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Axiomatic Design Theory

What is axiom?– is 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.

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Axiomatic Design Theory

Axiom 1: Independence Axiom

Axiom 2: Information Content

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Axiomatic Design Theory(Axiom 1)

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Axiom 1 – Design example

Hold hot water

Requirement:

hold hot (~100oC) water with hand

Grasp the holder

Hold water without consideration of

temperature

Resist heat conduction

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Isolating material

Grasp the holder

Hold water without consideration of

temperature

Resist heat conduction

DPDP

DP

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Axiom 1

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

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2

1

220

011

2

1

DP

DP

A

A

FR

FR

8

2

1

2221

1211

2

1

DP

DP

AA

AA

FR

FR

2

1

2221

11

2

1

DP

DP

AA

A

FR

FR

2

1

22

11

2

1

DP

DP

A

A

FR

FRUncoupled

Coupled

Decoupled

To satisfy the independence axiom, the design matrix must be either diagonal or triangular

(Diagonal matrix)

(Full matrix)

(Triangular matrix)

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Example – Axiom 1

Hinge

FR1=Provide access to items stored in the refrigerator

FR2=Minimize energy loss

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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

S1’=Horizontally hung door

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2

1

2221

11

2

1

DP

DP

AA

A

FR

FR

Hinge

2

1

22

11

2

1

DP

DP

A

A

FR

FR

Decoupled Uncoupled

The cold air stays inside when the door is opened

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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 bodyThe curvature at the bottom of the can etc.

Axiom 1 is focusing upon Functional independence but not physical independence

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Physical integrationPhysical integration

Notion: logical and physical

OneFR1/DP1

FR2/DP2

FR and DP in ADT refer to the logical level

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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

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Decoupled DesignDecoupled Design

2

1

2221

1211

2

1

DP

DP

AA

AA

FR

FR

2

1

2221

11

2

1

DP

DP

AA

A

FR

FR

2221212

1111

DPADPAFR

DPAFR

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Decoupled DesignDecoupled Design

2221212

1111

DPADPAFR

DPAFR

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

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Axiom 1 revision

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

Remark: In the recent development, decoupled situation of FR will also be considered in Axiom 1, i.e., acceptable as a better design.

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3

2

1

232221

131211

2

1

DP

DP

DP

AAA

AAA

FR

FR

Redundant design

2

1

2221

1211

2

1

DP

DP

AA

AA

FR

FR

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Redundant designRedundant design

2222

3131111

DPAFR

DPADPAFR

3

2

1

232221

131211

2

1

DP

DP

DP

AAA

AAA

FR

FR

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SummarySummary

1. Axiom 1 of ADT concerns coupling, decoupling, and uncoupling among functional requirements both in direct and indirect (through DP) manners.

2. Axiom 1 suggests the better design to be uncoupled or decoupled.

3. Logical design versus physical design.

4. Physical design refers to embodiment design.

5. Axiom 1 of ADT is only applicable to the conceptual design.

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SummarySummary

6. Redundant design concept: more DP than FR.

7. It is a relative concept about coupling, decoupling and uncoupling.