RTH straight

[shellixyz]

The aircraft will go down linearly until hitting rth_altitude just before starting to circle above home if RTH was started above rth_altitude and rth_straight is set to ON

[Mckenzie74]

Awesome!
That’s exactly what I try to do when coming back. I fly in cruise and pitch down just a little to achieve the ideal slope to home. Obviously I often do that wrong...

[teckel12]

@shellixyz How is this different than nav_rth_alt_mode = FIXED? And if it's different in some way, why not creating a new RTH altitude control mode, STRAIGHT for example? Maybe this is some FW-only thing that I'm not familiar with.

[shellixyz]

@teckel12 I believe FIXED will go down at the maximum pitch for planes until hitting rth_altitude. rth_straight is more efficient for FW. I added a setting instead of just adding an altitude mode because altitude mode is for specifying the altitude to start RTH at. This way you can still chose how you want it to behave altitude-wise before going home. You can still use MAX_ALT, FIXED_ALT or EXTRA_ALT. The only mode it doesn't make sense to use it with is CONST_ALT.

[shellixyz]

Tested again today with 2.1 as base. All working fine

Here is a demo video: https://youtu.be/RznTuZbgDLk

Settings used:

• rth_alt_mode = AT_LEAST
• rth_altitude = 10000 # 100 meters
• rth_home_altitude = 6000 # 60 meters
• rth_straight = ON

[expipiplus1]

Some diagrams to go with the existing ones would be useful I think.

[expipiplus1]

I had a go with this and got some strange behavior; the plane would pitch down and glide (as expected), but after a few seconds it would pitch up back to neutral and fly powered for a few seconds before pitching down again to repeat the cycle.

My config:
https://gist.github.com/f3322e691f2c2d95844ca98c6606e7e6

[shellixyz]

@expipiplus1 You probably need to tune ALTHOLD for your aircraft (altitude management PID loop settings nav_fw_pos_z_{p,i,d}).

Some diagrams to go with the existing ones would be useful I think.

You're right

[shellixyz]

I updated the code to make it clearer. I wrote this last year and didn't realize it was so obscure.

[wilco1967]

Just tried nav_rth_alt_mode = AT_LEAST_LINEAR_DESCENT at Yesterday development version.

However, linear descent doesn't seem to work.

When I enable RTH, it takes an immediate dive at what seems maximum down pitch angle, and stops only at 150 meters (nav_rth_altitude = 15000) as fast as it can while still far away.... Once it reaches 150 meters, it will continue RTH at 150 meters normally....

Plane: MiniTalon / R9M / MatekF722

here's the BB log
LOG00056.TXT

And here's my diff. (stripped of useless OSD lines)
iNav 2.2.0dev - MatekF722 - 20190601 DIFF.txt

This should be a great feature (once it works ;-).... Looking forward to be able to also have linear climb / descent during Waypoint missions as well.

Thanks !

[putimir]

Same thing exactly today - diving until almost reaching nav_rth_altitude and then proceeding RTH @ nav_rth_altitude

[digitalentity]

Yep, there seem to be a bug. See #4778

[wilco1967]

Update: 4-june
This issue has been resolved, and will probably be implemented in 2.2.0RC3
2.2.0 RC2 does NOT yet have the corrections, so be aware.

See #4778

Be aware of steep dives in RC2 or earlier versions, if trying nav_rth_alt_mode = AT_LEAST_LINEAR_DESCENT
It will do a RTH, but dive immediately to nav_rth_altitude