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

  

/* File: robot_cleaner.cpp
 * source file
 * auther : sonic
 * 
 */

#include "ros/ros.h"
#include "geometry_msgs/Twist.h"

ros::Publisher velocity_publisher;  //Declare a ros Publisher: velocity_publisher

//Declare the method to move the robot straight
void move(double speed, double distance, bool isForward);

int main(int argc, char **argv){
  //Initiate new ROS node named "talker"
  ros::init(argc, argv, "robot_cleaner");
  ros::NodeHandle n;
  ROS_INFO("Your robot cleaner node starts!");  //打印，用于调试。
  velocity_publisher = n.advertise<geometry_msgs::Twist>("/turtle1/cmd_vel",10);  //initiate the ros publisher 
  move(2.0, 5.0, 1);

}

//Definition of the method move()
void move(double speed, double distance, bool isForward){
	geometry_msgs::Twist vel_msg;
	//distance = speed * time
	
	//set a random linear velocity in the x-axis
	if (isForward)
		vel_msg.linear.x = abs(speed);
	else
		vel_msg.linear.x = -abs(speed);
	
	vel_msg.linear.y = 0;
	vel_msg.linear.z = 0;
	
	//set a random angular velocity in the y-axis
	vel_msg.angular.x = 0;
	vel_msg.angular.y = 0;
	vel_msg.angular.z = 0;

	//t0: the current time
	double t0 = ros::Time::now().toSec();
	double current_distance = 0;
	ros::Rate loop_rate(10);
	do{
		velocity_publisher.publish(vel_msg);
		double t1 = ros::Time::now().toSec();
		current_distance = speed * (t1 - t0);
		ros::spinOnce();
		loop_rate.sleep();
	}while (current_distance < distance);
	vel_msg.linear.x = 0; //stop it
	velocity_publisher.publish(vel_msg);
	//loop
	//publish the velocity
	//estimate the distance = speed *(t1-t0)
	//current_distance_moved_by_robot <= distance

	
}

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~ :)