Hello,


First of all, let me introduce my quad configuration and the crash details.
We have a Tarot T960 hexacopter configuration based on a APM 2.6. We have tested many times and it flies really stable.

This morning, we decided to do the first flight of a modification based on this frame, but in this case, just with 4 arms, in quad configuration. The controller in this flight test was a pixhawk with APM 3.2 version.


We were testing loiter mode in order to measure the time autonomy with a new battery ( Multistar 10000maH). It was stable and after 3 minutes of flight, something happened and drone fell free and crashed.


I have downloaded the log, but after analysing it, I can not figure what happened and which was the problem.


Please I need your help in order to determine which problems we had in order to not commit the same mistakes.

Thank you!!


* I recorded the crash, so I will update the topic with the link of the video. Probably it helps in the analysis.

*I have attached the log file.

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It's look's like a hardware fail, check your motors, esc props, perhaps motor nº3 

Thank you for the info Cala. Really fast reply :D

I would like to learn more about logging and how I can check failures. Could you please tell me how did you see this problem?

Thanks!

A la noche te posteo unas fotos

It looks like at 41,000 it started to roll right and pitch up.  The flight controller cut all power to motor number 3 to gain level altitude but it continued to roll.  It increased power to the other three motors so I would say it was motor number 4 that had the problem.

See that you are in nice loiter and at the end droll and roll separate, your hardware couldn't follow what controller was asking for, that'common mechanical failure log.

Carlos, adding to what cala and Michael are finding I see that current goes down to 0 quickly at the same time. that may be because AP is cutting some motors to stabilize, but also it can be some issue with power ditstribution to escs.

Hernan

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Thank you everyone for the help, it is very useful for me.

Here you can watch the video I uploaded a few hours ago. Probably it can show us more details about the problem.

https://www.youtube.com/watch?v=j67Sb6-OR1w

GLUP!!!

had similar problem and was the ESC programming. they cut off some motors due to low battery. this esc feature needs to be disabled. you have it disabled on all esc?

@Carlos,

problems with Quad have been already detected in the first minute of flight.

Current went down to 0 value (all motors gone temporary disarmed),

verified by AccZ went to -40, so 4 x G

Throttle totally inresponsive

thrOut went down to 0 in 1st minute

you could have saved your Quad setting proper failsafes to ground your quad if current went to 0 in the 1st minute.

Not sure while Kalman filter failed to safe your quad.

On another Current down to 0 even ( motors disarmed) throttle failed to go up again to safe your quad.

I need your telemetry log to study if the problems are not due to low radio signal .

Check your battery and power distribution for burnout connectors.

Darius, you still have a lot to learn about logs before you hand out advice.  According to the log, Carlos took the copter up, then landed it.  The region you see with zero current draw, and with the bump in accZ, is due to Carlos landing his copter.  An instantaneous spike of accZ down to -40 does not indicate freefall.  However, Carlos did take the copter back up and park it in loiter mode.  During loiter, after a few minutes, the altitude drops sharply and the accZ floats near 0.  THAT is the sign of freefall.

There is no failsafe setting for if current draw goes to zero.  I can't see a scenario in which such a failsafe would be useful.

You can check under the RAD tree on the log browser for radio strength.  Carlos' signal strength was fine.  There is also an error tag for if radio is lost.  Please read the documentation.

Carlos, I'm thinking mechanical failure.  The log does not indicate any kind of software error in the autopilot.  On the contrary, as it was falling the auotpilot was attempting to correct.  I am seeing the current drop to zero right as the freefall starts.  That indicates a power failure to all 4 motors... but the Pixhawk still recieved power.  Very interesting...

Is the new battery you're testing significantly heavier than what you normally fly?  Can you post the specs or links to the new and old battery?

Maybe PWM connector to motors popped out of pixhawk?  If that happens, the motors turn off.  It happened to me, thankfully while I was running the copter strapped to the bench.  After that I gued the connector in.  If you are able, definitely strap the copter down and move the throttle all around.  It's a safe (so long as you do it securely) way to find potential problems.

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