Neat experiements with fixed wing loss of GPS

#1

I thought folks might find this interesting. We recently did some PX4 fixed wing testing with firmware based on 1.8.0 where we forced the GPS driver to stop and watched the vehicle behavior. We would restart the GPS driver and watch where the vehicle position jumped to as a measure of how far off the EKF navigation solution had wandered.

Amazingly we had one loiter remain stable for > 6 minutes before the global position failsafe finally kicked in.

Based on this log (and a couple others we’ve done) I think the EKF position error estimate is optimistic, at least for our hardware setup and flight profiles.

Here is the flight log for those interested in diving into the details. Feel free to post your thoughts or observations in this discussion thread.
https://review.px4.io/plot_app?log=ba165f7d-113d-4c5d-b479-1fcf21e99175

FYI @dagar @Paul_Riseborough @Kjkinney

4 Likes
#2

Hi @Antiheavy,

It’s indeed a nice experiment. Thank you for sharing the results; which I’ll look into more details later tonight. According to the logs, the flight time was over 10 hours. Is that correct? Are you using solar cells? And, are you using a PixRacer as FC?

#3

The time is often wrong in flight review. The flight was much less than 1 hour. We are using a custom FMU-V4 board that is very similar to PixRacer.

#4

I have a xvert tailsitter which I fly in stabilized mode without gps. I also fly acro including loopings, steep turns, many consecutive circles… you notice that the attitude solution drifts slightly but it does not impose an issue and recovers really fast once you level out. So I’m not surprised by the above results.

#5

Should also note that the vehicle does not have an airspeed sensor

#6

Whereas the fixed wing in the log from the original post definitely had an Airspeed sensor.