Quadcopter kept elevating

🧪 Flight Testing & Log Analysis
1

Hi guys,
I tried taking off with my quadcopter using the commander takeoff, unfortunately something went really wrong and the quadcopter kept elevating to higher heights to the point where I killed it manually.
Personally I think the problem is with the GPS because the data does not seem to be valid, however, I have conducted a small test where I manually disconnected the GPS after takeoff and then not the same behaviour was observed.

https://logs.px4.io/plot_app?log=fee78cd1-ae0e-408d-912e-e36922ea1a4b

Thanks in advance

2

Hi,

The quad kept climbing because its altitude estimate was bad. The GPS altitude and the fused estimation never moved significantly, only the barometric height shows the climb.

The GPS Uncertainty plot shows a vertical (and horizontal) accuracy of about 10m, and the GPS fix degraded. So indeed the GPS data wasn’t very reliable. Also, you have some timeout flags in the watchdog, but I don’t know the exact meaning of them. I could imagine they are linked to your bad position estimate. Is this the first time that you experience problems with the GPS?

I have also noticed that you are using the LPE estimator, which is no longer maintained. Have you considered switching to EKF2?

I don’t know anything about LPE, but with EKF2 you could choose the primary height data from the barometric sensor if the GPS keeps being unreliable. Also, there are preflight checks on the position error and minimum satellite counts that prevent arming when the position estimate is too bad.

Hope that helps,
Thomas

3

Hello,

Thank you for your response.
Yes this is the first time I am really experiencing problems with the GPS, the weird part is I did a small GPS test before where I walked around with my quadcopter and then the accuracy was much better and there were no errors. I will read into these timeout flags what they exactly mean :wink:

I am using LPE estimator because simply said for me since I want it fully autonomous I could not get EKF2 to work and LPE offers as far as I know roughly the same possibility?

EDIT: I think the problem is indeed in the messages, apparantly something was doen with the GPS data, however, how could I reproduce this or ensure that this does not happen again?