初学URDF总结

看图理解很重要！

写URDF分步骤：

打开：http://wiki.ros.org/urdf/Tutorials/Create%20your%20own%20urdf%20file

1，描述最基本的：robot name，link，joint，以及joint的parent和child；

2，添加jiont的origin坐标——平移加旋转：每个link有自己的坐标系，jiont平移坐标为该joint相对于parent  link的坐标，旋转坐标为child  link相对于parent link坐标系的旋转，逆时针为正；

如针对jiont2：<origin xyz="-2 5 0" rpy="0 0 1.57" />    ## rpy="0 0 1.57"表示绕Z轴逆时针旋转90度

3，添加joint的旋转轴axis，单位化的旋转轴向量，相对于child link坐标系的旋转；

如针对jiont1： <axis xyz="-0.707 0.707 0" />    ##单位化的旋转轴向量

解析自己设计的.urdf文件

打开： http://wiki.ros.org/urdf/Tutorials/Parse%20a%20urdf%20file

urdf::Model model;   ## urdf::Model is a class containing robot model data structure.
model.initFile(urdf_file)  ##返回解析成功或失败

纠错：

$ catkin_make
$ .<path>/parser <path>my_robot.urdf
# ./devel/lib/robot_description/parser /src/robot_description/urdf/my_robot.urdf (for example)   ！！！！！这句改为<pre name="code" class="cpp"># ./devel/lib/robot_description/parser  src/robot_description/urdf/my_robot.urdf (for example)

codeapi

The URDF parser API contains the following methods:

• Parse and build tree from XML: urdf::Model::initXml
• Parse and build tree from File: urdf::Model::initFile
• Parse and build tree from String: urdf::Model::initString
• Get Root Link: urdf::Model::getRoot
• Get Link by name urdf::Model::getLink
• Get all Link's urdf::Model::getLinks
• Get Joint by name urdf::Model::getJoint

机器人状态发布器：

链接： http://wiki.ros.org/robot_state_publisher/Tutorials/Using%20the%20robot%20state%20publisher%20on%20your%20own%20robot

robot state publisher以节点方式使用：

如

<launch>
<param name="robot_description" command="cat $(find my_pkg)/my_model.xml" />
<node name="robot_state_publisher" pkg="robot_state_publisher" type="state_publisher" /> 
##robot_state_publisher默认使用robot_description参数
</launch>

或者

<launch>
<param name="pr2_description" command="cat $(find pkg)/model.xml" />
<node pkg="robot_state_publisher" type="robot_state_publisher" name="rob_st_pub" >
<remap from="robot_description" to="pr2_description" />
<remap from="joint_states" to="different_joint_states" />
</node>
</launch>

robot state publisher以库函数使用：

包含头文件

#include <robot_state_publisher/robot_state_publisher.h>

  // publish moving joints
  void publishTransforms(const std::map<std::string, double>& joint_positions,
                         const ros::Time& time);

  // publish fixed joints
  void publishFixedTransforms();

REFERENCE：ROS WIKI