Lecture 4 Structure of Complex Systems.pptx

Structure of Complex Systems
DR MUHAMMAD ASIM

Hierarchy of Complex Systems
 System is an integrated composite of people, products and processes
that provide a capability to satisfy a stated need or objective
• Systems may get inputs from other systems and may give its output to others too
 Systems consist of a number of major interacting elements, generally
called subsystems
• Each subsystem may in itself be quite complex
• Having many of the properties of a system
• May typically involve several technical disciplines and
• Generally composed of more simple functional entities
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System
System of
Systems
(Supra System)
System
Subsystem
Part
Subsystem
Component
Environment
Boundary
Input Output

 The next level of functional entities is a
component, which may be a middle level of
system elements
 The level below the component is referred to as
subcomponents, which perform elementary
functions and are composed of several parts
 The lowest level, composed of parts, represents
elements that perform no significant function
except in combination with other parts
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System
System of
Systems
(Supra System)
System
Subsystem
Part
Subsystem
Component
Environment
Boundary
Input Output

 A System is always identified by specifying its
limits, boundaries, or scope
• Boundaries are the interface between a system and its
subsystems or another system outside its boundary
 Everything outside the system boundaries may
be considered its environment
 System of Systems (SoS) is a set or
arrangement of systems that results when
independent and useful systems are integrated
into a larger system that delivers unique
capabilities.
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System
System of
Systems
(Supra System)
System
Subsystem
Part
Subsystem
Component
Environment
Boundary
Input Output

Fighter Aircraft Weapon System
 A fighter aircraft can be graded as a system
 Its subsystems could be an engine, flight control, avionics etc
 Further down below, thrust generator is component of an engine
 With rocket nozzles as its subcomponents, and
 Finally, seals could be the lowest level part
 Aircraft communicates with ATC system outside its system boundaries
and may provide information on physical environment in which an
aircraft flies
 A fighter aircraft weapon system could be part of a larger Air Defence
System; which may in turn fall in a System of Systems for defence of a
country’s frontiers
6

System Design Hierarchy Examples
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Domains – System Engr vs Design Specialist
8
Electronics
Electro-
Optical
Software Electro-
Mechanical
Mechanical Thermo-
Mechanical
Sub Components
Parts
Design
Specialist
Components
Sub Systems
Systems
Signals Data Materials Energy ...
...
...
Systems
Engineer
Breadth and Depth

System Building Blocks
 Method of partitioning system along functional and physical
dimensions.
 Each dimension can be decomposed into elements
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Washing Machine
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Import
Signal
Import
Electrical
Energy
Store
Detergent
Import
Water
Mix
Water &
Detergen
t
Start
Washing
Program
Mix
Laundry
& Water
Regulate
Washing
Program
Convert
Elect
Energy to
Rotational
Energy
Rotate
Laundry
in Suds
Separat
e
Laundry
& Suds
Export
Suds
Export
Clothes
Elect Energy
Suds
Laundry
Suds
Laundry
Elect Energy
Suds
Laundry
Water
Water
Detergent
Signal Signal Signal
Elect Energy
Laundry
Detergent
Water
Signal
System Boundary
Material
Signal
Energy
Function
Media

Functional Building Blocks
 Functional Elements - function is specification of behavior between input
and output
 Classes of functional elements based on three entities (information,
material and energy) that constitute media on which systems operate
• Signal Elements – sense and communicate information (propagating information)
• Data Elements – interpret, organize and manipulate information (static information)
• Material Elements – provide structure and transformation of materials
• Energy Elements – provide energy and motive power
 Criteria to define elements
• Significance - must perform a distinct and significant function, typically involving
several elementary functions
• Singularity - should fall largely within the technical scope of a single engineering
discipline
• Commonality - can be found in a wide variety of system types
11

System Functional Elements
12
 Four classes
 23 Functional
elements
 Around 5-6 in each
class

Physical Building Blocks
13
 Physical embodiments of functional elements
 Hierarchy is one level below a subsystem and above part i.e.,
Components

Component Design Elements
14
 Six categories
 31 component types
 31 associated
functional elements

Application of System Building Blocks
 Help suggest what kind of actions may be appropriate to achieve required
operational outcomes
 Help group the appropriate functional elements into subsystems and thus
may facilitate functional partitioning and definition
 Help visualize the physical architecture of the system
 Suggest the kinds of technology appropriate to their implementation,
including possible alternatives
 Provide an easily understood organization of hardware domain knowledge
Self Reading
15

System Environment - Boundaries
 The system environment may be broadly defined as everything outside
of the system that interacts with the system
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What’s Part of a System? (Within Boundaries)
 Developmental Control
• Does the system developer have control over the entity’s development?
• Can the developer influence the requirements of the entity, or are requirements
defined outside of the developer’s sphere of influence?
• Is funding part of the developer’s budget, or is it controlled by another organization?
 Operational Control
• Once fielded, will the entity be under the operational control of the organization that
controls the system?
• Will the tasks and missions performed by the entity be directed by the owner of the
system?
• Will another organization have operational control at times?
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What’s Part of a System? (Within Boundaries)
 Functional Allocation
• In the functional definition of the system, is the systems engineer “allowed” to allocate
functions to the entity?
 Unity of Purpose
• Is the entity dedicated to the system’s success?
• Once fielded, can the entity be removed without objection by another entity?
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System Environment – Context Diagram
 Displays the external entities and their
interactions with the system and instantly allows
the reader to identify those external entities
 The System
• This is the single geographic figure mentioned already
• Typically, this is an oval, circle, or rectangle in the
middle of the figure with only the name of the system
within
 External Entities
• These constitute all entities in which the system will
interact
• Sources for inputs into the system and destinations of
outputs from the system
 Interactions
• These represent the interactions between the external
entities and the system and are represented by arrows
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Interface & Interaction
 Interface is the point of interconnection
between entities
 Interaction is the situation or occurrence
in which two or more objects or events
act upon one another to produce a new
effect; the effect resulting from such a
situation or occurrence
 An interface sits between you and
technology
 When a driver rotates ignition key,
presses the gas pedal, and turns the
steering wheel, the car responds by
starting, going faster, and changing
direction
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System Environment - Environmental Interactions
 Primary Interactions - interact with the
system’s primary functions, that is,
represent functional inputs, outputs, and
controls
 Secondary Interactions - interact with the
system in an indirect nonfunctional
manner, such as physical supports,
ambient temperature
 Functional Interactions with environment
• System Operators
• Operational Maintenance
• Threats
• Support Systems
• System Housing
• Shipping and Handling Environment
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Interfaces
 External Interface
• Interface in which a system interacts with its
environment, including other systems
• Responsibility of the systems engineers
because they require knowledge of both the
system and its environment
 Internal Interface
• Interface in which a system interacts with
elements inside the system; the boundaries
between individual components
• Definition and implementation must often
include consideration of design tradeoffs
that impact the design of both components
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Interactions
 Interactions between two individual
elements of the system are affected
through the interface connecting the
two
 The interface between a car driver’s
hands and the steering wheel enables
the driver to guide (interact with) the
car by transmitting a force that turns
the steering wheel and thereby the
car’s wheels
 Functional interactions (guiding or
propelling the car) are affected by
physical interactions (turning the
steering wheel or the drive wheels) that
flow across (physical) interfaces
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Interface Elements
 Connectors, which facilitate the transmission of electricity, fluid, force,
and so on, between components;
 Isolators, which inhibit such interactions; and
 Converters, which alter the form of the interaction medium
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Consideration of Interface Elements
 The function of making or breaking a connection between two
components (i.e., enabling or disabling an interaction between them)
must be considered as an important design feature, often involved in
system control.
 The function of connecting nonadjacent system components by cables,
pipes, levers, and so on, is often not part of a particular system
component. Despite their inactive nature, such conducting elements
must be given special attention at the system level to ensure that their
interfaces are correctly configured.
 The relative simplicity of interface elements belies their critical role in
ensuring system performance and reliability. Experience has shown that
a large fraction of system failures occurs at interfaces. Assuring interface
compatibility and reliability is a particular responsibility of the systems
engineer.
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SoS
 A set or arrangement of systems that results when independent and useful systems are
integrated into a larger system that delivers unique capabilities
 Virtual SoSs lack a central management authority and a centrally agreed - upon purpose for
the SoS. Large - scale behavior emerges — and may be desirable — but this type of SoS
must rely upon relatively invisible mechanisms to maintain it.
 In collaborative SoSs, the component systems interact more or less voluntarily to fulfill agreed
- upon central purposes. Standards are adopted, but there is no central authority to enforce
them. The central players collectively decide how to provide or deny service, thereby providing
some means of enforcing and maintaining standards.
 Acknowledged SoSs have recognized objectives, a designated manager, and resources for an
SoS; however, the constituent systems retain their independent ownership, objectives,
funding, development and sustainment approaches. Changes in the systems are based on
collaboration between the SoS and the system.
 Directed SoSs are those in which the integrated SoS is built and managed to fulfill specific
purposes. It is centrally managed during long – term operation to continue to fulfill those
purposes as well as any new ones the system owners might wish to address. The component
systems maintain an ability to operate independently, but their normal operational mode is
subordinated to the central managed purpose.
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