(1) urdf的编写: https://blog.csdn.net/wubaobao1993/article/details/80947968
(2) urdf的gazebo属性: https://blog.csdn.net/wubaobao1993/article/details/80960584
(3) 将gazebo和ros连接起来: https://blog.csdn.net/wubaobao1993/article/details/81054570