Tutorial 2: Reading data from a break beam sensor

This tutorial shows how to subscribe to a break beam sensor topic to count parts on the conveyor belt.

Starting the environment for Tutorial 2

To start the environment, use this command:

ros2 launch ariac_gazebo ariac.launch.py competitor_pkg:=ariac_tutorials trial_name:=tutorial dev_mode:=True

Running tutorial 2

To start tutorial 2, open a new terminal and use this command:

ros2 launch ariac_tutorials tutorial.launch.py tutorial:=2

Expected output of tutorial 2

Listing 17 Tutorial 2 output
[tutorial_2.py-1] [INFO] [1705518089.680128815] [competition_interface]: Waiting for competition to be ready
[tutorial_2.py-1] [INFO] [1705518104.127781648] [competition_interface]: Competition state is: idle
[tutorial_2.py-1] [INFO] [1705518218.248132032] [competition_interface]: Competition state is: ready
[tutorial_2.py-1] [INFO] [1705518218.265702743] [competition_interface]: Competition is ready. Starting...
[tutorial_2.py-1] [INFO] [1705518218.305600507] [competition_interface]: Started competition.
[tutorial_2.py-1] [INFO] [1705518220.098969628] [competition_interface]: Competition state is: started
[tutorial_2.py-1] [INFO] [1705518296.002932807] [competition_interface]: Part detected on conveyor. Count: 1
[tutorial_2.py-1] [INFO] [1705518347.055104728] [competition_interface]: Part detected on conveyor. Count: 2
[tutorial_2.py-1] [INFO] [1705518395.987836035] [competition_interface]: Competition state is: order_announcements_done
[tutorial_2.py-1] [INFO] [1705518397.544910616] [competition_interface]: Part detected on conveyor. Count: 3
[tutorial_2.py-1] [INFO] [1705518449.918159654] [competition_interface]: Part detected on conveyor. Count: 4
[tutorial_2.py-1] [INFO] [1705518506.999705068] [competition_interface]: Part detected on conveyor. Count: 5

Code explanation for Tutorial 2

This is the node used for tutorial 2. The functions from competition_interface.py which are used are highlighted.

Listing 18 tutorial_2.py
#!/usr/bin/env python3

import rclpy
import threading
from rclpy.executors import MultiThreadedExecutor
from ariac_tutorials.competition_interface import CompetitionInterface

def main(args=None):
    interface = CompetitionInterface(enable_moveit=False)
    executor = MultiThreadedExecutor()

    spin_thread = threading.Thread(target=executor.spin)

    count = 0

    while rclpy.ok():
            if interface.conveyor_part_count > count:
                interface.get_logger().info(f"Part detected on conveyor. Count: {interface.conveyor_part_count}")
                count+= 1
        except KeyboardInterrupt:



if __name__ == '__main__':

The purpose of this tutorial is to log the number of parts that have been counted by the break beam sensor over the course of the competition. Whenever the break beam sensor senses a part and that part has not already been counted, interface._breakbeam_cb is run and interface.conveyor_part_count is incremented by one. Inside the node, whenever interface.conveyor_part_count is increased, the count is logged.