[TheOtherCliff]

VelocityRoam: System->Settings->VtolPathFollowerSettings In particular HorizontalVelMax and VerticalVelMax

RTB: In particular System->Settings->FlightModeSettings->ReturnToBaseVelocity (and ReturnToBaseAltitudeOffset).

There is a thread somewhere here in the forum where a user documents that RTB returns at a different speed based on whether it was selected with the mode switch, or with FC failsafe.

[trust]

DO either of these modes use any of the stabilization functions? What controls how stable the movement is?

[TheOtherCliff]

Every flight mode besides Manual is stabilized in some fashion.  Some will automatically level out, and others will not.

Thus each of these modes use the PIDs that are configured in the Settings->Stabilization tab.

[trust]

Let me try to understand. All modes use the basic PID functions whichever is set by the bank selected. Is that correct?
Then modes like VelocityRoam will use an additional set of control functions.
I look at the Settings>StabilizationSettings and see a number of items with units, whereas the bank PID settings are unit-less.
What are the VbarXXX values?

I changed the props on to 8x4.5 vs the 10x4.5 props and went to a 4s battery. Flight time about the same, but more stable in normal flight. But in both VelocityRoam and RTB, it starts out fine, but tends to speed up then slow down - over 6 seconds or so.

Here is an example video. Light winds.

I use Attitude mode stabilization, manually controlled up to about the 1m mark. From 1 to 2m, I'm flying with VelocityRoam. From 2m to about 2:40, it is running RTB. Especially here, it seems to tilt and go fast for about 7-8 seconds, slows, tilts back, then process repeats until it gets over target.
Neither of these modes seem as stable as the Attitude mode.
The direction of motion in both the VR and RTB are east/west - may have to do with the GPS issue. Just wondering if I can smooth this out more.

[TheOtherCliff]

The Vbar stuff is when you are using Vbar mode.  As I understand, this is a heli mode that makes a flybarless heli feel like it has a flybar.  If so, it does this by smoothing and delaying the input to output.  Smoother, but less stuntable.

The first thing that comes to mind about speeding up and slowing down is that there is variable wind blowing.  If you have telemetry, you can determine if it is really speeding up and slowing down by using GCS and telemetry to look at the GPS speed and the bank angle that you are actually noticing, at the same time.

The second thing is that some (probably VTOLPF) settings have been changed.  You would see in telemetry that indeed it is speeding up and slowing down.

The third thing is that you are using a slow ESC control protocol on at least one ESC.  (Output page) All banks that point to ESCs should be at least PWM@490Hz or PwmSync.  Be aware that PwmSync at least needs ESCs set up and calibrated for no higher than 1000 to 1900 (the default is 1000 to 2000).  You would see in telemetry that indeed it is speeding up and slowing down.
https://librepilot.atlassian.net/wiki/spaces/LPDOC/pages/12058743/ESC+Calibration

[trust]

I checked the settings - one thing I noticed is under the VtolPathFollower settings, the TreatCustomCraft was set to FixedWing, and that's clearly not what this is. I changed it to VTOL, will see if that changes anything. Should it?

[TheOtherCliff]

TreatCustomCraftAs is only used if the Vehicle page is set to Custom.  Custom is where you have to enter all the mixer table stuff manually.

If for instance your Vehicle page is set to Multicopter QuadX (or whatever it is actually called) then that is used, regardless of what TreatCustomCraftAs is set to, since the craft is not custom.