Gazebo Tutorial Course

Dependencies
Creating the ros package
Creating the robot
Creating the Simulation World
Simulation Launch File
Building

Dependencies

You need to install ROS 2 humble and Gazebo Sim for this project.

ROS2 Package dependencies

sudo apt install ros-humble-ros-gz-sim ros-humble-ros-gz-bridge ros-humble-xacro ros-humble-joint-state-publisher* ros-humble-rqt*

Creating the ros package

Go to the your ros2 workspace and create a Python package. urdf and xacro packages are dependencies of this package.

cd ~/ros2_ws/src \
ros2 pkg create gazebo_project --build-type ament_python --dependencies rclpy urdf xacro

Create the URDF directory to put the robot's URDF file

mkdir -p gazebo_project/urdf

Create the robot's urdf file

touch gazebo_project/urdf/robot.urdf

Create the world directory to put the simulation world file

mkdir -p gazebo_project/worlds

Create the demo_world.sdf file

touch gazebo_project/worlds/demo_world.sdf

Create the launch directory to put the launch files

mkdir -p gazebo_project/launch

Create the rviz.launch.py file to inspect robot's urdf with rviz.

touch gazebo_project/launch/rviz.launch.py

Create the simulation.launch.py to run simulation with created map and robot.

touch gazebo_project/launch/simulation.launch.py

Create the meshes directory to put the robot's .obj file

mkdir -p gazebo_project/meshes

Then, move smart_car.obj file from this repo to gazebo_project/meshes directory.

Creating the robot

Inside of the URDF file, add the xml and robot tags. Include the "common_properties.urdf" file that contains useful urdf macros.

<?xml version="1.0"?>

<robot name="robot" xmlns:xacro="http://ros.org/wiki/xacro">
  <xacro:include filename="$(find gazebo_project)/urdf/common_properties.urdf.xacro" />


</robot>

The rest of pieces will be added inside the <robot></robot> tag. Adding the dummy base link:

  <link name="base_link">
    <xacro:cuboid_inertia mass="1.0" x="0.1" y="0.1" z="0.1" />
  </link>

Adding the chassis link. Chassis' visual will be a .obj file named smart_car.obj that located in meshes folder in the project. The material tag that located inside of the visual properties ensure the lightning of the car is correct and working.

<link name="link_chassis">
    <visual name="chassis_visual">
      <origin rpy="1.57 0 1.57" xyz="0 0 0" />
      <geometry>
        <mesh filename="package://gazebo_project/meshes/smart_car.obj"
          scale="0.012 0.012
        0.013" />
      </geometry>
      <material name="white">
        <lighting>true</lighting>
        <cast_shadows>true</cast_shadows>
        <receive_shadows>true</receive_shadows>
        <color rgba="0.9 0.9 0.9 1.0" />
      </material>
    </visual>

    <collision>
      <origin xyz="0 0 0.625" rpy="0 0 0" />
      <geometry>
        <box size="2.4 1.0 1.0" />
      </geometry>
    </collision>

    <xacro:inertial_cuboid_with_pose mass="500.0" x="2.4" y="1.0" z="1.0">
      <origin xyz="0 0 0.625" rpy="0 0 0" />
    </xacro:inertial_cuboid_with_pose>
  </link>

Connect base_link and link_chassis.

  <joint name="joint_base_link_chassis" type="fixed">
    <origin rpy="0 0 0" xyz="0 0 0" />
    <child link="link_chassis" />
    <parent link="base_link" />
  </joint>

Adding Wheel Links

Rear left wheel link

  <link name="rear_left_wheel">
    <xacro:inertial_cylinder mass="11.0" radius="0.25" length="0.15" />
    <visual name="rear_left_wheel_visual">
      <geometry>
        <cylinder radius="0.25" length="0.15" />
      </geometry>
      <material name="Black">
        <color rgba="0.1 0.1 0.1 1" />
      </material>
    </visual>
    <collision>
      <geometry>
        <sphere radius="0.25" />
      </geometry>
      <friction>
        <ode>
          <mu>1.1</mu>
          <mu2>1.1</mu2>
        </ode>
      </friction>
    </collision>
  </link>

Rear right wheel link

  <link name="rear_right_wheel">
    <xacro:inertial_cylinder mass="11.0" radius="0.25" length="0.15" />

    <visual name="rear_right_wheel_visual">
      <geometry>
        <cylinder radius="0.25" length="0.15" />
      </geometry>
      <material name="Black">
        <color rgba="0.1 0.1 0.1 1" />
      </material>
    </visual>

    <collision>
      <geometry>
        <sphere radius="0.25" />
      </geometry>
      <friction>
        <ode>
          <mu>1.1</mu>
          <mu2>1.1</mu2>
        </ode>
      </friction>
    </collision>
  </link>

Front left wheel link

  <link name="front_left_wheel">
    <xacro:inertial_cylinder mass="11.0" radius="0.25" length="0.15" />

    <visual name="front_left_wheel_visual">
      <geometry>
        <cylinder radius="0.25" length="0.15" />
      </geometry>
      <material name="Black">
        <color rgba="0.1 0.1 0.1 1" />
      </material>
    </visual>

    <collision>
      <geometry>
        <sphere radius="0.25" />
      </geometry>
      <friction>
        <ode>
          <mu>1.1</mu>
          <mu2>1.1</mu2>
        </ode>
      </friction>
    </collision>
  </link>

Front right wheel link

  <link name="front_right_wheel">
    <xacro:inertial_cylinder mass="11.0" radius="0.25" length="0.15" />

    <visual name="front_right_wheel_visual">
      <geometry>
        <cylinder radius="0.25" length="0.15" />
      </geometry>
      <material name="Black">
        <color rgba="0.1 0.1 0.1 1" />
      </material>
    </visual>

    <collision>
      <geometry>
        <sphere radius="0.25" />
      </geometry>
      <friction>
        <ode>
          <mu>1.1</mu>
          <mu2>1.1</mu2>
        </ode>
      </friction>
    </collision>
  </link>

The front wheels also need a steering link.

Front left wheel steering link

  <link name="front_left_wheel_steering_link">
    <xacro:cuboid_inertia mass="1.0" x="0.1" y="0.1" z="0.1" />
  </link>

Front right wheel steering link

  <link name="front_right_wheel_steering_link">
    <xacro:cuboid_inertia mass="1.0" x="0.1" y="0.1" z="0.1" />
  </link>

Connecting Wheel Links to the Chassis

Connecting the rear_left_wheel and link_chassis.

  <joint type="revolute" name="rear_left_wheel_joint">
    <origin rpy="1.56 0 0" xyz="-0.9 0.64 0.25" />
    <child link="rear_left_wheel" />
    <parent link="link_chassis" />
    <axis rpy="0 0 0" xyz="0 0 1" />
    <limit lower="-1.79769e+308" upper="1.79769e+308"
      effort="100000" velocity="1000" />
  </joint>

Connecting the rear_right_wheel and link_chassis.

  <joint type="revolute" name="rear_right_wheel_joint">
    <origin rpy="1.56 0 0" xyz="-0.9 -0.64 0.25" />
    <child link="rear_right_wheel" />
    <parent link="link_chassis" />
    <axis rpy="0 0 0" xyz="0 0 1" />
    <limit lower="-1.79769e+308" upper="1.79769e+308"
      effort="100000" velocity="1000" />
  </joint>

Connecting the front_left_wheel_steering_link and link_chassis.

  <joint type="revolute" name="front_left_wheel_steering_joint">
    <origin rpy="-1.56 0 0" xyz="0.9 0.64 0.25" />
    <child link="front_left_wheel_steering_link" />
    <parent link="link_chassis" />
    <axis rpy="0 0 0" xyz="0 -1 0" />
    <limit effort="100000" velocity="1000" upper="0.8727" lower="-0.8727" />
  </joint>

Connecting the front_left_wheel and front_left_wheel_steering_link.

  <joint type="revolute" name="front_left_wheel_rotating_joint">
    <origin rpy="0 0 0" xyz="0 0 0" />
    <child link="front_left_wheel" />
    <parent link="front_left_wheel_steering_link" />
    <axis rpy="0 0 0" xyz="0 0 1" />
    <limit lower="-1.79769e+308" upper="1.79769e+308" effort="100000" velocity="1000" />
  </joint>

Connecting the front_right_wheel_steering_link and link_chassis.

  <joint type="revolute" name="front_right_wheel_steering_joint">
    <origin rpy="-1.56 0 0" xyz="0.9 -0.64 0.25" />
    <child link="front_right_wheel_steering_link" />
    <parent link="link_chassis" />
    <axis rpy="0 0 0" xyz="0 -1 0" />
    <limit effort="100000" velocity="1000" upper="0.8727" lower="-0.8727" />
  </joint>

Connecting the front_right_wheel and front_right_wheel_steering_link.

  <joint type="revolute" name="front_right_wheel_rotating_joint">
    <origin rpy="0 0 0" xyz="0 0 0" />
    <child link="front_right_wheel" />
    <parent link="front_right_wheel_steering_link" />
    <axis rpy="0 0 0" xyz="0 0 1" />
    <limit lower="-1.79769e+308" upper="1.79769e+308" effort="100000" velocity="1000" />
    <joint_properties damping="1.0" friction="1.0" />
  </joint>

Adding the Ackermann Steering System Plugin

After adding this plugin, car can be drivable on /cmd_vel topic with Twist messages. Odometry of the vehicle will be published in /odom topic. angular.z value of Twist message will steer front_left_wheel_steering_joint and front_right_wheel_steering_joint, linear.x value of Twist mesage will rotate front_left_wheel_rotating_joint and front_right_wheel_rotating_joint.

  <gazebo>
    <plugin filename="ignition-gazebo-ackermann-steering-system"
      name="ignition::gazebo::systems::AckermannSteering">
      <topic>/cmd_vel</topic>
      <odom_publish_frequency>10</odom_publish_frequency>
      <odom_topic>odom</odom_topic>
      <left_joint>front_left_wheel_rotating_joint</left_joint>
      <right_joint>front_right_wheel_rotating_joint</right_joint>
      <left_steering_joint>front_left_wheel_steering_joint</left_steering_joint>
      <right_steering_joint>front_right_wheel_steering_joint</right_steering_joint>
      <kingpin_width>1.0</kingpin_width>
      <steering_limit>0.8</steering_limit>
      <wheel_base>1.0</wheel_base>
      <wheel_separation>1.572</wheel_separation>
      <wheel_radius>0.31265</wheel_radius>
      <min_velocity>-10</min_velocity>
      <max_velocity>100</max_velocity>
      <min_acceleration>-30</min_acceleration>
      <max_acceleration>30</max_acceleration>
    </plugin>
  </gazebo>

Adding Joint State Publihser plugin to publihs real-time joint states.

  <gazebo>
    <plugin filename="ignition-gazebo-joint-state-publisher-system"
      name="ignition::gazebo::systems::JointStatePublisher" />
  </gazebo>

Adding IMU Sensor plugin

  <gazebo>
    <plugin filename="ignition-gazebo-imu-system"
      name="ignition::gazebo::systems::Imu">
    </plugin>
  </gazebo>
  <gazebo reference="link_chassis">
    <sensor name="imu_sensor" type="imu">
      <always_on>1</always_on>
      <update_rate>20</update_rate>
      <visualize>true</visualize>
      <topic>imu</topic>
    </sensor>
  </gazebo>

Our car is created. To test it, fill the rviz.launch.py with following lines. This launch file runs 3 nodes:

Robot State Publisher with robot URDF
Joint State Publisher to create initial joint states
RVIZ2 to visualize URDF with joint states

import os
from ament_index_python.packages import get_package_share_directory
from launch import LaunchDescription
from launch.substitutions import Command
from launch_ros.actions import Node


def generate_launch_description():
    use_sim_time = True
    package_directory = get_package_share_directory("gazebo_project")
    # path of the robot urdf file
    robot_desc_path = os.path.join(package_directory, "urdf", "robot.urdf")

    # Run robot state publisher
    robot_state_publisher_node = Node(
        package="robot_state_publisher",
        executable="robot_state_publisher",
        name="robot_state_publisher_node",
        output="screen",
        emulate_tty=True,
        parameters=[
            {
                "use_sim_time": use_sim_time,
                "robot_description": Command(["xacro ", robot_desc_path]),
            }
        ],
    )

    # Run joint state publisher
    joint_state_publisher_node = Node(
        package="joint_state_publisher",
        executable="joint_state_publisher",
        name="joint_state_publisher_node",
        output="screen",
        emulate_tty=True,
    )

    # Run Rviz2
    rviz_node = Node(
        package="rviz2",
        executable="rviz2",
        name="rviz2_node",
        output="screen",
        emulate_tty=True,
        parameters=[{"use_sim_time": use_sim_time}],
    )

    return LaunchDescription(
        [
            joint_state_publisher_node,
            robot_state_publisher_node,
            rviz_node,
        ]
    )

Do the Building and testing steps to test the URDF file.

Creating the Simulation World

Inside of the worlds/demo_world.sdf file, add the xml, sdf and world tags. World's name will be demo_world

<?xml version="1.0"?>
<sdf version="1.8">
    <world name="demo_world">
          <!-- Rest of the pieces -->
    </world>
</sdf>

The rest of pieces will be added inside the <world></world> tag.

Adding simulation step size and real-time factor:

        <physics name="1ms" type="ignored">
            <max_step_size>0.01</max_step_size>
            <real_time_factor>1.0</real_time_factor>
        </physics>

Adding essintial plugins:

        <plugin
            filename="libignition-gazebo-physics-system.so"
            name="ignition::gazebo::systems::Physics">
        </plugin>

        <plugin
            filename="libignition-gazebo-user-commands-system.so"
            name="ignition::gazebo::systems::UserCommands">
        </plugin>

        <plugin
            filename="libignition-gazebo-scene-broadcaster-system.so"
            name="ignition::gazebo::systems::SceneBroadcaster">
        </plugin>

Adding the gravity, magnetic field and atmosphere properties.

        <gravity>0 0 -9.8</gravity>
        <magnetic_field>5.565e-06 2.289e-05 -4.239e-05</magnetic_field>
        <atmosphere type='adiabatic' />

Adding the world's background color and light, enabling shadows of it.

        <scene>
            <ambient>0.4 0.4 0.4 1</ambient>
            <background>0.7 0.7 0.7 1</background>
            <shadows>true</shadows>
        </scene>

Adding the 100x100 ground plane:

        <model name='ground_plane'>
            <pose>0 0 0 0 0 0</pose>
            <self_collide>false</self_collide>
            <static>true</static>
            <link name='ground'>
                <pose>0 0 0 0 0 0</pose>
                <enable_wind>false</enable_wind>
                <visual name='visual'>
                    <geometry>
                        <plane>
                            <normal>0 0 1</normal>
                            <size>100 100</size>
                        </plane>
                    </geometry>
                    <material>
                        <ambient>0.8 0.8 0.8 1</ambient>
                        <diffuse>0.8 0.8 0.8 1</diffuse>
                        <specular>0.8 0.8 0.8 1</specular>
                        <emissive>0.0 0.0 0.0 1</emissive>
                    </material>
                </visual>
                <collision name='collision'>
                    <geometry>
                        <plane>
                            <normal>0 0 1</normal>
                            <size>100 100</size>
                        </plane>
                    </geometry>
                    <surface>
                        <friction>
                            <ode>
                            </ode>
                        </friction>
                        <bounce />
                        <contact />
                    </surface>
                </collision>
                <inertial>
                    <pose>0 0 0 0 0 0</pose>
                    <mass>1</mass>
                    <inertia>
                        <ixx>1</ixx>
                        <ixy>0</ixy>
                        <ixz>0</ixz>
                        <iyy>1</iyy>
                        <iyz>0</iyz>
                        <izz>1</izz>
                    </inertia>
                </inertial>
            </link>
        </model>

Adding the directional light named sun to 10m above:

        <light type="directional" name="sun">
            <cast_shadows>true</cast_shadows>
            <pose>0 0 10 0 0 0</pose>
            <diffuse>0.8 0.8 0.8 1</diffuse>
            <specular>0.2 0.2 0.2 1</specular>
            <attenuation>
                <range>1000</range>
                <constant>0.9</constant>
                <linear>0.01</linear>
                <quadratic>0.001</quadratic>
            </attenuation>
            <direction>-0.5 0.1 -0.9</direction>
        </light>

Add the apartment model 20 away through x-axis.

        <include>
            <uri>
                https://fuel.gazebosim.org/1.0/chapulina/models/Apartment
            </uri>
            <name>apartment</name>
            <pose>20 0 0 0 0 0</pose>
        </include>

Simulation world is prepared now. To test it, we need to create a launch file to start the simulation.

Simulation Launch File

To launch the simulation, fill the simulation.launch.py with following lines. This launch file launches 1 launch file and runs 3 nodes:

Gazebo Sim launch file starts the simulation with given world file, in this case demo_world.sdf.
Robot State Publisher publishes the robot URDF robot.urdf
Gazebo Sim Create node spawns the robot published from robot state publisher to the sim world with specified name and coordinates
Gazebo Bridge creates a communication bridge between ros and gazebo to send messages like /cmd_vel /imu etc.

Building and Testing

To build the project, it is needed to add the new directories to the setup.py

Add these lines to setup.py to build urdf, worlds, meshes and launch directories.

# at the top of setup py, add:
import os
from glob import glob

# in the data_files array, add:
        (os.path.join("share", package_name, "urdf"), glob("urdf/*")),
        (os.path.join("share", package_name, "meshes"), glob("meshes/*")),
        (os.path.join("share", package_name, "worlds"), glob("worlds/*")),
        (os.path.join("share", package_name, "launch"), glob("launch/*")),

Then, build the package and source install/setup.bash.

colcon build --packages-select gazebo_project && source install/setup.bash

IMPORTANT: If you make any changes to the files in this project, you need to do the build and source step!

To test to URDF file, run:

ros2 launch gazebo_project rviz.launch.py

Add set fixed frame to link_chassis and add RobotModel visualization.

To test the whole simulation, run:

ros2 launch gazebo_project simulation.launch.py

Do not run these 2 launch files at the same time.

References

turtlebot4_simulator by turtlebot.

gulerburak / gazebo_project Goto Github PK

gazebo_project's Introduction

Gazebo Tutorial Course

Contents

Dependencies

Creating the ros package

Creating the robot

Creating the Simulation World

Simulation Launch File

Building and Testing

References

gazebo_project's People

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