ROS启动乌龟追乌龟程序用的是roslaunch turtle_tf turtle_tf_demo.launch，其内容如下：

<launch>

  <node pkg="turtlesim" type="turtlesim_node" name="sim"/>
  <node pkg="turtlesim" type="turtle_teleop_key" name="teleop" output="screen"/>
  <!-- Axes -->
  <param name="scale_linear" value="2" type="double"/>
  <param name="scale_angular" value="2" type="double"/>
  <!-- 针对两个乌龟的tf广播 -->
  <node name="turtle1_tf_broadcaster" pkg="turtle_tf" type="turtle_tf_broadcaster.py" respawn="false" output="screen" >
    <param name="turtle" type="string" value="turtle1" />
  </node>
  <node name="turtle2_tf_broadcaster" pkg="turtle_tf" type="turtle_tf_broadcaster.py" respawn="false" output="screen" >
    <param name="turtle" type="string" value="turtle2" />
  </node>

  <node name="turtle_pointer" pkg="turtle_tf" type="turtle_tf_listener.py" respawn="false" output="screen" >
  </node>

</launch>

乌龟的程序,按下方向键,乌龟只走一段距离,是在cmd_vel的回调函数里更新乌龟的位置,取决于发布的twist消息和更新间隔dt,由Qt实现