Axiomatic Design Theory

1. Axiomatic Design Theory • Axiom • known to be true by understanding its meaning without proof. • a starting point for deducing and inferring other (theory dependent) truths. Axiomatic design theory: it is a design theory that has been verified by numerous applications. In other words, it is true (starting point) and accepted by engineers without proof.

2. Axiomatic Design Theory • Axiom 1: Independence Axiom • Axiom 2: Information Content

3. Axiomatic Design Theory(Axiom 1)

4. Axiom 1 – Design example X Requirement: hold hot (~100oC) water with hand X Hold hot water Grasp X with hand X Hold water without consideration of temperature X Resist heat over 100 o

5. material DP DP DP Resist heat over 100 Grasp X X Hold water with room temperature

6. The better design meets: • Design or function requirement (FR) should be independent or uncoupled on their own right • Design parameters (DP) should maintain the FR independent – i.e., not making FR coupled Axiom 1

8. Uncoupled (Diagonal matrix) To satisfy the independence axiom, the design matrix must be either diagonal or triangular Coupled (Full matrix) Decoupled (Triangular matrix)

9. Example – Axiom 1 Hinge FR1=Provide access to items stored in the refrigerator FR2=Minimize energy loss

10. S1’=Horizontally hung door Hinge FR1=Provide access to items stored in the refrigerator FR2=Minimize energy loss S1=Vertically hung door S2=Thermal insulation material in the door

11. Hinge Decoupled Uncoupled The cold air stays inside when the door is opened

12. 12 FRs: Contain axial pressure, Withstand a moderate impact when the can is dropped, Provide easy access to liquid, etc. Physical pieces: Just 3 (the body, the lid, the opener tab) DPs: 12 The thickness of the can body The curvature at the bottom of the can etc. Axiom 1 is focusing upon Functional independence but not physical independence

13. Physical integration FR and DP in ADT refer to the logical level FR1/DP1 One FR2/DP2 Notion: logical and physical

14. Solution principle 1 for opening type 1 of lid • At the conceptual design phase • Solution principle 2 for opening type 2 of lid • At the conceptual design phase • The geometry of each of them refers to the embodiment design phase • Their relationship (distance, material interface) refers to the embodiment design phase

15. Decoupled Design

16. Decoupled Design Step 1: Change DP1 to affect FR1 and FR2 Step 2: Change DP2 to affect FR2 Step 1 has also affected FR2 but in Step 2, this effect is changed back and to further affected by DP2 only

17. The better design meets: • Design or function requirement (FR) should be strongly independent or uncoupled on their own right • Design parameters (DP) should maintain the FR independent (strongly or weakly) – weakly independent means decoupled. Axiom 1 revision Remark: In the recent development, decoupled situation of FR will also be considered in Axiom 1, i.e., acceptable as a better design.

18. Redundant design

19. Redundant design

20. FR DP Design requirement Concept design Embodiment design Detail design

21. Summary • Axiom 1 of ADT concerns coupling, decoupling, and uncoupling among functional requirements both in direct and indirect (through DP) manners. • Axiom 1 suggests the better design to be uncoupled or decoupled. • Logical design versus physical design. • Physical design refers to embodiment design. • Axiom 1 of ADT is only applicable to the concept design.

22. Summary • Redundant design concept: more DP than FR. • It is a relative concept about coupling, decoupling and uncoupling.