RU2206123C2 - Device for evaluating optimal manufacture intervals for part - Google Patents

Abstract

FIELD: check-up devices for research and engineering purposes. SUBSTANCE: proposed device functions to find optimal maintenance intervals and respective downtime ratios including changes in part failure rate in the course of operation and also differentiated registration of time taken for serviceability check of part, for scheduled preventive maintenance, and for post-accident damage-recovery work, are taking into account. Newly introduced in device are five adders, multiplier, multiplying unit, four memory items, integrator, two timers, divider, three delay elements, two flip-flops, OR gate, two comparators, and two switches. EFFECT: enlarged functional capabilities. 1 cl, 1 dwg

Description

 The invention relates to control devices and can be used in scientific research and technology, where it is required to find optimal periods of product maintenance by the criterion of minimum downtime, taking into account changes in the failure rate of these products during operation.

 Known devices [1, 2], allowing to determine the optimal periods of service products, the failure rate of which varies over time. But these devices are product-oriented, the use of which substantially depends on the availability of expendable resources (for example, storage media, propulsion system propellants, etc.), and their supplies may not be replenished during the operation of the products. The criterion for optimizing service periods is a minimum of unproductive expenditure of these resources. These devices have a limited scope.

 It is also known a device [3], designed to find service periods for products that provide a minimum downtime of these products due to the timely detection or prevention of failures. However, this device is focused on products in which failures occur instantly (the latent failure time is assumed to be zero), and their intensity remains constant throughout the operation of the product. In this regard, the scope of this device is also limited. In addition, it does not differ in high speed, since the determination of the optimal values of the product service period is carried out over several cycles of its operation.

 The closest in technical essence to the claimed invention is a device [4], containing two time sensors, a nonlinearity block, two adders, an integrator, two division blocks, a delay element, two comparators, six memory elements, five keys, a multiplication block, a trigger, a multivibrator , differentiating element and inverter. It allows you to determine the optimal period of product maintenance by the criterion of maximum availability coefficient. The disadvantage of this device is the low accuracy of determining the desired value. This is due to the fact that the mathematical model implemented by the device has a simplified form and does not adequately reflect the product maintenance cycle.

 The aim of the proposed technical solution is to increase the accuracy of determining the optimal values of the period of maintenance of products in the face of changes in their reliability characteristics during operation. The goal is achieved through the implementation of a more accurate mathematical model that allows you to differentially take into account the time spent on monitoring the health of the product, on carrying out preventive maintenance and emergency recovery work. The criterion for optimizing service periods in the proposed device is the minimum downtime coefficient of the product. The lower the downtime factor, the longer the time during which the product can function as intended.

где τ - период обслуживания изделия (интервал времени между двумя соседними сеансами обслуживания);

- среднее время контроля работоспособности;

- среднее время проведения планово-предупредительной профилактики;

- среднее время аварийно-профилактического ремонта;
Р(τ) - вероятность безотказной работы изделия за время τ.The process of servicing products is cyclical in nature. The average duration of the service cycle is determined by the following ratio:

where τ is the product service period (time interval between two adjacent service sessions);

- the average time for monitoring performance;

- average time for preventive maintenance;

- the average time for emergency repairs;
P (τ) is the probability of failure-free operation of the product during time τ.

где

- среднее время работоспособного состояния изделия, а

- среднее время пребывания его в отказе на периоде τ.The health control of the product is carried out in scheduled sessions with a period of τ. In this regard, in the time interval between control sessions, the product can be not only in a healthy state, but also in failure. Therefore, the relation

Where

- the average working time of the product, and

- the average time spent in failure over the period τ.

определяется по формуле

Если результаты контроля покажут, что изделие работоспособно, то проводится плановая предупредительная профилактика. Если же оно окажется неработоспособным, то будет проведен аварийно-профилактический ремонт, в результате которого работоспособность будет восстановлена. При проведении операций контроля, планово-предупредительной профилактики и аварийно-профилактического ремонта, а также при нахождении в состоянии отказа изделие не может функционировать по назначению, т.е. изделие простаивает.Value

determined by the formula

If the results of the inspection show that the product is operational, then scheduled preventive maintenance is carried out. If it turns out to be inoperative, then emergency preventive maintenance will be carried out, as a result of which the operability will be restored. When conducting control operations, preventive maintenance and emergency preventive maintenance, as well as when in a state of failure, the product cannot function as intended, i.e. the product is idle.

В результате преобразований с учетом соотношений (2) и (3) получим

Из (5) видно, что коэффициент простоя является функцией не только периода обслуживания τ, но и безотказности изделия Р(τ). Известно, что важнейшим параметром безотказности является интенсивность отказов. Теория и практика эксплуатации обслуживаемых изделий показывает, что старение изделий сопровождается увеличением этой интенсивности. Как показывают исследования, функция К_П(τ) при некотором (оптимальном) значении периода τ^* имеет глобальный экстремум. Отклонения периода обслуживания от оптимального в сторону меньших или больших значений приводит к увеличению коэффициента простоя. Кроме того, возрастание интенсивности отказов влечет за собой смещение оптимального периода обслуживания в сторону меньших значений. Поэтому каждое очередное оптимальное значение необходимо находить с учетом возможного изменения этой интенсивности. На интервале одного цикла обслуживания (1) с достаточной степенью точности интенсивность отказов изделия можно считать постоянной.The downtime coefficient is understood to mean the ratio of the downtime of the product on the interval of the service cycle to the duration of this cycle, i.e.

As a result of transformations, taking into account relations (2) and (3), we obtain

It can be seen from (5) that the downtime coefficient is a function of not only the service period τ, but also the reliability of the product P (τ). It is known that the most important failure-free parameter is the failure rate. The theory and practice of the operation of serviced products shows that aging of products is accompanied by an increase in this intensity. Studies show that the function K _P (τ) for some (optimal) value of the period τ ^* has a global extremum. Deviations of the service period from the optimum towards smaller or larger values increase the downtime coefficient. In addition, an increase in the failure rate entails a shift in the optimal service period to lower values. Therefore, each successive optimal value must be found taking into account a possible change in this intensity. On the interval of one service cycle (1) with a sufficient degree of accuracy, the failure rate of the product can be considered constant.

Предложенная модель может быть реализована аппаратурно с помощью предлагаемого устройства.In connection with the above, the problem of determining the optimal period of maintenance of the product can be written as follows:

The proposed model can be implemented in hardware using the proposed device.

 The drawing shows a diagram of the device.

 The device contains: adders 1, 5, 6, 8, 26; multiplication block 2; block of nonlinearity 3; memory elements 4, 17, 18, 20; integrator 7; timers 9, 19; division block 10; delay elements 11, 13, 23; triggers 12, 14; element OR 15; comparators 16, 22; keys 21, 24, 25.

за время τ, которая поступает на второй вход блока перемножения 2 и на информационный вход интегратора 7. Значение параметра

со второго входа устройства поступает на первый вход блока перемножения 2, а значение параметра

с первого входа устройства поступает на первый вход первого сумматора 1. Значение

с выхода блока перемножения 2 поступает на второй вход первого сумматора 1. Значение времени τ с выхода первого таймера 9 поступает на первые входы сумматоров 6 и 8 непосредственно, а через третий элемент задержки 13 - на информационный вход третьего элемента памяти 18. Значение среднего времени работоспособного состояния изделия

если изделие обслуживать с периодом τ, с выхода интегратора 7 поступает на второй вход сумматора 6, на выходе которого формируется значение

и передается на первый вход третьего сумматора 5. Сигнал, соответствующий сумме

с выхода первого сумматора 1 подается на вторые входы третьего 5 и четвертого 8 сумматоров. На выходе третьего сумматора 5 формируется сигнал, соответствующий сумме

и подается на вход делимого блока деления 10. Сигнал, соответствующий сумме

с выхода четвертого сумматора 8 поступает на вход делителя блока деления 10 и через второй элемент задержки 11 на информационный вход второго элемента памяти 17. Значение

соответствующее среднему значению коэффициента простоя изделия, если его обслуживать с периодом τ, с выхода блока деления 10 поступает на первый вход первого компаратора 16 непосредственно, а через первый элемент задержки 23 на второй вход первого компаратора 16 и на информационный вход четвертого элемента памяти 20. Значение времени задержки Δτ первого 23, второго 11 и третьего 13 элементов задержки одинаковое и определяет точность вычисления оптимального периода технического обслуживания изделия. В первом компараторе 16 сравниваются между собой два значения К_пi(τ) и

Вначале

Как только К_пi(τ) станет меньше

на выходе первого компаратора 16 появится управляющий сигнал, который переведет второй триггер 12 в единичное состояние. Это означает, что найден i-й оптимальный период технического обслуживания τ $\genfrac{}{}{0ex}{}{\text{*}}{\text{i}}$ = τ-Δτ. Единичный сигнал с выхода второго триггера 12 поступает на управляющие входы трех элементов памяти 20, 18 и 17, трех ключей 24, 25 и 21, на вход второго таймера 19 и на вход установки нуля первого триггера 14. По спаду единичного сигнала с выхода первого триггера 14 (в момент установки его в нулевое состояние) приводятся в исходное нулевое состояние блок нелинейности 3, интегратор 7, первый таймер 9 и открывается первый элемент памяти 4. По единичному управляющему сигналу с выхода второго триггера 12 на выходах элементов памяти 20, 18 и 17 будут запомнены значения, действующие на их входах, в момент времени
τ $\genfrac{}{}{0ex}{}{\text{*}}{\text{i}}$ = τ-Δτ,
которые далее поступят на информационные входы ключей 24, 25 и 21 соответственно. В результате на втором выходе устройства будет значение оптимального периода технического обслуживания изделия τ $\genfrac{}{}{0ex}{}{\text{*}}{\text{i}}$ , а на первом выходе устройства будет среднее значение коэффициента простоя изделия К_пi, соответствующее оптимальному времени τ $\genfrac{}{}{0ex}{}{\text{*}}{\text{i}}$ и интенсивности отказов λ_i. Значение

с выхода первого ключа 21 поступает на второй вход второго компаратора 22. По фронту единичного управляющего сигнала с выхода второго триггера 12 запускается второй таймер 19. Значение времени с выхода второго таймера 19 поступает на первый вход пятого сумматора 26, на второй вход которого поступает значение τ $\genfrac{}{}{0ex}{}{\text{*}}{\text{i}}$ . Значение t+τ $\genfrac{}{}{0ex}{}{\text{*}}{\text{i}}$ с выхода пятого сумматора 26 поступает на первый вход второго компаратора 22. Как только значение сигналов на входах второго компаратора 22 станут равными, т.е. в момент времени

после начала вычисления i-го оптимального периода технического обслуживания изделия, на выходе второго компаратора 22 появится управляющий сигнал, который через элемент ИЛИ 15 переведет первый триггер 14 в единичное состояние. По фронту единичного сигнала с выхода первого триггера 14 второй триггер 12 приводится в исходное нулевое состояние, одновременно начинают работать блок нелинейности 3, интегратор 7 и первый таймер 9, а на выходе первого элемента памяти 4 будет значение интенсивности отказов λ_i+1, которым будет обладать изделие по истечении времени

с начала эксплуатации. По спаду единичного управляющего сигнала с выхода второго триггера 12 второй таймер 19 приводится в исходное нулевое состояние. Затем устройство определяет оптимальный период технического обслуживания изделия τ $\genfrac{}{}{0ex}{}{\text{*}}{\text{i+1}}$ аналогично тому, как оно определяло τ $\genfrac{}{}{0ex}{}{\text{*}}{\text{i}}$ , затем определяет τ $\genfrac{}{}{0ex}{}{\text{*}}{\text{i+2}}$ и т.д. до выключения устройства.The device operates as follows. By the signal "START", coming from the fourth input of the device through the OR element 15, the first trigger 14 is set to a single state. On the front of a single signal from the output of the first trigger 14, the second trigger 12 is set to zero, at the output of the first memory element 4, the value of the failure rate λ _i (i = 0) from the third input of the device is stored, and at the same time, the nonlinearity block 3 starts to work, integrator 7 and first timer 9 (ramp generator). In nonlinearity block 3 (for example, circuit 3-4-2 [5]), the time constant λ _{i of the} exponent is set by the value of the signal coming from the output of the first memory element 4. As a result, the function of the probability of product failure operation is formed at the output of nonlinearity 3

during the time τ, which goes to the second input of the multiplication unit 2 and to the information input of the integrator 7. The value of the parameter

from the second input of the device goes to the first input of the multiplication block 2, and the value of the parameter

from the first input of the device goes to the first input of the first adder 1. Value

from the output of the multiplication unit 2, it goes to the second input of the first adder 1. The time τ from the output of the first timer 9 goes directly to the first inputs of the adders 6, and through the third delay element 13, to the information input of the third memory element 18. The value of the average working time product status

if the product is serviced with a period τ, from the output of the integrator 7 goes to the second input of the adder 6, at the output of which the value is formed

and transmitted to the first input of the third adder 5. The signal corresponding to the sum

from the output of the first adder 1 is fed to the second inputs of the third 5 and fourth 8 adders. The output of the third adder 5 generates a signal corresponding to the sum

and fed to the input of the divisible division unit 10. The signal corresponding to the sum

from the output of the fourth adder 8 is fed to the input of the divider of the division unit 10 and through the second delay element 11 to the information input of the second memory element 17. Value

corresponding to the average value of the idle factor of the product, if it is serviced with a period of τ, the output of the division unit 10 goes to the first input of the first comparator 16 directly, and through the first delay element 23 to the second input of the first comparator 16 and to the information input of the fourth memory element 20. Value the delay time Δτ of the first 23, second 11 and third 13 delay elements is the same and determines the accuracy of calculating the optimal period of maintenance of the product. In the first comparator 16 two values of K _pi (τ) and

initially

As soon as К _pi (τ) becomes less

the control signal will appear at the output of the first comparator 16, which will translate the second trigger 12 into a single state. This means that the ith optimal maintenance period τ $\genfrac{}{}{0ex}{}{\text{*}}{\text{i}}$ = τ-Δτ. A single signal from the output of the second trigger 12 is fed to the control inputs of three memory elements 20, 18 and 17, three keys 24, 25 and 21, to the input of the second timer 19 and to the input of setting the zero of the first trigger 14. Upon the decline of a single signal from the output of the first trigger 14 (at the time of setting it to the zero state), the nonlinearity block 3, the integrator 7, the first timer 9 are brought to the initial zero state, and the first memory element 4 is opened. By a single control signal from the output of the second trigger 12 at the outputs of the memory elements 20, 18 and 17 will be remembered ny acting on their inputs at time
τ $\genfrac{}{}{0ex}{}{\text{*}}{\text{i}}$ = τ-Δτ,
which will then go to the information inputs of the keys 24, 25 and 21, respectively. As a result, at the second output of the device there will be a value of the optimal period of product maintenance τ $\genfrac{}{}{0ex}{}{\text{*}}{\text{i}}$ , and at the first output of the device there will be an average value of the idle factor of the product K _pi corresponding to the optimal time τ $\genfrac{}{}{0ex}{}{\text{*}}{\text{i}}$ and failure rate λ _i . Value

from the output of the first key 21 goes to the second input of the second comparator 22. On the front of a single control signal from the output of the second trigger 12, the second timer 19 starts. The time value from the output of the second timer 19 goes to the first input of the fifth adder 26, the second input of which receives the value τ $\genfrac{}{}{0ex}{}{\text{*}}{\text{i}}$ . Value t + τ $\genfrac{}{}{0ex}{}{\text{*}}{\text{i}}$ from the output of the fifth adder 26 is supplied to the first input of the second comparator 22. As soon as the value of the signals at the inputs of the second comparator 22 become equal, i.e. at time

after the start of the calculation of the i-th optimal period of product maintenance, a control signal will appear at the output of the second comparator 22, which will transfer the first trigger 14 to a single state through the OR element 15. On the front of a single signal from the output of the first trigger 14, the second trigger 12 is brought to its initial zero state, at the same time, the nonlinearity block 3, the integrator 7 and the first timer 9 begin to work, and at the output of the first memory element 4 there will be a value of the failure rate λ _{i + 1} , which will be possess the product after time

from the beginning of operation. By the decline of a single control signal from the output of the second trigger 12, the second timer 19 is brought to its initial zero state. Then the device determines the optimal period of product maintenance τ $\genfrac{}{}{0ex}{}{\text{*}}{\text{i + 1}}$ similar to how it determined τ $\genfrac{}{}{0ex}{}{\text{*}}{\text{i}}$ , then determines τ $\genfrac{}{}{0ex}{}{\text{*}}{\text{i + 2}}$ etc. before turning off the device.

 The positive effect that the proposed technical solution provides is that the device allows you to determine the optimal period of maintenance of the product by the criterion of the minimum downtime in the conditions of changing the rate of failure of the product during its operation.

Sources of information:
1. Grishin V.D., Timofeev A.N., Artemenko N.D. RF patent 2071115, M. Cl ⁶ G 07 C 3/08, 1996.

2. Grishin V.D., Timofeev A.N., Zhiryakov A.A. RF patent 2071118, M. Cl ⁶ G 07 S 3/08, 1996.

3. Vorobev G.N., Grishin V.D., Denchenkov V.A. Auto St USSR 1320825, M. Cl ⁴ G 07 C 3/08, 1997.

4. Vorobev G.N., Grishin V.D., Domozhirov V.T., Timofeev A.N. Auto St USSR 1773199, M. Cl ⁵ G 07 C 3/08, 1992.

 5. Tetelbaum IM, Schneider Yu.R. 400 schemes for AVM. - M .: Energy, 1978.

Claims (1)

 A device for determining the optimal period of maintenance of a product containing a multiplication unit, the output of which is connected to the second input of the first adder, a first timer, the output of which is connected to the first input of the second adder, and the input is connected to the output of the first trigger and to the first input of the nonlinearity block, the output of which connected to the second input of the integrator, the first memory element, the second timer, the division unit, the output of which is connected directly to the first input and through the first delay element to the second input of the first comparator, the second memory element, the first input of which is connected to the first inputs of the fourth memory element, the first key and the second key, the second input of which is connected to the output of the fourth memory element, and the output is the first output of the device, the output of the second memory element is connected to the second input of the first key, the third memory element, the second comparator and the third key, the output of which is the second output of the device, characterized in that the third, fourth and fifth adders, the second trigger, the second and third electronic delays and an OR element, the first input of which is connected to the fourth input of the device, the output is connected to the second input of the first trigger, and the second input is connected to the output of the second comparator, the second input of which is connected to the output of the first key, and the first input is connected to the output of the fifth adder, the second input of which is connected to the output of the third key, and the first input through the second timer is connected to the output of the second trigger and with the first inputs of the first trigger, the third memory element, third key and fourth memory element, the second the input of which is connected to the second input of the first comparator, the output of which is connected to the second input of the second trigger, the first input of which is connected to the output of the first trigger, to the first input of the integrator and to the second input of the first memory element, the first input of which is the third input of the device, and the output is connected with a second input of the nonlinearity block, the output of which is connected to the second input of the multiplication block, the first input of which is the second input of the device, the first input of which is the first input of the first adder, the output of which is connected to the second input of the third adder and to the first input of the fourth adder, the output of which through the second delay element is connected to the second input of the second memory element and directly connected to the second input of the division unit, the first input of which is connected to the output of the third adder, the first input of which is connected to the output of the second adder, the second input of which is connected to the output of the integrator, and the first input is connected directly to the second input of the fourth adder and through the third delay element with of the connections to the second input of the third memory element whose output is connected to the second input of the third switch.