I’m relatively new to Ardupilot, and am very inexperienced with log analysis. I just had my first fell-out-of-the-sky-like-a-brick crash, and I’m hoping the community could put some extra eyes on the logs.
The quad is a 690 frame, Cube Black w/ 4.0.3 stable / BLHeli32 ESCs using dshot (low RPM power protection disabled) / 15" props / Herelink.
This is the 3rd or 4th flight of the quad. I had just enabled throttle controlled harmonic notch (hadn’t wired up ESC telemetry yet) and was doing a short flight to check the post-filtering FFT.
After floating around in Loiter mode for a bit, I gave it some throttle-up to gain altitude. After a few seconds of climbing all of the motors stopped and it dropped out of the sky (fortunately damage appears limited to the landing gear and bottom frame plate).
Looking at the log, at about 12:23:25 ATT.Roll/Pitch just starts diverging from ATT.DesRoll/DesPitch and it looks like RCOU 9-12 are still trying to send signal to the motors as it starts to fall. I don’t think I’m seeing a failsafe or signs of a power issue.
So to me that says this is a desync or ESC issue (perhaps triggered for whatever reason by the throttle up).
If somebody could confirm this diagnosis and just make sure I’m not missing anything due to my inexperience (or doing something stupid), I’d really appreciate it.
You can see in this graph RCout11 (Motor 3) is commanded to maximum (failed motor or ESC) and RCout 12 (Motor 4) is commanded to minimum to try and compensate.
The odd thing is Motor 1 and 2 outputs really level out, but that might be expected…
Also note that RCout12 and RCout13 are identical:
SERVO12_FUNCTION,36 (Motor 4)
SERVO13_FUNCTION,36
I’d definitely check for any other power issues too. You can see here that current dropped to nothing and logging ended before reaching 0 altitude and there’s no crash disarm message or the usual attitude bounces and rolls.
You are missing vibrations and some other useful things from logs - set your logging to at least:
LOG_BITMASK,141310
MissionPlanner pops up a selector for the log types.
I got around to watching the video footage from the onboard camera and could clearly hear the ESC initialization beeps as the motors stopped, so ESC (or power issue resulting in ESC) issue confirmed.
If your ESC’s have any voltage cutoff, disable that too - allow Arducopter to decide when to land and how to handle the battery voltage.
ESC’s stopping mid-flight are not the best thing, and not all ESC’s are created equal.
