以下是Ubuntu 16.04下gazebo的安装方法：
https://github.com/ros-simulation/gazebo_ros_pkgs/issues/479
一、卸载当前已安装的不能运行的gazebo相关包，具体方法如下：
通过 “dpkg -l | grep gazebo”命令查找当前安装的gazebo包，然后通过“sudo apt-get remove gazebo7 gazebo7-common gazebo7-plugin-base libgazebo7:amd64 libgazebo7-dev:amd64”卸载。
sudo add-apt-repository "deb http://packages.osrfoundation.org/gazebo/ubuntu-stable xenial main"
wget http://packages.osrfoundation.org/gazebo.key -O - | sudo apt-key add -
sudo apt-get install gazebo9
You need also to install
ros-$ROS_DISTRO-gazebo9 ros_wrapper
ros-$ROS_DISTRO-gazebo9-ros-pkgs
ros-$ROS_DISTRO-gazebo9-ros-control
虽然可以安装gazebo9，但是启动gazebo的时候无法启动controllermanager，应该是需要将ubuntu16.04换成18.04才行，后续需要试验。