Patent Description:
Internal combustion engines are used in various vehicles, mobile machines, and stationary machines to perform work or generate power by the combustion of a fuel, such as diesel fuel. The combustion of diesel fuel may produce pollutants such as unburned hydrocarbons, carbon monoxide, and nitrogen oxides (NOx). Exhaust systems including aftertreatment devices, such as oxidation or selective catalytic reduction (SCR) catalysts, reduce the amount of potentially harmful emissions that are produced by internal combustion engines. SCR catalysts, for example, catalyze a reaction of a reductant (e.g., urea, ammonia) with NOx that converts NOx to harmless compounds. Aftertreatment systems may include other aftertreatment devices, such as particulate filters, and/or a plurality of catalysts to further assist in the reduction of unwanted emissions.

Such aftertreatment systems may inject the reductant into the flow of exhaust upstream of the catalyst such that the reductant reacts with the NOx in the catalyst to achieve a desired or target conversion of the NOx. At relatively low exhaust temperatures, the reaction may be relatively slow and an amount of reductant may be stored in the catalyst to achieve the desired conversion. Conversely, at relatively high exhaust temperatures, the reaction may be relatively fast such that storage of the reductant is negligible and/or not necessary. Further, the dosing, or amount, of reductant injected into the flow of exhaust is controlled to achieve the desired conversion. However, current control systems may not adequately account for the various reaction speeds at various temperatures. Accordingly, current control systems may not provide an appropriate and/or necessary dosing amount for achieving the desired conversion of NOx at both the relatively low and relatively high temperatures.

<CIT> ("the '<NUM> patent"), describes a method of controlling an injector for injecting a reductant into a selective catalytic reduction system of an internal combustion engine. The method of the '<NUM> patent includes measuring a value of NOx concentration and a value of ammonia concentration in the exhaust gas downstream of the selective catalytic reduction system. The measures of NOx concentration and ammonia concentration are compared to predetermined reference values. The method of the '<NUM> patent calculates and controls the quantity of reductant to be injected by the injector based on differences between the measured values and the predetermined reference values. However, the '<NUM> patent may not adequately account for the various reaction speeds of the reductant and the NOx at the various temperatures, and thus the calculated quantity of reductant to be injected may not be appropriate and may include inaccuracies.

The reductant dosing control system of the present disclosure may solve one or more of the problems set forth above and/or other problems in the art. The scope of the current disclosure, however, is defined by the attached claims, and not by the ability to solve any specific problem.

In accordance with the present invention, a method and a control system in as set forth in claims <NUM> and <NUM> is provided. Preferred embodiments of the invention are claimed in the dependent claims.

In one aspect, a method for controlling a dosing of reductant for an internal combustion engine system including a catalyst is disclose. The method inter alia includes: measuring a value indicative of inlet temperature of the catalyst; when the inlet temperature is less than or equal to a first threshold, adjusting the dosing of reductant according to a first process; and when the inlet temperature is greater than the first threshold, adjusting the dosing of reductant according to a second process, the second process being different than the first process.

In another aspect, a control system for an internal combustion engine system is disclosed. The system inter alia includes: a catalyst configured to receive exhaust from an internal combustion engine; a sensor configured to produce a signal indicative of an inlet temperature of the catalyst; and a controller configured to: measure a value indicative of the inlet temperature of the catalyst; when the inlet temperature is less than or equal to a first threshold, adjust a dosing of reductant according to a first process; and when the inlet temperature is greater than the first threshold, adjust the dosing of reductant according to a second process, the second process being different than the first process.

Both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the features, as claimed. As used herein, the terms "comprises," "comprising," "has," "having," "includes," "including," or other variations thereof, are intended to cover a non-exclusive inclusion such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements, but may include other elements not expressly listed or inherent to such a process, method, article, or apparatus. In this disclosure, unless stated otherwise, relative terms, such as, for example, "about," "substantially," and "approximately" are used to indicate a possible variation of ±<NUM>% in the stated value.

<FIG> illustrates a schematic view of an engine system <NUM> having a reductant dosing control system <NUM>. Engine system <NUM> includes an engine <NUM>, such as an internal combustion engine. Engine <NUM> may include, for example, a diesel engine, a gasoline engine, a gaseous fuel-powered engine, a dual fuel engine (e.g., an engine capable of running on both gaseous fuel and/or liquid fuel), or any other type of engine known in the art. Operation of engine <NUM> may produce power and a flow of exhaust. For example, each combustion chamber (not shown) of engine <NUM> may mix fuel with air and combust the mixture therein to produce the flow of exhaust. The flow of exhaust may contain carbon monoxide, nitrogen oxide (NOx), carbon dioxide, aldehydes, soot, oxygen, nitrogen, water vapor, hydrocarbons, and/or other type of exhaust gases and/or particulates.

As shown in <FIG>, engine system <NUM> also includes an exhaust system <NUM> and a reductant dosing control system <NUM>. Exhaust system <NUM> includes one or more components including a reductant injector <NUM> and a catalyst <NUM>. Exhaust system <NUM> may also include a filter <NUM>, such as a diesel particulate filter (DPF), for removing particulates and other emissions from the flow of exhaust. Filter <NUM> may include any type of filter material, such as, for example, ceramics (e.g., cordierite), silicon carbides, ceramic fibers, metal fibers, or the like. Filter <NUM> may be located downstream of engine <NUM> and may capture particulates, ash (e.g., soot), or other materials from the exhaust gas to prevent their discharge into the surrounding environment. The one or more components of exhaust system <NUM> may by fluidly connected via one or more exhaust flow lines <NUM>. Accordingly, the flow of exhaust may be fluidly communicated from engine <NUM> to exhaust system <NUM> by flow lines <NUM>. Although not shown, it is understood that exhaust system <NUM> may include other components such as, for example, one or more turbochargers, and/or any other components known in the art for treating or handling exhaust.

Reductant injector <NUM> may be located downstream of filter <NUM>. Injector <NUM> may be connected to a reductant supply (not shown) and may inject reductant into the flow of exhaust in flow lines <NUM>. The reductant may include, for example, urea, urea and water, ammonia, and/or any other elements or compounds capable of chemically reducing compounds (e.g., NOx) contained in the exhaust in the presence of the catalyst <NUM>, as detailed further below. Injector <NUM> may include a nozzle (not shown), a valve (not shown), and/or other flow control device configured to assist in controllably releasing a flow of reductant from the reductant supply into the flow of exhaust from engine <NUM>. The nozzle and/or valve may be any type of injector known in the art and may include any device capable of inj ecting and/or atomizing an injected fluid. While the exemplary embodiment depicts injector <NUM> downstream of filter <NUM>, it is understood that injector <NUM> may also be located upstream of filter <NUM>.

Catalyst <NUM> may be located downstream of injector <NUM> and filter <NUM>. Catalyst <NUM> may include a selective catalytic reduction (SCR) catalyst. For example, catalyst <NUM> may include catalyst materials, such as, for example, various ceramic materials (e.g., titanium oxide), oxides of base metals (e.g., vanadium, molybdenum, and/or tungsten), zeolites (e.g., iron zeolite or copper zeolite), various precious metals, and/or any other type of catalyst materials known in the art. Accordingly, catalyst <NUM> may chemically reduce, or convert, the amount of NOx in the flow of exhaust when the reductant is injected into the flow of exhaust, as detailed further below.

While the exemplary embodiment includes an injector <NUM>, a catalyst <NUM>, and a filter <NUM>, it is understood that exhaust system <NUM> may also include one or more additional components. For example, exhaust system <NUM> may include a system for regenerating the filter <NUM> by removing the particulate matter trapped by the filter <NUM>, other catalytic devices, such as a diesel oxidation catalyst (DOC) and/or an ammonia oxidation (AMOX) catalyst, additional catalytic devices located upstream of filter <NUM>, other exhaust gas treatment devices, and/or any other components known in the art.

Reductant dosing control system <NUM> includes a controller <NUM>, such as an engine control module (ECM), and a sensor system <NUM> connected to controller <NUM>. Sensor system <NUM> may include one or more sensors for measuring temperature, pressure, flow rate, amount of reductant injected (e.g., dosing), and/or other operating characteristics of engine system <NUM> and/or exhaust system <NUM>. For example, sensor system <NUM> may include a temperature sensor <NUM>, a mass flow rate sensor <NUM>, an upstream NOx sensor <NUM>, and a downstream NOx sensor <NUM>. Temperature sensor <NUM> may be located in flow line <NUM> at, near, and/or adjacent an inlet of catalyst <NUM> and may sense or measure a temperature of exhaust gas entering catalyst <NUM>. It is understood that temperature sensor <NUM> may be located anywhere along flow line <NUM> between engine <NUM> and catalyst <NUM>, and may include any type of temperature sensor known in the art.

Mass flow rate sensor <NUM> may be located in flow line <NUM> and/or may be located at engine <NUM> and may sense a flow rate of exhaust gas from engine <NUM>. For example, mass flow rate sensor <NUM> may include a flowmeter that measures the amount of exhaust gas that passes through the flowmeter during a time period to determine the flow rate of the exhaust gas in flow line <NUM>. It is understood that mass flow rate sensor <NUM> may be located anywhere along flow line <NUM> and may include any type of flow sensor known in the art.

Upstream NOx sensor <NUM> may be located in flow line <NUM> downstream of engine <NUM> and upstream of catalyst <NUM>. While the exemplary embodiment depicts upstream NOx sensor <NUM> located upstream of injector <NUM>, it is understood that upstream NOx sensor <NUM> may be located anywhere between engine <NUM> and catalyst <NUM>. Downstream NOx sensor <NUM> may be located in flow line <NUM> downstream of catalyst <NUM>, such as at, near, and/or adjacent an outlet of catalyst <NUM> and/or at, near, and/or adjacent a tail pipe (not shown) of exhaust system <NUM>. It is understood that downstream NOx sensor <NUM> may be located anywhere in flow line <NUM> downstream of catalyst <NUM>. Upstream and downstream NOx sensors <NUM>, <NUM> may include sensors that are configured to generate a measured value that is indicative of NOx concentration at the location of the respective NOx sensor <NUM>, <NUM>. NOx sensors <NUM>, <NUM> may also be cross sensitive to ammonia such that each NOx sensor <NUM>, <NUM> is also configured to generate a measured value that is indicative of ammonia concentration at the location of the respective NOx sensor <NUM>, <NUM>. It is understood that NOx sensors <NUM>, <NUM> may include any type of sensor for measuring NOx concentration as known in the art. Further, sensor system <NUM> may include any number and/or combination of sensors as necessary.

Controller <NUM> may also be in communication with injector <NUM> for regulating and controlling reductant injection into flow line <NUM>. For example, controller <NUM> may control a valve of injector <NUM> for controlling a dosing of reductant into flow line <NUM>, as detailed further below. As used herein "dosing" of reductant includes an amount and/or flow rate of reductant from injector <NUM>. Controller <NUM> may also be in communication with components of engine <NUM> for controlling aspects of engine <NUM>.

<FIG> illustrates a schematic view of the exemplary reductant dosing control system <NUM> for operation and/or control of at least portions of engine system <NUM>. System <NUM> may include inputs <NUM>, controller <NUM>, and outputs <NUM>. Inputs <NUM> may include, for example, inlet temperature signal <NUM> from temperature sensor <NUM>, exhaust mass flow rate signal <NUM> from flow rate sensor <NUM>, upstream NOx concentration signal <NUM> from upstream NOx sensor <NUM>, and downstream NOx concentration signal <NUM> from downstream NOx sensor <NUM>. Inlet temperature signal <NUM> may be determined or derived by controller <NUM> based on the measured value from the temperature sensor <NUM>. Accordingly the inlet temperature signal <NUM> may provide a current temperature at the inlet of catalyst <NUM>.

Controller <NUM> may determine or otherwise derive a current mass flow rate of exhaust from engine <NUM> based on the received mass flow rate signal <NUM>. In some embodiments, mass flow rate sensor <NUM> may not be needed, or may be used in addition to deriving exhaust mass flow rate signal <NUM>. Accordingly, controller <NUM> may derive exhaust mass flow rate signal <NUM> based on one or more engine operating conditions, such as engine speed, mass flow rate of air entering the engine <NUM>, and/or a fueling ratio of the engine <NUM>. For example, a value indicative of exhaust mass flow rate may be proportional to engine speed and/or may derived from the mass flow rate of air entering the engine <NUM> and the fueling ratio of engine <NUM>.

Controller <NUM> may determine or otherwise derive an upstream NOx concentration and a downstream NOx concentration in the exhaust based on the upstream and downstream NOx concentration signals <NUM>, <NUM>, respectively, in addition to other parameters, such as the inlet temperature signal <NUM> and the exhaust mass flow rate signal <NUM>.

Outputs <NUM> may include, for example, a dosing command signal <NUM>. Controller <NUM> also includes a dosing control module <NUM>. Dosing control module <NUM> may receive inputs <NUM>, implement a method <NUM> for controlling the dosing of reductant and control outputs <NUM>, as described with reference to <FIG> below.

Controller <NUM> may embody a single microprocessor or multiple microprocessors that may include means for controlling a dosing of reductant for engine system <NUM>. For example, controller <NUM> may include a memory, a secondary storage device, and a processor, such as a central processing unit or any other means for accomplishing a task consistent with the present disclosure. The memory or secondary storage device associated with controller <NUM> may store data and/or software routines that may assist controller <NUM> in performing its functions, such as the functions of method <NUM> of <FIG>. Further, the memory or secondary storage device associated with controller <NUM> may also store data received from the various inputs <NUM> associated with reductant dosing control system <NUM>. Numerous commercially available microprocessors can be configured to perform the functions of controller <NUM>. It should be appreciated that controller <NUM> could readily embody a general machine controller capable of controlling numerous other machine functions. Various other known circuits may be associated with controller <NUM>, including signal-conditioning circuitry, communication circuitry, hydraulic or other actuation circuitry, and other appropriate circuitry.

Controller <NUM> may also include stored and/or derived values for use by dosing control module <NUM>. For example, the stored and/or derived values may include one or more temperature thresholds, one or more conversion ratio (CR) maps, one or more storage models, a desired storage, and one or more dosing maps. Controller <NUM> may use the one or more temperature thresholds to trigger one or more control methods for controlling the dosing of reductant based on the inlet temperature signal <NUM>, as detailed further below with respect to <FIG>. For example, the temperature thresholds may include a first temperature threshold for triggering a first control of the dosing, and a second temperature threshold for triggering a second control of the dosing. In some embodiments, the second threshold may be equal to or substantially similar to the first threshold. The CR maps may include one or more maps or lookup tables for providing a target NOx conversion as a function of temperature and mass flow rate of the exhaust gas. For example, controller <NUM> may receive temperature signal <NUM> and exhaust mass flow rate signal <NUM>, and determine the corresponding target NOx conversion based on the temperature and mass flow rate. The target NOx conversion may be a value of conversion of NOx in the catalyst <NUM>, as detailed further below.

The storage model may provide an actual, estimated, or predicted storage of reductant in catalyst <NUM>. The storage model may be a model of the actual, estimated, or predicted storage of reductant in catalyst <NUM> based on one or more current operating conditions, such as, for example, the exhaust temperature, exhaust mass flow rate, O<NUM> in the exhaust, and/or the current reductant dosing derived from current operating conditions and dosing maps, detailed below. The model may include a physics-based model that is based on one or more physical and/or chemical equations to estimate or predict the storage of reductant in the catalyst <NUM>. The model may be built and calibrated during testing of engine system <NUM>.

The desired, or target, storage is a desired or target value or amount of reductant to be stored in catalyst <NUM>. The desired storage may correspond to a desired amount of reductant that is absorbed by the catalyst <NUM> for achieving the target NOx conversion. For example, the desired storage may include one or more maps or lookup tables of desired storage as a function of inlet temperature and exhaust mass flow rate. The desired storage may be dependent, or otherwise may be adjusted based, on a difference between an actual or measured NOx conversion and the target NOx conversion, as detailed further below.

The dosing maps may include one or more maps or lookup tables for providing a dosing (e.g., amount and/or flow rate) of reductant from injector <NUM>. The dosing maps may include a normalized parameter that indicates how much reductant to be injected. For example, the dosing maps may include a reductant (e.g., ammonia) to NOx ratio as a function of inlet temperature and mass flow rate of the exhaust. For example, the inlet temperature and mass flow rate may be inputs for the maps, and the maps may output a reductant to NOx ratio. The controller <NUM> may then control the injector <NUM> to achieve the output reductant to NOx ratio. Thus, the dosing maps may provide a dosing based on inlet temperature and mass flow of the exhaust. The dosing may be adjusted based on the desired storage and/or based on the difference between the measured NOx conversion and the target NOx conversion, as detailed further below with respect to <FIG>. Thus, controller <NUM> may determine or otherwise derive the current dosing based on the dosing maps and/or the adjusted dosing.

Dosing command signal <NUM> output may include control of aspects of engine system <NUM>. Controller <NUM> may derive dosing command signal <NUM> based on the dosing maps, as detailed below. Dosing command signal <NUM> may be sent to injector <NUM> to control the position of the valve and/or nozzle of injector <NUM> to control the dosing of reductant into flow line <NUM>. Accordingly, a value indicative of the dosing of reductant may be proportional, or otherwise may correspond, to the position of the valve and/or nozzle of injector <NUM>.

The disclosed aspects of the reductant dosing control system <NUM> of the present disclosure may be used in any engine system <NUM> having an exhaust system <NUM> that utilizes a catalyst <NUM>.

Referring to <FIG>, during the operation of engine system <NUM>, exhaust may flow from engine <NUM> into exhaust system <NUM> via flow lines <NUM>. The exhaust may flow through filter <NUM> such that filter <NUM> removes particulates and other emissions from the flow of exhaust. Injector <NUM> may inject reductant into the flow of exhaust at a desired dosing, as detailed below. Reductant injected into the flow of exhaust by injector <NUM> may be absorbed on the catalyst <NUM> so that the reductant may react with NOx in the flow of exhaust to form H<NUM>O (e.g., water vapor) and N<NUM> (e.g., nitrogen gas). For example, a mixture of urea and water injected by the injector <NUM> may decompose to ammonia, and the catalyst <NUM> may facilitate a reaction between the ammonia and NOx in the flow of exhaust to produce water and nitrogen gas, thereby removing NOx from the flow of exhaust. After exiting catalyst <NUM>, the flow of exhaust may be output from the exhaust system <NUM>, and released into the atmosphere (e.g., through a tail pipe). Further, controller <NUM> may control the dosing of reductant into the flow of exhaust based on one or more variables. For example, at relatively low exhaust temperatures (e.g., less than <NUM>° C), the reaction of the reductant and NOx in the catalyst <NUM> may be relatively slow. Accordingly, the reductant may be stored (e.g., absorbed) in the catalyst <NUM> as needed to achieve a target NOx conversion. Thus, the controller <NUM> may use a closed control loop to adjust the dosing of reductant based on, for example, a desired storage of reductant (e.g., ammonia) in the catalyst <NUM>, as detailed further below.

However, at relatively high exhaust temperatures (e.g., greater than <NUM>° C), the reaction of reductant and NOx in the catalyst <NUM> may be relatively fast and/or substantially instantaneous. For example, the reaction of reductant and NOx in the catalyst <NUM> may occur substantially immediately, such that storage of reductant in the catalyst <NUM> is not necessary and/or may be negligibly low. Further, in embodiments where the injector <NUM> is located upstream of the filter <NUM>, upstream catalysts may migrate into the filter due to relatively high temperatures. The reductant may then oxidize in the filter, and thus there may be less reductant at the catalyst <NUM> to react with the NOx in the exhaust, leading to a degradation in overall performance of the exhaust system <NUM>. Accordingly, the closed control loop dependent on a desired storage, as described above, may provide inaccurate dosing and the control loop may not be properly closed when the exhaust temperature is relatively high.

<FIG> illustrates a flowchart depicting an exemplary method <NUM> for controlling a dosing of reductant for engine system <NUM> including a catalyst <NUM>. In step <NUM>, module <NUM> may receive sensor measurements from sensors <NUM>-<NUM>. For example, module <NUM> may receive inlet temperature signal <NUM>, exhaust mass flow rate signal <NUM>, and upstream NOx concentration signal <NUM>, downstream NOx concentration signal <NUM>.

In step <NUM>, module <NUM> may compare a measured NOx conversion to a target NOx conversion. For example, module <NUM> may determine the measured NOx conversion based on the measured values of the upstream NOx concentration and the downstream NOx concentration. The measured NOx conversion is a difference between the measured values of the upstream NOx concentration and the downstream NOx concentration. Accordingly, the measured NOx conversion is a value indicative of the amount of NOx that has actually been converted. The target NOx conversion is a value indicative of the amount of NOx that is intended to be converted. For example, the target NOx conversion may correspond to a desired amount of NOx safely leaving engine system <NUM>. Module <NUM> can determine the target NOx conversion based on the conversion ratio maps, as detailed above. Further, as used herein, NOx conversion may also refer to total NOx concentration downstream of catalyst <NUM> (e.g., as measured by downstream NOx sensor <NUM>), a NOx concentration in a tailpipe (not shown) of exhaust system <NUM> (e.g., as measured by another NOx sensor), or any other value and/or measurement indicative of NOx in the exhaust gas downstream of catalyst <NUM>.

In step <NUM>, module <NUM> may determine a difference between the measured NOx conversion and the target NOx conversion. The difference may indicate an error between the measured NOx conversion and the target NOx conversion. For example, the difference may indicate the measured NOx conversion is higher than the target NOx conversion (e.g., there is too much NOx conversion), and/or may indicate the measured NOx conversion is lower than the target NOx conversion (e.g., there is not enough NOx conversion). Module <NUM> may use the error to adjust the dosing of reductant from injector <NUM>, as detailed below, such that the measured NOx conversion ratio is equal to or substantially similar to the target NOx conversion ratio.

In step <NUM>, module <NUM> may determine whether the inlet temperature is less than or equal to a first threshold. For example, module <NUM> may compare the measured inlet temperature, as determined from inlet temperature signal <NUM>, to the first threshold. The first threshold may be a predetermined inlet temperature value for triggering a first control of the dosing of reductant, as detailed above. For example, the first threshold may be <NUM>° C, such that that first control is triggered at relatively low exhaust temperatures.

As detailed above, module <NUM> may perform a closed control loop for controlling and adjusting the dosing of reductant based on storage of reductant in the catalyst <NUM> at relatively low exhaust temperatures. Accordingly, in step <NUM>, when the inlet temperature is less than or equal to the first threshold (step <NUM>: YES), module <NUM> may adjust a desired storage of reductant in catalyst <NUM> based on the difference between the measured NOx conversion and the target NOx conversion. For example, if the measured NOx conversion is lower than the target NOx conversion, the desired storage may be increased. Similarly, if the measured NOx conversion is higher than the target NOx conversion, the desired storage may be decreased.

In step <NUM>, module <NUM> may adjust the dosing of reductant based on the adjusted desired storage. For example, module <NUM> may adjust the dosing such that the actual, estimated, or predicted storage of reductant in catalyst <NUM> is equal to or substantially similar to the adjusted desired storage. To do so, module <NUM> may determine the actual, estimated, or predicted storage based on the storage model, as detailed above, and compare the actual, estimated, or predicted storage of reductant to the adjusted desired storage. If the actual, estimated, or predicted storage is not equal to or substantially similar to the adjusted desired storage, module <NUM> may adjust the dosing of reductant from injector <NUM>. For example, module <NUM> may adjust the dosing such that the dosing makes the actual, estimated, or predicted storage equal to or substantially similar to the adjusted desired storage.

Accordingly, module <NUM> may adjust the dosing based on the difference between the actual, estimated, or predicted storage and the adjusted desired storage. For example, if the actual, estimated, or predicted storage is lower than the adjusted desired storage, the dosing may be increased. Similarly, if the actual, estimated, or predicted storage is higher than the adjusted desired storage, the dosing may be decreased. Thus, the first control of dosing is a closed control loop in that the difference (e.g., error) between the measured NOx conversion and the target NOx conversion provides a feedback signal that is used to adjust the desired storage. The difference (e.g., error) between the actual, estimated, or predicted storage and the adjusted desired storage provides another feedback signal that is then used to adjust the dosing. For example, the feedback signal of the difference in storage can be used to generate a feedback dosing that is added to and/or subtracted from the current dosing (e.g., as determined from the current operating conditions and the dosing maps). As such, module <NUM> may adjust the dosing based on the adjusted desired storage to generate dosing command signal <NUM> output and send the dosing command signal <NUM> to injector <NUM> to adjust the dosing.

In step <NUM>, if the inlet temperature is greater than the first threshold (step <NUM>: NO), module <NUM> may determine whether the inlet temperature is greater than or equal to a second threshold. For example, module <NUM> may compare the measured inlet temperature, as determined from inlet temperature signal <NUM>, to the second threshold. The second threshold may be a predetermined inlet temperature value for triggering a second control of the dosing of reductant, as detailed above. For example, the second threshold may be <NUM>° C, such that the second control is triggered at relatively high exhaust temperatures. While the exemplary embodiment depicts the first and second thresholds being different, it is understood that the first and second thresholds may be equal or substantially similar. Further, the first and second thresholds may include any value of temperature as necessary.

As detailed above, the closed control loop based on storage may not be appropriate and/or may not be totally closed at relatively high temperatures due to the reaction of reductant and NOx in the exhaust occurring relatively fast at relatively high temperatures. For example, the desired storage at high temperatures may be relatively low and/or substantially negligible regardless of the difference in the measured NOx conversion and the target NOx conversion. Therefore, the feedback of the error in NOx conversion into the desired storage at high temperatures may create or cause inaccuracies in the control loop such that the adjusted dosing may be inaccurate, inappropriate, or insufficient for achieving the target NOx conversion. Accordingly, in step <NUM>, when the inlet temperature is greater than the second threshold (step <NUM>: YES), module <NUM> may adjust the dosing of reductant based on the difference (e.g., error) between the measured NOx conversion and the target NOx conversion. For example, if the measured NOx conversion is lower than the target NOx conversion, module <NUM> may increase the dosing. Similarly, if the measured NOx conversion is higher than the target NOx conversion, module <NUM> may decrease the dosing. Thus, module <NUM> may adjust the dosing such that the measured NOx conversion is equal to or substantially similar to the target NOx conversion.

Accordingly, the second control of dosing is a closed loop in that that the difference (e.g., error) between the measured NOx conversion and the target NOx conversion provides a feedback signal that is used to adjust the dosing directly. For example, the feedback signal may be added, subtracted, multiplied, and/or divided to the current dosing (e.g., as determined from the current operating conditions and the dosing maps) to adjust the dosing. As such, module <NUM> may adjust the dosing based on the difference between measured and target NOx conversions to generate a dosing command signal <NUM> output and send the dosing command signal <NUM> to injector <NUM> to adjust the dosing. Therefore, the second control of dosing accounts for the negligible storage at high temperatures and closes the loop by not including the feedback into the desired storage.

When the first and second thresholds of temperature are different and the inlet temperature is between the first and second thresholds, module <NUM> weights the adjusted dosing from the first and second controls of dosing to adjust the dosing accordingly. As such, in step <NUM>, when the inlet temperature is less than the second threshold (step <NUM>: NO), module <NUM> determines a first dosing value based on the adjusted desired storage. For example, module <NUM> may determine the first dosing value by the first control of dosing, as detailed above. In step <NUM>, module <NUM> determines a second dosing value based on the difference between the measured and target NOx conversions. For example, module <NUM> may determine the second dosing value by the second control of dosing, as detailed above. In step <NUM>, module <NUM> applies a weighting factor to the first dosing value and the second dosing value. The weighting factor may be a value between zero and one and may correspond to a proportional amount the inlet temperature is from the first threshold and the second threshold. For example, the first dosing value may be weighted more or higher if the inlet temperature is closer to the first threshold than the second threshold. Likewise, the second dosing value may be weighted more or higher if the inlet temperature is closer to the second threshold. In step <NUM>, module <NUM> adjusts the dosing based on the weighted first and second dosing values. For example, the adjusted dosing may be a weighted average of the first dosing value and the second dosing value based on how close the inlet temperature is to the first threshold and/or the second threshold. If the inlet temperature is directly between the first threshold and second threshold (e.g., the inlet temperature is an average of the first threshold and the second threshold), the adjusted dosing may be an average of the first dosing value and the second dosing value.

Reductant dosing control system <NUM> may provide a robust closed loop control system for adjusting dosing of reductant in an exhaust system <NUM>. For example, reductant dosing control system <NUM> may include a first control of dosing at relatively low temperatures, and a second control of dosing at relatively high temperatures. Such a control system <NUM> may close the control loop at high temperatures when storage of reductant in the catalyst <NUM> is substantially negligible. Accordingly, the control system <NUM> of the present disclosure may provide a more accurate and/or appropriate adjustment of dosing to achieve target NOx conversions at high temperatures. Further, such a reductant dosing control system <NUM> may reduce or eliminate performance degradation due to the reductant reacting with catalyst material that may have migrated from an upstream catalyst component into the filter <NUM> when injector <NUM> is located upstream of filter <NUM>. For example, the module <NUM> may adjust the dosing accordingly to compensate for the reduced reductant in the flow of exhaust. Therefore, reductant dosing control system <NUM> can account for the various reaction speeds of reductant and NOx at various temperatures to more effectively and accurately adjust the dosing to achieve target NOx conversions.

Claim 1:
A method (<NUM>) for controlling a dosing of reductant for an internal combustion engine system (<NUM>) including a catalyst (<NUM>), the method comprising:
measuring a value indicative of inlet temperature of the catalyst (<NUM>);
determining (<NUM>) whether the inlet temperature is less than or equal to a first temperature threshold; and
upon determining that the inlet temperature is less than or equal to the first temperature threshold, adjusting (<NUM>, <NUM>) the dosing of reductant according to a first process, wherein the first process includes:
adjusting (<NUM>) a desired storage of reductant in the catalyst (<NUM>), wherein the desired storage is a target amount of reductant that is absorbed by the catalyst; and
adjusting (<NUM>) the dosing of reductant based on the adjusted desired storage; or
upon determining that the inlet temperature is greater than the first temperature threshold, adjusting the dosing of reductant according to a second process, wherein the second process includes:
adjusting (<NUM>) the dosing of reductant based on a difference between a measured value indicative of nitrogen oxide (NOx) conversion downstream of the catalyst and a target value of NOx conversion.