Method and device for dynamic monitoring of gas sensors

A device for dynamic monitoring of at least one gas sensor in one of an exhaust duct of an internal combustion engine or an air supply channel of the internal combustion engine to determine a fault status of the gas sensor during operation of the internal combustion engine, the gas sensor having a low-pass behavior depending on one of geometry, measuring principle, aging, or soiling, the device comprising:

• a detection unit for measuring, using the gas sensor during the operation of the internal combustion engine in response to an operator torque request, a change of a gas state variable to produce a measured signal, which represents an actual value of the selected gas state variable output by the gas sensor;
• and
• a diagnostic unit for performing a dynamic diagnosis during the operation of the internal combustion engine, wherein the diagnostic unit:
• checks for a sufficient excitation of the measured signal representing the gas state variable by comparing a steepness of a transition of a signal of an excitation model, the signal of the excitation model based on the operator torque request to a predetermined threshold value;
• upon detection of the sufficient excitation, places a high-pass filter in series with the gas sensor, the high-pass filter having a limit frequency lower than a predetermined limit frequency of the low pass behavior of the gas sensor when the gas sensor is properly functioning, to filter the measured signal and a modeled signal modeling the gas sensor to produce higher-frequency components of the measured signal and higher-frequency components of the modeled signal;
• squares, using a multiplier, and integrates, using an integrator, the higher-frequency components of the measured signal and higher-frequency components of the modeled signal to produce higher-frequency signal energy components of the measured signal and higher-frequency signal energy components of the modeled signal;
• compares the higher-frequency signal energy components of the measured signal to the higher frequency signal components of the modeled signal;
• determines a time constant of the sensor based on the comparing;
• and
• determines the fault status of the gas sensor as indicating a faulty state of the gas sensor based on the comparing indicating that a low-pass limit frequency of the low-pass behavior of the gas sensor has decreased below the limit frequency of the high-pass filter as a result of aging or soiling of the sensor;
• wherein the device regulates operation of the internal combustion engine as a function of the determined time constant.

A method for dynamic monitoring of at least one gas sensor of an internal combustion engine, the method comprising:

• measuring, using the gas sensor during the operation of the internal combustion engine in response to an operator torque request, a change of a gas state variable to produce a measured signal, which represents an actual value of the selected gas state variable output by the gas sensor;
• checking for a sufficient excitation of the measured signal representing the gas state variable by comparing a steepness of a transition of a signal of an excitation model, the signal of the excitation model based on the operator torque request, to a predetermined threshold value;
• upon detection of the sufficient excitation, performing a dynamic diagnosis of the gas sensor during the operation of the internal combustion engine, wherein the performing the dynamic diagnosis includes:
• modeling operation of the gas sensor to produce a modeled signal;
• comparing higher-frequency signal energy components of the measured signal to higher frequency signal energy components of the modeled signal;
• and
• determining a time constant of the sensor based on the comparing;
• and
• regulating operation of the internal combustion engine as a function of the determined time constant.