[Navigation 2]4. First-Time Robot Setup Guide

Setting Up Transformations

Static Transform Publisher Demo

$ ros2 run tf2_ros static_transform_publisher 0.1 0 0.2 0 0 0 base_link base_laser

새 터미널 열어서

$ ros2 run tf2_ros tf2_echo base_link base_laser

Setting Up the URDF[실패 중]

Setting up the environment

$ sudo apt install ros-foxy-joint-state-publisher-gui
$ sudo apt install ros-foxy-xacro
$ ros2 pkg create --build-type ament_cmake sam_bot_description

Writing the URDF

src/description 아래에 sam_bot_description.urdf 파일을 만들고 내용을 채운다.

$ cd sam_bot_description/src/description/
$ gedit sam_bot_description.urdf

파일 내용

<?xml version="1.0"?>
<robot name="sam_bot" xmlns:xacro="http://ros.org/wiki/xacro">

</robot>
  <!-- Define robot constants -->
  <xacro:property name="base_width" value="0.31"/>
  <xacro:property name="base_length" value="0.42"/>
  <xacro:property name="base_height" value="0.18"/>

  <xacro:property name="wheel_radius" value="0.10"/>
  <xacro:property name="wheel_width" value="0.04"/>
  <xacro:property name="wheel_ygap" value="0.025"/>
  <xacro:property name="wheel_zoff" value="0.05"/>
  <xacro:property name="wheel_xoff" value="0.12"/>

  <xacro:property name="caster_xoff" value="0.14"/>
  
  <!-- Robot Base -->
  <link name="base_link">
    <visual>
      <geometry>
        <box size="${base_length} ${base_width} ${base_height}"/>
      </geometry>
      <material name="Cyan">
        <color rgba="0 1.0 1.0 1.0"/>
      </material>
    </visual>
  </link>
  <!-- Robot Footprint -->
  <link name="base_footprint"/>

  <joint name="base_joint" type="fixed">
    <parent link="base_link"/>
    <child link="base_footprint"/>
    <origin xyz="0.0 0.0 ${-(wheel_radius+wheel_zoff)}" rpy="0 0 0"/>
  </joint>
  
  <!-- Wheels -->
  <xacro:macro name="wheel" params="prefix x_reflect y_reflect">
    <link name="${prefix}_link">
      <visual>
        <origin xyz="0 0 0" rpy="${pi/2} 0 0"/>
        <geometry>
            <cylinder radius="${wheel_radius}" length="${wheel_width}"/>
        </geometry>
        <material name="Gray">
          <color rgba="0.5 0.5 0.5 1.0"/>
        </material>
      </visual>
    </link>

    <joint name="${prefix}_joint" type="continuous">
      <parent link="base_link"/>
      <child link="${prefix}_link"/>
      <origin xyz="${x_reflect*wheel_xoff} ${y_reflect*(base_width/2+wheel_ygap)} ${-wheel_zoff}" rpy="0 0 0"/>
      <axis xyz="0 1 0"/>
    </joint>
  </xacro:macro>

  <xacro:wheel prefix="drivewhl_l" x_reflect="-1" y_reflect="1" />
  <xacro:wheel prefix="drivewhl_r" x_reflect="-1" y_reflect="-1" />
  
  <!-- Caster Wheel -->
  <link name="front_caster">
    <visual>
      <geometry>
        <sphere radius="${(wheel_radius+wheel_zoff-(base_height/2))}"/>
      </geometry>
      <material name="Cyan">
        <color rgba="0 1.0 1.0 1.0"/>
      </material>
    </visual>
  </link>

  <joint name="caster_joint" type="fixed">
    <parent link="base_link"/>
    <child link="front_caster"/>
    <origin xyz="${caster_xoff} 0.0 ${-(base_height/2)}" rpy="0 0 0"/>
  </joint>

Build and launch

sam_bot_description 패키지 아래 package.xml파일을 수정한다.
<buildtool_depend> 줄 아래에 다음 내용을 추가한다.

  <exec_depend>joint_state_publisher</exec_depend>
  <exec_depend>joint_state_publisher_gui</exec_depend>
  <exec_depend>robot_state_publisher</exec_depend>
  <exec_depend>rviz</exec_depend>
  <exec_depend>xacro</exec_depend>

그 다음, launch파일을 생성한다.
sam_bot_description아래에 launch폴더를 만들어 그 안에 display.launch.py 파일을 만들자.

$ cd sam_bot_description/launch/
$ gedit display.launch.py

launch.py파일에는 다음 내용을 넣으면 된다.

import launch
from launch.substitutions import Command, LaunchConfiguration
import launch_ros
import os

def generate_launch_description():
    pkg_share = launch_ros.substitutions.FindPackageShare(package='sam_bot_description').find('sam_bot_description')
    default_model_path = os.path.join(pkg_share, 'src/description/sam_bot_description.urdf')
    default_rviz_config_path = os.path.join(pkg_share, 'rviz/urdf_config.rviz')

    robot_state_publisher_node = launch_ros.actions.Node(
        package='robot_state_publisher',
        executable='robot_state_publisher',
        parameters=[{'robot_description': Command(['xacro ', LaunchConfiguration('model')])}]
    )
    joint_state_publisher_node = launch_ros.actions.Node(
        package='joint_state_publisher',
        executable='joint_state_publisher',
        name='joint_state_publisher',
        condition=launch.conditions.UnlessCondition(LaunchConfiguration('gui'))
    )
    joint_state_publisher_gui_node = launch_ros.actions.Node(
        package='joint_state_publisher_gui',
        executable='joint_state_publisher_gui',
        name='joint_state_publisher_gui',
        condition=launch.conditions.IfCondition(LaunchConfiguration('gui'))
    )
    rviz_node = launch_ros.actions.Node(
        package='rviz2',
        executable='rviz2',
        name='rviz2',
        output='screen',
        arguments=['-d', LaunchConfiguration('rvizconfig')],
    )

    return launch.LaunchDescription([
        launch.actions.DeclareLaunchArgument(name='gui', default_value='True',
                                            description='Flag to enable joint_state_publisher_gui'),
        launch.actions.DeclareLaunchArgument(name='model', default_value=default_model_path,
                                            description='Absolute path to robot urdf file'),
        launch.actions.DeclareLaunchArgument(name='rvizconfig', default_value=default_rviz_config_path,
                                            description='Absolute path to rviz config file'),
        joint_state_publisher_node,
        joint_state_publisher_gui_node,
        robot_state_publisher_node,
        rviz_node
    ])

sam_bot_description아래에 rviz폴더를 만들어 그 안에 urdf_config.rviz 파일을 만들자.

$ cd sam_bot_description/rviz/
$ gedit urdf_config.rviz

urdf_config.rviz파일에는 다음 내용을 넣으면 된다.

Panels:
  - Class: rviz_common/Displays
    Help Height: 78
    Name: Displays
    Property Tree Widget:
      Expanded:
        - /Global Options1
        - /Status1
        - /RobotModel1/Links1
        - /TF1
      Splitter Ratio: 0.5
    Tree Height: 557
Visualization Manager:
  Class: ""
  Displays:
    - Alpha: 0.5
      Cell Size: 1
      Class: rviz_default_plugins/Grid
      Color: 160; 160; 164
      Enabled: true
      Name: Grid
    - Alpha: 0.6
      Class: rviz_default_plugins/RobotModel
      Description Topic:
        Depth: 5
        Durability Policy: Volatile
        History Policy: Keep Last
        Reliability Policy: Reliable
        Value: /robot_description
      Enabled: true
      Name: RobotModel
      Visual Enabled: true
    - Class: rviz_default_plugins/TF
      Enabled: true
      Name: TF
      Marker Scale: 0.3
      Show Arrows: true
      Show Axes: true
      Show Names: true
  Enabled: true
  Global Options:
    Background Color: 48; 48; 48
    Fixed Frame: base_link
    Frame Rate: 30
  Name: root
  Tools:
    - Class: rviz_default_plugins/Interact
      Hide Inactive Objects: true
    - Class: rviz_default_plugins/MoveCamera
    - Class: rviz_default_plugins/Select
    - Class: rviz_default_plugins/FocusCamera
    - Class: rviz_default_plugins/Measure
      Line color: 128; 128; 0
  Transformation:
    Current:
      Class: rviz_default_plugins/TF
  Value: true
  Views:
    Current:
      Class: rviz_default_plugins/Orbit
      Name: Current View
      Target Frame: <Fixed Frame>
      Value: Orbit (rviz)
    Saved: ~

마지막으로, CmakeLists.txt파일을 수정하자.
if(BUILD_TESTING) 문 위에 다음 내용을 추가한다.

install(
  DIRECTORY src launch rviz
  DESTINATION share/${PROJECT_NAME}
)

파일 수정이 끝났다.
workspace로 이동하여 build명령문을 실행하면 끝이 난다.

$ cd sam_bot_description/
$ colcon build
$ . install/setup.bash

$ ros2 launch sam_bot_description display.launch.py

project를 launch해보면 된다.

! 문제 발생: launch명령어를 실행하면 RVIZ가 실행되어야 하는데 그렇지 않았다
이렇게만 나온다.

문제 해결

-먼저 rviz자체가 실행이 안되나 싶어서

$ rviz2 

로 실행을 해봤는데 잘 됐다. rviz의 문제는 아닌 듯하다.
-참고 사이트: https://github.com/cyberbotics/webots_ros2/issues/145
-참고 사이트: https://github.com/ros-planning/navigation2_tutorials/blob/master/sam_bot_description/launch/display.launch.py

Setting up Odometry