Simulating for ‘resource optimization’ in robot‐assisted automatic assembly

In most manufacturing systems emphasis is now given to resource flexibility in operation. The aim is to respond swiftly to changes in product mix and/or market demands. Discrete event computer simulation is seen as a tool in defining a suitable system configuration at the preliminary design stage. Furthermore, simulation in dynamic form can represent the interactions between the system components and provide a detailed prediction of its performance. Although many existing computer simulation packages have reached a good level of general purpose modelling, by and large they lack the required versatility to deal with some specific features of manufacturing systems. One such important area is the robot‐assisted automatic assembly where minimization of non‐productive activities in the product assembly cycle is of vital interest. The paper introduces a flexible modelling technique which identifies the resource utilization and optimization levels during the individual processes of a product assembly cycle. Within the working constraints of an assembly system, an ‘optimal’ robot sequential cycle is obtained by implementing this modelling technique in GPSL (general purpose simulation language)

Multi-body dynamics: historical evolution and application

The historical developments in the discipline of engineering dynamics are briefly reviewed, with attention paid to the formulation and solution of the dynamic behaviour of multi-body systems. It is shown that the dynamic characteristics of practical multi-body systems are dependent upon the interactions of many physical phenomena that can induce, restrain or constrain motion of parts. The long process of understanding and formulating the physics of multi-body motions, in some cases with pioneering contributions centuries old, together with continual refinements in numerical techniques and enhanced computing power has resulted in the solution of quite complex and practical engineering problems. Linking the historical developments to the fundamental physical phenomena and their interactions, the paper presents solutions to two complex multi-body dynamic problems. The practical implications of the approach in design of these systems are highlighted

Special relativity: interpretation and implications for space-time geometry

The paper commemorates the centenary of the special theory of relativity, which effectively sets the limit for the structure of space-time to that of the stationary system. The long lasting debate for definition of concepts of instantaneity and simultaneity was thus resolved by the declaration of constancy of speed of light in vacuo as a law of physics. All motions were thus bounded by the light cone and described by the properties of differential geometry, firmly anchored in the calculus of variations. The key contribution underpinning the theory was the resolution of the contradiction imposed by the Galilean transformation through physical explanation and the adoption of the Lorentzian transformation. This highlighted the relative nature of both space and time and the linkage of these to preserve the sanctity of the light cone. The resulting space-time geometry was then founded on the traditional calculus of variation with the addition of this transformation. This retains the time as an independent coordinate and its linkage to space in an explicit form. One implication of this approach has been the retention of the concept of infinitum for some physical quantities as a drawback for use of the Lorentzian transformation. The paper shows that this singular behaviour need not arise if the explicit linkage in space-time is abandoned in favour of the implicit inclusion of time as a link between the curved structure of space and the speed of light, thus restating the calculus of variation in line with special relativity. This points to a closed loop space-matter field, which may belie the fabric of the continuum. One implication of this interpretation is that a small variation in speed of light within the field would be required to dispense with the aforementioned singular nature of the Lorentzian boost, while still remaining within the spirit of special relativity

Relativity: 300 years from a principle to reality

This technical note provides a brief background to the historical developments that led to the generalization of Galileo's principle of relativity, leading to Einstein's general theory of relativity. Therefore, its primary purpose is to mark the contributions made in physics of motion on this occasion—the marking of the new Millennium. To keep with the tradition set in this journal, this note contains a new analysis in respect of reported super-luminal observations in gain-assisted light propagation, in particular vis-à-vis their concordance with the general theory of relativity. The incompleteness principle, as an axiom of observation, is introduced here to resolve this issue

Physics of causality and continuum: questioning nature

This article commemorates three distinct periods in the growing understanding of physics of motion during the Renaissance (referring to advancement of art) period, the age of enlightenment (scientific renaissance: the Newtonian mechanics), and the adoption of field concept, embodied in the theory of relativity. Emphasis is put on Newton's immense and fundamental contributions and those of his immediate and subsequent contemporaries, leading to Lagrangian dynamics, which is the cornerstone of many contributions to this journal. In particular, a generic geometric interaction potential is introduced within a closed field, which conforms to Newton's law of universal gravitation and extends to the scale of microcosm, thus embedding gravity with other forces of nature. The implications of these extensions to the Newtonian potential are discussed

Editorial: commemorating Einstein's special theory of relativity

Editorial: commemorating Einstein's special theory of relativit

Editorial

Editoria

An introduction to multi-physics multi-scale approach

Dynamics and tribology, described in this book, may be regarded as subsets of physics of motion (in a multi-physics perspective). Dynamics is the study of motion of entities caused by the underlying forces. Historically, in the discipline of dynamics and within engineering these entities have been considered to be assembly of parts (a system), solid inertial elements (a component) and rigid particles. When the study of motion of a material point (a generic term used to describe these entities; a particle, a body: a conglomerate of such particles or a system: an assembly or cluster of bodies) is observation-based only (without regard to the underlying cause: force), then the field of investigation is referred to as kinematics. In the case of a multibody or a many-body system, kinematics refer to studies with no degrees of freedom; relative motions between their constituent material points (their motion is pre-specified)

Editorial

Editoria

Blood flow measurement using a highly filled carbon polymer sandwich sensor and an elasto‐pseudo compressible vascular flow

Vascular grafts are widely employed in clinical practice and still pose significant problems of compatibility and longevity, particularly when the prosthesis is to replace arteries of small diameter. Once a graft has been implanted in the vascular tree, there is no easy way of assessing its interactions with the surrounding tissue. Doppler flow probes or some imaging techniques are commonly used to monitor flow velocity in vascular prostheses. It is, however, difficult to monitor a patient's recovery on a continuous basis. Continuous means of measurement can be quite invaluable. This paper presents a high‐carbon filled polymer (HCFP) sensor that is developed for blood flow measurement in vascular grafts. Furthermore, a computational fluid dynamics model of incompressible blood flow in elastic blood vessels is presented