Engineering design process
- 1. BEST Robotics and The Engineering Design Process Mark D. Conner The Engineering Academy at Hoover High School www.eahoover.com
- 3. Editorial comments are provided free of charge! • “Learning” in the absence of context is memorization. • True learning requires context – a bigger picture. – When we will ever use this? • So, how do you make participation in BEST a true learning experience? – Use BEST as a context – Place BEST into context
- 10. Design is about creating – form and function achieving objectives within given constraints.
- 15. Define the problem in detail without implying a particular solution. Problem Definition • Clarify design objectives Establish requirements Establish functions Identify constraints • Identify constraints • actions the design must perform restrictions or limitations on a • non‐negotiable objectives desired attributes and behavior • Establish functions • behavior, a value, or some other • expressed as “doing” statements and/or functions • aspect of performance expressed as “being” statements • Establish requirements • typically involve output based on • (not “doing”) stated as clearly defined limits input • often the result of guidelines and standards
- 16. Objectives, constraints, functions and requirements may be broad‐based. • Some items are absolute – others may be negotiable – Functionality (inputs, outputs, operating modes) – Performance (speed, resolution) – Cost – Ease of use – Reliability, durability, security – Physical (size, weight, temperature) – Power (voltage levels, battery life) – Conformance to applicable standards – Compatibility with existing product(s)
- 17. Both functional and non‐functional requirements may be placed on a design. • Functional requirements: – support a given load – respond to voice commands – (output based on input) • Non-functional requirements (usually form-focused): – size, weight, color, etc. – power consumption – reliability – durability – etc.
- 18. Design involves creativity within boundaries. Consider any viable solution concept. Conceptual Design • Establish design • Generate design Establish design alternatives specifications specifications • Generate design alternatives • precise descriptions of properties • must live within the design space • numerical values corresponding • let the creativity flow to performance parameters and • attributes don’t marry the first idea • beware of “you/we can’t…” and “you/we have to…”
- 19. Nail down enough design details that a decision can be made. Preliminary Design • “Flesh out” leading conceptual designs • “Flesh out” leading conceptual designs • Model, analyze, test, and evaluate • Model conceptual Model, analyze, test Model, analyze designs • determine the optimal design proof‐of‐concept cardboard or scale models qualitative and/or quantitative • simulation results computer models (CAD, FEM) • mathematical models
- 21. Time to go from idea to reality. Detailed Design • Refine and optimize choices made in preliminary design • Articulate specific parts and dimensions • Fabricate prototype and move toward production
- 24. The design process begins with some initial problem statement. • Initial Problem Statement – Design a “safe” ladder. • Design problems are often ill-structured and openended. • Asking questions is a great way to begin defining the problem to be addressed.
- 25. Learning to ask good questions is a valuable tool for a successful designer. Problem Definition • Clarifying objectives – How is the ladder to be used? – How much should it cost? • Identifying constraints – How is safety defined? – What is the most the client is willing to spend? • Establishing functions – Can the ladder lean against a supporting surface? – Must the ladder support someone carrying something? • Establishing requirements – Should the ladder be portable? – How much can it cost?
- 26. It’s best to ask as many questions as possible at the beginning of the process! Conceptual Design • Establishing design specifications – How much weight should a safe ladder support? – What is the “allowable load” on a step? – How high should someone on the ladder be able to reach? • Generating design alternatives – Could the ladder be a stepladder or an extension ladder? – Could the ladder be made of wood, aluminum, or fiberglass?
- 27. More specific questions are needed as you move through the stages of the design process. Preliminary Design • Planning for modeling and analyzing – What is the maximum stress in a step support the “design load?” – How does the bending deflection of a loaded step vary with the material of which the step is made? • Planning for testing and evaluating – Can someone on the ladder reach the specified height? – Does the ladder meet OSHA’s safety specifications?
- 28. Questions also help in the iterative nature of the design process. Detailed Design • Refining and optimizing the design – Is there a more economic design? – Is there a more efficient design (e.g. less material)?
- 30. Remember, ill‐structured and open‐ended. • Initial Problem “Statement” – “How would you feel about a four-year engineering program?” – “Great! Go figure out what it looks like.”
- 31. Knowing who to ask is sometimes more important than knowing what to ask. Problem Definition • Clarifying objectives – Who is the target audience? – What personnel resources are available? • Identifying constraints – What budget will be available? – How many sections are permitted? – What academic infrastructure exists? – Where does this live relative to the SDE? • Establishing functions – What should graduates be prepared for? – Will the program encompass only electives or will it include core courses? • Establishing requirements – What are appropriate pre-requisites, if any? – Can students skip electives?
- 32. Conceptual Design • Establishing design specifications – Can/should the engineering electives have a weighted GPA? – Is a minimum GPA required to stay in the program? • Generating design alternatives – Could the program be curricular? Extracurricular? Both? – Are we required to use an existing curriculum? – Will dedicated computer resources be available?
- 33. Preliminary Design • Planning for modeling and analyzing – What high school engineering curricula are already available? – What schools are implementing the various models? – Is data available from these schools? – Are site visits a possibility? • Planning for testing and evaluating – How do we know if the program is successful during start-up? – How do we measure success relative to our stated objective(s)?
- 34. Detailed Design • Refining and optimizing the design – From the teachers’ perspectives, what is definitely working and what isn’t? – From the students’ perspectives, what is definitely working and what isn’t? – What needs modifying before we know? – What software/hardware is considered state-ofthe-art? – What feedback are we getting from graduates once they enter college?
- 36. Some simple tools can help organize the design process. Problem Definition Conceptual Design Preliminary Design • Attributes List • Pairwise Comparison Chart •Objectives/Constraints Tree •Design Specifications • Function‐Means Tree • 6‐3‐5 Method • Gallery Method
- 37. An Attributes List contains a list of objectives, constraints, functions, and requirements. • Problem Definition Partial attributes list for “safe ladder” design – Used outdoors on level ground – Used indoors on floors or other smooth surfaces – Could be a stepladder or short extension ladder – Step deflections should be less than 0.05 inches – Should allow a person of medium height to reach/work at levels up to 11 feet – Must support weight of an average worker – Must be safe – Must meet OSHA requirements – Must be portable between job sites – Should be relatively inexpensive – Must not conduct electricity – Should be light
- 38. A Pairwise Comparison Chart allows the designer to order/rank the objectives • “0” if column objective > row objective • “1” if row objective > column objective • Higher score = more important Problem Definition Pairwise comparison chart (PCC) for a ladder design Goals Cost Portability Usefulness Durability Score Cost •••• 0 0 1 1 Portability 1 •••• 1 1 3 Usefulness 1 0 •••• 1 2 Durability 0 0 0 •••• 0
- 40. Sample Design Specifications for the Ladder project. Conceptual Design • • • • • • Extended length of 8 feet Unextended length of 5 feet Support 350 pounds with a deflection of < 0.1 inches Total weight not to exceed 20 pounds Outside width of 20 inches Inside width of at least 16 inches
- 42. The 6‐3‐5 Method is one way to begin generating design alternatives. Preliminary Design • 6 team members • 3 ideas each (described in words or pictures) • 5 other team members review each design idea • No discussions allowed during the process • Can be modified to N–3–(N-1)
- 43. The Gallery Method can be used in small or large groups to develop design alternatives. Preliminary Design • Each individual sketches a design idea • All sketches are posted • Every member can comment on any idea
- 48. Bonus Slides
- 49. Questions for BEST Robot • The scoring strategy tends to drive the design – What type of steering is desired? – How many degrees-of-freedom does the robot need? – What maximum reach must the robot have? – How fast does the robot need to be? – How much weight must the robot lift? – What physical obstacles must the robot overcome?
- 50. A Pairwise Comparison Chart for a BEST Robot • • • “0” if column objective > row objective “1” if row objective > column objective Higher score = more important Goals Speed Drive Power Lift Power Degrees‐of‐ freedom Simple Controls Score Speed •••• 1 1 1 1 4 Drive Power 0 •••• 1 0 0 1 Lift Power 0 0 •••• 1 0 1 Degrees‐of‐ freedom 0 1 0 •••• 0 1 Simple Controls 0 1 1 1 •••• 3
- 51. A partial Attributes List for a 2008 BEST robot • • • • • • • • • Must be less than 24 pounds Must fit into a 24-inch cube Able to pick up individual plane parts Able to assemble plane parts Able to drive over a 1” x 4” board Able to close and open switch Should have zero-radius turn Should be able to carry a fully-assembled plane Should be able to lift a fully-assembled plane to a height of at least 36 inches
- 52. Sample Goals/Constraints for a 2008 BEST robot • Goals – Assemble parts on the warehouse racks – Grabber rotation of at least 90 degrees – Single grabber to grab/hold each individual part and the assembled plane – Reach the part on the top, back rack position • Constraints – Must fit in a 24-inch cube – Must weigh less than 24 pounds – Fixed height between warehouse racks