Does Form follow Function? Connecting Function Modelling and Geometry Modelling for Design Space Exploration

The aerospace industry, representative of industries developing complex products, faces challenges from changes in user behaviour, legislation, environmental policy. Meeting these challenges will require the development of radically new products. Radically new technologies and solutions need to be explored, investigated, and integrated into existing aerospace component architectures. The currently available design space exploration (DSE) methods, mainly based around computer-aided design (CAD) modelling, do not provide sufficient support for this exploration. These methods often lack a representation of the product’s architecture in relation to its design rationale (DR)—they do not illustrate how form follows function. Hence, relations between different functions and solutions, as well as how novel ideas relate to the legacy design, are not captured. In particular, the connection between a product’s function and the embodiment of its solution is not captured in the applied product modelling approaches, and can therefore not be used in the product development process.To alleviate this situation, this thesis presents a combined function and geometry-modelling approach with automated generation of CAD models for variant concepts. The approach builds on enhanced function means (EF-M) modelling for representation of the design space and the legacy design’s position in it. EF-M is also used to capture novel design solutions and reference them to the legacy design’s architecture. A design automation (DA) approach based on modularisation of the CAD model, which in turn is based on the functional decomposition of the product concepts, is used to capture geometric product information. A combined function-geometry object model captures the relations between functions, solutions, and geometry. This allows for CAD models of concepts based on alternative solutions to be generated.The function- and geometry-exploration (FGE) approach has been developed and tested in collaboration with an aerospace manufacturing company. A proof-of-concept tool implementing the approach has been realised. The approach has been validated for decomposition, innovation, and embodiment of new concepts in multiple studies involving three different aerospace suppliers. Application of FGE provides knowledge capture and representation, connecting the teleological and geometric aspects of the product. Furthermore, it supports the exploration of increasingly novel solutions, enabling the coverage of a wider area of the design space.The connection between the modelling domains addresses a research gap for the “integration of function architectures with CAD models”.While the FGE approach has been tested in laboratory environments as well as in applied product development projects, further development is needed to refine CAD integration and user experience and integrate additional modelling domains

Progressive surface modeling scheme from unorganised curves

This paper presents a novel surface modelling scheme to construct a freeform surface progressively from unorganised curves representing the boundary and interior characteristic curves. The approach can construct a base surface model from four ordinary or composite boundary curves and support incremental surface updating from interior characteristic curves, some of which may not be on the final surface. The base surface is first constructed as a regular Coons surface and upon receiving an interior curve sketch, it is then updated. With this progressive modelling scheme, a final surface with multiple sub-surfaces can be obtained from a set of unorganised curves and transferred to commercial surface modelling software for detailed modification. The approach has been tested with examples based on 3D motion sketches; it is capable of dealing with unorganised design curves for surface modelling in conceptual design. Its limitations have been discussed

Transforming shape: hybrid practice as group activity

Printed textile and garment design are generally taught and practised as separate disciplines. Integrated CAD software enables textile and clothing designers to envisage printed garments by assimilating graphic imagery with 2D garment shapes and 3D visualizations. Digital fabric printing can be employed to transpose print-filled garment shapes directly onto cloth. During a recently completed practice-led PhD (1998-2003), I researched the aesthetic design potential of combining new CAD technology with garment modelling methods to create new innovative printed textiles/garments. The merging of physical and screen-based making resulted in a hybrid 3D approach to the body, cloth and print referred to as the 'simultaneous design method'. In 2001 this hybrid practice provided the catalyst for a collaborative textile research project at the Nottingham Trent University, UK. The group included surface, shape and multimedia designers. The key group aim was to explore the transforming effects of computer-aided textile design through dialogues between two and three dimensions. In parallel with my own practice, print and embroidery were considered from a 3D starting-point through the relating of geometric cloth shapes to the form. Each designer took an idiosyncratic approach to the selection and integration of imagery with the shapes. The novel consideration of the final modelled textile at the start of the designing process influenced each designer in different ways, leading to a collection of contrasting, original outcomes that were displayed in the exhibition Transforming Shape (UK 2001, Denmark 2003). The exhibition demonstrated the design opportunities (and limitations) of new and existing technologies, specifically the relationship between innovative textile imagery and three-dimensional form. The designs illustrated the premise that surface designs can be engineered through different pattern shapes and that engineer-printed shapes transform the body

Use of 3D body motion to freeform surface design

This paper presents a novel surface modelling approach by utilising a 3D motion capture system. For designing a large-sized surface, a network of splines is initially set up. Artists or designers wearing motion markers on their hands can then change shapes of the splines with their hands. Literarily they can move their bodies freely to any positions to perform their tasks. They can also move their hands in 3D free space to detail surface characteristics by their gestures. All their design motions are recorded in the motion capturing system and transferred into 3D curves and surfaces correspondingly. This paper reports this novel surface design method and some case studies

A novel updating modelling methodology for free-form surface modifications in the early stages of design

The paper describes the first implementation of a method in which an initial CAD model is updated from a physical model. The method is based on image-mapping in which an initial CAD model is updated from images of a soft rapid prototype model (RPM) which has been sculpted in order to carry out formal developments. The RP model is made by a 3Dimensional-colour printer, has a built-in contrasting grid composed by parallel planes in the X, Y and/or Z co-ordinates and has special consistency allowing it to be easily sculpted with hand modifications. During the sculpting process changes on the surface affect the lines on the RPM, which are the external presence of the internal grid planes and are corresponding to the initial CAD construction lines. These lines (profiles) then are visually contrasted by making use of identical perspective transformations and viewpoints for the virtual model and the RP model image. The initial CAD model is then updated by modifying the surface’s construction lines to match the lines on the RP image by moving control points, such as in the Z direction

Integrated product relationships management : a model to enable concurrent product design and assembly sequence planning

The paper describes a novel approach to product relationships management in the context of concurrent engineering and product lifecycle management (PLM). Current industrial practices in product data management and manufacturing process management systems require better efficiency, flexibility, and sensitivity in managing product information at various levels of abstraction throughout its lifecycle. The aim of the proposed work is to manage vital yet complex and inherent product relationship information to enable concurrent product design and assembly sequence planning. Indeed, the definition of the product with its assembly sequence requires the management and the understanding of the numerous product relationships, ensuring consistency between the product and its components. This main objective stresses the relational design paradigm by focusing on product relationships along its lifecycle. This paper gives the detailed description of the background and models which highlight the need for a more efficient PLM approach. The proposed theoretical approach is then described in detail. A separate paper will focus on the implementation of the proposed approach in a PLM-based application, and an in-depth case study to evaluate the implementation of the novel approach will also be given

Embracing additive manufacture: implications for foot and ankle orthosis design

<p>Abstract</p> <p>Background</p> <p>The design of foot and ankle orthoses is currently limited by the methods used to fabricate the devices, particularly in terms of geometric freedom and potential to include innovative new features. Additive manufacturing (AM) technologies, where objects are constructed via a series of sub-millimetre layers of a substrate material, may present the opportunity to overcome these limitations and allow novel devices to be produced that are highly personalised for the individual, both in terms of fit and functionality.</p> <p>Two novel devices, a foot orthosis (FO) designed to include adjustable elements to relieve pressure at the metatarsal heads, and an ankle foot orthosis (AFO) designed to have adjustable stiffness levels in the sagittal plane, were developed and fabricated using AM. The devices were then tested on a healthy participant to determine if the intended biomechanical modes of action were achieved.</p> <p>Results</p> <p>The adjustable, pressure relieving FO was found to be able to significantly reduce pressure under the targeted metatarsal heads. The AFO was shown to have distinct effects on ankle kinematics which could be varied by adjusting the stiffness level of the device.</p> <p>Conclusions</p> <p>The results presented here demonstrate the potential design freedom made available by AM, and suggest that it may allow novel personalised orthotic devices to be produced which are beyond the current state of the art.</p

An assembly oriented design framework for product structure engineering and assembly sequence planning

The paper describes a novel framework for an assembly-oriented design (AOD) approach as a new functional product lifecycle management (PLM) strategy, by considering product design and assembly sequence planning phases concurrently. Integration issues of product life cycle into the product development process have received much attention over the last two decades, especially at the detailed design stage. The main objective of the research is to define assembly sequence into preliminary design stages by introducing and applying assembly process knowledge in order to provide an assembly context knowledge to support life-oriented product development process, particularly for product structuring. The proposed framework highlights a novel algorithm based on a mathematical model integrating boundary conditions related to DFA rules, engineering decisions for assembly sequence and the product structure definition. This framework has been implemented in a new system called PEGASUS considered as an AOD module for a PLM system. A case study of applying the framework to a catalytic-converter and diesel particulate filter sub-system, belonging to an exhaust system from an industrial automotive supplier, is introduced to illustrate the efficiency of the proposed AOD methodology

A novel haptic model and environment for maxillofacial surgical operation planning and manipulation

This paper presents a practical method and a new haptic model to support manipulations of bones and their segments during the planning of a surgical operation in a virtual environment using a haptic interface. To perform an effective dental surgery it is important to have all the operation related information of the patient available beforehand in order to plan the operation and avoid any complications. A haptic interface with a virtual and accurate patient model to support the planning of bone cuts is therefore critical, useful and necessary for the surgeons. The system proposed uses DICOM images taken from a digital tomography scanner and creates a mesh model of the filtered skull, from which the jaw bone can be isolated for further use. A novel solution for cutting the bones has been developed and it uses the haptic tool to determine and define the bone-cutting plane in the bone, and this new approach creates three new meshes of the original model. Using this approach the computational power is optimized and a real time feedback can be achieved during all bone manipulations. During the movement of the mesh cutting, a novel friction profile is predefined in the haptical system to simulate the force feedback feel of different densities in the bone