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

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.