initial_positions seems to be having no effect

[ravijo]

I am using ur_robot_driver on ROS Humble (Ubuntu 22.04.3 LTS). Based on the documentation, the initial_positions can be used to set the initial joint values for the UR arm. But it seems to be having no effect.

Objective

I am trying to generate arm trajectory in simulation (i.e., no real robot) using MoveIt APIs with the UR arm.

Steps

1. I tried following the Mock hardware section but it was reporting following errors:

$ ros2 launch ur_robot_driver ur_control.launch.py ur_type:=ur5e robot_ip:=yyy.yyy.yyy.yyy use_mock_hardware:=true \
              launch_rviz:=false initial_joint_controller:=joint_trajectory_controller
[ur_ros2_control_node-1] [ERROR] [1694335857.294092578] [UR_Client_Library]: Failed to get address for yyy.yyy.yyy.yyy:30002
[ur_ros2_control_node-1] [INFO] [1694335857.833236460] [io_and_status_controller]: Waiting for system interface to initialize...

2. Later, by following this post that suggest using use_fake_hardware, I was able to get rid of the above errors.
3. Finally, based on the documentation, I tried setting the initial_positions but no sucess. Below is my launch file:

from launch import LaunchDescription
from launch_ros.actions import Node
from launch.substitutions import PathJoinSubstitution
from launch_ros.substitutions import FindPackageShare
from launch.actions import IncludeLaunchDescription
from launch.launch_description_sources import PythonLaunchDescriptionSource
from ur_moveit_config.launch_common import load_yaml


def generate_launch_description():
    ur_driver_launch = IncludeLaunchDescription(
        PythonLaunchDescriptionSource(
            PathJoinSubstitution([FindPackageShare("ur_robot_driver"), "launch", "ur_control.launch.py"])
        ),
        launch_arguments={
            "ur_type": "ur3e",
            "robot_ip": "yyy.yyy.yyy.yyy",
            "use_fake_hardware": "True",
            "launch_rviz": "False",
            "initial_joint_controller": "scaled_joint_trajectory_controller",
            # loading from YAML does not work
            # "initial_positions": load_yaml("my_pkg", "config/initial_positions.yaml"),
            # directly assigning a dict also does not work
            "initial_positions": {
                "shoulder_pan_joint": 1.0,
                "shoulder_lift_joint": -0.5,
                "elbow_joint": 1.0,
                "wrist_1_joint": -2.0,
                "wrist_2_joint": -1.5,
                "wrist_3_joint": -0.3,
            },
        }.items(),
    )

    ur_moveit_launch = IncludeLaunchDescription(
        PythonLaunchDescriptionSource(
            PathJoinSubstitution([FindPackageShare("ur_moveit_config"), "launch", "ur_moveit.launch.py"]),
        ),
        launch_arguments={
            "ur_type": "ur3e",
            "launch_rviz": "True",
        }.items(),
    )

    return LaunchDescription([ur_driver_launch, ur_moveit_launch])

Issues

1. The Mock hardware section needs more testing or explanation. At present, it seems not working as reported above.
2. The initial_positions seems to be having no effect.

[ShahhhVihaan]

@ravijo I'm dealing with the same problem. If you were able to find a solution I'd appreciate some help. Also @fmauch do you have any ideas as to why the flag isn't working?

[Spartan-Velanjeri]

+1, facing the same issue

[jozefkosecky]

the same issue

[VinDp]

Hey @ravijo,
sorry for the late answer, but contrary to what the documentation states, it is not possible to specify the initial_positions as launch argument for ur_control.launch.py. It apparently was a legacy missing feature, so thanks for spotting it, we will soon update the documentation.
The way in which you can change them is to go in the config folder of the description package and change the values in initial_positions.yaml.

Instead, regarding mock_hardware: for Humble the argument is use_fake_hardware instead of use_mock_hardware. I tested it and it seems to work.

[VinDp]

Since there are no follow ups and the issue is solved, I will close it.
Feel free to re-open if still relevant.