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Chapter 3 From Chapter 2 we had these

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Names aren't important the ideas of flowdown and increasing design detail are! ... Notice the synergism that can/should occur. Results in time and $ savings. EMIS 7307 ... – PowerPoint PPT presentation

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Title: Chapter 3 From Chapter 2 we had these


1
Chapter 3 From Chapter 2 we had these steps
in the SE process
  • Problem definition
  • Consumer need
  • Feasibility
  • System operational requirements
  • Maintenance and support concepts
  • Determine/prioritize TPMs
  • Functional analysis
  • Requirements allocation
  • System synthesis
  • Design integration
  • TE
  • Production
  • Operational use
  • Retirement

2
Chapter 3
From SE Fundamentals
3
Chapter 3
  • Notice how the steps on previous slide map into
    Fig 3.1.
  • In Fig 3.2 the MIL-STD-490 terms are used.
  • Type A, B etc.
  • Names arent important the ideas of flowdown and
    increasing design detail are!
  • Well use the 490 terminology but understand
    the meaning behind the type.

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6
Chapter 3
  • Type A (system spec) - usually only 1.
  • Technical, performance, operational and support
    characteristics of the system as whole.
  • Feasibility,operational requirements, functional
    analysis products go here.
  • Defines subsystems.
  • Has a Section 4!

7
Chapter 3
  • Type B (development spec) - usually several.
  • Technical, performance, operational and support
    characteristics of specific subsystems.
  • Performance, effectiveness, and support
    characteristics are included.
  • Defines assemblies or CSCIs.
  • Has a Section 4!

8
Chapter 3
  • Type C (product spec) - usually many.
  • Design details.
  • Hardware separate from software.
  • Has a Section 4!
  • Type D and E
  • Specific process and material requirements.

9
Chapter 3
From SE Fundamentals
10
Chapter 3
  • The requirement allocation process selects
    assignments of specific allocated requirements to
    specific specifications.
  • See Fig 3.3 for an example of a spec tree.
  • Order of precedence is important!

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12
Chapter 3
From SE Fundamentals
13
Chapter 3
From SE Fundamentals
14
Chapter 3
  • See Fig 3.4.
  • Type A,
  • TPMs usually here.
  • These are the typically used sections.
  • The essence is the important part but, using this
    format is comfortable within DOD.
  • Types B, C etc are typically laid-out the same.
  • Next page from SEF Guide.

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Chapter 3
From SE Fundamentals
17
Chapter 3
From SE Fundamentals
18
Chapter 3
Blanchard selects 12 design disciplines for
further discussion because they have been
historically inadequately integrated into system
developments and mainstream design effort. They
are
  • software development
  • reliability
  • maintainability
  • human factors
  • safety
  • security
  • producibility
  • logistics
  • disposability
  • quality
  • environmental
  • value/cost

Well discuss them briefly, be sure to be aware
of the existence of them all and the type of
engineering they accomplish!
19
Percent of Specification Requirements Involving
Software


F-22
B-2
F-16
F-15
F-111
A-7
F-4
Ref Lockheed - Martin Corp.
20
Chapter 3
  • Software engineering things to know
  • Same processes and flow in the system engineering
    of software as hardware.
  • Software engineers may have their own special
    names but they are equivalent.
  • Testing subroutines, subprograms and integration
    into programs flows in a similar fashion as
    hardware.

21
Chapter 3
  • Software engineering things to know
  • Verification can include evaluating the
    consequences of every data path regardless of
    its use likelihood.
  • Stress testing explores the limits of i/o,
    throughput and processing.
  • Software QC deals with subjects like - were the
    standards followed?
  • Following three charts are examples of software
    development methodologies...

22
Structured Analysis, Structured Design
23
Test Planning
Certification 1
Certification 2
Certification 3
24
Object Oriented Design
  • Effort
  • Implementation
  • Detailed Design
  • Broad Design
  • Software requirements
  • Requirements analysis
  • Time

Basic Classes
Specific Classes
I disagree with the authors note 12 page 140.
Objects are determined by the functional flowdown.
25
Chapter 3
  • Reliability Engineering things to know
  • Probability based.
  • Item is considered reliable if the mission of the
    device is accomplished.
  • Implies a component may fail its mission while
    the system may not fail its mission and vice
    versa
  • R, MTBF and ? are important parameters.
  • R e-t? where t operating time and ? average
    failure rate.
  • e-t? represents the probability of zero failures
    in t.

26
Chapter 3
  • Reliability Engineering things to know
  • Look at the typical failure curves in Fig 3.8
    and 3.9
  • Whats the difference between a software failure
    and a hardware failure?
  • Note the effects of redundancy on reliability in
    Fig 3.11.
  • In Fig 3.14 items 1-5 are for SEs, and 17-20 for
    testers (also SEs).

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29
Chapter 3
  • Reliability Engineering things to know
  • Importance of FRACAS!
  • Suggest an automated problem identification and
    notification system!
  • Anyone who suspects a problem documents it and
    then it gets dispositioned (i.e. reviewed and
    actions assigned to correct as required).
  • Lets look at the reliability qualification
    testing paragraph page 155, para7
  • Notice the synergism that can/should occur
  • Results in time and savings

30
Chapter 3
  • Maintainability Engineering things to know
  • Maintainability is the ability of an item to be
    maintained.
  • Maintenance is the action to restore or retain a
    specified operating condition.
  • See the time relationships in Fig 3.17.
  • A log-normal distribution is typical of
    maintenance times. See Fig 3.18.

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33
Chapter 3
  • Maintainability Engineering things to know
  • See Fig 3.19. How many were false alarms?
  • Availability is the factor of interest to your
    customer.
  • A? MTBM/(MTBM MDT)
  • If one has or anticipates low A? whats the fix?
  • Lots of units, Lots of spares, Lots of
    maintenance personnel, Lots of !
  • Maintainability demonstrations are valuable but
    extremely expensive (See page 169)
  • Look for alternative ways to get the data.

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35
Chapter 3
  • Human factors engineering things to know
  • Human as a part of the system!
  • Called ergonomics, considers
  • Size (page 172)
  • Senses.
  • Physiological factors.
  • Psychological factors.
  • Interface called MMI.
  • This interface requires as much or more
    definition as machine to machine. This can be a
    big time consumer.

36
Chapter 3
  • Human factors engineering things to know
  • Mockups and simulators likely required during
    design.
  • Human subjects typical of end user (I.Q.,
    training, etc.) needed as test subjects during
    design.
  • See Fig 3.26 for tasks especially 15- testing.

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38
Chapter 3
  • Safety engineering things to know
  • This is not about conducting a test safely.
  • This is about designing a system to minimize
    human and hardware/software exposure to unsafe
    conditions.
  • When a hazard cant be eliminated then safety
    engineering determines a safe (acceptable risk)
    way to deal with it.

39
Chapter 3
  • Safety engineering things to know
  • Notice how many of the ilities come together
    synergistically (integrated by the SEMP) to
    support safety.
  • Paragraph 3 section 3.4.5 page 180.

40
Chapter 3
  • Security engineering things to know
  • Prevents planned introduction of faults/failures.
  • Similar to preventing inadvertent faults by
    careless operators except for intent.
  • Includes encryption techniques and devices.
  • Virus detectors and physical access barriers are
    examples.

41
Chapter 3
  • Producibility engineering things to know
  • Objective is to convert the results of RD
    efforts into something that can be produced
    outside the lab.
  • Minimize the following
  • critical materials
  • critical processes
  • proprietary items
  • special production tooling
  • unrealistic tolerances
  • special test systems
  • highly skilled personnel
  • production/procurement lead times

42
Chapter 3
  • Logistics engineering things to know
  • Figure 3.32 is a good summary of the elements of
    logistics.
  • Figure 3.33 shows when engineering can influence
    the design to reduce risk and costs.
  • Logistics is an area with tremendous lifetime
    costs !
  • OTE is the typical place for evaluation of the
    logistics stream.

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45
Chapter 3
  • Quality engineering things to know
  • QC and QA are after the fact i.e. checking the
    final product.
  • TQM and QFD are from the beginning.
  • Emphasis on the following
  • Customer satisfaction no satisfaction no
    quality.
  • Continuous improvement.
  • Variability minimization (6 sigma).
  • Everyone (not just an inspector) involved.

46
Chapter 3
  • Environmental engineering things to know
  • Ecological, political and social factors.
  • Affects test choices e.g.
  • Bombing range in Puerto Rico.
  • Sonar test impact on whales.
  • Use and retirement issues.
  • Lithium batteries in airplanes.
  • Nuclear leftovers like old submarine reactors
    -where do you dispose of them?

47
Chapter 3
  • Value/Cost engineering things to know
  • See page 202 for examples of figures of merit.
  • From a functional flow diagram, estimate the
    costs of the various functions from beginning to
    end.
  • Lots of models exist.
  • Appendix B provides details and examples.
  • LCC analysis may justify expensive testing.
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