【ROS学习】移动机器人建模仿真(1)

最近实验室的项目中用到了ROS，所以就学了一些。前期先将ROS官网中的基本教程了解了一遍，对于它大体有了一些基本的认识。本文主要是实现一个移动机器人3D URDF建模，其中添加了相机信息和2D雷达信息采集装置，在Gazebo中做仿真实验。

3D URDF建模

移动机器人包括主体，两个*、一个万向轮、相机模块和2D雷达模块。

接下来我们先要建立ROS工作空间mycar_ws，

cd 
mkdir mycar_ws
cd mybcar_ws
catkin init
mkdir src
catkin_make
echo "source ~/mycar_ws/devel/setup.bash" >> ~/.bashrc

在工作空间中建立mycar_description功能包，命令如下： 

cd src
catkin_create_pkg mycar_description roscpp rospy #加入这两个依赖项便于后期用Python或C++写相应的代码

在所建立的mycar_description功能包中，创建urdf文件夹，并在其中分别创建mycar.xacro、mycar.gazebo、mycar_materials.xacro这三个文本。

• mycar.xacro：是这三者中主要部分，将来负责读取其他两个文本中的内容，并在这个文本中用URDF描述这个移动机器人。
• mycar.gazebo：这个文件运用特定的gazebo标签对移动机器人模型进行包装，使其可以在Gazebo中进行仿真。
• mycar_materials.xacro：这个文件夹负责对移动机器人外观进行修饰。

这三个文件具体内容如下：

mycar.xacro

<?xml version='1.0'?>

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

	<xacro:property name="cameraSize" value="0.05"/>
  <xacro:property name="cameraMass" value="0.1"/>

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

  <link name='chassis'>
    <pose>0 0 0.1 0 0 0</pose>

    <inertial>
      <mass value="10.0"/>
      <origin xyz="0.0 0 0.1" rpy=" 0 0 0"/>
      <inertia
          ixx="0.5" ixy="0" ixz="0"
          iyy="1.0" iyz="0"
          izz="0.1"
      />
    </inertial>

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


  <link name="left_wheel">
    <!--origin xyz="0.1 0.13 0.1" rpy="0 1.5707 1.5707"/-->
    <collision name="collision">
      <origin xyz="0 0 0" rpy="0 1.5707 1.5707"/>
      <geometry>
        <cylinder radius="0.1" length="0.05"/>
      </geometry>
    </collision>
    <visual name="left_wheel_visual">
      <origin xyz="0 0 0" rpy="0 1.5707 1.5707"/>
      <geometry>
        <cylinder radius="0.1" length="0.05"/>
      </geometry>
    </visual>
    <inertial>
      <origin xyz="0 0 0" rpy="0 1.5707 1.5707"/>
      <mass value="5"/>
      <cylinder_inertia m="5" r="0.1" h="0.05"/>
      <inertia
        ixx="1.0" ixy="0.0" ixz="0.0"
        iyy="1.0" iyz="0.0"
        izz="1.0"/>
    </inertial>
  </link>

  <link name="right_wheel">
    <!--origin xyz="0.1 -0.13 0.1" rpy="0 1.5707 1.5707"/-->
    <collision name="collision">
      <origin xyz="0 0 0" rpy="0 1.5707 1.5707"/>
      <geometry>
        <cylinder radius="0.1" length="0.05"/>
      </geometry>
    </collision>
    <visual name="right_wheel_visual">
      <origin xyz="0 0 0" rpy="0 1.5707 1.5707"/>
      <geometry>
        <cylinder radius="0.1" length="0.05"/>
      </geometry>
    </visual>
    <inertial>
      <origin xyz="0 0 0" rpy="0 1.5707 1.5707"/>
      <mass value="5"/>
      <cylinder_inertia m="5" r="0.1" h="0.05"/>
      <inertia
        ixx="1.0" ixy="0.0" ixz="0.0"
        iyy="1.0" iyz="0.0"
        izz="1.0"/>
    </inertial>
  </link>


  <joint type="continuous" name="left_wheel_hinge">
    <origin xyz="0.1 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="100" velocity="100"/>
    <joint_properties damping="0.0" friction="0.0"/>
  </joint>

  <joint type="continuous" name="right_wheel_hinge">
    <origin xyz="0.1 -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="100" velocity="100"/>
    <joint_properties damping="0.0" friction="0.0"/>
  </joint>

	<link name="camera">
    <collision>
      <origin xyz="0 0 0" rpy="0 0 0"/>
      <geometry>
        <box size="${cameraSize} ${cameraSize} ${cameraSize}"/>
      </geometry>
    </collision>

    <visual>
      <origin xyz="0 0 0" rpy="0 0 0"/>
      <geometry>
        <box size="${cameraSize} ${cameraSize} ${cameraSize}"/>
      </geometry>
      <material name="green"/>
    </visual>

    <inertial>
      <mass value="${cameraMass}" />
      <origin xyz="0 0 0" rpy="0 0 0"/>
      <box_inertia m="${cameraMass}" x="${cameraSize}" y="${cameraSize}" z="${cameraSize}" />
      <inertia ixx="1e-6" ixy="0" ixz="0" iyy="1e-6" iyz="0" izz="1e-6" />
    </inertial>
  </link>

  <joint name="camera_joint" type="fixed">
    <axis xyz="0 1 0" />
    <origin xyz=".2 0 0" rpy="0 0 0"/>
    <parent link="chassis"/>
    <child link="camera"/>
  </joint>


  <joint name="hokuyo_joint" type="fixed">
    <axis xyz="0 1 0" />
    <origin xyz=".15 0 .1" rpy="0 0 0"/>
    <parent link="chassis"/>
    <child link="hokuyo"/>
  </joint>

  <!-- Hokuyo Laser -->
  <link name="hokuyo">
    <collision>
      <origin xyz="0 0 0" rpy="0 0 0"/>
      <geometry>
    <box size="0.1 0.1 0.1"/>
      </geometry>
    </collision>

    <visual>
      <origin xyz="0 0 0" rpy="0 0 0"/>
      <geometry>
        <mesh filename="package://mycar_description/meshes/hokuyo.dae"/>
      </geometry>
    </visual>

    <inertial>
      <mass value="1e-5" />
      <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>
  </link>


</robot>

mycar.gazebo

<?xml version="1.0"?>
<robot>


  <gazebo>
    <plugin name="differential_drive_controller" filename="libgazebo_ros_diff_drive.so">
      <legacyMode>false</legacyMode>
      <alwaysOn>true</alwaysOn>
      <updateRate>20</updateRate>
      <leftJoint>left_wheel_hinge</leftJoint>
      <rightJoint>right_wheel_hinge</rightJoint>
      <wheelSeparation>0.4</wheelSeparation>
      <wheelDiameter>0.1</wheelDiameter>
      <torque>20</torque>
      <commandTopic>mycar/cmd_vel</commandTopic>
      <odometryTopic>odom</odometryTopic>
      <odometryFrame>odom</odometryFrame>
      <robotBaseFrame>chassis</robotBaseFrame>
    </plugin>
  </gazebo>

  <gazebo reference="chassis">
      <material>Gazebo/Orange</material>
    </gazebo>
	
	<gazebo reference="left_wheel">
    <material>Gazebo/Blue</material>
  </gazebo>

  <gazebo reference="right_wheel">
    <material>Gazebo/Blue</material>
  </gazebo>


  <gazebo reference="camera">
    <material>Gazebo/Green</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>mycar/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="gpu_ray" name="head_hokuyo_sensor"> -->
      <sensor type="ray" name="head_hokuyo_sensor">
      <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>-1.570796</min_angle>
            <max_angle>1.570796</max_angle>
          </horizontal>
        </scan>
        <range>
          <min>0.1</min>
          <max>30.0</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_gpu_laser.so"> -->
	<plugin name="gazebo_ros_head_hokuyo_controller" filename="libgazebo_ros_laser.so">
        <topicName>/mycar/laser/scan</topicName>
        <frameName>hokuyo</frameName>
      </plugin>
    </sensor>
  </gazebo>
	
</robot>

mycar_materials.xacro

<?xml version="1.0"?>
<robot>

  <material name="black">
    <color rgba="0.0 0.0 0.0 1.0"/>
  </material>

  <material name="blue">
    <color rgba="0.0 0.0 0.8 1.0"/>
  </material>

  <material name="green">
    <color rgba="0.0 0.8 0.0 1.0"/>
  </material>

  <material name="grey">
    <color rgba="0.2 0.2 0.2 1.0"/>
  </material>

  <material name="orange">
    <color rgba="${255/255} ${108/255} ${10/255} 1.0"/>
  </material>

  <material name="brown">
    <color rgba="${222/255} ${207/255} ${195/255} 1.0"/>
  </material>

  <material name="red">
    <color rgba="0.8 0.0 0.0 1.0"/>
  </material>

  <material name="white">
    <color rgba="1.0 1.0 1.0 1.0"/>
  </material>

</robot>

接着在这个功能包中创建launch文件夹，在其中创建mycar.launch。这个文件是用于启动Gazebo仿真器并将创建好的移动机器人模型载入其中。

mycar.launch

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

  <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 file="$(find gazebo_ros)/launch/empty_world.launch">
    <arg name="world_name" value="$(find mycar_description)/worlds/mycar.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>

  
  <param name="robot_description" command="$(find xacro)/xacro.py '$(find mycar_description)/urdf/mycar.xacro'"/>

  <node name="mybot_spawn" pkg="gazebo_ros" type="spawn_model" output="screen"
   args="-urdf -param robot_description -model mybot" />
  <node name="joint_state_publisher" pkg="joint_state_publisher" type="joint_state_publisher" />
  <node name="robot_state_publisher" pkg="robot_state_publisher" type="state_publisher" />

</launch>

<arg name="world_name" value="$(find mycar_description)/worlds/mycar.world"/> 这一句代码的意思是去mycar_description包的worlds文件夹中找mycar.world文件。所以在这里我们需要在mycar_description功能包中创建worlds文件夹，并在其中创建mycar.world文件。

mycar.world

<?xml version="1.0" ?>
<sdf version="1.4">
  <!-- We use a custom world for the rrbot so that the camera angle is launched correctly -->

  <world name="default">

    <include>
      <uri>model://ground_plane</uri>
    </include>

    <include>
      <uri>model://sun</uri>
    </include>

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

  </world>
</sdf>

建立完这些文件之后，对工作空间进行编译，具体操作如下：

cd ~/mycar_ws
catkin_make
source devel/setup.bash
roslaunch mycar_descripition mycar.launch

 

未完待续。。。