ROS机器人操作系统

文章目录

前言

一、服务模型

二、实现方法

1.创建一个服务器

如何实现一个服务器

• 初始化ROS节点；
• 创建Server实例；
• 循环等待服务请求，进入回调函数；
• 在回调函数中完成服务功能的处理，并反馈应答数据。
c++

/**
 * 该例程将执行/turtle_command服务，服务数据类型std_srvs/Trigger
 */

#include <ros/ros.h>
#include <geometry_msgs/Twist.h>
#include <std_srvs/Trigger.h>

ros::Publisher turtle_vel_pub;
bool pubCommand = false;

// service回调函数，输入参数req，输出参数res
bool commandCallback(std_srvs::Trigger::Request  &req,
                                std_srvs::Trigger::Response &res)
{
        pubCommand = !pubCommand;

    // 显示请求数据
    ROS_INFO("Publish turtle velocity command [%s]", pubCommand==true?"Yes":"No");

        // 设置反馈数据
        res.success = true;
        res.message = "Change turtle command state!"

    return true;
}

int main(int argc, char **argv)
{
    // ROS节点初始化
    ros::init(argc, argv, "turtle_command_server");

    // 创建节点句柄
    ros::NodeHandle n;

    // 创建一个名为/turtle_command的server，注册回调函数commandCallback
    ros::ServiceServer command_service = n.advertiseService("/turtle_command", commandCallback);

        // 创建一个Publisher，发布名为/turtle1/cmd_vel的topic，消息类型为geometry_msgs::Twist，队列长度10
        turtle_vel_pub = n.advertise<geometry_msgs::Twist>("/turtle1/cmd_vel", 10);

    // 循环等待回调函数
    ROS_INFO("Ready to receive turtle command.");
      // 设置循环的频率
        ros::Rate loop_rate(10);

        while(ros::ok())
        {
                // 查看一次回调函数队列
        ros::spinOnce();

                // 如果标志为true，则发布速度指令
                if(pubCommand)
                {
                        geometry_msgs::Twist vel_msg;
                        vel_msg.linear.x = 0.5;
                        vel_msg.angular.z = 0.2;
                        turtle_vel_pub.publish(vel_msg);
                }

                //按照循环频率延时
            loop_rate.sleep();
        }
    return 0;
}

python

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# 该例程将执行/turtle_command服务，服务数据类型std_srvs/Trigger

import rospy
import thread,time
from geometry_msgs.msg import Twist
from std_srvs.srv import Trigger, TriggerResponse

pubCommand = False;
turtle_vel_pub = rospy.Publisher('/turtle1/cmd_vel', Twist, queue_size=10)

def command_thread():	
	while True:
		if pubCommand:
			vel_msg = Twist()
			vel_msg.linear.x = 0.5
			vel_msg.angular.z = 0.2
			turtle_vel_pub.publish(vel_msg)
			
		time.sleep(0.1)

def commandCallback(req):
	global pubCommand
	pubCommand = bool(1-pubCommand)

	# 显示请求数据
	rospy.loginfo("Publish turtle velocity command![%d]", pubCommand)

	# 反馈数据
	return TriggerResponse(1, "Change turtle command state!")

def turtle_command_server():
	# ROS节点初始化
    rospy.init_node('turtle_command_server')

	# 创建一个名为/turtle_command的server，注册回调函数commandCallback
    s = rospy.Service('/turtle_command', Trigger, commandCallback)

	# 循环等待回调函数
    print "Ready to receive turtle command."

    thread.start_new_thread(command_thread, ())
    rospy.spin()

if __name__ == "__main__":
    turtle_command_server()

2.代码编译规则

add_executable(turtle_command_server src/turtle_command_server.cpp)
target_link_libraries(turtle_command_server ${catkin_LIBRARIES})

3.运行服务器

$ cd ~/catkin_ws
$ catkin_make
$ source devel/setup.bash
$ roscore
$ rosrun turtlesim turtlesim_node
$ rosrun learning_service turtle_command_server
$ rosservice call /turtle_command "{}"

rosservice call发送指令