I was setting up my new airplane with me new APM2 and noticed that I had a very unsteady display on the Mission Planner. The artificial horizon and other parameters were jumping around a little. This was with both USB and telemetry connection.
I had the GPS mounted on top of the APM2. I found that if I unplugged the GPS that everything was steady. I hooked up my old Media Tech GPS and all was well. Has anyone else had this problem?
Next order I will have to get a longer GPS cable and relocate the new GPS to see if that solves the problem. The problem is that the new 3DR/uBlox GPS very HUGE and it’s not easy to find room for it.
Has anyone tried to shield the gps cable?
It's not a shielding issue. It has to do with the AHRS using GPS velocty readings. When I took my set up outdoors the twitching stopped. It doesnt matter if you have a good 3d lock indoors. Mulipath reflections of the GPS signals couse unreliable insantanius velocity readings which filter though the attitude calculations.
I've been testing outside. (just over ground level, no electronics - only USB power, APM2.5, GPS)
- powering by external, stable 5,5v does not improve it.
- There were less shaking in the open, but not "perfect"
now I got more questions:
1.-It seems flying near buildings , and indoors, (if any fix) - will be unstable
2.- how will the "gps velocity readings" be affected by big airframe, or other electronics that could give reflections ?
3.- doing aerobatics, inverted flight, I guess the GPS could go even more crazy ? - or not ?
4.- why does AHRS need to use the GPS "so fast" ? - I understand to cancel drift, but this fast response ?
5.- mikrokopter are using basically the same GPS module and I don't remember to have seen AHI jump around.