[TheOtherCliff]

Sorry.  I still don't see a problem.  You immediately went from RTB hover into VR landing.

It will do something that looks like an oscillation in order to come to a stop.  It is flying along, and to stop it must bank in a direction to apply the brakes.  Then when stopped, it removes the bank and becomes level.  That is the minimum that it must do to stop.  Depending on your tuning and other settings, this stopping procedure can be anything from slow and smooth to quick and jerky.  There might be some ringing too (decreasing oscillation that goes away) if something like PIDs are too high.

If you have RTB configured to go into a hover when it gets to base and you just let it sit there and hover, does it continue to oscillate or does it smooth out?  Does it do the same thing if you travel in VR and then suddenly stop?  I am guessing at this point that your Stabilization PIDs may be too high or that your control rates (like Stabilization->Advanced->MaxRateLimit is too high or one of the VtolPathFollowerSettings PID settings has been set too high.

[startrek66]

Sorry.  I still don't see a problem.  You immediately went from RTB hover into VR landing.

It will do something that looks like an oscillation in order to come to a stop.  It is flying along, and to stop it must bank in a direction to apply the brakes.  Then when stopped, it removes the bank and becomes level.  That is the minimum that it must do to stop.  Depending on your tuning and other settings, this stopping procedure can be anything from slow and smooth to quick and jerky.  There might be some ringing too (decreasing oscillation that goes away) if something like PIDs are too high.

If you have RTB configured to go into a hover when it gets to base and you just let it sit there and hover, does it continue to oscillate or does it smooth out?  Does it do the same thing if you travel in VR and then suddenly stop?  I am guessing at this point that your Stabilization PIDs may be too high or that your control rates (like Stabilization->Advanced->MaxRateLimit is too high or one of the VtolPathFollowerSettings PID settings has been set too high.

Thanks for the reply. I answer you questions

Q. If you have RTB configured to go into a hover when it gets to base and you just let it sit there and hover, does it continue to oscillate or does it smooth out? 

A. Yes. continue without diminishing


Q. Does it do the same thing if you travel in VR and then suddenly stop?

A. No. in VR mode if I stop the quad it stabilizes immediately and I able to make stable movies.

Do you think it's a Pid regulation problem?

[TheOtherCliff]

It may be one of the VtolPathFollowerSettings PIDs in System->Settings.  I would play around with settings in VtolPathFollowerSettings.  Press red up arrow "Save" at top of page to make your changes permanent.

[startrek66]

It may be one of the VtolPathFollowerSettings PIDs in System->Settings.  I would play around with settings in VtolPathFollowerSettings.  Press red up arrow "Save" at top of page to make your changes permanent.

I do not have much experience with these parameters and therefore not knowing the meaning I do not know where to focus my attention. Are there any examples of adjusting these pid or an explanation of their meaning? Moreover, according to you it might be a good choice to see what happens if instead of stopping the quadcopter on the vertical of the base program it for an automatic landing?

[TheOtherCliff]

The reason I didn't give an exact thing to adjust is that I don't know which and would have to play with it myself if I were having this problem.

I am guessing that the oscillation is in the horizontal direction, so anything that can influence that:
HorizontalPosP
HorizontalVelPID.Kp,Ki,Kd
VelocityFeedForward
BrakeHorizontalVelPID.Kp,Ki,Kd

I would try cutting each each one in half, only one setting at a time.  Put each back to default before trying another.  VelocityFeedForward I would try both doubling and halving.  I didn't research whether BrakeHorizontalVelPID is active or not in this case.  I rather doubt it.

Notice that there is a separate PID for VelocityRoam mode.  The P term is higher in VR mode.  VR is what works for you, but using that higher P term in other modes would make oscillation worse.  The fact that there is a separate PID for VR and it is higher makes me want to try lowering HorizontalVelPID.Kp even further as the first thing to try.  I would try lowering HorizontalPosP as the second thing to try.

[startrek66]

I did some tests again and uploaded two new videos showing the problem. I lowered the kp from 0.15 to 0.10 and the oscillation seems sweeter. I intervened on the parameter you indicated to change first.






I also tried to change the phase from hold to land and everything works perfectly. there are absolutely no oscillations. One hypothesis is that the definition of the code has remained incomplete?

[TheOtherCliff]

It does not happen in VR mode.  I find that puzzling.  Did you say that it used to work OK?

One more thing that I should have said sooner, is that I would recalibrate the mag sensor.  Be aware that the calibration is always gathering data, not just when you press the button 6 times.

I would also look for loose or cracked components (motor, arm).

For mag calibration:
- be far away from large things and metal things like car, LP gas tank, tall buildings, maybe even a watch
- it is best to use telemetry, not USB cable
- once calibration is started, do not put the model on the ground
- don't rotate it very fast

I see that you are using a standard PixHawk GPS/mag  Do you have Aux Mag Usage set to Aux Only (this is not default)?  (You should.)

You should also be using the default GPS protocol of Ublox (not NMEA).

I am guessing that RTB hover still lets you control yaw.  Maybe next time you could try slowly rotating yaw around 360 degrees while in RTB hover.

Here is a link to a fast east west oscillation that we never really did figure out.
https://forum.librepilot.org/index.php?topic=382.0

[startrek66]

It does not happen in VR mode.  I find that puzzling.  Did you say that it used to work OK?

One more thing that I should have said sooner, is that I would recalibrate the mag sensor.  Be aware that the calibration is always gathering data, not just when you press the button 6 times.

I would also look for loose or cracked components (motor, arm).

For mag calibration:
- be far away from large things and metal things like car, LP gas tank, tall buildings, maybe even a watch
- it is best to use telemetry, not USB cable
- once calibration is started, do not put the model on the ground
- don't rotate it very fast

I see that you are using a standard PixHawk GPS/mag  Do you have Aux Mag Usage set to Aux Only (this is not default)?  (You should.)

You should also be using the default GPS protocol of Ublox (not NMEA).

I am guessing that RTB hover still lets you control yaw.  Maybe next time you could try slowly rotating yaw around 360 degrees while in RTB hover.

Here is a link to a fast east west oscillation that we never really did figure out.
https://forum.librepilot.org/index.php?topic=382.0

Q. Did you say that it used to work OK?
A. I did not understand,

Q. I would also look for loose or cracked components (motor, arm).
A. No component is broken

Q. I see that you are using a standard PixHawk GPS/mag  Do you have Aux Mag Usage set to Aux Only (this is not default)?  (You should.)
A. MAG is Aux Only


Q. You should also be using the default GPS protocol of Ublox (not NMEA).
A. Ublox

I will recalibrating the mag. Should I recalibrate it with what frequency?

[TheOtherCliff]

I will recalibrating the mag. Should I recalibrate it with what frequency?

Long ago I heard it said that the mag should be recalibrated frequently.  Even as often as at the beginning of each flying day.  I only recalibrate it if I have problems, which is basically never.  I have flown the same calibration for over a year, at sites 50km apart.  For me, a good calibration does not seem to need to be redone if you don't travel far.  If I flew at a site a long way away or a lot different (plains to mountains or central to ocean coast), I would recalibrate.

Q. Did you say that it used to work OK?
A. I did not understand,

Just trying to be certain whether it ever worked correctly for you.

... I saw these fluctuations today for the first time. With the VR mode there are absolutely no. these oscillations have appeared with RTB mode. I made a video

Next time I have my favorite GPS quad flying, I will try to remember to test RTB-hover again.  I guess I maybe have tested it once or twice because I forgot to change RTBNextCommand to Land.

[startrek66]

I will recalibrating the mag. Should I recalibrate it with what frequency?

Long ago I heard it said that the mag should be recalibrated frequently.  Even as often as at the beginning of each flying day.  I only recalibrate it if I have problems, which is basically never.  I have flown the same calibration for over a year, at sites 50km apart.  For me, a good calibration does not seem to need to be redone if you don't travel far.  If I flew at a site a long way away or a lot different (plains to mountains or central to ocean coast), I would recalibrate.

Q. Did you say that it used to work OK?
A. I did not understand,

Just trying to be certain whether it ever worked correctly for you.

... I saw these fluctuations today for the first time. With the VR mode there are absolutely no. these oscillations have appeared with RTB mode. I made a video

Next time I have my favorite GPS quad flying, I will try to remember to test RTB-hover again.  I guess I maybe have tested it once or twice because I forgot to change RTBNextCommand to Land.

Q. Did you say that it used to work OK?
A. I did not understand,[/quote]
Just trying to be certain whether it ever worked correctly for you.

Ok. The fact that I don't explain is why these oscillations only appear when the quadricopter stops in hovering waiting over the takeoff Point. If the setting is RTB + Land There are no problems and the Quadricopter lands in a stable way.

[TheOtherCliff]

Here is another user / thread with the same problem: oscillation in RTB hover.
https://forum.librepilot.org/index.php?topic=4466.0

[startrek66]

Here is another user / thread with the same problem: oscillation in RTB hover.
https://forum.librepilot.org/index.php?topic=4466.0

Well, let's put our experiences together. Can we create a single discussion?