【ROS】消息通讯——动作action的来龙去脉

本文档详细介绍了如何在ROS中创建一个名为`action_tutorials`的功能包，包括修改`package.xml`和`CMakeLists.txt`文件，定义动作文件`DoDishes.action`，创建动作客户端和服务器节点。客户端`DoDishes_client`负责发送任务并接收完成通知，服务器端`DoDishes_server`模拟执行任务并提供进度反馈。通过运行这些节点，可以观察到动作的交互过程。

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1. 创建功能包：

在这里插入图片描述

2. 修改功能包说明文件package.xml：

<?xml version="1.0"?>
<package>
  <name>action_tutorials</name>
  <version>0.0.0</version>
  <description>The action_tutorials package</description>
  <maintainer email="hcx@todo.todo">hcx</maintainer>
  <license>TODO</license>
  <buildtool_depend>catkin</buildtool_depend>
  <build_depend>actionlib</build_depend>
  <build_depend>actionlib_msgs</build_depend>
  <build_depend>roscpp</build_depend>
  <run_depend>actionlib</run_depend>
  <run_depend>actionlib_msgs</run_depend>
  <run_depend>roscpp</run_depend>
  <export>  </export>
</package>

3. CMake编译配置文件CMakeLists.txt：

cmake_minimum_required(VERSION 2.8.3)
project(action_tutorials)


find_package(catkin REQUIRED COMPONENTS
  actionlib
  actionlib_msgs
  roscpp
)

find_package(catkin REQUIRED genmsg actionlib_msgs actionlib)

add_action_files(DIRECTORY action FILES DoDishes.action)

generate_messages(DEPENDENCIES actionlib_msgs)

include_directories(
  ${catkin_INCLUDE_DIRS}
)


add_executable(DoDishes_client src/DoDishes_client.cpp)
target_link_libraries( DoDishes_client ${catkin_LIBRARIES})
add_dependencies(DoDishes_client ${${PROJECT_NAME}_EXPORTED_TARGETS})

add_executable(DoDishes_server src/DoDishes_server.cpp)
target_link_libraries( DoDishes_server ${catkin_LIBRARIES})
add_dependencies(DoDishes_server ${${PROJECT_NAME}_EXPORTED_TARGETS})

4. 添加动作文件：

与CMakeLists.txt对应，add_action_files(DIRECTORY action FILES DoDishes.action)：
在这里插入图片描述
内容如下：—用于分割目标、结果、反馈，顺序不能打乱

# Define the goal
uint32 dishwasher_id  # Specify which dishwasher we want to use
---
# Define the result
uint32 total_dishes_cleaned
---
# Define a feedback message
float32 percent_complete

5. 创建动作客户端节点：

与CMakeLists.txt对应，add_executable(DoDishes_client src/DoDishes_client.cpp)：
在这里插入图片描述
内容如下：

#include <actionlib/client/simple_action_client.h>
#include "action_tutorials/DoDishesAction.h"

typedef actionlib::SimpleActionClient<action_tutorials::DoDishesAction> Client;

// 当action完成后会调用该回调函数一次
void doneCb(const actionlib::SimpleClientGoalState& state,
        const action_tutorials::DoDishesResultConstPtr& result)
{
    ROS_INFO("Yay! The dishes are now clean");
    ros::shutdown();
}

// 当action激活后会调用该回调函数一次
void activeCb()
{
    ROS_INFO("Goal just went active");
}

// 收到feedback后调用该回调函数
void feedbackCb(const action_tutorials::DoDishesFeedbackConstPtr& feedback)
{
    ROS_INFO(" percent_complete : %f ", feedback->percent_complete);
}

int main(int argc, char** argv)
{
    ros::init(argc, argv, "do_dishes_client");

    // 定义一个客户端
    Client client("do_dishes", true);

    // 等待服务器端
    ROS_INFO("Waiting for action server to start.");
    client.waitForServer();
    ROS_INFO("Action server started, sending goal.");

    // 创建一个action的goal
    action_tutorials::DoDishesGoal goal;
    goal.dishwasher_id = 1;

    // 发送action的goal给服务器端，并且设置回调函数
    client.sendGoal(goal,  &doneCb, &activeCb, &feedbackCb);

    ros::spin();

    return 0;
}

6. 创建动作服务器节点：

与CMakeLists.txt对应，add_executable(DoDishes_server src/DoDishes_server.cpp)：
在这里插入图片描述
内容如下：

#include <ros/ros.h>
#include <actionlib/server/simple_action_server.h>
#include "action_tutorials/DoDishesAction.h"

typedef actionlib::SimpleActionServer<action_tutorials::DoDishesAction> Server;

// 收到action的goal后调用该回调函数
void execute(const action_tutorials::DoDishesGoalConstPtr& goal, Server* as)
{
    ros::Rate r(1);
    action_tutorials::DoDishesFeedback feedback;

    ROS_INFO("Dishwasher %d is working.", goal->dishwasher_id);

    // 假设洗盘子的进度，并且按照1hz的频率发布进度feedback
    for(int i=1; i<=10; i++)
    {
        feedback.percent_complete = i * 10;
        as->publishFeedback(feedback);
        r.sleep();
    }

    // 当action完成后，向客户端返回结果
    ROS_INFO("Dishwasher %d finish working.", goal->dishwasher_id);
    as->setSucceeded();
}

int main(int argc, char** argv)
{
    ros::init(argc, argv, "do_dishes_server");
    ros::NodeHandle n;

    // 定义一个服务器
    Server server(n, "do_dishes", boost::bind(&execute, _1, &server), false);

    // 服务器开始运行
    server.start();

    ros::spin();

    return 0;
}