Strange behavior, refuses to stabilize at all

Yesterday I did some PID tuning on the bench -- copter tied with a string on one axis and free on the other, went for a test flight and all was well - flew marvelously!

Today I tied down the machine for another session of tuning, but it simply would not stabilize at all. Power on, throttle up to hover throttle (~50%), leave the copter on it's own and it simply flips over as if there's no control board on it. Does not try to oppose rotation at all and does not seem like forcing itself into the upside down position... Motors sound like just spinning at the same rpms, regardless of frame angle of rotation.

Batteries freshly charged, so I think it's not lack of power... tried with another set - same result.

Looking at the hud on the flight data screen, everything looks perfect - both roll and pitch work perfectly.

Tried erasing eeprom, default pids, reconfiguring from scratch- no luck.

Here's the log from a test in my hand, you can see roll and pitch values change, but not motor rpms ..

APM1 2560 board, x hexacopter, jdrones 880 motors, 12x38 balanced props, 30A simonk escs, 2x2200 3s lipos.

AC 2.8.1, MP 1.2.19 mav 1.0

Please advice and thanks in advance,

Teo

2012-11-10 19-06 2.log

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  • Ok, today I started "from scratch". Erase EEPROM, reflash 2.8.1, recalibrate radio. Got the same behavior. Then I thought that the escs have gone haywire. So I hooked them to a receiver that outputs throttle on 6 channels and tested without the AP in between. Strangely enough the ESCs have lost their calibration.... Ideas ? 

    So after re-calibrating them things went a bit more back to normal, except that two of the motors start a tad later than the other 4. Anyway I dialed down stab_p to 4, rate_p to 0.13 (from the default .175) and Imax to 3.0 and took it for a test hover.

    Now it flips on takeoff :)

  • Forget to mention -- tried both stabilize and acro modes.

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