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Optimization: Design for

‘ilities

Mark E. Sampson

EMIS 8340

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 • Irony• …

[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.” Cows drink…

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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.

[Lacy 1992]

Sony Trinitron can handle 32g shock loading

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Design for Manufacturing…What is Six Sigma?

• Six Sigma is essentially a reactive quality improvement strategy that uses statistical methods to remove defects and optimize processes

• Statistical sampling of resultproduces a Normal distribution

• Goal is to reduce number of samples outside the limit/goal.

• Six-Sigma goal is 6 standarddeviations from the mean

Sigma Level

Defects per million opportunities

1 690,000

2 308,537

3 66,807

4 6,210

5 233

6 3.4

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Six Sigma In You Daily Life

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Isn’t Three Sigma Level (99.7% Yield) Good Enough for Quality?

• Virtually no modern computer would function.• 10,800,000 healthcare claims would be mishandled each

year.• 18,900 US Saving bonds would be lost every month.• 54,000 checks would be lost each night by a single bank.• 4,050 invoices would be sent out incorrectly each month

by a modest-sized telecommunications company.• 540,000 erroneous call details would be recorded each

day from a regional telecommunications company.• 270 million erroneous credit card transactions would be

recorded each year in the United States.

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Cost of QualitySigma Level Defects per Million Opportunities

(DPMO)Cost of Quality

2 308,537 (Non-Competitive) Not Applicable

3 66,807 25 – 40% of Sales

4 6,210 (Industry Standard) 15 – 25% of Sales

5 233 5 – 15% of Sales

6 3.4 (World Class) < 1% of Sales

Each Sigma Level Shift provides a 10% net income improvement.

[GE 1998 Annual Report]

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The 4-Sigma Wall…• There are only so many defects you can squeeze

out of development process before reaching the point of diminishing returns where the fix is more expensive the problem

• …what’s called the 4-sigma wall and what DFSS is about

• DFSS is a proactive,defect avoidanceapproach to design

Time

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Improve Quality via Process Improvement

Diminishing Returns with Process Improvement

DFSS

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DFSS Window of Opportunity

“Design in” quality early when costs are low

Rel

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DFSS

Concept Design Development Production

SixSigma

Everyone knows you can’t test in quality—you need to address it from the beginning. DFSS is after addressing product quality goals from the start.

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Murphy’s Law 39: “Toast always falls butter-side down”

• Oxford University, Murphy Center of Excellence, Toast Study enlisted 10,000 students to perform sampling

…of 1,000,000 pieces of toast, 623,000 land on the floor butter side down <1 sigma-level process

62.3% of ToastFalls butter-sidedown

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A Six-Sigma approach for dealing with toast…• Using a Define, Measure, Analyze, Improve,

Control approach…• We would focus on the results--How to improve

the probability of toast landing butter side up:1. Raise table height (3 m)2. Embedded Gyroscopes3. Smaller pieces of toast4. Strapping toast to the back of a cat5. Spring loaded plates

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A DFSS approach for dealing with toast…

• Using a Identify opportunity, Define requirements, Develop concept, Optimize design, Verify it,

• We would focus on the product-How to avoid toast sliding off the plate/table

1. Outlaw toast2. Fences on plates3. Toasters on/in the table4. Sticky toast (Velcro?)

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Design for Manufacturing...cont.

Lean manufacturing…all about removing waste…

1. Overproduction: to produce more than demanded or produce it before it is needed. It is visible as storage of material.

2. Inventory or Work In Process (WIP): is material between operations due to large lot production or processes with long cycle times;

3. Transportation 4. Processing waste: asking why a specific processing step is needed and why

a specific product is produced. All unnecessary processing steps should be eliminated;

5. Motion: of the workers, machines, and transport 6. Waiting: for a machine to process should be eliminated. 7. Making defective products: is pure waste.

[isixsigma institute, advancedmanufacturing.com]

“No greater waste than doing something efficiently that shouldn’t be done at all.”