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Simulation of URDF, Gazebo and Rviz | ROS Noetic Tutorial 8

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Design a User-defined robot of your choice (or you can use the URDF file) and enable the LIDAR Scanner so that any obstacle placed on the path of the light scan will cut the light rays. Visualize the robot in the Gazebo workspace, and also show the demonstration in RViz. 


(NB: Gain knowledge on wiring URDF file and .launch file for enabling any user-defined robot to get launched in the gazebo platform.)


SLAM:

One of the most popular applications of ROS is SLAM(Simultaneous Localization and Mapping). The objective of the SLAM in mobile robotics is to construct and update the map of an unexplored environment with the help of the available sensors attached to the robot which will be used for exploring.


URDF:

Unified Robotics Description Format, URDF, is an XML specification used in academia and industry to model multibody systems such as robotic manipulator arms for manufacturing assembly lines and animatronic robots for amusement parks. URDF is especially popular with users of the Robotics Operating System, ROS.


Explorer_bot.urdf file


<?xml version="1.0"?>

<robot name="custom_bot">


<link name="base_link">

    <visual>

        <geometry>

            <box size="0.6 0.3 0.1"/>

        </geometry>

        <material name="red">

            <color rgba="1 0.0 0.0 1"/>

        </material>

    </visual>

    <collision>

        <geometry>

            <box size="0.6 0.3 0.1"/>

        </geometry>

    </collision>

    <inertial>

        <mass value="1.0"/>

        <inertia ixx="0.015" ixy="0" ixz="0" iyy="0.0375" iyz="0.0" izz="0.0375"/>

    </inertial>

    

</link>


<link name="front_caster_of_wheel">

    <visual>

        <geometry>

            <box size="0.1 0.1 0.1"/>

        </geometry>

        <material name="green">

            <color rgba="0.0 0.1 0.0 1"/>   

        </material>

    </visual>

    <collision>

        <geometry>

            <box size="0.1 0.1 0.1"/>

        </geometry>

    </collision>

    <inertial>

        <mass value="0.1"/>

        <inertia ixx="0.00083" ixy="0" ixz="0" iyy="0.00083" iyz="0.0" izz="0.000167"/>

    </inertial>

</link>

<joint name="front_caster_of_wheel_joint" type="continuous">

   <axis xyz="0.0 0.0 1"/>

   <parent link="base_link"/>

   <child link="front_caster_of_wheel"/>

   <origin xyz="0.3 0.0 0.0" rpy="0.0 0.0 0.0"/>

</joint>


<link name="front_wheel">

    <visual>

        <geometry>

            <cylinder radius="0.035" length="0.05"/>

        </geometry>

        <material name="black">

            

        </material>


    </visual>

    <collision>

        <geometry>

            <cylinder radius="0.035" length="0.05"/>

        </geometry>

    </collision>

    <inertial>

        <mass value="0.1"/>

        <inertia ixx="5.1458e-5" ixy="0" ixz="0" iyy="5.1458e-5" iyz="0.0" izz="6.125e-5"/>

    </inertial>

</link>


<joint name="front_wheel_joint" type="continuous">

    <axis xyz="0.0 0.0 1"/>

    <parent link="front_caster_of_wheel"/>

    <child link="front_wheel"/>

    <origin xyz="0.05 0.0 -0.05" rpy="-1.5708 0.0 0.0"/>

    

</joint>


<link name="right_wheel">

    <visual>

        <geometry>

            <cylinder radius="0.035" length="0.05"/>

        </geometry>

        <material name="black">

            <color rgba="0.0 0.0 0.0 1"/>

        </material>


    </visual>

    <collision>

        <geometry>

            <cylinder radius="0.035" length="0.05"/>

        </geometry>

    </collision>

    <inertial>

        <mass value="0.1"/>

        <inertia ixx="5.1458e-5" ixy="0" ixz="0" iyy="5.1458e-5" iyz="0.0" izz="6.125e-5"/>    </inertial>

</link>


<joint name="right_wheel_joint" type="continuous">

    <axis xyz="0.0 0.0 1"/>

    <parent link="base_link"/>

    <child link="right_wheel"/>

    <origin xyz="-0.2825 -0.125 -0.05" rpy="-1.5708 0.0 0.0"/>

    

</joint>

<link name="left_wheel">

    <visual>

        <geometry>

            <cylinder radius="0.035" length="0.05"/>

        </geometry>

        <material name="black">

            <color rgba="0.0 0.0 0.0 1"/>

        </material>


    </visual>

    <collision>

        <geometry>

            <cylinder radius="0.035" length="0.05"/>

        </geometry>

    </collision>

    <inertial>

        <mass value="0.1"/>

        <inertia ixx="5.1458e-5" ixy="0" ixz="0" iyy="5.1458e-5" iyz="0.0" izz="6.125e-5"/>    </inertial>

</link>


<joint name="left_wheel_joint" type="continuous">

    <axis xyz="0.0 0.0 1"/>

    <parent link="base_link"/>

    <child link="left_wheel"/>

    <origin xyz="-0.2825 0.125 -0.05" rpy="-1.5708 0.0 0.0"/>

    

</joint>

<link name="laser_scanner">

    <visual>

        <geometry>

            <box size="0.1 0.1 0.1"/>

        </geometry>

    </visual>


    <collision>

        <geometry>

            <box size="0.1 0.1 0.1"/>

        </geometry>

    </collision>


    <inertial>

        <mass value="1e-5"/>

        <inertia ixx="1e-6" ixy="0" ixz="0.0" iyy="1e-6" iyz="0.0" izz="1e-6"/>

    </inertial>

</link>


<joint name="laser_scanner_joint" type="fixed">

    <axis xyz="0.0 1 0.0"/>

    <parent link="base_link"/>

    <child link="laser_scanner"/>

    <origin xyz="0.0 0.0 0.08" rpy="0.0 0.0 0.0"/>

</joint>


<gazebo reference="laser_scanner">

    <sensor type="ray" name="laser">

        <pose>0 0 0 0 0 0</pose>

        <visualize>true</visualize>

        <update_rate>40</update_rate>

        <ray>

            <scan>

                <horizontal>

                    <samples>720</samples>

                    <resolution>1</resolution>

                    <min_angle>-1.578</min_angle>

                    <max_angle>1.578</max_angle>

                </horizontal>

            </scan>

            <range>

                <min>0.1</min>

                <max>10</max>

                <resolution>0.1</resolution>

            </range>

        </ray>

        <plugin name="Lidar" filename="libgazebo_ros_laser.so">

            <topicName>/scan</topicName>

            <frameName>laser_scanner</frameName>

        </plugin>

    </sensor>

</gazebo>



<gazebo>

    <plugin name="explorer_bot_controller"   filename="libgazebo_ros_diff_drive.so">

        <leftJoint>left_wheel_joint</leftJoint>

        <rightJoint>right_wheel_joint</rightJoint>

        <legacyMode>false</legacyMode>

        <robotBaseFrame>base_link</robotBaseFrame>

        <wheelSeparation>0.25</wheelSeparation>

        <wheelDiameter>0.07</wheelDiameter>

        <publishWheelJointState>true</publishWheelJointState>

    </plugin>     

</gazebo>

   <gazebo>

    <plugin name="joint_state_publisher"     filename="libgazebo_ros_joint_state_publisher.so">

        <jointName>front_caster_of_wheel_joint, front_wheel_joint</jointName>

    </plugin>

</gazebo>

<gazebo reference="base_link">

    <material>Gazebo/Orange</material>

</gazebo>

<gazebo reference="front_caster_of_wheel">

    <material>Gazebo/Red</material>

  </gazebo>

  <gazebo reference="front_wheel">

    <material>Gazebo/Black</material>

  </gazebo>

  <gazebo reference="left_wheel">

    <material>Gazebo/Black</material>

  </gazebo>

  <gazebo reference="right_wheel">

    <material>Gazebo/Black</material>

  </gazebo>

</robot>


Gazebo_explorer.launch file


<?xml version="1.0"?>

<launch>

<param name="robot_description" textfile="$(find explorer_bot)/urdf/explorer_bot.urdf" />


    <include file="$(find gazebo_ros)/launch/empty_world.launch"/>


    <node name="spawn_urdf" pkg="gazebo_ros" type="spawn_model"  args="-param robot_description -urdf -model explorer_bot" />


    <node name="Rsp" pkg="robot_state_publisher" type="robot_state_publisher" output="screen"/>

</launch>



Gazebo
URDF and Gazebo



URDF and Gazebo

URDF and Gazebo





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