使用urdf语言编写差速机器人模型

以下是一个差速机器人的urdf模型例子：

<?xml version="1.0"?>
<robot name="diff_robot">
  <link name="base_link">
    <visual>
      <geometry>
        <box size="0.5 0.5 0.2" />
      </geometry>
      <material name="silver">
        <color rgba="0.75 0.75 0.75 1" />
      </material>
    </visual>
  </link>

  <joint name="left_wheel_joint" type="continuous">
    <parent link="base_link" />
    <child link="left_wheel_link" />
    <origin xyz="0.25 -0.25 0" rpy="0 0 0" />
    <axis xyz="0 0 1" />
  </joint>

  <link name="left_wheel_link">
    <visual>
      <geometry>
        <cylinder length="0.05" radius="0.15" />
      </geometry>
      <material name="black">
        <color rgba="0 0 0 1" />
      </material>
    </visual>
    <collision>
      <geometry>
        <cylinder length="0.05" radius="0.15" />
      </geometry>
    </collision>
    <inertial>
      <mass value="0.1" />
      <inertia ixx="0.0001" ixy="0" ixz="0" iyy="0.0001" iyz="0" izz="0.0001" />
    </inertial>
  </link>

  <joint name="right_wheel_joint" type="continuous">
    <parent link="base_link" />
    <child link="right_wheel_link" />
    <origin xyz="0.25 0.25 0" rpy="0 0 0" />
    <axis xyz="0 0 1" />
  </joint>

  <link name="right_wheel_link">
    <visual>
      <geometry>
        <cylinder length="0.05" radius="0.15" />
      </geometry>
      <material name="black">
        <color rgba="0 0 0 1" />
      </material>
    </visual>
    <collision>
      <geometry>
        <cylinder length="0.05" radius="0.15" />
      </geometry>
    </collision>
    <inertial>
      <mass value="0.1" />
      <inertia ixx="0.0001" ixy="0" ixz="0" iyy="0.0001" iyz="0" izz="0.0001" />
    </inertial>
  </link>

  <transmission name="left_wheel_transmission">
    <type>transmission_interface/SimpleTransmission</type>
    <joint name="left_wheel_joint">
      <hardwareInterface>hardware_interface/VelocityJointInterface</hardwareInterface>
    </joint>
    <actuator name="left_wheel_motor">
      <hardwareInterface>hardware_interface/EffortJointInterface</hardwareInterface>
      <mechanicalReduction>1</mechanicalReduction>
    </actuator>
  </transmission>

  <transmission name="right_wheel_transmission">
    <type>transmission_interface/SimpleTransmission</type>
    <joint name="right_wheel_joint">
      <hardwareInterface>hardware_interface/VelocityJointInterface</hardwareInterface>
    </joint>
    <actuator name="right_wheel_motor">
      <hardwareInterface>hardware_interface/EffortJointInterface</hardwareInterface>
      <mechanicalReduction>1</mechanicalReduction>
    </actuator>
  </transmission>

  <gazebo reference="base_link">
    <material>Gazebo/Black</material>
    <mu1>1000</mu1>
    <mu2>1000</mu2>
    <kp>1000000.0</kp>
    <kd>100.0</kd>
    <maxVel>100.0</maxVel>
    <minDepth>0.001</minDepth>
    <maxContacts>20</maxContacts>
  </gazebo>
</robot>

其中， `<link>` 标签定义了机器人的每个链接， `<joint>` 标签定义了链接之间的关节， `<transmission>` 标签定义了驱动链接的传动。此外， `<gazebo>` 标签定义了机器人在Gazebo仿真环境中的物理属性。