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@@ -21,6 +21,77 @@ The *RRBot* URDF files can be found in the ``description/urdf`` folder.
 
 .. include:: ../../doc/run_from_docker.rst
 
+
+RRBot Architecture Overview
+---------------------------
+
+.. image:: ros2_control_demo_example_1.png
+   :width: 600
+   :align: center
+   :alt: ROS 2 Control Demo Example 1 Architecture Overview
+
+This section provides an overview of how **ROS2 Control** components interact in *Example 1 (RRBot System Position Only)*. It summarizes the relationship between the hardware interface, controllers, and the robot’s URDF.
+
+A custom hardware interface ``RRBotSystemPositionOnlyHardware`` is implemented in:
+``ros2_control_demo_example_1/rrbot_hardware_interface.cpp``
+
+This hardware plugin:
+
+- Inherits from ``hardware_interface::SystemInterface``
+- Defines how to **read joint positions** (from hardware, simulated here)
+- Defines how to **write commands** (set joint positions)
+- Is registered in a ``plugin.xml`` file so the **ResourceManager** can load it
+
+From the UML:
+
+- ``hardware_interface::SystemInterface`` → implemented by the RRBot hardware plugin
+- ``hardware_interface::ResourceManager`` → manages your hardware plugin after loading it
+
+The robot description is defined in:
+``rrbot.urdf.xacro``
+
+The URDF contains:
+
+- Links and joints of the robot
+- A ``<ros2_control>`` tag specifying which hardware plugin to load
+
+When launched, **ros2_control** reads this URDF and knows:
+
+- Which joints exist
+- Which hardware plugin provides those joints
+
+From the UML:
+
+- ``robot_config (URDF)`` → parsed into **``hardware_interface::HardwareInfo``** and passed to **ResourceManager**
+
+The ``controller_manager::ControllerManager`` is the core ROS2 node.
+
+Responsibilities:
+
+- Loads your hardware plugin (via **ResourceManager**)
+- Loads and manages controllers (defined in a YAML config file)
+
+From the UML:
+
+- ``controller_manager::ControllerManager`` → central node
+- Uses ``controllers_config (YAML)`` and ``robot_config (URDF)`` to configure everything
+
+**Forward Command Controller**
+
+- ``forward_position_controller`` (from ``forward_command_controller`` package)
+- Directly forwards position commands to the hardware interface
+
+**Joint State Broadcaster**
+
+- Publishes ``/joint_states``
+- Allows visualization of the robot in RViz
+
+From the UML:
+
+- ``controller_interface::ControllerInterface`` → base class for controllers
+- ``forward_command_controller::ForwardCommandController`` → used in this demo
+- ``joint_state_broadcaster::JointStateBroadcaster`` → publishes joint states
+
 Tutorial steps
 --------------------------
 
@@ -501,3 +572,14 @@ Controllers from this demo
   * ``Joint State Broadcaster`` (`ros2_controllers repository <https://github.com/ros-controls/ros2_controllers/tree/{REPOS_FILE_BRANCH}/joint_state_broadcaster>`__): :ref:`doc <joint_state_broadcaster_userdoc>`
   * ``Forward Command Controller`` (`ros2_controllers repository <https://github.com/ros-controls/ros2_controllers/tree/{REPOS_FILE_BRANCH}/forward_command_controller>`__): :ref:`doc <forward_command_controller_userdoc>`
   * ``Joint Trajectory Controller`` (`ros2_controllers repository <https://github.com/ros-controls/ros2_controllers/tree/{REPOS_FILE_BRANCH}/joint_trajectory_controller>`__): :ref:`doc <joint_trajectory_controller_userdoc>`
+
+
+
+Additional Resources for this demo
+----------------------------------
+* `UML Class Diagram of example_1 <https://github.com/ros-controls/ros2_control_demos/tree/{REPOS_FILE_BRANCH}/example_1/doc/ros2_control_demo_example_1.svg>`__  a visual representation of the RRBot hardware interface architecture.
+
+* `Summary Explanation of example_1 <https://github.com/ros-controls/ros2_control_demos/tree/{REPOS_FILE_BRANCH}/example_1/doc/summary_explanation_example_1.md>`__  a step-by-step explanation of the demo’s architecture and component interaction.
+
+
+