ROS进阶学习手记 5 – 使用Eclipse开发robot_cleaner
接上一节，
======= 开始用Eclipse写一个发布给Turtlesim_node驱动和角度Msg的 my_node1 =====
参考Youtube上两个视频：
[CS460] ROS Tutorial 4.1 Turtlesim Cleaner Application - An Overview
[CS460] ROS Tutorial 4.2 Moving in a Straight Line (Turtlesim Cleaner)
我们来在Eclipse里写这个node的代码。
2015年7月21日09:59:26
建立一个名为robot_cleaner的Package，生成robot_cleaner_node，向turtlesim_node发送msg.
topic info:
topic_name: /turtle1/cmd_vel
topic_type: geometry_msgs/Twist
Message info:
$ rosmsg show geometry_msgs/Twist
show the data struct:
geometry_msgs/Vector3 linear
float64 x
float64 y
float64 z
geometry_msgs/Vector3 angular
float64 x
float64 y
float64 z
$ rostopic echo /turtle1/cmd_vel
得到：
linear:
x: 0.0
y: 0.0
z: 0.0
angular:
x: 0.0
y: 0.0
z: 2.0
Package Dependency:
roscpp
rospy
std_msgs
geometry_msgs
message_generation
1. Create the Package:
$ cd ~/catkin_ws/src/
$ catkin_create_pkg robot_cleaner roscpp rospy std_msgs geometry_msgs message_generation
2. Generate the Eclipse Files for dev. in Eclipse IDE
$ cd ~/catkin_ws //这实际上是Workspace的路径，catkin_ws = catkin workspace
$ catkin_make --force-cmake -G"Eclipse CDT4 - Unix Makefiles"
$ . ~/catkin_ws/devel/setup.bash
to generate the .project file and then run:
$ awk -f $(rospack find mk)/eclipse.awk build/.project > build/.project_with_env && mv build/.project_with_env build/.project
此时刷新Eclipse里的Project Explorer，可以看到“robot_cleaner”这个项目。
【问题】： 为何要在Terminal里建立Package再生成Eclipse File，不能直接在Eclipse里创建Package么？怎么创建？
3. 在Eclipse里创建cpp源文件
Project@Build -> [Source directory] -> robot_cleaner ->src ->单击鼠标右键-> new ->file ->File name:robot_cleaner.cpp
[如图片]:
4. 编辑cpp源文件
1. /* File: robot_cleaner.cpp
2. * source file
3. * auther : sonic
4. *
5. */
6.
7. #include "ros/ros.h"
8. #include "geometry_msgs/Twist.h"
9.
10. ros::Publisher velocity_publisher; //Declare a ros Publisher: velocity_publisher
11.
12. //Declare the method to move the robot straight
13. void move(double speed, double distance, bool isForward);
14.
15. int main(int argc, char **argv){
16. //Initiate new ROS node named "talker"
17. ros::init(argc, argv, "robot_cleaner");
18. ros::NodeHandle n;
19. ROS_INFO("Your robot cleaner node starts!"); //打印，用于调试。
20. velocity_publisher = n.advertise<geometry_msgs::Twist>("/turtle1/cmd_vel",10); //initiate the ros publisher
21. move(2.0, 5.0, 1);
22.
23. }
24.
25. //Definition of the method move()
26. void move(double speed, double distance, bool isForward){
27. geometry_msgs::Twist vel_msg;
28. //distance = speed * time
29.
30. //set a random linear velocity in the x-axis
31. if (isForward)
32. vel_msg.linear.x = abs(speed);
33. else
34. vel_msg.linear.x = -abs(speed);
35.
36. vel_msg.linear.y = 0;
37. vel_msg.linear.z = 0;
38.
39. //set a random angular velocity in the y-axis
40. vel_msg.angular.x = 0;
41. vel_msg.angular.y = 0;
42. vel_msg.angular.z = 0;
43.
44. //t0: the current time
45. double t0 = ros::Time::now().toSec();
46. double current_distance = 0;
47. ros::Rate loop_rate(10);
48. do{
49. velocity_publisher.publish(vel_msg);
50. double t1 = ros::Time::now().toSec();
51. current_distance = speed * (t1 - t0);
52. ros::spinOnce();
53. loop_rate.sleep();
54. }while (current_distance < distance);
55. vel_msg.linear.x = 0; //stop it
56. velocity_publisher.publish(vel_msg);
57. //loop
58. //publish the velocity
59. //estimate the distance = speed *(t1-t0)
60. //current_distance_moved_by_robot <= distance
61.
62.
63. }
5. 修改Catkin Make List文件
文件： CMakelists.txt
加入如下代码：
add_executable(robot_cleaner_node src/robot_cleaner.cpp) #specify which cpp should be compile and create the execute
target_link_libraries(robot_cleaner_node ${catkin_LIBRARIES})
add_dependencies(robot_cleaner_node robot_cleaner_gencpp)
6. 编译、运行和调试你的executables
Eclipse -> Project -> Build Project…
7. 运行和调试你的executables
先来看看能不能动哈：
$ rosrun turtlesim turtlesim_node
$ rosrun robot_cleaner robot_cleaner_node
我们看到robot_cleaner_node 打印出：“The robot cleaner node starts!”， 并且乌龟向右移动了。
OK， 至此，我们就完成了一个可以发布geometry_msg的node.
练习1：让turtle画个圆，如何？
练习2：让turtle走到pose = 特定位置的点，怎么弄？（涉及到从turtlesim_node接收topic="/turtle1/pose"的信息，并实时规划linear.x 和 angular.z 的值）
欢迎通过评论提交各位的代码~ :)