Ros2 Turtlebot3 pose topic subscriber isn't triggered. [Python]

Question

Hello,

I'm trying to catch turtlebot position so I can plot its trajectory.

More precisely, I'm trying to build and run a ros2 subscriber on "/Turtle_2/pose", where "/Turtle_2" is my turtlebot namespace. Using this subscriber, I want to store the turtlebot position in a memory to plot all of them. But as a first step, I wan to print("Hello") when the subscriber is triggered by a new message published on this "/Turtle_2/pose" topic, which is not.

For confidentiality reason, I cannot give you more code than my subscriber. I'm sry about that.

NB:

• ros2 topic list contain the topic I'm looking for.

• ros2 topic echo /Turtle_2/pose plot indeed real time information about my turtle position.

• Running the subscriber don't plot anything (no trigger message nor error message)

• OS ubuntu 20.04.2 LTS ; Gnome 3.36.8

• Ros2 Foxy installed

• Subscriber code :

  import rclpy from rclpy.node import Node

  from nav_msgs.msg import Odometry from std_msgs.msg import String from geometry_msgs.msg import PoseStamped

  class MinimalSubscriber(Node):

   def __init__(self):
       super().__init__('minimal_subscriber')
       self.subscription = self.create_subscription(
           PoseStamped,
           '/Turtle_2/pose',
           self.listener_callback,
           10)
  
   def listener_callback(self, msg):
       self.get_logger().info('HELLO')
  

  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()

• This subscriber work on other topics like "Turtle_2/odom"

• result of ros2 topic info -v /Turtle_2/pose:

  Type: geometry_msgs/msg/PoseStamped

  Publisher count: 1

  Node name: natnet_client Node namespace: /Turtle_2 Topic type: geometry_msgs/msg/PoseStamped Endpoint type: PUBLISHER GID: 01.0f.69.56.05.b0.02.00.01.00.00.00.00.00.12.03.00.00.00.00.00.00.00.00 QoS profile: Reliability: RMW_QOS_POLICY_RELIABILITY_BEST_EFFORT Durability: RMW_QOS_POLICY_DURABILITY_VOLATILE Lifespan: 2147483651294967295 nanoseconds Deadline: 2147483651294967295 nanoseconds Liveliness: RMW_QOS_POLICY_LIVELINESS_AUTOMATIC Liveliness lease duration: 2147483651294967295 nanoseconds

  Subscription count: 0

Any idea will be appreciated, thanks in advance.

---

Originally posted by Hedwin on ROS Answers with karma: 21 on 2022-03-01

Post score: 1

Answer 1

A guy from my laboratory found the solution:

There was king of a communication problem, so the subscriber qos profile had to be redefined :

qos_sensor = QoSProfile(
    reliability=QoSReliabilityPolicy.RMW_QOS_POLICY_RELIABILITY_BEST_EFFORT,
    history=QoSHistoryPolicy.RMW_QOS_POLICY_HISTORY_KEEP_LAST,
    depth=1
)


self.get_logger().info('Use QoS Sensor')

self.subscription = self.create_subscription(
    PoseStamped,
    'Turtle_2/pose',
    self.listener_callback,
    qos_profile=qos_sensor)

Thanks to everyone who tried to help

---

Originally posted by Hedwin with karma: 21 on 2022-03-15

This answer was ACCEPTED on the original site

Post score: 1