Patent ID: 8701388

Claim:
A method of controlling an exhaust treatment system having a particulate filter, a first selective catalytic reduction device and a second selective catalytic reduction device for reducing an amount of NOx in an exhaust gas passing through the exhaust treatment system, the first selective catalytic reduction device having a first activation temperature above which NOx is reduced in association with a first active volume of the first selective catalytic reduction device, the second selective catalytic reduction device having a second activation temperature that is greater than the first activation temperature and above which NOx is reduced in association with a second active volume of the second selective catalytic reduction device, the method comprising: providing an electronic control module configured to operate the exhaust treatment system in a cold start state, a low temperature state, and a high temperature state, the electronic control module further configured to determine a temperature of the exhaust gas and to control an injection of a reductant to the exhaust treatment system; and in the electronic control module: selectively determining based on the temperature of the exhaust gas and the first activation temperature and the second activation temperature, whether the exhaust treatment system is operating in the cold start state, the low temperature state, or the high temperature state, wherein the high temperature state is indicated when the temperature of the exhaust gas is greater than the second activation temperature, wherein the second low temperature state is indicated when the temperature of the exhaust gas is greater than the first activation temperature and less than the second activation temperature, and wherein the cold start state is indicated when the temperature of the exhaust gas is less than the first activation temperature; estimating a reductant dose; and controlling an injection of the reductant dose to the exhaust treatment system; wherein, if the control state is exhaust treatment system is operating in the cold start state, then said estimating is based on a temperature of a heater associated with the particulate filter; wherein, if the exhaust treatment system is operating in the low temperature state, then said estimating is based on the first active volume; and wherein, if the exhaust treatment system is operating in the high temperature state, then said estimating is based on the second active volume.