从turtlesim到贪吃蛇……（补充）

原文如下：

从turtlesim到贪吃蛇……

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部分提示：

背下来但是不理解，忘得特别快！！！

综合项目案例一：贪吃蛇实现
1. 这个项目实现，需要用到哪些已经学过的知识点？
总-分
2. 如何将这些知识点融合（综合）完成此案例？
3. 每个知识点在此综合项目中的组成部分或位置？
4. 设计方案（草案）完成项目构思？
5. 编程实现各部分的功能并测试？
6. 将各部分的功能进行有机组合实现此项目案例？
分-总
综合拆解成单元，单元组成综合。
复杂变简单，简单变复杂

1. 车队现象！
领队负责路径规划，其他参与者负责跟随
第一种：领队找队友-贪吃蛇
第二种：队友找领队-集群

2. 图形化使用turtlesim；扩展生成新的机器人（用cpp代码实现而非API接口）；领队需要使用键盘遥控；

3. 集群和贪吃蛇联系，如何改变和应用？

4. 如何利用上述知识点进行设计？

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一个有问题的程序如下（请不要参考）： 

#include <ros/ros.h>
#include <tf/transform_listener.h>
#include <geometry_msgs/Twist.h>
#include <turtlesim/Spawn.h>

int main(int argc, char** argv)
{

	ros::init(argc, argv, "my_tf_listener");


	ros::NodeHandle node;


	ros::service::waitForService("/spawn");
	ros::ServiceClient add_turtle = node.serviceClient<turtlesim::Spawn>("/spawn");
	turtlesim::Spawn srv;
	add_turtle.call(srv);

	ros::service::waitForService("/spawn");
	ros::ServiceClient add_turtle3 = node.serviceClient<turtlesim::Spawn>("/spawn");
	turtlesim::Spawn srv3;
	add_turtle.call(srv3);

	ros::service::waitForService("/spawn");
	ros::ServiceClient add_turtle4 = node.serviceClient<turtlesim::Spawn>("/spawn");
	turtlesim::Spawn srv4;
	add_turtle.call(srv4);

	ros::service::waitForService("/spawn");
	ros::ServiceClient add_turtle5 = node.serviceClient<turtlesim::Spawn>("/spawn");
	turtlesim::Spawn srv5;
	add_turtle.call(srv5);

	ros::service::waitForService("/spawn");
	ros::ServiceClient add_turtle6 = node.serviceClient<turtlesim::Spawn>("/spawn");
	turtlesim::Spawn srv6;
	add_turtle.call(srv6);

	ros::service::waitForService("/spawn");
	ros::ServiceClient add_turtle7 = node.serviceClient<turtlesim::Spawn>("/spawn");
	turtlesim::Spawn srv7;
	add_turtle.call(srv7);







	ros::Publisher turtle_vel = node.advertise<geometry_msgs::Twist>("/turtle2/cmd_vel", 10);

	ros::Publisher turtle_vel3 = node.advertise<geometry_msgs::Twist>("/turtle3/cmd_vel", 10);

	ros::Publisher turtle_vel4 = node.advertise<geometry_msgs::Twist>("/turtle4/cmd_vel", 10);

	ros::Publisher turtle_vel5 = node.advertise<geometry_msgs::Twist>("/turtle5/cmd_vel", 10);

	ros::Publisher turtle_vel6 = node.advertise<geometry_msgs::Twist>("/turtle6/cmd_vel", 10);

	ros::Publisher turtle_vel7 = node.advertise<geometry_msgs::Twist>("/turtle7/cmd_vel", 10);


	tf::TransformListener listener;

	tf::TransformListener listener3;


	ros::Rate rate(10.0);
	while (node.ok())
	{
		// 
		tf::StampedTransform transform;
		try
		{
			listener.waitForTransform("/turtle2", "/turtle1", ros::Time(0), ros::Duration(3.0));
			listener.lookupTransform("/turtle2", "/turtle1", ros::Time(0), transform);
		}
		catch (tf::TransformException &ex) 
		{
			ROS_ERROR("%s",ex.what());
			ros::Duration(1.0).sleep();
			continue;
		}

		// 
		geometry_msgs::Twist vel_msg;
		vel_msg.angular.z = 4.0 * atan2(transform.getOrigin().y(),
				                        transform.getOrigin().x());
		vel_msg.linear.x = 2.0 * sqrt(pow(transform.getOrigin().x(), 2) +
				                      pow(transform.getOrigin().y(), 2));
		turtle_vel.publish(vel_msg);


		if(vel_msg.linear.x<0.01){
			// 
			tf::StampedTransform transform3;
			try
			{
				listener3.waitForTransform("/turtle3", "/turtle2", ros::Time(0), ros::Duration(3.0));
				listener3.lookupTransform("/turtle3", "/turtle2", ros::Time(0), transform);
			}
			catch (tf::TransformException &ex) 
			{
				ROS_ERROR("%s",ex.what());
				ros::Duration(1.0).sleep();
				continue;
			}

			// 
			geometry_msgs::Twist vel_msg3;
			vel_msg3.angular.z = 4.0 * atan2(transform3.getOrigin().y(),
						                transform3.getOrigin().x());
			vel_msg3.linear.x = 2.0 * sqrt(pow(transform3.getOrigin().x(), 2) +
						              pow(transform3.getOrigin().y(), 2));
			turtle_vel3.publish(vel_msg3);
		}

		rate.sleep();
	}
	return 0;
};

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