ROS2 Bridge not working with LRAUV Simulator

[prasilva98]

Environment

• OS Version:
  source - humble branch with gazebo garden

Description

• Expected behavior: I tried to create a ROS bridge between the maritime lrauv simulator to control the fins and thrusters.
• Actual behavior: The bridge for the thruster works fine but not for the fins and I can't figure out why.

Steps to reproduce

1. gz sim
2. select lrauv_control_demo
3. ros2 run ros_gz_bridge parameter_bridge /model/tethys/joint/propeller_joint/cmd_thrust@std_msgs/msg/[email protected]
4. ros2 run ros_gz_bridge parameter_bridge /model/tethys/joint/horizontal_fins_joint/0/cmd_pos@std_msgs/msg/[email protected]

Output

In step 3 you will see that the bridge works and you are able to control the thurster. However in step 4 I get this warning:
[WARN] [1733327666.759352233] [ros_gz_bridge]: Failed to create a bridge for topic [/model/tethys/joint/vertical_fins_joint/0/cmd_pos] with ROS2 type [std_msgs/msg/Float64] to topic [/model/tethys/joint/vertical_fins_joint/0/cmd_pos] with Gazebo Transport type [gz.msgs.Double].

I don't think the topic name is wrong or the msg types because I can publish to that using gz topic -t /model/tethys/joint/vertical_fins_joint/0/cmd_pos -m gz.msgs.Double -p 'data: -0.17' and the vehicle starts to turn.

Hopefully somebody has dealt with this.

[prasilva98]

I am pretty sure I know what is causing it.

ros2 run ros_gz_bridge parameter_bridge /model/tethys/joint/horizontal_fins_joint/cmd_pos@std_msgs/msg/[email protected]
[INFO] [1733341747.825102000] [ros_gz_bridge]: Creating GZ->ROS Bridge: [/model/tethys/joint/horizontal_fins_joint/cmd_pos (gz.msgs.Double) -> /model/tethys/joint/horizontal_fins_joint/cmd_pos (std_msgs/msg/Float64)] (Lazy 0)
[INFO] [1733341747.827184515] [ros_gz_bridge]: Creating ROS->GZ Bridge: [/model/tethys/joint/horizontal_fins_joint/cmd_pos (std_msgs/msg/Float64) -> /model/tethys/joint/horizontal_fins_joint/cmd_pos (gz.msgs.Double)] (Lazy 0)

If I remove the "/0/" the bridge causes no issues.
If I add any number between the "/ /" the parameter bridge raises an issue example:

ros2 run ros_gz_bridge parameter_bridge /model/tethys/joint/4/horizontal_fins_joint/cmd_pos@std_msgs/msg/[email protected]
[INFO] [1733341701.255371834] [ros_gz_bridge]: Creating GZ->ROS Bridge: [/model/tethys/joint/4/horizontal_fins_joint/cmd_pos (gz.msgs.Double) -> /model/tethys/joint/4/horizontal_fins_joint/cmd_pos (std_msgs/msg/Float64)] (Lazy 0)
[WARN] [1733341701.255852702] [ros_gz_bridge]: Failed to create a bridge for topic [/model/tethys/joint/4/horizontal_fins_joint/cmd_pos] with ROS2 type [std_msgs/msg/Float64] to topic [/model/tethys/joint/4/horizontal_fins_joint/cmd_pos] with Gazebo Transport type [gz.msgs.Double]

I assume this could be some sort of parsing issue correct?

[prasilva98]

I figured out a workaround. From my understanding you can't specify ROS2 topics with a single number in the path. This is what is causing the issue. The workaround is top map the ROS topic to a different topic like so:

# Full set of configurations
- ros_topic_name: "/model/tethys/joint/horizontal_fins_joint/cmd_pos"
  gz_topic_name: "/model/tethys/joint/horizontal_fins_joint/0/cmd_pos"
  ros_type_name: "std_msgs/msg/Float64"
  gz_type_name: "gz.msgs.Double"
  lazy: true                # Default "false"
  direction: BIDIRECTIONAL  # Default "BIDIRECTIONAL" - Bridge both directions
                            # "GZ_TO_ROS" - Bridge Gz topic to ROS
                            # "ROS_TO_GZ" - Bridge ROS topic to Gz