The engineering design process

The Engineering Design Process

- Creative process

- Problem solving – the big picture
- No single "correct" solution
- Technical aspects only small part

Elements of Design the Process

ØProblem Identification
ØResearch Phase
ØRequirements Specification
ØConcept Generation
ØDesign Phase
ØPrototyping Phase
ØSystem Integration
ØMaintenance Phase


Needs Identification

1.Collect information
2.Interpret information
3.Organize needs hierarchy
4.Determine relative importance of needs
5.Review outcomes and process


Requirements Specification


ØIdentifies requirements design must satisfy for success
1. Marketing requirements
§Customer needs
2. Engineering requirements
§Applies to technical aspects
§Performance requirements


Properties of Engineering Requirements

1.Abstract – what, not how
2.Unambiguous – unique and specific
ØUnlike marketing requirements
3.Traceable – satisfy need?
4.Verifiable – test/measure


Example Engineering Requirements


vPerformance and Functionality
1.Will identify skin lesions with a 90% accuracy
2.Should be able to measure within 1mm
vReliability
1.Operational 99.9% of the time
2.MTBF of 10 years
vEnergy
1.Average power consumption of 2 watts
2.Peak current draw of 1

Concept Generation and Evaluation

ØExplore many solutions
§Brainstorm
ØSelect the best solution
§Based on needs and constraints
ØCreativity
§ Development of new ideas
ØInnovation
§ Bringing creative ideas to reality


Concept Generation

ØSubstitute
ØCombine
ØAdapt
ØModify
ØPut to other use
ØEliminate
ØRearrange or reverse

Barriers to Creativity

ØPerceptual blocks
ØLimiting problem space
ØEmotional blocks
•Fear of failure – “fail early and often”
ØEnvironmental blocks
• Engineering cultural bias
ØIntellectual and expressive blocks
• Understand tools

Design Considerations

1)WORST CASE DESIGN
ØComponent variation
ØEnvironmental conditions
ØUse computer simulations

2) RELIABILITY
Ømeasured by MTBF, failure rate = 1/MTBF
Ømechanical parts fail first
Ødesign redundancy into system
Øsimple system/fewer parts = more reliable
3) SAFETY
Øidentify failure modes
Øprovide protection
4) TEST
Ødesign for ease of test
5) PRODUCTION/MANUFACTURING
Øconsider ease of assembly


Design Methodologies: Top-Down

ØAlso called “functional decompostion“
Øimplementation details considered only at the lowest level
Øtop‑down design, is not so clean and linear in practice
ØOften implementation‑level commitments are made at high levels in the design process


Design Methodologies

CASE‑BASED:
ØResearch a specific, similar design case study
ØModel your process on that
INCREMENTAL REDESIGN:
ØFind an existing design and "unravel" the design from the bottom up
ØModify as required
ØDetailed and least global aspects of the design are explored and redesigned, if necessary, first



ITERATIVE REFINEMENT:
ØAn iterative top‑down approach
ØFirst a rough, approximate and general design is completed
ØThen we do it finer, more exact and more specific
ØThis process continues iteratively until the complete detail design in done


BOTTOM‑UP DESIGN:
ØOpposite of top‑down
ØStart at the bottom with detail design
ØTo do this, you must have some idea of where you are going. So, often this becomes...
HYBRID DESIGN:
ØCombines aspects of both top‑down and bottom‑up
ØMore practical design approach then pure top‑down
ØStart with a top‑down approach, but have feedback from the bottom


"EXPLORER" METHOD:
ØTypically used for new design ideas or research. It is useful in initial design and specification stages, and is often used when in "unfamiliar territory":
1)Move in some direction; e.g. toward the library, telephone, domain expert's office, etc.
2)Look at what you find there.
3)Record what you find in your notebook.
4)Analyze findings in terms of where you want to be.
5)Use results of analysis to choose next direction.
6)Back to 1) and continue exploring


Design Group (Team)

ØEngineering projects require diverse skills
ØThis creates a need for group (team) work
ØSelect members based on skills
1.Technical
2.Problem-solving
3.Interpersonal


ØDevelop decision making guidelines
1.Decision by authority (leader)
2.Expert Member
3.Average member opinion
4.Majority
5.Consensus


ØTeams that spend time together tend to be successful teams
ØRespect each other
1.Listen actively
2.Consider your response to others
3.Constructively criticize ideas, not people
4.Respect those not present
5.Communicate your ideas effectively
6.Manage conflict constructively

ØHold effective meetings
1.Have an agenda
2.Show up prepared
3.Pay attention
4.Schedule time and place of next meeting
5.Summarize
ØAssign tasks and responsibilities


Project Management

ØWork breakdown structure
üHierarchical breakdown of tasks and deliverables need to complete project
ØActivity
1.Task – action to accomplish job
2.Deliverable – e.g. circuit or report


ØDefine for each activity
1.Work to be done
2.Timeframe
3.Resources needed
4.Responsible person(s)
5.Previous dependent activities
6.Checkpoints/deliverables for monitoring progress