Design Tools 1

William Oakes, P.E

Director of EPICS

Assoc. Prof. Engineering Education

Learning Objectives

At the end of this session, you will be able to:

1. Describe a specification

2. Describe a decision matrix

3. Categorize potential failures for a design

4. Perform a functional decomposition

5. Create a personna

EPICS Balance

Service-learning is a balance of the learning of design and the service we contribute the communities through completed designs and support

Service• To our partners,

meeting needs in the community

Learning• Becoming good

designers, professionals & active citizens

Complimentary goals that enhance each other

Design Tool: Engineering

specifications

Specifications Development

What does your project partner need?o Don’t just rely on what they want, find out what they

needo Understand the problems and issues you are

addressingo Who will use product and who will benefit from it?

Gather Datao Talk to Project Partner and others impacted by the

project How will the problem be worked?

o Criteria for design teamso How will teams be integratedo Transition plans for multiple semesters

Gather input from project partner on specificationso Develop a specifications document and share it

Customer Requirements

Types of customer requirementso Functional performanceoHuman factorsoPhysicalo Time (reliability)oCostoStandardso Test MethodoService & maintenance

Customer Requirements

For a cell phone, make a list of Ten customer requirements

Design Specifications

Answers the “how” questionQuantified

oShould be able to measure whether you meet it

Objective quantitiesA set of units should be associated

with each specificationForms the basis for your

specifications document

Design Requirements

Starting with the customer requirements for a cell phone, make a

list of design requirements

Defining Requirements

BenchmarksoWhat is availableoWhy did they use their approachoPatent searches

• avoid infringement• Protect IP

Are we smarter than everyone else?oOr did we miss something?

Design TargetsSet standards to meet with your designHow good is goodCan be a living document

oDon’t compromise on goals, but refine as the design progresses

Tool make design trade offsoDesign decisionsoCommunication with project partner

Decision Matrix

Table with alternativesQuantify categories and score

alternativeso Importance in different categories

Use judgement to do reality checksLeaves documentation of thought

process of designoCan be shared in design reviews

Decision Matrix

    Ideas to be compared

Criteria for Comparison

Weights Scores

    Totals

Decision MatrixExample: Getting a Job

Criteria Wts

Co. A Co. B Co. C Co. D

Location 5 5x5=25 5x1=5 5x3=15 5x4=20

Salary 4

Bonus 2

Job 3

Training 2

Boss 2

Totals

Design Tool: Defining the

System

Functional Decomposition

Breaking tasks or functions of the system down to the finest level

Create a tree diagram starting at the most general function of your systemoWhat is the purpose of your system?

Break this function down into simpler subtasks or subfunctions

Continue until you are at the most basic functions or tasks

Functional Decomposition Diagram

Overall Function

Subfunction 1

Subfunction 2

Subfunction 3

Sample Diagram – Bike Fender

Protect rider from water and dirt off wheel

Shield riderSteer water

away from rider

Attach Splashguard

Functional Decomposition

Each function has a box withoAn action verbo The object(s) on which the verb actsoPossibly a modifier giving details of the

functionoKnown flows of materials, energy, control

or informationConsider WHAT not HOW

Create a functional decomposition diagram for

a mechanical pencil

Prepare them to share

DFMEA :Design for

Robustness

DFMEA Steps

1. Review the design2. Brainstorm potential failure modes3. List potential effects of failure4. Rank failures

a) Severityb) Occurrencec) Detectiond) RPN = Severity X Occurrence X Detection

5. Develop action plan6. Implement fixes7. Revisit potential failure risks

In a group, Identify one project to use as an example for this

exercise

Describe the project so the whole group understands it

Brainstorm Failures

What could go wrong?What could break?Are there systems your design relies

upon?o e.g. myEPICS software authenticates

through Purdue’s career accounts. What if the server goes down?

Are there things that could fail over time?

Brainstorm a list of potential failures for the project

Rate failuresRating (1 to 10)

Severity How severe are the consequences to the failure

Occurrence How often are the failures likely to occur?

Detection How easily are the failures detected?

DFMEA Calculations

Scores for Severity, Occurrence and Detectiono 1 to 10o 1 = Lowo 10 = High

Risk Priority Number (RPN)oRPN =Severity X Occurrence X Detection

DFMEA MatrixFailure mode

Effect of Failure

Severity Occurrence Detection RPN Rating

Example

http://en.wikipedia.org/wiki/Failure_mode_and_effects_analysis, accessed 22 Aug. 2011

Example Chart

Identify the failure scenario that should be addressed first

Develop an action plan to address the failure scenario

Continue the process

Implement the plan to eliminate the failure scenario

Revisit other potential failure risksoPrioritizeoEliminate failure scenarios

Continue until risks are below determined thresholdsoShow to the design reviews for

confirmation

Questions/Discussion