Method for determining a diagnosis of a fluid delivery system, a control system configured for determining a diagnosis of a fluid delivery system, and a vehicle comprising the control system

Abstract

A method (400) for determining a diagnosis of a fluid delivery system (270, 370) is presented. The fluid delivery system (270, 370) comprises two or more dosing units (271, 272, 371, 372), a pump (274, 374) and one fluid pressure sensor (280, 380). The method is performed under normal operation of the fluid delivery system (270, 370), and comprises: - determining (410) two or more individual dosed masses of fluid (Qdose_ind_1, Qdose_ind_2, …, Qdose_ind_m) being individually dosed by the two or more dosing units (271, 272, 371, 372), respectively; - determining (420) a simultaneous dosed mass of fluid (Qdose_sim) being simultaneously dosed by all of the two or more dosing units (271, 272, 371, 372) together; and - determining (430) the diagnosis of the fluid delivery system (270, 370) based on the two or more individual dosed masses of fluid (Qdose_ind_1, Qdose_ind_2, …, Qdose_ind_m) and corresponding two or more individual requested masses of fluid (Qreq_ind_1, Qreq_ind_2, …, Qreq_ind_m), respectively, and based on the simultaneous dosed mass of fluid (Qdose_sim) and a corresponding simultaneous requested mass of fluid (Qreq_sim).

Description

[0001] METHOD FOR DETERMINING A DIAGNOSIS OF A FLUID DELIVERY SYSTEM, A CONTROL SYSTEM CONFIGURED FOR DETERMINING A DIAGNOSIS OF A FLUID DELIVERY SYSTEM, AND A VEHICLE COMPRISING THE CONTROL SYSTEM

[0002] Technical field

[0003] The present invention relates to a method for determining a diagnosis of a fluid delivery system, to a control system configured for determining a diagnosis of a fluid delivery system, and to a vehicle comprising the control system.

[0004] The invention also relates to a computer program and a computer program product, which implement the method according to the invention.

[0005] Background

[0006] The following background description constitutes a description of the background to the present invention, and thus need not necessarily constitute prior art.

[0007] In connection with increased government interests concerning pollution and air quality, primarily in urban areas, emission standards and regulations regarding emissions from combustion engines have been drafted in many jurisdictions.

[0008] Such emission standards often comprise requirements defining acceptable limits of exhaust emissions from combustion engines in for example vehicles. For example, emission levels of nitrogen oxides NOx, hydrocarbons CxHy, carbon monoxide CO and particles PM are often regulated by such standards for most types of vehicles. Vehicles equipped with combustion engines typically give rise to such emissions in varying degrees. In this document, the invention will be described mainly for its application in vehicles, i.e. for internal combustion engines. However, the invention may be used in substantially any application where combustion engines are used, for example in vessels such as ships or aeroplanes / helicopters, wherein regulations and standards for such applications limit emissions from the combustion engines.

[0009] In an effort to comply with these emission standards and regulations, the exhausts caused by the combustion of the combustion engine are treated (purified). A common way of treating exhausts from a combustion engine comprises a so-called catalytic purification process, which is why vehicles equipped with a combustion engine usually comprise at least one catalyst. There are different types of catalysts, where the different respective types may be suitable depending on for example the combustion concept, combustion strategies and / or fuel types which are used in the vehicles, and / or the types of compounds in the exhaust stream to be purified. In relation to at least nitrous gases (nitrogen monoxide, nitrogen dioxide), referred to below as nitrogen oxides NOx, vehicles often comprise at least one catalyst, wherein an additive / reductant is supplied to the exhaust stream resulting from the combustion in the combustion engine, in order to reduce nitrogen oxides NOx, primarily to nitrogen gas and aqueous vapour. This is described in more detail below.

[0010] Selective catalytic reduction (SCR) catalysts are a commonly used type of catalysts for this type of reduction, primarily for heavy goods vehicles. Selective catalytic reduction catalysts usually use ammonia NH3, or a composition from which ammonia may be generated / formed, as a reductant / additive to reduce the amount of nitrogen oxides NOx in the exhausts. The reductant, for example urea, is injected into the exhaust stream resulting from the combustion engine upstream of the catalyst. The reductant added to the catalyst is adsorbed (stored) in the catalyst, in the form of ammonia NH3, so that a redox-reaction may occur between nitrogen oxides NOx in the exhausts and ammonia NH3 available via the reductant.

[0011] For an exhaust treatment system comprising two or more selective catalytic reduction catalysts, two or more dosing / dosage units are configured for injecting the reductant into the exhaust stream, one dosing unit being configured upstream of each selective catalytic reduction catalyst. The reductant is provided to the two or more dosing units by a reductant delivery system, which in general terms is a fluid delivery system providing a fluid to the two or more dosing units.

[0012] Another possible implementation of such a fluid delivery system, being configured for providing fluid to two or more dosing units, is a fuel delivery system configured for providing a fuel to an engine. In this implementation, the fluid is thus a fuel, such as e.g. petrol / gasoline, and the dosing units are fuel injections valves of the engine. Summary

[0013] It is important to be able to accurately monitor a fluid delivery system. For example, dosing of the reductant is subjected to stringent legal requirements, demanding efficient and simple monitoring concepts of the performance of the fluid delivery system, i.e. of the reductant delivery system. Also, for fuel delivery systems, it is very important that an accurate amount of fuel is always injected into the engine for engine efficiency and fuel consumption reasons, demanding a very accurate fuel delivery system.

[0014] However, the fluid delivery systems are often provided with only one fluid pressure sensor. Due to the limited physical sensor input provided by this single fluid pressure sensor, certain properties of the fluid delivery system cannot be directly measured.

[0015] Further, conventional systems for monitoring fluid delivery systems are complicated to calibrate and / or are too slow to be able to adapt to fast changes possibly occurring in the fluid delivery system.

[0016] It is therefore an objective of the present invention to provide a diagnosis of a fluid delivery system such that these problems are at least partly solved.

[0017] According to a first aspect of the present invention, this objective is achieved through the above-mentioned method for determining a diagnosis of a fluid delivery system, the fluid delivery system comprising two or more dosing units, a pump and one fluid pressure sensor.

[0018] The method comprises:

[0019] - determining, under normal operation of the fluid delivery system, two or more individual dosed masses of fluid being individually dosed by the two or more dosing units, respectively;

[0020] - determining, under normal operation of the fluid delivery system, a simultaneous dosed mass of fluid being simultaneously dosed by all of the two or more dosing units together; and

[0021] - determining the diagnosis of the fluid delivery system based on the two or more individual dosed masses of fluid and corresponding two or more individual requested masses of fluid for the two or more dosing units, respectively, and based on the simultaneous dosed mass of fluid and a corresponding simultaneous requested mass of fluid.

[0022] The presented solution enables the model or models used to be passively and continuously updated in real time, i.e. during normal operation of the fluid delivery system. Conventional performance monitoring of fluid delivery systems requires intrusive manipulation of the system control and operation to be able to monitor the system, e.g. for estimate a dosing error. Conventional legislation has accepted such intrusions due to the difficulty of the monitoring requirements.

[0023] The presented solution can, however, robustly implement a monitoring concept which does not require any intrusive actions. The determination of a diagnosis for the fluid delivery system may instead perform its evaluations during any reasonable and normal driving cycle. Thus, the presented determination of a diagnosis for the fluid delivery system does not affect the behavior of the fluid delivery system and its application. For example, the diagnosis does not affect the emissions from an exhaust treatment system, in which the reductant is provided by a fluid delivery system in form of a reductant delivery system being diagnosed. Also, the diagnosis does not affect the efficiency and / or fuel consumption of the engine when the fuel is provided to the engine by a fluid delivery system in form of a fuel delivery system being diagnosed.

[0024] The presented solution provides real time estimation of the performance of the fluid delivery system. In addition to providing real time update and / or monitoring of several of the key properties utilized by the model, such as e.g. pump flow, return flow and system elasticity, the solution utilizes the current logic and calculations under normally occurring operating conditions for the vehicle.

[0025] Hereby, an improved diagnostic of the fluid delivery system, and an increased robustness of the monitoring of the fluid delivery system are enabled.

[0026] Further, the herein presented diagnosis determination requires little calibration, because it is based on physical properties of the fluid delivery system that are already known in the vehicle. The diagnosis determination therefore has the possibility to independently be used on a wide range of applications. According to an embodiment of the present invention, the two or more individual dosed masses of fluid are determined based on two or more models of the individual dosing performed by the two or more dosing units, respectively.

[0027] By determining two or more individual dosed masses of fluid based on models of the physical features of the fluid delivery system, and specifically based on the features of the individual dosing, results in a robust diagnostic of the fluid delivery system, which requires little calibration and is possible to implement in a wide range of applications. By the determination of the two or more individual dosed masses, a pinpointing of error sources is also facilitated. This differs from prior art solutions that use the work of the pump or the change in the fluid level in the tank to diagnose the delivery performance of the system.

[0028] According to an embodiment of the present invention, the two or more individual dosed masses of fluid are determined based on the two or more models according to: where:

[0029] - Qdose_ind_k is the individual dosed mass of fluid for dosing unit k during a time interval from t_open_DU_k to t_close_DU_ki

[0030] - k is an integer equal to or smaller than m; k = 1 , 2, ... , m; where m is an integer equal to or higher than 2; m = 2, 3, ... , M;

[0031] - Qpump is a fluid mass output by the pump during a time interval from t_0Pen_Du_k to t_close_DU_k;

[0032] - Qretum is a fluid mass returning from the two or more dosing units during a time interval from t_open_Du_k to t_ciose_Du_k;

[0033] - t_oPen_Du_k is a point in time at which dosing unit k becomes the only dosing unit being in an open state;

[0034] - t_ciose_Du_k is a point in time at which dosing unit k ceases to be the only dosing unit being in an open state; and

[0035] - B is a system variable associated with an elasticity of the fluid delivery system. Hereby, the individual dosed mass of fluid Qdosejnd_k for dosing unit k may efficiently and accurately be determined. The model-based determination of the individually dosed mass of fluid for dosing unit k is further robust and requires little calibration.

[0036] According to an embodiment of the present invention, the simultaneous dosed mass of fluid is determined based on a model of the simultaneous dosing performed by the two or more dosing units.

[0037] By determining the simultaneous dosed mass of fluid based on a model of the physical features of the fluid delivery system, and specifically based on the features of the simultaneous dosing, a robust diagnostic of the fluid delivery system is provided, which requires little calibration and is possible to implement in a wide range of applications.

[0038] The determination of the simultaneous dosed mass of fluid may be used for evaluation of the fluid delivery system during its normal operation. Many values / samples for the simultaneous dosed mass of fluid may hereby be provided, such that errors / problems may be quickly identified.

[0039] The evaluation / diagnosis may hereby be performed during synchronized dosing, and may be used for identifying a dosing error on a system / global level. Thus, a system / global error may be identified based on the simultaneous dosed mass of fluid, which may be identified regardless of which control of the dosing units is used. This may be utilized for first identifying that there is some kind of problem in the system. The individual dosed mass of fluid may thereafter be utilized for identifying the faulty dosing unit causing the system / global dosing error.

[0040] According to an embodiment of the present invention, the simultaneous dosed mass of fluid is determined based on the model according to: where:

[0041] - Qdose_sim is the simultaneous dosed mass of fluid for dosing units 1 to m during a time interval from t_open_DU_1-m to t_close_DU_any;

[0042] - m is an integer equal to or higher than two; m = 2, 3, ... , M; - Qpump is a fluid mass output by the pump during a time interval from t_Open_Du_i-m to t_close_DU_anyi

[0043] - Qretum is a fluid mass returning from the two or more dosing units during a time interval from t_open_DU_1-m to t_close_DU_any;

[0044] - t_oPen_Du_i -m is a point in time when at least one dosing unit changes from a closed state to an open state, such that all dosing units 1 to m thereafter are in an open state;

[0045] - t_Ciose_Du_any is a point in time when at least one dosing unit changes from an open state to a closed state; and

[0046] - B is a system variable associated with an elasticity of the fluid delivery system.

[0047] Hereby, the simultaneous dosed mass of fluid Qdose_sim may efficiently and accurately be determined. The model-based determination of the simultaneous dosed mass of fluid Qdose_sim is further robust and requires little calibration.

[0048] According to an embodiment of the present invention, the determination of the diagnosis of the fluid delivery system comprises:

[0049] - determining two or more individual dosing errors based on the two or more individual dosed masses of fluid and the corresponding two or more individual requested masses of fluid, respectively;

[0050] - comparing the two or more individual dosing errors with two or more individual error thresholds, respectively;

[0051] - determining a simultaneous dosing error based on the simultaneous dosed mass of fluid and the corresponding simultaneous requested mass of fluid; and

[0052] - comparing the simultaneous dosing error with a simultaneous error threshold.

[0053] Thus, the residuals, i.e. the individual and simultaneous dosing errors Qerror_ind_k, are utilized for efficiently detecting if there is a fault in the fluid delivery system, such that it may be determined if a fault code shall be set or not.

[0054] According to an embodiment of the present invention, the determination of the two or more individual dosing errors is performed according to: where:

[0055] - Qerror_ind_k is the individual error for dosing unit k;

[0056] - Qreq_ind_k is the individual requested mass of fluid from dosing unit k;

[0057] - Qdose_ind_k is the individual dosed mass of fluid from dosing unit k; and

[0058] - k is an integer equal to or smaller than m; k = 1 , 2, m; where m is an integer equal to or higher than 2; m = 2, 3, ... , M.

[0059] Hereby, the residual Qerror_ind_k, i.e. the individual error for dosing unit k, may be efficiently and accurately determined.

[0060] According to an embodiment of the present invention, the determination of the simultaneous dosing error is performed according to: z, > Qreq_sim~ Qdose_sim error_sim ~ req_sim > where:

[0061] - Qerror_sim is the simultaneous dosing error for all dosing units;

[0062] - Qreq_sim is the simultaneous requested mass of fluid from all dosing units; and

[0063] - Qdose_sim is the simultaneous dosed mass of fluid of all dosing units.

[0064] Hereby, the residual Qen-or_sim, i.e. the simultaneous dosing error for all dosing units, may be efficiently and accurately determined.

[0065] According to an embodiment of the present invention, the method further comprises:

[0066] - determining, under normal operation of the fluid delivery system, a zero dosing mass of fluid based on a model for all of the two or more dosing units being closed.

[0067] The model-based zero dosing mass of fluid Qd ose_zero may be utilized for efficient detection of dosing accuracy related faults or other faults in the fluid delivery system, such as possible clogging and / or leakage. This information may be used to further improve fault detection isolation, i.e. to pinpoint the faulty system component.

[0068] According to an embodiment of the present invention, the zero dosing mass of fluid is determined based on the model according to: where:

[0069] - Qdose_zero is the zero dosing mass fluid during a time interval when all of dosing units 1 to m are in a closed state;

[0070] - m is an integer equal to or higher than two; m = 2, 3, ... , M;

[0071] - Qpump is a fluid mass output by the pump;

[0072] - Qretum is a fluid mass returning from the two or more dosing units;

[0073] - t_ciose_Du_i-m is a point in time when at least one dosing unit changes from an open state to a closed state, such that all of dosing units 1 to m thereafter are in a closed state; and

[0074] - t_oPen_Du_any is a point in time when at least one dosing unit changes from a closed state to an open state, such that at least one of dosing units 1 to m thereafter is in an open state;

[0075] - B is a system variable associated with an elasticity of the fluid delivery system.

[0076] Hereby, the zero dosing mass fluid Qd ose_zero may be efficiently and accurately determined.

[0077] According to an embodiment of the present invention, if a determined value for the zero dosing mass of fluid differs from zero when all of the two or more dosing units are closed, the determined value for the zero dosing mass of fluid is utilized for one or more in the group of:

[0078] - determining a fluid mass Qpump output by the pump;

[0079] - determining a fluid mass Qretum returning from the two or more dosing units;

[0080] - determining a diagnosis of a performance of the pump;

[0081] - determining a diagnosis of a performance of a return system configured for providing a return flow of fluid from the two or more dosing units; and

[0082] - determining a system variable associated with an elasticity of the fluid delivery system.

[0083] Thus, in addition to the detection of dosing accuracy related faults, the presented method also provides the possibility to detect other faults in the fluid delivery system, such as clogging and / or leakage. The detection of such other faults may be utilized for faulty component isolation.

[0084] According to an embodiment of the present invention, the one pressure sensor is configured at one in the group of:

[0085] - one of the at least two dosing units;

[0086] - the pump; and

[0087] - a separate sensor component.

[0088] The presented diagnosis of a fluid delivery system may thus be utilized for various pressure sensor layouts.

[0089] According to an embodiment of the present invention,

[0090] - the fluid delivery system is a reductant delivery system configured for providing a reductant to an exhaust treatment system; and

[0091] - the fluid is the reductant.

[0092] Hereby, a robust and real time monitoring of the reductant delivery system is provided, which is performed during normal operation of an exhaust treatment system.

[0093] According to an embodiment of the present invention,

[0094] - the fluid delivery system is a fuel delivery system configured for providing a fuel to an engine; and

[0095] - the fluid it the fuel.

[0096] Hereby, a robust and real time monitoring of the fuel delivery system is provided, which is performed during normal operation of an engine.

[0097] According to a second aspect of the present invention, the objective is achieved through a control system configured for determining a diagnosis of a fluid delivery system, the fluid delivery system comprising two or more dosing units, a pump and one fluid pressure sensor; wherein the control system is configured to:

[0098] - determine, under normal operation of the fluid delivery system, two or more individual dosed masses of fluid being individually dosed by the two or more dosing units, respectively;

[0099] - determine, under normal operation of the fluid delivery system, a simultaneous dosed mass of fluid being simultaneously dosed by all of the two or more dosing units together; and

[0100] - determine the diagnosis of the fluid delivery system based on the two or more individual dosed masses of fluid and corresponding two or more individual requested masses of fluid for the two or more dosing units, respectively, and based on the simultaneous dosed mass of fluid and a corresponding simultaneous requested mass of fluid.

[0101] According to a third aspect of the present invention, the objective is achieved through a vehicle comprising:

[0102] - a fluid delivery system comprising two or more dosing units and one fluid pressure sensor; and

[0103] - a herein described control system.

[0104] According to a fourth aspect, the invention relates to a computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the herein described methods.

[0105] The computer program has corresponding advantages as mentioned for the method according to the first aspect.

[0106] According to a fifth aspect, the invention relates to a computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out the herein described methods.

[0107] The computer-readable medium has corresponding advantages as mentioned for the method according to the first aspect.

[0108] It will be appreciated that all the embodiments described for the method aspects of the invention are applicable also to one or more of the control system aspect, the vehicle aspect, the computer program aspect and the computer-readable medium aspect of the invention. Thus, all the embodiments described for the method aspects of the invention may be performed / implemented by the herein described control system, vehicle, computer program and / or the computer-readable medium. The control system may also be a processing device, i.e. a device. The control system aspects, the vehicle aspect, the computer program aspect and the computer- readable medium aspect, and their embodiments, have advantages corresponding to the advantages mentioned above for the method aspect and its embodiments.

[0109] Brief list of figures

[0110] The invention will be illustrated in more detail below, along with the enclosed drawings, where similar references are used for similar parts, and where:

[0111] Figure 1 shows an example vehicle, in which various aspects and embodiments of the present invention may be implemented,

[0112] Figure 2 shows an example of a fluid delivery system in form of a fuel delivery system, in which various aspects and embodiments of the present invention may be implemented,

[0113] Figure 3 shows an exhaust treatment system and a fluid delivery system in form of a reductant delivery system, in which various aspects and embodiments of the present invention may be implemented,

[0114] Figure 4 shows a flow chart for the method according to some aspects and embodiments of the invention,

[0115] Figure 5 schematically illustrates a non-limiting example of a timeline for open and closed states for the dosing units, and corresponding points in time,

[0116] Figure 6 schematically illustrates a control unit in which the aspects and embodiments of the present invention may be implemented.

[0117] Description of preferred embodiments

[0118] Figure 1 schematically shows an example vehicle 100 comprising a powertrain. The powertrain comprises a combustion engine 101 , which in a customary manner, via an output shaft 102 of the combustion engine 101 is connected to a gearbox 103 via a clutch 106. An output shaft 107 from the gearbox 103 may drive the wheels 113, 114 e.g. via a final drive 108, such as e.g. a customary differential, and the drive shafts 104, 105 connected to the final drive 108.

[0119] The combustion engine 101 , e.g. an internal combustion engine driven by a fuel, such as e.g. petrol / gasoline, may be controlled by the engine’s control system via a control system / arrangement / unit / device 190. Likewise, the clutch 106 and the gearbox 103 may be controlled by the vehicle’s control system, with the help of one or more applicable control devices (not shown). Naturally, the vehicle’s powertrain may also be of another type, such as a type with a conventional automatic gearbox, or a type with a hybrid driveline, etc.

[0120] The vehicle 100 also comprises an exhaust treatment / purification system 350 for treatment / purification of exhaust emissions resulting from combustion in the combustion chamber of the combustion engine 101 . The exhaust treatment system 350 may be a herein described exhaust treatment system 350, being controlled by a control system / arrangement / unit / device 190.

[0121] Figure 2 schematically shows some parts of a fluid delivery system comprising two fuel dosing units, here exemplified as a fuel delivery system 270 comprising a first fuel injection valve 271 and a second fuel injection valve 272, a fuel container / tank 275, and a fuel pump 274. The first fuel injection valve 271 , the second fuel injection valve 272 and / or the fuel pump 274 may be controlled by a control system / arrangement / unit / device 290.

[0122] The fuel delivery system 270 is equipped with one fluid pressure sensor 280. The fluid pressure sensor 280 may be configured at the first fuel injection valve 271 , at the second fuel injection valve 272, or at the fuel pump 274. The fluid pressure sensor 280 may also be configured as a separate sensor component somewhere in the fuel delivery system 270. In figure 2, the fluid pressure sensor 280 is configured at the second fuel injection valve 272, as an example illustration. The fluid pressure sensor 280 is connected to the control system / arrangement / unit / device 290, and is configured to provide sensor signal information to the control system / arrangement / unit / device 290.

[0123] Figure 3 schematically shows an exhaust treatment system 350, in which the herein presented fluid delivery system may be implemented as a reductant / additive delivery system 370.

[0124] The exhaust treatment system 350 is connected via an exhaust pipe 302 to a combustion engine 301 . Exhausts are generated at combustion in the engine 301 , and the exhaust stream 303 (indicated with arrows) is led to an upstream dosing unit 371 , which is comprised in the reductant / additive delivery system 370 and is configured to add a reductant / additive into the exhaust stream 303. A first / upstream selective catalytic reduction catalyst (SCRi) 330 is arranged downstream of the first / upstream dosing unit 371.

[0125] The first / upstream selective catalytic reduction catalyst 330 is arranged to reduce nitrogen oxides NOx in the exhaust stream 303, through the use of the reductant / additive added to the exhaust stream by the first / upstream dosing unit 371 . In more detail, the first / upstream selective catalytic reduction catalyst 330 uses the reductant / additive, for example ammonia NHs, or a substance from which ammonia NHs may be generated / formed / released, for the reduction of nitrogen oxides NOx in the exhaust stream 303. This reductant / additive may for example consist of the above mentioned AdBlue, and may be provided from a container / tank 375. The injection of the reductant / additive may be controlled by a control system / arrangement / unit / device 390.

[0126] Downstream of the first / upstream selective catalytic reduction catalyst 330, the exhaust treatment system 350 may further comprise a coated diesel particulate filter (cDPF) 310, which is coated with a catalytically oxidising coating, for example comprising at least one precious metal for catching and oxidising soot and ash. Alternatively, a diesel oxidation catalyst (DOC) followed downstream by a diesel particulate filter (DPF / cDPF) may be arranged in the exhaust treatment system 350 instead of the coated diesel particulate filter. Thus, either of a coated diesel particulate filter 310 and a diesel oxidation catalyst followed by a diesel particulate filter is arranged downstream of the first / upstream selective catalytic reduction catalyst 330 in the exhaust treatment system 350.

[0127] Downstream of the particulate filter 310, the exhaust treatment system 350 comprises a second / downstream dosing unit 372, which is comprised in the reductant / additive delivery system 370 and is configured to supply reductant / additive to the exhaust stream 303. The downstream reductant / additive comprises ammonia NHs, or a substance, for example AdBlue, from which ammonia NHs may be generated / formed / released, as described above. The downstream reductant / additive is here be the same reductant / additive as the above mentioned additive injected by the first / upstream dosing unit 371 , and also come from the same reductant container / tank 375. The injection of the reductant / additive may be controlled by the control system / arrangement / unit / device 390.

[0128] A fluid pump 374 is arranged in the reductant / additive delivery system 370 for pumping the reductant / additive from the reductant container / tank 375 to the first / upstream dosing unit 371 and to the second / downstream dosing unit 372 via hoses and / or piping. Thus, the first / upstream dosing unit 371 , the second / downstream dosing unit 372, the reductant container / tank 375, the fluid pump 374, and hoses and / or piping, including a return system between the second / downstream dosing unit 372 and the reductant container / tank 375, are included in the herein presented reductant delivery system 370. The fluid pump 374 may be controlled by a control system / arrangement / unit / device 390.

[0129] According to an embodiment of the invention, an evaporation arrangement may be arranged at the first / upstream 371 and / or second / downstream 372 dosing units, respectively, to increase the speed of the decomposition of urea into ammonia, and / or to mix the additive with the emissions, and / or to vaporise the additive.

[0130] The exhaust treatment system 350 also comprises a second / downstream reduction catalyst device (SCR2) 320, which is arranged downstream of the second / downstream dosing unit 372. The second / downstream reduction catalyst device 320 is arranged to reduce nitrogen oxides NOx in the exhaust stream 303 through use of the reductant / additive injected by the second / downstream dosing unit 372, and possibly also reductant / additive remaining in the exhaust stream 303 which was injected by the first / upstream dosing unit 371 .

[0131] According to an embodiment, the exhaust treatment system 350 may further comprise an ammonia slip catalyst arrangement (ASC) 340 arranged downstream of the second / downstream reduction catalyst device 320 for oxidation of a residue of reductant / additive in the exhaust stream 303, as shown in figure 3, respectively. The ammonia slip catalyst arrangement 340 removes an reductant / additive residue from the exhaust stream 303.

[0132] After passing through the components of the exhaust treatment system, the exhaust stream is emitted into the environment at the tailpipe of the exhaust treatment system.

[0133] The reductant / additive delivery system 370 is equipped with one fluid pressure sensor 380. The fluid pressure sensor 380 may be configured at the first / upstream dosing unit 371 , the second / downstream dosing unit 372, or at the fluid pump 374. The fluid pressure sensor 380 may also be configured as a separate sensor component somewhere in the reductant delivery system 370. As an example, the fluid pressure sensor 380 is configured at the second / downstream dosing unit 372 in figure 3. The fluid pressure sensor 380 is connected to the control system / arrangement / unit / device 390, and is configured to provide sensor signal information to the control system / arrangement / unit / device 390.

[0134] The method 400, illustrated by the flow-chart in figure 4, determines a diagnosis of a fluid delivery system 270, 370 comprising two or more dosing units 271 , 272, 371 , 372, a pump 274, 374 and one fluid pressure sensor 280, 380, for example a fluid delivery system 270, 370 as illustrated in figures 2-3. The method steps of figure 4 may be performed in another order than illustrated in figure 4, as long as the information needed for performing a method step is available when the step is to be performed. In a first step 410 of the method 400, two or more individual dosed masses of fluid Qdose_ind_1 , Qdose_ind_2, Qdose_ind_m being individually dosed by the two or more dosing units 271 , 272, 371 , 372, respectively, are determined under normal operation of the fluid delivery system 270, 370. Thus, the two or more individual dosed masses of fluid Qdosejnd_i , Qdosejnd_2, ... , Qdose_ind_m are here determined under normal operation, which in this document means that they are determined passively while the fluid delivery system 270, 380 provides its normal fluid delivery.

[0135] In this document, normal operation of the fluid delivery system 270, 370 means that the fluid delivery system 270, 370 provides the fluid without any special control procedures or exceptions from the ordinary control of the fluid delivery system 270, 370 taking place, i.e. without the need for intrusive actions in the control of the fluid delivery system 270, 370. During normal operation, a fluid injection / dosing quantity and an injection period time for each dosing unit may thus be controlled freely, i.e. without restrictions / intrusions, based on the fluid needs of the application, i.e. based on the needs of the system the fluid is delivered to. The method 400 may in other words be seen as being passively and / or continuously performed during normal work cycles of the fluid delivery system 270, 370.

[0136] For example, if the fluid delivery system 270, 370 is a fuel delivery system 270, the determination of the two or more individual dosed masses of fluid Qdosejnd , Qdosejnd_2, ... , Qdose_ind_m is passively performed during normal operation of the engine 201 , i.e. while the fuel delivery system 270 provides fuel for normal / ordinary injection into the engine 201 for driving the engine. Alternatively, if the fluid delivery system 270, 370 is a reductant delivery system 370, the determination of the two or more individual dosed masses of fluid Qdose_ind_i , Qdose_ind_2, ... , Qdose_ind_m is passively performed during normal operation of the exhaust treatment system 350, i.e. while the reductant delivery system 370 provides reductant for normal / ordinary injection into the exhaust gases in order utilize the reductant in one or more reduction catalyst devices to purify the exhaust gases.

[0137] According to an embodiment, the determination of the two or more individual dosed masses of fluid Qdose_ind_i , Qdose_ind_2, ... , Qdose_ind_m is accumulated over time, i.e. the determination is based on two or more measurements separated in time. In a second step 420 of the method 400, a simultaneous dosed mass of fluid Qdose_sim, which is simultaneously dosed by all of the two or more dosing units 271 , 272, 371 , 372 together, is determined under normal operation of the fluid delivery system 270, 370.

[0138] In a third step 430 of the method 400, a diagnosis of the fluid delivery system 270, 370 is determined based on the two or more determined individual dosed masses of fluid Qdosejnd , Qdosejnd_2, ... , Qdosejnd_m and corresponding two or more individual requested masses of fluid Qreqjndj , Qreq_indj, ... , Qreq_ind_m for the two or more dosing units 271 , 272, 371 , 372, respectively, and based on the simultaneous dosed mass of fluid Qdose_sim and a corresponding simultaneous requested mass of fluid Qreq_sim. Thus, for each one of the two or more dosing units 271 , 272, 371 , 372, an individual dosed mass of fluid Qdosejnd , Qdosejnd_2, ... , Qdose_ind_m is determined and compared to the corresponding individual requested mass of fluid Qreq nd , Qreqjnd , ... , Qreq_ind_m for that dosing unit. Also, the simultaneous dosed mass of fluid Qdose_sim is compared to the corresponding requested simultaneous mass of fluid Qreq_sim. The diagnosis of the fluid delivery system 270, 370 is then determined based on these comparisons.

[0139] As is understood by a skilled person, the method 400 may be applied on a fluid delivery system 270, 370 comprising essentially any number of at least two dosing units. Also, the dosing units may be grouped together in at least two groups, where each group comprises at least one dosing unit, in which case each of the individual dosed masses of fluid Qdosejndj , Qdosejnd , ... , Qdosejnd_m may be an estimation of a dosed mass for such a group of dosing units.

[0140] According to an embodiment, the two or more individual dosed masses of fluid Qdosejndj , Qdosejndj, ... , Qdosejnd_m are determined 410 based on two or more models of the individual dosing performed by the two or more dosing units 271 , 272, 371 , 372, respectively. Thus, the determination 410 of the two or more individual dosed masses of fluid Qdosejndj , Qdosejndj, ... , Qdose_ind_m is here model-based, which means that the determination of the two or more individual dosed masses of fluid Qdosejndj , Qdosejndj, ... , Qdosejnd_m is performed by applying a mathematical model, which is based on the physics of the fluid delivery system 270, 370. Such a model may for example define or describe relationships between pressure and flow dynamics of the fluid delivery system 270, 370:

[0141] Where:

[0142] - p is a bulk modulus of the fluid delivery system;

[0143] - V is a pressurized volume of the fluid delivery system;

[0144] - q is a mass flow (g / min) through the fluid delivery system;

[0145] - Q is a mass (g);

[0146] - AQ is a total / net change in mass; and

[0147] - dp / dt is a time derivative of the pressure

[0148] This expression / model shows that the total mass change in the fluid delivery system 270, 370, over a given time interval multiplied by the ratio of the bulk modulus and the pressurized volume V, corresponds to the pressure derivative integrated over the same time interval. If the term is replaced with the term B the expression / model of equation 3 may be written as: where:

[0149] - B is a system variable associated with an elasticity of the fluid delivery system 270, 370.

[0150] Equation 4, which describes the pressure dynamics of the fluid delivery system 270, 370 may be rearranged in order to solve the injected mass Qdose: To calculate the injected mass Qdose, it is assumed that the pump mass Qpump can be modelled using the following relationship:

[0151] Where

[0152] - NpUmp is the measured pump speed and Dpumpis the pump’s displacement.

[0153] The returned mass back Qretum returning from the two or more dosing units 271 , 272, 371 , 372, e.g. to the container / tank 275, 375 can be modelled using the orifice equation: where

[0154] - Cdis known as the discharge coefficient;

[0155] - p is the density of the fluid;

[0156] - psysis the measured system pressure; and

[0157] - Patm is the measured atmospheric pressure.

[0158] For cost, robustness, space and weight reasons, as well as for other reasons, the fluid delivery system 270, 370 is typically implemented as comprising only one single fluid pressure sensor 280, 380. Thus, the fluid delivery system 270, 370 is equipped with a single fluid pressure sensor 280, 380, for example configured to measure the pressure in either the fluid pump 274, 374, in a dosing unit 271 , 272, 371 , 382, or as a separated pressure sensor component in the fluid delivery system 270, 370. The control system 290, 390 thus has very little feedback from the hardware to use for analyzing the system performance with regards to, for example dosing accuracy, leakages and blockages.

[0159] According to an embodiment, the two or more individual dosed masses of fluid Qdosejnd , Qdosejnd_2, ... , Qdose_ind_m are therefore determined 410 based on the two or more above mentioned models of the individual dosing being performed by the two or more dosing units 271 , 272, 371 , 372, respectively, according to: where:

[0160] - Qdose_ind_k is the individual dosed mass of fluid for dosing unit k during a time interval from t_open_DU_k to t_close_DU_ki

[0161] - k is an integer equal to or smaller than m; k = 1 , 2, ... , m; where m is an integer equal to or higher than 2; m = 2, 3, ... , M;

[0162] - Qpump is a fluid mass output by the pump 274, 374 during a time interval from t_open_DU_k to t_close_DU_ki

[0163] - Qreturn is a fluid mass returning from the two or more dosing units 271 , 272, 371 , 372 during a time interval from t_Open_ou_k to t_Ciose_Du_k;

[0164] - t_oPen_Du_k is a point in time at which dosing unit k becomes the only dosing unit being in an open state, i.e. a point in time at which dosing unit k changes from closed state to open state when the rest of the dosing units are in closed state, or when dosing unit k remains in open state when a last one of the remaining dosing units changes from open state to closed state such that all of the other dosing units are in closed state;

[0165] - t_Ciose_Du_k is a point in time at which dosing unit k ceases to be the only dosing unit being in an open state, i.e. a point in time at which dosing unit k changes from open state to closed state, or when any of the other dosing units changes from closed state to open; and

[0166] - B is a system variable associated with an elasticity of the fluid delivery system 270, 370.

[0167] By integrating all the individual masses from the start of the injection to the end of the injection for each dosing unit 271 , 272, 371 , 372, the individual dosed mass

[0168] Qdosejnd_k can be estimated continuously and for each individual dosing unit 271 , 272, 371 , 372.

[0169] Further, when several dosing units are open simultaneously, the total mass of these dosing units 271 , 272, 371 , 372 can be estimated individually as well, by integrating each contribution between the opening and closing event of the respective dosing unit 271 , 272, 371 , 372. According to an embodiment, the simultaneous dosed mass of fluid Qdose_sim is then determined 420 based on a model of the simultaneous dosing performed by the two or more dosing units 271 , 272, 371 , 372.

[0170] For example, the simultaneous dosed mass of fluid Qdose_sim may be determined 420 based on the model according to: where:

[0171] - Qdose_sim is the simultaneous dosed mass of fluid for dosing units 1 to m during a time interval from t_open_DU_1-m to t_close_DU_any;

[0172] - m is an integer equal to or higher than two; m = 2, 3, ... , M;

[0173] - Qpump is a fluid mass output by the pump 274, 374 during a time interval from t_open_DU_1-m to t_close_DU_any;

[0174] - Qreturn is a fluid mass returning from the two or more dosing units 271 , 272, 371 , 372 during a time interval from t_Open_Du_i-m to t_Ciose_Du_any;

[0175] - t_oPen_Du_i -m is a point in time when at least one dosing unit changes from a closed state to an open state, such that all dosing units 1 to m thereafter are in an open state;

[0176] - t_Ciose_Du_any is a point in time when at least one dosing unit changes from an open state to a closed state; and

[0177] - B is a system variable associated with an elasticity of the fluid delivery system 270,370.

[0178] According to an embodiment schematically illustrated in the flow chart of figure 4, the determination 430 of the diagnosis of the fluid delivery system 270, 370 comprises the step of determining 432 two or more individual dosing errors Qerrorjnd_i , Qerror nd_2, ... , Q error_ind_m based on the two or more individual dosed masses of fluid Qdosejnd_i , Qdosejnd_2, ... , Qdose_ind_m and the corresponding two or more individual requested masses of fluid Qreq_ind_1 , Qreq_ind_2, ... , Qreq_ind_m, respectively.

[0179] Then, the two or more individual dosing errors Qerrorjnd_i , Q error_ind_2, ... , Qerror_ind_m are compared 434 with two or more individual error thresholds Qerror_th_i, Qerror_th_2, ... , Qerror_th_m, respectively. The two or more individual error thresholds Qerror_th_i , Qerror_th_2, Qerror_th_m may generally have values such that a degraded dosing capacity of a dosing unit is possible to detect, i.e. such that the degraded dosing capacity can be distinguished from a normal dosing capacity. For an exhaust treatment system, the two or more individual error thresholds Qerror_th_i , Qerror_th_2, ... , Qerror_th_m may be determined based on possible emissions associated with the two or more individual dosing errors Qerror_ind_1 , Qerror_ind_2, ... , Qerror_ind_m and / or an emission regulation under which the exhaust treatment system is used. The two or more individual error thresholds Qerror_th_i , Qerror_th_2, ... , Qerror_th_m may also be determined based on a conversion efficiency of the one or more selective catalytic reduction catalysts in which the reductant should be utilized for treatment of the exhaust gases. For example, the two or more individual error thresholds Qerror_th_i, Qerror_th_2, ... , Qerror_th_m may be determined such that, if the fluid / reductant delivery system is faulty, the failure of the fluid / reductant delivery system should be diagnosed before the one or more selective catalytic reduction catalysts are diagnosed as having too low conversion efficiency. As a non-limiting example, the two or more individual error thresholds Qerror_th_i, Qerror_th_2, ... , Qerror_th_m may correspond to a fraction of a normal dosing capacity, for example in the range of 20-40% under-dosing.

[0180] A simultaneous dosing error Qen-or_sim is also determined 436 based on the simultaneous dosed mass of fluid Qdose_sim and the corresponding simultaneous requested mass of fluid Qreq_sim.

[0181] Then, the simultaneous dosing error Qerror_sim is compared 438 with a simultaneous error threshold Qerror_th_sim. The simultaneous error threshold Qerror_th_sim may for example be determined based on regulations and / or legislations. For a reductant delivery system, the legislation may state that a fault should be detected if the reductant injection is less than a certain level, for example if the reductant injection is less than 50% of the expected / requested reductant injection. Such levels indicated in regulations and / or legislations typically apply to the total reductant injection.

[0182] Thus, the residuals, i.e. the two or more individual dosing errors Qerrorjnd_i , Qerror_ind_2, ... , Q error_ind_m and the simultaneous dosing error Qerror_sim are compared 434, 348 with corresponding individual Qerror_th_i , Qerror_th_2, ... , Q error_th_m and simultaneous Qerror_th_sim threshold values, respectively, to determine whether or not the dosing error is large enough to determine that a diagnosis fault code shall be set, or not.

[0183] Thus, the above described model is used for estimating the dosed mass of each dosing unit 271 , 272, 371 , 372 in the fluid delivery system 270, 370 integrated continuously / passively over time. This enables the possibility to provide some very efficient monitoring concepts. For example, the estimated / modelled total dosed mass for each dosing unit 271 , 272, 371 , 372 in the fluid delivery system 270, 370, given by the model may be compared with that of the amount of fluid that is requested. A difference between the requested and modelled fluid may be constructed as a residual to indicate the dosing error for each dosing unit 271 , 272, 371 , 372.

[0184] According to an embodiment, the determination 432 of the two or more individual dosing errors Qerror_ind_i , Q error_ind_2, ... , Qerror_ind_m is performed as: where:

[0185] - Qerrorjnd_k is the individual error for dosing unit k;

[0186] - Qreqjnd_k is the individual requested mass of fluid from dosing unit k;

[0187] - Qdose_ind_k is the individual dosed mass of fluid from dosing unit k; and

[0188] - k is an integer equal to or smaller than m; k = 1 , 2, ... , m; where m is an integer equal to or higher than 2; m = 2, 3, ... , M.

[0189] Further, according to an embodiment, the determination 434 of the simultaneous dosing error Qerror_sim is performed as:

[0190] _ Qreq_sim~Qdose_sim d d \ error_sim ~ > \^M- * U req_sim where:

[0191] - Qerror_sim is the simultaneous dosing error for all dosing units;

[0192] - Qreq_sim is the simultaneous requested mass of fluid from all dosing units; and

[0193] - Qdose_sim is the simultaneous dosed mass of fluid of all dosing units.

[0194] According to an embodiment, the method further comprises a step of determining

[0195] 440 a zero dosing mass of fluid Qdose_zero based on a model for all of the two or more dosing units 271 , 272, 371 , 372 being closed. The determination 440 is performed during normal operation of the fluid delivery system 270, 370.

[0196] The zero dosing mass of fluid Qdose_zero may be determined 240 based on a model according to: where:

[0197] - Qdose_zero is the zero dosing mass fluid during a time interval when all of dosing units 1 to m are in a closed state;

[0198] - m is an integer equal to or higher than two; m = 2, 3, ... , M;

[0199] - Qpump is a fluid mass output by the pump 274, 374;

[0200] - Qreturn is a fluid mass returning from the two or more dosing units 271 , 272, 371 , 372;

[0201] - t_Ciose_Du_i-m is a point in time when at least one dosing unit changes from an open state to a closed state, such that all of dosing units 1 to m thereafter are in a closed state; and

[0202] - t_oPen_Du_any is a point in time when at least one dosing unit changes from a closed state to an open state, such that at least one of dosing units 1 to m thereafter is in an open state;

[0203] - B is a system variable associated with an elasticity of the fluid delivery system 270, 370.

[0204] Figure 5 schematically illustrates a non-limiting example of dosing unit k (DU k) and at least one other dosing unit (DU others) changing between closed states (0) and open states (1 ) over time. Figure 5 also illustrates the above mentioned points in time t_open_DU_k, t_close_DU_k, t_open_DU_1-m, t_close_DU_1-m, t_open DU_any, and t_ _close_DU_any.

[0205] As illustrated in the example, the first and second t_0Pen_Du_k are points in time at which dosing unit k becomes the only dosing unit being in an open state, because dosing unit k changes from closed state to open state when the other dosing units are in a closed state. At the third t_Open_Du_k, dosing unit k remains in an open state when the other dosing units change from an open state to a closed state, such that all of the other dosing units are in a closed state after that point in time. The first and second t_Open_Du_any are points in time at which dosing unit k changes from closed state to open state when the other dosing units are in a closed state, such that at least one dosing units is in an open state after those points in time. The third t_oPen_Du_any is a point in time at which both dosing unit k and the other dosing units change from closed state to open state.

[0206] The first t_Open_Du_i-m is a point in time when the other dosing units change from a closed state to an open state, such that all dosing units thereafter are in an open state. At the second t_Open_Du_i-m, both dosing unit k and the other dosing units change from a closed state to an open state, such that all dosing units thereafter are in an open state.

[0207] The first and third t_ciose_Du_k are points in time at which dosing unit k ceases to be the only dosing unit being in an open state, because dosing unit k changes from an open state to a closed state. At the second t_Open_Du_k, the other dosing units change from a closed state to an open state, such that dosing unit k thereafter is not to be the only dosing unit being in an open state.

[0208] The first and second t_ciose_Du_i-m are points in time at which dosing unit k changes from an open state to a closed state, such that all of the dosing units thereafter are in a closed state. At the third t_ _close_DU_1-m, both dosing unit k and the other dosing units change from an open state to a closed state, such that all of dosing units thereafter are in a closed state.

[0209] The first t_ciose_Du_any is a point in time at which the other dosing units change from an open state to a closed state. At the second t_ _close_DU_any, both dosing unit k and the other dosing units change from an open state to a closed state.

[0210] According to some embodiments, the zero dosing mass estimate Qdose zero, i.e. the dosing mass fluid when all of dosing units 1 to m are in a closed state, may be considered to comprise information about the pump 274, 374. Therefore, the zero dosing mass estimate Qdose zeromay be utilized for determining 441 a fluid mass Qpump output by the pump 274, 374, possibly by adjusting an already estimated value for the pump fluid mass Qpump. The zero dosing mass estimate Qdose zeromay also be utilized for determining 443 a diagnosis of a performance of the pump 274, 374, possibly by comparing the zero dosing mass estimate Qdose zerowith a threshold value under the assumption that the pump 274, 374 has impaired performance relative the estimated pump fluid mass Qpump. This threshold value may be determined based on a flow margin of the pump 274, 374 in relation to the application system, e.g. an exhaust treatment system. Thus, the threshold value may be associated with such a flow margin. For example, if the pump 274, 374 is designed to have 15% over-capacity for the application system, i.e. if the pump 274, 374 is designed to have a 15 % flow margin, the threshold value may be chosen such that the pump is identified as faulty if the pump 274, 374 is not able to provide enough fluid for the application system, i.e. if the pump 274, 374 performance has degraded with 15%.

[0211] According to some embodiments, the zero dosing mass estimate Qdose zeromay comprise information about the return flow from the two or more dosing units 271 , 272, 371 , 372. Therefore, the zero dosing mass estimate Qdose zeromay be utilized for determining 442 a fluid mass Qretum returning from the two or more dosing units 271 , 272, 371 , 372, possibly by adjusting an already estimated value for the return fluid mass Qretum. The zero dosing mass estimate Qdose zeromay also be utilized for determining 444 a diagnosis of a performance of a return system 276, 376 configured for providing a return flow of fluid from the two or more dosing units 271 , 272, 371 , 372, possibly by comparing the zero dosing mass estimate Qdose zerowith a threshold value under the assumption that the return system 276, 376 has impaired performance relative the estimated return fluid mass Qretum. This threshold value may for example be determined such that a faulty return flow is identified if the return fluid mass Qretum increases to a level at which the fluid delivery system cannot provide enough fluid to the application system. The threshold value may also be determined based on a minimal flow needed for pump controllability and / or based on component cooling aspects.

[0212] These determinations 441 , 442, 443, 444 explore the fact that when there is no dosing for an extended period of time, the system should reach a steady state prressure,’ which means that the termJ^t_-colposeen_-l“-nmydt jnequation 12 is zero; ’ the |asterm jnequation 12 is zero, such that equation 12 > -i is reduced to Qdose zero= QPumP~ Qreturn)- According to an embodiment, each of the determinations 441 , 442, 443, 444 may be performed by assuming that the estimations of the other parameters are correct.

[0213] Since the dosing rate is zero by definition in the steady state, because all dosing units 1 to m are in a closed state, the pump flow must therefore be equal to the return flow, i.e. Qpump= Qreturn- Therefore, if the zero dosing mass estimate Qdose zerohas a non-zero value, it is an indication that there is a deviation in the flow of the return system 276, 376, a deviation in the pump performance and / or is a leakage or a blockage in the fluid delivery system 270, 370.

[0214] According to an embodiment, if the mass estimate Qdose zerohas a value larger than zero; Qdose zero> 0; then this may be an indication that the pump 274, 374 is faulty, since the value of the fluid mass Qpump output by the pump 274, 374 seems to have a too high value. Conversely, if the mass estimate Qdose zerohas a value smaller than zero; Qdose zero< 0; then this may be an indication that the return system 276, 376 is faulty, since the value of the fluid mass Qpump output by the pump 274, 374 seems to have a too low value, which is unlikely.

[0215] According to an embodiment, the zero dosing mass estimate Qdose zeromay comprise information about the elasticity of the fluid delivery system 270, 370 and the pressurized volume V of the fluid delivery system 270, 370. Therefore, the mass estimate Qdose zeromay be utilized for determining 445 the system variable B associated with an elasticity of the fluid delivery system 274, 374. Thus, the mass estimate Qdose zerois then utilized for determining the B-term of the mass flow equations 8, 9 & 12, being relates to the bulk modulus for the elasticity of the fluid delivery system 270, 370 and the pressurized volume V.

[0216] During short periods of no dosing when no steady state pressure is reached, for examprle duringaa gaap between two consecutive dosing events,’ the termJ^t_-colposeen_-^l-nmydt will have a non-zero value. Assuming that the there is no significant deviation detected at steady state pressure, i.e. at longer periods of a no dosing condition, the pressure rate of change can here, according to an embodiment, be used to estimate the B-term, also under normal operation, i.e. without the need for intrusive actions and in “real time”.

[0217] According to an aspect, a control system 290, 390 configured for determining a diagnosis of a fluid delivery system 270, 370 is presented. The fluid delivery system 270, 370 comprises two or more dosing units 271 , 272, 371 , 372, a pump 274, 374 and one fluid pressure sensor 280, 380, as described above.

[0218] The control system 290, 390 is configured to determine 410, under normal operation of the fluid delivery system 270, 370, two or more individual dosed masses of fluid Qdose_ind_1 , Qdose_ind_2, ... , Qdose_ind_m being individually dosed by the two or more dosing units 271 , 272, 371 , 372, respectively.

[0219] The control system 290, 390 is also configured to determine 420, under normal operation of the fluid delivery system 270, 370, a simultaneous dosed mass of fluid Qdose_sim being simultaneously dosed by all of the two or more dosing units 271 , 272, 371 , 372 together.

[0220] The control system 290, 390 is configured to determine 430 a diagnosis of the fluid delivery system 270, 370 based on the two or more individual dosed masses of fluid Qdosejnd , Qdosejnd_2, ... , Qdosejnd_m and corresponding two or more individual requested masses of fluid Qreqjnd , Qreq nd_2, ... , Qreq_ind_m for the two or more dosing units 271 , 272, 371 , 372, respectively, and based on the simultaneous dosed mass of fluid Qdose_sim and a corresponding simultaneous requested mass of fluid Qreq_sim.

[0221] According to an aspect, a vehicle 100 comprising a fluid delivery system 270, 370 comprising two or more dosing units 271 , 272, 371 , 372, one fluid pressure sensor 280, 380, and a herein described control system 290, 390 is presented.

[0222] A person skilled in the art will realise that a method 400 for determining a diagnosis of a fluid delivery system 270, 370 according to the present invention may also be implemented in a computer program, which when executed in a computer will cause the computer to execute the method. The computer program usually forms a part of a computer program product 503, wherein the computer program product comprises a suitable digital non-volatile I permanent I persistent I durable storage medium on which the computer program is stored. Said non- volatile / permanent / persistent / durable computer readable medium consists of a suitable memory, e.g.: ROM (Read-Only Memory), PROM (Programmable Read- Only Memory), EPROM (Erasable PROM), Flash, EEPROM (Electrically Erasable PROM), a hard disk device, etc.

[0223] Figure 6 schematically shows a control device 500 / 190 / 290 / 390. The control device 500 / 190 / 290 / 390 comprises a calculation unit 501 , which may consist of essentially a suitable type of processor or microcomputer, e.g. a circuit for digital signal processing (Digital Signal Processor, DSP), or a circuit with a predetermined specific function (Application Specific Integrated Circuit, ASIC). The calculation unit 501 is connected to a memory unit 502, installed in the control device 500 / 190 / 290 / 390, providing the calculation device 501 with e.g. the stored program code and / or the stored data, which the calculation device 501 needs in order to be able to carry out calculations. The calculation unit 501 is also set up to store interim or final results of calculations in the memory unit 502.

[0224] Further, the control device 500 / 190 / 290 / 390 is equipped with devices 511 , 512, 513, 514 for receiving and sending of input and output signals, respectively. These input and output signals may contain wave shapes, pulses, or other attributes, which may be detected as information by the devices 511 , 513 for the receipt of input signals, and may be converted into signals that may be processed by the calculation unit 501 . These signals are then provided to the calculation unit 501. The devices 512, 514 for sending output signals are arranged to convert the calculation result from the calculation unit 501 into output signals for transfer to other parts of the vehicle’s control system, and / or the component(s) for which the signals are intended.

[0225] Each one of the connections to the devices for receiving and sending of input and output signals may consist of one or several of a cable; a data bus, such as a CAN (Controller Area Network) bus, a MOST (Media Oriented Systems Transport) bus, or any other bus configuration; or of a wireless connection. A person skilled in the art will appreciate that the above-stated computer can be constituted by the computing unit 501 and that the above- stated memory can be constituted by the memory unit 502.

[0226] Generally, control systems in modern vehicles consist of a communications bus system, consisting of one or several communications buses to connect a number of electronic control devices (ECUs), or controllers, and different components localised on the vehicle. Such a control system may comprise a large number of control devices, and the responsibility for a specific function may be distributed among more than one control device. Vehicles of the type shown, thus often comprise significantly more control devices than what is shown in Figures 1-3 and 6, which is well known to a person skilled in the art within the technology area.

[0227] As a person skilled in the art will realise, the control device 500 / 190 / 290 / 390 in figure 6 may comprise one or several of the control devices 190, 290 and 390 in figures 1-3, respectively.

[0228] The present invention, in the embodiment shown, is implemented in the control device 500 / 190 / 290 / 390. The invention may, however, also be implemented wholly or partly in one or several other control devices, already existing in the vehicle, or in a control device dedicated to the present invention.

[0229] Here and in this document, control units, control entities or processing arrangements are sometimes described as being arranged for performing the methods and / or steps 410, 420, 430, 440, 450, 432, 434, 436, 438, 441 , 442, 443, 444, 445 according to the invention. This also includes that the units, entities or processing arrangements are designed to and / or configured to perform these method steps.

[0230] One or more control entities 610, 620, 630, 640, 650, 632, 634, 636, 638, 641 , 642, 643, 644, 645 may be arranged for performing the methods and / or steps. Such entities 610, 620, 630, 640, 650, 632, 634, 636, 638, 641 , 642, 643, 644, 645 may be arranged as separate entities, or may be logically separated but physically implemented in the same unit, or may be both logically and physically arranged together. These control entities 610, 620, 630, 640, 650, 632, 634, 636, 638, 641 , 642, 643, 644, 645 may for example correspond to groups of instructions, which can be in the form of programming code, that are input into, and are utilized by a processor / computing unit 501 when the entities are active and / or are utilized for performing its method steps, respectively.

[0231] A person skilled in the art will also realise that the above control system 500 / 190 / 290 / 390 may be modified according to the different embodiments of the method according to the invention. In addition, the invention relates to the motor vehicle 100, for example a car, a truck or a bus, or another unit comprising at least one control system 500 / 190 / 290 / 390 according to the invention, such as for example a vessel.

[0232] The present invention is not limited to the embodiments of the invention described above, but relates to and comprises all embodiments within the scope of the enclosed independent claims.

Claims

Claims1 . A method (400) for determining a diagnosis of a fluid delivery system (270, 370), the fluid delivery system (270, 370) comprising two or more dosing units (271 , 272, 371 , 372), a pump (274, 374) and one fluid pressure sensor (280, 380); the method comprising:- determining (410), under normal operation of the fluid delivery system (270, 370), tWO Or more individual dosed masses of fluid (Qdose_ind_1 , Qdose_ind_2, ... , Qdose_ind_m) being individually dosed by the two or more dosing units (271 , 272, 371 , 372), respectively;- determining (420), under normal operation of the fluid delivery system (270, 370), a simultaneous dosed mass of fluid (Qdose_sim) being simultaneously dosed by all of the two or more dosing units (271 , 272, 371 , 372) together; and- determining (430) the diagnosis of the fluid delivery system (270, 370) based on the tWO Or more individual dosed masses of fluid (Qdose_ind_1 , Qdose_ind_2, ... , Qdose_ind_m) and corresponding two or more individual requested masses of fluid (Qreqjnd , Qreq_ind_2, ... , Qreq_ind_m) for the two or more dosing units (271 , 272, 371 , 372), respectively, and based on the simultaneous dosed mass of fluid (Qdose_sim) and a corresponding simultaneous requested mass of fluid (Qreq_sim).

2. The method (400) as claimed in claim 1 , wherein the two or more individual dosed masses of fluid (Qdosejnd_i , Qdosejnd_2, ... , Qdose_ind_m) are determined (410) based on two or more models of the individual dosing performed by the two or more dosing units (271 , 272, 371 , 372), respectively.

3. The method (400) as claimed in claim 2, wherein the two or more individual dosed masses of fluid (Qdosejnd_i , Qdosejnd_2, ... , Qdose_ind_m) are determined (410) based on the two or more models according to:where:- Qdose_ind_k is the individual dosed mass of fluid for dosing unit k during a time interval from t_open_DU_k to t_close_DU_k;- k is an integer equal to or smaller than m; k = 1 , 2, ... , m; where m is an integerequal to or higher than 2; m = 2, 3, ... , M;- Qpump is a fluid mass output by the pump (274, 374) during a time interval from t_open_DU_k to t_close_DU_ki- Qretum is a fluid mass returning from the two or more dosing units (271 , 272, 371 , 372) during a time interval from t_0Pen_Du_k to t_ciose_Du_k;- t_oPen_Du_k is a point in time at which dosing unit k becomes the only dosing unit being in an open state;- t_ciose_Du_k is a point in time at which dosing unit k ceases to be the only dosing unit being in an open state; and- B is a system variable associated with an elasticity of the fluid delivery system (270, 370).

4. The method (400) as claimed in any one of claims 1 -3, wherein the simultaneous dosed mass of fluid (Qdose_sim) is determined (420) based on a model of the simultaneous dosing performed by the two or more dosing units (271 , 272, 371 , 372).

5. The method (400) as claimed in claim 4, wherein the simultaneous dosed mass of fluid (Qdose_sim) is determined (420) based on the model according to:where:- Qdose_sim is the simultaneous dosed mass of fluid for dosing units 1 to m during a time interval from t_open_DU_1-m to t_close_DU_any;- m is an integer equal to or higher than two; m = 2, 3, ... , M;- Qpump is a fluid mass output by the pump (274, 374) during a time interval from t_open_DU_1-m to t_close_DU_any;- Qretum is a fluid mass returning from the two or more dosing units (271 , 272, 371 , 372) during a time interval from t_Open_Du_i-m to t_Ciose_Du_any;- t_oPen_Du_i -m is a point in time when at least one dosing unit changes from a closed state to an open state, such that all dosing units 1 to m thereafter are in an open state;- t_Ciose_Du_any is a point in time when at least one dosing unit changes from an open state to a closed state; and- B is a system variable associated with an elasticity of the fluid delivery system (270, 370).

6. The method (400) as claimed in any one of claims 1 -5, wherein the determination (430) of the diagnosis of the fluid delivery system (270, 370) comprises:- determining (432) two or more individual dosing errors (Qerrorjnd , Qerror_ind_2, ... , Qerror_ind_m) based on the two or more individual dosed masses of fluid (Qdosejnd_i , Qdosejnd_2, ... , Qdose_ind_m) and the corresponding two or more individual requested masses of fluid (Qreqjnd_1 , Qreq_ind_2, ... , Qreq_ind_m), respectively;- comparing (434) the two or more individual dosing errors (Qerrorjndj , Qerror nd_2, ... , Qerrorjnd_m) With tWO Or more individual error thresholds (Qerror_th_1 , Qerror_th_2, ... , Qerror_th_m), respectively;- determining (436) a simultaneous dosing error (Qerror_sim) based on the simultaneous dosed mass of fluid (Qdose_sim) and the corresponding simultaneous requested mass of fluid (Qreq_sim); and- comparing (438) the simultaneous dosing error (Qen-or_sim) with a simultaneous error threshold (Qerror_th_sim).

7. The method (400) as claimed in claim 6, wherein the determination (432) of the two or more individual dosing errors (Qerrorjndj , Qerrorjnd_2, ... , Qerror_ind_m) is performed according to:where:- Qerrorjndj is the individual error for dosing unit k;- Qreqjndj is the individual requested mass of fluid from dosing unit k;- Qdose_ind_k is the individual dosed mass of fluid from dosing unit k; and- k is an integer equal to or smaller than m; k = 1 , 2, ... , m; where m is an integer equal to or higher than 2; m = 2, 3, ... , M.

8. The method (400) as claimed in claim 6, wherein the determination (434) of the simultaneous dosing error (Qerror_sim) is performed according to:_ Qreq_sim Qdose_sim error sim ~ > req_sim where:- Qerror_sim is the simultaneous dosing error for all dosing units;- Qreq_sim is the simultaneous requested mass of fluid from all dosing units; and- Qdose_sim is the simultaneous dosed mass of fluid of all dosing units.

9. The method (400) as claimed in any one of claims 1 -8, the method (400) further comprising:- determining (440), under normal operation of the fluid delivery system (270, 370), a zero dosing mass of fluid (Qd ose_zero ) based on a model for all of the two or more dosing units (271 , 272, 371 , 372) being closed.

10. The method (400) as claimed in claim 9, wherein the zero dosing mass of fluid (Qd ose_zero ) is determined (240) based on the model according to:where:- Qdose_zero is the zero dosing mass fluid during a time interval when all of dosing units 1 to m are in a closed state;- m is an integer equal to or higher than two; m = 2, 3, ... , M;- Qpump is a fluid mass output by the pump (274, 374);- Qretum is a fluid mass returning from the two or more dosing units (271 , 272, 371 , 372);- t_ciose_Du_i-m is a point in time when at least one dosing unit changes from an open state to a closed state, such that all of dosing units 1 to m thereafter are in a closed state; and- t_oPen_Du_any is a point in time when at least one dosing unit changes from a closed state to an open state, such that at least one of dosing units 1 to m thereafter is in an open state;- B is a system variable associated with an elasticity of the fluid delivery system (270, 370).11 . The method (400) as claimed in any one of claims 9-10, wherein, if a determined value for the zero dosing mass of fluid (Qdose_zero) differs from zero whenall of the two or more dosing units (271 , 272, 371 , 372) are closed, the determined value for the zero dosing mass of fluid (Qdose_zero) is utilized for one or more in the group of:- determining (441 ) a fluid mass Qpump output by the pump (274, 374);- determining (442) a fluid mass Qretum returning from the two or more dosing units (271 , 272, 371 , 372);- determining (443) a diagnosis of a performance of the pump (274, 374);- determining (444) a diagnosis of a performance of a return system (276, 376) configured for providing a return flow of fluid from the two or more dosing units (271 , 272, 371 , 372); and- determining (445) a system variable (B) associated with an elasticity of the fluid delivery system (274, 374).

12. The method (400) as claimed in any one of claims 1-11 , wherein the one pressure sensor (280, 380) is configured at one in the group of:- one of the at least two dosing units (271 , 272, 371 , 372);- the pump (274, 374); and- a separate sensor component.

13. The method (400) as claimed in any one of claims 1-12, wherein- the fluid delivery system (270, 370) is a reductant delivery system (370) configured for providing a reductant to an exhaust treatment system (350); and- the fluid is the reductant.

14. The method (400) as claimed in any one of claims 1-12, wherein- the fluid delivery system (270, 370) is a fuel delivery system (270) configured for providing a fuel to an engine (201 ); and- the fluid it the fuel.

15. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method according to any one of claims 1 -14.

16. A computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out the method according to any one of claims 1 -14.

17. A control system (290, 390) configured for determining a diagnosis of a fluid delivery system (270, 370), the fluid delivery system (270, 370) comprising two or more dosing units (271 , 272, 371 , 372), a pump (274, 374) and one fluid pressure sensor (280, 380); wherein the control system (290, 390) is configured to:- determine (410), under normal operation of the fluid delivery system (270, 370), two or more individual dosed masses of fluid (Qdosejnd_i , Qdose nd_2, ... , Qdose nd_m) being individually dosed by the two or more dosing units (271 , 272, 371 , 372), respectively;- determine (420), under normal operation of the fluid delivery system (270, 370), a simultaneous dosed mass of fluid (Qdose_sim) being simultaneously dosed by all of the two or more dosing units (271 , 272, 371 , 372) together; and- determine (430) the diagnosis of the fluid delivery system (270, 370) based on the tWO Or more individual dosed masses of fluid (Qdose_ind_1 , Qdose_ind_2, ... , Qdose_ind_m) and corresponding two or more individual requested masses of fluid (Qreqjnd , Qreq_ind_2, ... , Qreq_ind_m) for the two or more dosing units (271 , 272, 371 , 372), respectively, and based on the simultaneous dosed mass of fluid (Qdose_sim) and a corresponding simultaneous requested mass of fluid (Qreq_sim).

18. A vehicle (100) comprising:- a fluid delivery system (270, 370) comprising two or more dosing units (271 , 272, 371 , 372) and one fluid pressure sensor (280 ,380); and- a control system (290, 390) according to claim 17.

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