Leonid Ozirkovskyy

Об’єктами розгляду в статті є дві модифікації відмовостійкої системи для джерел безперебійного електроживлення з конфігураціями (N+M) та 2×(N+M), для яких передбачено профілактичне технічне обслуговування. Подані надійнісні моделі для обох конфігурацій відмовостійких систем джерел безперебійного електроживлення, які дозволяють дослідити залежність їх надійності від періодичності профілактичного технічного обслуговування.

В статті представлено розроблення та впровадження високотехнологічного інформаційного середовища, яке суттєво збільшить різноманітність форм одержання знань та умінь, необхідних для ефективної професійної та соціальної діяльності майбутніх фахівців. В даній роботі представлено особливості розробки та впровадження такого середовища з врахуванням не тільки чисто технічних та педагогічних аспектів і специфіки навчального закладу, а й з точки зору забезпечення сталого розвитку на невідворотності досягнення результату. The paper presents the development and implementation of high-tech environment that will significantly increase the diversity of obtaining knowledgе and skills necessary for effective professional and social activities for future professionals. This paper presents the features of the development and implementation of such an environment, taking into account not only the purely technical and educational aspects and the specific institution, but also in terms of sustainable ...

The article is devoted to the problem of ensuring a given level of functional safety of safety critical radio electronic systems at the stage of their system engineering. A special feature of these systems is that their functional safety depends on the reliability of the hardware or software and the efficiency of their behavior algorithms. It should be noted that there are no models, methods and techniques which allow evaluating the level of the safety with a complex consideration of the above mentioned features.The article presents a new characteristic of the safety of behavior algorithms – the frequency of fall into the emergency state and presents new method of synthesis of the safe behavior algorithms for critical application systems. This method allows including a reasonable number of time and functional redundancy into the behavior algorithm to provide the required level of functional safety.

This paper presents the model of radio telemetry system with short-term use and the research of its efficiency indexes. The technique based on scheme of paths method and the mission-related software prototype were applied for this task. The software prototype provides real-time solution for multivariate analysis and parametric synthesis of behavior algorithms of radio telemetry system with short-term use. The features those are critical in terms of evaluating efficiency indexes of such systems are highlighted.

The safety of radio electronic systems for critical applications is traditionally ensured by inducing structural redundancy. This paper shows a developed technique for ensuring a required level of safety of such systems by inducing time and functional redundancy into its behavior algorithm. The defined safety characteristic is proposed for quantitative efficiency estimation of the induced redundancy. Presented in the article is the synthesis technique of safe behavior algorithms on the basis of safety characteristic minimization of increased values. The developed technique was tested through solving the synthesis problem of the behavior algorithm of the target detection radio electronic complex system.

Thesis devotes to the formulation and solution of scientific problems for the efficiency estimation of target search and detection algorithms at radio-electronics sighting complexes, i.e.: development of estimation tools for system design. These tools will cut down the expenses of time and material resources. In thesis the following problems are solved . The structurally-automatic model, the Marcov model and logical-probability model of target search and detection algorithms are developed. The technique for efficiency estimation of target search and detection algorithms at radio-electronics sighting complexes has been created. For modeling of a target search and detection algorithms at radio-electronics sighting complexes models of fault-tolerance systems with combined structural redundancy and with majority structure capable to reconfiguration are created . Choice and comparative analysis of methods for construction of mathematical models of fault-tolerance systems with taking into account of aging effect and arbitrary process duration distribution of technical service are executed . Obtained results were implemented in Lviv Radio Engineering Institute and into training process for the experts engaged in the designing of radio-electronics systems and complexes. Key words: radio-electronics complex, radio-electronics system, algorithm, system design, mathematical model, reliability.

ABSTRACT The paper presents ways to improve of methods for solving problems of radioelectronic systems reliability engineering. Displaying the proposed improvement of existing modeling technologies, which are based on state space method and logical-probabilistic method.

A thesis submitted in fulfilment of the Doctor of Engineering Science Degree in Specialty 05.12.17 – Radio and Television Systems. – Lviv Polytechnic National University, Ministry of Education and Science of Ukraine, Lviv, 2020. This thesis presents the solution of the actual scientific problem of development the theoretical basis of complex maintenance of safety critical radio electronic system (SCRES) with a required level of functional safety and reliability. The developed means (methods, models, algorithms and techniques) enable an identifying the weaknesses in the SCRES design in terms of functional safety at the stage of system design. This allows an engineer to reasonably induce necessary types of redundancy (structural, temporary, functional) to increase both functional safety and reliability of SCRES. Thus, the developed tools give the opportunity to synthesize a fault-tolerant structure, behavior algorithm and maintenance strategy, which ensure that the SCRES will not fall into an emergency. Modern methods of assessing functional safety indexes are based on the determination of minimal cut sets, which show the weaknesses of the SCRES. To obtain minimal cut sets, these methods use fault trees, dynamic fault trees, event trees, or binary decision diagrams. However, the known methods don’t allow to take into account the impact on the SCRES functional safety of fault-tolerant majority structures with reconfiguration, fault-tolerant two-tier majority structures, maintenance strategies, temporary and functional redundancy in behavior algorithms. Also, a significant disadvantage of existing methods is that they don’t give the opportunity to obtain both functional safety indexes and reliability indexes on the basis of a single model. So, it can lead to the condition when the reliability of the SCRES is reduced with the induction of additional tools for increasing functional safety. Also, these methods aren’t suitable enough for solving synthesis tasks via multivariate analysis for a short period time, what is very important at the stage of system design. In the dissertation, a new method is proposed for automated definition of types of inoperable states. This method provides a classification of inoperable states of the SCRES according to the level of critical failures and allows obtaining trajectories of accidents. Based on this method, a new technique is proposed for development of complex dynamic models of SCRES in the form of a graph of states and transitions. This technique, unlike the existing ones, allows determining both minimal cut sets and reliability indexes of SCRES without constructing appropriate fault tree. To reflect the relationship between indexes of functional safety and reliability of fault-tolerant structures, behavior algorithms and maintenance strategies, new indexes and characteristics of functional safety are proposed: the accident function; frequency of fall into an accident state; probability of fall into a pre-accident state; the average value of the probability of a minimal cut set existence. New models of strategies for planned and preventive maintenance and emergency recovery have been developed to take into account the impact of SCRES downtime on functional safety indexes during maintenance and repair procedures. These models enabled the development of method for synthesizing a maintenance strategy which guarantees to maintain a required level of functional safety of the SCRES. New method was developed to calculate the average value of the probability of the minimal cut set existence that gives an opportunity to solve the problem of minimizing impact of latent failures on the functional safety. This method makes it possible to obtain dependable values of the probabilities of the minimal cut sets existence for cases when the minimal cut set contains only latent failures or a combination of latent and active failures. New models of fault-tolerant SCRESs with majority structures were developed, which, in contrast to the existing ones, allow to take into account the impact of the use of reconfiguration of the majority structure, two-tier majority structure, maintenance and repair on the functional safety. The proposed models make it possible to solve the problem of synthesis of fault-tolerant systems for SCRES with a required level of functional safety and appropriate level of structural redundancy, that is especially important for onboard information and control systems of aircrafts, including unmanned vehicles, for which mass and size restrictions are critical. New methodology for the synthesis of safe behavior algorithms of the SCRES was developed, which, in contrast to the existing ones, takes into account the impact of time and functional redundancy on the functional safety of SCRES. This methodology shows the way to achieve a required level of probability of the task execution with the minimum value of the frequency of accidents.

The problem of development of program models of the fault-tolerant system with the mixed structural redundancy is solved. For designing of program models an advanced technology of analytical modeling of the systems is used. This technology takes into account all features of structure and behavior of the system under the action of refusals and two variants of realization of maintenance service strategy. It provides possibility of multiple analysis at the small expenses of time. The results of researches of the fault-tolerant system, which illustrate possibilities of decision of tasks of reliability analysis and reliability synthesis, are resulted in the article.

In this paper we propose a new term accident rate function. Such term gave a possibility to provide the quantative assessment for operational safety in the fault tolerant systems with high responsiblity purposes. Moreover, we propose a binary structural automata model. Using the proposed binary structural automata model in the ASNA software, we provide a possibility to build models of the fault tolerant systems in the form of a graph of states and transitions, in an automatic way. Obtained graph of states and transitions is used to define the accident rate function. The authenticity of the emergency rate function is confirmed by the coincidence of two calculated values. One value is obtained based on accident rate function at determined time interval and the other value is the probability of minimal cut sets obtained based on fault tree at a similar time interval. Using the ASNA software to get the accident rate function and the usage of new methodology of forming the accident rate ...

The paper presents the approach to automation of the searching the scheme of paths (SoP) as a model for evaluation the efficiency indexes of behavior algorithms of radio electronic complex systems (RECS). Radio electronic complex systems are analyzed as structural-algorithmic systems. The software prototype based on SoP method can be applied for the research of efficiency indexes of such systems. This software prototype provides quick solution for multivariate analysis and parametric synthesis of behavior algorithms of RECSs. Case study of SoP method and software prototype application is discussed.

In the article there is description of determination of the accepted radio signal at the different heights of transmission and receiving aerials taking into account interference of waves, that depends on the present obstacles and areas of Frenel.

The article presents a new method of developing a unified model for estimating safety and reliability of complex technical systems for critical application at the stage of their systems design. It is possible to obtain availability function and accident function based on this unified model.

This paper is aimed at analyzing the maintenance strategy for the base stations in the cellular network where one maintenance team is responsible for network maintenance and emergency situations elimination. To build a mathematical model, the process of maintenance and repair is presented as a queuing system for which a system of linear differential equations is developed on the basis of the theory of Markov processes. On the basis of the developed module, the solution of the parametric synthesis problem of the maintenance strategy for the base stations in the cellular communication network with the relative maintenance priority is presented.

Fault-tolerant system with combined structural redundancy is used in the design of the server node memory and an uninterruptible power supply system of very important purposes. Suggested reliable models of such devices have a high degree of adequacy and allows to solve problems which contains multiple choice analysis with acceptable to the designer time expense.

The article presents the method of the quantitative assessment of the exploitation risk of the navigation information system of air drones. With this method, it's possible to measure the probability of the failure of the system without the development of the failure tree. The presented method provides the way to solve the problem of decreasing the level of the exploitation risks of the navigation information system of the air drone on the stage of the system engineering. Presented method is based on the new mathematical models of the components of the navigation information system with detailed representation of the critical failure state.

Providing the high availability level for the Instrumentation and Control (I&C) Systems in Nuclear Power Plants (NPP) is highly important. The availability of the critical NPP I&C systems depends on the hardware and software reliability behavior. The high availability of the I&C systems is ensured by the following measures: structural redundancy with choice of the I&C system configurations (two comparable sub-systems in the I&C system, majority voting "2oo3", "2oo4", etc.), maintenance of the I&C system, which implies the repair (changing) of no operational modules, using the N-version programming, software updates, automatic software restart after temporary interrupts caused by the hardware fault. This paper proposes solution of the following case: the configuration of the fault-tolerant I&C system with known reliability indexes of hardware (failure rate and temporary failure rate) is chosen, the maintenance strategy of hardware (mean time to repair, numbers of repair) is specified. In these circumstances it is important to determine quantitative requirements to software reliability: number of software updates during operation I&C system, acceptable duration of the new software version development, acceptable duration of the automatic software restart, determination of acceptable failure rate for each software version. The value of the operational software parameters is determined for the specified availability level of the I&C system. The planned number of software updates determines the duration of testing in order to identify and correct the design faults. Duration of the software testing is limited to the moment when predicted model shows a specified number of hidden (undetected) design faults. To solve this issue, the availability model of the fault-tolerant I&C system was developed in the discrete-continuous stochastic system form. We have estimated the influence of the I&C system on the operational software parameters. Two configurations of I&C systems are presented in this paper: two comparable sub-systems in I&C system, and I&C system with majority voting "2oo3".

During design of Instrumentation and Control (I&C) Systems in Nuclear Power Plants (NPP) engineer should take into account requirements for high reliability and safety. Engineer also needs to consider that addition of redundant subsystems (such as reactor protection, monitoring systems etc.) decreases the reliability of the whole I&C system. In this article we present the method for solution of the problem of improving NPP I&C systems safety by improving their reliability. The method is based on the state-transition model of NPP I&C system with split critical failure state. The key feature of this method is the possibility to calculate indicators of reliability and safety using one model. This possibility allows investigating the influences of the maintenance strategies and fault-tolerance design on the system's safety.

The object of consideration is the electronic system of long-term operation. Consider options for systems maintenance and without it. In systems without maintenance is an important consideration reconfiguration of majority Structure and aging of its elements. For the systems with maintenance is an important a choice of strategy maintenance. A mathematical model for both versions of fault-tolerant systems with majority structure.

Models of fault-tolerant system with a combined structural redundancy, which includes the structure of “K of N” with N-th number of technical systems in the core and their sliding redundancy are presented. Exploitation of system does not provide for maintenance and therefore the using procedures of reconfiguration of the core of structure of “K of N” are examined. Possibilities of models researching two variants of realization of the procedure reconfiguration of the core of structure of “K of N” are demonstrated.

Modern complex mission-critical systems are built as fault-tolerant systems, i.e. having the ability to function while some of their separate elements have a fault. The complexity of such fault-tolerant systems makes their reliability models quite big and complex. Therefore, such requirements for building models, as the high level of credibility and the appropriate level of formalization, are imposed on these models, which allows to implement the automation to their creating and analysis of reliability and, therefore, using modern computer tools. The combination of analytical methods for the research on reliability and computing capability of modern computers is a promising direction for further development of methods of reliability theory.

The developed software ASNA-2, which is an improved version of the software ASNA-1, is based on the technology of automated estimation of reliability indexes of fault-tolerant systems. This software is designed for automated evaluation of the reliability indexes of fault-tolerant hardware – software systems. This paper describes a software ASNA-2 with the peculiarities of procedures of reliability analysis of fault-tolerant systems.

The object of consideration is fault-tolerant radioelectronic system with redundancy and maintenance without automatic replacement of modules that are out of order. A structural-automatic model for such systems, which allows to determine the reliability indexes of such systems is developed.

В статті представлено особливості розробки та застосування системи дистанційного навчання на базі Moodle для підвищення кваліфікації працівників підприємства. Визначено особливості та обмеження традиційного застосування системи дистанційного навчання Moodle та шляхи їх усунення.

The subject of research is to determine the functional safety indicators of a fault-tolerant safety-critical system, namely, the minimal cut sets’ probability for a given duration of the system’s operation, using the state transition diagram (STD). The aim is to create a new method for analyzing the functional safety of a fault-tolerant safety-critical system. This method is based on the methodology of developing models of operational reliability behavior in the form of STD. This methodology provides a detailed representation of inoperable states and their relation with pre-failure (inoperable critical) states. The task is to propose a new classification for inoperable states of the STD to obtain all possible emergencies in the same space of inoperable states. This approach allows consideration the correlations between the failures, that it is impossible to use the fault trees. Since the space of inoperable states can reach hundreds and thousands of states, a method is proposed for ...

The methodology of assessing the functional safety and availability indexes of the cellular communication system, taking into account not only the reliability of its components, but also the parameters of its maintenance strategy is presented in the article. The correct choice of maintenance parameters of the cellular communication system will reduce the frequency of emergency and ensure a given coefficient of readiness during operation. The methodology is based on a stochastic model of operational behavior of cellular base stations. This technique will be useful both for the stage of system design of the cellular communication system and for the stage of its operation. Thus, at the stage of system design, the methodology allows for a given value of its functional safety, to determine acceptable to the designer values of reliability and parameters of maintenance strategy. At the stage of operation-the methodology allows to determine the required values of the parameters of the maintenance strategy for a cellular base station with a known value of its functional safety, which should provide the repair service of the communications company.

The effectiveness of guard signaling complexes (GSC), when there is an important validity of the classification of moving objects (MO), is evaluated by the following indexes: probability of GSC task execution; probability of partial fulfillment of the task; probability of user’s “deception”. Accordingly, the performance indicators of the GSC, in turn, depend on the indexes of the functionality of its constituents: probability of fixation of moving object by seismic sensor, probability of correct classification of MO type and probability of receiving radio signal by the system of receiving and displaying information (SRDI). The article describes a discrete-continuous stochastic model of of GSC reaction to moving object crossing control zone, in which three seismic sensors are installed. Majority principle of identifying the type of moving object was used on the receiving part of the complex. A comparative analysis of the effectiveness of guard signaling complexes using one, two and t...

In this article results of researches of strategies of maintenances of fault-tolerant informative systems are described. A design process is carried out on the basis of original approach. This approach is realized on application of structurally - automatics models for construction of Markov models.

This paper presents the technique of constructing models of behavior algorithms of radio electronic complex system using new scheme of paths method. This technique allows estimation of the efficiency indexes of RECS taking into account behavior algorithm's features, hardware and software reliability and self-diagnostics procedures.

Hardware/software systems provide flexible implementation of microprocessors, microcontrollers and various peripheral devices and supply the ability to perform almost any functional algorithm that can be simply modified or replaced. For reliability estimation of hardware/software systems we must take into account not only the loss of efficiency, which was caused by the hardware failures, but the abnormal functioning, that was caused by software failures. All these features of hardware/software systems must be considered in their models for reliability indexes estimation. Development of mathematical models of hardware/software system begins with establishing the cause-and-effect relationships of its efficiency violations. Basing on these cause-and-effect relationships the structural-automatic model, which is formalized representation of structure and behavior of hardware/software system, was developed. This structural-automatic model and software module ASNA allows obtaining the anal...

Research of preventive maintenance effect on reliability of fault-tolerant uninterruptible power supply is important in determination of the requirements for maintenance. In this paper the objects under consideration are two variants of the fault-tolerant system for uninterruptible power supply with (N+M) and 2×(N+M) redundant configurations, which are provided by preventive maintenance. There are given reliability models for both configurations of faulttolerant system for uninterruptible power supplies, which allows investigating the dependence of their reliability on the frequency of preventive maintenance, in this paper. Reliability models for fault-tolerant systems are formed as graphs of states and transitions. Determination of the reliability parameters is associated with the solution of system of Kolmogorov Chapman differential equations, formed according to the developed graphs. These models are useful both at the design stage (to determine the structure of the fault-toleran...

In the following article is conducted design of optical circles of telecommunications network model for reliability behavior research and has been demonstrated all stages o f model design. On the bases of design model is dedicated choice of optical data components of network.

The safety of radio electronic systems for critical applications is traditionally ensured by inducing structural redundancy. This paper shows a developed technique for ensuring a required level of safety of such systems by inducing time and functional redundancy into its behavior algorithm. The defined safety characteristic is proposed for quantitative efficiency estimation of the induced redundancy. Presented in the article is the synthesis technique of safe behavior algorithms on the basis of safety characteristic minimization of increased values. The developed technique was tested through solving the synthesis problem of the behavior algorithm of the target detection radio electronic complex system. SYNTEZA ALGORYTMÓW BEZPIECZNEGO POSTĘPOWANIA W SYSTEMACH RADIOELEKTRONICZNYCH DO ZASTOSOWAŃ W SYTUACJACH KRYTYCZNYCH Streszczenie. Bezpieczeństwo radiowych systemów elektronicznych używanych w sytuacjach krytycznych jest tradycyjnie zapewnione przez wprowadzenie redundancji strukturalnej. W pracy zaproponowano sposób zapewnienia określonego poziomu bezpieczeństwa radiowych systemów elektronicznych poprzez wprowadzenie redundancji czasowej i funkcjonalnej do algorytmu postępowania. Aby zmierzyć wydajność wprowadzonej redundancji, zaproponowano określone cechy bezpieczeństwa. Artykuł przedstawia metodę syntezy algorytmów bezpiecznego postępowania na podstawie minimalizacji wzrostu wartości określonych cech bezpieczeństwa. Opracowana metoda została przetestowana podczas rozwiązywania problemu syntezy algorytmu postępowania dla złożonego systemu radioelektronicznego przeznaczonego do wykrywania celów. Słowa kluczowe: bezpieczeństwo, inżynieria bezpieczeństwa, algorytm postępowania, projekt systemu

This work proposes a new methodology for assessment of the average probability of minimal cut sets. This methodology deals with minimal cut sets assessed considering latent and evident failures or only latent failures. For latent and evident failures, the existing techniques provide the assessment only for the worst cases/scenarios. For only latent failures, the existing techniques provide significantly overstated values for the average probability of minimal cut sets. Such under/overstated assessment is not acceptable for the exploitation of the safety-critical radio-electronic system.

In this paper we propose a new term-accident rate function. Such term gave a possibility to provide the quantative assessment for operational safety in the fault tolerant systems with high responsiblity purposes. Moreover, we propose a binary structural automata model. Using the proposed binary structural automata model in the ASNA software, we provide a possibility to build models of the fault tolerant systems in the form of a graph of states and transitions, in an automatic way. Obtained graph of states and transitions is used to define the accident rate function. The authenticity of the emergency rate function is confirmed by the coincidence of two calculated values. One value is obtained based on accident rate function at determined time interval and the other value is the probability of minimal cut sets obtained based on fault tree at a similar time interval. Using the ASNA software to get the accident rate function and the usage of new methodology of forming the accident rate function from the subarray of non-functioning states makes the process of obtaining the results in an automatic way. As a result, the proposed approach gives a possibility to perform multivariant analysis of functional safety for the systems with high responsibility purpose.

– The article presents a new method of developing a unified model for estimating safety and reliability of complex technical systems for critical application at the stage of their systems design. It is possible to obtain availability function and accident function based on this unified model.

https://www.morebooks.de/gb/p_9783659633669
Монография посвящена решению одной задачи актуальной научно-прикладной проблемы проектирования эффективных стратегий технического обслуживания и ремонта базовых станций сетей сотовой связи с оптимальными значениями параметров по критерию минимума затрат на техническое обслуживание и ремонт при условии обеспечения заданного уровня надежности. В монографии представлены новые математические модели стратегий технического обслуживания и ремонта, учитывающие: размещение базовых станций сетей сотовой связи; многоэтапность технического обслуживания и ремонта; выполнения одной ремонтной бригадой двух видов восстановительных работ (планового технического обслуживания и аварийного восстановления); отключение оборудования базовой станции при обслуживании. Представленные модели дают возможность проектировать новые и усовершенствовать существующие стратегии технического обслуживания и ремонта, а также обосновано выбирать лучшие стратегии из совокупности конкурентных вариантов. Кроме этого, модели позволяют дифференцировано оценивать стоимость проведения различных этапов технического обслуживания и ремонта.
https://www.morebooks.de/gb/p_9783659633669

In the presented work the idea of improvement the state space
method for building safety models of complex technical systems for critical application is proposed. Result of the this improvement one single model is developed on which due to the split state of critical failure state quantitative reliability and safety quantitative indicators of the system can be obtained.
Unlike traditional models as in a fault trees, dynamic tree failures and FMEA /FMECA-models the proposed model to allow to take into account independencies between accidental situations. This model allows to investigate the trend of risk indicators accidental situations variance from increasing
system reliability through the use of fault-tolerant configurations and maintenance usage.

Thesis devotes to the formulation and solution of scientific problems for the efficiency estimation of target search and detection algorithms at radio-electronics sighting complexes, i.e.: development of estimation tools for system design. These tools will cut down the expenses of time and material resources. In thesis the following problems are solved . The structurally-automatic model, the Marcov model and logical-probability model of target search and detection algorithms are developed. The technique for efficiency estimation of target search and detection algorithms at radio-electronics sighting complexes has been created. For modeling of a target search and detection algorithms at radio-electronics sighting complexes models of fault-tolerance systems with combined structural redundancy and with majority structure capable to reconfiguration are created . Choice and comparative analysis of methods for construction of mathematical models of fault-tolerance systems with taking into account of aging effect and arbitrary process duration distribution of technical service are executed . Obtained results were implemented in Lviv Radio Engineering Institute and into training process for the experts engaged in the designing of radio-electronics systems and complexes. Key words: radio-electronics complex, radio-electronics system, algorithm, system design, mathematical model, reliability.

A thesis submitted in fulfilment of the Doctor of  Engineering Science Degree in Specialty 05.12.17 – Radio and Television Systems. – Lviv Polytechnic National University, Ministry of Education and Science of Ukraine, Lviv, 2020.
This thesis presents the solution of the actual scientific problem of development the theoretical basis of complex maintenance of safety critical radio electronic system (SCRES) with a required level of functional safety and reliability. The developed means (methods, models, algorithms and techniques) enable an identifying the weaknesses in the SCRES design in terms of functional safety at the stage of system design. This allows an engineer to reasonably induce a necessary types of redundancy (structural, temporary, functional) to increase both functional safety and reliability of SCRES. Thus, the developed tools give the opportunity to synthesize a fault-tolerant structure, behavior algorithm and maintenance strategy, which ensure that the SCRES will not fall into an emergency.
Modern methods of assessing functional safety indexes are based on the determination of minimal cut sets, which show the weaknesses of the SCRES. To obtain minimal cut sets, these methods use fault trees, dynamic fault trees, event trees, or binary decision diagrams. However, the known methods don’t allow to take into account the impact on the SCRES functional safety of fault-tolerant majority structures with reconfiguration, fault-tolerant two-tier majority structures, maintenance strategies, temporary and functional redundancy in behavior algorithms. Also, a significant disadvantage of existing methods is that they don’t give the opportunity to obtain both functional safety indexes and reliability indexes on the basis of a single model. So, it can lead to the condition when the reliability of the SCRES is reduced with the induction of additional tools for increasing functional safety. Also, these methods aren’t suitable enough for solving synthesis tasks via multivariate analysis for a short period time, what is very important at the stage of system design.
In the dissertation, a new method is proposed for automated definition of types of inoperable states. This method provides a classification of inoperable states of the SCRES according to the level of critical failures and allows obtaining trajectories of accidents. Based on this method, a new technique is proposed for development of complex dynamic models of SCRES in the form of a graph of states and transitions. This technique, unlike the existing ones, allows determining both minimal cut sets and reliability indexes of SCRES without constructing appropriate fault tree.
To reflect the relationship between indexes of functional safety and reliability of fault-tolerant structures, behavior algorithms and maintenance strategies, new indexes and characteristics of functional safety are proposed: the accident function; frequency of fall into an accident state; probability of fall into a pre-accident state; the average value of the probability of a minimal cut set existence.
New models of strategies for planned and preventive maintenance and emergency recovery have been developed to take into account the impact of SCRES downtime on functional safety indexes during maintenance and repair procedures. These models enabled the development of method for synthesizing a maintenance strategy which guarantees to maintain a required level of functional safety of the SCRES. New method was developed to calculate the average value of the probability of the minimal cut set existence that gives an opportunity to solve the problem of minimizing impact of latent failures on the functional safety. This method makes it possible to obtain dependable values of the probabilities of the minimal cut sets existence for cases when the minimal cut set contains only latent failures or a combination of latent and active failures.
New models of fault-tolerant SCRESs with majority structures were developed, which, in contrast to the existing ones, allow to take into account the impact of the use of reconfiguration of the majority structure, two-tier majority structure, maintenance and repair on the functional safety. The proposed models make it possible to solve the problem of synthesis of fault-tolerant systems for SCRES with a required level of functional safety and appropriate level of structural redundancy, that is especially important for onboard information and control systems of aircrafts, including unmanned vehicles, for which mass and size restrictions are critical.
New methodology for the synthesis of safe behavior algorithms of the SCRES was developed, which, in contrast to the existing ones, takes into account the impact of time and functional redundancy on the functional safety of SCRES. This methodology shows the way to achieve a required level of probability of the task execution with the minimum value of the frequency of accidents.
Keywords: reliability, functional safety, reliable engineering, fault–tolerant systems, behavior algorithm, maintenance, majority system, safety critical radio electronic system.

A thesis submitted in fulfilment of the Doctor of Engineering Science Degree in Specialty 05.12.17 – Radio and Television Systems. – Lviv Polytechnic National University, Ministry of Education and Science of Ukraine, Lviv, 2020.
This thesis presents the solution of the actual scientific problem of development the theoretical basis of complex maintenance of safety critical radio electronic system (SCRES) with a required level of functional safety and reliability. The developed means (methods, models, algorithms and techniques) enable an identifying the weaknesses in the SCRES design in terms of functional safety at the stage of system design. This allows an engineer to reasonably induce  necessary types of redundancy (structural, temporary, functional) to increase both functional safety and reliability of SCRES. Thus, the developed tools give the opportunity to synthesize a fault-tolerant structure, behavior algorithm and maintenance strategy, which ensure that the SCRES will not fall into an emergency.
Modern methods of assessing functional safety indexes are based on the determination of minimal cut sets, which show the weaknesses of the SCRES. To obtain minimal cut sets, these methods use fault trees, dynamic fault trees, event trees, or binary decision diagrams. However, the known methods don’t allow to take into account the impact on the SCRES functional safety of fault-tolerant majority structures with reconfiguration, fault-tolerant two-tier majority structures, maintenance strategies, temporary and functional redundancy in behavior algorithms. Also, a significant disadvantage of existing methods is that they don’t give the opportunity to obtain both functional safety indexes and reliability indexes on the basis of a single model. So, it can lead to the condition when the reliability of the SCRES is reduced with the induction of additional tools for increasing functional safety. Also, these methods aren’t suitable enough for solving synthesis tasks via multivariate analysis for a short period time, what is very important at the stage of system design.
In the dissertation, a new method is proposed for automated definition of types of inoperable states. This method provides a classification of inoperable states of the SCRES according to the level of critical failures and allows obtaining trajectories of accidents. Based on this method, a new technique is proposed for development of complex dynamic models of SCRES in the form of a graph of states and transitions. This technique, unlike the existing ones, allows determining both minimal cut sets and reliability indexes of SCRES without constructing appropriate fault tree.
To reflect the relationship between indexes of functional safety and reliability of fault-tolerant structures, behavior algorithms and maintenance strategies, new indexes and characteristics of functional safety are proposed: the accident function; frequency of fall into an accident state; probability of fall into a pre-accident state; the average value of the probability of a minimal cut set existence.

New models of strategies for planned and preventive maintenance and emergency recovery have been developed to take into account the impact of SCRES downtime on functional safety indexes during maintenance and repair procedures.
These models enabled the development of method for synthesizing a maintenance strategy which guarantees to maintain a required level of functional safety of the SCRES. New method was developed to calculate the average value of the probability of the minimal cut set existence that gives an opportunity to solve the problem of minimizing impact of latent failures on the functional safety. This method makes it possible to obtain dependable values of the probabilities of the minimal cut sets existence for cases when the minimal cut set contains only latent failures or a combination of latent and active failures.
New models of fault-tolerant SCRESs with majority structures were developed, which, in contrast to the existing ones, allow to take into account the impact of the use of reconfiguration of the majority structure, two-tier majority structure, maintenance and repair on the functional safety. The proposed models make it possible to solve the problem of synthesis of fault-tolerant systems for SCRES with a required level of functional safety and appropriate level of structural redundancy, that is especially important for onboard information and control systems of aircrafts, including unmanned vehicles, for which mass and size restrictions are critical.
New methodology for the synthesis of safe behavior algorithms of the SCRES was developed, which, in contrast to the existing ones, takes into account the impact of time and functional redundancy on the functional safety of SCRES. This methodology shows the way to achieve a required level of probability of the task execution with the minimum value of the frequency of accidents.

Thesis devotes to the formulation and solution of scientific problems for the  efficiency estimation of target search and detection algorithms at radio-electronics sighting complexes, i.e.: development of estimation tools  for system design. These tools will cut down the expenses of time and material resources.
In thesis the following problems are solved . The structurally-automatic model,  the Marcov  model and  logical-probability  model  of target search and detection algorithms are developed. The technique for efficiency estimation of target search and detection algorithms at radio-electronics sighting complexes has been created. For modeling of a target search and detection algorithms at  radio-electronics sighting complexes models of fault-tolerance systems with combined structural redundancy and with majority structure capable to reconfiguration are created . Choice and comparative analysis of methods for construction of mathematical models of fault-tolerance systems with taking into account of aging effect and arbitrary process duration distribution of technical service are executed .
Obtained results were implemented in Lviv Radio Engineering Institute and into training process for the experts engaged in the designing of radio-electronics systems and complexes.
Key words: radio-electronics complex, radio-electronics system, algorithm, system design, mathematical model, reliability.

At the engineering design stage of  complex systems for critical application  (CSCA) two important tasks need to be solved, namely to provide a specified level of reliability and a given level of safety.
Provision of a given level of reliability is carried out by in-troducing various types of redundancy into the structure and algo-rithm of the CSCA behavior. Thus, raising safety levels leads to a lower level of reliability, and increasing the level of reliability can lead to increased safety, but in most cases it does not lead.
Therefore, the task of developing a method for creation of unified model is actual.  The unified model will be possible to define both indicators of reliability and safety.
To construct a single model, modification of the advanced state space method was made. The modified method allows to receive an array of failure states, on the basis of which there is an opportunity to analyze the emergence of emergency situations during the operation of the CSCA due to the failure of individual elements and subsystems. For the received  of cut sets array, a method of combining disabling states in separate emergency situa-tions was developed, taking into account the fact that the same incapacitated states can enter into various emergency situations.
Determining the minimum cut sets from a reliable model of a research object in the form of a state graph allows you to take into account the belonging of a certain part of the incapacitated states to two or more emergencies.
The main difference between the proposed method and the others is the possibility of obtaining a function of emergency, which will enable to analyze the change of minimal cut sets in time, and this will allow the design of maintenance strategies for CSCA, which will ensure the needed level of reliability and safety.
The method of obtaining the reliability and safety indexes of the CSCA using the state graph is presented in Fig. 1
Thus, based on the use of an improved method of space of states with a split state of critical refusal, one can determine the probability of occurrence of minimal cut sets without the construc-tion of a failure tree. Such a technique allows solving the problem of reducing the level of exploitation risk of the CSCA at the stage of system engineering with significantly less time than using the failure tree.