Beginner Question - Log Analysis - Unstable Quad at Takeoff

Hello, I am new to drones - have set up an Arris 900 M with Cuav V5+ running PX4 using Qgroundcontrol. I have gone through all the calibration with the sensors and believe that its configured well.

On take off about 3’ about AGL the quadracopter becomes unstable. Reviewing the log the Yaw, Pitch and Roll go way beyond the setpoints. Why is this happening?

I have posted the logs here:

The Quad Copter:

Hi, this airframe might need some careful tuning. Have a look here:

If I was new to drones, I would start off with a smaller/cheaper model, and fly it using RC in stabilized mode, which can be a little difficult on throttle control initially. Then once I know the feel, I would swap to something bigger/more expensive.

I would again try to fly in stabilized (or if that’s too hard) in altitude control mode and stay very close to the ground to check how roll and pitch behave.

If it starts becoming unstable, land immediately, and reduce some of the gains.
In this case I would start of with reducint MC_ROLL_P and MC_PITCH_P from 6.5 down to 3 4 or so. If that’s stable, follow the tuning guide mentioned above.

Just doing an auto takeoff into position mode is not a good idea with a new/untuned airframe.

@MaEtUgR add what you think, I haven’t done this in a while :slight_smile:

Thanks Julian, will check these out.

Any chance you can take a quick look at the logs?

Hi, the drone seems to have bad vibrations which is evident from Raw Acceleration in the log.
ref: (Log Analysis using Flight Review | PX4 User Guide)

You can try these:

  1. (Vibration Isolation | PX4 User Guide)
  2. PID tuning

I have brought the pid tuning down very low and still have major problems. Seems like the computer does not do compensation.

Here is an updated log:

Have you also tried following the steps in the tuning guide?

Julian, that is my next step. Waiting for a new propeller…