5,171 research outputs found
A next generation manufacturing control system for a lean production environment
This thesis focuses on addressing the need for a new approach to the design and
implementation of manufacturing control systems for the automotive industry and in
particular for high volume engine manufacture. Whilst the operational domain in the
automotive industry has moved to lean production techniques, the design of presentday
manufacturing control systems is still based on systems intended for use in a mass
production environment. The design and implementation of current manufacturing
control systems is therefore inappropriate when viewed from a business context. The
author proposes that it is possible to create a more appropriate manufacturing control
systems based on an optimised use of advanced manufacturing technology within the
complete business context.
Literature is reviewed to provide a detailed understanding of the relationship between
modem operating practices and the application of contemporary control systems. The
primary tasks of manufacturing control systems, within the context of a structured
systems approach to manufacturing technology, production management and
industrial economics are identified. A study of modem manufacturing control system
technology is carried out, highlighting the fundamental principles that influence
application engineering in this area.
The thesis develops a conceptual design framework that aids the identification of
attributes required of a next generation manufacturing control system (NGCS), in
order to enhance the business performance of lean automotive manufacturing. The
architecture for a next generation control system is specified and a Proof of concept
system implemented. Potential advances over contemporary practice are identified
with the aid of a practical implementation at a major automotive manufacturer
Realising the open virtual commissioning of modular automation systems
To address the challenges in the automotive industry posed by the need to rapidly manufacture more
product variants, and the resultant need for more adaptable production systems, radical changes are
now required in the way in which such systems are developed and implemented. In this context, two
enabling approaches for achieving more agile manufacturing, namely modular automation systems
and virtual commissioning, are briefly reviewed in this contribution. Ongoing research conducted at
Loughborough University which aims to provide a modular approach to automation systems design
coupled with a virtual engineering toolset for the (re)configuration of such manufacturing
automation systems is reported. The problems faced in the virtual commissioning of modular
automation systems are outlined. AutomationML - an emerging neutral data format which has
potential to address integration problems is discussed. The paper proposes and illustrates a
collaborative framework in which AutomationML is adopted for the data exchange and data
representation of related models to enable efficient open virtual prototype construction and virtual
commissioning of modular automation systems. A case study is provided to show how to create the
data model based on AutomationML for describing a modular automation system
Resolved Depletion Zones and Spatial Differentiation of N2H+ and N2D+
We present a study on the spatial distribution of N2D+ and N2H+ in thirteen
protostellar systems. Eight of thirteen objects observed with the IRAM 30m
telescope show relative offsets between the peak N2D+ (J=2-1) and N2H+ (J=1-0)
emission. We highlight the case of L1157 using interferometric observations
from the Submillimeter Array and Plateau de Bure Interferometer of the N2D+
(J=3-2) and N2H+ (J=1-0) transitions respectively. Depletion of N2D+ in L1157
is clearly observed inside a radius of ~2000 AU (7") and the N2H+ emission is
resolved into two peaks at radii of ~1000 AU (3.5"), inside the depletion
region of N2D+. Chemical models predict a depletion zone in N2H+ and N2D+ due
to destruction of H2D+ at T ~ 20 K and the evaporation of CO off dust grains at
the same temperature. However, the abundance offsets of 1000 AU between the two
species are not reproduced by chemical models, including a model that follows
the infall of the protostellar envelope. The average abundance ratios of N2D+
to N2H+ have been shown to decrease as protostars evolve by Emprechtinger et
al., but this is the first time depletion zones of N2D+ have been spatially
resolved. We suggest that the difference in depletion zone radii for N2H+ and
N2D+ is caused by either the CO evaporation temperature being above 20 K or an
H2 ortho-to-para ratio gradient in the inner envelope.Comment: Accepted to ApJ. 44 pages 13 Figure
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