The Process of Design Jason M. Keith Fuel Cells and Alternative Fuels Enterprise Michigan Technological University Houghton, MI 49931
Rationale for this Presentation Design is usually taught discipline-specific at the end of the undergraduate curriculum CM4850 Process Analysis & Design MEEM4900 Senior Design EE4900 Design Fundamentals One of the most challenging subjects for students to learn and practicing engineers to use Participants in AFG enterprise have various interests, disciplines, and class standing AFG has a new project that requires a significant design effort
What do I need? (Crowl, 2005) To be successful at design you need: Strong understanding of technical issues (comes from your core courses) Methodology of design (focus of this presentation) Soft skills (more of an art but best learned by experience) Communication Decision making Time management Budget management Others
So what is Engineering Design? Dym & Little (2000): The organized, thoughtful development and testing of characteristics of new objects that have a particular configuration or perform some desired function(s) that meets our aims without violating any special limitations. There are often additional concerns such as: No single correct solution Conflicting specifications Incomplete, extraneous, or incorrect data Tradeoffs (especially when balancing economics & environment)
Can you give me an example? Garden Design Project (Crowl, 2005) 1. Find garden design resources in library 2. Check zoning on gardens; check with neighbors 3. Decide where to locate the garden - accessibility, sun, water drainage issues 4. Decide on garden size - estimate crop yield to determine number of plants, then use plant spacing tables 5. Sketch layout of garden - dimensions, where plants will be located 6. Determine materials required - seeds, plants, fertilizer, hoses, tools, etc.
Can you give me an example? Garden Design Project (Crowl, 2005) 7. Develop planting schedule 8. Schedule work for preparation and planting 9. Maintain garden 10. Harvest crops and replant new ones 11. Prepare garden for fall & winter 12. Eat (or sell) your vegetables Real engineering design is like this example except the costs are higher, there is more work, there are a lot of people involved, and decisions need to be made
The Prescriptive Model of Design 1. Problem Definition 2. Conceptual Design 3. Preliminary Design 4. Detailed Design 5. Design Communication This model looks sequential but in real design the Process is not linear! Real design requires feedback through verification, validation, and iteration
Problem Definition Phase of Design Clarify objectives and gather information to develop an engineering statement of what the client wants Given client statement, clarify objectives for the design Establish user requirements for the design Identify constraints for the design Establish functions for the design We can do this with: objectives tree, pairwise comparison charts, weighted objectives trees, function-means tree, functional analysis, requirements matrix
Problem Definition Phase of Design We can do this with the following tools and techniques: objectives tree, pairwise comparison charts, weighted objectives trees, function-means tree, functional analysis, requirements matrix Ways of obtaining useful information include: Literature review, brainstorming, user surveys and questionnaires, structured interviews
Objectives Tree
Combined Tree
Dog on Chair
Pairwise Comparison Charts
Weighted Objectives Tree
Black Box
Transparent Box
Function-Means Tree
Conceptual Design Phase of Design Look for different concepts or schemes of candidate designs that can be used to achieve client objectives Address some but not all technical objectives, being sure to maintain a high-level approach Establish design specifications Generate design alternatives that satisfy the above requirements
Conceptual Design Phase of Design We can do this with these tools: - performance specification method - quality function deployment - morphological chart Using: brainstorming, divergent thinking, benchmarking, reverse engineering
A Boy and his Dog
Performance Specification Curve
Morphological Chart
Another Morph Chart
Preliminary Design Phase of Design Identify principal attributes of the design concept Flush out proposed design schemes Look at design subsystems and lower level functions Use rules of thumb and make final choice from proposed concepts Methods: weighted objectives tree, pairwise comparison chart, numerical evaluation matrix Means: metrics definition, prototype development, simulation / computer analysis, proof-of-concept
Numerical Evaluation Matrix
Another Numerical Evaluation Matrix
References Crowl D. Introduction to Chemical Engineering Design (2005 draft). Dym, C. L. and Little, P. Engineering Design: A Project-Based Introduction, Wiley, New York (2000).