cart_pole.sdf

<?xml version="1.0"?>
<sdf version="1.7">
  <model name="CartPole">
    <link name="Cart">
      <inertial>
        <mass>10.0</mass>
        <!-- For this model case, with the cart not having any rotational
             degrees of freedom, the values of the inertia matrix do not
             participate in the model. Therefore we just set them to zero
             (or near to zero since sdformat does not allow exact zeroes
             for inertia values). -->
        <inertia>
          <ixx>1.0e-20</ixx>
          <iyy>1.0e-20</iyy>
          <izz>1.0e-20</izz>
          <ixy>0</ixy>
          <ixz>0</ixz>
          <iyz>0</iyz>
        </inertia>
      </inertial>
      <visual name="cart_visual">
        <geometry>
          <box>
            <size>0.24 0.12 0.12</size>
          </box>
        </geometry>
      </visual>
      <collision name="cart_collision">
        <geometry>
          <box>
            <size>0.24 0.12 0.12</size>
          </box>
        </geometry>
      </collision>

    </link>
    <link name="Pole">
      <!-- The pole is modeled as a point mass at the end of a pole. -->
      <!-- The length of the pole is 0.5 meters. -->
      <pose>0 0 -0.5 0 0 0</pose>
      <inertial>
        <mass>1.0</mass>
        <!-- A point mass has zero rotational inertia.
             We must specify small values since otherwise sdformat throws an
             exception. -->
        <inertia>
          <ixx>1.0e-20</ixx>
          <iyy>1.0e-20</iyy>
          <izz>1.0e-20</izz>
          <ixy>0</ixy>
          <ixz>0</ixz>
          <iyz>0</iyz>
        </inertia>
      </inertial>
      <visual name="pole_point_mass">
        <geometry>
          <sphere>
            <radius>0.05</radius>
          </sphere>
        </geometry>
      </visual>
      <collision name="pole_point_mass_collision">
        <geometry>
          <sphere>
            <radius>0.05</radius>
          </sphere>
        </geometry>
      </collision>

      <visual name="pole_rod">
        <pose>0 0 0.25 0 0 0</pose>
        <geometry>
          <cylinder>
            <radius>0.025</radius>
            <length>0.5</length>
          </cylinder>
        </geometry>
      </visual>
    </link>
    <joint name="CartSlider" type="prismatic">
      <parent>world</parent>
      <child>Cart</child>
      <axis>
        <xyz>1.0 0.0 0.0</xyz>
      </axis>
    </joint>
    <joint name="PolePin" type="revolute">
      <!-- Pose of the joint frame in the pole's frame (located at the point
           mass) -->
      <pose>0 0 0.5 0 0 0</pose>
      <parent>Cart</parent>
      <child>Pole</child>
      <axis>
        <xyz>0.0 -1.0 0.0</xyz>
        <limit>
          <!-- The pole pin joint is not actuated. -->
          <effort>0</effort>
        </limit>
      </axis>
    </joint>
  </model>
</sdf>