1weaver innovation tool: axiomatic design (a brief introduction) jonathan weaver udm me department
TRANSCRIPT
1Weaver
Innovation Tool: Axiomatic Design (A Brief Introduction)
Jonathan WeaverUDM ME Department
2Weaver
References
• Nam P. Suh, The Principles of Design, Oxford Series on Advanced Manufacturing, 1990.
• K. Yang & B. El-Haik, Design for Six Sigma: A Roadmap for Product Development, McGraw Hill, 2003.
• Deo & Suh, Axiomatic Design of Customizable Automotive Suspension, Proceedings of ICAD2004, ICAD-2004-38.
• Lui & Soderborg, Improving an Existing Design Based on Axiomatic Design Principles, Proceedings of ICAD2000, ICAD-055.
3Weaver
Axiomatic Design
• Most principally based on the work of Nam Suh at MIT• The ultimate goal of Axiomatic Design is to establish a science base
for design and to improve design activities by providing the designer with a theoretical foundation based on logical and rational thought processes and tools.
• Other goals:– To make human designers more creative– Reduce the random search process– Minimize the iterative trial-and-error process– Determine the best designs among those proposed– Endow the computer with creative power through the creation of
the science base for the design field
4Weaver
Axiomatic Design (Cont.)
• Complete coverage of Axiomatic design is a very long endeavor; here we’ll just introduce it
• Axioms are general principles or self-evident truths that cannot be derived or proven to be true except that there are no counter-examples or exceptions.
• Two axioms were identified by examining the common elements that are always present in good designs, be it a product, process, or systems design. They were also identified by examining actions taken during the design stage that resulted in dramatic improvements.
5Weaver
Axiomatic Design (Cont.)
• The two Axioms:
– Independence Axiom: The independence of Functional Requirements (FRs) must be always maintained, where FRs are defined as the minimum number of independent functional requirements that characterize the design goals.
– Information Axiom: Among those designs that satisfy the Independence Axiom, the design that has the smallest information content is the best design.
6Weaver
Axiomatic Design (Cont.)
• Violating Axiom 1 results in a coupled design
• Violating Axiom 2 results in system complexity
7Weaver
Axiomatic Design (Cont.)
• The Independence Axiom is often misunderstood. Many people confuse between the functional independence with the physical independence.
• The Independence Axiom requires that the functions of the design be independent from each other, not the physical parts.
• The second axiom would suggest that physical integration is desirable to reduce the information content, if the functional independence can be maintained.
• Both axioms can be illustrated using a faucet as an example.
8Weaver
Axiomatic Design (Cont.)
• Let’s discuss the ‘classic’ faucet design problem from the perspective of axiomatic design
– What are the two principle functional requirements?
– What are the two principle design parameters?
– Is it axiomatic?
9Weaver
Axiomatic Design (Cont.)
• How about now?
10Weaver
Axiomatic Design (Cont.)
• Matrices can be an effective way to understand the mapping between functional parameters and design parameters
• For the faucet design examples:
11Weaver
Axiomatic Design (Cont.)
• In the ideal case of total independence, the matrix mapping functional requirements to design parameters is square and diagonal, the design is called uncoupled and each design parameter can be manipulated to meet a particular functional requirement without affecting the other parameters or functions
Design Parameters
DP1 DP2 DP3 DP4
Functions
FR1 X
FR2 X
FR3 X
FR4 X
12Weaver
Axiomatic Design (Cont.)
• In the decoupled case, the matrix is upper/lower triangular. The design may be treated as uncoupled if the design parameters are fixed in the order dictated by the matrix
Design Parameters
DP1 DP2 DP3 DP4
Functions
FR1 X
FR2 X X
FR3 X X X
FR4 X X X X
13Weaver
Axiomatic Design (Cont.)
• In the coupled case (highly undesirable), the matrix is populated above and below the main diagonal (possibly completely populated). There is an innovation opportunity with such designs if they can be decoupled!
Design Parameters
DP1 DP2 DP3 DP4
Functions
FR1 X X X X
FR2 X X X X
FR3 X X X X
FR4 X X X X
14Weaver
Axiomatic Design (Cont.)
• Consult Nam Suh’s work for details on the conceptualization process of mapping functional requirements to physical solutions, and ultimately to processes.
15Weaver
Automotive Suspension Example (based on Deo & Suh’s paper)
• Problem: comfort/handling tradeoffs involving damping and stiffness of suspension
• Active suspensions have drawbacks: power, size weight, cost
• This paper looks at adaptive systems wherein some design parameters are changed in response to some information
• A novel adaptive suspension architecture is proposed which allows independent control of stiffness, damping and ride height
16Weaver
Prior Art on Variable Stiffness and Ride Height
• A typical solution is an air spring, but as shown below, this design is coupled (the number of FR’s exceeds the number of DP’s)
DP 1: Amount of Air
FR1: Control Ride Height X
FR 2: Control Stiffness X
17Weaver
Proposed Architecture
From Deo & Suh
18Weaver
Mapping of Functional Requirements to Design Parameters
DP 1: Pivot Position
DP 2: Cam Position
DP 3: Orifice Control
FR 1: Stiffness X
FR 2: Ride Height X X
FR 3: Damping X
As discussed in the paper, a feedback control system can eliminate the coupling.
Consult the paper for more details.
19Weaver
Automotive NVH Example
• Liu and Soderborg investigate the effect of a number of design parameters on NVH characteristics
• The effect of those parameters on NVH as a percent of the total response is measured and tabularized on the next page
20Weaver
From Liu & Soderborg
Note that it is highly coupled and the best order to attach the problem is not obvious – until it is re-ordered as shown on the next page.
21Weaver
From Liu & Soderborg
Now the best order – and the necessary tradeoffs along the way – are clear!