Need help with analysis of logs for bad Pixhawk crash running APM 3.3.3

[Geoffrey Heller]

Hello Everyone,

About a month ago I experienced a bad crash of my (clone) Pixhawk driven quad.  This crash resulted in the total destruction of the quad and also nearly destroyed a $500 window.  

The experience was very disconcerting for me, and I decided I would not fly again until I had understood what went wrong.

Flight was in a field near a house.  I was standing on the back porch.  I was practicing maneuvers in Stabilize mode and then at one point I heard an EKF Error announced.  A few moments later the quad started leaning towards me and accelerated in my direction.  It was non-responsive to controls at this point.  Fortunately it missed me but it slammed full speed into the house, destroying itself and nearly taking out a brand new window.  The crash was hard enough to leave 1/2" dents in the siding of the house.

So what happened?

I have been looking at the log files since the crash, and feel that the crash is possibly related to IMU.GYRY and IMU2.GYRY drifting apart by (what appears to be) a small amount.  Is this the gyro drift issue that others had seen in the past?  Or was this caused by aliasing due to some high-frequency vibration which doesn't seem to appear in the logs?  Was this caused by a poor quality gyro mounted on a clone Pixhawk?

Here are my notes:

Physical configuration

----------------

Platform is DJI F450 clone

Using clone Pixhawk (Ebay) with attached M8N GPS / Compass

Pixhawk mounted on Anti-Vibration plate

Pixhawk running APM:Copter V3.3.3

ESCs are Hobbysky XRotor 20A flashed with BLHeli (latest version)

Motors are Sunnysky x2212 KV980

Battery is 3S 4500

Props are 10"

TIMELINE

--------

37:48 - IMU.GYRY and IMU2.GYRY drift apart for the first time

37:48 - EKF3.IMX,IMY,IMZ exceed recommended max of 50

37:52 - Start of Sharp spike in RCIN.C3.   Spike ends one second later at 37:53 (pilot attempting correction?)

37:52 - We see a corresponding spike in MAG.MagX which goes from 200 to 400

37:53 - We see EKF3.IVN, IVE and IVD diverge.  

37:54 - We see EKF4.SMX cross the 1.0 limit (Magnetometer inconsistency)

37:55 - EKF3.IVN, IVE and IVD go flatline

Output of Mission Planner's automatic log file analyzer:

------------------------------------------

Test: Balance/Twist = NA - 

Test: Brownout = GOOD - 

Test: Compass = FAIL - Large change in mag_field (366.09%)

Max mag field length (596.92) > recommended (550.00)

Test: Dupe Log Data = GOOD - 

Test: Empty = GOOD - 

Test: Event/Failsafe = GOOD - 

Test: GPS = FAIL - Min satellites: 0, Max HDop: 99.99

Test: IMU Mismatch = GOOD - (Mismatch: 0.66, WARN: 0.75, FAIL: 1.50)

Test: Parameters = GOOD - 

Test: PM = NA - 

Test: Pitch/Roll = NA - 

Test: Thrust = NA - 

Test: VCC = GOOD - 

At this point I could really use some help in analyzing this log file.  I would very much like to know what exactly happened here.  Additionally, I am hoping this data can serve as a guide for the developers working on the APM EKF code.

https://drive.google.com/a/frostpaw.com/folderview?id=0B9Zssttp6CFibDVCN2hUNlZsTzg&usp=sharing

Thank you!

-Geoffrey

[Linus Casassa]

Hi Geoffrey,

Did you find the issue?

Regards,

Linus

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Linus Casassa
+56 9 97776941