feat(commander): external modes setpoint types & reliability by bkueng · Pull Request #27683 · PX4/PX4-Autopilot

bkueng · 2026-06-17T13:57:54Z

Background

This started out with reliability issues: DDS topics do not use reliable transfer, which for most cases is fine as topics are regularly updated or checked for a reply. But there are some exceptions:

mode_completed signalling
fw setpoint configuration
config overrides
vehicle control mode (setpoint configuration)

We started to see topic drops in very rare cases for modes that switch between setpoint types.

Solution

The cleanest solution would be to use reliable transfer for these topics.
I tried that in the past and it resulted in severe topic drops for all telemetry messages, making it unusable.

So this PR addresses the cases individually, there is a simple solution for each:

the topic is re-published continuously until there is a mode switch
similar: ensure the configuration is re-published regularly
a confirmation is added to PX4
for this one I took the opportunity to do a bigger change, see next section

Setpoint types

This PR switches from using VehicleControlMode to a specific setpoint type message with reply.
Reasons:

in case a VehicleControlMode was dropped (e.g. when the mode switched setpoint type), no confirmation was returned, and resulting in wrong controller flags.
cleaner interface separation: external modes do not need to configure (or know) which controller to run for a certain setpoint
allows for external modes to check for compatibility: e.g. a mode using fixed-wing setpoint types can now be rejected on a multicopter.
allows for further extensions, like a setpoint timeout

It also adds a timeout to the setpoint config, but is not implemented yet.

PX4 internal modes also make use of this (except they do not need to publish the topics as it's known at compile-time). So the new information flow is:

nav_state -> setpoint type -> vehicle control mode flags

Apart from the added setpoint type compatibility check, the behavior is expected to be the same.

Adding a new setpoint type

When adding a new setpoint message, a new type needs to be added to msg/versioned/SetpointConfig.msg, and handled in src/modules/commander/ModeUtil/setpoint_types.cpp. Then it can be used for internal and/or external modes.

Other changes

remove unused VehicleAngularAccelerationSetpoint.msg
remove unused flag_control_acceleration_enabled

This depends on Auterion/px4-ros2-interface-lib#209

Note: it is a breaking API change for external modes and requires updating both sides. The API version is incremented and if there is a mismatch, an external mode raises an appropriate exception.

github-actions · 2026-06-19T08:03:54Z

💡 Commit messages could be improved

Not blocking, but these commit messages could use some cleanup.

Commit	Message	Suggestion
`545b14f329`	chore: use setpoint_config in mc_raptor and mc_nn_control	Missing conventional commit format (e.g. "feat(ekf2): add something")

See the commit message convention for details.

This comment will be automatically removed once the issues are resolved.

github-actions · 2026-06-19T08:12:37Z

🔎 FLASH Analysis

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Updated: 2026-06-30T08:30:59

azerupi

Looks good to me

beniaminopozzan · 2026-06-20T10:08:27Z

@bkueng

The cleanest solution would be to use reliable transfer for these topics.
I tried that in the past and it resulted in severe topic drops for all telemetry messages, making it unusable.

would you consider having different QoS for different topics?

bkueng · 2026-06-29T11:18:29Z

would you consider having different QoS for different topics?

That is what I tested, only setting some topics as reliable, but it affected all other topics too.

Allows an external mode to check if the request got processed

Important for external modes in case a topic sample gets dropped.

Switches from using VehicleControlMode to a specific setpoint type message with reply. Reasons: - in case a VehicleControlMode was dropped (e.g. when the mode switched setpoint type), no confirmation was returned, and resulting in wrong controller flags. - cleaner interface separation: external modes do not need to configure (or know) which controller to run for a certain setpoint - allows for external modes to check for compatibility: e.g. a mode using fixed-wing setpoint types can now be rejected on a multicopter. - allows for further extensions, like a setpoint timeout This makes it a bit more effort to add a new setpoint type. Specifically, setpoint_types.cpp needs to be extended when adding a new setpoint message. PX4 internal modes also make use of the setpoint types. The information flow is: nav_state -> setpoint type -> vehicle control mode flags It also adds a timeout to the setpoint config, but is not implemented yet. This changes the interface for external modes and thus the compatibility version is increased.

…abled

mahima-yoga

Thanks!

bkueng · 2026-07-03T07:40:35Z

@mrpollo do you want to hold off with merging this?
We also tested this on a Skynode in SIH with some of our modes.

mahima-yoga · 2026-07-03T08:56:42Z

Since it's ready to be merged I wouldn't hold off since it's a really good improvement and also solves some sporadic issues with setpoint reliability. @mrpollo - would appreciate if this could be in the 1.18 release

mrpollo · 2026-07-03T19:32:41Z

I think this is fine to come in now for v1.18, the only thing I am now thinking is the Test Team doesn't currently have any test cards that include a companion computer and code running using the ROS 2 interface, we should likely have a test that does, even if its just a simple behavior API check that can be verified with a log. If anyone wants to help me describe how that would work I would make sure you get a proper dinner on me ;)

mahima-yoga · 2026-07-03T22:57:25Z

@mrpollo sure! Happy to help

bkueng · 2026-07-06T08:11:48Z

Thanks everyone.

I can also help. Probably the simplest is to run the goto example: https://github.com/Auterion/px4-ros2-interface-lib/tree/main/examples/cpp/modes/goto.
It can be started from any location and it flies a fixed pattern.

bkueng commented Jun 17, 2026

View reviewed changes

Comment thread msg/versioned/SetpointConfig.msg

bkueng changed the title ~~feat: external modes setpoint types & reliability~~ feat(commander): external modes setpoint types & reliability Jun 18, 2026

github-actions Bot added the kind:feature Request or change that adds new functionality. label Jun 18, 2026

sfuhrer added this to PX4 v1.18 Release Jun 18, 2026

github-project-automation Bot moved this to Todo in PX4 v1.18 Release Jun 18, 2026

bkueng force-pushed the external_modes_setpoint_types branch from 436b382 to 1ec77b1 Compare June 19, 2026 08:03

azerupi approved these changes Jun 19, 2026

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mahima-yoga reviewed Jun 25, 2026

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Comment thread src/modules/commander/ModeUtil/setpoint_types.cpp

Comment thread src/modules/commander/ModeUtil/control_mode.cpp

bkueng added 3 commits June 30, 2026 09:54

chore(msg): remove unused VehicleAngularAccelerationSetpoint.msg

69ac9a5

fix(commander): add config_overrides_confirm topic

5469402

Allows an external mode to check if the request got processed

fix(navigator): resend mode_completed when mode is completed

426667d

Important for external modes in case a topic sample gets dropped.

bkueng force-pushed the external_modes_setpoint_types branch from 1ec77b1 to 48e0d07 Compare June 30, 2026 07:55

bkueng added 4 commits June 30, 2026 10:24

chore(VehicleControlMode): remove unused flag_control_acceleration_en…

2e55b89

…abled

chore: use setpoint_config in mc_raptor and mc_nn_control

545b14f

chore(commander): remove unused flag_control_termination_enabled flag

df468e7

bkueng force-pushed the external_modes_setpoint_types branch from 48e0d07 to df468e7 Compare June 30, 2026 08:25

mrpollo removed this from PX4 v1.18 Release Jun 30, 2026

mahima-yoga approved these changes Jul 2, 2026

View reviewed changes

mrpollo approved these changes Jul 3, 2026

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mrpollo merged commit 5d2cec9 into main Jul 3, 2026
76 of 77 checks passed

mrpollo deleted the external_modes_setpoint_types branch July 3, 2026 19:33

mrpollo mentioned this pull request Jul 6, 2026

docs(test_cards): add MC_11 companion computer ROS 2 external mode #27824

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bkueng commented Jun 17, 2026

Background

Solution

Setpoint types

Adding a new setpoint type

Other changes

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