参考文档：http://www.autolabor.com.cn/book/ROSTutorials/index.html
1.5 ROS架构
1.5.1ROS文件系统
ROS文件系统级指的是在硬盘上ROS源代码的组织形式，其结构大致可以如下图所示：
WorkSpace --- 自定义的工作空间
|--- build:编译空间，用于存放CMake和catkin的缓存信息、配置信息和其他中间文件。
|--- devel:开发空间，用于存放编译后生成的目标文件，包括头文件、动态&静态链接库、可执行文件等。
|--- src: 源码
|-- package：功能包(ROS基本单元)包含多个节点、库与配置文件，包名所有字母小写，只能由字母、数字与下划线组成
|-- CMakeLists.txt 配置编译规则，比如源文件、依赖项、目标文件
|-- package.xml 包信息，比如:包名、版本、作者、依赖项...(以前版本是 manifest.xml)
|-- scripts 存储python文件
|-- src 存储C++源文件
|-- include 头文件
|-- msg 消息通信格式文件
|-- srv 服务通信格式文件
|-- action 动作格式文件
|-- launch 可一次性运行多个节点
|-- config 配置信息
|-- CMakeLists.txt: 编译的基本配置
1.package.xml
该文件定义有关软件包的属性，例如软件包名称，版本号，作者，维护者以及对其他catkin软件包的依赖性。请注意，该概念类似于旧版 rosbuild 构建系统中使用的manifest.xml文件。
下面是我之前包名里的package.xml
<?xml version="1.0"?>
<package format="2">
<name>hello_vscode</name> //包名
<version>0.0.0</version> //版本
<description>The hello_vscode package</description>
<!-- One maintainer tag required, multiple allowed, one person per tag -->
<!-- Example: -->
<!-- <maintainer email="[email protected]">Jane Doe</maintainer> -->
<maintainer email="[email protected]">ether</maintainer> //作者
<!-- One license tag required, multiple allowed, one license per tag -->
<!-- Commonly used license strings: -->
<!-- BSD, MIT, Boost Software License, GPLv2, GPLv3, LGPLv2.1, LGPLv3 -->
<license>TODO</license>
<!-- Url tags are optional, but multiple are allowed, one per tag -->
<!-- Optional attribute type can be: website, bugtracker, or repository -->
<!-- Example: -->
<!-- <url type="website">http://wiki.ros.org/hello_vscode</url> -->
<!-- Author tags are optional, multiple are allowed, one per tag -->
<!-- Authors do not have to be maintainers, but could be -->
<!-- Example: -->
<!-- <author email="[email protected]">Jane Doe</author> -->
<!-- The *depend tags are used to specify dependencies -->
<!-- Dependencies can be catkin packages or system dependencies -->
<!-- Examples: -->
<!-- Use depend as a shortcut for packages that are both build and exec dependencies -->
<!-- <depend>roscpp</depend> -->
<!-- Note that this is equivalent to the following: -->
<!-- <build_depend>roscpp</build_depend> -->
<!-- <exec_depend>roscpp</exec_depend> -->
<!-- Use build_depend for packages you need at compile time: -->
<!-- <build_depend>message_generation</build_depend> -->
<!-- Use build_export_depend for packages you need in order to build against this package: -->
<!-- <build_export_depend>message_generation</build_export_depend> -->
<!-- Use buildtool_depend for build tool packages: -->
<!-- <buildtool_depend>catkin</buildtool_depend> -->
<!-- Use exec_depend for packages you need at runtime: -->
<!-- <exec_depend>message_runtime</exec_depend> -->
<!-- Use test_depend for packages you need only for testing: -->
<!-- <test_depend>gtest</test_depend> -->
<!-- Use doc_depend for packages you need only for building documentation: -->
<!-- <doc_depend>doxygen</doc_depend> -->
<buildtool_depend>catkin</buildtool_depend> //用catkin编译
<build_depend>roscpp</build_depend> //建立依赖，创建工作包时的三个依赖项
<build_depend>rospy</build_depend>
<build_depend>std_msgs</build_depend>
<build_export_depend>roscpp</build_export_depend> //导出依赖
<build_export_depend>rospy</build_export_depend>
<build_export_depend>std_msgs</build_export_depend>
<exec_depend>roscpp</exec_depend> //执行依赖
<exec_depend>rospy</exec_depend>
<exec_depend>std_msgs</exec_depend>
<!-- The export tag contains other, unspecified, tags -->
<export>
<!-- Other tools can request additional information be placed here -->
</export>
</package>
2.CMakelists.txt
文件CMakeLists.txt是CMake构建系统的输入，用于构建软件包。任何兼容CMake的软件包都包含一个或多个CMakeLists.txt文件，这些文件描述了如何构建代码以及将代码安装到何处。
cmake_minimum_required(VERSION 3.0.2)
project(hello_vscode) //工作包名
## Compile as C++11, supported in ROS Kinetic and newer
# add_compile_options(-std=c++11)
## 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
roscpp //编译时依赖这三个外部包实现
rospy
std_msgs
)
## System dependencies are found with CMake's conventions
# find_package(Boost REQUIRED COMPONENTS system)
## 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()
################################################
## Declare ROS messages, services and actions ##
################################################
## 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 ...)
## Generate messages in the 'msg' folder
# add_message_files(
# FILES
# Message1.msg
# Message2.msg
# )
## Generate services in the 'srv' folder
# add_service_files(
# FILES
# Service1.srv
# Service2.srv
# )
## Generate actions in the 'action' folder
# add_action_files(
# FILES
# Action1.action
# Action2.action
# )
## Generate added messages and services with any dependencies listed here
# generate_messages(
# DEPENDENCIES
# std_msgs
# )
################################################
## Declare ROS dynamic reconfigure parameters ##
################################################
## 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
## Generate dynamic reconfigure parameters in the 'cfg' folder
# generate_dynamic_reconfigure_options(
# cfg/DynReconf1.cfg
# cfg/DynReconf2.cfg
# )
###################################
## catkin specific configuration ##
###################################
## 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 hello_vscode
# CATKIN_DEPENDS roscpp rospy std_msgs
# DEPENDS system_lib
)
###########
## Build ##
###########
## Specify additional locations of header files
## Your package locations should be listed before other locations
include_directories(
# include
${catkin_INCLUDE_DIRS}
)
## Declare a C++ library
# add_library(${PROJECT_NAME}
# src/${PROJECT_NAME}/hello_vscode.cpp
# )
## Add cmake target dependencies of the library
## as an example, code may need to be generated before libraries
## either from message generation or dynamic reconfigure
# add_dependencies(${PROJECT_NAME} ${${PROJECT_NAME}_EXPORTED_TARGETS} ${catkin_EXPORTED_TARGETS})
## Declare a C++ executable
## With catkin_make all packages are built within a single CMake context
## The recommended prefix ensures that target names across packages don't collide
add_executable(hello_vscode_c src/hello_vscode_c.cpp) //添加可执行的c++文件
## Rename C++ executable without prefix
## The above recommended prefix causes long target names, the following renames the
## target back to the shorter version for ease of user use
## e.g. "rosrun someones_pkg node" instead of "rosrun someones_pkg someones_pkg_node"
# set_target_properties(${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(hello_vscode_c //为C++文件映射的名称
${catkin_LIBRARIES}
)
#############
## Install ##
#############
# 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/hello_vscode_p.py //配置scripts目录下的python文件
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 ${CATKIN_PACKAGE_SHARE_DESTINATION}
# )
#############
## Testing ##
#############
## Add gtest based cpp test target and link libraries
# catkin_add_gtest(${PROJECT_NAME}-test test/test_hello_vscode.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)
1.5.2 ROS文件系统相关命令
ROS 的文件系统本质上都还是操作系统文件，我们可以使用Linux命令来操作这些文件，不过，在ROS中为了更好的用户体验，ROS专门提供了一些类似于Linux的命令，这些命令较之于Linux原生命令，更为简介、高效。文件操作，无外乎就是增删改查与执行等操作，接下来，我们就从这五个维度，来介绍ROS文件系统的一些常用命令。
1.增（添加）
catkin_create_pkg 自定义包名 依赖包 === 创建新的ROS功能包
sudo apt install xxx === 安装 ROS功能包 (后期会频繁用到)
2.删（删除）
sudo apt purge xxx ==== 删除某个功能包 （与增相反）
3.查
rospack list === 列出所有功能包
rospack find 包名 === 查找某个功能包是否存在，如果存在返回安装路径
roscd 包名 === 进入某个功能包
rosls 包名 === 列出某个包下的文件
apt search xxx === 搜索某个功能包
4.改
rosed 包名 文件名 === 修改功能包文件<font color="red">
需要先安装 vim 在终端输入 sudo apt install vim
示例：
输入 rosed turtlesim Color.msg后出现下面页面
5.执行
5.1 roscore
roscore === 是 ROS 的系统先决条件节点和程序的集合， 必须运行 roscore 才能使 ROS 节点进行通信。
roscore 将启动:
--ros master
--ros 参数服务器
--rosout 日志节点
用法：
roscore
或（指端口号）
roscore -p xxxx
5.2rosrun
rosrun 包名 可执行文件名 === 运行指定的ROS节点
示例：
rosrun turtlesim turtlesim_node 启动小乌龟
5.3roslaunch
roslaunch 包名 launch文件名 === 执行某个包下的 launch 文件
1.5.3ROS计算图
1.计算图简介
文件运行时之前的关系
使用工具ros_graph查看节点运行情况
2.计算图安装
在终端中输入(注意替换distro,替换名为当前ROS版本，比如：kinetic、melodic、Noetic等)
$ sudo apt install ros-<distro>-rqt
示例：$ sudo apt install ros-noetic-rqt
$ sudo apt install ros-<distro>-rqt-common-plugins
示例： $ sudo apt install ros-noetic-rqt-common-plugins
安装完后再终端中输入rosrun rqt_graph rqt_graph前面一个rqt是包，后一个是节点
只rqt_graph 也可以启动计算图
3.计算图演示
以启动小乌龟为例
在vscode环境中启动小乌龟：在先前的建立的start_turtle.launch下，在终端依次中输入
source ./devel/setuo.bash //建立环境变量
roslaunch hello_vscode start_turtle.launch //包名+建立的启动文件名
启动完小乌龟后在外部终端中输入
rosrun rqt_graph rqt_graph或rqt_graph
2.1 话题通信
话题通信是ROS中使用频率最高的一种通信模式，话题通信是基于发布订阅模式的，也即:一个节点发布消息，另一个节点订阅该消息。
应用场景：雷达、摄像头、GPS等传感器的采集
组成：发布方、订阅方、话题
2.1 .1 话题通信理论模型
模型包含三个角色：
ROS Master (管理者) --管理匹配话题
Talker (发布者)
Listener (订阅者)
流程图：
按以下步骤实现：
0.Talker注册
1.Listener注册
2.ROS Master 实现信息匹配
3.Listener 向 Talker 发送请求
4.Talker 确认请求
5.Listener 与 Talker 件里连接
6.Talker 向 Listener发送消息
注意：
1.使用的协议由 RPC 和 TCP ；
2.步骤0和步骤1没有顺序关系；
3.talker 和 listener 都可以存在多个；
4.talker 和 listener 建立连接后， master 就可以关闭了；
5.上述流程已经封装了，以后直接调用即可。
话题通信应用时的关注点：
0.大部分实现已经被封装了
1.话题设置
2.关注发布者实现
3.关注订阅者实现
4.关注消息载体
2.1 .2 话题通信基本操作A(C++)
需求:
编写发布订阅实现，要求发布方以10HZ(每秒10次)的频率
发布文本消息，订阅方订阅消息并将消息内容打印输出。
分析:
在模型实现中，ROS master 不需要实现，而连接的建立也已经被封装了，需要关注的关键点有三个:
发布方
接收方
数据(此处为普通文本)
流程:
1.编写发布方实现；
2.编写订阅方实现；
3.编辑配置文件；
4.编译并执行。
新建一个工作空间demo03_ws
输入code .进入vscode,在src目录新建一个功能包，点击Create Catkin Package
建立包名
导入依赖包
在scr目录上新 建一个C++文件
发布方实现
代码示例：
#include "ros/ros.h"
#include "std_msgs/String.h"
/*
发布方实现：
1.包含头文件;
ROS中文本类型 ---> std_msgs/String.h
2.初始化 ROS 节点;
3.创建节点句柄;
4.创建发布者对象;
5.编写发布逻辑并发布数据;
*/
int main(int argc, char *argv[])
{
// 2.初始化 ROS 节点
ros::init(argc,argv,"erGouZi");
// 3.创建节点句柄;
ros::NodeHandle nh;
// 4.创建发布者对象;
ros::Publisher pub = nh.advertise<std_msgs::String>("fang",10); //缓存个数为10
// 5.编写发布逻辑并发布数据;
//先创建被发布的消息
std_msgs::String msg;
//编写循环，循环中发布数据
while (ros::ok())
{
msg.data = "hello";
pub.publish(msg);
}
return 0;
}
编写完代码后修改CmakeLists.txt文件中的映射名和源文件名
在修改指向文件名为映射文件名
修改完后编译运行一下
编译完成后打开终端
水平分割另起一个终端输入rostopic echo +建立的话题名称
打印发布者发布的话题数据：rostopic echo 话题名称
回车后输出结果为：
hello为fang这个话题下发布者发出的消息