ROS专题----机器人模型urdf简明笔记

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----ROS机器人模型urdf简明笔记----

ROS库--URDF

使用URDF从头开始构建可视机器人模型
了解如何构建一个可以在Rviz中查看的机器人的视觉模型
使用URDF构建可移动机器人模型
了解如何在URDF中定义活动关节
向URDF模型添加物理和冲突属性
了解如何向链接添加碰撞和惯性属性，以及如何为关节添加关节动力学。
使用Xacro清理URDF文件
学习一些技巧，以减少使用Xacro URDF文件中的代码量

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全部源码：http://download.csdn.net/detail/zhangrelay/9775629

1 简单的几何形状

这里包括形状，大小，位置，角度和材质等。以下面代码为例，简单介绍一下：

<?xml version="1.0"?><robot name="visual">  <material name="red">    <color rgba="0.8 0 0 1"/>  </material>    <material name="green">    <color rgba="0 0.8 0 1"/>  </material>  <material name="blue">    <color rgba="0 0 0.8 1"/>  </material>  <material name="black">    <color rgba="0 0 0 1"/>  </material>  <material name="white">    <color rgba="1 1 1 1"/>  </material>  <link name="base_link">    <visual>      <geometry>        <cylinder length="0.6" radius="0.2"/>      </geometry>      <material name="red"/>    </visual>  </link>  <link name="right_leg">    <visual>      <geometry>        <box size="0.6 .1 .2"/>      </geometry>      <origin rpy="0 1.57075 0" xyz="0 0 -0.3"/>      <material name="blue"/>    </visual>  </link>  <joint name="base_to_right_leg" type="fixed">    <parent link="base_link"/>    <child link="right_leg"/>    <origin xyz="0 -0.22 .25"/>  </joint>  <link name="right_base">    <visual>      <geometry>        <box size="0.4 .1 .1"/>      </geometry>      <material name="white"/>    </visual>  </link>  <joint name="right_base_joint" type="fixed">    <parent link="right_leg"/>    <child link="right_base"/>    <origin xyz="0 0 -0.6"/>  </joint>  <link name="right_front_wheel">    <visual>      <origin rpy="1.57075 0 0" xyz="0 0 0"/>      <geometry>        <cylinder length="0.1" radius="0.035"/>      </geometry>      <material name="black"/>      <origin rpy="0 0 0" xyz="0 0 0"/>    </visual>  </link>  <joint name="right_front_wheel_joint" type="fixed">    <axis rpy="0 0 0" xyz="0 1 0"/>    <parent link="right_base"/>    <child link="right_front_wheel"/>    <origin rpy="0 0 0" xyz="0.133333333333 0 -0.085"/>  </joint>...............  <link name="head">    <visual>      <geometry>        <sphere radius="0.2"/>      </geometry>      <material name="white"/>    </visual>  </link>  <joint name="head_swivel" type="fixed">    <parent link="base_link"/>    <child link="head"/>    <origin xyz="0 0 0.3"/>  </joint>  <link name="box">    <visual>      <geometry>        <box size=".08 .08 .08"/>      </geometry>      <material name="green"/>    </visual>  </link>  <joint name="tobox" type="fixed">    <parent link="head"/>    <child link="box"/>    <origin xyz="0.1814 0 0.1414"/>  </joint></robot>

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其中，geometry中包含形状和大小，如cylinder box，大小依据形状不同采用不同表示，如length radius size等；

原点是origin；相对于该点的位置和角度分别用xyz rpy表示；parent link是父节点，child link是子节点。fixed frame固定坐标；

当然，还有颜色等其他配置属性。

使用下面命令查看效果，注意model路径：

roslaunch urdf_tutorial display.launch model:=/home/relaybot/ROS_tutorial/src/urdf_tutorial-kinetic/urdf/05-visual.urdf

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2 由静到动让模型运动起来

这里只需要注意一个要点，就是关节joint，上节一般是fixed，这里可以有continuous，revolute，prismatic。

还需要补充的是robot_state_publisher和joint_state_publisher。分别如下图所示：

运行下面命令，注意模型路径：

roslaunch urdf_tutorial display.launch model:=/home/relaybot/ROS_tutorial/src/urdf_tutorial-kinetic/urdf/06-flexible.urdf gui:=True

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3 添加物理和碰撞属性

需要注意亮点即可，碰撞collision，物理inertial。

  <link name="base_link">    <visual>      <geometry>        <cylinder length="0.6" radius="0.2"/>      </geometry>      <material name="blue"/>    </visual>    <collision>      <geometry>        <cylinder length="0.6" radius="0.2"/>      </geometry>    </collision>    <inertial>      <mass value="10"/>      <inertia ixx="1.0" ixy="0.0" ixz="0.0" iyy="1.0" iyz="0.0" izz="1.0"/>    </inertial>  </link>

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roslaunch urdf_tutorial display.launch model:=/home/relaybot/ROS_tutorial/src/urdf_tutorial-kinetic/urdf/07-physics.urdf

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4 使用xacro简化urdf文件

这里给出两个参考网址：xacro和在urdf中使用xacro。

roslaunch urdf_tutorial display.launch model:=/home/relaybot/ROS_tutorial/src/urdf_tutorial-kinetic/urdf/08-macroed.urdf.xacro

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5 在Gazebo中使用urdf

参考网址：http://gazebosim.org/tutorials?tut=ros_urdf

完成配置后，启动命令：

roslaunch urdf_tutorial gazebo.launch

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6 rviz和Gazebo中实现同步控制

运行下面命令：

roslaunch urdf_tutorial control.launch

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附录：

TF：

Graph：

display.launch

<launch>  <arg name="model" default="$(find urdf_tutorial)/urdf/r2d2.xacro"/>  <arg name="gui" default="true" />  <arg name="rvizconfig" default="$(find urdf_tutorial)/rviz/urdf.rviz" />  <param name="robot_description" command="$(find xacro)/xacro.py $(arg model)" />  <param name="use_gui" value="$(arg gui)"/>  <node name="joint_state_publisher" pkg="joint_state_publisher" type="joint_state_publisher" />  <node name="robot_state_publisher" pkg="robot_state_publisher" type="state_publisher" />  <node name="rviz" pkg="rviz" type="rviz" args="-d $(arg rvizconfig)" required="true" /></launch>

gazebo.launch

<launch>  <!-- these are the arguments you can pass this launch file, for example paused:=true -->  <arg name="paused" default="false"/>  <arg name="use_sim_time" default="true"/>  <arg name="gui" default="true"/>  <arg name="headless" default="false"/>  <arg name="debug" default="false"/>  <arg name="model" default="$(find urdf_tutorial)/urdf/r2d2.xacro"/>  <!-- We resume the logic in empty_world.launch, changing only the name of the world to be launched -->  <include file="$(find gazebo_ros)/launch/empty_world.launch">    <arg name="debug" value="$(arg debug)" />    <arg name="gui" value="$(arg gui)" />    <arg name="paused" value="$(arg paused)"/>    <arg name="use_sim_time" value="$(arg use_sim_time)"/>    <arg name="headless" value="$(arg headless)"/>  </include>  <param name="robot_description" command="$(find xacro)/xacro.py $(arg model)" />  <!-- push robot_description to factory and spawn robot in gazebo -->  <node name="urdf_spawner" pkg="gazebo_ros" type="spawn_model"        args="-z 1.0 -unpause -urdf -model robot -param robot_description" respawn="false" output="screen" />  <node pkg="robot_state_publisher" type="robot_state_publisher"  name="robot_state_publisher">    <param name="publish_frequency" type="double" value="30.0" />  </node></launch>

control.launch

<launch>  <arg name="model" default="$(find urdf_tutorial)/urdf/r2d2.xacro"/>  <arg name="rvizconfig" default="$(find urdf_tutorial)/urdf.rviz" />  <include file="$(find urdf_tutorial)/launch/gazebo.launch">    <arg name="model" value="$(arg model)" />  </include>  <node name="rviz" pkg="rviz" type="rviz" args="-d $(arg rvizconfig)" />  <!-- This param file is where any environment-agnostic (live or simulation)  configuration should be loaded, including controllers -->  <rosparam command="load" file="$(find urdf_tutorial)/config/control.yaml" />  <!-- This node loads the two controllers into a controller manager (real or simulated). The  controllers are defined in config/control.yaml -->  <node name="r2d2_controller_spawner" pkg="controller_manager" type="spawner"    args="r2d2_joint_state_controller          r2d2_diff_drive_controller          r2d2_head_controller          r2d2_gripper_controller          --shutdown-timeout 3"/>  <node name="rqt_robot_steering" pkg="rqt_robot_steering" type="rqt_robot_steering">    <param name="default_topic" value="/r2d2_diff_drive_controller/cmd_vel"/>  </node></launch>

r2d2.xacro

<?xml version="1.0"?><robot name="r2d2" xmlns:xacro="http://ros.org/wiki/xacro">  <xacro:property name="width" value=".2" />  <xacro:property name="leglen" value=".6" />  <xacro:property name="polelen" value=".2" />  <xacro:property name="bodylen" value=".6" />  <xacro:property name="baselen" value=".4" />  <xacro:property name="wheeldiam" value=".07" />  <xacro:property name="pi" value="3.1415" />  <material name="red">    <color rgba="0.8 0 0 1"/>  </material>    <material name="green">    <color rgba="0 0.8 0 1"/>  </material>  <material name="blue">    <color rgba="0 0 0.8 1"/>  </material>  <material name="black">    <color rgba="0 0 0 1"/>  </material>  <material name="white">    <color rgba="1 1 1 1"/>  </material>  <xacro:macro name="default_inertial" params="mass">    <inertial>      <mass value="${mass}" />      <inertia ixx="1.0" ixy="0.0" ixz="0.0" iyy="1.0" iyz="0.0" izz="1.0" />    </inertial>  </xacro:macro>  <link name="base_link">    <visual>      <geometry>        <cylinder radius="${width}" length="${bodylen}"/>      </geometry>      <material name="red"/>    </visual>    <collision>      <geometry>        <cylinder radius="${width}" length="${bodylen}"/>      </geometry>    </collision>    <xacro:default_inertial mass="10"/>  </link>    <!-- This block provides the simulator (Gazebo) with information on a few additional    physical properties. See http://gazebosim.org/tutorials/?tut=ros_urdf for more-->    <gazebo reference="base_link">      <material>Gazebo/Red</material>    </gazebo>  <xacro:macro name="wheel" params="prefix suffix reflect">    <link name="${prefix}_${suffix}_wheel">      <visual>        <origin xyz="0 0 0" rpy="${pi/2} 0 0" />        <geometry>          <cylinder radius="${wheeldiam/2}" length="0.1"/>        </geometry>        <material name="black"/>        <origin xyz="0 0 0" rpy="0 0 0" />      </visual>      <collision>        <origin xyz="0 0 0" rpy="${pi/2} 0 0" />        <geometry>          <cylinder radius="${wheeldiam/2}" length="0.1"/>        </geometry>        <origin xyz="0 0 0" rpy="0 0 0" />      </collision>      <xacro:default_inertial mass="1"/>    </link>    <joint name="${prefix}_${suffix}_wheel_joint" type="continuous">      <axis xyz="0 1 0" rpy="0 0 0" />      <parent link="${prefix}_base"/>      <child link="${prefix}_${suffix}_wheel"/>      <origin xyz="${baselen*reflect/3} 0 -${wheeldiam/2+.05}" rpy="0 0 0"/>    </joint>    <!-- This block provides the simulator (Gazebo) with information on a few additional    physical properties. See http://gazebosim.org/tutorials/?tut=ros_urdf for more-->    <gazebo reference="${prefix}_${suffix}_wheel">      <mu1 value="200.0"/>      <mu2 value="100.0"/>      <kp value="10000000.0" />      <kd value="1.0" />      <material>Gazebo/Black</material>    </gazebo>    <!-- This block connects the wheel joint to an actuator (motor), which informs both    simulation and visualization of the robot -->    <transmission name="${prefix}_${suffix}_wheel_trans" type="SimpleTransmission">      <type>transmission_interface/SimpleTransmission</type>      <actuator name="${prefix}_${suffix}_wheel_motor">        <mechanicalReduction>1</mechanicalReduction>      </actuator>      <joint name="${prefix}_${suffix}_wheel_joint">        <hardwareInterface>VelocityJointInterface</hardwareInterface>      </joint>    </transmission>  </xacro:macro>  <xacro:macro name="leg" params="prefix reflect">    <link name="${prefix}_leg">      <visual>        <geometry>          <box size="${leglen} .1 .2"/>        </geometry>        <origin xyz="0 0 -${leglen/2}" rpy="0 ${pi/2} 0"/>        <material name="blue"/>      </visual>      <collision>        <geometry>          <box size="${leglen} .1 .2"/>        </geometry>        <origin xyz="0 0 -${leglen/2}" rpy="0 ${pi/2} 0"/>      </collision>      <xacro:default_inertial mass="10"/>    </link>    <!-- This block provides the simulator (Gazebo) with information on a few additional    physical properties. See http://gazebosim.org/tutorials/?tut=ros_urdf for more-->    <gazebo reference="${prefix}_leg">      <material>Gazebo/Blue</material>    </gazebo>    <joint name="base_to_${prefix}_leg" type="fixed">      <parent link="base_link"/>      <child link="${prefix}_leg"/>      <origin xyz="0 ${reflect*(width+.02)} .25" />    </joint>    <link name="${prefix}_base">      <visual>        <geometry>          <box size="${baselen} .1 .1"/>        </geometry>        <material name="white"/>      </visual>      <collision>        <geometry>          <box size="${baselen} .1 .1"/>        </geometry>      </collision>      <xacro:default_inertial mass="10"/>    </link>    <joint name="${prefix}_base_joint" type="fixed">      <parent link="${prefix}_leg"/>      <child link="${prefix}_base"/>      <origin xyz="0 0 ${-leglen}" />    </joint>    <xacro:wheel prefix="${prefix}" suffix="front" reflect="1"/>    <xacro:wheel prefix="${prefix}" suffix="back" reflect="-1"/>  </xacro:macro>  <xacro:leg prefix="right" reflect="-1" />  <xacro:leg prefix="left" reflect="1" />  <joint name="gripper_extension" type="prismatic">    <parent link="base_link"/>    <child link="gripper_pole"/>    <limit effort="1000.0" lower="-${width*2-.02}" upper="0" velocity="0.5"/>    <origin rpy="0 0 0" xyz="${width-.01} 0 .2"/>    <limit effort="30" velocity="0.2"/>    <dynamics damping="0.0" friction="0.0"/>  </joint>  <link name="gripper_pole">    <visual>      <geometry>        <cylinder length="${polelen}" radius=".01"/>      </geometry>      <origin xyz="${polelen/2} 0 0" rpy="0 ${pi/2} 0 "/>    </visual>    <collision>      <geometry>        <cylinder length="${polelen}" radius=".01"/>      </geometry>      <origin xyz="${polelen/2} 0 0" rpy="0 ${pi/2} 0 "/>    </collision>    <xacro:default_inertial mass=".05"/>  </link>  <transmission name="gripper_extension_trans" type="SimpleTransmission">    <type>transmission_interface/SimpleTransmission</type>    <actuator name="gripper_extension_motor">      <mechanicalReduction>1</mechanicalReduction>    </actuator>    <joint name="gripper_extension">      <hardwareInterface>PositionJointInterface</hardwareInterface>    </joint>  </transmission>  <xacro:macro name="gripper" params="prefix reflect">    <joint name="${prefix}_gripper_joint" type="revolute">      <axis xyz="0 0 ${reflect}"/>      <limit effort="1000.0" lower="0.0" upper="0.548" velocity="0.5"/>      <origin rpy="0 0 0" xyz="${polelen} ${reflect*0.01} 0"/>      <parent link="gripper_pole"/>      <child link="${prefix}_gripper"/>      <limit effort="30" velocity="1.0"/>      <dynamics damping="0.0" friction="0.0"/>    </joint>    <link name="${prefix}_gripper">      <visual>        <origin rpy="${(reflect-1)/2*pi} 0 0" xyz="0 0 0"/>        <geometry>          <mesh filename="package://pr2_description/meshes/gripper_v0/l_finger.dae"/>        </geometry>      </visual>      <collision>        <geometry>          <mesh filename="package://pr2_description/meshes/gripper_v0/l_finger.dae"/>        </geometry>        <origin rpy="${(reflect-1)/2*pi} 0 0" xyz="0 0 0"/>      </collision>      <xacro:default_inertial mass=".05"/>    </link>    <transmission name="${prefix}_gripper_trans" type="SimpleTransmission">      <type>transmission_interface/SimpleTransmission</type>      <actuator name="${prefix}_gripper_motor">        <mechanicalReduction>1</mechanicalReduction>      </actuator>      <joint name="${prefix}_gripper_joint">        <hardwareInterface>PositionJointInterface</hardwareInterface>      </joint>    </transmission>    <joint name="${prefix}_tip_joint" type="fixed">      <parent link="${prefix}_gripper"/>      <child link="${prefix}_tip"/>    </joint>    <link name="${prefix}_tip">      <visual>        <origin rpy="${(reflect-1)/2*pi} 0 0" xyz="0.09137 0.00495 0"/>        <geometry>          <mesh filename="package://pr2_description/meshes/gripper_v0/l_finger_tip.dae"/>        </geometry>      </visual>      <collision>        <geometry>          <mesh filename="package://pr2_description/meshes/gripper_v0/l_finger_tip.dae"/>        </geometry>        <origin rpy="${(reflect-1)/2*pi} 0 0" xyz="0.09137 0.00495 0"/>      </collision>      <xacro:default_inertial mass=".05"/>    </link>  </xacro:macro>  <xacro:gripper prefix="left" reflect="1" />  <xacro:gripper prefix="right" reflect="-1" />  <link name="head">    <visual>      <geometry>        <sphere radius="${width}"/>      </geometry>      <material name="green"/>    </visual>    <collision>      <geometry>        <sphere radius="${width}"/>      </geometry>    </collision>    <xacro:default_inertial mass="2"/>  </link>  <joint name="head_swivel" type="continuous">    <parent link="base_link"/>    <child link="head"/>    <axis xyz="0 0 1"/>    <origin xyz="0 0 ${bodylen/2}"/>    <limit effort="30" velocity="1.0"/>    <dynamics damping="0.0" friction="0.0"/>  </joint>    <!-- This block provides the simulator (Gazebo) with information on a few additional    physical properties. See http://gazebosim.org/tutorials/?tut=ros_urdf for more-->    <gazebo reference="head">      <material>Gazebo/Orange</material>    </gazebo>  <!-- This block connects the head_swivel joint to an actuator (motor), which informs both  simulation and visualization of the robot -->  <transmission name="head_swivel_trans" type="SimpleTransmission">    <type>transmission_interface/SimpleTransmission</type>    <actuator name="$head_swivel_motor">      <mechanicalReduction>1</mechanicalReduction>    </actuator>    <joint name="head_swivel">      <hardwareInterface>PositionJointInterface</hardwareInterface>    </joint>  </transmission>  <link name="box">    <visual>      <geometry>        <box size=".08 .08 .08"/>      </geometry>      <material name="blue"/>      <origin xyz="-0.04 0 0"/>    </visual>    <collision>      <geometry>        <box size=".08 .08 .08"/>      </geometry>    </collision>    <xacro:default_inertial mass="1"/>  </link>  <joint name="tobox" type="fixed">    <parent link="head"/>    <child link="box"/>    <origin xyz="${.707*width+0.04} 0 ${.707*width}"/>  </joint>  <!-- Gazebo plugin for ROS Control -->  <gazebo>    <plugin name="gazebo_ros_control" filename="libgazebo_ros_control.so">      <robotNamespace>/</robotNamespace>    </plugin>  </gazebo></robot>

补充链接与资料：

1urdf http://wiki.ros.org/urdf

2xacro http://wiki.ros.org/xacro

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