ND2 - Project 2 - localization - files

Worlds Files (define environment)

A world is a collection of models such as your robot, cup, ground and sky.

<?xml version="1.0" ?>

<sdf version="1.4">

  <world name="default">

    <!-- Ground plane -->
    <include>
      <uri>model://ground_plane</uri>
    </include>

    <!-- Light source -->
    <include>
      <uri>model://sun</uri>
    </include>

    <!-- World camera -->
    <gui fullscreen='0'>
      <camera name='world_camera'>
        <pose>4.927360 -4.376610 3.740080 0.000000 0.275643 2.356190</pose>
        <view_controller>orbit</view_controller>
      </camera>
    </gui>

  </world>
</sdf>

Unified Robot Description Format (URDF) (define robot)

URDF can only describe a robot with rigid links connected by joints, not flexible links or parallel linkage.

Divided into 2 files (xacro / gazebo)

udacity_bot.xacro (robot specific information like links, joints, actuators, etc.)

visual + collision + inertial

<?xml version='1.0'?>

<robot name="udacity_bot" xmlns:xacro="http://www.ros.org/wiki/xacro">

  <xacro:include filename="$(find udacity_bot)/urdf/udacity_bot.gazebo" />

  <!-- footprint LINK -->
  <link name="robot_footprint"></link>

  <!-- footprint - chassis JOINT -->
  <joint name="robot_footprint_joint" type="fixed">
    <origin xyz="0 0 0" rpy="0 0 0" />
    <parent link="robot_footprint"/>
    <child link="chassis" />
  </joint>

  <!-- chassis LINK -->
  <link name='chassis'>
    <pose>0 0 0.1 0 0 0</pose>

    <inertial>
      <mass value="15.0"/>
      <origin xyz="0.0 0 0" rpy=" 0 0 0"/>
      <inertia
          ixx="0.1" ixy="0" ixz="0"
          iyy="0.1" iyz="0"
          izz="0.1"
      />
    </inertial>

    <collision name='collision'>
      <origin xyz="0 0 0" rpy=" 0 0 0"/> 
      <geometry>
        <box size=".4 .2 .1"/>
      </geometry>
    </collision>

    <visual name='chassis_visual'>
      <origin xyz="0 0 0" rpy=" 0 0 0"/>
      <geometry>
        <box size=".4 .2 .1"/>
      </geometry>
    </visual>

    <collision name='back_caster_collision'>
      <origin xyz="-0.15 0 -0.05" rpy=" 0 0 0"/>
      <geometry>
        <sphere radius="0.05"/>
      </geometry>
      <surface>
        <friction>
          <ode>
            <mu>0</mu>
            <mu2>0</mu2>
            <slip1>1.0</slip1>
            <slip2>1.0</slip2>
          </ode>
        </friction>
      </surface>
    </collision>

    <visual name='back_caster_visual'>
      <origin xyz="-0.15 0 -0.05" rpy=" 0 0 0"/>
      <geometry>
        <sphere radius="0.05"/>
      </geometry>
    </visual>

    <collision name='front_caster_collision'>
      <origin xyz="0.15 0 -0.05" rpy=" 0 0 0"/>
      <geometry>
        <sphere radius="0.05"/>
      </geometry>
      <surface>
        <friction>
          <ode>
            <mu>0</mu>
            <mu2>0</mu2>
            <slip1>1.0</slip1>
            <slip2>1.0</slip2>
          </ode>
        </friction>
      </surface>
    </collision>

    <visual name='front_caster_visual'>
      <origin xyz="0.15 0 -0.05" rpy=" 0 0 0"/>
      <geometry>
        <sphere radius="0.05"/>
      </geometry>
    </visual>

  </link>

  <!-- right wheel LINK -->
  <link name='right_wheel'>
    <inertial>
      <mass value="5.0"/>
      <origin xyz="0 0 0" rpy=" 0 1.5707 1.5707"/>
      <inertia
          ixx="0.1" ixy="0" ixz="0"
          iyy="0.1" iyz="0"
          izz="0.1"
      />
    </inertial>

    <collision>
      <origin xyz="0 0 0" rpy=" 0 1.5707 1.5707"/>
      <geometry>
        <cylinder length="0.05" radius="0.1"/>
      </geometry>
    </collision>

    <visual>
      <origin xyz="0 0 0" rpy=" 0 1.5707 1.5707"/>
      <geometry>
        <cylinder length="0.05" radius="0.1"/>
      </geometry>
    </visual>
  </link>

  <!-- right wheel - chassis JOINT -->
  <joint type="continuous" name="right_wheel_hinge">
    <origin xyz="0 0.15 0" rpy="0 0 0"/>
    <child link="right_wheel"/>
    <parent link="chassis"/>
    <axis xyz="0 1 0" rpy="0 0 0"/>
    <limit effort="10000" velocity="1000"/>
    <joint_properties damping="1.0" friction="1.0"/>
  </joint>

  <!-- left wheel - LINK -->
  <link name='left_wheel'>
    <inertial>
      <mass value="5.0"/>
      <origin xyz="0 0 0" rpy=" 0 1.5707 1.5707"/>
      <inertia
          ixx="0.1" ixy="0" ixz="0"
          iyy="0.1" iyz="0"
          izz="0.1"
      />
    </inertial>

    <collision>
      <origin xyz="0 0 0" rpy=" 0 1.5707 1.5707"/>
      <geometry>
        <cylinder length="0.05" radius="0.1"/>
      </geometry>
    </collision>

    <visual>
      <origin xyz="0 0 0" rpy=" 0 1.5707 1.5707"/>
      <geometry>
        <cylinder length="0.05" radius="0.1"/>
      </geometry>
    </visual>
  </link>

  <!-- left wheel - JOINT -->
  <joint type="continuous" name="left_wheel_hinge">
    <origin xyz="0 -0.15 0" rpy="0 0 0"/>
    <child link="left_wheel"/>
    <parent link="chassis"/>
    <axis xyz="0 1 0" rpy="0 0 0"/>
    <limit effort="10000" velocity="1000"/>
    <joint_properties damping="1.0" friction="1.0"/>
  </joint>

  <!-- camera - LINK -->
  <link name='camera'>
    <inertial>
      <mass value="0.1"/>
      <origin xyz="0 0 0" rpy=" 0 0 0"/>
      <inertia
          ixx="1e-6" ixy="0" ixz="0"
          iyy="1e-6" iyz="0"
          izz="1e-6"
      />
    </inertial>

    <collision name='camera_collision'>
      <origin xyz="0 0 0" rpy=" 0 0 0"/>
      <geometry>
        <box size="0.05 0.05 0.05" />
      </geometry>
    </collision>

    <visual name='camera_visual'>
      <origin xyz="0 0 0" rpy=" 0 0 0"/>
      <geometry>
        <box size="0.05 0.05 0.05" />
      </geometry>
    </visual>
  </link>

  <!-- camera - chassis JOINT -->
  <joint type="fixed" name="camera_joint">
    <origin xyz="0.2 0 0" rpy="0 0 0"/>
    <child link="camera"/>
    <parent link="chassis"/>
  </joint>

  <!-- laser rangefinder - LINK -->
  <link name='hokuyo'>
    <inertial>
      <mass value="0.1"/>
      <origin xyz="0 0 0" rpy=" 0 0 0"/>
      <inertia
          ixx="1e-6" ixy="0" ixz="0"
          iyy="1e-6" iyz="0"
          izz="1e-6"
      />
    </inertial>

    <collision name='hokuyo_collision'>
      <origin xyz="0 0 0" rpy=" 0 0 0"/>
      <geometry>
        <box size="0.1 0.1 0.1" />
      </geometry>
    </collision>

    <visual name='hokuyo_visual'>
      <origin xyz="0 0 0" rpy=" 0 0 0"/>
      <geometry>
        <mesh filename="package://udacity_bot/meshes/hokuyo.dae"/>
      </geometry>
    </visual>
  </link>

  <!-- laser rangefinder - chassis JOINT -->
  <joint type="fixed" name="hokuyo_joint">
    <origin xyz="0.15 0 0.1" rpy="0 0 0"/>
    <child link="hokuyo"/>
    <parent link="chassis"/>
  </joint>
</robot>

udacity_bot.gazebo (gazebo specific info like robot material, frictional constants, and plugins to control the robot in gazebo)

<?xml version="1.0"?>
<robot>
  <!-- wheels control plugin -->
  <gazebo>
    <plugin name="differential_drive_controller" filename="libgazebo_ros_diff_drive.so">
      <legacyMode>false</legacyMode>
      <alwaysOn>true</alwaysOn>
      <updateRate>10</updateRate>
      <leftJoint>left_wheel_hinge</leftJoint>
      <rightJoint>right_wheel_hinge</rightJoint>
      <wheelSeparation>0.4</wheelSeparation>
      <wheelDiameter>0.2</wheelDiameter>
      <torque>10</torque>
      <commandTopic>cmd_vel</commandTopic>
      <odometryTopic>odom</odometryTopic>
      <odometryFrame>odom</odometryFrame>
      <robotBaseFrame>robot_footprint</robotBaseFrame>
    </plugin>
  </gazebo>

  <!-- right wheel -->
  <gazebo reference="right_wheel">
    <material>Gazebo/Green</material>
  </gazebo>

  <!-- left wheel -->
  <gazebo reference="left_wheel">
    <material>Gazebo/Green</material>
  </gazebo>

  <!-- chassis -->
  <gazebo reference="chassis">
    <material>Gazebo/Blue</material>
  </gazebo>

  <!-- camera -->
  <gazebo reference="camera">
    <material>Gazebo/Red</material>
    <sensor type="camera" name="camera1">
      <update_rate>30.0</update_rate>
      <camera name="head">
        <horizontal_fov>1.3962634</horizontal_fov>
        <image>
          <width>800</width>
          <height>800</height>
          <format>R8G8B8</format>
        </image>
        <clip>
          <near>0.02</near>
          <far>300</far>
        </clip>
      </camera>
      <plugin name="camera_controller" filename="libgazebo_ros_camera.so">
        <alwaysOn>true</alwaysOn>
        <updateRate>0.0</updateRate>
        <cameraName>udacity_bot/camera1</cameraName>
        <imageTopicName>image_raw</imageTopicName>
        <cameraInfoTopicName>camera_info</cameraInfoTopicName>
        <frameName>camera</frameName>
        <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>

  <!-- hokuyo -->
  <gazebo reference="hokuyo">
    <sensor type="ray" name="head_hokuyo_sensor">
      <pose>0 0 0 0 0 0</pose>
      <visualize>false</visualize>
      <update_rate>40</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>0.10</min>
          <max>30.0</max>
          <resolution>0.01</resolution>
        </range>
        <noise>
          <type>gaussian</type>
          <!-- Noise parameters based on published spec for Hokuyo laser
               achieving "+-30mm" accuracy at range < 10m.  A mean of 0.0m and
               stddev of 0.01m will put 99.7% of samples within 0.03m of the true
               reading. -->
          <mean>0.0</mean>
          <stddev>0.01</stddev>
        </noise>
      </ray>
      <plugin name="gazebo_ros_head_hokuyo_controller" filename="libgazebo_ros_laser.so">
        <topicName>/udacity_bot/laser/scan</topicName>
        <frameName>hokuyo</frameName>
      </plugin>
    </sensor>
  </gazebo>

</robot>

A link contains [1]visual [2]inertial [3]collision

https://classroom.udacity.com/nanodegrees/nd209/parts/c199593e-1e9a-4830-8e29-2c86f70f489e/modules/8855de3f-2897-46c3-a805-628b5ecf045b/lessons/91d017b1-4493-4522-ad52-04a74a01094c/concepts/304b7bc0-6fe8-4614-bd09-4a545665adad#

https://bitbucket.org/osrf/gazebo/src/afe08834571835008fa7419f1feba5b7f89b9d62/plugins/DiffDrivePlugin.cc?at=gazebo7&fileviewer=file-view-default

Launch Files

<?xml version="1.0" encoding="UTF-8"?>

<launch>
  <!--define args-->
  <arg name="world" default="empty"/> 
  <arg name="paused" default="false"/>
  <arg name="use_sim_time" default="true"/>
  <arg name="gui" default="true"/>
  <arg name="headless" default="false"/>
  <arg name="debug" default="false"/>

  <!--include robot launch files-->
  <include file="$(find udacity_bot)/launch/robot_description.launch"/>

  <!--include launch files from gazebo-->
  <include file="$(find gazebo_ros)/launch/empty_world.launch">
    <arg name="world_name" value="$(find udacity_bot)/worlds/udacity.world"/>
    <arg name="paused" value="$(arg paused)"/>
    <arg name="use_sim_time" value="$(arg use_sim_time)"/>
    <arg name="gui" value="$(arg gui)"/>
    <arg name="headless" value="$(arg headless)"/>
    <arg name="debug" value="$(arg debug)"/>
  </include>

  <!--spawn a robot node in gazebo world-->
  <node name="urdf_spawner" pkg="gazebo_ros" type="spawn_model" respawn="false" output="screen" args="-urdf -param robot_description -model udacity_bot"/>
</launch>

more about gazebo empty_world.launch

https://github.com/ros-simulation/gazebo_ros_pkgs/blob/kinetic-devel/gazebo_ros/launch/empty_world.launch

Adaptive Monte Carlo Localization (AMCL) dynamically adjusts the number of particles over a period of time