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Systems Engineering
Systems Engineering and Analysis
Benjamin S Blanchard & Wolter J Fabrycky
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Design from a systems perspective
A system is an assembly or combination of elements
or parts forming a complex or unitary whole.
(Power system, transportation system ..)
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3
Elements of a system
Black Box Recorders/DataloggersConsist Building:
Car Identification,
Numbering &
Orientation
EP Braking
Seat Reservation Displays
Destination Displays
Public Address
Doors
Engine Controls,
Traction
Maintenance
Automation
Refrigeration
Wayside Systems
Lighting
GPS Location
Signaling
Monitoring &
Diagnostics
HVAC
Dispatch &
Emergency
Communications with
Control Center
Auxiliary Power
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Elements of System
Components (operating parts of system)
Attributes (properties of the componentsinductance, capacitance, impedance)
Relationships (link between components -redundancy)
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Product Life Cycle
Conceptual-Preliminary
Design
DetailedDesign &
Development
Productionand/or
Construction
Product use,Phase-out
and Disposal
ACQUISITION PHASE UTILISATION PHASE
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Design Consideration Hierarchy
Syst
emV
alue
Economic Factors(Life cycle cost)
Technical Factors(System effectiveness)
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Third Order Economic Considerations
Life
CycleCost
Research &Development Cost
Production Cost
Operation/utilisationcost
Maintenance &support cost
Retirement &disposal cost
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Third Order Technical Considerations
Syste
mE
ffectiv
eness
Performance
Operational availability
Reliability/Dependability
Producibility
Supportability
Disposability
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Fourth Order Economic
Considerations
Research cost
Design cost
Data cost
Contractor cost
Manufacturing cost
Test & evaluation costOperating cost
Maintenance cost
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Fourth Order Technical Considerations
Size, weight, and shape
Speed of performance
Reliability
Maintainability
Ergonomics
Safety
Flexibility (adaptability)
Pollutability
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Fifth Order Considerations
Technical Factors
Accessibility
Aesthetics
Controls and displays
Energy consumption
Interchangeability
Inventory levels
Shelf life/ storage
Transportability
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Ergonomics
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Ergonomics
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Ergonomics
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Ergonomics
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Aesthetics
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Aesthetics
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Aesthetics
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Conceptual Design Phase
Identification of Need
System Feasibility Analysis
System Requirements Analysis
System Specification
Preliminary System Design
Advance System
PlanningResearch
Technology
Development &
Application
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Systems Requirements Analysis
Operational requirements
Maintenance and support requirements
Technical performance measures (TPMs)
Functional analysis and allocation (system
level)
Analysis, synthesis and evaluation
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Operational Requirements
Operational distribution or deployment
# of sites and geographic distribution!
Mission profile or scenario
What functions must it perform?
Performance & related parameters
throughput, power output, size, weight Utilisation requirements
duty cycle, up time, down time
Effectiveness requirements
availability, reliability, failure rate
Operational life cycle (horizon)Spares inventory control
Environment
temperature, shock and vibration, noise, humidity, terrain
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Maintenance and support requirements
Levels of maintenance
type of maintenance and facility location
Repair policies
design may be non-repairable, partially repairable or fully repairable
Organisational responsibilities
customer, supplier, a third party or a combination Logistic support elements
spares, test & support equipment, training etc
Effectiveness requirements
availability of spares, test equipment reliability, level of
training Environment
temperature, shock and vibration, noise, humidity, terrain
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Technical Performance Measures (TPM)
These lead to the desired characteristics that
should be incorporated into the design design
criteria
TPM Metric Benchmark Weighting
Velocity
(km/h)
1000 (min) 850 32
Availability
(operational)
95% 90% 45
Size (m) 30 m long
18 m wide
12 m high
20 m long
25 m wide
12 m high
13
Weight (kg) 500 kg 580 kg 10
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Functional Analysis and Allocation
System
Requirements
Detailed DesignCriteria
ResourceRequirements
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Functional Allocation
HighL
evelFunctions
Lower Level FunctionSubsystem 1
Lower level functionSubsystem 2
Lower level FunctionSubsystem 3
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Functional Allocation
Tract
ionSy
stem Power System
Control system
Cooling System
Fault IndicationSystem
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Synthesis, Analysis and Evaluation
Define problem
Identify measures (TPMs & DDPs)
Select appropriate evaluation techniques
Develop model to facilitate evaluation process
Acquire input data Evaluate each of the candidates
Perform a sensitivity analysis
Identify potential areas of risk
Make a recommendationTrade off analysis leads into synthesis
Synthesis is design
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System Specification
This is the single most important engineering
design document.
Defines system functional baseline
Feasibility analysis
Operational requirements
Top level functional analysis
Identifies critical TPMs and DDPs
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System Specification
System specification leads into one or moresubordinate specifications:
Development specification pertains toresearch, design & development
Product specification pertains to inventory thatcan be procured off the shelf
Process specification pertains to services thatare performed on any component of the system
Material specification pertains to raw material,mixtures or semi-fabricated materials that areused in the fabrication of a product
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