Actuator Outputs for Standart VTOL

[manumerous]

Currently I try to reverse engineer the actuator output data for the flaps of the standart VTOL used in gazebo.

When looking at the actuator_outputs topic in the log files it seems that there are 3 outputs active for servo outputs. However, the standard VTOL only has two elevons and the mixer file of the model as specified here only generates two outputs for the servos by mixing pitch and roll command as expected.

Could it be that for this model the code somehow logs the roll command (left /right or vise versa) separate from the pitch command instead of the actual actuator outputs? At least this seems to be the case when looking at the model.

I tried to find the place in the PX4-Autopilot where this message is published but didn't find anything yet. Maybe the uorb topic is called differently than the topic name in the log?

[Jaeyoung-Lim]

@manumerous Here is the mixer file for the standard_vtol in SITL: https://github.com/PX4/PX4-Autopilot/blob/master/ROMFS/px4fmu_common/mixers-sitl/standard_vtol_sitl.main.mix

and documentation on how mixers work in PX4: https://docs.px4.io/master/en/concept/mixing.html

Could it be that for this model the code somehow logs the roll command (left /right or vise versa) separate from the pitch command instead of the actual actuator outputs? At least this seems to be the case when looking at the model.

Could you elaborate on what you mean by this? If you are talking about thrust/moment commands independent to the actuator configurations, this is logged in actuator_controls_* topic

[manumerous]

@Jaeyoung-Lim thanks for pointing out that we have separate mixers for sitl.

Thanks I had already found the documentation of the mixers and used it today to analyze the mixer files I linked above. :)

In that mixer file it seems that we really have one elevator and two separate ailerons instead of the two elevons (combined elevetar and airlerons) shown in the model:

That was the reason why I was thinking about two elevons and why the 3 outputs for only 2 actuators did not make sense to me. So is the model shown in the simulation just not showing the elevator?

[Jaeyoung-Lim]

Yes, you can see that the elevator exists in the sdf file, without a visual element