Rostopic info /cmd_vel gives an error

Course Support ROS Basics In 5 Days (Python)
1

When I run rostopic info /cmd_vel the shellbash throws the following error:
ERROR: Unknown topic /cmd_vel
I’m trying to make the exercise 3.1 but I’m stock there.
Thanks.

2

To get the info about a topic, we need to check if the topic is used by a particular robot. Enter following command and see if the topic is used or not
cmd → rostopic list | grep “/cmd_vel”

If yes then we can troubleshoot more. If no - then you found your problem

3

While @krunalna is right, the /cmd_vel topic should be available in this unit. Here’s what I got:

user:~$ rostopic info /cmd_vel
Type: geometry_msgs/Twist

Publishers: None

Subscribers:
 * /gazebo (http://1_simulation:41025/)

Maybe you have modified the system in some way? In any case the system should reset to its default state when you come back. Please let us know if you still have this problem then.

4

Thanks for your answers, you where right @bayodesegun once I’ve come back to the project it is working fine.

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