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ROS探索总结(八)——键盘控制

文章目录

如果尝试过前面的例子,有没有感觉每次让机器人移动还要在终端里输入指令,这也太麻烦了,有没有办法通过键盘来控制机器人的移动呢?答案室当然的了。我研究了其他几个机器人键盘控制的代码,还是有所收获的,最后移植到了smartcar上,实验成功。

一、创建控制包

        首先,我们为键盘控制单独建立一个包:
  1. ROScreate-pkg smartcar_teleop rospy geometry_msgs std_msgs roscpp
  2. rosmake
        如果你已经忘记了怎么建立包,请参考:http://www.ros.org/wiki/ROS/Tutorials/CreatingPackage

二、简单的消息发布

        在机器人仿真中,主要控制机器人移动的就是        在机器人仿真中,主要控制机器人移动的就是Twist()结构,如果我们编程将这个结构通过程序发布成topic,自然就可以控制机器人了。我们先用简单的python来尝试一下。
        之前的模拟中,我们使用的都是在命令行下进行的消息发布,现在我们需要把这些命令转换成python代码,封装到一个单独的节点中去。针对之前的命令行,我们可以很简单的在smartcar_teleop /scripts文件夹下编写如下的控制代码:
 #!/usr/bin/env python
import roslib; roslib.load_manifest('smartcar_teleop')
import rospy
from geometry_msgs.msg import Twist
from std_msgs.msg import String

class Teleop:
    def __init__(self):
        pub = rospy.Publisher('cmd_vel', Twist)
        rospy.init_node('smartcar_teleop')
        rate = rospy.Rate(rospy.get_param('~hz', 1))
        self.cmd = None
	
        cmd = Twist()
        cmd.linear.x = 0.2
        cmd.linear.y = 0
        cmd.linear.z = 0
        cmd.angular.z = 0
        cmd.angular.z = 0
        cmd.angular.z = 0.5

        self.cmd = cmd
        while not rospy.is_shutdown():
            str = "hello world %s" % rospy.get_time()
            rospy.loginfo(str)
            pub.publish(self.cmd)
            rate.sleep()

if __name__ == '__main__':Teleop()
 python代码在ROS重视不需要编译的。先运行之前教程中用到的smartcar机器人,在rviz中进行显示,然后新建终端,输入如下命令:
  1. rosrun smartcar_teleop teleop.py
        也可以建立一个launch文件运行:
  1. <launch>
  2.   <arg name=”cmd_topic” default=”cmd_vel” />
  3.   <node pkg=”smartcar_teleop” type=”teleop.py” name=”smartcar_teleop”>
  4.     <remap from=”cmd_vel” to=”$(arg cmd_topic)” />
  5.   </node>
  6. </launch>
        在rviz中看一下机器人是不是动起来了!

三、加入键盘控制

        当然前边的程序不是我们要的,我们需要的键盘控制。

1、移植

        因为ROS的代码具有很强的可移植性,所以用键盘控制的代码其实可以直接从其他机器人包中移植过来,在这里我主要参考的是erratic_robot,在这个机器人的代码中有一个erratic_teleop包,可以直接移植过来使用。
首先,我们将其中src文件夹下的keyboard.cpp代码文件直接拷贝到我们smartcar_teleop包的src文件夹下,然后修改CMakeLists.txt文件,将下列代码加入文件底部:
     rosbuild_add_boost_directories()  
    rosbuild_add_executable(smartcar_keyboard_teleop src/keyboard.cpp)  
    target_link_libraries(smartcar_keyboard_teleop boost_thread)  
编译完成后,运行smartcar模型。重新打开一个终端,打开键盘控制节点:
        在终端中按下键盘里的“W”、“S”、“D”、“A”以及“Shift”键进行机器人的控制。效果如下图:

2、复用

       因为代码是我们直接复制过来的,其中有很多与之前erratic机器人相关的变量,我们把代码稍作修改,变成自己机器人可读性较强的代码。
 
#include 
#include 
#include 
#include 
#include 
#include <sys/poll.h>

#include <boost/thread/thread.hpp>
#include <ros/ros.h>
#include <geometry_msgs/Twist.h>

#define KEYCODE_W 0x77
#define KEYCODE_A 0x61
#define KEYCODE_S 0x73
#define KEYCODE_D 0x64

#define KEYCODE_A_CAP 0x41
#define KEYCODE_D_CAP 0x44
#define KEYCODE_S_CAP 0x53
#define KEYCODE_W_CAP 0x57

class SmartCarKeyboardTeleopNode
{
    private:
        double walk_vel_;
        double run_vel_;
        double yaw_rate_;
        double yaw_rate_run_;
        
        geometry_msgs::Twist cmdvel_;
        ros::NodeHandle n_;
        ros::Publisher pub_;

    public:
        SmartCarKeyboardTeleopNode()
        {
            pub_ = n_.advertise("cmd_vel", 1);
            
            ros::NodeHandle n_private("~");
            n_private.param("walk_vel", walk_vel_, 0.5);
            n_private.param("run_vel", run_vel_, 1.0);
            n_private.param("yaw_rate", yaw_rate_, 1.0);
            n_private.param("yaw_rate_run", yaw_rate_run_, 1.5);
        }        
        ~SmartCarKeyboardTeleopNode() { }
        void keyboardLoop();
        
        void stopRobot()
        {
            cmdvel_.linear.x = 0.0;
            cmdvel_.angular.z = 0.0;
            pub_.publish(cmdvel_);
        }
};
SmartCarKeyboardTeleopNode* tbk;
int kfd = 0;
struct termios cooked, raw;
bool done;

int main(int argc, char** argv)
{
    ros::init(argc,argv,"tbk", ros::init_options::AnonymousName | ros::init_options::NoSigintHandler);
    SmartCarKeyboardTeleopNode tbk;
    
    boost::thread t = boost::thread(boost::bind(&SmartCarKeyboardTeleopNode::keyboardLoop, &tbk));
    
    ros::spin();
    
    t.interrupt();
    t.join();
    tbk.stopRobot();
    tcsetattr(kfd, TCSANOW, &cooked);
    
    return(0);
}

void SmartCarKeyboardTeleopNode::keyboardLoop()
{
    char c;
    double max_tv = walk_vel_;
    double max_rv = yaw_rate_;
    bool dirty = false;
    int speed = 0;
    int turn = 0;
    
    // get the console in raw mode
    tcgetattr(kfd, &cooked);
    memcpy(&raw, &cooked, sizeof(struct termios));
    raw.c_lflag &=~ (ICANON | ECHO);
    raw.c_cc[VEOL] = 1;
    raw.c_cc[VEOF] = 2;
    tcsetattr(kfd, TCSANOW, &raw);
    
    puts("Reading from keyboard");
    puts("Use WASD keys to control the robot");
    puts("Press Shift to move faster");
    
    struct pollfd ufd;
    ufd.fd = kfd;
    ufd.events = POLLIN;
    
    for(;;)
    {
        boost::this_thread::interruption_point();
        
        // get the next event from the keyboard
        int num;
        
        if ((num = poll(&ufd, 1, 250)) < 0) { perror("poll():"); return; } else if(num > 0)
        {
            if(read(kfd, &c, 1) < 0)
            {
                perror("read():");
                return;
            }
        }
        else
        {
            if (dirty == true)
            {
                stopRobot();
                dirty = false;
            }
            
            continue;
        }
        
        switch(c)
        {
            case KEYCODE_W:
                max_tv = walk_vel_;
                speed = 1;
                turn = 0;
                dirty = true;
                break;
            case KEYCODE_S:
                max_tv = walk_vel_;
                speed = -1;
                turn = 0;
                dirty = true;
                break;
            case KEYCODE_A:
                max_rv = yaw_rate_;
                speed = 0;
                turn = 1;
                dirty = true;
                break;
            case KEYCODE_D:
                max_rv = yaw_rate_;
                speed = 0;
                turn = -1;
                dirty = true;
                break;
                
            case KEYCODE_W_CAP:
                max_tv = run_vel_;
                speed = 1;
                turn = 0;
                dirty = true;
                break;
            case KEYCODE_S_CAP:
                max_tv = run_vel_;
                speed = -1;
                turn = 0;
                dirty = true;
                break;
            case KEYCODE_A_CAP:
                max_rv = yaw_rate_run_;
                speed = 0;
                turn = 1;
                dirty = true;
                break;
            case KEYCODE_D_CAP:
                max_rv = yaw_rate_run_;
                speed = 0;
                turn = -1;
                dirty = true;
                break;              
            default:
                max_tv = walk_vel_;
                max_rv = yaw_rate_;
                speed = 0;
                turn = 0;
                dirty = false;
        }
        cmdvel_.linear.x = speed * max_tv;
        cmdvel_.angular.z = turn * max_rv;
        pub_.publish(cmdvel_);
    }
}
参考链接:http://ros.org/wiki/turtlebot_teleop/Tutorials/Teleoperation
http://www.ros.org/wiki/simulator_gazebo/Tutorials/TeleopErraticSimulation

3、创新

        虽然很多机器人的键盘控制使用的都是C++编写的代码,但是考虑到python的强大,我们还是需要尝试使用python来编写程序。
首先需要理解上面C++程序的流程。在上面的程序中,我们单独创建了一个线程来读取中断中的输入,然后根据输入发布不同的速度和角度消息。介于线程的概念还比较薄弱,在python中使用循环替代线程。然后需要考虑的只是如何使用python来处理中断中的输入字符,通过上网查找资料,发现使用的API和C++的基本是一致的。最终的程序如下:
#!/usr/bin/env python
# -*- coding: utf-8 -*
import  os
import  sys
import  tty, termios
import roslib; roslib.load_manifest('smartcar_teleop')
import rospy
from geometry_msgs.msg import Twist
from std_msgs.msg import String
# 全局变量
cmd = Twist()
pub = rospy.Publisher('cmd_vel', Twist)
def keyboardLoop():
    #初始化
    rospy.init_node('smartcar_teleop')
    rate = rospy.Rate(rospy.get_param('~hz', 1))

    #速度变量
    walk_vel_ = rospy.get_param('walk_vel', 0.5)
    run_vel_ = rospy.get_param('run_vel', 1.0)
    yaw_rate_ = rospy.get_param('yaw_rate', 1.0)
    yaw_rate_run_ = rospy.get_param('yaw_rate_run', 1.5)

    max_tv = walk_vel_
    max_rv = yaw_rate_

    #显示提示信息
    print "Reading from keyboard"
    print "Use WASD keys to control the robot"
    print "Press Caps to move faster"
    print "Press q to quit"

    #读取按键循环
    while not rospy.is_shutdown():
        fd = sys.stdin.fileno()
        old_settings = termios.tcgetattr(fd)
		#不产生回显效果
        old_settings[3] = old_settings[3] & ~termios.ICANON & ~termios.ECHO
        try :
            tty.setraw( fd )
            ch = sys.stdin.read( 1 )
        finally :
            termios.tcsetattr(fd, termios.TCSADRAIN, old_settings)

        if ch == 'w':
            max_tv = walk_vel_
            speed = 1
            turn = 0
        elif ch == 's':
            max_tv = walk_vel_
            speed = -1
            turn = 0
        elif ch == 'a':
            max_rv = yaw_rate_
            speed = 0
            turn = 1
        elif ch == 'd':
            max_rv = yaw_rate_
            speed = 0
            turn = -1
        elif ch == 'W':
            max_tv = run_vel_
            speed = 1
            turn = 0
        elif ch == 'S':
            max_tv = run_vel_
            speed = -1
            turn = 0
        elif ch == 'A':
            max_rv = yaw_rate_run_
            speed = 0
            turn = 1
        elif ch == 'D':
            max_rv = yaw_rate_run_
            speed = 0
            turn = -1
        elif ch == 'q':
            exit()
        else:
            max_tv = walk_vel_
            max_rv = yaw_rate_
            speed = 0
            turn = 0

        #发送消息
        cmd.linear.x = speed * max_tv;
        cmd.angular.z = turn * max_rv;
        pub.publish(cmd)
        rate.sleep()
		#停止机器人
        stop_robot();

def stop_robot():
    cmd.linear.x = 0.0
    cmd.angular.z = 0.0
    pub.publish(cmd)

if __name__ == '__main__':
    try:
        keyboardLoop()
    except rospy.ROSInterruptException:
        pass
参考链接:http://blog.csdn.net/marising/article/details/3173848
http://nullege.com/codes/search/termios.ICANON

四、节点关系图

        代码下载地址:

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        希望大家一同学习,共同进步!

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