double_differential

double_differential.urdf

<?xml version="1.0"?>
<robot name="tank_double_differential">

  <!-- Materials -->
  <material name="chassis_grey">
    <color rgba="0.5 0.5 0.5 1.0"/>
  </material>
  <material name="main_drive_blue">
    <color rgba="0.1 0.3 0.8 1.0"/>
  </material>
  <material name="steer_drive_red">
    <color rgba="0.8 0.1 0.1 1.0"/>
  </material>
  <material name="track_black">
    <color rgba="0.1 0.1 0.1 1.0"/>
  </material>

  <!-- Dummy Base -->
  <link name="base_link" />

  <link name="fixed_platform_link">
    <visual>
      <origin xyz="0 0.2 0" rpy="1.5708 0 0"/>
      <geometry>
        <cube size="0.1 0.1 0.05" />
      </geometry>
      <material name="chassis_grey" />
    </visual>
  </link>

  <joint name="fixed_platform_joint" type="fixed">
    <parent link="base_link" />
    <child link="fixed_platform_link" />
    <origin xyz="0 0 0" rpy="0 0 0" />
  </joint>

  <!-- ========================================== -->
  <!-- INPUT 1: MAIN DRIVE (Forward/Reverse)      -->
  <!-- ========================================== -->

  <link name="carrier_shaft_link">
    <visual>
      <origin xyz="0 0 0" rpy="1.5708 0 0" />
      <geometry>
        <cylinder radius="0.1" length="0.8" />
      </geometry>
      <material name="main_drive_blue" />
    </visual>
  </link>

  <joint name="main_drive_joint" type="continuous">
    <parent link="base_link" />
    <child link="carrier_shaft_link" />
    <origin xyz="0 0 0" rpy="0 0 0" />
    <axis xyz="0 1 0" />
  </joint>

  <!-- ========================================== -->
  <!-- INPUT 2: STEERING DRIVE (Left/Right)       -->
  <!-- ========================================== -->

  <link name="steer_input_link">
    <visual>
      <origin xyz="0 0 0" rpy="1.5708 0 0" />
      <geometry>
        <cylinder radius="0.08" length="0.2" />
      </geometry>
      <material name="steer_drive_red" />
    </visual>
  </link>

  <joint name="steer_drive_joint" type="continuous">
    <parent link="base_link" />
    <child link="steer_input_link" />
    <origin xyz="-0.3 0 0" rpy="0 0 0" />
    <axis xyz="0 1 0" />
  </joint>

  <!-- ========================================== -->
  <!-- OUTPUTS (Superposition of Main + Steer)    -->
  <!-- ========================================== -->

  <!-- Left Drive Sprocket -->
  <link name="left_sprocket_link">
    <visual>
      <origin xyz="0 0 0" rpy="1.5708 0 0" />
      <geometry>
        <cylinder radius="0.35" length="0.15" />
      </geometry>
      <material name="track_black" />
    </visual>
  </link>

  <joint name="left_mix_joint" type="continuous">
    <parent link="carrier_shaft_link" />
    <child link="left_sprocket_link" />
    <origin xyz="0 0.475 0" rpy="0 0 0" />
    <axis xyz="0 1 0" />
    <mimic joint="steer_drive_joint" multiplier="1.0" />
  </joint>

  <!-- Right Drive Sprocket -->
  <link name="right_sprocket_link">
    <visual>
      <origin xyz="0 0 0" rpy="1.5708 0 0" />
      <geometry>
        <cylinder radius="0.35" length="0.15" />
      </geometry>
      <material name="track_black" />
    </visual>
  </link>

  <joint name="right_mix_joint" type="continuous">
    <parent link="carrier_shaft_link" />
    <child link="right_sprocket_link" />
    <origin xyz="0 -0.475 0" rpy="0 0 0" />
    <axis xyz="0 1 0" />
    <mimic joint="steer_drive_joint" multiplier="-1.0" />
  </joint>

</robot>