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1

2 Cybernetics

2 Cybernetics—the study of control and connections in nature, science, and society
Basic concepts:
Organization (systems theory)
Information (information theory)
Control (control theory)

2

3 Organization. Systems theory

3 Systems theory — the study of systems in general, with the goal of elucidating principles that can be applied to:
- all types of systems
- at all nesting levels
- in all fields of research.

3

4 Organization

4 Organization—formation of systems
Cybernetic system:
• interacting structures and processes combined
for the execution of a common function
• which function is different from functions of
the separate components

4

5 General Properties of Cybernetic systems

5 • Interact with the environment and with other
systems — connections
• Have hierarchical structure:
- consist of subsystems
- are subsystems of other systems
• Preserve their general structure in changing
environmental conditions

5

6 Cybernetic Systems

6 Can be characterized using three types of
functions describing the changes of system:
• component states
• structure and connections
• transmitted signals

6

7 Types Of Systems By The Degree Of Determinism Of Their Response

7 • Deterministic -
components interact in a predetermined way and response is predictable. Example: machine
• Probabilistic -
response can not be exactly predicted. Example: weather

7

8 Types Of Systems By The Type Of lnteraction With The Environment

8 Closed
• the components interact with each other only
• no interactions with the environment
Open
• the components interact with the
environment as well

8

9 Elements Of The lnteraction

9 Perception of signals from other systems using sensors (receptors)
Examples: eyes, ears, etc.
Transmission of signals to other systems using effectors
Examples: organs of speech, gestures, etc

9

10 Biological Cybernetic Systems

10 Biological cybernetic systems characteristics
• varying complexity
• probabilistic
• multi-level hierarchical organization
Basic properties
• self-organization
• self-regulation

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11 Biological Systems - Complexity

11 Very complex:
• large number of components
• complex and interrelated connections
between the components

11

12 Biological Systems - Determinism

12 Probabilistic:
• large number of components
• large number of connections between the
components
• strong external influences

12

13 Biological Systems - Organization

13 Complex two-way hierarchy - Each component can
be regarded as a system of lower-level components
• The low level components perform independently
of the higher level components as long as they are
able to process all the important input information
• The high level components control the lower level
components

13

14 Information

14 • Any set of related data
• Any meaningful event, which results in an
action
• The state of a system of interest
Information reduces ambiguity, removes the
lack of knowledge

14

15 lnformation Theory

15 Study of information:
• acquisition
• transmission
• storing and retaining
• processing
• measuring

15

16 Communication System

16 [pic] the mathematical theory of communication:
info source-> message -> transmitter-> signal-> received signal-> receiver -> message -> destination

16

17 Messages, Signals, and Channels

17 • Message - the transmitted information
• Signal - the physical carrier of the message
• Communication channel- the medium in
which the signal propagates
Examples (signal - channel):
• sound wave - air
• light wave - optical fibre
• electric signal- wire in an electronic device

17

18 Alphabet (Code)

18 • Alphabet - a set of simple signals which can be
used to send any message
• Encoding (by transmitter) – generation (using
an alphabet) of a signal which carries the
message
• Recoding - altering the alphabet
• Decoding (by receiver) - extraction of the
message from the signal

18

19 Alphabet (Code) example

19 [pic]

19

20 Isomorphism And Noise

20 • lsomorphic signals - physically different signals
which carry the same message
- Recoding should ensure the initial and recoded signals are isomorphic
• Noise - communication system disturbances which modify the signal
- Channel fidelity indicator - the signal to
noise ratio (SNR)

20

21 Storing And Retaining lnformation

21 Memory- the ability of a system to store and
retain information, and to recall it for use at a
later moment
Ways to memorize information:
• by changing the states of system components
• by changing the structure of the system (the
connections between its components)

21

22 Measuring lnformation

22 lf an experiment is to produce any one of a set of N
equally likely events, the amount of information I received when we learn which event has occurred is:
I = 𝐥𝐨𝐠𝟐N
Unit of measurement: the bit
One bit is the amount of information received when we learn which one of 2 (two) equally likely events has occurred. Example: tossing a coin

22

23 Information in the human DNA

23 • DNA contains 4 bases. Any nucleotide contains only one base. Therefore, the information carried by one nucleotide is 2 bits.
• The chromosomal DNA of one human sperm contains 10^9 nucleotides, i.e. information of 2X10^9 bits.

23

24 Control

24 • Control — actions effecting a system and aimed at reaching a specific goal
• Regulation - control for maintaining a specific state or process
• Cybernetic Control System — One that is selfcontained
in its performance monitoring and correction capabilities

24

25 Program And Reference

25 • Program - the set of rules (algorithm) used to
control a system
• Reference—the law describing how the controlled system must behave
• The program and/or reference may be included in the control system itself or be received from another cybemetic system at a higher hierarchical level

25

26 Control System

26 Controlling subsystem – processes information, generates and sends control messages (commands)
• Controlled subsystem – changes according to the messages received
• Connections – communication subsystems transferring information between the controlling and controlled subsystems

26

27 Open-Loop Control

27 Controlling subsystem -> Controlled subsystem
• The execution of the control messages is not monitored
• Used if noise is missing and the properties of the controlled system do not change
->
Forward-coupling connection —transmits control messages from the controlling to the controlled subsystem

27

28 Closed-Loop Control

28 Controlling subsystem ->

28

29 Closed Loop Control System in the Body (Reflex Arc)

29 • Receptors
Transform the stimulus into excitation
• Afferent (sensory) neurons
Back-coupling (feedback) channel
• Neural centre
Controlling subsystem (issues commands)
• Efferent (motor) neurons
Forward-coupling channel
• Effectors
Respond to the commands

29

30 Positive Feedback

30 Positive feedback (self-reinforcing loop) - the control results in increased divergence of the controlled subsystem.
Divergence - the difference between the current and preceding states of a system The controlled process accelerates until the limiting constraints of the controlled subsystem are reached.

30

31 Significance Of Positive Feedback Loops

31 Beneficial:
—amplify vital processes
—provide adaptation - fast response to external factors
and transition from the initial state to another, more appropriate state
Detrimental:
—aggravate morbid conditions

31

32 Beneficial Positive Feedback

32 Products of food digestion:

32

33 Detrimental Positive Feedback

33 Cardiac insufficiency reduces blood supply to the heart:

33

34 Stress and Positive Feedback

34 • A psychological event resulting in preoccupation with weight;
• Food avoidance leading to elevated cortisol levels mobilizing stored liver glycogen to increase blood glucose;
Resulting positive feedback loop (in the absence of timely medical intervention) promote adverse effects, even death.

34

35 Negative Feedback

35 • Negative feedback (self-correcting loop or balancing loop) - the control results in balancing of the controlled subsystem
Balancing - minimizing the difference between the controlled parameter and the reference (setpoint)
• Ensures the quality and reliability of the control system

35

36 Negative Feedback Regulation System

36 Determine the error ΔX of the actual value X relative to the setpoint Xo.
Generate a control message such as to reduce ΔX.

36

37 Significance Negative Feedback Loops

37 Ensure:
• stability of body functions
• constant values of vital parameters
• resistance to external factors
Basic mechanism of:
• Homeostasis (the stable condition inside the body)
• the balance of energy and metabolites in the body
• the control of the populations of species etc.

37

38 Negative Feedback - example

38 Regulation of body core temperature:
• Body temperature exceeds the setpoint:
—lntensity heat loss from the body – vasodilation sweating, flat lying skin hairs, etc.
—Reduce heat production - restricted movements, less food consumption, etc.
• Body temperature is below the setpoint:
—Reduce heat loss
—lntensify heat production - shivering, metabolic efficiency. etc

38

39 Types Of Control And Quality Of The Control System

39 Control area — area between the curves of the reference and actual values of the controlled parameter

39

40 Scientific Modelling

40 Model—a simplified physical or mathematical representation of a system used for its investigation
• Modelling—methods for investigation of systems
using their models
Types of models;
• mathematical
• physical
• biological

40

41 Scientific Modelling and Simulation

41 • The model represents the system itself, whereas the simulation represents the operation of the system over time.
• Computer simulation has become a useful part of modeling many natural systems in physics, chemistry and biology
• Medical simulators have been developed for training procedures ranging from the basics to laparoscopic surgery and trauma care, etc.

41

42 Mathematical model

42 • Mathematical description of some aspects of the real system.
• Uses mathematics and computers to produce information about the studied system.
Example: Regulation of blood glucose concentration.

42

43 Physical model

43 Material object performing similarly to the real system.
Example: Electrical circuit modeling transitional processes in a nerve fibre.

43

44 Biological model

44 Laboratory animal used to reproduce specific conditions of the human body.
Requires less simplifying assumptions than mathematical
and physical models.
Example: Investigation of infections, poisons, pharmaceuticals, etc.