1,720,957 research outputs found
KF distance observer and destructive collision avoidance for laser cutting head
No full textNowadays laser technology is largely employed in industrial application, in particular in metal sheet cutting. The core element is represented by the laser head which is movable relative to the workpiece and has to focus the laser beam at very precise positions. A stiff distance controller keeps the laser head at a stable and very close height from the workpiece (at most few millimeters) to guarantee a good cutting quality. Therefore, it is highly exposed to risk of collisions with production scraps and with cutting table grids. This paper proposes a sensor fusion algorithm based on a discrete-time Extended Kalman Filter (EKF), which provides a noise-free laser head distance measurement and a local estimation of the geometric sheet surface slope. These features allow a quick identification both of collisions with protruded parts and laser head exits from the workpiece's edges. The presented solution aims to use only typical measurements and informations available in a standard CNC system of a laser cutting machine, without any additional sensors
Performance improvement of an industrial servopositioner using load side acceleration measurements
No full textNowadays, industrial servopositioning systems are used in many applications that demand high positioning accuracy, while requiring at the same time high dynamic movements. However, these systems often suffer from mechanical non-idealities, primarily the elasticity induced by the trasmission, which leads to load oscillation when using a standard collocated controller approach. While load side position sensors can be added to allow the use of control strategies that reduce the vibrations, this solution is often impractical in industrial environment. In this paper, we propose the use of the Acceleration Aided Kalman Filter (AAKF), which requires a low-cost load side MEMS accelerometer, to obtain accurate and robust estimates of load variables. Using load side information, two different control approaches are implemented, a PID with Active Damping and a Model Predictive Controller (MPC). The experimental results confirm that both control algorithms work as intended, considerably reducing load side vibration while using high dynamic movements, therefore reducing the cycle time of the positioning. Thus, the AAKF is validated as an effective alternative to the standard load position sensor in industrial environment
Minimum curvature path planning for a dual stage positioning system
No full textThe use of two-stage positioning systems is becoming widespread in the manufacturing industry, as they allow shortening the completion of tasks while maintaining high positioning accuracy. This paper proposes a path planning algorithm which splits the movements to be executed by the two actuators, in such a way to obtain a beneficial effect on the Macro actuator motion, in terms of smoothness and limited vibration onset. The algorithm takes advantage of the spline properties to generate a smooth geometric path and to easily account for micro actuator limited range of motion. Compared to other methods described in literature, the proposed solution only needs a sequence of end-effector poses (not related by a time law) to generate a proper sequence of poses in the joint space. The proposed solution is carried out by solving a linearly constrained quadratic programming problem
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Comparing the attitude toward the COVID-19 and the 2020/21 and 2019/20 flu vaccination campaigns among Italian healthcare workers
Full text linkBackground: While the uptake of the COVID-19 vaccine among healthcare workers (HCWs) is suboptimal, vaccine hesitancy has not been characterized in detail in this population. Objective: The aim of this study was to compare the prevalence of health-related conditions reported by HCWs during the COVID-19, 2020/21 flu, and 2019/20 flu vaccination campaigns, so to test the hypothesis that HCWs were more prone to report health conditions during the COVID-19 campaign. Methods: We analyzed vaccination questionnaires of 176 hospital-based HCWs who underwent the COVID-19 and the 2020/21 flu vaccinations; 2019/20 flu vaccination questionnaires were available for 130 of them. Outcomes included self-reported allergies, chronic diseases, and use of medications. We tested for prevalence equality, analyzed differences using the kappa statistics and concordance correlation, and explored factors associated with differences in reporting. Results: There was no difference in the proportion of HCWs reporting allergies in the three questionnaires, while chronic diseases were more frequently reported in the COVID-19 than in both 2020/21 (p = 0.04) and 2019/20 flu questionnaires (p = 0.02). Furthermore, a higher proportion of HCWs reported medications use in the COVID-19 vaccination questionnaire, compared to both the 2020/21 and the 2019/20 flu vaccination questionnaires (p < 0.001 for both). In each vaccine campaign, women reported more conditions than men, and the difference between chronic disease reports was greater for women than for men. Conclusions: Our results show more frequent reporting of health conditions during the COVID-19 than the flu vaccination campaigns, providing quantitative evidence of hesitancy of HCWs towards the COVID-19 vaccine
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
