使用gazebo工具对机器人的urdf模型进行仿真时，执行命令：roslaunch seven_dof_arm_gazebo seven_dof_arm_gazebo_control.launch，出现如下错误：

主要原因是没有安装相应的ros控制软件包。

ERROR] [1571208919.660838700, 0.574000000]: Could not load controller 'joint_state_controller' because controller type 'joint_state_controller/JointStateController' does not exist.
[ERROR] [1571208919.660891569, 0.574000000]: Use 'rosservice call controller_manager/list_controller_types' to get the available types
[ERROR] [1571208920.662791, 1.280000]: Failed to load joint_state_controller

解决方法： 

$> sudo apt-get update
$> sudo apt-get install ros-kinetic-joint-state-controller
$> rospack profile

 参考：https://github.com/qboticslabs/mastering_ros/issues/10

[ERROR] [1571210918.068977205, 0.181000000]: Could not load controller 'joint1_position_controller' because controller type 'position_controllers/JointPositionController' does not exist.
[ERROR] [1571210918.069693846, 0.181000000]: Use 'rosservice call controller_manager/list_controller_types' to get the available types

解决方法 ：sudo apt-get install ros-indigo-position-controllers

https://github.com/qboticslabs/mastering_ros/issues/7

最好在安装ros的时候一起安装控制器插件，通过如下命令：

$ sudo apt-get install ros-kinetic-joint-state-controller : This will install joint_state_controller package

$ sudo apt-get install ros-kinetic-effort-controllers : This will install Effort controller

$ sudo apt-get install ros-kinetic-position-controllers : This will install position controllers

sudo apt-get install ros-kinetic-joint-trajectory-controller

参考：https://github.com/qboticslabs/mastering_ros/issues/7