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Condition-based preventive maintenance of machine tools

100%

Neugebauer R. , Fischer J.

tom Vol. 9, No. 3

64--76

Machine tools are expected to be highly available. Unintended failure incurs high costs for repairs and through production losses. Maintenance is a major cost factor and is still mostly reactive today, as a result of failures. Maintenance plans by manufacturers that require preventive maintenance based on running hours are often not implemented consistently. It would be ideal to perform condition-dependent preventive maintenance of the most critical and cost-intensive assemblies of a machine tool. This would make it possible to move repair times into non-productive periods and to procure any spare parts at the right time. Eventually, this would lead to cost savings. This article describes the design of a condition monitoring system for machine tools and shows ways of monitoring the most critical machine tool assemblies.

Cost-effective image acquisition system for precise PC-based measurement

80%

Pribula O. , Sedivy J. , Fischer J.

Przegląd Elektrotechniczny

2011

tom R. 87, nr 7

259-263

Image sensors based on the CMOS technology became commonly used sources of image information in PC-based vision systems. Image information is converted directly on the chip to a stream of synchronous digital data which can be transferred to a PC using the cost-effective interface introduced in this contribution. The CMOS image sensor together with the developed interface can be considered as a simple image acquisition system - USB camera matching all features of distributed image acquisition and processing model described in this article. Concept of the USB camera is enhanced by additional data merged with each image frame transferred to the PC. This feature makes the developed device suitable for tasks where the precise timing of image acquisition together with an external synchronization is required. Based on the VHDL model of the used CMOS image sensor and the designed PC interface with the USB driver, the critical timing and maximal USB data throughput limitations are analyzed and discussed.

Informacja o obrazie z czujnika obrazu typu CMOS jest bezpośrednio przetwarzana w strumień transferowany do komputera. Kamera USB może być traktowana jako system pobierania i przetwarzania informacji. W artkule analizowany jest taki system, a szczególnie timing i szybkość przepływu danych.

Designing effective habitat studies: quantifying multiple sources of variability in bat activity

70%

Fischer J. , Stott J. , Law B. S. , Adams M. D. , Forrester R. I.

tom 11

nr 1

Common aims of habitat studies are to differentiate between (i) suitable and unsuitable sites for a given species, and (ii) sites used by different communities of species. To quantify differences between sites, field data of site use must be precise enough that true underlying between-site variability is not masked by within-site measurement error. We designed a pilot study to guide the development of a survey protocol for a habitat study on bats in an agricultural landscape in southeastern Australia. Three woodland sites and two scattered tree sites of 2 ha each were surveyed for nine consecutive nights. At three locations within each site (spaced > 50 m apart) one or two Anabat detectors were mounted 1 m above ground or in a tree (2 m above ground). We used mixed regression models to quantify multiple sources of variability in bat calling activity, and graphical data analysis to visualise how increases in survey effort were likely to affect inference. For the five most active species, we found that typically over 40% of variability in nightly detections occurred at the between-site level; approximately 10% occurred between locations within sites; approximately 20% was explained by night-to-night differences; and approximately 30% of variability was not attributable to systematic variation within experimental units. Differences in community composition between sites were clearly evident when two or more detectors per site were used for four or more nights. We conclude with six general considerations for the design of effective habitat studies. These are to (i) consider key contrasts of interest; (ii) use data from mild, calm, dry nights only; (iii) calibrate detectors; (iv) use multiple detectors where possible, or move a single detector within a site; (v) survey for multiple nights; and (vi) where vertical differentiation in habitat use is likely, mount detectors at different heights. These considerations need to be balanced within the context of financial and logistical constraints.

Na Okręgowym Zjeździe Delegatów Spółdzielni Mleczarskich w...

60%

Fischer J.

Przegląd Mleczarski

1959

nr 08