Trans RINA, Vol 156, Part C1, Intl J Marine Design, Jan -Dec2014
of spaces in complex vessels represents unique blend of experience, judgment and tradition. In addition, the decision knowledge required to identify and justify the relationships, i.e., interactions, between objects in the design is often tacit, qualitative and not explicitly available. For example, factors such as habitability, operability and convenience are difficult to describe quantitatively; but, without specific consideration, can result in difficulties for the ship and crew’s overall functioning. Given a collection of objects in a design, there are two primary categories of rationales describing configuration: interactions and compromises. Interaction rationales
describe the spatial proximities between
objects in the design and the reasons, i.e., rationale, justifying such relationships. Compromise or trade-off rationale
describes the preferred priority competing or conflicting interactions [55].
Identification of interaction rationale is important in ship design because it motivates proper analysis (in design) and forms the basis of compromise or trade-off decisions. Without knowledge of the interactions in the design, it is difficult to understand the consequences of compromises.
Rationales can also provide an increase in the relative quality of knowledge in the ship design process. The “Knowledge- Cost-Freedom” curve shown in Figure 15 illustrates the benefits of increased knowledge during the early stages of design. As knowledge becomes obtainable earlier in the design process, design freedom increases, committed costs can be postponed to a later point in the design cycle and overall design time can be reduced. This is especially important during periods of reduced capital reinvestment in complex ships.
between
present in the rationale database. Subsequently, it uses these gaps to instruct the design generation module to produce designs likely to trigger naval architects into expressing targeted rationale. At the same time, user expressed rationale is also incorporated into designs. Through two independent test cases, the RCT proved to be an effective and usable tool for the capture of configuration rationale. van Oers and Hopman [56] developed a simpler and faster version of a novel type of parametric ship description, based
on mathematical
packing problems. Where the description is still able to apply large and concurrent changes to the entire ship description, i.e., the shape and size of envelope, subdivision and -crucially- the configuration of systems inside and on the envelope. descriptions
took considerable computational
Existing packing-based effort,
however, which limits their suitability for a range applications, hence the need to reduce the computational effort by describing the ship in ‘2.5D’. This describes the ship configuration in three transverse ‘slices’. Main benefit is that this reduced the number of transverse positions to
consider, which helps to lower the
computational effort by a factor of three to seven. Figure 16 shows three example designs from various studies performed with the packing-approach.
Figure 16: Three examples of feasible ship designs generated by the 2.5D and 3D packing approach: a frigate (left), a mine-counter-measures vessel (top), and a deepwater drillship (right) [56].
An interactive design exploration approach geared
Figure 15: Distribution of cost, knowledge and design freedom during the early stages of design. [55]
de Nucci and Hopman [55] described a methodology for capturing configuration rationale in complex ship design. The approach uses Reactive Knowledge Capturing to “trigger” the expression of design rationale. Once expressed the rationale is (re)structured in an argument based semi-formal
ontology. This
captures dependency structures relationships
arrangement also between objects and in the design. A dedicated feedback
mechanism for expanding the knowledge (rationale) base is presented. This methodology first identifies gaps
C-16
towards early stage ship design was proposed in the work of Duchateau et al. [57], which allows the naval architect to perform requirements elucidation better. The proposed approach gives the naval architect the means to explore and assess a broad range of design options, which are integrated into coherent design solutions, thus covering a large area of the design space. Interactive visualization methods, together with
pareto-front
techniques were developed to give the naval architect the means to identify emerging
relationships process through
requirements and the design solutions. This insight is then used by the naval architect to steer and control the design exploration
a feedback
mechanism within the approach (Figure 17). This empowers the naval architect to not only identify, but also act upon the emerging
relationships between
requirements and the design, which can then either be avoided within the interactive approach or communicated
visualization between
©2014: The Royal Institution of Naval Architects
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