Analysis of images recorded during welding processes,

Abstract In the paper elements of a system of assessment of a welding process and welded joints have been presented. The system was based on the application of one thermovision and two CCD cameras. In the paper exemplary results of processing and analysis of thermal and ordinary images have been discussed. Introduction The course of a welding process significantly influences the quality of welds. In order to obtain high quality joints proper parameters of welding process are required to be stable. In most cases by a correct welded joints one assumes the joints which are characterized not only by required mechanical properties but also by aesthetic quality. While the selection of proper welding parameters for an experienced welder does not make difficulties, the stability of these parameters is often not easy to be ensured. Abnormality of the process is caused by numerous factors which are often random. Examples are instability of passing of a filler wire, smudges of dirt, inaccuracy of preparation of element edges, deformations of elements as effects of thermal phenomena. These factors are reasons of common welding defects, such as excessive undercuts, partial or lack of joint penetration, cracks, overheatings, excessive convexity or concavity of a face of weld, blisters, bubbles and holes Maintenance of the high quality welding process and welds can be obtained by means of constant control of process parameters. One describes different approaches to the process inspection. Examples are measurements of amperage, voltage and flow of shielding gas The main problem concerning the application of vision systems seems to be a proper image analysis. In welding industry methods based on image analysis are being used for seam tracking Issues described in the paper are a part of investigations aimed at development of a system of controlling automatic welding processes. According to this approach, the vision system consists of three cameras. A crucial role is played be an IR camera, which observes a welding arc and pool, and the joint that is getting cold. Observation of the process is also aided by two CCD cameras, which record correspondingly images representing the arc and the joint. There are two goals of image analysis. The first one is to asses the stability of welding process, which is performed by means of determination of geometrical parameters of the arc. Secondly, some common defects of joints are supposed to be detected. It should be stressed that the application of IR camera lets us to detect not only surface defects but also defects and phenomena that do not manifest themselves on the surface. Presented experiments were carried out with the use of series of samples divided into some groups characterized by: correctly prepared surface, surface covered with rust, and parts covered with some impurities Overview of the vision system The welding process can be realized with the use of different devices. In industrial production automated and equipped with robots stands are commonly used, they enable MIG or MAG welding. Usually in such automated processes elements to be joined move and a welding device passing the filled wire is motionless. The vision system elaborated within the framework of the research described in the paper has been assigned to such processes. General overview of the system was presented in figure 1. The system let us to record, archive, process, analyze and recognize two types of images acquired by three presented cameras: -hot area that includes sub-areas of arc, metal in fluid and solidification phases and welded elements, -self-cooling area consisting of weld and welded elements sub-areas. The system has included hardware and software part

Evaluation of machinery technical state on the basis of statistical features of thermographic images

Termografia jest jedną z bardzo dynamicznie rozwijających się dziedzin nauki, umożliwiającą bezkontaktowy pomiar temperatury. Znajduje ona coraz częściej zastosowanie w diagnostyce maszyn i urządzeń. Za pomocą kamery termowizyjnej możliwa jest obserwacja rozkładu temperatury w wielu punktach obserwowanego obiektu i jej jednoczesny bezkontaktowy pomiar oraz rejestracja w postaci obrazu termograficznego. Ogromny potencjał informacyjny, jaki posiada obraz termograficzny, stanowi źródło informacji diagnostycznych przydatnych w diagnozowaniu maszyn i urządzeń. W celu wydobycia tych informacji konieczne jest prowadzenie analizy obrazu termograficznego. W artykule przedstawiono wyniki badań termograficznych polegających na wyznaczaniu wybranych cech statystycznych serii obrazów termograficznych rejestrowanych w równoodległych chwilach czasu podczas działania maszyny wirnikowej.Thermography is one of the most dynamically developing domains of science, which allows us to carry out non-contact temperature measurement. It finds more often and often the application in machinery and apparatus diagnostics. With the use of a thermographic camera one can simultaneously observe the distribution of temperature in many points of an object, measure it and record in the form of a thermographic image. Immense informative potential of a thermographical image is a source of diagnostic information, which can be used in diagnosing of machines and apparatus. In order to extract this information, thermographical image analysis is necessary to be applied. In the article results of thermographical investigations were presented. The research consists in recording of thermographical images during operation of rotating machinery and their analysis with the use of statistical analysis methods of images

Thermographic Criteria of Evaluation of Technical Condition of Machinery and Equipment

Infrared thermography is used for the diagnosis purposes of various machines and devices. Despite the huge potential of thermography as a diagnostic tool, beginning thermographers are not always able to correctly assess and classify condition of the investigated object. The article presents an overview of current standards, and characterizes the methods and criteria for assessing the condition of machines and equipment

Identification of technical state on the basis of analysis of state trajectory in eigenspace

Dysponując danymi uczącymi zarejestrowanymi podczas działania obiektu w różnych chwilach czasu "makro" oraz w różnych stanach technicznych, możliwe jest wyznaczenie przekształcenia przestrzeni wartości cech do przestrzeni wartości cech głównych. Posiadając parametry przekształcenia, można wyznaczyć wartości cech głównych w dowolnych chwilach czasu "makro". Poz.wala to na wyznaczenie trajektorii wartości cech głównych w dziedzinie czasu "makro" w oparciu o nowe, wcześniej nie analizowane dane pochodzące z badanego obiektu lub obiektu tej samej klasy. Wyznaczone trajektorie mogą być cennym źródłem informacji o zachodzących zmianach stanu technicznego maszyny podczas jej eksploatacji.Learning data obtained during machine operation in different moments of "macro" time and with taking into account different technical states make it possible to obtain transformation of a space of feature values of observed signals to the eigenspace of feature values. Basing on parameters of this transformation it is possible to obtain feature eigenvalues in any moment of "macro" time. It allows us to determine feature eigenvalues trajectory in "macro" time domain on the basis of new data which was previously unanalyzed and was taken from investigated object. Determined trajectories can be an important source of information about technical state of a machine

Identyfikacja stanu technicznego maszyn na podstawie wyników analizy Fouriera obrazów termowizyjnych

In the article results of analysis of sequence of infrared images with use 1D Fourier transform is presented. Images were analyzed in the same way like this known from branch of active thermography where pulse phase method is applied in order to detect structural defects in the materials. Research was carried out with use of thermovision images recorded during operation of rotating machinery. The amplitude and phase images which described different technical states of observed machines were calculated. In order to generate the most informative images of amplitude and phase a procedure of frequency selection was proposed. Qualitative and quantitative estimation of the amplitude and the phase images shows that presented way of sequence of infrared image analysis provide useful diagnostic data which allow identification changes of machine technical state.W artykule przedstawiono wyniki analizy obrazów termowizyjnych z zastosowaniem jednowymiarowej transformaty Fouriera. Obrazy analizowano w sposób znany z dziedziny termografii aktywnej gdzie dla potrzeb detekcji defektów materiałowych stosowana jest metoda impulsowo fazowa. Badania przeprowadzono na obrazach zarejestrowanych podczas działania maszyny wirnikowej w różnych stanach technicznych. W wyniku analizy zarejestrowanych termogramów wyznaczono amplitudogramy i fazogramy reprezentujące różne stany techniczne maszyny. Jakościowa i ilościowa analiza obrazów amplitudy i fazy wskazują, że prezentowane podejście do analizy sekwencji obrazów termowizyjnych umożliwia identyfikację zmian stanu technicznego maszyny

Application of Wavelets transform of thermograms to identification of machine state changes

W artykule przedstawiono metodologię i przykład zastosowania transformaty falkowej termogramów do identyfikacji zmian stanu maszyny. Podstawą do wnioskowania o stanie maszyny są sygnały diagnostyczne uzyskane na podstawie obrazów szczegółów i aproksymacji powstałych po przekształceniu falkowym o odpowiednio dobranej funkcji bazowej oraz poziomie dekompozycji. Przykład przedstawiony w artykule wskazuje, że jest możliwa identyfikacja zmian stanu maszyny. Uzyskane wyniki pozwalają również stwierdzić, że sygnały diagnostyczne szczegółów i aproksymacji wzajemnie się uzupełniają dlatego powinny być rozpatrywane łącznie w procesie analizy.This paper presents an application of wavelet transform of thermograms to identifying a change in the machine state. Sequences of infrared images were recorded during an active diagnostic experiment. Identification of change in the machine state was made on the basis of analysis of diagnostic signals which were extracted from new images of details and approximation obtained as an effect of the wavelet transform. Obtaining the relevant diagnostic signals is connected with appropriate choice of the wavelet and decomposition level, as well as selection of relevant features of the images being the result of the wavelet decomposition. Selection of the wavelet type as well as the decomposition level were performed on the basis of preliminary experiments. In order to estimate the decomposed images and obtain the diagnostic signals, typical statistical features were considered. The results obtained for exemplary diagnostic signals show the usability of the proposed approach and allow the identification of the machine state change. It is concluded that the diagnostic signals extracted from images of approximation and details should be considered jointly for the effective machine state assessment because they complement each other from the machine state changes detection point of view. In order to find a class of relevant features of the new image obtained during the wavelet transform, additional research is necessary

Method of tracking of HAZ properties based on sequence of infrared images

Arc welding is commonly applied in industry. Assessment of the quality of welded joints is one of crucial tasks especially in automated applications. In the paper preliminary research devoted to the evaluation of Heat Affected Zone (HAZ) properties using method of tracking of defined Region of Interest (ROI) on infrared images continuously acquired during welding process. The proposed method can be useful to detection of welding instabilities as well as welded joint defects

Conception of joint signal anaysis

W artykule przedstawiono ogólną koncepcję łącznej analizy sygnałów oraz przykład metody stosującą tę koncepcję do klasyfikacji stanu maszyny wirnikowej. Koncepcja oparta jest na uogólnionym oknie danych, umożliwiającym analizę sygnałów obserwowanych jednocześnie w wielu kanałach pomiarowych w dziedzinie czasu "mikro" oraz czasu "makro". Dla potrzeb łącznej analizy sygnałów wprowadzono pojęcie dodatkowego sygnału pomocniczego, którego wartości określane są na podstawie wartości wybranego sygnału wielokanałowego. Przeprowadzono czynny eksperyment diagnostyczny mający na celu weryfikację proponowanej koncepcji. Wynikiem eksperymentu był zbiór danych uczących, pozwalający na zbudowanie klasyfikatora diagnostycznego oraz przeprowadzenie klasyfikacji stanu maszyny.In the paper an idea of joint signal analysis and example of its application to classification of rotating machinery state were presented. The conception is based on the generalized data window which enables us to describe simultaneously several diagnostic signals, which are observed with the use of a few channels both in the "micro" and "macro" time domains. For the need of this analysis an idea of additional virtual signals was introduced. Values of these signals are estimated on the basis of values of a selected multichannel signal. In order to verify the proposed conception active diagnostic experiment was carried out. The experiment result was a set of learning data which enables as to construct a diagnostic classifier. Exemplary results of classification of technical machine state based on the proposed conception were also presented