Wavelet Modeling of Control Stochastic Systems at Complex Shock Disturbances

This article is devoted to the development of methodological supports and experimental software tools for accuracy analysis and information processing in control stochastic systems (CStS) with complex shock disturbances (ShD) by means of wavelet Haar–Galerkin technologies. Basic new results include methods and algorithms of stochastic covariance analysis and modeling on the basis of the Galerkin method and wavelet expansion for linear, linear with parametric noises, and quasilinear CStS with ShD. Results are illustrated by an information-control system at ShD. New stochastic effects accumulation for systematic and random errors are detected and investigated.

Evaluation of the SteamVR Motion Tracking System with a Custom-Made Tracker

The paper presents the research of the SteamVR tracker developed for a man-portable air-defence training system. The tests were carried out in laboratory conditions, with the tracker placed on the launcher model along with elements ensuring the faithful reproduction of operational conditions. During the measurements, the static tracker was moved and rotated in a working area. The range of translations and rotations corresponded to the typical requirements of a shooting simulator application. The results containing the registered position and orientation values were plotted on 3D charts which showed the tracker’s operation. Further analyses determined the values of the systematic and random errors for measurements of the SteamVR system operating with a custom-made tracker. The obtained results with random errors of 0.15 mm and 0.008° for position and orientation, respectively, proved the high precision of the measurements.

Global component analysis of errors in three satellite-only global precipitation estimates

Revealing the error components of satellite-only precipitation products (SPPs) can help algorithm developers and end-users understand their error features and improve retrieval algorithms. Here, two error decomposition schemes are employed to explore the error components of the IMERG-Late, GSMaP-MVK, and PERSIANN-CCS SPPs over different seasons, rainfall intensities, and topography classes. Global maps of the total bias (total mean squared error) and its three (two) independent components are depicted for the first time. The evaluation results for similar regions are discussed, and it is found that the evaluation results for one region cannot be extended to another similar region. Hit and/or false biases are the major components of the total bias in most overland regions globally. The systematic error contributes less than 20 % of the total error in most areas. Large systematic errors are primarily due to missed precipitation. It is found that the SPPs show different topographic patterns in terms of systematic and random errors. Notably, among the SPPs, GSMaP-MVK shows the strongest topographic dependency of the four bias scores. A novel metric, namely the normalized error component (NEC), is proposed as a means to isolate the impact of topography on the systematic and random errors. Potential methods of improving satellite precipitation retrievals and error adjustment models are discussed.

The method for evaluation errors of automated measurements of base tangent length by three-axis indicator on five-axis CNC machine

The article provides an overview of studies of various errors in the process of measuring parts with three-coordinate probes on CNC machines. The paper considers a method for estimating systematic and random errors in the process of measuring the length of the base tangent using control maps and probabilistic and statistical methods for processing multiple repeated inputs of a three-coordinate indicator to the measured side surfaces of the wheel teeth. The method is designed to assess the acceptability of the measurement process by technologists and adjusters. The data of experimental estimation of random and systematic errors of measurement of the length of the base tangent on a five-coordinate CNC machine with a three-coordinate indicator of Mahr are presented. The obtained error values for the five-axis machine under study allow us to measure the length of the base tangent for the purposes of periodic monitoring and adjustment of the machine when processing oblique cylindrical wheels with universal disk or end mills

Measurement of resonance frequency by amplitude and phase methods using digital frequency scanning

A theoretical and experimental study of methods for measuring the resonance frequency from the amplitude-frequency and phase-frequency characteristics of the resonator (amplitude and phase methods, respectively) has been carried out. In this case, digital frequency scanning was used to determine the resonant frequency. On the basis of the theory of probabilities, analytical expressions are derived that describe the dependences of systematic and random errors on the position of the resonance frequency in the interval between the nearest discrete frequencies, as well as on the noise level. The reliability of the derived expressions was confirmed in the course of a virtual experiment with a computer model of the resonator. It is also shown that the errors of the amplitude and phase methods for the noise level, at which no more than two discrete frequencies are recorded, practically coincide. However, if more than two discrete frequencies are recorded, then the indicated errors differ significantly, which is demonstrated using the experimental graphs. In this case, the errors in measuring the resonance frequency by the phase method practically do not depend on the frequency tuning step with a decrease in this step and linearly depend on the phase noise level. When measuring the resonance frequency by the amplitude method, the errors decrease with decreasing frequency tuning step, and for this case, an empirical formula is proposed for the dependence of systematic and random errors on the frequency tuning step and the amplitude noise level. The research results can be used in the construction of digital resonance sensors.

Clinically oriented contour evaluation using geometric and dosimetric indices based on simple geometric transformations

Background: In radiotherapy, geometric indices are often used to evaluate the accuracy of contouring; however, the ability of geometric indices to identify the error of contouring results is limited, mainly because it does not consider any clinical background. To study the relationship between geometric indices and dosimetric indices, four different types of targets were selected to introduce the systematic and random geometric errors in the delineation process. Materials and Methods: The C-shaped target outlined in the American Association of Physicists in Medicine (AAPM) TG-119 report (The report of Task Group 119 of the AAPM) and the targets of three actual cases of oropharyngeal cancer, metastatic spine cancer, and prostate cancer were selected as the test contours that needed to be modified. Python software was used to perform translation, scaling, rotating and sine function transformation to introduce systematic and random errors into the above contours. These geometrically transformed contours were regarded as reference contours corrected by systematic and random errors. The corresponding dosimetric indices were obtained from the original dose distribution of the radiotherapy plan, and correlations (R²) between geometric and dosimetric indices were quantified through linear regression. The Wilcoxon signed rank test was used to compare the ability of spatial-direction discrimination between the geometric indices of different directions of transformations. Results: The correlations between the geometric and dosimetric indices were inconsistent for the targets. For systematic errors, except for the sine function transformation (R²: 0.023–0.04, p＞0.05), the geometric transformations of the C-shaped target’s planning target volume (C-PTV) had correlations with the dosimetric indices D98% and Dmean (R²: 0.689–0.988), 80% of which were strongly correlated (R² > 0.8). For the random errors, the correlation coefficients of the actual cases were also high, R2 > 0.384, p < 0.05. The results of Wilcoxon signed rank test showed that only the p-values of volumetric geometric indices of C-PTV were less than 0.05. Conclusions: Clinically, an assessment of the contour accuracy of the region of interest is not feasible based on geometric indices alone, and should be combined with dosimetric indices. Keywords: Contour evaluation, Geometric indices, Dosimetric indices, Geometric transformation

Comparative analysis methods of assessment of commodity structure of spruce stands

В последние годы снизилось качество работ по отводу и таксации лесосек. Существующие и применяемые в таксации методы не обеспечивают необходимую точность конечных результатов, поскольку их использование часто не соответствует требованиям «Наставления по отводу и таксации лесосек». Таким образом, актуальной задачей становится изучение ошибок в определении товарной структуры древостоев и выявление возможных причин их возникновения с целью дальнейшего совершенствования лесотаксационных работ. На основании материалов таксации постоянных пробных площадей ели европейской была выполнена материально-денежная оценка древостоев по сортиментным и товарным таблицам, произведен расчет грубых, систематических и случайных ошибок выхода крупной, средней, мелкой деловой древесины, дров, ликвидной древесины и отходов. Для оценки влияния различных факторов на появление и величину ошибок были выполнены корреляционный и однофакторный дисперсионный анализы. Проведенный анализ позволил установить, что основными показателями, оказывающими влияние на расхождения в выходе сортиментов различных категорий древесины, при использовании товарных и сортиментных таблиц, являются средние высоты древостоев, а также разряды высот. Это связано с малым числом значений высот, представленных для каждой из ступеней толщины в товарных таблицах. Сортиментные таблицы, в силу большей вариабельности данного таксационного показателя, позволяют более точно определять товарную структуру древостоев. Выявленные закономерности демонстрируют необходимость совершенствования сортиментных и товарных таблиц для уменьшения расхождения получаемых результатов с фактическим выходом сортиментов, что позволит повысить качество лесотаксационных работ. In recent years, the quality of work on the allocation and taxation of cutting areas has decreased. Existing methods used in the taxation do not provide the required accuracy of results since their application often does not meet the criteria of the “Manual on the allocation and taxation of cutting areas”. Thus, the study of errors in determining the product structure of forest stands as well as identifying possible causes for their occurrence in order to improve forest taxation works becomes an urgent task. Based on the taxation materials of the permanent European spruce plots, material and monetary assessment of the stands was made using assortment and commodity tables, and gross, systematic, and random errors of the output of large, medium, small commercial timber, firewood, liquid wood, and waste were calculated. Сorrelation analysis and one-way analysis of variance were performed to assess the influence of various factors on the appearance and magnitude of the errors. The analysis made it possible to establish that the main indicators that influence the discrepancies in the output of assortments of different categories of wood, when using commodity and assortment tables, are the average heights of stands, as well as height categories. This is due to the small number of height values presented for each of the thickness steps in the product tables. Assortment tables, due to the greater variability of this taxation indicator, allow you to more accurately determine the product structure of stands. The revealed patterns demonstrate the high need to improve assortment and commodity tables in order to reduce the discrepancy between obtained results and the actual output of assortments, which will improve the quality of forest taxation work.