My Hex flew great yesterday at the park, I even tried a few high speed maneuvers in AltHold to stress the airframe a bit, and it didn't break a sweat.
Encouraged from the great results, I drove about 30 minutes to a lake nearby hoping to get some scenic flying. I lift it about 6 feet off the ground (ok, rookie mistake, I should have gone higher to get to some safe altitude) and slide a bit to the right. Once stopped, I can hear it kill the throttle for a split second. Unfortunately it's enough to hit the ground and crack the landing skids, then flip on its back and keep running the props in the dirt.
I suspected a power glitch but alas, looking at the log I can see 'CTUN.ThrOut' dip for a split second, which is what made it crash. A big thanks to whomever can shed some light on why it'd do that.
The log is only 60 seconds, I think 'CTUN' is interesting. BarAlt and Alt differ in the last seconds when the crash happened. But the barometric one is the correct one. I wonder what could cause that.
Replies
This is the auto analysis for the crash. I think the compass problem happens once the drone lands on its back, because the ublox compass gets yanked from the top of the craft. Not sure what's that IMU Mismatch.
Size (kb) 428.84765625
No of lines 5966
Duration 0:00:24
Vehicletype ArduCopter
Firmware Version V3.2
Firmware Hash c8e0f3e1
Hardware Type
Free Mem 0
Skipped Lines 0
Test: Autotune = UNKNOWN - No ATUN log data
Test: Balance/Twist = GOOD -
Test: Brownout = GOOD -
Test: Compass = FAIL - Large compass off params (X:-245.00, Y:-23.00, Z:-33.00)
Large compass offset in MAG data:
X: -245.00
Large change in mag_field (43.87%)
Max mag field length (585.07) > recommended (550.00)
Test: Dupe Log Data = GOOD -
Test: Empty = GOOD -
Test: Event/Failsafe = FAIL - ERR found: CRASH
Test: GPS = GOOD -
Test: IMU Mismatch = FAIL - Check vibration or accelerometer calibration. (Mismatch: 5.21, WARN: 0.75, FAIL: 1.50)
Test: Parameters = GOOD -
Test: PM = GOOD -
Test: Pitch/Roll = GOOD -
Test: Thrust = GOOD -
Test: VCC = GOOD -
Looking at IMU and IMU2 there's a divergence the moment the throttle dips, one show an acceleration upwards and one downwards (AccZ). What could be the cause of that? Is IMU2 the one inside the pixhawk or inside the ublox6 compass/GPS unit?
Do you have any digital servos connected to it? I would get a similar result with my 450 trex when my digital servos would back feed high voltage back through the pixhawk. I installed a diode to correct the problem.
Nope, no digital servo connected to the pixhawk, only ESCs. Good tip though.