inse6400 complex systems
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8/17/2019 INSE6400 Complex Systems
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Structure of Complex System
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The American Mathematician Warren WeaverIn 1948 defines three types of problems:◦ Problems of Simplicity: a few variables
◦ Problems of Disorganized Complexity: billions or
trillions of variables.◦ Problems of organized complexity: Moderate
numbers of variables
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System Engineer raises the question of howdeep that understanding of a broadknowledge needs to be in the developmentof a complex system
System Engineer must recognize suchfactors as program risks, technologicalperformance limits, and interfacingrequirements, and make trade-off analysesamong design alternatives.
System building block provide an importantinsight by examining the structuralhierarchy of modern systems.
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System Complexity
What Makes a System Complex?
How does Complexity evolve?
What are the ways of dealing with Complexity?
Are we gaining or losing?
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• Complex: composed of interconnected or interwoven parts.
– Does not stipulate the number of interconnected parts. A
complex system may consist of a small number of parts
connected in complicated ways.
– A large number of disconnected parts is not complex system,
for example a large collection of books.
– The items that distinguish a complex system from a
collection of parts are the connections.
– The manifestation of a complex system is the dependence
upon the interfaces. – Different configurations of interfaces lead to much different
systems, different arrangements of parts constitute the same
collection
What Characterizes Complexity?
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What Makes a System Complex?
1. Impossible for an individual to comprehend all of the
design; exceeds human intellectual capacity
2. Complexity is Inherent, not Accidental
– Complex problem domains• Needs and requirements change and evolve
• Difficulty expressing needs and requirements
• Expansion of previous system
– Difficulty managing development• Systems are becoming increasingly large & complex
• Coordination of large team efforts very costly
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Simplification Approaches◦ Decomposition:
Algorithmic imperative: by progressive steps in ahierarchical process
Object-oriented: by tangible entities which exhibitwell-defined behaviors
◦ Abstraction:
Extraction of essential elements
Inherent in models and modeling
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1.Complex Systems decomposition◦ How decompose, lots of ways, pending idea?
◦ Where do you “cut”?
◦ Decomposition is hierarchical; what defines the
levels & depths?◦ Align with specialties, functional vs. physical?
2.Every cut creates an interface◦ What are the characteristics of the interfaces
(internal/external), complexity, testability,responsibility?
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3.Optimality◦ What constitutes the “best” decomposition?
◦ What is good enough?
◦ How do we recover from a bad choice?
4.What are the implications for integration &testing?◦ How do we handle testing of internal interfaces?
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Are We Gaining or Losing?
• Arguably, hardware capabilities are increasing at anexponential rate.
• Software is becoming a larger part of modern systems than
it has been in the past and software is more complex
and more “opaque.”
• Technology is compounding with complex systems being
embedded in other complex systems.
• Systems engineering practices and procedures and products
appear to be evolving at a much slower rate.
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Hierarchic systems are common in bothnatural and man-made systems◦ Physics: atom nucleus neutron, proton,
electron
◦ Organization: director manager general staff
◦ Book: chapter section paragraph
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Model of Complex System:
◦ Consists of a number of major interacting elements◦ Majority of systems are developed by an integrated acquisition
process
Definition of System Level:
System → Subsystems → Components → Subcomponents → Parts
System – serves as parts of more complex aggregates or super-systems and perform a significant useful service with only the aidof human operators and standard infrastructure ( e.g. highways,fueling stations, communication lines, etc)
Subsystem- performs a closely related subset of the overall systemfunctions
Component- refer to a range of mostly lower level, middle ofsystem level. Perform elementary functions.
Parts- perform in combination with other parts
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Systems Communicationsystems Informationsystems Materialprocessingsystem
Aerospacesystem
Sub-systems Signal networks Databases Materialpreparation
Engines
Components Signal receivers Data displays Powertransfer
Thrustgenerators
Sub-components
Signal amplifiers Cathode raytubes
Gear trains Rocketnozzles
Parts Transformer LED Gears Seals
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• System Engineer’s Domain
- Extends down through the component level
- Is as detailed as a system engineer usually needs togo
- Extends across several system categories
• Design Specialist’s Domain
- Extends from the part level up through the
component level- Overlaps the domain of the systems engineers
- Is usually limited to a single technology/discipline
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Knowledge domain of systems engineer and design specialist
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System Decomposition
Enterprise
System/
Functional Options
Subsystem
Component/
Building Blocks
Subcomponents
Parts
Domain of theSystems Engineering
Domain of the
Technical Specialist
External Systems
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Building Blocks –The Concept
• A library of commonly occurring system elements
• A means for classifying system constituents according to:
– functional characteristics
–
physical characteristics
• A useful tool for modeling system architecture and its
synthesis
• Useful for visualizing potential architectures of system
concepts
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Functional elements◦ Signal elements: sense and communicate
information
◦ Data elements: interpret, organize, and manipulate
information◦ Material elements: provide structure and
transformation of materials
◦ Energy elements: provide energy and motive power
Physical elements◦ Electronic, electro-optical, electro-mechanical,
mechanical, thermo-mechanical, software
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Signal Functional Elements
Functional Element Physical Examples
Input signal TV camera
Transmit signal Radio transmitter
Transduce signal Antenna
Receive signal Radio receiver
Process signal Image processor
Output signal TV display, speaker
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Data Functional Elements
Functional element Physical Examples
Input data Keyboard
Process data CPUControl system Windows, UNIX
Control Processing Word Processor, analysis program
Store data Magnetic disk
Output data Printer, display
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Material Functional Elements
Functional element Physical Examples
Support material Airframe, auto body
Store material Container, enclosure
React material Autoclave, smelter
Form material Milling machine, foundry
Join material Welding, riveting
Control position Auto tool feed, power steering
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Energy Functional Elements
Functional element Physical Examples
Generate thrust Rocket, turbojet
Generate torque Gas turbine
Generate electricity Power plant, solar cells
Control temperature Furnace, refrigerator
Control motion Transmission, power brakes
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Functional Element: Signal, Data, Material, Energy
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Physical Building Blocks
Category Component Examples
Electronic Receiver, transmitter
Electro-optic Optical sensing, fiber optics
Electro-mechanical Electric generator, data storage,transducer
Mechanical Container, material processor,material reactor
Thermo-mechanical Jet & rotary engine, Heating & AC
Software Operating system, applications firmware
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Physical Elements: Electronics, EO, EM, Mechanics, TM, Software
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- Identifying actions capable of achievingoperational outcomes- Facilitating functional partitioning and
definition
- Identifying subsystem and componentinterfaces- Visualizing the physical architecture of the
system- Suggesting types of component
implementation technology- Helping software engineers acquire
hardware domain knowledge
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Summary of Building Blocks
• Provides a structured view of the necessary knowledge base
for systems engineers
• Provides a mechanism for deductive decomposition offunctional architectures to components
• Provides a structured view of a wide variety of systems
• Provides ingredients for modeling system architecture
• Provides a strong link to the concept of object-oriented design
• Building Blocks are fundamental to the concept ofmodularization, which in turn, is fundamental to successfulsystem design.
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Not easy to identify what is part of the systemand what is part of the environment
Determining criteria◦ Developmental control: do we have control over the
entity’s development? ◦ Operational control: will the tasks and missions
performed by the entity be directed by the owner of thesystem?
◦ Functional allocation: are we “allowed” to allocatefunctions to the entity in the functional definition?
◦ Unity of purpose: is the entity dedicated to the system’ssuccess
Key concept: control
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Human users and operators are often treatedas external entities◦ Focus on the operator interface
◦ Still important in a functional aspect
Examples◦ Network of roads and service stations
automobile
◦ Electrical power grid data processing system
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Display the external entities and theirinteractions with the system
External entities: sources for inputs into thesystem and destinations of outputs from the
system Interactions: represented by arrows, the direction
or flow of a particular interaction◦ Application or company-specific labels can be used
◦
Five categories: data, signals, materials, energy andactivities
The system: represented by an oval in the center
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Inputs and outputs◦ Operate on external stimuli and/or materials in such a manner as
to process these inputs in a useful way
System operators◦ Emphasize human-machine interface◦ Complex to define and test
Operational maintenance◦ Affect system readiness and operational reliability◦ Provide access for monitoring, testing and repair requirements
Threats◦ Either natural (e.g., salt water) or man-made (e.g., thief)
Support systems◦
Part of the infra-structure on which the system depends forcarrying out its mission
System housing: provide protection Shipping and handling environment
◦ Transport from the manufacturing site to the operating site
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Instrument landing
system (ILS)
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Interfaces◦ External and internal
◦ Identification and description of interfaces as partof system concept definition
◦ Coordination and control of interfaces to maintainsystem integrity
◦ Three types: connectors, isolators and converters
Interactions◦
Take place via interfaces
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Type Electrical Mechanical Hydraulic Human
machine
Interactionmedium
Current Force Fluid Information
Connectors Cableswitch
Jointcoupling
Pipe valve Displaycontrol
panelIsolators RF shield
insulatorShock mountbearing
Seal Coverwindow
Converter Antenna
A/Dconverter
Gear train
piston
Reducing
valvepump
Keyboard
Though interface elements are relatively simple,
a large fraction of system failures occurs at
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A set or arrangement of systems that resultswhen independent and useful systems areintegrated into a larger system that deliversunique capabilities.
Characteristics◦ Operational independence of the individual system◦ Managerial independence of the individual system◦ Geographic distribution◦ Emergent behavior (not necessarily related to
component system)◦ Evolutionary development◦ Self-organization and adaptations
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An airport
support trucks
baggage-handling equipment
Air traffic control Satellites,
Radars
aircraft
Car
Taxi
Shuttle bus
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Consists of Multiple SoSs
Enterprise “anything that consists ofpeople, processes, technology, systems, and
other resources across organizations andlocations interacting with each other and theirenvironment to achieve a common mission orgoal
Example Government agencies and departments
Cities and countries
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Chapter 3:“Structure of complex systems” ,
Book:
“Systems Engineering: Principles and Practice”