Compatiability Analysis and Case Studies of Axiomatic Design and TRIZ.docx

1、Compatiability Analysis and Case Studies of Axiomatic Design and TRIZCompatiability Analysis and Case Studies of Axiomatic Design and TRIZThis is part 2 of a 2-part article. Part 1 appeared in August, 2000. A Comparison of TRIZ and Axiomatic Design.Kai Yang and Hongwei Zhangkyangmie.eng.wayne.eduDep

2、artment of Industrial and Manufacturing EngineeringWayne State UniversityDetroit, MI 48202, USAABSTRACTThis is our second research paper in comparisons of TRIZ and Axiomatic Design. In this paper, design problem solving approaches of Axiomatic Design and TRIZ are analyzed and compared in detail, and

3、 several case studies are discussed to support our point of view about these two methodologies.INTRODUCTIONThe first research paper in comparisons of TRIZ and Axiomatic Design, these two methodologies are reviewed and briefly compared. The conclusion is that some design rules in AD and problem-solvi

4、ng tools in TRIZ are related and share the same ideas in essence. The objectives of this paper is to compare and contrast TRIZ and Axiomatic Design problem solving methods in detail, and to discuss the possibility of integration of them. The long-term goal of this work is to develop a generic framew

5、ork and tools to help designers make and understand correct design decisions.The body of this paper is divided into five parts. The first part discusses the domain mapping theory in AD and contradiction transformation idea in TRIZ. The second and third parts analyze two axioms and their possible cor

6、responding techniques in TRIZ. The fourth part presents complementarity of these two methodologies using a case study, and the last part discusses the advantages and limitations of TRIZ and Axiomatic design.DOMAIN MAPPING IN AD AND CONTRADICTION TRANSFORMATION IN TRIZAD states that design is the cre

7、ation of synthesized solutions in the form of products, processes, or systems that satisfy perceived needs through the mapping between the FRs in functional domain and the DPs in physical domain, through the proper selection of DPs that satisfy FRs. To conduct design, one must determine the design o

8、bjective by defining it in terms of functional requirements. Then to satisfy these functional requirements, a physical embodiment characterized in terms of design parameters must be created. The design process involves relating these FRs of the functional domain to the DPs of the physical domain.TRI

9、Z, on the other hand, states that some design problem may be modeled as a technical contradiction, which is the functional conflict or coupling. A problem requires creativity when attempts to improve some functional attributes lead to deterioration of other functional attributes. A design problem as

10、sociated with a pair of functional contradiction can be resolved either by finding a trade-off between the contradictions, or by overcoming it. TRIZ does not accept trade-offs, and it stresses that an ideal design solution is to overcome the conflict.Extensive studies in invention problem solving de

11、monstrate that a functional contradiction is derived from a physical one. In order to overcome a functional conflict, one has to identify a physical element of the system that controls the competing attributes, and this element must be modified in such a way that it would meet the opposite requireme

12、nts to its state. Transforming a functional contradiction in system level into a physical contradiction in component level is always required in TRIZ. Figure 1 illustrates this idea.The following Ampoules Sealing case study demonstrates that TRIZ and AD theory offer the compatible ideas in problem s

13、olving.Ampoules Sealing Case StudyIn a manufacturing process a burner is used to seal ampoules containing drugs. The problem is that the flame may overheat the drug in ampoules and degrade the drugs. What should we do in this situation?Let us use AD theory and TRIZ to analyze the manufacturing proce

14、ss and then compare their similarity and differences. From AD standpoint, the functional requirements in the functional domain of this manufacturing process may be expressed as two independent requirements that satisfy the Axiom 1.FR1 = seal ampoulesFR2 = protect drugs from deterioration during the

15、processThe original design selects only one design parameter in its physical domain, which is:DP1 = heat by a burner.There are two FRs but only one DP in the design solution. The number of DPs is less than the number of FRs. Based on the Theorem 1, the design is either a coupled design result, or th

16、e FRs cannot be satisfied. It is clearly that this is a coupled design because DP1 affects both FR1 and FR2. The design equation is:In order to satisfy two FRs independently, the process design should be decoupled. Theorem 2 states: when a design is coupled due to the greater number of FRs than DPs

17、(i.e, mn), it may be decoupled by addition of new DPs so as to make the number of FRs and DPs equal to each other. If a subset of the design matrix containing nn elements, one can constitute a triangular design matrix to decouple the previous design.So, the coupled design represented by above equati

18、on can be modified into a decoupled design by adding a DP and changing the design matrix into a triangular one as follows:If the burner represents DP1, what is DP2? It is obvious that DP2 should counteract the effect of the heat produced by the burner. In practice, water is an ideal component to off

19、set the heat. So, the one possible design solution is given in figure 2.From TRIZ standpoint, this design problem situation can be easily modeled as the technical contradiction (functional conflict) in the system level: we want to heat ampoule top (attribute 揂) to seal ampoules but it causes degrada

20、tion to medicine (attribute 揃).TRIZ contradiction analysis states that at the heart of a technical contradiction is hidden a physical one. In order to overcome the technical contradiction, a physical component should be modified in such a way that it would meet the opposite requirements. In this amp

21、oule sealing case, the heat improves 揂 (seal), but degrades 揃(medicine in the ampoule). So, the ampoules should be hot to improve seal, and it should be cold to not damage the medicine. Clearly the ampoule is the physical component that controls the technical contradiction.TRIZ Knowledge Base tools

22、provide several separation principles to overcome physical contradictions. Three most frequently used principles are separation of opposite properties in space, separation of opposite properties in time and separation of opposite properties between whole system and its components.Careful examination

23、 of three separation principles, it is not difficulty to recognize that separation in space should be used in this situation. In order to make the top of an ampoule hot and other part cold, it is proposed to surround the ampoules with a water jacket. The water takes excess heat away from ampoules to

24、 prevent overheating the drag (see figure 2).INDEPENDENCE AXIOM IN AD AND SEPARATION PRINCIPLES IN TRIZIndependence Axiom in AD implies that the design matrix be of a special form. The consequences of applying Axiom 1 to the design matrix are as follows:It is desirable to have a square matrix, i.e.,

25、 n=mThe matrix should be either diagonal or triangular.In real design situation, we need to search for DPs that yield a diagonal or triangular design matrix. The degree of independence can be treated as the definition of tolerance.There are a hierarchy in both the functional domain and the physical

26、domain, and a zigzagging process between two domains in design process. The domain process is most straightforward when the solution consists of uncoupled design at each level. When the design is uncoupled, we can deal with the individual FRs of a hierarchical level without considering other FRs of

27、the same level and proceeding hierarchical levels. When the design is coupled, we must consider the effect of a decision on other FRs and DPs. Figure 3 shows the design matrices and structure models. Therefore, the designer should try to find solutions by attempting to uncouple or decoupled design i

28、n every level of design hierarchy.The problem is how to decouple a coupled design. It is obvious to modify design matrix to be either diagonal or triangular. In practice, many coupled designs undergo changes and become a decoupled design through a trial and error process that is in opposition to TRI

29、Z methodology.In TRIZ methodology, a coupled design is defined as the existence of a contradiction. Removal of dependency of coupling means to overcome a technical or physical contradiction by applying inventive principles or separation principles. Thus, these principles can serve, with AD corollari

30、es and theorems, as the guidelines of de-coupling a coupled design.The design process of the Paper Handling Mechanism 11 illustrates how separation principles in TRIZ aid to satisfy Axiom 1 in AD.Paper Handling Mechanism Case StudyThe function of the paper handling mechanism used in an automatic tel

31、ler machine is 搃solate one bill from piled bills, which is the first FR of the system. Several physical structures can be used to realize this functional requirement, such as friction, vacuum and leafing etc. Friction method is selected and its mechanism is showed in figure 4.However, this DP does n

32、ot always work correctly because the friction is changeable under some circumstances. If the friction force working on the tope of bill becomes too large by some accident, two or more bills will be sent forwards, and if it becomes too small the top bill may not be isolated. So, we have to decompose the first level functional requirement into two functional requirements: 揼ive a forward force to the first bill and 揼ive a backward force to the second bill. To satisfy these two requirements, the new DP of this design is a pair of rollers rotating in the sa