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python ROS2時間同步

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最近1周一直研究ROS2的時間同步，翻越很多博客，很少有人使用ROS2進行時間同步的代碼，無奈不斷嘗試與源碼閱讀，終于將其搞定，
為此，本博客將介紹基于python的ROS2的時間同步方法 。
本博客內容結構為話題發布代碼 ， 話題訂閱與時間同步代碼，代碼文件夾結構及結果顯示圖片 。本博客假設2個publisher和一個scribe，同步是在scibe中完成 。
一.話題發布代碼
發布1為第二個發布者，可理解為某傳感器
publisher1代碼如下:
#!/usr/bin/env python3import rclpyfrom rclpy.node import Nodefrom std_msgs.msg import String,Float32,Int32import cv2# from std_msgs.msg import Headerimport timeclass NodePublisher(Node):def __init__(self,name):super().__init__(name)self.get_logger().info("大家好，我是%s!" % name)self.num=0self.command_publisher1 = self.create_publisher(Int32,"command1", 10)self.timer = self.create_timer(0.4, self.timer_callback)## self.inputdata1()def inputdata1(self):msg = Int32() #String()period=0.5print("publisher1-周期",period)self.get_logger().info(f'發布了指令：{msg.data}')#打印一下發布的數據num=0while True:num=num+1msg.data = https://www.huyubaike.com/biancheng/num #str(num)self.command_publisher_.publish(msg)# time.sleep(period)self.get_logger().info(f'發布了指令：{msg.data}')#打印一下發布的數據def timer_callback(self):msg = Int32() #String()self.num+=1msg.data = https://www.huyubaike.com/biancheng/self.num #str(num)self.command_publisher1.publish(msg)self.get_logger().info(f'發布了指令：{msg.data}')#打印一下發布的數據def main(args=None):rclpy.init(args=args) # 初始化rclpynode = NodePublisher("topic_publisher1")# 新建一個節點rclpy.spin(node) # 保持節點運行，檢測是否收到退出指令（Ctrl+C）rclpy.shutdown() # 關閉rclpy發布2為第二個發布者，可理解為某傳感器
publisher2代碼如下:
#!/usr/bin/env python3import rclpyfrom rclpy.node import Nodefrom std_msgs.msg import String,Float32,Int32import timeclass NodePublisher(Node):def __init__(self,name):super().__init__(name)self.get_logger().info("大家好，我是%s!" % name)self.num=0self.command_publisher2= self.create_publisher(Int32,"command2", 10)self.timer = self.create_timer(0.2, self.timer_callback)#def timer_callback(self):msg = Int32() #String()self.num+=1msg.data = https://www.huyubaike.com/biancheng/self.num #str(num)self.command_publisher2.publish(msg)self.get_logger().info(f'發布了指令：{msg.data}')#打印一下發布的數據def main(args=None):rclpy.init(args=args) # 初始化rclpynode = NodePublisher("topic_publisher2")# 新建一個節點rclpy.spin(node) # 保持節點運行，檢測是否收到退出指令（Ctrl+C）rclpy.shutdown() # 關閉rclpy二.話題訂閱及時間同步代碼
訂閱發布者信息 ， 并將其同步，可理解為同步不同傳感器
scriabe代碼如下：
#!/usr/bin/env python3import rclpyfrom rclpy.node import Nodeimport message_filtersfrom std_msgs.msg import String,Float32,Int32import message_filtersfrom sensor_msgs.msg import Image, CameraInfodef callback(image_sub,info_sub):res=int(info_sub.data)-int(image_sub.data)print("publisher1:\t{}\tpubsher2:\t{}\t{}".format(str(image_sub.data),str(info_sub.data),res))def main(args=None):rclpy.init(args=args) # 初始化rclpyscribe_node=Node('scribe_time')image_sub = message_filters.Subscriber(scribe_node, Int32,'command1')info_sub = message_filters.Subscriber(scribe_node, Int32,'command2')ts = message_filters.ApproximateTimeSynchronizer([image_sub, info_sub], 10, 0.1, allow_headerless=True) # allow_headerless=True,可以不使用時間戳# ts = message_filters.TimeSynchronizer([image_sub, info_sub], 10) # 這個需要時間戳才可調用ts.registerCallback(callback)rclpy.spin(scribe_node)rospy.spin()【python ROS2時間同步】三.參數配置及文件格式
setup.py設置如下：
from setuptools import setuppackage_name = 'topic_time'setup(name=package_name,version='0.0.0',packages=[package_name],data_files=[('share/ament_index/resource_index/packages',['resource/' + package_name]),('share/' + package_name, ['package.xml']),],install_requires=['setuptools'],zip_safe=True,maintainer='root',maintainer_email='root@todo.todo',description='TODO: Package description',license='TODO: License declaration',tests_require=['pytest'],entry_points={'console_scripts': ["publisher1_node = topic_time.publisher1:main","publisher2_node = topic_time.publisher2:main","subscribe_node = topic_time.subscribe:main","subscribe2_node = topic_time.subscribe2:main"],},)文件格式如下：

python ROS2時間同步

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通過以上代碼將可看到同步的scribe中發布1時間無間隔，發布2時間間隔為4，恰好與設置周期同等，結果顯示如下：
python ROS2時間同步

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