Курсовая работа: Working out of the search algorithm of failures of Air Conditioning System of TU-154
For functional systems of the aircraft it is typical the appearance simultaneously several signs during failures appearance, that is underlined presence of several signs (+) in the columns of the table 1.
Data analysis attests that some signs may be shown in appearance of different failures and defects of aggregates, that’s why in penultimate line there are written number of diagnoses, which are controlled by each sign. If some sign is shown in appearance of several diagnoses, then its appearance may be caused by appearance of either one diagnose or another one, and also when diagnoses appear together. That’s why in the last line of the table there are written possible combinations of the diagnoses. In spite of that during analysis of functional systems of the aircraft it is considered that simultaneous appearance of several types of the failures of aggregates, but from theoretical point of view accounting uncertainty of information about the state of aggregates, in the case of appearance of such situation it is necessary to take into account this possibility. For usage of mathematical apparatus of theory of information it is necessary to define values of probabilities qi of appearance of this or that diagnose. For their calculation in penultimate column of the table there are written number of cases of appearance of each diagnose by statistical data, which are collected for some period of AT operation. It is evident that it is not possible to calculate probability of diagnose appearance, but it is possible to get their evaluation. Control of one or several parameters (signs) of the system, which is called check, gives information j about presence of aggregate diagnose. Quantity of information, accounting that we consider dichotomy, is evaluated as difference between level of system state uncertainty before H (S) and after check H (S/nj):
J= H (S) - H (S/nj). (2)
Level of uncertainty of system states before the check in condition that system can be unworkable as a result of appearance of only one any diagnose from their general quantity with probability qk is calculated by the formula:
(3)
Level of uncertainty of system states after the check:
(4)
Where 
- total probability of appearance of m diagnoses, which are enveloped by the check ni; qn - probability of appearance of diagnose from totality m, enveloped by the check ni.
Then 
(5)
Setting of the diagnose in the system should be begun from the check ni, which carries the greatest quantity of information. As a result of making of the check table 1 is transformed. We will two tables as a result of this. If in the first check it is fixed that sign was confirmed (such situation is signed as R = 1), diagnoses should be looking for in that totality, with which this sign has stochastic relation. Second step for refinement of diagnose is made with the help of transformed table, which includes m diagnoses. As in the previous case setting of diagnose will be made with taking into account quantity of information, got during second check. Quantity of information in this case is calculated by the formula:
(6)
If R = 0, that means sign is not confirmed, then search of diagnose is made by another transformed table, which includes diagnoses from the number m+1…N. in such case quantity of information is calculated by formula:
(7)
For usage of expressions (1) - (7) it is made table of calculated-informational data (table 2).
Table of calculated-informational data.Table 2
|
№ | Parameters and features | System components diagnoses |
Sq |
I | |||||
| D1 | D2 | D3 | D4 | D5 |
D6 | ||||
| 1 | X1 | 0.25 | 0 | 0 | 0 | 0 | 0 | 0,25 | 0.81 |
| 2 | X1 | 0 | 0.31 | 0 | 0 | 0 | 0 | 0,31 | 0.88 |
| 3 | X1 | 0.25 | 0.31 | 0 | 0 | 0 | 0 | 0.56 | 0.98 |
| 4 | X2 | 0.25 | 0 | 0 | 0 | 0 | 0 | 0.25 | 0.81 |
| 5 | X2 | 0 | 0 | 0 | 0 | 0.13 | 0 | 0.13 | 0.55 |
| 6 | X2 | 0.25 | 0 | 0 | 0 | 0.13 | 0 | 0.38 | 0.95 |
| 7 | X3 | 0 | 0 | 0. 19 | 0 | 0 | 0 | 0. 19 | 0.69 |
| 8 | X3 | 0 | 0 | 0 | 0.06 | 0 | 0 | 0.06 | 0.32 |
| 9 | X3 | 0 | 0 | 0. 19 | 0.06 | 0 | 0 | 0.25 | 0.81 |
| 10 | X4 | 0 | 0 | 0 | 0 | 0 | 0.06 | 0.06 | 0.32 |
| 11 | X5 | 0 | 0 | 0 | 0 | 0.13 | 0 | 0.13 | 0.55 |
Algorithm for checking of aggregate state. Table 3
|
№ row |
Sq |
I | ||||||
| D1 | D2 | D3 | D4 | D5 | D6 | |||
| 1 | 0.25 | 0 | 0 | 0 | 0 | 0 | 0,25 | 0.81 |
| 2 | 0 | 0.31 | 0 | 0 | 0 | 0 | 0,31 | 0.88 |
| 3 | 0.25 | 0.31 | 0 | 0 | 0 | 0 | 0.56 | 0.98 |
| 4 | 0.25 | 0 | 0 | 0 | 0 | 0 | 0.25 | 0.81 |
| 5 | 0 | 0 | 0 | 0 | 0.13 | 0 | 0.13 | 0.55 |
| 6 | 0.25 | 0 | 0 | 0 | 0.13 | 0 | 0.38 | 0.95 |
| 7 | 0 | 0 | 0. 19 | 0 | 0 | 0 | 0. 19 | 0.69 |
| 8 | 0 | 0 | 0 | 0.06 | 0 | 0 | 0.06 | 0.32 |
| 9 | 0 | 0 | 0. 19 | 0.06 | 0 | 0 | 0.25 | 0.81 |
| 10 | 0 | 0 | 0 | 0 | 0 | 0.06 | 0.06 | 0.32 |
| 11 | 0 | 0 | 0 | 0 | 0.13 | 0 | 0.13 | 0.55 |
| # | D1 | D2 | Sq | I |
| 1 | 0.44 | 0.44 | 0.98 | |
| 2 | 0.55 | 0.55 | 0.99 | |
| 4 | 0.44 | 0.44 | 0.98 | |
| 5 | 1.00 | 0 | ||
| 6 | 0.44 | 0.44 | 0.98 | |
| 7 | 1.00 | 0 | ||
| 8 | 1.00 | 0 | ||
| 9 | 1.00 | 0 | ||
| 10 | 1.00 | 0 | ||
| 11 | 1.00 | 0 |
| # | D3 | D4 | D5 | D6 | Sq | I |
| 1 | 1.00 | 0 | ||||
| 2 | 1.00 | 0 | ||||
| 4 | 1.00 | 0 | ||||
| 5 | 0.29 | 0.29 | 0.86 | |||
| 6 | 0.29 | 0.29 | 0.86 | |||
| 7 | 0.43 | 0.43 | 0.98 | |||
| 8 | 0.13 | 0.13 | 0.56 | |||
| 9 | 0.43 | 0.13 | 0.56 | 0.99 | ||
| 10 | 0.13 | 0.13 | 0.56 | |||
| 11 | 0.29 | 0.29 | 0.86 |
| # | D5 | D6 | Sq | I |
| 1 | 1.00 | 0 | ||
| 2 | 1.00 | 0 | ||
| 4 | 1.00 | 0 | ||
| 5 | 0.65 | 0.65 | 0.93 | |
| 6 | 0.65 | 0.65 | 0.93 | |
| 7 | 1.00 | 0 | ||
| 8 | 1.00 | 0 | ||
| 10 | 0.29 | 0.29 | 0.86 | |
| 11 | 0.65 | 0.65 | 0.93 | |
| # | D3 | D4 | Sq | I |
| 1 | 1.00 | 0 | ||
| 2 | 1.00 | 0 | ||
| 4 | 1.00 | 0 | ||
| 5 | 1.00 | 0 | ||
| 6 | 1.00 | 0 | ||
| 7 | 0.76 | 0.76 | 0.79 | |
| 8 | 0.23 | 0.23 | 0.76 | |
| 10 | 1.00 | 0 | ||
| 11 | 1.00 | 0 |
Description of obtained algorithm
So, using this algorithm of malfunctions discovering we can compose an order of system checking, namely, steps of inspection (diagnostics). These steps are:
1. Check internal cavity of air-to-air heat exchanger
2. Check correctness of tubes installation
3. Check fittings of air-cycle machine