Inav: Rounding of way point turns for fixed wing

[moggiex]

Current Behavior

When using Waypoints in a FW model, when it reaches a WP, it banks like a processed squirrel on crack after his next nut if the angle to the next WP is too great ( > 90 degrees) :D

In 2.5.1 nav_fw_control_smoothness was added to smooth things out for FW nav modes. This works as expected. YAY!

However it has an undesired effect (assumed) as it works for all NAV modes, so in 3D Cruise a model that was "tight" and reactive to fly (in 2.4), now just wanders around the sky if this value is too high (eg 7 or more) as it doesn't correct fast enough especially in a strong wind.

For absolute clarity I was looking for this to smooth out the harsh turns when in WayPoint mode. Which it does, but with the effect above. So now I know I was wrong, nav_fw_control_smoothness is a global setting, all good, that works as expected.

Update: To add further clarity to why this would be desirable, a model that is known to have tip stall issues, say a Sonic Modell binary as an example, having the model change directions abruptly, with other factors such as a tail wind or cross wind, may cause the model to stall itself if the turn in a WP is too harsh. Multi rotors, not an issue, some FW models in the right conditions, yea they need some smoothness in those turns!

Desired Behavior

My feature request is that can we have some "rounding" on the turns for FW in waypoint mode so the turns are not so harsh?

This is separate to nav_fw_control_smoothness and specific to turns in a WP mode.

You can see how harsh the turns are in this video near the end https://www.youtube.com/watch?v=Y1AZMsZJCXo scroll to 29:00 for DVR footage

Suggested Solution

Adding a setting is something like a value that allows for a turn radius, say 30 metres to make the turn at a WP a lot more smooth for FW models, rather than banking like a processed squirrel on crack after his next nut if the turn is too tight to the next WP :D

Who does this impact? Who is this for?

Those using waypoints with a FW model.

Additional context

Commits here https://github.com/iNavFlight/inav/pull/5655

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[moggiex]

This new setting is different to nav_wp_radius which is defined as

Waypoint radius [cm]. Waypoint would be considered reaches if machine is within this radius

This is the turn radius when the FW model reached the way point (whose size is defined by nav_wp_radius).

Matt