ros2 lifcycle介绍

ros2 lifcycle

简介

ROS 2 引入了托管节点（Managed Nodes）的概念，这类节点也被称为生命周期节点（LifecycleNode）。 LifecycleNode 内部包含一个 有限状态机，通过调用表示连续后继状态的转换ID即可实现状态切换。

• Primary States (steady states):

  • unconfigured
  • inactive
  • active
  • finalized

• Transition States (intermediate states):

  • configuring
  • activating
  • deactivating
  • cleaningup
  • shuttingdown

• 状态跳转触发事件如下，通过外部指令（如终端指令）去触发 :
  • configure
  • activate
  • deactivate
  • cleanup
  • shutdown

• 创建驱动实例(new) : * --> unconfigured
• 配置ip端口等参数(configure) : unconfigured --> configuring --> inactive
• 启动lidar 连接,开始发送数据(activate) : inactive --> activating --> active
• 关闭lidar 连接,停止发送数据(deactivate) : active --> deactivating --> inactive
• 清理资源(cleanup) : inactive --> cleanup --> unconfigured
• 结束(shutdown) : unconfigured --> shuttingdown --> finalized
• 删除实例(delete) : finalized --> o

代码结构及使用

• state.hpp : 状态定义
• transition.hpp : 跳转
• lifecycle_node_impl.hpp,lifecycle_node.hpp : 状态机实现
• lifecycle_node_interface.hpp : 定义的事件响应函数(虚函数)，这个就是子类需要继承实现的，如下所示：

/// rclcpp_lifecycle/include/rclcpp_lifecycle/node_interfaces/lifecycle_node_interface.hpp

 enum class CallbackReturn : uint8_t
  {
    SUCCESS = lifecycle_msgs::msg::Transition::TRANSITION_CALLBACK_SUCCESS,
    FAILURE = lifecycle_msgs::msg::Transition::TRANSITION_CALLBACK_FAILURE,
    ERROR = lifecycle_msgs::msg::Transition::TRANSITION_CALLBACK_ERROR
  };


virtual CallbackReturn on_configure(const rclcpp_lifecycle::State & previous_state);
virtual CallbackReturn on_activate(const rclcpp_lifecycle::State & previous_state);
virtual CallbackReturn on_deactivate(const rclcpp_lifecycle::State & previous_state);
virtual CallbackReturn on_cleanup(const rclcpp_lifecycle::State & previous_state);
virtual CallbackReturn on_shutdown(const rclcpp_lifecycle::State & previous_state);

• 例如要写 liddar驱动，继承关系为 LidarDriver --> LifecycleNode --> LifecycleNodeInterface ;
• 需要 override 以上函数，和自己的内部实现相关；

命令行指令

获取当前状态

$ ros2 lifecycle get /lc_talker

unconfigured [1]

发送事件，开始状态跳转

$ ros2 lifecycle set /lc_talker configure

Transitioning successful

查看当前可跳转状态

$ ros2 lifecycle list lc_talker

- configure [1]
  Start: unconfigured
  Goal: configuring
- shutdown [5]
  Start: unconfigured
  Goal: shuttingdown

查看所有跳转状态

$ ros2 lifecycle list lc_talker -a

- configure [1]
  Start: unconfigured
  Goal: configuring
- transition_success [10]
  Start: configuring
  Goal: inactive
- transition_failure [11]
  Start: configuring
  Goal: unconfigured
- transition_error [12]
  Start: configuring
  Goal: errorprocessing

[...]

- transition_error [62]
  Start: errorprocessing
  Goal: finalized

参考

• docs.ros.org/en/ros2_pac…

• design.ros2.org/articles/no…

• github.com/ros2/demos/…