Patent ID: 8386204

Claim:
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.