System and method for adaptive control of ammonia-NOx ratio
An ammonia to NOx ratio (ANR) control system includes an internal combustion engine configured to combust fuel, a valve configured to provide the fuel to the internal combustion engine, and a selective catalytic reduction (SCR) catalyst connected to the internal combustion engine to receive exhaust generated by combustion of the fuel with the internal combustion engine. The system also includes a reductant injector configured to inject reductant for the SCR catalyst, a sensor connected downstream of the SCR catalyst, and a controller. The controller may be configured to: receive NOx level signals or NH 3 level signals from the sensor, generate commands for controlling the reductant injector, and determine, with a perturbation-based control algorithm and based on the NOx or NH 3 level signals, commands for controlling the reductant injector.
1 . An ammonia to NOx ratio (ANR) control system, comprising:
an internal combustion engine configured to combust fuel;
a valve configured to provide the fuel to the internal combustion engine;
a selective catalytic reduction (SCR) catalyst connected to the internal combustion engine to receive exhaust generated by combustion of the fuel with the internal combustion engine;
a reductant injector configured to inject reductant for the SCR catalyst;
a sensor connected downstream of the SCR catalyst; and
a controller configured to:
receive NOx level signals or NH 3 level signals from the sensor,
generate commands for controlling the reductant injector, and
determine, with a perturbation-based control algorithm that employs extremum-seeking control and based on the NOx or NH 3 level signals, commands for controlling the reductant injector for adjusting a position of the reductant injector according to the extremum-seeking control performed with the controller.
2 . The ANR control system of claim 1 , wherein the perturbation-based control algorithm generates commands for maximizing an objective function.
3 . The ANR control system of claim 1 , wherein the perturbation-based control algorithm generates commands for maximizing an objective function.
4 . The ANR control system of claim 1 , further including a temperature sensor configured to detect a temperature associated with the exhaust, the controller being further configured to enable the perturbation-based control algorithm in response to the detected temperature exceeding a threshold temperature.
5 . The ANR control system of claim 4 , wherein the controller is further configured to disable the perturbation-based algorithm when the detected temperature is below the threshold temperature.
6 . The ANR control system of claim 1 , wherein the perturbation-based control algorithm generates a first adjustment that causes an increase in the ANR and a second adjustment that causes a decrease in the ANR, adjustments being made in a repeating manner to cause fluctuations in the ANR.
7 . The ANR control system of claim 1 , wherein the perturbation-based control algorithm causes fluctuations in an amount of reductant injected with the reductant injector.
8 . A method for controlling an ammonia-NOx ratio (ANR) for an internal combustion engine, the method comprising:
receiving a first signal from a sensor, the sensor being a NOx sensor or an NH 3 sensor;
determining a first command for a reductant injector based on the first signal;
adjusting the first command;
controlling the reductant injector based on the adjusted first command;
receiving a second signal from the sensor;
determining a second command for the reductant injector based on the second signal;
adjusting the second command via an algorithm that seeks an objective by making adjustments to commanded reductant injections; and
controlling the reductant injector based on the adjusted second command, the adjustments to the first command and to the second command causing repeating variations in an amount of reductant injected via the reductant injector according to adjustments to the commanded reductant injections that are associated with the objective.
9 . The method of claim 8 , wherein the repeating variations are generated as part of an extremum-seeking control algorithm.
10 . The method of claim 8 , wherein the first command corresponds to a desired ANR, the adjustment to the first command causing a deviation from the desired ANR.
11 . The method of claim 8 , wherein the first command corresponds to a desired ANR, the adjustment to the first command causing a deviation from the desired ANR by an amount, a magnitude of the amount being based on an objective function or on a cost function.
12 . The method of claim 8 , wherein the first adjustment increases the ANR associated with the first command and the second adjustment decreases the ANR associated with the second command.
13 . The method of claim 8 , wherein the repeating variations are associated with a sinusoidal perturbation.
14 . The method of claim 8 , wherein the adjustments to at least one of the first command or the second command cause changes to the ANR in response to the internal combustion engine receiving a different fuel type.
15 . A system for controlling an ammonia to NOx ratio (ANR) for an internal combustion engine, the system comprising:
an internal combustion engine configured to combust gaseous fuel;
an admission valve for providing the gaseous fuel to the internal combustion engine;
a catalyst connected to the internal combustion engine to receive exhaust formed by combustion of the gaseous fuel with the internal combustion engine;
a NOx sensor configured to detect oxygen present in the exhaust or an NH 3 sensor configured to detect NH 3 present in the exhaust; and
a controller configured to:
receive signals output from the NOx sensor or from the NH 3 sensor,
generate commands for controlling the admission valve,
determine a desired ANR, and
adjust the desired ANR by generating an adjusted ANR command that is above or that is below the desired ANR as part of an adaptive control strategy that generates fluctuations that change a magnitude and a sign of the adjusted ANR command.
16 . The system of claim 15 , wherein the adaptive control strategy employs extremum seeking control.
17 . The system of claim 15 , further including a temperature sensor, wherein the controller is further configured to transition from a mode in which the adaptive control strategy is enabled to a mode in which the adaptive control strategy is disabled based on temperature detected with the temperature sensor.
18 . The system of claim 15 , wherein the controller is further configured to employ proportional-integral control or proportional-integral-derivative control when the adaptive control strategy is disabled.
19 . The system of claim 15 , wherein the controller is further configured to employ proportional-integral control or proportional-integral-derivative control when a temperature associated with the catalyst is below a threshold temperature.
20 . The system of claim 15 , wherein the adaptive control strategy is configured to reduce a magnitude by which the adjusted ANR command is above or below the desired ANR based on an objective function or a cost function.