CN111980788A

CN111980788A - System and method for determining virtual ambient air temperature around an aftertreatment system

Info

Publication number: CN111980788A
Application number: CN202010421204.8A
Authority: CN
Inventors: 沙朗·S·索纳瓦尼; 普里扬卡·马杜卡·索万什; 西达尔特·巴斯卡尔
Original assignee: Cummins Emission Solutions Inc
Current assignee: Cummins Emission Solutions Inc
Priority date: 2019-05-21
Filing date: 2020-05-18
Publication date: 2020-11-24
Anticipated expiration: 2040-05-18
Also published as: CN111980788B

Abstract

The present application relates to systems and methods for determining a virtual ambient air temperature around an aftertreatment system. An aftertreatment system includes a selective catalytic reduction system, an outlet NOx sensor configured to measure an amount of NOx gases in an exhaust gas downstream of an aftertreatment component, an inlet exhaust gas temperature sensor, a feed temperature sensor, a coolant temperature sensor, and a reductant tank temperature sensor. A controller is operably coupled to each of the sensors and is configured to: in response to the virtual AAT determination criteria being met, a virtual AAT value is determined based on the feed temperature, the coolant temperature, the reductant agent temperature, and/or the inlet exhaust gas temperature. The controller determines a NOx sensor dew point delay timer for an outlet NOx sensor included in the aftertreatment system based on the virtual AAT value and the outlet exhaust gas temperature, and activates the outlet NOx sensor in response to the NOx sensor dew point delay timer being met.

Description

System and method for determining virtual ambient air temperature around an aftertreatment system

Technical Field

The present disclosure relates generally to aftertreatment systems for use with Internal Combustion (IC) engines.

Background

The exhaust aftertreatment system is configured to receive and treat exhaust gas (exhaust gas) produced by the IC engine. Typically, exhaust aftertreatment systems include any of several different components that reduce the level of harmful exhaust emissions present in the exhaust gas. For example, certain exhaust aftertreatment systems for diesel-powered IC engines include a Selective Catalytic Reduction (SCR) system including a catalyst prepared to react with ammonia (NH)₃) NOx (percentage of NO and NO) in the presence₂) Conversion to harmless nitrogen (N)₂) And water vapor (H)₂O). Typically, in such aftertreatment systems, an exhaust gas reductant (e.g., a diesel exhaust fluid, such as a urea solution) is injected into the SCR system to provide a source of ammonia and mixed with the exhaust gas to partially reduce the NOx gases. The reduced byproducts of the exhaust gas are then fluidly transferred to a catalyst included in the SCR system to decompose substantially all of the NOx gases into relatively harmless byproducts that are exhausted from the aftertreatment system.

In order to efficiently introduce (insert) the reducing agent into the aftertreatment system, it is desirable to measure the amount of NOx gases and/or ammonia in the exhaust gas. NOx sensors are used to measure the amount or level of NOx gases in the exhaust gas upstream and/or downstream of the SCR system. NOx sensors typically include sensing and/or heating elements, such as ceramic sensing and heating elements, encapsulated in a protective body (shield) or housing (case). In cold ambient conditions, water may condense on the sensing and heating elements in the form of water droplets. Opening or activating the NOx sensor before the condensed water evaporates can cause the sensing and/or heating elements to crack (crack) due to thermal stress. Therefore, it is desirable to ensure that water droplets are sensed and heated at the NOx sensor before activating the NOx sensorThe pieces are evaporated. In general, as to when to activate NO_XThe determination of the sensor is based on a physical Ambient Air Temperature (AAT) measured via an AAT sensor. Failure of a physical AAT sensor or unavailability of a physical AAT sensor may result in inaccurate determination of AAT, which may result in the NOx sensor being activated before reaching its dew point and cause the NOx sensor to malfunction.

SUMMARY

Embodiments described herein relate generally to systems and methods for determining a virtual AAT when physical measurements of the AAT are unavailable in an aftertreatment system or when a physical AAT sensor fails. The virtual AAT is used to determine a NOx sensor temperature dew point delay timer, and a NOx sensor included in the aftertreatment system is activated upon expiration of the NOx sensor temperature dew point delay timer.

In some embodiments, an aftertreatment system comprises: a selective catalytic reduction system configured to treat exhaust gas produced by an engine; an outlet NOx sensor configured to measure an amount of NOx gases in the exhaust gas downstream of the aftertreatment component; an inlet exhaust gas temperature sensor configured to measure an inlet exhaust gas temperature of exhaust gas flowing into the selective catalytic reduction system; a charge temperature sensor configured to determine a charge temperature of charge air (charge air) entering the engine; a coolant temperature sensor configured to determine a coolant temperature of coolant flowing through the engine; a reductant tank temperature sensor configured to determine a reductant temperature of a reductant stored in a reductant storage tank of the aftertreatment system; and a controller operatively coupled to each of the outlet NOx sensor, the inlet exhaust gas temperature sensor, the feed temperature sensor, the coolant temperature sensor, and the reductant tank temperature sensor, the controller configured to: in response to the virtual AAT determination criteria being met, determining a virtual AAT value based on the feed temperature, the coolant temperature, the reductant temperature, and/or the inlet exhaust gas temperature, estimating a NOx sensor dew point delay timer for an outlet NOx sensor included in the aftertreatment system based on the virtual AAT value and the outlet exhaust gas temperature, and activating the outlet NOx sensor in response to the NOx sensor dew point delay timer being met.

In some embodiments, a method for determining a virtual AAT external to an aftertreatment system coupled to an engine, comprises: determining, by a charge air temperature sensor, a charge air temperature of charge air entering the engine in response to the virtual AAT determination criterion being met; determining, by a coolant temperature sensor, a coolant temperature of a coolant flowing through an engine; determining, by a reductant tank temperature sensor, a reductant temperature of a reductant stored in a reductant storage tank of an aftertreatment system; determining an inlet exhaust gas temperature of exhaust gas entering the aftertreatment system by an inlet exhaust gas temperature sensor; and determining, by the controller, a virtual AAT value based on the feed air temperature, the coolant temperature, the reductant agent temperature, and/or the inlet exhaust gas temperature; estimating, using a controller, a NOx sensor dew point delay timer for a NOx sensor included in the aftertreatment system based on the virtual AAT value and the outlet exhaust gas temperature; and activating, using the controller, the NOx sensor in response to the NOx sensor dew point delay timer being met.

It should be understood that all combinations of the foregoing concepts and additional concepts discussed in greater detail below (assuming such concepts are not mutually inconsistent) are contemplated as being part of the inventive subject matter disclosed herein. In particular, all combinations that appear in the claimed subject matter of the present disclosure are contemplated as being part of the inventive subject matter disclosed herein.

Brief Description of Drawings

The foregoing and other features of the present disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only several embodiments in accordance with the disclosure and are, therefore, not to be considered limiting of its scope, the disclosure will be described with additional specificity and detail through use of the accompanying drawings.

Fig. 1A is a schematic diagram of an aftertreatment system, according to an embodiment.

FIG. 1B is a block diagram of an outlet NOx sensor that may be included in the aftertreatment system of FIG. 1A, according to an embodiment.

FIG. 2 is a schematic block diagram of a control module that may include a controller of the aftertreatment system of FIG. 1A, according to an embodiment.

3A-3B are schematic flow diagrams of methods for determining a virtual AAT and, thus, a NOx sensor dew point delay timer, according to embodiments.

Fig. 4A-4B are schematic flow diagrams of methods for determining a virtual AAT using a feed temperature, a coolant temperature, a reductant temperature of a reductant stored in a reductant storage tank, and/or an inlet exhaust gas temperature, according to embodiments.

Throughout the following detailed description, reference is made to the accompanying drawings. In the drawings, like reference numerals generally identify like components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not intended to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and make part of this disclosure.

Detailed Description

In order to efficiently introduce the reductant into the aftertreatment system, it is desirable to measure the amount of NOx gases and/or ammonia in the exhaust gas. NOx sensors are used to measure the amount or level of NOx gases in the exhaust gas upstream and/or downstream of the SCR system. The NOx sensor may include a ceramic sensing and/or heating element. In cold ambient conditions, water may condense on the sensing and heating elements in the form of water droplets. Opening or activating the NOx sensor before the condensed water evaporates may cause the sensing and/or heating elements to break due to thermal stress. Therefore, accurate determination of the dew point is necessary to protect the NOx sensor.

Typically, the NOx sensor dew point delay timer is determined using AAT via a physical AAT sensor and an outlet exhaust gas temperature sensor. The NOx sensor dew point delay timer corresponds to a time delay after which the NOx sensor is activated to ensure that the NOx sensor has reached the dew point prior to activation. For example, the dew point delay timer may include a counter having a time period determined based on AAT (e.g., a physical AAT or a virtual AAT as described herein). The dew point delay timer is started once the engine producing the exhaust gas is started, and the NOx sensor is activated once the dew point delay timer is over.

Failure of the physical AAT sensor or unavailability of the physical AAT sensor may result in inaccurate determination of the AAT and, thus, the NOx sensor dew point delay timer. For example, the sensing element and the heating element of the NOx sensor may be arranged inside the protective body or the sensor housing. The NOx sensor is disposed in the aftertreatment system such that the sensor housing is exposed to the exhaust gas. As the exhaust flows through the aftertreatment system, the sensor housing temperature reaches an exhaust temperature, which is typically above the dew point temperature at which water condensing on the sensing or heating element evaporates, and after a certain period of time, the sensing and heating elements of the NOx sensor rise to the exhaust temperature.

In some cases, there may be a temperature difference of greater than 100 degrees celsius or more between the outlet exhaust gas temperature and the sensing/heating element (e.g., when the engine is first started) such that the temperature of the outlet exhaust gas may be greater than the dew point, but the temperature of the sensing/heating element may still be below the dew point. If the NOx sensor is activated or turned on when the actual temperature of the NOx sensor sensing/heating element is less than the dew point, this may result in the NOx sensor sensing or heating element breaking, causing the sensing or heating element to fail, and thus causing the NOx sensor to fail. For example, the outlet exhaust gas temperature at the outlet of the SCR system may be 200-250 degrees Celsius, but the temperature of the sensing and heating elements of the NOx sensor may still be less than 100 degrees Celsius. If the NOx sensor is activated based on the outlet exhaust gas temperature before all of the water evaporates, the heating element is raised to a high operating temperature (e.g., up to 800 degrees Celsius), causing the water droplets condensed thereon to rapidly evaporate, causing localized thermal stress, and in some cases, causing the heating element to crack, causing the NOx sensor to fail.

In contrast, various embodiments of the systems and methods described herein may provide one or more benefits, including, for example: (1) allowing a virtual AAT value to be determined and used in place of a physical AAT value when the physical AAT sensor is unavailable or fails; (2) allowing accurate estimation of the NOx sensor dew point delay timer based on the virtual AAT and outlet exhaust gas temperature, thereby preventing breakage of the sensing or heating elements of the NOx sensor; and (3) reduce the failure rate of the NOx sensor, thereby reducing maintenance costs.

Fig. 1A is a schematic diagram of an aftertreatment system 100, according to an embodiment. Aftertreatment system 100 is coupled to engine 10 (e.g., a diesel engine, a gasoline engine, a natural gas engine, a biodiesel engine, a dual-fuel engine, an alcohol engine, E85, or any other suitable internal combustion engine) and is configured to receive exhaust gas (e.g., diesel exhaust gas) from engine 10. The aftertreatment system 100 is configured to reduce constituents of the exhaust gas, such as NOx gases (e.g., NO)₂、N₂O、NO₃Etc.), CO, etc. Aftertreatment system 100 may include a reductant storage tank 110, a reductant introduction assembly 120, a feed air manifold 130, and a coolant circulation system 140, and an SCR system 150. Although various embodiments of aftertreatment system 100 are described with respect to a diesel aftertreatment system including an SCR system, the concepts described herein are equally applicable to any other aftertreatment system including a NOx sensor (e.g., an aftertreatment system including a three-way catalyst, etc.).

The aftertreatment system 100 includes a housing 101 defining an interior volume. The housing 101 may be formed from a rigid, heat and corrosion resistant material, such as stainless steel, iron, aluminum, metal, ceramic, or any other suitable material. The housing 101 may have any suitable cross-section, such as circular, square, rectangular, oval, elliptical, polygonal, or any other suitable shape.

The SCR system 150 is positioned in an interior volume defined by the housing 101. The SCR system 150 includes an SCR catalyst 154 that is formulated to selectively decompose a component of the exhaust gas. The inlet exhaust gas temperature sensor 106 is disposed upstream of the SCR system 150 and is configured to determine a temperature of exhaust gas entering the SCR system 150.

Any suitable catalyst may be used as the SCR catalyst 154, such as, for example, a rhodium, cerium, iron, manganese, copper, vanadium based catalyst, any other suitable catalyst, or a combination thereof. The SCR catalyst 154 may be disposed on a suitable substrate, such as, for example, a ceramic (e.g., cordierite) or metal (e.g., chrome aluminum cobalt refractory steel (kanthal)) monolithic core, which may, for example, define a honeycomb structure. A coating (washcoat) may also be used as a support material for the SCR catalyst 154. Such coating materials may include, for example, alumina, titania, silica, any other suitable coating material, or combinations thereof. Exhaust gas (e.g., diesel exhaust) may flow over and/or around the SCR catalyst 154 such that any NOx gases included in the exhaust gas are further reduced to produce an exhaust gas that is substantially free of NOx gases. In some embodiments, the SCR system 150 may include a Selective Catalytic Reduction Filter (SCRF) system or any other aftertreatment component configured to decompose constituents of the exhaust gas flowing through the aftertreatment system 100 (e.g., NOx gases, such as nitrous oxide, nitric oxide, nitrogen dioxide, etc.) in the presence of a reductant, as described herein.

In some embodiments, a plurality of aftertreatment components may be positioned within the interior volume defined by the housing 101 in addition to the SCR system 150. Such aftertreatment components may include, for example, filters (e.g., particulate matter filters, catalytic filters, etc.), oxidation catalysts (e.g., carbon monoxide and/or hydrocarbon catalysts), mixers, baffles, or any other suitable aftertreatment components. In particular embodiments, the aftertreatment system 100 may include an ammonia oxidation (AMOx) catalyst positioned downstream of the SCR system 150 and configured to decompose unconsumed ammonia that leaks (slip) downstream of the SCR system 150.

An inlet conduit 102 is coupled to an inlet of the housing 101 and is configured to receive exhaust gases from the engine 10 and deliver the exhaust gases to an interior volume defined by the housing 101. Further, an outlet conduit 104 is coupled to an outlet of the housing 101 and is configured to discharge treated exhaust gas into the environment. An inlet NOx sensor 103 may be disposed in the inlet conduit 102 and configured to determine an amount of NOx gases included in the exhaust gas entering the aftertreatment system 100. In some embodiments, the inlet NOx sensor 103 may comprise a physical NOx sensor. In other embodiments, the inlet NOx sensor 103 may comprise a virtual NOx sensor. Although shown as including an inlet NOx sensor 103, in some embodiments, a pressure sensor, an oxygen sensor, or any other sensor configured to measure one or more exhaust gas parameters (e.g., temperature, pressure, flow rate, amount of NOx in the exhaust gas, etc.) may also be disposed in the inlet duct 102.

An outlet NOx sensor 105 may be positioned in the outlet duct 104 and configured to determine an amount of NOx gases in the exhaust gas emitted into the environment after passing through the SCR system 150. Further, an outlet temperature sensor 111 may also be disposed in the outlet conduit 104 and configured to measure an outlet exhaust gas temperature of the exhaust gas exiting the aftertreatment system 100. In other embodiments, one or more other sensors may also be disposed in the outlet conduit 104, such as a particulate matter sensor, an oxygen sensor, or any other sensor configured to determine one or more parameters of the exhaust gas being discharged into the environment via the outlet conduit 104.

In some embodiments, outlet NOx sensor 105 may include a sensing element and a heating element. For example, FIG. 1B shows a block diagram of an outlet NOx sensor 105 according to an embodiment. The outlet NOx sensor includes a housing 108 (e.g., a metal housing), with a sensing element 107 and a heating element 109 disposed within the housing 108. The sensing element 107 is configured to sense an amount (e.g., concentration) of NOx gases included in exhaust gas emitted from the aftertreatment system 100, and the heating element 109 is configured to heat the sensing element 107 to a predetermined temperature (e.g., greater than 300, 400, 500, 600, 700, or 800 degrees celsius, including 300, 400, 500, 600, 700, or 800 degrees celsius). In some embodiments, the inlet NOx sensor 103 may be similar in structure and function to the outlet NOx sensor 105. In other embodiments, the inlet NOx sensor 103 comprises a virtual sensor.

The reductant storage tank 110 is configured to store reductant. The reductant is formulated to facilitate decomposition of a component of the exhaust gas (e.g., NOx gases included in the exhaust gas). Any suitable reducing agent may be used. In some embodiments, the exhaust gas comprises diesel exhaust, and the reductant comprises a diesel exhaust treatment fluid. For example, the diesel exhaust fluid may include urea, an aqueous solution of urea, or any other fluid including ammonia, byproducts, or any other diesel exhaust fluid as known in the art (e.g., named as

Commercially available diesel exhaust treatment fluid). In a particular embodiment, the reductant comprises an aqueous urea solution having a particular ratio of urea to water. For example, the reductant may include an aqueous urea solution including 32.5% urea by volume and 67.5% deionized water by volume, or 40% urea by volume and 60% deionized water by volume. Reductant tank temperature sensor 116 is operatively coupled to reductant storage tank 110 and is configured to determine a reductant temperature of the reductant contained within reductant storage tank 110.

The reductant port 156 may be positioned on the inlet conduit 102 or the housing 101 and configured to allow introduction of reductant into the flow path of exhaust gas flowing through the aftertreatment system 100. The reductant introduction assembly 120 is fluidly coupled to the reductant storage tank 110. The reductant introduction assembly 120 is configured to selectively introduce reductant into the exhaust flow path through the reductant port 156. The reductant introduction assembly 120 may include a pump configured to pump a predetermined amount of reductant into the flow path of the exhaust gas. The pump may include, for example, a centrifugal pump, a suction pump (suction pump), a positive displacement pump, a diaphragm pump, or any other suitable pump.

A screen, check valve, pulsation damper, or other structure may also be positioned downstream of the pump to provide reductant to the exhaust. In various embodiments, reductant introduction assembly 120 may further include a mixing chamber configured to receive pressurized reductant at a controllable rate from a metering valve positioned downstream of the pump. The mixing chamber may also be configured to receive air or any other inert gas (e.g., nitrogen), for example, from an air supply unit to deliver a combined flow of air and reductant into the exhaust gas through the reductant port 156. In various embodiments, a nozzle may be disposed in the reductant port 156 and configured to deliver a stream (stream) or jet (jet) of reductant into the interior volume of the housing 101 to deliver the reductant into the exhaust gas.

In various embodiments, the reductant introduction assembly 120 may further include a dosing valve for selectively delivering reductant from the reductant introduction assembly 120 into the exhaust flow path. The dispensing valve may comprise any suitable valve, such as a butterfly valve, a gate valve, a check valve (e.g., a tilting disk check valve, a swinging check valve, an axial check valve, etc.), a ball valve, a spring-loaded valve, an air-assisted eductor, a solenoid valve, or any other suitable valve.

Intake manifold 130 is fluidly coupled to engine 10 and is configured to deliver intake air to a fuel induction system that may be included in engine 10. The fuel induction system may use the charge air to provide an air/fuel mixture to the engine 10. A feed temperature sensor 136 is coupled to the feed air manifold 130 and is configured to measure a temperature of the feed air flowing through the feed air manifold 130.

The coolant circulation system 140 is operatively coupled to the engine 10 and is configured to circulate coolant through the engine 10 (to cool the engine 10). A coolant temperature sensor 146 is operatively coupled to the coolant circulation system 140 and is configured to determine a temperature of the coolant.

Aftertreatment system 100 also includes a controller 170, and controller 170 may be operably coupled to the various sensors and components included in aftertreatment system 100 using any type and any number of wired or wireless connections. For example, the wired connection may include a serial cable, a fiber optic cable, a CAT5 cable, or any other form of wired connection. The wireless connection may include the internet, Wi-Fi, cellular, radio, bluetooth, ZigBee, and the like. In one embodiment, a Controller Area Network (CAN) bus provides for the exchange of signals, information, and/or data. The CAN bus includes any number of wired and wireless connections.

Controller 170 is operatively coupled to inlet NOx sensor 103, outlet NOx sensor 105, inlet exhaust gas temperature sensor 106, outlet exhaust gas temperature sensor 111, reductant tank temperature sensor 116, feed air temperature sensor 136, and coolant temperature sensor 146. Controller 170 may be configured to receive the inlet NOx amount signal from inlet NOx sensor 103 and determine an inlet NOx amount of NOx gases entering aftertreatment system 100. Further, the controller 170 may be configured to receive an outlet NOx amount signal from the outlet NOx sensor 105 and determine an amount of NOx gases included in the exhaust gas emitted from the aftertreatment system 100 after passing through the aftertreatment system 100.

In some embodiments, a vehicle or equipment including the aftertreatment system 100 may also include a physical AAT sensor 16, the physical AAT sensor 16 configured to physically measure AAT. The controller 170 may also be operably coupled to the physical AAT sensor and configured to determine the AAT based on the AAT signal received from the physical AAT sensor.

In some embodiments where physical AAT sensors 16 are available, the controller 170 may be configured to interpret physical AAT sensor signals received from the physical AAT sensors 16 and determine whether the physical AAT data provided by the AAT sensor signals is valid (e.g., whether the data is within a predetermined range). In response to the physical AAT data being valid, the controller 170 is configured to estimate the NOx sensor dew point delay timer based on the physical AAT data and the outlet exhaust gas temperature, for example, using an equation, algorithm, or look-up table. The NOx sensor dew point delay timer may correspond to a time delay to activate outlet NOx sensor 105 that allows outlet NOx sensor 105 to reach its dew point. Controller 170 may be configured to determine whether the NOx sensor dew point delay timer is met. The timer being satisfied may include the timer ending after running its determined period of time. In response to the NOx sensor dew point delay timer being met, controller 170 activates outlet NOx sensor 105.

For example, after the estimated NOx sensor dew point delay timer expires, controller 170 may activate heating element 109. Once exhaust gas begins to flow through the aftertreatment system 100, the NOx sensor dew point delay timer corresponds to an estimated period of time for the outlet NOx sensor 105 or the inlet NOx sensor 103 to reach its dew point or water boiling point. If the inlet NOx sensor 103 or the outlet NOx sensor 105 (e.g., the heating element 109 included in the outlet NOx sensor 105) is activated before the water condensed on the NOx sensor 103, 105 (e.g., on the heating element 109 or the sensing element 107) evaporates, the heating element 109 of the

NOx sensor

103, 105 may crack, causing the

NOx sensor

103, 105 to malfunction. Activating the NOx sensor after the estimated NOx sensor dew point delay timer is met ensures that any water condensed on the

NOx sensor

103, 105 has evaporated, thereby preventing the

NOx sensor

103, 105 from malfunctioning.

In response to the virtual AAT determination criteria being met, the controller 170 is configured to determine a virtual AAT in place of the physical AAT and use the virtual AAT to estimate the NOx sensor dew point delay timer. For example, the controller 170 may receive a feed temperature signal from the feed temperature sensor 136 and determine the feed temperature therefrom. Controller 170 may also receive a coolant temperature signal from coolant temperature sensor 146 of the coolant flowing through engine 10 and determine the coolant temperature therefrom. In addition, controller 170 receives a reductant temperature signal from reductant tank sensor 116 and an inlet exhaust temperature signal from inlet exhaust temperature sensor 106 and determines a reductant temperature and an inlet exhaust temperature, respectively, therefrom. The controller 170 is configured to determine a virtual AAT value based on the feed temperature, the coolant temperature, the reductant agent temperature, and/or the inlet exhaust gas temperature.

In some embodiments, the controller 170 may be programmed to determine that the virtual AAT determination criterion is satisfied when data from the physical AAT sensor is invalid or the physical AAT sensor (e.g., physical AAT sensor 16) is not present. For example, if a physical AAT sensor is not present (i.e., the vehicle or equipment comprising the aftertreatment system 100 does not include a physical AAT sensor), the controller 170 may be configured to continue to determine a virtual AAT by default. When a physical AAT sensor is present, if the physical AAT sensor data is invalid (e.g., corrupted, unreadable by the controller 170, outside a predetermined range, or has a signal-to-noise ratio (SNR) less than a threshold), the controller 170 may continue to determine the virtual AAT value.

In some embodiments, controller 170 is programmed to determine that the virtual AAT determination criteria are satisfied when the virtual AAT enable criteria are satisfied and the user criteria are satisfied. For example, the virtual AAT enable criteria being met may include the coolant temperature sensor state of the coolant temperature sensor 146 being valid, the feed temperature sensor state of the feed temperature sensor 136 being valid, the inlet exhaust gas temperature sensor state of the inlet exhaust gas temperature sensor 106 being valid, the reductant tank temperature sensor state of the reductant tank sensor 116 being valid, and the engine 10 being started. The controller 170 may be configured to determine whether the state of each respective sensor is valid (e.g., whether the output value of each of the

sensors

106, 116, 136, 146 is within a predetermined threshold, varies within a predetermined range, or has an SNR less than an SNR threshold). Further, the user criteria being met may include controller 170 receiving an instruction from a user for determining a virtual AAT and for using the virtual AAT and the outlet exhaust gas temperature to determine a NOx sensor dew point delay timer.

However, if the virtual AAT enable criteria are not met (e.g., sensor data received from one or more of the

sensors

106, 116, 136, 146 is invalid or the engine is off) or the user criteria are not met (e.g., the controller 170 receives an instruction from the user not to use the virtual AAT value instead of the physical AAT value), the controller 170 is configured to use the default AAT value as the virtual AAT value. The default AAT value may be a temperature value that protects the NOx sensor from premature activation before the sensing element (e.g., sensing element 107) and the heating element (e.g., heating element 109) of the NOx sensor reach the dew point. In particular embodiments, the default AAT value may be in the range of 20-30 degrees Celsius.

In response to each of the virtual AAT enable criteria and the user criteria being met, the controller 170 is configured to estimate a NOx sensor dew point delay timer based on the virtual AAT and the outlet exhaust gas temperature. As described above, the controller 170 is configured to determine the virtual AAT based on at least one of the feed temperature, the coolant temperature, the reductant agent temperature, and the inlet exhaust gas temperature.

In some embodiments, controller 170 may be configured to determine whether an aftertreatment system off time (off time) status is valid (e.g., the duration of time aftertreatment system 100 and thus controller 170 has been deactivated since the last shut down). In response to the aftertreatment system off time status being valid, controller 170 determines whether the aftertreatment system off time is equal to or greater than an aftertreatment system off time threshold (e.g., a predetermined off duration, such as 8 hours, sufficient to cool the coolant and reductant to AAT). In response to the aftertreatment system off time being equal to or greater than the aftertreatment system off time threshold, the controller 170 is configured to determine the virtual AAT as an average of the feed temperature, the reductant temperature, and the inlet exhaust temperature.

In response to at least one of the aftertreatment system off time status being invalid or the aftertreatment system off time being less than the aftertreatment system off time threshold, the controller 170 is configured to determine whether the coolant temperature is equal to or greater than a coolant temperature threshold (e.g., a temperature in the range of 30-40 degrees celsius). In response to the coolant temperature being equal to or greater than the coolant temperature threshold, the controller 170 is configured to determine the standard deviation of the feed temperature, the reductant agent temperature, and the inlet exhaust gas temperature. In response to the standard deviation being less than the standard deviation threshold, the controller 170 determines the virtual AAT value as an average of the feed temperature, the reductant agent temperature, and the inlet exhaust gas temperature. However, in response to the standard deviation being equal to or greater than the standard deviation threshold, the controller 170 determines the virtual AAT value as the minimum of the feed temperature, the reductant temperature, and the inlet exhaust gas temperature.

In response to the coolant temperature being less than the coolant temperature threshold, the controller 170 is configured to determine whether the minimum of the feed temperature, the reductant agent temperature, and the inlet exhaust gas temperature is equal to or greater than a cold start threshold (e.g., a predetermined temperature in the range of 10-20 degrees celsius). In response to the minimum value being equal to or greater than the cold start threshold, the controller 170 is configured to determine the virtual AAT value as the minimum of the feed temperature, the reductant agent temperature, and the inlet exhaust gas temperature. However, in response to the minimum value being less than the cold start threshold, the controller 170 is configured to determine whether the inlet exhaust gas temperature is equal to or greater than an inlet exhaust gas cold temperature threshold (e.g., a predetermined temperature in the range of zero degrees celsius to 5 degrees celsius). In response to the inlet exhaust gas temperature being less than the inlet exhaust gas cooling temperature threshold, the controller 170 is configured to determine the virtual AAT value as an average of the feed temperature, the reductant agent temperature, and the inlet exhaust gas temperature. Further, in response to the inlet exhaust gas temperature being equal to or greater than the inlet exhaust gas cooling temperature threshold, the controller 170 is configured to determine the virtual AAT value as an average of the feed temperature, the reductant agent temperature.

In particular embodiments, the controller 170 may be part of a control module. For example, fig. 2 is a schematic block diagram of a control circuit 171 including a controller 170 according to an embodiment. Controller 170 includes a processor 172, a memory 174 or any other computer-readable medium, and a communication interface 176. In addition, the controller 170 further includes a temperature determination circuit 174a, a physical AAT sensor signal verification circuit 174b, a virtual AAT determination circuit 174c, a NOx sensor dew point delay timer determination circuit 174d, and a NOx sensor activation circuit 174 e. It should be understood that the controller 170 illustrates only one embodiment of the controller 170, and that any other controller capable of performing the operations described herein may be used.

Processor 172 may include a microprocessor, a Programmable Logic Controller (PLC) chip, an ASIC chip, or any other suitable processor. The processor 172 is in communication with the memory 174 and is configured to execute instructions, algorithms, commands, or other programs stored in the memory 174.

Memory 174 includes any of the memory and/or storage components discussed herein. For example, memory 174 may include RAM and/or cache memory of processor 172. The memory 174 may also include one or more storage devices (e.g., hard disk drives, flash drives, computer-readable media, etc.) local or remote to the controller 170. The memory 174 is configured to store a look-up table, algorithm, or instructions.

In one configuration, the temperature determination circuit 174a, the physical AAT sensor signal validation circuit 174b, the virtual AAT determination circuit 174c, the NOx sensor dew point delay timer determination circuit 174d, and the NOx sensor activation circuit 174e are embodied as a machine or computer readable medium (e.g., a readable medium stored in memory 174) that is executable by a processor (e.g., processor 172). As described herein, a machine-readable medium (e.g., memory 174) facilitates performing certain operations to enable receiving and sending of data, among other uses. For example, a machine-readable medium may provide instructions (e.g., commands, etc.) to, for example, retrieve data. In this regard, the machine-readable medium may include programmable logic that defines a frequency of data acquisition (or data transmission). Thus, the computer-readable medium may include code, which may be written in any programming language, including but not limited to Java or the like and any conventional procedural programming languages, such as the "C" programming language or the like. The computer readable program code may be executed on one processor or on multiple remote processors. In the latter case, the remote processors may be connected to each other through any type of network (e.g., CAN bus, etc.).

In another configuration, the temperature determination circuit 174a, the physical AAT sensor signal verification circuit 174b, the virtual AAT determination circuit 174c, the NOx sensor dew point delay timer determination circuit 174d, and the NOx sensor activation circuit 174e are embodied as hardware units, such as electronic control units. Accordingly, the temperature determination circuit 174a, the physical AAT sensor signal validation circuit 174b, the virtual AAT determination circuit 174c, the NOx sensor dew point delay timer determination circuit 174d, and the NOx sensor activation circuit 174e may be embodied as one or more circuit components, including but not limited to processing circuits, network interfaces, peripherals, input devices, output devices, sensors, and the like.

In some embodiments, the temperature determination circuit 174a, the physical AAT sensor signal verification circuit 174b, the virtual AAT determination circuit 174c, the NOx sensor dew point delay timer determination circuit 174d, and the NOx sensor activation circuit 174e may take the form of one or more analog circuits, electronic circuits (e.g., Integrated Circuits (ICs), discrete circuits, system-on-a-chip (SOC) circuits, microcontrollers, etc.), telecommunications circuits, hybrid circuits, and any other type of "circuit. In this regard, the temperature determination circuit 174a, the physical AAT sensor signal verification circuit 174b, the virtual AAT determination circuit 174c, the NOx sensor dew point delay timer determination circuit 174d, and the NOx sensor activation circuit 174e may include any type of components for accomplishing or facilitating the effectuation of the operations described herein. For example, a circuit as described herein may include one OR more transistors, logic gates (e.g., NAND, AND, NOR, OR, XOR, NOT, XNOR, etc.), resistors, multiplexers, registers, capacitors, inductors, diodes, wiring, AND so forth.

Accordingly, the temperature determination circuit 174a, the physical AAT sensor signal verification circuit 174b, the virtual AAT determination circuit 174c, the NOx sensor dew point delay timer determination circuit 174d, and the NOx sensor activation circuit 174e may also include programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices, and the like. In this regard, the temperature determination circuit 174a, the physical AAT sensor signal verification circuit 174b, the virtual AAT determination circuit 174c, the NOx sensor dew point delay timer determination circuit 174d, and the NOx sensor activation circuit 174e may include one or more memory devices for storing instructions executable by the processors of the temperature determination circuit 174a, the physical AAT sensor signal verification circuit 174b, the virtual AAT determination circuit 174c, the NOx sensor dew point delay timer determination circuit 174d, and the NOx sensor activation circuit 174 e. The one or more memory devices and the processor may have the same definitions as provided below with respect to the memory 174 and the processor 172.

In the illustrated example, the controller 170 includes a processor 172 and a memory 174. The processor 172 and memory 174 may be constructed or configured to execute or implement the instructions, commands, and/or control processes described herein with respect to the temperature determination circuit 174a, the physical AAT sensor signal verification circuit 174b, the virtual AAT determination circuit 174c, the NOx sensor dew point delay timer determination circuit 174d, and the NOx sensor activation circuit 174 e. Thus, the depicted configuration represents the foregoing arrangement, wherein the temperature determination circuit 174a, the physical AAT sensor signal validation circuit 174b, the virtual AAT determination circuit 174c, the NOx sensor dew point delay timer determination circuit 174d, and the NOx sensor activation circuit 174e are embodied as machine or computer readable media. However, as mentioned above, this illustration is not meant to be limiting as the present disclosure contemplates other embodiments, such as the aforementioned embodiments in which the temperature determination circuit 174a, the physical AAT sensor signal verification circuit 174b, the virtual AAT determination circuit 174c, the NOx sensor dew point delay timer determination circuit 174d, and the NOx sensor activation circuit 174e, or at least one of the temperature determination circuit 174a, the physical AAT sensor signal verification circuit 174b, the virtual AAT determination circuit 174c, the NOx sensor dew point delay timer determination circuit 174d, and the NOx sensor activation circuit 174e, are configured as a hardware unit. All such combinations and variations are intended to fall within the scope of the present disclosure.

Processor 172 may be implemented as one or more general processors, Application Specific Integrated Circuits (ASICs), one or more Field Programmable Gate Arrays (FPGAs), Digital Signal Processors (DSPs), a set of processing elements, or other suitable electronic processing elements. In some embodiments, one or more processors may be shared by multiple circuits (e.g., the temperature determination circuit 174a, the physical AAT sensor signal validation circuit 174b, the virtual AAT determination circuit 174c, the NOx sensor dew point delay timer determination circuit 174d, and the NOx sensor activation circuit 174e may comprise or otherwise share the same processor, which in some example embodiments may execute instructions stored via different regions of memory or otherwise accessed instructions). Alternatively or additionally, one or more processors may be configured to perform certain operations independently of or otherwise in conjunction with one or more co-processors. In other example embodiments, two or more processors may be coupled via a bus to enable independent, parallel, pipelined, or multithreaded instruction execution. All such variations are intended to fall within the scope of the present disclosure. Memory 174 (e.g., RAM, ROM, flash memory, hard disk memory, etc.) may store data and/or computer code to facilitate the various processes described herein. Memory 174 may be communicatively connected to processor 172 to provide computer code or instructions to processor 172 for performing at least some of the processes described herein. Further, memory 174 may be or include tangible, non-transitory, volatile memory or non-volatile memory. Thus, memory 174 may include a database component, an object code component, a script component, or any other type of information structure for supporting the various activities and information structures described herein.

Communication interface 176 may include a wireless interface (e.g., jack, antenna, transmitter, receiver, communication interface, wired terminal, etc.) for communicating data with various systems, devices, or networks, e.g., using a CAN protocol such as J1939. In some embodiments, the communication interface 176 may include an ethernet card and port for sending and receiving data via an ethernet-based communication network and/or a Wi-Fi communication interface to communicate with the inlet NOx sensor 103, the outlet NOx sensor 105, the inlet exhaust gas temperature sensor 106, the outlet exhaust gas temperature sensor 111, the reductant tank temperature sensor 116, the feed air temperature sensor 136, the coolant temperature sensor 146, another controller (e.g., an engine control unit), and, in some embodiments, the physical AAT sensor 16 (when such sensors are available). Communication interface 176 may be configured to communicate via a local or wide area network (e.g., the internet, etc.) and may use various communication protocols (e.g., IP, LON, bluetooth, ZigBee, radio, cellular, near field communication, etc.).

The temperature determination circuit 174a is configured to receive the physical AAT sensor signal from the physical AAT sensor 16, the inlet exhaust gas temperature signal from the inlet exhaust gas temperature sensor 106, the reductant tank temperature signal from the reductant tank temperature sensor 116, the feed temperature signal from the feed temperature sensor 136, and the coolant temperature signal from the coolant temperature sensor 146 in embodiments where a physical AAT sensor is present. The controller 170 is configured to interpret these signals and thereby determine the physical AAT, inlet exhaust gas temperature, reductant agent temperature, feed air temperature, and coolant temperature, respectively.

The physical AAT sensor signal verification circuit 174b is configured to determine whether the physical AAT sensor signal is valid. For example, the physical AAT sensor signal verification circuitry 174b is configured to determine whether the physical AAT sensor signal is readable and undamaged, within a predetermined range, or has an acceptable SNR to determine its validity.

As previously described herein, the virtual AAT determination circuit 174c is configured to determine the virtual AAT in response to the physical AAT signal being invalid (e.g., unreadable or corrupted) or the physical AAT sensor not being present. Further, as previously described herein, the virtual AAT determination circuit 174c may be configured to determine the virtual AAT in response to the virtual AAT enable criteria and the user criteria being met. As previously described herein, the virtual AAT determination circuit 174c determines the virtual AAT based on at least one of the reductant agent temperature, the inlet exhaust gas temperature, the feed temperature, and the coolant temperature.

As previously described herein, the NOx sensor dew point delay timer determination circuit 174d is configured to estimate the NOx sensor dew point delay timer based on the determined virtual AAT value and the outlet exhaust gas temperature value. Further, the NOx sensor activation circuit 174e is configured to determine whether the estimated NOx sensor dew point delay timer is met (i.e., ended) and activate the NOx sensor (e.g., a heating element and a sensing element included in the NOx sensor) in response to the NOx sensor dew point delay timer being met.

Fig. 3A-3B are schematic flow diagrams of a method 200 for determining a virtual AAT of ambient air external to an aftertreatment system (e.g., aftertreatment system 100) including a NOx sensor (e.g., and/or outlet NOx sensor 105). Although described with respect to controller 170, method 200 may be performed with any other controller 170 or in any other post-processing system.

The method 200 includes interpreting 202 physical AAT sensor informationA number, such as a signal received from a physical AAT sensor. At 204, it is determined (e.g., by the controller 170) whether the physical AAT sensor data received from the physical AAT sensor signal is valid. In response to the physical AAT sensor data being valid (204: YES), method 200 includes, at 206, determining a NOx sensor dew point delay timer based on the physical AAT. At 208, method 200 determines that the NOx sensor dew point timer has reached or ended. In response to NO_XThe sensor dew point delay time ends and the NOx sensor is activated at 210.

If it is determined at 204 that the physical AAT sensor data is not valid (204: NO), the method proceeds to operation 212 and determines whether the virtual AAT enabling criteria are met and the user criteria are met as previously described herein. In response to at least one of the virtual AAT enable criteria or the user criteria not being met (212: no), the method 200 proceeds to operation 212 and a default value is used as the virtual AAT value (e.g., by the controller 170) as previously described herein. In response to each of the virtual AAT enable criteria and the user criteria being met (212: yes), at 216, a virtual AAT is determined (e.g., by controller 170) based on an inlet exhaust gas temperature (e.g., determined by inlet exhaust gas temperature sensor 106), a reductant temperature (e.g., determined by reductant tank temperature sensor 116), a feed air temperature (e.g., determined by feed air temperature sensor 136), and a coolant temperature (e.g., determined by coolant temperature sensor 146). At 218, a NOx sensor dew point delay timer is estimated based on the virtual AAT. The method 200 then proceeds to operation 208.

Fig. 4A-4B are schematic flow diagrams of a method 300 for determining a virtual AAT using a feed temperature, a coolant temperature, a reductant temperature of a reductant stored in a reductant storage tank, and/or an inlet exhaust gas temperature, according to an embodiment. Method 300 includes determining a coolant temperature (e.g., via coolant temperature sensor 146), a feed temperature (e.g., via feed temperature sensor 136), a reductant temperature (e.g., via reductant tank temperature sensor 116), and an inlet exhaust temperature (e.g., via inlet exhaust temperature sensor 106) at 302.

At 304, it is determined (e.g., by controller 170) whether the post-processing system off time status signal is valid, as previously described herein. If the off-time status is valid (304: Yes), then at 306, it is determined (e.g., by controller 170) whether an aftertreatment system off-time (e.g., a period of time during which aftertreatment system 100 is inactive or off) determined from the aftertreatment off-time value is greater than or equal to an aftertreatment system off-time threshold. In response to the aftertreatment system off time being greater than the aftertreatment system off time threshold (306: no), the method 300 proceeds to operation 308 and the virtual AAT value is determined as an average of the feed air temperature, the reductant agent temperature, and the inlet exhaust gas temperature. Then, at 310, a NOx sensor dew point delay timer is estimated based on the virtual AAT and the outlet exhaust gas temperature.

In response to the aftertreatment system off time status signal being invalid (304: no) or the aftertreatment off time being less than the aftertreatment system off time threshold (306: no), at 312, it is determined whether the coolant temperature is equal to or greater than the coolant temperature threshold as previously described herein. In response to the coolant temperature being equal to or greater than the coolant temperature threshold (312: yes), it is determined whether the standard deviation of the feed temperature, the inlet exhaust gas temperature, and the reductant agent temperature is equal to or greater than the standard deviation threshold. In response to determining that the standard deviation of any of the feed temperature, the inlet exhaust gas temperature, and the reductant agent temperature is less than the standard deviation (314: no), the method 300 proceeds to operation 308 and the method proceeds as previously described herein.

If it is determined that the standard deviation of the feed temperature, the inlet exhaust gas temperature, and the reductant agent temperature is equal to or greater than the standard deviation threshold, then at 316, the virtual AAT value is determined to be the minimum of the feed temperature and the reductant agent temperature. The method 300 then proceeds to operation 310.

If it is determined at operation 312 that the coolant temperature is less than the coolant temperature threshold (312: NO), the method 300 proceeds to operation 318 and determines whether the minimum of the charge temperature, the inlet exhaust gas temperature, and the reductant agent temperature is equal to or greater than a cold start threshold (e.g., a predetermined temperature of the exhaust gas when the engine 10 is cold started). In response to the minimum value being equal to or greater than the cold start threshold (318: yes), the method 300 proceeds to operation 316.

If it is determined that the minimum value is less than the cold start threshold (318: no), then at 320, it is determined whether the inlet exhaust gas temperature is equal to or greater than an inlet exhaust gas temperature threshold (e.g., the temperature of the exhaust gas entering the SCR system 150 at the time of a cold start of the engine 10). In response to determining that the inlet exhaust temperature is less than the inlet exhaust temperature threshold (320: no), the method 300 proceeds to operation 308. If it is determined that the inlet exhaust gas temperature is equal to or greater than the inlet exhaust gas temperature threshold (320: YES), then at 322, the virtual AAT value is determined as an average of the feed temperature and the reductant temperature. The method 300 then proceeds to operation 310.

It should be noted that the term "example" as used herein to describe various embodiments is intended to mean that such embodiment is a possible example, representation, and/or illustration of a possible embodiment (and such term is not intended to imply that such embodiment must be a particular or best example).

The term "coupled" and similar terms as used herein mean that two components are directly or indirectly joined to each other. Such joining may be fixed (e.g., permanent) or movable (e.g., removable or releasable). Such joining may be achieved with the two members or the two members and any additional intermediate members being integrally formed as a single unitary body with one another or with the two members or the two members and any additional intermediate members being attached to one another.

It is important to note that the construction and arrangement of the various exemplary embodiments are illustrative only. Although only a few embodiments have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter described herein. Further, it is to be understood that features from one embodiment disclosed herein may be combined with features of other embodiments disclosed herein, as would be understood by one of ordinary skill in the art. Other substitutions, modifications, changes and omissions may also be made in the design, operating conditions and arrangement of the various exemplary embodiments without departing from the scope of the present inventions.

While this specification contains many specific implementation details, these should not be construed as limitations on the scope of any invention or of what may be claimed, but rather as descriptions of features specific to particular implementations of particular inventions. In this specification, certain features that are described in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

Aspects of the disclosure may be implemented in one or more of the following embodiments.

1) An aftertreatment system, comprising:

a selective catalytic reduction system configured to treat exhaust gas produced by an engine;

an outlet NOx sensor configured to measure an amount of NOx gases in the exhaust gas downstream of the aftertreatment component;

an inlet exhaust gas temperature sensor configured to measure an inlet exhaust gas temperature of exhaust gas flowing into the selective catalytic reduction system;

a charge temperature sensor configured to determine a charge air temperature of charge air entering the engine;

a coolant temperature sensor configured to determine a coolant temperature of coolant flowing through the engine;

a reductant tank temperature sensor configured to determine a reductant temperature of a reductant stored in a reductant storage tank of the aftertreatment system; and

a controller operably coupled to each of the outlet NOx sensor, the inlet exhaust gas temperature sensor, the charge temperature sensor, the coolant temperature sensor, and the reductant tank temperature sensor, the controller programmed to, in response to a virtual ambient air temperature determination criterion being met:

determining a virtual ambient air temperature value based on the feed air temperature, the coolant temperature, the reductant agent temperature, and/or the inlet exhaust gas temperature,

estimating a NOx sensor dew point delay timer for the outlet NOx sensor included in the aftertreatment system based on the virtual ambient air temperature value and outlet exhaust gas temperature, an

Activating the outlet NOx sensor in response to the NOx sensor dew point delay timer being met.

2) The aftertreatment system of 1), wherein the outlet NOx sensor includes a sensing element and a heating element, and wherein activating the outlet NOx sensor includes activating the heating element.

3) The aftertreatment system of any one of 1) -2), wherein:

the aftertreatment system includes a physical ambient air temperature sensor, and

the controller is programmed to determine that the virtual ambient air temperature determination criteria are met when data from the physical ambient air temperature sensor is invalid.

4) The aftertreatment system of any one of 1) -3), wherein the controller is programmed to determine that the virtual ambient air temperature determination criterion is satisfied when a virtual ambient air temperature enable criterion is satisfied and a user criterion is satisfied.

5) The aftertreatment system of 4), wherein the controller is programmed to determine that the virtual ambient air temperature enable criteria are met when:

a coolant temperature sensor state of the coolant temperature sensor is active;

the feeding temperature sensor state of the feeding temperature sensor is effective;

an inlet exhaust gas temperature sensor state of the inlet exhaust gas temperature sensor is valid;

the reducing agent tank temperature sensor of the reducing agent tank temperature sensor is in an effective state; and

the engine is started.

6) The aftertreatment system of 4) or 5), wherein the controller is configured to use a default ambient air temperature value stored in a memory of the controller as the virtual ambient air temperature value in response to at least one of the virtual ambient air temperature enable criterion or the user criterion not being met.

7) The aftertreatment system of any of 1) -6), wherein the NOx sensor dew point delay timer corresponds to a time delay in activating the outlet NOx sensor that allows the outlet NOx sensor to reach the outlet NO_XThe dew point of the sensor.

8) The aftertreatment system of any one of 1) -7), wherein the controller is configured to:

determining whether the aftertreatment system off time status is valid,

in response to the aftertreatment system off time status being valid, determining whether an aftertreatment system off time is equal to or greater than an aftertreatment system off time threshold, an

In response to the aftertreatment system off time being equal to or greater than the aftertreatment system off time threshold, determining the virtual ambient air temperature value as an average of the feed air temperature, the reductant agent temperature, and the inlet exhaust gas temperature.

9) The aftertreatment system of 8), wherein the controller is configured to:

determining whether the coolant temperature is equal to or greater than a coolant temperature threshold in response to at least one of the aftertreatment system off time status being invalid or an aftertreatment system off time being less than the aftertreatment system off time threshold,

determining a standard deviation of the feed air temperature, the reductant agent temperature, and the inlet exhaust gas temperature in response to the coolant temperature being equal to or greater than the coolant temperature threshold, an

In response to the standard deviation being less than a standard deviation threshold, determining the virtual ambient air temperature value as an average of the feed air temperature, the reductant agent temperature, and the inlet exhaust gas temperature.

10) The aftertreatment system of 9), wherein the controller is configured to:

in response to the standard deviation being equal to or greater than the standard deviation threshold, determining the virtual ambient air temperature value as the minimum of the feed air temperature, the reductant agent temperature, and the inlet exhaust gas temperature.

11) The aftertreatment system of 9), wherein the controller is configured to:

in response to the coolant temperature being less than the coolant temperature threshold, determining whether a minimum of the feed air temperature, the reductant agent temperature, and the inlet exhaust gas temperature is equal to or greater than a cold start threshold, an

In response to the minimum value being equal to or greater than the cold start threshold, determining the virtual ambient air temperature value as the minimum of the feed air temperature, the reductant agent temperature, and the inlet exhaust gas temperature.

12) The aftertreatment system of 11), wherein the controller is further configured to:

in response to the minimum value being less than the cold start threshold, determining whether the inlet exhaust gas temperature is equal to or greater than an inlet exhaust gas cold temperature threshold, an

In response to the inlet exhaust gas temperature being less than the inlet exhaust gas cold temperature threshold, determining the virtual ambient air temperature value as an average of the feed air temperature and the reductant agent temperature.

13) The aftertreatment system of claim 12), wherein the controller is further configured to:

determining the virtual ambient air temperature value as an average of the feed air temperature, the reductant agent temperature, and the inlet exhaust gas temperature in response to the inlet exhaust gas temperature being equal to or greater than the inlet exhaust gas cooling temperature threshold.

14) A method for determining an ambient air temperature external to an aftertreatment system coupled to an engine, the method comprising:

determining, by a charge temperature sensor, a charge air temperature of charge air entering the engine in response to a virtual ambient air temperature determination criterion being met;

determining, by a coolant temperature sensor, a coolant temperature of a coolant flowing through the engine;

determining, by a reductant tank temperature sensor, a reductant temperature of a reductant stored in a reductant storage tank of the aftertreatment system;

determining, by an inlet exhaust gas temperature sensor, an inlet exhaust gas temperature of exhaust gas entering the aftertreatment system;

determining, using a controller, a virtual ambient air temperature value based on the feed air temperature, the coolant temperature, the reductant agent temperature, and/or the inlet exhaust gas temperature;

estimating, using the controller, a NOx sensor dew point delay timer for a NOx sensor included in the aftertreatment system based on the virtual ambient air temperature value and an outlet exhaust gas temperature; and

activating the NOx sensor using the controller in response to the NOx sensor dew point delay timer being met.

Claims

1. An aftertreatment system, comprising:

2. The aftertreatment system of claim 1, wherein the outlet NOx sensor includes a sensing element and a heating element, and wherein activating the outlet NOx sensor includes activating the heating element.

3. The aftertreatment system of any one of claims 1-2, wherein:

4. The aftertreatment system of any one of claims 1-3, wherein the controller is programmed to determine that the virtual ambient air temperature determination criterion is satisfied when a virtual ambient air temperature enabling criterion is satisfied and a user criterion is satisfied.

5. The aftertreatment system of claim 4, wherein the controller is programmed to determine that the virtual ambient air temperature enable criteria are met when:

a coolant temperature sensor state of the coolant temperature sensor is active;

the engine is started.

6. The aftertreatment system of claim 4 or 5, wherein the controller is configured to use a default ambient air temperature value stored in a memory of the controller as the virtual ambient air temperature value in response to at least one of the virtual ambient air temperature enable criterion or the user criterion not being met.

7. The aftertreatment system of any of claims 1-6, wherein the NOx sensor dew point delay timer corresponds to a time delay in activating the outlet NOx sensor that allows the outlet NOx sensor to reach the outlet NO_XThe dew point of the sensor.

8. The aftertreatment system of any one of claims 1-7, wherein the controller is configured to:

determining whether the aftertreatment system off time status is valid,

9. The aftertreatment system of claim 8, wherein the controller is configured to:

10. The aftertreatment system of claim 9, wherein the controller is configured to:

11. The aftertreatment system of claim 9, wherein the controller is configured to:

12. The aftertreatment system of claim 11, wherein the controller is further configured to:

13. The aftertreatment system of claim 12, wherein the controller is further configured to:

14. A method for determining an ambient air temperature external to an aftertreatment system coupled to an engine, the method comprising: