Eml4550 engineering design methods
1 / 27

EML4550 - Engineering Design Methods - PowerPoint PPT Presentation

  • Uploaded on

EML4550 - Engineering Design Methods. Concept Selection Settling on one or more promising ideas to pursue to final design Hyman: Chapter 9, Sec. 9.1 & 9.2 Ulrich and Eppinger: Chapters 5 and 6 Dym and Little: Sections 6.1 – 6.3. Plan Design/ Development Project. Perform Economic

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

PowerPoint Slideshow about ' EML4550 - Engineering Design Methods' - clemance-legend

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Eml4550 engineering design methods

EML4550 - Engineering Design Methods

Concept Selection

Settling on one or more promising ideas to pursue to final design

Hyman: Chapter 9, Sec. 9.1 & 9.2

Ulrich and Eppinger: Chapters 5 and 6

Dym and Little: Sections 6.1 – 6.3

Concept development diagram











Concept Development Diagram



















Concept selection
Concept Selection

  • The ‘Concept Generation’ phase spawned many ideas (good and bad) and potential solutions to the problem at hand

  • How do we select from all these competing concepts?

  • A ‘method’ is needed to systematically weed out poor concepts and select the best one to proceed with to Final Design

Concept selection methods
Concept Selection Methods

  • External decision (customers, consultants, etc.)

  • Product “Champion” (strong personal decision)

  • Intuition (no rational method)

  • Pros and Cons (systematic but subjective)

  • Prototype and test (hardware, expensive and time-consuming)

  • Decision matrices (match characteristics vs. pre-specified and weighted criteria)

Concept selection methods cont
Concept Selection Methods (Cont.)

  • Although all methods are used in practice, most of the ‘subjective’ methods are very case-specific

  • Decision matrices represent the most ‘rational’ approach to concept selection

  • We will focus this section on the Decision Matrix method

Concept selection why a structured approach
Concept Selection: Why a Structured Approach?

  • A customer-focused product (use the needs as guidelines)

  • A competitive design (do not overlook competing designs)

  • Better product-process coordination (forces manufacturing issues into the trade-off)

  • Reduced time to market (accelerated ‘downselect’)

  • Effective group decision-making (minimize ‘arbitrary’ decisions and maximize team exposure)

  • Documentation of decision process (not lost in someone’s ‘memory’)

Concept selection why a structured approach cont
Concept Selection: Why a Structured Approach? (Cont.)

  • Need to balance:

    • Desire to have an expedient ‘downselect’

      • Expediency: proceed to design sooner

      • Faster time-to market

      • Less cost of ‘carrying’ many concepts forward

    • Desire ‘to know more’ before deciding

      • Risk of making a mistake (pick a loser)

      • Risk of avoiding a concept because it is new (potential big winner)

      • Engineers tend to be conservative

Decision matrix method
Decision Matrix Method

  • Stage 1: Concept Screening

    • Apply an initial ‘filter’ to ‘weed out’ bad concepts and determine likely ‘winners’. Apply some elements of ‘scoring’ for the purposes of ranking only

  • Stage 2: Concept Scoring

    • Apply weighted criteria to the concepts and proceed with a quantitative ‘scoring’ system to pick a winner (or winners)

Decision matrix method cont
Decision Matrix Method (Cont.)

  • Each Stage has 6 steps:

  • Prepare the selection matrix

  • Rate the concepts

  • Rank the concepts

  • Combine and improve the concepts

  • Select one or more concepts

  • Reflect on the results of the process

Screening step 1 prepare selection matrix
Screening: Step 1 - Prepare Selection Matrix

  • Develop a set of criteria

    • Customer needs (condensed into criteria)

    • Corporate needs (cost, manufacturing, liability, image, etc.)

  • Give equal weight to all criteria

Screening step 2 rate the concepts
Screening: Step 2 - Rate the Concepts

  • Give +, -, or neutral rating to each concept based on criteria

  • Use general notions (no need to get ‘specific’)

  • Use team consensus (or majority vote)

  • Refine or split criteria if team consensus is hard to reach

Screening step 3 rank concepts
Screening: Step 3 - Rank Concepts

  • Add scores and build a ranking

  • Identify a “benchmark” concept (from ranking or from external products - competition)

  • Group the concepts into three categories: “possible winners”, “neutral”, and “losers”

Screening step 4 combine and improve concepts
Screening: Step 4 - Combine and Improve Concepts

  • Are we throwing away as ‘loser’ a ‘good’ concept because it has one or two negatives? Can they be neutralized?

  • Can two concepts be combined to preserve ‘better than’ qualities while neutralizing ‘worse than’ items? Can we derive a concept that takes the ‘best of both worlds’?

Screening step 5 select one or more concepts
Screening: Step 5 - Select one or more concepts

  • If there is a ‘clear’ winner, then select it and proceed with it


  • However, usually more than one concept will survive the screening

  • Number of concepts to carry forward will depend on resources and time available

Screening step 6 reflect on the process
Screening: Step 6 - Reflect on the Process

  • Did we achieve consensus?

  • Were all the team members treated equally? No trampling?

  • Did we avoid personal agendas? Department politics?

    It is very disruptive to team spirit to ‘drop’ a concept that someone was championing. Grudges linger for a long time within a team

Concept screening1
Concept Screening

An example

Scoring step 1 prepare selection matrix
Scoring: Step 1 - Prepare Selection Matrix

  • Using the same selection criteria used in screening give relative weight to each (must add to 100%)

    • It is possible to slightly modify the criteria in light of the surviving concepts

    • Weights to each criterion are given by team consensus or related to customer needs

An example

Scoring step 2 rate the concepts
Scoring: Step 2 - Rate the Concepts

  • As with screening, give a ‘score’ to each concept based on a ‘quantitative’ (yet still subjective) numbering scale as follows:

    Relative Performance

    1 - Much worse than reference concept

    2 - Worse than reference concept

    3 - Same as reference concept

    4 - Better than reference concept

    5 - Much better than reference concept

Scoring step 3 rank the concepts
Scoring: Step 3 - Rank the Concepts

  • Compute score for each concept

Scoring step 4 combine and improve concepts
Scoring: Step 4 - Combine and Improve Concepts

  • As before, can concepts be combined to arrive at a better solution?

    • Looking at the concepts in the new light of ‘scoring’ can encourage the team to improve on the initial ideas

Scoring step 5 select one or more concepts
Scoring: Step 5 - Select One or More Concepts

  • The final selection is never easy

  • Do ‘parametric’ studies by assigning different weight distributions and see which concepts come on top on each try

Scoring step 6 reflect on the process
Scoring: Step 6 - Reflect on the Process

  • Are we ready to proceed with the ‘winning’ concept?

  • Did the method facilitate the selection?

  • Can the method be improved?

Concept selection caveats
Concept Selection: Caveats!

  • Decomposition of product quality

    • Failure to capture relationship among criteria

  • Subjective criteria

    • Methodical, but still high content of subjectivity

  • Where to include cost

    • Derived from customer needs, but how about ‘manufacturing’ the product, not all parameters known

  • Selecting elements of complex systems

    • Can a complex concept be reduced to a set of simpler concepts? How about interactions between sub-concepts?

  • Applying concept selection throughout the development process

    • The same approach can apply to the selection of concepts within a design effort when developing sub-systems of a larger system

Concept selection implications to project
Concept Selection: Implications to Project

  • If many concepts are considered, perform a screening

  • Record results of screening (and criteria used)

  • Decision matrix for the selection and scores for each concept

  • Presentation of the ‘winning’ concept