=Paper= {{Paper |id=Vol-3288/paper4 |storemode=property |title=Method of Estimating the Values of Reliability Indicators of Objects with Variable Structure |pdfUrl=https://ceur-ws.org/Vol-3288/paper4.pdf |volume=Vol-3288 |authors=Sergii Gnatiuk,Lev Sakovich,Yana Kuryata,Roman Odarchenko,Viktor Gnatyuk |dblpUrl=https://dblp.org/rec/conf/cpits/GnatiukSKOG22 }} ==Method of Estimating the Values of Reliability Indicators of Objects with Variable Structure== https://ceur-ws.org/Vol-3288/paper4.pdf
Method of Estimating the Values of Reliability Indicators
of Objects with Variable Structure
Sergii Gnatiuk1, Lev Sakovich2, Yana Kuryata2, Roman Odarchenko3, and Viktor Gnatyuk3
1
  Administration of the State Service for Special Communications and Information Protection of Ukraine,
13 Solomianska str., Kyiv, 03110, Ukraine
2
  Institute of Special Communication and Information Protection of the National Technical University of Ukraine
“Kyiv Polytechnic Institute named after Igor Sikorsky,” 37 Peremohy ave., Kyiv, 03056, Ukraine
3
  National Aviation University, 1 Liubomyra Huzara ave., Kyiv, 03058, Ukraine

                 Abstract
                 The article proposes to improve the method of estimating the values of operating time on failure,
                 the average recovery time and the coefficient of readiness of radio equipment with variable
                 structure. The essence of improvement is to take into account the operating time of the
                 individual components of the product in the possible modes of use for its intended purpose. In
                 known works, this fact is not taken into account, so the results of calculations give an
                 underestimation of the values of reliability indicators, which, in turn, leads to an overestimation
                 of the cost of the product. An example of using the method is given and the effect of its
                 application is shown.

                 Keywords 1
                 Reliability indicators, multi-mode objects, variable structure, operating time on failure, average
                 recovery time.


1. Introduction                                                                                        time, the requirements for the value of failure time
                                                                                                       and the average recovery time of these products
                                                                                                       have not changed.
    Modern research in the field of reliability
                                                                                                           Modern foreign sources consider various
theory of complex technical systems is aimed at
                                                                                                       aspects of ensuring the reliability of electronic
creating objects with specified values of
                                                                                                       means - from improving the quality of the element
reliability indicators through the introduction of
                                                                                                       base to predicting changes in the values of
redundancy of the least reliable structural
                                                                                                       reliability over time, but methods for assessing the
elements, and the production of so-called
                                                                                                       reliability of objects with variable structure are
“absolutely reliable systems” in which the
                                                                                                       also not considered [9–15].
readiness factor A ≥ 0.997 [1–5] (in some cases,
                                                                                                           Thus, the task arises to ensure the required
for example, for interplanetary spacecraft, robots
                                                                                                       level of reliability of products while minimizing
to study other planets). In addition, special
                                                                                                       their cost. To solve it, it is necessary to improve
attention is paid to the development of software-
                                                                                                       the existing methods of calculating the values of
controlled radio equipment and systems, which
                                                                                                       reliability of complex technical objects, taking
also affects their reliability [4–7]. However, the
                                                                                                       into account their properties: multi-mode,
complexity of modern radio equipment and the
                                                                                                       multifunctionality, the presence of redundancy,
density of installation is constantly increasing:
                                                                                                       which leads to changes in the structure of the
only in the radio stations of the tactical level of
                                                                                                       object during its intended use. Currently, there are
control over the past thirty years, the number of
                                                                                                       not only practical but also theoretical methods for
elements and the density of installation has
                                                                                                       calculating the efficiency of systems with a
increased more than six times [8]. At the same
                                                                                                       variable structure, which can change randomly at

CPITS-2022: Cybersecurity Providing in Information and Telecommunication Systems, October 13, 2022, Kyiv, Ukraine
EMAIL: sgnatuk30@gmail.com (S. Gnatiuk); lev@sakovich.com.ua (L. Sakovich); ganaga@ukr.net (Y. Kuryata);
roman.odarchenko@npp.nau.edu.ua (R. Odarchenko); viktor.hnatiuk@npp.nau.edu.ua (V. Gnatyuk)
ORCID: 0000-0002-1541-7058 (S. Gnatiuk); 0000-0002-8257-7086 (L. Sakovich); 0000-0002-8625-6693 (Y. Kuryata); 0000-0002-7130-
1375 (R. Odarchenko); 0000-0002-4916-7149 (V. Gnatyuk)
             ©️ 2022 Copyright for this paper by its authors.
             Use permitted under Creative Commons License Attribution 4.0 International (CC BY 4.0).
             CEUR Workshop Proceedings (CEUR-WS.org)



                                                                                              33
short intervals. The change in structure always              directions of automation of calculations of
occurs depending on the change in the functions              reliability indicators of electronic means and their
performed by the system [1, 2].                              changes over time also investigated.
                                                                 A promising direction in the development of
2. Forming the Purpose                                       radio-electronic means of the communication
                                                             industry is the introduction of software-controlled
                                                             means, the quality of which also affects the
   The purpose of the article is to improve the              reliability of individual products and the
method of estimating the values of reliability               communication system as a whole.
indicators of objects with a variable structure,                 The value of the complex indicator of the
taking into account the operating time of                    reliability of radio-electronic means—their
individual sets of elements in possible modes of             availability factor—is significantly affected not
use for their intended purpose.                              only by the MTBF, but also by the average
                                                             recovery time, so in special technical literature,
3. Mathematical Model                                        research, and dissertation work, attention is paid
                                                             to improving the quality of diagnostic support for
    Approximate calculation of the reliability of            repair. During the quantitative assessment of the
radio-electronic means (REM) without taking into             values of reliability indicators of electronic
account the property of their multi-mode is                  means, which are determined by design tasks, do
performed under the following assumptions:                   not take into account the property of multi-mode,
 Failures of elements are independent.                      which leads to changes in the structure of objects
 Failure of at least one element entails the                during their intended use.
    failure of the equipment.                                    At present, there are not only engineering
                                                             methods but also theoretical developments of
 Intensity of element failures does not depend
                                                             reliability analysis of technical systems with
    on time, i.e. λі = const.                                changing structure, which is due to its multi-
 Elements operate in typical (nominal) modes.               functionality and multimode, when in separate
 Elements of the same type are equally reliable.            modes of operation the corresponding sets of
    The second condition practically means that              elements are used. Multi-mode properties used in
redundancy is not applied in the equipment, and              the development of diagnostic software, but when
elements that perform auxiliary functions should             assessing reliability, it is traditionally believed
be excluded from the calculations. In other words,           that all elements of the object operate
in the approximate calculation, it is assumed that           simultaneously,        and      this   significantly
all elements of the equipment are connected in               underestimates the MTBF.
series, with both complete and partial failure of                Today, in modern domestic and foreign
any element leading to equipment failure.                    publications on topical issues of the reliability of
    Means of various purposes are continuously               complex technical objects and systems, some
developing and improving in the direction of                 directions for increasing the values of their
improving quality indicators by consumer                     reliability indicators considered. However, these
requirements through the introduction of new                 publications do not consider the issues of complex
schematic and design solutions, as well as the use           consideration of the reliability of individual
of modern element base. This causes a                        components of software-controlled multi-mode
corresponding complication for products, which               communication facilities with changing structures
does not lead to an improvement in the values of             during the assessment of their performance in
their reliability indicators. Therefore, the issue of        both the design process and refinement during
ensuring the required level of reliability of                trial operation.
modern electronic means is very important for                    There is a problem with increasing the
both manufacturers and consumers.                            accuracy of a quantitative assessment of the
    There are known methods of ensuring the                  reliability of radio-electronic means with a change
required values of reliability indicators of radio-          in structure by using a new model that takes into
electronic means by reserving the least reliable             account the operating time of individual elements
structural units, which increases their cost and             of the object in various modes of operation and
weight, and dimensions, as well as the volume of             increases the accuracy of calculations taking into
spare tools and accessories for the implementation           account the peculiarities of construction and
of current repairs by the aggregate method. The              intended use of these objects.


                                                        34
    The development task standardizes the mean              elements and a core consisting of elements 7 and
time between failures and the average recovery              8, which are used in all modes of operation.
time of existing, modernized, and prospective                   In the traditional approximate calculation of
multimode radio electronic devices. Therefore,              reliability, the minimum and maximum values of
during the design, it is mandatory to perform a             the parameter of the flow of failures of individual
reliability calculation with a quantitative                 elements in (Zi) are summed up, after which the
assessment of all reliability indicators, which are         limits of change and the average values of the
then checked during trial operation.                        MTBF are determined
    Communication equipment belongs to the                                      T          1 L            .                            (1)
                                                                                                  Zi
class of objects with changing structures, which
can be single and multifunctional, multimode with
                                                                                                 і 1
a fixed or arbitrary change of operating modes.
                                                               In this case, the real operating time of
    To model these objects, the well-known                  individual elements is not taken into account.
mathematical apparatus of set theory was used,
                                                               If the value of the parameter ZRi of failures of
but only during the development of diagnostic               individual elements of the product is known, then
software. Set-theoretic models allow us to                  for each mode of operation we obtain:
estimate the power of sets of elements used in
separate modes of operation, as well as their                      Z R1  Z1  Z 4  Z 5  Z 7  Z 8 ;      (2)
interconnection.                                                  Z R2  Z 2  Z 4  Z 6  Z 7  Z8 ;                                   (3)
    For example, with a fixed change of modes, it
                                                                  Z R3  Z 3  Z 5  Z 6  Z 7  Z8 .     (4)
is advisable to use a model of the "garland" type,
when with each step the number of elements of the              In this case, the MTBF of the product in each
object increases. This leads to a decrease in               operating mode is equal:
MTBF and an increase in the average recovery                                     1           1          1
                                                                     T1             ; T2      ; T3       .                           (5)
time, which worsens the value of the complex                                    Z R1        ZR2        Z R3
reliability indicator - the facility availability
                                                                If there is additional data on the time of
factor.
                                                            operation of the product in individual modes (Трі),
    When arbitrarily changing the operating
                                                            it is possible to calculate the value of the relative
modes of a radio receiver or radio station, it is
                                                            utilization factor of each element accordingly:
advisable to use a set-theoretic model with
intersections of subsets of elements that have a                          T p1               Tp 2                  Tp3
                                                                  u1             ; u2                 ; u3              ;            (6)
core (for example, amplifiers, power supply or                             Tp                Tp                    Tp
generator equipment). In this case, the reliability                      T p1  T p 2            T p1  T p 3            T p 2  T p 3 ; (7)
of individual subsets of elements is significantly                u4                   ; u5                   ; u6 
                                                                             Tp                      Tp                         Tp
affected by the time of their operation in a given
mode (for example, the operating time of the radio                u7  1; u8  1; Tp  Tp1  Tp 2  Tp3 ;                               (8)
station in the "receive" mode is many times longer          where Тр is the total operating time of the product
than in the "transmit" mode), that is, the technical        in all possible modes.
resource of the elements is calculated unevenly.                This allows, taking into account the specific
    To take into account this circumstance, it is           operating time of each element of the product, to
proposed to apply the coefficient of use for each           quantify the predicted number of their failures and
subset of elements in possible modes of operation           the product as a whole:
of the product, which is calculated as the ratio of                               8                  8                    8     Tpi
the operating time of a subset of elements to the                 N  Tp  U i Z i   Z iTpi                                       . (9)
total operating time of the product in all possible                             i 1                i 1                 i 1   Ti
modes. Its value can be quantified from the                     Then the failure rate of the product as a whole
analysis of the use of communication means,                 is equal:
which is reflected in the hardware logs of                                              N     8
communication nodes.                                                         Z             U i Z i ,                                (10)
    Consider the use of these proposals on the                                          T p i 1
example of a multi-mode object, the scheme of               where T pi / Ti  N i is MTBF of individual
which shown in Fig. 1. The object operates in
three modes, each of which uses five of the eight           subsets of elements, and MTBF taking into
total subsets of elements. This is a set-theoretic          account the operating time of subsets of elements
model with strong intersections of a subset of              in separate modes, respectively T  T p / N .


                                                       35
Figure 1: An example of a multi-mode technical object with a core and a strong intersection of a subset
of elements

   Suppose that all subsets of elements in the                product, taking into account its multi-mode
example under consideration are equally reliable              properties, has increased several T /  T  1,6
(Zi=Z) and in each mode of operation the product              times, or by (T  T ) / T 100%  37,5% .
operates for the same time ( T pi  T p / 3 ), then we            Obviously, the greater the number of possible
obtain                                                        modes of operation of the product, the more
              u1  u2  u3  1/ 3;                            accurate is the estimate of the MTBF value taking
                                                              into account the multi-mode property. But, this
              u4  u5  u6  2 / 3;               (11)
                                                              requires additional initial data for the predicted
              u7  u8  1.                                    time of operation of the product in each mode.
   The total number of product failures during                    The MTBF of electronic equipment as a whole
                                8                             (T) depends on the operating time of individual
operation T p is N  ZT p      U  5ZT , and
                               i 1
                                      i       p               parts of the product used in various operating
                                                              modes (Ti), which in turn is determined by the
MTBF is T  1/ 5Z .                                           failure rate of this subset of elements (Zi)
    Under the same conditions with the traditional            Ti  1 / Z i .
conditional calculation of reliability we obtain                  The multi-mode property of radio electronic
T   1/ 8Z , that is, the real value of MTBF of the          equipment is taken into account by introducing


                                                         36
the coefficient of use of individual sets of                                         The probability of product failure due to a
elements depending on the relative time of their                                  defect among the elements Li is
operation ui  T pi / T p ; i  1, n ; where n is the                                           Tpi            uiT p
                                                                                         Ni                            uZ
number of subsets of radio electronic equipment                                                                      i i , (15)
                                                                                         N TiTp i1 ui Z i
                                                                                                 n            1
                                                                                                                 Tp Z   Z
elements used in different modes;
                                                                                                              Zi
   T p is total operating time of radio electronic
                                                                                  while T i 1 ui Z i  1 .
                                                                                                n
means.
    In this case, the total number of product                                        The average recovery time of the product is a
failures over time T p is                                                         discrete random variable, the mathematical
                                                                                  expectation of which is the sum of products of its
                       n     T pi                   n
              N                     T p U i Z i ,                 (12)        possible values (Ki) by the probability of their
                      i 1    Ti                i 1                              occurrence (uizi/z). Then the estimated recovery
and the failure rate parameter of the radio                                       time of radio electronic means (without taking
electronic means as a whole is equal to                                           into account the metrological reliability of
                                                                                  measuring instruments) is equal to
             Tp                                                 1
        T                   1 n                                ;   (13)                                         t n
              N
                                u Z      i     i
                                                                Z                                   Т ВР  t y       ui Z i og 2 Li .
                                                                                                                   Z i1
                                                                                                                                                  (16)
                                   i 1
                                                                                      In this case, the complex indicator of product
where Z is parameter of the product failure rate.
                                                                                  reliability is availability factor, is equal to
   Another indicator of the reliability of radio
                                                                                                               T
electronic means, which is standardized and set by                                                     A            
the guiding documents, is the average recovery                                                               Т  TВР
time TB. It depends on the qualification of the                                                                                               . (17)
                                                                                           1
performers (t is average time of parameter                                                             n                          n
                                                                                                                                       
checking, and ty is average time of fault                                                       1  t  ui Z i og 2 Li  t y  ui Z i 
elimination), quality of metrological and                                                             i 1                   i 1     
diagnostic support, power of subsets of elements                                      The readiness factor U 1  A .
used in separate modes of the product operation,                                      This expression does not take into account the
and probability of their failure.                                                 probability of correct diagnosis P = pk, where р is
   When searching for defects during the current                                  the probability of correct assessment of the result
repair by programs based on the use of conditional                                of the test of the parameter of radio electronic
algorithms of the minimum form, the average                                       means, as well as the metrological reliability of
number of checks                                                                  measuring instruments P(τ), where τ is the period
              K i  og 2 Li ; i  1, n ;      (14)                               of testing of measuring instruments.
                                                                                      Thus, the objective function of the research is
where Ki is the average number of inspections to                                  minimization of the value of the complex
find defects in a subset of elements Li, among                                    indicator of product reliability is availability
which it is necessary to determine the faulty one.                                factor with restrictions on the permissible values
   Average number of inspections during the                                       of MTBF (Td) and mean time to failure (Tvd),
current repair of the product, in general                                         determined by the guidelines, at a given mode of
                             1 n                                                  operation ( Т pi , ui ), takes the form:
               Ki              og 2 Li .
                             n i 1                                                                 U ( x)  min U ( x* );
   In this case, the total number of elements of                                                            x*  ;                               (18)
                                               n
                                                                                     x  ( Li , ui , Tpi , Z i , n, t , t y , P( ), T , Т В ),
radio electronic means L                      L provided that
                                              i 1
                                                            i
                                                                                  where x is parameters affecting product
the elements of subsets are used only in certain                                  reliability; x* is their importance in solving the
modes of operation, and the average number of                                     problem;  is the range of permissible limits for
            1 n
checks K i   og 2 Li .
                                                                                  changing parameter values.
            n i 1




                                                                             37
   Groups of uncontrollable parameters:                        with the one obtained by the proposed model of
    Li , n , Z i are depend on the product circuit and         reliability of objects with a variable structure (U):
the reliability of the element base.                                               100(U   U ) / U % .        (19)
   Groups of controlled parameters under
operating conditions:                                              The results are summarize in table 1, which is
                                                               a mathematical model for estimating the values of
    Tpi , ui are depend on the operating product mode;
                                                               reliability indicators of radio-electronic means
   t, t y are depend on the qualification of the               with a variable structure.
performers and the conditions for restoring                        The proposed model differs from the known
performance;                                                   ones by taking into account the operating time of
    К is depend on the quality of diagnostic                   the product in individual modes, the probability of
software and the form of conditional algorithms                failure in each mode of operation and the
for finding defects;                                           metrological reliability of measuring instruments.
     р, P( ) are depend on the measuring                          The adequacy of the model is confirmed by the
                                                               fact that the formulas obtained in the right column
equipment used during the current repair to assess
the values of signals at the control points of the             of Table. 1 with u i  1 and Р( )  1 and without
product.                                                       taking into account the probability of failure of
   In this case, as an indicator of efficiency, it is          subsets of elements are transformed into known
advisable to use the relative reduction of the                 expressions, which are given in the left column of
unavailability coefficient, the value of which is              Table 1. This model is the mathematical basis of
calculated using known methods ( U  ), compared               the method for estimating the values of reliability
                                                               indicators of objects with a variable structure.

Table 1
Mathematical model of estimation of values of reliability indicators of radio electronic means with
variable structure
                                                     Functional dependences
             Indicator           Without taking into account           With taking into account
                                          multimode                           multimode
                                                           n                                        n
      Failure rate parameter                     Z    Zi                                  Z   ui Z i
                                                          i 1                                     i 1
  MTBF (mean time to failure)                     T   1/ Z                                 T  1/ Z
                                                                 n                                        n
     Total number of failures                   N   Tp  Z i                              N  Tp  ui Z i
                                                               i 1                                     i 1
                                                               n
                                                         t                                        t n
   Estimated average recovery
              time
                                              ty 
                                          Т ВР              og 2 Li
                                                         n i1
                                                                                   Т ВР  t y       ui Z i og 2 Li
                                                                                                  Z i 1
                                                                             1 n
   Average number of checks                                           Ki       og 2 Li
                                                                             n i 1
 Probability of correct diagnosis                                            Р  рк
                                                             
                                                           TВР                                       TВР
      Average recovery time                       TВ                                      TВ 
                                                            Р                                      Р  Р ( )
                                                            T                                        T
    Product availability factor                 A                                          A 
                                                     T   TВ                                  T  TВ
  Coefficient of unreadiness of                         TВ                                       TВ
                                                U                                         U 
           the product                               T   TВ                                  T  TВ
                                                                           U  U
    Effect of using the model                                                   100%
                                                                             U


                                                         38
                                                            the values of which affect all other indicators of
4.      Developed Method                                    reliability.
                                                                The block diagram of the algorithm for the
                                                            implementation of the advanced method is shown
   The purpose of the method, its essence, initial          in Fig. 2, where it is additionally marked: Td is the
data, limitations and assumptions, as well as the           allowable value of the product operating time to
result of use are shown in the block diagram of             failure, Tvd is the allowable recovery time of the
Fig. 1. The proposed mathematical apparatus is              product during maintenance. The values of these
summarized in Table 1, where for the first time             indicators are in the guiding documents.
the coefficients of use of sets of product elements,




Figure 2: Block diagram of the algorithm for implementing the method of estimating the values of
reliability indicators of objects with variable structure



                                                       39
    Other source data are obtained: L, n, Li are             the operating time for failure is equal T' =1007
from the analysis of the product scheme; Zi is               hours. During the current repair of the radio
calculation of the failure parameter of sets of              station using measuring equipment with
elements according to known methods [1, 2, 5];               metrological characteristics p = 0.997 and
Tp, Tpi are from the analysis of the product                 P(τ) = 0.96 [16–19]. If conditional diagnostic
operation mode during operation; p, P(τ) are                 algorithms are used during the current repair, then
depending on the type of measuring equipment                  K  8,86 . Assuming that the qualification of
[16–19]; t, ty are on the analysis of work of experts        specialists provides t = 3,5 min and ty = 8 min, we
of repair body depending on their qualification.             obtain      the     average      recovery      time
    Consider the use of the results on the example           𝑇в′ = 43 min. These indicators fully meet the
of estimating the values of the reliability of the           requirements for the reliability of similar objects
fifth generation radio [8].                                  Td ≥ 1000 hours and Tvd ≤ 60 min, while
    Theoretical is multiple model of the radio               A' = 0.9993 (𝑈 ′ = 0,0007).
station is shown in Fig. 3, where M1 is the set of               The results of calculations for the same initial
elements used in the “transmission” mode; M2 is              data according to the algorithm of Fig. 2 using the
in the “reception” mode; M12 is core used in both            mathematical model of reliability of Table 2
modes of operation (subsystems of power supply,              taking into account the properties of the radio in
control and operation, generator equipment,                  two modes depending on the ratio of operating
antenna) [20, 21]. The total number of elements of           time to “receive” (U2) or “transmit” are shown in
the radio station is L = 4096, of which L3 = 512             Fig. 5–8.
elements are used in both modes, in the “receive”                Comparison of the results with the prototype
mode L2 = 3072 elements and in the “transmit”                (calculation of similar indicators without taking
mode L1 = 1024 elements. With Z1 = 307 • 10-6                into account the multimode of the radio station)
hours-1, Z2 = 532 • 10-6 hours-2, Z3 = 154 • 10-6            shows that at 90% of the radio station operating
hours-1.                                                     time in the “reception” mode (u2 = 0,9), which
    Without taking into account the properties of            often occurs in practice, we have a refinement
multimode we obtain (n = 3):                                 time of 33% (T = 1507 h), the average recovery
            3
     Z    Z  993 10 hours ,
                               6       -1                   time by 14% (TB=50 min) and a decrease in the
                                                (20)         coefficient of unpreparedness by 28% (U =
           i 1    i
                                                             0.000548).

Table 2
Mathematical model for estimating the values of reliability indicators of objects with variable
structure
                            Indicator                                Functional dependencies
        The utilization factor of the sets of elements і                 ui=Tpi/Tp; 𝑖 = ̅̅̅̅̅
                                                                                        1, 𝑛
                                                                                          𝑛

                  Product failure flow parameter                                    𝑍 = ∑ 𝑢𝑖 𝑍𝑖
                                                                                         𝑖=1
                  Product operating time to failure                                  T=1/Z
                                                                                       𝑛
                                                                                    1
   The average number of inspections during maintenance                          𝐾 = ∑ log 2 𝐿𝑖
                                                                                    𝑛
                                                                                         𝑖=1
                  Probability of correct diagnosis                                   𝑃 = 𝑝𝐾
                                                                                     𝑡
                                                                                𝑡𝑦 + 𝑍 ∑𝑛𝑖=1 𝑢𝑖 𝑍𝑖 log 2 𝐿𝑖
           The average recovery time of the product                        𝑇𝐵 =
                                                                                       𝑃 · 𝑃(𝜏)
                    Product readiness ratio                                      𝐴 = 𝑇⁄𝑇 + 𝑇𝐵 )
       The coefficient of unpreparedness of the product                         𝑈 = 𝑇𝐵 ⁄(𝑇 + 𝑇𝐵 )




                                                        40
Figure 3: Block diagram of using the method of quantitative assessment of the values of reliability
indicators of objects with variable structure




Figure 4: Theoretical-multiple model of a tactical radio station

   That is, it was possible to use elements of              The operating time for failure decreases,
lower cost to ensure the necessary requirements              because in this mode most of the elements of
for the reliability of the radio station during its          radio stations are used (Fig. 5).
design and production.                                      The average recovery time also does not
   Analysis of the obtained dependences shows
                                                             increase significantly as the probability of
that with increasing relative operating time of the
                                                             failure in the receiving part of the radio station
radio station in the “reception” mode:
                                                             increases, and this pattern is maintained at any
                                                             time during the test t (Fig. 6);



                                                      41
Figure 5: Dependence of operating time on the
failure of the radio station on the relative
operating time in the mode “reception”                     Figure 7: Dependence of the readiness factor of
                                                           the radio station on the relative operating time
                                                           in the "reception" mode




Figure 6: Dependence of the average recovery
time of radio stations on the relative operating
time in the "reception" mode
                                                           Figure 8: Dependence of the coefficient of
                                                           unpreparedness of the radio station on the
                                                           relative operating time in the “reception” mode

    Due to the decrease in the value of operating          5.      Conclusions
time to failure T and increase the average recovery
time Tv also decreases the complex reliability                1. The paper proposes the improvement of the
indicator is readiness factor A (Fig. 7) and,              method of quantitative assessment of reliability
accordingly, increases the value of the                    indicators of objects with variable structure, the
unpreparedness factor U (Fig. 8).                          algorithm of realization is given and the
    These trends are maintained at any values of           advantages over the existing methods are shown.
the average time of the test t, moreover, its                 2. It is established that the use of multi-mode
reduction by improving the skills of performers            properties, which affects the structure of the
and improving diagnostic support (the choice of            object, improves the value of reliability
tests with less labor) leads to an increase in the         indicators: both the failure time and the average
coefficient of readiness (A).                              recovery time.



                                                      42
    3. The essence of the method improvement and             [12] M. Catelani, L. Ciani, Experimental Tests
its scientific novelty is to take into account the                and Reliability Assessment of Electronic
properties of many modes of the object and the                    Ballast System, Microelectronics Reliability,
operating time of individual subsets of elements                  vol. 52, iss. 9–10, 2012, pp. 1833–1836. doi:
in possible modes when used as intended.                          10.1016/j.microrel.2012.06.077.
    4. Further research should be directed to assess         [13] Y. Wan, et al., Thermal Reliability
the values of reliability of the communication                    Prediction and Analysis for High–Density
system, taking into account the possibility of                    Electronic Systems based on the Markov
changing its structure during its intended use,                   Process, Microelectronics Reliability, vol.
especially in training and combat operations, as                  56,      2016,      pp.     182–188.      doi:
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of the system.                                               [14] V. Buriachok, V. Sokolov, P. Skladannyi,
                                                                  Security rating metrics for distributed
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