啰啰嗦嗦讲满整整51分钟的直播回放如下：
- ROS2官方教程14 (dingtalk.com)
https://h5.dingtalk.com/group-live-share/index.htm?encCid=41b6de7bfdba9689f8fc78dd4aafa8c2&liveUuid=b6aecc5b-b447-4593-b9c4-fbd25a805a50#/
官方-主题教程：
- ros2 topic pub --rate 1 /turtle1/cmd_vel geometry_msgs/msg/Twist "{linear: {x: 2.0, y: 0.0, z: 0.0}, angular: {x: 0.0, y: 0.0, z: 1.8}}"
官方-发布和订阅（Python）：
发布源码：
import rclpy
from rclpy.node import Node
from std_msgs.msg import String
class MinimalPublisher(Node):
def __init__(self):
super().__init__('minimal_publisher')
self.publisher_ = self.create_publisher(String, 'topic', 10)
timer_period = 0.5 # seconds
self.timer = self.create_timer(timer_period, self.timer_callback)
self.i = 0
def timer_callback(self):
msg = String()
msg.data = 'Hello World: %d' % self.i
self.publisher_.publish(msg)
self.get_logger().info('Publishing: "%s"' % msg.data)
self.i += 1
def main(args=None):
rclpy.init(args=args)
minimal_publisher = MinimalPublisher()
rclpy.spin(minimal_publisher)
# Destroy the node explicitly
# (optional - otherwise it will be done automatically
# when the garbage collector destroys the node object)
minimal_publisher.destroy_node()
rclpy.shutdown()
if __name__ == '__main__':
main()订阅源码：
import rclpy
from rclpy.node import Node
from std_msgs.msg import String
class MinimalSubscriber(Node):
def __init__(self):
super().__init__('minimal_subscriber')
self.subscription = self.create_subscription(
String,
'topic',
self.listener_callback,
10)
self.subscription # prevent unused variable warning
def listener_callback(self, msg):
self.get_logger().info('I heard: "%s"' % msg.data)
def main(args=None):
rclpy.init(args=args)
minimal_subscriber = MinimalSubscriber()
rclpy.spin(minimal_subscriber)
# Destroy the node explicitly
# (optional - otherwise it will be done automatically
# when the garbage collector destroys the node object)
minimal_subscriber.destroy_node()
rclpy.shutdown()
if __name__ == '__main__':
main()通过3年多ROS2教学发现，学生掌握这些非常轻松，但是知识迁移的能力欠缺，此处说明。
比如使用主题发布字符串如何实现：
- 参考python代码思考
from std_msgs.msg import String
msg.data = 'Hello World: %d' % self.i
ros2 topic pub --rate 1 /turtle1/cmd_vel geometry_msgs/msg/Twist "{linear: {x: 2.0, y: 0.0, z: 0.0}, angular: {x: 0.0, y: 0.0, z: 1.8}}"
改为：
字符串消息发布
ros2 topic pub -r 1 /py_msg std_msgs/msg/String "{ data: My Hello World }"
字符串消息订阅
ros2 topic echo /py_msg
同样类比一下：
geometry_msgs/msg/Twist
from geometry_msgs.msg import Twist
速度消息发布如何使用python代码实现
import rclpy
from rclpy.node import Node
# from std_msgs.msg import String
from geometry_msgs.msg import Twist
class MinimalPublisher(Node):
def __init__(self):
super().__init__('my_pub')
self.publisher_ = self.create_publisher(Twist, 'turtle1/cmd_vel', 10)
timer_period = 1 # seconds
self.timer = self.create_timer(timer_period, self.timer_callback)
self.i = 0
def timer_callback(self):
vel = Twist()
# vel.data = 'My Hello World: %d' % self.i
vel.linear.x=1.0
vel.angular.z=0.01*self.i
self.publisher_.publish(vel)
self.get_logger().info('Publishing: x"%f"' % vel.linear.x)
self.get_logger().info('Publishing: z"%f"' % vel.angular.z)
self.i += 1
def main(args=None):
rclpy.init(args=args)
minimal_publisher = MinimalPublisher()
rclpy.spin(minimal_publisher)
# Destroy the node explicitly
# (optional - otherwise it will be done automatically
# when the garbage collector destroys the node object)
minimal_publisher.destroy_node()
rclpy.shutdown()
if __name__ == '__main__':
main()这种思考和研究的方法，是通用的，掌握了学习官方文档的速度和效率都会快很多。
-End-
