接上篇，继续学习ROS通信编程基础
一、话题编程
步骤：
- 创建发布者
- 初始化ROS节点
- 向ROS Master注册节点信息，包括发布的话题名和话题中的消息类型
- 按照一定频率循环发布消息
- 创建订阅者
- 初始化ROS节点
- 订阅需要的话题
- 循环等待话题消息，接受到消息后进行回调函数
- 回调函数中完成消息处理
- 添加编译选项
- 设置需要编译的代码和生成的可执行文件
- 设置链接库
- 设置依赖
- 运行可执行程序
talker.cpp
#include<sstream>
#include"ros/ros.h"
#include"std_msgs/String.h"
int main(int argc,char **argv)
{
//ROS节点初始化
ros::init(argc,argv,"talker");
//创建节点句柄
ros::NodeHandle n;
//创建一个Publisher，发布名为chatter的topic，消息类型为std_msgs::String
ros::Publisher chatter_pub=n.advertise<std_msgs::String>("chatter",1000);
//设置循环的频率
ros::Rate loop_rate(10);
int count=0;
while(ros::ok())
{
//初始化std_msgs::String类型的消息
std_msgs::String msg;
std::stringstream ss;
ss<<"hello world"<<count;
msg.data=ss.str();
//发布消息
ROS_INFO("%s",msg.data.c_str());
chatter_pub.publish(msg);
//循环等待回调函数
ros::spinOnce();
//接受循环频率延时
loop_rate.sleep();
++count;
}
return 0;
}
listener.cpp
#include"ros/ros.h"
#include"std_msgs/String.h"
//接收到订阅的消息，会进入消息的回调函数
void chatterCallback(const std_msgs::String::ConstPtr& msg)
{
//将接收到的消息打印处理
ROS_INFO("I heard:{%s}",msg->data.c_str());
}
int main(int argc,char **argv)
{
//初始化ROS节点
ros::init(argc,argv,"listener");
//创建节点句柄
ros::NodeHandle n;
//创建一个Subscriber，订阅名为chatter的topic，注册回调函数chatterCallback
ros::Subscriber sub=n.subscribe("chatter",1000,chatterCallback);
//循环等待回调函数
ros::spin();
return 0;
}
在CMakeLists.txt末尾添加编译选项
add_executable(talker src/talker.cpp)
target_link_libraries(talker ${catkin_LIBRARIES})
add_executable(listener src/listener.cpp)
target_link_libraries(listener ${catkin_LIBRARIES})
编译
cd catkin_ws
catkin_make
运行程序
# 以下是对于Ubantu 16.04的操作，其他版本的也许操作会简洁很多
roscore
#打开新终端
cd ~/catkin_ws
#下面这一步是为了保证rosrun命令能够找到相应的功能包，有可以省去这一步骤的方法，各位可以自行查找
source ~/catkin_ws/devel/setup.bash
rosrun learning_communication talker
#打开新终端
cd ~/catkin_ws
source ~/catkin_ws/devel/setup.bash
rosrun learning_communication listener
如图，发送了hello world的同时接收了hello world。
二、服务编程
定义服务请求与应答的方式
- 定义srv文件
mkdir ~/catkin_ws/src/learning_communication/srv sudo nano AddTwoInts.srv - AddTwoInts.srv
int64 a int64 b --- int64 sum - 用gedit打开package.xml，在里面添加功能包依赖
<build_depend>message_generation</build_depend> <exec_depend>message_runtime</exec_depend> - 在CMakeLists.txt添加编译选项
步骤：
- 创建服务器
- 初始化ROS节点
- 创建Serve实例
- 循环等待服务请求，进入回调函数
- 在回调函数中完成服务功能的处理，并反馈应答数据
- 创建客户端
- 初始化ROS节点
- 创建一个Client实例
- 发布服务请求数据
- 等待Serve处理之后的应答结果
- 添加编译选项
- 设置需要编译的代码和生成的可执行文件
- 设置链接库
- 设置依赖
- 运行可执行程序
server.cpp
#include<ros/ros.h>
#include"learning_communication/AddTwoInts.h"
//service回调函数，输入参数req，输出参数res
bool add(learning_communication::AddTwoInts::Request &req,learning_communication::AddTwoInts::Response &res)
{
//将输入的参数中的请求数据相加，结果放到应答变量中
res.sum=req.a+req.b;
ROS_INFO("request: x=%1d,y=%1d",(long int)req.a,(long int)req.b);
ROS_INFO("sending back response:[%1d]",(long int)res.sum);
return true;
}
int main(int argc,char **argv)
{
//ROS节点初始化
ros::init(argc,argv,"add_two_ints_server");
//创建节点句柄
ros::NodeHandle n;
//创建一个名为add_two_ints的server,注册回调函数add()
ros::ServiceServer service=n.advertiseService("add_two_ints",add);
//循环等待回调函数
ROS_INFO("Ready to add two ints.");
ros::spin();
return 0;
}
client.cpp
#include<cstdlib>
#include<ros/ros.h>
#include"learning_communication/AddTwoInts.h"
int main(int argc,char **argv)
{
//ROS节点初始化
ros::init(argc,argv,"add_two_ints_client");
//从终端命令行获取两个加数
if(argc!=3)
{
ROS_INFO("usage:add_two_ints_client X Y");
return 1;
}
//创建节点句柄
ros::NodeHandle n;
//创建一个client，请求add_two_ints_service
//service消息类型是learning_communication::AddTwoInts
ros::ServiceClient client=n.serviceClient<learning_communication::AddTwoInts>("add_two_ints");
//创建learning_communication::AddTwoInts类型的service消息
learning_communication::AddTwoInts srv;
srv.request.a=atoll(argv[1]);
srv.request.b=atoll(argv[2]);
//发布service请求，等待加法运算的应答请求
if(client.call(srv))
{
ROS_INFO("sum: %1d",(long int)srv.response.sum);
}
else
{
ROS_INFO("Failed to call service add_two_ints");
return 1;
}
return 0;
}
关于编译时一直出现这样的报错，注意看是不是有些比如这个符号“_”没打。
添加编译设置
编译通过
输入指令
roscore
#打开新终端
source ~/catkin_ws/devel/setup.bash
rosrun learning_communication server
#打开新终端
source ~/catkin_ws/devel/setup.bash
rosrun learning_communication client 11 12
三、动作编程
动作是一种基于ROS消息实现的问答通信机制，它包含连续反馈，可以在任务过程中止运行。
动作（Action）的接口
练习ROS动作编程： 客户端发送一个运动坐标，模拟机器人运动到目标位置的过程。包括服务端和客户端的代码实现，要求带有实时位置反馈。
创建工作区间
#创建功能包
cd catkin_ws/src/
catkin_create_pkg learn_action std_msgs rospy roscpp
#编译功能包
cd ~/catkin_ws
catkin_make
source ~/catkin_ws/devel/setup.bash
创建action文件夹，并在里面创建TurtleMove.action文件
# Define the goal
float64 turtle_target_x
# Specify Turtle's target position
float64 turtle_target_y
float64 turtle_target_theta
---
# Define the result
float64 turtle_final_x
float64 turtle_final_y
float64 turtle_final_theta
---
# Define a feedback message
float64 present_turtle_x
float64 present_turtle_y
float64 present_turtle_theta
在learn_action的src文件夹下，创建TurtleMove_server.cpp文件和TurtleMove_client.cpp文件
TurtleMove_server.cpp
/* 此程序通过通过动作编程实现由client发布一个目标位置 然后控制Turtle运动到目标位置的过程 */
#include <ros/ros.h>
#include <actionlib/server/simple_action_server.h>
#include "learn_action/TurtleMoveAction.h"
#include <turtlesim/Pose.h>
#include <turtlesim/Spawn.h>
#include <geometry_msgs/Twist.h>
typedef actionlib::SimpleActionServer<learn_action::TurtleMoveAction> Server;
struct Myturtle
{
float x;
float y;
float theta;
}turtle_original_pose,turtle_target_pose;
ros::Publisher turtle_vel;
void posecallback(const turtlesim::PoseConstPtr& msg)
{
ROS_INFO("Turtle1_position:(%f,%f,%f)",msg->x,msg->y,msg->theta);
turtle_original_pose.x=msg->x;
turtle_original_pose.y=msg->y;
turtle_original_pose.theta=msg->theta;
}
// 收到action的goal后调用该回调函数
void execute(const learn_action::TurtleMoveGoalConstPtr& goal, Server* as)
{
learn_action::TurtleMoveFeedback feedback;
ROS_INFO("TurtleMove is working.");
turtle_target_pose.x=goal->turtle_target_x;
turtle_target_pose.y=goal->turtle_target_y;
turtle_target_pose.theta=goal->turtle_target_theta;
geometry_msgs::Twist vel_msgs;
float break_flag;
while(1)
{
ros::Rate r(10);
vel_msgs.angular.z = 4.0 * (atan2(turtle_target_pose.y-turtle_original_pose.y, turtle_target_pose.x-turtle_original_pose.x)-turtle_original_pose.theta);
vel_msgs.linear.x = 0.5 * sqrt(pow(turtle_target_pose.x-turtle_original_pose.x, 2) + pow(turtle_target_pose.y-turtle_original_pose.y, 2));
break_flag=sqrt(pow(turtle_target_pose.x-turtle_original_pose.x, 2) + pow(turtle_target_pose.y-turtle_original_pose.y, 2));
turtle_vel.publish(vel_msgs);
feedback.present_turtle_x=turtle_original_pose.x;
feedback.present_turtle_y=turtle_original_pose.y;
feedback.present_turtle_theta=turtle_original_pose.theta;
as->publishFeedback(feedback);
ROS_INFO("break_flag=%f",break_flag); if(break_flag<0.1) break; r.sleep(); } // 当action完成后，向客户端返回结果 ROS_INFO("TurtleMove is finished.");
as->setSucceeded();
}
int main(int argc, char** argv)
{
ros::init(argc, argv, "TurtleMove_server");
ros::NodeHandle n,turtle_node;
ros::Subscriber sub =turtle_node.subscribe("turtle1/pose",10,&posecallback);//订阅小乌龟的位置信息
turtle_vel = turtle_node.advertise<geometry_msgs::Twist>("turtle1/cmd_vel",10);//发布控制小乌龟运动的速度
// 定义一个服务器
Server server(n, "TurtleMove", boost::bind(&execute, _1, &server), false);
// 服务器开始运行
server.start();
ROS_INFO("server has started.");
ros::spin();
return 0;
}
TurtleMove_client.cpp
#include <actionlib/client/simple_action_client.h>
#include "learn_action/TurtleMoveAction.h"
#include <turtlesim/Pose.h>
#include <turtlesim/Spawn.h>
#include <geometry_msgs/Twist.h>
typedef actionlib::SimpleActionClient<learn_action::TurtleMoveAction> Client;
struct Myturtle
{
float x;
float y;
float theta;
}turtle_present_pose;
// 当action完成后会调用该回调函数一次
void doneCb(const actionlib::SimpleClientGoalState& state, const learn_action::TurtleMoveResultConstPtr& result)
{
ROS_INFO("Yay! The TurtleMove is finished!");
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 learn_action::TurtleMoveFeedbackConstPtr& feedback)
{
ROS_INFO(" present_pose : %f %f %f", feedback->present_turtle_x, feedback->present_turtle_y,feedback->present_turtle_theta);
}
int main(int argc, char** argv)
{
ros::init(argc, argv, "TurtleMove_client");
// 定义一个客户端
Client client("TurtleMove", 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
learn_action::TurtleMoveGoal goal;
goal.turtle_target_x = 1;
goal.turtle_target_y = 1;
goal.turtle_target_theta = 0;
// 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;
}
在package.xml里面添加依赖
<build_depend>message_generation</build_depend>
<build_depend>actionlib</build_depend>
<build_depend>actionlib_msgs</build_depend>
<exec_depend>message_runtime</exec_depend>
<exec_depend>actionlib</exec_depend>
<exec_depend>actionlib_msgs</exec_depend>
添加完就是这样
修改learn_action里面的CMakeLists.txt，添加代码
添加编译选项
add_executable(TurtleMove_client src/TurtleMove_client.cpp)
target_link_libraries(TurtleMove_client ${catkin_LIBRARIES})
add_dependencies(TurtleMove_client ${PROJECT_NAME}_gencpp)
add_executable(TurtleMove_server src/TurtleMove_server.cpp)
target_link_libraries(TurtleMove_server ${catkin_LIBRARIES})
add_dependencies(TurtleMove_server ${PROJECT_NAME}_gencpp)
编译
roscore
＃开一个新终端窗口
source ./devel/setup.bash
rosrun turtlesim turtlesim.node
＃新终端
source ./devel/setup.bash
rosrun learn_action TurtleMove_server
＃新终端
source ./devel/setup.bash
rosrun learn_action TurtleMove_client
运行结果如下
