Discussions

Attached is a log of my quad in a near crash.  I have been tuning this quad and up until this flight all has been well.  It has been extremely stable since the autotune and fine tweaks of the PID's.  In today’s flight, I switched from PosHold to Drift mode at around 18:03:39 in the logs and at that point the quad went psycho instantly rolling and pitching violently starting a huge oscillation.  3 seconds after it started I switched back to PosHold which fortunately stabilized the Quad very quickly and it flew stable for the rest of the flight.

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At the point of switching from PosHold to Drift one can see the Divergence in Roll and DesRoll and Pitch Vs DesPitch with the desired being opposite to the required.  I have switched from Poshold to Drift on previous flights and not had any issues so I’m concerned as to what may have caused this.  Can anyone assist in helping determine what might have caused this to occur so I can make sure it doesn’t happen again?  Mechanically the quad is sound, nothing loose etc but I have noticed small twitches when changing flight modes.

The log test indicates that the quad exceeded the maximum lean angle and reached 65°.  Not sure why it has no MAG data as I have fully calibrated the quad including the Live Calibration and compass and CompassMOT.

I think my PID’s are fairly good as the DesRoll/Roll and pitch seem to be fairly close, (except for when switching the flight mode) but would welcome any suggestions to tighten them up.  (Possibly reducing Roll ‘D’?)  I also do not have AHRS_EKF_USE enabled, would this have helped reduce the oscillations, should I enable this?

Test: Autotune = UNKNOWN - No ATUN log data

Test: Balance/Twist = GOOD -

Test: Brownout = GOOD -

Test: Compass = GOOD - No MAG data, unable to test mag_field interference

Test: Dupe Log Data = GOOD -

Test: Empty = GOOD -

Test: Event/Failsafe = GOOD -

Test: GPS = GOOD -

Test: IMU Mismatch = GOOD - (Mismatch: 0.47, WARN: 0.75, FAIL: 1.50)

Test: Parameters = GOOD -

Test: PM = GOOD -

Test: Pitch/Roll = FAIL - Roll (-65.59, line 34087) > maximum lean angle (45.00)

Test: Thrust = GOOD -

Test: VCC = GOOD -

Quad, T-Motor MT2814-10 KV770, T-Motor 30A ESC, 12” Carbon Props, Pixhawk v3.2., 2*4S6000  All up weight 3.5kg.

Thanks for helping!

2015-01-25 17-56-15.rar