An Integrated Vision-Force System for Peg-in-hole Assembly Operations

In this article the integration of an artificial vision system and a 6-component force-torque sensor for high accuracy insertions is proposed. The former has the advantage of intervening before the contact of the two parts and providing an initial correction to allow the force sensor action; the latter is charged of completing the operation through the control of a neural network. An experimental facility has been developed for performance assessment. Two monochromatic CCD cameras are positioned with the optical axes perpendicular to each other, outside the working area in order not to interfere with the assembly operations. During tests it has been shown that the artificial vision system yields a fast, reliable and accurate measurement, by direct comparison with a co-ordinate-measuring machine. Results show that the use of an integrated vision-force sensor represents a complete solution to the peg-in-hole problem. Furthermore the 3-D localisation algorithm implemented on the vision system and the problems concerned with the system engineering are dealt with

Analyses of stone surfaces by optical methods

Ornamental stone products are generally used for decorative cladding. A major quality parameter is their aesthetical appearance, which directly impacts their commercial value. The surface quality of stone products depends on the presence of defects both due to the unpredictability of natural materials and to the actual manufacturing process. This work starts reviewing the literature about optical methods for stone surface inspection. A classification is then proposed focusing on their industrial applicability in order to provide a guideline for future investigations. Three innovative systems are proposed and described in details: a vision system, an optical profilometer and a reflectometer for the inspection of polished, bush-hammered, sand-blasted, flame-finished, waterjet processed, and laser engraved surfaces

Design and development of a vision based leather trimming machine

The objective of the work described in this paper is to demonstrate a laboratory prototype for trimming the external part of a hide, assuming that the resulting machine would eventually form part of a completely automatic system in which hides are uploaded, inspected and parts for assembly are downloaded without manual intervention and prior sorting. Detailed literature and international standards are included. The expected advantages of integrating all vision based functions in a single machine, whose basic architecture is proposed in the paper, are also discussed. The developed system is based on a monochrome camera following the leather contour. This work focuses on the image processing algorithms for defect detection on leather and the NC programming issues related to the path following optimization, which have been successfully tested with different leather types

A new catalog of photometric redshifts in the Hubble Deep Field

Using the newly available infrared images of the Hubble Deep Field in the J, H, and K bands and an optimal photometric method, we have refined a technique to estimate the redshifts of 1067 galaxies. A detailed comparison of our results with the spectroscopic redshifts in those cases where the latter are available shows that this technique gives very good results for bright enough objects (AB(8140) < 26.0). From a study of the distribution of residuals (Dz(rms)/(1+z) ~ 0.1 at all redshifts) we conclude that the observed errors are mainly due to cosmic variance. This very important result allows for the assessment of errors in quantities to be directly or indirectly measured from the catalog. We present some of the statistical properties of the ensemble of galaxies in the catalog, and finish by presenting a list of bright high-redshift (z ~ 5) candidates extracted from our catalog, together with recent spectroscopic redshift determinations confirming that two of them are at z=5.34 and z=5.60.Comment: 28 pages, 12PS+4JPEG figures, aaspp style. Accepted for publication in The Astrophysical Journal. The catalog, together with a clickable map of the HDF, Tables 4 and 5 (HTML, LaTeX or ASCII format), and the figures, are available at http://bat.phys.unsw.edu.au/~fsoto/hdfcat.htm

Diamond wire cutting of cast iron

Diamond wire has been the standard industrial practice in stone excavation for over three decades now. Today new applications in the construction and controlled demolition industry are emerging, which involve the cutting of metals and sometimes diamond wire seems the only viable solution. Diamond tool life cutting metals is about one order of magnitude lower than stone, so a better knowledge of this process is of direct industrial interest. In this paper we report the main results of experimental tests for a cylindrical and a tapered electroplated diamond bead cutting cast iron UNI G250. Experimental data to estimate the optimal process parameters and predict tool life are reported and an experimental model is presented. In addition a new tool wear criterion and a new standardized testing method for diamond bead cutting of cast iron and to compare the performance of different diamond bead ..

The Process Control in Manufacturing: Inspection of Ball Bearings

A real industrial case has been analyzed and is discussed in this paper. Significant percentage of defective ball bearings is not detected during the final inspection in the only manual station of the automatic assembly line. The main specifications of an inspection system, which is based on artificial vision, are pointed out. The system configuration (camera, lighting and ball bearing support) is described in detail. The visibility of all surfaces has been optimized using one central conic and four lateral mirrors. In off-line tests, the described algorithms allowed the recognition of most surface defects. Interactive and user-friendly calibration procedures have also been defined

HI Fluctuations at Large Redshifts: II - the Signal Expected for GMRT

For the GMRT, we calculate the expected signal from redshifted HI emission at two frequency bands centered at 610 and 325 MHz. The study focuses on the visibility-visibility cross-correlations, proposed earlier as the optimal statistical estimator for detecting and analyzing this signal. These correlations directly probe the power spectrum of density fluctuations at the redshift where the radiation originated, and thereby provide a method for studying the large scale structures at large redshifts. We present detailed estimates of the correlations expected between the visibilities measured at different baselines and frequencies. Analytic fitting formulas representing the salient features of the expected signal are also provided. These will be useful in planning observations and deciding an optimal strategy for detecting this signal.Comment: 16 pages including 7 figures, published in JAp

Sustained impairment of human cytomegalovirus (HCMV)-specific CD4+ and CD8+ T cell response is responsible for recurrent episodes of disseminated HCMV infection in a D+R- hand transplant recipient

Human cytomegalovirus (HCMV) infection is the major viral complication in solid organ transplant recipients. Seronegative recipents (R-) of organs from seropositive donors (D+) appear to be at higher risk of developing symptomatic HCMV infection. To what extent systemic life-threatening complications can be risked for non-life-saving transplant procedures? A case report describing successful treatment of repeated episodes of active HCMV infection in a D+R- hand recipient in the absence of HCMV-specific T-cell immunity is presented. In the attempt to save both the patient and the transplanted hand, a preemptive treatment strategy was adopted with the aim to boost the constitution of the virus-specific T-cell immune response and simultaneously avoid onset of disease. Careful monitoring of HCMV load in blood and HCMV-specific T-cell immunity guided administration of repeated courses of antiviral treatment and avoided emergence of HCMV-related symptoms. Following establishment of HCMV-specific CD4+ and CD8+ T-cell response, preemptive treatment was no longer required due to sustained HCMV disappearance from blood. The patient is now well, and his hand too. In conclusion, evaluation of virus-specific T-cell immunity is of crucial importance in D+R- transplant recipients and careful monitoring of HCMV-specific T cell mediated response should always parallel monitoring of HCMV load in transplant recipients

Programma Nazionale di Ricerca SPI (Sistemi di Produzione Innovativi) - Tema 5: Sistema automatizzato flessibile e adattativo di saldatura - Linea 3.3: Controllo di processo: controllo on-line - Relazione finale

Sulla base degli accordi di collaborazione con gli altri partner del progetto, quest’attivita` di sviluppo è stata orientata all’integrazione tra le diverse parti del sistema finale di saldatura robotizzato allo scopo di realizzare un dimostratore per un caso di interesse industriale: la placcatura di lastre con saldatrice robotizzata MIG/MAG presso l’Ansaldo Energia di Legnano (MI). Per fare questo è stato necessario, tra l’altro, progettare e realizzare un’attrezzatura completa per lo svolgimento di prove sperimentali di saldatura presso detto partner industriale, onde poter disporre di immagini correttamente acquisite. Secondo quanto stabilito sono stati analizzati: la pozza fusa e il cordone in fase di solidificazione, ed è stato creato un atlante di immagini ottenute da saldature create artificialmente con difetti. Sono stati analizzati i problemi di integrazione tra il sistema di analisi dell’immagine del giunto saldato messo a punto e il sistema di acquisizione sviluppato dall’Istituto RTM di Vico Canavese (Ivrea). Sulle immagini acquisite con il sistema sviluppato e su quelle fornite dall’Istituto RTM sono stati implementati e testati gli algoritmi di analisi ed è stata individuata una possibile strategia di controllo. E’ stata inoltre ampliata e aggiornata la ricerca bibliografica

Influence of cross-sectional geometry on mixing in a T-shaped micro-junction

Microfluidics is gaining increasing interest in the field of chemical engineering, as miniaturization may lead to a significant intensification of chemical processes. Since the flow is laminar, achieving a good mixing of reactants is one of the main challenges. The simplest geometry is constituted by a T-shaped mixer in which the two inlets join perpendicularly the mixing channel. The inlet cross section is usually square while the mixing channel cross-section is a rectangle as straight walls facilitate experimental and modelling analysis. The present work, on the contrary, is aimed at investigating through Computational Fluid Dynamics the effect of a cross-section with lateral inclined walls, to emulate a microfabrication technology based on laser machining. The presence of inclined walls is found to hamper mixing at high Reynolds numbers as the flow is unable to break the mirror symmetry and thus to undergo the engulfment regime. However, at low Reynold numbers the mixing is improved because the vortex regime presents a lower degree of symmetry with respect to that of T-mixers with straight walls