/Fuzzy-System

Example implementation of the Fuzzy System based on temperature error

Primary LanguagePython

Fuzzy Logic System

Description

Many fuzzy control systems are tasked to keep a certain variable close to a specific value. For instance, the temperature for an industrial chemical process or for home heating management system might need to be kept relatively constant.

In order to do this, the system could look like this:

  • Antecednets (Inputs):

    • error: How far away is the temperature from where we want it to be?
    • delta: How fast is the temperature changing?

  • Consequents (Outputs):

    • output: How much should we adjust the temperature?

  • Fuzzy sets (Membership Functions):

    • Negative Big: nb = -2
    • Negative Small: ns = -1
    • Zero: ze = 0
    • Positive Small: ps = 1
    • Positive Big: pb = 2

  • Rules:

    • Negative Big: IF error == nb OR delta == nb
    • Negative Small: IF error <= ns AND delta <= ps OR error <= ps AND delta <= ns
    • Zero: IF error AND delta == ze
    • Positive Small: IF error >= ps AND delta >= ns OR error >= ns AND delta >= ps
    • Positive Big: IF error == pb OR delta == pb

The system is implemented in Python and uses the scikit-fuzzy library.

Installation

To install the system, you must first install the dependencies. The dependencies are listed in the requirements.txt file. To install the dependencies, run the following command:

pip install -r requirements.txt

Usage

To use the system, you must first create a new Python file. In this file, you must import the fuzzy_system function from the fuzzy_system module. You can then create a new instance of the Fuzzy System and get output predictions based on your input values.

from fuzzy_system import fuzzy_system

sim = fuzzy_system()

sim.input["error"] = -2
sim.input["delta"] = 0
print(sim.output["output"])
# Prints -1

sim.input["error"] = 2
sim.input["delta"] = 0
print(sim.output["output"])
# Prints 1

sim.input["error"] = 0
sim.input["delta"] = 0
print(sim.output["output"])
# Prints 0

Full set of Rules

Rule Negative Big:

  • IF error == nb AND delta == nb THEN output = nb.
  • IF error == nb AND delta == ns THEN output = nb.
  • IF error == ns AND delta == nb THEN output = nb.

Rule Negative Small:

  • IF error == nb AND delta == ze THEN output = ns.
  • IF error == nb AND delta == ps THEN output = ns.
  • IF error == ns AND delta == ns THEN output = ns.
  • IF error == ns AND delta == ze THEN output = ns.
  • IF error == ze AND delta == ns THEN output = ns.
  • IF error == ze AND delta == nb THEN output = ns.
  • IF error == ps AND delta == nb THEN output = ns.

Rule Zero:

  • IF error == nb AND delta == pb THEN output = ze.
  • IF error == ns AND delta == ps THEN output = ze.
  • IF error == ze AND delta == ze THEN output = ze.
  • IF error == ps AND delta == ns THEN output = ze.
  • IF error == pb AND delta == nb THEN output = ze.

Rule Positive Small:

  • IF error == ns AND delta == pb THEN output = ps.
  • IF error == ze AND delta == pb THEN output = ps.
  • IF error == ze AND delta == ps THEN output = ps.
  • IF error == ps AND delta == ps THEN output = ps.
  • IF error == ps AND delta == ze THEN output = ps.
  • IF error == pb AND delta == ze THEN output = ps.
  • IF error == pb AND delta == ns THEN output = ps.

Rule Positive Big:

  • IF error == ps AND delta == pb THEN output = pb.
  • IF error == pb AND delta == ps THEN output = pb.
  • IF error == pb AND delta == pb THEN output = pb.