Internals about Robot Movement

asked 2015-05-14 00:09:11 -0500

Kushal
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updated 2015-05-14 23:40:53 -0500

As explained on "http://learn.turtlebot.com/" in the video about the teleoperation functionality ie. after running the command "roslaunch turtlebot_teleop keyboard_teleop.launch", some questions arise that are as follows:

What does it actually do after taking the input from keyboard?
1. Is turtlebot_teleop an ROS node that publishes to some "ROS Topic" and we have a corresponding "NODE" implemented as a subscriber listening to that Topic? If so, are the components "ROS Topic" and "NODE" already implemented in ROS environment or Turtlebot Package? If so, to which topic(name) is the teleop node publishing and which node is listening to that topic?
2. Or does it directly control the robot movements? If so, what exactly is the information provided to robot for movements? Are there any direct APIs for this?
Can you provide some example source code to control the turtlebot movements?

answered 2015-05-15 06:45:37 -0500

Martin Peris
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Hi Kushal,

You are on the right track, turtlebot_teleop is a ROS package that contains a launch file called keyboard_teleop.launch. Said launch file invokes a ROS node called turtlebot_teleop_keyboard that takes the input from the keyboard and outputs geometry/Twist messages to the topic cmd_vel_mux/input/teleop. Those Twist messages contain the linear and angular speed that the robot should follow. Then there is another node that subscribes to the same topic and actually moves the robot. The listening node is actually a nodelet that depends on the underlying hardware of your turtlebot.
I can not think of a simple example right now, but you can check out the navigation stack

I hope this helps

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Hi Martin, Thank you very much for the response. Your answer provides the information required and will be helpful in progressing further. Thanks a lot.

Kushal ( 2015-05-15 07:44:55 -0500 )edit

Dear Martin, Thanks!, even I was looking for these answers. I just started to learn ROS last week. I have questions: cmd_vel_mux a default topic available ? what is name of listening nodelet, which actually moves the robot, is available by default in Turtle-Bot environment? or need to implement?

mahantesh_kothiwale ( 2015-05-18 07:06:57 -0500 )edit

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