启动仿真环境及各种节点（amcl,move_base,map_server）后，在rviz中设定机器人的目标位置，后台日志报错
[ INFO] [1571974242.864525935, 40.511000000]: Got new plan
[ERROR] [1571974242.964186066, 40.612000000]: Extrapolation Error: Lookup would require extrapolation into the future. Requested time 40.585000000 but the latest data is at time 40.521000000, when looking up transform from frame [odom] to frame [map]
解决：move_base的包的版本有问题（用的是melodic），用kinetic的版本，重新加到navigation的文件夹下，重新编译即可
下载地址：https://github.com/ros-planning/navigation
问题2：
[WARN]Map update loop missed its desired rate of 10.0000Hz... the loop actually to took 0.1665 seconds
解决：修改move_base.launch文件中的频率，使其低于实际的回环的频率即可，这里改为5Hz就可以了
<node pkg="move_base" type="move_base" respawn="false" name="move_base" output="screen">
<param name="base_local_planner" value="dwa_local_planner/DWAPlannerROS" />
<param name="controller_frequency" value="5.0"/>
<param name="controller_patiente" value="15.0"/>
问题3：
[ WARN] [1571977808.693309245, 5.969000000]: local_costmap: Parameter "plugins" not provided, loading pre-Hydro parameters