Papers by Alan Pennington
Palgrave Macmillan UK eBooks, 1980
A prototype system for design and manufacture using B-spline curves and patches is described. A n... more A prototype system for design and manufacture using B-spline curves and patches is described. A number of examples illustrate the capabilities of the system. An assessment of the technique is given.
An example of the use of transient acceleration feedback is described. The use of two load masses... more An example of the use of transient acceleration feedback is described. The use of two load masses allows the effectiveness of the technique to be studied at a low (38Hz) and a high (88Hz) drive natural frequency. The control system response is evaluated, for input signals, by step and frequency response tests; the output stiffness is assessed by single-tooth milling loads and impact loads. A considerable enhancement of static and dynamic accuracy is demonstrated. Nomenclature: C, the linearised viscous friction coefficient; Ka the gain contant of the acceleration sensor; Kp the position loop gain constant(= K 1 K2); K 1 the forward sequence gain constant before the minor loop summing point of the position loop; K 2 the forward sequence gain constant of the minor loop; k 1 the linearised cross port leakage coefficient; kp the linearised pressure droop; Tv the minor loop transient network time constant; T M the servo-valve torque-motor time constant; Ve the position-error voltage;
Springer eBooks, 1989
A new method for incorporating sculptured surfaces into a Constructive Solid Geometry (CSG) envir... more A new method for incorporating sculptured surfaces into a Constructive Solid Geometry (CSG) environment is described. As a preliminary, an overview of a general scheme for computations on CSG represented solids is given. The system, known as Inner Set Outer Set (ISOS), involves inner and outer bounding polyhedral approximations to the primitive solids and is detailed in [Beac89]. A method for simultaneous creation of both sculptured primitives and approximating geometry, by sweeping B-spline curves, appears in [Saia88]. This paper is concerned with expanding and adapting these methods to shapes of a less constrained nature, bounded by B-spline surfaces. The task encompasses theoretical groundwork in finding inner-bounding polyhedra and a reformulation of the underlying method.
The integration of sculptured surface and solid modelling techniques across a common geometric do... more The integration of sculptured surface and solid modelling techniques across a common geometric domain continues as an active source of research and development in computer aided geometric design. Although much progress has been made, fundamental difficulties remain due to the differing approaches to shape representation and subsequent evaluation found in the two modelling paradigms. The first part of the paper reviews some of the issues arising when addressing the integration of existing sculptured surface representations into a Constructive Solid Geometry (CSG) based solid modeller. The second part describes work at Leeds which proposes the use of a new evaluation technique known as ISOS (Inner Set Outer Set) for CSG defined objects which incorporate both quadric and B-spline surface geometry.
Elsevier eBooks, 1991
The contact pressure distribution at the cone clutch operating interface of a transmission synchr... more The contact pressure distribution at the cone clutch operating interface of a transmission synchroniser may have a significant effect upon gear shift quality and reliability. Modifications have been made to a standard finite element package to facilitate accurate predictions of such contact pressure distributions. Results illustrating the effect of varying shift lever load;, material properties and cup/cone differential angle are presented for the particular case of a commercial vehicle pin-type synchroniser. Tests have been carried out on production components over a large number of operating cycles to accurately measure wear signatures which, using pin-on-disc wear data, are then converted to pressure distributions. Good agreement between numerical and experimentally-derived interfacial pressures is obtained for certain assumed values of friction material modulus. Additional assumptions in the finite element approach and implications of the results for synchroniser design are discussed.
Elsevier eBooks, 1994
Engineering and business complexity varies from manufacturing sector to sector to drive a range o... more Engineering and business complexity varies from manufacturing sector to sector to drive a range of integrating technologies. This paper addresses three of these: information exchange standardisation, new developments in the description of geometry related to product functionality, and layer manufacturing for rapid prototyping.
If probe paths for coordinate measuring machines are to be generated automatically then methods m... more If probe paths for coordinate measuring machines are to be generated automatically then methods must be developed that can determine which surfaces need to be inspected. Evolving computer based systems supporting engineering design and manufacture are adopting the concept of a Product Model as the central source for the data required by the various activities in the design and production cycle. This paper outlines a product model capable of representing data relating to a component’s geometry, dimensions, specification and manufacturing processes. An inspection planning application then uses the product model to determine which surfaces need to be inspected to ensure that the product conforms to the product specification.
Journal of mechanical engineering science, Jun 1, 1974
The modelling of the control valve is shown to be a factor of prime importance in the design of e... more The modelling of the control valve is shown to be a factor of prime importance in the design of electrohydraulic systems. The process required to model a commercially available valve is described in detail, with equal attention to the production of the experimental data and the identification of the model parameters. The quality of the decisions made in the construction of a model is shown to be most critically evaluated when derivative feedback loops are employed. A study of a system with negative transient acceleration feedback is included to illustrate the effectiveness of a third-order model. It is demonstrated that the use of a digital computer is essential for this type of system design.
New products introduced by consumer goods companies operating in many market sectors are often no... more New products introduced by consumer goods companies operating in many market sectors are often not as successful as expected even though they are functionally reliable and produced to a consistent standard. They do not seem to connect with the feelings of customers who are rejecting anything that does not truly satisfy them in the way that they want to live. The Japanese realised earlier than most that their product development methods just did not reveal the deep insights into customers’ feelings that enabled emotional needs to be satisfied. They have developed methods and tools to overcome this, supporting the creation of products targeted to meet those needs, that they call Kansei Engineering. This report is about a mission to Japan to study that. Experience of the use of Kansei Engineering was sought from the food and drink (Asahi Breweries Ltd.), packaging (Toppan Printing Co. Ltd.), building products (Matsushita Electric Works Ltd.), cosmetics (Shiseido Company Ltd., Milbon Co...
Proceedings of SPIE, Oct 1, 2001
ABSTRACT In the age of manufacturing globalization, individual organizations are finding it incre... more ABSTRACT In the age of manufacturing globalization, individual organizations are finding it increasingly difficult to compete: prices are being driven down, quality demands are being increased and lead times are being reduced. Under these market conditions, it is networks, rather than individual organizations, that compete. The majority of manufacturing organizations operate, at some scale, within 'manufacturing chains or networks.' This is the basis of the 'Virtual Enterprise (V-E).' For V-Es to be viable, they must consistently perform in the way that is required by their stakeholders. Hence, there is a need for tools to allow potential V-E structures to be configured and evaluated: so- called V-E design tools. A key aspect of any V-E design tool is a well-founded way of describing V-Es. This is an early step in the establishment of tools to enable the evaluation of V-E configurations. Such a characterization would support the evaluation of V-E configuration alternatives. Other authors have argued that the individual elements (organizations) and the relationships between them are critical to the performance of the V-E. This paper describes a characterization scheme that draws upon other published research, and is a first step in systematizing V-E descriptions. The characterization scheme is evaluated through a case study.
ABSTRACT Development of IT and its applications have led to significant changes in business proce... more ABSTRACT Development of IT and its applications have led to significant changes in business processes. To pursue agility, flexibility and best service to customers, enterprises focus on their core competence and dynamically build relationships with partners to form virtual enterprises as customer driven temporary demand chains/networks. Building the networked enterprise needs responsively interactive decisions instead of a single-direction partner selection process. Benefits and risks in the combination should be systematically analysed, and aggregated information about value-adding abilities and risks of networks needs to be derived from interactions of all partners. In this research, a hierarchical information model to assess partnerships for designing virtual enterprises was developed. Internet technique has been applied to the evaluation process so that interactive decisions can be visualised and made responsively during the design process. The assessment is based on the process which allows each partner responds to requirements of the virtual enterprise by planning its operational process as a bidder. The assessment is then produced by making an aggregated value to represent prospect of the combination of partners given current bidding. Final design is a combination of partners with the greatest total value-adding capability and lowest risk.
Proceedings of the Design Society
Applications of machine learning technologies are becoming ubiquitous in many sectors and their i... more Applications of machine learning technologies are becoming ubiquitous in many sectors and their impacts, both positive and negative, are widely reported. As a result, there is substantial interest from the engineering community to integrate machine learning technologies into design workflows with a view to improving the performance of the product development process. In essence, machine learning technologies are thought to have the potential to underpin future generations of data-enabled engineering design system that will deliver radical improvements to product development and so organisational performance. In this paper we report learning from experiments where we applied machine learning to two shape-based design challenges: in a given collection of designed shapes, clustering (i) visually similar shapes and (ii) shapes that are likely to be manufactured using the same primary process. Both challenges were identified with our industry partners and are embodied in a design case st...
Systems Engineering
The architectures of extended enterprises, including the supply networks that design, develop and... more The architectures of extended enterprises, including the supply networks that design, develop and support large, complex, engineered products, often reflect system‐level design decisions made very early in the product development process. Design tools used at this, preliminary design, stage focus on the physics and optimization of product system behaviors. Comparable tools for the consideration of extended enterprise perspectives at this stage are not available despite the costs of non‐quality often attributed to supply chain issues related to early design decisions. This paper introduces an interface to a discrete event simulation package that derives supply chain processes from product system architectures, so enabling the quantification and visualization of supply chain risk in early design decisions. The interface uses input data, in the form of a product architecture and associated make‐buy scenarios, which are available in the preliminary design process. Supplier data needed t...
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Papers by Alan Pennington