Issue in moveit2 tutorial regarding robot_description_semantic parameter

edit

Assuming https://github.com/ros-planning/movei... is opened by OP, resolution there was simply wrong software version https://github.com/ros-planning/movei.... In OP's case, which uses the specific tutorial, that was probably it.

A bit more generic answer:

The error Could not find parameter robot_description_semantic and ... can happen (not limited to the referenced tutorial). I keep getting it.

Potential root causes: A MoveGroup node is unable to "get (ROS) parameter" robot_description* somehow.

Recommended steps to narrow down a root cause and solve:

Step-1. Identify which node the error is happening in. In terminal output you should see the node name along with the error. In the following example, I can see robot-laputa node:

Eg.

[robot-laputa-24] [ERROR] [1685818539.857625507] [robot-laputa]: Could not find parameter robot_description_semantic and did not receive robot_description_semantic via std_msgs::msg::String subscription within 10.000000 seconds.
[robot-laputa-24] Error:   Could not parse the SRDF XML File. Error=XML_ERROR_EMPTY_DOCUMENT ErrorID=15 (0xf) Line number=0
[robot-laputa-24]          at line 694 in /tmp/binarydeb/ros-galactic-srdfdom-2.0.3/src/model.cpp
[robot-laputa-24] [ERROR] [1685818539.863908388] [moveit_rdf_loader.rdf_loader]: Unable to parse SRDF                                      
[robot-laputa-24] [FATAL] [1685818539.864152922] [move_group_interface]: Unable to construct robot model. Please make sure all needed information is on the parameter server.
[robot-laputa-24] terminate called after throwing an instance of 'std::runtime_error'
[robot-laputa-24]   what():  Unable to construct robot model. Please make sure all needed information is on the parameter server.

Step-2. Try 'get parameter' by yourself before the error occurs, if you could, to see what parameters are set or not. In my case when this error is happening, ros2 param get tends to fail with another errors though.

Step-3. Fix where params set e.g. .launch.py if any. You may have something like the following.:

E.g.

_node_motion = Node(
    package="foo", executable="node_exec", arguments=[],
    name="node_exec_name",
    parameters=[
        robot_description,
        robot_description_semantic,
        robot_description_kinematics,
    ],        
)

Make sure the specific parameter that is causing an error is generated as expected. Also make sure parameter names are correct (one of my error modes was I was passing a wrong key name, e.g. In the following, key "robot_desc" is not what Moveit is looking for, but this as a ROS parameter is totally valid so setting it doesn't cause any error. Moveit returns the error because there's simply no parameter with a key "robot_description")..

robot_description = {"robot_desc": robot_description_config.toxml()}

Btw for how those parameters are generated, as a ROS2 learner I've been seeing 2 ways to generate these params in .launch.py. I'm listing them up here since I haven't seen anywhere where these are summarized.

Option-a. "Manual" approach where you generate each variable by referring to the corresponding resources: moveit2_tutorials/doc/tutorials/quickstart_in_rviz/launch/demo.launch.py#L105:

:
robot_description_config = xacro.process_file(
    os.path.join(
        get_package_share_directory("moveit_resources_panda_moveit_config"),
        "config",
        "panda.urdf.xacro",
    )
)
robot_description = {"robot_description": robot_description_config.toxml()}

robot_description_semantic_config = load_file(
    "moveit_resources_panda_moveit_config", "config/panda.srdf"
)
robot_description_semantic = {
    "robot_description_semantic": robot_description_semantic_config
}

:

# Start the actual move_group node/action server
run_move_group_node = Node(
    package="moveit_ros_move_group",
    executable="move_group",
    output="screen",
    parameters=[
        robot_description,
        robot_description_semantic,
        kinematics_yaml,
        ompl_planning_pipeline_config,
        trajectory_execution,
        moveit_controllers,
        planning_scene_monitor_parameters,
    ],
)

Option-b. Automated approach: moveit2_tutorials/doc ... (more)