I was following the instruction in this post

https://answers.ros.org/question/4143...

and I was able to launch 3 robots in the environment. the only problem is they can not use the map. I tested the map before using one robot and it worked.

does any one have an idea what could be the problem ??

the warning appears:

[ WARN] [1520822669.083386275, 5.051000000]: Request for map failed; trying again... [ WARN] [1520822669.111106811, 5.078000000]: Timed out waiting for transform from robot2_tf/base_link to map to become available before running costmap, tf error: canTransform: target_frame map does not exist.. canTransform returned after 0.1 timeout was 0.1. [ WARN] [1520822669.115123720, 5.082000000]: Timed out waiting for transform from robot1_tf/base_link to map to become available before running costmap, tf error: canTransform: target_frame map does not exist.. canTransform returned after 0.103 timeout was 0.1. [ WARN] [1520822669.133585376, 5.100000000]: Timed out waiting for transform from robot3_tf/base_link to map to become available before running costmap, tf error: canTransform: target_frame map does not exist.. canTransform returned after 0.103 timeout was 0.1. 

and these are the launch files I am using:

1st: one_robot.launch

2nd: robots.launch

3rd: move_base

4th: robots_nav.launch