A Telemetry-driven Approach to Simulate Data-intensive Manufacturing Processes

Abstract Telemetry enables the collection of data from remote points to support monitoring, analysis and visualization. It is largely adopted in Formula One car racing, where streams of live data collected from hundreds of sensors installed on car components are transmitted to the pitwall to be used as input of real-time car performance simulations. The aim of this paper is to evaluate the potential of a telemetry-driven approach in a manufacturing environment, where researchers are still looking for efficient methods to perform valuable simulations of the production processes on the basis of real data coming from the factory. The telemetry could contribute to the implementation of a virtual image of the real factory, which in turn could be used to simulate the factory performance, allowing to predict failures or investigate problems, and to reduce costly downtime. This study addresses in particular the efforts to combine and adapt methods and techniques borrowed from the field of Formula One car racing. Moreover, the investigation of the exploitation possibilities of the factory telemetry is paired with the design of a software application supporting this technology, starting from the elicitation and specification of the functional requirements

Synchronizing physical and digital factory: benefits and technical challenges

Abstract The Digital Twin is a representation of characteristics and behavior of a factory according to various levels of detail and the scope it addresses. Its full range of capabilities can be exploited when it is synchronized with the real world. Indeed, in this case, it can be used to mirror the real operating conditions for simulating the real-time behavior, and thus forecasting factory performances. However, we are still far from its large-scale diffusion. The purpose of this work is to analyze both the major challenges that still have to be faced and some potential solutions for each of the identified challenges

Semantic Virtual Factory supporting interoperable modelling and evaluation of production systems

Modelling, simulation and evaluation of manufacturing systems are relevant activities that may strongly impact on the competitiveness of production enterprises both during the design and the operational phases. This paper addresses the application of a semantic data model for virtual factories to support the design and the performance evaluation of manufacturing systems, while exploiting the interoperability between various Digital Enterprise Technology tools. The paper shows how a shared ontology-based framework can be used to generate consistent 3D virtual environments and discrete event simulation models, demonstrating this way how the proposed solution can provide an interoperable backbone for heterogeneous software tools

A SEMANTIC FRAMEWORK FOR GRAPH-BASED ENTERPRISE SEARCH

Various recent studies have shown that in many companies workers can spend near half of their time looking for information. Effective internal search tools could make their job more efficient. However, a killer application for this type of solutions is still not available. This paper introduces an envisioned architecture, which should represent the foundations of a new generation of tools for searching information within enterprises

BIG DATA: THE CURRENT WAVE FRONT OF THE TSUNAMI

In recent years, a real tsunami has flooded many human activities. Genomics, Astronomy, Particle Physics and Social Sciences are just a few examples of fields which have been intensively invaded by a massive amount of data coming from simulation, experiments or exploration. This huge pile of data requires a new way to deal with, a real paradigmatic shift respect to the past as for theories, technologies or approaches in data management. This work outlines the current wave front of Big Data, starting from a possible characterization of this new paradigm to its most compelling applications and tools, with an exploratory research of Big Data challenges in manufacturing engineering

FLAMES spectroscopy of low-mass stars in the young clusters sigma Ori and lambda Ori

Aims. We performed a detailed membership selection and studied the accretion properties of low-mass stars in the two apparently very similar young (1-10 Myr) clusters sigma Ori and lambda Ori. Methods. We observed 98 and 49 low-mass (0.2-1.0 M_sun) stars in sigma Ori and lambda Ori respectively, using the multi-object optical spectrograph FLAMES at the VLT, with the high-resolution (R=17,000) HR15N grating (6470-6790 AA). We used radial velocities, Li and Halpha to establish cluster membership and Halpha and other optical emission lines to analyze the accretion properties of members. Results. We identified 65 and 45 members of the sigma Ori and lambda Ori clusters, respectively and discovered 16 new candidate binary systems. We also measured rotational broadening for 20 stars and estimated the mass accretion rates in 25 stars of the sigma Ori cluster, finding values between 10^-11 and 10^-7.7 M_sun yr^-1 and in 4 stars of the lambda Ori cluster, finding values between 10^-11 and 10^-10.1 M_sun yr-1. Comparing our results with the infrared photometry obtained by the Spitzer satellite, we find that the fraction of stars with disks and the fraction of active disks is larger in the sigma Ori cluster (52+-9% and 78+-16%) than in lambda Ori (28+-8% and 40+-20%) Conclusions. The different disk and accretion properties of the two clusters could be due either to the effect of the high-mass stars and the supernova explosion in the lambda Ori cluster or to different ages of the cluster populations. Further observations are required to draw a definitive conclusion.Comment: 14 pages, 9 figures, 9 tables, accepted for publications in A&

An assessment of Li abundances in weak-lined and classical T Tauri stars of the Taurus-Auriga association

Accurate measurements of lithium abundances in young low-mass stars provide an independent and reliable age diagnostics. Previous studies of nearby star forming regions have identified significant numbers of Li-depleted stars,often at levels inconsistent with the ages indicated by their luminosity. We aim at a new and accurate analysis of Li abundances in a sample of ~100 pre-main sequence stars in Taurus-Auriga using a homogeneous and updated set of stellar parameters and model atmospheres appropriate for the spectral types of the sample stars.We compute Li abundances using published values of the equivalent widths of the Li 6708 A doublet obtained from medium/high resolution spectra. We find that the number of significantly Li-depleted stars in Taurus-Auriga is greatly reduced with respect to earlier results. Only 13 stars have abundances lower than the interstellar value by a factor of 5 or greater. All of them are weak-lined T Tauri stars drawn from X-ray surveys; with the exception of four stars located near the L1551 and L1489 dark clouds, all the Li-depleted stars belong to the class of dispersed low-mass stars, distributed around the main sites of current star formation. If located at the distance of Taurus-Auriga, the stellar ages implied by the derived Li abundances are in the range 3-30 Myr, greater than the bulk of the Li-rich population with implication on the star formation history of the region. In order to derive firm conclusions about the fraction of Li-depleted stars of Taurus-Auriga, Li measurements of the remaining members of the association should be obtained, in particular of the group of stars that fall in the Li-burning region of the HR diagram.Comment: Accepted for publication in Astronomy & Astrophysics. 20 pages, 5 figure

The stellar association around Gamma Velorum and its relationship with Vela OB2

We present the results of a photometric BVI survey of 0.9 square degrees around the Wolf-Rayet binary gamma^2 Vel and its early-type companion gamma^1 Vel. Several hundred PMS stars are identified and the youth of a subset of these is confirmed by the presence of lithium, H-alpha emission and X-ray activity. We show that the PMS stars are kinematically coherent and spatially concentrated around gamma Vel. The PMS stars have similar proper motions to gamma Vel, to main-sequence stars around gammaVel and to early-type stars of the wider Vela OB2 association of which gamma^2 Vel is the brightest member. The ratio of main-sequence stars to low-mass (0.1-0.6 Msun) PMS stars is consistent with a Kroupa mass function. Main-sequence fitting to stars around gamma Vel gives a distance modulus of 7.76+/-0.07 mag, consistent with a similarly-determined distance for Vela OB2 and with interferometric distances to gamma^2 Vel. High-mass stellar models indicate an age of 3-4 Myr for gamma^2 Vel, but the low-mass PMS stars have ages of ~10 Myr according to low-mass evolutionary models and 5-10 Myr by empirically placing them in an age sequence with other clusters based on colour-magnitude diagrams and lithium depletion. We conclude that the low-mass PMS stars form a genuine association with gamma Vel and that this is a subcluster within the larger Vela OB2 association. We speculate that gamma^2 Vel formed after the low-mass stars, expelling gas, terminating star formation and unbinding the association. The velocity dispersion of the PMS stars is too low for this star forming event to have produced all the stars in Vela OB2. Instead, star formation must have started at several sites within a molecular cloud, either sequentially or, simultaneously after some triggering event [abridged].Comment: Accepted for publication in MNRA