Accel 2 clipping

PX4 Autopilot
1

Hello. I have a Cube Orange on the quadcopter giving me this “Accel 2 clipping. Not safe to fly” warning. But it continues to fly normally. I am looking for solutions. As researched this topic it seems like caused by the vibration but from graph it seems normal. Could somebody help me?
log file is too big so I upload it to the drive.
Log file: 09_33_14.ulg - Google Drive

2

Hi @Vacoff,

From what I know, accel clipping is happening when the sensor could not measure the acceleration because its amplitude is greater than the maximum measurable value. Suddenly, if there are too many measurements on the accelerometer, the average acceleration will be 0g instead of -1g, suddenly the ekf will “fall in free fall” and the controller will compensate. A link that a maintainer provided me once here

So according to the log, I would say that Accel 2 is continuously vibrating in red comparing to the 2 others. I guess the first step should be to improve the mounting of the FCU in your drone to reduce that.

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I think the vibration topic will be explained during the PX4 dev summit as many people are getting difficulties to make it works properly

P.S: it is easier for people to analyse your case to provide directly the link to the log review rather than the file itself

https://logs.px4.io/plot_app?log=02897e73-035b-43eb-8ad9-edc67585a728

1 Like
3

thank you for your response. as if the mounting was bad why only the 3rd accelerometer would raise an error? Shouldn’t all three behave similarly? As now it is mounted on the double sided foam cubes. I will change it and then do some more tests.

P.s: thank you for your feedback, I saw the method you mention just after posting.

4

here is the another flight where were no warnings. the vibration graph looks similar to this one.

https://logs.px4.io/plot_app?log=7fed8475-04c5-4e83-97c1-444515e9d6c3

5

In documentation I read :

Three IMU’s

  • these consist of 2 on the IMU board
  • 1 fixed to the FMU

If you can find the ID of Accel 3 maybe you can define if it’s the one fixed to the FMU. For the mounting foam, at least in my case, I got better results with a foam tape rather than the double foam they included in the package

6

After mounting Cube Orange on the vibration dampening pad the warning is gone. And vibration metrics looks better. Until the warning comes back this is the solution.