The application of multi-objective robust design methods in ship design

When designing large complex vessels, the evaluation of a particular design can be both complicated and time consuming. Designers often resort to the use of concept design models enabling both a reduction in complexity and time for evaluation. Various optimisation methods are then typically used to explore the design space facilitating the selection of optimum or near optimum designs. It is now possible to incorporate considerations of seakeeping, stability and costs at the earliest stage in the ship design process. However, to ensure that reliable results are obtained, the models used are generally complex and computationally expensive. Methods have been developed which avoid the necessity to carry out an exhaustive search of the complete design space. One such method is described which is concerned with the application of the theory of Design Of Experiments (DOE) enabling the design space to be efficiently explored. The objective of the DOE stage is to produce response surfaces which can then be used by an optimisation module to search the design space. It is assumed that the concept exploration tool whilst being a simplification of the design problem, is still sufficiently complicated to enable reliable evaluations of a particular design concept. The response surface is used as a representation of the concept exploration tool, and by it's nature can be used to rapidly evaluate a design concept hence reducing concept exploration time. While the methodology has a wide applicability in ship design and production, it is illustrated by its application to the design of a catamaran with respect to seakeeping. The paper presents results exploring the design space for the catamaran. A concept is selected which is robust with respect to the Relative Bow Motion (RBM), the heave, pitch and roll at any particular waveheading. The design space is defined by six controllable design parameters; hull length, breadth to draught ratio, distance between demihull centres, coefficient of waterplane, longitudinal centre of floatation, longitudinal centre of buoyancy, and by one noise parameter, the waveheading. A Pareto-optimal set of solutions is obtained using RBM, heave, pitch and roll as criteria. The designer can then select from this set the design which most closely satisfies their requirements. Typical solutions are shown to yield average reductions of over 25% in the objective functions when compared to earlier results obtained using conventional optimisation methods

Multi-objective robust concept exploration within the made-to-order sector

Concept exploration is an activity of fundamental importance when designing large, complex made-to-order engineering products. At the concept design stage of the design process, it is essential that many design alternatives are evaluated. In the case of large made-to-order products, the evaluation of a particular design can be both complicated and time consuming. Under these circumstances, designers often resort to the use of concept design models enabling both a reduction in complexity and time for evaluation. Stochastic optimisation methods are then typically used to explore the design space facilitating the selection of optimum or near optimum designs. These optimisation methods can however increase the concept exploration time considerably due to their often random search manner. The objective of this work is therefore to produce a generic framework that would enable a designer to efficiently explore the design space within the MTO domain facilitating the selection of robust designs

On the frontal ablation of Alaska tidewater glaciers

Thesis (Ph.D.) University of Alaska Fairbanks, 2013Sea level rise is a major problem that society will face in the coming century. One of the largest unknown components of sea level rise is frontal ablation (the sum of mass loss through calving and subaqueous melting) from glaciers and ice sheets. Using estimates of ice thickness, rates of glacier length change, and glacier velocities, we present a record of frontal ablation over the period 1985-2012 for 20 Alaska tidewater glaciers. We also present a new method for estimating ice thickness by solving the continuity equation between adjacent flowlines. Because of the wealth of data available, we apply this method to Columbia Glacier, Alaska. The mean ice thickness and volume of Columbia Glacier were approximately halved over the period 1957-2007, from 281 m to 143 m, and from 294 km�_ to 134 km�_, respectively. Using bedrock slope and considering how waves of thickness change propagate through the glacier, we conclude that the rapid portion of this tidewater glacier's retreat is likely nearing an end. We present a 64 year record of length change for 50 Alaska tidewater glaciers, over the period 1948-2012. Most (31) glaciers retreated over the period. Examination of the onset of glacier retreats indicates a correlation between high summer sea surface temperature and the triggering of retreat. Finally, we present a 27 year record of surface velocity for 20 Alaska tidewater glaciers derived from Landsat imagery. Surface velocities vary by as much as 80% throughout the year, indicating that using measurements from one time of year may bias estimates of frontal ablation. The total mean rate of frontal ablation for these 20 glaciers over the period 1985-2012 is 16.2 � 6.5 Gt a����_. Extending this to the remaining 30 Alaska tidewater glaciers yields an estimate of frontal ablation of 18.3 � 7.3 Gt a����_, approximately 50% of the climatic mass balance of the region. This indicates the important, non-negligible role frontal ablation can play in regional mass balance, even where tidewater glaciers cover a small fraction of the total area.Chapter 1. Introduction -- Chapter 2. Using surface velocities to calculate ice thickness and bed topography: a case study at Columbia Glacier, Alaska -- Chapter 3. Alaska tidewater glacier terminus positions, 1948-2012 -- Chapter 4. Alaska tidewater glacier velocities and frontal ablation, 1985-2012 -- Chapter 5. Conclusions

A metric to represent the evolution of CAD/analysis models in collaborative design

Computer Aided Design (CAD) and Computer Aided Engineering (CAE) models are often used during product design. Various interactions between the different models must be managed for the designed system to be robust and in accordance with initially defined specifications. Research published to date has for example considered the link between digital mock-up and analysis models. However design/analysis integration must take into consideration the important number of models (digital mock-up and simulation) due to model evolution in time, as well as considering system engineering. To effectively manage modifications made to the system, the dependencies between the different models must be known and the nature of the modification must be characterised to estimate the impact of the modification throughout the dependent models. We propose a technique to describe the nature of a modification which may be used to determine the consequence within other models as well as a way to qualify the modified information. To achieve this, a metric is proposed that allows the qualification and evaluation of data or information, based on the maturity and validity of information and model

Workshop session: mapping success in collaborative engineering

Successful collaborative engineering practices have demonstrated significant benefits to industry: improving efficiency; eliminating rework due to information inconsistencies; managing complexity and automating parts of the collaborative design process. Despite these benefits, collaborative endeavours fail due to obstacles such as: sharing knowledge through ineffective communication methods; co-ordinating stakeholders with divergent objectives; managing teams with cultural and leadership differences; and configuring collaborative networks towards a long-term and strategic vision. Changing innovation landscapes have the potential to radically advance collaborative practices to develop more user-centred, innovative and customised products in a timelier manner. The Collaborative Design SIG has been working to define the characteristics of successful collaborative practices through previous workshops exploring the changing innovation landscape. These characteristics present complex challenges to conventional industrial practice and confounds the benefits gained from wide-spread implementation. These challenges could, for example, relate to the complexities of extending knowledge management practices beyond the boundaries of the organisation and the subsequent manipulation of this knowledge; the operation of formal and informal collaborative networks that manages ambiguity, equivocality, and conflicting constraints; the adaptation of organisational structures to become more flexible, agile and open; and the ownership of the product development process. This workshop will bring together collaborative design and innovation researchers with the aim of creating a coherent, integrated, and more holistic understanding and definition of collaborative engineering enablers and inhibitors. The workshop will bring together the domains of industry and academia to facilitate networking and knowledge exchange benefiting all participants

An integrated decision support environment for organisational decision making

Traditional decision support systems are based on the paradigm of a single decision maker working at a stand-alone computer or terminal who has a specific decision to make with a specific goal in mind. Organisational decision support systems aim to support decision makers at all levels of an organisation (from executive, middle management managers to operators), who have a variety of decisions to make, with different priorities, often in a distributed environment. Such systems are designed and developed with extra functionality to meet the challenge. This paper proposes an Integrated Decision Support Environment (IDSE) for organisational decision making. The IDSE is designed and developed based on distributed client/server networking, with a combination of tight and loose integration approaches for information exchange and communication. The prototype of the IDSE demonstrates a good balance between flexibility and reliability

A multi-agent based system to enable strategic and operational design coordination

This paper presents two systems which individually focus on different aspects of design coordination, namely strategic and operational. The systems were developed in parallel and individually contain related models that represent specific frames from a Design Coordination Framework developed by Andreasen et al. [1]. The focus of the strategic design management system is the management of design tasks, decisions, information, goals and rationale within the design process, whereas the focus of the operational design coordination system is the coordination of tasks and activities with respect to the near-optimal utilisation of available resources. A common interface exists which enables the two systems to be integrated and used as a single system with the aim of managing both strategicand operational design coordination. Hence, the objective of this work is to enable the design process to be conducted in a timely and appropriate manner

Coordination approaches and systems - part II : an operational perspective

This is the second of two papers surveying research in coordination approaches and systems. This paper is concerned with operational coordination, which is aimed at coordinating activities such that the design process can be performed in a near optimal manner with respect to time, and the allocation and utilisation of resources. Aspects of coordination categorised as operational include resource management, scheduling and planning. The first of these two papers presents a review of coordination from a strategic perspective, which is concerned with the decision management aspects of coordination. Greater emphasis is now being placed on the significance of organising the design process as this affects time to market, product quality, cost, and consequently product success. The aim of this paper is to present a fundamental review of operational coordination approaches and systems. The 1990s has seen much progress being made towards a greater understanding and appreciation of coordination in various disciplines through the development of a wide range of approaches and systems. However, there remains a requirement to formally identify the key issues involved in coordination such that a widely accepted representation can be agreed upon. Consequently, research should continue to be supported in the exploration for a unified approach to coordination which will permit a broader and greater understanding of those aspects involved

Knowledge re-use for decision support

Effective decision support has already been identified as a fundamental requirement for the realisation of Network Enabled Capability. Decision making itself is a knowledge-intensive process, and it is known that right decisions can only be reached based on decision maker's good judgement, which in turn is based on sufficient knowledge. It is not unusual for decision makers to make incorrect decisions because of insufficient knowledge. However, it is not always possible for decision makers to have all the knowledge needed for making decisions in complex situations without external support. The re-use of knowledge has been identified as providing an important contribution to such support, and this paper considers one, hitherto unexplored, aspect of how this may be achieved. This paper is concerned with the computational view of knowledge re-use to establish an understanding of a knowledge-based system for decision support. The paper explores knowledge re-use for decision support from two perspectives: knowledge provider's and knowledge re-user's. Key issues and challenges of knowledge re-use are identified from both perspectives. A structural model for knowledge re-use is proposed with initial evaluation through empirical study of both experienced and novice decision maker's behaviour in reusing knowledge to make decisions. The proposed structural model for knowledge re-use captures five main elements (knowledge re-uers, knowledge types, knowledge sources, environment, and integration strategies) as well as the relationships between the elements, which forms a foundation for constructing a knowledge-based decision support system. The paper suggests that further research should be investigating the relationship between knowledge re-use and learning to achieve intelligent decision support