使用機器人操作系統ROS 2和仿真軟件Gazebo 9環境綜合測試教程（三）

在完成教程（一）搭建機器人和（二）命令遙控可視化后，將仿真機器人用于更為逼真的環境，可以測試如SLAM，區域覆蓋以及場館巡邏算法，這里環境均采用aws提供模型，分別為smallhouse和bookstore，環境適用于ROS2和ROS1全部案例，但ROS1內容不做講解，這里只簡要敘述一下ROS2中調試和使用的過程。

ROS2和Gazebo9中mobot室內環境仿真測試

在環境中添加機器人模型：

在launch中添加機器人需要注意如上差異，如添加一個urdf格式機器人可參考如下命令：

ros2 service call /spawn_entity 'gazebo_msgs/SpawnEntity' '{name: "urdf_ball", xml: ""}'

更多內容參考：https://github.com/ros-simulation/gazebo_ros_pkgs/wiki/ROS-2-Migration:-Spawn-and-delete

如果需要在制定位置插入機器人，需要查閱spawn_entity.py源碼：

# Encode xml object back into string for service call

entity_xml = ElementTree.tostring(xml_parsed)

# Form requested Pose from arguments

initial_pose = Pose()

initial_pose.position.x = float(self.args.x)

initial_pose.position.y = float(self.args.y)

initial_pose.position.z = float(self.args.z)

q = quaternion_from_euler(self.args.R, self.args.P, self.args.Y)

initial_pose.orientation.w = q[0]

initial_pose.orientation.x = q[1]

initial_pose.orientation.y = q[2]

initial_pose.orientation.z = q[3]

注意這里的initial_pose和表中參數的對應情況，不再贅述。

mobot加入smallhouse場景如下所示，支持多機器人！后續補充：

可以在此環境中復習，前2課所學過的全部內容。

啟動文件smallhouse.launch.py代碼如下：

import os

from ament_index_python.packages import get_package_share_directory

from launch import LaunchDescription

from launch.actions import ExecuteProcess, DeclareLaunchArgument

from launch.actions import IncludeLaunchDescription

from launch_ros.actions import Node

from launch.conditions import IfCondition

from launch.launch_description_sources import PythonLaunchDescriptionSource

from launch.substitutions import LaunchConfiguration

# this is the function launch system will look for

def generate_launch_description():

robot_name = 'mobot'

world_file_name = 'smallhouse.world'

# full path to urdf and world file

world = os.path.join(get_package_share_directory(robot_name), 'worlds', world_file_name)

urdf = os.path.join(get_package_share_directory(robot_name), 'urdf', 'mobot.urdf')

# read urdf contents because to spawn an entity in

# gazebo we need to provide entire urdf as string on command line

#small_house = launch.actions.IncludeLaunchDescription(

# launch.launch_description_sources.PythonLaunchDescriptionSource(

# os.path.join(

# get_package_share_directory('aws_robomaker_small_house_world'),

# 'launch',

# 'small_house.launch.py')))

# Spawn mobot

spawn_mobot = Node(

package='gazebo_ros',

node_executable='spawn_entity.py',

node_name='spawn_entity',

#node_namespace=namespace_,

output='screen',

#emulate_tty=True,

arguments=['-entity',

'mobot',

'-x', '3.5', '-y', '1.0', '-z', '0.1',

'-file', urdf

]

)

#xml = open(urdf, 'r').read()

# double quotes need to be with escape sequence

#xml = xml.replace('"', '\\"')

# this is argument format for spwan_entity service

#spwan_args = '{name: \"mobot\", xml: \"' + xml + '\"}'

# create and return launch description object

return LaunchDescription([

# start gazebo, notice we are using libgazebo_ros_factory.so instead of libgazebo_ros_init.so

# That is because only libgazebo_ros_factory.so contains the service call to /spawn_entity

ExecuteProcess(

cmd=['gazebo', '--verbose', world, '-s', 'libgazebo_ros_factory.so'],

output='screen'),

# tell gazebo to spwan your robot in the world by calling service

# ExecuteProcess(

# cmd=['ros2', 'service', 'call', '/spawn_entity', 'gazebo_msgs/SpawnEntity', spwan_args],

# output='screen'),

#small_house,

spawn_mobot,

])

機器人初始位置為x: 3.5 y: 1.0 z: 0.1，參考如下文檔片段：

Robot Simulation - Initial Position

Do not use (0,0,0) for the initial position as it will collide with the lounge chairs. Instead, a resonable position is (3.5,1.0,0.0).

機器人可以加載已有的ROS2功能包，如導航功能包等。

具體參考：2020年ROS機器人操作系統用戶官方調查?文末的介紹。

關于環境綜合測試更多截圖如下所示：

smallhouse：

navigation2:

bookstore:

navigation2:

下一節將講解如何制作一個跟隨機器人～mobot-follow～

機器人

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