System and method for adaptive control of ammonia-NOx ratio

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 NH3 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.

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 NH3 sensor configured to detect NH3 present in the exhaust;
• and
• a controller configured to:
• receive signals output from the NOx sensor or from the NH3 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.