Turtlebot3.md

@@ -52,6 +52,7 @@ Turtlebot3 burger is the smallest turtlebot3 mobile robot. It is composed of 2 D
 ```
 (Remote PC)>roslaunch turtlebot3_gazebo turtlebot3_world.launch
 ```
+(if you need to use /clock in your ros package, you have to be aware about /use_sim_time parameter)
 + Control burger with keyboard
 ```
 (Remote PC)>roslaunch turtlebot3_teleop turtlebot3_teleop_key.launch
@@ -121,6 +122,7 @@ Also the TurtleBot3 can be used as a mobile manipulator capable of manipulating
 ```
 (Remote PC)>roslaunch turtlebot3_gazebo turtlebot3_world.launch
 ```
+(if you need to use /clock in your ros package, you have to be aware about /use_sim_time parameter)
 + Control waffle with keyboard
 ```
 (Remote PC)>roslaunch turtlebot3_teleop turtlebot3_teleop_key.launch