Vol 28, No 4 (2020)
Informatics, Computer Science and Control
Parametric identification in inverse heat conduction problems under interval uncertainty based on neural networks
Abstract
The application of parametric identification methods used to solve inverse problems of technological thermophysics under conditions of interval uncertainty of parameters is considered. To solve such problems under the action of disturbing factors, artificial neural networks can be used that reproduce the structure of the operator of the direct problem with a small dimension of the desired vector of parameters. A variant of constructing a neural network for solving the boundary inverse heat conduction problem with a known structure of a mathematical operator, characterized by a small number of parameters, is proposed. The method allows the use of a priori information about the admissible range of belonging of the identified characteristics or their parameters. The input data for the neural network model are all possible realizations of temperature states, obtained as a reaction to the input action, which is an identifiable characteristic that satisfies all permissible options for the combination of parameters.
The solution of the problem is an iterative procedure, at each step of which, using a neural network, the value of one of the parameters specifying the parametric representation of the desired value is refined. The combination of neural network technologies with high-quality information about the regularities of non-stationary heat conduction processes makes it possible to increase the accuracy of solving the problem of parametric identification under conditions of disturbances. Variants of solving the boundary inverse problem of heat conduction with one- and two-parameters representation of the desired characteristic under the conditions of disturbances are demonstrated. The accuracy of solving the problem is investigated depending on the intensity of the disturbing effect
6-18
Two-channel time-optimal control of nonstationary heat conductive process with account for response time of boundary control actions
Abstract
The formulation and calculation method of time-optimal control algorithms of the heating process of an unlimited plate with two external concentrated control actions by the value of heat fluxes on its surfaces in a heating installation with extraneous heat exchange are proposed. The main feature of the problem is to take into account of response time of both control actions created by the dynamics of heat transfer processes in a furnace body. 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 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 two-cannel time-optimal control of temperature field in furnaces with extraneous heat exchanger, results of solution and its analysis are carried out.
19-31
Adaptive system for maintaining the quality of the field oil treatment
Abstract
The paper deals with the issues of creating an adaptive system for maintaining the quality of field oil treatment. The proposed system is based on a mathematical model of the oil preparation process, which allows predicting the quality indicators of commercial products. To prevent the deviation of the commercial oil quality indicators from the standard values, the system predicts new values of the technological regime parameters and the time of their correction. The mathematical model of the process is implemented in a software product for modeling and calculating processes and devices "MiR PiA Process". The proposed system constantly adapts the mathematical model to the real operating mode of the installation on the basis of instrumentation and automation data, as well as periodically obtained results of laboratory analyzes.
32-49
Relay system with variable hysteresis structure synthesis as an alternative to sliding mode control
Abstract
The paper researches algorithms for controlling relay systems with negative variable hysteresis in the static characteristic of the control device and variable structure. These algorithms simplify the control device by excluding the time variable from the control law. A comparison with the sliding control mode using the derivative in the control law is made. The described control algorithms are examined by the example of a ventilation and heating system with a three-point valve as a control device. Digital modeling of the developed algorithms confirms the effectiveness of their use in a wide range of controlled objects for a number of qualitative indicators of the relay automatic control systems functioning. It is shown that the transition characteristics of automatic control systems under the same initial conditions have a monotonous character and the same transition time. At the same time, the control with negative variable hysteresis is easier to implement and configure.
50-61
Models for the assessment of robotic vehicle maintenance efficiency
Abstract
Maintenance and repair are of great importance in creating and operating a system of unmanned vehicles for agricultural enterprises. The article proposes a methodology for assessing the effectiveness of robotic vehicles' functioning in terms of operation and maintenance. It is suggested to use the method of Data Envelopment Analysis based on fractional rational programming models. The parameters of robotic vehicles have been determined, for which a comparative assessment is carried out. The leading indicators of the maintenance and repair system efficiency are the downtime ratio for maintenance, the vehicle drift rate from the line, the reliability of the vehicle aggregates, robotic vehicle residual life, mileage per month, and the operation and maintenance unit cost. The basic models are the Cooper – Charnes – Rhodes and Bunker – Charnes – Cooper models using the super-efficiency frontier's construction. The analysis of solutions for various subsets of parameters of robotic vehicles is carried out. The production possibility set diagrams are plotted, and target changes in vehicles' parameters and the maintenance system are determined to achieve the efficiency frontier. The development of the maintenance system was assessed using the Malmquist index, and the reasons for the unsatisfactory operation of robotic vehicles were identified. Conclusions are made to improve the organization of the maintenance system.
62-76
Instrumentation, Metrology and Informative-measurings devices and systems
Ensor networks - distributed information measuring and information control systems
Abstract
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.
77-88
Calculating of asymmetry and excess coefficients for chromatographic peaks by using chebyshev – hermite functions and gram – charlier series
Abstract
The paper deals with the development of an algorithm for computation of excess and asymmetry coefficients for chromatographic peak, given by Gram-Charlier series. Investigation of possibility using direct transformation of coefficients of signal decoding in Chebyshev-Hermite basis to terms of the Gram-Charlier series weights are described. By applying coding in Chebyshev-Hermite basis algorithm to Gram-Charlier series system of linear equations that depend of excess and asymmetry coessicients are formed. Solution of this system of equations is sought coefficients. Errors of formed algorithm are described in dependence to errors of estimation shift and RMS width. The computer algebra system Wolfram Mathematica 11.3 was used for calculations and graphical presentation of the simulation results.
89-105
Electrical Engineering
Simulation and research of the power supply system for multigenerator microwave heating installation
Abstract
The task is to study electromagnetic processes in the power supply system of a dielectric heating installation, in which a group of industrial packaged magnetrons creates microwave oscillations. A simulation model of the power supply system for multigenerator microwave heating installation was created in the Matlab&Simulink programming environment. The model allows you to obtain information of voltage and current instantaneous and integral values in the power supply system, and to calculate energy characteristics of the system. Simulation was carried out for the case when the sources of microwave oscillations are "2M164" packaged magnetrons. Based on the simulation results, the influence of the mains voltage parameters on the operating mode of the microwave installation was determined also the need for voltage stabilization was shown to ensure the preset operating mode of the installation. It is shown that the pulsed operation mode of magnetrons is the cause of the consumed current distortion and the current presence in the neutral wire.
106-117
Optimization of operation mode of distribution networks with active-adaptive elements
Abstract
Power supply is reproduced from its own sources of electricity or from existing electrical networks. Therefore, the most important task is to develop measures to maintain the quality of electrical energy on the tires of the end user. Distributed power generation is the construction of additional sources of electricity in the immediate vicinity of consumers. Currently, the main interests of consumers are the possibility of redundancy, due to savings in reducing costs, increased efficiency of joint generation of heat and electricity. Various energy companies have begun to rely more heavily on existing support from distributed generation sources during peak loads, using these capacities to reduce losses and improve network performance. Alternative generation can be additional sources of active power. Distributed generation facilities currently account for about seven percent of the total electricity generation in Russia. This indicator is half the global scale, but distributed generation has already taken place in Russia as a phenomenon, and this industry is actively developing. Significant depreciation of fixed assets in energy complexes, high accident rates, planned and unscheduled shutdowns are among the most significant problems of the Russian energy sector. Renewable energy is an alternative energy sector based on the use of virtually inexhaustible resources for generating electricity (solar, wind, river, sea, geothermal, etc.). renewable energy has both advantages and disadvantages. Gas distributed generation is the most efficient energy technology. The popularity of distributed generation and the introduction of "smart" networks has many prerequisites. The benefits that the owner of distributed generation receives are obvious.
118-130
Structural and parametric identification of the circular transfer table
Abstract
The paper discusses the issue of improving the accuracy of reproducing the task signal by a circular transfer table, which is most widely used both for autonomous operation and as part of electromechanical systems, for example, coordinate boring machines. The disadvantage of traditional table designs is the presence of backlash in the supply of motion from the electric motor to the faceplate, the faceplate fixing devices, that limits the static and dynamic accuracy in the faceplate position and, consequently, in the processing of the part. The paper discusses a fundamentally new design of the table - in the form of a mechatronic module, which has the electric motor and faceplate connected without a gearbox. This made it possible to eliminate the disadvantages of the traditional transfer table and ensure high statistical and dynamic accuracy in reproducing the task signal.
131-141
Hybrid magnetic bearing
Abstract
Increase of energy efficiency and decrease of weight-size parameters is an important problem for improvement of magnetic bearings. Using of permanent magnets on base of rare earth metals is promising direction for improvement of consumer properties of magnetic bearings. In a paper some questions of integrate of permanent magnets in a radial magnetic bearing for rotor weight offsetting was considered. Simple mathematical model that link carrying capacity with pole dimensions was consider. The dimensions poles of a hybrid magnetic bearing in identical external size was calculation by using proposed policy. Hereafter magnetic field was researched by means of numerical simulation for traditional and hybrid magnetic bearings and traction performance depending on control current was founded for various location of rotor. Analytical calculation and numerical simulation demonstrate that traction force creating by permanent magnets offset of rotor weight in full but traction force creating by electromagnets full provide operating traction force. Installations of permanent magnets render possible decrease of magneto motive force of control poles, size of a coil and finally, increase of energy efficiency of a magnetic bearing. Using of permanent magnets essentially action on traction performance of a magnetic bearing. Operating point was displaced in mean region of traction performance curve. In results all coil of electromagnets happened in equal terms on temperature. Considered properties of a hybrid magnetic bearing may have to influence on a dynamic performance of a control system positive.
142-154
Asynchronous motor rotation speed observer
Abstract
The paper is devoted to the mathematical foundations of creating sensorless speed stabilization systems for induction motors with scalar control. There are many applications of AC electric drives where scalar control is required, and the use of speed sensors is impossible for technical or economic reasons. Most modern observers of the asynchronous motor speed are intended for electric drives with vector control and are based on solving differential equations using Kalman filters or an adaptive model of an asynchronous motor. The paper discusses a new approach to creating a speed observer, based on solving the algebraic equation of the induction motor mechanical characteristics. The change in the rotor speed of the motor under the influence of the load torque and the variation of the stator voltage is analyzed. A coefficient connecting the speed of an induction motor with voltage is introduced. It is shown that its value depends on the initial conditions and the moment of loading. The nonlinear relationship between the torque developed by the motor and the stator current is taken into account. As a result, the analytical relationship is found that connects the speed of an induction motor with the effective values of the stator voltage and current and the frequency of these values. An assessment of the adequacy of the obtained formula for calculating the induction motor speed in a scalar frequency control system is carried out. The results of field experiments are presented, which show that the maximum error in calculating the speed from the found analytical dependence does not exceed 4.3%. It is concluded that the use of the formula obtained is essential in the asynchronous motor speed observer of the electric drive with scalar control.
155-166