Snuk-io Challenge

This repo contains the solution for the Snuk.io distributed systems challenge. The purpose of the challenge is to create a prototype for a simple heating control device.

Conditions of operation:

• 1 single room
• multiple temperature sensors
• 1 radiator valve (actuator)

The key point is to maintain the temperature of the room at 22C by setting the valve openness from 0 (fully closed) to 100 (fully open).

The technology behind this control system involves a MQTT brocker and the python paho-mqtt library.

Usage

• run mqtt brocker with docker:

   docker run -it -p 1883:1883 --name=mosquitto  toke/mosquitto
  

• install python 3
• install the following python modules:
  • numpy
  • paho-mqtt
• execute the main python script file:

  python main.py
  

Solution

The implementation involves two main actors:

• publishers: represent nodes that send temperature to MQTT brocker witht he following format.

topic: /readings/temperature

{
  "sensorID": "sensor-1",
  "type": "temperature",
  "value": 25.3
}

The number of temperature sensors in the room can be modified with the variable numNodes. The interval at which the sensors send the data to the brocker can be modified with the variable interval

There are 2 ways of generating temperature data :

genTempCase = 0 generates uniform data with a specified interval (minRange and maxRange) genTempCase = 1 generates random temp values within a given interval (minRange and maxRange)

• subscriber: receives message from the temperature publisher, performs several calculations, and publishes a message to control the valve.

topic: /actuators/room-1

{
  "level": 14
}

The suscriber parses all data received through the /readings/temperature topic and waits for all the sensors to report in order to calculate the average temperature of the room.

In order to avoid changing the openess/closeness of the valve all time and control the time in which the valve operates, several samples are saved in a temperature array. For example, if interval time is 10 seconds and sample is set to ten, actuator will only change temperature every 100 seconds. **

After all samples are collected, the code applies a simple fuzzy logic control with 3 ranges:

• If current temperature is above threshold, close the valve 0%. (fast movement)
• If current temperature is below threshold, open the valve 100%. (fast movement)
• If current temperature is in between +- middleRangeInterval, keep valve close for a certain amount of time. For example: setPoint = 22 and interval = 0.5. If current temperature is between 21.5 and 22.5, decrease valve firing period
• If current temperature interval is in between max/min threshold and middleRange threshold, apply a proportion (%) of openess.

Additional information

• A simple fuzzy logic control was used due to time constraint, however, the best idea would be to implement a PID controller with corrent PID tunings.

• It would be best to implement another way of simulating temperature, probably defining test cases for increasing and decreasing temperature uniformly.

Next Steps

The things to to next prior to this prototype would be:

• code a more efficient way of simulating temperature sensors
• add some test cases to simulate several temperature behaviours
• change fuzzy logic control to PID control
• Wrap subscriber and publisher code in a class and creat a json file for controlling interval settings (OOP)