Pj Clarkson

A SIMULATED ANNEALING ALGORITHM FOR MULTIOBJECTIVE OPTIMIZATION

This paper describes a novel implementation of the Simulated Annealing algorithm designed to explore the trade-off between multiple objectives in optimization problems. During search, the algorithm maintains and updates an archive of non-dominated solutions between each of the competing objectives. At the end of search, the final archive corresponds to a number of optimal solutions from which the designer may choose a particular configuration. A new acceptance probability formulation based on an annealing schedule with multiple temperatures (one for each objective) is proposed along with a novel restart strategy. The performance of the algorithm is demonstrated on three examples. It is concluded that the proposed algorithm offers an effective and easily implemented method for exploring the trade-off in multiobjective optimization problems.

The development of a multi-objective Tabu Search algorithm for continuous optimisation problems

While there have been many adaptations of some of the more popular meta-heuristics for continuous multi-objective optimisation problems, Tabu Search has received relatively little attention, despite its suitability and effectiveness on a number of real-world design optimisation problems. In this paper we present an adaptation of a single-objective Tabu Search algorithm for multiple objectives. Further, inspired by path relinking strategies common in discrete optimisation problems, we enhance our algorithm to allow it to handle problems with large numbers of design variables. This is achieved by a novel parameter selection strategy that, unlike a full parametric analysis, avoids the use of objective function evaluations, thus keeping the overall computational cost of the procedure to a minimum. We assess the performance of our two Tabu Search variants on a range of standard test functions and compare it to a leading multi-objective Genetic Algorithm, NSGA-II. The path relinking-inspired parameter selection scheme gives a clear performance improvement over the basic multi-objective Tabu Search adaptation and both variants perform comparably with the NSGA-II.

Assessing Organizational Capabilities: Reviewing and Guiding the Development of Maturity Grids

Managing and improving organizational capabilities is a significant and complex issue for many companies. To support management and enable improvement, performance assessments are commonly used. One way of assessing organizational capabilities is by means of maturity grids. While maturity grids may share a common structure, their content differs and very often they are developed anew. This paper presents both a reference point and guidance for developing maturity grids. This is achieved by reviewing 24 existing maturity grids and by suggesting a roadmap for their development. The review places particular emphasis on embedded assumptions about organizational change in the formulation of the maturity ratings. The suggested roadmap encompasses four phases: planning, development, evaluation, and maintenance. Each phase discusses a number of decision points for development, such as the selection of process areas, maturity levels, and the delivery mechanism. An example demonstrating the roadmaps utility in industrial practice is provided. The roadmap can also be used to evaluate existing approaches. In concluding the paper, implications for management practice and research are presented.

Design for patient safety: A review of the effectiveness of design in the UK health service

In 2002 the UK Department of Health and the Design Council jointly commissioned a scoping study to deliver ideas and practical recommendations for a design approach to reduce the risk of medical error and improve patient safety across the National Health Service (NHS). The research was undertaken by the Engineering Design Centre at the University of Cambridge, the Robens Institute for Health Ergonomics at the University of Surrey and the Helen Hamlyn Research Centre at the Royal College of Art. The research team employed diverse methods to gather evidence from literature, key stakeholders, and experts from within healthcare and other safety-critical industries in order to ascertain how the design of systems—equipment and other physical artefacts, working practices and information—could contribute to patient safety. Despite the multiplicity of activities and methodologies employed, what emerged from the research was a very consistent picture. This convergence pointed to the need to better understand the healthcare system, including the users of that system, as the context into which specific design solutions must be delivered. Without that broader understanding there can be no certainty that any single design will contribute to reducing medical error and the consequential cost thereof.

Countering design exclusion: bridging the gap between usability and accessibility

It is known that many people are being excluded unnecessarily from using products, services and environments that are essential for supporting independence and quality of life. Such exclusion often arises from designers taking inadequate account of the end user’s functional capabilities when making design decisions. This paper addresses how traditional usability techniques can be extended to include accessibility issues by considering the spread of user functional capabilities across the population. A series of measures for evaluating the level of design exclusion based on those capabilities is also presented.

A Matrix-Calculation-Based Algorithm for Numerical Change Propagation Analysis

Engineering changes (ECs) are raised throughout the lifecycle of engineering products. A single change to one component produces knock-on effects on others necessitating additional changes. This change propagation significantly affects the development time and cost and determines the products success. Predicting and managing such ECs is, thus, essential to companies. Some prediction tools model change propagation by algorithms, whereof a subgroup is numerical. Current numerical change propagation algorithms either do not account for the exclusion of cyclic propagation paths or are based on exhaustive searching methods. This paper presents a new matrix-calculation-based algorithm which can be applied directly to a numerical product model to analyze change propagation and support change prediction. The algorithm applies matrix multiplications on mutations of a given design structure matrix accounting for the exclusion of self-dependences and cyclic propagation paths and delivers the same results as the exhaustive search-based Trail Counting algorithm. Despite its factorial time complexity, the algorithm proves advantageous because of its straightforward matrix-based calculations which avoid exhaustive searching. Thereby, the algorithm can be implemented in established numerical programs such as Microsoft Excel which promise a wider application of the tools within and across companies along with better familiarity, usability, practicality, security, and robustness.

Web-based knowledge management for distributed design

Contemporary product design is a knowledge-intensive process undertaken by virtual teams dispersed across multiple organizations. Successful design requires contextual knowledge of the target market. Knowledge management and decision support can assist in this task. By considering AI as a form of writing, we can represent knowledge in a transparent and modifiable form, which better supports the multiplicity of contexts required in real design. To assist designers in conceptual-design evaluation, we have implemented the WebCADET Web-based decision-support tool. Based on a knowledge-server architecture, WebCADET operates in design-guidance, knowledge-viewing and knowledge-capture modes. We discuss our efforts in developing WebCADET and deploying four WebCADET servers at different locations for various applications.

Using an engineering change methodology to support conceptual design

Most designs are modifications from previous products and lessons learned from earlier designs can be beneficial when developing new products. This paper introduces a support tool for the conceptual design phase, which is based on connectivity models of past designs and allows designers to assess the risk of change spreading between components and facilitates a visual analysis of these change models. Based on the example of a new generation of diesel engine design, this paper shows how the ability to predict change propagation can guide designers through conceptual design allowing them to analyse design alternatives and foresee potential problems arising from the product architecture.

Reflecting communication: a key factor for successful collaboration between embodiment design and simulation

The need for integration of computer-aided design and computer-aided engineering environments stems from the business priority to reduce product cycle times. It is exacerbated by the coexistence of two different paradigms: a topological one in embodiment design and a functional one in simulation. This dualism places increasing demands on human communication between design and simulation engineers. This paper claims that reflecting communication is a key factor for successful collaboration. Reflection is used in both senses of the Latin word ‘reflectare’: to trigger active thinking about and consideration of communication, as well as to mirror perceptions of a given situation by people collaborating. The paper reports on the development and application of a maturity-grid approach to diagnose the current and desired states of communication between design engineers and simulation engineers in the car body development of a German automotive manufacturer. Results include three themes: one, the importance of understanding of the collaborators’ information needs; two, the importance of orientation, e.g., indicated by the engineers’ overview of sequence of tasks in the design process; and three, the importance of reflection.

Biobjective Design Optimization for Axial Compressors Using Tabu Search

At present, optimization is an enabling technology in innovation. Multi-objective and multidisciplinary optimization tools are essential in the design process for real-world applications. In turbomachinery design, these approaches give insight into the design space and identify the tradeoffs between the competing performance measures. This paper describes the application of a novel multi-objective variant of the tabu search algorithm to the aerodynamic design optimization of turbomachinery blades. The aim is to improve the performance of a specific stage and eventually of the whole engine. The integrated system developed for this purpose is described. It combines the optimizer with an existing geometry parameterization scheme and a well-established computational fluid dynamics package. Its performance is illustrated through a case study in which the flow characteristics most important to the overall performance of turbomachinery blades are optimized.