第八弹 ROS发布者Publisher的编程实现

2023-05-16

1. 话题模型（发布与订阅）

2. 创建功能包

catkin_create_pkg learning_topic roscpp rospy std_msgs geometry_msgs turtlesim
建立一个名为learning_topic的功能包，依赖于roscpp，std_msgs等库。

3. Ubuntu下创建ROS功能包程序

在基础命令中，我们学习了一些命令。忘掉的小伙伴可以再去复习一下，传送门：https://blog.csdn.net/txr152111/article/details/119052597

touch就是用来创建文件的。在src目录下打开终端，或者cd到这个地址。

touch velocity_publisher.cpp

实现一个发布者的基本步骤：

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
创建消息数据
按照一定的频率循环发布消息

velocity_publisher.cpp里的代码（已修改无误）：

建议亲自动手敲一波：

/*
*该例程将用于发布turtle/cmd_vel话题，消息类型geometry_msgs：：Twist
*/
#include<ros/ros.h>      //很多ROS里的API和函数从里面调用
#include<geometry_msgs/Twist.h>   //twist：转动，扭动。Twist.h线速度、角速度等消息订阅的头文件

int main(int argc,char **argv)
{
	//ROS节点初始化
	ros::init(argc,argv,"velocity_publisher");
	
	//创建节点句柄
	ros::NodeHandle n;

	//创建一个Publisher，发布名为/turtle/cmd_vel的topic，消息类型为geometry_msgs：：Twist，队列长度10
	ros::Publisher turtle_vel_pub  = n.advertise<geometry_msgs::Twist>("/turtle1/cmd_vel",10);

	//设置循环的频率
	ros::Rate loop_rate(10);

	int count = 0;
	while(ros::ok())
	{
		//初始化geometyr_msgs::Twist类型的消息
		geometry_msgs::Twist       vel_msg;
		vel_msg.linear.x = 0.2;
		vel_msg.angular.z = 0.2;

		//发布消息
		turtle_vel_pub.publish(vel_msg);
		ROS_INFO("Publish turtle velocity command[%0.2f m/s ， %0.2f rad/s]",vel_msg.linear.x,vel_msg.angular.z);
	
		//按照循环频率延时
		loop_rate.sleep();
	}
	return 0;

}

4. 配置发布者代码编译规则

如何配置CMakeLists.txt中的编译规则？

设置需要编译的代码和生成的可执行代码（C++）

add_executable(velocity_publisher src/velocity_publisher.cpp)

（这句话的目的是把src/velocity_publisher.cpp文件编译成velocity_publisher可执行文件）

设置链接库

target_link_libraries(velocity_publisher ${catkin_LIBRARIES})

（把可执行文件与ROS相关的库做一些链接）

把这两句话复制到：

5 编译并运行发布者

要回到功能包的根目录catkin_ws进行编译。

catkin_make

成功编译时这样的：

没成功的时候是这样的：（节选）

learning_topic/CMakeFiles/velocity_publisher.dir/build.make:62: recipe for target 'learning_topic/CMakeFiles/velocity_publisher.dir/src/velocity_publisher.cpp.o' failed
make[2]: *** [learning_topic/CMakeFiles/velocity_publisher.dir/src/velocity_publisher.cpp.o] Error 1
CMakeFiles/Makefile2:1420: recipe for target 'learning_topic/CMakeFiles/velocity_publisher.dir/all' failed
make[1]: *** [learning_topic/CMakeFiles/velocity_publisher.dir/all] Error 2
Makefile:140: recipe for target 'all' failed
make: *** [all] Error 2
Invoking "make -j2 -l2" failed

这就需要我们去找错，这和我们用编译器不太一样：

要去找红的error：比如上边的代码中出现了两类错误，一是只用了中文逗号，而是打错了单词，都给你指出来了，修改后即可成功编译。

编译成功后，设置环境变量：

source devel/setup.bash

为了避免每次都要运行这句话，在主文件夹下摁住“Ctrl+H”显示隐藏文件：

添加完后保存退出。（在安装ROS的时候应该已经设置过了）

添加环境变量后，重启终端，并且可以再任意位置输入命令：

一个终端输一个，使用三个终端：

roscore                           #ros环境

rosrun turtlesim turtlesim_node   #调出小海龟

rosrun learning_topic velocity_publisher  #运行刚刚写的程序的编译文件

5. CMakeLists.txt文件解读（主要机翻，仅供参考）

提供版本（VERSION）信息和工程的名字（本次是“learning_topic”）

cmake_minimum_required(VERSION 3.0.2)   
project(learning_topic)

## 编译为 C++11，支持 ROS Kinetic 及更新版本
# add_compile_options(-std=c++11)

            
## Compile as C++11, supported in ROS Kinetic and newer
# add_compile_options(-std=c++11)

## 查找 catkin 宏和库
## if COMPONENTS list like find_package(catkin REQUIRED COMPONENTS xyz)
##是用的，还找其他的catkin包
下面是所需要的依赖包，如roscpp、rospy、std_msgs等。

## Find catkin macros and libraries
## if COMPONENTS list like find_package(catkin REQUIRED COMPONENTS xyz)
## is used, also find other catkin packages
find_package(catkin REQUIRED COMPONENTS
  geometry_msgs
  roscpp
  rospy
  std_msgs
  turtlesim
)

## 系统依赖是通过 CMake 的约定找到的
# find_package(Boost REQUIRED COMPONENTS system)

## System dependencies are found with CMake's conventions
# find_package(Boost REQUIRED COMPONENTS system)

## 如果包有 setup.py，则取消注释。此宏确保安装其中声明的模块和全局脚本
＃＃看
http://ros.org/doc/api/catkin/html/user_guide/setup_dot_py.html
# catkin_python_setup()

## Uncomment this if the package has a setup.py. This macro ensures
## modules and global scripts declared therein get installed
## See http://ros.org/doc/api/catkin/html/user_guide/setup_dot_py.html
# catkin_python_setup()

########声明 ROS 消息、服务和操作###########

## 要从此包中声明和构建消息、服务或操作，请执行以下步骤：
## * 让 MSG_DEP_SET 成为您在消息/服务/操作中使用的消息类型的包的集合（例如 std_msgs、actionlib_msgs、...）。
## * 在 package.xml 文件中：
## * 为“message_generation”添加一个 build_depend 标签
## * 为 MSG_DEP_SET 中的每个包添加 build_depend 和 exec_depend 标签
## * 如果 MSG_DEP_SET 不为空，则已拉入以下依赖项
## 但可以肯定地声明：
## * 为“message_runtime”添加一个 exec_depend 标签
## * 在这个文件（CMakeLists.txt）中：
## * 将“message_generation”和MSG_DEP_SET中的每个包添加到
## find_package(catkin REQUIRED COMPONENTS ...)
## * 将“message_runtime”和MSG_DEP_SET中的每个包添加到
## catkin_package(CATKIN_DEPENDS ...)
## * 根据需要取消注释下面的 add_*_files 部分
## 并列出每个要处理的 .msg/.srv/.action 文件
## * 取消注释下面的 generate_messages 条目
## * 将 MSG_DEP_SET 中的每个包添加到 generate_messages(DEPENDENCIES ...)

## To declare and build messages, services or actions from within this
## package, follow these steps:
## * Let MSG_DEP_SET be the set of packages whose message types you use in
##   your messages/services/actions (e.g. std_msgs, actionlib_msgs, ...).
## * In the file package.xml:
##   * add a build_depend tag for "message_generation"
##   * add a build_depend and a exec_depend tag for each package in MSG_DEP_SET
##   * If MSG_DEP_SET isn't empty the following dependency has been pulled in
##     but can be declared for certainty nonetheless:
##     * add a exec_depend tag for "message_runtime"
## * In this file (CMakeLists.txt):
##   * add "message_generation" and every package in MSG_DEP_SET to
##     find_package(catkin REQUIRED COMPONENTS ...)
##   * add "message_runtime" and every package in MSG_DEP_SET to
##     catkin_package(CATKIN_DEPENDS ...)
##   * uncomment the add_*_files sections below as needed
##     and list every .msg/.srv/.action file to be processed
##   * uncomment the generate_messages entry below
##   * add every package in MSG_DEP_SET to generate_messages(DEPENDENCIES ...)

##在'msg'文件夹中生成消息

## Generate messages in the 'msg' folder
# add_message_files(
#   FILES
#   Message1.msg
#   Message2.msg
# )

##在'srv'文件夹中生成服务

## Generate services in the 'srv' folder
# add_service_files(
#   FILES
#   Service1.srv
#   Service2.srv
# )

##在'action'文件夹中生成动作

## Generate actions in the 'action' folder
# add_action_files(
#   FILES
#   Action1.action
#   Action2.action
# )

##使用此处列出的任何依赖项生成添加的消息和服务

## Generate added messages and services with any dependencies listed here
# generate_messages(
#   DEPENDENCIES
#   geometry_msgs#   std_msgs
# )

###################声明ROS动态重配置参数######################

##在此声明和构建动态重新配置参数
## 打包，请按照以下步骤操作：
## * 在 package.xml 文件中：
## * 为“dynamic_reconfigure”添加 build_depend 和 exec_depend 标签
## * 在这个文件（CMakeLists.txt）中：
## * 添加“dynamic_reconfigure”到
## find_package(catkin REQUIRED COMPONENTS ...)
## * 取消注释下面的“generate_dynamic_reconfigure_options”部分
## 并列出每个要处理的 .cfg 文件

## To declare and build dynamic reconfigure parameters within this
## package, follow these steps:
## * In the file package.xml:
##   * add a build_depend and a exec_depend tag for "dynamic_reconfigure"
## * In this file (CMakeLists.txt):
##   * add "dynamic_reconfigure" to
##     find_package(catkin REQUIRED COMPONENTS ...)
##   * uncomment the "generate_dynamic_reconfigure_options" section below
##     and list every .cfg file to be processed

##在'cfg'文件夹中生成动态重配置参数

## Generate dynamic reconfigure parameters in the 'cfg' folder
# generate_dynamic_reconfigure_options(
#   cfg/DynReconf1.cfg
#   cfg/DynReconf2.cfg
# )

##############catkin具体配置#####################

## catkin_package 宏为你的包生成 cmake 配置文件
## 声明要传递给依赖项目的东西
## INCLUDE_DIRS：如果您的包包含头文件，则取消注释
## LIBRARIES：你在这个项目中创建的依赖项目也需要的库
## CATKIN_DEPENDS：catkin_packages 依赖的项目也需要
## DEPENDS：这个项目的系统依赖，依赖项目也需要catkin_package(
# INCLUDE_DIRS include
# LIBRARIES learning_topic
# CATKIN_DEPENDS geometry_msgs roscpp rospy std_msgs turtlesim
# DEPENDS system_lib
)

## The catkin_package macro generates cmake config files for your package
## Declare things to be passed to dependent projects
## INCLUDE_DIRS: uncomment this if your package contains header files
## LIBRARIES: libraries you create in this project that dependent projects also need
## CATKIN_DEPENDS: catkin_packages dependent projects also need
## DEPENDS: system dependencies of this project that dependent projects also need
catkin_package(
#  INCLUDE_DIRS include
#  LIBRARIES learning_topic
#  CATKIN_DEPENDS geometry_msgs roscpp rospy std_msgs turtlesim
#  DEPENDS system_lib
)

##############################编译############################

## 声明一个 C++ 库
# add_library(${PROJECT_NAME}
# src/${PROJECT_NAME}/learning_topic.cpp
# )

##添加库的cmake目标依赖
##作为例子，可能需要在库之前生成代码
##来自消息生成或动态重新配置
# add_dependencies(${PROJECT_NAME} ${${PROJECT_NAME}_EXPORTED_TARGETS} ${catkin_EXPORTED_TARGETS})

## 声明一个 C++ 可执行文件
## 使用 catkin_make，所有包都在单个 CMake 上下文中构建
## 推荐的前缀确保跨包的目标名称不会冲突
# add_executable(${PROJECT_NAME}_node src/learning_topic_node.cpp)

## 重命名不带前缀的 C++ 可执行文件
## 上面推荐的前缀导致目标名称过长，下面重命名
## 目标回到较短的版本以方便用户使用
## 例如“rosrun someones_pkg node”而不是“rosrun someones_pkg someones_pkg_node”
# set_target_properties(${PROJECT_NAME}_node PROPERTIES OUTPUT_NAME node PREFIX "")

##添加可执行文件的cmake目标依赖项
## 与上面的库相同
# add_dependencies(${PROJECT_NAME}_node ${${PROJECT_NAME}_EXPORTED_TARGETS} ${catkin_EXPORTED_TARGETS})

## 指定库以链接库或可执行目标
# target_link_libraries(${PROJECT_NAME}_node
# ${catkin_LIBRARIES}
# )

## Declare a C++ library
# add_library(${PROJECT_NAME}
#   src/${PROJECT_NAME}/learning_topic.cpp
# )

## Add cmake target dependencies of the library
## as an example, code may need to be generated before libraries
## either from message generation or dynamic reconfigure
# add_dependencies(${PROJECT_NAME} ${${PROJECT_NAME}_EXPORTED_TARGETS} ${catkin_EXPORTED_TARGETS})

## Declare a C++ executable
## With catkin_make all packages are built within a single CMake context
## The recommended prefix ensures that target names across packages don't collide
# add_executable(${PROJECT_NAME}_node src/learning_topic_node.cpp)

## Rename C++ executable without prefix
## The above recommended prefix causes long target names, the following renames the
## target back to the shorter version for ease of user use
## e.g. "rosrun someones_pkg node" instead of "rosrun someones_pkg someones_pkg_node"
# set_target_properties(${PROJECT_NAME}_node PROPERTIES OUTPUT_NAME node PREFIX "")

## Add cmake target dependencies of the executable
## same as for the library above
# add_dependencies(${PROJECT_NAME}_node ${${PROJECT_NAME}_EXPORTED_TARGETS} ${catkin_EXPORTED_TARGETS})

## Specify libraries to link a library or executable target against
# target_link_libraries(${PROJECT_NAME}_node
#   ${catkin_LIBRARIES}
# )

################安装##################

# 所有安装目标都应该使用 catkin DESTINATION 变量
# 见 http://ros.org/doc/api/catkin/html/adv_user_guide/variables.html

## 标记可执行脚本（Python 等）以供安装
##相对于setup.py，可以选择目的地
#catkin_install_python（程序
# 脚本/my_python_script
# 目的地 ${CATKIN_PACKAGE_BIN_DESTINATION}
# )

## 标记要安装的可执行文件
## 见 http://docs.ros.org/melodic/api/catkin/html/howto/format1/building_executables.html
# 安装（目标 ${PROJECT_NAME}_node
# 运行时目的地 ${CATKIN_PACKAGE_BIN_DESTINATION}
# )

## 标记要安装的库
## 见 http://docs.ros.org/melodic/api/catkin/html/howto/format1/building_libraries.html
# 安装（目标 ${PROJECT_NAME}
# 存档目的地 ${CATKIN_PACKAGE_LIB_DESTINATION}
# 图书馆目的地 ${CATKIN_PACKAGE_LIB_DESTINATION}
# 运行时目的地 ${CATKIN_GLOBAL_BIN_DESTINATION}
# )

## 标记cpp头文件以供安装
# 安装（目录包含/${PROJECT_NAME}/
# 目的地 ${CATKIN_PACKAGE_INCLUDE_DESTINATION}
# FILES_MATCHING 模式 "*.h"
# 模式“.svn”排除
# )

## 标记其他安装文件（例如启动和包文件等）
#安装（文件
##我的文件1
##我的文件2
# 目的地 ${CATKIN_PACKAGE_SHARE_DESTINATION}
# )

# all install targets should use catkin DESTINATION variables
# See http://ros.org/doc/api/catkin/html/adv_user_guide/variables.html

## Mark executable scripts (Python etc.) for installation
## in contrast to setup.py, you can choose the destination
# catkin_install_python(PROGRAMS
#   scripts/my_python_script
#   DESTINATION ${CATKIN_PACKAGE_BIN_DESTINATION}
# )

## Mark executables for installation
## See http://docs.ros.org/melodic/api/catkin/html/howto/format1/building_executables.html
# install(TARGETS ${PROJECT_NAME}_node
#   RUNTIME DESTINATION ${CATKIN_PACKAGE_BIN_DESTINATION}
# )

## Mark libraries for installation
## See http://docs.ros.org/melodic/api/catkin/html/howto/format1/building_libraries.html
# install(TARGETS ${PROJECT_NAME}
#   ARCHIVE DESTINATION ${CATKIN_PACKAGE_LIB_DESTINATION}
#   LIBRARY DESTINATION ${CATKIN_PACKAGE_LIB_DESTINATION}
#   RUNTIME DESTINATION ${CATKIN_GLOBAL_BIN_DESTINATION}
# )

## Mark cpp header files for installation
# install(DIRECTORY include/${PROJECT_NAME}/
#   DESTINATION ${CATKIN_PACKAGE_INCLUDE_DESTINATION}
#   FILES_MATCHING PATTERN "*.h"
#   PATTERN ".svn" EXCLUDE
# )

## Mark other files for installation (e.g. launch and bag files, etc.)
# install(FILES
#   # myfile1
#   # myfile2
#   DESTINATION ${CATKIN_PACKAGE_SHARE_DESTINATION}
# )

#######################测试#########################

## 添加基于 gtest 的 cpp 测试目标和链接库
# catkin_add_gtest(${PROJECT_NAME}-test test/test_learning_topic.cpp)
# if(TARGET ${PROJECT_NAME}-test)
# target_link_libraries(${PROJECT_NAME}-test ${PROJECT_NAME})
＃endif（）

## 添加要由 python 鼻子测试运行的文件夹
#catkin_add_nosetests（测试）

## Add gtest based cpp test target and link libraries
# catkin_add_gtest(${PROJECT_NAME}-test test/test_learning_topic.cpp)
# if(TARGET ${PROJECT_NAME}-test)
#   target_link_libraries(${PROJECT_NAME}-test ${PROJECT_NAME})
# endif()

## Add folders to be run by python nosetests
# catkin_add_nosetests(test)

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