ENGR 107: Engineering Fundamentals

1. ENGR 107: Engineering Fundamentals Lecture 7: The Engineering Design Process: Making Design Decisions Using Tradeoff Analyses C. Schaefer September 29, 2003

2. Stuff • Review Project 1 • Yacht design handouts • Yacht diagram: • http://www.cnn.com/interactive/sailing/yacht.diagram/ • Lecture Egnineering Fundamentals 107

3. Project 2 Begins!! • For each Team, all functional groups shall provide cost ROM’s, Bills of Material, and a list of required tools to the Systems Engineering Group and to me by next Monday. • Systems Engineering group: preliminary schedule and budget due next Wednesday. • Design and Manufacturing Groups: begin conceptual and preliminary design of your respective systems. • Handout $$ and radios on Wednesday. Egnineering Fundamentals 107

4. Engineering Decisions • Engineering decision – selecting a specific solution to a design problem from a set of alternative solutions • Trade-off analysis – an analysis technique in which the performance of various design alternatives are evaluated by varying different design parameters within a design space defined by parameter boundaries or design constraints. • Payoff function – a mathematical model that relates system performance to various design parameters that the designer can control. Egnineering Fundamentals 107

5. Analyze Potential Solutions • Narrow the ideas generated during the brainstorming phase to several realistic alternatives. • Analytical techniques to narrow choice: • Estimation (“back of the envelope” calculations). • Common sense. • Economic analysis. • Engineering analysis. • Computer analysis. Egnineering Fundamentals 107

6. Using Models in the Decision Making Process Math models often implemented as computer models. • Mathematical models. • Computer models. • CAD (computer aided design) • Simulink • Scale models. • Wind tunnel models • Mockups • Diagrams or graphs. • Free body diagrams Egnineering Fundamentals 107

7. Model Features • Should represent the dynamics of the system being represented. • Good fidelity: simple to understand and manipulate but good enough to generate believable results. • Should address the most important design parameters. Ignore higher order terms. • Should be repeatable. • Should be of modest complexity: complexity often a function of time and budget constraints on design process. • Easily modified. Egnineering Fundamentals 107

8. Mathematical Models • Uncovers relations between the various aspects of the problem that may not be apparent in verbal descriptions. • Enables comparisons of many possible solutions. • Illustrates cause-and-effect relationships. • Defines the type of data required to solve the problem. • Can be used for prediction and forecasting. • Aids in identifying areas of risk and uncertainty. Egnineering Fundamentals 107

9. Mathematical Model Example:Yacht Rating Measurement Formula Egnineering Fundamentals 107

10. Payoff Function:Length = f (Sail Area, Displacement) Egnineering Fundamentals 107

11. Excel Spreadsheet Solution Egnineering Fundamentals 107

12. Parametric Analysis Egnineering Fundamentals 107

13. Parametric Analysis Egnineering Fundamentals 107

14. Parametric Analysis Egnineering Fundamentals 107

15. Payoff Function:Sail Area = f (Length, Displacement) Egnineering Fundamentals 107

16. Excel Spreadsheet Solution Egnineering Fundamentals 107

17. Parametric Analysis Egnineering Fundamentals 107

18. Payoff Function:Displacement = f (Sail Area, Length) Egnineering Fundamentals 107

19. Excel Spreadsheet Solution Egnineering Fundamentals 107

20. Parametric Analysis Egnineering Fundamentals 107

21. How Important are the Criteria in the Decision Process? Egnineering Fundamentals 107