在使用Gazebo接入ros2_control的时候出现parameter无法解析的错误

yepraywong

以下是根据小鱼的课程编辑的代码：

fishbot.ros2_contro.xacro

<?xml version="1.0"?>
<robot xmlns:xacro="http://www.ros.org/wiki/xacro">
    <xacro:macro name="fishbot_ros2_control">
        <!-- This '<ros2_control>' will be seen by '<gazebo>' -->
        <ros2_control name="FishBotGazeboSystem" type="system">
            <hardware>
                <plugin>gazebo_ros2_control/GazeboSystem</plugin>
            </hardware>
            <joint name="left_wheel_joint">
                <!-- 利用速度接口控制轮子输出的转速 -->
                <command_interface name="velocity">
                    <param name="min">-1</param>
                    <param name="max">1</param>
                </command_interface>
                <!-- 利用速度接口控制轮子输出的力 -->
                <command_interface name="effort">
                    <param name="min">-0.1</param>
                    <param name="max">0.1</param>
                </command_interface>
                <!-- position 表示轮子转了多少度 -->
                <!-- velocity 轮子转速 -->
                <!-- effort 轮子输出的力 -->
                <state_interface name="position" />
                <state_interface name="velocity" />
                <state_interface name="effort" />
            </joint>
            <joint name="right_wheel_joint">
                <command_interface name="velocity">
                    <param name="min">-1</param>
                    <param name="max">1</param>
                </command_interface>
                <command_interface name="effort">
                    <param name="min">-0.1</param>
                    <param name="max">0.1</param>
                </command_interface>
                <state_interface name="position" />
                <state_interface name="velocity" />
                <state_interface name="effort" />
            </joint>
        </ros2_control>
    <gazebo>
        <plugin filename="libgazebo_ros2_control.so" name="gazebo_ros2_control">
            <parameters>$(find fishbot_description)/config/fishbot_ros2_controller.yaml</parameters>
        </plugin>
    </gazebo>
    </xacro:macro>
</robot>

fishbot_ros2_controller.yaml

controller_manager:
  ros__parameters:
    update_rate: 100  # Hz
    use_sim_time: true

fishbot.urdf.xacro

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

<!-- base -->
<!-- 'find fishbot_description' is to find pkgs' share directory -->
<xacro:include filename="$(find fishbot_description)/urdf/fishbot/base.urdf.xacro"/>
<!-- sensors -->
<xacro:include filename="$(find fishbot_description)/urdf/fishbot/sensor/imu.urdf.xacro"/>
<xacro:include filename="$(find fishbot_description)/urdf/fishbot/sensor/camera.urdf.xacro"/>
<xacro:include filename="$(find fishbot_description)/urdf/fishbot/sensor/laser.urdf.xacro"/>
<!-- wheels -->
<xacro:include filename="$(find fishbot_description)/urdf/fishbot/actuator/wheel.urdf.xacro"/>
<!-- casters -->
<xacro:include filename="$(find fishbot_description)/urdf/fishbot/actuator/caster.urdf.xacro"/>
<!-- plugins -->
<xacro:include filename="$(find fishbot_description)/urdf/fishbot/plugins/gazebo_control_plugin.xacro"/>
<xacro:include filename="$(find fishbot_description)/urdf/fishbot/plugins/gazebo_sensor_plugin.xacro"/>
<xacro:include filename="$(find fishbot_description)/urdf/fishbot/fishbot.ros2_control.xacro"/>


<xacro:base_xacro length="0.12" radius='0.10'/>
<xacro:imu_xacro xyz="0.0 0.0 0.02"/>
<xacro:camera_xacro xyz="0.10 0.0 0.075"/>
<xacro:laser_xacro xyz="0.0 0.0 0.10"/>

<xacro:wheel_xacro wheel_name="left_wheel" xyz="0 0.10 -0.06"/>
<xacro:wheel_xacro wheel_name="right_wheel" xyz="0 -0.10 -0.06"/>
<!-- 0.076 = 0.06(half of base link's height) + 0.032(wheels' radius) - 0.016(caster's radius) -->
<xacro:caster_xacro caster_name="back_caster" xyz="-0.08 0.0 -0.076"/>
<xacro:caster_xacro caster_name="front_caster" xyz="0.08 0.0 -0.076"/>

<!-- using plugins -->
<!-- 因为使用两轮差速控制硬件和gazebo ros2 control相冲突 -->
<!-- 所以在使用ros2 control的时候需要把两轮差速控制硬件的插件注释掉 -->
<xacro:gazebo_sensor_plugin />
<xacro:fishbot_ros2_control />

</robot>

gazebo_sim.launch.py

import launch
import launch.launch_description_sources
import launch_ros
# find first_robot.urdf file's directory
from ament_index_python.packages import get_package_share_directory
import os

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


def generate_launch_description():
    # the code below return the fishbot_description path under the 'share' directory
    urdf_package_path = get_package_share_directory('fishbot_description')
    # obtain the xacro file's path
    default_xacro_path = os.path.join(urdf_package_path, 'urdf', 'fishbot/fishbot.urdf.xacro')
    # default gazebo file's path
    default_gazebo_world_path = os.path.join(urdf_package_path, 'world', 'custom_room.world')

    # declare a param for the xacro directory
    action_declare_arg_mode_path = launch.actions.DeclareLaunchArgument(
        name='model',default_value=str(default_xacro_path),description='file path of loaded model'
    )
    
    substituted_command_result = Command(['xacro ', LaunchConfiguration('model')])
    robot_description_value = launch_ros.parameter_descriptions.ParameterValue(substituted_command_result, value_type=str)

    action_robot_state_publisher = launch_ros.actions.Node(
        package='robot_state_publisher',
        executable='robot_state_publisher',
        parameters=[{'robot_description':robot_description_value}]
        # 这里的parameters参数是用来向节点传递配置参数的,来获取机器人的 URDF 文件内容
    )

    # launch gazebo
    action_launch_gazebo = launch.actions.IncludeLaunchDescription(
        launch.launch_description_sources.PythonLaunchDescriptionSource(
            [get_package_share_directory('gazebo_ros'),'/launch','/gazebo.launch.py']
        ),
        launch_arguments=[('world',default_gazebo_world_path),('verbose','true')]
    )
    
    action_spawn_entity = launch_ros.actions.Node(
        package='gazebo_ros',
        executable='spawn_entity.py',
        arguments=['-topic','/robot_description','-entity','fishbot']
    )

    return launch.LaunchDescription([
        action_declare_arg_mode_path,
        action_robot_state_publisher,
        action_launch_gazebo,
        action_spawn_entity
    ])

build并source了之后，运行命令：ros2 launch fishbot_description gazebo_sim.launch.py出现如下错误信息：

[INFO] [launch]: All log files can be found below /home/rayray/.ros/log/2024-11-03-15-32-19-623161-ruirui-6405
[INFO] [launch]: Default logging verbosity is set to INFO
[INFO] [robot_state_publisher-1]: process started with pid [6417]
[INFO] [gzserver-2]: process started with pid [6419]
[INFO] [gzclient-3]: process started with pid [6421]
[INFO] [spawn_entity.py-4]: process started with pid [6423]
[robot_state_publisher-1] [INFO] [1730619140.442733183] [robot_state_publisher]: got segment back_caster_link
[robot_state_publisher-1] [INFO] [1730619140.442932242] [robot_state_publisher]: got segment base_footprint
[robot_state_publisher-1] [INFO] [1730619140.442947571] [robot_state_publisher]: got segment base_link
[robot_state_publisher-1] [INFO] [1730619140.442955913] [robot_state_publisher]: got segment camera_link
[robot_state_publisher-1] [INFO] [1730619140.442963330] [robot_state_publisher]: got segment camera_optical_link
[robot_state_publisher-1] [INFO] [1730619140.442970904] [robot_state_publisher]: got segment front_caster_link
[robot_state_publisher-1] [INFO] [1730619140.443010637] [robot_state_publisher]: got segment imu_link
[robot_state_publisher-1] [INFO] [1730619140.443018315] [robot_state_publisher]: got segment laser_cylinder_link
[robot_state_publisher-1] [INFO] [1730619140.443025876] [robot_state_publisher]: got segment laser_link
[robot_state_publisher-1] [INFO] [1730619140.443038634] [robot_state_publisher]: got segment left_wheel_link
[robot_state_publisher-1] [INFO] [1730619140.443046157] [robot_state_publisher]: got segment right_wheel_link
[gzclient-3] Gazebo multi-robot simulator, version 11.10.2
[gzclient-3] Copyright (C) 2012 Open Source Robotics Foundation.
[gzclient-3] Released under the Apache 2 License.
[gzclient-3] http://gazebosim.org
[gzclient-3] 
[gzserver-2] Gazebo multi-robot simulator, version 11.10.2
[gzserver-2] Copyright (C) 2012 Open Source Robotics Foundation.
[gzserver-2] Released under the Apache 2 License.
[gzserver-2] http://gazebosim.org
[gzserver-2] 
[spawn_entity.py-4] [INFO] [1730619140.932122723] [spawn_entity]: Spawn Entity started
[spawn_entity.py-4] [INFO] [1730619140.932722353] [spawn_entity]: Loading entity published on topic /robot_description
[spawn_entity.py-4] /opt/ros/humble/local/lib/python3.10/dist-packages/rclpy/qos.py:307: UserWarning: DurabilityPolicy.RMW_QOS_POLICY_DURABILITY_TRANSIENT_LOCAL is deprecated. Use DurabilityPolicy.TRANSIENT_LOCAL instead.
[spawn_entity.py-4]   warnings.warn(
[spawn_entity.py-4] [INFO] [1730619140.935257380] [spawn_entity]: Waiting for entity xml on /robot_description
[spawn_entity.py-4] [INFO] [1730619140.947043458] [spawn_entity]: Waiting for service /spawn_entity, timeout = 30
[spawn_entity.py-4] [INFO] [1730619140.947584792] [spawn_entity]: Waiting for service /spawn_entity
[spawn_entity.py-4] [INFO] [1730619141.703951446] [spawn_entity]: Calling service /spawn_entity
[gzserver-2] [Msg] Waiting for master.
[gzserver-2] [Msg] Connected to gazebo master @ http://127.0.0.1:11345
[gzserver-2] [Msg] Publicized address: 192.168.1.7
[gzserver-2] [Msg] Loading world file [/home/rayray/URDFLearning/URDFLearn_ws/install/fishbot_description/share/fishbot_description/world/custom_room.world]
[gzserver-2] [Wrn] [Event.cc:61] Warning: Deleting a connection right after creation. Make sure to save the ConnectionPtr from a Connect call
[gzclient-3] 
[gzclient-3] libcurl: (5) Unsupported proxy syntax in 'http://127.0.0.1 :7890/'
[gzserver-2] [INFO] [1730619142.516533608] [depth_camera]: Publishing camera info to [/camera_sensor/camera_info]
[gzserver-2] [INFO] [1730619142.517603375] [depth_camera]: Publishing depth camera info to [/camera_sensor/depth/camera_info]
[gzserver-2] [INFO] [1730619142.518202683] [depth_camera]: Publishing pointcloud to [/camera_sensor/points]
[spawn_entity.py-4] [INFO] [1730619142.670410667] [spawn_entity]: Spawn status: SpawnEntity: Successfully spawned entity [fishbot]
[gzclient-3] [Msg] Waiting for master.
[gzclient-3] [Msg] Connected to gazebo master @ http://127.0.0.1:11345
[gzclient-3] [Msg] Publicized address: 192.168.1.7
[gzclient-3] [Wrn] [Event.cc:61] Warning: Deleting a connection right after creation. Make sure to save the ConnectionPtr from a Connect call
[gzserver-2] [INFO] [1730619142.792004313] [gazebo_ros2_control]: Loading gazebo_ros2_control plugin
[gzserver-2] [INFO] [1730619142.798491513] [gazebo_ros2_control]: Starting gazebo_ros2_control plugin in namespace: /
[gzserver-2] [INFO] [1730619142.798567602] [gazebo_ros2_control]: Starting gazebo_ros2_control plugin in ros 2 node: gazebo_ros2_control
[gzserver-2] [INFO] [1730619142.809044792] [gazebo_ros2_control]: connected to service!! robot_state_publisher
[gzserver-2] [INFO] [1730619142.812920852] [gazebo_ros2_control]: Received urdf from param server, parsing...
[gzserver-2] [INFO] [1730619142.812998897] [gazebo_ros2_control]: Loading parameter files /home/rayray/URDFLearning/URDFLearn_ws/install/fishbot_description/share/fishbot_description/config/fishbot_ros2_controller.yaml
[gzserver-2] [rcutils|error_handling.c:65] an error string (message, file name, or formatted message) will be truncated
[gzserver-2] [ERROR] [1730619142.813820165] [gazebo_ros2_control]: parser error Couldn't parse parameter override rule: '--param robot_description:=<?xml version="1.0" ?>
[gzserver-2] <!-- =================================================================================== -->
[gzserver-2] <!-- |    This document was autogenerated by xacro from /home/rayray/URDFLearning/URDFLearn_ws/install/fishbot_description/share/fishbot_description/urdf/fishbot/fishbot.urdf.xacro | -->
[gzserver-2] <!-- |    EDITING THIS FILE BY HAND IS NOT RECOMMENDED                                 | -->
[gzserver-2] <!-- =================================================================================== -->
[gzserver-2] <robot name="fish_robot">
[gzserver-2]   <link name="base_footprint"/>
[gzserver-2]   <link name="base_link">
[gzserver-2]     <!-- Components' appearance -->
[gzserver-2]     <visual>
[gzserver-2]       <!-- Offset and rotation along it's own geometric center -->
[gzserver-2]       <ori, at ./src/rcl/arguments.c:343
[gzserver-2] 
[INFO] [spawn_entity.py-4]: process has finished cleanly [pid 6423]
[gzclient-3] [Wrn] [Event.cc:61] Warning: Deleting a connection right after creation. Make sure to save the ConnectionPtr from a Connect call
[INFO] [gzclient-3]: process has finished cleanly [pid 6421]

应该就是parser error Couldn't parse parameter override rule: '--param robot_description:=<?xml version="1.0" ?>这个错误一直解决不了，排除了很久的代码也没有找到问题，恳请各位大佬前辈帮帮忙，有前辈遇到过类似的问题吗

机器人小伊

您遇到的问题是由于Gazebo尝试解析通过--param传递的机器人描述（URDF/XACRO）字符串时出错。这通常发生在Gazebo的ROS 2插件尝试从参数服务器获取URDF信息时，但获取到的格式不正确或解析方式有误。

从错误信息来看，Gazebo尝试解析的URDF字符串被错误地直接放在了命令行参数中，而通常这应该是通过参数服务器正确加载的XML格式文件。这里的错误提示显示XML内容被直接作为字符串解析，导致解析失败。

解决步骤

确保URDF/XACRO文件正确加载：
- 确保fishbot.urdf.xacro文件正确无误，并且所有包含的文件路径都是正确的。
- 使用xacro命令行工具检查XACRO文件是否可以被正确解析：
```
xacro --inorder fishbot_description/urdf/fishbot/fishbot.urdf.xacro
```
  确保输出是一个有效的URDF XML。
检查参数服务器上的robot_description：
- 在运行Gazebo之前，确保robot_description参数已经被正确设置到参数服务器上。您可以通过ROS 2命令行工具查看：
```
ros2 param get /robot_state_publisher robot_description
```
  这应该输出您的URDF XML内容。
检查Gazebo的ROS 2插件配置：
- 在您的fishbot.ros2_control.xacro文件中，您配置了Gazebo的ROS 2控制插件来加载fishbot_ros2_controller.yaml。确保这个YAML文件正确无误，并且路径正确。
- 确保Gazebo的ROS 2插件配置正确，并且它应该通过参数服务器获取robot_description，而不是直接从命令行参数获取。
修改启动文件：
- 您的gazebo_sim.launch.py文件看起来是正确设置了robot_description参数。但是，确保在Gazebo尝试访问这个参数之前，robot_state_publisher已经运行并发布了这个参数。
- 您可以尝试调整节点启动的顺序，确保robot_state_publisher在Gazebo之前完全启动并运行。
调试和日志：
- 增加日志输出，特别是在设置robot_description参数和Gazebo尝试读取这个参数的地方。
- 检查Gazebo的日志文件，看是否有更详细的错误信息。
环境问题：
- 确保您的ROS 2和Gazebo环境配置正确，所有依赖都已正确安装。

通过上述步骤，您应该能够定位问题的根源，并找到解决方法。如果问题仍然存在，可能需要更详细地检查Gazebo的ROS 2插件的源代码，看看它是如何处理robot_description参数的。

以上为生成回答，仅供参考～

小鱼

@yepraywong urdf格式错误吧，仔细检查

yepraywong

@小鱼解决啦！把注释里的冒号全部删除就不报错了，应该是冒号影响了解析。

开心

@小伊运行ros2 param get /robot_state_publisher robot_description
提示Node not found

小鱼

@43996173 先运行节点

solito1

@yepraywong 注释里的冒号是指的哪里呢，我也遇到了相同的报错