Fault detection system for a drive system with a selective catalytic reduction unit and a subsequent method

Abstract

Fault detection system (112) for a drive system (110) with a selective catalytic reduction unit, SCR (206), comprising: a memory (54) configured to store a fault detection algorithm relating to nitrogen oxides, NOx, in the propulsion system (110); and a processor (50) which is operationally coupled to the memory (54) and programmed to: (a) to obtain a first NOx concentration value relating to an upstream input (203) of the SCR unit (206) and (b) a second NOx concentration value relating to a downstream output (205) of the SCR unit (206); (a) and (b) to be temporarily stored in response to receiving (a) and (b) and to repeat the retrieval and buffering until buffered N values ​​have been obtained, where N is a pre-programmed number; to calculate a front-end average of NOx and a front-end standard deviation using the cached N-values; to calculate a downstream average of NOx and a downstream standard deviation using the cached N values; to use the upstream average of NOx, the upstream standard deviation, the downstream average of NOx and the downstream standard deviation as input for the fault detection algorithm relating to nitrogen oxides, NOx, in the propulsion system (110) in order to generate a linear correlation factor; and A non-acceptable part with the best performance, BPU, is detected when the linear correlation factor is greater than a pre-programmed error threshold; where the error detection algorithm includes rules for generating a Pearson correlation; and where the processor (50) is further programmed to: In addition to (a) and (b), to obtain: (c) an upstream mass flow rate value, (d) an upstream temperature value, (e) a downstream mass flow rate value, (f) a downstream temperature value, and (g) a urea value; and Temporarily storing (a), (b), (c), (d), (e), (f) and (g) in response to obtaining (a), (b), (c), (d), (e), (f) and (g); and where each of the cached N values ​​comprises a respective (a), (b), (c), (d), (e), (f) and (g).

Description

[0001] The present description refers generally to mobile platforms and in particular to the detection of selective catalytic reduction (SCR) failures depending on nitrogen oxide levels.

[0002] Some mobile platforms, such as certain diesel vehicles, use selective catalytic reduction (SCR), coupled directly or indirectly to the vehicle's engine, to reduce nitrogen oxides in the exhaust gas. SCR units generally convert nitrogen oxides (also known as NOx) into nitrogen and water using a solution of ammonia or urea (NH3). The amount of NH3 injected depends on the measured / detected amount of NOx. If an SCR fails, its malfunction is indicated by its inability to convert nitrogen oxides into nitrogen and water. Therefore, in the case of an unacceptable or failing SCR, the detected / captured upstream NOx (as used here, "upstream" is the exhaust airflow measured after the engine and before the SCR treatment) and the detected / captured downstream NOx (as used here, "downstream" is the exhaust airflow measured after the SCR treatment) are almost equal.

[0003] Accordingly, many available SCR fault detection solutions use an upstream and a downstream NOx sensor and identify a fault by determining the SCR-NOx conversion efficiency using the data collected between the upstream and downstream NOx sensors. However, a technical problem arises when the NOx sensors degrade (and their collected data is affected by gain and / or offset), leading to an inaccurate determination of the SCR-NOx conversion efficiency. This technical problem is further compounded because some government regulatory bodies require that there be no gap between a best-performing unacceptable (BPU) SCR and a BPU NOx sensor; that is, the gap between the detection capability of the NOx sensors and the sensitivity of the SCR monitor must be eliminated.

[0004] DE 10 2017 201 400 A1 describes a method for fault detection in an SCR system of an internal combustion engine in a motor vehicle, which has two SCR catalysts and at least two nitrogen oxide sensors, wherein a first nitrogen oxide sensor is arranged between and a second nitrogen oxide sensor is arranged downstream of the two SCR catalysts. The method comprises the following steps: A signal is continuously acquired at the first nitrogen oxide sensor, and the mass of ammonia at the first nitrogen oxide sensor is determined from this. Subsequently, an overdose is carried out by increasing the mass of reducing agent introduced, whereby the mass of ammonia converted in the first SCR catalyst exceeds the mass of ammonia required for nitrogen oxide reduction, until the ammonia level at the first SCR catalyst exceeds the maximum ammonia level of the first SCR catalyst.Subsequently, an initial check is performed to determine whether ammonia slip is present at the first SCR catalyst, depending on the signal from the first nitrogen oxide sensor, and an initial fault detection of at least the second SCR catalyst is carried out by an evaluation criterion if ammonia slip is present at the first SCR catalyst.

[0005] US 2017 / 0003259A1 describes a method and apparatus for testing and diagnosing at least one NOx sensor in the exhaust system of a diesel engine under field conditions. The field test apparatus can be connected to a truck with a lean-burn diesel engine via an on-board diagnostic connector. The field test apparatus is designed to initiate a test cycle and diagnose at least one NOx sensor in the truck's exhaust system. The test cycle is performed as a test sequence with the engine running in a stationary truck under at least two different operating conditions, while the NOx-related values ​​output by the at least one NOx sensor are measured over a predefined period. At least one operating condition is achieved by simultaneously opening the exhaust gas recirculation valve and controlling the backpressure valve to increase the backpressure.A special algorithm is used to compare the measured values ​​with a predefined model and to provide a numerical summary and statistical evaluation of the sensor function. The numerical summary reveals the probability that at least one NOx sensor is functioning correctly, thus enabling an informed decision as to whether or not the at least one NOx sensor needs to be replaced.

[0006] PAPULA, Lothar: Mathematics for Engineers and Natural Scientists - Volume 3 : Wiesbaden: Vieweg+Teubner Verlag 2011 - ISBN 978-3-8348-1227-8 describes a calculation of correlation coefficients.

[0007] DE 10 2010 026 206 A1 describes a system comprising a sampling module, a correlation determination module, and an injector control module. The sampling module samples a first and second signal, indicating the amount of nitrogen oxides (NOx) upstream and downstream, respectively, of a selective catalytic reduction (SCR) catalyst. The second signal also indicates the amount of ammonia downstream of the SCR catalyst when ammonia is released from the SCR catalyst. The correlation determination module determines a correlation value between the first and second signals, where the correlation value represents the probability that ammonia will be released from the SCR catalyst. Based on the correlation value, the injector control module controls the amount of reducing agent injected into the exhaust gas upstream of the SCR catalyst.

[0008] The following description provides a technical solution to the aforementioned technical problem, in addition to addressing related issues. Furthermore, additional desirable features and characteristics of the system and the method will become apparent from the detailed description below and the accompanying claims, which should be considered in conjunction with the accompanying drawings and the preceding background information.

[0009] The invention is defined by the independent claims.

[0010] A fault detection system for a propulsion system with a selective catalytic reduction (SCR) unit is provided. The system comprises: a memory configured to store a fault detection algorithm relating to nitrogen oxides (NOx) in the propulsion system, and a processor operationally coupled to the memory and programmed to: (a) obtain a first NOx concentration value relating to an upstream input of the SCR unit, and (b) obtain a second NOx concentration value relating to a downstream output of the SCR unit; buffer (a) and (b) in response to obtaining (a) and (b), and repeat the retrieval and buffering until buffered NOx values ​​have been obtained.where N is a pre-programmed number; to calculate an upstream average NOx value and an upstream standard deviation using the cached N values; to calculate a downstream average NOx value and a downstream standard deviation using the cached N values; to use the upstream average NOx value, the upstream standard deviation, the downstream average NOx value, and the downstream standard deviation as input for the fault detection algorithm relating to nitrogen oxides, NOx, in the propulsion system to generate a linear correlation factor and to identify a high-performing but non-acceptable part, BPU.if the linear correlation factor is greater than a pre-programmed error threshold. The error detection algorithm includes rules for generating a Pearson correlation. The processor is further programmed to obtain, in addition to (a) and (b): (c) an upstream mass flow value, (d) an upstream temperature value, (e) a downstream mass flow value, (f) a downstream temperature value, and (g) a urea value, and to buffer (a), (b), (c), (d), (e), (f), and (g) in response to obtaining (a), (b), (c), (d), (e), (f), and (g). Each of the buffered N values ​​comprises a respective (a), (b), (c), (d), (e), (f), and (g).

[0011] According to one embodiment, the processor is further programmed to send a fault message to a central platform controller in response to the detection of a BPU component.

[0012] According to another embodiment, the pre-programmed error threshold lies between 0.75 and 0.85.

[0013] According to another embodiment, the processor is further programmed to: process the cached N values ​​to determine whether the temperature values ​​are within an acceptable temperature range; process the cached N values ​​to determine whether the mass flow values ​​are within an acceptable mass flow range; and process the cached N values ​​to determine whether the urea values ​​are within an acceptable urea range.

[0014] According to another embodiment, the processor is further programmed to discard all cached values ​​and restart data collection when it detects that the temperature values ​​are not within an acceptable temperature range, the mass flow values ​​are not within an acceptable mass flow range, or the urea values ​​are not within an acceptable urea range.

[0015] In one example, a propulsion system for a vehicle is described. The propulsion system comprises: a selective catalytic reduction unit (SCR unit) with an upstream and a downstream side; an upstream nitrogen oxide (NOx) sensor providing an upstream NOx concentration value; a downstream nitrogen oxide (NOx) sensor providing a downstream NOx concentration value; a urea source coupled to the SCR unit providing a urea value; and a control circuit comprising a processor programmed by programming instructions to obtain (a) the upstream NOx concentration value, (b) the urea value, and (c) the downstream NOx concentration value; and to buffer (a), (b), and (c) in response to obtaining (a), (b), and (c).and repeat the obtaining and buffering process until buffered N values ​​are obtained, where N is a pre-programmed number; using the buffered N values, calculate an upstream NOx average and upstream standard deviation; using the buffered N values, calculate a downstream NOx average and downstream standard deviation; use the upstream NOx average, upstream standard deviation, downstream NOx average, and downstream standard deviation as input for a fault detection algorithm relating to nitrogen oxides (NOx) in the propulsion system to generate a linear correlation factor;and to identify a subset with the best performance that is not acceptable (BPU) if the linear correlation factor is greater than a pre-programmed error threshold.

[0016] The exemplary embodiments are described below in conjunction with the following drawing figures, where identical numbers denote identical elements, and where: Fig. Figure 1 is a functional block diagram showing an SCR fault detection system implemented on board a vehicle; Fig. Figure 2 is a functional block diagram of the SCR fault detection system; and Fig. Figure 3 is a process flow diagram that illustrates an example procedure for SCR fault detection in a mobile platform.

[0017] The following detailed description is merely exemplary. Furthermore, there is no intention of being bound by any express or implied theory presented in the preceding technical field, background, summary, or the following detailed description.

[0018] For the sake of brevity, conventional techniques relating to signal processing, data transmission, signaling, control, machine learning models, radar, lidar, image analysis, and other functional aspects of the systems (and the individual operating components of the systems) are not described in detail here. Furthermore, the connecting lines shown in the various figures contained herein are intended to represent exemplary functional relationships and / or physical couplings between the various elements. It should be noted that many alternative or additional functional relationships or physical connections may exist in an embodiment of this disclosure.

[0019] As previously mentioned, in the case of an SCR malfunction, the upstream and downstream NOx values ​​are nearly identical. Accordingly, many available SCR fault detection solutions use an upstream and a downstream NOx sensor and identify a fault by determining the SCR-NOx conversion efficiency using the data from both sensors. However, a technical problem arises when the NOx sensors degrade (and their data is affected by gain and / or offset), leading to an inaccurate determination of the SCR-NOx conversion efficiency. This technical problem is further compounded because some government regulatory bodies require that there be no gap between a best-performing unacceptable (BPU) SCR and a BPU NOx sensor, i.e.,The gap between the detection capability of the NOx sensors and the sensitivity of the SCR monitor must be eliminated.

[0020] The technical solution provided by exemplary embodiments of the SCR fault detection system compares detected upstream NOx and detected downstream NOx to assess the linearity of their relationship and is independent of separate changes in position and scale (offset / gain) in the detected upstream and downstream data. Exemplary embodiments can provide a technologically enhanced SCR fault alarm by detecting the strength of a linear relationship between detected upstream NOx and detected downstream NOx. In exemplary embodiments, the SCR fault warning can be delivered to other vehicle applications, such as a central platform control unit, for use in practical applications, such as the illumination of fault warning lights.The technologically improved SCR fault detection system and procedure is described in more detail in connection with the following figures.

[0021] Fig. Figure 1 shows an exemplary mobile platform according to an exemplary embodiment. The mobile platform is a vehicle 100 and comprises a body 102, a chassis 104, one or more wheels 106, one or more drive shafts (or axles) 108, and a drive system 110. In various embodiments, the vehicle 100 comprises an automobile; however, this may vary in other embodiments. The vehicle 100 can be any type of automobile and / or other vehicle, such as a sedan, station wagon, truck, or sport utility vehicle (SUV), and can have two-wheel drive (2WD) (i.e., rear-wheel drive or front-wheel drive), four-wheel drive (4WD), or all-wheel drive (AWD).

[0022] The body 102 is arranged on the chassis 104 and essentially encloses the other components of the vehicle 100. The body 102 and the chassis 104 can together form a frame. The wheels 106 are each rotatably coupled to the chassis 104 near a respective corner of the body 102. In one embodiment, each wheel 106 comprises a wheel assembly that includes a tire, a wheel, and associated components (and which, for the purposes of this application, are also collectively referred to as "wheel 106"). The drive system 110 is coupled to at least some of the wheels 106 via one or more of the drive axles 108 and drives the wheels 106 via the axles 108. While the vehicle 100 is in Fig. Figure 1 is shown with four wheels 106 and two axles 108, but the vehicle 100 can have any number of wheels 106, axles 108 and / or other components in various other embodiments.

[0023] As described in more detail below, the drive system 110 comprises at least one SCR unit and the SCR fault detection system, which is generally represented as system 112. The drive system 110 is communicatively coupled to the central platform control unit 114 and the instrument panel 116.

[0024] The central platform controller 114 can receive and integrate communications from a variety of modules and systems known to be present in the vehicle 100 described above. The central platform controller 114 can also engage in bidirectional communication with onboard object detection modules. The central platform controller 114 communicates user and operational inputs to the propulsion system 110 and other onboard systems. Accordingly, inputs supplied by the central platform controller 114 to the system 112 can include user inputs, mobile applications and systems, off-board communication (e.g., via a transceiver), a geographic positioning system (GPS), and infotainment systems.

[0025] The instrument panel 116 may include display units, user input devices, speakers, and the like. With respect to this disclosure, the instrument panel 116 may have one or more malfunction indicator lamps (MILs) to convey a malfunction message to a user and the relevant technicians.

[0026] In Fig. Figure 2 now shows part 200 of the drive system 110. The SCR fault detection system 112 is depicted as a control circuit 202, which is connected to various sensors along an exhaust gas flow path, which is described below. On the left, the upstream part 203 represents the exhaust gas flow after the engine but before the SCR. On the right, downstream 205 represents the exhaust gas flow located after the SCR. The exhaust gases upstream 203 can be exposed to a first NOx sensor 208, a first mass flow sensor 214, and a first temperature sensor 220 as they enter a first SCR unit 206 (left). A urea or NH3 storage tank and a pump 228 are shown in operational connection with the first SCR unit 206. On the output side of the first SCR unit 206, there can be a second NOx sensor 210, a second temperature sensor 222 and a second mass flow sensor 216.In some embodiments, the exhaust gas outlet of the first SCR unit 206 is the downstream exhaust gas 205.

[0027] In some embodiments, an optional second SCR unit 226 is provided, which receives the exhaust gas flow from the first SCR unit 206 as its input. The urea or NH3 storage tank and the pump 228 are shown in operational connection with the optional second SCR unit 226. A third NOx sensor 212, a third temperature sensor 224, and a third mass flow sensor 218 may be present at the output side of the optional second SCR unit 226. In some embodiments, the exhaust gas output of the second SCR unit 226 is the downstream exhaust gas 205.

[0028] As used herein, the control circuit 202 facilitates communication and / or interaction between the components of System 112 and performs additional processes, tasks and / or functions to support the operations attributed to System 112, as described herein.

[0029] The in connection with Fig. The functional blocks described in 1-2, including the control circuit 202, can be implemented using any hardware, software, firmware, electronic control components, processing logic and / or processors, individually or in any combination, including but not limited to: application-specific integrated circuits (ASICs), a field-programmable gate array (FPGA), an electronic circuit, a processor (shared, dedicated or as a group) and memory executing one or more software or firmware programs, a combinational logic circuit and / or other suitable components providing the functionality associated with the functional block.

[0030] In various embodiments, such as in Fig. As shown in Figure 2, the control circuit 202 is implemented as an extended computer system comprising a processor 50, a computer-readable storage device or media (memory 54) for storing instructions, algorithms and / or programs, such as program 56 and a variety of pre-programmed thresholds and parameters 58, an interface 52 and a bus 51.

[0031] The processor 50 can execute the program 56. Depending on the embodiment, the processor 50 can be implemented or realized with a general-purpose processor (shared, dedicated, or grouped), a microprocessor or microcontroller and memory executing one or more software or firmware programs, a content-addressable memory, a digital signal processor, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), any suitable programmable logic device, a combinational logic circuit with discrete gates or transistor logic, discrete hardware components and memory devices, and / or any combination thereof, to perform the functions described herein.

[0032] The program 56 stored in memory 54, when executed by processor 50, can cause processor 50 to implement the tasks and functions described herein, including the implementation of a fault detection algorithm to identify a best-performing SCR unit (BPU) that is not performing as expected. Memory 54 can also be used by processor 50 to cache multiple acquired data points simultaneously, to store results of comparisons and analyses, and the like. Accordingly, the computer-readable storage device or medium, memory 54, can include volatile and non-volatile storage, such as read-only memory (ROM), random-access memory (RAM), and keep-alive memory (KAM).KAM is a persistent or non-volatile memory that can be used to store various operating parameters 58 while the processor 50 is switched off. The memory 54 can be implemented using any number of known memory devices, such as PROMs (programmable read-only memory), EPROMs (electrically erasable PROMs), EEPROMs (electrically erasable PROMs), flash memory, or other electrical, magnetic, optical, or combined memory devices capable of storing data, some of which are executable instructions used by the processor 50 in controlling the vehicle 100. The information in the memory 54 can be organized in a procedure and / or imported from an external source during an initialization or installation process; it can also be programmed via a user input device.

[0033] Interface 52 supports bidirectional communication with the control circuit 202, e.g., from a system driver and / or another computer system, and can be implemented using any suitable method and device. Interface 52 includes the hardware and software to support one or more communication protocols for wired and / or wireless communication between the processor 50 and external sources, such as satellites, the cloud, communication towers, and ground stations. In one embodiment, interface 52 receives various data from the sensors of the drive system 110. Interface 52 may also include one or more network interfaces for communication with technicians and / or one or more memory interfaces for connection to storage devices, such as the memory 54.Bus 51 is used to transmit programs, data, status, and other information or signals between the various components of the extended computer system of the control circuit 202. Bus 51 can be any suitable physical or logical means of connecting computer systems and components, including, but not limited to, direct hard-wired connections, fiber optics, infrared, and wireless bus technologies.

[0034] In other embodiments of the system 112, the control circuit 202 can be implemented as state machine logic and / or perform operations in accordance with the logic in a programmable logic array or similar.

[0035] While the exemplary embodiment of System 112 is described in connection with a fully functional extended computer system, those skilled in the art will recognize that the mechanisms of this description can be distributed as a program product including the program 56 and the pre-programmed parameters 58. Such a program product may comprise one or more program code modules containing an ordered list of executable instructions for implementing logical functions, performing algorithmic operations, and managing the flow of data through System 112. When executed by a processor (e.g., Processor 50), the instructions in the program code modules cause the processor to receive and process signals and to perform logic, calculations, methods, and / or algorithms as described herein.

[0036] After development, the program code modules that constitute a program product can be stored and distributed individually or collectively, using one or more types of non-transient, computer-readable, signal-carrying media to store and distribute the instructions, such as a non-transient computer-readable medium. Such a program product can take a variety of forms, and the present description applies equally regardless of the type of computer-readable signal-carrying medium used for distribution. Examples of signal-carrying media include writable media such as floppy disks, hard disks, memory cards, and optical discs, as well as transmission media such as digital and analog communication links.It is estimated that cloud-based storage and / or other techniques can also be used as storage and as a software product for time-based display of release requests in certain implementations.

[0037] When considering Fig. 3 and with continued reference to Fig. Figures 1-2 show that, in various embodiments, the steps of a processor-executable method 300 for SCR fault detection can be arranged in one or more program code modules. For illustration, the following description of the method 300 may refer to elements mentioned above in connection with Figures 1-2. In practice, parts of the method 300 can be executed by different components of the described system 112. It should be noted that the method 300 can include any number of additional or alternative operations and tasks, as described in Figures 1-2. Fig. The tasks shown in the three examples do not have to be performed in the order shown, and the procedure 300 can be integrated into a more comprehensive procedure or method with additional functionality not described in detail here. Furthermore, one or more of the tasks shown in the three examples can be performed in the three examples. Fig. The tasks shown in 3 may be omitted in an embodiment of method 300, as long as the intended overall functionality is maintained.

[0038] At 302, system 112 is initialized. When implemented as an extended computer system (e.g., Fig.1) Initialization at 302 may include uploading, installing, or updating the instructions that constitute the program 56 and the pre-programmed parameters 58 for execution by the processor 50. During initialization, a pre-programmed range may be set for any combination of: (i) acceptable temperatures, (ii) acceptable mass flow (this is a volumetric measurement of the exhaust air flow), and (iii) an acceptable amount of NH3 in memory. The one or more pre-programmed ranges are assigned to the first SCR unit 206. In embodiments using the second SCR unit 226, a second or more of the pre-programmed ranges are assigned to the second SCR unit 226. In various embodiments, the second or multiple pre-programmed ranges are different from the first pre-programmed ranges.In various embodiments, the second or multiple second pre-programmed areas are the same as the three pre-programmed areas. During initialization, a buffer size (N) is set, where N is the number of times to capture sequentially acquired samples. An initial error threshold (a number between 0 and 1) is also set during initialization.

[0039] At 304, the system 112 begins to receive acquired data values. At 304, the system 112 can (a) receive a first NOx concentration value from the first NOx sensor 208, which relates to an upstream input 203 of the first SCR unit 206, and (b) receive a second NOx concentration value from the second NOx sensor 210, which relates to a downstream output 205. In various embodiments, at 304, the system 112 can also (c) receive a first mass flow value from the mass flow sensor 214 (i.e., upstream), (d) receive a first temperature value from the temperature sensor 220 (i.e., upstream), (e) receive a second mass flow value from the mass flow sensor 216 (i.e., downstream), and (f) receive a second temperature value from the temperature sensor 222 (i.e., downstream). In various embodiments, the system 112 at 304 can also obtain and temporarily store a urea concentration value for each of the N collections (g).Retrieving these additional values ​​allows the determination of temperature drops by the SCR unit 206 and any variation in mass flow by the SCR unit 206.

[0040] In embodiments with a second SCR unit 226, the output of the first SCR unit 206 is the input to the second SCR unit 226, and the output of the second SCR unit 226 is the downstream output 205. In these embodiments, the system 112 can obtain a third NOx concentration value from the third NOx sensor 212 (h), which belongs to a downstream output 205 of the second SCR unit 226. A second urea value is obtained for the second SCR unit 226, the second urea value being independent of the urea storage value for the first SCR unit 206. In embodiments with a second SCR unit 226, the system 112 can also obtain (i) a third mass flow value from the mass flow sensor 218 and (j) a third temperature value from the temperature sensor 224.

[0041] At 306, system 112 begins buffering and stores (i.e., buffers or acquires) at least N sequentially acquired measurements for (a) and (b). In other words, for each of the N acquisitions, there can be at least two different measurements: upstream NOx and downstream NOx. This can be described as a data chain of size 2 or as an assignment of two elements at each of N points in the buffer of size N. In various embodiments, each of the buffered N values ​​contains a respective (a), (b), (c), (d), (e), and (f). In various embodiments, each of the buffered N values ​​includes a respective (a), (b), (c), (d), (e), (f), and (g). In various embodiments, each of the buffered N values ​​includes a respective (a), (b), (c), (d), (e), (f), (g), (h), (i), and (j).

[0042] In 308, preprocessing of the cached values ​​is performed. In various embodiments, the preprocessing includes the calculation of an upstream average value of NOx, which can be denoted here as X, and an upstream standard deviation of X (sigma-x) using the cached N values. In 308, the preprocessing also includes the calculation of a downstream average NOx, which can be denoted here as Y, and a downstream standard deviation of Y (sigma-y) using the cached N values.

[0043] In various embodiments, the preprocessing includes confirmation (by comparing the value with the pre-programmed range) that: the temperature values ​​are within the acceptable temperature range, the mass flow rates are within the acceptable mass flow rate range, and the urea values ​​are within the acceptable urea range. In various embodiments, if system 112 detects that any of the values ​​are outside the range, it discards all collected, cached values ​​and restarts data collection.

[0044] At 310, the processor can use the upstream NOx average, upstream standard deviation, downstream NOx average, and downstream standard deviation as input for the fault detection algorithm relating to nitrogen oxides (NOx) in the propulsion system to generate a linear correlation factor (LCF). In various embodiments, the processing at 310 includes performing a Pearson correlation, in which: 0<=LCF=abs((Covariance(X,Y)) / (sigma−x*sigma−y))∗∗exp<=1;

[0045] Here, "abs" stands for taking the absolute value and **exp for increasing the absolute value to the exponential power.

[0046] When the LCF is one, the relationship between upstream and downstream NOx is linear, and when the LCF is zero, the relationship between upstream and downstream NOx is nonlinear. Acceptable SCR units exhibit a nonlinear or, at best, weakly linear relationship between upstream and downstream NOx. Programming the error threshold to a value close to zero is a more conservative approach, as it allows more weakly linear relationships to fail, but may cause some of the worst-performing units (WPA) to fail. Programming the error threshold to a value close to 1 is a more lenient approach, but may allow some of the best-performing units (BPU) to pass through, which is unacceptable. Therefore, at 310, the LCF is compared to the pre-programmed error threshold.In various embodiments, the error threshold lies between 0.75 and 0.85. If the LCF is less than or equal to the error threshold, the procedure can revert to 300 and then to 304.

[0047] At 312, when the LCF is greater than the fault threshold, a BPU part has been detected. In various embodiments, the BPU part is the SCR unit 206. In various embodiments, in response to the detection of a BPU part, the method 300 also provides a fault message to the central platform controller 114. Using the fault warning, the central platform controller 114 can illuminate warning lights on the instrument panel 116 and / or transmit warnings or messages to personal electronic devices or service providers.

[0048] Thus, the provided System 112 and Method 300 offer a technological solution to the technical problem of SCR fault detection. The provided embodiments are robust against varying offsets and gains of the NOx sensors, representing a technological improvement over available SCR failure detection strategies for drive systems. The use of these embodiments enables designers to achieve a six-sigma separation between BPU and WPA SCRs, regardless of the NOx sensor failure mode.

Images