NU CITMOT 601 Systems Engineering

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NU CIT-MOT 601 Systems Engineering

• Chapter 2

Systems, Life Cycle, and Approaches BRINGING
SYSTEMS INTO BEING
Benjamin S. Blanchard Walter J. Fabrycky,
"System Engineering and Analysis", 4th Ed.
Prentice Hall, 2006
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Engineering for Product Competitiveness

• Products must meet customer expectations
• Systems engineering is to provide systems and
  products that meet expectations cost-effectively
• Improved methods for defining product and system
  requirements
• Define systems functionally before physically
• Overall system hierarchy Interrelationships and
  Intra-relationships
• Integration of engineering and other related
  disciplines
• Establishing a disciplined approach with
  appropriate review, evaluation and feedback

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Motives For Engineering Optimum Systems

• High competition
• Globalization
• Ever demanding customers
• Technology Development
• Great strides in Science, Technology, and tools
• Limited resources

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The System Life Cycle Engineering

• Acquisition phase
• Need
• Conceptual design
• Detailed design
• Production and/ or construction
• Utilization phase
• Delivery/ use
• Support and improvement
• - Phase out/ retirement/ Discard

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1 - Conceptual Design

• Feasibility studies are conducted to determine
  design parameters
• Economic feasibility study
• Market study ---- System boundaries (volume/
  quantities), price ranges, competition, life
  expectancy, capital/ funding.
• Technical feasibility ---- resources availability
  (suppliers, capital/ funding, ..), designs,
• Feasibility study involves
• Needs analysis
• Functional requirements
• System operational requirements
• System maintenance concept
• Advanced product/ system planning (Plans
  Specifications)

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2 - Preliminary Design

• System Functional Analysis
• Functional analysis
• System operational functions
• System maintenance functions
• Preliminary Synthesis and Allocation of Design
  Criteria
• Allocation of performance factors, design
  factors, and effectiveness requirements

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2 - Preliminary Design

• System Optimization
• System and subsystem trade-offs analysis
• Evaluation of alternatives
• System and subsystem analysis
• System Synthesis and Definition
• Preliminary design, performance metrics,
  configuration and arrangement of chosen system
  (analyses, data prototyping, physical models,
  testing, etc.)
• Detailed specification

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3 - Detailed Design and Development

• System-Product Design
• Detailed design of functional system (equipment
  s/w)
• Detailed design of system maintenance and
  logistic support elements
• Design support functions
• Design data and documentation
• System analysis and evaluation
• Design review

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3 - Detailed Design and Development

• System Prototype Development
• Development of system prototype model
• Development of system maintenance and logistic
  support requirements
• System Prototype Test and Evaluation
• Test preparation
• Testing
• Modification for corrective actions

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4 Production and/or Construction

• System assessment, analysis and evaluation
• Modifications for corrective action and/or for
  product improvement

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5 Utilization and Support

• System assessment, analysis and evaluation
• Continued modification for corrective action or
  for product improvement

6 Phase-out and Disposal
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Designing For The Life Cycle

• Considerations
• Acquisition process
• Standards
• Ability to integrate
• user compatibility
• Serviceability/ Support
• ...
• For shorter Development cycle
• Teams
• Concurrent engineering

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System Engineering Definitions

• Systems Engineering
• An interdisciplinary collaborative approach to
  derive, evolve, and verify a life cycle balanced
  system solution which satisfies customer
  expectations and meets public acceptability

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System Engineering Definitions

• Characteristics of Systems Engineering
• Top-down approach that views the system as a
  whole
• A life Cycle orientation that addresses phases of
  system life cycle
• Initial definition of system requirements,
  relating such requirements to design evaluation
  criteria and performance measures
• An interdisciplinary or team approach throughout
  the system design and development
• The use of appropriate technologies and
  management principles in a synergetic manner

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The System ProcessLife-Cycle Process and Steps

• Phase
• Conceptual Design
• Preliminary Design
• Detailed Design
• Production
• Operational Use

• Baseline
• System Specification
• Functional allocation
• Design/ Material/ Processes
• Optimize
• Open ended

Figure 2.4 pp 26
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The System ProcessTop-Down and Bottom-Up
Approaches

• Top-Down Approach
• Starts from the systems functional
  requirements, (top where system input is known)
  and breaking it down into sub-functions
  identifying relationships, input, output and
  devising requirements (process) for each.
• Bottom-Up Approach
• Starts from the output requirement (Bottom),
  identifying what does it take for this output to
  be realized (functions, input, output), leading
  to top, where system input is determined.

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The System ProcessTop-Down and Bottom-Up
Approaches

• Top-Down Approach
• Does not guarantee exactly the required
  outcome, however recognizes the need and
  limitations all along
• Bottom-Up Approach
• May guarantee the outcome, however, does not
  recognize limitations at the design stage, which
  require iterations.
• Best approach is a combination of the two

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The System ProcessFeedback In System Engineering
Process
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The System ProcessOther System Engineering Models
Waterfall Process Model
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The System ProcessOther System Engineering Models
Vee Process Model
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The System ProcessOther System Engineering Models
Spiral Process Model
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System Design Evaluation

• At all stages, it is essential to evaluate
  alternative designs
• To evaluate is to assess satisfying the
  requirements
• Requirements analysis establishes the baseline
  for evaluation
• Design criteria depends on the stage
• Criteria are classified as
• System level criteria
• Sub-system level criteria
• Components level criteria
• ...

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System Design Criteria - Decomposition
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System Design Evaluation

• The technical performance measures (TPMs)
  refelect the overall performance of the system
• The design-dependent parameters (DDPs) are
  identified at subsystem level
• Many factors, measures of effectiveness,
  trade-offs at all levels to be considered
• Follow the design consideration hierarchy (Fig.
  2.9 pp 35)

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Design Consideration Hierarchy
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System Design Evaluation

• An iterative, continuous process

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Generating Evaluating Design alternatives

• Morphology for design synthesis, analysis, and
  evaluation

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Implementing System Engineering

• Due to the following factors there is an
  increased trend in the use of system eng.
  Methodology
• New technology is being introduced
• Increased customer demands/ needs
• Life cycles are being extended
• Cost increase
• Limited resources
• ..
• The use of strictly bottom-up approach proved
  unreliable

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Implementing System Engineering
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Applications of System Engineering

• Large-scale systems with many components.
• Small-scale systems with relatively few
  components.
• Manufacturing systems.
• Introduction of advanced technologies / new
  systems.
• System that are highly equipment, software,
  facilities, or data intensive.
• Systems having several suppliers.
• ... etc

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Management of System Engineering

• System engineering is applicable in all phases of
  life cycle
• Greatest benefits are derived from emphasis in
  early stages

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Management of System Engineering

• Objective is to influence the design in the early
  phases of acquisition, effectively and
  efficiently
• It leads to the identification of the individual
  design disciplinary needs proceeding from system
  level to subsystem levels
• Goal is to ensure that requirements are properly
  balanced and integrated
• Applicable engineering disciplines responsible
  for the design of the individual system elements
  to be properly integrated
• System engineering first establishes the
  requirements then ensure proper integration
  throughout the life cycle

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Integration of Disciplines
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Management of System Engineering

• System engineering must be addressed in terms of
  both technology and management.
• Concurrent Engineering
• Communication

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Potential Benefits of System Engineering

• Reduction in costs along the life cycle
• Reduction in system acquisition time
• More visibility and less risk associated with
  design decisions