Optimization: Design for ‘ilities

1. EMIS 8390 Systems Engineering Tool—applying tools to engineering systems Optimization: Design for ‘ilities UPDATED 10/20/04 Mark E. Sampson

2. Design for… • EMI/EMC • Environment • Disposal • Human Factors, Usability, Training • Safety • Manufacturing/Produceability • Reliability, Maintainability, Availability • Logistics/Supportability • Security • Testability • Liability • Politics • … $150/vehicleliability for disposal EU Auto Mfg’s are required to balance vehicle content by country. [SE Handbook 11] [Lacy 1992]

3. 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

4. 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 person • Perceptions: “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… Jack and Jill went went 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.” [Bailey 1982]

5. 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

6. Design for Reliability...continued • FMEA’s… a “simple” 10 step process • Capture product functions • Capture product block diagram to identify potential physical interfaces • Identify potential failure modes (corrosion, electrical short, torque fatigue,…) • What is the effect of the failure (injury, stop-operating, degraded performance, noise, odor,…) • Rank the severity (1-no impact up to 10-serious,injury) • How likely is the failure to occur (1-not likely up to 10-inevitable) • Identify controls that prevent or detectors that warn • Determine the probability of detection • Compute the RPN for each RPN = (Severity) x (Probability) x (Detection) • Action high RNP failure modes • …lots of tools out there to use for this…many of them free, excel-addins, access DB’s, etc. Warning: Peel fruit from cellophane before eating www.fmeainfocentre.com

7. Design for Reliability...continued • Fault Trees • Fishbone diagrams • Root cause analysis • Petri Nets • Identify all possible contributors to the fault. • Identify all possible impacting issues to those contributors • …keep going • Many tools that can help… • Relex • Aralia • Blocksim • … Clapham railway accident 1988

8. 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: • Field • Intermediate • Depot • Contractor • …which will dictate your logistics supportrequirements. • Discussion on Design for Logistics/Supportability by Gerard Ibarra Ibarra & Assoc. Sony Trinitron can handle 32g shock loading [Lacy 1992]