Systems Engineering and Analysis - Chapter 2.pdf

Bringing Systems into Being
Chapter 2

Engineered System
 Engineered systems or Human-made
systems may be recognized by the
following characteristics:
 They have a functional purpose in response to
an identified need and have the ability to achieve
some stated operational objective
 They are brought into being and operate over a
life-cycle, beginning with a need and ending with
phase-out and disposal
 They are composed of a combination of
resources, such as humans, information,
software, materials, equipment, facilities, and
money.

Engineered System
 Engineered systems are composed of
subsystems and related components that
interact with each other to produce the system
response or behavior.
 Engineered systems are part of a hierarchy and
are influenced by external factors from larger
systems of which they are a part.
 Engineered systems are embedded into the
natural world and interact with it in desirable as
well as undesirable ways.

Engineering the system and
the product
 The purpose of engineering activities
of design and analysis is to determine
how physical factors may be altered to
create the most utility for the least
cost, in terms of product cost, product
service cost, and social cost

the product
 An interdisciplinary approach
embraces both the product and
associated capabilities for production
or construction, product and
production system maintenance, and
phase-out and disposal.

the product
 The cost-effectiveness of the resulting
technical entities can be enhanced by
placing emphasis on the following:
 Improving methods for defining product and
system requirements as they relate to true
customer needs. This should be done early in
the design phase, along with a determination of
performance, effectiveness, and essential
system characteristics.

the product
 Addressing the total system with all of its
elements from a life-cycle perspective and from
the product or prime equipment to its elements of
support. This means defining the system in
functional terms before identifying hardware,
software, people, facilities, information, or
combinations thereof.
 Considering the overall system hierarchy and
interactions between various levels in the
hierarchy. This includes intra-relationships among
system elements and interrelationships between
higher and lower levels within the system.

the product
 Organizing and integrating the necessary
engineering and related disciplines into the main
systems –engineering effort in a timely
concurrent manner.
 Establishing a disciplined approach with
appropriate review, evaluation, and feedback
provisions to insure orderly and efficient
progress from the initial identification of need
through phase-out and disposal.

Engineering the product
competitiveness
 For product competitiveness, it is the
product, or consumer good, that must
meet customer expectations.
 The systems engineering challenge is
to bring products and systems into
being that meet these expectations
cost-effectively.

competitiveness
 Effects of competition
 Available resources dwindle.
 Many organizations downsize, looking to
improve their operations, and seeking
international partners.
 Reduction of the number of suppliers and
subcontractors able to respond.

competitiveness
 To ensure economic competitiveness
regarding the end item, engineering
must become more closely associated
with economics and economic
feasibility. This is best accomplished
through a life-cycle approach to
engineering.

Product and System Life
Cycles
 The life cycle begins with
 the identification of a need and extends
 through conceptual and preliminary
design,
 detail design and development,
 production and/or construction,
 product utilization, phase-out, and
disposal.

Cycles
 System life-cycle engineering goes beyond
the product life cycle. It must simultaneously
embrace the life cycle of the manufacturing
process, the life cycle of the maintenance
and support capability, and the life cycle of
the phase-out and disposal process.

Cycles

Cycles
 The life cycle for the maintenance and
logistic support activities is also needed to
service the product during use and to
support the manufacturing capability during
its duty cycle.
 Logistic and maintenance requirements
planning should be initiated concurrently to
integrate system design features that will
ease phase-out and disposal.

Cycles
 To the extent possible, life-cycle thinking
should invoke end-of-life considerations for
recyclability, reusability, and disposability.

Designing for the life cycle
 Life-cycle focused design is simultaneously
responsive to customer needs (i.e., to requirements
expressed in functional terms) and to life-cycle
outcomes.
 Design should not only transform a need into a
product/system configuration, but should ensure the
design’s compatibility with related physical and
functional requirements
 It should also consider operational outcomes
expressed as producibility, reliability,
maintainability, usability, supportability,
serviceability, disposability, and others, as well as
performance, effectiveness, and affordability.

Designing for the life cycle
 The numbered blocks in figure 2.3 “map” the four
coordinated life cycles depicted in figure 2.2 as
follows:
 The acquisition phase – Figure 2.3, Blocks 1,2,3,
and 4
 The production or construction phase – Figure 2.3,
Block 4.
 The utilization and support phase – Figure 2.3, Block
5.
 The phase-out and disposal phase – Figure 2.3, lock
6

Life-Cycle Process Phases
and Steps
 Figure 2.4 illustrates the major life cycle
process phases and selected milestones for
a typical system
 Figure 2.4 (Blocks 0.1 to 0.8) shows the
basic steps in the systems engineering
process to be iterative in nature, providing a
top-down definition of the system, and then
proceeding down to the subsystem level.

Life-Cycle Process Phases
and Steps

System Design Considerations
 The systems engineering process is
suggested as a preferred approach for
bringing systems, products, and structures
into being that will be cost-effective and
globally competitive
 Many of the numerous system design
considerations that should be identified and
studied when developing design criteria are
shown in fig. 2.6.

Development of Design
Criteria
 Definition of a need at the system level is
the starting point for determining customer
requirements and developing design criteria
(figure 2.7).
 The requirements for the system as an
entity are established by describing the
functions that must be performed.
 Both operational functions and maintenance
and support functions must be described at
the top level.

Criteria
 In design evaluation, an early step that fully
recognizes design criteria is the establishment of a
baseline against which a given alternative or design
configuration may be evaluated, i.e. requirement
analysis.

Criteria
 Some important definitions in design
requirements
 Design-dependent parameters (DDPs) – attributes
and/or characteristics inherent in the design to be
predicted or estimated (e.g., weight, design life,
reliability, producibility, maintainability, and
pollutability). These are a subset of the design
considerations for which the producer is primarily
responsible.
 Design-independent parameters (DIPs) – factors
external to the design that must be estimated and
forecasted for use in design evaluation ( e.g., fuel
cost per pound, interest rates, labor rates, and
material cost per pound). These depend upon the
production and operating environment of the system.

Criteria
 Technical performance measures (TPMs) –
predicted and/or estimated values for design-
dependent parameters. They also include values
for higher level (derived) design considerations
(e.g., availability, cost, flexibility, and
supportability).

Criteria

Considering Multiple Criteria
 In figure 2.7, the TPMs at the top level reflect the
overall performance characteristics of the system
as it accomplishes its mission objectives in
response to the needs of the customers.
 Measures of effectiveness (MOEs) such as system
size and weight, range and accuracy and so on
must be specified in terms of some level of
importance, as determined by the customer and the
criticality of the functions to be performed.

Morphology for Synthesis,
Analysis, and Evaluation

Recognizing and Managing
Life-Cycle Impacts
 Referring to the figure below, experience
indicates that there can be a large
commitment in terms of technology
applications, the establishment of a system
configuration and its performance
characteristics, the obligation of resources,
and potential life-cycle cost at the early
stages of a program.

Recognizing and Managing Life-Cycle
Impacts

Recognizing and Managing Life-
Cycle Impacts
 The objective is to influence design
early, in an effective and efficient
manner, through a comprehensive
 Needs analysis
 Requirements definition
 Functional analysis and allocation

Potential Benefits from
Systems Engineering

Systems Engineering
 Application of systems engineering
can lead to the following benefits
 Reduction in the cost of system design
and development, production and/or
construction, system operation and
support, system retirement and material
disposal; hence a reduction in life-cycle
cost should occur.

Systems Engineering
 Reduction in system acquisition time (or
the time from the initial identification of a
customer need to the delivery of a
system to the customer).
 More visibility and a reduction in the risks
associated with the design decision-
making process.

Systems Engineering and Analysis - Chapter 2.pdf

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