NH3 slip detection using a NOx sensor

Abstract

A method for NH3 slip detection using a system output NOx sensor (150), comprising: Accessing a temperature value for a catalyst (106); if the temperature value for the catalyst (106) exceeds a predetermined temperature value and one or more first preconditions are met: Accessing a plurality of system output NOx measurement signals from the system output NOx sensor (150) located downstream of the catalyst (106), Determine a variety of estimated system output NOx values, Calculating a plurality of delta values ​​over a first predetermined period of time based on the system output NOx measurement signals and the estimated system output NOx values, and Setting a flag indicating NH3 slip for an exhaust system (190) in response to an average of the plurality of delta values ​​exceeding a first predetermined value; and if the temperature value for the catalyst (106) is below the predetermined temperature value and one or more second preconditions are met: Accessing a plurality of system output NOx measurement signals over a second predetermined period of time, Calculating an average of the plurality of system output NOx measurement signals, and Setting the flag indicating NH3 slip for the exhaust system (190) in response to the calculated average of the plurality of system output NOx measurement signals exceeding a second predetermined value.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 62 / 355,708, filed June 28, 2016, the contents of which are incorporated herein by reference in their entirety. TECHNICAL FIELD

[0002] The present application generally relates to the field of aftertreatment systems for internal combustion engines. BACKGROUND

[0003] In internal combustion engines, such as diesel engines, nitrogen oxide compounds (NOx compounds) can be released into the exhaust gas. To reduce NOx emissions, an SCR process can be used to convert the NOx compounds into neutral compounds such as diatomic nitrogen, water, or carbon dioxide with the help of a catalyst and a reducing agent. The catalyst can be contained in a catalyst chamber of an exhaust system, for example of a vehicle or a power generation unit. A reducing agent, such as ammonia anhydride or urea, is usually introduced into the exhaust stream upstream of the catalyst chamber. To introduce the reducing agent for the SCR process into the exhaust stream, an SCR system can meter or otherwise introduce the reducing agent through a dosing module that vaporizes or sprays the reducing agent into an exhaust pipe of the exhaust system upstream of the catalyst chamber.The SCR system may include one or more sensors to monitor conditions within the exhaust system.

[0004] From US 2015 / 0 218 993 A1 an exhaust gas treatment system is known which comprises a catalytic device configured to receive an exhaust gas flow and an injector upstream of the catalytic device in an exhaust gas flow direction which injects a reducing agent into the exhaust gas flow.

[0005] A controller is configured to determine a change in the amount of NOx and a change in the amount of reductant downstream of the catalytic device due to a change in the amount of reductant injected by the injector. The controller is configured to determine a slip factor corresponding to a relative weight of a NOx slip rate exiting the catalytic device compared to a reductant slip rate exiting the catalytic device, and to determine a dosing command to provide to the injector based at least in part on the slip factor and the change in the amount of NOx and the change in the amount of reductant downstream of the catalytic device.

[0006] EP 2 187 009 A2 discloses an exhaust gas treatment system comprising a selective catalytic reduction catalyst and a dosing controller responsive to exhaust gas operating conditions to control the dosing rate of a reducing agent, such as aqueous urea, into the exhaust stream. The dosing controller is configured to reduce the dosing rate when either a sudden increase in exhaust mass air flow is detected or when an exhaust temperature gradient is in a rising state. The dosing controller is also configured to interrupt dosing when the measured ammonia concentration exceeds an ammonia threshold, provided the exhaust temperature gradient is also in a rising state.

[0007] From US 2013 / 0 064 717 A1, an engine exhaust gas purification device is known, comprising: a selective reduction type NOx catalyst; an oxidation catalyst arranged on an upstream side of the NOx catalyst; a reducing agent adding device that adds a NOx reducing agent to an exhaust gas of an engine; a control device that controls the reducing agent adding device; and a NO2 ratio calculating device that estimates an NO2 ratio of the exhaust gas flowing into the NOx catalyst.The NO2 ratio of the exhaust gas flowing into the NOx catalyst is calculated using a catalytic reaction model that numerically models the oxidation reaction of NO in the oxidation catalyst. The NO2 ratio is reflected to calculate the amount of ammonia adsorbed on the NOx catalyst using a catalytic reaction model that numerically models a chemical reaction related to the reduction of NOx in the NOx catalyst. US 2011 / 0 185 707 A1 discloses a method for determining NH3 and NOx slip through an SCR catalyst. For this purpose, signals from NOx sensors located upstream and downstream of an SCR catalyst are processed and provide information on NH3 and NOx slip. The information provided by NOx sensors can be used to reduce engine emissions, at least under certain conditions. DEPICTION

[0008] The implementations described here refer to NH3 slip detection using a system output NOx sensor.

[0009] One implementation relates to a method for detecting NH3 slip using a system output NOx sensor. The method includes accessing a temperature value of a catalyst, determining that the temperature value of the catalyst exceeds a predetermined value, determining that one or more preconditions are met, accessing a system output NOx measurement signal from the system output NOx sensor, determining an estimated system output NOx value, calculating a delta value based on the system output NOx measurement signal and the estimated system output NOx value, and setting a flag indicative of NH3 slip for an exhaust system in response to an average of delta values, including the calculated delta value, exceeding a predetermined value for a predetermined period of time.

[0010] In some implementations, the one or more preconditions include determining a correlation between the system output NOx measurement signal and an engine output NOx measurement signal. In some implementations, the one or more preconditions include determining that an engine or idle event has not occurred. In some implementations, the one or more preconditions include the system output NOx measurement signal exceeding a predetermined value. In some implementations, determining the estimated system output NOx value is based on a filtered system output NOx measurement signal from the system. In some implementations, the predetermined temperature value is 300 degrees Celsius. In some implementations, calculating the delta value includes a difference between the system output NOx measurement signal and the estimated system output NOx value.

[0011] Another implementation relates to a method for detecting NH3 slip using a system output NOx sensor. The method includes accessing a temperature value of a catalyst, determining that the temperature value of the catalyst is below a predetermined value, determining that one or more preconditions are met, accessing a plurality of system output NOx measurement signals, calculating an average of the plurality of system output NOx measurement signals, and setting a flag indicative of NH3 slip for an exhaust system in response to the calculated average of the plurality of system output NOx measurement signals exceeding a predetermined value for a predetermined period of time.

[0012] In some implementations, the one or more preconditions include determining a correlation between the system output NOx measurement signal and an engine output NOx measurement signal. In some implementations, the predetermined temperature value is 300 degrees Celsius. In some implementations, the plurality of system output NOx measurement signals are received from the system output NOx sensor.

[0013] Another implementation relates to a system including an exhaust aftertreatment system having a catalyst and a system output NOx sensor. The system also includes a controller configured to access a temperature value of the catalyst, determine that the temperature value of the catalyst exceeds a predetermined value, determine that one or more first preconditions are met, access a system output NOx measurement signal from the system output NOx sensor, determine an estimated system output NOx value, calculate a delta value based on the system output NOx measurement signal and the estimated system output NOx value, and set a flag indicative of NH3 slip for an exhaust aftertreatment system in response to an average of delta values, including the calculated delta value, exceeding a predetermined value for a predetermined period of time.

[0014] In some implementations, the one or more first preconditions include determining a correlation between the system output NOx measurement signal and an engine output NOx measurement signal. In some implementations, the one or more first preconditions include determining that an engine or idle event has not occurred. In some implementations, the one or more first preconditions include the system output NOx measurement signal exceeding a predetermined value. In some implementations, determining the estimated system output NOx value is based on a filtered system output NOx measurement signal of the system. In some implementations, calculating the delta value includes a difference between the system output NOx measurement signal and the estimated system output NOx value.In some implementations, the controller is further configured to determine that the temperature value of the catalyst is below a predetermined value, determine that one or more second preconditions are met, access a plurality of system output NOx measurement signals, calculate an average of the plurality of system output NOx measurement signals, and set the flag indicating NH3 slip for an exhaust aftertreatment system in response to the calculated average of the plurality of system output NOx measurement signals exceeding a predetermined value for a predetermined period of time. In some implementations, the one or more second preconditions include determining a correlation between the system output NOx measurement signal and an engine output NOx measurement signal. In some implementations, the predetermined temperature value is 300 degrees Celsius. SHORT DESCRIPTION

[0015] The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the disclosure will become apparent from the description, drawings, and claims, in which: Fig. 1 is a schematic diagram of an exemplary selective catalytic reduction system with an exemplary reductant delivery system for an exhaust system; Fig. 2 is a graphical diagram showing increases in a delta value between a measured SONOX signal and an estimated SONOX value, indicating NH3 slip using a system output NOx sensor; Fig. 3 is a graphical diagram illustrating correlation values ​​between a measured SONOX signal and an engine output NOx measurement signal as a precondition for detecting NH3 slip using a system output NOx sensor; Fig. 4 is a graphical diagram showing increases in a delta value between a measured SONOX signal and an estimated SONOX value after an engine or idle event as a precondition for detecting NH3 slip using a system output NOx sensor; Fig. 5 is a graphical diagram illustrating measured SONOX signals at low catalyst temperatures to detect NH3 slip using a system output NOx sensor; and Fig. 6 is a process diagram for detecting NH3 slip using a system output NOx sensor.

[0016] It should be noted that some or all of the figures are schematic representations for illustrative purposes. The figures are provided for the purpose of illustrating one or more implementations with the explicit understanding that they will not be used to limit the scope or meaning of the claims. DETAILED DESCRIPTION

[0017] The following are more detailed descriptions of various concepts related to and implementations of methods, apparatus, and systems for NH3 slip detection using a system output NOx sensor. The various concepts presented above and described in detail below can be implemented in one of numerous ways, as the described concepts are not limited to any particular implementation. Examples of specific implementations and applications are provided primarily for illustrative purposes. I. Overview

[0018] In some exhaust systems, a sensor module may be located downstream of an SCR catalyst to detect one or more emissions in the exhaust stream behind the SCR catalyst. For example, a NOx sensor may be positioned after the SCR catalyst to detect NOx within the exhaust gas leaving the vehicle's tailpipe. Such emission sensors may be useful for providing feedback to a control unit to modify an operating parameter of the vehicle's aftertreatment system. For example, a NOx sensor may be used to detect an amount of NOx leaving the vehicle's exhaust system, and if the detected NOx is too high or too low, the control unit may modify an amount of reductant supplied by a dosing module.

[0019] In some cases, other sensors may be included to detect other compounds, such as an NH3 sensor. However, such sensors can increase the cost and complexity of the system. Accordingly, it may be useful to utilize the cross-sensitivity of a NOs sensor to detect when NH3 slip occurs. II. Overview of the aftertreatment system

[0020] Fig. 1 illustrates an aftertreatment system 100 with an exemplary reductant delivery system 110 for an exhaust system 190. The aftertreatment system 100 includes a diesel particulate filter (DPF) 102, the reductant delivery system 110, a decomposition chamber or reactor 104, an SCR catalyst 106, and a sensor 150.

[0021] The DPF 102 is configured to remove particulate matter, such as soot, from exhaust gas flowing within the exhaust system 190. The DPF 102 includes an inlet through which the exhaust gas enters and an outlet through which the exhaust gas exits after particulate matter has been substantially filtered from the exhaust gas and / or particulate matter has been converted to carbon dioxide.

[0022] The decomposition chamber 104 is configured to convert a reductant, such as urea, aqueous ammonia solution, or DEF, into ammonia. The decomposition chamber 104 includes a reductant delivery system 110 with a dosing module 112 configured to dose the reductant into the decomposition chamber 104. In some implementations, the reductant is injected prior to the SCR catalyst 106. The reductant droplets then undergo the processes of vaporization, thermolysis, and hydrolysis to form gaseous ammonia within the exhaust system 190. The decomposition chamber 104 includes an inlet in fluid communication with the DPF 102 to receive the exhaust gas containing NOx emissions, and an outlet for the exhaust gas, NOx emissions, ammonia, and / or remaining reductant to flow to the SCR catalyst 106.

[0023] The decomposition chamber 104 includes the dosing module 112 attached to the decomposition chamber 104 such that the dosing module 112 can dose the reductant into the exhaust gases flowing into the exhaust system 190. The dosing module 112 can include an isolator 114 disposed between a portion of the dosing module 112 and the portion of the decomposition chamber 104 to which the dosing module 112 is mounted. The dosing module 112 is fluidly coupled to one or more reductant sources 116. In some implementations, a pump 118 can be used to pressurize the reductant source 116 for supply to the dosing module 112.

[0024] The dosing module 112 and the pump 118 are also electrically or communicatively coupled to a controller 120. The controller 120 is configured to control the dosing module 112 to dose reducing agent into the decomposition chamber 104. The controller 120 may also be configured to control the pump 118. The controller 120 may include a microprocessor, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), etc., or combinations thereof. The controller 120 may include a memory, including, but not limited to, an electronic, optical, magnetic, or other data storage or transmission device capable of providing program instructions to a processor, ASIC, FPGA, etc.The memory may include a memory chip, an electrically erasable programmable read-only memory (EEPROM), an erasable programmable read-only memory (EPROM), a flash memory, or other suitable memory from which the controller 120 can read instructions. The instructions may include code from any suitable programming language.

[0025] In certain implementations, the controller 120 is structured to perform certain operations, such as those described herein with respect to Fig. 6. In certain implementations, controller 120 represents part of a processing subsystem that includes one or more computing devices with storage, processing, and communication hardware. Controller 120 may be a single device or a distributed device, and the functions of controller 120 may be performed by hardware and / or as computer instructions on a non-transitory, computer-readable data storage medium.

[0026] In certain implementations, the controller 120 includes one or more modules or circuits structured to functionally perform the operations of the controller 120. In certain implementations, the controller 120 may include a NOx value correction module for performing the Fig. 6. The description herein, including the modules, emphasizes the structural independence of the aspects of the controller 120 and illustrates a possible grouping of operations and responsibilities of the controller 120. Other groupings that perform similar overall operations are to be considered within the scope of the present application. Modules may be implemented in hardware and / or as computer instructions on a non-transitory, computer-readable data storage medium, and modules may be distributed across various hardware or computer-based components. More detailed descriptions of specific embodiments of the control operations are provided in the section on Fig. to find.

[0027] Exemplary and non-limiting module implementation elements include sensors that provide any value specified herein, sensors that provide any value that is a precursor to a value specified herein, datalink and / or network hardware including communication chips, oscillating crystals, communication links, cables, twisted pair wiring, coaxial wiring, shielded wiring, transmitters, receivers and / or transceivers, logic circuits, hard-wired logic circuits, reconfigurable logic circuits in a specific, non-volatile state configured according to the module specification, actuators including at least one electrical, hydraulic or pneumatic actuator, a solenoid, an operational amplifier, analog control elements (springs, filters, integrators, adders, dividers,amplification elements) and / or digital control elements.,

[0028] The SCR catalyst 106 is configured to contribute to the reduction of NOx emissions by accelerating a NOx reduction process between the ammonia and NOx of the exhaust gas into diatomic nitrogen, water, and / or carbon dioxide. The SCR catalyst 106 includes an inlet in fluid communication with the decomposition chamber 104, from which exhaust gas and reductant are received, and an outlet in fluid communication with one end of the exhaust system 190.

[0029] The exhaust system 190 may further include a diesel oxidation catalyst (DOC) in fluid communication with the exhaust system 190 (e.g., downstream of the SCR catalyst 106 or upstream of the DPF 102) to oxidize hydrocarbons and carbon monoxide in the exhaust gas.

[0030] In some embodiments, the DPF 102 may be positioned downstream of the decomposition chamber or reactor tube 104. For example, the DPF 102 and the SCR catalyst 106 may be combined into a single unit, such as an SDPF. In some embodiments, the dosing module 112 may instead be positioned downstream of a turbocharger or upstream of a turbocharger.

[0031] The sensor 150 may be coupled to the exhaust system 190 to detect a condition of the exhaust flow through the exhaust system 190. In some implementations, the sensor 150 may have a portion disposed within the exhaust system 190, e.g., a tip of the sensor 150 may extend into a portion of the exhaust system 190. In other implementations, the sensor 150 may receive exhaust through another conduit, such as a sample tube extending from the exhaust system 190. While the sensor 150 is illustrated as being positioned downstream of the SCR catalyst 106, it should be understood that the sensor 150 may be positioned at other locations of the exhaust system 190, including upstream of the DPF 102, within the DPF 102, between the DPF 102 and the decomposition chamber 104, within the decomposition chamber 104, between the decomposition chamber 104 and the SCR catalyst 106, within the SCR catalyst 106, or behind the SCR catalyst 106.Additionally, two or more sensors 150 may be used to detect a condition of the exhaust gas, such as two, three, four, five, or six sensors 150, with each sensor 150 located at one of the aforementioned positions of the exhaust system 190. III. Implementations of NH3 slip detection using a NOx sensor

[0032] Methods and systems for NH3 or ammonia slip detection using a NOx sensor are described here. Ammonia slip detection may be dependent on the temperature of an SCR catalyst.

[0033] A first method is applicable when the SCR catalyst has a high temperature, such as above 300°C. The method involves tracking a difference between an unfiltered system output NOx (SONOX) measurement signal, such as from a NOx sensor downstream of the SCR catalyst, similar to sensor 150 in Fig. 1, and an estimated SONOX signal. A NOx sensor may be cross-sensitive to NH3, for example, due to the detection material used. When there is a release of NH3 at the tailpipe, the NOx sensor's cross-sensitivity to NH3 causes the measured SONOX output to rise sharply in response. The SONOX measurement signal rises faster than the estimated SONOX signal, resulting in a sharp increase in the difference, or delta, between the two signals. Since a large NH3 slip at the tailpipe tends to decay much more slowly than a sudden tailpipe NOx increase, a large delta between the raw SONOX measurement and the estimated SONOX value over a predetermined time period indicates NH3 slip.

[0034] A controller such as the controller 120 from Fig. 1, receives the raw SONOX measurement signal from the NOx sensor and calculates an estimated SONOX value. The estimated SONOX value can be calculated using a filtered SONOX measurement value. The controller then determines a difference, or delta, between the unfiltered SONOX measurement signal and an estimated SONOX value. The controller stores the determined difference value over a period of time. If there is a sudden release of NH3 at the tailpipe, the NOx sensor's cross-sensitivity to NH3 causes the measured SONOX output value to rise sharply in response over a short period of time. The unfiltered SONOX measurement signal rises much faster than the estimated SONOX value, resulting in a sharp increase in the delta between the two values. Referring to Fig. 2, the highlighted sections 202, 204 show such increases in the delta 206, 208 between the measured SONOX signal and the estimated SONOX value. Since a large tailpipe NH3 slip tends to decay much more slowly than a sudden tailpipe NOx increase, a sufficiently large delta maintained over a predetermined period of time (for example, using an average of stored delta values ​​that exceed a predetermined value) can be used to detect NH3 slip. As the SONOX measurement signal increases, the estimated SONOX value increases at a slower rate. When the SONOX measurement signal decreases to a value below the estimated SONOX value, the estimated SONOX value is reset to the current value of the SONOX measurement signal.

[0035] In some implementations, preconditions must be met to distinguish between conditions that cause an increased delta between a SONOX measurement signal and an estimated SONOX value before using the NOx sensor cross-sensitivity to detect NH3 slip and / or setting a flag indicating that NH3 slip has occurred. A first precondition that must be met is that the SONOX measurement signal differs from the engine output NOx measurement signal by a predetermined amount and / or does not correlate well with the engine output NOx measurement. As described in Fig. As shown in Figure 3, a system 300 exhibiting NH3 slip at the tailpipe exhibits a lower degree of cross-correlation 310 between the engine output NOx and SONOX measurement signals compared to a degree of cross-correlation 330 between the engine output NOx and SONOX measurement signals in a system 320 that does not exhibit NH3 slip. The amount of offset caused by the NH3 slip on the SONOX measurement signal lowers the degree of correlation because the measured SONOX signal is greater than the engine output NOx signal due to the SONOX sensor's cross-sensitivity to the elevated NH3. Thus, if the correlation level is persistently higher than expected for a predetermined time, the NH3 slip detection can be suspended and / or a flag value of 0 (or conversely 1, depending on the implementation) can be set for a variable for the cross-correlation condition.

[0036] Another precondition may involve the engine not operating during long engine or idle events. An engine or idle event of a predetermined length results in engine output NOx decreasing to very low levels, accompanied by a corresponding decrease in SONOX to very low levels. During the long engine event, dosing is at a minimum level because no engine output NOx enters the system, resulting in the NH3 storage in the SCR being depleted during a long engine event. At the end of a long engine / idle event, when the engine output NOx level suddenly increases, the SCR may not be able to reduce NOx efficiently due to the depleted NH3 storage capacity, resulting in a sudden increase in the SONOX level, as highlighted in section 400 of Fig. 4. Thus, a large delta can be determined between the unfiltered SONOX measurement signal and the estimated or filtered SONOX value after the long engine or idle event. Thus, if an idle event occurs followed by an increase in the engine output NOx and SONOX measurement signals, NH3 slip detection can be suspended for a predetermined fixed duration in response to the end of a long engine or idle event. This means that a flag value of 0 (or conversely 1, depending on the implementation) can be set for a variable for a long engine / idle precondition.

[0037] A further precondition may involve the SONOX measurement signal being above one or more minimum thresholds. This means that the presence of NH3 slip at the tailpipe would introduce a minimum level of offset to the SONOX measurement signal. Thus, if the SONOX measurement signal is below a predetermined value, NH3 slip detection can be suspended because there is no or minimal NH3 slip. This means that a flag value of 0 (or conversely 1, depending on the implementation) can be set for a variable for a SONOX threshold precondition.

[0038] A second method is applicable when the SCR catalyst is at a low temperature, such as below 300°C. SONOX values ​​are low when the SCR bed temperature is low, such as during engine idle events and / or when no load is present, because the engine output NOx levels are also low. Therefore, when the SCR bed temperature drops below a predetermined temperature, the corresponding SONOX measurement signal also drops to a low or minimal value within a short period of time. If residual NH3 is present in the tailpipe, the NOx sensor's cross-sensitivity toward NH3 will result in a positive offset in the SONOX measurement signal. That is, if NH3 slip occurs after the engine enters an engine idle or low load event, then the NOx sensor will detect the NH3 slip as NOx even though there is minimal engine output NOx (and therefore minimal measured SONOX should be present).During engine or idle events over a predetermined period of time, the controller stores the SONOX measurement signal for a predetermined period of time. If the average of the SONOX measurement signals during this period exceeds a predetermined value after the predetermined period of time since the start of the idle event, the high SONOX measurement signal indicates NH3 slip, as highlighted in 500 and illustrated in . Fig. 5. That is, since engine output NOx is at low or minimum levels during engine operation or idling, an elevated SONOX measurement signal indicates NH3 slip at the tailpipe.

[0039] A precondition to be met for low-temperature NH3 slip detection may include determining that the SONOX measurement signal differs from the engine output NOx measurement signal by a predetermined amount and / or does not correlate well with the engine output NOx measurement. As described in Fig. As shown in Figure 5, a system 500 exhibiting NH3 slip at the tailpipe exhibits a lower degree of cross-correlation between the engine output NOx and SONOX measurement signals compared to a system 510 exhibiting no NH3 slip. The amount of offset caused by the NH3 slip on the SONOX measurement signal lowers the degree of correlation. Thus, if the degree of correlation is persistently higher than expected for a predetermined time, NH3 slip detection may be suspended and / or a flag value of 0 (or conversely 1, depending on the implementation) may be set for a variable representing the cross-correlation condition.

[0040] Fig.6 shows a flowchart of a process 600 implemented by the controller 120 for the methods described herein. The process 600 includes accessing a temperature value for a catalyst (block 610). Accessing the temperature value for a catalyst may be performed by a temperature sensor upstream of a catalyst, downstream of the catalyst, positioned in the catalyst bed, and / or as a virtual temperature based on upstream exhaust conditions.

[0041] Process 600 further includes comparing the temperature to a predetermined value, such as 300 degrees Celsius (block 620). If the temperature is above the predetermined value, then the process continues to determine whether a first set of preconditions is met (block 630). If the temperature is equal to or below the predetermined value, then the process continues to determine whether a second set of preconditions is met (block 632).

[0042] Determining whether the first set of preconditions is met may include accessing one or more flag values ​​indicating whether the preconditions are met or not. The first set of preconditions may include one or more of the cross-correlation condition, the long engine / idle precondition, and / or the threshold SONOX precondition. Determining whether the first set of preconditions is met may include comparing the flag values ​​to a value of 0 (or 1, depending on the implementation) to verify that the first set of preconditions is met. If the first set of preconditions is not met, process 600 may end (block 690). If the first set of preconditions is met, process 600 continues by accessing a SONOX measurement signal (block 640).

[0043] Accessing the SONOX measurement signal (block 640) may include accessing one or more values ​​stored on a storage medium and / or reading an input value from a SONOX sensor. Process 600 determines an estimated SONOX value (block 650) from the retrieved SONOX measurement signal (block 640). In some implementations, the estimated SONOX value may be calculated using a filtered SONOX measurement value from the retrieved SONOX measurement signal (block 640). Process 600 includes calculating and storing a delta value (block 660). The delta value may be calculated between the retrieved unfiltered SONOX measurement signal (block 640) and one or more estimated SONOX values ​​(block 650). The process 600 further includes determining that the mean of one or more delta values ​​is greater than a predetermined value (block 670).In some cases, the average of the one or more delta values ​​is based on a number of delta values ​​over a predetermined time period. If the average of one or more delta values ​​is greater than the predetermined value, then an NH3 slip flag may be set (block 680) to indicate that NH3 slip is present. If the average of one or more delta values ​​is less than or equal to the predetermined value, then the process ends (block 690).

[0044] Returning to comparing the temperature to a predetermined value, such as 300 degrees Celsius (block 620), if the temperature is below the predetermined value, then the process continues to determine whether a second set of preconditions is met (block 632). Determining whether the second set of preconditions is met may include accessing one or more flag values ​​that indicate whether the preconditions are met or not. The second set of preconditions may include the cross-correlation condition. Determining whether the second set of preconditions is met may include comparing the flag values ​​to a value of 0 (or 1, depending on the implementation) to check whether the second set of preconditions is met. If the second set of preconditions is not met, then the process 600 may end (block 690).If the second set of preconditions is met, process 600 continues by accessing a SONOX measurement signal (block 642).

[0045] Accessing the SONOX measurement signal (block 642) may include accessing one or more values ​​stored on a storage medium and / or reading an input value from a SONOX sensor. Process 600 determines whether an average of one or more of the retrieved SONOX measurement signal values ​​is greater than a predetermined value (block 672). In some cases, the average of the one or more of the retrieved SONOX measurement signal values ​​is based on a number of retrieved SONOX measurement signal values ​​over a predetermined period of time. If the average of one or more of the retrieved SONOX measurement signal values ​​is greater than the predetermined value, then an NH3 slip flag may be set (block 680) to indicate that NH3 slip is present. If the average of one or more of the retrieved SONOX measurement signal values ​​is less than or equal to the predetermined value, then the process ends (block 690).

[0046] The term "controller" includes all types of devices, apparatus, and machines for processing data, including, for example, a programmable processor, a computer, a system on a chip (SOC), or multiple thereof, a portion of a programmed processor, or combinations of the foregoing. The device may include dedicated logic circuitry, such as an FPGA or ASIC. The device may also include, in addition to hardware, code that creates an execution environment for the computer program in question, such as code representing processor firmware, a protocol stack, a database management system, an operating system, a cross-platform runtime environment, a virtual machine, or a combination of one or more thereof.The device and the execution environment can implement various different computing model infrastructures, such as distributed computing and grid computing infrastructures.

[0047] A computer program (also known as a program, script, or code) can be written in any form of programming language, including compiled or interpreted languages, declarative or procedural languages, and it can be deployed in any form, for example, as a stand-alone program or as a module, component, subroutine, object, or other unit suitable for use in a computing environment. A computer program may, but is not necessarily, equivalent to a file in a file system. A program may be stored in a section of a file containing other programs or data (for example, one or more scripts stored in a markup language document), in a single dedicated file for the program in question, or in multiple coordinated files (for example, files storing one or more modules, subroutines, or pieces of code).

[0048] Although this document contains many specific implementation details, these should not be construed as limitations on the scope of what may be claimed, but rather as descriptions of features specific to particular implementations. Certain features described in this specification in the context of separate implementations may also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation may also be implemented in multiple implementations, separately or in any suitable subcombination.In addition, although the above features may be described as functioning in certain combinations and may initially be claimed as such, in some cases one or more features from a claimed combination may be singled out from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination.

[0049] Similarly, while operations are illustrated in the drawings in a particular order, this should not be understood to require that these operations be performed in that particular order or in sequential order, or that all of the illustrated operations be performed to achieve desirable results. Under certain circumstances, the separation of various system components in the implementations described above may not be understood to require such separation in all implementations, and it should be understood that the described components and systems may generally be integrated into a single product or may be packaged in multiple products embodied on tangible media.

[0050] As used herein, "essentially" and similar terms are intended to have a broad meaning consistent with common and accepted usage by those skilled in the art to which the subject matter of this disclosure relates. It will be apparent to those skilled in the art reading this disclosure that these terms are intended to permit description of certain described and claimed features without limiting the scope of those features to the precise numerical ranges provided. Accordingly, these terms are to be construed to indicate that insignificant or insignificant modifications or variations to the described and claimed subject matter are considered within the scope of the invention as recited in the appended claims.In addition, it is stated that limitations of the claims, in the event that the term "means" is not used therein, are not to be interpreted as constituting "means plus function" limitations under the United States patent laws.

[0051] The terms "coupled" and the like, as used herein, mean the direct or indirect connection of two components to one another. This connection can be stationary (e.g., permanent) or movable (e.g., removable or detachable). This connection can be achieved by the two components, or the two components and any other intermediate components, being integrally formed with one another as a single unitary body, or by the two components, or the two components and any other intermediate components, being attached to one another.

[0052] The terms "fluidly coupled" or "in fluid communication," and the like, as used herein, mean that the two components or objects have a path formed between the two components or objects in which a fluid, such as water, air, gaseous reductant, gaseous ammonia, etc., can flow, either with or without intervening components or objects. Examples of fluid couplings or configurations for enabling fluid communication may include tubes, channels, or any other suitable components for enabling the flow of a fluid from one component to another.

[0053] It is important to note that the construction and arrangement of the system shown in the various example implementations are merely illustrative and not restrictive. It is desired that all changes and modifications that fall within the spirit and / or scope of the described implementations be protected. It is understood that some features are not necessary, and implementations lacking the various features are considered within the scope of the application, which scope is defined by the following claims. In reading the claims, it is intended that the use of words such as "a," "an," "at least one," or "at least one portion" / "at least one portion / part," and their declinations, is not intended to limit the claim to only one subject matter, unless the claim expressly states otherwise.Where the terms “at least one section” / “at least one share / portion” and / or “a section” / “a share / portion” are used, the subject matter may include a section / a share / portion and / or the entire subject matter, unless expressly stated otherwise.

Claims

[1] A method for NH3 slip detection using a system output NOx sensor (150), comprising: Accessing a temperature value for a catalyst (106); if the temperature value for the catalyst (106) exceeds a predetermined temperature value and one or more first preconditions are met: Accessing a plurality of system output NOx measurement signals from the system output NOx sensor (150) located downstream of the catalyst (106), Determine a variety of estimated system output NOx values, Calculating a plurality of delta values ​​over a first predetermined period of time based on the system output NOx measurement signals and the estimated system output NOx values, and Setting a flag indicating NH3 slip for an exhaust system (190) in response to an average of the plurality of delta values ​​exceeding a first predetermined value; and if the temperature value for the catalyst (106) is below the predetermined temperature value and one or more second preconditions are met: Accessing a plurality of system output NOx measurement signals over a second predetermined period of time, Calculating an average of the plurality of system output NOx measurement signals, and Setting the flag indicating NH3 slip for the exhaust system (190) in response to the calculated average of the plurality of system output NOx measurement signals exceeding a second predetermined value. [2] The method of claim 1, wherein the one or more first preconditions include determining a correlation between the system output NOx measurement signal and an engine output NOx measurement signal. [3] The method of claim 1 or 2, wherein the one or more first preconditions include determining that no engine or idle event has occurred. [4] The method of any one of claims 1 to 3, wherein the one or more first preconditions include the system output NOx measurement signal exceeding a predetermined value. [5] A method according to any one of claims 1 to 4, wherein determining the estimated system output NOx value is based on a filtered system output NOx measurement signal of the system. [6] Method according to one of claims 1 to 5, wherein the predetermined temperature value is 300 degrees Celsius. [7] The method of any one of claims 1 to 6, wherein calculating the delta value comprises a difference between the system output NOx measurement signal and the estimated system output NOx value. [8] The method of any one of claims 1 to 7, wherein the one or more second preconditions include determining a correlation between the system output NOx measurement signal and an engine output NOx measurement signal. [9] The method of any one of claims 1 to 8, wherein the plurality of system output NOx measurement signals are received from the system output NOx sensor. [10] System comprising: an exhaust aftertreatment system comprising a catalyst (106) and a system output NOx sensor (150) arranged downstream of the catalyst (106); and a controller (120) configured to: Accessing a temperature value for the catalyst (106); if the temperature value for the catalyst (106) exceeds a predetermined temperature value and one or more first preconditions are met: Accessing a plurality of system output NOx measurement signals from the system output NOx sensor (150), Determine a variety of estimated system output NOx values, Calculating a plurality of delta values ​​over a first predetermined period of time based on the system output NOx measurement signals and the estimated system output NOx values, and Setting a flag indicating NH3 slip for an exhaust system (190) in response to an average of the plurality of delta values ​​exceeding a first predetermined value; and if the temperature value for the catalyst (106) is below the predetermined temperature value and one or more second preconditions are met: Accessing a plurality of system output NOx measurement signals over a second predetermined period of time, Calculating an average of the plurality of system output NOx measurement signals, and Setting the flag indicating NH3 slip for the exhaust system (190) in response to the calculated average of the plurality of system output NOx measurement signals exceeding a second predetermined value. [11] The system of claim 10, wherein the one or more first preconditions include determining a correlation between the system output NOx measurement signal and an engine output NOx measurement signal. [12] The system of claim 10 or 11, wherein the one or more first preconditions include determining that no engine or idle event has occurred. [13] A system according to any one of claims 10 to 12, wherein the one or more first preconditions include the system output NOx measurement signal exceeding a predetermined value. [14] The system of any one of claims 10 to 13, wherein determining the estimated system output NOx value is based on a filtered system output NOx measurement signal of the system. [15] The system of any one of claims 10 to 14, wherein calculating the delta value comprises a difference between the system output NOx measurement signal and the estimated system output NOx value. [16] The system of any one of claims 10 to 15, wherein the one or more second preconditions include determining a correlation between the system output NOx measurement signal and an engine output NOx measurement signal. [17] System according to one of claims 10 to 16, wherein the predetermined temperature value is 300 degrees Celsius.

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