1.解决No link elements found in urdf file问题

2.sart@sart-Lenovo-S41-70:~$ roslaunch smartcar_description smartcar_display.rviz.launch
… logging to /home/sart/.ros/log/0d2e56ee-e5a8-11ea-9feb-54ee75633e82/roslaunch-sart-Lenovo-S41-70-29361.log
Checking log directory for disk usage. This may take awhile.
Press Ctrl-C to interrupt
Done checking log file disk usage. Usage is <1GB.

No such file or directory: /home/sart/catkin_ws/src/smartcar_description/urdf/smartcar.urdf.xacro [Errno 2] No such file or directory: ‘/home/sart/catkin_ws/src/smartcar_description/urdf/smartcar.urdf.xacro’
Invalid tag: Cannot load command parameter [robot_description]: command [/opt/ros/indigo/share/xacro/xacro.py ‘/home/sart/catkin_ws/src/smartcar_description/urdf/smartcar.urdf.xacro’] returned with code [2].

Param xml is
The traceback for the exception was written to the log file
##报错
3.
[ERROR] [1599116079.059180744]: No link elements found in urdf file
[robot_state_publisher-3] process has died [pid 4319, exit code -11, cmd /opt/ros/indigo/lib/robot_state_publisher/state_publisher __name:=robot_state_publisher __log:=/home/sart/.ros/log/55687e3c-edb2-11ea-b3d1-54ee75633e82/robot_state_publisher-3.log].
log file: /home/sart/.ros/log/55687e3c-edb2-11ea-b3d1-54ee75633e82/robot_state_publisher-3*.log

解决：
新建工作空间，直接将该文件夹拷贝到该工作空间下，步骤如下：
sart@sart-Lenovo-S41-70:~$ mkdir test_ws/src -p
sart@sart-Lenovo-S41-70:~$ cd test_ws/src
sart@sart-Lenovo-S41-70:~/test_ws/src$ cd smartcar_description/
sart@sart-Lenovo-S41-70:~/test_ws/src/smartcar_description$ rosmake smartcar_description --pre-clean
sart@sart-Lenovo-S41-70:~/test_ws/src/smartcar_description$ cd …
sart@sart-Lenovo-S41-70:~/test_ws/src$ cd …
sart@sart-Lenovo-S41-70:~/test_ws$ catkin_make
在运行就没问题了