Loiter and auto-land drift/un-precise | PID tuning

Hi guys,

I am actually buiding an hexa with Navio+/Raspberry pi 2.
I made my first test flight with success in Stabilize and Halt-hold mode. The drone is very responsive and after tuning the trims, the drone was very stable and was not drifting much as well as the alt-holding was working very perfectly with high precision. I am impressed already by Navio by the way.
However, the Loiter mode did not give me as much joy, after taking off in Stabilize mode, I switched to Loiter and the drone started swinging from left to right with more and more amplitude until I switched back to Stabilize to avoid crash. The auto-land did exactly the same thing. The GPS had 3D lock with HDOP of 1 with +/- 0.3.
I am actually focusing to Tuning PIDs since I think it is the root cause, but, does someone with more experience could help me to figure out what is wrong here ?
Thanks guys.

What are you using to isolate the vibration? Please post a picture of your drone. You may have magnetic interference with the compass…

Fabien, i will be following your post because i am experiencing almost the same problems. In my case GPS some times take more then 5 min to get a lock, some times 2 min then if i unpower navio+ and power it back on it never gets a lock again, despite of the time( 30 min waiting). Few times that i had a lock it flew very unstable, like yours. Hope we find a solution.

Hi Plinio,

I am actually using the base of a Raspberry Case where there is 4 points of support in rubber. The rubber is really hard and may isolate only from high frequencies vibrations. I am also balancing the propellers to decrease the vibrations. Do you know how I could determine in any ground station if vibrations are too high ?
The Navio board is mounted on the raspberry and is installed between the 2 plates of the F550 frame (hexa), the bottom frame of the body is used as distribution board since there is common ground and power distribution for each arms.

I will send pictures tonight. Thank you Plinio.

I can help for your GPS problems, I went through that problem as well. Basically, you have interferencies with the GPS/GNSS. GNSS are operating roughly between 1.1Ghz and 1.6Ghz, if Navio cannot get the 3D fix or HDOP around 1 or 2, it means that the signal/noise ratio is too bad and the error correction mechanism cannot repair all the errors. Therefore, you need to determine first if you have a reception problem or interference problem.
You can do the following test :smile:
Before doing the following procedure, I assume you are in an open space and you are aware about how to change ip address of the Raspberry pi and your computer and streaming telemetry through UDP.

  1. Disconnect all radio based communication from your drone (to isolate the Navio from any frequencies that can make interferencies)
  2. Plug Ethernet cable to your computer and raspberry pi and start ArduCopter and send telemetry through ethernet cable to your computer using UDP.
  3. Check if GPS fix comes fast in GCS, if it never comes you have either hardware problem or reception problem (antenna problem). If the GPS fix comes fast (between 30 seconds and 2 minutes) it means you have interference problem and you dont have the problem right now because your radios are off.
  4. If you are in the case of interference problem, just switch on one by one your communication systems and wait 2 minutes after switching one, if the HDOP raise after switching on one communication system, you found the one that is causing interferencies.

For me, it was the RC transmitter, it is a OrangeRX 1W 433Mhz, it appeared that the transmitter was causing interference’s on the GPS, I added a low pass 900Mhz filter on the transmitter and it solved the problem.
Mostly, cheap wireless hardware are not filtered because filters are expensive, therefore, cheap hardware are most likely causing interferencies.


I suspect now of a bad connection on the GPS cable, after tweaking with it, i had a GPS lock. Yes i dont have anything to interfere with gps yet. i have a quad only no VTX or other transmitters. Only receivers on board.

It sounds like as compass interference…