6.2.3章节通过参数修改model参数报错格式不对

[43996173]

运行报错：

tingbo@DESKTOP-NHH5E05:~/chapt6/chapt6_ws$ ros2 launch fishbot_description display_robot.launch.py model :=/home/tingbo/chapt6/chapt6_ws/src/fishbot_description/urdf/first_robot.urdf.xacro
malformed launch argument 'model', expected format '<name>:=<value>'
tingbo@DESKTOP-NHH5E05:~/chapt6/chapt6_ws$ ros2 launch fishbot_description display_robot.launch.py model := /home/tingbo/chapt6/chapt6_ws/src/fishbot_description/
urdf/first_robot.urdf.xacro
malformed launch argument 'model', expected format '<name>:=<value>'
tingbo@DESKTOP-NHH5E05:~/chapt6/chapt6_ws$ ros2 launch fishbot_description display_robot.launch.py <model> :
= </home/tingbo/chapt6/chapt6_ws/src/fishbot_descripti
on/urdf/first_robot.urdf.xacro>
bash: 未预期的记号 "newline" 附近有语法错误

[43996173]

@43996173
display_robot.launch.py代码：

import launch
import launch_ros
from ament_index_python.packages import get_package_share_directory



def generate_launch_description():
    urdf_tutorial_path = get_package_share_directory('fishbot_description')
    default_model_path = urdf_tutorial_path + '/urdf/first_robot.urdf'
    #print (str(default_model_path))
    default_rviz_config_path = urdf_tutorial_path + '/config/rviz/display_model.rviz'
    action_declare_arg_mode_path = launch.actions.DeclareLaunchArgument(
        name='model', default_value=str(default_model_path),
        description='URDF的绝对路径')
    robot_description=launch_ros.parameter_descriptions.ParameterValue(
        launch.substitutions.Command(
            ['xacro ', launch.substitutions.LaunchConfiguration('model')]),
            value_type=str)
    robot_state_publisher_node = launch_ros.actions.Node (
        package='robot_state_publisher',
        executable='robot_state_publisher',
        parameters=[{'robot_description':robot_description}])
    joint_state_publisher_node = launch_ros.actions.Node(
        package='joint_state_publisher',
        executable='joint_state_publisher',
    )
    rviz_node = launch_ros.actions.Node(
        package='rviz2',
        executable='rviz2',
        arguments=['-d', default_rviz_config_path]
    )
    return launch.LaunchDescription([
        action_declare_arg_mode_path,
        joint_state_publisher_node,
        robot_state_publisher_node,
        rviz_node
    ])

first_robot.urdf.xacro代码：

<?xml version="1.0"?>
<robot xmlns:xacro="http://www.ros.org/wiki/xacro" name="first_robot">
    <!--声明base模块-->
    <xacro:macro name="base_link" params="length radius">
        <link name="base_link">
            <visual>
                <origin xyz="0.0 0.0 0.0" rpy="0.0 0.0 0.0"/>
                <geometry>
                    <cylinder radius="${length}" length="${length}"/>
                </geometry>
                <material name="white">
                    <color rgba="1.0 1.0 1.0 0.5"/>
                </material>
                
            </visual>
            
        </link>
        
    </xacro:macro>
    <!--声明imu模块-->
    <xacro:macro name="imu_link" params="imu_name xyz">
        <link name="${imu_name}_link">
            <visual>
                <origin xyz="0.0 0.0 0.0" rpy="0.0 0.0 0.0"/>
                <geometry>
                    <box size="0.02 0.02 0.02"/>
                </geometry>
            </visual>
            <material name="black">
                <color rgba="0.0 0.0 0.0 0.5"/>
                
            </material>
            
        </link>
        <joint name="${imu_name}_joint" type="fixed">
            <parent link="base_link"/>
            <child link="${imu_name}_link"/>
            <origin xyz="${xyz}"/>
        </joint>
    </xacro:macro>
    <!--传递参数调用base_link模块-->
    <xacro:base_link length="0.12" radius="0.1"/>
    <!--传递参数调用imu模块-->
    <xacro:imu_link imu_name="imu_up" xyz="0 0 0.02" />
    <xacro:imu_link imu_name="imu_down" xyz="0.0 0.0 -0.02" />
</robot>