ROS学习初探之自建小车模型并进行仿真（三）

在gazebo环境中，用电脑键盘控制小车

在上一节，我们配置好了xacro文件，那么这一节我们实现小车在gazebo环境中通过键盘控制节点动起来。

一、配置各个文件

修改CMakeLists.txt文件

下面是我修改的由SolidWorks导出的tianbot_mini_description功能包的CMakeLists.txt文件:

cmake_minimum_required(VERSION 2.8.3)

project(tianbot_mini_description)

find_package(catkin REQUIRED COMPONENTS
  urdf
  xacro
  gazebo_plugins
  gazebo_ros
  gazebo_ros_control
  roscpp
  rospy
  controller_manager
  message_generation
  std_msgs
)


catkin_package(
  CATKIN_DEPENDS urdf xacro
)

include_directories(
  ${catkin_INCLUDE_DIRS}
)

修改package.xml文件

下面是我修改的由SolidWorks导出的tianbot_mini_description功能包的package.xml文件，这里配置好各个话题的依赖:

<?xml version="1.0"?>
<package format="2">
  <name>tianbot_mini_description</name>
  <version>1.0.0</version>
  <description>
    <p>URDF Description package for tianbot_mini_description</p>
    <p>This package contains configuration data, 3D models and launch files
for tianbot_mini_description robot</p>
  </description>
  <author>TODO</author>
  <maintainer email="[email protected]" />
  <license>BSD</license>
  <buildtool_depend>catkin</buildtool_depend>
  <depend>roslaunch</depend>
  <depend>robot_state_publisher</depend>
  <depend>rviz</depend>
  <depend>joint_state_publisher</depend>
  <depend>gazebo</depend>
<build_depend>urdf</build_depend>
  <build_depend>xacro</build_depend>
  <build_export_depend>urdf</build_export_depend>
  <build_export_depend>xacro</build_export_depend>
  <exec_depend>urdf</exec_depend>
  <exec_depend>xacro</exec_depend>
<build_depend>gazebo_plugins</build_depend>
  <build_depend>gazebo_ros</build_depend>
  <build_depend>gazebo_ros_control</build_depend>
  <build_depend>roscpp</build_depend>
  <build_depend>rospy</build_depend>
  <build_export_depend>gazebo_plugins</build_export_depend>
  <build_export_depend>gazebo_ros</build_export_depend>
  <build_export_depend>gazebo_ros_control</build_export_depend>
  <build_export_depend>roscpp</build_export_depend>
  <build_export_depend>rospy</build_export_depend>
  <exec_depend>gazebo_plugins</exec_depend>
  <exec_depend>gazebo_ros</exec_depend>
  <exec_depend>gazebo_ros_control</exec_depend>
  <exec_depend>roscpp</exec_depend>
  <exec_depend>rospy</exec_depend>
  
  <export>
    <architecture_independent />
  </export>
</package>

修改yaml文件

打开tianbot_mini_description/config/joint_names_tianbot_mini_description.yaml文件，修改为以下所示:

controller_joint_names: ['', 'left_wheel_joint', 'right_wheel_joint', 'caster_wheel_joint', 'casterball_joint', ]
controllers: {
   base_controller: {
       type: diff_controller, 
       base_frame_id: base_footprint, 
       ticks_meter: 4100, 
       Kp: 12, 
       Kd: 12, 
       Ki: 0, 
       Ko: 50, 
       accel_limit: 1.0 
    }
}

加入激光雷达插件

在tianbot_mini_description/urdf文件夹中新建lidar_gazebo.xacro文件

<?xml version="1.0"?>
<robot xmlns:xacro="http://www.ros.org/wiki/xacro" name="lidar">

        <!-- Create laser reference frame -->
 <gazebo reference="lidar_Link"> 
            <sensor type="ray" name="rplidar">
                <pose>0 0 0 0 0 0</pose>
                <visualize>false</visualize>
                <update_rate>5.5</update_rate>
                <ray>
                    <scan>
                      <horizontal>
                        <samples>360</samples>
                        <resolution>1</resolution>
                        <min_angle>-3</min_angle>
                        <max_angle>3</max_angle>
                      </horizontal>
                    </scan>
                    <range>
                      <min>0.10</min>
                      <max>6.0</max>
                      <resolution>0.01</resolution>
                    </range>
                    <noise>
                      <type>gaussian</type>
                      <mean>0.0</mean>
                      <stddev>0.01</stddev>
                    </noise>
                </ray>
                <plugin name="gazebo_rplidar" filename="libgazebo_ros_laser.so">
                    <topicName>/scan</topicName>
                    <frameName>lidar_Link</frameName>
                </plugin>
            </sensor>
        </gazebo>


</robot>

接着再创建tianbot_mini_run.urdf.xacro文件，内容如下:

<?xml version="1.0"?>
<robot name="tianbot_mini" xmlns:xacro="http://www.ros.org/wiki/xacro">

    <xacro:include filename="$(find tianbot_mini_description)/urdf/tianbot_mini.urdf.xacro" />
 <xacro:include filename="$(find tianbot_mini_description)/urdf/lidar_gazebo.xacro" />


    <tianbot_mini/>

</robot>

这里相当于把小车和雷达结合在一起了，这样只需要在launch文件中调用这个xacro文件，就相当于调用激光雷达小车了。

配置launch文件

完成上述工作后，我们打开tianbot_mini_description/launch文件夹，创建tianbotmini_laser_gazebo.launch文件，我们先看看自动生成的gazebo.launch文件:

<launch>
  <include
    file="$(find gazebo_ros)/launch/empty_world.launch" />
  <node
    name="tf_footprint_base"
    pkg="tf"
    type="static_transform_publisher"
    args="0 0 0 0 0 0 base_link base_footprint 40" />
  <node
    name="spawn_model"
    pkg="gazebo_ros"
    type="spawn_model"
    args="-file $(find tianbot_mini_description)/urdf/urdf/tianbot_mini_description.urdf -urdf -model tianbot_mini_description"
    output="screen" />
  <node
    name="fake_joint_calibration"
    pkg="rostopic"
    type="rostopic"
    args="pub /calibrated std_msgs/Bool true" />
</launch>

基于gazebo.launch文件以及古月老师的资料，我们在tianbotmini_laser_gazebo.launch文件编写代码:

<launch>

  <!-- 设置launch文件的参数 -->
    <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"/>

    <!-- 运行gazebo仿真环境 -->
    <include file="$(find gazebo_ros)/launch/empty_world.launch">
        <arg name="debug" value="$(arg debug)" />
        <arg name="gui" value="$(arg gui)" />
        <arg name="paused" value="$(arg paused)"/>
        <arg name="use_sim_time" value="$(arg use_sim_time)"/>
        <arg name="headless" value="$(arg headless)"/>
    </include>
       
    <!-- 加载机器人模型描述参数 -->
    <param name="robot_description" command="$(find xacro)/xacro --inorder '$(find tianbot_mini_description)/urdf/tianbot_mini_run.urdf.xacro'" /> 

    <!-- 运行joint_state_publisher节点，发布机器人的关节状态  -->
    <node name="joint_state_publisher" pkg="joint_state_publisher" type="joint_state_publisher" ></node> 

    <!-- 运行robot_state_publisher节点，发布tf  -->
    <node name="robot_state_publisher" pkg="robot_state_publisher" type="robot_state_publisher"  output="screen" >
        <param name="publish_frequency" type="double" value="50.0" />
    </node>

    <!-- 在gazebo中加载机器人模型-->
    <node name="urdf_spawner" pkg="gazebo_ros" type="spawn_model" respawn="false" output="screen"
          args="-urdf -model mbot -param robot_description"/> 
    <node
    name="fake_joint_calibration"
    pkg="rostopic"
    type="rostopic"
    args="pub /calibrated std_msgs/Bool true" />
    <node
    name="tf_footprint_base"
    pkg="tf"
    type="static_transform_publisher"
    args="0 0 0.0215 0 0 0 base_footprint base_link 40" />

</launch>

保存后，我们可以在gazebo中打开我们的小车了，打开终端，输入:

roslaunch tianbot_mini_description tianbotmini_laser_gazebo.launch

如上图，打开的的是一个gazebo的空环境，我们可以放一些障碍物进去
打开一个新终端，打开rviz

rosrun rviz rviz 

在rviz中设置"Fixed Frame"为"base_footprint"，先添加一个RobotModel插件，然后添加一个LaserSCan类型的插件，修改插件订阅的话题为"/scan"，就可以看到界面中的激光数据了。

二、键盘控制

这里我直接当了掉包侠，因为我看到古月老师的mbot_teleop功能包里面，py文件里控制程序发布的话题与我机器人的话题一致，所以我改都不用改，直接

roslaunch mbot_teleop mbot_teleop.launch 
也可以
rosrun mbot_teleop mbot_teleop.py 

就能通过键盘控制节点控制小车运动了。
我们可以看一看古月老师的mbot_teleop.py文件:

#!/usr/bin/env python
# -*- coding: utf-8 -*-

import rospy
from geometry_msgs.msg import Twist
import sys, select, termios, tty

msg = """
Control mbot!
---------------------------
Moving around:
   u    i    o
   j    k    l
   m    ,    .

q/z : increase/decrease max speeds by 10%
w/x : increase/decrease only linear speed by 10%
e/c : increase/decrease only angular speed by 10%
space key, k : force stop
anything else : stop smoothly

CTRL-C to quit
"""

moveBindings = {
        'i':(1,0),
        'o':(1,-1),
        'j':(0,1),
        'l':(0,-1),
        'u':(1,1),
        ',':(-1,0),
        '.':(-1,1),
        'm':(-1,-1),
           }

speedBindings={
        'q':(1.1,1.1),
        'z':(.9,.9),
        'w':(1.1,1),
        'x':(.9,1),
        'e':(1,1.1),
        'c':(1,.9),
          }

def getKey():
    tty.setraw(sys.stdin.fileno())
    rlist, _, _ = select.select([sys.stdin], [], [], 0.1)
    if rlist:
        key = sys.stdin.read(1)
    else:
        key = ''

    termios.tcsetattr(sys.stdin, termios.TCSADRAIN, settings)
    return key

speed = .2
turn = 1

def vels(speed,turn):
    return "currently:\tspeed %s\tturn %s " % (speed,turn)

if __name__=="__main__":
    settings = termios.tcgetattr(sys.stdin)
    
    rospy.init_node('mbot_teleop')
    pub = rospy.Publisher('/cmd_vel', Twist, queue_size=5)

    x = 0
    th = 0
    status = 0
    count = 0
    acc = 0.1
    target_speed = 0
    target_turn = 0
    control_speed = 0
    control_turn = 0
    try:
        print msg
        print vels(speed,turn)
        while(1):
            key = getKey()
            # 运动控制方向键（1：正方向，-1负方向）
            if key in moveBindings.keys():
                x = moveBindings[key][0]
                th = moveBindings[key][1]
                count = 0
            # 速度修改键
            elif key in speedBindings.keys():
                speed = speed * speedBindings[key][0]  # 线速度增加0.1倍
                turn = turn * speedBindings[key][1]    # 角速度增加0.1倍
                count = 0

                print vels(speed,turn)
                if (status == 14):
                    print msg
                status = (status + 1) % 15
            # 停止键
            elif key == ' ' or key == 'k' :
                x = 0
                th = 0
                control_speed = 0
                control_turn = 0
            else:
                count = count + 1
                if count > 4:
                    x = 0
                    th = 0
                if (key == '\x03'):
                    break

            # 目标速度=速度值*方向值
            target_speed = speed * x
            target_turn = turn * th

            # 速度限位，防止速度增减过快
            if target_speed > control_speed:
                control_speed = min( target_speed, control_speed + 0.02 )
            elif target_speed < control_speed:
                control_speed = max( target_speed, control_speed - 0.02 )
            else:
                control_speed = target_speed

            if target_turn > control_turn:
                control_turn = min( target_turn, control_turn + 0.1 )
            elif target_turn < control_turn:
                control_turn = max( target_turn, control_turn - 0.1 )
            else:
                control_turn = target_turn

            # 创建并发布twist消息
            twist = Twist()
            twist.linear.x = control_speed; 
            twist.linear.y = 0; 
            twist.linear.z = 0
            twist.angular.x = 0; 
            twist.angular.y = 0; 
            twist.angular.z = control_turn
            pub.publish(twist)

    except:
        print e

    finally:
        twist = Twist()
        twist.linear.x = 0; twist.linear.y = 0; twist.linear.z = 0
        twist.angular.x = 0; twist.angular.y = 0; twist.angular.z = 0
        pub.publish(twist)

    termios.tcsetattr(sys.stdin, termios.TCSADRAIN, settings)

三、小结

本小节我们通过键盘控制节点控制控制gazebo环境中的小车。下一节博主说一说怎样进行gazebo环境的搭建。其实我感觉最重要的工作就是配置好xacro文件，剩下的包，可以参考调用古月老师的mbot功能包，然后再稍作修改就可以啦。剩下的内容还有gmapping，小车的自动探索导航等，最后应该还有一个教大家如何对模型表面进行贴纸的教程，各位敬请期待。

参考资料

1.古月老师的<<ROS机器人开发实践>>