ROS机器人开发实践学习笔记3

  摘要: 刚刚开始学习ROS,打算入机器人的坑了,参考教材是《ROS及其人开发实践》胡春旭编著 机械工业出版社 华章科技出品。本来以为可以按照书上的步骤一步步来,但是,too young to simple啊,程序员的苦逼日子开始了,特地记录如下。

  今天居然发现,不是linux没有安装成功,只是没有办法找到boot/efi下的引导文件,充分利用Manjaro • 18.1.0-rc6的u盘启动选项detect  efi功能就可以实现U盘引导硬盘上的系统的功能了,也不错,居然还有这样操作哈哈。

  一、创建并配置工作空间(workspace)

  工作空间是存放工程开发相关文件的文件夹,现在较新版本的ROS默认使用catkin编译系统,该编译系统的空间比较特殊,所以需要特殊的方式创建。

  1、创建工作空间

    mkdir -p  ~/catkin_ws/src                    #在home目录下创建两级目录,先创建catkin目录,再创建src目录,必须使用-p选项

    cd  ~/catkin_ws/src                      #切换到src目录

    catkin_init_workspace                      #初始化工作空间

  2、编译工作空间,此时工作空间为空,经过编译会生成很多文件,严格来说是迁移来很多文件

    cd   ~/catkin_ws/

    catkin_make                        #catkin自己的编译命令

  3、初始化环境变量,使环境变量生效

    source   devel/setup.bash                    #其实就是运行编译生成的devel目录下的setup.bash文件

  4、验证环境变量是否有效

    echo   $ROS_PACKAGE_PATH                  #打印当前工作空间的路径,结果如下:,包括刚刚创建的工作空间的目录就对了,否则,要好好找找原因了。

municationk@developk:~/catkin_ws$ echo $ROS_PACKAGE_PATH
/home/municationk/catkin_ws/src:/opt/ros/melodic/share

  二、在工作空间创建功能包,ROS系统的实现主要靠功能包实现各个功能

  功能包中包含了许多文件和配置信息及编译信息等,现在较新版本的ROS默认使用catkin编译系统,该编译系统对功能包要求比较特殊,所以需要特殊的方式创建。

  1、创建功能包,应用catkin_create_pkg命令

       cd  ~/catkin_ws/src                      #切换到代码空间,也就是工作空间的src目录

    catkin_create_pkg  learning_com  std_msgs  rospy   roscpp     #创建功能包,并指定有三个功能包依赖

  2、再次编译工作空间,并设置环境变量

    cd   ~/catkin_ws/

    catkin_make                        #编译

    source   devel/setup.bash                   #设置环境变量

  三、在工作空间创建功能包,实现一个简单的发布、订阅程序:主要是添加两个cpp源码talker.cpp和listener.cpp,修改一个编译配置文件CMakeList.txt,修改一个功能包配置文件package.xml文件

  1、talker.cpp在工作空间的代码空间的功能包的代码空间中,本文中为:~/catkin_ws/src/learning_com/src/目录中,内容

  1 /**
  2  * 该例程将发布chatter话题,消息类型String
  3  */
  4 
  5 #include 
  6 #include "ros/ros.h"
  7 #include "std_msgs/String.h"
  8 
  9 int main(int argc, char **argv)
 10 {
 11     // ROS节点初始化
 12     ros::init(argc, argv, "talker");
 13 
 14     // 创建节点句柄
 15     ros::NodeHandle n;
 16 
 17     // 创建一个Publisher,发布名为chatter的topic,消息类型为std_msgs::String
 18     ros::Publisher chatter_pub = n.advertise("chatter", 1000);      
 19 
 20     // 设置循环的频率
 21     ros::Rate loop_rate(10);
 22 
 23     int count = 0;
 24     while (ros::ok())
 25     {
 26         // 初始化std_msgs::String类型的消息
 27         std_msgs::String msg;
 28         std::stringstream ss;
 29         ss << "hello world " << count;
 30         msg.data = ss.str();
 31 
 32         // 发布消息
 33         ROS_INFO("%s", msg.data.c_str());
 34         chatter_pub.publish(msg);
 35 
 36         // 循环等待回调函数
 37         ros::spinOnce();
 38 
 39         // 按照循环频率延时
 40         loop_rate.sleep();
 41         ++count;
 42     }
 43 
 44     return 0;
 45 }

  2、listener.cpp在工作空间的代码空间的功能包的代码空间中,本文中为:~/catkin_ws/src/learning_com/src/目录中,内容

  1 /**                                                                           
  2  * 该例程将订阅chatter话题,消息类型String
  3  */
  4 
  5 #include "ros/ros.h"
  6 #include "std_msgs/String.h"
  7 
  8 // 接收到订阅的消息后,会进入消息回调函数
  9 void chatterCallback(const std_msgs::String::ConstPtr& msg)
 10 {
 11     // 将接收到的消息打印出来
 12     ROS_INFO("I heard: [%s]", msg->data.c_str());
 13 }
 14 
 15 int main(int argc, char **argv)
 16 {
 17     // 初始化ROS节点
 18     ros::init(argc, argv, "listener");
 19 
 20     // 创建节点句柄
 21     ros::NodeHandle n;
 22 
 23     // 创建一个Subscriber,订阅名为chatter的topic,注册回调函数chatterCallback
 24     ros::Subscriber sub = n.subscribe("chatter", 1000, chatterCallback);
 25 
 26     // 循环等待回调函数
 27     ros::spin();
 28 
 29     return 0;
 30 }

  3、CMakeList.txt在工作空间的代码空间的功能包的代码空间中,本文中为:~/catkin_ws/src/learning_com/目录中,内容

  1 cmake_minimum_required(VERSION 2.8.3)                                                                                                                                           
  2 project(learning_com)
  3 
  4 ## Compile as C++11, supported in ROS Kinetic and newer
  5 # add_compile_options(-std=c++11)
  6 
  7 ## Find catkin macros and libraries
  8 ## if COMPONENTS list like find_package(catkin REQUIRED COMPONENTS xyz)
  9 ## is used, also find other catkin packages
 10 find_package(catkin REQUIRED COMPONENTS
 11   roscpp
 12   rospy
 13   std_msgs
 14 )
 15 
 16 ## Specify additional locations of header files
 17 ## Your package locations should be listed before other locations
 18 include_directories(
 19   include
 20   ${catkin_INCLUDE_DIRS}
 21 )
 22 
 23 ## Declare a C++ library
 24 # add_library(${PROJECT_NAME}
 25 #   src/${PROJECT_NAME}/learning_communication.cpp
 26 # )
 27 
 28 add_executable(talker src/talker.cpp)
 29 target_link_libraries(talker ${catkin_LIBRARIES})
 30 add_dependencies(talker ${PROJECT_NAME}_generate_messages_cpp)
 31 
 32 add_executable(listener src/listener.cpp)
 33 target_link_libraries(listener ${catkin_LIBRARIES})
 34 add_dependencies(talker ${PROJECT_NAME}_generate_messages_cpp)
 35 
 36 ## Mark other files for installation (e.g. launch and bag files, etc.)
 37 # install(FILES
 38 #   # myfile1
 39 #   # myfile2
 40 #   DESTINATION ${CATKIN_PACKAGE_SHARE_DESTINATION}
 41 # )
 42 
 43 #############
 44 ## Testing ##
 45 #############
 46 
 47 ## Add gtest based cpp test target and link libraries
 48 # catkin_add_gtest(${PROJECT_NAME}-test test/test_learning_communication.cpp)
 49 # if(TARGET ${PROJECT_NAME}-test)
 50 #   target_link_libraries(${PROJECT_NAME}-test ${PROJECT_NAME})
 51 # endif()
 52 
 53 ## Add folders to be run by python nosetests
 54 # catkin_add_nosetests(test)
~                                                   

  实际的内容更多,只需要关注:1,2,10~14,18~21,28~34这些行就够了

  4、package.xml在工作空间的代码空间的功能包的代码空间中,本文中为:~/catkin_ws/src/learning_com/目录中,内容

  1 xml version="1.0"?>
  2 <package format="2">
  3   <name>learning_comname>
  4   <version>0.0.0version>
  5   <description>The learning_communication packagedescription>
  6 
  7   <maintainer email="[email protected]">municationkmaintainer>
  8 
  9   <license>TODOlicense>
 10 
 11   <buildtool_depend>catkinbuildtool_depend>
 12   <build_depend>roscppbuild_depend>
 13   <build_depend>rospybuild_depend>
 14   <build_depend>std_msgsbuild_depend>
 15   <build_export_depend>roscppbuild_export_depend>
 16   <build_export_depend>rospybuild_export_depend>
 17   <build_export_depend>std_msgsbuild_export_depend>
 18   <exec_depend>roscppexec_depend>
 19   <exec_depend>rospyexec_depend>
 20   <exec_depend>std_msgsexec_depend>
 21 
 22   <export>
 23     
 24 
 25   export>
 26 package>  

  同上,内容比较多,有用就这些就够了。

  5、编译功能包,并设置环境变量

    cd   ~/catkin_ws/

    catkin_make                        #编译

    source   devel/setup.bash                   #设置环境变量

  测试,打开三个终端,在第一终端输入:roscore,第二个终端输入:rosrun  learning_com talker   第三个终端输入:rosrun  learning_com listener

  在第一终端输入:roscore,

  

municationk@developk:~/catkin_ws$ roscore 
... logging to /home/municationk/.ros/log/41d00338-b742-11e9-bb4a-d39af2b318a5/roslaunch-developk-11230.log
Checking log directory for disk usage. This may take awhile.
Press Ctrl-C to interrupt
Done checking log file disk usage. Usage is <1GB.

started roslaunch server http://developk:45561/
ros_comm version 1.14.3


SUMMARY
========

PARAMETERS
 * /rosdistro: melodic
 * /rosversion: 1.14.3

NODES

auto-starting new master
process[master]: started with pid [11240]
ROS_MASTER_URI=http://developk:11311/

setting /run_id to 41d00338-b742-11e9-bb4a-d39af2b318a5
process[rosout-1]: started with pid [11251]
started core service [/rosout]

  第二个终端输入:rosrun  learning_com talker

municationk@developk:~/catkin_ws$ rosrun learning_com talker
[ INFO] [1564988563.784974961]: hello world 0
[ INFO] [1564988563.885031740]: hello world 1
[ INFO] [1564988563.985024808]: hello world 2
[ INFO] [1564988564.085013935]: hello world 3
[ INFO] [1564988564.185028269]: hello world 4
[ INFO] [1564988564.285029076]: hello world 5
[ INFO] [1564988564.385029776]: hello world 6
[ INFO] [1564988564.485037478]: hello world 7
[ INFO] [1564988564.585027521]: hello world 8
[ INFO] [1564988564.685035509]: hello world 9
[ INFO] [1564988564.785033638]: hello world 10
[ INFO] [1564988564.885032052]: hello world 11
[ INFO] [1564988564.985045949]: hello world 12
[ INFO] [1564988565.085036609]: hello world 13
[ INFO] [1564988565.185046211]: hello world 14
[ INFO] [1564988565.285035685]: hello world 15
[ INFO] [1564988565.385040617]: hello world 16
[ INFO] [1564988565.485035166]: hello world 17
[ INFO] [1564988565.585033846]: hello world 18
[ INFO] [1564988565.685045276]: hello world 19
[ INFO] [1564988565.785045671]: hello world 20
[ INFO] [1564988565.885033669]: hello world 21
[ INFO] [1564988565.985047584]: hello world 22
[ INFO] [1564988566.085030408]: hello world 23
[ INFO] [1564988566.185034201]: hello world 24
[ INFO] [1564988566.285026831]: hello world 25
[ INFO] [1564988566.385031470]: hello world 26
[ INFO] [1564988566.485012264]: hello world 27
[ INFO] [1564988566.585025410]: hello world 28

  第三个终端输入:rosrun  learning_com listener

municationk@developk:~/catkin_ws$ rosrun learning_com listener
[ INFO] [1564988569.085433644]: I heard: [hello world 53]
[ INFO] [1564988569.185483579]: I heard: [hello world 54]
[ INFO] [1564988569.285412983]: I heard: [hello world 55]
[ INFO] [1564988569.385413951]: I heard: [hello world 56]
[ INFO] [1564988569.485403072]: I heard: [hello world 57]
[ INFO] [1564988569.585392842]: I heard: [hello world 58]
[ INFO] [1564988569.685406999]: I heard: [hello world 59]
[ INFO] [1564988569.785430346]: I heard: [hello world 60]
[ INFO] [1564988569.885437192]: I heard: [hello world 61]
[ INFO] [1564988569.985383334]: I heard: [hello world 62]
[ INFO] [1564988570.085448900]: I heard: [hello world 63]
[ INFO] [1564988570.185430490]: I heard: [hello world 64]
[ INFO] [1564988570.285360554]: I heard: [hello world 65]
[ INFO] [1564988570.385351604]: I heard: [hello world 66]
[ INFO] [1564988570.485397283]: I heard: [hello world 67]
[ INFO] [1564988570.585397681]: I heard: [hello world 68]
[ INFO] [1564988570.685402230]: I heard: [hello world 69]
[ INFO] [1564988570.785393468]: I heard: [hello world 70]
[ INFO] [1564988570.885363100]: I heard: [hello world 71]
[ INFO] [1564988570.985392078]: I heard: [hello world 72]
[ INFO] [1564988571.085475920]: I heard: [hello world 73]
[ INFO] [1564988571.185429095]: I heard: [hello world 74]
[ INFO] [1564988571.285393208]: I heard: [hello world 75]
[ INFO] [1564988571.385433165]: I heard: [hello world 76]
[ INFO] [1564988571.485432988]: I heard: [hello world 77]
[ INFO] [1564988571.585488144]: I heard: [hello world 78]
[ INFO] [1564988571.685395075]: I heard: [hello world 79]
[ INFO] [1564988571.785379391]: I heard: [hello world 80]
[ INFO] [1564988571.885424095]: I heard: [hello world 81]
[ INFO] [1564988571.985416266]: I heard: [hello world 82]

  当在第二个终端中使用ctrl+c将程序中talker的publisher退出:

[ INFO] [1564988684.485031189]: hello world 1207
[ INFO] [1564988684.585041383]: hello world 1208
[ INFO] [1564988684.685035838]: hello world 1209
[ INFO] [1564988684.785028755]: hello world 1210
[ INFO] [1564988684.885037794]: hello world 1211
[ INFO] [1564988684.985037237]: hello world 1212
[ INFO] [1564988685.085037514]: hello world 1213
[ INFO] [1564988685.185037370]: hello world 1214
[ INFO] [1564988685.285035278]: hello world 1215
[ INFO] [1564988685.385038330]: hello world 1216
[ INFO] [1564988685.485038069]: hello world 1217
[ INFO] [1564988685.585033289]: hello world 1218
[ INFO] [1564988685.685036926]: hello world 1219
[ INFO] [1564988685.785037248]: hello world 1220
[ INFO] [1564988685.885031570]: hello world 1221
[ INFO] [1564988685.985032773]: hello world 1222
[ INFO] [1564988686.085030804]: hello world 1223
[ INFO] [1564988686.185031407]: hello world 1224
[ INFO] [1564988686.285031990]: hello world 1225
[ INFO] [1564988686.385032176]: hello world 1226
[ INFO] [1564988686.485039157]: hello world 1227
[ INFO] [1564988686.585043363]: hello world 1228
[ INFO] [1564988686.685048856]: hello world 1229
[ INFO] [1564988686.785040098]: hello world 1230
[ INFO] [1564988686.885051605]: hello world 1231
^C[ INFO] [1564988686.985104558]: hello world 1232
municationk@developk:~/catkin_ws$ 

  第三个终端中的lisenter的subscriber也无法接受数据:

[ INFO] [1564988683.685365358]: I heard: [hello world 1199]
[ INFO] [1564988683.785432435]: I heard: [hello world 1200]
[ INFO] [1564988683.885411699]: I heard: [hello world 1201]
[ INFO] [1564988683.985359765]: I heard: [hello world 1202]
[ INFO] [1564988684.085305814]: I heard: [hello world 1203]
[ INFO] [1564988684.185308442]: I heard: [hello world 1204]
[ INFO] [1564988684.285348116]: I heard: [hello world 1205]
[ INFO] [1564988684.385234823]: I heard: [hello world 1206]
[ INFO] [1564988684.485375722]: I heard: [hello world 1207]
[ INFO] [1564988684.585385628]: I heard: [hello world 1208]
[ INFO] [1564988684.685397073]: I heard: [hello world 1209]
[ INFO] [1564988684.785395362]: I heard: [hello world 1210]
[ INFO] [1564988684.885395528]: I heard: [hello world 1211]
[ INFO] [1564988684.985422434]: I heard: [hello world 1212]
[ INFO] [1564988685.085454179]: I heard: [hello world 1213]
[ INFO] [1564988685.185441077]: I heard: [hello world 1214]
[ INFO] [1564988685.285378556]: I heard: [hello world 1215]
[ INFO] [1564988685.385396991]: I heard: [hello world 1216]
[ INFO] [1564988685.485434675]: I heard: [hello world 1217]
[ INFO] [1564988685.585420842]: I heard: [hello world 1218]
[ INFO] [1564988685.685352301]: I heard: [hello world 1219]
[ INFO] [1564988685.785442642]: I heard: [hello world 1220]
[ INFO] [1564988685.885395217]: I heard: [hello world 1221]
[ INFO] [1564988685.985383329]: I heard: [hello world 1222]
[ INFO] [1564988686.085378470]: I heard: [hello world 1223]
[ INFO] [1564988686.185359547]: I heard: [hello world 1224]
[ INFO] [1564988686.285419784]: I heard: [hello world 1225]
[ INFO] [1564988686.385437478]: I heard: [hello world 1226]
[ INFO] [1564988686.485451254]: I heard: [hello world 1227]
[ INFO] [1564988686.585436616]: I heard: [hello world 1228]
[ INFO] [1564988686.685407657]: I heard: [hello world 1229]
[ INFO] [1564988686.785376388]: I heard: [hello world 1230]
[ INFO] [1564988686.885540877]: I heard: [hello world 1231]

  正好符合了通信中的,有发送才有接收,发送中断了,接受不到数据了,自然就停下了。ROS中的话题通信主要依赖roccore,因此,无论是先运行终端2或终端3都无所谓,但是,一定要先运行终端1的命令。

  

 

转载于:https://www.cnblogs.com/guochaoxxl/p/11303128.html

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