Vol 29, No 2 (2021)

Informatics, Computer Science and Control

The initialization of initial generating equipment maintenance schedules while a heuristic method is used

Gubin P.Y., Oboskalov V.P.


Currently, heuristic methods based on iterative changing of feasible solutions set provide a perspective tool for generation equipment maintenance scheduling in power systems. Wherein effectiveness of a heuristic method depends significantly on the initial set of possible schedules or in other words quality of the method initialization. In this case, a widely used methodology of building the initial array of solutions on the basis of pseudorandom uniform generation of control variables seems to be only palliative way to access the problem.

This paper proposes alternative initialization procedure drawing on the example of generating units maintenance planning with heuristic differential evolution method. The principle of this method is to get initial set of solutions utilizing normal probability distribution to generate pseudorandom deviations from the suboptimal maintenance schedule which is to be preliminarily formed using directed search method. Following this approach allows to improve probabilistic characteristics of resultant maintenance schedule – in particular to decrease median value of an objective function and its coefficient of variation, and to maximize probability to get the combination of units outage moments completely suiting operational constraints.

Vestnik of Samara State Technical University. Technical Sciences Series. 2021;29(2):6-23
pages 6-23 views

A strategy choosing method for solving the problem of a guard movement while searching for a criminal under condi-tions of uncertainty

Voroszheykin V.N., Baranov A.S.


The work is devoted to the issue of the complex use of technical means and physical security forces while ensuring the safety of several objects located in the controlled area. The method proposed is for solving the problem of choosing a strategy for searching for a criminal by a security officer while minimizing the time of knowing the direction of movement of the first one to one of the two objects. The proposed method is based on a criminal search strategy implemented by the security guard’s movement control system, which includes two straight sections of their path, which are formed based on information from the security alarm sensors. A mathematical model has been developed for calculating the parameters of controlling the movements of a guard and an algorithm for the control system operation, which makes it possible to implement an optimal search strategy depending on the location of objects, a guard, a criminal, and information from technical means of protection.

Vestnik of Samara State Technical University. Technical Sciences Series. 2021;29(2):24-46
pages 24-46 views

Two-channel time-optimal control of nonstationary heat conductive process with account for response time of boundary control actions

Il’ina N.A.


The task of organization a closed time-optimal control system of linear object with distributed parameters of parabolic type is considered. The object has two lumped internal controls for the power of heat sources excited in the electromagnetic field of an inductor. The proposed method for the synthesis of optimal controllers uses an alternance method for calculating the optimal program controls for each of the control actions. An example of the construction of a quasi-optimal time control system for the process of periodic induction heating of a metal workpiece with constant values of the feedback coefficients calculated for the most characteristic initial spatial distribution is given.

Vestnik of Samara State Technical University. Technical Sciences Series. 2021;29(2):47-60
pages 47-60 views

Fuzzy optimization of feedback control at induction heating

Rapoport E.Y., Rogachev N.G.


The problem of multi-criteria fuzzy-optimal feedback control of an induction heater as an object of technological thermophysics with distributed parameters is considered. A general formulation of the fuzzy optimization problem is given, including requirements for the final and intermediate states and taking into account the fuzziness of competing quality criteria. When solving the problem, interconnected electromagnetic and thermal models of the induction heating process were used. The secondary source method was used to simulate electromagnetic processes, and the differential-difference method was used to simulate thermal conductivity. The numerical method for solving the problem is based on the presentation of the control algorithm in the form of an a priori non-fixed and variable system of rules determined during the heating process. The obtained results of numerical modeling confirm the effectiveness of the proposed fuzzy-optimal method for determining the positional control of objects with distributed parameters.

Vestnik of Samara State Technical University. Technical Sciences Series. 2021;29(2):61-75
pages 61-75 views

Instrumentation, Metrology and Informative-measurings devices and systems

Ensor networks – distributed information measuring and information control systems

Likhttsinder B.Y.


The problems of control and management of geographically distributed objects are considered. The sensor networks operating on the ZigBee technology are considered. The characteristics of the 802.15.4 ZigBee standard are given. The advantages of this technology are shown when building networks that are not very critical to traffic delays. The elements of such a network are considered. The primary converters used in such networks and their energy characteristics are considered. The issues of reducing and compensating delays in control circuits are considered.

It is shown that modern wireless sensor networks can be considered as distributed information measuring and information control systems.

Vestnik of Samara State Technical University. Technical Sciences Series. 2021;29(2):76-87
pages 76-87 views

Theoretical-experimental study of dependence of natural frequencies of oscillations plates from application thickness

Yaroslavkina E.E., Suslov A.V.


The paper considers the problem of asphalt-resin-paraffin deposits in the production of oil and oil products. Methods of sediment measurement have been studied. Computer simulation of dependence of natural frequencies of metal plate oscillations on thickness of deposits was carried out. Correlation dependence of oscillation frequency of the control object on thickness of deposits is confirmed. The obtained results allow prospective investigation of pipe-wires deposits thickness.

Vestnik of Samara State Technical University. Technical Sciences Series. 2021;29(2):88-99
pages 88-99 views

Electrical Engineering

The design of the electromagnetic aluminum mold of periodic action

Bazarov A.A., Navasardyan A.A., Bondareva N.V.


This publication discusses a set of issues on computer modeling of electromagnetic and thermal processes in an induction crystallizer of an aluminum melt, in which forces are created between the melt and the inductor coil, compressing the column of liquid material and preventing direct contact of the melt with the crucible walls. In known induction systems using electromagnetic pressure on molten metal, for crystallization, the parameters of the inductor are selected so that, with sufficient force, the temperature does not rise due to internal sources of heat release with sufficient water cooling of the surface. In the proposed work, heat removal mainly occurs through contact with a water-cooled support surface.

The aim of the work is to determine the process parameters at which the required electromagnetic force is formed on the melt wall, taking into account the change in the current density at the interface between the solid and liquid phases of aluminum.

When determining the parameters of induction crystallizers, the temperature dependences of the thermophysical properties were used. Variants of the inductor realization are investigated, which makes it possible to cover the entire volume of the melt, inside which significant changes in the electrical conductivity of aluminum and the power of internal heat sources are observed. Obtaining a cylindrical shape of the ingot, in contrast to the known electromagnetic crystallizers, is achieved by determining the design of the inductor, which provides a decrease in the repulsive electromagnetic force acting on the side surface of the melt in height. The results of the study showed the possibility of using the crystallizer at various ratios of the height and diameter of the melt column, and the intensity of cooling. The efficiency of the process for aluminum increases with an increase in the radius of the melt column, which also leads to a decrease in shape distortion in the region of the upper end.

Vestnik of Samara State Technical University. Technical Sciences Series. 2021;29(2):100-116
pages 100-116 views

Correction of the static characteristic of a frequency converter to reduce the amplitudes of resonance vibrations of the vibrating table

Vedernikov A.S., Dunaev D.I.


It is known that vibration systems of directional vibrations based on asynchronous vibration motors are currently widely used in practice, but at the same time they have a significant drawback - a sharp increase in vibration amplitudes when passing through the resonance zone at the time of acceleration and deceleration of vibration motors, which negatively affects their operation. The article discusses a vibration table with two unbalanced asynchronous vibration motors. The calculation scheme and equations of motion of such a vibration system are presented. It is shown that the vibration table as a control object is an oscillatory link with a pronounced resonant frequency. The equations of motion of asynchronous vibration motors with scalar frequency control are given. A structural diagram of a vibration table with unbalanced exciters has been developed, the modeling of which made it possible to determine the amplitudes of resonant oscillations. It is proposed to apply correction of the static characteristics of the frequency converter, which connects the effective value of the output voltage with the frequency, to reduce the resonance amplitudes. Equations of the desired static characteristics of the inverter and analytical dependences for calculating the necessary coefficients for its implementation are given. A computational model has been developed that makes it possible to take into account the effect of the corrected static characteristic of the frequency converter on the operation of the vibrating table at the stages of acceleration and deceleration. The results of computer simulation are given, convincingly showing that the correction of the static characteristics of the inverter is an effective means of reducing the amplitudes of resonant oscillations. It is shown that modern frequency converters have functionality that makes it easy to correct the dependence of the effective value of the output voltage on the frequency. The need to adjust the static characteristics of the inverter for a specific type of product tested on the vibration table is noted.

Vestnik of Samara State Technical University. Technical Sciences Series. 2021;29(2):117-128
pages 117-128 views

Program complex for optimization of surface hardening of steel billets

Popov A.V., Pleshivtseva Y.E.


The aim of the paper is to develop program complex in software MATLAB with integrated numerical 2D nonlinear FLUX model, which is used for solving optimal inductor design and control problems for heating stage of surface induction hardening. Considered program complex is based on alternance method, that allows to write systems of transcendental equations, closed with respect to all unknown design and control parameters of the process. The suggestion for implementation of obtained optimal control algorithm is presented.

Vestnik of Samara State Technical University. Technical Sciences Series. 2021;29(2):129-144
pages 129-144 views

Synthesis of the finite controller for the servo drive with the synchronous motor

Starikov A.V., Kirdyashev V.A.


The paper is devoted to the synthesis of a finite controller for a digital servo drive with a synchronous motor, as well as to the determination of the possibility and area of its application. A block diagram of the single-loop servo drive is considered, which contains a digital finite controller that ensures the completion of transient processes in a strictly defined number of clock cycles of the sampling period. The form of the discrete transfer function of the finite controller is proposed. The transfer function of the closed-loop electric drive with the proposed type of controller is found. The system of equations was compiled and solved, which makes it possible to determine the tuning parameters of the finite controller for the servo drive with the synchronous motor. The results of computer simulation are given, showing that the transient processes in the control and disturbing effects in the servo drive are completed in 6 clock cycles of the sampling period. A formula is obtained for calculating the output signal of a finite controller for digital technical implementation on a microcontroller. A computational model of the considered digital electric drive has been developed, taking into account the limitation of current and voltage in the power converter. At small sampling periods, a servo drive with the finite controller is shown to require current limitation at the level of 16 nominal values. At low limiting values, the drive becomes unstable. To ensure the operability of an electric drive with the finite controller, it is proposed to increase the sampling period. It is shown that, in this case the servo drive remains stable in the entire range of displacements even under current and voltage limitations at the level of nominal values. The simulation results made it possible to conclude that the developed electric drive has a high speed of response, since during the development of the control action, the entry into the zone of ± 1 discrete from the set value is 0.022 s. It is shown that the presence of a static positioning error, which increases with an increase in the sampling period, is a negative effect of the finite control application in the servo drive with the synchronous motor. The electric drive in question is proposed to be supplied with one more position loop with an integral controller, which allows to compensate for the static positioning error.

Vestnik of Samara State Technical University. Technical Sciences Series. 2021;29(2):145-157
pages 145-157 views

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