Minor update to ros2 control subsection

Author: TheNoobInventor

README.md

@@ -689,6 +689,9 @@ A system component has reading and writing capabilities, these are expressed as
   </joint>
 </ros2_control>
 ```
+
+A similar system hardware component is configured for Gazebo Fortress in this [URDF](./lidarbot_gz/urdf/lidarbot_gz.urdf.xacro) file.
+
 #### Sensor
 
 A sensor provides information about changes to a physical phenomenon it is observing. A sensor component has only reading capabilities and is related to a joint or a link in the URDF file. This component type can be configured as an externally connected sensor, with its own `<ros2_control>` tags, or as an integrated sensor embedded in system component `<ros2_control>` tags. The MPU6050 module is configured as an externally connected sensor component and is associated with a fixed link named `imu_link`. This configuration is shown in the code snippet below which is available in the MPU6050 section of this [xacro file](./lidarbot_description/urdf/ros2_control.xacro).
@@ -715,6 +718,8 @@ A sensor provides information about changes to a physical phenomenon it is obser
 </ros2_control>
 ```
 
+However, a standalone [IMU sensor plugin](https://gazebosim.org/docs/fortress/sensors/#imu-sensor) was used to simulate an IMU sensor in Gazebo Fortress.
+
 #### Actuator
 
 This component type only has 1 DOF. Some examples of these include motors and valves. Actuator components are related to a single joint and have both reading and writing capabilities, however, obtaining state feedback is not mandatory if is inaccessible; for instance, controlling a DC motor that has no encoders.
@@ -879,6 +884,7 @@ ros2 launch lidarbot_bringup lidarbot_bringup_launch.py
 
 ### Robot localization
 
+
 TODO:
 
 ekf.yaml