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Optimization: Design for

‘ilities

Mark E. SampsonUPDATED 10/20/04

EMIS 8390

Systems Engineering Tool—applying tools to engineering systems

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Design for…

• EMI/EMC• Environment• Disposal• Human Factors, Usability, Training• Safety• Manufacturing/Produceability• Reliability, Maintainability, Availability• Logistics/Supportability• Security• Testability• Liability• Politics • …

[SE Handbook 11] [Lacy 1992]

$150/vehicleliability for disposal

EU Auto Mfg’s are required to balance vehicle content by country.

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Design for EMI/EMC

• Electro-Magnetic Interference (EMI)…unwanted interaction between electronic systems

• Electro-Magnetic Compatibility (EMC)…ability for electronic systems to operate near each other without unwanted interactions

• Nearly everything has electronics in it and you need to design for it.

…some examples from health care…

Baylor Medical Center Dallas is transmitting medical telemetry in the band 186-192 MHz with 0.01 watts power.

WFAA TV Dallas begins transmitting DTVsignals at the same frequencies with 316,000 watts power.

Baylor spends $200k for new medical equipment to remediate the problem.

In 2002, a patient was over-infused with epinephrine when a nearby cell phone was activated.

[SE Handbook 11 ] [Lacy 1992] www.mohca.org

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Design for Humans…Human Factors

• Design for human interactions/limitations…Reaction time: hear & respond: 150ms, see & respond: 200ms,…Stimulus thresholds: Pressure on fingertips .05-.1.1erg (1 erg=1mg

dropped 1cm)Temperature: Skin temp:91.4’, 60’-105’ ok, < feels cold, > feels hot Anthropometric measure…no such thing as an average person.

Design for the 95th percentile personPerceptions: “giving meaning to stimuli”

“…can be thought as merging immediate & remote past applied to the present to make sense of it. An experienced perceiver can make sense of it, if it matches up”

Perceptions are real, and real in their consequences…

Three-Mile Island…

[Bailey 1982]

Jack and Jill wentwent up the

hill to fetch a a pail of milk

FINISHED FILES ARE THE RE-SULT OF YEARS OF SCIENTIF-

IC STUDY COMBINED WITH THE EXPERIENCE OF MANY YEARS

“dealing with an unprecedented problem, nothing in their experience enabled them to make sense of what was happening…the result was a series of missteps, misdiagnosis, changing a minor incident into one costing ~$2 billion dollars.”

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Design for Reliability/safety...Designing products for Murphy—”anything that can go wrong will go wrong”

• You can’t manufacture in reliability…you design it in. Reliability needs to be considered from the start.

“A large safety factor does not necessarily translate into a reliable product. Instead it often leads to an overdesigned product with reliability problems”

--Failure Analysis Beats Murphy’s Law Mechanical Engineering, Sept. 1993

To design for reliability, you need to understand possible failure modes. Several important tools can help:

• Fault Trees• FMEA’s (Failure Modes

Effects Analysis)• Root Cause Analysis • Fish Bones• Sneak Circuit Analysis

[SE Handbook 11 ] [Lacy 1992] www.fmeainfocentre.com

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Design for Reliability...continued

• FMEA’s… a “simple” 10 step process1. Capture product functions2. Capture product block diagram to identify potential physical interfaces3. Identify potential failure modes (corrosion, electrical short, torque fatigue,…)4. What is the effect of the failure (injury, stop-operating, degraded performance, noise,

odor,…)5. Rank the severity (1-no impact up to

10-serious,injury)6. How likely is the failure to occur

(1-not likely up to 10-inevitable)7. Identify controls that prevent or

detectors that warn 8. Determine the probability of detection9. Compute the RPN for each  

RPN = (Severity) x (Probability) x (Detection)

10. Action high RNP failure modes

…lots of tools out there to use for this…many of them free, excel-addins, access DB’s, etc.

www.fmeainfocentre.com

Warning: Peel fruit from

cellophane

before eating

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Design for Reliability...continued

• Fault Trees• Fishbone diagrams• Root cause analysis• Petri Nets 1. Identify all possible contributors to the fault.2. Identify all possible impacting issues to

those contributors3. …keep going

Many tools that can help…RelexAraliaBlocksim…

Clapham railway accident 1988

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Design for Maintainability...

• What is the maintenance concept for the product?• Compatible with your maintenance organization • Robust to technology changes…

Example: TV maintenance over last 20 yrs…In house troubleshooting/replace tubes or take to shop, replace circuit boards, …buy a new TV.

• Based on concept of operations…• Delivered in levels

• Cars: 1 level-dealers• Copy machines: customer location• Military: 3-4 levels:

1. Field2. Intermediate3. Depot4. Contractor

…which will dictate your logistics supportrequirements.

Discussion on Design for Logistics/Supportability by Gerard Ibarra Ibarra & Assoc.

[Lacy 1992]

Sony Trinitron can handle 32g shock loading