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EN
The purpose of this study is to perform automatic measurement of a screw thread profile acquired with a 3D vision system. Measurements are carried out using a laser triangulation method. The triangulation method requires a calibration procedure to be performed on a measurement stand. The first stage of the calibration procedure allows one to compensate for lens and perspective distortion. Calculated projection model coefficients are also used to transform the image coordinate system into the world coordinate system. Next, a specially designed calibration target with known geometric dimensions is used to position the object’s rotation axis on the measurement plane and prepare it for the measurement procedure. This paper presents the algorithms used to perform a measurement for a single cross-section of a screw thread. For the chosen screw thread, the pitch, flank angles, and the radiuses at the crest and root are measured.
PL
Celem przedstawionych w artykule badań jest przeprowadzenie zautomatyzowanego pomiaru elementu gwintowanego. Pomiar profilu gwintu wykonano przy pomocy systemu wizyjnego 3D opartego na zasadzie triangulacji laserowej. W artykule przedstawiono opis kalibracji stanowiska pomiarowego. Pierwszy etap procedury kalibracyjnej pozwala na kompensację dystorsji układu optycznego oraz zniekształcenia perspektywicznego. Wyznaczone na tym etapie współczynniki macierzy projekcji wykorzystywane są również do transformacji układu współrzędnych obrazu do układu współrzędnych świata. Na kolejnym etapie specjalnie przygotowany cel kalibracyjny, o znanych parametrach geometrycznych, wykorzystany został do wypozycjonowania osi obrotu elementu na płaszczyźnie pomiarowej - wyznaczonej przez wiązkę laserową. W artykule przedstawiono algorytmy wykorzystane podczas wykonywania pomiarów na obrazie pojedynczego przekroju poprzecznego elementu gwintowanego. Przedstawione metody pozwalają na wyznaczenie skoku, kąta zarysu oraz promieni wierzchołka i dna zarysu gwintu.
EN
This paper presents a method allowing for the quality inspection of a screw thread directly on a production line. The parameter evaluation was performed on a surface partial image obtained using 3D laser triangulation. Three characteristic values are being measured for each element: minor pitch, major pitch, and pitch diameter. The paper contains an overview and discussion of methods commonly used for screw thread measurements. The non-tactile 3D imaging method that was selected for this task is fast enough to be used on every element which leaves the production line, and it is accurate enough to provide reliable data about the quality of the final product. Thread parameter assessment is based on a two-stage algorithm. The first step provides data about the overall placement of the elements, along with a rough estimate of the major diameter. The final values are then calculated using the least squares minimization method. This algorithm was verified using synthetic data representing an ideal thread contour, and then implemented for the analysis of the actual thread surface of a 3D image. Detailed algorithm execution time measurements were presented, along with our method to decrease computational costs for performing measurements on each screw thread.
PL
Artykuł przedstawia metodę kontroli jakości elementów gwintowanych możliwą do realizacji bezpośrednio na linii produkcyjnej. Pomiar parametrów został przeprowadzony, bazując na częściowym obrazie gwintu wykonanym przy pomocy triangulacji laserowej. Opisano metodę pozwalającą na wyznaczenie trzech charakterystycznych parametrów gwintu: średnicy wewnętrznej, średnicy wewnętrznej oraz skoku gwintu. W pracy przedstawiono przegląd metod powszechnie wykorzystywanych do pomiaru parametrów gwintu. Do realizacji zadania wybrano ostatecznie bezstykową metodę obrazowania 3D, charakteryzującą się szybkością wystarczającą, by można ją było zastosować dla każdego elementu opuszczającego linię produkcyjną oraz dokładnością pozwalającą skutecznie oszacować jakość produktów opuszczających linię produkcyjną. Opracowany algorytm wyznaczania parametrów gwintu składa się z dwóch etapów. W wyniku kroku pierwszego otrzymano zgrubną informację o położeniu oraz parametrach obrazowanego obiektu. Drugi krok pozwala na dokładne wyznaczenie szukanych parametrów z wykorzystaniem minimalizacji funkcji błędu. Algorytm został zweryfikowany z wykorzystaniem danych opisujących kontur idealny, a następnie wykorzystany do analizy danych pochodzących z rzeczywistego pomiaru. W artykule zaprezentowano dokładne dane dotyczące czasu wykonywania algorytmu wraz z metodą skrócenia czasu obliczeń dla każdego pojedynczego elementu.
EN
This paper presents a review of methods used for the acquisition of 3D images. A classification of such methods into contact and contactless and into active and passive methods is given. Special attention is given to show imaging methods that can be used for tasks involving product-manufacturing systems.
PL
W artykule zaprezentowano przegląd metod wykorzystywanych w akwizycji obrazów 3D. Przedstawiono klasyfikację tych metod z podziałem na metody kontaktowe i bezkontaktowe, aktywne oraz pasywne. Szczególną uwagę poświęcono metodom obrazowania, które mogą być stosowane w procesach wytwarzania produktów.
EN
The essence of the undertaken topic is application of the continuous sky-hook control strategy and the Extended Kalman Filter as the state observer in the 2S1 tracked vehicle suspension system. The half-car model of this suspension system consists of seven logarithmic spiral springs and two magnetorheological dampers which has been described by the Bingham model. The applied continuous skyhook control strategy considers nonlinear stiffness characteristic of the logarithmic spiral springs. The control is determined on estimates generated by the Extended Kalman Filter. Improve of ride comfort is verified by comparing simulation results, under the same driving conditions, of controlled and passive vehicle suspension systems.
EN
Nowadays, in positron emission tomography (PET) systems, a time of fl ight (TOF) information is used to improve the image reconstruction process. In TOF-PET, fast detectors are able to measure the difference in the arrival time of the two gamma rays, with the precision enabling to shorten signifi cantly a range along the line-of-response (LOR) where the annihilation occurred. In the new concept, called J-PET scanner, gamma rays are detected in plastic scintillators. In a single strip of J-PET system, time values are obtained by probing signals in the amplitude domain. Owing to compressive sensing (CS) theory, information about the shape and amplitude of the signals is recovered. In this paper, we demonstrate that based on the acquired signals parameters, a better signal normalization may be provided in order to improve the TOF resolution. The procedure was tested using large sample of data registered by a dedicated detection setup enabling sampling of signals with 50-ps intervals. Experimental setup provided irradiation of a chosen position in the plastic scintillator strip with annihilation gamma quanta.
EN
The article contains results of a conceptual work and research which develops a semi-active suspension of the 2S1 caterpillar platform. The results are collected on designed and built test stands and used in three alternative models of the platform suspension system. The first one is based on the existing construction of the platform. The other two have been modernized by using new solutions in the tracked vehicles suspension technology associated with a torsional spring element. The authors assumed simulation conditions for straight line driving while the model overcomes an obstacle in one track. The results of simulations are compared and analyzed to improve parameters of the vehicle suspension.
EN
This article is focused on data acquisition system (DAQ) designed especially to be used in positron emission tomography (PET) or single-photon emission computed tomography. The system allows for continuous registration of analog signals during measurement. It has been designed to optimize registration and processing of the information carried by signals from the detector system in PET scanner. The processing does not require any rejection of data with a trigger system. The proposed system possesses also an ability to implement various data analysis algorithms that can be performed in real time during data collection.
8
Content available remote Simulations of γ quanta scattering in a single module of the J-PET detector
EN
This article describes the simulations of the scattering of annihilation γ quanta in a strip of a plastic scintillator. Such strips constitute the basic detection modules in a newly proposed positron emission tomography (PET), which utilizes plastic scintillators instead of inorganic crystals. An algorithm simulating the chain of Compton scatterings was elaborated and a series of simulations have been conducted for the scintillator strip with a cross-section of 5×19 mm. The results indicate that secondary interactions occur only in the case of about 8% of the events and only 25% of these events take place in the distance larger than 0.5 cm from the primary interaction. Also, the light signals produced at the primary and secondary interactions overlap with the delay, the distribution of which is characterized by a full width at half-maximum (FWHM) of about 40 ps.
EN
This paper describes three methods regarding the production of plastic scintillators. One method appears to be suitable for the manufacturing of plastic scintillators, revealing properties which fulfill the requirements of novel positron emission tomography scanners based on plastic scintillators. The key parameters of the manufacturing process are determined and discussed.
10
Content available remote List-mode reconstruction in 2D strip PET
EN
Using a theory of list-mode maximum likelihood expectation-maximization (MLEM) algorithm, in this contribution, we present a derivation of the system response kernel for a novel positron emission tomography (PET) detector based on plastic scintillators.
11
Content available remote J-PET analysis framework for the prototype TOF-PET detector
EN
Novel time-of-flight positron emission tomography (TOF-PET) scanner solutions demand, apart from the state-of-the-art detectors, software for fast processing of the gathered data, monitoring of the whole scanner, and reconstruction of the PET image. In this article, we present an analysis framework for the novel STRIP-PET scanner developed by the J-PET collaboration in the Institute of Physics of the Jagiellonian University. This software is based on the ROOT package used in many particle physics experiments.
EN
A novel PET detector consisting of strips of polymer scintillators is being developed by the Jagiellonian Positron Emission Tomograph (J-PET) collaboration. The map of efficiency and the map of geometrical acceptance of the two-strip J-PET scanner are presented. The map of efficiency was determined using the Monte Carlo simulation software GEANT4 Application for Tomographic Emission (GATE), which is based on GEANT4. Both maps were compared using a method based on the χ2-test.
EN
The complexity of the hardware and the amount of data collected during the PET imaging process require application of modern methods of efficient data organization and processing. In this article, we will discuss the data structures and the flow of collected data from the novel TOF-PET medical scanner that is being developed at the Jagiellonian University. The developed data format reflects the registration process of the γ quanta emitted from positron electron annihilation, front-end electronic structure, and required input information for the image reconstruction. In addition, the system database fulfills possible demands of the evolving J-PET project.
14
Content available remote Computing support for advanced medical data analysis and imaging
EN
We discuss computing issues for data analysis and image reconstruction of positron emission tomography based on time-of-flight medical scanner or other medical scanning devices producing large volumes of data. Service architecture based on grid and cloud concepts for distributed processing is proposed and critically discussed.
15
Content available remote Calibration of photomultipliers gain used in the J-PET detector
EN
Photomultipliers are commonly used in commercial PET scanner as devices that convert light produced in scintillator by gamma quanta from positron-electron annihilation into electrical signal. For proper analysis of obtained electrical signal, a photomultiplier gain curve must be known, since gain can be significantly different even between photomultipliers of the same model. In this article, we describe single photoelectron method used for photomultiplier calibration applied for J-PET scanner, a novel PET detector being developed at Jagiellonian University. A description of calibration method, an example of calibration curve, and a gain of few Hamamatsu R4998 photomultipliers are presented.
EN
A method of the determination of a γ-quantum absorption point in a plastic scintillator block using a matrix of wavelength-shifting (WLS) strips is proposed. An application of this method for the improvement of position resolution in newly proposed positron emission tomography (PET) detectors based on plastic scintillators is presented. The method enables to reduce parallax errors in the reconstruction of images, which occurs in the presently used PET scanners.
EN
All of the present methods for calibration and monitoring of time-of-flight positron emission tomography (TOF-PET) scanner detectors utilize radioactive isotopes, such as 22Na or 68Ge, which are placed or rotate inside the scanner. In this article, we describe a novel method based on the cosmic rays application to the PET calibration and monitoring methods. The concept allows to overcome many of the drawbacks of the present methods and it is well suited for newly developed TOF-PET scanners with a large longitudinal field of view. The method enables also the monitoring of the quality of the scintillator materials and in general allows for the continuous quality assurance of the PET detector performance.
EN
This article presents an application of a novel technique for precise measurements of time and charge based solely on a field programmable gate array (FPGA) device for positron emission tomography (PET). The described approach simplifies electronic circuits, reduces the power consumption, lowers costs, merges front-end electronics with digital electronics, and also makes more compact final design. Furthermore, it allows to measure time when analog signals cross a reference voltage at different threshold levels with a very high precision of ~15 ps (rms) and thus enables sampling of signals in a voltage domain.
EN
A positron emission tomography (PET) scan does not measure an image directly. Instead, a PET scan measures a sinogram at the boundary of the field-of-view that consists of measurements of the sums of all the counts along the lines connecting the two detectors. Because there is a multitude of detectors built in a typical PET structure, there are many possible detector pairs that pertain to the measurement. The problem is how to turn this measurement into an image (this is called imaging). Significant improvement in PET image quality was achieved with the introduction of iterative reconstruction techniques. This was realized approximately 20 years ago (with the advent of new powerful computing processors). However, three-dimensional imaging still remains a challenge. The purpose of the image reconstruction algorithm is to process this imperfect count data for a large number (many millions) of lines of response and millions of detected photons to produce an image showing the distribution of the labeled molecules in space.
EN
The article presents examples of vibration signals analysis derived from the research of prototype reclaimer REGMAS. After the division of the time-frequency analysis methods of measuring signals, their non-parametric and parametric models were estimated. At the end of the article the summary and conclusions were set.
PL
W artykule zaprezentowano przykłady analizy sygnałów wibracji uzyskanych z badań prototypowego regeneratora mas formierskich REGMAS. Po dokonaniu podziału czasowo-częstotliwościowych metod analizy sygnałów pomiarowych, wyznaczono ich modele parametryczne i nieparametryczne. Na końcu zawarto podsumowanie oraz wnioski końcowe dotyczące przedstawionych analiz.
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