Computer Aided Design is currently expanding its boundaries to include more design features in its processes. Design is identified as an iterative process converging to solutions satisfying a set of constraints. Its close relation with optimisation indicate that there is strong potential for the integration of optimisation and CAD. The problem addressed in this thesis lies in interfacing the geometric representation of design with other non-geometric aspects. The example of free-form curve modelling is taken to investigate such relationships. Assumptions are made that Optimisation is powered by Evolutionary Computing algorithms like Genetic Algorithms (GA). The geometric definition of curves is commonly supported by NURBS, whose construction constraints are defined locally at the data points. Here the NURBS formulation is used with GA in an attempt to provide complementary handles on the curves shape other than the usual data point coordinates and control points weights. Differential properties are used for optimising NURBS, Hermite interpolation allows for the definition of higher order constraints (tangent, normal, bi-normal) at data points. The assignment of parameter values at the data points, known as parameterisation also provides control of the curve’s shape. Curve optimisation is also performed at the geometric modelling level. Old mathematical theorems established by Frénet and further developed by other mathematicians provide means of defining a curve’s shape with it’s intrinsic equations. Such representation is possible by using Function Representation (F-rep) algebra available in the ACIS software. Frep allows more generic and exact means of interfacing with the curve’s geometry and new functionality for curve inspection and optimisation are proposed in this thesis. The integration of optimisation findings and CAD are documented in the definition of a framework. The framework architecture proposed reconstructs a new CAD environment from separate elements bolted together in a generic Application Programming Interface (API) named “Oli interface”. Functionality created to interface optimisation and CAD makes a requirement list of the work that both sides should undertake to achieve design optimisation in the CAD environment.

This thesis presents a knowledge based manufacturing advisor for Computer Aided Design. The aim of the project has been to develop techniques that can help designers to evaluate the manufacturability of moulded parts during the design process. One of the major achievements in the research has been the development of a novel feature recognition approach to allow moulding features to be recognised from a CAD model. Existing feature recognition techniques are not appropriate for moulded parts and a new feature recognition approach has been developed that uses a mid-surface abstraction from the CAD solid model as the basis for feature recognition. The feature recognition methodology presented in this research is a graph based technique that uses an attributed mid-surface adjacency graph as the basis for feature recognition. Feature recognition algorithms have been developed for a range of common moulding features. Two evaluation techniques are presented that measure the quality of the feature recognition results and provide a confidence measure for the manufacturing advice that is generated. The first evaluation technique uses the Hausdorff distance to measure the similarity of the mid-surface model to the CAD solid model that was used to generate it, and the second uses a face mapping technique to evaluate the completeness of the feature recognition results. A demonstrator for the knowledge based manufacturing advisor has been developed which incorporates the feature recognition software and an expert system for moulding advice. The expert system provides an interactive software environment in which the user can input details about their part design, and receive tailored manufacturing advice for a range of moulding processes. The demonstrator has been tested on a range of realistic moulded parts.

Typical construction projects involving a large number of stakeholders working together require a tremendous amount of collaboration amongst them. In order to reduce the cost and length of the project life cycle undertaken by the design team and to avoid any catastrophic problems at later stages in the life cycle, technologies such as BIM and CAD tools have been adopted to support more efficient design assessment. This research is to explore a human-centric collaborative environment for the construction sector that can allow multi-functional team members to come together to visualise, explore, assess and design optimised building solutions. It resulted in creating a collaboration platform that integrates multi-functional interfaces allowing teams to explore the design from their own perspectives. Within this multi-user environment the concept of private and public spaces were explored in order to enhance design exploration, both individually and as a team. The environment was tested for the utility, likability and usefulness of the collaborative design system taking the design of a bathroom for a disabled client as a case study. The final results suggest that in overall it could potentially enhance the multi-functional collaborative design.

This thesis presents studies on the design of a novel two-handed spatial interface for engineering assembly, informed by a number of qualitative studies using a realistic assembly model within a fully working virtual environment (VE). The results show that the two-handed spatial interface has the potential to reduce task-performance times by more than 25%, over an existing one-handed spatial interface. The VE is the IVPS (Interactive Virtual Prototyping System) at University of Leeds, which supports interactive engineering assembly. The main contribution of this research is to demonstrate an improved understanding of task performance for engineering assembly. By understanding the assembly task-performance through the evaluation of the existing IVPS using a desktop-based interface, the strengths and weakness of the existing interaction techniques are studied. The results strongly suggest that there is a need to know if more expressive spatial interaction could improve the task-performance for engineering assembly within a VE. By understanding the assembly task-performance through an evaluation of a one-handed spatial interaction model within the IVPS, a number of problems in spatial selection and positioning have been identified. They are the problems of scale (such as selecting a very small feature from a component), slide (such as manipulating constrained components in an assembly), global precision (such as manipulating the entire scene in which some components are long way from the centre of rotation) and related precision (such as manipulating the selected component related to the other components). A novel cube-based two-handed spatial interface has therefore been designed to overcome these problems in spatial selection and positioning. It assigns to the nondominant hand tasks such as positioning that can be performed by a sequence of 1DOF sub-tasks. This leaves the dominant-hand to perform the tasks such as 6DOF manipulation of assemblies, selection and attachment. This interface uses a physical cube to provide the user with a spatial frame of reference. The evaluation results show that the cube-based two-handed spatial interface has the potential to reduce the task-performance time by more than 25%, over the existing one-handed spatial interface. A tentative hypothesis is finally generalized and offers opportunities for further research.

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This thesis presents research into the possibility of developing a computerised system that can evaluate the aesthetics and engineering aspects of solid shapes. One of the research areas is also to include such an evaluation system into an existing evolutionary CAD system which utilizes the Genetic Algorithms (GAs) technology. An extensive literature survey has been carried out to better understand and clarify the vagueness and subjectivity of the concept of aesthetics, which leads to the work of defining and quantifying a set of aesthetic parameters. This research achieves its novelty in aiming to assist designers in evaluating the aesthetics and functional aspects of designs early in the conceptual design stage, and its inclusion into an evolutionary CAD system. The field of Computer Aided Design (CAD) lacks the aesthetics aspect of the design, which is very crucial in evaluating designs especially considering the trend towards virtual prototypes replacing physical prototypes. This research has managed to suggest, define and quantify a set of aesthetic and functional elements or parameters, which will be the basis of solid shape evaluation. This achievement will help designers in determining the fulfilment of design targets, where the designers will have a full control to determine the priority of each evaluation element in the developed system. In achieving this, computer software including a programming language package and CAD software are involved, which eventually led to the development of a prototype system called Computer Aided Aesthetics and Functions Evaluation (CAAFE). An evolutionary CAD system called Evolutionary Form Design (EFD), which utilizes GAs, has been available for few years now. It evolves shapes for quick and creative suggestions, however it lacks the automated evaluation and aesthetics aspects of the design. This research has worked into the integrating of CAAFE into EFD, which led to a system that could evolve objects based on a selected and weighed aesthetic and functional elements. Finally, surveys from users have also been presented in this thesis to offer improvement to the scoring system within the CAAFE system.

Engineering design involves a series of activities to handle data, including capturing and storing data, retrieval and manipulation of data. This also applies throughout the entire product lifecycle (PLC). Unfortunately, a closed loop of knowledge and information management system has not been implemented for the PLC. As part of product lifecycle management (PLM) approaches, computer-aided design (CAD) systems are extensively used from embodiment and detail design stages in mechanical engineering. However, current CAD systems lack the ability to handle semantically-rich information, thus to represent, manage and use knowledge among multidisciplinary engineers, and to integrate various tools/services with distributed data and knowledge. To address these challenges, a general-purpose semantic annotation approach based on CAD systems in the mechanical engineering domain is proposed, which contributes to knowledge management and reuse, data interoperability and tool integration. In present-day PLM systems, annotation approaches are currently embedded in software applications and use diverse data and anchor representations, making them static, inflexible and difficult to incorporate with external systems. This research will argue that it is possible to take a generalised approach to annotation with formal annotation content structures and anchoring mechanisms described using general-purpose ontologies. In this way viewpoint-oriented annotation may readily be captured, represented and incorporated into PLM systems together with existing annotations in a common framework, and the knowledge collected or generated from multiple engineering viewpoints may be reasoned with to derive additional knowledge to enable downstream processes. Therefore, knowledge can be propagated and evolved through the PLC. Within this framework, a knowledge modelling methodology has also been proposed for developing knowledge models in various situations. In addition, a prototype system has been designed and developed in order to evaluate the core contributions of this proposed concept. According to an evaluation plan, cost estimation and finite element analysis as case studies have been used to validate the usefulness, feasibility and generality of the proposed framework. Discussion has been carried out based on this evaluation. As a conclusion, the presented research work has met the original aim and objectives, and can be improved further. At the end, some research directions have been suggested.

Numerous works have been produced on the topic of Design for Manufacturing (DFM) to better educate the designers of products as to various methods of manufacturing and their specific requirements. It is the common aim of these works to eliminate so called "over the wall" product development in which procedurally ignorant designers pass largely un-producible design concepts to manufacturers, who are then required to make necessary refinements and changes. When applied correctly, DFM results in the efficient and economical production of well-designed products, whose forms have been attuned to the particular requirements of their final method of production at an early stage of development. However, one aspect of using such approaches is that design intent is frequently compromised for the sake of manufacturability and innovative design concepts are often dismissed as being unfeasible. Recent advances in additive manufacturing technologies and their use in the direct manufacture of end-use products from digital data sources has brought about a new method of production that is known as Rapid Manufacturing (RM). Unlike conventional subtractive machining processes, such as milling and turning which generate forms by removing material from a stock billet, RM parts are grown from an empty part bed using the controlled addition of specialised build materials. Additive manufacturing requires no forming tools, is unrestricted by many conventional process considerations and is capable of producing practically any geometry. The freedoms that are associated with this technology facilitate the design and realisation of product concepts that would be unachievable with any other method of production. This promotes an almost boundless design philosophy in which innovative product solutions can be designed to best meet the needs of specification criteria, rather than the production process with which they are to be made. However, unlike other forms of manufacturing, the newness of this technology means that there is no proven aid or tool to assist industrial designers in exploiting the freedoms that it offers. Using information that was collated in the literature review and case study projects, a systematic design approach was proposed and then tested in a series of user trials with groups of industrial design students and practicing industrial design professionals. The results of these trials are discussed, showing a common acknowledgement from both groups that the proposed DFRM tool was of assistance and that it had an influence upon their design work. However, whilst the student group were generally receptive toward tool uptake, the experienced designers showed more of a reluctance to abandon their own "tried and tested" methods in favour of the unknown and unproven approach. It is concluded that this attitude would be fairly representative of wider opinion and that the future uptake of any such tool would be reliant upon sufficient evidence of its successful application. Hence, suggestions are made for future work to continue tool development and for more validation trials to be conducted with its intended user group.

Modern engineering design optimization relies to a large extent on computer simulations of physical phenomena. The computational cost of such high-fidelity physics-based analyses typically places a strict limit on the number of candidate designs that can be evaluated during the optimization process. The more global the scope of the search, the greater are the demands placed by this limited budget on the efficiency of the optimization algorithm. This thesis proposes a number of enhancements to two popular classes of global optimizers. First, we put forward a generic algorithm template that combines population-based stochastic global search techniques with local hillclimbers in a Lamarckian learning framework. We then test a specific implementation of this template on a simple aerodynamic design problem, where we also investigate the feasibility of using an adjoint flow-solver in this type of global optimization. In the second part of this work we look at optimizers based on low-cost global surrogate models of the objective function. We propose a heuristic that enables efficient parallelisation of such strategies (based on the expected improvement infill selection criterion). We then look at how the scope of surrogate-based optimizers can be controlled and how they can be set up for high efficiency.

Reliable cost estimation is important for economic production, cost control and maintaining competitive advantage in manufacturing contract bidding. Therefore, estimating the manufacturing cost of a machined part is of critical importance in CNC manufacture. Computers aided systems the link to manufacturers CAD systems and databases have been used since the 1980’s to identify product cost and enable a company to evaluate resource utilisation. While the concept of an integrated costing system has made significant advances in integrating the design function with the cost estimation process, there are still major gaps in acquisition and application of detailed product data for generation of timely and reliable costing information feedback to engineers. Integrated costing systems are information intensive and require significant manufacturing data support. A major obstacle is the bespoke nature of the available cost relevant data and their storage in company specific database tailored to individual company practices. Thus there is need to consider standardisation of information from the design of component through to their process planning and manufacture. This will allow seamless exchange of detailed, cost relevant, information between other computers aided systems and costing systems to facilitate automatic and reliable cost information feedback. In this research a novel framework is specified and designed for enabling detailed product information that exists across CNC manufacturing, to be utilised for generation of reliable cost estimates. The standards based costing proposed in this thesis framework facilitates high-level integration of various CAx resources and increases the availability of product creation process (PCP) data that are applicable in costing process. A prototype implementation of the unified costing framework is utilised to demonstrate the capabilities of the framework. The demonstration is conducted using two industrially inspired prismatic test components where the components machining cycles were timed with a stop watch and the actual result compared with the prototype system estimated result to determine its reliability. The research shows that implementation of manufacturing standard that contain structured representation PCP information together with an effective data retrieval mechanism and computational algorithms can provide a standard compliant framework to realise an information rich (detailed) costing system. The potential of the proposed framework is not limited to enabling the use of detailed information that exist within manufacturing facility to generate cost information; it also provides a standard compliant approach for the development of future generations of costing systems.