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Volume 11, 2004

 

 

Validity a checking in technological modules

 

Vencislav Ananiev,

 Burgas "prof. d-r. As. Zlatarov" University,  Burgas, Bulgaria

e-mail ananievi@abv.bg

 

 

The technological  modules TM with high degree of automation ATM have particular place in modern production. Work АТМ under difficult ways and conditions- unceasing production and temples of requirement. The Amortization and refusals more intensive than usual machines and productions.

The break-down have heavy results they bring before presto other machines because they dependent one from other

          For repair and technical usage big role has checking. True last is necessary guarantee probability for the no-failure operation Рбр/t - It is necessary answer conditions:

  

Рбр/t/ ³ Рбр/н/  ,                                                                (1)

 where;

          Рбр/t/- probability for no-failure operation ATM at certain length of time

            Рбр/н/- probability for the no-failure operation determined by the producer - normal.

Here offer a method for increasing validity a checking for TM technical condition. Attached criterion for the achievement minimum mistake during the parameter measurement. For this method is necessary enclose technical facilities, which have a pledge determined work. They are defined on base actual condition of elements. It allows to forecast condition АТМ in determined period of their work.

Validity a check (diacritical and forecasted), Дк is defined on the base a condition - it is necessary to reach minimum probability, not to find a refusal Рно,

when using necessary devices for the measurement and checking.

 

 

Дк = f [ k. minРно ] ,   (2)

where;

          k - coefficient dependencies

Validity a checking АТМ depends straight from accuracy checking methods and conditions. Scheme such interaction and dependency is shown on figs. 1.

 

 

 

 

 

 

 

 


figs. 1.

 From here seen that accuracy a checking will be determined by percentage error d, , which is result followings mistakes:

 

d = dкиа + dс + dу ,  (3)

 where;

          dкиа-  error of Instruments for checking,

          dс-  systematic mistake - it constant or is changed on some law,

          dу- mistake from conditions a checking, when they are distinguished from reasonable conditions

 Total error in general case is a random variable and her minimize is possible when reduce  dкиа, dс or dу. For this possible use three methods.

The first method is the best. This method will water dependency between dкиа and error of measurement, which is determined by the producer of a measurement as a allowed. Deflection with this nominal value is DПкиа and it is distribute  from the normal distribution.

 Random quantity distribution on law Gauss:

 

 

 

 

In this event a formula takes type:

 

 

 

 

 

where;

          s - detour from nominal value.

 fig.2

From the fig.2 we have: The real confidence interval has a length  ±3s and it's bigger from the nominal interval, with 2sн he is  symmetric.  So interval ±2s, where are  67% from results is possible accept for confidential. In this case the confidence interval  is  reduce  when Instruments for checking are old. The new confidence interval is has a   length  ±2s as a length of the nominal interval.

So component  mistake  dкиа vastly decrease.

The second method is minimizing the systematic mistake dс. Our goal is finding the errors end excluded from total result. Necessary is the measurements to du by equivalent conditions.  

The third method is depended from the conditions and inspection. In this case is minimized the inherited errors  dу.

 

References:

1.     Дамянов Й., Справочник на машиностроителя, Техника, София, 1981г.

2.     Димитров  Д., Взаимозаменяемост, стандартизация и технически измервания, Техника, София, 1987г.

3.     Жовдак В.А. Мищенко И.В. Прогнозирование надежности элементов конструкций с учетом технологических и эксплуатационных факторов. Харьков, ХГПУ, 1999.

4.     Гнуриан В. Е., Теория вероятностей и математическая статистика, Москва, “Висшая школа”, 1977г.

5.     Janushevskis, A., Onzevs, O., Auzins, J., Boyko, A. Tool for Automation of Optimisation Calculations of Mechanical System Vibrations. // In: Journal of Vibroengineering. No. 4, 4 pp., Kaunas. 2001.

6.     Петров Н. И., Синтез на функционални и стохастични методи и системи за диагностика и ремонт, дисертация  ВА “Г. С. Раковски”, София

 

 

 

 

 

 

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