Reliability Of Technical Systems Research Articles

Методологічний підхід до розв’язання проблеми надійності функціонування автомобільних транспортних систем

An analysis of methods and techniques for solving the problem of increasing and ensuring the appropriate level of reliability of technical systems was carried out, which made it possible, based on the use of analogies, to find out the directions for ensuring the reliability of automobile transport systems. The essence of the concept of the reliability of the functioning of automobile transport systems for the transportation of goods and passengers from a methodological point of view is clarified. The insufficiency of regulatory and legal documentation for the development of methods and techniques for assessing the reliability of transport systems is substantiated. The synthesis of the concepts of "management" and "reliability" of the functioning of transport systems in comparison with similar concepts of technical systems is considered. The expert method and methodology of expert assessment of the reasons for failures of the production subsystem of the motor vehicle enterprise and its services are considered. It was found that factor analysis in combination with expert assessment makes it possible to assess the significance of the reasons for failure of transport systems and their frequency. In accordance with the classification of failures of technical systems, an analysis of their belonging to automobile transport systems was carried out. The classification of failures of technical systems according to different sets of features is analyzed. It was established that the classification of failures of automobile transport systems is based on the use of analogy with the classification of failures of technical systems, as well as on the results of the analysis of the factors of the causes of failures that occur in the production system of the carrier's enterprise. It was revealed that the selection of significant factors affecting the failure of automobile transport systems is based on the method of expert evaluations, their ranking by importance was carried out, and their relative frequencies were calculated. The results of the factor analysis of the reasons for the failure of the production subsystem of the motor vehicle enterprise are given. It is assumed that by analogy with technical automobile transport systems, they are also subject to decomposition by stages of the life cycle. Therefore, a sudden failure of automobile transport systems is characterized by a sudden change in the values of one or more initial parameters agreed with the customer, and a gradual one occurs as a result of a slow, gradual deterioration of the functioning characteristics of the subsystem or the system as a whole or a participant in the transportation of goods and passengers.

Some aspects of ventilation system quality indicators

The article analyzes the factors affecting the performance and efficiency of industrial ventilation systems, as well as evaluated the technology and constructive reliability of indoor climate systems. The purpose of the work was to find ways to improve energy efficiency as a priority indicator of modern industrial ventilation systems in conditions of significant and ever-increasing need to save energy consumption costs. The work uses analytical research methods based on theories of probability and reliability of technical systems, analysis of known scientific and own practical results. In the course of the study, the results were obtained allowing to estimate the efficiency of the ventilation system not only in terms of the installed capacity and efficiency of the ventilation unit, but also taking into account such important indicators as energy efficiency, process reliability and functional purpose of the system. The ways of increasing the complex aerodynamic parameter of the ventilation system with the possible elimination of energy costs are determined.

COMPLEX DESIGNING ALGORITHM FOR SPACECRAFT ENERGY-CONVERTING EQUIPMENT

Introduction. The complication of the spacecraft payload requires the use of non-standard circuits. The analysis of scientific and technical publications shows that there is no formalized methodology for spacecraft energy-converting equipment designing. Reviewed publications consider some design algorithms taking into account one (efficiency) or two criteria (efficiency, weight and size characteristics). At the same time, the issues of ensuring trouble-free operation of energy-converting equipment are not sufficiently considered which leads to rejection of most part of proposed circuitsolutions and reduces developer efficiency.
 
 The research purpose is to form a spacecraft energy–converting equipment designing algorithm, taking into account the reliability, efficiency and relative power coefficient requirements.
 
 Materials and methods. The main provisions of the electrical circuit theory and the theory of technical systems reliability were used. All calculations were carried out in Mathcad 15.0.
 
 Research results. The article step-by-step discusses the design process using the example of boost and buck voltage converters. It is shown that taking into account the reliability requirements leads to a decrease of weight and size indicators (due to the additional mass of redundant elements) and efficiency (due to power losses on redundant elements). Converters with an AC-current node based on a double active bridge (active front end bridge inverter) and add-voltage circuits are considered. It can be seen that the use of converters with AC-current node in spacecraft energy-converting equipment is complicated because of low reliability or high weight and size meters.
 
 Conclusions. A converter circuit must ensure operation in the event of a single failure of a random power element. At the same time, scheme with a minimum number of power elements have the greatest prospects for application. A converter energy characteristic must be evaluated after ensuring the reliability.

Solution of the integral equation for the average cost of restoration in the theory of reliability of technical systems

Failures of elements during the operation of technical and many other systems are, as a rule, random in nature. This leads to various models of the recovery process, studied in probability theory and mathematical reliability theory. During the restoration process, failed elements are restored or replaced with new ones, and there is often a change in the costs and quality of the restored elements (time-to-failure distribution functions). The work examines the cost function (average cost of restoration) in the process of restoration of order k1,k2,in which, according to a certain rule, the costs of each restoration and the distribution functions of operating time change. Considering, that the recovery function (average number of failures) is well studied in reliability theory, a solution to the integral equation for the cost function is obtained through the recovery function of the model under consideration. For the order restoration process k1,k2,a formula is obtained for calculating the cost function through the restoration function of a simple process formed by the convolution of all distribution functions of the periodic part. For practical application, explicit formulas are obtained for the cost function during the restoration process, in which the periodic part is distributed according to an exponential law oran Erlang law of order with the same exponent α. The resulting formulas can be used to study the properties of the cost function and solve optimization problems in strategies for carrying out the restoration process in terms of price, quality, risk, if, for example, the average number of failures is taken as quality, the average cost of restorations as price, the dispersion of the number of failures as the risk, or cost of restoration.

Evaluation of the maintenance system readiness using the semi-Markov model taking into account hidden factors

Modelling the time that the system remains in a given state using classical distributions is not always possible. In many cases, empirical distributions are multimodal due to the influence of external, hidden factors and the selection of the best classical distributions may lead to erroneous results. In the article the method of diagnosis of influence of hidden factors into sojourn time of semi-Markov models was presented. In order to capture hidden factors, the authors proposed to model the distributions of the sojourn time with a mixture of distributions, which is a significant novelty in relation to the studies presented in the literature. Hidden factors directly affect the reliability of technical systems. Detecting the existence of these factors enables more accurate modeling of system readiness. Paying attention to irregularities caused by hidden factors makes it possible to reduce system maintenance costs. Such a system model provides complete information and enables a reliable assessment of the system readiness and maintenance.

Application of the algorithm for finding the outer median of a graph in the problems of determining the reliability of technical systems

The problem of locating a service center for technical systems with known values of failure flows is considered. This problem was solved using the minisum algorithm of graph theory. The dependence of the system availability factor on the average time between failures and the average recovery time of the system elements is obtained. It is shown that the optimal location of the maintenance point is the median of the graph located at one of its vertices.

Review Models and Methods for Determining and Predicting the Reliability of Technical Systems and Transport

Modern power and transportation systems are subject to high requirements for reliability and performance in performing their specified functions. At the same time, these requirements are constantly increasing with the increasing complexity of technology and the introduction of electronics and computer technology into its structure. This is fully applicable to energy and transportation infrastructure, including electric vehicles. The complexity of the systems and increasing requirements for them have led to the fact that the problem of increasing their operational reliability has acquired great importance. The article presents a review of methods and justification of ensuring a high level of reliability and serviceability of technical systems as one of the most important tasks in the creation and operation of complex systems, such as modern energy and transportation systems. It is shown that a significant reserve in solving the problem of increasing the reliability and performance of technical systems is the information on failures and malfunctions of these systems obtained from the field of operation. The methodology of collection and processing of statistical information on failures of vehicles described by different distribution laws is outlined.

Fault-tolerant and resilient design of potentially dangerous systems

Increasing customer expectations, global competition and sustainability considerations have led to more and more complex technical systems. The performance, efficiency and quality are increasing, but also the possibility for faults. Designers need to develop technical systems, which will not fail as a consequence of these faults but will be resilient, i.e. they are capable to behave in an acceptable manner in the presence of faults. In recent years, strategies, methods and tools were proposed which may assist designers in this endeavor, both in the field of systematic fault-tolerant design and in the field of resilience engineering. Similar goals are pursued by strategies, methods and tools which aim to increase the safety and reliability of technical systems; these are even formulated in several international standards. This paper proposes a sensible structure to combine and integrate these strategies, methods and tools and is explaining this structure and concrete design aspects based on the development of three potentially dangerous systems - a lifting mast for an agricultural tractor, a power lift for an agricultural vehicle and a log splitting device.

Optimal maintenance tasks taking into account cost indicators

The reliability of technical systems plays a key role in ensuring their efficient operation over time. This article discusses the importance of reliability in maintaining preset parameters of the functioning of a system and its dependence on operating conditions. Maintenance is done to maintain the reliability of a system and control its functionality. The authors propose methods for selecting quality indicators and the optimal frequency of preventive maintenance and emphasise the importance of considering cost aspects when making decisions on maintenance. In conclusion, the article offers a brief algorithm for quality control of technical systems while placing an emphasis on system safety and economic efficiency. The study demonstrates the need to develop and apply new cost-based analysis methods to determine optimal maintenance strategies for technical systems. Overall, the article provides recommendations for improving maintenance operations and increasing the reliability of technical systems.

Research on Increasing the Operational Reliability of Technical Systems

Abstract The role of the reliability of military systems in the success of the mission is one of the most important elements that military logistics must take into account and should constantly return to for its improvement and growth. Increased reliability ensures long availability and low maintenance costs. In the case of military vehicles, intensively demanded in operation, there are several components permanently subject to wear and failure. Between these, the clutch is a sub-assembly of the motor vehicles that causes most of the breakdowns, thus jeopardizing the missions undertaken and causing insecurity regarding their use. A solution has been developed in order to extend the lifespan of the clutch, and by means of this solution its reliability is increased. This solution is based on both clutch resizing and reliability calculations, which will help us to choose an optimal solution from a technical, economic and reliability point of view. Compared to the initial situation, by increasing the diameter of the clutch disc from 360 mm to 400 mm, the reliability of the friction disc has increased by 61.64 %.

OPTIMIZATION OF PARALLEL LINKS IN REDUNDANT UTILITY STRUCTURES

The publication states that an important problem in the design, operation and reconstruction of various networks of engineering infrastructure is to determine the reliability of structurally complex systems. Modeling the reliability of technical systems seems to be a rather complex task. It is emphasized that the ways of rational redundancy of a complex structure of systems presuppose the well-known method of minimal paths and connections. The problem of the optimal arrangement of a system with a redundant structure has certain limitations in accordance with the available resources, such as the lower value of the probability of the system's connectivity, which serves as an optimization criterion. The paper investigates a system with identical components. The article discusses many possible forms of the structure of the system. Structural reliability expressions are calculated for all combinations used in determining the lower and upper values ​​of structural reliability. In the process of constructing a redundant structure, it is necessary to determine a variant of its form, which maximizes the value of reliability under the established restrictions on the available resources invested in the construction and operation of the system using the cost parameter for some form of its structure. The peculiarity of the system reliability function is considered when it increases, which has a discrete argument and consists of a number of some functions. In the presented geometric model, a number of operations are used to determine and concretize the requirements for the variants of the forms of the components of the system under study for their different properties, and the forms that do not meet these conditions for the variants of the component in terms of resources are removed. Here the requirements for the probability of connectivity are defined, according to which unsuccessful forms of possible structures of the system are removed. The work uses an algorithm to extract from a set of reasonable options for some options for components by resources. The specified variant of the structure form is assumed to be optimal according to the criteria. If the number of variants of the structure shape is large enough, then to find the optimal solution, another algorithm is used, in which the value of the objective function is checked, which determines the conditions for the probability of connectivity in design decisions. It is noted that in practical application the obtained solutions can be approximate.

Проблемный метод обучения в формировании профессиональной компетентности будущих бакалавров техносферной безопасности

Technosphere safety is a complex issue that depends directly on the level of professional competence of the people involved. The present research featured the problem-based method of teaching technogenic safety to Bachelor's Degree students. It involved a detailed analysis of the professionally-oriented training of technosphere safety bachelors. The analysis revealed some reasons behind the low efficiency of the current approach. The problem method is a promising resource for improving learning efficiency. The article introduces the content and application conditions of the problem method. The new approach was tested as part of lectures on Reliability of Technical Systems and Technogenic Risk. The problem method proved effective and improved the motivation of the future bachelors of technosphere safety.

Economic damages from low-quality electric energy

The problems of maintaining the quality indicators of electrical energy and, in particular, voltage dips as well as the consequences of voltage dips in electrical networks of industrial enterprises are considered. A classification of electrical consumers according to their sensitivity to voltage dips in critical areas is given. The main measures to prevent technical consequences of voltage dips are described. In order to ensure predictable operation of protection systems, it is necessary to analyse and prepare measures to improve power quality. To this end, high accuracy class recorders can be successfully used and measurements should be made at characteristic points of the network, power centres and at the common connection points of consumers. The consequences of voltage dips have been allocated to economic damage at companies. Without a general account of the damage caused by poor power quality, it is not possible to correctly calculate the economic effect of improving the reliability of technical systems, both in design and in operation. Therefore, it is proposed to use contextual factors of energy efficiency. Hence, an approach to the selection of surge protection measures is derived which requires consideration of the cost-benefit test of the technical measures. Thus, in order to select any of the surge protection measures, it is first necessary to analyse the statistical data, to understand the cause of the equipment outage and then to make a technically and economically sound decision to improve the reliability of the electricity supply. It is possible that the simplest and most effective solution for surge protection may not be in the electrical part but in the process or instrumentation system.

APPLICATION OF OFFICE INFORMATION TECHNOLOGIES TO SOLVE THE PROBLEMS OF OPTIMAL STRUCTURAL RESERVATION OF SYSTEMS

Problem statement. The problems of optimal structural redundancy of systems are usually formulated as a nonlinear problem of mathematical programming with integer variables, and to solve them, usually, various optimization methods are used, which requires the development of special algorithms and appropriate software. However, in the case of clarifying the original task of optimal redundancy, there is often a need to adjust the developed algorithms and software. All this greatly complicates obtaining the desired results. Another approach to solving problems of optimal redundancy of systems is the use of office information technology, the tool environment of which is adapted to solve mathematical problems, including optimization problems. This approach does not require the development of special algorithms and software. However, issues related to the effectiveness of the information technology used to solve this problem require further scientific and practical study. This article formulates a model of optimal design of redundant systems according to the criterion of minimum cost while ensuring the required level of reliability during a given time. This model is written in terms of a nonlinear problem of mathematical programming with integer variables and is numerically implemented in the operating environment of an Excel spreadsheet when the main object of the designed system consists of 6 elements. The optimal options for reserving this object according to the schemes of "hot" and "cold" redundancy are obtained. The purpose of the article is to show the effectiveness and efficiency of the MS Excel spreadsheet to solve problems of optimal structural redundancy of systems. Conclusions. This article discusses issues related to the problem of solving problems of optimal design of redundant systems in the tool environment of the MS Excel spreadsheet. Examples of solving the problems of separate "hot" and separate "cold" redundancy of a 6-element object prove the effectiveness and efficiency of the MS Excel spreadsheet to solve this problem. In addition, the developed optimization model can be successfully used in practical tasks to ensure the reliability of technical systems in the early stages of their design.

Оптимизация норм межремонтных пробегов тяговых электродвигателей локомотивов на основе результатов исследования распределения отказов на полигоне Дальневосточной железной дороги

Objective: Optimization of the rates of overhaul runs on the basis of the results of the study of the distribution of failures of traction motors caused by a critical decrease in the insulation resistance of the windings to reduce the cost of eliminating the consequences of unscheduled repairs of locomotives. Methods: Mathematical statistics, probability theory, theory of reliability of technical systems are applied. Results: A cause-and-effect analysis was carried out of cases when locomotives were placed for unscheduled repairs in 2019–2020. An element has been determined that limits the rates of overhaul mileage of traction electric motors of locomotives. The theoretical distribution of failures of traction electric motors due to a critical decrease in the insulation resistance of its windings is obtained. The optimization of the norms of overhaul runs of locomotives was carried out according to the conditions of current repairs in the amount of TR-2 relative to traction electric motors. It was revealed that the failures are mainly associated with the first period of operation of traction motors. As a result of the analysis of the reasons for the failure of traction electric motors, it was found that most cases of unscheduled repairs fall on the first interval of locomotive runs due to the poor quality of repairs. In this case, the first normal peak of failures falls on the mileage in the modal interval from 156 to 234 thousand kilometers, when the overhaul mileage on TP-2 is 250 thousand kilometers, which necessitates its optimization within the preceding modal interval. Practical importance: The presented version of optimization of overhaul runs can be used to determine the rationality of establishing the norms for the periods of maintenance and repair operations on locomotive units under the conditions of a planned preventive control system for their technical condition

Оптимизация возвышения наружного рельса в железнодорожных кривых на основе стоимости межремонтного цикла

Objective: To determine the optimal elevation of the outer rail in a curved track section based on technical and economic criteria, calculating the life cycle cost using the methods of life cycle re-source management, risks, and reliability analysis (URRAN methodology). Methods: The authors used multivariate analysis, point estimation, the probability theory and mathematical statistics, the theory of reliability of technical systems, the URRAN methodology, field observations of the condi-tion of the curved track sections and the scope of work during their maintenance. Results: A model of the overhaul cycle of a curved track section has been developed. The dependences of the change in the intensity of the accumulation of faults and the cost of track maintenance during the overhaul cycle on the average values of undamped train accelerations when moving along the sur-veyed sections are presented. The optimal values of undamped acceleration are determined for various operating conditions of railway curves, which provide the minimum track maintenance costs. The authors have found that the minimum cost of the overhaul cycle is the factor for choos-ing the optimal undamped acceleration during the overhaul cycle. The optimal elevation of the out-er rail has been calculated and the actual values in the investigated sections have been analyzed. The method’s economic efficiency is calculated in the form of the ratio of the difference between the costs of the overhaul cycle for the actual and optimal elevations of the outer rail. Practical im-portance: Optimization of the elevation of the outer rail will enable minimizing the intensity of the accumulation of faults and, therefore, reduce the cost of maintenance on the track. The total cost of routine track maintenance will be reduced by 5–10 %.

Forecasting the reliability of technical systems of agro-industrial production based on the results of statis-tical modeling

Forecasting the reliability of technical systems of agro-industrial production based on the results of statis-tical modeling

АНАЛИЗ НЕОДНОРОДНЫХ ЭЛЕКТРОМЕХАНИЧЕСКИХ СИСТЕМ НА ОСНОВЕ ТОПОЛОГИЧЕСКОГО ПОДХОДА

Stricter requirements for the efficiency and reliability of technical systems predetermine an in-depth study of electromechanical systems. The study involves taking into account the heterogeneity of their physical and vector space as operational factors that have a significant impact on the energy efficiency and reliability of the object. The proposed topological approach to the study of heterogeneous electromechanical systems (NEMS) is based on the analysis of their vector space. The multidimensionality, heterogeneity, and composite nature of the vector space are analyzed. Typical examples of the restrictions imposed on space vectors by the connection schemes of three-phase and multiphase NEMS windings are given. The main energy field is presented and the principle of the formation of the effective energy state of NEMS is formulated. Describes the tasks and method of implementing the operational diagnostics of NEMS based on the topological approach. In conditions of uncertainty, as well as heterogeneous quality, insufficient data, the feasibility of sharing the methods of fuzzy cognitive and logical analysis and modeling is substantiated. A cascade hybrid model is proposed, as well as methods for studying the vector space and operational diagnostics of NEMS based on it.

Classification of knowledge factors risk when working with tubular lentil conveyors

Conveyor transport of mining enterprises is a constant source of accidents. With increasing depth of mines and quarries and with an increase of the load on the transport systems, the problems of ensuring the safety and health of people, environmental protection. The solution of these problems is associated with the development of the theory of reliability of technical systems and the assessment of technogenic risks. Currently, in connection with the tightening of environmental requirements, a promising area is the use of tubular belt conveyors that cause the least damage to the environment compared with other types of conveyor transport. Due to the more complex processes occurring when tubular conveyors operate, risk factors and their consequences differ significantly from risk factors for other types of conveyor transport. Based on the experience of operation and from the preliminary analysis of the processes occurring during the operation of tubular conveyors, for them a classification of risk factors is external and internal factors, as well as risk factors affecting a person. The risk factors from external influences include temperature, humidity, dustiness of the atmosphere, soil instability, weather conditions, physical properties of load, geometry of the route. Internal risk factors are errors in designing, calculating the constructive and regime parameters of the conveyor, violation of the rules of operation and safety. Risk factors affecting a person when working a tubular conveyor are classified as mechanical, thermal, electrical and chemical. In addition, risk factors for a tubular conveyor are classified according to individual nodes of drive, stand, and belt. The risks of the failure of supports rollers of the tubular conveyor are considered. It is given a failure tree, where possible rollers failures are listed in detail and the risks of the torsion of the tubular belt leading to the conveyor failures.

ALGORITHMS AND SOFTWARE SUITE FOR RELIABILITY ASSESSMENT OF COMPLEX TECHNICAL SYSTEMS

Context. One of the most essential properties of technical systems is their reliability, i.e. the ability of the system to perform intended functions, preserving with time the values of operation indicators within the predefined boundaries. The failure cost for modern complex technical system can be very high, which can result in events of different severity ranging from economic losses to harm to human life and health. Hence, the requirements for their reliability constantly increase. The reliability assessment of complex technical systems can be simplified by the combination of analytical research methods with computational capabilities of modern computers. The most widely used analytical methods are based on the theory of Markov processes which in turn provide the possibility to determine the time dependencies of probabilities of the system to be in defined states (operating, recovering, failure etc.), and thus the values and time dependencies of the reliability indices needed. These methods can be successfully used for the reliability analysis of different kinds of technical systems: both non-recovered and recovered; non-redundant and redundant of different redundancy types, maintenance priorities etc. However, the application of these methods for complex technical systems containing large number of elements meets the high dimensional calculation problem, which makes it impossible to perform these tasks manually. Hence the problem of automation of complex technical system reliability modeling using modern computational systems is very relevant research topic. To solve this problem, one can use specific algorithmic and software techniques described in this paper.Objective. The goal of this article is to develop the algorithms for automated RBD processing and reliability indices assessment of complex technical systems along with the software suite for automated reliability assessment.Method. To perform the reliability analysis the RBD approach is used which allows one to represent and visualize each element of the system in the form of a rectangle, joined by the lines in parallel or in series with other elements of the system. To obtain the reliability indices values the mathematical model of technical system reliability behavior using Markovian random process was suggested. The algorithm of RBD processing and automatic determination of operability conditions of a technical system was further considered. To calculate the minimum and maximum number of operational and failure states for the system of n elements and r recoveries the paper introduces a mathematical model based on combinatorial approach. To develop the software suite the objectoriented approach was used.Results. The algorithms and software suite allows us to easily construct RBD for a technical system, to automatically determine the operability condition with execution time of about 10 sec for 1,000 elements with mixed type of connection, to form automatically a state-and-transition matrix along with the corresponding differential equation system and solve it with total execution time of about 35 sec for 109 states and, thus to obtain the numerical values of reliability indices for the technical system studied. A case study of the reliability assessment for the system consisting of 22 elements using RBD shows that the total time of software execution is 36.712 sec. During executing of this test case the most time (35.168 sec) was spent for execution of the algorithm for construction of a state-and-transition graph consisting of 52,694 states.Conclusions. The algorithms and methods for automated reliability indices assessment of complex technical systems based on RBD approach, as well as model for estimating the number of total and working system states are presented. The modular structure of the developed software suite makes it flexible and gives an opportunity to add and make modifications of modules fast and without significant program changes.