Vol 28, No 2 (2020)

Informatics, Computer Science and Control
Research algorithm restoring signals in the basis of exponential functions
Batishchev V.I., Zolin A.G.

The paper proposes a method for constructing digital filters for solving inverse problems of recovering signals, time series, and images using an approximation approach. The considered inverse problems belong to the class of incorrectly posed ones and require the use of certain regularizing procedures to synthesize optimal reconstruction algorithms and solve computational problems associated with this.

In this regard, a method is proposed for constructing an approximation model of the weight function of the inverse (reconstruction) filter, based on the criterion of the minimum quadratic error of the mismatch of the distorted signal model obtained after the direct (distorting) filter processes the reconstructed (unknown) signal and the existing distorted signal. The weight function of the direct filter is assumed to be known.

The statement of the problem of reconstructing signals, time series, and images in the case of a one-dimensional point scattering function is formulated. An algorithm is presented that allows one to reduce the amount of computation when finding the values ​​of the weight function of the inverse filter.

The algorithms were tested on model examples when processing real images obtained by remote sensing of the Earth, as well as on specially formed contrast images. To quantify the quality of reconstruction, a relative mean-square measure of the difference between the reference and reconstructed signals (images) was used. The results of testing show that using this approach allows to reduce the error of recovery, which gives an advantage in solving problems of approximation and data recovery.

Vestnik of Samara State Technical University. Technical Sciences Series. 2020;28(2):6-21
Forming of the diameter tolerances of the insulated core to provide the guaranteed achievement of the required quality indicators of the symmetrical communication cable (lan-cable)
Denisov V.Y.

A LAN-cable was considered as an object of research. A mathematical description of the mutual influence on the far and near ends in symmetrical communication cables is presented. It’s assumed that the tightening of the tolerance for the diameter of the insulated core will ensure the guaranteed achievement of the required quality indicators of the symmetrical communication cable. An algorithm for calculating the mutual influence between two and four circuit is given. A mathematical description was obtained and a simulation model of the mutual influence on the near and far ends was constructed for two twisted pairs, taking into account the length of the chain and the frequency of the transmitted signal. Computer studies were performed when the diameters of isolated LAN-cable cores were varied, taking into account its length, the mutual influence on the near end of the coefficients of the capacitive coupling, and transient attenuation on the near end. The obtained results confirmed the hypothesis and are the basis for the synthesis of automatic control systems for the LAN-cable manufacturing process.

Vestnik of Samara State Technical University. Technical Sciences Series. 2020;28(2):22-40
Two-channel time-optimal control of induction heating process with maximum temperature constraint
Il`ina N.A.

The formulation and method of solution of the problem of time-optimal control of induction heating process of an unlimited plate with two control actions on the value of internal heat sources with technological constraint in relation to a one-dimensional model of the temperature field are proposed. The problem is solved under the conditions of a given accuracy of uniform approximation of the final temperature distribution over the thickness of the plate to the required. The method of finite integral transformations is used to search for the input-output characteristics of an object with distributed parameters with two control actions. The preliminary parameterization of control actions based on analytical optimality conditions in the form of the Pontryagin maximum principle is used. At the next stage reduction is performed to the problem of semi-infinite optimization, the solution of which is found using the alternance method. The alternance properties of the final resulting temperature state at the end of the optimal process lead to a basic system of relations, which, if there is additional information about the shape of the temperature distribution curve, is reduced to a system of equations that can be solved. An example of solving the problem of time-optimal control of temperature field of an unlimited plate with two offices is carried out in two stages. At first stage the case of induction heating without maximum temperature constraints is considered, at the second stage is carried out on the basis of the results of the first stage to obtain the solution subject to the limitation on the maximum temperature of the heated billet.

Vestnik of Samara State Technical University. Technical Sciences Series. 2020;28(2):41-58
Dynamic model of waste heat boiler based on recurrent neural network
Lusenko D.S., Danilushkin I.A.

The work is devoted to the development of a dynamic model of a waste heat boiler based on a recurrent neural network. The developed model can be used to create computer simulators for gas turbine plant operators, technologists and operating personnel. The object of modeling is presented as a complex thermodynamic system. The dynamic processes taking place inside the boiler are non-linear and interconnected. Changes in the technological parameters of the exhaust gases occur in ranges that do not allow to obtain an acceptable quality of the linearized model. Due of the difficulty of creating a mathematical description that takes into account the operation of the installation in different modes, recurrent neural networks were chosen to implement the simulation task. Based on the recurrent neural network, a dynamic model was synthesized that describes the change in the technological parameters of the waste heat boiler in the “Power boost”, “Rated Load”, “Power reduction” operating modes. The model output is the temperature of the network water behind the boiler. The created model takes into account the change in the water flow through the boiler, the change in the inlet water temperature, the increase and decrease in the temperature and pressure of the exhaust gas at the inlet of the waste heat boiler. In the formation of training and test samples for the neural network, archival trends obtained during the operation of the waste heat boiler were used. The article provides experimental data, a description of the stages of the synthesis of a neural network model, structural and graphic schemes, simulation results with explanations.

Vestnik of Samara State Technical University. Technical Sciences Series. 2020;28(2):59-72
Instrumentation, Metrology and Informative-measurings devices and systems
Features of measuring absolute permeability of rocks
Pescov A.V.

Aspects of gas permeability measurement on samples of terrigenic and carbonate rocks of oil and gas collectors, as well as artificial samples on the domestic Darsimeter plant are considered. The following types of reservoir rocks were used for the study: pore, fractured, cavernous. The scope of application of the Darcy Law for pore-type rocks was clarified, which is limited to small pore pressures. Permeability coefficients were determined taking into account the gas slip-law effect of Klinkenberg on regression equations. Apparent permeability at low pressure drops was determined. For a number of samples with low permeability, the pore size was calculated to relate to the apparent permeability value. The calculation was carried out on the basis of the obtained values of structural coefficients of rocks by the method of electrical resistivity and on the basis of porosity values determined using the Preobrazhenskiy method.For a number of crack and capillary samples, the relationship between the pressure gradient and the filtration rate became nonlinear, and types of filtration laws were determined. Establishing the applicability of Darcy 's law or nonlinear law was controlled by constructing indicator curves and calculating the Reynolds number. For terrigenic rocks of high permeability, errors of measurement of gas permeability coefficients at different pressure drop intervals were determined: dispersion and coefficient of variation showing low values were calculated.

Vestnik of Samara State Technical University. Technical Sciences Series. 2020;28(2):73-83
Evaluation of metrological reliability of measuring instruments by method of generating functions
Yashin V.N.

An article deals with problems related to the assessment of metrological reliability of measuring instruments by method of generating functions. Metrological reliability of measuring instruments is the most important characteristic that determines the accuracy and reliability of physical quantities measurements. In the suggested article, a confidence indicator is proposed as an evaluation of metrological reliability. The quantitative value of confidence indicator can be estimated by means of the method of generating functions. This is a scientific novelty of the work. Relevance of the problem of assessing the measuring instruments metrological reliability evaluation is substantiated in this paper since the current trend towards structural and functional complexity of measuring instruments may lead to decreasing of their reliability and, in particular, metrological reliability. The main goal of this work is to systematize the problems of reliability of measuring instruments and evaluate their metrological reliability using the method of generating functions. On the base of selected mathematical model of the evolution of error of measurement and proposed indicator of metrological reliability means of the method of generating functions allow to carry out metrological forecast of variability of the error of measurement depending on time. The model of gradual failures with a discrete change of the error over time, which is typical for a certain class of measuring instruments, for example, measuring time intervals, was chosen as a model for the evolution of the error of measuring instruments. The method of generating functions used for evaluating the metrological reliability of measuring instruments has made it possible to increase the efficiency of the algorithm for quantitative evaluation of metrological reliability of measuring instruments by simplifying the mathematical operations that underlie it.

Vestnik of Samara State Technical University. Technical Sciences Series. 2020;28(2):84-96
Electrical Engineering
Induction heating system aluminum alloy cylindrical billets
Bazarov A.A., Danilushkin A.I., Zhivotyagin D.I.

This publication discusses the task of developing an induction heating system for billets made of aluminum alloy with a given limit on the permissible temperature deviation. The purpose of the work is to determine the parameters of the inductor sections and the settings of the control system to achieve a given distribution of the billet before being fed under the press. The complexity of the problem is associated with the presence of several heater sections that differ in length from the workpieces, which leads to an additional factor leading to an increase in the unevenness in the distribution of temperature in the load. The model of the electromagnetic process is built taking into account the change in resistivity in the workpieces. When searching for a more efficient calculation algorithm, a joint solution to the thermal and electromagnetic problems is considered, which allows to simplify the procedure for exchanging data between applications. This approach is very convenient for solving problems that are not connected with harsh conditions with the achievement of the final state. When modeling thermal processes, the formulation of the problem takes into account all the features associated with radiant heat transfer between extended surfaces having different temperatures, temperature dependences of the workpiece parameters, a varying heat release region due to displacement. As options for a heating system, software control and a multichannel system with control correction for temperature control at one point are considered. When simulating a multi-channel heating control system, built-in software functions were used that made it possible to form control actions for each channel and recommend the location of temperature sensors providing high-quality control of heating.

Vestnik of Samara State Technical University. Technical Sciences Series. 2020;28(2):97-110
To the question of damage, maintenance and repairs of submersible electric equipment for oil production
Romanov V.S., Goldshtein V.G.

In optimizing and managing the life cycles of submersible electrical equipment (SEE) for oil production, an integrated approach to the organization of maintenance and repairs (MRO) is advisable based on the development of a more advanced strategy for carrying out repair cycles. It is stated that the maintenance and repair strategies adopted by the oil industry do not fully ensure operational efficiency, which leads to an increase in premature equipment failures, a reduction in turnaround times and, as a result, losses for oil companies. The advantages and disadvantages of approaches to organizing the operation of SEE on the operating time and the actual state in the planning, implementation of maintenance and repair, as well as the feasibility of their complex application are evaluated. It is proposed to use statistical models to make an informed decision on determining the composition and period of MRO, forecasting the boundary states of sets in general and specific SEE electrical installations. At a given operating time, it is possible to determine the basic laws of the appearance of defects and the mean time between failures (MTBF) of the elements, as well as the fleet of equipment of oil-producing enterprises as a whole. The results obtained are the rationale for a set of recommendations to improve operational efficiency and optimize life cycle management of submersible electrical equipment for oil production.

Vestnik of Samara State Technical University. Technical Sciences Series. 2020;28(2):111-123

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