Errors occur when roslaunching the tutorials on Descartes

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Hey guys,

  I am a novice in the moveit and ROS and i have installed the Descartes and the descartes_tutorials repository in my ros. The building is finished, but when i roslaunching the tutorials using 

roslaunch descartes_tutorials tutorial1.launch

some errors, which is listed as followed, occurred

ERROR: cannot launch node of type [descartes_tutorial1/tutorial1]: descartes_tutorial1
ROS path [0]=/opt/ros/indigo/share/ros
ROS path [1]=/home/aicrobo/code/ros_groovy/src
ROS path [2]=/home/aicrobo/catkin_ws/src
ROS path [3]=/opt/ros/indigo/share
ROS path [4]=/opt/ros/indigo/stacks

Have i missed some steps or the problem is the "robot_description"?

// Name of description on parameter server. Typically just "robot_description". const std::string robot_description = " robot_description";

The robot description is the package name which is generated by Moveit setup assistant?