ROSROS2机器⼈命令（cli）和基础编程（rclpy）的⾼效学习
⽅法
啰啰嗦嗦讲满整整51分钟的直播回放如下：
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}}"
网上支付
官⽅-发布和订阅（Python）：
发布源码：
1import rclpy
de import Node
3
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4from std_msgs.msg import String
5
6
7class MinimalPublisher(Node):
8
9 def __init__(lf):
10 super().__init__('minimal_publisher')
11 lf.publisher_ = lf.create_publisher(String, 'topic', 10)
12 timer_period = 0.5 # conds
13 lf.timer = lf.create_timer(timer_period, lf.timer_callback)
14 lf.i = 0
15
16 def timer_callback(lf):
17 msg = String()
18 msg.data = 'Hello World: %d' % lf.i
19 lf.publisher_.publish(msg)
20 lf.get_logger().info('Publishing: "%s"' % msg.data)
21 lf.i += 1
22
23
24def main(args=None):
初二英语单词表25 rclpy.init(args=args)
26
27 minimal_publisher = MinimalPublisher()
28
29 rclpy.spin(minimal_publisher)
30
英语文章阅读31 # Destroy the node explicitly
32 # (optional - otherwi it will be done automatically
33 # when the garbage collector destroys the node object)
34 minimal_publisher.destroy_node()
35 rclpy.shutdown()
36
37
38if __name__ == '__main__':
39 main()
订阅源码：
1import rclpy
de import Node
3
4from std_msgs.msg import String
5
6
7class MinimalSubscriber(Node):
8
9 def __init__(lf):
10 super().__init__('minimal_subscriber')
11 lf.subscription = lf.create_subscription(
12 String,
13 'topic',
教育部考试中心托福网考网上报名
pumpkin14 lf.listener_callback,
四级听力在线练习15 10)
16 lf.subscription # prevent unud variable warning
17
18 def listener_callback(lf, msg):
19 lf.get_logger().info('I heard: "%s"' % msg.data)
20
21
22def main(args=None):
23 rclpy.init(args=args)
24
25 minimal_subscriber = MinimalSubscriber()
26
27 rclpy.spin(minimal_subscriber)
28
29 # Destroy the node explicitly
30 # (optional - otherwi it will be done automatically
31 # when the garbage collector destroys the node object)
32 minimal_subscriber.destroy_node()
33 rclpy.shutdown()英语聊天室
34
35
36if __name__ == '__main__':
37 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' % lf.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
1import rclpy
de import Node
3
4# from std_msgs.msg import String
5from geometry_msgs.msg import Twist
6
7
8
9class MinimalPublisher(Node):
10
11 def __init__(lf):
12 super().__init__('my_pub')
13 lf.publisher_ = lf.create_publisher(Twist, 'turtle1/cmd_vel', 10)
14 timer_period = 1 # conds
15 lf.timer = lf.create_timer(timer_period, lf.timer_callback)
16 lf.i = 0
17
小学生课堂游戏18 def timer_callback(lf):
19 vel = Twist()
20# vel.data = 'My Hello World: %d' % lf.i
21 vel.linear.x=1.0
22 vel.angular.z=0.01*lf.i
23 lf.publisher_.publish(vel)
24 lf.get_logger().info('Publishing: x"%f"' % vel.linear.x)
25 lf.get_logger().info('Publishing: z"%f"' % vel.angular.z)
26 lf.i += 1
27
28
29def main(args=None):
30 rclpy.init(args=args)中国教育考试院官网
31
32 minimal_publisher = MinimalPublisher()
33
34 rclpy.spin(minimal_publisher)
35
36 # Destroy the node explicitly
37 # (optional - otherwi it will be done automatically
38 # when the garbage collector destroys the node object)
39 minimal_publisher.destroy_node()
40 rclpy.shutdown()
41
42
43if __name__ == '__main__':
44 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-
