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The issue has been fixed, as Geoff said, you need to add the TF prefix to Gazebo. In this case a good explanation of how to do this is given in: https://github.com/open-rmf/free_fleet/issues/60#issuecomment-920665293

The issue has been fixed, as Geoff said, you need to add the TF prefix to Gazebo. In this case a good explanation of how to do this is given in: https://github.com/open-rmf/free_fleet/issues/60#issuecomment-920665293

The issue has been fixed, as Geoff said, you need to add the TF prefix to Gazebo. In this case a good explanation of how to do this is given in: https://github.com/open-rmf/free_fleet/issues/60#issuecomment-920665293

The gazebo xacro file now looks like this:

<?xml version="1.0"?>
<robot name="turtlebot3_waffle_pi_sim" xmlns:xacro="http://ros.org/wiki/xacro">

  <xacro:arg name="laser_visual"  default="false"/>
  <xacro:arg name="camera_visual" default="false"/>
  <xacro:arg name="imu_visual"    default="false"/>

  <gazebo reference="base_link">
    <material>Gazebo/DarkGrey</material>
  </gazebo>

  <gazebo reference="wheel_left_link">
    <mu1>0.1</mu1>
    <mu2>0.1</mu2>
    <kp>500000.0</kp>
    <kd>10.0</kd>
    <minDepth>0.001</minDepth>
    <maxVel>0.1</maxVel>
    <fdir1>1 0 0</fdir1>
    <material>Gazebo/FlatBlack</material>
  </gazebo>

  <gazebo reference="wheel_right_link">
    <mu1>0.1</mu1>
    <mu2>0.1</mu2>
    <kp>500000.0</kp>
    <kd>10.0</kd>
    <minDepth>0.001</minDepth>
    <maxVel>0.1</maxVel>
    <fdir1>1 0 0</fdir1>
    <material>Gazebo/FlatBlack</material>
  </gazebo>

  <gazebo reference="caster_back_right_link">
    <mu1>0.1</mu1>
    <mu2>0.1</mu2>
    <kp>1000000.0</kp>
    <kd>100.0</kd>
    <minDepth>0.001</minDepth>
    <maxVel>1.0</maxVel>
    <material>Gazebo/FlatBlack</material>
  </gazebo>

  <gazebo reference="caster_back_left_link">
    <mu1>0.1</mu1>
    <mu2>0.1</mu2>
    <kp>1000000.0</kp>
    <kd>100.0</kd>
    <minDepth>0.001</minDepth>
    <maxVel>1.0</maxVel>
    <material>Gazebo/FlatBlack</material>
  </gazebo>

  <gazebo reference="imu_link">
    <sensor type="imu" name="imu">
      <always_on>true</always_on>
      <visualize>$(arg imu_visual)</visualize>
    </sensor>
    <material>Gazebo/Grey</material>
  </gazebo>

  <gazebo>
    <plugin name="turtlebot3_waffle_pi_controller" filename="libgazebo_ros_diff_drive.so">
      <commandTopic>cmd_vel</commandTopic>
      <odometryTopic>odom</odometryTopic>
      <odometryFrame>$(arg botname)/odom</odometryFrame>
      <odometrySource>world</odometrySource>
      <publishOdomTF>true</publishOdomTF>
      <robotBaseFrame>$(arg botname)/base_footprint</robotBaseFrame>
      <publishWheelTF>false</publishWheelTF>
      <publishTf>true</publishTf>
      <publishWheelJointState>true</publishWheelJointState>
      <legacyMode>false</legacyMode>
      <updateRate>30</updateRate>
      <leftJoint>wheel_left_joint</leftJoint>
      <rightJoint>wheel_right_joint</rightJoint>
      <wheelSeparation>0.287</wheelSeparation>
      <wheelDiameter>0.066</wheelDiameter>
      <wheelAcceleration>1</wheelAcceleration>
      <wheelTorque>10</wheelTorque>
      <rosDebugLevel>na</rosDebugLevel>
    </plugin>
  </gazebo>

  <gazebo>
    <plugin name="imu_plugin" filename="libgazebo_ros_imu.so">
      <alwaysOn>true</alwaysOn>
      <bodyName>imu_link</bodyName>
      <frameName>imu_link</frameName>
      <topicName>imu</topicName>
      <serviceName>imu_service</serviceName>
      <gaussianNoise>0.0</gaussianNoise>
      <updateRate>0</updateRate>
      <imu>
        <noise>
          <type>gaussian</type>
          <rate>
            <mean>0.0</mean>
            <stddev>2e-4</stddev>
            <bias_mean>0.0000075</bias_mean>
            <bias_stddev>0.0000008</bias_stddev>
          </rate>
          <accel>
            <mean>0.0</mean>
            <stddev>1.7e-2</stddev>
            <bias_mean>0.1</bias_mean>
            <bias_stddev>0.001</bias_stddev>
          </accel>
        </noise>
      </imu>
    </plugin>
  </gazebo>

  <gazebo reference="base_scan">
    <material>Gazebo/FlatBlack</material>
    <sensor type="ray" name="lds_lfcd_sensor">
      <pose>0 0 0 0 0 0</pose>
      <visualize>$(arg laser_visual)</visualize>
      <update_rate>5</update_rate>
      <ray>
        <scan>
          <horizontal>
            <samples>360</samples>
            <resolution>1</resolution>
            <min_angle>0.0</min_angle>
            <max_angle>6.28319</max_angle>
          </horizontal>
        </scan>
        <range>
          <min>0.120</min>
          <max>3.5</max>
          <resolution>0.015</resolution>
        </range>
        <noise>
          <type>gaussian</type>
          <mean>0.0</mean>
          <stddev>0.01</stddev>
        </noise>
      </ray>
      <plugin name="gazebo_ros_lds_lfcd_controller" filename="libgazebo_ros_laser.so">
        <topicName>scan</topicName>
        <frameName>$(arg botname)/base_scan</frameName>
      </plugin>
    </sensor>
  </gazebo>

<!--link : https://www.raspberrypi.org/documentation/hardware/camera/-->
  <gazebo reference="camera_rgb_frame">
    <sensor type="camera" name="Pi Camera">
      <always_on>true</always_on>
      <visualize>$(arg camera_visual)</visualize>
      <camera>
          <horizontal_fov>1.085595</horizontal_fov>
          <image>
              <width>640</width>
              <height>480</height>
              <format>R8G8B8</format>
          </image>
          <clip>
              <near>0.03</near>
              <far>100</far>
          </clip>
      </camera>
      <plugin name="camera_controller" filename="libgazebo_ros_camera.so">
        <alwaysOn>true</alwaysOn>
        <updateRate>30.0</updateRate>
        <cameraName>camera</cameraName>
        <frameName>$(arg botname)/camera_rgb_optical_frame</frameName>
        <imageTopicName>rgb/image_raw</imageTopicName>
        <cameraInfoTopicName>rgb/camera_info</cameraInfoTopicName>
        <hackBaseline>0.07</hackBaseline>
        <distortionK1>0.0</distortionK1>
        <distortionK2>0.0</distortionK2>
        <distortionK3>0.0</distortionK3>
        <distortionT1>0.0</distortionT1>
        <distortionT2>0.0</distortionT2>
      </plugin>
    </sensor>
  </gazebo>

</robot>

and the tf tree looks like this:

image description

Even though this seems to be running well, feedback on other places in the xacro file where TF prefixes should be added would be highly appreciated, and again, thank you to everyone who helped me through this.

The issue has been fixed, as Geoff said, you need to add the TF prefix to Gazebo. In this case a good explanation of how to do this is given in: https://github.com/open-rmf/free_fleet/issues/60#issuecomment-920665293

The gazebo xacro file now looks like this:

<?xml version="1.0"?>
<robot name="turtlebot3_waffle_pi_sim" xmlns:xacro="http://ros.org/wiki/xacro">

  <xacro:arg name="laser_visual"  default="false"/>
  <xacro:arg name="camera_visual" default="false"/>
  <xacro:arg name="imu_visual"    default="false"/>

  <gazebo reference="base_link">
    <material>Gazebo/DarkGrey</material>
  </gazebo>

  <gazebo reference="wheel_left_link">
    <mu1>0.1</mu1>
    <mu2>0.1</mu2>
    <kp>500000.0</kp>
    <kd>10.0</kd>
    <minDepth>0.001</minDepth>
    <maxVel>0.1</maxVel>
    <fdir1>1 0 0</fdir1>
    <material>Gazebo/FlatBlack</material>
  </gazebo>

  <gazebo reference="wheel_right_link">
    <mu1>0.1</mu1>
    <mu2>0.1</mu2>
    <kp>500000.0</kp>
    <kd>10.0</kd>
    <minDepth>0.001</minDepth>
    <maxVel>0.1</maxVel>
    <fdir1>1 0 0</fdir1>
    <material>Gazebo/FlatBlack</material>
  </gazebo>

  <gazebo reference="caster_back_right_link">
    <mu1>0.1</mu1>
    <mu2>0.1</mu2>
    <kp>1000000.0</kp>
    <kd>100.0</kd>
    <minDepth>0.001</minDepth>
    <maxVel>1.0</maxVel>
    <material>Gazebo/FlatBlack</material>
  </gazebo>

  <gazebo reference="caster_back_left_link">
    <mu1>0.1</mu1>
    <mu2>0.1</mu2>
    <kp>1000000.0</kp>
    <kd>100.0</kd>
    <minDepth>0.001</minDepth>
    <maxVel>1.0</maxVel>
    <material>Gazebo/FlatBlack</material>
  </gazebo>

  <gazebo reference="imu_link">
    <sensor type="imu" name="imu">
      <always_on>true</always_on>
      <visualize>$(arg imu_visual)</visualize>
    </sensor>
    <material>Gazebo/Grey</material>
  </gazebo>

  <gazebo>
    <plugin name="turtlebot3_waffle_pi_controller" filename="libgazebo_ros_diff_drive.so">
      <commandTopic>cmd_vel</commandTopic>
      <odometryTopic>odom</odometryTopic>
      <odometryFrame>$(arg botname)/odom</odometryFrame>
      <odometrySource>world</odometrySource>
      <publishOdomTF>true</publishOdomTF>
      <robotBaseFrame>$(arg botname)/base_footprint</robotBaseFrame>
      <publishWheelTF>false</publishWheelTF>
      <publishTf>true</publishTf>
      <publishWheelJointState>true</publishWheelJointState>
      <legacyMode>false</legacyMode>
      <updateRate>30</updateRate>
      <leftJoint>wheel_left_joint</leftJoint>
      <rightJoint>wheel_right_joint</rightJoint>
      <wheelSeparation>0.287</wheelSeparation>
      <wheelDiameter>0.066</wheelDiameter>
      <wheelAcceleration>1</wheelAcceleration>
      <wheelTorque>10</wheelTorque>
      <rosDebugLevel>na</rosDebugLevel>
    </plugin>
  </gazebo>

  <gazebo>
    <plugin name="imu_plugin" filename="libgazebo_ros_imu.so">
      <alwaysOn>true</alwaysOn>
      <bodyName>imu_link</bodyName>
      <frameName>imu_link</frameName>
      <topicName>imu</topicName>
      <serviceName>imu_service</serviceName>
      <gaussianNoise>0.0</gaussianNoise>
      <updateRate>0</updateRate>
      <imu>
        <noise>
          <type>gaussian</type>
          <rate>
            <mean>0.0</mean>
            <stddev>2e-4</stddev>
            <bias_mean>0.0000075</bias_mean>
            <bias_stddev>0.0000008</bias_stddev>
          </rate>
          <accel>
            <mean>0.0</mean>
            <stddev>1.7e-2</stddev>
            <bias_mean>0.1</bias_mean>
            <bias_stddev>0.001</bias_stddev>
          </accel>
        </noise>
      </imu>
    </plugin>
  </gazebo>

  <gazebo reference="base_scan">
    <material>Gazebo/FlatBlack</material>
    <sensor type="ray" name="lds_lfcd_sensor">
      <pose>0 0 0 0 0 0</pose>
      <visualize>$(arg laser_visual)</visualize>
      <update_rate>5</update_rate>
      <ray>
        <scan>
          <horizontal>
            <samples>360</samples>
            <resolution>1</resolution>
            <min_angle>0.0</min_angle>
            <max_angle>6.28319</max_angle>
          </horizontal>
        </scan>
        <range>
          <min>0.120</min>
          <max>3.5</max>
          <resolution>0.015</resolution>
        </range>
        <noise>
          <type>gaussian</type>
          <mean>0.0</mean>
          <stddev>0.01</stddev>
        </noise>
      </ray>
      <plugin name="gazebo_ros_lds_lfcd_controller" filename="libgazebo_ros_laser.so">
        <topicName>scan</topicName>
        <frameName>$(arg botname)/base_scan</frameName>
      </plugin>
    </sensor>
  </gazebo>

<!--link : https://www.raspberrypi.org/documentation/hardware/camera/-->
  <gazebo reference="camera_rgb_frame">
    <sensor type="camera" name="Pi Camera">
      <always_on>true</always_on>
      <visualize>$(arg camera_visual)</visualize>
      <camera>
          <horizontal_fov>1.085595</horizontal_fov>
          <image>
              <width>640</width>
              <height>480</height>
              <format>R8G8B8</format>
          </image>
          <clip>
              <near>0.03</near>
              <far>100</far>
          </clip>
      </camera>
      <plugin name="camera_controller" filename="libgazebo_ros_camera.so">
        <alwaysOn>true</alwaysOn>
        <updateRate>30.0</updateRate>
        <cameraName>camera</cameraName>
        <frameName>$(arg botname)/camera_rgb_optical_frame</frameName>
        <imageTopicName>rgb/image_raw</imageTopicName>
        <cameraInfoTopicName>rgb/camera_info</cameraInfoTopicName>
        <hackBaseline>0.07</hackBaseline>
        <distortionK1>0.0</distortionK1>
        <distortionK2>0.0</distortionK2>
        <distortionK3>0.0</distortionK3>
        <distortionT1>0.0</distortionT1>
        <distortionT2>0.0</distortionT2>
      </plugin>
    </sensor>
  </gazebo>

</robot>

and the tf tree looks like this:

image description

Even though this seems to be running well, feedback on other places in the xacro file where TF prefixes should be added would be highly appreciated, and again, thank you to everyone who helped me through this.

The issue has been fixed, as Geoff said, you need to add the TF prefix to Gazebo. In this case a good explanation of how to do this is given in: https://github.com/open-rmf/free_fleet/issues/60#issuecomment-920665293

The Minor edits had to be done to the launch and urdf xacro files, and the gazebo xacro file now looks like this:

<?xml version="1.0"?>
<robot name="turtlebot3_waffle_pi_sim" xmlns:xacro="http://ros.org/wiki/xacro">

  <xacro:arg name="laser_visual"  default="false"/>
  <xacro:arg name="camera_visual" default="false"/>
  <xacro:arg name="imu_visual"    default="false"/>

  <gazebo reference="base_link">
    <material>Gazebo/DarkGrey</material>
  </gazebo>

  <gazebo reference="wheel_left_link">
    <mu1>0.1</mu1>
    <mu2>0.1</mu2>
    <kp>500000.0</kp>
    <kd>10.0</kd>
    <minDepth>0.001</minDepth>
    <maxVel>0.1</maxVel>
    <fdir1>1 0 0</fdir1>
    <material>Gazebo/FlatBlack</material>
  </gazebo>

  <gazebo reference="wheel_right_link">
    <mu1>0.1</mu1>
    <mu2>0.1</mu2>
    <kp>500000.0</kp>
    <kd>10.0</kd>
    <minDepth>0.001</minDepth>
    <maxVel>0.1</maxVel>
    <fdir1>1 0 0</fdir1>
    <material>Gazebo/FlatBlack</material>
  </gazebo>

  <gazebo reference="caster_back_right_link">
    <mu1>0.1</mu1>
    <mu2>0.1</mu2>
    <kp>1000000.0</kp>
    <kd>100.0</kd>
    <minDepth>0.001</minDepth>
    <maxVel>1.0</maxVel>
    <material>Gazebo/FlatBlack</material>
  </gazebo>

  <gazebo reference="caster_back_left_link">
    <mu1>0.1</mu1>
    <mu2>0.1</mu2>
    <kp>1000000.0</kp>
    <kd>100.0</kd>
    <minDepth>0.001</minDepth>
    <maxVel>1.0</maxVel>
    <material>Gazebo/FlatBlack</material>
  </gazebo>

  <gazebo reference="imu_link">
    <sensor type="imu" name="imu">
      <always_on>true</always_on>
      <visualize>$(arg imu_visual)</visualize>
    </sensor>
    <material>Gazebo/Grey</material>
  </gazebo>

  <gazebo>
    <plugin name="turtlebot3_waffle_pi_controller" filename="libgazebo_ros_diff_drive.so">
      <commandTopic>cmd_vel</commandTopic>
      <odometryTopic>odom</odometryTopic>
      <odometryFrame>$(arg botname)/odom</odometryFrame>
      <odometrySource>world</odometrySource>
      <publishOdomTF>true</publishOdomTF>
      <robotBaseFrame>$(arg botname)/base_footprint</robotBaseFrame>
      <publishWheelTF>false</publishWheelTF>
      <publishTf>true</publishTf>
      <publishWheelJointState>true</publishWheelJointState>
      <legacyMode>false</legacyMode>
      <updateRate>30</updateRate>
      <leftJoint>wheel_left_joint</leftJoint>
      <rightJoint>wheel_right_joint</rightJoint>
      <wheelSeparation>0.287</wheelSeparation>
      <wheelDiameter>0.066</wheelDiameter>
      <wheelAcceleration>1</wheelAcceleration>
      <wheelTorque>10</wheelTorque>
      <rosDebugLevel>na</rosDebugLevel>
    </plugin>
  </gazebo>

  <gazebo>
    <plugin name="imu_plugin" filename="libgazebo_ros_imu.so">
      <alwaysOn>true</alwaysOn>
      <bodyName>imu_link</bodyName>
      <frameName>imu_link</frameName>
      <topicName>imu</topicName>
      <serviceName>imu_service</serviceName>
      <gaussianNoise>0.0</gaussianNoise>
      <updateRate>0</updateRate>
      <imu>
        <noise>
          <type>gaussian</type>
          <rate>
            <mean>0.0</mean>
            <stddev>2e-4</stddev>
            <bias_mean>0.0000075</bias_mean>
            <bias_stddev>0.0000008</bias_stddev>
          </rate>
          <accel>
            <mean>0.0</mean>
            <stddev>1.7e-2</stddev>
            <bias_mean>0.1</bias_mean>
            <bias_stddev>0.001</bias_stddev>
          </accel>
        </noise>
      </imu>
    </plugin>
  </gazebo>

  <gazebo reference="base_scan">
    <material>Gazebo/FlatBlack</material>
    <sensor type="ray" name="lds_lfcd_sensor">
      <pose>0 0 0 0 0 0</pose>
      <visualize>$(arg laser_visual)</visualize>
      <update_rate>5</update_rate>
      <ray>
        <scan>
          <horizontal>
            <samples>360</samples>
            <resolution>1</resolution>
            <min_angle>0.0</min_angle>
            <max_angle>6.28319</max_angle>
          </horizontal>
        </scan>
        <range>
          <min>0.120</min>
          <max>3.5</max>
          <resolution>0.015</resolution>
        </range>
        <noise>
          <type>gaussian</type>
          <mean>0.0</mean>
          <stddev>0.01</stddev>
        </noise>
      </ray>
      <plugin name="gazebo_ros_lds_lfcd_controller" filename="libgazebo_ros_laser.so">
        <topicName>scan</topicName>
        <frameName>$(arg botname)/base_scan</frameName>
      </plugin>
    </sensor>
  </gazebo>

<!--link : https://www.raspberrypi.org/documentation/hardware/camera/-->
  <gazebo reference="camera_rgb_frame">
    <sensor type="camera" name="Pi Camera">
      <always_on>true</always_on>
      <visualize>$(arg camera_visual)</visualize>
      <camera>
          <horizontal_fov>1.085595</horizontal_fov>
          <image>
              <width>640</width>
              <height>480</height>
              <format>R8G8B8</format>
          </image>
          <clip>
              <near>0.03</near>
              <far>100</far>
          </clip>
      </camera>
      <plugin name="camera_controller" filename="libgazebo_ros_camera.so">
        <alwaysOn>true</alwaysOn>
        <updateRate>30.0</updateRate>
        <cameraName>camera</cameraName>
        <frameName>$(arg botname)/camera_rgb_optical_frame</frameName>
        <imageTopicName>rgb/image_raw</imageTopicName>
        <cameraInfoTopicName>rgb/camera_info</cameraInfoTopicName>
        <hackBaseline>0.07</hackBaseline>
        <distortionK1>0.0</distortionK1>
        <distortionK2>0.0</distortionK2>
        <distortionK3>0.0</distortionK3>
        <distortionT1>0.0</distortionT1>
        <distortionT2>0.0</distortionT2>
      </plugin>
    </sensor>
  </gazebo>

</robot>

and the tf tree looks like this:

image description

Even though this seems to be running well, feedback on other places in the xacro file where TF prefixes should be added would be highly appreciated, and thank you to everyone who helped me through this.

The issue has been fixed, as Geoff said, you need to add the TF prefix to Gazebo. In this case a good explanation of how to do this is given in: https://github.com/open-rmf/free_fleet/issues/60#issuecomment-920665293

Minor edits had to be done to the launch and urdf xacro files, files according to the github link above, and the gazebo xacro file now looks like this:

<?xml version="1.0"?>
<robot name="turtlebot3_waffle_pi_sim" xmlns:xacro="http://ros.org/wiki/xacro">

  <xacro:arg name="laser_visual"  default="false"/>
  <xacro:arg name="camera_visual" default="false"/>
  <xacro:arg name="imu_visual"    default="false"/>

  <gazebo reference="base_link">
    <material>Gazebo/DarkGrey</material>
  </gazebo>

  <gazebo reference="wheel_left_link">
    <mu1>0.1</mu1>
    <mu2>0.1</mu2>
    <kp>500000.0</kp>
    <kd>10.0</kd>
    <minDepth>0.001</minDepth>
    <maxVel>0.1</maxVel>
    <fdir1>1 0 0</fdir1>
    <material>Gazebo/FlatBlack</material>
  </gazebo>

  <gazebo reference="wheel_right_link">
    <mu1>0.1</mu1>
    <mu2>0.1</mu2>
    <kp>500000.0</kp>
    <kd>10.0</kd>
    <minDepth>0.001</minDepth>
    <maxVel>0.1</maxVel>
    <fdir1>1 0 0</fdir1>
    <material>Gazebo/FlatBlack</material>
  </gazebo>

  <gazebo reference="caster_back_right_link">
    <mu1>0.1</mu1>
    <mu2>0.1</mu2>
    <kp>1000000.0</kp>
    <kd>100.0</kd>
    <minDepth>0.001</minDepth>
    <maxVel>1.0</maxVel>
    <material>Gazebo/FlatBlack</material>
  </gazebo>

  <gazebo reference="caster_back_left_link">
    <mu1>0.1</mu1>
    <mu2>0.1</mu2>
    <kp>1000000.0</kp>
    <kd>100.0</kd>
    <minDepth>0.001</minDepth>
    <maxVel>1.0</maxVel>
    <material>Gazebo/FlatBlack</material>
  </gazebo>

  <gazebo reference="imu_link">
    <sensor type="imu" name="imu">
      <always_on>true</always_on>
      <visualize>$(arg imu_visual)</visualize>
    </sensor>
    <material>Gazebo/Grey</material>
  </gazebo>

  <gazebo>
    <plugin name="turtlebot3_waffle_pi_controller" filename="libgazebo_ros_diff_drive.so">
      <commandTopic>cmd_vel</commandTopic>
      <odometryTopic>odom</odometryTopic>
      <odometryFrame>$(arg botname)/odom</odometryFrame>
      <odometrySource>world</odometrySource>
      <publishOdomTF>true</publishOdomTF>
      <robotBaseFrame>$(arg botname)/base_footprint</robotBaseFrame>
      <publishWheelTF>false</publishWheelTF>
      <publishTf>true</publishTf>
      <publishWheelJointState>true</publishWheelJointState>
      <legacyMode>false</legacyMode>
      <updateRate>30</updateRate>
      <leftJoint>wheel_left_joint</leftJoint>
      <rightJoint>wheel_right_joint</rightJoint>
      <wheelSeparation>0.287</wheelSeparation>
      <wheelDiameter>0.066</wheelDiameter>
      <wheelAcceleration>1</wheelAcceleration>
      <wheelTorque>10</wheelTorque>
      <rosDebugLevel>na</rosDebugLevel>
    </plugin>
  </gazebo>

  <gazebo>
    <plugin name="imu_plugin" filename="libgazebo_ros_imu.so">
      <alwaysOn>true</alwaysOn>
      <bodyName>imu_link</bodyName>
      <frameName>imu_link</frameName>
      <topicName>imu</topicName>
      <serviceName>imu_service</serviceName>
      <gaussianNoise>0.0</gaussianNoise>
      <updateRate>0</updateRate>
      <imu>
        <noise>
          <type>gaussian</type>
          <rate>
            <mean>0.0</mean>
            <stddev>2e-4</stddev>
            <bias_mean>0.0000075</bias_mean>
            <bias_stddev>0.0000008</bias_stddev>
          </rate>
          <accel>
            <mean>0.0</mean>
            <stddev>1.7e-2</stddev>
            <bias_mean>0.1</bias_mean>
            <bias_stddev>0.001</bias_stddev>
          </accel>
        </noise>
      </imu>
    </plugin>
  </gazebo>

  <gazebo reference="base_scan">
    <material>Gazebo/FlatBlack</material>
    <sensor type="ray" name="lds_lfcd_sensor">
      <pose>0 0 0 0 0 0</pose>
      <visualize>$(arg laser_visual)</visualize>
      <update_rate>5</update_rate>
      <ray>
        <scan>
          <horizontal>
            <samples>360</samples>
            <resolution>1</resolution>
            <min_angle>0.0</min_angle>
            <max_angle>6.28319</max_angle>
          </horizontal>
        </scan>
        <range>
          <min>0.120</min>
          <max>3.5</max>
          <resolution>0.015</resolution>
        </range>
        <noise>
          <type>gaussian</type>
          <mean>0.0</mean>
          <stddev>0.01</stddev>
        </noise>
      </ray>
      <plugin name="gazebo_ros_lds_lfcd_controller" filename="libgazebo_ros_laser.so">
        <topicName>scan</topicName>
        <frameName>$(arg botname)/base_scan</frameName>
      </plugin>
    </sensor>
  </gazebo>

<!--link : https://www.raspberrypi.org/documentation/hardware/camera/-->
  <gazebo reference="camera_rgb_frame">
    <sensor type="camera" name="Pi Camera">
      <always_on>true</always_on>
      <visualize>$(arg camera_visual)</visualize>
      <camera>
          <horizontal_fov>1.085595</horizontal_fov>
          <image>
              <width>640</width>
              <height>480</height>
              <format>R8G8B8</format>
          </image>
          <clip>
              <near>0.03</near>
              <far>100</far>
          </clip>
      </camera>
      <plugin name="camera_controller" filename="libgazebo_ros_camera.so">
        <alwaysOn>true</alwaysOn>
        <updateRate>30.0</updateRate>
        <cameraName>camera</cameraName>
        <frameName>$(arg botname)/camera_rgb_optical_frame</frameName>
        <imageTopicName>rgb/image_raw</imageTopicName>
        <cameraInfoTopicName>rgb/camera_info</cameraInfoTopicName>
        <hackBaseline>0.07</hackBaseline>
        <distortionK1>0.0</distortionK1>
        <distortionK2>0.0</distortionK2>
        <distortionK3>0.0</distortionK3>
        <distortionT1>0.0</distortionT1>
        <distortionT2>0.0</distortionT2>
      </plugin>
    </sensor>
  </gazebo>

</robot>

and the tf tree looks like this:

image description

Even though this seems to be running well, feedback on other places in the xacro file where TF prefixes should be added would be highly appreciated, and thank you to everyone who helped me through this.