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





Component history



Vendor assessment (Hx, failure, etc.)
Vendor audit (check facility)
Vendor evaluation (inspect incoming)
Vendor qualification (on-list?)
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



Apply this to
design

System design
Parameter design
Tolerance design
Two types of variables


Control factors
Noise factors
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