Hi,
The PX4 architecture uses a "mixer" to convert high-level thrust and torque commands into actuator commands, tailored to the airframe's geometry. For more details, refer to the Control Allocation (Mixing) documentation.
For the mentioned SITL example, you can refer to the `generate_force_and_torques()` method in `~\PX4-Autopilot-1.14.3\src\modules\simulation\simulator_sih\sih.cpp`, to understand the derived quadcopter mixer matrix.
Note: The mixer defined in Simulink for this example uses a notation for roll and pitch that is opposite to that of the SIH plant mixer matrix used.
If you are not familiar with mixers and want to directly write Roll, Pitch, and Yaw values using the PX4 mixer, you can publish thrust to the uORB topic `VehicleThrustSetpoint` and roll, pitch, and yaw to `VehicleTorqueSetpoint`, respectively. Refer to this example: PX4 Hardware-in-the-Loop (HITL) Simulation with Manual Control for Fixed-Wing Plant in Simulink, which demonstrates a similar workflow for a different airframe(Plane).
Note: When writing to the uORB values, ensure that both inputs are normalized to the range [-1, 1] in the vehicle body FRD frame, where the Z-axis points downward . Additionally, with this workflow, you need to configure QGroundControl (QGC) to set the correct channels according to the plant being used.
Regards,
