Introduction to Systems Engineering1 ______________________________________________________________ Bassam Odeh Ch 2 Structure of Complex System Bassam

Introduction to Systems Engineering Bassam Odeh 1

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Ch 2Structure of Complex System

Bassam Odeh


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Introduction

• System Engineer raises the question of how deep that understanding of a broad knowledge needs to be in the development of a complex system

• System Engineer must recognize such factors as program risks, technological performance limits, and interfacing requirements, and make trade-off analyses among design alternatives.

• System building block provide an important insight by examining the structural hierarchy of modern systems.


______________________________________________________________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?


______________________________________________________________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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What Makes a System Complex (cont’d)?

3.Human Limitations– Fundamental single-channel processing

speed limits (order: 40 bytes/sec, 5 secs/“chunk”)

– Fundamental limit to parallel processing (order 7)


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Examples of Complexity

• PC: hierarchic decomposition• Structure of plants and animals: cellular systems• Structure of matter: electrons, protons, neutrons

(quarks)• Structure of business systems


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Subdividing Complexity

• Simplification Approaches– Decomposition:

• Algorithmic imperative: by progressive steps in a hierarchical process

• Object-oriented: by tangible entities which exhibit well-defined behaviors

– Abstraction:• Extraction of essential elements• Inherent in models and modeling


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Decomposition

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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Decomposition (cont’d)

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?


______________________________________________________________Are We Gaining or Losing?

Arguably, hardware capabilities are increasing at anexponential rate.

Software is becoming a larger part of modern systems thanit 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 productsappear to be evolving at a much slower rate.


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Hierarchy of Complex Systems

• Model of Complex System:- Consists of a number of major interacting elements- Majority of systems are developed by an integrated acquisitionprocess• 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 aid of human operators and standard infrastructure ( e.g. highways, fueling stations, communication lines, etc)

: Subsystem- performs a closely related subset of the overall system functions

: Component- refer to a range of mostly lower level, middle of system level

: Parts- perform in combination with other parts


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System Design Hierarchy

Model of Complex System : System, Subsystem, Component, Parts


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System Engineer vs. Design Specialist

• System Engineer’s Domain:

- Extends down through the component level

- Is as detailed as a system engineer usually needs to go

- 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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System Engineer vs. Design Specialist

Knowledge domain of systems engineer and design specialist


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System Building BlocksMethods of Functional Design


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System Building Blocks with Elements

• Basic building blocks of all engineered systems. Characterized by functional and physical attributes. Significant, performing a distinct and significant function. Singular, within the scope of a single engineering discipline. Common, with functions founded in a variety of system types• Functional Building Block- elements:- Functional equivalents of components, four classes by medium. Signal element: sense and communicate information. Data element: interpret, organize, and manipulate information. Material element: provide structure and process materials. Energy element: provide energy and power• Physical Building Block- elements:. Electronics, Electro-Optical, Electro-mechanical, Mechanical,

Thermomechanical, Software


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System Decomposition

Enterprise

System/Functional Options

Subsystem

Component/Building Blocks

Subcomponents

Parts

Domain of the Systems Engineering

Domain of theTechnical Specialist

External Systems


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Developmental Options

• Derived from predecessor system– largely deductive, straightforward– may be sub-optimal

• Derived from past experience with other systems– may lack appropriate experience– likely to be sub-optimal

• Composed “bottom up” from Building Blocks– largely deductive– structured– weakly constrained

• “Imagineering”– unstructured, inductive– unconstrained


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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 Categories

Signals Materialgenerate, modify, support, transform, transmit, distribute shape, alter composition, alter location

Data Energydevelop, distribute, transmit, convert, receive analyze, store, convert


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Signal Functional Elements

Functional Element Physical Examples

Input signal TV camera, FAX, scanner

Transmit signal Radio transmitter, audio amplifier

Transduce signal Antenna, sonar

Receive signal TV tuner

Process signal Image processor, filter

Output signal TV display, speaker


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Data Functional Elements

Functional element Physical Examples

Input data Keyboard, modem

Process data CPU, parallel processor

Control system DOS, UNIX

Control Processing Word Processor, analysis program

Store data Magnetic disk

Output data Printer, display


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Material Functional Elements


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


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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System Functional Elements

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 Building Block

Physical Elements: Electronics, EO, EM, Mechanics, TM, Software


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Application of System Building Block

- Identifying actions capable of achieving operational outcomes

- Facilitating functional partitioning and definition- Identifying subsystem and component interfaces- Visualizing the physical architecture of the

system- Suggesting types of component implementation

technology- Helping software engineers acquire hardware

domain knowledge


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System Environment – outside the system

- System Environment – outside the system:

- System operators, Maintenance, Housing, and Support Systems

- Shipping, Storage, and Handling

- Weather and other physical environments


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Current Systems and Building Blocks

Systems can generally be subdivided into three major components:hardware, software, and human-computer interfaces (HCI).

Hardware: most hardware systems and components are already thought of in terms of components, innovative designs maybe.

Software: most software is NOT constructed from building blocks. A relatively new field called Patterns is an attempt to develop software building (beyond the scope of this course).

HCI: HCI is composed of hardware and software and reflects the comments above. Conceptually, HCI does not have many building blocks yet.


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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 of functional 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 of modularization, which in turn, is fundamental to successful system design.


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System Environment- Example

-System operators, Maintenance, Housing, and Support Systems-Shipping, Storage, and Handling, Weather and physical environments


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System Interface and Interactions

System Interface are a critical systems engineering:

- Effect interactions between components- Require identification, specification, coordination,

and control- Require that test interfaces be provided for

integration andmaintenance- Include elements that connect, isolate, or convert

interactions


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System Interface - Example

Functional Interface and Physical Interfaces


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Chapter 2 Summary

Bassam Odeh


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Complex Systems

• Complex Systems may be represented by a hierarchical structure in that they are composed of parts, subcomponents, components, and subsystems


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Systems Engineer Domain

• The domain of systems engineering:

– Extends down through the component level– Is detailed as a systems engineer usually

needs to go– Extend across several system categories


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Design Specialist Domain

• The domain of the design specialist

– Extend from the part up through the component level

– Overlaps the domain of the systems engineer– Is usually limited to single

technology/discipline


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System Building Blocks – Component Level

• System Building Blocks are at the level of components and are:– The basic building blocks of all engineered systems– Characterized by both functional and physical

attributes– Significant, performing a distinct and significant

function– Singular, within the scope of single engineering

discipline– Common, with functions found in a variety of system

types


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Functional Elements Categories

• Functional elements are functional equivalents of components and are categorized into four classes by operating medium:– Signal elements, which sense and communicate

information– Data elements, which interpret, organize, and

manipulate information– Material elements, which provide structure and

process material– Energy elements, which provide energy or power


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Physical Components Categories

• Components are physical embodiment of functional elements, which are categorized into six classes by materials of construction:– Electronics– Electro-Optical– Electromechanical– Mechanical– Thermo-mechanical– Software


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System Building Blocks Benefits

• System building blocks models can be useful in:– Identifying actions capable of achieving operational

outcomes– Facilitating functional partitioning and definition– Identifying subsystem and component interfaces– Visualizing the physical architecture of the system– Suggesting types of component implementation

technology – Helping software engineers acquire hardware domain

knowledge


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System Environment

• The system environment, that is everything outside the system that interacts with it, includes:– System operator (part of the system function

but outside the delivered system)– Maintenance, housing, and support systems– Shipping, storage, and handling– Weather and other physical environments


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Interfaces Critical Systems Engineering Concern

• Interfaces are a critical systems engineering concern, which:– Effect interactions between components– Require identification, specification,

coordination, and control– Require that test interfaces be provided for

integration and maintenance– Include elements that connect, isolate, or

convert interaction

Documents

Introduction to Systems Engineering1 ______________________________________________________________ Bassam Odeh Ch 2 Structure of Complex System Bassam