1.Upgrading from simulator_gazebo
http://gazebosim.org/wiki/Tutorials/1.9/Overview_of_new_ROS_integration
2.gazebo userguide
http://gazebosim.org/user_guide/started__components__plugins.html
3.ros 编写一个plugin
http://www.ros.org/wiki/pluginlib/Tutorials/Writing%20and%20Using%20a%20Simple%20Plugin