Failure-free Operation Research Articles

METHODICAL APPARATUS FOR ENSURING THE CORRECTION OF SINGLE ERRORS AND DETECTION OF DOUBLE ERRORS IN STORAGE DEVICES

The analysis of errors that occur during the operation of static storage devices (SD) is carried out. The conclusion is drawn that single and double errors are most likely to occur in memory devices (single errors appear with a probability of up to 80 %, double errors up to 20 – 25 %, and errors of other multiplicity account for up to 2 %). Methods for protecting storage devices from single and double errors are considered. It has been established that at present, for the correction of single errors and the detection of double errors, a modified Hamming code is widely used, which uses for this purpose an additional parity bit for all bits of the code set. The necessity of developing a code that corrects single errors and detects double errors while reducing information redundancy is substantiated. Regularities have been identified that make it possible to form rules for encoding information, and when decoding, to form three additional checks for an error sign to determine erroneous bits in the event of indistinguishable error syndromes. The corrective ability of the proposed method of information coding is investigated. It has been established that the proposed code allows correcting all single errors, detecting all double errors and, at the same time, correcting some of the double errors that simultaneously occur in information and check bits. A regular information coding procedure is described for correcting single and detecting double errors while reducing information redundancy by one check bit and, consequently, reducing hardware costs associated with storing the values of check bits in a memory device. A comparative evaluation of the detection ability and information redundancy of the proposed method with a modified Hamming code is carried out using the example of coding an 11-bit information word. It has been established that for the code (15,11), the implementation of the proposed method makes it possible to detect all single and double errors, correct 100 % of single errors and 27 % of double errors, and use four check digits for these purposes (one less check digit than modified Hamming code). The conclusion is made that the reduction of information redundancy makes it possible to increase the code speed and reduce hardware costs associated with storing the values of a given bit in a memory device and, therefore, increase the probability of failure-free operation and reliability of the memory device operation while reducing information and hardware redundancy.

МЕТОД АНАЛІТИЧНОГО МОДЕЛЮВАННЯ БЕЗВІДМОВНОСТІ БОЙОВИХ ЗАСОБІВ ЗЕНІТНИХ РАКЕТНИХ ВІЙСЬК

The article sets out a method for analytical modeling of the recoverability of anti-aircraft missile forces using the example of a self-propelled fire launcher (SOU) of the Buk anti-aircraft missile system. The main attention is paid to one of the properties of technical reliability, namely the reliability of weapons and military equipment. This is especially true of the IWT anti-aircraft missile forces, the failure to fulfill the tasks of which due to failures in operation can lead to serious consequences in operation or battle. The improved method of mathematical modeling of reliability allows taking into account the possibility of developing elements of aging and wear of MCS components in the process of expending the released resource at the operation stage, as well as taking into account the conditions of hostilities by using and developing a mathematical model in the form of a Weibull distribution in order to obtain more guaranteed indicators of reliability. It is advisable to select the final value of the mean hour of MTBF failure taking into account reaching the value of the ratio between the number of MTBF disabled due to only limited technical reliability and the amount of equipment that failed due to enemy fire action. This will increase the efficiency of the system for updating damaged MDS during hostilities, and improve the planning of production activities of repair bodies. It will also be possible to increase the overall combat effectiveness of the anti-aircraft missile regiment in the process of repelling a raid of air attack vehicles. When setting the specified ratio value, the required MTBF value can be calculated (before failure). The improved method of mathematical modeling adequately reflects the failure-free operation of the combat vehicles of the Buk anti-aircraft missile system, taking into account the conditions of hostilities. Keywords: probability of failure-free operation, failure-free simulation, continuous operation time, distribution parameters, time between failures, limited technical reliability.

Methods for determining the probability of failure-free operation of the engine of machines with an electronic control system

The method for determining the probability of failure-free operation of the electronic control system of the engine of machines, which allows not to release them on the line in a pre-failure state, is presented, and the main reasons for the occurrence of failures and malfunctions in its elements are presented. The given information can be applied in the course of forecasting the residual resource of the given system.

Choosing Methodology of How to Manage Distributed Information Systems under Conditions of High Dynamics of Network Infrastructure

Purpose of research. is to identify a distributed system control method that, based on known parameters, would reduce the resource consumption of computing devices. An information system resource is probability of failure-free operation (FFO), which decreases over time for each node, the faster the higher its load.Methods. Frequency of system reconfiguration becomes relatively high with high dynamics of edge layer of a network and the need for reconfiguration is unpredictable. Reducing the total time spent on reconfiguration allows to increase time spent on solving functional computing tasks of the system and thereby reducing nodes load. Reconfiguration time can be reduced both by reducing failure detection time in distributed system and by reducing searching time for new configuration. A method for reducing failure detection time is described. The applicability analysis of system management methods (centralized, distributed leader, decentralized) is carried out on the basis of obtained analytical evaluations of failure detection time by the system in control conditions through one or another method. A numerical experiment allows to distinguish areas of system parameters, where it is preferable to use the method with a distingods. Frequency of system reconfiguration becomes relatively high with high dynamics of edge layer of a network and the need for reconfiguration is unpredictable. Reducing the total time spent on reconfiguration allows to increase time spent on solving functional computing tasks of the system and thereby reducing nodes load. Reconfiguration time can be reduced both by reducing failure detection time in distributed system and by reducing searching time for new configuration. A method for reducing failure detection time is described. The applicability analysis of system management methods (centralized, distributed leader, decentralized) is carried out on the basis of obtained analytical evaluations of failure detection time by the system in control conditions through one or another method. A numerical experiment allows to distinguish areas of system parameters, where it is preferable to use the method with a distinuished leader.Results. The main result of this work is a method of choosing how to manage distributed information systems in conditions of high dynamics of network infrastructure, focused on reducing of resource consumption in computing devices.Conclusion. The system reconfiguration time could be reduced by selecting the most appropriate control method. In this case, the time for solving functional tasks of application is increased, the workload of computing nodes is reduced, and therefore FFO values are increased over the planning horizon.

Determination of the optimal period for replacement of pipelines

The goal is to create and test an algorithm for finding places for the optimal replacement of sections of the heating network of the district heating system to maintain the standard values of trouble-free operation with a minimum of financial costs.Methods. To carry out computer modeling, mathematical methods were used to calculate the flow distribution in branched and looped thermal-hydraulic circuits. A systemic model of the heating network with an indication of the parameters used in the construction of the function of minimum costs, and a method for determining the places of replacement of pipelines of the heating network to maintain the indicator of failure-free operation above the standard have been developed.Results. An algorithm is proposed to implement the principle of increasing the reliability of district heating networks through the development of a system model of a heating network. As a result of using the technique, a schedule for the optimal replacement of pipelines for the area under consideration over the next 30 years was obtained. It is shown that the proposed complex method of qualitative and quantitative assessment of the efficiency of district heating networks allows one to identify an indicator of failure-free operation, which may be higher than the standard for the entire period of time. It has been established that the optimal timing for replacing individual sections of heating networks is due to the variation of the input parameters of the heating network: the year of laying the pipelines of this system, the year for which the calculation is made, the diameter of the pipeline and its length, the type of pipeline laying and the area of its location, and the output parameters — the costs of maintaining system and the likelihood of system uptime.Conclusion. Based on the results obtained, a comprehensive method for assessing the cost of maintaining the operability of district heating networks is recommended. It is shown that the proposed method improves the quality of management decisions to ensure trouble-free operation of the heat supply system. In the future, it is planned to develop guidelines for the use of the proposed method in the development of a section of reliability and survivability of promising heat supply schemes for cities and towns.

Fault-Tolerant Performance of the Novel Five-Phase Doubly-Fed Induction Generator

The article presents the concept of a new design of a multiphase doubly-fed induction generator (DFIG). The innovative design approach is based on the use of a five-phase power supply from the rotor side of generator with a three-phase classic stator power supply. Modern three-phase doubly-fed induction generators are the dominant choice for Wind Energy Conversion Systems (WECS). Solutions of this type are sensitive to the loss of at least one phase of the power supply from the rotor side due to the failure of the rotor side inverter. The proposed design solution in the form of a multi-phase power supply in the rotor circuit is aimed at extending the range of possible failure-free operation of the generator system, and thus reducing system downtime as a result of failure of power electronic systems. The correctness of the adopted conceptual assumptions was confirmed by the results of laboratory tests. The main contribution is to prove that the use of five phase rotor winding significantly improves the overall reliability of the proposed electrical energy generation system.

НАДЕЖНОСТЬ И УСЛОВИЯ ЭКСПЛУАТАЦИИ ЗАДНИХ МОСТОВ АВТОБУСОВ

The results of the analysis of failures of the rear axle of Higer buses are presented, the structure of work to eliminate failures in the conditions of the bus fleet is considered. The processes of forming the reliability of the rear axle of buses under the influence of six sets of factors, reflecting: the design features of the car and the rear axle, the system of maintenance and repair, climatic and road conditions, the intensity of operation, the characteristics of the driver, are analyzed. A classification of factors has been developed, the possibility of correcting the frequency of maintenance has been proved, taking into account the permissible level of probability of the failure-free operation of the rear axle of the bus.

Particular aspects of determining reliability indicators of thermoelectric generator modules using experimental data

Resource tests allowed finding that the relative degradation of output power and efficiency of thermoelectric generator modules is not subject to linear law. This means that the distribution law for the failure time of such modules does not «copy» the distribution of their initial parameters, i.e. is neither normal nor logarithmically normal. Therefore, the aim of this paper is to find or select from among the existing such a failure time distribution law, which would clearly take into account the scattering of the rates of relative degradation of the parameters of thermoelectric generator modules. The paper substantiates the need to use diffusion-nonmonotonic failure time distribution for processing the results of resource tests of thermoelectric generator modules in order to determine their standardized reliability indicators and relative errors of the obtained values. It is proposed to determine the point estimates of the parameters of the law, namely the average failure time and the parameter of variation of the rate of degradation processes not by formulas obtained by the method of maximum likelihood, but by smoothing the probability of failure-free operation obtained by tests. The least squares method and Newton's method are used. Estimates obtained by the method of maximum likelihood serve as an initial approximation for Newton's method. This allows achieving significantly less error in determining standardized reliability indicators than when using the method of maximum likelihood.

SPACECRAFT RELIABILITY CALCULATIONS USING STATISTICAL REGULARITIES IN OCCURRENCES OF FAILURES IN DEVICES, UNITS AND ASSEMBLIES DURING THEIR OPERATION

The paper addresses reliability analysis of manned spacecraft with the use of statistical regularities in in-flight failures of their devices, units and assemblies. It formulates validity criteria for using a device failure in reliability analysis, proposes a method for analyzing and classifying failures which enables factoring in different types of failures in reliability analyses. It considers a hypothesis of the absence of statistically significant differences in probabilities of individual valid failures and demonstrates the feasibility of its adoption with the use of dispersion analysis. A method is developed for evaluating product reliability using a functional relationship between reliability and the number of failures occurring in flight which makes it possible to significantly simplify reliability analysis for complex products, to establish the number of in-flight failures that is acceptable from the standpoint of the product reliability requirements, to study various product architectures from the standpoint of reliability criteria. It proposes a method for evaluating the lower boundary for the probability of manned spacecraft completing their missions based on the failure modes, effects and criticality analysis, and demonstrates the feasibility of optimizing the product redundancy scheme based on the fault tolerance requirements. Key words: manned spacecraft, flight, failure, fault tolerance, classification of failures, reliability, probability of failure-free operation, statistical analysis, dispersion analysis.

Design and technological optimization of rubber-reinforced thin-layer movable joints in the structure of a pipeline vibration-isolating compensator

Thin-layer rubber-metal elements have been widely used in various fields of technology, including helicopter construction, support parts for bridges, shock absorbers in industrial and civil construction. Their work reliability is determined by the design and technological performance features, which require experimental testing and parametric optimization. The article presents the samples and basic models testing results which were aimed at increasing the strength indicators stability of the adhesive ``rubber-metal'' joints and ensuring the failure-free operation of a rubber-metal product in the structure of a pipeline vibration-isolating compensator.

Influence of Contamination of Gear Oils in Relation to Time of Operation on Their Lubricity

The quality and reliability of consumables, including gear oils, results in the failure-free operation of the transmission components in heavy trucks. It is known that oil viscosity is essential for all lubricated tribopairs for wear and friction reduction in all vehicles with a gearbox. Viscosity may be influenced by the contamination that wear products can impart on the oil. Oil contamination can also affect lubrication efficiency in the boundary friction conditions in gearboxes where slips occur (including bevel and hypoid gearboxes). The present research focused on this issue. An obvious hypothesis was adopted, where it was theorized that exploiting the contaminants that are present in gear oil may affect how the lubricating properties of gear oils deteriorate. Laboratory tests were performed on contaminants that are commonly found in gear oil using the Parker Laser CM20. The study was designed to identify a number of different solid particles that are present in oil. At the second stage, friction tests were conducted for a friction couple “ball-on-disc” in an oil bath at 90 °C on a CSM microtribometer. The quantitative contamination of the gear oils that contained solid particles and the curves representing the friction coefficients of fresh oils with a history of exploitation were compared. The test results were statistically analysed. Exploitation was shown to have a significant impact on the contamination of gear oils. It was revealed that the contamination and the mileage had no effect on the tested oils.

CONSIDERATION OF THE "CONDITION-BASED" ALGORITHM OF AVIATION EQUIPMENT OPERATION WITH THE USE OF GROUND MEANS OF TECHNICAL CONTROL AND ON-BOARD MEASURING SYSTEMS IN THE STATE AVIATION OF UKRAINE

The article highlights the main aspects and features of the algorithm of aviation equipment operation "condition-based" with the use of ground technical means of control and on-board measuring systems and the formation of decision- making principles for further operation of aircraft.
 To develop methods of technical diagnostics of any technical equipment, it is necessary to identify which parameters characterize its condition and reliability as well as to establish diagnostic criteria and limit values of the controlled parameters.
 Depending on the nature of the parameters being controlled, there are parametric and physical methods of diagnostics. Based on the results of the diagnostics, we must get a straight answer: whether or not it is necessary to perform repairs or maintenance of the equipment being tested, taking into account the ensuring of failure-free operation before the next diagnostics.
 Currently, a large number of different measuring equipment that can measure signals that meet the parameters of the object of control and diagnostics are successfully used to objectively determine the technical condition of aircraft.
 The use of the laboratory for technical diagnostics of aviation equipment in conjunction with on-board measuring systems will provide an opportunity to make a quality technical diagnostics and reasonable conclusion to decide on further operation of the sample of aviation equipment. The use of mentioned laboratory will also predict the occurrence of failures of aviation equipment systems and units.
 Only a comprehensive approach to the technical diagnostics of aviation equipment with employment of all means of technical control (ground, on-board) will prevent sudden failures of aviation equipment systems.

Reliability in mechanical systems projects

Sufficient safety of the parts, which determines the safety of the system specified by the technical assignment, is the necessary quality of the project, the subject of the design engineer’s attention and the customer’s requirement. An extensive task is the collection of data for iterative refinement of the resource for project details in a probabilistic aspect. It can be significantly reduced when using approximate methods for estimating the resource at intermediate stages of refining the project to the required resource with a calculated probability of failure-free operation. Thus, by the analysis of dimensionless relations of parameters of models of fatigue damage development, it is possible to obtain tools of numerical estimation of technological and constructive techniques of increase of a resource of details and their rational combination. The paper deals with the numerical measures of various directions of upgrading the fatigue life of the parts, derived from the dimensionless relations of the parameters of fatigue damage development models.

Computational and Experimental Study of the Stress State of the Opposed Compressor Connecting Rod to Assess the Probability of Failure-Free Operation

Computational and Experimental Study of the Stress State of the Opposed Compressor Connecting Rod to Assess the Probability of Failure-Free Operation

ДОСЛІДЖЕННЯ ТОЧНОСТІ УНІФІКОВАНОГО ПІДХОДУ МЕТОДУ ФУНКЦІЙ ПРАЦЕЗДАТНОСТІ ДЛЯ ФУНКЦІЇ КОЕФІЦІЄНТУ ЗАПАСУ

The article dwells on the accuracy of the unified approach of the survival function method (SFM), which is used to determine the probability of failure-free operation (PFFO) of the launch vehicles mechanical systems at the design stage. For the survival function in the form of a safety factor, which is universal, depending on the order of its expansion in the Taylor series, as well as the order of used numerical characteristics of the input parameters (factors determine the main errors of the unified approach), the accuracy of obtaining the numerical characteristics of the state variable and, ultimately, PFFO is analyzed. The case of normal distribution of bearing capacity and stress was considered, as well as the case when the indicated random variables followed the Gram-Charlier distributions. An expression is proposed for the density of the safety factor distribution in the case when the bearing capacity and stress are described by the Gram-Charlier distributions.
 The calculations have confirmed that the linearization method (first-order approximation) for nonlinear survival functions and non-normal distributions of its arguments can lead to a significant deviation of the reliability factor from the exact value. The orders of expansion of the survival function in the Taylor series and the numerical characteristics of its arguments are determined, which are recommended for practical use for PFFO determination in case of non-linear survival functions, as well as the case when the input parameters have non-normal distributions. Separately, the case of limiting the order of the used numerical characteristics of the survival functions arguments is considered, and recommendations are made to improve the accuracy of the SFM unified approach. For non-normal distributions of bearing capacity and stress, a very slow convergence of the numerical characteristics of the third and fourth orders to exact values was obtained with increasing orders of expansion of the survival functions in the Taylor series and used numerical characteristics of the input parameters. The Gram-Charlier distribution, used to describe the state variable in nonlinear models, allows obtaining a PFFO value closer to the exact one than the normal distribution.

Mathematical and Simulation Model for Reliability Analysis of a Heterogeneous Redundant Data Transmission System

In the actual study, we carried out a reliability analysis of a repairable redundant data transmission system with the use of the elaborated mathematical and simulation model of a closed heterogeneous cold standby system. The system consists of one repair unit and two different data sources with an exponential cumulative distribution function (CDF) of their uptime and a general independent CDF of their repair time. We consider five special cases of the general independent CDF; including Gamma, Weibull-Gnedenko, Exponential, Lognormal and Pareto. We study the system-level reliability, defined as the steady-state probability (SSP) of failure-free system operation. The proposed analytical methodology made it possible to assess the reliability of the whole system in the event of failure of its components. Specific analytic expressions and asymptotic valuations are obtained for the steady-state probabilities of the system and the SSP of failure-free system operation. A simulation model of the system in cases where it is not workable to obtain expressions for the steady-state probabilities of the system in an explicit analytical form was considered, in particular for constructing the empirical system reliability function. The issue of sensitivity analysis of reliability characteristics of the considered system to the types of repair time distributions was also studied. The simulation modeling was done with the R statistics package.

The Domain of Residual Lifetime Attraction for the Classical Distributions of the Reliability Theory

The asymptotic behavior of the residual lifetime of the system and its characteristics are studied for the main distributions of reliability theory. Sufficiently precise and simple conditions for the domain of attraction of the exponential distribution are proposed, which are applicable for a wide class of distributions. This approach allows us to take into account important information about modeling the failure-free operation of equipment that has worked reliably for a long time. An analysis of the domain of attraction for popular distributions with “heavy tails” is given.

Devising a method to control the operational quality and reliability of fiber-optical communication lines

The lack of recommendations in the normative and technical documentation related to fiber-optic communication lines (FOCL) for assessing their technical condition necessitated devising a method to control the lines' quality and reliability of operation. The method creates the basis for calculating the quality and reliability indicators of FOCL operation and suggests measures to improve them. It determines the methods of control, as well as the acquisition, accounting, and analysis of damage statistics with and without interruption of communication. The graphic sequence of implementation of the stages of the method demonstrates that resolving the task to control these indicators should involve: – managing the acquisition and actual acquisition of operational data on damages (the causes, nature, quantity, the duration of communication breakdown and complete elimination of damage); – determining the quality and reliability indicators of FOCL operation annually; – analysis of the obtained results and the development (correction) of measures to comply with the norms of these indicators; – the implementation of measures to comply with the norms of quality and reliability of FOCL operation (if necessary). Based on the operational data from a line operator acquired over three years in the specified climatic zone (a cable of the type OKLBg-3 DA12-3×4E-0.4F3.5/0.22N18-12/0), the methodical component of the method was examined. The obtained results on the operational quality (damage density, average damage duration, break (downtime) of communication) and reliability indicators (FOCL readiness factor) of a subscriber access network without reservation showed that the line had low efficiency. The communication breakdown over three years amounted to K=12,569.8 stream∙hours. The downtime at this volume of digital stream∙hours has led to significant economic losses. Line operators have been given recommendations for the proper FOCL operation and ensuring a normalized value of the line readiness coefficient. To this end, it is necessary to reduce the time to re-link and prolong the line's failure-free operation

Spectral analysis of gas dynamic processes in the inlet system of a piston engine with turbocharger

THE PURPOSE. To carry out a comparative analysis of the spectra of gas-dynamic characteristics of flows in the intake systems of piston engines with and without turbocharging, to assess the degree of influence of the turbocharger on the flow structure in such systems, and also to propose a method for the gas-dynamic improvement of processes in the system under consideration. METHODS. Due to the complexity of the object of research, an experimental approach was taken as a basis. The experiments were carried out on a single-cylinder piston engine model, which could be equipped with a turbocharger. A system for collecting and processing experimental data based on an analog-to-digital converter was used in the study. Data on changes in local values of velocity and static pressure of pulsating flows in the intake system during the engine's operating cycle were obtained using a constant temperature hot-wire anemometer and a fast-acting pressure sensor. Spectral analysis of functions of flow velocity and pressure versus time was carried out on the basis of the fast Fourier transform algorithm.RESULTS. The article presents a comparative analysis of the spectra of the amplitudes of the velocity and pressure pulsations in the intake system of an engine with and without turbocharging. Also proposed is a method for stabilizing the pulsating flow in the intake system by installing a leveling grid in the outlet channel of the turbocharger compressor. CONCLUSION. It is shown that the installation of a turbocharger leads to a significant change in the structure of gas flows in the intake system of the engine. It has been established that the presence of a leveling grid in the intake system of a turbocharged piston engine leads to a decrease in the low-frequency amplitudes of the flow velocity and pressure pulsations up to 30%. It is shown that the probability of failure-free operation of an automobile engine (cylinder diameter – 82 mm, piston stroke – 71 mm) increases by almost 1% when a leveling grille is used in the intake system.

Study of the main parameters of the household waste hydroseparation system

The article explores the development of new biotechnologies; recycling and maximum waste detoxification and ecologisation of industrial and agricultural production; improvement of technological processes of land reclamation and land protection. The authors developed a methodology for assessing the environmental friendliness of recycling processes and a hydroseparation system to ensure environmental safety in waste management under natural and man-made influences. They investigated the properties of household waste and established the extent of their impact on environmental protection. The research developed a device for hydro-separation of household waste, supported by a utility model and equipped with a central rotor drum for mixing and crushing household waste in the hydroseparation chamber. The authors propose a methodology for calculating the reliability of systems using a logical scheme and a verbal formula to determine the dependence of the system reliability function on the reliability functions of the blocks, i.e. by compiling a logical model of the failure-free operation of the system.