IE673Session 3 - System Thinking1 An Introduction to System Thinking

IE673 Session 3 - System Thinking 1

An Introduction to System Thinking


Contents

• What is a system?

• System Stability

• Things in Common

• Change and Growth

• Putting the Pieces Together

• Complex Systems


What is a System?

• Use “system” in everyday sense

• A collection of parts which interact with each other to function as a whole

• A “heap” is not a system

• “Heaps” are not essentially change by adding or subtracting from the “heap”

• A system can be part of larger systems

– subsystems form a hierarchy


Hierarchical System

• Particle

• Atom

• Molecule

• Cell Nucleus

• Brain Cell

• Brain

• Nervous System

• Individual

• Local community

• State

• Nation

• World Civilization

• World Ecosystem

• Planet Earth

• Solar System

• Galaxy

• Universe


Systems and Stability

• If start at different point, still same results -- why?• A system of smaller units is more stable

– Protons & neutrons - smallest natural particles

– Large atoms unstable - uranium


Systems and Stability (continued)

• Holds true for maximum size of animals– Whales and dinosaurs

• A group of 5 versus 5000• A large group is a mob unless higher levels of

system organizations are created



• Even if gigantic low-level systems were possible, a series of higher level systems would be easier– Millions of possible molecules

– 92 atoms

– 3 particles - protons, neutrons, electrons



• System definition key word - interact• One part has effect on system - system has effect

on one part– Circular relationship or loop

• Example - bicycle and rider– A two part system

– Combined, can do things individual can not

– Constant small adjustment for “errors”



“Input” Brain Muscles Bicycle “Output”

Information



• Feedback loop– Provides Stability

– Cancels out slight changes

– “Negative” feedback loop

• Negative feed back loops– Occur by the thousands

– Are in our everyday life


Stability

• Negative feedback loops are everywhere– The thermostat

– Body temperature

– Float valves

– Thirst

– Inventories

– Group membership

– Predator and prey


Stability

• Systems can– “Aim” at a fixed “target”

– “Track” a moving “target”

• Tracking systems– Get feedback on how far it is from where it should be

– Uses the feedback to reduce the difference


Stability

• Tracking systems– Set-back thermostat

– Radar-controlled anti-aircraft guns

– Satellite docking systems

– Sun tracking solar collectors

– Driving a car

– Riding a bicycle


Stability

• Tracking systems– Human/Mechanical

• Person starts system going

• Guides with series of corrections

• System works so fast and so smoothly in some cases - hard to believe there is time for negative feedback to work

• Common in natural and social systems– Sunflower

– Politicians

– Companies


Things in Common

• Self-stabilizing systems make an active response to change– Bicycle

• An active response to change requires the use of energy– Wind generator


Active Systems

• Almost all living systems are active in sense that they continue to function and use energy even when dormant– Must stay active when at rest or die


Active Systems

• General rule– The more complex a system - the more energy spent on

maintenance

– Holds for social systems• Isolated peasant community vs a modern community


Things in Common

• System limitations– Amount and kind of change

• “Exposure”

• “Heat Stroke”

– Many negative feedback systems stable over wide range, but fail abruptly when pushed beyond its limits


Things in Common

• Loose systems– Negative feedback does not prevent change

– Negative feedback responds to change and keeps it under control

– The result is a characteristic wobble - “sloppy”


Things in Common

• Reaction times– Every negative feedback system has time limits

– Reaction time is most important

– The minimum amount of time necessary for one complete circuit

– If too slow, fast change can damage system


• Anticipation– Sometimes can’t afford the delay

– Systems cope - react to warnings

– Need ability to interpret warnings

– Inadequate reaction time due to responding to problems rather than warnings

Things in Common


• Counter-intuitive systems– Behavior contrary to common sense

– Predator - prey

– High blood pressure

– Rent control

• The “obvious” solution doesn’t work– negative feedback loops fight direct intervention

– Change the way pieces interact

– Don’t try to “out-muscle” the system

Things in Common


• Hidden systems– Hard to predict how system will react

– Feedback loops needed are not in sight• African village

• 1929 tariff on imports

Things in Common


• Vulnerable systems– Even the most stubborn system is vulnerable to

interference with information flow• Slight breeze and bicycle

– Can be used to advantage to change way system acts

Things in Common


• How?– Negative feedback loop breakdown

– system becomes unstable and breaks down

– A different kind of feedback - positive

Change and Growth


• Negative feedback works to cancel out change• Positive feedback works to cause more change

– Sound amplifier - “squawk”

– Interest on money

– Living things

– Knowledge

– Power

Change and Growth


• Plus and minus– The organization of every complex system is built out

of the same two elements - positive and negative loops

– Can apply knowledge about one system to another

Putting Things Together


• Simple system - one of each type of loop– Population growth

• Multiple loops– Add factors that could affect the loops

Putting Things Together


• Characteristics

• Self-stabilizing

• Goal-seeking

• Program-following

• Self re-programming

• Anticipatory

• Environment modifying

• Self-replication

• Self-maintaining and repairing

• Self-reorganizing

• Self-programming

Complex Systems


• Problems of complexity• The tragedy of the Commons• Cost of information

– Rule of thumb• Make each decision at the lowest possible level, but be ready

to shift the control of the situation to a higher level if a serious problem occurs

• The distortion of feedback

• Loss of predictability (due to flexibility)

Complex Systems

Documents

IE673Session 3 - System Thinking1 An Introduction to System Thinking