Wind turbines are nowadays one of the most promising energy sources. Every year, the amount of energy produced from the wind grows steadily. Investors demand turbine manufacturers to produce bigger, more efficient and robust units. These requirements resulted in fast development of condition-monitoring methods. However, significant sizes and varying operational conditions can make diagnostics of the wind turbines very challenging. The paper shows the case study of a wind turbine that had suffered a serious rolling element bearing (REB) fault. The authors compare several methods for early detection of symptoms of the failure. The paper compares standard methods based on spectral analysis and a number of novel methods based on narrowband envelope analysis, kurtosis and cyclostationarity approach. The very important problem of proper configuration of the methods is addressed as well. It is well known that every method requires setting of several parameters. In the industrial practice, configuration should be as standard and simple as possible. The paper discusses configuration parameters of investigated methods and their sensitivity to configuration uncertainties
In this paper, some issues of building a reliable, distributed measurement system for monitoring of water quality in reservoir Lake Dobczyckie are presented. The system is based on a measurement station that has the shape of a floating buoy which is supposed to be at anchor on the reservoir. Wireless data transmission problems that were encountered during the development of the buoy, modeling a radio link, and measurements of actual signal strength on the reservoir are discussed. A mathematical approach to procedures of early situation assessment was conducted, and specialized procedures were designed for measurement stations of the system. It is also discussed how such computations can improve a qualitative assessment of system performance in terms of real-time messaging
This paper presents a solution that utilises ultrasonic technology to allow monitoring snow layer thickness or water level based on measurement from air. It describes the principle of operation of a measurement device using three methods of compensating for changing external factors affecting appliance’s precision. Block diagram of the device is also provided. In order to verify the proposed solutions, the research team tested the device in laboratory and operating conditions. The results obtained this way make it possible to select a configuration of device operation depending on the required measurement precision and limitations associated with installing the system for actual operation.
The purpose of this work is to distinguish between Acoustic Emission (AE) signals coming from mechanical friction and AE signals coming from concrete cracking, recorded during fourteen seismic simulations conducted with the shaking table of the University of Granada on a reinforced concrete slab supported on four steel columns. To this end, a particular criterion is established based on the Root Mean Square of the AE waveforms calculated in two different temporal windows. This criterion includes a parameter calculated by optimizing the correlation between the mechanical energy dissipated by the specimen (calculated by means of measurements with accelerometers and displacement transducers) and the energy obtained from the AE signals recorded by low-frequency piezoelectric sensors located on the specimen. The final goal of this project, initiated four years ago, is to provide a reliable evaluation of the level of damage of Reinforced Concrete specimens by means of AE signals to be used in future Structural Health Monitoring strategies involving RC structures.
This paper presents results obtained from a laboratory investigation conducted on material from a pressure vessel after longterm operation in the oil refinery industry. The tested material contained structural defects which arose from improper heat treatment during steel plate manufacturing. Complex tensile tests with acoustic emission signal recording were conducted on both notched and unnotched specimens. The detailed analysis of different acoustic emission criteria allowed as to detect each stage of plastic deformation and microstructural damage processes after a long-term operation, and unused carbon steels during quasi-static axial tension testing. The acoustic emission activity, generated in the typical stages of material deformation, was correlated by microscopy observations during the tensile test. The results are to be used as the basis for new algorithms for the assessment of the structural condition of in-service pressure equipment.
The order Passeriformes is the most successful group of birds on Earth, however, its representatives are rare visitors beyond the Polar Front zone. Here we report a photo−documented record of an Austral Negrito ( Lessonia rufa ), first known occurrence of this species in the South Shetland Islands and only the second such an observation in the Antarctic region. This record was made at Lions Rump, King George Island, part of the Antarctic Specially Protected Area No. 151 (ASPA 151). There is no direct evidence of how the individual arrived at Lions Rump, but ship assistance cannot be excluded.
Here we report a photo−documented record of a barn swallow ( Hirundo rustica ) from the South Shetland Islands. We also review previous records of passerine vagrants in the Antarctic (south of the Antarctic Convergence Zone). This barn swallow is the first re− corded member of the Hirundinidae family on King George Island and is only the second passerine recorded in the South Shetland Islands. This sighting, along with previous records of austral negrito and austral trush represent the southernmost sightings of any passerine bird anywhere in the world.
Winglets are introduced into modern aircraft to reduce wing aerodynamic drag and to consequently optimize the fuel burn per mission. In order to be aerodynamically effective, these devices are installed at the wing tip section; this wing region is generally characterized by relevant oscillations induced by flights maneuvers and gust. The present work is focused on the validation of a continuous monitoring system based on fiber Bragg grating sensors and frequency domain analysis to detect physical condition of a skin-spar bonding failure in a composite winglet for in-service purposes. Optical fibers are used as deformation sensors. Short Time Fast Fourier Transform (STFT) analysis is applied to analyze the occurrence of structural response deviations on the base of strain data. Obtained results showed high accuracy in estimating static and dynamic deformations and great potentials in detecting structural failure occurrences.
Real-time monitoring of deformation of large structure parts is of great significance and the deformation of such structure parts is often accompanied with the change of curvature. The curvature can be obtained by measuring changes of strain, surface curve and modal displacement of the structure. However, many factors are faced with difficulty in measurement and low sensitivity at a small deformation level. In order to measure curvature in an effective way, a novel fibre Bragg grating (FBG) curvature sensor is proposed, which aims at removing the deficiencies of traditional methods in low precision and narrow adjusting. The sensor combines two FBGs with a specific structure of stainless steel elastomer. The elastomer can transfer the strain of the structure part to the FBG and then the FBG measures the strain to obtain the curvature. The performed simulation and experiment show that the sensor can effectively amplify the strain to the FBG through the unique structure of the elastomer, and the accuracy of the sensor used in the experiment is increased by 14% compared with that of the FBG used for direct measurement.
The condition monitoring techniques like acoustic emission, vibration analysis, and infrared thermography, used for the failure diagnosis of bearings, require longer processing time, as they have to perform acoustical measurement followed by signal processing and further analysis using special software. However, for any bearing, its period of usage can be easily determined within an hour, by measuring the bearing sound, using sound level meter (SLM). In this paper the acoustical analysis of the spindle bearing of a radial drilling machine was performed using SLM, by measuring the sound pressure level of the bearing in decibels, for different frequencies, while muting all the other noises. Then using an experimental set up, two database readings were taken, one for new bearing and the other for completely damaged bearing, both are SKF6207, which itself is the spindle bearing. From these three sets of sound pressure level readings, the period of usage of the spindle bearing, was calculated using an interpolation equation, by substituting the life of the bearing from the manufacturer’s catalogue. Therefore, for any machine with a SKF6207 bearing, its usage time can be estimated using the database readings and one measurement on that machine, all with the same speed.
This paper presents the results of direct 3−D fault displacement monitoring along the northern shore of Hornsund Fjord, SW Spitsbergen, Svalbard. The fault displacements have been recorded using three permanently installed optical−mechanical crack gauges since 2009. The monitoring data from all three sites provided evidence for a remarkable slip event that lasted from September 2011 to May 2012. The cause is discussed in some detail with consideration given to both exogenic (temperature changes, surface processes) and endogenic processes (isostatic rebound and regional seismicity). It is proposed that transient fault slips recorded had a tectonic origin and were caused by approximately W−E oriented compression corresponding to regional compression in the Svalbard area.
The quantity of deposited metals was determined in the tissues of Cepaea nemoralis, Lumbricus terrestris and Geotrupes stercorarius, as well as in plant and soil samples from two locations characterized by different levels of human impact. The bioaccumulation factor (BAF) of metals in the bodies of these invertebrate taxa occupying the same habitats was compared, in relation to their content in Taraxacum officinale leaves and in the soil. Analysis of the content of metals in the bodies of selected species belonging to different taxonomic groups demonstrates the usefulness of these invertebrates in biomonitoring.
This paper describes the concept of controlling the advancement speed of the shearer, the objective of which is to eliminate switching the devices off to the devices in the longwall and in the adjacent galleries. This is connected with the threshold limit value of 2% for the methane concentration in the air stream flowing out from the longwall heading, or 1% methane in the air flowing to the longwall. Equations were formulated which represent the emission of methane from the mined body of coal in the longwall and from the winnings on the conveyors in order to develop the numerical procedures enabling a computer simulation of the mining process with a longwall shearer and haulage of the winnings. The distribution model of air, methane and firedamp, and the model of the goaf and a methanometry method which already exist in the Ventgraph-Plus programme, and the model of the methane emission from the mined longwall body of coal, together with the model of the methane emission from the winnings on conveyors and the model of the logic circuit to calculate the required advancement speed of the shearer together all form a set that enables simulations of the control used for a longwall shearer in the mining process. This simulation provides a means for making a comparison of the output of the mining in the case of work using a control system for the speed advancement of the shearer and the mining performance without this circuit in a situation when switching the devices off occurs as a consequence of exceeding the 2% threshold limit value of the methane concentration. The algorithm to control a shearer developed for a computer simulation considers a simpler case, where the logic circuit only employs the methane concentration signal from a methane detector situated in the longwall gallery close to the longwall outlet.
The paper puts forward and implements a method of designing and creating a modelling simulation environment for extensive and complete analysis of economical lighting on highways. From a general design viewpoint, the proposed solution explores the concept of a network description language (SMOL), which has been designed to describe the necessary network functions, mechanisms, and devices for the purpose of their computer simulation and verification. The presented results of the performed research confirm the usability of intelligent lighting on highways, both in the sense of the design concept and in the aspect of saving energy.
In this work problems associated with requirements related to pollution emissions in compliance with more restrictive standards, low-emission combustion technology, technical realization of the monitoring system as well as algorithms allowing combustion process diagnostics are discussed. Results of semi-industrial laboratory facility and industrial (power station) research are presented as well as the possibility of application of information obtained from the optical fibre monitoring system for combustion process control. Moreover, directions of further research aimed to limit combustion process environmental negative effects are presented.
Embedding cardiac system sensing devices in wheelchairs is both necessary and attractive. Elders, diabetics, or stroke victims are a substantial group needing permanent cardiac monitoring, without restriction of their already limited mobility. A set of sensing devices was embedded in a wheelchair to monitor the user without his awareness and intervention. A dual-wavelength reflection photoplethysmogram (PPG), and a ballistocardiogram (BCG) based on MEMS accelerometers and on electromechanical film sensors are output by the hardware. Tests were conduced on twenty one subjects, for an immobility scenario. Additional recordings were made for helped propulsion over a tiled floor course, with good results in keeping track of acceleration BCG and PPG. A treadmill was also used for tests, providing a smooth floor and constant speed and inclination. The PPG and acceleration BCG could be continuously monitored in all the tests. The developed system proves to be a good solution to monitor cardiac activity of wheelchair users even during motion.
The function of a new estimation procedure of long-term noise indicators is considered in this study. New possibilities are related to the stochastic modelling of the control data formation mechanism. Assuming the mathematical formalism based on the adaptive model of exponential smoothing of control data, the need of controlling at each estimation stage of long-term noise indicators, the adherence to the model assumptions is formulated. The procedure of its realisation is described in the paper. The tracking signal method referred to the tested errors of the assumed model was applied. The ratio of the sum of model errors in relation to the average absolute error, generated by the assumed approximation, was selected as the representative of the tracking signal. Conditions for the acceptation of the model assumption were defined. The analysis of functionality of the developed solution was illustrated by the results of a continuous noise monitoring recorded at one of the main arteries in Kraków.
The implemented online urban noise pollution monitoring system is presented with regard to its conceptual assumptions and technical realization. A concept of the noise source parameters dynamic assessment is introduced. The idea of noise modeling, based on noise emission characteristics and emission simulations, was developed and practically utilized in the system. Furthermore, the working system architecture and the data acquisition scheme are described. The method for increasing the speed of noise map calculation employing a supercomputer is explained. The practical implementation of noise maps generation and visualization system is presented, together with introduced improvements in the domain of continuous noise monitoring and acoustic maps creation. Some results of tests performed using the system prototype are shown. The main focus is put on assessing the efficiency of the acoustic maps created with the discussed system, in comparison to results obtained with traditional methods.
Random nature of corona processes in UHV power lines and the accompanying noise is the reason that in practice the best determination of acoustic parameters, necessary for the noise evaluation, is obtained from the continuous monitoring procedure. However because of considerable fluctuations (both the useful signal part and the interfering components), careful selection of monitored parameters is necessary to enable a possibility of automatic determination of the parameters that are required for long-term evaluation of corona noise. In the present work a practical realization is shown for estimation of corona noise parameters, based on the data obtained from continuous monitoring stations, making use of the statistical spectra measurement and characteristic features of corona process acoustic signal. Selected results are presented from continuous monitoring of corona noise generated at a 400 kV power line, with special attention focused on definitions of the measured quantities, which enable automatic estimation of the basic factors required for noise evaluation. Accompanying monitoring of environmental conditions, including humidity, precipitation intensity and fog density, that are well correlated with the corona process intensity, which might definitely increase the filtration efficiency of environmental disturbances and on the other hand, it enables verification of calculation methods applied to corona noise. The paper also contains a description of practical approach to selection signal parameters of corona noise in continuous monitoring stations.
Balanced distribution of air in coal-fired boiler is one of the most important factors in the combustion process and is strongly connected to the overall system efficiency. Reliable and continuous information about combustion airﬂow and fuel rate is essential for achieving optimal stoichiometric ratio as well as efficient and safe operation of a boiler. Imbalances in air distribution result in reduced boiler efficiency, increased gas pollutant emission and operating problems, such as corrosion, slagging or fouling. Monitoring of air ﬂow trends in boiler is an effective method for further analysis and can help to appoint important dependences and start optimization actions. Accurate real-time monitoring of the air distribution in boiler can bring economical, environmental and operational benefits. The paper presents a novel concept for online monitoring system of air distribution in coal-ﬁred boiler based on real-time numerical calculations. The proposed mathematical model allows for identification of mass ﬂow rates of secondary air to individual burners and to overﬁre air (OFA) nozzles. Numerical models of air and flue gas system were developed using software for power plant simulation. The correctness of the developed model was verified and validated with the reference measurement values. The presented numerical model for real-time monitoring of air distribution is capable of giving continuous determination of the complete air flows based on available digital communication system (DCS) data.
The present paper is devoted to the discussion and review of the non-destructive testing methods mainly based on vibration and wave propagation. In the first part, the experimental methods of actuating and analyzing the signal (vibration) are discussed. The piezoelectric elements, fiber optic sensors and Laser Scanning Doppler Vibrometer (SLDV) method are described. Effective detecting of the flaws needs very accurate theoretical models. Thus, the numerical methods, e.g. finite element, spectral element method and numerical models of the flaws in isotropic and composite materials are presented. Moreover, the detection of the damage in structures, which are subjected to cyclic or static loads, is based on the analyzing of the change in natural frequency of the whole structure, the change of internal impedance of the material and the change in guided waves propagating through the investigated structure. All these cases are characterized in detail. At the end of this paper, several applications of the structural health monitoring systems in machine design and operation are presented.