Theoretical prerequisites in the organization of the construction of diagnostic systems, microprocessor blocks of a typesetting group of railway automation and telemechanics

. The article presents the results of theoretical research in the organization of the construction of a diagnostic system, microprocessor blocks of a typesetting group of railway automation and telemechanics. Products made with the use of microcontrollers, using mathematical expressions to determine the criteria for evaluating the diagnostic process, were subject to research. A graph of the theory of Petri nets of transitions of the diagnostic system of blocks of a set group has been developed and analyzed to


Introduction
Great opportunities in improving the efficiency of technical means of railway automation and telemechanics are reserved in the organization of their operation and maintenance according to actual need.At the same time, the need for maintenance of objects is determined by their actual state, and not by operating time or expired service life.However, the introduction of such a principle into the practice of servicing technical objects is associated with the need to assess their condition.The process of assessing the state of technical objects is called diagnostics.
The diagnostic procedure, in which part of the predetermined functions are performed by a human operator, provides for a significant interaction between the object and the technical means subject to diagnostics; as a rule, such systems are part of an automated one.At present, when programmable microcontrollers are widely used in automatic systems, there are opportunities for the development and application of fully automatic diagnostic systems, which is very important for the conditions of railway transport, with its high requirements for ensuring the safe movement of trains [1,4].The use of microelectronic technologies in the blocks of the dial-up group of the route relay interlocking system makes it possible to assign diagnostic functions to built-in programmable devices, which, in addition to managing objects, have the ability to carry out diagnostic operations between train operations.The analysis of the technological process of railway stations shows that there is a sufficient amount of time for diagnosing devices between the operations of closing and opening routes, even if we assume that the inter-train interval is a minimum time of 8-10 minutes.
The high efficiency of the diagnostic process can be achieved only when the specific of the technological process of the railway transport station operation are taken into account as much as possible in the diagnostic process.In the result of it is the train schedule and the inter-train interval, which requires a thorough analysis of the software, the list of equipment of its condition, between route assignments.
It can be assumed that the diagnostic process consists of several stages.At the first stage, it is supposed to consider the process of diagnosing taking into account the selected criteria, and on their basis, the requirements for the algorithms of the diagnosing process are determined [6 -12].
At the second stage, the process of designing the microcontroller software is carried out [4].
Finally, at the third stage, the effectiveness of diagnostics and its software should be evaluated [5,12].
Let us consider one of the methods for evaluating the effectiveness of the process of diagnosing the elements of a dial-up group of a block route relay interlocking system.For this purpose, as a criterion for evaluating the organization of interaction between the elements of the diagnostic system.It is proposed to use the probability of the absence of a defect at an arbitrary point in time when the blocks of the dial-up group are in working condition (there is a process of installing and opening routes, or a period between the procedures for setting routes).This criterion is usually called the indicator of readiness and denoted by   [13,14,15].
It is logical to assume that this indicator is directly dependent on the total probability of the elements of the blocks of the set group at an arbitrary moment of time in the subset of n states, which includes all situations when there are no failures in the blocks that are in operation.It should be assumed that there is a study of the question of how often it is necessary to carry out a diagnostic procedure In [6,9], the following expressions are proposed for calculating the frequency of diagnosis: where  0 − frequency of diagnosis; Т  − period of optimal polling of the diagnosed unit;  − block element failure rate;   − time of diagnosing the block under study;  − block usage intensity (route setting/opening);   − the probability of the block being in the period of setting/opening routes   − the probability of the block staying during the absence of a task, opening routes  ′ − intensity of failures in the period of absence of assignment/opening of routes and defects in the diagnostic device in standby mode.Known [13,14] is an indicator close to the availability factor -the utilization factor (К  ).This is the probability value of finding an object at an arbitrary point in time t in a healthy state, taking into account the fact that serviceable objects are scheduled for preventive maintenance,  И (), i.e., they are excluded from the working cycle.Statistically, the coefficient of utilization is explained by the following expression.
where  − number of object failures in a time interval (0, ); − the number of preventive measures in the time interval (0, );  − number of working cycles in a time interval (0, );   − the time of maintaining the health of the object in  − m cycle;   −duration  −check;   − repair time after  − object failure.In doing so, it should be borne in mind that   () → 1. Let's define numerical values, for example, the time interval (0, ) for blocks of a stacking group can reach several years, the variableis determined by the results of statistical observation,  − is determined by the standard values of maintenance work, blocks of a stacked group,   − is determined by the results of statistical analysis, the numerical values of the variables   and   are determined by the regulatory documents for preventive maintenance and equipment repair, the variable  is determined by the intensity of the station, assuming that routes will be set during the year with a time interval of 8-10 minutes, this variable can reach the values (24 × 365 × 60)/8 = 65700 cycles.
Since the devices of the dial group of the block route interlocking system are designed for continuous use and can be diagnosed during the absence of train operation at the station, i.e. in a special mode, this operation with the help of ideally reliable technical means.The graph of transitions of the diagnostic system from state to state, made on the basis of the theory of Petri nets, is shown in fig. 1 [3].Graph positions represent the following states:the object is used for its intended purpose and there are no defects in it; -the stacking unit is used for its intended purpose and a defect has occurred in it that did not lead to failure;the device under test in the diagnostic mode, if a failure occurs in it, which is eliminated;there was a failure of the dial block, which is being restored.
The indicator of readiness for this case is estimated by the probability of finding the object in the state ( = 1) and is calculated by the formula (1), where 0 and  0 -failure and recovery rates of stacked group blocks;  -intensity of diagnosing blocks of a type-setting group.
It can be seen from expressions (1) that the indicator of readiness of the system for diagnosing blocks of a set group depends on the organization of diagnosing, the intensities of the occurrence of defects and failures of the object and  0 , as well as its testability, i.e. characterizes the proposed diagnostic system more fully.
Consider the procedure for changing the state of the object of diagnosis, performed on the basis of the Petri net graph.According to the system of equations ( 2), the stacking group block being in a normal working condition, i.e. the process of setting or opening route1 is in progress, it can go to another state3 when the transition conditions 7 are met, i.e. depends on the organization of diagnostics according to the variable, which contributes to the transition of the system to position 3, and it is also possible to change the state at the transition  4 in accordance with the indicators of the intensities of the occurrence of defects in stacked blocks  0 , which contributes to the transition of the system to position4, in addition, the system can move to position 2, at the transition 2 accordance with the indicators of the intensity of the occurrence of failures of stacked blocks .
The elements that ensure the fulfillment of the conditions for transitions from one state to another are the variables   where  = 7, consider the values of these variables: the input function of the variable  1 is the expression ( 1 ) = { 0 , 4}from which it follows that, taking into account the intensity of restoring the blocks of the stacking group  0 , the device from the state with the presence of failure 4, after recovery, it will switch to normal operation; the variable  2 whose input actions are described by the formula ( 2 ) = {, 1}from which it follows that if there is a value of the intensity of the occurrence of defects in the block of the typesetting group, the device is able to move from the normal operating state 1 to position 2 when a defect occurs in the device; the variable  3 is the input action, which is described by the formula ( 3 ) = {2,  0 }from which it follows that, taking into account the failure rates of the blocks of the stacked group and according to its output function ( 3 ) = {4}, the E3S Web of Conferences 458, 09025 (2023) EMMFT-2023 https://doi.org/10.1051/e3sconf/202345809025diagnosed device will go from state 2 when the stacked block is used for its intended purpose and a the defect will go to state 4 corresponding to the presence of a failure in the device being diagnosed; the variable  4 is determined by the input function ( 4 ) = { 0 , 1}from which it follows that when the diagnosing object is in position 1 and in the presence of a variable intensity of the occurrence of defects in stacked blocks  0 , the diagnosed object must move to position 4 according to the output function О( 4 ) = {4}; the variable  5 , in accordance with its input function ( 5 ) = {, 3}, is able to change the state of the diagnosed object and, in the presence of the testability component , the diagnosed object according to the output function О( 5 ) = {1}from the state of the object in the diagnostic mode, if a defect occurs in it, which is eliminated, to the position 1; the variable  6 in accordance with its input function ( 6 ) = { 0 , 3}in the presence of a known variable intensity of the occurrence of defects in the stacking blocks  0 , capable of transferring the diagnosed object from the state in the diagnostic mode, if a defect occurs in it, which is eliminated in position 4, corresponding to the presence of a failure in the stacking block; variable  7 in accordance with its input function ( 7 ) = {, 1}in the presence of a component reflecting the organization of diagnosis , according to the output function О( 7 ) = {3}., the device will go into the state of the diagnostic mode, the block of the dial group.
Assuming that the organization of the system for diagnosing the elements of the stacking block, taking into account the Gaussian law of distribution of their time before the occurrence of a defect, then the stacking block is considered to be able to perform its functions and is operable and no damage has been detected in it (there are no defects), while the implementation of the random process reflecting the change in parameters, composing the block of the typesetting group, remains inside some area.The output of the characteristics of the constituent elements of the block beyond the boundaries of the region, limiting the space of permissible deviations, gives reason to assume that a failure may occur.The time interval that determines the moment before the first crossing of the boundaries of the area with operating parameters is a random variable, the probability of the value of which corresponds to the Gaussian distribution law, which reflects the indicators that characterize the reliability of the block of the typesetting group.
For example, when periodically, with a constant period of time (T), with the help of reliable microelectronic means, in a special mode, the elements of a block of a dial-up group are diagnosed, provided that the block is in constant use.In this case, the process of interaction of the elements of diagnostics can be in one of three positions, namely, the blocks of the typesetting group are in the operating mode, a defect is possible in them, a serviceable block is diagnosed; the elements are in the diagnosing position and, based on the results of this action, if necessary, are restored.In this case, the mathematical formula for determining the probability of a failure in a stacking unit over a time interval T will take the form where  and  -mathematical expectation and standard deviation of a random value of time before a failure occurs in the device being diagnosed.
It is known [8] that a semi-Markov process is a random process that changes its states in accordance with a previously known probability distribution law.While the time spent by a random process in one of the states, which is also a random characteristic, the distribution law of which depends, both on the current state and on the state to which it will move at the next moment in time.
The following postulates are taken as the basis for constructing the model, which allow us to consider the functioning of the blocks of the stacking group of the route centralization system as semi-Markovian: -the change of states and the residence time of the elements of the set group are arbitrary distributions of probabilities.As a result, two sets of independent flows are provided (the time of transition from the standby state to the working state is random, the time of the working state is also random, because it depends on the type of route, the number of axes on the route); -the statistical characteristics of dialing group block processes that occur during their change (setting or canceling routes) and the time the system stays in the states determined by the station attendant's movement time during this period are determined.Setting or canceling routes and will not depend on the number of already established routes (the system is homogeneous) and the access path of each possible state of the system; -actions in which the state of the elements of the system changes, when performing control functions, takes place over a period of time equal to several seconds.
Using the apparatus of the theory of semi-Markov processes, we obtain an expression for determining the readiness factor where   − traceability;   − maintainability;  1 − the average time the object stays in good condition for a period of time Т, we obtain from the following expression Using expression (3) in formulas ( 4) and ( 5) and due to the fact that the probability of a malfunction in the blocks of the dial group is negligible, we obtain Expression (6) reflects the dependence of К  on the testability indicators   ; maintainability  ; reliability ,  и периодичности диагностирования .
The approximate value of the optimal diagnosis period at which the maximum К  is reached can be calculated by the formula The method of analysis, organization and construction of the system for diagnosing the blocks of the typesetting group of railway automation and telemechanics is considered, taking into account the use of an individual programmable microcontroller in each block.The introduction of additional diagnostic functions into the controller software required a change in the principles for constructing the maintenance of these devices by employees of the signaling and communication distance.The application of the diagnostic procedure involves the use of an automatic system, since it excludes the functions performed by specialists, the well-known criteria for evaluating the diagnostic system, based on the use of known statistical characteristics of devices of typesetting blocks, are considered.As a result of the analysis of the functioning of the system of block route centralization, mathematical expressions were obtained to determine the criteria for evaluating the process of diagnosing.The graph of transitions of the system for diagnosing blocks of the typesetting group has been developed and analyzed to determine the indicator of readiness.The method of obtaining К  and its mathematical expression using the apparatus of semi-Markov processes with the law of distribution of time before the occurrence of failures (Gaussian) is of a general nature and therefore can be used with other initial data.The above method allows calculating with sufficient reliability the maximum value of К Г and the corresponding optimal period of diagnosis for different values of statistical indicators.An analysis of the expression obtained for К  makes it possible to determine the dependence of these indicators   ,   , reliability and frequency of diagnosis.