Add new flight mode: Altitude Cruise #25435

sfuhrer · 2025-08-15T14:39:50Z

Solved Problem

Systems without position estimation can only be flown in manual modes. All manual modes for copters require a constant user input to move (if you let go of the sticks they stop/level out). It's thus very cumbersome to fly long distances that way.
it's currently not possible to proceed flying in the set direction in a manually controlled mode if the manual control link is lost (MC and FW)

Solution

add new flight mode, as PX4 custom mode
for MC: interpret roll and pitch stick axes as "rate of change of roll/pitch tilt". This leads to a similar stick feeling as in Acro mode, though the max tilt is always respected (you cannot flip the drone). The throttle and yaw sticks are the same as in Altitude mode.
for FW: pitch, throttle and yaw sticks the same as in Altitude, roll stick: sets "rate of change of roll angle setpoint".
add option in COM_RCL_EXCEPT to discard manual control losses in this mode, though require valid manual control to enter the mode. This way one can set the course and altitude and then cover long distances without triggering failsafes if manual control is lost (enabling the data link failsafe NAV_DLL_ACT is strongly recommended for this case to avoid fly-aways)

Changelog Entry

For release notes:

Feature: Add new flight mode: Altitude Cruise

Alternatives

naming?

Test coverage

Partially flight tested (on MC, without manual control link loss)

Context

The original name proposed was "Cruise mode", but due to the conflict with the standard mode cruise was discarded. "Voyager" implies something similar: a mode that is meant for covering long distances in a manual mode but was deemed to abstract.
Thus the current proposal goes for "Altitude Cruise":

clear connection to Altitude mode
clear indication that it's meant for long distance, straight flights
still has some distinction to MAVLink standard mode "Cruise" by adding "Altitude"

Todos:

MC Position controller: enable to use Voyager without stick inputs (avoid it failsaving, keep tilt and altitude until new inputs arrive)
flight test on real drone MC
implement FW Flight Mode Manger changes
flight test FW

github-actions · 2025-08-15T14:46:33Z

🔎 FLASH Analysis

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Updated: 2025-08-29T13:33:11

dakejahl

"hockey puck mode" 😆

dagar · 2025-08-16T04:11:13Z

Coast or drift?

hamishwillee · 2025-08-20T02:20:46Z

Docs when you're done please.

sfuhrer · 2025-08-20T15:35:12Z

Coast or drift?

Both are valid options. What I don't like about them:

coast: could imply a "power-off" flight, like a glide. And for fixed-wing it doesn't give any hint on how it distinguishes from the current Altitude mode (the extinguishers are: you can disable manual control loss failsafe and you can setup a roll angle against the wind cross wind that is kept)
drift: MC: agree more catchy, but for FW the actual opposite is the case, it drifts less (due to reason explained above)

MaEtUgR

Nice!
The only nit-picks I'd have are the name Voyager which I'd prefer Cruise, Drift, Coast, ... just because of intuitiveness but it's up for discussion. And I'll have to clean up the inheritance structure of the tasks but this pr is in line with the current architecture.

src/modules/flight_mode_manager/tasks/AltitudeVoyager/FlightTaskAltitudeVoyager.cpp

MaEtUgR · 2025-08-21T16:56:59Z

Ouch CI is real. The deadzone for the stick library is currently a multicopter parameter. Short term we could make that part optional e.g. only calculate the deazone expo things if the parameter exists and longer term the deadzone is probably a more global thing that depends on the input and not on the multicopter use case. The expo of course is use case dependent. I haven't thought about that sorry.
https://github.com/PX4/PX4-Autopilot/actions/runs/17132740115/job/48601079770?pr=25435#step:8:10550

dakejahl · 2025-08-22T02:26:40Z

I like "cruise mode" and the mavlink spec says it should not be used for multicopters unless PRd to update. Should we just update the mavlink spec? I do think it's most suitable. Unless "cruise mode" as-is in the mavlink spec serves a slightly different purpose?

Signed-off-by: Silvan Fuhrer <silvan@auterion.com>

Signed-off-by: Silvan <silvan@auterion.com>

Signed-off-by: Silvan Fuhrer <silvan@auterion.com>

…siveness Signed-off-by: Silvan <silvan@auterion.com>

Signed-off-by: Silvan <silvan@auterion.com>

Signed-off-by: Silvan Fuhrer <silvan@auterion.com>

github-actions · 2025-08-29T13:25:55Z

/en/flight_modes_mc/manual_altitude_cruise.md

PageNotInTOC: Page not in Table of Contents (/home/runner/work/PX4-Autopilot/PX4-Autopilot/docs/en/SUMMARY.md)

sfuhrer · 2025-08-29T16:12:16Z

@MaEtUgR @dagar @dakejahl @bresch are you all good with calling it "Altitude Cruise"? The "Voyager" was a bit too abstract.
Altitude Cruise seems like the best compromise:

clear connection to Altitude mode
clear indication that it's meant for long distance, straight flights
still has some distinction to MAVLink standard mode "Cruise" by adding "Altitude"

dakejahl · 2025-08-29T20:08:19Z

Altitude Cruise sounds good to me!

sfuhrer requested a review from MaEtUgR August 15, 2025 14:39

sfuhrer force-pushed the pr-add-voyager-mode-main branch from fda36d6 to a93676c Compare August 15, 2025 14:43

dakejahl reviewed Aug 15, 2025

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sfuhrer force-pushed the pr-add-voyager-mode-main branch from 967982b to 0d9a806 Compare August 21, 2025 15:40

sfuhrer marked this pull request as ready for review August 21, 2025 15:40

sfuhrer force-pushed the pr-add-voyager-mode-main branch from 0d9a806 to aa38cec Compare August 21, 2025 16:18

MaEtUgR previously approved these changes Aug 21, 2025

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src/modules/flight_mode_manager/tasks/AltitudeVoyager/FlightTaskAltitudeVoyager.cpp Outdated Show resolved Hide resolved

sfuhrer dismissed MaEtUgR’s stale review via 3ef0ce3 August 27, 2025 06:41

github-actions bot added the Documentation 📑 Anything improving the documentation of the code / ecosystem label Aug 29, 2025

sfuhrer force-pushed the pr-add-voyager-mode-main branch from 0f540ea to b399a4a Compare August 29, 2025 09:33

sfuhrer and others added 9 commits August 29, 2025 11:34

Add Altitude Voyager mode

a67dfe6

Signed-off-by: Silvan Fuhrer <silvan@auterion.com>

FlightTaskManualVoyager: do not failsafe without stick update

9d8e4c7

Signed-off-by: Silvan <silvan@auterion.com>

MC mode manager: remove MAN_TILT_TAU from voyager control

2da8a7f

Signed-off-by: Silvan Fuhrer <silvan@auterion.com>

FWModeManager: refactor: remove unnecessary _nav_state

c45b382

Signed-off-by: Silvan Fuhrer <silvan@auterion.com>

Move Stick class into a globally available library

27538e4

FixedWingModeManager: use Sticks library

47ea2a9

MC FlightModeManager: increase voyager acceleration generation respon…

3e9d58d

…siveness Signed-off-by: Silvan <silvan@auterion.com>

docs: add voyager mode

527cc60

Signed-off-by: Silvan <silvan@auterion.com>

Commander: fix command voyger not documented

bb0fad6

Signed-off-by: Silvan Fuhrer <silvan@auterion.com>

sfuhrer force-pushed the pr-add-voyager-mode-main branch from b399a4a to bb0fad6 Compare August 29, 2025 09:34

sfuhrer added 2 commits August 29, 2025 11:36

docs: fix naming of voyager file

5e3763b

Signed-off-by: Silvan Fuhrer <silvan@auterion.com>

FlightModeManager: improve comment

5e13376

Signed-off-by: Silvan Fuhrer <silvan@auterion.com>

sfuhrer changed the title ~~Add new flight mode: Altitude Voyager~~ Add new flight mode: Altitude Cruise Aug 29, 2025

Rename Voyager to Altitude Cruise

20c5890

Signed-off-by: Silvan Fuhrer <silvan@auterion.com>

sfuhrer force-pushed the pr-add-voyager-mode-main branch from be4bd4e to 20c5890 Compare August 29, 2025 13:25

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