1. 1 ME886.3 Topic 1: System and System Design (II)

2. Science-based design: making a better system

3. Introduction: System and Design  A system is a set of elements that are connected  An element may further be decomposed into smaller elements; in this case, the element may be called subsystem  Design is a decision-making process starting from requirements to system structures

4. Introduction: System and Design  Requirement consists of functional requirement (FR) and constraint requirement (CR). FR: A function or functions a device or system has to achieve or a role or roles a device or system has to play. CR: A condition or situation where a device or system achieves a required function.

5. CR has two types:  A condition must be met; for instance, the pedal of a bike must be in black color  A condition has a range; for instance, the cost of a system under design must be less than X dollars Introduction: System and Design

6. Design parameter (DP): Description of the structural element to meet both the functional and constraint requirements Introduction: System and Design

7. Science-based Design 1.General design phase theory 2.Design theory and methodology 3.Design modeling and optimization Towards a Better System

8. 2. General design phase Conceptual design Embodiment design Detailed design

9. Conceptual design Develop a technical specification. Technical specification: a document of customer’s requirement in the technical term. Example Customer’ s requirement: Need a drill to penetrate common steel Technical specification: Be able to penetrate into the material with HRC>30 This is also called DP

10. Conceptual design Develop solution principle What is solution principle: solution versus solution principle Example Requirement: Rotation to translation Solution principle: - Crank-slider - Rack-and-pinion Remark: for machine design, it refers to kinematic design (principal dimension is given but not material and volume) Solution principle is DP

11. Making a statement of what without including the means to achieve it Realize the rotation to translation through a linkage Means The means restrict the possibility of having the means of rack and pinion

12. Embodiment Design Requirement: FR: To materialize a crank-slider kinematic linkage for load of 50 KN CR: To make device as light as possible Embodiment crank- slider linkage: Layout is DP

13. Detailed Design Develop a complete specification for each individual component ready for manufacturing Requirement: FR: To specify geometrical details ready for manufacturing CR: To be easy for manufacturing and assembly Detailed piston component ready for manufacturing Details for manufacturing are DP

14. Science-based Design 1.General design phase 2.Design theory and methodology 3.Design modeling and optimization Towards a Better System

15. 3. Design theory and methodology General Axiom 1: Making what to do and how to do separately. In particular while describing what it is, not be affected by how to realize it Example (Rotation to translation) Requirement statement: When a rotary motor turns, it connects with a rod which further transfers motion to a slider to realize a translation ……. Requirement statement: When a rotary motor turns, it connects with a rod which further transfers motion to a slider to realize a translation ……. The above statement has violated Design Axiom 1

16. 16 Problem -0 Problem -1.1 Problem -1.2 Problem -2.1 Problem -2.2 Complexity Simplicity 3. Design theory and methodology General Axiom 2: Divide and conquer

17. 17 Hold hot water Requirement: hold hot (~100 o C) water with hand Grasp water Hold normal water Resist heat exchange General Axiom 2: Divide and conquer

18. 18 Grasp water Hold normal water Resist heat exchange Ceramic material

19. 3. Design theory and methodology General Axiom 3: Generalization of design Current design problem Generic design problem Other design problems along with their solutions A solution to the current design problem Remark: The above process is in fact an analogy process to lead to innovation

20. Science-based Design 1.General design process 2.Design theory and methodology 3.Design modeling and optimization Towards a Better System

21. 4. Design modeling and optimization 1.Mathematical model for design objects at a different level (conceptual object, embodiment object, detailed object) 2.Variables defined for structural features, and mathematical relations defined for the whole structure along with its behavior 3.Varying of the variables to seek the best behavior

22. 5. Designer’s cognitive process 1.Team-based brain storm and white-box communication 2.Diversification in team composition and in task management 3.Confidence 4.Removal of unnecessary constraints

23. 6. Summary  Design is a marriage of human designers and science-based processes,  Science-based processes are: general design process, design theory and methodology, and modeling and optimization,  Design theory and methodology has three general axioms.  Designer’s cognitive process includes four guidelines,