Model-based monitoring for selective catalytic reduction device in aftertreatment assembly

A method for controlling operation of an aftertreatment assembly, the assembly including a selective catalytic reduction (SCR) device having a catalyst and configured to receive an exhaust gas, a reductant injector and a controller having a processor and a tangible, non-transitory memory, the method comprising:

• obtaining at least one estimated parameter, including obtaining an outlet nitrogen oxide (NOx) concentration (y1) in the exhaust gas exiting the SCR device, via the controller;
• obtaining at least one threshold parameter based at least partially on a catalyst degradation model, including obtaining a threshold NOx concentration (yT) in the exhaust gas exiting the SCR device, via the controller;
• wherein the catalyst degradation model is based at least partially on a predetermined threshold storage capacity (ΘT);
• determining a catalyst status based on a comparison of the at least one estimated parameter and the at least one threshold parameter, including comparing a first integration of the outlet NOx concentration over time (∫y1dt) and a second integration of the threshold NOx concentration over time (∫yTdt), and if the first integration exceeds the second integration (∫y1dt>∫yTdt), then generating a diagnostic signal, via the controller;
• and
• controlling operation of the assembly based at least partially on the catalyst status, via the controller.

An aftertreatment assembly comprising:

• a selective catalytic reduction (SCR) device having a catalyst and configured to receive an exhaust gas;
• a controller operatively connected to the SCR device, the controller having a processor and a tangible, non-transitory memory on which is recorded instructions for executing a method of model-based monitoring of the SCR device;
• wherein execution of the instructions by the processor causes the controller to:
• obtain at least one estimated parameter, including obtaining an outlet nitrogen oxide (NOx) concentration (y1) in the exhaust gas exiting the SCR device;
• obtain at least one threshold parameter based at least partially on a catalyst degradation model, including obtaining a threshold NOx concentration (yT) in the exhaust gas exiting the SCR device, the catalyst degradation model being based at least partially on a predetermined threshold storage capacity (ΘT);
• determine a catalyst status based on a comparison of the at least one estimated parameter and the at least one threshold parameter;
• and
• control operation of the assembly based at least partially on the catalyst status;
• wherein obtaining the at least one estimated parameter includes obtaining an estimated storage capacity (Θ) of the catalyst based at least partially on an extended Kalman filter and a capacity aging model;
• and
• wherein the capacity aging model is based at least partially on a sample time (k), the outlet NOx concentration (y1) of the exhaust gas exiting the SCR device, an outlet ammonia concentration (y2), an inlet NOx concentration (u1) of the exhaust gas entering the SCR device, an inlet dose (u2) injected by the reductant injector, a plurality of predetermined parameters (rR, rO, rD, rA), and a predetermined look-up factor (K(T, F/V)) of a flow rate (F) of the exhaust gas entering the SCR device, a volume (V) and a temperature (T) of the SCR device.