Failure-free Operation Research Articles

ПОВЫШЕНИЕ ЭНЕРГОЭФФЕКТИВНОСТИ И НАДЕЖНОСТИ ГОРНЫХ ПРЕДПРИЯТИЙ НА ОСНОВЕ АНАЛИЗА ГРАФИКОВ ЭЛЕКТРИЧЕСКИХ НАГРУЗОК

This article presents the results of calculation and analysis of indicators of graphs of electrical loads, energy efficiency and evaluation of reliability indicators of power supply systems of the scheme on the example of mining enterprises. The expediency of substantiating the preliminary analysis of electrical load profiles with the subsequent use of a general logical-probabilistic method for calculating the reliability of power supply systems is substantiated. А comparative analysis of the calculation of reliability indicators (availability coefficient, average operating time, average recovery time, probability of failure-free operation) for individual consumers in case of failure of several elements is presented. The influence of the reliability of individual elements on the reliability of the system as a whole is evaluated. А comprehensive approach is proposed to solve the problem of assessing energy efficiency indicators (specific electricity consumption for open-pit mining, specific electricity consumption for processing plants, the number of hours of power use) and reliability indicators of power supply systems for mining enterprises by applying a logical-probabilistic calculation method under the condition of limited power supply. Recommendations for improving energy efficiency and analyzing the reliability of power supply to industrial enterprises are given.

О НЕКОТОРЫХ ОСОБЕННОСТЯХ ОПРЕДЕЛЕНИЯ КАЧЕСТВА ПРОДУКЦИИ НА ПРИМЕРЕ ДАННЫХ ОДНОГО ИЗ ВЕДУЩИХ ОТЕЧЕСТВЕННЫХ АВТОПРОИЗВОДИТЕЛЕЙ

The article proposes a method for describing the probability distribution density of the failure-free operation of a product in the form of a two-parameter exponential function. Based on the data of one of the leading domestic car manufacturers, examples are considered and an assessment of the obtained theoretical distributions is carried out. In this work, to assess the quality of products, it is proposed to use the indicator of the average time spent on warranty service and car repairs during the first year of its operation.

СОХРАНЕНИЕ РЕСУРСА ВЫЧИСЛИТЕЛЬНОГО УЗЛА БРОКЕРА ТУМАННОГО СЛОЯ В ПРИЛОЖЕНИЯХ ОБРАБОТКИ ДАННЫХ

In accordance with the concept of fog computing, when processing large amounts of data, the computing workload shifts from the “cloud” to the edge of the network, to the nodes of the fog layer. At the same time, however, a very small number of published works deal with the issues of reducing with that the residual resource of peripheral devices, which, as a rule, are not of a high computational power comparing with devices in data centers. The reliability indicator, the probability of failure-free operation are also associated with such a characteristic as the average residual resource – the value of the reciprocal of the failure rate, and in general, the decreasing trend of the value characterizes the safety of the computing resource of the device and the time during which its operation will be expedient due to the allowable failure rate. Modern implementations of the concept of fog computing suggest the presence of a so-called cloud-fog broker, which is entrusted with the functions of computing scheduling that can be performed by nearby fog layer nodes. Obviously, in this case, the cloud-fog broker operates with an increased load, and it is quite reasonable to raise the question of saving the resource of the node. The article is concerned with the study of comparing the “selfish” strategy of distributing the computational load over the nodes of the foggy layer in the network and the approach based on the choice of a node for computing based on the simulation of the average residual resource. The proposed algorithm makes it possible, depending on the preferences in the safety of the resource of the node, to implement the choice of device. The simulation performed demonstrates the expediency of including the fog layer broker in the subset of considered candidates for load distribution even in the case when, in accordance with the “selfish” approach, it is more profitable for the broker to transfer calculations to the next node. The latter is also relevant for the case when it is a priority to reduce resource consumption for a group of devices, including a broker

Разработка математической модели функционирования электротехнических комплексов релейной защиты цифровых подстанций

The issues of introduction of electrical digital substations in the Russian Federation are considered. An existing criteria analysis for assessing the modern relay protection devices efficiency is carried out and an assessment of their sufficiency is made. A mathematical model development of the digital substations relay protection complexes operation has been developed using the queuing theory, the graphs theory and Markov chains. The failure-free operation probability calculated value of the relay protection complexes corresponds to the long-term analysis data. This indicates that the mathematical model is correct. The proposed mathematical model makes it possible to take into account the impact of the maintenance quality on the digital substation relay protection complexes efficiency.

Methodological approach to estimating the probability of failure-free operation of complex technical systems taking into account the characteristics of the control system based on the Bayesian Belief Network

Methodological approach to estimating the probability of failure-free operation of complex technical systems taking into account the characteristics of the control system based on the Bayesian Belief Network

An Algorithm for building a mathematical model in Bayesian belief networks for reliability analysis

The application of Bayesian belief networks in the analysis of reliability is considered. An algorithm for constructing a mathematical model in Bayesian belief networks is developed. An example of reliability analysis of a radioelectronic system by using Bayesian belief networks is given. It is shown that the developed model of Bayesian networks allows estimating the probability of failure-free operation, identifying possible failures and modeling failure states. Keywords Bayesian networks, reliability, reliability analysis, electronic system, fault tree analysis

Mechanisms of ensuring the accuracy and reliability of data transmission over a radio channel using relay technology and their implementation on transceivers with LoRa modulation

The article is devoted to a detailed description of the algorithms of the operation of the relay-race data transmission system over a radio channel, which ensure high reliability of transporting the results of monitoring the operation of extended objects to the central control panel. The feature of the system is operation at a low power level of transmitters, energy efficiency, which ensures a long-term operation without maintenance, the ability to replace failed elements quickly without stopping the entire system, mobility — quick installation and start-up of the system. Energy efficiency and operation of the radio channel with a low transmitter power level is ensured by the use of SX 1276 (LoRa) transceivers. The accuracy and reliability of data transmission is ensured by original algorithms, which are described in the paper. In the relay data transmission system, it is possible to use up to 255 relay nodes with their installation at a distance of up to 4 km from each other. Two options of building a system with relay-race transmission have been developed: a system with a simple handover, a system with transmission «Through one». The second option provides more reliable data transfer and higher probability of uptime. With the number of relay nodes equal to 50, the probability of failure-free operation of a simple system is 0.268, and for the system with «Through one» transmission is 0.985.

РАСЧЕТ ПОКАЗАТЕЛЕЙ НАДЕЖНОСТИ ЗАДНЕГО МОСТА АВТОБУСА В УСЛОВИЯХ НЕЧЕТКОЙ ФОРМАЛИЗАЦИИ ПАРАМЕТРОВ ОТКАЗОВ

The article deals with the issues of constructing a rear axle reliability scheme. On the basis of statistical analysis, estimates of the parameters of the Weibull reliability model for individual axle nodes are obtained, which are the basis for calculating rear axle reliability schemes. For the main nodes that are used in the reliability scheme, the proximity to the Rayleigh model is shown, which is used as the base model. The article proposes an approach for calculating the reliability of a bridge based on the use of fuzzy sets. It is assumed that the parameters of reliability models represent fuzzy numbers. To calculate the scheme on the basis of classical methods, transformations of the membership functions of the parameters of the reliability models of parts are obtained. As a result, reliability indicators such as the probability of failure-free operation, the probability of failure, and others are also fuzzy numbers or fuzzy functions.

Control of complex thermoelectric cooling units with mixed electrical connection in a uniform temperature field

The possibility of optimal thermal management of a number of temperature-dependent and heat-loaded elements of radio electronic equipment with calculated power dissipation is considered. Studies have been carried out in a uniform temperature field using a set of thermoelectric cooling devices and defined geometry of thermocouple branches. The correlation for determining the relative operating current depending on the relative temperature drop for a given supply voltage, thermal load and geometry of thermoelements branches has been obtained; the range of valid values of the relative operating current has been determined. Acomparative analysis of the basic parameters, reliability indices and dynamic characteristics of a group of thermoelectric devices included in the complex for different supply voltages and heat loads has been made. The possibility of selecting supply voltages of thermoelectric devices complex with regard to limiting factors for mass-size, power, dynamic and reliability characteristics to ensure the optimum thermal mode of a number of thermo-dependent elements of radio electronic equipment has been shown. With increasing supply voltage of thermoelectric devices complex with mixed electrical connection in uniform temperature field at given thermal load and geometry of thermoelements branches the following results are achieved. Steady-state time increases, the number of thermoelements increases, the cooling coefficient decreases, the amount of consumed energy increases, the heat dissipation capacity of the heat sink increases, and the functional dependence of the probability of failure-free operation on the total supply voltage has a maximum.

OPTIMAL FAULT DETECTION OF RIVER SHIP HULLS

The issue of determining the reliability of the hulls of inland and river-sea-going vessels after a known number of years of operation under given condition is considered. It is accepted that fault detection of a ship’s hull is a survey, measurement and evaluation of defects in each element of the ship’s hull in order to establish the methods and scope of repairs that ensure its reliable operation until the next regular survey under specified operating conditions. It is shown that the volume of residual thicknesses can be significantly reduced using the statistical data on wear rates presented in the Rules of the Russian River Register. At the same time, the reduction in the scope of measuring the parameters of defects retains the probability of detecting all defects of the hull elements to the level of 0.95, and the probability of failure-free operation of the hull until the next survey, after the elimination of the identified defects will be at least 0.95. A form of table for processing the values of the residual thicknesses of all elements in the inspection report and instructions for filling it out are given. Explanations for using the results of measurements and calculations at determining the technical condition of certain elements in the group and the ship’s hull as a whole are given. The last column of the table indicates the method of eliminating the defect of an element and groups of elements, and in the conclusion of the inspection report, the method of repair and its scope for the entire hull of the ship providing a suitable assessment of the condition after repair are indicated. The main advantage of this paper, in difference from the previous studies of the authors in this area, is that user-friendly (the designer of the defect report tables) nomograms, which allow you to reduce the number of measurements of the residual thicknesses of hull structure elements in the online mode, have been created. The performed study, allowing you to reduce the number of measurements while guaranteeing the reliable operation of the ship’s hull, will let the shipowner to reduce the cost of repair work by reducing the number of days of ship standing on the slipway (in the dock). In addition, the ship repair company will be able to free up its production facilities for the purpose of their subsequent loading with other ship repair or shipbuilding orders, which will increase the efficiency of their activities.

A COMPREHENSIVE STUDY OF THE INFLUENCE OF DAMAGES OF THE STATOR WINDING OF ASYNCHRONOUS MOTORS DURING OPERATION OF VEHICLES

The efficiency of providing transportation is related to increasing the reliability of the transportation infrastructure. To ensure reliable and economical operation, it is necessary to develop systems of functional diagnostics of the main elements of vehicles, which provide continuous control of the technical condition of its main elements. Monitoring the state of asynchronous electric motors as part of electric drives of vehicles is an important modern issue, the solution of which depends on the reliability of the entire transport infrastructure. The most common type of damage in motors during operation is an inter-turn short circuit in the stator winding phase. Turn-to-turn closures are difficult to detect, but if they are present, the engine continues to operate with a change in its operating and electrodynamic indicators and characteristics. However, depending on the degree of turn-to-turn closures (the number of closed turns) in the winding phase, the probability and time of an emergency stop of the electric drive increase. In this paper, the influence of turn-to-turn closures of varying degrees on mechanical, electrical and energy parameters and engine characteristics under various operating modes has been studied. In the course of the research, a mathematical model of an induction motor was used with the established adequacy of the simulation results and the possibility of creating an asymmetric rotating stator field. The adopted simulation model of an induction motor with a squirrel-cage rotor is written in retarded coordinates. Also, studies were carried out on the effect of turn-to-turn closures on the ripple coefficient of the electromagnetic torque and the unbalance coefficient of the stator phase currents. Based on the data obtained, recommendations are given on choosing the most effective method of electric current for diagnosing interturn faults in assessing the technical condition and predicting the failure-free operation of an asynchronous electric motor for use as part of an electric motor under construction. - in diagnostic systems of cars.

MATHEMATICAL MODEL OF COMPUTER SYSTEM RELIABILITY IN RESIDUAL CLASSES

The subject of the article is the construction of a mathematical model of the reliability of a computer system (CS) that operates in a system of residual classes (RNS). This mathematical model is based on the use of structural sliding reservation. The purpose of the article is to increase the reliability of the CS, which operates in the system of residual classes, as well as to calculate and compare the reliability, in terms of the probability of failure-free operation, of the CS in the RNS and the ternary computing system, which operates in the positional binary number system (PBNS). Tasks: to analyze the influence of the number system used on the reliability of the CS; to investigate the properties of the RNS and determine their influence on the structure of the CS in the RNS; build a mathematical model of reliability and, on its basis, perform the calculation and comparative analysis of the reliability of the CS in the RNS and the tripled CS in the PBNS. Research methods: methods of analysis and synthesis of computer systems, number theory, coding theory in RNS, reliability theory. The following results are obtained. The paper shows that the provision of a given level of reliability in the design of the CS using the RNS is due to the presence of various types of redundancy at the same time: structural, informational, temporal, functional and load. In RNS, these types of redundancy can be effectively used to improve the reliability of the CS. The CS in the RNS represents a computational structure that is identical in structure and principle of operation to the sliding structural redundancy model in the PBNS in the case of a loaded (hot) mode of operation of the redundant elements. Proceeding from this, the paper presents a mathematical model of the reliability of the CS in the RNS. In this paper, the calculation and comparative analysis of the reliability of a tripled computing structure in a PBNS with an ideal majority element and a CS in an RNS with an ideal reliability automaton are carried out. Conclusions. As shown by the results of calculations and comparative analysis in some time intervals of operation, the probability of non-failure operation of the CS in the RNS is higher than the probability of non-failure operation of the aircraft in the PBNS with a tripled majority structure. This implies the effective use of the RNS to improve the reliability of the CS.

RELIABILITY ANALYSIS OF PRECISION GEARS WITH MODIFIED INITIAL TOOTH CONTOUR

The article presents the results of a theoretical study that was conducted as part of the search for solutions to the problems of calculating the operational reliability of gears of a new generation that have a significant deviation in the geometry of the profile of the teeth and the entire engagement from the standard initial contour. A method of plotting the wear of the working surfaces of gear teeth has been developed. The essence of the method is that the equation of the worn surface can be obtained by calculating the full variational derivative of the functional of the energy action of wear. Since wear reduces accuracy, the method is used to calculate the probability of failure-free operation of precision gears by the express method. The proposed article is one of the first works on the calculation of the operational reliability of precision gears with teeth profiled by the involute epitrochoid.

Probabilistic indicators of imperfect inspections used in modeling condition-based and predictive maintenance

This study proposes mathematical models for assessing the probabilistic indicators of imperfect inspections conducted when performing condition-based and predictive maintenance. The inspections used in mentioned types of maintenance differ in decision rules regarding system operability at the time of checkup. Contrary to the previous studies, we present the decision rule for each type of inspection on the time axis, which allows the formulation of the set of mutually exclusive events at discrete times. The correct and incorrect decisions correspond to true-positive, false-positive, true-negative, and false-negative events. We propose general expressions for computing the probabilities of possible decisions for both types of inspection. The paper introduces the effectiveness indicators of condition-based and predictive maintenance such as average operating costs, total error probability, and a posteriori probability of failure-free operation. We illustrate the developed approach by calculating the probabilities of correct and incorrect decisions using a specific stochastic deterioration process. The results of the calculations verify that probabilities of correct and incorrect decisions for both types of inspection are very substantially time-dependent despite the large number of published studies where these probabilities are independent of time.

Temporal Verification of Relay-Based Railway Traffic Control Systems Using the Integrated Model of Distributed Systems

Relay-based traffic control systems are still used in railway control systems. Their correctness is most often verified by manual analysis, which does not guarantee correctness in all conditions. Passenger safety, control reliability, and failure-free operation of all components require formal proof of the control system’s correctness. Formal evidence allows certification of control systems, ensuring that safety will be maintained in correct conditions and the in event of failure. The operational safety of systems in the event of component failure cannot be manually checked practically in the event of various types of damage to one component, pairs of components, etc. In the article, we describe the methodology of automated system verification using the IMDS (integrated model of distributed systems) temporal formalism and the Dedan tool. The novelty of the presented verification methodology lays in graphical design of the circuit elements, automated verification liberating the designer from using temporal logic, checking partial properties related to fragments of the circuit, and fair verification preventing the discovering of false deadlocks. The article presents the verification of an exemplary relay traffic control system in the correct case, in the case of damage to elements, and the case of an incorrect sequence of signals from the environment. The verification results are shown in the form of sequence diagrams leading to the correct/incorrect final state.

Methods for the reliability optimization of district-distributed heating systems with prosumers

District-distributed heating systems are considered as the result of the development of existing district heating systems, in which various energy technologies are integrated to achieve maximum efficiency of the heating to consumers. The distributed sector in these systems is associated, first of all, with the implementation of prosumers. The problem statement is determining such values of reliability parameters of components (in particular, failure rates) of studied system that provide the required level of reliability of heating to consumers at the minimum cost for ensuring this level of reliability taking into account the redundancy of prosumers. A methodology is based on the nodal probability of failure-free operation index, the Markov random process, the laws of heat transfer processes in heat supply, and some other methods. A case example is considered, an analysis of the results obtained is carried out, and directions for further research are formulated.

Improving tools for diagnosing technical condition of ship electric power installations

Existing information-measuring systems (IMS) do not fully correspond to the tasks of monitoring electric power installations (EPI) in terms of their characteristics. The capabilities of IMS have certain limitations regarding the probability of measurement results and the degree of invariance to the influence of operational factors. This proves that for modern failure-free EPI technical operation, new diagnostic tools are in demand. Such means should be seamlessly integrated in IMS to enable high operational efficiency and performance reliability. Therefore, it is of particular relevance to tackle the scientific and technical issue of rational combination of protection and preservation of the characteristics of fiber-optic sensors of relative humidity control systems in ship EPI. To solve the problem, the chosen object of this study is the processes of formation and transformation of the diagnostic signal in the means of humidity control. It has been established that the improvement of the characteristics of the control means can be achieved through the synthesis of known optical circuits and the latest materials. To register the parameters of relative humidity, a new circuitry solution was proposed for the sensor based on fiber-optic and elements made of nanomaterials. The main feature of the proposed monitoring tool is invariance to operational destabilizing factors. The scope of application of the obtained research results involves distributed fiber-optic systems for monitoring the technical condition of ship electric power systems. The introduction of a new means for measuring humidity will make it possible to achieve an increase in the efficiency of use and reliability of EPI by reducing the accident rate by 6...11 %, as well as a decrease in operating costs by USD 8...10 per 1 kWh of generated power per year of operation with an average load

Определение теплового состояния элементов турбокомпрессора поршневого двигателя

The power boost of heat engines is conditioned by the increase in the load on all its elements and related units. The turbocharger is one of the most common units that provide the power boost of a heat engine. The reliability of the turbocharger and its tribo-couplings guarantees the stable operation of not only it, but also the machine as a whole. An increase in the rotor speed leads to an increase in the thermal loading of the turbocharger elements. In this regard, timely assessment of the thermal state of the tribocoupling components, temperature distribution over the shaft, housing and other elements of the turbocharger is an urgent task. An algorithm for calculating heat transfer between the elements of a turbocharger has been developed, and an assessment of the heat load of radial multilayer plain bearings of a flexible asymmetric rotor has been made. The simulation was carried out in the ANSYS Fluent software package. The experimental data of the manufacturing plant were used as boundary conditions. The results of the calculation are given: the distribution of thermal fields in the turbocharger housing and the temperature in the area of ??the turbine and compressor plain bearings. Dependences of temperatures in the bearing area on the rotor speed are obtained. The calculation results were verified by comparing the temperatures in the turbine and compressor plain bearings with the data given in the publications of other authors. The temperature values in the outer and inner layers of the bearing were the initial data for calculating the dynamics of the turbocharger rotor, taking into account the thermal deformations of the tribocouple elements. The results of the research will be used to assess the stability of the movement of the rotor, the failure-free operation of the bearing assembly, as well as the reliability and durability of the turbocharger as a whole.

Planning of a Group of Dynamic Systems Operation Program Based on the Failure Time Prediction

The article is devoted to the justification of group of dynamic systems (DS) operation program based on the failure time prediction. The following assumptions are made: the group includes DS operating under the same conditions, but having different service life; the composition of the DS includes a number of potentially faulty elements with similar values of reliability indicators; for each element a number of parameters are measured and the failure of the DS occurs when at least one of the controlled parameters leaves the tolerance range. The use of a piecewise linear regression model of parameter drift corresponding to the life cycle of DS is justified. The rule of correction of the linear model is formed based on the results of last measurements of the controlled parameters. A unified algorithm for calculating the reliability characteristics in a group of DS based on the drift of controlled parameters is proposed. At the first step, the probability of failure-free operation for a given time and a gamma-percent resource is calculated for one controlled parameter. At the second step, the time moment of a DS failure (which is assumed to happen when at least one controlled parameter leaves the tolerance range) is calculated. At the third step, the reliability characteristics of a group of DS are predicted using a mixture of distributions. The realization of a random variable corresponding to a random mixture is modeled as follows: first, DS is selected at random, then a random variable is modeled in accordance with its distribution function. The mixture distribution function is expressed as a weighted sum of the component distribution functions. Model examples allowing to rank the considered DS according to the predicted failure time with subsequent adjustment of the operation program are considered.

Agricultural Equipment Design Optimization Based on the Inversion Method

A representative statistical analysis of the operational information of the reliability of tillage units, which have operating devices with an oscillating motion, was carried out. The results of the working condition of thirteen cultivators in operation, with an accumulated operating time of more than 280 thousand hectares, were considered. A field investigation was carried out in seven regions in Ukraine, characterizing various edaphoclimatic conditions. The occurrence of sudden failures due to the fracture of the elastic struttings of cultivator operating devices was established. There were 42 sudden failures among 260 tested struttings. The inversion method was proposed to determine the elastic elements’ loading parameters being a combination of the theoretical reliability model, which was adapted to the probability of failure-free operation prediction due to the fact of sudden failures, and statistical model-specific indicators that were obtained depending on the operating elastic struttings. The given approach, based on the evaluation of the operating tillage units, made it possible to determine the impact of the load on the existing designs of the machines and their elements leading to the sudden failures. It was possible to present such an influence in the form of a probabilistically justified reserve factor, which had an empirical basis and allowed for the design of the next generation of technical systems and their elements to correct the theoretically assumed load value. Constructive and technological changes in the design, based on the approach described in this article, provide an opportunity to manage the level of reliability for economic and image reasons.