models/chair/chair.urdf

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

  <!-- Base link at the top of the front right leg -->
  <link name="chair_link">
    <visual>
      <geometry>
        <sphere radius="0.001"/>
      </geometry>
      <origin xyz="0 0 0" rpy="0 0 0"/>
      <material name="invisible">
        <color rgba="0 0 0 0"/>
      </material>
    </visual>
    <collision name="chair">
      <geometry>
        <sphere radius="0.001"/>
      </geometry>
      <origin xyz="0 0 0" rpy="0 0 0"/>
    </collision>
    <inertial>
      <mass value="0.001"/>
      <inertia ixx="0.000001" ixy="0" ixz="0" iyy="0.000001" iyz="0" izz="0.000001"/>
    </inertial>
  </link>

  <!-- Base link at the top of the front right leg -->
  <link name="base">
    <visual>
      <geometry>
        <sphere radius="0.001"/>
      </geometry>
      <origin xyz="0 0 0" rpy="0 0 0"/>
      <material name="invisible">
        <color rgba="0 0 0 0"/>
      </material>
    </visual>
    <inertial>
      <mass value="0.001"/>
      <inertia ixx="0.000001" ixy="0" ixz="0" iyy="0.000001" iyz="0" izz="0.000001"/>
    </inertial>
  </link>

  <!-- Seat -->
  <link name="seat">
    <visual>
      <geometry>
        <box size="0.36 0.39 0.02"/>
      </geometry>
      <origin xyz="0 0 0" rpy="0 0 0"/>
      <material name="wood">
        <color rgba="0.6 0.4 0.2 1.0"/>
      </material>
    </visual>
    <collision>
      <geometry>
        <box size="0.36 0.39 0.02"/>
      </geometry>
      <origin xyz="0 0 0" rpy="0 0 0"/>
    </collision>
    <inertial>
      <mass value="1.0"/>
      <inertia ixx="0.012" ixy="0" ixz="0" iyy="0.01" iyz="0" izz="0.02"/>
    </inertial>
  </link>

  <!-- Front left leg -->
  <link name="front_left_leg">
    <visual>
      <geometry>
        <cylinder radius="0.02" length="0.44"/>
      </geometry>
      <origin xyz="0 0 0" rpy="0 0 0"/>
      <material name="wood">
        <color rgba="0.6 0.4 0.2 1.0"/>
      </material>
    </visual>
    <collision>
      <geometry>
        <cylinder radius="0.02" length="0.44"/>
      </geometry>
      <origin xyz="0 0 0" rpy="0 0 0"/>
    </collision>
    <inertial>
      <mass value="0.01"/>
      <inertia ixx="0.001" ixy="0" ixz="0" iyy="0.001" iyz="0" izz="0.0001"/>
    </inertial>
  </link>

  <!-- Front right leg -->
  <link name="front_right_leg">
    <visual>
      <geometry>
        <cylinder radius="0.02" length="0.44"/>
      </geometry>
      <origin xyz="0 0 0" rpy="0 0 0"/>
      <material name="wood">
        <color rgba="0.6 0.4 0.2 1.0"/>
      </material>
    </visual>
    <collision>
      <geometry>
        <cylinder radius="0.02" length="0.44"/>
      </geometry>
      <origin xyz="0 0 0" rpy="0 0 0"/>
    </collision>
    <inertial>
      <mass value="0.01"/>
      <inertia ixx="0.001" ixy="0" ixz="0" iyy="0.001" iyz="0" izz="0.0001"/>
    </inertial>
  </link>

  <!-- Back left leg -->
  <link name="back_left_leg">
    <visual>
      <geometry>
        <cylinder radius="0.02" length="0.44"/>
      </geometry>
      <origin xyz="0 0 0" rpy="0 0 0"/>
      <material name="wood">
        <color rgba="0.6 0.4 0.2 1.0"/>
      </material>
    </visual>
    <collision>
      <geometry>
        <cylinder radius="0.02" length="0.44"/>
      </geometry>
      <origin xyz="0 0 0" rpy="0 0 0"/>
    </collision>
    <inertial>
      <mass value="0.01"/>
      <inertia ixx="0.001" ixy="0" ixz="0" iyy="0.001" iyz="0" izz="0.0001"/>
    </inertial>
  </link>

  <!-- Back right leg -->
  <link name="back_right_leg">
    <visual>
      <geometry>
        <cylinder radius="0.02" length="0.44"/>
      </geometry>
      <origin xyz="0 0 0" rpy="0 0 0"/>
      <material name="wood">
        <color rgba="0.6 0.4 0.2 1.0"/>
      </material>
    </visual>
    <collision>
      <geometry>
        <cylinder radius="0.02" length="0.44"/>
      </geometry>
      <origin xyz="0 0 0" rpy="0 0 0"/>
    </collision>
    <inertial>
      <mass value="0.01"/>
      <inertia ixx="0.001" ixy="0" ixz="0" iyy="0.001" iyz="0" izz="0.0001"/>
    </inertial>
  </link>

  <!-- Backrest (tilted back support) -->
  <link name="backrest">
    <visual>
      <geometry>
        <box size="0.36 0.015 0.41"/>
      </geometry>
      <origin xyz="0 0 0" rpy="0 0 0"/>
      <material name="wood">
        <color rgba="0.6 0.4 0.2 1.0"/>
      </material>
    </visual>
    <collision>
      <geometry>
        <box size="0.36 0.015 0.41"/>
      </geometry>
      <origin xyz="0 0 0" rpy="0 0 0"/>
    </collision>
    <inertial>
      <mass value=".5"/>
      <inertia ixx="0.012" ixy="0" ixz="0" iyy="0.02" iyz="0" izz="0.01"/>
    </inertial>
  </link>

  <!-- Joint connecting base_link to seat -->

  <joint name="baselink_to_base" type="fixed">
    <parent link="chair_link"/>
    <child link="base"/>
    <origin xyz="0 0 0" rpy="0 0 0"/>
  </joint>

  <joint name="base_to_seat" type="fixed">
    <parent link="base"/>
    <child link="seat"/>
    <origin xyz="0.16 -0.18 0." rpy="0 0 0"/>
  </joint>

  <!-- Joint connecting front left leg to seat -->
  <joint name="seat_to_front_left_leg" type="fixed">
    <parent link="seat"/>
    <child link="front_left_leg"/>
    <origin xyz="0.15 0.15 -0.23" rpy="0 0 0"/>
  </joint>

  <!-- Joint connecting front right leg to seat -->
  <joint name="seat_to_front_right_leg" type="fixed">
    <parent link="seat"/>
    <child link="front_right_leg"/>
    <origin xyz="0.15 -0.15 -0.23" rpy="0 0 0"/>
  </joint>

  <!-- Joint connecting back left leg to seat -->
  <joint name="seat_to_back_left_leg" type="fixed">
    <parent link="seat"/>
    <child link="back_left_leg"/>
    <origin xyz="-0.15 0.15 -0.23" rpy="0 0 0"/>
  </joint>

  <!-- Joint connecting back right leg to seat -->
  <joint name="seat_to_back_right_leg" type="fixed">
    <parent link="seat"/>
    <child link="back_right_leg"/>
    <origin xyz="-0.15 -0.15 -0.23" rpy="0 0 0"/>
  </joint>

  <!-- Joint connecting backrest to seat (tilted back 15 degrees) -->
  <joint name="seat_to_backrest" type="fixed">
    <parent link="seat"/>
    <child link="backrest"/>
    <origin xyz="0 -0.23 0.2" rpy="0.21 0 0"/>
  </joint>

</robot>