Diff drive ros2_control interface issue with hardware robot

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1

I am trying to make a diff drive robot. I am using esp32 with microros_arduino. I have successfully created cmd_vel subscriber, left_motor_encoder, and right_motor_encoder publisher topics in esp32. And also successfully connected with the PC over wifi network. I am using my PC as a microprocessor instead of Raspberry Pi or Jetson.

The issue is that I am stuck at the diff drive ros2_control interface. I am using this pkg. When i launch this file, rviz2 simulation appears, and when I move the robot via cmd_vel. It moves but the wheels does not rotate. wheel position does not change in /joint_state topic, But the velocity changes.
Furthermore, i am unable to configure how can i interface my actual robot (not just simulation). How can I use encoder information with ros2 diff drive control. Your guidance is needed.

here are some codes related to the ros2_control.

from launch import LaunchDescription
from launch.actions import DeclareLaunchArgument
from launch.conditions import IfCondition
from launch.substitutions import Command, FindExecutable, LaunchConfiguration, PathJoinSubstitution
from launch_ros.actions import Node
from launch_ros.substitutions import FindPackageShare

def generate_launch_description():

arg_show_rviz = DeclareLaunchArgument(
    "start_rviz",
    default_value="false",
    description="start RViz automatically with the launch file",
)

# Get URDF via xacro
robot_description_content = Command(
    [
        PathJoinSubstitution([FindExecutable(name="xacro")]),
        " ",
        PathJoinSubstitution(
            [FindPackageShare("diffbot_description"), "urdf", "diffbot_system.urdf.xacro"]
        ),
    ]
)
robot_description = {"robot_description": robot_description_content}

diffbot_diff_drive_controller = PathJoinSubstitution(
    [
        FindPackageShare("ros2_control_demo_bringup"),
        "config",
        "diffbot_diff_drive_controller.yaml",
    ]
)

node_robot_state_publisher = Node(
    package="robot_state_publisher",
    executable="robot_state_publisher",
    output="screen",
    parameters=[robot_description],
)

controller_manager_node = Node(
    package="controller_manager",
    executable="ros2_control_node",
    parameters=[robot_description, diffbot_diff_drive_controller],
    output={
        "stdout": "screen",
        "stderr": "screen",
    },
)

spawn_dd_controller = Node(
    package="controller_manager",
    executable="spawner.py",
    arguments=["diffbot_base_controller"],
    output="screen",
)
spawn_jsb_controller = Node(
    package="controller_manager",
    executable="spawner.py",
    arguments=["joint_state_broadcaster"],
    output="screen",
)

rviz_config_file = PathJoinSubstitution(
    [FindPackageShare("diffbot_description"), "config", "diffbot.rviz"]
)
rviz_node = Node(
    package="rviz2",
    executable="rviz2",
    name="rviz2",
    arguments=["-d", rviz_config_file],
    #condition=IfCondition(LaunchConfiguration("start_rviz")), I just commented this
)

return LaunchDescription(
    [
        arg_show_rviz,
        node_robot_state_publisher,
        controller_manager_node,
        spawn_dd_controller,
        spawn_jsb_controller,
        rviz_node,
    ]
)

and other files are same exatly as given in pkg.

1 Like
2

ros2_control gives you motor speed value and wait the encoder value, you should match that value with your real robot, you can do that this folder https://github.com/ros-controls/ros2_control_demos/blob/foxy/ros2_control_demo_hardware/src/diffbot_system.cpp