teleop.py

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# Author: Peter David Fagan
""" Definition of an abstract base class for device teleoperation. """
 
import rclpy
 
from abc import ABC, abstractmethod
import threading
from rclpy.node import Node
 
# messages/services
from geometry_msgs.msg import TwistStamped
from sensor_msgs.msg import Joy
from std_srvs.srv import Trigger
 
 
class TeleopDevice(ABC, Node):
    """
    An abstract base class for a teleoperation device.
 
    This class expects both the `publish_command` and `record` methods to be overridden by inheriting classes.
    """
 
    def __init__(self, node_name, device_name, device_config, ee_frame_name):
        super().__init__(node_name=node_name)
        self.device_name = device_name
        self.device_config = device_config
        self.ee_frame_name = ee_frame_name
 
        # default subscriber and publisher setup
        self.joy_subscriber = self.create_subscription(
            Joy, "/joy", self.publish_commandpublish_command, 10
        )
        self.twist_publisher = self.create_publisher(
            TwistStamped, "/servo_node/delta_twist_cmds", 10
        )
        self.servo_node_start_client = self.create_client(
            Trigger, "/servo_node/start_servo"
        )
        self.servo_node_stop_client = self.create_client(
            Trigger, "/servo_node/stop_servo"
        )
 
        self.teleop_thread = None  # gets created when teleop starts
 
    def start_teleop(self):
        """
        Starts servo client and teleop process.
        """
        try:
            # start servo client
            self.servo_node_start_client.wait_for_service(10.0)
            self.servo_node_start_client.call_async(Trigger.Request())
 
            # spin the teleop node
            # use multithreaded because Servo has concurrent processes for moving the robot and avoiding collisions
            ex = rclpy.executors.MultiThreadedExecutor()
            ex.add_node(self)
            self.teleop_thread = threading.Thread(target=ex.spin, daemon=True)
            self.teleop_thread.start()
        except Exception as e:
            print(e)
 
    def stop_teleop(self):
        """
        Stops servo client and teleop process.
        """
        try:
            self.servo_node_stop_client.wait_for_service(10.0)
            self.servo_node_stop_client.call_async(Trigger.Request())
            self.teleop_thread.join()
        except Exception as e:
            print(e)
 
    @abstractmethod
    def publish_command(self):
        """
        Publishes the teleop command.
        """
        pass
 
    @abstractmethod
    def record(self):
        """
        Records trajectory data.
        """
        pass