ddrobot2.urdf

<?xml version='1.0'?>
<robot name="dd_robot">

  <!-- Base Link -->
  <link name="base_link">
    <visual>
      <origin xyz="0 0 0" rpy="0 0 0" />
      <geometry>
          <box size="0.5 0.5 0.25"/>
      </geometry>
    </visual>
  </link>

  <!-- Right Wheel -->
  <link name="right_wheel">
    <visual>
      <origin xyz="0 0 0" rpy="1.570795 0 0" />
      <geometry>
          <cylinder length="0.1" radius="0.2" />
      </geometry>
    </visual>
  </link>
  <joint name="joint_right_wheel" type="continuous">
    <parent link="base_link"/>
    <child link="right_wheel"/>
    <origin xyz="0 -0.30 0" rpy="0 0 0" /> 
    <axis xyz="0 1 0" />
  </joint>

  <!-- Left Wheel -->
  <link name="left_wheel">
    <visual>
      <origin xyz="0 0 0" rpy="1.570795 0 0" />
      <geometry>
          <cylinder length="0.1" radius="0.2" />
      </geometry>
    </visual>
  </link>
  <joint name="joint_left_wheel" type="continuous">
    <parent link="base_link"/>
    <child link="left_wheel"/>
    <origin xyz="0 0.30 0" rpy="0 0 0" /> 
    <axis xyz="0 1 0" />
  </joint>

</robot>