[Bug] fixed-wing airspeed and wind estimation problem in SITL

[TigerWuu]

Describe the bug

PX4 software-in-the-loop calculates the airspeed using differential pressure in SensorAirspeed.cpp in the simulation module. However, SensorAirspeed.cpp generates the fake differential pressure by body velocity, it will induce some airspeed calculating and wind estimation problems when the wind comes from the x-axis of the body frame
I think a more feasible modification is using the wind triangle concept, obtaining the ground speed from uorb topic and true wind value from gazebo plugin, and calculating the true airspeed to generate the differential pressure. What do you guys think?

To Reproduce

1. Follow the steps in https://docs.px4.io/main/en/ros2/user_guide.html to install PX4 autopilot, ROS2 and gazebo sim.
2. Open a standard_vtol in the windy.sdf
3. Set the wind magnitude as (0, -2, 0) using the wind tag in the sdf file. 0 -2 0
4. Arm the drone and transition to the fixed wing mode, fly straightly to the north.
5. Open the plotjuggler to monitor the wind estimation value in the /fmu/out/wind

Expected behavior

the windspeed_east and windspeed_north value should converge to real value (0, -2)

Screenshot / Media

No response

Flight Log

No response

Software Version

Flight controller

No response

Vehicle type

Hybrid VTOL

How are the different components wired up (including port information)

No response

Additional context

No response

[Jaeyoung-Lim]

@TigerWuu Thanks for reporting the bug. Feel free to open a pull request for the fix

[TigerWuu]

@Jaeyoung-Lim Hi, I have fixed the wind estimation problem the following is the result. Now the estimations look much more normal.

I modified two repositories to fix this problem, gz-sim and PX4-Autopilot. The current information flow will be like this

• gz-sim : I added a new plugin WindEffectPub.cc referring to the WindEffect.cc, which will publish the wind information to /world/$myworld$/wind_info topic
• PX4-Autopilot : I modified the gz_bridge.cpp to receive the wind information from GZ and publish to a new message wind_gz, then the Sensor _airspeed_sim.cpp will receive the wind_gz message and vehicle_local_position to calculate the true airspeed from wind triangle.

However, I have the following problem with PR, I am currently working on

• PX4 V1.14
• GZ sim garden 7.9.0

cause I run into the same issue as #23705, if I use the latest version of px4 and gz sim

• PX4 V1.15
• GZ sim harmonic 8.6.0

what should I do? should I wait until this bug fixed then apply my modification into the latest version of px4 and gz?

[Jaeyoung-Lim]

@TigerWuu Thanks for looking into the problem.

You would have to reapply your modification to the latest 'main' of the PX4 repository to apply your changes. Otherwise your changes would not get applied in future versions