A Complexity Metric for Practical Ship Design 1 JeanDavid Caprace ANAST – University of Liège...

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Transcript of A Complexity Metric for Practical Ship Design 1 JeanDavid Caprace ANAST – University of Liège...
A Complexity Metric forPractical Ship Design
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JeanDavid Caprace
ANAST – University of Liège – Belgium
PRADS – September 2010
• Boundaries – What, How and Why?• Background• How to measure the ship complexity• Presentation of the test case on a passenger ship• Conclusion
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OutlineOf this presentation
• Ship designer problem selection of the best design alternative
• Evaluation of the design alternative many attributes (economic, technical, environmental, safety)
• Every design change impact on how much producing/maintaining the ship will cost
• Understand the impact every time the designer make a change
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BoundariesWhat? – Selection of the best design alternative
• Complex design– Are more fragile– Leads to more surprises (always bad)– Leads to longer development schedule– Causes costly late design modification– Fosters suboptimal tradeoffs between
competing goals– Makes followup of design more difficult
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BoundariesWhat? – Selection of the best design alternative
How well you handle your
design comes down to how
well you handle complexity!
• To give a quantitative and objective metric for the designer – Design evaluation tool
• To find an alternative to the cost evaluation during the design– Expected to be faster– Easier to implement– “Real time”
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BoundariesHow? – Reduction of the product complexity
• Design for X Optimize total benefits– Design for production– Design for assembly– Design to cost– Design for safety– Design for environment– Design for maintenance– Design for simplicity
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BoundariesWhy? – To optimize the life cycle of the product
Design for life cycle
• Very hard to find a formal definition of complex systemcomplex system
• Complexity often implies– Many parts with a lot of redundancy– Many relationships/interactions among the
parts– Combination effects that are not easily
predicted– A form of a hierarchy
• If complexity increase LCCost increase
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BackgroundWhat is a complex system?
• Engineers are using everyday the word “complexity”• Sometimes it is easy to feel the complexity …
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Complexity evaluationWhat is a complex system?
• Engineers are using everyday the word “complexity”• Sometimes not …
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Complexity evaluationWhat is a complex system?
• Complexity affects design, manufacturing, assembly operations, maintenance, dismantling, etc.
• Difficult to measure each factors involved in complexity assessment– Number of components– Number of connections– Number of assembly– Geometry and shape– Production processes– Density– Etc.
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Complexity evaluationA challenge
• Industry has already attempted to measure complexity– Using empirical measures– Problem proliferation of possible measures
• number of item, production sequence and assemblies, etc.
– So many metrics • how to select the most appropriate indicators ?• do you have the sufficient accuracy ?• how can you tell if the overall complexity is bring reduced if one
measure falls but another rises ?
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Complexity evaluationA challenge
• Complexity related to …– Number of parts/connections– Complexity of each parts
• Different complexities– Manufacturing complexity– Assembly complexity– Process complexity– Maintenance complexity– Etc.
• Study limited to steel structure
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Complexity evaluationTheoretical consideration
• Steel structure complexity– Shape complexity (Csh)
– Assembly complexity (Cas)
– Material complexity (Cmt)
Complexity evaluationDifferent factors
• Shape complexity (Csh)– Ability to perform the
manufacturing of individual parts of the product
– Based on sphericity of the product components –
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Complexity evaluationDifferent factors
Csh= 0
Csh= 0.194
Csh= 0.329
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Complexity evaluationDifferent factors
• Shape complexity (Csh)
Similar to the material density Reduce number of part and reduce the Csh of each part
• Assembly complexity (Cas)– Ability to easily assemble the
components of a product– Based on a recursive
formulation similar to the Shannon Entropy
– n nonisomorphic subtrees
Complexity evaluationDifferent factors
simple complex
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Complexity evaluationDifferent factors
• Assembly complexity (Cas)
Lifts and stairs high assembly complexity Use concepts of modularity and use standardization
• Material complexity (Cmt)– Ability to use different types
of material and scantling in a product Standardization
– Based on the number of different material and scantling used in the product
Complexity evaluationDifferent factors
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Complexity evaluationDifferent factors
• Material complexity (Cmt)
Material and scantling standardization is required
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Complexity evaluationDifferent factors
• Global complexity
– Weighted Sum– Minimization of the
correlation coefficient– Production time vs
Complexity– R² = 0.76
• It’is always possible to design something so complicated that you can never get it right!• This methodology provides:
– An aid for the designers compare different design alternatives– A monitoring of the sources of complexity which helps to determine the
consequences of decision making– A spotting of the sources of complexity and cost which helps to reduce design
effort– An objective, quantifiable, unambiguous metrics of complexity
• Results:– Reduction of lead time and life cycle cost
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Conclusion and recommendationsOf this presentation
• This research have been limited to:– Ship’s structure (i.e. mainly steel parts and not outfitting)– Complexity evaluation during production (i.e. not on maintenance
or dismantling)– Large passenger ships
• Additional researches are thus required– Outfitting components (HVAC, pipes, electrical cables, etc.)– Take into account of maintenance and dismantling stage– To test the methodology on other types of ships
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Future workOf this presentation