Autotune PID terriblly bad--copter 3.3

Firmware :copter 3.3 hex;
Weight:about 6kg,with Anti-Vibration Platform like below ;

I landed the copter and save the pid after it was sucessfully autotuned in a good weather.Then I refly my copter, it vibrate so heavily that I almost can’t control it. It seems that it fly well before I first landed the copter.

Is the autotune imperfect at present? Or the autotune is not recommend?

I’m sorry the log was lost because the test was done months ago .

Tough to say. What were the conditions at the time you tuned it? Was the vehicle properly configured (props/motors balanced, COG set properly, etc). Was there wind while you were tuning it?

I’ve used autotune many times with no ill effects. Usually it corrects any issues I have with vibrations.

I wil try to redo the basic tuning first. I used to think the attitude algorithm will balance out the props/motors balanced, COG set.

Sounds like you should redo the autotune. It has always worked well for me.

Autotune works well when my copter is 450mm. I used to think the bigger size affect the pid result.
Maybe the COG cause my bad PID.

Feeling that the copter is not controlled well with this kind of anti vibration mount can happen if Pixhawk is mounted in a too soft manner. How did you mount Pixhawk on it ? With extra soft foam ?

I use 3M glue as below to joint the pixhawk and Anti-Vibration Platform
I see the offficial statement “AutoTune is sometimes unable to find a good tune for frames with very soft dampening on the APM or very flexible arms.”
Does that means the Anti-Vibration Platform may cause the frames to be more flexible? I once try to remove the Anti-Vibration Platform, but it cause the copter bunch heavily! So I remount the Platform,and the bunch-problem gone!

This foam should be OK. Check that the blue balls are well seated in the plastic mount. Sometimes one come off and you do not see it.

Thanks! I check the blue balls and they are all well seated.
I’m thinking whether is this Anti-Vibration Platform too soft?
Everytime the autotune fail, I try to tune the copter manually. Although I’m not good at tuning,it flies much better that before,with less shaking.

I used this anti-vibration platform without issues on mutliples builds, but all are AP ship that fly softly. I never auto-tuned with them yet. I am happy enough with the default parameters and some little manual tuning.

what’s the diameter of your copter?My copter is 980mm

Your copter’s frame is flexing, the autotune resulted in very high gains. Try to lover the gains and it will be good!

Diameter on mine is 850mm