[example_9] Add gazebo bridge node for clock sync-ing

[Juliaj]

The main change is to add a Gazebo bridge node to fix following Gazebo runtime error after launching the example. The error will cause Gazebo to be terminated.

ros2 launch ros2_control_demo_example_9 rrbot_gazebo.launch.py gui:=true

# logs 
[gazebo-1] terminate called after throwing an instance of 'std::runtime_error'
[gazebo-1]   what():  can't compare times with different time sources
[gazebo-1] Stack trace (most recent call last) in thread 270397:
[gazebo-1] #14   Object "[0xffffffffffffffff]", at 0xffffffffffffffff, in 
[gazebo-1] #13   Object "/lib/x86_64-linux-gnu/libc.so.6", at 0x7d5de3d29c3b, in 
[gazebo-1] #12   Object "/lib/x86_64-linux-gnu/libc.so.6", at 0x7d5de3c9caa3, in 
[gazebo-1] #11   Object "/lib/x86_64-linux-gnu/libstdc++.so.6", at 0x7d5dde2ecdb3, in 
[gazebo-1] #10   Object "/opt/ros/jazzy/opt/gz_sim_vendor/lib/libgz-sim8.so.8", at 0x7d5ddd34ed45, in 
[gazebo-1] #9    Object "/home/juliajia/ros2_control_ws/install/gz_ros2_control/lib/libgz_ros2_control-system.so", at 0x7d5daa9717c5, in gz_ros2_control::GazeboSimROS2ControlPlugin::PostUpdate(gz::sim::v8::UpdateInfo const&, gz::sim::v8::EntityComponentManager const&)
[gazebo-1] #8    Object "/home/juliajia/ros2_control_ws/install/controller_manager/lib/libcontroller_manager.so", at 0x7d5daa486561, in controller_manager::ControllerManager::update(rclcpp::Time const&, rclcpp::Duration const&)
[gazebo-1] #7    Object "/opt/ros/jazzy/lib/librclcpp.so", at 0x7d5da96e2a90, in 
[gazebo-1] #6    Object "/lib/x86_64-linux-gnu/libstdc++.so.6", at 0x7d5dde2bb390, in __cxa_throw
[gazebo-1] #5    Object "/lib/x86_64-linux-gnu/libstdc++.so.6", at 0x7d5dde2a5a54, in std::terminate()

The additional changes are to fix following warnings reported.

• One is related to the color (e.g. Gazebo/Orange). Change made based on https://gazebosim.org/api/sim/8/migrationsdf.html#:~:text=Materials.

[gazebo-1] [Wrn] [SdfEntityCreator.cc:949] Using an internal gazebo.material to parse Gazebo/Orange
[gazebo-1] [Wrn] [SdfEntityCreator.cc:933] Gazebo does not support Ogre material scripts. See https://gazebosim.org/api/sim/8/migrationsdf.html#:~:text=Materials for details.

• The mismatched update rate from controller manager and Gazebo sim. Increased the update_rate for controller manager.

[gazebo-1] [WARN] [1743040617.401316543] [gz_ros_control]:  Desired controller update period (0.1 s) is slower than the gazebo simulation period (0.001 s).

There are more warnings that appear unrelated to the example based on my initial check. I am open to change if it's not the case. For example

[gazebo-1] [GUI] [Wrn] [Application.cc:908] [QT] file::/WorldStats/WorldStats.qml:53:3: QML RowLayout: Binding loop detected for property "x"

[gazebo-1] Warning [parser_urdf.cc:1220] Attribute value string not set

[christophfroehlich]

@Mergifyio backport mergify/bp/humble/pr-482

[mergify]

backport mergify/bp/humble/pr-482

✅ Backports have been created

• #757 [example_9] Add gazebo bridge node for clock sync-ing (backport #755) has been created for branch mergify/bp/humble/pr-482

[christophfroehlich]

Thanks, you are totally right.
I'm just wondering why the test succeeds without your changes, this should not happen. Calling manually the same as within the test fails:
ros2 launch ros2_control_demo_example_9 rrbot_gazebo.launch.py gui:=false

[christophfroehlich]

Ah, we are testing only the rrbot.launch.py without gazebo 🙈