Write a Proposition Node - VerifiableRobotics/LTL_stack GitHub Wiki

Writing an INPUT (environment) proposition node

For this ROS node, you need one Publisher sending Bool messages to the topic: <example_name>/inputs/<input_name>. <example_name> is the name of your example and <input_name> is the name of the input proposition.

Below is an input node example.

#! /usr/bin/env python
import argparse
import rospy
import std_msgs.msg

if __name__ == "__main__":
    parser = argparse.ArgumentParser(description="Get AprilTag")
    parser.add_argument('node_name', type=str, help='Specify name of ros node')
    parser.add_argument('node_publish_topic', type=str, help='Specify name of publishing topic to the controller')

    # parse argument
    args, unknown = parser.parse_known_args()
    rospy.init_node(args.node_name)

    # Set up publisher to an input topic
    # e.g: arg.node_publish_topic = "example_name/inputs/input_name"
    pub = rospy.Publisher(args.node_publish_topic, std_msgs.msg.Bool, queue_size=10)
    rate = rospy.Rate(10) # set publish rate

    while not rospy.is_shutdown():
        #FILL IN information to process



        # publish to the input topic
        pub.publish(True)
        rate.sleep()

You can start the input node above by first copying the code to a file:input_node.py. Then use the command python input_node.py <node_name> <topic_name>. Replace <node_name> and <topic_name> with yours.

Writing an OUTPUT (system) proposition node

For this ROS node, you need one Subscriber retrieving Bool messages from the topic: <example_name>/outputs/<output_name>. <example_name> is the name of your example and <output_name> is the name of the output proposition.

Below is an output node example.

#! /usr/bin/env python
import argparse
import rospy
import std_msgs.msg

class OutputProcess(object):
    def __init__(self):
        self.controller_request_bool = False

    def callback(self, data):
        # save latest info
        self.controller_request_bool = data.data

if __name__ == "__main__":
    parser = argparse.ArgumentParser(description="Set velocity of robot.")
    parser.add_argument('node_name', type=str, help='Specify name of ros node')
    parser.add_argument('node_subscribe_topic', type=str, help='Specify controller topic to respond to')

    # get arguments
    args, unknown = parser.parse_known_args()

    rospy.init_node(args.node_name)
    rate = rospy.Rate(10) # set publish rate

    a = OutputProcess()

    # subsribe to an output proposition topic
    # e.g: arg.node_subscribe_topic = "example_name/outputs/output_name"
    rospy.Subscriber(args.node_subscribe_topic, std_msgs.msg.Bool, callback=a.callback)

    while not rospy.is_shutdown():
        if a.controller_request_bool:

            # FILL IN response to the valuation of the output



            pass

        rate.sleep()

You can start the input node above by first copying the code to a file:output_node.py. Then use the command python output_node.py <node_name> <topic_name>. Replace <node_name> and <topic_name> with yours.

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