xml文件看看哪里错了

代码如下，清看看哪里出错了
报错：

Error [parser.cc:340] Error parsing XML in file [/home/milk/velodyne_plugin/build/../velodyne.world]: Error reading end tag.

<?xml version="1.0" ?>
<sdf version="1.5">
  <world name="default">
    <!-- A global light source -->
    <include>
      <uri>model://sun</uri>
    </include>
    <!-- A ground plane -->
    <include>
      <uri>model://ground_plane</uri>
    </include>

    <!-- A testing model that includes the Velodyne sensor model -->
    <model name="my_velodyne">

      <include>
        <uri>model://velodyne_hdl32</uri>
      </include>

      <!-- Attach the plugin to this model -->
      <plugin name="velodyne_control" filename="./libvelodyne_plugin.so"/>
      <velocity>25</velocity>
      </plugin>

    </model>

  </world>
</sdf>

如有帮助，请采纳一下，谢谢！如有不清楚可以在问额。
这里写错了。

 <!-- Attach the plugin to this model -->
      <plugin name="velodyne_control" filename="./libvelodyne_plugin.so">
      <velocity>25</velocity>
      </plugin>