ROS基础——话题、服务、动作编程
ROS基础——话题、服务、动作编程
--工作空间--
| 文件夹名称 | 用途 |
|---|---|
| src | 代码空间（Source Space ） |
| build | 编译空间（Build Space） |
| devel | 开发空间（Development Space） |
| install | 安装空间（Install Space） |
1.环境变量配置
source /home/lyy/catkin_ws/devel/setup.bash#该环境变量设置只对当前终端有效，lyy是用户名
将上面命令放置到~/.bashrc文件中，让其对所有终端都有效
sudo nano ~/.bashrc
检查环境变量：echo $ROS_PACKAGE_PATH
2.功能包
1.创建功能包
cd ~/catkin_ws/src
catkin_create_pkg learning_communication std_msgs rospy roscpp
catkin_create_pkg 功能包名字 依赖
std_msgs：定义的标准的数据结构
rospy：提供python编程接口
roscpp：提供c++编程接口
2.编译功能包
cd ~/catkin_ws
catkin_make
3.ROS通信编程
1.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
在src目录下创建talker.cpp，代码如下：
include
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;
}
和listener.cpp，代码如下：
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;
}
2.添加编译选项
打开Cmakelist.txt文件在末尾加上：
add_executable(talker src/talker.cpp)
target_link_libraries(talker ${catkin_LIBRARIES})
add_executable(listener src/listener.cpp)
target_link_libraries(listener ${catkin_LIBRARIES})
再把路径换到catkin_ws，执行编译命令
catkin_make
运行一次：
roscore
rosrun learning_communication talker
rosrun learning_communication listener
3.自定义话题消息
先在learning_communication下创建msg文件夹定义，创建Person.msg文件，并添加如下内容：
string name
uint8 sex
uint8 age
uint8 unknown=0
uint8 male=1
uint8 female=2
在package.xml中添加功能包依赖
<build_depend>message_generation</build_depend>
<exec_depend>message_runtime</exec_depend>
在CMakeLists.txt中添加编译选项
4.服务编程
先创建srv文件夹，并创建srv文件
mkdir ~/catkin_ws/src/learning_communication/srv
cd ~/catkin_ws/src/learning_communication/srv
gedit AddTwoInts.srv
在srv文件里添加以下内容：
int64 a
int64 b
int64 sum
在package.xml中添加功能包依赖
<build_depend>message_generation</build_depend>
<exec_depend>message_runtime</exec_depend>
在CMakeList.txt中添加编译选项
（1）创建服务器
返回到src目录创建server.cpp，代码如下：
include<ros/ros.h>
include"learning_communication/AddTwoInts.h"
//service回调函数，输入参数req，输出参数res，该函数提供两个int值求和的服务，int值从req里获取，返回数据装入res内，这些数据类型都定义在srv文件内部，函数返回一个boolean值
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;
}
（2）创建客户端
在相同路径下创建client.cpp，代码如下：
include
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，为add_two_ints service创建一个client，之后会调用
ros::ServiceClient client=n.serviceClient<learning_communication::AddTwoInts>("add_two_ints");
//创建learning_communication::AddTwoInts类型的service消息，此处给request成员赋值
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，此处就是在调用service，如果成功call()会返回true，srv.response将是合法值
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;
}
（3）添加编译选项
设置CMakeLists.txt文件
add_executable(server src/server.cpp)
target_link_libraries(server ${catkin_LIBRARIES})
add_dependencies(server ${PROJECT_NAME}_gencpp)
add_executable(client src/client.cpp)
target_link_libraries(client ${catkin_LIBRARIES})
add_dependencies(client ${PROJECT_NAME}_gencpp)
编译。
roscore
rosrun learning_communication server
rosrun learning_communication client 1 2
此处的1 2为两个任意整数
4.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。
动作是一种基于ROS消息实现的问答通信机制，包含连续反馈，可以在任务过程里中止运行。
1.创建小海龟移动的文件
创建turtleMoveAction.cpp文件，代码：
/*
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 "learning_communication/TurtleMoveAction.h"
include <turtlesim/Pose.h>
include <turtlesim/Spawn.h>
include <geometry_msgs/Twist.h>
typedef actionlib::SimpleActionServer<learning_communication::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 learning_communication::TurtleMoveGoalConstPtr& goal, Server* as)
{
learning_communication::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");
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;
}
2.创建客户端文件
创建turtleMoveClient.cpp文件，代码如下：
include <actionlib/client/simple_action_client.h>
include "learning_communication/TurtleMoveAction.h"
include <turtlesim/Pose.h>
include <turtlesim/Spawn.h>
include <geometry_msgs/Twist.h>
typedef actionlib::SimpleActionClient<learning_communication::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 learning_communication::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 learning_communication::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
learning_communication::TurtleMoveGoal goal;
goal.turtle_target_x = 8;
goal.turtle_target_y = 8;
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;
}
3.创建action文件
先创建文件夹action，再在里面创建TurtleMove.action文件，代码：
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
4.添加编译选项
CMakeLists文件添加：
add_executable(turtleMoveClient src/turtleMoveClient.cpp)
target_link_libraries(turtleMoveClient ${catkin_LIBRARIES})
add_dependencies(turtleMoveClient ${PROJECT_NAME}_gencpp)
add_executable(turtleMove src/turtleMoveAction.cpp)
target_link_libraries(turtleMove ${catkin_LIBRARIES})
add_dependencies(turtleMove ${PROJECT_NAME}_gencpp)
package.xml文件里添加：
<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>
5.运行可执行程序
roscore
rosrun turtlesim turtlesim_node
rosrun learning_communication turtleMove
rosrun learning_communication turtleMoveClient
需要在四个终端按顺序运行
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