ROS2-humble用xacro工具建小车模型

新开一个终端，然后创建ws03_simulations工作空间

ctrl + alt + t

mkdir -p ws03_simulations/src

cd src

创建功能包，然后进入vscode

ros2 pkg create urdf01_rviz --packages-type ament_cmake

cd ..

code .

进入vscode后在功能包urdf01_rviz下新建urdf、rviz、launch文件夹，如下图

colcon build，编译完成后在install/urdf01_rviz/share/urdf01_rviz目录下可以看见刚才新建的三个文件夹——urdf、rviz、launch

在package.xml文件中添加以下代码：

<exec_depend>ros2launch</exec_depend>

<exec_depend>xacro</exec_depend>

<exec_depend>robot_state_publisher</exec_depend>

<exec_depend>joint_state_publisher</exec_depend>

<exec_depend>rviz2</exec_depend>

添加后如下图

 在CMakeLists.txt中添加以下代码：

install(DIRECTORY launch rviz urdf

DESTINATION share/${PROJECT_NAME}

)

添加后如下图

urdf文件夹下新建demo06_base_urdf.xacro文件

demo06_base_urdf.xacro中代码如下

<!--
    使用 xacro 优化 URDF 版的小车底盘实现：

    实现思路
    1.将一些常量、变量封装为 xacro:property
      比如:PI 值、小车底盘半径、离地间距、车轮半径、宽度 ....
    2.使用 宏 封装驱动轮以及支撑轮实现，调用相关宏生成驱动轮与支撑轮

-->
<!-- 根标签，必须声明 xmlns:xacro -->
<robot name="my_base" xmlns:xacro="http://www.ros.org/wiki/xacro">
    <!-- 封装变量、常量 -->
    <xacro:property name="PI" value="3.141"/>
    <!-- 宏:黑色设置 -->
    <material name="black">
        <color rgba="0.0 0.0 0.0 1.0" />
    </material>
    <!-- 底盘属性 -->
    <xacro:property name="base_footprint_radius" value="0.001" /> <!-- base_footprint 半径  -->
    <xacro:property name="base_link_radius" value="0.1" /> <!-- base_link 半径 -->
    <xacro:property name="base_link_length" value="0.08" /> <!-- base_link 长 -->
    <xacro:property name="earth_space" value="0.015" /> <!-- 离地间距 -->

    <!-- 底盘 -->
    <link name="base_footprint">
      <visual>
        <geometry>
          <sphere radius="${base_footprint_radius}" />
        </geometry>
      </visual>
    </link>

    <link name="base_link">
      <visual>
        <geometry>
          <cylinder radius="${base_link_radius}" length="${base_link_length}" />
        </geometry>
        <origin xyz="0 0 0" rpy="0 0 0" />
        <material name="yellow">
          <color rgba="0.8 0.8 0.0 1.0" />
        </material>
      </visual>
    </link>

    <joint name="base_link2base_footprint" type="fixed">
      <parent link="base_footprint" />
      <child link="base_link" />
      <origin xyz="0 0 ${earth_space + base_link_length / 2 }" />
    </joint>

    <!-- 驱动轮 -->
    <!-- 驱动轮属性 -->
    <xacro:property name="wheel_radius" value="0.0325" /><!-- 半径 -->
    <xacro:property name="wheel_length" value="0.015" /><!-- 宽度 -->
    <!-- 驱动轮宏实现 -->
    <xacro:macro name="add_wheels" params="name flag">
      <link name="${name}_wheel">
        <visual>
          <geometry>
            <cylinder radius="${wheel_radius}" length="${wheel_length}" />
          </geometry>
          <origin xyz="0.0 0.0 0.0" rpy="${PI / 2} 0.0 0.0" />
          <material name="black" />
        </visual>
      </link>

      <joint name="${name}_wheel2base_link" type="continuous">
        <parent link="base_link" />
        <child link="${name}_wheel" />
        <origin xyz="0 ${flag * base_link_radius} ${-(earth_space + base_link_length / 2 - wheel_radius) }" />
        <axis xyz="0 1 0" />
      </joint>
    </xacro:macro>
    <xacro:add_wheels name="left" flag="1" />
    <xacro:add_wheels name="right" flag="-1" />
    <!-- 支撑轮 -->
    <!-- 支撑轮属性 -->
    <xacro:property name="support_wheel_radius" value="0.0075" /> <!-- 支撑轮半径 -->

    <!-- 支撑轮宏 -->
    <xacro:macro name="add_support_wheel" params="name flag" >
      <link name="${name}_wheel">
        <visual>
            <geometry>
                <sphere radius="${support_wheel_radius}" />
            </geometry>
            <origin xyz="0 0 0" rpy="0 0 0" />
            <material name="black" />
        </visual>
      </link>

      <joint name="${name}_wheel2base_link" type="continuous">
          <parent link="base_link" />
          <child link="${name}_wheel" />
          <origin xyz="${flag * (base_link_radius - support_wheel_radius)} 0 ${-(base_link_length / 2 + earth_space / 2)}" />
          <axis xyz="1 1 1" />
      </joint>
    </xacro:macro>

    <xacro:add_support_wheel name="front" flag="1" />
    <xacro:add_support_wheel name="back" flag="-1" />

</robot>

urdf文件夹下新建demo07_camera_urdf.xacro文件

demo07_camera_urdf.xacro中代码如下

<!-- 摄像头相关的 xacro 文件 -->
<robot name="my_camera" xmlns:xacro="http://www.ros.org/wiki/xacro">
    <!-- 摄像头属性 -->
    <xacro:property name="camera_length" value="0.01" /> <!-- 摄像头长度(x) -->
    <xacro:property name="camera_width" value="0.025" /> <!-- 摄像头宽度(y) -->
    <xacro:property name="camera_height" value="0.025" /> <!-- 摄像头高度(z) -->
    <xacro:property name="camera_x" value="0.08" /> <!-- 摄像头安装的x坐标 -->
    <xacro:property name="camera_y" value="0.0" /> <!-- 摄像头安装的y坐标 -->
    <xacro:property name="camera_z" value="${base_link_length / 2 + camera_height / 2}" /> <!-- 摄像头安装的z坐标:底盘高度 / 2 + 摄像头高度 / 2  -->

    <!-- 摄像头关节以及link -->
    <link name="camera">
        <visual>
            <geometry>
                <box size="${camera_length} ${camera_width} ${camera_height}" />
            </geometry>
            <origin xyz="0.0 0.0 0.0" rpy="0.0 0.0 0.0" />
            <material name="black" />
        </visual>
    </link>

    <joint name="camera2base_link" type="fixed">
        <parent link="base_link" />
        <child link="camera" />
        <origin xyz="${camera_x} ${camera_y} ${camera_z}" />
    </joint>
</robot>

urdf文件夹下新建demo08_laser_urdf.xacro文件

demo08_laser_urdf.xacro中代码如下

<!--
    小车底盘添加雷达
-->
<robot name="my_laser" xmlns:xacro="http://www.ros.org/wiki/xacro">

    <!-- 雷达支架 -->
    <xacro:property name="support_length" value="0.15" /> <!-- 支架长度 -->
    <xacro:property name="support_radius" value="0.01" /> <!-- 支架半径 -->
    <xacro:property name="support_x" value="0.0" /> <!-- 支架安装的x坐标 -->
    <xacro:property name="support_y" value="0.0" /> <!-- 支架安装的y坐标 -->
    <xacro:property name="support_z" value="${base_link_length / 2 + support_length / 2}" /> <!-- 支架安装的z坐标:底盘高度 / 2 + 支架高度 / 2  -->

    <link name="support">
        <visual>
            <geometry>
                <cylinder radius="${support_radius}" length="${support_length}" />
            </geometry>
            <origin xyz="0.0 0.0 0.0" rpy="0.0 0.0 0.0" />
            <material name="red">
                <color rgba="0.8 0.8 0.8 1.0" />
            </material>
        </visual>
    </link>

    <joint name="support2base_link" type="fixed">
        <parent link="base_link" />
        <child link="support" />
        <origin xyz="${support_x} ${support_y} ${support_z}" />
    </joint>


    <!-- 雷达属性 -->
    <xacro:property name="laser_length" value="0.05" /> <!-- 雷达长度 -->
    <xacro:property name="laser_radius" value="0.03" /> <!-- 雷达半径 -->
    <xacro:property name="laser_x" value="0.0" /> <!-- 雷达安装的x坐标 -->
    <xacro:property name="laser_y" value="0.0" /> <!-- 雷达安装的y坐标 -->
    <xacro:property name="laser_z" value="${support_length / 2 + laser_length / 2}" /> <!-- 雷达安装的z坐标:支架高度 / 2 + 雷达高度 / 2  -->

    <!-- 雷达关节以及link -->
    <link name="laser">
        <visual>
            <geometry>
                <cylinder radius="${laser_radius}" length="${laser_length}" />
            </geometry>
            <origin xyz="0.0 0.0 0.0" rpy="0.0 0.0 0.0" />
            <material name="black" />
        </visual>
    </link>

    <joint name="laser2support" type="fixed">
        <parent link="support" />
        <child link="laser" />
        <origin xyz="${laser_x} ${laser_y} ${laser_z}" />
    </joint>
</robot>

urdf文件夹下新建demo09_lcar_urdf.xacro文件

demo09_lcar_urdf.xacro中代码如下

<!-- 组合小车底盘、摄像头与雷达 -->
<robot name="my_car_camera" xmlns:xacro="http://www.ros.org/wiki/xacro">
    <xacro:include filename="demo06_base_urdf.xacro" />
    <xacro:include filename="demo07_camera_urdf.xacro" />
    <xacro:include filename="demo08_laser_urdf.xacro" />
</robot>

在launch文件夹下新建demo09_car_xacro.launch.py文件

from launch import LaunchDescription
from launch_ros.actions import Node
from launch.actions import DeclareLaunchArgument
from launch.substitutions import LaunchConfiguration
from ament_index_python.packages import get_package_share_directory
from launch_ros.parameter_descriptions import ParameterValue
from launch.substitutions import Command

def generate_launch_description():


    model = DeclareLaunchArgument(name="model",default_value=get_package_share_directory("urdf01_rviz") + "/urdf/demo09_car_urdf.xacro")
    p_value = ParameterValue(Command(["xacro ",LaunchConfiguration("model")]))
    robot_state_pub = Node(package="robot_state_publisher",
        executable="robot_state_publisher",
        parameters=[{"robot_description":p_value}] #robot_description的值p_value其实就是urdf文件的内容
    ) 

    joint_state_pub = Node(package="joint_state_publisher",executable="joint_state_publisher")
    
    rviz2 = Node(package="rviz2",executable="rviz2")

    return LaunchDescription([model,robot_state_pub,joint_state_pub,rviz2])

colcon build

ros2 launch urdf01_rviz demo09_car_xacro.launch.py

rviz启动后Fixed Frame选择boot_footprint，添加RobotModel和TF插件，如下图所示