EMIS 7307 Chapter 3 From Chapter 2 we

EMIS 7307 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 • T&E • Production • Operational use • Retirement 1

EMIS 7307 Chapter 3 From SE Fundamentals 2

EMIS 7307 Chapter 3 • Notice how the steps on previous slide map into Fig 3. 1 and Fig 1. 12. • In Fig 3. 2 the MIL-STD-490 terms are used. – Type A, B etc. – Names aren’t important the ideas of flowdown and increasing design detail are! – We’ll use the “ 490” terminology but understand the meaning behind the type. 3

EMIS 7307 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! 4

EMIS 7307 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! 5

EMIS 7307 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. 6

EMIS 7307 Chapter 3 From SE Fundamentals 7

EMIS 7307 Chapter 3 • The requirement allocation process selects assignments of specific allocated requirements to specifications. • See Fig 3. 3 for an example of a spec “tree”. – Order of precedence is important! 8

EMIS 7307 Chapter 3 From SE Fundamentals 9

EMIS 7307 Chapter 3 From SE Fundamentals 10

EMIS 7307 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. 11

EMIS 7307 Chapter 3 From SE Fundamentals 12

EMIS 7307 Chapter 3 From SE Fundamentals 13

EMIS 7307 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 We’ll discuss them briefly, be sure to be aware of the existence of them all and the type of engineering they accomplish! 14

EMIS 7307 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. 15

EMIS 7307 Chapter 3 • Software engineering things to know: – Verification can include evaluating the consequences of every data path regardless of it’s 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. . . 16

EMIS 7307 Structured Analysis, Structured Design User Requirements Analysis User Requirements Specifications Software Requirements Specification System/Broad Design Logical Design Program/Detailed Design Physical Design Implementation/Coding Program Testing: Units Program Testing: System Program Use Software Maintenance 17

EMIS 7307 Requirements Analysis Design 1 Implement 1 Design 2 Implement 2 Design 3 Implement 3 Test Planning Certification 1 Certification 2 Certification 3 18

EMIS 7307 Object Oriented Design Effort Basic Classes Specific Classes Implementation Detailed Design Broad Design Software requirements Requirements analysis Time I disagree with the author’s note 12 page 127. Objects are determined by the functional flowdown. 19

EMIS 7307 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 it’s mission while the system may not fail it’s 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. 20

EMIS 7307 Chapter 3 • Reliability Engineering things to know: – Look at the typical failure curves in Fig 3. 8. – What’s 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 SE’s, and 17 -20 for testers (also SE’s). 21

EMIS 7307 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). – Let’s look at the reliability qualification testing paragraph page 142, para 7 • Notice the synergism that can/should occur – Results in time and $ savings 22

EMIS 7307 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. 23

EMIS 7307 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 what’s the fix? • Lots of units, Lots of spares, Lots of maintenance personnel, Lots of $$$$! – Maintainability demonstrations are valuable but extremely expensive (See page 156) • Look for alternative ways to get the data. 24

EMIS 7307 Chapter 3 • Human factors engineering things to know: – Human as a part of the system! – Called ergonomics, considers: • • • Size (page 159). 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. 25

EMIS 7307 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. 26

EMIS 7307 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 can’t be eliminated then safety engineering determines a safe (acceptable risk) way to deal with it. 27

EMIS 7307 Chapter 3 • Safety engineering things to know: – Notice how many of the “ilities” come together synergistically (integrated by the SEMP) to support safety. • Paragraph 1 section 3. 4. 5 page 167. 28

EMIS 7307 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. 29

EMIS 7307 Chapter 3 • Producibility engineering things to know: • Objective is to convert the results of R&D 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 30

EMIS 7307 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 ! – OT&E is the typical place for evaluation of the logistics “stream”. 31

EMIS 7307 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 quality. Continuous improvement. Variability minimization (6 sigma). Everyone (not just an inspector) involved. 32

EMIS 7307 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? 33

EMIS 7307 Chapter 3 • Value/Cost engineering things to know: – See top of page 188 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. 34