Week 6 - Systems Engineering and Analysis

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Week 6 - Systems Engineering and Analysis

• Buede ch 8 Wasson ch 40
• Physical Architecture

Believe it or not well even apply this topic
to the Newton free world of software! Image of
Second Life from http//secondlifetalk.com/.
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Functional vs. Physical
Buede starts here for Wasson, see slide 47!

• Functional
• What the system must do.
• Physical
• How the system will do it.

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Physical Architecture

• Provides system resources for every function in
  the Functional Architecture
• Resource types
• Hardware
• Software
• Facilities
• People
• Procedures

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Physical Architecture-2

• Must be a Physical Architecture for each system
  associated with the system life cycle.
• Two types of Physical Architectures
• Generic and Instantiated.

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Physical Architecture-3

• For software
• We are used to having a design experience that
  feels free of physical limitations!

Dont like the way the world actually looks?
Add/change/delete your own features! Image from
http//www.indiamike.com/india/chai-and-chat-f73/n
asa-world-wind-software-t12187/
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Physical Architecture-4

• For software
• Physical means real like
• What families of components would we choose?
• What bottom up characteristics would fit?
• Without going all the way to naming those pieces
• But this is systems engineering, and we also can
  learn from design work that does have some
  physical reality

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Generic Physical Architecture for Elevator
Figure 8.2
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Elevator First Level Functional Model
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Functional Allocation 1-1 and Onto
Figure 8.4
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Functional Allocation Goal

• Allocate Functions ? Components.
• There is great advantage to having Functional and
  Physical Architectures match (one-to-one and
  onto).

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Functional Allocation Goal

• There is great advantage to having Functional and
  Physical Architectures match (one-to-one and
  onto).
• When does this happen ??
• When does this not happen ??

Product or system architecture decisions ??
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Two Levels of Physical Architecture

• Generic physical architecture description of the
  partitioned elements of the physical architecture
  without any specification of the performance
  characteristics of the physical resources that
  comprise each element
• Instantiated physical architecture generic
  physical architecture to which complete
  definitions of the performance characteristics of
  the resources have been added

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The Process

• Generic Physical Architecture provides common
  designators for physical resources. (No real
  physical items).
• Morphology Box to create and list instantiated
  architectures options for choice.
• Create many alternate instantiations to choose
  from.

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Morphological Box for Hammer
(Top row generic components, 320 possible
combinations)
Table 8.3
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Morphological Box for Auto Navigation Support
System
Figure 8.5
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We can use morphological boxes with software, too
Image from http//hcil2.cs.umd.edu/trs/2004-17/200
4-17.html
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Pairwise Infeasible Combinations within a
Morphological Box
Hammer Example
Figure 8.6
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Matches first level Functional decomposition
Compare lower levels to functional
decomposition Is it 1-to-1 ??
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Block Diagrams of Physical Architecture(Most
common graphical representation)
Figure 8.7
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Block diagram for software
Image from http//techpubs.sgi.com/library/tpl/cgi
-bin/getdoc.cgi?collhdwrdbbksfname/SGI_EndUse
r/RASC_UG/ch04.html.
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Issues in Physical Architecture Development

• Functional performance, availability (cost,
  safety, fault tolerance), and other system-wide
  traits.
• Commercial and product line factors.
• Operational architecture finishes this process.
• Looking ahead physical architecture elements
  are added as mechanisms on the Functional
  Architecture to produce the Operational
  Architecture.

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Vehicle Theft Deterrence

• Its fairly easy to understand conceptually how
  an effective system could work

See https//www.youtube.com/watch?vEe3L9BQQ4Gs
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Example- Vehicle Theft
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Vehicle Theft Example
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Major Concepts for Physical Architecture

• Centralized vs. Decentralized
• Modular vs. Integral
• Standardization, Serviceability
• COTS components

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Mostly Software Example FBI Fingerprint
Identification System

• IAFIS Integrated Automated Fingerprint
  Identification System
• ITN/FBI Identification Tasking and Networking
  segment focus of this case study
• III/FBI Interstate Identification Index segment
• AFIS/FBI Automated Fingerprint Identification
  System segment

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ITN/FBI Identification Tasking and Networking

• RFP identified subelements
• TPS Ten-print Processing Subelement was key
• Processed paper cards with 10 fingerprints
• Organized as work stations within a workgroup
  (distributed system)
• Processed 30,000 per day
• Scanned, converted to binary data, and analyzed
• Images had to be compressed by at least 10 to 1
• Average time to perform a fingerprint image
  comparison was 60 seconds
• Time allowed for display of human-machine
  interface was 1 second from time of request

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Critical Design Issues for TPS

• Implementation of wavelet scalar quantization
  (WSQ) algorithm (hardware vs. software)
• Workstation capabilities
• Server capabilities
• Workflow management capabilities
• Communications interface

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Alternate Design Allocation Options Studied
Figure 8.8
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Morphological Box of Instantiated Design Option
2 new alternatives (g h) identified
Table 8.5
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Use of Redundancy to Achieve Fault Tolerance

• Hardware adds extra hardware to enable detection
  of and recovery from errors
• Software N-version
• N different software developers for same routine
• Comparison of results via voting
• Seldom used due to expense of software
  development
• Information adding extra bits of information to
  enable error detection
• Time replaces hardware or software redundancy
  when there is slack processing time -
  recalculation

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Hardware Redundancy -A crucial choice for
software

• Passive extra hardware operating concurrently
  using voting
• Errors are masked or hidden (system unaware)
• Approaches
• N-modular redundancy (NMR)
• Triplicated TMR masks 1 error
• 5MR masks 2 errors
• Triplicated NMR
• Active detects errors, confines damage, recovers
  from errors, isolates/reports fault
• Duplication with comparison extra hardware with
  comparison, not voting
• Hot standby extra hardware, only one reporting,
  monitor of outputs to detect error
• Cold standby extra hardware inactive until error
  detected
• Pair-and-a-spare Duplication with comparison
  hot standby
• Hybrid combinations of the above

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TMR Triplicated TMR
Voter is single point of failure
Issues with Voting
Figure 8.9
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Software Implementation of Triplicated TMR
Figure 8.10
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Active Hardware Redundancy Duplication with
Comparison
Figure 8.11
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Hot Standby Sparing, N-1 Replicas
Figure 8.12
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Pair-and-a-spare
Figure 8.13
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Practicality of Redundancy

• How practical is redundancy ?
• In your car.
• In an airplane.

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Redundancy Warning

• Redundant components and systems must truly be
  independent systems.
• Often a single point of failure takes out all
  redundant systems.
• Space Shuttle Challenger (o-rings)
• Genesis space vehicle (g-switches)
• UA 232 Sioux City (hydraulic systems) (P.242)

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Discussion Q1

• The physical architecture for
• the hammer
• what does the functional architecture look like

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Discussion Q2

• For the drink machine functional architecture,
  does Hatley Pirbhai or Energy, Materials, Signal
  Flows work better with respect to giving a
  functional architecture that produces a more
  realistic physical architecture.

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Discussion Q3

• For the ATM machine, develop an external systems
  diagram and a first level function decomposition
  for the Acme ATM Company a manufacturer and
  seller of ATM machines.
• Consider the possible uses of the functional
  model and physical implementations of the system.

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Discussion Q4

• Given the first level decomposition for the ATM
  machine
• Sketch the generic physical architecture
• Sketch a morphological box and some possible
  instantiated physical implementations

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Wassons Ch 40

• Lets look at Wassons recommended methodology

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Wassons Domain solution challenges (Sec 40.6)

1. Solution space validation
2. Technical design integrity
3. Multi-domain solution agreement
4. Risk identification and mitigation
5. Environment, safety and health
6. System solution stability
7. System support
8. Interfaces
9. System optimization
10. Phases and modes of operation

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Step 2 Allocate capabilities
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Extra Slides

• See the last slide!

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Example - F-22 Physical Architecture
Figure 8.1
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Work Breakdown Structure - WBS

• MIL-STD-881B WBS for defense material items.
• WBS is often similar to Physical Architecture
  work organized along lines of resources for
  development or procurement.
• Examples Aircraft system (10 elements, 17
  resource categories)
• (See Blanchard and Fabrycky Section 18.2.)

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WBS Elements and Related Life Cycle Phases
Table 8.1
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Resource Categories for Generic Air Vehicle
Table 8.2
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Development Process for the Physical Architecture
Figure 8.3
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Functional Allocation 1-1 and onto
Figure 8.4
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Option Creation Techniques
Table 8.4