gmapping doesn't publish the tf from map->odom

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I recently try to run SLAM gmapping on Husky robot. I build the map successfully but don't get the tf from map to odom. Even the frame "map" doesn't exist.

I have some the questions.

1. whether the time synchronization has an impact on that?

   I have used the command "ntpdate -p robot_ip" to check it. I get the following result.

   server 192.168.5.112, stratum 0, offset 0.000000, delay 0.00000 8 May 10:23:58 ntpdate[4259]: no server suitable for synchronization found

2. whether rate of publishing tf has an impact on that?

   I tried to change the value of parameter "transform_publish_period" of gmapping so that it is consistent with the rate of others publishing.

All trials don‘t resolve my problem. What’s wrong? Thanks for any advise.