introduction to cbm of machines by imran

7/29/2019 introduction to cbm of machines by imran

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WUS ANN MODEL


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WUs ANN MODEL

It is used to predict Remaining Useful Life (RUL)

Inputs are:

Age at inpecton

Actual condition monitoring measurement

Output:Life percentage

Ref: [1]


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WUs ANN MODEL STRUCTURE

Ref: [1]


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WUs ANN MODEL STRUCTURE

ti is the age of the equipment at the currentinspection point tti1 is the age at the previous inspection point

i 1

z1iand z1i1 are the values of measurement 1at the current and previous inspection points,

respectively

z2iand z2i1 are the values of measurement 2at the current and previous inspection points,respectively.

Ref: [1]


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WUs ANN MODEL

Can handle unequally spaced inspection points

Can take multiple condition monitoringmeasurement i.e. Acoustic, vibrations, oil data etc

Takes actual values of condition monitoring

measurements as inputs

Ref: [1]


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WUs ANN MODEL PROCEDURE

Ref: [1]


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OBSERVATIONS

Actual condition monitoring measurements are

used to train the ANN model.

Training set is from the available failure

histories

Actual condition monitoring measurements are

used as inputs to predict life.

No validation process is used while training

ANNRef: [1]


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ISSUES WITH ACTUAL VALUES

Actual condition monitoring values are

collected at inspection points in practical

applications

Include noise

Have fluctuations

Whereas degradation is monotonic process

Actual values as inputs compromise accuracy

of prediction of ANN

Ref: [1]


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ISSUES WITH ACTUAL VALUES

Ref: [1]


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ZHIGANG TIANS ANN MODEL


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DIFFERENCES

Fitted condition monitoring values are used as

inputs instead of actual

Fitted values are used as training set to train

ANN

Actual values are used as validation set

Output is the same as that ofWus model, i.e.

Life percentage

Ref: [1]


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FITTING ACTUAL VALUES

Weibull Distribution Failure Rate Function is

used for fitting actual values

z(t) =Y + K (t-1)/

where tis the age of the unitz(t)is the fitted measurement valueKis the scale parameter

Yis the values at age zero

(t-1) / is the failure rate function for the

2-parameter Weibull distribution.

Ref: [1]


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FITTED VALUES

Ref: [1]


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TIANS MODEL STRUCTURE

Ref: [1]


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INDICATOR OF HEALTH CONDITION

Life percentage, as indicator of health condition

Difficult to find single indicator that changes

monotonically with degradation of eqpt

Establishing failure threshold is difficult Life percentage is good indicatore, because:

health condition index and the life percentage is

monotonically non-decreasing.

Life percentage is also able to indicate when the failure

occurs, that is, the failure occurs when the life percentage

reaches 100%.

Ref: [1]


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TRAINING

Fitted measurement values are used as training set

Actual values are used as validation set

Example:

4 Failure histories

30,30,40 and 40 inspection points for each failure history respectively

So we will have ( 29 + 29 + 39 +39 = 136 ) 136 training pairs.

These 136 pairs will be fitted and used for training

The same 136 pairs without fitting will be used for validating

Ref: [1]


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TRAINING

Ref: [1]


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MERITS

Since it predicts percentage life therefore

there is no need to define failure threshold

Validation of model is donePrediction accuracy is improved as

compared to Wus Model

Ref: [1]


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CONCL


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?


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THANK YOU

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introduction to cbm of machines by imran