ROS问题：no transform from [left_back_wheel] to [base_link]_Linux系统教程

软件环境：Ubuntu 16.04

ROS kinetic

问题发现：

使用URDF创建机器人3D仿真模型

地址：http://www.linuxdiyf.com/linux/23990.html

在URDF文件中构建机器人模型，并通过*.launch文件启动RViz观察构建的URDF文件，能启动Rviz但发现有如下错误提示：

Traceback (most recent call last):

File "/opt/ros/kinetic/lib/joint_state_publisher/joint_state_publisher", line 361, in <module>

jsp = JointStatePublisher()

File "/opt/ros/kinetic/lib/joint_state_publisher/joint_state_publisher", line 41, in __init__

robot = xml.dom.minidom.parseString(description).getElementsByTagName('robot')[0]

File "/usr/lib/python2.7/xml/dom/minidom.py", line 1928, in parseString

return expatbuilder.parseString(string)

File "/usr/lib/python2.7/xml/dom/expatbuilder.py", line 940, in parseString

return builder.parseString(string)

File "/usr/lib/python2.7/xml/dom/expatbuilder.py", line 223, in parseString

parser.Parse(string, True)

xml.parsers.expat.ExpatError: XML or text declaration not at start of entity: line 1, column 1

[joint_state_publisher-1] process has died [pid 9426, exit code 1, cmd /opt/ros/kinetic/lib/joint_state_publisher/

joint_state_publisher __name:=joint_state_publisher __log:=/home/mingde-yao/.ros/log/8db3b6bc-74da-11e6-9418-000c297f6d5a/

joint_state_publisher-1.log].

log file: /home/mingde-yao/.ros/log/8db3b6bc-74da-11e6-9418-000c297f6d5a/joint_state_publisher-1*.log

在Rviz中是这个样子：

使用下面指令:

check_urdf *.urdf

查看urdf文件没有问题。

尝试1：

搜索发现 hitgavin网友也有类似的问题，但我进行如下操作后：

sudo apt-get install unicode

发现问题并没有得到解决。

尝试2：hitgavin网友提到了这篇文章（http://www.linuxdiyf.com/linux/23992.html）

根据回答如下：

Your example works fine for me, except it doesn't like extra spaces before the

<?xml version="1.0"?>

line, but I assume that's just formatting for this page.

遂检查自己的URDF文件，问题得到解决！

对于初学者来说，写东西的时候一定要注意格式！

ROS问题：no transform from [left_back_wheel] to [base_link]