parameter server hangs after launching the move_group(ROS2 Jazzy)

[GerardHarkema]

Dear reader,

When I launch one of the robot configurations from the xarm_moveit_config package and try to access the parameter server—via the command line, a C++ node, or a Python node—I am unable to retrieve any parameters.

I tried to investigate where the problem occurs, and it seems to be related to how the move_group node is started in the _robot_moveit_common2.launch.py launch file of the xarm_moveit_config package. When I comment out the line that launches the move_group_node (see below), I am able to access the parameter server correctly.

    return [
        RegisterEventHandler(event_handler=OnProcessExit(
            target_action=rviz2_node,
            on_exit=[EmitEvent(event=Shutdown())]
        )),
        rviz2_node,
        static_tf,
        move_group_node, #<-- comment out
        robot_planner_node_launch
    ]

I suspect that the issue is related to the MoveIt configuration, but I have not been able to identify the exact cause.

Could you please help me solve this problem?

Kind regards,

[vimior]

@GerardHarkema
Hello, could you please provide the startup command? Also, what parameters do you need to obtain? (Please provide an example of the command or code you would like to obtain.)

[GerardHarkema]

Hello,

The easiest way to reproduce the error:

Launching in terminal 1:

ros2 launch xarm_moveit_config xarm5_moveit_gazebo.launch.py

and starting in terminal 2:

ros2 param list

[GerardHarkema]

This is my (stripes)code:

#include <cstdio>
#include <iostream>
#include <fstream>
#include <thread>
#include <chrono>
using namespace std;
//#include <pluginlib/class_loader.hpp>

// MoveIt
#include <moveit/robot_model_loader/robot_model_loader.h>
#include <moveit/planning_interface/planning_interface.h>
#include <moveit/planning_scene/planning_scene.h>
#include <moveit/kinematic_constraints/utils.h>
#include <moveit_msgs/msg/display_trajectory.hpp>
#include <moveit_msgs/msg/planning_scene.h>
//#include <moveit_visual_tools/moveit_visual_tools.h>
#include <moveit/move_group_interface/move_group_interface.h>
#include <ament_index_cpp/get_package_share_directory.hpp>

static const rclcpp::Logger LOGGER = rclcpp::get_logger("my_uf_demo_cpp");

int main(int argc, char ** argv)
{
    (void) argc;
    (void) argv;

    printf("My uFactory xarm5 demo CPP\n");
 
    rclcpp::init(argc, argv);
    
    auto move_group_node = rclcpp::Node::make_shared("move_group", rclcpp::NodeOptions().automatically_declare_parameters_from_overrides(true));
    
    // Load robot description from file if not provided as parameter
    if (!move_group_node->has_parameter("robot_description_semantic")) {
        RCLCPP_WARN(LOGGER, "Could not read robot_description_semantic parameter");   
    }
 
    // We spin up a SingleThreadedExecutor for the current state monitor to get information
    // about the robot's state.
    rclcpp::executors::SingleThreadedExecutor executor;
    executor.add_node(move_group_node);
    std::thread([&executor]() { executor.spin(); }).detach();
 
    // Give move_group time to initialize
    std::this_thread::sleep_for(std::chrono::seconds(2));
 
    // MoveIt operates on sets of joints called "planning groups" and stores them in an object called
    // the ``JointModelGroup``. Throughout MoveIt, the terms "planning group" and "joint model group"
    // are used interchangeably.
    static const std::string PLANNING_GROUP = "xarm5";

 
    // The
    // :moveit_codedir:`MoveGroupInterface<moveit_ros/planning_interface/move_group_interface/include/moveit/move_group_interface/move_group_interface.h>`
    // class can be easily set up using just the name of the planning group you would like to control and plan for.
    moveit::planning_interface::MoveGroupInterface move_group(move_group_node, PLANNING_GROUP);

    return 0;
}

this is the output:
```bash
ros2 run my_uf_demo_cpp demo 
My uFactory xarm5 demo CPP
[WARN] [1767864380.726407033] [my_uf_demo_cpp]: Could not read robot_description_semantic parameter
[ERROR] [1767864392.871117049] [move_group]: Could not find parameter robot_description_semantic and did not receive robot_description_semantic via std_msgs::msg::String subscription within 10.000000 seconds.
Error:   Could not parse the SRDF XML File. Error=XML_ERROR_EMPTY_DOCUMENT ErrorID=13 (0xd) Line number=0
         at line 732 in ./src/model.cpp
[ERROR] [1767864392.899391458] [moveit_731375253.moveit.ros.rdf_loader]: Unable to parse SRDF
[FATAL] [1767864392.904134754] [moveit_731375253.moveit.ros.move_group_interface]: Unable to construct robot model. Please make sure all needed information is on the parameter server.
terminate called after throwing an instance of 'std::runtime_error'
  what():  Unable to construct robot model. Please make sure all needed information is on the parameter server.
[ros2run]: Aborted

[vimior]

@GerardHarkema
I'm sorry for the long delay in replying.
I've tested it and confirmed that after starting move_group, the ros2 param list command doesn't return anything; you need to specify a node to get a return value (ros2 param list /move_group). I haven't found the cause of this problem yet. I checked the moveit GitHub repository and found that it also has this issue. We will continue to investigate and notify you here of any progress.

[GerardHarkema]

I'am still interested in the solution.