ROS<ERROR: cannot launch node of type>

在学习ros/tf2函数库的时候,在launch文件中添加了节点之后发现无法启动,出现一下错误:

... logging to /home/xzchuang/.ros/log/76b69150-e5f4-11e7-a49a-484d7ec9f3d5/roslaunch-Vostro-14838.log
Checking log directory for disk usage. This may take awhile.
Press Ctrl-C to interrupt
Done checking log file disk usage. Usage is <1GB.

started roslaunch server http://Vostro:35366/

SUMMARY
========

PARAMETERS
 * /rosdistro: kinetic
 * /rosversion: 1.12.12
 * /turtle1_tf2_broadcaster/turtle: turtle1
 * /turtle2_tf2_broadcaster/turtle: turtle2

NODES
  /
    listener (learning_tf2/turtle_tf2_listener.py)
    sim (turtlesim/turtlesim_node)
    teleop (turtlesim/turtle_teleop_key)
    turtle1_tf2_broadcaster (learning_tf2/turtle_tf2_broadcaster.py)
    turtle2_tf2_broadcaster (learning_tf2/turtle_tf2_broadcaster.py)

ROS_MASTER_URI=http://localhost:11311

process[sim-1]: started with pid [14855]
process[teleop-2]: started with pid [14856]
process[turtle1_tf2_broadcaster-3]: started with pid [14857]
process[turtle2_tf2_broadcaster-4]: started with pid [14868]
ERROR: cannot launch node of type [learning_tf2/turtle_tf2_listener.py]: can't locate node [turtle_tf2_listener.py] in package [learning_tf2]
Reading from keyboard
---------------------------
Use arrow keys to move the turtle.
[turtle2_tf2_broadcaster-4] killing on exit
[turtle1_tf2_broadcaster-3] killing on exit
[sim-1] killing on exit
[teleop-2] killing on exit
shutting down processing monitor...
... shutting down processing monitor complete
done

经过排查,发现是当前用户对当前文件(turtle_tf2_listener.py)没有可执行的权限,修改()之后,一切正常

xzchuang@Vostro:~/catkin_ws/src/learning_tf2/nodes$ ll
总用量 28
drwxrwxr-x 3 xzchuang xzchuang 4096 1221 14:10 ./
drwxrwxr-x 6 xzchuang xzchuang 4096 1221 14:06 ../
drwxrwxr-x 3 xzchuang xzchuang 4096 1221 14:10 .idea/
-rwxrwxr-x 1 xzchuang xzchuang 1569 1221 11:01 static_turtle_tf2_broadcaster.py*
-rwxrwxr-x 1 xzchuang xzchuang 1006 1221 11:23 turtle_tf2_broadcaster.py*
-rwxrwxr-x 1 xzchuang xzchuang 1176 1221 14:08 turtle_tf2_listener2.py*
-rw-rw-r-- 1 xzchuang xzchuang 1176 1221 14:10 turtle_tf2_listener.py
xzchuang@Vostro:~/catkin_ws/src/learning_tf2/nodes$ chmod +x turtle_tf2_listener.py 
xzchuang@Vostro:~/catkin_ws/src/learning_tf2/nodes$ ll
总用量 28
drwxrwxr-x 3 xzchuang xzchuang 4096 1221 14:10 ./
drwxrwxr-x 6 xzchuang xzchuang 4096 1221 14:06 ../
drwxrwxr-x 3 xzchuang xzchuang 4096 1221 14:10 .idea/
-rwxrwxr-x 1 xzchuang xzchuang 1569 1221 11:01 static_turtle_tf2_broadcaster.py*
-rwxrwxr-x 1 xzchuang xzchuang 1006 1221 11:23 turtle_tf2_broadcaster.py*
-rwxrwxr-x 1 xzchuang xzchuang 1176 1221 14:08 turtle_tf2_listener2.py*
-rwxrwxr-x 1 xzchuang xzchuang 1176 1221 14:10 turtle_tf2_listener.py*
### 解决方案 当遇到 `cannot locate node` 的错误时,通常是因为 ROS 环境未正确设置或依赖项缺失。以下是针对该问题的具体分析和解决方案: #### 1. 检查工作空间的构建状态 确保已经成功克隆并构建了 `cartographer_ros` 和其相关依赖包。可以按照以下步骤操作: - 使用 `wstool` 合并所需的 `.rosinstall` 文件[^3]。 - 构建整个工作空间以确保所有必要的节点被正确编译。 ```bash cd ~/catkin_ws/src wstool merge -t src https://raw.githubusercontent.com/googlecartographer/cartographer_ros/master/cartographer_ros.rosinstall wstool update sudo apt-get install ros-<distro>-cartographer-ros catkin_make_isolated --install --use-ninja source devel_isolated/setup.bash ``` > **注意**: `<distro>` 应替换为当前使用的 ROS 版本(如 kinetic、melodic 或 noetic)。[^3] #### 2. 验证环境变量配置 确认 ROS 路径已正确加载至环境中。可以通过以下命令验证路径是否包含 `cartographer_ros`: ```bash echo $ROS_PACKAGE_PATH ``` 如果输出不包含 `/path/to/catkin_ws/devel_isolated`, 则需要重新 source 工作空间下的 setup 文件: ```bash source ~/catkin_ws/devel_isolated/setup.bash ``` #### 3. 排查命名冲突或其他潜在问题 有时由于拼写错误或多余的空格可能导致节点无法找到。例如,在 launch 文件中定义节点时,应严格遵循正确的格式[^4]: ```xml <node pkg="cartographer_ros" type="cartographer_node" name="cartographer_node"/> <node pkg="cartographer_ros" type="cartographer_occupancy_grid_node" name="cartographer_occupancy_grid_node"/> ``` 如果有任何多余字符(如空格),需修正后再尝试启动。 #### 4. 测试单个节点功能 为了进一步排查问题根源,可分别手动测试两个主要节点的功能性: ```bash rosrun cartographer_ros cartographer_node rosrun cartographer_ros cartographer_occupancy_grid_node ``` 若以上命令均能正常执行,则说明 launch 文件可能存在配置不当;反之则可能是安装过程存在问题。 --- ### 总结 通过上述方法逐一排除可能原因后,基本能够定位并修复 `cannot locate node` 错误。重点在于确保开发环境一致性以及各组件间相互兼容性良好。
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