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1.
Using neural networks in the process of calibrating the microsimulation models in the analysis and design of roundabouts in urban areas
Irena Ištoka Otković, 2011, doktorska disertacija

Opis: The thesis researches the application of neural networks in computer program calibration of traffic micro-simulation models. The calibration process is designed on the basis of the VISSIM micro-simulation model of local urban roundabouts. From the five analyzed methods of computer program calibration, Methods I, II and V were selected for a more detailed research. The three chosen calibration methods varied the number of outgoing traffic indicators predicted by neural networks and a number of neural networks in the computer program calibration procedure. Within the calibration program, the task of neural networks was to predict the output of VISSIM simulations for selected functional traffic parameters - traveling time between the measurement points and queue parameters (maximum queue and number of stopping at the roundabout entrance). The Databases for neural network training consisted of 1379 combinations of input parameters whereas the number of output indicators of VISSIM simulations was varied. The neural networks (176 of them) were trained and compared for the calibration process according to training and generalization criteria. The best neural network for each calibration method was chosen by using the two-phase validation of neural networks. The Method I is the calibration method based on calibration of a traffic indicator -traveling time and it enables validation related to the second observed indicator – queue parameters. Methods II and V connect the previously described calibration and validation procedures in one calibration process which calibrates input parameters according to two traffic indicators. Validation of the analyzed calibration methods was performed on three new sets of measured data - two sets at the same roundabout and one set on another location. The best results in validation of computer program calibration were achieved by the Method I which is the recommended method for computer program calibration. The modeling results of selected traffic parameters obtained by calibrated VISSIM traffic model were compared with: values obtained by measurements in the field, the existing analysis methods of operational roundabouts characteristics (Lausanne method, Kimber-Hollis, HCM) and modeling by the uncalibrated VISSIM model. The calibrated model shows good correspondence with measured values in real traffic conditions. The efficiency of the calibration process was confirmed by comparing the measured and modeled values of delays, of an independent traffic indicator that was not used in the process of calibration and validation of traffic micro-simulation models. There is also an example of using the calibrated model in the impact analysis of pedestrian flows on conflicting input and output flows of vehicles in the roundabout. Different traffic scenarios were analyzed in the real and anticipated traffic conditions.
Ključne besede: traffic models, traffic micro-simulation, calibration of the VISSIM model, computer program calibration method, neural networks in the calibration process, micro-simulation of roundabouts, traffic modeling parameters, driving time, queue parameters, delay
Objavljeno: 02.06.2011; Ogledov: 3012; Prenosov: 204
.pdf Polno besedilo (13,21 MB)

2.
New approach to uncertainty evaluation in the calibration of gauge block comparators
Andrej Godina, Bojan Ačko, Marjan Družovec, 2007, izvirni znanstveni članek

Opis: Gauge blocks (GBs) are being calibrated by two methods: interferometric calibration and calibration by mechanical comparison to reference GB. While interferometric method represents primary level, comparison is more suitable for calibrating industrial GBs because of lower costs and shorter calibration time. Although no significant changes in equipment happened in last decade, improvements in mechanical comparison are on-going. In addition to the uncertainty of the reference GB calibration, uncertainty of the GB comparator is the most important contribution to total uncertainty of the mechanical calibration. The article introduces a new approach for evaluating the uncertainty of GB comparator calibration. The uncertainty budget and results of analytical and experimental evaluation of all contributions are presented. This approach results in lower end-effect uncertainty and a slightly higher length dependent uncertainty, in comparison with the uncertainty evaluation procedure as described in EA document EA-10/02.
Ključne besede: measurements, calibration, measuring uncertainty, gauge block, comparator, CMC, mechanical comparison
Objavljeno: 31.05.2012; Ogledov: 937; Prenosov: 9
URL Polno besedilo (0,00 KB)

3.
Simulation of line scale contamination in calibration uncertainty model
Marjan Družovec, Bojan Ačko, Andrej Godina, Tatjana Welzer Družovec, 2008, izvirni znanstveni članek

Opis: Precise calibration of quartz line scales is very important for assuring traceability of microscopic measurements. Very significant influence in calibration uncertainty budget is represented by uncertainty of line centre detection. Line centre is usually detected through video signal processing using different types of algorithms. This paper is presenting calibration procedure that was developed in the Laboratory for Production Measurement at the Faculty of Mechanical Engineering in Maribor. It is focused in uncertainty analysis and especially in the influence of line scale contamination on determination of line centre position. Different types of line scale contamination like dirt spots, scratches, line edge incorrectness, and line intensity were simulated in order to test the ability of the line centre detection algorithm to eliminate such influences from the measurement results.
Ključne besede: line scale, calibration, uncertainty, video-positioning system, simulation
Objavljeno: 31.05.2012; Ogledov: 713; Prenosov: 4
URL Polno besedilo (0,00 KB)

4.
Influence of temperature variations on calibrated cameras
Peter Podbreznik, Božidar Potočnik, 2008, izvirni znanstveni članek

Opis: The camera parameters are changed due to temperature variations, which directly influence calibrated cameras accuracy. Robustness of calibration methods were measured and their accuracy was tested. An error ratio due to camera parameters change with respect to total error originated during calibration process was determined. It pointed out that influence of temperature variations decrease by increasing distance of observed objects from cameras.
Ključne besede: camera calibration, perspective projection matrix, epipolar geometry, temperature variation
Objavljeno: 31.05.2012; Ogledov: 726; Prenosov: 4
URL Polno besedilo (0,00 KB)

5.
Analytical camera model supplemented with influence of temperature variations
Peter Podbreznik, Božidar Potočnik, 2008, izvirni znanstveni članek

Opis: A camera in the building site is exposed to different weather conditions. Differences between images of the same scene captured with the same camera arise also due to temperature variations. The influence of temperature changes on camera parameters were modelled and integrated into existing analytical camera model. Modified camera model enables quantitatively assessing the influence of temperature variations.
Ključne besede: camera calibration, analytical model, intrinsic parameters, extrinsic parameters, temperature variations
Objavljeno: 31.05.2012; Ogledov: 573; Prenosov: 1
URL Polno besedilo (0,00 KB)

6.
Measurement uncertainty in calibration of measurement surface plates flatness
Andrej Gusel, Bojan Ačko, Vedran Mudronja, 2009, izvirni znanstveni članek

Opis: Ravno merilno površino, kot je to na primer merilna plošča, lahko smatramo kot izhodišče za izvajanje večine meritev oblike in lege merjenih objektov. Da bi merilne plošče v ta namen zadovoljivo uporabljali, moramo najprej zagotoviti, da so res ravne in primerne za meritve. Ravnost merilne ploskve ugotavljamo posredno, tako da najprej določimo premost posameznih linij, ki so sestavni del merilne mreže. Te linije so še dodatno razdeljene na merilne korake, ki so prirejeni meram merilne opreme. Premost merilne linije izračunamo z merjenjem nagiba posameznega merilnega položaja za vsako linijo posebej, neravnost celotne površine pa tako, da rezultate po linijah povežemo v celoto. Osnove, postopki in merilne naprave za izvajanje meritev so torej znani, neznanka pa ostaja negotovost tovrstne kalibracije merilne površine. Meritev brez ustrezno izražene negotovosti ne pomeni ničesar, zato moramo zagotoviti, da bomo lahko negotovost določili. Pričujoči članek predstavlja nov pristop določanja merilne negotovosti pri merjenju ravnosti, ki temelji na uporabi metode Monte Carlo. Pri tem celoten merilni sistem razstavimo na posamezne komponente ter ocenimo njihovo veličino in vplive le teh, meritve pa simuliramo. Zanima nas tudi vpliv parametrov merilne mreže na meritev.
Ključne besede: production measurements, length measurements, measuring uncertainty, calibration, uncertainty measurement, flatness measurement
Objavljeno: 31.05.2012; Ogledov: 739; Prenosov: 7
URL Polno besedilo (0,00 KB)

7.
Thread gauge calibration for industrial applications
Tadeja Primožič Merkač, Bojan Ačko, 2010, izvirni znanstveni članek

Opis: There are two most commonly used methods for calibration of thread rings, with different measuring uncertainty. The method of mechanical sensing with two balls is mostly used on one-axial measuring machines and on coordinate measuring machines. However, the method of calculating the core diameter of the thread ring combined with the technique of adaptation (in accordance with the method of the smallest squares) is used on the profile scanner. The required tolerances, which are very narrow for adjustable and laboratory thread ring, so the measuring uncertainty may be too high when using the method of mechanical sensing with two balls, and the low quality of some control rings, are the decisive factors for choosing an appropriate method in the industry. This also depends on the laboratoryćs capability of executing a specific method. The measurements of the core diameter of thread rings, which are the main topic of this article, were included into an international inter-comparison in which the main subject was the same thread ring as the one mentioned in this article.
Ključne besede: thread ring gauge, calibration, pitch diameter, measurement uncertainty, dimensional measurements
Objavljeno: 31.05.2012; Ogledov: 737; Prenosov: 2
URL Polno besedilo (0,00 KB)

8.
Calibration of electronic levels using a special sine bar
Bojan Ačko, 2005, izvirni znanstveni članek

Opis: Electronic levels are designated for the precise measurement of inclination angles within the range of +- 3 mm/m. They are very often used for checking the straightness of machine tool guides as well as the flatness of different kindsof machine tool tables and surface plates. Typical resolution of such instruments is 1 m/m. Electronic levels are calibrated by using very precise angle generators. One such generator is a sine bar. Sine bars are cheap and enable fast and simple calibrations. Commercial sine bars however are not precise enough. We, therefore, decided to design a special sine bar, which would be able to generate angles within an uncertainty of 1 mžm. This sine barwas designed by the laboratory staff and manufactured in our workroom. We have also created a calibration procedure, which has already been accredited. Uncertainty analysis, including experimental measurements, shows that the planned uncertainty has been reached. The sine bar design, calibration procedure and uncertainty evaluation are presented in this article.
Ključne besede: production measurements, measuring uncertainty, calibration, inclination angles, flatness measurements, sine bar, electronic level
Objavljeno: 01.06.2012; Ogledov: 952; Prenosov: 9
URL Polno besedilo (0,00 KB)

9.
Analysis of the influence of car-following input parameters on the modelled travelling time
Irena Ištoka Otković, Tomaž Tollazzi, Matjaž Šraml, 2013, kratki znanstveni prispevek

Opis: The calibration process is a basic condition of traffic model application in local conditions. The choice of input parameters, which are used in calibration process, influences the success of the calibration process itself; therefore, the goal is to choose parameters with a larger influence on the modelling process. This paper offers a detailed analysis of car-following input parameters and their influence on the modelled travelling time. The experimental basis was a one-lane roundabout, and the tool used for traffic simulation was the VISSIM microsimulation traffic model. The results show that the car-following input parameters should be a part of the set of input parameters, which will enter the process of calibration. The examined car-following input parameters affect the capacity of intersections and results show that it is necessary to revise the range of input values of one of the observed car-following input parameters.
Ključne besede: car-following input parameters, input parameters for the process of calibration, VISSIM
Objavljeno: 11.07.2017; Ogledov: 42; Prenosov: 4
.pdf Polno besedilo (680,10 KB)

10.
Analysis of neural network responses in calibration of microsimulation traffic model
Irena Ištoka Otković, Damir Varevac, Matjaž Šraml, 2015, izvirni znanstveni članek

Opis: Microsimulation models are frequently used in traffic analysis. Various optimization methods are used in calibration, and the one method that has shown success is neural networks. This paper shows the responses of neural networks during calibration of a microsimulation traffic model. We analyzed two calibration methods by applying neural networks and comparing their neural network learning (according to their achieved correlation and the mean error of prediction) and their generalization ability (comparison of generalization results was analyzed in two steps). The best correlation between the microsimulation results and neural network prediction was 88.3%, achieved for the traveling time prediction, on which the first calibration method is based.
Ključne besede: microsimulation traffic models, calibration, response of neural networks, traveling time, queue parameters
Objavljeno: 02.08.2017; Ogledov: 43; Prenosov: 1
.pdf Polno besedilo (1,07 MB)

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