Partitioning Tasks to Product Development Teams

The principle of partitioning tasks among product development teams so as to minimize the cost of interactions across design teams is an important characteristic of complex engineered systems. Although there is growing literature that deals with the proper organization of product development tasks, little attention is given to rigorous modeling of the phenomena. To fill the void, we present a mathematical formulation for the problem. Two main issues are addressed by the model: 1) how to specify task dependencies, and 2) how to optimally partition the tasks among a number of teams. Characteristics of the problem are analyzed, and an efficient solution procedure is proposed. The developed model and solution technique can be applied to various scales of the product design and development process, and may open a variety of interesting questions.

Incorporating Uncertainty in Diagnostic Analysis of Mechanical Systems

The increase in complexity of modern mechanical systems can often lead to systems that are difficult to diagnose, and therefore require a great deal of time and money to return to a normal operating condition. Analyzing mechanical systems during the product development stages can lead to systems optimized in the area of diagnosability, and therefore to a reduction of life cycle costs for both consumers and manufacturers and an increase in the useable life of the system. A methodology for diagnostic evaluation of mechanical systems incorporating indication uncertainty is presented. First, Bayes formula is used in conjunction with information extracted from the Failure Modes and Effects Analysis (FMEA), Fault Tree Analysis (FTA), component reliability, and prior system knowledge to construct the Component-Indication Joint Probability Matrix (CIJPM). The CIJPM, which consists of joint probabilities of all mutually exclusive diagnostic events, provides a diagnostic model of the system. The Replacement Matrix is constructed by applying a predetermined replacement criterion to the CIJPM. Diagnosability metrics are extracted from a Replacement Probability Matrix, computed by multiplying the transpose of the Replacement Matrix by the CIJPM. These metrics are useful for comparing alternative designs and addressing diagnostic problems of the system, to the component and indication level. Additionally, the metrics can be used to predict cost associated with fault isolation over the life cycle of the system.

Designers in Organisations

Design processes in current industrial contexts require integration between different disciplines and functions, not only within an organisation but also across organisational and even national borders. Many barriers to integration can be observed, however, in multi-disciplinary and multifunctional design projects. One of these barriers is the lack of organisational, management, and social knowledge and skills, on the level of team members as well as on the level of project management. To achieve a sufficient level of integration technical knowledge and skills are necessary but not sufficient. Organisational, management, and social skills are necessary too. In our research on organisation and management of business processes we have found that this last category of knowledge needs improvement for the largest part of design team members and managers. As designers are professionals who have been employed because of their knowledge and skills, gained through prior academic or professional education, the question can be asked to what extent organisational, management, and social knowledge is included in this education. One way to answer this question is by studying the knowledge and skills deemed important for performing design tasks. An important source of this knowledge can be found in journal articles in the area of engineering design. The authors of these articles are in most cases also the ones transferring this knowledge to future designers. In this paper, a study of 94 recently published journals articles is described, which reveals, that organisational, management, and social skills are not yet a major focus of attention. In particular the number of empirical studies on the organisational, social, and managerial behaviour of designers in practical contexts is scarce in the engineering research community. These results will be confronted with results from management and social sciences research. We argue that the gap between these two fields of research needs to be bridged to better prepare designers for their task in current industrial contexts.

The Culture of Design and Production in Abbasid Samarra

The paper discusses the culture of design produced by a particular patronage pattern of city building; the case study is that of Samarra in the 9th century. It investigates the process through which mechanical mass production of art transforms the Late Antique visual forms into new vocabulary that acquires universal popularity and new cultural significance.

A Clock Grammar: The Use of a Parallel Grammar in Performance-Based Mechanical Synthesis

Effective methods of computational synthesis for mechanical systems must represent both function and structure in order to generate physical designs with desired behaviors. To this aim, a parallel grammar for mechanical synthesis was developed based on a Function-Behavior-Structure design model. This parallel grammar was implemented for the domain of mechanical clocks and watches in order to demonstrate the flexibility and strengths of the approach. Designs were produced using a fully parametric parts library. Incorporating performance considerations, generate-and-test methods were then used to produce clock designs that satisfy different sets of spatial constraints to demonstrate the potential of the method for general mechanical synthesis problems.

A Method of Form Selection for Large Scale Structures

This paper presents a new method for modelling the efficiency of large-scale structural forms. Parametric equations, which include all design parameters and also the effect of buckling, are developed. Shape transformers, envelope efficiency parameter and scaling factor are introduced to describe the geometrical properties of cross-sections and to allow interaction between form and cross-sectional shape selection. Design charts provide insight and understanding and assist the selection of different structural concepts at the preliminary stage of design.

Modularization of Design Knowledge as a Basis for a High Quality Competence Pool in Product Development

Contents of product development knowledge have to be available in a broad range and rank high in quality for teaching, learning and application. Individuality in presenting and high flexibility in use and arrangement are requested. Furthermore, the collaboration of different authors with different background is aimed to create a common competence pool in the range of product development. Therefore an approach to modularization, filing and accessing of various contents of product development knowledge will be applied. Contents of product development knowledge are modularized based on three levels — elements, modules and containers — and they are linked and integrated into the competence pool. Considering the requirements of different users, individual and specific documents can be created out of the modularized contents, e.g., material for a specific lecture. Appropriate modularization is considered as a basis for higher quality and improvement of communication and collaboration.

A Systematic Approach to the Reconstruction of Ancient Chinese Escapement Regulators

It is generally believed that the first escapement regulator invented is the waterwheel steelyard-clepsydra device made in ancient China by Su Song during the Northern Song Dynasty (960~1,127 AD). The device, which was a unique feature of the ancient Chinese escapement regulators, was used in Su’s famous clock tower, Shui Yun Yi Xiang Tai (Water-Powered Armillary Sphere and Celestial Globe). Evidence found in certain historical literature, however, suggests that the astronomical clocks made before the Northern Song Dynasty were also equipped with escapement regulators. But due to insufficient literature on the specific design of the devices and the fact that none of the earlier escapement regulators have been recovered, it has been very difficult to recreate the original mechanism design. Therefore, in view of this problem, we wish to present a reconstruction design procedure for the ancient machinery in this paper. By combining the innovative mechanism design methodology with the mechanical evolution and variation theory, we can systematically recreate all feasible and appropriate designs that are consistent with the science theories and techniques of the subject time period. In this paper, the waterwheel steelyard-clepsydra device made by Su Song was adopted as the original design for the reconstruction of ancient Chinese escapement regulators. Utilizing the procedure proposed in this paper, the reconstruction designs we recreated included 12 six-bar and eight-joint waterwheel steelyard-clepsydra devices, among which 10 were with four-bar linkages and 2 were with rope-and-pulley mechanisms. These results can be further used in the study of ancient Chinese mechanical clocks, especially in reconstruction research.

Flexible Multistage Bayesian Models for Use in Conceptual Design

During conceptual design, designers need tools to help improve design decisions and reduce design times. We are working to develop techniques to create Bayesian surrogate models that respond to designers’ needs during conceptual stages of the design process. Bayesian surrogate models give analytical form to the overall performance of a system and can evolve along with the design. Bayesian surrogate models provide a mathematically rigorous framework in which computational models can be updated based on previous outcomes. In this paper, we present techniques that allow the addition or suppression of parameters without discarding previously obtained information. We also present a case study that illustrates how a surrogate model is constructed in stages when parameters are added or suppressed during the design process. Visualization tools, such as plots of the main effects of parameters, can be derived from surrogate models. These tools can be used to provide knowledge about the parameters that influence the design. Finally, a design problem is used to illustrate how Bayesian surrogate models can inform the designer about tradeoffs that would not be apparent from simulation data alone.

Planning and Scheduling Based on an Explicit Representation of the State of the Design

This paper describes a computational model that provides planning information useful for scheduling the design process. The model aims to reduce uncertainty in the design process and with it the risk of rework. The view is taken that planning is concerned with choosing between alternative actions and action sequences, but not with resource allocation. The planning model is based on an explicit representation of the state of the design process, the definition of the design capabilities as a pool of tasks, and on the generation and selection of plans by evaluating their reliability. Classical decision theory is used for evaluating the plans: a state-action net is built and analyzed as a Markov decision process. The model produces plans based on qualified task dependencies. These plans can be used as a basis for manual and automated scheduling. In an example industrial case study, a reduction of over 30% in the expected rework was predicted.