Product Development

Chapter 6

Hardware & Software Techniques Block diagram the system (Visio) Redundancy

Active: failure of one parallel component - the second still works

Standby: failure of component – replacement MTBF=mean time between failures = 1/λ

Active MTBF=3/(2λ) Standby MTBF=2/λ

MIL-HDBK-217

Where to get λ? Google MIL-HDBK-217…

For example, see www.sqconline.com/reliability/index.html

Try wire wound resistor in a missile…

Component Selection Considerations Component reliability

Vendor assessment (Hx, failure, etc.) Vendor audit (check facility) Vendor evaluation (inspect incoming) Vendor qualification (on-list?)

Component history military & reliability groups government info bases

Safety (FMEA, etc.)

Hardware & Software Techniques ctd. Component Derating

Practice of limiting the stresses Use 2 watt R in 1 watt situation, decrease failure

rate >30% (T, humidity, P, V, I, friction, vibration) Usage ratio = max stress/stress rating (.5-.9) Goal is reliability! Pacemaker example

Hardware & Software Techniques ctd. Safety Margin

=(mean safety factor) - 1

=(mean strength/mean stress) - 1 Elevator – safety margin~2 Medical devices – Fries - .5 and up.

Load Protection Environment (see 112) Product misuse Design for variation (6 sigma)

Experimental Design

Statistical Approach Effective approach for

multivariable situations Taguachi method

Design Process System design Parameter design Tolerance design

Two types of variables Control factors Noise factors

Apply this to design

Software Development and Engineering Management Planning for safety

(FDA!) Planning for risk

assessment Planning for method

Waterfall Incremental delivery Spiral Cleanroom Code and fix, …

Software Development and Engineering Management Choose design method

Top-down Data driven OOP

Language (Assembler/C++/Qbasic etc.) Testing Requirements Hazard Analysis!!! (FDA)

Software Development and Engineering Management

Requirements traceability (FDA)

Software architecture design Well defined modules (logical) Other vendor – standalone Single purpose modules Cohesion & coupling

Implementation (coding) Integration

Structured/Unstructured Design Techniques Computer/database assisted:

Ideation - ‘Innovation Workbench’

TRIZ Techoptimizer Others…

Example done in class, another in text

Axiomatic Design

Nam Suh, MIT Requirements, design parameters, process

variables, customer needs = vectors Try to solve, disassociate functional

requirements and design parameters Highly mathematical Acclaro Software

Reverse Engineering and Redesign Opportunities increase with age of technology Disassembly of product and inventory and

analysis of parts Allows for the potential update or modification

of the parts with technological advances Can drastically increase productivity or

effectiveness in a dated product

Design Techniques

Very structured approach Pahl and Beitz, Engineering Design Design method contains 8 distinct steps

Semistructured Wilcox, Engineering Design for Electrical

Engineers Ulrich and Eppinger Product Design and

Development

The Clean-Room Approach To Reverse-Engineering: “One person or group takes a device apart and

describes what it does in as much detail as possible at a higher level of abstraction than the specific code. That description is then given to another group or person who has absolutely no knowledge of the specific device in question. This second party then builds a new device based on the description. The end result is a new device that works identically to the original but was created without any possibility of specifically copying the original. “

-Mathew Schwartz