Method for the diagnosis of the EGR cooler efficiency in a diesel engine
View Patent ↗A method is provided for the diagnosis of the EGR cooler efficiency in a Diesel engine that includes but is not limited to construction of a model for determining the temperature drop y=ΔT in the EGR cooler, the model having a parameter vector θ and an input vector x; performing a model calibration phase in order to estimate the bias h 0 of the system; calculation of a set of primary residuals ε(θ 0 , x, ΔT), staffing from the model equation and using the results of the calibration phase; calculation of a set of improved residuals ε N (θ 0 ): ɛ N ( θ 0 ) = 1 N ∑ k = 1 N ( ɛ ( θ 0 , x k , y k ) - h 0 ) where N is the number of samples on which the diagnostic test is performed; calculation of a diagnostic index S: S=ε T N R 0 −1 ε N and, use of the diagnostic index S in order to diagnose the efficiency of the EGR cooler.
1. A method for a diagnosis of an efficiency of an exhaust gas recirculation (EGR) cooler in a diesel engine, comprising the steps of:
constructing, with an engine control unit (ECU), a model for determining the temperature drop y=ΔT in the EGR cooler, the model having a parameter vector θ and an input vector x;
performing, with the ECU, a model calibration phase in order to estimate the bias h 0 of the system;
calculating, with the ECU, a set of primary residuals ε (θ 0 , x, ΔT), starting from a model equation and using the results of a calibration phase;
calculating, with the ECU, a set of improved residuals ε N (θ 0 ):
ɛ
N
(
θ
0
)
=
1
N
∑
k
=
1
N
(
ɛ
(
θ
0
,
x
k
,
y
k
)
-
h
0
)
where N is the number of samples on which a diagnostic test is performed;
calculating, with the ECU, a diagnostic index S:
S=ε N T R 0 −1 ε N
where R 0 is a correlation matrix calculated from a healthy system; and
utilizing the diagnostic index S in order to diagnose the efficiency of the EGR cooler.
2. The method for the diagnosis of the efficiency of the EGR cooler in the diesel engine, of claim 1 , further comprising:
determining, with the ECU, the optimal values θ of a model parameter vector θ using a representative of N samples of experimental data set taken on the healthy system;
estimating, with the ECU, the bias h 0 of the system based on at least of the optimal values θ of the model parameter vector, of the input vector x and of the temperature drop y=ΔT of the EGR cooler;
calculating, with the ECU, matrix E on experimental data relating to the healthy system:
E ij =ε j (θ 0 ,x i ,y i 0 )− h 0i
calculating, with the ECU, a covariance matrix R 0 of an healthy improved residual matrix:
R 0 =cov( E )
wherein model parameters θ 0 , the bias h 0 and the covariance matrix R 0 are calculated only during the calibration phase.
3. The method for the diagnosis of the efficiency of the EGR cooler in the diesel engine as in claim 1 , wherein an estimation of the bias h 0 of the system follows:
h
0
=
E
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=
1
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k
=
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K
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ɛ
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θ
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k
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.
4. The method for the diagnosis of the efficiency of the EGR cooler in the diesel engine as in claim 1 , wherein the model for determining the temperature drop in the EGR cooler obeys:
T in −T out =k 1 ·T H 2 O ·( P exhaust −P intake ) k 2 ·T exhaust k 3 ·N eng k 4
where:
T in =temperature at the inlet of the EGR cooler,
T out =temperature at the outlet of the EGR cooler,
T H2O =coolant temperature,
P exhaust pressure at the outlet of the EGR cooler,
P intake =pressure at the inlet of the EGR cooler,
T exhaust =temperature at an exhaust of the EGR cooler, and
N eng =engine speed.
5. The method for the diagnosis of the efficiency of the EGR cooler in the diesel engine as in claim 4 , wherein the parameter vector θ (k 1 , k 2 , k 3 , k 4 ) is identified and validated from a set of steady state test bench measurements.
6. The method for the diagnosis of the EGR cooler in a Diesel engine as in claim 1 , wherein a distribution of values of the diagnostic index S is Gaussian and the statistical χ 2 (chi-square) distribution is used in order to define a diagnostic threshold index that univocally set the probability to find a EGR cooler fault.