System and method for monitoring and detecting faults in a closed-loop system

A system for monitoring a tracking error signal indicative of a difference between a reference value of a variable of a closed-loop system to be controlled and a measured value of the variable being controlled and detecting faults in the closed-loop system, comprising:

• a first filter module adapted to receive the tracking error signal and filter the tracking error signal to isolate a band of frequency components impacted by deviation in the tracking error signal caused by a fault to be detected, said isolated band being a subband having less frequency components than a band of frequency components corresponding to the tracking error signal, the subband present in a bandwidth of a tracking error signal of a corresponding predetermined nominal version of the closed-loop system, and the subband having a cutoff frequency toward a lower end of the band of frequency components corresponding to the tracking error signal;
• a second filter module communicatively coupled with the first filter module and adapted to receive the filtered tracking error signal and generate an accumulated error signal from the filtered tracking error signal;
• and
• a fault processing module communicatively coupled with the second filter module and adapted to receive the accumulated error signal and compare the accumulated error signal with a stored predetermined fault threshold characteristic and provide an indication of fault in the closed-loop system if the accumulated error signal meets the predetermined fault threshold characteristic, said comparison based on a difference between spectral power of the subband of the filtered tracking error signal and spectral power of the subband present in the bandwidth of the tracking error signal of the corresponding predetermined nominal version of the closed-loop system.

An internal combustion engine system, comprising:

• an engine;
• an intake manifold connected to the engine;
• an intake body fluidly connected to the intake manifold, said intake body including a chamber through which charge air flows;
• an exhaust manifold connected to the engine;
• an exhaust gas recirculation (EGR) passage fluidly connected at one end thereof to the exhaust manifold and at another end thereof to the chamber of the intake body, wherein exhaust gas flow through said EGR passage is controlled by an EGR closed-loop system as a function of an exhaust flow tracking error signal;
• and
• a monitor for detecting faults in the EGR closed-loop system, said monitor including:
• a first filter element that receives the exhaust tracking error signal and filters the tracking error signal to isolate a band of frequency components impacted by deviation in the error signal caused by a fault to be detected and provide a filtered tracking error signal having the isolated frequency band, said isolated band being a subband having less frequency components than a band of frequency components corresponding to the tracking error signal, the subband present in a bandwidth of a tracking error signal of a corresponding predetermined nominal version of the closed-loop system, and the subband having a cutoff frequency toward a lower end of the band of frequency components corresponding to the tracking error signal;
• a second filter element communicatively coupled with the first filter element and adapted to receive the filtered tracking error signal and generate an accumulated error signal from the filtered tracking error signal;
• and
• a fault processing element communicatively coupled with the first filtering module and adapted to receive the accumulated error signal, compare the accumulated error signal with a stored predetermined fault threshold characteristic, and provide an indicator of fault in the closed-loop system if the accumulated error signal meets the predetermined threshold, said comparison based on a difference between spectral power of the subband of the filtered tracking error signal and spectral power of the subband present in the bandwidth of the tracking error signal of the corresponding predetermined nominal version of the closed-loop system.