ros机器人编程实践（16.2）- 仿真SmartCar之模型“飞起来“

前言

上一篇博客：ros机器人编程实践（16.1）- 仿真SmartCar之搭建模型
上一章已经成功搭建SmartCar模型，这一章在基础上做一些优化，并让他跑起来

准备工作

安装arbotix功能包，用于发布速度命令并执行

sudo apt-get install ros-kinetic-arbotix

安装joint-state-publisher发布器，可以控制速度

sudo apt-get install ros-kinetic-joint-state-publisher-gui

创建配置文件

创建配置文件夹config

cd ~/SmartCar_ws/src/smartcar_description
mkdir config

创建配置文件

cd config
sudo gedit smartcar_arbotix.yaml

贴上如下代码：

port: /dev/ttyUSB0
baud: 115200
rate: 20
sync_write: True
sync_read: True
read_rate: 20
write_rate: 20

controllers: {
   #  Pololu motors: 1856 cpr = 0.3888105m travel = 4773 ticks per meter (empirical: 4100)
   base_controller: {type: diff_controller, base_frame_id: base_link, base_width: 0.26, ticks_meter: 4100, Kp: 12, Kd: 12, Ki: 0, Ko: 50, accel_limit: 1.0 }
}

注：这个配置文件和odom坐标系有关，笔者学的也不深入，不是很理解这里的原理，不过不重要

优化urdf模型文件

根据古月居老师的讲解，gazebo对urdf的文件支持不如xacro文件，所以将上篇博客写的urdf改成xacro

cd ~/SmartCar_ws/src/smartcar_description/urdf
gedit gazebo.urdf.xacro
gedit smartcar.urdf.xacro
gedit smartcar_body.urdf.xacro

gazebo.urdf.xacro：

<robot xmlns:controller="http://playerstage.sourceforge.net/gazebo/xmlschema/#controller" 
	xmlns:interface="http://playerstage.sourceforge.net/gazebo/xmlschema/#interface" 
	xmlns:sensor="http://playerstage.sourceforge.net/gazebo/xmlschema/#sensor" 
	xmlns:xacro="http://ros.org/wiki/xacro" 
	name="smartcar_gazebo">



<xacro:macro name="smartcar_sim">
    <gazebo reference="base_link">
        <material>Gazebo/Bluematerial>
        <turnGravityOff>falseturnGravityOff>
    gazebo>

    <gazebo reference="right_front_wheel">
        <material>Gazebo/FlatBlackmaterial>
	gazebo>

	<gazebo reference="right_back_wheel">
        <material>Gazebo/FlatBlackmaterial>
    gazebo>

    <gazebo reference="left_front_wheel">
        <material>Gazebo/FlatBlackmaterial>
    gazebo>

    <gazebo reference="left_back_wheel">
        <material>Gazebo/FlatBlackmaterial>
    gazebo>

    <gazebo reference="head">
        <material>Gazebo/Whitematerial>
    gazebo>

xacro:macro>

robot>

smartcar.urdf.xacro:

<robot name="smartcar"  
    xmlns:xi="http://www.w3.org/2001/XInclude"
	xmlns:gazebo="http://playerstage.sourceforge.net/gazebo/xmlschema/#gz"
    xmlns:model="http://playerstage.sourceforge.net/gazebo/xmlschema/#model"
	xmlns:sensor="http://playerstage.sourceforge.net/gazebo/xmlschema/#sensor"
	xmlns:body="http://playerstage.sourceforge.net/gazebo/xmlschema/#body"
    xmlns:geom="http://playerstage.sourceforge.net/gazebo/xmlschema/#geom"
    xmlns:joint="http://playerstage.sourceforge.net/gazebo/xmlschema/#joint"
	xmlns:controller="http://playerstage.sourceforge.net/gazebo/xmlschema/#controller"
	xmlns:interface="http://playerstage.sourceforge.net/gazebo/xmlschema/#interface"
	xmlns:rendering="http://playerstage.sourceforge.net/gazebo/xmlschema/#rendering"
    xmlns:renderable="http://playerstage.sourceforge.net/gazebo/xmlschema/#renderable"
    xmlns:physics="http://playerstage.sourceforge.net/gazebo/xmlschema/#physics"
	xmlns:xacro="http://ros.org/wiki/xacro">

  <include filename="$(find smartcar_description)/urdf/smartcar_body.urdf.xacro" />

  
  <smartcar_body/>

  <smartcar_sim/>

robot>

smartcar_body.urdf.xacro:

<robot name="smartcar" xmlns:xacro="http://ros.org/wiki/xacro">
  <property name="M_PI" value="3.14159"/>

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

  <property name="base_x" value="0.33" />
  <property name="base_y" value="0.33" />

  <xacro:macro name="smartcar_body">


	<link name="base_link">
	<inertial>
      <origin xyz="0 0 0.055"/>
      <mass value="100.0" />
      <inertia ixx="1.0" ixy="0.0" ixz="0.0" iyy="1.0" iyz="0.0" izz="1.0"/>
    inertial>
    <visual>
      <geometry>
        <box size="0.25 .16 .05"/>
      geometry>
	  <origin rpy="0 0 0" xyz="0 0 0.055"/>
      <material name="blue">
	  <color rgba="0 0 .8 1"/>
      material>
   visual>
   <collision>
      <origin rpy="0 0 0" xyz="0 0 0.055"/>
      <geometry>
        <box size="0.25 .16 .05" />
      geometry>
    collision>
  link>


 <link name="left_front_wheel">
	<inertial>
      <origin  xyz="0.08 0.08 0.025"/>
      <mass value="1" />
       <inertia ixx="1.0" ixy="0.0" ixz="0.0" iyy="1.0" iyz="0.0" izz="1.0"/>
    inertial>
    <visual>
      <geometry>
        <cylinder length=".02" radius="0.025"/>
      geometry>
      <material name="black">
        <color rgba="0 0 0 1"/>
      material>
    visual>
    <collision>
      <origin rpy="0 1.57075 1.57075" xyz="0.08 0.08 0.025"/>
      <geometry>
         <cylinder length=".02" radius="0.025"/>
      geometry>
    collision>
  link>

  <joint name="left_front_wheel_joint" type="continuous">
    <axis xyz="0 0 1"/>
    <parent link="base_link"/>
    <child link="left_front_wheel"/>
    <origin rpy="0 1.57075 1.57075" xyz="0.08 0.08 0.025"/>
    <limit effort="100" velocity="100"/>
    <joint_properties damping="0.0" friction="0.0"/>
  joint>

  <link name="right_front_wheel">
	<inertial>
      <origin xyz="0.08 -0.08 0.025"/>
      <mass value="1" />
       <inertia ixx="1.0" ixy="0.0" ixz="0.0" iyy="1.0" iyz="0.0" izz="1.0"/>
    inertial>
    <visual>
      <geometry>
        <cylinder length=".02" radius="0.025"/>
      geometry>
      <material name="black">
        <color rgba="0 0 0 1"/>
      material>
    visual>
    <collision>
      <origin rpy="0 1.57075 1.57075" xyz="0.08 -0.08 0.025"/>
      <geometry>
         <cylinder length=".02" radius="0.025"/>
      geometry>
    collision>
  link>

  <joint name="right_front_wheel_joint" type="continuous">
    <axis xyz="0 0 1"/>
    <parent link="base_link"/>
    <child link="right_front_wheel"/>
    <origin rpy="0 1.57075 1.57075" xyz="0.08 -0.08 0.025"/>
    <limit effort="100" velocity="100"/>
    <joint_properties damping="0.0" friction="0.0"/>
 joint>

 <link name="left_back_wheel">
    <inertial>
      <origin xyz="-0.08 0.08 0.025"/>
      <mass value="1" />
       <inertia ixx="1.0" ixy="0.0" ixz="0.0" iyy="1.0" iyz="0.0" izz="1.0"/>
    inertial>
    <visual>
      <geometry>
        <cylinder length=".02" radius="0.025"/>
      geometry>
      <material name="black">
        <color rgba="0 0 0 1"/>
      material>
   visual>
   <collision>
       <origin rpy="0 1.57075 1.57075" xyz="-0.08 0.08 0.025"/>
      <geometry>
         <cylinder length=".02" radius="0.025"/>
      geometry>
    collision>
  link>

  <joint name="left_back_wheel_joint" type="continuous">
    <axis xyz="0 0 1"/>
    <parent link="base_link"/>
    <child link="left_back_wheel"/>
    <origin rpy="0 1.57075 1.57075" xyz="-0.08 0.08 0.025"/>
    <limit effort="100" velocity="100"/>
    <joint_properties damping="0.0" friction="0.0"/>
  joint>

  <link name="right_back_wheel">
	<inertial>
       <origin xyz="-0.08 -0.08 0.025"/>
       <mass value="1" />
       <inertia ixx="1.0" ixy="0.0" ixz="0.0" iyy="1.0" iyz="0.0" izz="1.0"/>
    inertial>
    <visual>
      <geometry>
        <cylinder length=".02" radius="0.025"/>
      geometry>
      <material name="black">
        <color rgba="0 0 0 1"/>
      material>
   visual>
   <collision>
      <origin rpy="0 1.57075 1.57075" xyz="-0.08 -0.08 0.025"/>
      <geometry>
         <cylinder length=".02" radius="0.025"/>
      geometry>
    collision>
  link>


  <joint name="right_back_wheel_joint" type="continuous">
    <axis xyz="0 0 1"/>
    <parent link="base_link"/>
    <child link="right_back_wheel"/>
    <origin rpy="0 1.57075 1.57075" xyz="-0.08 -0.08 0.025"/>
    <limit effort="100" velocity="100"/>
    <joint_properties damping="0.0" friction="0.0"/>
  joint>

  <link name="head">
	<inertial>
      <origin xyz="0.08 0 0.08"/>
      <mass value="1" />
      <inertia ixx="1.0" ixy="0.0" ixz="0.0" iyy="1.0" iyz="0.0" izz="1.0"/>
    inertial>
    <visual>
      <geometry>
        <box size=".02 .03 .03"/>
      geometry>
	  <material name="white">
		<color rgba="1 1 1 1"/>
	  material>
     visual>
     <collision>
      <origin xyz="0.08 0 0.08"/>
      <geometry>
         <cylinder length=".02" radius="0.025"/>
      geometry>
    collision>
  link>

  <joint name="tobox" type="fixed">
    <parent link="base_link"/>
    <child link="head"/>
    <origin xyz="0.08 0 0.08"/>
  joint>
  xacro:macro>

robot>

让模型飞起来

在rviz中启动模型

roslaunch smartcar_description smartcar_display.rviz.launch

和上一节一样添加模型如下图：

这里Fixed Frame选择odom坐标系：

发布速度命令：

rostopic pub -r 10 /cmd_vel geometry_msgs/Twist '{linear: {x: 0.5, y: 0, z: 0}, angular: {x: 0, y: 0, z: 0.5}}'

前面三个参数是x,y,z三个方向的速度，后面三个参数是绕x,y,z三个轴旋转的角速度，上述命令就是让小车以0.5m/s的线速度，0.5rad/s的角速度画圆。
执行效果：