ros的actionlib

ROS中常用的通讯机制是topic和service,但是很多场景下.这两种通讯机制不能满足要求,如果获取运动过程的状态,service1来发布运动目标.虽然可以获得反馈,但是反馈
只有一次,对于运动控制的数据太少了,而且如果反馈没有收到,也只能傻傻等待,其他事也做不了,actionlib就是这样一个解决多个反馈数据的通讯机制.

使用action来发送一个机器人的运动目标,机器人接收到这个action后,就可以开始运动,在运动完成中不断反馈当前的运动状态,在运动过程中我们可以取消运动,让机器人停止,
如果机器人完成了运动目标,那么action会返回任务完成的标志.

ros中的message是通过.msg文件来定义的,service是通过.srv定义的,action是通过.action文件定义的.
.action文件:
#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
编译后会生成一系列的.msg文件

客户端:
#include<actionlib/client/simple_action_client.h>
#inlcude "action_tutorials/DoDishesAction.h"

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

//当action完成后会回调用一次
viod doneCb(const actionlib::SimpleClientGoalState& state,
          const action_tutorials::DoDishesResultConstPtr& result)
{
    ROS_INFO("Yes! The dishes are now clean");
    ros::shutdown();
}

//当action激活后会调用回调函数一次
void actionCb()
{
  ROS_INFO("Coal just went active");
  
}
//收到feedback后调用的回到函数
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);
  
  //等待一个服务器端
  
  ROS_INFO("Waitong for action server to start.");
  client.waitForServer();
  ROS_INFO("Action server started, sending gaol.");
  
  //创建一个action的gaol
  action_tutorials::DoDishesGoal goal;
  goal.dishwasher_id = 1;
  
  //发送action的gaol给服务器端,并且设置回调函数
  client.sendGoal(goal, &doneCb, &activeCb, &feedbackCb);
  
  ros::spin();
  
  return 0;
  
  }

服务端:
#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->disheswasher_id);
    
    //假设洗盘子的进度,并且按照1HZ的频率发布进度的feedback
    for(int i=1;i<=10;i++)
    {
    feedback.pencent_complete = i*10;
    
    as->publishFeedback(feedback);
    r.sleep();
    }
    
    //当action完成后,向客户端反馈结果
    ROS_INFO("Dishwasher %d fish working.",goal->dishwasher_id);
    as->setSucceeded();
        
}

int main(int argc,char ** argv)
{
  ros::init(argc,argv,"do_disges_server");
  ros::NodeHandle n;
  
  //定义一个服务器
  Server server(n, "do_dishes",boost::bind(&execute,_1 , &server),false);
  
  //服务器开启运行
  server.start();
  
  ros::spin();
  return 0;
}