文章目录
实验环境
ubuntu18.04
ROS Melodic Morenia
一、话题、服务模式编程
1.1创建工作空间
mkdir -p ~/comm_ws/src
cd ~/comm_ws/src
catkin_init_workspace
编译工作空间
cd ..
catkin_make
设置环境变量
source devel/setup.bash
echo $ROS_PACKAGE_PATH
创建功能包
cd ~/comm_ws/src
catkin_create_pkg learning_communication std_msgs rospy roscpp
编译功能包
catkin_make
source ~/comm_ws/devel/setup.bash
1.2 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
1.2.1 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;
}
1.2.2 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;
}
设置CMakeLists.txt文件
add_executable(talker src/talker.cpp)
target_link_libraries(talker ${catkin_LIBRARIES})
add_executable(listener src/listener.cpp)
target_link_libraries(listener ${catkin_LIBRARIES})
1.2.3 编译
cd ~/comm_ws/
catkin_make
1.2.4 运行可执行文件
新开的终端需要配置:source devel/setup.bash
1.2.5 自定义话题消息
定义msg文件
mkdir ~/comm_ws/src/learning_communication/msg
cd ~/comm_ws/src/learning_communication/msg
vim Person.msg
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>
修改CMakeLists.txt
编译
查看自定义消息
source devel/setup.sh
rosmsg show Person
1.3 服务编程
1.3.1 定义服务请求与应答的方式
定义srv文件
mkdir ~/comm_ws/src/learning_communication/srv
cd ~/comm_ws/src/learning_communication/srv
vim AddTwoInts.srv
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>
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
1.3.2 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;
}
1.3.3 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;
}
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)
1.3.4 编译
1.3.5 运行可执行文件
要先运行server,再运行client
roscore
rosrun learning_communication server
rosrun learning_communication client
二. ROS动作编程
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。
2.1 turtleMove.cpp
创建小乌龟移动的“服务文件”turtleMove.cpp
2.2 turtleMoveClient.cpp
#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 = 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;
}
2.3 创建action文件夹
在功能包目录下创建action文件夹,并在此文件夹下创建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
2.4 修改文件
修改CMakeList.txt文件
add_executable(turtleMoveClient src/turtleMoveClient.cpp)
target_link_libraries(turtleMoveClient ${catkin_LIBRARIES})
add_dependencies(turtleMoveClient ${PROJECT_NAME}_gencpp)
add_executable(turtleMove src/turtleMove.cpp)
target_link_libraries(turtleMove ${catkin_LIBRARIES})
add_dependencies(turtleMove ${PROJECT_NAME}_gencpp)
修改package.xml文件
<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>
2.5 编译
2.6 运行
在四个终端按顺序分别运行下面命令
roscore
rosrun turtlesim turtlesim_node
rosrun learning_communication turtleMove
rosrun learning_communication turtleMoveClient
三、分布式通信
在两台电脑上演示ROS的分布式通信
3.1 主机
两台电脑保证在一个局域网内,输入命令查看主机ip
ifconfig
开启ros
roscore
新建一个终端,输入
export ROS_IP=xxx.xxx.xxx #本机IP
export ROS_MASTER_URI=http://xxx.xxx.xxx:11311/ #主机IP
rosrun turtlesim turtlesim_node
source ~/.bashrc
3.2 从机
开启一个终端,输入
export ROS_IP=X.X.X.X #本机ip
export ROS_MASTER_URI=http://x.x.x.x:11311 #主机IP
source ~/.bashrc
rosrun turtlesim turtle_teleop_key
3.3 运行结果
四、总结
ros 进行动作编程是进行嵌入式开发的一个核心步骤,也是帮助我们更好的了解机器学习的一项重要基础,通过动作编程,我们可以了解到机器人是如何进行我们人类行为得规划的,这也为我们未来进入人工智能打下一个良好的开端。