A dynamics-driven approach to precision machines design for micro-manufacturing and its implementation perspectives

Precision machines are essential elements in fabricating high quality micro products or micro features and directly affect the machining accuracy, repeatability and efficiency. There are a number of literatures on the design of industrial machine elements and a couple of precision machines commercially available. However, few researchers have systematically addressed the design of precision machines from the dynamics point of view. In this paper, the design issues of precision machines are presented with particular emphasis on the dynamics aspects as the major factors affecting the performance of the precision machines and machining processes. This paper begins with a brief review of the design principles of precision machines with emphasis on machining dynamics. Then design processes of precision machines are discussed, and followed by a practical modelling and simulation approaches. Two case studies are provided including the design and analysis of a fast tool servo system and a 5-axis bench-top micro-milling machine respectively. The design and analysis used in the two case studies are formulated based on the design methodology and guidelines

Changing a semantics: opportunism or courage?

The generalized models for higher-order logics introduced by Leon Henkin, and their multiple offspring over the years, have become a standard tool in many areas of logic. Even so, discussion has persisted about their technical status, and perhaps even their conceptual legitimacy. This paper gives a systematic view of generalized model techniques, discusses what they mean in mathematical and philosophical terms, and presents a few technical themes and results about their role in algebraic representation, calibrating provability, lowering complexity, understanding fixed-point logics, and achieving set-theoretic absoluteness. We also show how thinking about Henkin's approach to semantics of logical systems in this generality can yield new results, dispelling the impression of adhocness. This paper is dedicated to Leon Henkin, a deep logician who has changed the way we all work, while also being an always open, modest, and encouraging colleague and friend.Comment: 27 pages. To appear in: The life and work of Leon Henkin: Essays on his contributions (Studies in Universal Logic) eds: Manzano, M., Sain, I. and Alonso, E., 201

Shape control of large space structures

A survey has been conducted to determine the types of control strategies which have been proposed for controlling the vibrations in large space structures. From this survey several representative control strategies were singled out for detailed analyses. The application of these strategies to a simplified model of a large space structure has been simulated. These simulations demonstrate the implementation of the control algorithms and provide a basis for a preliminary comparison of their suitability for large space structure control

Correlating low energy impact damage with changes in modal parameters: diagnosis tools and FE validation

This paper presents a basic experimental technique and simplified FE based models for the detection, localization and quantification of impact damage in composite beams around the BVID level. Detection of damage is carried out by shift in modal parameters. Localization of damage is done by a topology optimization tool which showed that correct damage locations can be found rather efficiently for low-level damage. The novelty of this paper is that we develop an All In One (AIO) package dedicated to impact identification by modal analysis. The damaged zones in the FE models are updated by reducing the most sensitive material property in order to improve the experimental/numerical correlation of the frequency response functions. These approximate damage models(in term of equivalent rigidity) give us a simple degradation factor that can serve as a warning regarding structure safety

New Inter-Modal Freight Technology and Cost Comparisons

Freight carried by rail has traditionally been mainly low value bulk commodities. As Western economies advance the market for such freight services is at best static, and forms a smaller proportion of the total demand for freight transport. There is thus an urgent need for British Rail and other rail systems to develop practical and cost effective inter-modal systems, which offer high quality services to consignors of consumer goods whose premises are not usually connected to the rail network. The new developments are of two types. Either they involve transferring the body of a road vehicle from road to rail, or moving the complete semi-trailer of an articulated outfit by rail. Each system has disadvantages in terms of volume or tare weight when compared to road, but each system may attract different commodities. Though the costs of inter-modal systems vary, their cost structures have similarities, consisting of collection and delivery costs, terminal, and rail movement elements. The break- even distance of each system depends on the extent to which low rail haulage charges offset the other costs incurred. However, traffic will only be attracted to inter-modal in sufficient quantities to enable viable services to be provided over a limited number of long distance routes. These services must also approach, if not equal the competition in terms of quality of service attributes, particularly reliability, if they are to overcome customer resistance. To assess the distances over which these new inter-modal systems will be cost competitive a cost model has been developed. The paper decribes how the model works, and the sources from which data was obtained. A separate paper (Working Paper 276) reports on a study to find the value placed by shippers on quality of service attributes, and a third paper (Working Paper 286) brings the two together to reach conclusions on the future role of inter-modal systems