Fix conflicting multicopter controllers via launch-time selection

[Copilot]

The model.sdf contained both MulticopterAttitudeControl and MulticopterAccelerationControl plugins running simultaneously. Both publish to command/motor_speed and control the same rotors, causing conflicts when users send commands to multiple topics.

Changes

Separated controller configurations into dedicated model files:

• model_attitude.sdf - attitude controller only (subscribes to cmd/att)
• model_acceleration.sdf - acceleration controller only (subscribes to cmd/acc)
• model.sdf - now contains only attitude controller for backward compatibility

Added launch-time controller selection:

• New controller argument in start_sim.launch.xml (defaults to attitude)
• Dynamically loads model_$(var controller).sdf based on user selection

Documentation:

• CONTROLLERS.md - detailed controller comparison and usage
• Updated README.md with selection examples

Usage

# Attitude control (default)
ros2 launch rmf_gz start_sim.launch.xml controller:=attitude

# Acceleration control
ros2 launch rmf_gz start_sim.launch.xml controller:=acceleration

Only one controller loads per instance, preventing motor command conflicts.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Simultaneous / conflicting controllers?</issue_title>
<issue_description>There are two control plugins operating simultaneously within the model.sdf.

I,e, the acceleration and attitude controllers.

If the user chooses to even send a message to more than one during simulation, they both will conflict with each other and become unusable? How can we over come this? Would a launch file argument help for this?

Ref:

Here:

rmf_gz/resources/robots/rmf/model.sdf

Line 616 in 976f910

<plugin filename="libgz-sim-multicopter-attitude-control-system.so" name="gz::sim::systems::MulticopterAttitudeControl">

and
here:

rmf_gz/resources/robots/rmf/model.sdf

Line 667 in 976f910

<plugin filename="libgz-sim-multicopter-acceleration-control-system.so" name="gz::sim::systems::MulticopterAccelerationControl">

</issue_description>

<agent_instructions>Suggest solutions to fix discrepancies that may occur due to this setup in a clean way.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Simultaneous / conflicting controllers? #1

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