ROS_control: Controller Spawner couldn't find the expected controller_manager ROS interface.

[HanyuSylvieSun]

process[rrbot/controller_spawner-1]: started with pid [17740]
process[robot_state_publisher-2]: started with pid [17741]
[INFO] [1526937150.881932, 0.000000]: Controller Spawner: Waiting for service controller_manager/load_controller
[WARN] [1526937150.882767, 0.000000]: wait_for_service(/rrbot/controller_manager/load_controller): failed to contact, will keep trying
[WARN] [1526937181.048728, 0.000000]: Controller Spawner couldn't find the expected controller_manager ROS interface.
[rrbot/controller_spawner-1] process has finished cleanly
log file: /home/pennsunglab-01/.ros/log/e33acc58-5d2f-11e8-8dd3-484d7eca7561/rrbot-controller_spawner-1*.lo

It's giving me above error when I run the ros control.
I have installed the controller-manager successfully.
Any idea why?

[CesMak]

Controller Spawner couldn't find the expected controller_manager ROS interface.

this error occured once to me cause of the fact, that I did not linked the joints correctely check your joints namespaces etc.