ROS 2中如何将URDF加载到RViz

在本教程中，将学习在ROS 2中如何将URDF加载到RViz中。统一机器人描述格式URDF是ROS中机器人建模的标准格式。

目录

一、前提条件

二、创建一个ROS 2软件包

三、创建其它目录

四、创建URDF文件

五、添加依赖项

六、创建启动文件

七、添加RViz配置文件

八、编译构建软件包

九、在RViz中启动机器人

一、前提条件

·已在Ubuntu Linux 20.04操作系统中安装好ROS 2 Foxy Fitzroy

·如果使用的是ROS 2的其它发行版，则需要在本教程中提到“foxy”的任何地方将“foxy”替换为您的发行版名称（例如“galactic”）。

·强烈建议您获取最新版本的 ROS 2。如果您使用的是较新版本的 ROS 2，仍然可以按照本教程中的所有步骤进行操作。一切都能正常工作的。

·您已经创建好了一个ROS 2工作空间。在本教程中该工作空间的名称为“dev_ws”，代表“开发工作空间”。

·您已经完成了上一教程的学习，已经了解了URDF是什么，且已经安装好了ROS 2的重要相关软件包。

可以在Google Drive此处找到本教程的完整代码。

二、创建一个ROS 2软件包

现在让我们在工作空间中创建一个ROS 2软件包。

在一个新的终端窗口中，进入到您工作空间存放源代码的src目录：

cd ~/dev_ws/src

现在使用以下命令来创建一个名为two_wheeled_robot的软件包：

ros2 pkg create --build-type ament_cmake two_wheeled_robot

三、创建其它目录

进入到该软件包目录中：

cd ~/dev_ws/src/ two_wheeled_robot

使用以下命令来创建一些其它目录：

mkdir config launch maps meshes models params rviz worlds

键入以下命令以确认这些目录创建成功：

dir

四、创建URDF文件

在本节中将会逐步构建该移动机器人。该机器人将会用一种表示机器人模型的 XML 文件即统一机器人描述格式（URDF）定义。

打开一个新的终端窗口，并键入以下命令：

cd ~/dev_ws/src/ two_wheeled_robot
cd urdf

创建一个名为two_wheeled_robot.urdf的新文件：

gedit two_wheeled_robot

在这个文件中，我们会定义机器人的外观（即视觉属性）、机器人在碰撞到物体时的行为（即碰撞属性）及其质量（即惯性属性）。

在该URDF文件中复制粘贴下面这段代码：

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

  <!-- ****************** ROBOT CONSTANTS *******************************  -->
  <!-- Define the size of the robot's main chassis in meters -->
  <xacro:property name="base_width" value="0.39"/>
  <xacro:property name="base_length" value="0.70"/>
  <xacro:property name="base_height" value="0.20"/>
 
  <!-- Define the shape of the robot's two back wheels in meters -->
  <xacro:property name="wheel_radius" value="0.14"/>
  <xacro:property name="wheel_width" value="0.06"/>

  <!-- x-axis points forward, y-axis points to left, z-axis points upwards -->
  <!-- Define the gap between the wheel and chassis along y-axis in meters -->
  <xacro:property name="wheel_ygap" value="0.035"/>

  <!-- Position the wheels along the z-axis -->
  <xacro:property name="wheel_zoff" value="0.05"/>

  <!-- Position the wheels along the x-axis -->
  <xacro:property name="wheel_xoff" value="0.221"/>

  <!-- Position the caster wheel along the x-axis -->
  <xacro:property name="caster_xoff" value="0.217"/>

  <!-- Define intertial property macros  -->
  <xacro:macro name="box_inertia" params="m w h d">
    <inertial>
      <origin xyz="0 0 0" rpy="${pi/2} 0 ${pi/2}"/>
      <mass value="${m}"/>
      <inertia ixx="${(m/12) * (h*h + d*d)}" ixy="0.0" ixz="0.0" iyy="${(m/12) * (w*w + d*d)}" iyz="0.0" izz="${(m/12) * (w*w + h*h)}"/>
    </inertial>
  </xacro:macro>

  <xacro:macro name="cylinder_inertia" params="m r h">
    <inertial>
      <origin xyz="0 0 0" rpy="${pi/2} 0 0" />
      <mass value="${m}"/>
      <inertia ixx="${(m/12) * (3*r*r + h*h)}" ixy = "0" ixz = "0" iyy="${(m/12) * (3*r*r + h*h)}" iyz = "0" izz="${(m/2) * (r*r)}"/>
    </inertial>
  </xacro:macro>

  <xacro:macro name="sphere_inertia" params="m r">
    <inertial>
      <mass value="${m}"/>
      <inertia ixx="${(2/5) * m * (r*r)}" ixy="0.0" ixz="0.0" iyy="${(2/5) * m * (r*r)}" iyz="0.0" izz="${(2/5) * m * (r*r)}"/>
    </inertial>
  </xacro:macro>

  <!-- ****************** ROBOT BASE FOOTPRINT ***************************  -->
  <!-- Define the center of the main robot chassis projected on the ground -->	
  <link name="base_footprint"/>

  <!-- The base footprint of the robot is located underneath the chassis -->
  <joint name="base_joint" type="fixed">
    <parent link="base_footprint"/>
    <child link="base_link" />
    <origin xyz="0.0 0.0 ${(wheel_radius+wheel_zoff)}" rpy="0 0 0"/>
  </joint>

  <!-- ********************** ROBOT BASE *********************************  -->
  <link name="base_link">
    <visual>
      <origin xyz="0 0 -0.05" rpy="1.5707963267949 0 3.141592654"/>
      <geometry>
        <mesh filename="package://two_wheeled_robot/meshes/robot_base.stl" />
      </geometry>
      <material name="Red">
        <color rgba="${255/255} ${0/255} ${0/255} 1.0"/>
      </material>
    </visual>

    <collision>
      <geometry>
        <box size="${base_length} ${base_width} ${base_height}"/>
      </geometry>
    </collision>

    <xacro:box_inertia m="40.0" w="${base_width}" d="${base_length}" h="${base_height}"/>
 
  </link>

  <gazebo reference="base_link">
    <material>Gazebo/Red</material>
  </gazebo>

  <!-- *********************** DRIVE WHEELS ******************************  -->

  <xacro:macro name="wheel" params="prefix x_reflect y_reflect">
    <link name="${prefix}_link">
      <visual>
        <origin xyz="0 0 0" rpy="1.5707963267949 0 0"/>
        <geometry>
            <cylinder radius="${wheel_radius}" length="${wheel_width}"/>
        </geometry>
        <material name="White">
          <color rgba="${255/255} ${255/255} ${255/255} 1.0"/>
        </material>
      </visual>
 
      <collision>
        <origin xyz="0 0 0" rpy="${pi/2} 0 0"/>
        <geometry>
          <cylinder radius="${wheel_radius}" length="${wheel_width}"/>
        </geometry>
      </collision>
 
      <xacro:cylinder_inertia m="110.5" r="${wheel_radius}" h="${wheel_width}"/>
 
    </link>

    <!-- Connect the wheels to the base_link at the appropriate location, and 
         define a continuous joint to allow the wheels to freely rotate about
         an axis -->
    <joint name="${prefix}_joint" type="revolute">
      <parent link="base_link"/>
      <child link="${prefix}_link"/>
      <origin xyz="${x_reflect*wheel_xoff} ${y_reflect*(base_width/2+wheel_ygap)} ${-wheel_zoff}" rpy="0 0 0"/>
      <limit upper="3.1415" lower="-3.1415" effort="30" velocity="5.0"/>
      <axis xyz="0 1 0"/>
    </joint>
  </xacro:macro>

  <!-- Instantiate two wheels using the macro we just made through the 
       xacro:wheel tags. We also define the parameters to have one wheel
       on both sides at the back of our robot (i.e. x_reflect=-1). -->
  <xacro:wheel prefix="drivewhl_l" x_reflect="-1" y_reflect="1" />
  <xacro:wheel prefix="drivewhl_r" x_reflect="-1" y_reflect="-1" />

  <!-- *********************** CASTER WHEEL ******************************  -->
  <!-- We add a caster wheel. It will be modeled as sphere.
       We define the wheel’s geometry, material and the joint to connect it to 
       base_link at the appropriate location. -->
  <link name="front_caster">
    <visual>
      <geometry>
        <sphere radius="${(wheel_radius+wheel_zoff-(base_height/2))}"/>
      </geometry>
      <material name="White">
        <color rgba="${255/255} ${255/255} ${255/255} 1.0"/>
      </material>
    </visual>
    <collision>
      <origin xyz="0 0 0" rpy="0 0 0"/>
      <geometry>
        <sphere radius="${(wheel_radius+wheel_zoff-(base_height/2))}"/>
      </geometry>
    </collision>
    <xacro:sphere_inertia m="10.05" r="${(wheel_radius+wheel_zoff-(base_height/2))}"/>
  </link>

  <gazebo reference="front_caster">
    <mu1>0.01</mu1>
    <mu2>0.01</mu2>
    <material>Gazebo/White</material>
  </gazebo>

  <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>
 
  <!-- *********************** IMU SETUP *********************************  -->
  <!-- Each sensor must be attached to a link.                              --> 
 
  <joint name="imu_joint" type="fixed">
    <parent link="base_link"/>
    <child link="imu_link"/>
    <origin xyz="-0.10 0 0.05" rpy="0 0 0"/>
  </joint>

  <link name="imu_link"/>

  <!-- *********************** LIDAR SETUP **********************************  -->
  <joint name="lidar_joint" type="fixed">
    <parent link="base_link"/>
    <child link="lidar_link"/>
    <origin xyz="0.215 0 0.13" rpy="0 0 0"/>
  </joint>

  <link name="lidar_link">
 
    <collision>
     <origin xyz="0 0 0" rpy="0 0 0"/>
     <geometry>
      <cylinder radius="0.0508" length="0.18"/>
     </geometry>
    </collision>
 
    <visual>
     <origin xyz="0 0 0" rpy="0 0 0"/>
     <geometry>
      <cylinder radius="0.0508" length="0.18"/>
     </geometry>
     <material name="Black">
          <color rgba="${0/255} ${0/255} ${0/255} 1.0"/>
     </material>
    </visual>
 
    <inertial>
      <mass value="0.114" />
      <origin xyz="0 0 0" rpy="0 0 0"/>
      <inertia ixx="0.001" ixy="0" ixz="0" iyy="0.001" iyz="0" izz="0.001" />
    </inertial>
  </link>

</robot>

保存并关闭该文件。

五、添加依赖项

现在来添加一些我们项目要依赖的软件包。使用以下命令进入到 package.xml 文件中：

cd ~/dev_ws/src/two_wheeled_robot
gedit package.xml

在<buildtool_depend>标签之后添加以下几行：

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

保存并关闭该文件。

我们会用到Joint State Publisher和Robot State Publisher。此外还会用到RViz来可视化机器人模型。

六、创建启动文件

现在来创建启动文件。打开一个新的终端窗口并键入以下命令：

cd ~/dev_ws/src/ two_wheeled_robot
cd launch
gedit two_wheeled_robot.launch.py

将下面这段代码复制并粘贴到该文件中：

# Author: Addison Sears-Collins
# Date: September 14, 2021
# Description: Launch a two-wheeled robot URDF file using Rviz.
# https://automaticaddison.com

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

def generate_launch_description():

  # Set the path to this package.
  pkg_share = FindPackageShare(package='two_wheeled_robot').find('two_wheeled_robot')

  # Set the path to the RViz configuration settings
  default_rviz_config_path = os.path.join(pkg_share, 'rviz/rviz_basic_settings.rviz')

  # Set the path to the URDF file
  default_urdf_model_path = os.path.join(pkg_share, 'urdf/two_wheeled_robot.urdf')

  ########### YOU DO NOT NEED TO CHANGE ANYTHING BELOW THIS LINE ##############  
  # Launch configuration variables specific to simulation
  gui = LaunchConfiguration('gui')
  urdf_model = LaunchConfiguration('urdf_model')
  rviz_config_file = LaunchConfiguration('rviz_config_file')
  use_robot_state_pub = LaunchConfiguration('use_robot_state_pub')
  use_rviz = LaunchConfiguration('use_rviz')
  use_sim_time = LaunchConfiguration('use_sim_time')

  # Declare the launch arguments  
  declare_urdf_model_path_cmd = DeclareLaunchArgument(
    name='urdf_model', 
    default_value=default_urdf_model_path, 
    description='Absolute path to robot urdf file')
 
  declare_rviz_config_file_cmd = DeclareLaunchArgument(
    name='rviz_config_file',
    default_value=default_rviz_config_path,
    description='Full path to the RVIZ config file to use')
 
  declare_use_joint_state_publisher_cmd = DeclareLaunchArgument(
    name='gui',
    default_value='True',
    description='Flag to enable joint_state_publisher_gui')
 
  declare_use_robot_state_pub_cmd = DeclareLaunchArgument(
    name='use_robot_state_pub',
    default_value='True',
    description='Whether to start the robot state publisher')

  declare_use_rviz_cmd = DeclareLaunchArgument(
    name='use_rviz',
    default_value='True',
    description='Whether to start RVIZ')
 
  declare_use_sim_time_cmd = DeclareLaunchArgument(
    name='use_sim_time',
    default_value='True',
    description='Use simulation (Gazebo) clock if true')
 
  # Specify the actions

  # Publish the joint state values for the non-fixed joints in the URDF file.
  start_joint_state_publisher_cmd = Node(
    condition=UnlessCondition(gui),
    package='joint_state_publisher',
    executable='joint_state_publisher',
    name='joint_state_publisher')

  # A GUI to manipulate the joint state values
  start_joint_state_publisher_gui_node = Node(
    condition=IfCondition(gui),
    package='joint_state_publisher_gui',
    executable='joint_state_publisher_gui',
    name='joint_state_publisher_gui')

  # Subscribe to the joint states of the robot, and publish the 3D pose of each link.
  start_robot_state_publisher_cmd = Node(
    condition=IfCondition(use_robot_state_pub),
    package='robot_state_publisher',
    executable='robot_state_publisher',
    parameters=[{'use_sim_time': use_sim_time, 
    'robot_description': Command(['xacro ', urdf_model])}],
    arguments=[default_urdf_model_path])

  # Launch RViz
  start_rviz_cmd = Node(
    condition=IfCondition(use_rviz),
    package='rviz2',
    executable='rviz2',
    name='rviz2',
    output='screen',
    arguments=['-d', rviz_config_file])
 
  # Create the launch description and populate
  ld = LaunchDescription()

  # Declare the launch options
  ld.add_action(declare_urdf_model_path_cmd)
  ld.add_action(declare_rviz_config_file_cmd)
  ld.add_action(declare_use_joint_state_publisher_cmd)
  ld.add_action(declare_use_robot_state_pub_cmd)  
  ld.add_action(declare_use_rviz_cmd) 
  ld.add_action(declare_use_sim_time_cmd)

  # Add any actions
  ld.add_action(start_joint_state_publisher_cmd)
  ld.add_action(start_joint_state_publisher_gui_node)
  ld.add_action(start_robot_state_publisher_cmd)
  ld.add_action(start_rviz_cmd)

  return ld

保存并关闭该文件。

可以在此处查阅更多有关启动（launch）文件的信息。

七、添加RViz配置文件

现在来添加一个配置文件，该配置文件将会使用适当的设置初始化RViz，以便可以在RViz启动后立即浏览该机器人。

打开一个新的终端窗口，并键入以下命令：

cd ~/dev_ws/src/ two_wheeled_robot
cd rviz
gedit rviz_basic_settings.rviz

将下面这段代码复制粘贴到该文件中，然后保存并关闭该文件：

Panels:
  - Class: rviz_common/Displays
    Help Height: 78
    Name: Displays
    Property Tree Widget:
      Expanded:
        - /Global Options1
        - /Status1
        - /RobotModel1
        - /TF1
        - /TF1/Frames1
      Splitter Ratio: 0.5
    Tree Height: 617
  - Class: rviz_common/Selection
    Name: Selection
  - Class: rviz_common/Tool Properties
    Expanded:
      - /2D Goal Pose1
      - /Publish Point1
    Name: Tool Properties
    Splitter Ratio: 0.5886790156364441
  - Class: rviz_common/Views
    Expanded:
      - /Current View1
    Name: Views
    Splitter Ratio: 0.5
Visualization Manager:
  Class: ""
  Displays:
    - Alpha: 0.5
      Cell Size: 1
      Class: rviz_default_plugins/Grid
      Color: 160; 160; 164
      Enabled: true
      Line Style:
        Line Width: 0.029999999329447746
        Value: Lines
      Name: Grid
      Normal Cell Count: 0
      Offset:
        X: 0
        Y: 0
        Z: 0
      Plane: XY
      Plane Cell Count: 10
      Reference Frame: <Fixed Frame>
      Value: true
    - Alpha: 1
      Class: rviz_default_plugins/RobotModel
      Collision Enabled: false
      Description File: ""
      Description Source: Topic
      Description Topic:
        Depth: 5
        Durability Policy: Volatile
        History Policy: Keep Last
        Reliability Policy: Reliable
        Value: /robot_description
      Enabled: true
      Links:
        All Links Enabled: true
        Expand Joint Details: false
        Expand Link Details: false
        Expand Tree: false
        Link Tree Style: Links in Alphabetic Order
        base_footprint:
          Alpha: 1
          Show Axes: false
          Show Trail: false
        base_link:
          Alpha: 1
          Show Axes: false
          Show Trail: false
          Value: true
        drivewhl_l_link:
          Alpha: 1
          Show Axes: false
          Show Trail: false
          Value: true
        drivewhl_r_link:
          Alpha: 1
          Show Axes: false
          Show Trail: false
          Value: true
        front_caster:
          Alpha: 1
          Show Axes: false
          Show Trail: false
          Value: true
        gps_link:
          Alpha: 1
          Show Axes: false
          Show Trail: false
        imu_link:
          Alpha: 1
          Show Axes: false
          Show Trail: false
        lidar_link:
          Alpha: 1
          Show Axes: false
          Show Trail: false
          Value: true
      Name: RobotModel
      TF Prefix: ""
      Update Interval: 0
      Value: true
      Visual Enabled: true
    - Class: rviz_default_plugins/TF
      Enabled: true
      Frame Timeout: 15
      Frames:
        All Enabled: false
        base_footprint:
          Value: false
        base_link:
          Value: false
        drivewhl_l_link:
          Value: true
        drivewhl_r_link:
          Value: true
        front_caster:
          Value: false
        gps_link:
          Value: false
        imu_link:
          Value: false
        lidar_link:
          Value: false
      Marker Scale: 1
      Name: TF
      Show Arrows: false
      Show Axes: true
      Show Names: true
      Tree:
        base_footprint:
          base_link:
            drivewhl_l_link:
              {}
            drivewhl_r_link:
              {}
            front_caster:
              {}
            gps_link:
              {}
            imu_link:
              {}
            lidar_link:
              {}
      Update Interval: 0
      Value: 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
    - Class: rviz_default_plugins/SetInitialPose
      Topic:
        Depth: 5
        Durability Policy: Volatile
        History Policy: Keep Last
        Reliability Policy: Reliable
        Value: /initialpose
    - Class: rviz_default_plugins/SetGoal
      Topic:
        Depth: 5
        Durability Policy: Volatile
        History Policy: Keep Last
        Reliability Policy: Reliable
        Value: /goal_pose
    - Class: rviz_default_plugins/PublishPoint
      Single click: true
      Topic:
        Depth: 5
        Durability Policy: Volatile
        History Policy: Keep Last
        Reliability Policy: Reliable
        Value: /clicked_point
  Transformation:
    Current:
      Class: rviz_default_plugins/TF
  Value: true
  Views:
    Current:
      Class: rviz_default_plugins/Orbit
      Distance: 4.434264183044434
      Enable Stereo Rendering:
        Stereo Eye Separation: 0.05999999865889549
        Stereo Focal Distance: 1
        Swap Stereo Eyes: false
        Value: false
      Focal Point:
        X: 0.31193429231643677
        Y: 0.11948385089635849
        Z: -0.4807402193546295
      Focal Shape Fixed Size: true
      Focal Shape Size: 0.05000000074505806
      Invert Z Axis: false
      Name: Current View
      Near Clip Distance: 0.009999999776482582
      Pitch: 0.490397572517395
      Target Frame: <Fixed Frame>
      Value: Orbit (rviz)
      Yaw: 1.0503965616226196
    Saved: ~
Window Geometry:
  Displays:
    collapsed: false
  Height: 846
  Hide Left Dock: false
  Hide Right Dock: false
  QMainWindow State: 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
  Selection:
    collapsed: false
  Tool Properties:
    collapsed: false
  Views:
    collapsed: false
  Width: 1200
  X: 246
  Y: 77

八、编译构建软件包

现在就可以编译构建该软件包了。打开一个新的终端窗口并输入以下命令：

cd ~/dev_ws/src/two_wheeled_robot
gedit CMakeLists.txt

将下面这个代码段添加到CMakeLists.txt文件中的if(BUILD_TESTING)代码行前面：

install(
  DIRECTORY config launch maps meshes models params rviz src urdf worlds
  DESTINATION share/${PROJECT_NAME}
)

保存并关闭该文件。

编译该软件包：

cd ~/dev_ws/
colcon build

如果在您的工作空间中还有其它软件包，而且您只想构建two_wheeled_robot软件包，则需要键入以下命令：

colcon build --packages-select two_wheeled_robot

九、在RViz中启动机器人

打开一个新的终端窗口，并输入以下命令：

cd ~/dev_ws/
ros2 launch two_wheeled_robot two_wheeled_robot.launch.py

在RViz中启动该机器人后的输出结果应该如下图所示：

本教程就是这样。

完成所有任务后，请在所有终端窗口中按 CTRL+C 组合键关闭所有程序。

*英语原文地址：automaticaddison.com/ho