ROS MasterClass Checkpoint 1

This project is for ROS MasterClass from theconstruct.ai and for the full Souuce code checkout my_rb1_robot repositories

Task 1 Build RB1 URDF Replica

1. Create a new ROS package inside my_rb1_robot named my_rb1_description with rospy, urdf and xacro as dependencies.

   • $ catkin_create_pkg my_rb1_description rospy urdf xacro

2. Inside the package, create a urdf folder. Inside this folder, create a file named my_rb1_robot.urdf.

   • $ cd my_rb1_description/
   • $ mkdir urdf
   • $ touch urdf/my_rb1_robot.urdf

compute the moments of inertia:

moments of inertia

Robot base: m =25 h=0.3 r= 0.25 * ixx = iyy = 0.578125 * izz = 0.78125

wheel : m=1 h=0.05 r=0.025 * ixx = iyy = 3.6459 * izz = 0.0003125

Caster Wheel = m=1 r=0.03 * ixx = iyy = izz 0.00036

1. To visualize the robot

   • $ mkdir launch
   • $ touch launch/display.launch

<?xml version="1.0"?>
<launch>
  <param name="my_rb1_description" command="cat '$(find my_rb1_description)/urdf/my_rb1_robot.urdf'"/>
  <!-- send fake joint values -->
  <node name="joint_state_publisher_gui" pkg="joint_state_publisher_gui" type="joint_state_publisher_gui" />
  <!-- Combine joint values -->
  <node name="robot_state_publisher" pkg="robot_state_publisher" type="robot_state_publisher"/>
  <!-- Show in Rviz   -->
  <node name="rviz" pkg="rviz" type="rviz" />
</launch>

To view the Robot in Rviz run the following commnand: - $ roslaunch my_rb1_description display.launch - Change the frixed framd value in Fixed Frame dropdown to base_footprint - change the Alpha value in the RobotModel dropdown to 0.5

To push the code to Github run the followin comands: - $ git config --global user.name "Mohammad Alshamsi"

• $ git config --global user.email "alshamsi.mohammad@gmail.com"

• $ git status

• $ git add my_rb1_description/

• $ git commit -m "ceate my_rb1_robot.urdf file"

• $ git tag task1

• Create a new repository on GitHub my_rb1_robot (don’t tick the ‘CREATE README” option) https://github.com/MohammadRobot/my_rb1_robot.git

• Generate Personal access tokens

• git remote add origin https://github.com/MohammadRobot/my_rb1_robot.git

• $ git branch -M main

• $ git push -u origin main

Task 2 Spawn robot in simulation

• $ cd ~/catkin_ws/src/my_rb1_robot/
• $ catkin_create_pkg my_rb1_gazebo
• $ mkdir my_rb1_gazebo/launch
• $ cp /home/user/simulation_ws/src/warehouse_robot_lab/rb1_base_sim/rb1_base_gazebo/launch/empty_warehouse.launch my_rb1_gazebo/launch/
• $ touch my_rb1_gazebo/launch/my_rb1_robot_warehouse.launch
• $ mv my_rb1_gazebo/launch/empty_warehouse.launch my_rb1_gazebo/launch/my_rb1_robot_warehouse.launch

Add the follow to the my_rb1_robot_warehouse.launch

<!-- Adding URF file -->  
    <param name="robot_description" command="cat '$(find my_rb1_description)/urdf/my_rb1_robot.urdf'" />
    <arg name="x" default="-0.3"/>
    <arg name="y" default="-1.3"/>
    <arg name="z" default="0.25"/>

    <!-- Spawn the Robot-->
    <node name="mybot_spawn" pkg="gazebo_ros" type="spawn_model" output="screen"
          args="-urdf -param robot_description -model my_rb1_robot -x $(arg x) -y $(arg y) -z $(arg z)" />

    <!-- launch other nodes -->
    <node name="joint_state_publisher" pkg="joint_state_publisher" type="joint_state_publisher"/>
    <node name="robot_state_publisher" pkg="robot_state_publisher" type="robot_state_publisher"/>

• $ roslaunch my_rb1_gazebo my_rb1_robot_warehouse.launch

To chage the color of the robot in Gazebo add the following to URDF file

<!-- Gazebo Tags for Robot Color-->
    <gazebo reference="base_link">
        <material>Gazebo/Black</material>
    </gazebo>
    <gazebo reference="front_caster">
        <material>Gazebo/Grey</material>
    </gazebo>
    <gazebo reference="back_caster">
        <material>Gazebo/Grey</material>
    </gazebo>
    <gazebo reference="left_wheel">
        <material>Gazebo/Red</material>
    </gazebo>
    <gazebo reference="right_wheel">
        <material>Gazebo/Red</material>
    </gazebo>
    <gazebo reference="front_laser">
        <material>Gazebo/Blue</material>
    </gazebo>

• $ git add my_rb1_description/urdf/my_rb1_robot.urdf
• $ git add my_rb1_gazebo/
• $ git commit -m "Complete Task 2 Spawn robot in simulation"
• $ git tag task2
• $ git push -u origin task2
• $ git push -u origin main

Task 3 Add sensor plugins

• Add libgazebo_ros_diff_drive.so plugin to URDF file

    <!-- Gazebo Plugin for actuators and sensors -->
    <gazebo>
        <plugin filename="libgazebo_ros_diff_drive.so" name="differential_drive_controller">
            <alwaysOn>true</alwaysOn>
            <updateRate>20</updateRate>
            <leftJoint>joint_base_left_wheel</leftJoint>
            <rightJoint>joint_base_right_wheel</rightJoint>
            <wheelSeparation>0.4</wheelSeparation>
            <wheelDiameter>0.05</wheelDiameter>
            <torque>5</torque>
            <commandTopic>cmd_vel</commandTopic>
            <odometryTopic>odom</odometryTopic>
            <odometryFrame>odom</odometryFrame>
            <robotBaseFrame>base_link</robotBaseFrame>
        </plugin>
    </gazebo>

• Add llibgazebo_ros_laser.so plugin to URDF file

    <!-- Gazebo Laser Scan -->
    <gazebo reference="front_laser">
        <sensor type="ray" name="head_hokuyo_sensor">
            <pose>0 0 0 0 0 0</pose>
            <visualize>true</visualize>
            <update_rate>20</update_rate>
            <ray>
                <scan>
                    <horizontal>
                        <samples>720</samples>
                        <resolution>1</resolution>
                        <min_angle>-1.570796</min_angle>
                        <max_angle>1.570796</max_angle>
                    </horizontal>
                </scan>
                <range>
                    <min>0.20</min>
                    <max>10.0</max>
                    <resolution>0.01</resolution>
                </range>
                <noise>
                    <type>gaussian</type>
                    <mean>0.0</mean>
                    <stddev>0.01</stddev>
                </noise>
            </ray>
            <plugin name="gazebo_ros_head_hokuyo_controller" filename="libgazebo_ros_laser.so">
                <topicName>/scan</topicName>
                <frameName>sensor_laser</frameName>
            </plugin>
        </sensor>
    </gazebo>

• $ git add my_rb1_description/urdf/my_rb1_robot.urdf
• $ git add my_rb1_gazebo/launch/my_rb1_robot_warehouse.launch
• $ git commit -m "complete Task 3 Add sensor plugins"
• $ git tag task3
• $ git push -u origin task3

• $ git push -u origin main

• $ roslaunch my_rb1_gazebo my_rb1_robot_warehouse.launch

• to drive the robot run the following commnad

  ``` $ rostopic pub /cmd_vel geometry_msgs/Twist “linear:

  x: 0.2

  y: 0.0

  z: 0.0

  angular:

  x: 0.0

  y: 0.0

  z: 0.0” `` * to view laser data run$ rostopic echo /scan`

Referance

• For Git commnad check Git Cheat Sheets