Inquiry Regarding Coordinate Systems and Roll/Pitch Commands in Gazebo/SITL Simulation

[eren1998-256]

Dear All
Hello ,
I am currently working on a university project focused on the implementation and testing of a fixed-wing guidance algorithm in the Gazebo/SITL simulation environment, using the Arduplane control platform. Additionally, I am using the ROS platform and the MAVROS package to receive controller messages and send commands to the fixed-wing UAV.

Based on my initial research into the coordinate systems used in MAVROS, it appears that the package employs the ENU (East-North-Up) coordinate system for sending roll and pitch reference commands to Arduplane. These commands are sent through the "/mavros/setpoint_raw/attitude" topic.

I have implemented a two-dimensional guidance algorithm accordingly and tested its output by sending it to the SITL simulation via the aforementioned tools. However, based on the simulation results in Gazebo, the fixed-wing UAV exhibits unusual behavior, particularly with constant oscillations around the roll axis.

I would greatly appreciate your guidance in addressing the following questions:

What coordinate systems are used in SITL/Gazebo simulation and the ROS package for sending and receiving commands and messages?
In which coordinate system should the output of my guidance algorithm, which provides roll, pitch, and thrust references for the inner loop, be computed? Additionally, is the topic I am using suitable for sending these commands?
Thank you in advance for your time and assistance. I look forward to your valuable insights.
Warm regards.