CN112765899B - Turboshaft engine multi-target performance prediction method based on Bayesian classifier chain - Google Patents
Turboshaft engine multi-target performance prediction method based on Bayesian classifier chain Download PDFInfo
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Abstract
The invention discloses a multi-target performance prediction method of a turboshaft engine based on a Bayes classifier chain, which connects Bayes classifiers according to the relation among target variables, establishes a chain performance prediction model, and predicts the qualification probability of a plurality of performance target variables of the turboshaft engine simultaneously through posterior probability reasoning after the attribute variable state of the turboshaft engine to be predicted is given. Meanwhile, in order to ensure the accuracy of the result, different connection sequences of the target variable are considered, the prediction results of all models are averaged, and the final performance prediction result of the target variable is obtained, so that the production can be guided, and the factory yield of the turboshaft engine is improved.
Description
Technical Field
The invention belongs to the technical field of aero-engines, and particularly relates to a method for predicting multi-target performance of an engine.
Background
The turboshaft engine is a highly complex precision thermal machine, is generally used as a power source of a helicopter, and has extremely high requirements on the manufacturing level. Generally, a qualified turboshaft engine has two performance parameter indicators to be considered: power and critical cross-sectional temperature. In order to ensure that the helicopter can be always provided with sufficient and stable power, the power of the engine has the lowest qualified limit; meanwhile, in order to ensure the working life of the engine and the safety of the helicopter, the index of the critical section temperature has the highest qualified limit. However, in actual production, the manufactured engine is difficult to meet the qualified requirements of two indexes by one trial run, and multiple trial runs are often tried after the engine is reassembled, so that the labor and material costs are greatly increased. The performance of the turboshaft engine can be accurately and effectively predicted, so that the risk can be predicted in advance, and the production link can be guided, so that the ex-factory yield of the turboshaft engine is improved.
For the performance prediction of an aircraft engine, at the present stage, there are two main methods: model-based methods and data-based methods. The model-based method carries out performance prediction work by constructing an accurate engine mathematical model, and the application of the method needs to be established on the basis of deep research on the structure and the principle of an engine. Furthermore, the method is overly dependent on the accuracy of the mathematical model, and the model prediction results are susceptible to noise and modeling uncertainty. Data-based methods do not require prior knowledge of the engine system, but rather predict its performance directly from collected engine data, of which machine learning algorithms are a typical representative. With the rise of artificial intelligence and the accumulation of a large amount of engine data in recent years, data-based methods attract more and more researchers and are gradually becoming the first solution in the field of aircraft engine performance prediction.
The Beijing university of aerospace school, 2008, 34 (3) discloses a method for predicting performance parameters of an aircraft engine, which comprises the steps of decomposing original data of the engine into a plurality of groups of subsequences on different scales by utilizing wavelet transformation, respectively selecting an autoregressive moving average model or a summation autoregressive moving average model for prediction according to the characteristics of each subsequence, and finally synthesizing all prediction results to obtain a total prediction result. However, the current data-based prediction methods have the following disadvantages: modeling prediction is inefficient, prediction of multiple performance parameter indexes cannot be considered simultaneously, and specific performance qualified prediction probability cannot be given.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a multi-target performance prediction method of a turboshaft engine based on a Bayes classifier chain, which connects Bayes classifiers according to the relation among target variables, establishes a chain-shaped performance prediction model, and can predict the qualification probability of a plurality of performance target variables of the turboshaft engine to be predicted at the same time through posterior probability reasoning after the attribute variable state of the turboshaft engine to be predicted is given. Meanwhile, in order to ensure the accuracy of the result, different connection sequences of the target variable are considered, the prediction results of all models are averaged, and the final performance prediction result of the target variable is obtained, so that the production can be guided, and the factory yield of the turboshaft engine is improved.
The technical scheme adopted by the invention for solving the technical problem comprises the following steps:
step 1: collecting performance parameter data and design parameter data of a turboshaft engine;
acquiring performance parameter data of the turboshaft engine by testing a plurality of turboshaft engines, wherein the performance parameter data comprises measurement data of power P and key section temperature T during the test of the turboshaft engine;
obtaining design parameter data of a turboshaft engine, wherein the design parameter data comprises the sizes of N different parts in the turboshaft engine;
and 2, step: determining a target variable and an attribute variable, and setting a qualified condition of the target variable; discretizing each variable to obtain a probability distribution table and a conditional probability table of the target variable and conditional probability tables of various states of the attribute variables under different target variables; the method comprises the following specific steps:
step 2-1: setting the power P and the critical section temperature T of the turboshaft engine as target variables, and setting the sizes of N different parts in the turboshaft engine as attribute variables, wherein the x is represented as 1 ,x 2 ,…,x i ,…,x N ,i=1,2,…,N;
Step 2-2: setting the minimum qualified condition of the power P as a KW; setting the maximum qualified condition of the critical section temperature T as b ℃, wherein a and b respectively represent two normal constants;
step 2-3: dividing the power P into two sections by taking the minimum qualified condition of the power P as a boundary, and counting the probability distribution table P of the power P in the two sections by the data obtained in the step 1 r (P); dividing the critical section temperature T into two sections by taking the maximum qualified condition of the critical section temperature T as a boundary, and counting the probability distribution table P of the critical section temperature T in the two sections according to the data obtained in the step 1 r (T);
The data statistical power P and the key section temperature T obtained in the step 1 belong to a conditional probability table P of different segments in a priori manner r (P | T) and P r (T|P);
Step 2-4: each attribute variable x 1 ,x 2 ,…,x N The method is characterized in that the method is divided into e sections by adopting an equal frequency method, the e sections are respectively expressed as states 0,1, \8230, e-1,0,1, \8230, and e-1 represents the state of an attribute variable and does not represent the actual value of the attribute variable; for the ith attribute variable, the threshold values adopted for dividing the attribute variable into e segments are respectively In correspondence with the state 0, the state,in correspondence with the state 1, the state of the mobile terminal,corresponding to the state 2, and so on,corresponding to state e-1;
step 2-5: counting N attribute variables by the data obtained in the step 1, and taking the power P and the key section temperature T as prior numbers to belong to a conditional probability table P in different states r (x i P) and P r (x i |T);
And step 3: obtaining a performance prediction result of the turboshaft engine on the target variable power P and the key section temperature T under a Bayes classifier chain performance prediction model based on a naive Bayes classifier and taking the target variable power P as a chain head through posterior probability reasoning; the specific process is as follows:
step 3-1: the Bayes classifier chain performance prediction model with the target variable power P as the chain head comprises two classifiers, wherein the first classifier is used for predicting the target variable power P, the target variable power P is used as a father node, and each attribute variable x is 1 ,x 2 ,…,x N As child nodes; the second classifier is used for predicting the key section temperature T of the target variable, taking the key section temperature T of the target variable as a father node and taking each attribute variable x 1 ,x 2 ,…,x N And the target variable power P as child nodes;
step 3-2: setting an attribute variable x 1 ,x 2 ,…,x N Respectively, is y 1 ,y 2 ,…,y N ,y 1 ,y 2 ,…,y N ∈[0,1,…,e-1](ii) a Predicting power PHELpass (PHELpass) according to a first classifier of a Bayes classifier chain performance prediction model taking target variable power P as a chain head>a) The probability of (d);
the posterior probability of power Pqualified (P > a) is then:
the posterior probability of unqualified power P (P ≦ a) is:
according to the basic properties of conditional probabilities, there are:
substituting the numerical value in the conditional probability table obtained in the step 2 to solve P r (x 1 =y 1 ,x 2 =y 2 ,…,x N =y N ) Finally, calculating to obtain power PHELpass (PHELpass)>a) Has a probability of P r (P>a|x 1 =y 1 ,x 2 =y 2 ,…,x N =y N )=m%;
If m% is less than 50%, judging that the power P of the turboshaft engine to be predicted is unqualified under a Bayes classifier chain performance prediction model taking the target variable power P as a chain head; if m% is more than or equal to 50%, judging that the power P of the turboshaft engine to be predicted is qualified under a Bayes classifier chain performance prediction model taking the target variable power P as a chain head;
step 3-3: predicting the probability of the qualified temperature T (T is less than or equal to b) of the key section according to a second classifier of a Bayes classifier chain performance prediction model taking the target variable power P as a chain head;
the posterior probability of the key section temperature T qualified (T is less than or equal to b) is as follows:
wherein, when m% <50%, it is [ < no ]; when m% is more than or equal to 50%, the signal is more than or equal to the number;
the posterior probability of the critical section temperature T disqualification (T > b) is:
according to the basic properties of conditional probabilities, there are:
substituting the numerical value in the conditional probability table obtained in the step 2 to solve P r (x 1 =y 1 ,x 2 =y 2 ,…,x N =y N P ^ a), the probability of obtaining the critical section temperature Tpass (T ≦ b) finally calculated as P r (T≤b|x 1 =y 1 ,x 2 =y 2 ,…,x N =y N ,P⊙a)=n%;
If n% <50%, judging that the critical section temperature T of the turboshaft engine to be predicted is unqualified under a Bayes classifier chain performance prediction model taking the target variable power P as a chain head; if n% is more than or equal to 50%, judging that the critical section temperature T of the turboshaft engine to be predicted is qualified under a Bayes classifier chain performance prediction model taking the target variable power P as a chain head;
and 4, step 4: the performance prediction results of the turboshaft engine on the target variable power P and the key section temperature T under a Bayes classifier chain performance prediction model based on a naive Bayes classifier and taking the target variable key section temperature T as a chain head are obtained through posterior probability reasoning; the specific process is as follows:
step 4-1: the Bayes classifier chain performance prediction model taking the target variable key section temperature T as the chain head comprises two classifiers, wherein the first classifier is used for predicting the target variable key section temperature T, the target variable key section temperature T is used as a father node, and each attribute variable x is subjected to prediction 1 ,x 2 ,…,x N As child nodes; the second classifier takes the target variable power P as a parent node and takes each attribute variable x as the prediction of the target variable power P 1 ,x 2 ,…,x N And the target variable key section temperature T is taken as a child node;
step 4-2: predicting the probability of the qualification (T is less than or equal to b) of the key section temperature T according to a first classifier of a Bayes classifier chain performance prediction model taking the target variable key section temperature T as a chain head;
the posterior probability of the key section temperature T qualified (T is less than or equal to b) is as follows:
the posterior probability of the critical section temperature T disqualification (T > b) is:
according to the basic properties of conditional probabilities, there are:
substituting the numerical value in the conditional probability table obtained in the step 2 to solve P r (x 1 =y 1 ,x 2 =y 2 ,…,x N =y N ) Finally, the probability that the critical section temperature T is qualified (T is less than or equal to b) is calculated and obtained as P r (T≤b|x 1 =y 1 ,x 2 =y 2 ,…,x N =y N )=s%;
If s% <50%, judging that the critical section temperature T of the turboshaft engine to be predicted is unqualified under a Bayes classifier chain performance prediction model taking the target variable critical section temperature T as a chain head; if s% is more than or equal to 50%, judging that the critical section temperature T of the turboshaft engine to be predicted is qualified under a Bayes classifier chain performance prediction model taking the target variable critical section temperature T as a chain head;
step 4-3: predicting the probability of power P qualification (P > a) according to a second classifier of a Bayes classifier chain performance prediction model taking the target variable key section temperature T as a chain head;
the posterior probability of power Pqualified (P > a) is then:
wherein, when s%<When the content of the organic acid is 50 percent,is composed of>Number; when the s% is more than or equal to 50%,is no more than number;
the posterior probability of unqualified power P (P ≦ a) is:
according to the basic properties of conditional probabilities, there are:
substituting the numerical value in the conditional probability table obtained in the step 2 to solve Finally, the power P qualified is obtained through calculation (P)>a) Has a probability of
If the r% is less than 50%, judging that the power P of the turboshaft engine to be predicted is unqualified under a Bayes classifier chain performance prediction model taking the target variable key section temperature T as a chain head; if the r% is more than or equal to 50%, judging that the power P of the turboshaft engine to be predicted is qualified under a Bayes classifier chain performance prediction model taking the key section temperature T of the target variable as a chain head;
and 5: averaging the qualification probability prediction results of the power P and the key section temperature T obtained in the step 3 and the step 4 under a Bayes classifier chain performance prediction model with the target variable power P and the target variable key section temperature T as chain heads respectively to finally obtain: the final qualification probability prediction result of the power P of the turboshaft engine to be predicted isThe final qualification probability prediction result of the critical section temperature T is
Step 6: if it is notFinally judging that the power P of the turboshaft engine to be predicted is unqualified; if it is notFinally judging that the power P of the turboshaft engine to be predicted is qualified;
if it is notFinally judging that the critical section temperature T of the turboshaft engine to be predicted is unqualified; if it is usedAnd finally judging that the critical section temperature T of the turboshaft engine to be predicted is qualified.
Preferably, said e =3.
The invention has the following beneficial effects:
1. the method disclosed by the invention completes the construction of a Bayes classifier chain performance prediction model based on a naive Bayes classifier, performs performance prediction on the turboshaft engine through posterior probability reasoning, and is simple and efficient in modeling and prediction processes.
2. The method can predict two performance parameter indexes at the same time, considers the possible correlation between the two indexes, and better accords with the actual situation of engine performance prediction compared with a single-target prediction method.
3. The method can effectively utilize the test data of the turboshaft engine to predict the performance of the turboshaft engine, and the prediction accuracy is ensured by averaging the prediction results of different models. In addition, the final given result is the specific performance qualified prediction probability, which is beneficial to scientific quantitative evaluation of the performance of the turboshaft engine and has important significance for improving the overall reliability of the turboshaft engine.
Drawings
FIG. 1 is a schematic flow diagram of the process of the present invention.
Fig. 2 is a model for predicting the performance of a chain of a bayesian classifier with a target variable power P as a chain head according to an embodiment of the present invention.
FIG. 3 is a Bayesian classifier chain performance prediction model with a target variable critical section temperature T as a chain head according to an embodiment of the present invention.
Detailed Description
The invention is further illustrated with reference to the following figures and examples.
Step 1: collecting performance parameter data and design parameter data of the turboshaft engine;
acquiring performance parameter data of the turboshaft engine by testing a plurality of turboshaft engines, wherein the performance parameter data comprises measurement data of power P and key section temperature T during the test of the turboshaft engine, and the data type is continuous;
obtaining design parameter data of a turboshaft engine, wherein the design parameter data comprises the sizes of N different parts in the turboshaft engine, and the data type is continuous; these design parameters are generally considered to have an effect on the performance of the engine and may be determined by the experience of the skilled person or by reference to relevant literature;
step 2: determining a target variable and an attribute variable, and setting a qualified condition of the target variable; discretizing each variable to obtain a probability distribution table and a conditional probability table of the target variable and conditional probability tables of various states of the attribute variables under different target variables; the method comprises the following specific steps:
step 2-1: setting the power P and the critical section temperature T of the turboshaft engine as target variables, and setting the sizes of N different parts in the turboshaft engine as attribute variables, wherein the x is represented as 1 ,x 2 ,…,x i ,…,x N ,i=1,2,…,N;
Step 2-2: setting the minimum qualified condition of the power P as a KW; setting the maximum qualified condition of the temperature T of the key section as b ℃, wherein a and b respectively represent two normal constants;
step 2-3: dividing the power P into two sections by taking the minimum qualified condition of the power P as a boundary, and counting the probability distribution table P of the power P in the two sections by the data obtained in the step 1 r (P);Dividing the critical section temperature T into two sections by taking the maximum qualified condition of the critical section temperature T as a boundary, and counting the probability distribution table P of the critical section temperature T in the two sections according to the data obtained in the step 1 r (T);
The data statistical power P and the key section temperature T acquired in the step 1 are mutually prior conditional probability tables P belonging to different sections r (P | T) and P r (T|P);
Step 2-4: each attribute variable x 1 ,x 2 ,…,x N The method comprises the steps of respectively dividing the sections into sections e by adopting an equal frequency method, and respectively representing the sections e into states 0,1, \8230, e-1,0,1, \8230, wherein the e-1 represents the state of an attribute variable and does not represent the actual value of the attribute variable; for the ith attribute variable, the threshold values adopted for dividing the ith attribute variable into e segments are respectively In correspondence with the state 0, the state,in correspondence with the state 1, the state of the mobile terminal,corresponding to the state 2, and so on,corresponding to state e-1;
step 2-5: counting N attribute variables by the data obtained in the step 1, and taking the power P and the key section temperature T as prior numbers to belong to a conditional probability table P in different states r (x i P) and P r (x i |T);
And step 3: obtaining a performance prediction result of the turboshaft engine on the target variable power P and the key section temperature T under a Bayes classifier chain performance prediction model based on a naive Bayes classifier and taking the target variable power P as a chain head through posterior probability reasoning; the specific process is as follows:
step 3-1: taking target variable power P as chainThe first Bayes classifier chain performance prediction model comprises two classifiers, wherein the first classifier is used for predicting target variable power P, the target variable power P is used as a father node, and each attribute variable x is used as a parent node 1 ,x 2 ,…,x N As child nodes; the second classifier is used for predicting the key section temperature T of the target variable, taking the key section temperature T of the target variable as a father node and taking each attribute variable x 1 ,x 2 ,…,x N And the target variable power P as child nodes;
step 3-2: setting an attribute variable x 1 ,x 2 ,…,x N Respectively, is y 1 ,y 2 ,…,y N ,y 1 ,y 2 ,…,y N ∈[0,1,…,e-1](ii) a Predicting power Pqualified (Pqualified) according to a first classifier of a Bayes classifier chain performance prediction model taking target variable power P as a chain head>a) The probability of (d);
the a posteriori probability of power phir (P > a) is then:
the posterior probability of unqualified power P (P ≦ a) is:
according to the basic properties of conditional probabilities, there are:
substituting the numerical value in the conditional probability table obtained in the step 2 to solve P r (x 1 =y 1 ,x 2 =y 2 ,…,x N =y N ) Finally, calculating to obtain power PHELpass (PHELpass)>a) Has a probability of P r (P>a|x 1 =y 1 ,x 2 =y 2 ,…,x N =y N )=m%;
If m% is less than 50%, judging that the power P of the turboshaft engine to be predicted is unqualified under a Bayes classifier chain performance prediction model taking the target variable power P as a chain head; if m% is more than or equal to 50%, judging that the power P of the turboshaft engine to be predicted is qualified under a Bayes classifier chain performance prediction model taking the target variable power P as a chain head;
step 3-3: predicting the probability of the qualified temperature T (T is less than or equal to b) of the key section according to a second classifier of a Bayes classifier chain performance prediction model taking the target variable power P as a chain head;
the posterior probability of the key section temperature T qualified (T is less than or equal to b) is as follows:
wherein, when m% <50%, it is [ < no ]; when m% is more than or equal to 50%, the signal is more than or equal to the mark;
the posterior probability of the critical section temperature T disqualification (T > b) is:
according to the basic properties of conditional probabilities, there are:
substituting the numerical value in the conditional probability table obtained in the step 2 to solve P r (x 1 =y 1 ,x 2 =y 2 ,…,x N =y N P | _ a), the probability that the critical section temperature T is qualified (T ≦ b) is finally calculated as P r (T≤b|x 1 =y 1 ,x 2 =y 2 ,…,x N =y N ,P⊙a)=n%;
If n% <50%, judging that the critical section temperature T of the turboshaft engine to be predicted is unqualified under a Bayes classifier chain performance prediction model taking the target variable power P as a chain head; if n% is more than or equal to 50%, judging that the critical section temperature T of the turboshaft engine to be predicted is qualified under a Bayes classifier chain performance prediction model taking the target variable power P as a chain head;
and 4, step 4: the performance prediction results of the turboshaft engine on the target variable power P and the key section temperature T under a Bayes classifier chain performance prediction model based on a naive Bayes classifier and taking the target variable key section temperature T as a chain head are obtained through posterior probability reasoning; the specific process is as follows:
step 4-1: the Bayes classifier chain performance prediction model taking the target variable key section temperature T as the chain head comprises two classifiers, wherein the first classifier is used for predicting the target variable key section temperature T, the target variable key section temperature T is used as a father node, and each attribute variable x is subjected to prediction 1 ,x 2 ,…,x N As child nodes; the second classifier is used for predicting the target variable power P, taking the target variable power P as a parent node and classifying each attribute variable x 1 ,x 2 ,…,x N And the target variable key section temperature T is used as a child node;
step 4-2: predicting the probability of qualified critical section temperature T (T is less than or equal to b) according to a first classifier of a Bayes classifier chain performance prediction model taking the target variable critical section temperature T as a chain head;
the posterior probability of the key section temperature T qualified (T is less than or equal to b) is as follows:
the posterior probability of the critical section temperature T disqualification (T > b) is:
according to the basic properties of conditional probabilities, there are:
substituting the numerical value in the conditional probability table obtained in the step 2 to solve P r (x 1 =y 1 ,x 2 =y 2 ,…,x N =y N ) Finally, the probability that the critical section temperature T is qualified (T is less than or equal to b) is calculated and obtained as P r (T≤b|x 1 =y 1 ,x 2 =y 2 ,…,x N =y N )=s%;
If s% <50%, judging that the critical section temperature T of the turboshaft engine to be predicted is unqualified under a Bayes classifier chain performance prediction model taking the target variable critical section temperature T as a chain head; if s% is more than or equal to 50%, judging that the key section temperature T of the turboshaft engine to be predicted is qualified under a Bayes classifier chain performance prediction model taking the key section temperature T of the target variable as a chain head;
step 4-3: predicting the probability of power P qualification (P > a) according to a second classifier of a Bayes classifier chain performance prediction model taking the target variable key section temperature T as a chain head;
the a posteriori probability of power phir (P > a) is then:
wherein, when s%<When the content of the organic acid is 50 percent,is composed of>Number; when the s% is more than or equal to 50%,is no more than number;
the posterior probability of unqualified power P (P ≦ a) is:
according to the basic properties of conditional probabilities, there are:
substituting the numerical value in the conditional probability table obtained in step 2 to solve Finally, the power P qualified is obtained through calculation (P)>a) Has a probability of
If the r% is less than 50%, judging that the power P of the turboshaft engine to be predicted is unqualified under a Bayes classifier chain performance prediction model taking the target variable key section temperature T as a chain head; if the r% is more than or equal to 50%, judging that the power P of the turboshaft engine to be predicted is qualified under a Bayes classifier chain performance prediction model taking the key section temperature T of the target variable as a chain head;
and 5: averaging the qualification probability prediction results of the power P and the key section temperature T obtained in the step 3 and the step 4 under a Bayes classifier chain performance prediction model with the target variable power P and the target variable key section temperature T as chain heads respectively to finally obtain: the final qualification probability prediction result of the power P of the turboshaft engine to be predicted isThe final qualification probability prediction result of the critical section temperature T is
Step 6: if it is notFinally judging that the power P of the turboshaft engine to be predicted is unqualified; if it is notFinally judging that the power P of the turboshaft engine to be predicted is qualified;
if it is notFinally judging that the critical section temperature T of the turboshaft engine to be predicted is unqualified; if it is usedAnd finally judging that the critical section temperature T of the turboshaft engine to be predicted is qualified.
The specific embodiment is as follows:
1. performance parameter data and design parameter data of the turboshaft engine are collected. The specific mode is as follows:
in the embodiment, the actual test run data of a batch of turboshaft engines of a certain model provided by a certain manufacturer is taken as a research object, and a plurality of main design parameters which are found in the long-term production process and have the greatest influence on the performance of the engine, namely three part size variables in the engine are respectively marked as X, Y and Z according to the suggestions of technicians of the manufacturer; and two performance parameter indexes, namely power P and the measurement data of the key section temperature T during test run. All data are continuous data.
2. And (3) determining a target variable and an attribute variable according to the data collected in the step (1), and setting a qualified condition of the target variable. Discretizing each variable to obtain a probability distribution table and a conditional probability table of two target variables and a conditional probability table of each state of the attribute variables of different target variables. The specific mode is as follows:
and (3) setting the power P and the critical section temperature T in the turboshaft engine data collected in the step (1) as target variables. According to the knowledge from manufacturers, on the premise of fully considering dynamic performance and safety, the minimum qualified power of a certain model of turboshaft engine is 1130KW, the temperature of the key section of the engine is not higher than 895 ℃ when the turboshaft engine is used, so that the qualified conditions of two target variables P and T are respectively 1130KW and 895 ℃, the two target variables are respectively discretized into two intervals by taking the qualified conditions as boundaries, and a probability distribution table and a conditional probability table are calculated. The method comprises the steps of setting size variables X, Y and Z of parts in three engines as attribute variables, respectively discretizing the attribute variables into three sections by adopting an equal frequency method, and respectively representing the three sections as states 0,1 and 2 for convenient representation, wherein 0,1 and 2 represent variable states and do not represent actual values. And counting the conditional probability tables of the three attribute variables relative to the two target variables.
TABLE 1 probability distribution Table for target variable P
TABLE 2 probability distribution Table for target variable T
TABLE 3 conditional probability table of target variables P
Table 4 conditional probability table of target variable T
Table 5 conditional probability table of attribute variables X with respect to P
Table 6 conditional probability table of attribute variables Y with respect to P
Table 7 conditional probability table of attribute variables Z with respect to P
Table 8 conditional probability table of attribute variables X with respect to T
Table 9 conditional probability table of attribute variables Y with respect to T
Table 10 conditional probability table of attribute variables Z with respect to T
3. And constructing a Bayesian classifier chain performance prediction model taking the target variable P as a chain head. The concrete method is as follows:
a. first, a first classifier in the Bayesian classifier chain performance prediction model is established. The first classifier is a prediction for the target variable P and can be obtained based on a naive bayes classifier based on the probability distribution table of the target variable P in table 1 obtained in step 2 and the conditional probability tables of the attribute variables with respect to the target variable P in tables 5 to 7. The graph of the classifier can be represented as pointing to three attribute variables from a target variable, wherein the target variable P is a parent node, and the attribute variables X, Y and Z are child nodes.
b. A second classifier in the Bayesian classifier chain performance prediction model is then established. The second classifier is for the prediction of the target variable T and can be based on a naive bayes classifier, and is obtained from the table 2 probability distribution table of the target variable T, the table 3 conditional probability table of the target variable P and the table 8-table 10 conditional probability tables of the attribute variables with respect to the target variable T, which are obtained in step 2. It should be noted that, in this classifier, the target variable T is the parent node, and the attribute variables X, Y, Z plus the target variable P of the first classifier are collectively used as the child node.
The finally established Bayesian classifier chain performance prediction model taking the target variable P as the chain head is shown in FIG. 2.
4. And (3) according to the Bayes classifier chain performance prediction model which is constructed in the step 3 and takes the target variable P as the chain head, combining a plurality of probability tables in the step 2, and for a specific turboshaft engine, obtaining the performance prediction results of the two target variables under the performance prediction model through posterior probability reasoning. The specific mode is as follows:
a. firstly, the performance of the target variable P is predicted according to a first classifier in a classifier chain performance prediction model. Assuming that the state values of the attribute variable combination (X, Y, Z) of the turboshaft engine to be predicted at present are (0, 1, 2), according to the naive Bayes characteristic of the first classifier constructed in the step 3, under the condition that the state of the target variable P is known, the state values of the attribute variables are mutually independent, and the posterior probability of P qualification (P > 1130) is as follows:
in the above formula, P in the molecule r (P>1130 64.03% from Table 1, P r (X=0|P>1130),P r (Y=1|P>1130 ) and P r (Z=2|P>1130 30.82%,30.14% and 28.77% from tables 5 to 7, respectively. These found values are substituted into the above equation:
the posterior probability of the same obtained P disqualification (P < = 1130) is as follows:
according to the basic properties of conditional probabilities, there are:
obtaining by solution:
P r (X=0,Y=1,Z=2)=0.04107053
obtaining:
in the bayesian classifier chain performance prediction model with the target variable P as the chain head, the qualification probability of the target variable P of the engine to be predicted is 41.66%, and the probability value is less than 50%, so that the engine is more likely to be in a disqualification state in view of the prediction result.
b. Next, the performance of the target variable T is predicted according to a second classifier in the classifier chain performance prediction model. In this classifier, there are four input variables: and X, Y, Z and P, wherein the values of X, Y and Z are known conditions (0, 1, 2), and the value of the state of P is set to be (P < = 1130) according to the prediction result of the first classifier. According to the naive Bayes characteristic of the second classifier constructed in the step 3, under the condition that the state of the target variable T is known, the state values of X, Y, Z and P are mutually independent, and the posterior probability of T qualification (T < = 895) is as follows:
p in the molecule of the above formula r (T. Ltoreq.895) is 67.54% in terms of P as shown in Table 2 r (X=0|T≤895),P r (Y=1|T≤895),P r (Z =2 calucin T. Ltoreq.895) and P r (P.ltoreq.1130 Y.ltoreq.895) 33.12%,37.66%,35.71% and 48.70% as seen in tables 8, 9, 10 and 3, respectively. These found values are substituted into the above equation:
the posterior probability of T disqualification (T > 895) is given by the same equation:
according to the basic properties of conditional probabilities, there are:
obtaining by solution:
P r (X=0,Y=1,Z=2,P≤1130)=0.01544833
obtaining:
in the Bayes classifier chain performance prediction model with the target variable P as the chain head, the qualification probability of the target variable T of the engine to be predicted is 94.84%.
In summary, in the bayesian classifier chain performance prediction model with the target variable P as the chain head, when the state value of the attribute variable combination (X, Y, Z) of the turboshaft engine to be predicted is (0, 1, 2), the qualification probability prediction result of the target variable P is 41.66%, and the state is biased to the unqualified state; the prediction result of the qualification probability of the target variable T is 94.84%, and the target variable T is biased to a qualification state.
5. And repeating the step 3 and the step 4, similarly constructing a Bayes classifier chain performance prediction model taking the target variable T as a chain head, and solving the performance prediction results of the two target variables under the performance prediction model for the same turboshaft engine to be predicted. The specific mode is as follows:
firstly, the step 3 is repeated, the sequence of P and T in the classifier chain is changed, and a Bayesian classifier chain performance prediction model which is established by adopting the same method and takes the target variable T as the chain head is shown in FIG. 3. The first classifier is used for predicting a target variable T, the target variable T is a father node, and attribute variables X, Y and Z are used as child nodes; the second classifier is used for predicting a target variable P, the target variable P is a father node, and the attribute variables X, Y and Z and the target variable T of the first classifier are taken as child nodes in a unified mode.
And then, by repeating the posterior probability reasoning process of the 4 th step, the performance prediction of two target variables is carried out aiming at the same turboshaft engine to be tested, and the following results can be obtained: in a Bayes classifier chain performance prediction model taking a target variable T as a chain head, when the state value of an attribute variable combination (X, Y, Z) of a turboshaft engine to be predicted is (0, 1, 2), the qualification probability prediction result of the target variable P is 29.70%, and the target variable P is biased to be in an unqualified state; the prediction result of the qualification probability of the target variable T was 78.11%, and the state was biased toward the qualification state.
6. And averaging the results obtained by the performance prediction models of the different classifier chains constructed in the 4 th step and the 5 th step to obtain the final performance prediction results of the two target variables. The concrete method is as follows:
the performance prediction model constructed by comprehensively considering two classifier chains in different sequences can be obtained by averaging the qualification probability prediction results of two target variables: when the state value of the attribute variable combination (X, Y, Z) of the turboshaft engine to be predicted is (0, 1, 2), the final qualified probability prediction result of the target variable P is 35.68%, and the final qualified probability prediction result is biased to be in an unqualified state; the final qualification probability prediction result of the target variable T is 86.48%, and the final qualification probability prediction result is biased to be in a qualification state. For any given turboshaft engine to be predicted, specific performance prediction results of two target variables of the turboshaft engine can be accurately and efficiently obtained through the method.
Claims (2)
1. A multi-target performance prediction method of a turboshaft engine based on a Bayesian classifier chain is characterized by comprising the following steps:
step 1: collecting performance parameter data and design parameter data of the turboshaft engine;
acquiring performance parameter data of the turboshaft engine by testing a plurality of turboshaft engines, wherein the performance parameter data comprises measurement data of power P and key section temperature T during test of the turboshaft engine;
obtaining design parameter data of a turboshaft engine, wherein the design parameter data comprises the sizes of N different parts in the turboshaft engine;
step 2: determining a target variable and an attribute variable, and setting a qualified condition of the target variable; discretizing each variable to obtain a probability distribution table and a conditional probability table of the target variable and conditional probability tables of various states of the attribute variables of different target variables; the method comprises the following specific steps:
step 2-1: setting the power P and the critical section temperature T of the turboshaft engine as target variables, and setting the sizes of N different parts in the turboshaft engine as attribute variables, wherein the x is represented as 1 ,x 2 ,…,x i ,…,x N ,i=1,2,…,N;
Step 2-2: setting the minimum qualified condition of the power P as a KW; setting the maximum qualified condition of the temperature T of the key section as b ℃, wherein a and b respectively represent two normal constants;
step 2-3: dividing the power P into two sections by taking the minimum qualified condition of the power P as a boundary, and counting the probability distribution table P of the power P in the two sections by the data obtained in the step 1 r (P); dividing the critical section temperature T into two sections by taking the maximum qualified condition of the critical section temperature T as a boundary, and counting the probability distribution table P of the critical section temperature T in the two sections according to the data obtained in the step 1 r (T);
The data statistical power P and the key section temperature T acquired in the step 1 are mutually prior conditional probability tables P belonging to different sections r (P | T) and P r (T|P);
Step 2-4: each attribute variable x 1 ,x 2 ,…,x N Respectively dividing the obtained product into e segments by using an equal frequency method, and respectively representing the e segments in intervalsState 0,1, \8230, e-1,0,1, \8230, e-1 all represent attribute variable states and do not represent actual values of attribute variables; for the ith attribute variable, the threshold values adopted for dividing the attribute variable into e segments are respectively In correspondence with the state 0, the state,in correspondence with the state 1, the state of the mobile terminal,corresponding to the state 2, and so on,corresponding to state e-1;
step 2-5: counting N attribute variables by the data obtained in the step 1, and taking the power P and the key section temperature T as prior numbers to belong to a conditional probability table P of different states r (x i P) and P r (x i |T);
And 3, step 3: obtaining a performance prediction result of the turboshaft engine on the target variable power P and the key section temperature T under a Bayes classifier chain performance prediction model based on a naive Bayes classifier and taking the target variable power P as a chain head through posterior probability reasoning; the specific process is as follows:
step 3-1: the Bayes classifier chain performance prediction model taking the target variable power P as the chain head comprises two classifiers, wherein the first classifier is used for predicting the target variable power P, the target variable power P is used as a father node, and each attribute variable x is used 1 ,x 2 ,…,x N As child nodes; the second classifier is used for predicting the key section temperature T of the target variable, taking the key section temperature T of the target variable as a father node and taking each attribute variable x 1 ,x 2 ,…,x N And the target variable power P as child nodes;
step 3-2: setting an attribute variable x 1 ,x 2 ,…,x N Respectively, is y 1 ,y 2 ,…,y N ,y 1 ,y 2 ,…,y N ∈[0,1,…,e-1](ii) a Predicting power Pqualified (P) according to a first classifier of a Bayes classifier chain performance prediction model taking target variable power P as a chain head>a probability of;
the posterior probability of power P qualification is then:
the posterior probability that the power P is unqualified, namely that P is less than or equal to a, is as follows:
according to the basic properties of conditional probabilities, there are:
substituting the numerical value in the conditional probability table obtained in step 2 to solve P r (x 1 =y 1 ,x 2 =y 2 ,…,x N =y N ) Finally, the probability of qualified power P is calculated to be P r (P>a|x 1 =y 1 ,x 2 =y 2 ,…,x N =y N )=m%;
If m% is less than 50%, judging that the power P of the turboshaft engine to be predicted is unqualified under a Bayes classifier chain performance prediction model taking the target variable power P as a chain head; if m% is more than or equal to 50%, judging that the power P of the turboshaft engine to be predicted is qualified under a Bayes classifier chain performance prediction model taking the target variable power P as a chain head;
step 3-3: predicting the probability that the critical section temperature T is qualified, namely T is less than or equal to b according to a second classifier of a Bayes classifier chain performance prediction model taking the target variable power P as a chain head;
the posterior probability of the key section temperature T being qualified is:
wherein, when m% <50%, it is [ < no ]; when m% is more than or equal to 50%, the signal is more than or equal to the mark;
the posterior probability of the critical section temperature T disqualification, namely T > b is as follows:
according to the basic properties of conditional probabilities, there are:
substituting the numerical value in the conditional probability table obtained in the step 2 to solve P r (x 1 =y 1 ,x 2 =y 2 ,…,x N =y N P ^ a), the probability of obtaining the qualified critical section temperature T by final calculation is P r (T≤b|x 1 =y 1 ,x 2 =y 2 ,…,x N =y N ,P⊙a)=n%;
If n% <50%, judging that the critical section temperature T of the turboshaft engine to be predicted is unqualified under a Bayes classifier chain performance prediction model taking the target variable power P as a chain head; if n% is more than or equal to 50%, judging that the critical section temperature T of the turboshaft engine to be predicted is qualified under a Bayes classifier chain performance prediction model taking the target variable power P as a chain head;
and 4, step 4: obtaining a performance prediction result of the turboshaft engine on the target variable power P and the key section temperature T under a Bayes classifier chain performance prediction model based on a naive Bayes classifier and taking the target variable key section temperature T as a chain head through posterior probability reasoning; the specific process is as follows:
step 4-1: the Bayes classifier chain performance prediction model taking the target variable key section temperature T as the chain head comprises two classifiers, wherein the first classifier is used for predicting the target variable key section temperature T, the target variable key section temperature T is used as a father node, and each attribute variable x is subjected to prediction 1 ,x 2 ,…,x N As child nodes; the second classifier takes the target variable power P as a parent node and takes each attribute variable x as the prediction of the target variable power P 1 ,x 2 ,…,x N And the target variable key section temperature T is taken as a child node;
step 4-2: predicting the qualified probability of the key section temperature T according to a first classifier of a Bayes classifier chain performance prediction model taking the target variable key section temperature T as a chain head;
the posterior probability of the key section temperature T being qualified is:
the posterior probability that the critical section temperature T is unqualified is as follows:
according to the basic properties of conditional probabilities, there are:
substituting the numerical value in the conditional probability table obtained in the step 2 to solve P r (x 1 =y 1 ,x 2 =y 2 ,…,x N =x N ) Finally, the probability of obtaining the qualification of the temperature T of the key section by calculation is P r (T≤b|x 1 =y 1 ,x 2 =y 2 ,…,x N =y N )=s%;
If s% is less than 50%, judging that the critical section temperature T of the turboshaft engine to be predicted is unqualified under a Bayes classifier chain performance prediction model taking the target variable critical section temperature T as a chain head; if s% is more than or equal to 50%, judging that the key section temperature T of the turboshaft engine to be predicted is qualified under a Bayes classifier chain performance prediction model taking the key section temperature T of the target variable as a chain head;
step 4-3: predicting the qualified probability of the power P according to a second classifier of a Bayes classifier chain performance prediction model taking the target variable key section temperature T as a chain head;
the posterior probability of power qualification P is:
wherein, when s%<When the content of the organic acid is 50 percent,is composed of>Number; when the s% is more than or equal to 50%,is no more than number;
the posterior probability that the power P is unqualified is as follows:
according to the basic properties of conditional probabilities, there are:
substituting the numerical value in the conditional probability table obtained in step 2 to solve The probability of qualified power P is finally calculated to be
If the r% is less than 50%, judging that the power P of the turboshaft engine to be predicted is unqualified under a Bayes classifier chain performance prediction model taking the target variable key section temperature T as a chain head; if the r% is more than or equal to 50%, judging that the power P of the turboshaft engine to be predicted is qualified under a Bayes classifier chain performance prediction model taking the key section temperature T of the target variable as a chain head;
and 5: averaging the qualification probability prediction results of the power P and the key section temperature T obtained in the step 3 and the step 4 under a Bayes classifier chain performance prediction model taking the target variable power P and the target variable key section temperature T as chain heads respectively to finally obtain: the final qualification probability prediction result of the power P of the turboshaft engine to be predicted isThe final qualification probability prediction result of the critical section temperature T is
Step 6: if it is notFinally judging that the power P of the turboshaft engine to be predicted is unqualified; if it is notFinally judging that the power P of the turboshaft engine to be predicted is qualified;
2. The turbo shaft engine multi-target performance prediction method based on the Bayesian classifier chain as recited in claim 1, wherein e =3.
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