit briefly. 

This proves that :

1. The APM worked all the time, not a brownout.

2. there is not a bad join between the Power Module and the PDB, (sort of)

  • I also checked and rechecked the solder joins on the "deans" connectors and all the wiring.
  • The Low voltage cutoff is not the problem, battery never went below 11V
  • Its cant be the MODE CHANGE bug, as I did not change modes there, and I think its been fixed anyway.

So now the next things to look at are :

- check if the ESC's did not go into THERMAL cutout. I do have 2 ESCs stacked tightly in the frame.

- check if vibrations could have caused it, but doubtful as it was fine on previous flights, and for 2.5 munutes of this flight.

-watch the video in slomo to try and establish if all, only one or more of the motors stopped.


(does the APM log contain each motor output seperately?)

Upwards and onwards!!

Re: volt logs.

Is it possible the logging frequency is much lower than the ESC frequency? Ie you might miss a spike inbetween two log samples, but the ESC picked it up and did the voltage cutoff?

That link is straight from the ESC 20 AMP with SimonK product page - there is a link on the top that says "data sheet". http://store.3drobotics.com/products/esc-20-amp-SimonK

I agree the values sound odd, and if I remember correctly, the manual that came with the ESC is completely different in appearance. 

You mentioned the only damage was one broken propeller. Is it possible the blade broke in flight and that is what caused the crash. I have had blades break on my Hex in flight. Came down hard, but with 5 motors still working it was manageable. Actually got video of one that was in front of my camera. I could also hear the change in the audio. Good luck.

@Rodney, no Bud , dont think so, saw the prop splinter off when it hit the ground, plus , check the video, you will see what I mean..

Further Tests today :

  • Compassmot test gave 12% Mag interference
  • ESC's were only mildly warm after 4 minutes of test running at 75% throttle while holding it down
  • Vibration Tests were EXCELLENT, with X and Y at +/- 1.5, and Y at +/- 2

I have now exhausted everything I can think of. This is the worrying part. The uncertanty.

During one duration test on the ground (We hold the copter down by hand , and up the throttle to 75%, DO NOT TRY THIS AT HOME), after about 2 minutes the right front lower motor clearly started spinning slower than the rest, and always a bit slower, then suddenly it woke up and was spinning like the others. I checked the esc temps, and everything else possible, but no apparent reason was found. Will try to replicate and Video it this weekend.

Wessie - 

Just worth mentioning after seeing your motor is spinning slower. When I first received my brand new 850kv motors, 1 was broken - it would spin, but after close inspection, this one motor would always stop 1-3 seconds before the other 3 when cutting the throttle off while on the floor - the copter was wobbly/unstable because of it. Replaced and all was well. Also, when I applied slight pressure on the broken motor, it had some play (would move up and down 0.1cm, where the other 3 absolutely did not). 

I hear you Ralph, thanx for that, will re-check them. The only thing is that the Y6 flies GREAT, and does everything it should, then flips over for no reason. If it is a bad motor it would misbehave all the time, would it not?

Yea the THEORY is that it will fly on with one motor out, So perhaps 2 or more quit. I am listening to the failure point over and over again to try to determine if they ALL stopped briefly, or just one side or what.

Damn I hope I get to the bottom of this. Going to do as much flying as possible this weekend (Have Plenty spare props!) and hopefully i will be able to draw some conclusions. I am itching to do some waypoint missions and TTL and Fence tests, but not until I trust this ship can fly out an entire battery without incident.

While I am at it, I would like to thank everyone who is contributing to this thread, who took some time to look at a graph or Log file, and helped in any way. 

I have been playing with APM since R1, and still I have learned so many more things with the new software. It is my hope that someone will read the posts, and learn form my experiences with the copter, and hopefully I would be able to repay the favour by helping someone down the line again.

For your next few flights you might want to "ENABLE MOTORS" to turn on motor logging. It may help you see if one or more of the motors is not running as well as the rest.

What else should one enable ?

your logic is totally sound - but sometimes it's the silliest thing :\.  I agree, since it is intermittent it's hard to fully point the finger at the motor..  this leads me to believe something is up with one of your ESC's. do you have any more logs of your tests today that included failures (falling out of the sky)? i'll look through them. i'm assuming you have tried different batteries, right? and you do have a 3DR power module?

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