1 - Basics Of Cybernetics Flashcards
The object of cybernetics
Cybernetics = the study of control and connections in nature, science and society Basic concepts: - organization - information - control
Cybernetic Systems
Organization - definition
System 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 Organization = formation of systems
Cybernetic systems
Cybernetic system - definition
Cybernetic system = interacting structures and processes combined for the execution of a common function. Which function is diff from functions of the separate components
General properties of cybernetic systems:
- interact with environment and with other systems - connections
- have hierarchical structure - consists of subsystems
- preserve their general structure in changing environmental conditions
Cybernetic systems
Types of systems by complexity
3 types:
- component states
- structure and connections
- transmitted signals
Cybernetic systems
Types of systems by the degree of determinism of their response
- Deterministic = components act in a predetermined way and response is predictable e.g. machine
- Probabilistic = response can not be exactly predicted e.g. weather
Cybernetic systems
Type of systems by the type of interaction with the environment
- Closed = the components interact with each other only and no interactions with the environment
- Open = the components interact with the environment as well
Cybernetic systems
Elements of the interaction
- perception of signals from other systems using sensors (receptors) e.g. eyes, ears etc
- transmission of signals to other systems using effectors e.g. organs of speech, gestures etc
Cybernetic systems
Biological cybernetic systems - properties
Characteristics: - varying complexity - probabilistic - multi-level hierarchical organization Basic properties: - self-organization - self-regulation
Cybernetic systems
Biological systems - complexity
Very complex:
- large number of components
- complex and interrelated connections between components
Cybernetic systems
Biological systems - determinism
Probabilistic:
- large number of components
- large number of connections between the components
- strong external influences
Cybernetic systems
Biological systems - organization
Complex 2-way hierarchy
- low level components = perform independently of the higher level components as long as they are able to process all the important input info
- high level components = control the lower level components
Information theory
Information - definition
- any set of related data
- any meaningful event, which results in an action
- the state of a system of interest
Info reduces ambiguity and lack of knowledge
Information theory
Transmission of information - messages, signals and channels
Message = the transmitted info
Signal = the physical carrier of the message
Communication channel = the medium in which the signal propagates
E.g. sound wave (signal) - air (channel)
Information theory
Alphabet (code), encoding, recording, decoding
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
Recording = altering the alphabet
Decoding (by receiver) = extraction of the message from the signal
Information theory
Isomorphism and noise, signal-to-nose ratio
Isomorphic signals = physically diff signals which carry the same message
Noise = communication system disturbances which modify the signal
Information theory
Storing and retaining information
Memory = the ability of a system to store and retain info, and to recall it for use at a later moment
Ways to memorize info:
- change the states of system components
- change the structure of the system
Information theory
Measuring information - the bit
Unit of measurement = the bit
One bit is the amount of info received when we learn which one of 2 equally likely events has occurred e.g. tossing a coin
Control and regulation systems
Control and regulation - definitions
Control = actions effecting a system and aimed at reaching a specific goal Regulation = control for maintaining a specific state or process
Control and regulation systems
Program and reference
Program = the set of rules used to control a system Reference = the law describing how the controlled system must behave
Control and regulation systems
Control system - definition
Cybernetic control system = one that is self-contained in its performance monitoring and correction capabilities
Control and regulation systems
Open-loop control
- 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 controlling -> controlled subsystem
Control and regulation systems
Closed-loop control
- execution of the control messages is monitored
- used if noise is present and/or the properties of the controlled system change
- back-coupling connection = transmits data messages from controlled -> controlling subsystem
Control and regulation systems
Closed-loop control system in the body (reflex arc)
- receptors: transform the stimulus into excitation
- afferent (sensory) neurons: back-coupling channel
- neural centre: controlling subsystem
- efferent (motor) neurons: forward-coupling channel
- effectors: respond to the commands
Positive and negative feedback
Positive feedback
Positive feedback = the control results in increased divergence of the controlled system
Controlled process accelerates until the limiting constraints of the controlled subsystem are reached
Positive and negative feedback
Significance of positive feedback loops
Beneficial: - amplify vital processes - provide adaptation (fast response to external factors) Detrimental: - aggravate morbid conditions
Positive and negative feedback
Beneficial feedback - example
Products of food digestion:
- stimulate secretion of gastric juice
- more products of food digestion leads to increased secretion of gastric juice
- more products of food digestion, etc (arrow to beginning)
Positive and negative feedback
Detrimental positive feedback - example
Cardiac insufficiency reduces blood supply to the heart:
- capacity of heart to pump blood is reduced
- supply of blood to heart is further reduced
- capacity of heart to pump blood is reduced even more, etc (arrow to beginning)
Positive and negative feedback
Negative feedback
Negative feedback = the control results in balancing of the controlled subsystem
Ensures the quality and reliability of the control system
Positive and negative feedback
Negative feedback regulation system
- determine the error deltaX of the actual value X relative to the setpoint Xo
- generate a control message such as to reduce deltaX
Positive and negative feedback
Significance of negative feedback loops
Ensure: - stability of body functions - constant values of vital parameters - resistance to external factors Basic mechanism of: - homeostasis - balance of energy and metabolites in the body - control of the populations of species etc
Positive and negative feedback
Negative feedback - example
Regulation of body core temp:
- Body temp exceeds setpoint
- intensity heat loss from body (vasodilation swearing, flat lying skin hairs etc)
- reduce heat production (restricted movements, less food consumption etc) - Body temp below setpoint
- reduce heat loss
- intensify heat production (shivering, metabolic efficiency etc)
Positive and negative feedback
Types of control and quality of the control system
Static control GRAPH
Dynamic control GRAPH
Quality of control : min control area
Modelling
Models and modelling
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
Modelling
Mathematical models
- mathematical description of some aspects of the real system
- uses mathematics and computers to produce info about the studied system
- e.g. regulation of blood glucose conc
Modelling
Physical models
- material object performing similarly to the real system
- e.g. electrical circuit modeling transitional processes in a nerve fiber
Modelling
Biological model
- lab animal used to reproduce specific conditions of the human body
- requires less simplifying assumptions than mathematical and physical models
- e.g. investigation of infections, poisons, pharmaceuticals, etc
