Please help! Huge roll oscillation on my new miniquad

I’ve just built a miniquad with DALRC 265 frame, Emax motor 2205s, and littlebee 30a blheli, DAL bullnose 5 inch prop. I use Pixhawk 2 as a flight controller, PID as default.
I have some serious problems with this new setup:

  • The copter fly with huge oscillation on roll axis. And the battery drains fast.
  • It can stabilize itself, but I cannot control the altitude. When I increase just a little throttle control, the copter climb really fast and uncontrollable with 4s battery, the only way to reduce the altitude is to completely cut off throttle to let it fall down. I changed to 3s and it still very hard to keep it hover.
  • In Alt Hold, the copter cannot hold its altitude but drop its altitude quickly, so I have to switch to Stabilize mode to take control. However, when I switch to Land mode, it’s able to land very calmly.
    Here is the short flight video:
    https://www.youtube.com/watch?v=qkmUFvoEpTw

Is there anyway to fix the issues? This is my thesis project, and it’s really make me nervous now. Any suggestion is truly appreciated. I have attached 3 log files with 3s battery.
2017-03-09 18-25-02.log (2.5 MB)
2017-03-09 18-34-53.log (1.7 MB)
2017-03-09 18-29-52.log (4.2 MB)

You will have to turn the rate P and I down to 0.1 and stabilised P down to 3 then start working your way up

It looks like the default PIDs are too high for your setup. You need to tune them. At the very least, you need to lower the rate P and I values. There’s a good guide here on how to tune your quad:

Hi, thank you so much for driving me to the right direction on PID tuning. I’ve followed your suggestions and the comprehensive tuning guide, the result is pretty good.
Here is my PID value for 3s 5500mAh battery:

  • stabilize kP to 3
  • rate Roll: kP=0.08, kI=0.01, kD=0
    The copter fly really stable, no oscillation, and the motors are just a little bit warm, longer battery life. So my assumption is that the oscillation problem drains the battery.

However, when I change to 3s 2200mAh full charged, with the same PID above, the copter oscillates on roll axis again until the battery remains half full (@11.5V).

Do I need to further reduce rate kP as guided, or is there any other way out. Also, I’ve tried autotune, but I don’t have enough battery to complete the process. Is there a way to pause autotune to change battery?

Auto tune won’t work on such a small machine