Method and device for controlling urea injection, vehicle and storage medium

Abstract

The invention relates to a method and device for controlling urea injection, a vehicle and a storage medium, and the method comprises the steps that the ammonia content of an SCR outlet of an exhaust system of the vehicle is obtained; matching a urea injection control strategy of the vehicle based on the ammonia content; and under the condition that the urea injection control strategy is a first preset leakage control strategy, the ammonia storage amount of SCR is estimated based on the SCR historical remaining ammonia content, the SCR inlet temperature and the SCR outlet temperature of the vehicle, and the urea injection control strategy is corrected through the ammonia storage amount so that the vehicle can be controlled to conduct urea injection according to the corrected urea injection control strategy. Therefore, the technical problems that in the related technology, due to the fact that the size of the preceding-stage SCR is small, N2O is likely to be generated on the preceding-stage SCR, ammonia leakage is likely to be caused by over-spraying, an NOx sensor at an inlet of the backward-stage SCR is affected, the backward-stage SCR is caused to be sprayed mistakenly, and emission exceeds the standard are solved.

Description

Technical Field

[0001] The present application relates to the field of post-processing technology, and in particular to a method, device, vehicle and storage medium for controlling urea injection. Background Art

[0002] Based on vehicle emission issues, the emission requirements for pollutants such as NOx will be further tightened. In order to make vehicle emissions meet the corresponding emission requirements, more attention needs to be paid to the coordinated reduction of multiple pollutants under low temperature conditions.

[0003] In the related technologies, the dual SCR (Selective Catalytic Reduction) technology route can effectively utilize the engine exhaust outlet temperature to achieve rapid urea injection.

[0004] However, in the related art, the volume of the front-stage SCR is relatively small and the total ammonia storage capacity is low. Once oversprayed, ammonia leakage is likely to occur. The leaked ammonia will not only affect the NOx sensor at the inlet of the rear-stage SCR, causing the problem of misspray at the rear stage, but also easily generate N2O at the front stage, causing emissions to exceed the standard, which needs to be improved. Summary of the invention

[0005] The present application provides a method, device, vehicle and storage medium for controlling urea injection, so as to solve the technical problems in the related art that N2O is easily generated on the front-stage SCR due to its relatively small volume, and ammonia leakage is easily caused by overspray, thereby affecting the NOx sensor at the inlet of the rear-stage SCR, causing the rear-stage SCR to spray incorrectly, resulting in excessive emissions, and the like.

[0006] A first aspect of the present application provides a method for controlling urea injection, comprising the following steps: obtaining an ammonia content at an SCR outlet of an exhaust system of a vehicle; matching a urea injection control strategy of the vehicle based on the ammonia content; when the urea injection control strategy is a first preset leakage control strategy, estimating an ammonia storage amount of the SCR based on a historical retained ammonia content of the SCR of the vehicle, an SCR inlet temperature, and an SCR outlet temperature, and using the ammonia storage amount to correct the urea injection control strategy, so as to control the vehicle to perform urea injection according to the corrected urea injection control strategy.

[0007] Optionally, in one embodiment of the present application, the matching of the urea injection control strategy of the vehicle based on the ammonia content includes: when the ammonia content is zero, determining that the urea injection control strategy of the vehicle is a non-leakage control strategy; when the ammonia content is less than a first preset threshold, determining that the urea injection control strategy of the vehicle is the first preset leakage control strategy, wherein the first preset threshold is obtained by an upstream NOx value and a downstream NOx value; when the ammonia content is greater than a second preset threshold, determining that the urea injection control strategy of the vehicle is a second preset leakage control strategy, and determining that the exhaust system is in an ammonia leakage state under the second preset leakage control strategy, wherein the second preset threshold is obtained by the NOx value at the SCR outlet and the downstream NOx value.

[0008] Optionally, in one embodiment of the present application, after matching the urea injection control strategy of the vehicle based on the ammonia content, it also includes: when the urea injection control strategy is the no-leakage control strategy, determining the urea injection amount based on the current conversion efficiency of the SCR of the vehicle.

[0009] Optionally, in one embodiment of the present application, after matching the urea injection control strategy of the vehicle based on the ammonia content, the method further includes: controlling the vehicle to stop urea injection when the urea injection control strategy is the second preset leakage control strategy.

[0010] Optionally, in one embodiment of the present application, the estimating the ammonia storage amount of the SCR based on the historical retained ammonia content of the SCR of the vehicle, the SCR inlet temperature and the SCR outlet temperature includes: judging whether the average value of the SCR inlet temperature and the SCR outlet temperature is greater than a preset temperature threshold; if the average value is greater than the preset temperature threshold, resetting the historical retained ammonia content of the SCR to zero; if the average value is less than or equal to the preset temperature threshold, obtaining the ammonia limit storage amount and the ammonia limit conversion efficiency at the corresponding temperature based on the SCR inlet temperature and the SCR outlet temperature, and using the ammonia limit storage amount as the historical retained ammonia content of the SCR; obtaining the ammonia storage amount of the SCR based on the historical retained ammonia content of the SCR and a pre-constructed ammonia storage calculation formula.

[0011] Optionally, in one embodiment of the present application, the estimating the ammonia storage amount of the SCR based on the historical retained ammonia content of the SCR of the vehicle, the SCR inlet temperature and the SCR outlet temperature also includes: determining whether the vehicle is in an idle condition; if the vehicle is in the idle condition, estimating the ammonia storage amount of the SCR using a pre-constructed fuzzy lookup table, wherein the fuzzy lookup table is obtained by the ammonia storage amount and the limiting conversion efficiency of the SCR at different temperatures and air speeds.

[0012] Optionally, in one embodiment of the present application, the using the ammonia storage amount to correct the urea injection control strategy includes: matching a corresponding urea injection amount correction coefficient based on the ammonia storage amount; and correcting the urea injection amount in the urea injection control strategy using the urea injection amount correction coefficient.

[0013] A second aspect of the present application provides a device for controlling urea injection, including: an acquisition module, used to acquire the ammonia content at the SCR outlet of the exhaust system of a vehicle; a matching module, used to match the urea injection control strategy of the vehicle based on the ammonia content; a first control module, used to estimate the ammonia storage amount of the SCR based on the historical retained ammonia content of the SCR of the vehicle, the SCR inlet temperature and the SCR outlet temperature when the urea injection control strategy is a first preset leakage control strategy, and use the ammonia storage amount to correct the urea injection control strategy to control the vehicle to perform urea injection according to the corrected urea injection control strategy.

[0014] Optionally, in one embodiment of the present application, the matching module includes: a first determination unit, used to determine that the urea injection control strategy of the vehicle is a non-leakage control strategy when the ammonia content is zero; a second determination unit, used to determine that the urea injection control strategy of the vehicle is the first preset leakage control strategy when the ammonia content is less than a first preset threshold, wherein the first preset threshold is obtained by an upstream NOx value and a downstream NOx value; a third determination unit, used to determine that the urea injection control strategy of the vehicle is a second preset leakage control strategy when the ammonia content is greater than a second preset threshold, and determine that the exhaust system is in an ammonia leakage state under the second preset leakage control strategy, wherein the second preset threshold is obtained by the NOx value at the SCR outlet and the downstream NOx value.

[0015] Optionally, in one embodiment of the present application, it further includes: a second control module, configured to determine the urea injection amount based on a current conversion efficiency of the SCR of the vehicle when the urea injection control strategy is the non-leakage control strategy.

[0016] Optionally, in one embodiment of the present application, the method further includes: a third control module, configured to control the vehicle to stop urea injection when the urea injection control strategy is the second preset leakage control strategy.

[0017] Optionally, in one embodiment of the present application, the first control module includes: a first judgment unit, used to judge whether the average value of the SCR inlet temperature and the SCR outlet temperature is greater than a preset temperature threshold; a reset unit, used to reset the SCR historical retained ammonia content to zero when the average value is greater than the preset temperature threshold; a first calculation unit, used to obtain the ammonia limit storage amount and ammonia limit conversion efficiency at the corresponding temperature based on the SCR inlet temperature and the SCR outlet temperature when the average value is less than or equal to the preset temperature threshold, and use the ammonia limit storage amount as the SCR historical retained ammonia content; a second calculation unit, used to obtain the ammonia storage amount of the SCR based on the SCR historical retained ammonia content and a pre-constructed ammonia storage calculation formula.

[0018] Optionally, in one embodiment of the present application, the first control module further includes: a second judgment unit, used to judge whether the vehicle is in an idle condition; a lookup unit, used to estimate the ammonia storage amount of the SCR using a pre-built fuzzy lookup table when the vehicle is in the idle condition, wherein the fuzzy lookup table is obtained by the ammonia storage amount and the limiting conversion efficiency of the SCR at different temperatures and air speeds.

[0019] Optionally, in one embodiment of the present application, the first control module includes: a matching unit, used to match a corresponding urea injection amount correction coefficient based on the ammonia storage amount; and a correction unit, used to correct the urea injection amount in the urea injection control strategy using the urea injection amount correction coefficient.

[0020] A third aspect of the present application provides a vehicle, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the method for controlling urea injection as described in the above embodiment.

[0021] A fourth aspect of the present application provides a computer-readable storage medium, wherein the computer-readable storage medium stores computer instructions, and the computer instructions are used to enable the computer to execute the method for controlling urea injection as described in the above embodiment.

[0022] A fifth aspect of the present application provides a computer program product, including a computer program, which, when executed, is used to implement the above method for controlling urea injection.

[0023] The embodiment of the present application can match the corresponding urea injection control strategy according to the ammonia content at the SCR outlet of the vehicle's exhaust system, and when the urea injection control strategy is the first preset leakage control strategy, based on the vehicle's SCR historical retained ammonia content, SCR inlet temperature and SCR outlet temperature, the ammonia storage amount of the SCR can be estimated without an offline storage device, and the urea injection control strategy can be corrected using the ammonia storage amount, thereby controlling the vehicle to perform urea injection according to the corrected urea injection control strategy, so as to correct the urea injection amount according to different working conditions, and solve the problem of excessive emissions by controlling urea injection. Thus, the technical problems in the related art that N2O is easily generated on the front-stage SCR due to the relatively small volume of the front-stage SCR, and ammonia leakage is easily caused by overspray, thereby affecting the NOx sensor at the rear-stage SCR inlet, causing the rear-stage SCR to spray incorrectly, resulting in excessive emissions, etc.

[0024] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0026] Figure 1 A flowchart of a method for controlling urea injection according to an embodiment of the present application;

[0027] Figure 2 A schematic diagram of a post-processing structure of a vehicle according to an embodiment of the present application;

[0028] Figure 3 It is a schematic diagram of the principle of a method for controlling urea injection according to an embodiment of the present application;

[0029] Figure 4 is a flow chart of a method for controlling urea injection according to one embodiment of the present application;

[0030] Figure 5 A schematic diagram of the structure of a device for controlling urea injection provided according to an embodiment of the present application;

[0031] Figure 6 It is a schematic diagram of the structure of a vehicle provided according to an embodiment of the present application. DETAILED DESCRIPTION

[0032] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0033] The following describes the method, device, vehicle and storage medium for controlling urea injection of the embodiment of the present application with reference to the accompanying drawings. In view of the related art mentioned in the above background technology, due to the relatively small volume of the front-stage SCR, N2O is easily generated on the front-stage SCR, and ammonia leakage is easily caused by overspray, thereby affecting the NOx sensor at the inlet of the rear-stage SCR, causing the rear-stage SCR to mis-spray, resulting in excessive emissions and other technical problems, the present application provides a method for controlling urea injection, in which the corresponding urea injection control strategy can be matched according to the ammonia content at the outlet of the SCR of the exhaust system of the vehicle, and when the urea injection control strategy is the first preset leakage control strategy, based on the historical ammonia content of the SCR of the vehicle, the SCR inlet temperature and the SCR outlet temperature, the ammonia storage amount of the SCR is estimated without an offline storage device, and the urea injection control strategy is corrected by using the ammonia storage amount, so as to control the vehicle to perform urea injection according to the corrected urea injection control strategy, so as to correct the urea injection amount according to different working conditions, and solve the problem of excessive emissions by controlling urea injection. As a result, the technical problems in the related art, such as the generation of N2O on the front-stage SCR due to its relatively small size, and the leakage of ammonia due to overspray, which affects the NOx sensor at the inlet of the rear-stage SCR, causes the rear-stage SCR to spray incorrectly, and leads to excessive emissions, are solved.

[0034] Specifically, Figure 1 A schematic flow chart of a method for controlling urea injection provided in an embodiment of the present application.

[0035] like Figure 1 As shown, the method for controlling urea injection includes the following steps:

[0036] In step S101 , the ammonia content at the SCR outlet of the exhaust system of the vehicle is obtained.

[0037] In actual implementation, the embodiment of the present application can obtain the ammonia content at the SCR outlet by setting a sensor or detection equipment, such as a Fourier transform infrared spectrometer (FTIR), a chemiluminescence detector (CLD), etc.

[0038] For example, when using a NOx sensor for detection, the embodiment of the present application can determine the NOx sensor delay time by determining the common exhaust flow of the post-processing equipment and the diameter and length of the SCR, and then delay the signal to ensure that the acquired data is the converted gas.

[0039] In step S102, a urea injection control strategy for the vehicle is matched based on the ammonia content.

[0040] Furthermore, according to the obtained ammonia content, embodiments of the present application can determine the actual exhaust state of the vehicle, such as a non-leakage state, a slight leakage state, and a leakage state, etc., and then determine different urea injection control strategies according to different exhaust states to solve the problem that over-injection causes ammonia leakage and emission exceeds the standard.

[0041] Optionally, in an embodiment of the present application, matching the urea injection control strategy of the vehicle based on the ammonia content includes: when the ammonia content is zero, determining the urea injection control strategy of the vehicle as a non-leakage control strategy; when the ammonia content is less than a first preset threshold, determining the urea injection control strategy of the vehicle as a first preset leakage control strategy, where the first preset threshold is obtained from the upstream NOx value and the downstream NOx value; when the ammonia content is greater than a second preset threshold, determining the urea injection control strategy of the vehicle as a second preset leakage control strategy, and determining that the exhaust system is in an ammonia leakage state under the second preset leakage control strategy, where the second preset threshold is obtained from the NOx value at the SCR outlet and the downstream NOx value.

[0042] In some embodiments, matching the urea injection control strategy of the vehicle according to the ammonia content can be divided into three cases:

[0043] 1. When there is no NH3 at the SCR outlet, determine the urea injection control strategy of the vehicle as a non-leakage control strategy.

[0044] 2. When NOx_US (upstream NOx value) > NOx_DS (downstream NOx value) + NH3, in this case, ammonia leakage has occurred, but the leakage amount is very small, and determine the urea injection control strategy of the vehicle as a first preset leakage control strategy.

[0045] 3. When NOx < NOx_DS + NH3, an ammonia leakage problem has occurred, and determine the urea injection control strategy of the vehicle as a second preset leakage control strategy.

[0046] Optionally, in an embodiment of the present application, after matching the urea injection control strategy of the vehicle based on the ammonia content, it further includes: when the urea injection control strategy is a non-leakage control strategy, determining the urea injection amount based on the current conversion efficiency of the SCR of the vehicle.

[0047] Wherein, when the urea injection control strategy is a non-leakage control strategy, the ammonia storage amount is the actual conversion efficiency. At this time, embodiments of the present application can determine the current ammonia storage amount according to the current conversion efficiency of the SCR of the vehicle, and then determine the urea injection amount according to the current ammonia storage amount.

[0048] Optionally, in one embodiment of the present application, after matching the urea injection control strategy of the vehicle based on the ammonia content, the method further includes: when the urea injection control strategy is a second preset leakage control strategy, controlling the vehicle to stop the urea injection action.

[0049] Among them, when the urea injection control strategy is the second preset leakage control strategy, it means that the vehicle has an ammonia leakage problem and needs to stop injection.

[0050] In step S103, when the urea injection control strategy is the first preset leakage control strategy, the ammonia storage amount of the SCR is estimated based on the historical ammonia content of the SCR of the vehicle, the SCR inlet temperature and the SCR outlet temperature, and the ammonia storage amount is used to correct the urea injection control strategy to control the vehicle to perform urea injection according to the corrected urea injection control strategy.

[0051] It is understandable that when the amount of ammonia leakage is small, directly calculating the conversion efficiency will result in a lower conversion efficiency result. At this time, the vehicle will determine that more urea needs to be sprayed, thereby aggravating the ammonia leakage. Therefore, it is necessary to estimate the existing ammonia storage amount to avoid such problems.

[0052] The embodiment of the present application can estimate the actual ammonia storage amount according to the historical SCR retained ammonia content, SCR inlet temperature and SCR outlet temperature of the vehicle, and correct the injected urea.

[0053] Optionally, in one embodiment of the present application, the ammonia storage amount of the SCR is estimated based on the vehicle's SCR historical retained ammonia content, SCR inlet temperature and SCR outlet temperature, including: determining whether the average value of the SCR inlet temperature and the SCR outlet temperature is greater than a preset temperature threshold; if the average value is greater than the preset temperature threshold, resetting the SCR historical retained ammonia content to zero; if the average value is less than or equal to the preset temperature threshold, obtaining the ammonia limit storage amount and the ammonia limit conversion efficiency at the corresponding temperature based on the SCR inlet temperature and the SCR outlet temperature, and using the ammonia limit storage amount as the SCR historical retained ammonia content; obtaining the ammonia storage amount of the SCR based on the SCR historical retained ammonia content and a pre-constructed ammonia storage calculation formula.

[0054] As a possible way to achieve this, SCR historical ammonia retention θ origin For a post-processing device whose status is previously unknown, there is no ammonia storage data that can be stored offline, which will cause the initial status of the post-processing to be unclear. If the ammonia storage is not estimated and the ammonia leakage is not managed, a large amount of ammonia leakage will occur, causing serious emission pollution. Complex operating conditions may occur during the normal operation of the system. The embodiment of the present application can use the system operating conditions to estimate the SCR status and then estimate the ammonia storage amount. The specific method is exemplified as follows:

[0055] Temperature sensor detection: When the average value of the SCR outlet temperature and inlet temperature exceeds 400°C, the temperature is too high and there is no ammonia storage capacity, so the θ is reset. origin is 0;

[0056] Comparison of ammonia storage and ammonia conversion efficiency: It is necessary to conduct ammonia storage experiments on SCR to obtain the ammonia limit storage capacity and ammonia limit conversion efficiency at different air speeds and temperatures. NOx sensor detection: By determining the common exhaust flow of the post-processing equipment and the diameter and length of the SCR, the NOx sensor delay time is determined, and the signal is delayed to ensure that the data for calculation is the converted gas. When it is detected that the SCR outlet NOx value is higher than the outlet NOx value, the SCR outlet ammonia leakage is serious and the ammonia is fully stored, the θ origin Set it to the ammonia storage limit value at this space velocity.

[0057] Furthermore, the ammonia storage calculation formula is:

[0058] Among them, θ origin For SCR historical storage of ammonia, Ammonia converted by urea injection, Ammonia consumed by NOx.

[0059] Optionally, in one embodiment of the present application, estimating the ammonia storage amount of the SCR based on the historical retained ammonia content of the SCR, the SCR inlet temperature and the SCR outlet temperature of the vehicle also includes: determining whether the vehicle is in an idle condition; if the vehicle is in an idle condition, estimating the ammonia storage amount of the SCR using a pre-built fuzzy lookup table, wherein the fuzzy lookup table is obtained by the ammonia storage amount and the limiting conversion efficiency of the SCR at different temperatures and air speeds.

[0060] The idling condition is a condition that often occurs during the operation of the system. NOx emissions will also be generated under the idling condition. The embodiment of the present application can estimate the ammonia storage value at this time by detecting the average temperature and conversion efficiency of the SCR at this time and looking up the fuzzy table.

[0061] The creation process of the fuzzy lookup table can be as follows:

[0062] For example, the current SCR temperature range is 0 to 400°C, the conversion efficiency is 0 to 100%, and the ammonia storage is 0 to 100% of the ammonia storage limit under the current operating conditions.

[0063] Step S1: In the embodiment of the present application, the input variables may be determined as the average temperature and conversion efficiency of the SCR and normalized, and the output variable may be the ammonia storage amount.

[0064] Step S2: The present embodiment can design a membership function:

[0065] The temperature membership function design can be shown in Table 1, where Table 1 is a temperature-level comparison table.

[0066] Table 1

[0067] Low temperature 0-175℃ medium low temperature 175℃-225℃ Medium temperature 225℃-300℃ high temperature 300℃-400℃

[0068] The NOx conversion efficiency membership function may be shown in Table 2, wherein Table 2 is a conversion efficiency-grade comparison table.

[0069] Table 2

[0070]

[0071]

[0072] The ammonia storage amount membership function may be shown in Table 3, wherein Table 3 is an ammonia storage amount-level comparison table.

[0073] Table 3

[0074] Small amount 0-30％ Moderate 20％-80％ Large 70％-100％

[0075] Step S3: The embodiment of the present application can formulate fuzzy rules.

[0076] The embodiment of the present application can formulate fuzzy rules based on experience or experimental data. For example:

[0077] If the temperature is high and the NOx conversion efficiency is low, then the ammonia storage should be increased.

[0078] If the temperature is low and the NOx conversion efficiency is high, then the ammonia storage should be reduced.

[0079] If the temperature is moderate and the NOx conversion efficiency is moderate, then the ammonia storage level should be moderate.

[0080] Step S4: The embodiment of the present application can perform fuzzy reasoning.

[0081] The embodiment of the present application can infer the membership of the output variable through fuzzy rules based on the membership of the input variable.

[0082] Step S5: Defuzzification.

[0083] The embodiment of the present application can convert the result of fuzzy reasoning into a specific control action. Commonly used methods include the maximum membership method and the centroid method.

[0084] Optionally, in one embodiment of the present application, the urea injection control strategy is corrected using the ammonia storage amount, including: matching a corresponding urea injection amount correction coefficient based on the ammonia storage amount; and correcting the urea injection amount in the urea injection control strategy using the urea injection amount correction coefficient.

[0085] According to the aforementioned steps, the embodiment of the present application has obtained the urea injection amount corresponding to the ammonia storage amount, estimated the ammonia storage of the currently running SCR system, and corrected the urea injection amount.

[0086] In actual operation, as the amount of ammonia storage increases, the embodiment of the present application can determine the correction coefficient f according to the urea injection proportional coefficient lookup table to correct the actual urea injection amount. The proportional coefficient lookup table can be shown in Table 4.

[0087] Table 4

[0088]

[0089] Combined with 2 to Figure 4 As shown, a method for controlling urea injection according to an embodiment of the present application is described in detail by taking an embodiment as an example.

[0090] like Figure 2 As shown, it is a post-processing structure diagram of an embodiment of the present application, based on Figure 2 With the structure shown, the embodiment of the present application can detect the ammonia content at the outlet and inlet of the SCR, and detect the temperature at various positions.

[0091] Combination Figure 3 and Figure 4 As shown, the embodiment of the present application may include the following steps:

[0092] Step S401: Perform an ammonia storage experiment to obtain the ammonia storage amount and the limit conversion efficiency. In the embodiment of the present application, an ammonia storage experiment can be performed to obtain the ammonia storage amount and the limit conversion efficiency of the SCR at different temperatures and space velocities, and the ammonia storage amount and the limit conversion efficiency can be made into a map.

[0093] Step S402: Build a urea injection control model. The urea injection control model consists of two parts. One is to achieve urea injection by controlling the conversion efficiency θ through PID. The conversion efficiency of SCR is calculated by detecting the inlet and outlet NOx values. The NOx sensor will be affected by NH3, so when ammonia leaks, the NOx sensor value will increase. So there may be three situations:

[0094] 1. When there is no NH3 at the outlet, θ is the actual conversion efficiency;

[0095] 2. In the case of NOx_US>NOx_DS+NH3, ammonia leakage has occurred, but the leakage amount is very small. Directly calculating the conversion efficiency will be considered to be low, and more urea needs to be sprayed, which will increase the ammonia leakage. It is necessary to estimate the existing ammonia storage amount to avoid such problems. The embodiment of the present application can estimate the actual ammonia storage amount and correct the injected urea.

[0096] 3. When NOx < NOx_DS + NH3, ammonia leakage has occurred and spraying needs to be stopped.

[0097] Step S403: Build an ammonia storage estimation model. To avoid the situation in case 2 of S402, identify the ammonia storage amount in the SCR.

[0098] Historical ammonia retention θ in the SCR origin For a post-treatment device with an unknown previous state and no ammonia storage data that can be stored offline, it will cause the initial state of the post-treatment to be unknown. If ammonia storage is not estimated and ammonia leakage is not managed, a large amount of ammonia leakage will occur, causing serious emission pollution. Complex working conditions will occur during the normal operation of the system. The embodiments of the present application can estimate the SCR state using the system working conditions, and then estimate the ammonia storage amount. Specific methods are exemplified as follows:

[0099] Temperature sensor detection: When the average value of the SCR outlet temperature and the inlet temperature exceeds 400 °C, the temperature is too high, there is no ammonia storage amount, and reset θ origin to 0;

[0100] Ammonia storage and ammonia conversion efficiency comparison: An ammonia storage experiment needs to be carried out on the SCR to obtain the ammonia limit storage amount and ammonia limit conversion efficiency at different space velocities and different temperatures. NOx sensor detection: By determining the common exhaust gas flow rate of the post-treatment device, the diameter and length of the SCR, determine the NOx sensor delay time, and delay the signal to ensure that the data for calculation is the converted gas. When the detected NOx value at the SCR outlet is higher than the outlet NOx value, the ammonia leakage at the SCR outlet is serious, and the ammonia has been stored full, set θ origin to the ammonia storage limit value at this space velocity.

[0101] Furthermore, the ammonia storage calculation formula is

[0102] where θ origin is the historical ammonia retention in the SCR, is the ammonia converted from urea injection, is the ammonia consumed by NOx.

[0103] Idle condition comparison: The idle condition is a working condition that often occurs during the system operation. NOx emissions will also be generated under the idle condition. The embodiments of the present application can estimate the ammonia storage value at this time by detecting the average temperature and conversion efficiency of the SCR at this time and looking up the fuzzy table.

[0104] Step S404: Build a fuzzy control model.

[0105] The creation process of the fuzzy lookup table can be as follows:

[0106] For example, the current SCR temperature range is 0 to 400°C, the conversion efficiency is 0 to 100%, and the ammonia storage is 0 to 100% of the ammonia storage limit under the current operating conditions.

[0107] Step S1: In the embodiment of the present application, the input variables may be determined as the average temperature and conversion efficiency of the SCR and normalized, and the output variable may be the ammonia storage amount.

[0108] Step S2: The present embodiment can design a membership function:

[0109] The temperature membership function design can be shown in Table 1.

[0110] The NOx conversion efficiency membership function can be shown in Table 2.

[0111] The ammonia storage capacity membership function can be shown in Table 3.

[0112] Step S3: The embodiment of the present application can formulate fuzzy rules.

[0113] The embodiment of the present application can formulate fuzzy rules based on experience or experimental data. For example:

[0114] If the temperature is high and the NOx conversion efficiency is low, then the ammonia storage should be increased.

[0115] If the temperature is low and the NOx conversion efficiency is high, then the ammonia storage should be reduced.

[0116] If the temperature is moderate and the NOx conversion efficiency is moderate, then the ammonia storage level should be moderate.

[0117] Step S4: The embodiment of the present application can perform fuzzy reasoning.

[0118] The embodiment of the present application can infer the membership of the output variable through fuzzy rules based on the membership of the input variable.

[0119] Step S5: Defuzzification.

[0120] The embodiment of the present application can convert the result of fuzzy reasoning into a specific control action. Commonly used methods include the maximum membership method and the centroid method.

[0121] Step S405: Correct the urea injection amount.

[0122] According to step S402, the embodiment of the present application has obtained the urea injection amount, and through steps S403 and S404, the ammonia storage of the currently running SCR system is estimated to obtain the system state of the SCR, and the urea injection amount is corrected.

[0123] In actual operation, as the amount of ammonia storage increases, the embodiment of the present application can determine the correction coefficient f according to the urea injection proportional coefficient lookup table to correct the actual urea injection amount. The proportional coefficient lookup table can be shown in Table 4.

[0124] According to the method for controlling urea injection proposed in the embodiment of the present application, the corresponding urea injection control strategy can be matched according to the ammonia content at the SCR outlet of the vehicle's exhaust system, and when the urea injection control strategy is the first preset leakage control strategy, the ammonia storage amount of the SCR can be estimated without an offline storage device based on the historical ammonia content of the vehicle's SCR, the SCR inlet temperature and the SCR outlet temperature, and the urea injection control strategy can be corrected using the ammonia storage amount, thereby controlling the vehicle to perform urea injection according to the corrected urea injection control strategy, so as to correct the urea injection amount according to different working conditions, and solve the problem of excessive emissions by controlling urea injection. Thus, the technical problems in the related art that N2O is easily generated on the front-stage SCR due to the relatively small volume of the front-stage SCR, and ammonia leakage is easily caused due to overspray, thereby affecting the NOx sensor at the inlet of the rear-stage SCR, causing the rear-stage SCR to spray incorrectly, resulting in excessive emissions, etc.

[0125] Next, a device for controlling urea injection according to an embodiment of the present application will be described with reference to the accompanying drawings.

[0126] Figure 5 Schematic diagram of a block diagram of a device for controlling urea injection according to an embodiment of the present application.

[0127] like Figure 5 As shown, the device 10 for controlling urea injection includes: an acquisition module 100 , a matching module 200 and a first control module 300 .

[0128] Specifically, the acquisition module 100 is used to acquire the ammonia content at the SCR outlet of the exhaust system of the vehicle.

[0129] The matching module 200 is used to match the urea injection control strategy of the vehicle based on the ammonia content.

[0130] The first control module 300 is used to estimate the ammonia storage amount of the SCR based on the historical ammonia content of the SCR, the SCR inlet temperature and the SCR outlet temperature of the vehicle when the urea injection control strategy is the first preset leakage control strategy, and to correct the urea injection control strategy using the ammonia storage amount to control the vehicle to perform urea injection according to the corrected urea injection control strategy.

[0131] Optionally, in one embodiment of the present application, the matching module 200 includes: a first determination unit, a second determination unit and a third determination unit.

[0132] The first determination unit is used to determine that the urea injection control strategy of the vehicle is a no-leakage control strategy when the ammonia content is zero.

[0133] The second determination unit is used to determine that the urea injection control strategy of the vehicle is a first preset leakage control strategy when the ammonia content is less than a first preset threshold, wherein the first preset threshold is obtained by an upstream NOx value and a downstream NOx value.

[0134] The third determination unit is used to determine that the urea injection control strategy of the vehicle is a second preset leakage control strategy when the ammonia content is greater than a second preset threshold value, and determine that the exhaust system is in an ammonia leakage state under the second preset leakage control strategy, wherein the second preset threshold value is obtained by the NOx value at the SCR outlet and the downstream NOx value.

[0135] Optionally, in one embodiment of the present application, the device 10 for controlling urea injection further includes: a second control module.

[0136] The second control module is used to determine the urea injection amount based on the current conversion efficiency of the SCR of the vehicle when the urea injection control strategy is a non-leakage control strategy.

[0137] Optionally, in one embodiment of the present application, the device 10 for controlling urea injection further includes: a third control module.

[0138] The third control module is used to control the vehicle to stop the urea injection action when the urea injection control strategy is the second preset leakage control strategy.

[0139] Optionally, in one embodiment of the present application, the first control module 300 includes: a first judgment unit, a reset unit, a first calculation unit and a second calculation unit.

[0140] The first judgment unit is used to judge whether the average value of the SCR inlet temperature and the SCR outlet temperature is greater than a preset temperature threshold.

[0141] The reset unit is used to reset the SCR historical retained ammonia content to zero when the average value is greater than a preset temperature threshold.

[0142] The first calculation unit is used to obtain the ammonia limit storage amount and the ammonia limit conversion efficiency at the corresponding temperature based on the SCR inlet temperature and the SCR outlet temperature when the average value is less than or equal to the preset temperature threshold, and use the ammonia limit storage amount as the SCR historical retained ammonia content.

[0143] The second calculation unit is used to obtain the ammonia storage amount of the SCR based on the historical retained ammonia content of the SCR and a pre-constructed ammonia storage calculation formula.

[0144] Optionally, in one embodiment of the present application, the first control module 300 further includes: a second judgment unit and a search unit.

[0145] The second judgment unit is used to judge whether the vehicle is in an idle condition.

[0146] The search unit is used to estimate the ammonia storage amount of the SCR using a pre-built fuzzy search table when the vehicle is in an idle condition, wherein the fuzzy search table is obtained from the ammonia storage amount and the limit conversion efficiency of the SCR at different temperatures and air speeds.

[0147] Optionally, in one embodiment of the present application, the first control module 300 includes: a matching unit and a correction unit.

[0148] The matching unit is used to match the corresponding urea injection amount correction coefficient based on the ammonia storage amount.

[0149] The correction unit is used to correct the urea injection amount in the urea injection control strategy by using the urea injection amount correction coefficient.

[0150] It should be noted that the above explanation of the embodiment of the method for controlling urea injection is also applicable to the device for controlling urea injection in this embodiment, which will not be described in detail here.

[0151] According to the device for controlling urea injection proposed in the embodiment of the present application, the corresponding urea injection control strategy can be matched according to the ammonia content at the SCR outlet of the vehicle's exhaust system, and when the urea injection control strategy is the first preset leakage control strategy, the ammonia storage amount of the SCR can be estimated without an offline storage device based on the historical ammonia content of the SCR of the vehicle, the SCR inlet temperature and the SCR outlet temperature, and the urea injection control strategy can be corrected using the ammonia storage amount, thereby controlling the vehicle to perform urea injection according to the corrected urea injection control strategy, so as to correct the urea injection amount according to different working conditions, and solve the problem of excessive emissions by controlling urea injection. Thus, the technical problems in the related art that N2O is easily generated on the front-stage SCR due to the relatively small volume of the front-stage SCR, and ammonia leakage is easily caused due to overspray, thereby affecting the NOx sensor at the inlet of the rear-stage SCR, causing the rear-stage SCR to spray incorrectly, resulting in excessive emissions, etc.

[0152] Figure 6 A schematic diagram of the structure of a vehicle provided in an embodiment of the present application. The vehicle may include:

[0153] A memory 601 , a processor 602 , and a computer program stored in the memory 601 and executable on the processor 602 .

[0154] When the processor 602 executes the program, the method for controlling urea injection provided in the above embodiment is implemented.

[0155] Furthermore, the vehicle also includes:

[0156] The communication interface 603 is used for communication between the memory 601 and the processor 602 .

[0157] The memory 601 is used to store computer programs that can be executed on the processor 602 .

[0158] The memory 601 may include a high-speed RAM memory, and may also include a non-volatile memory (non-volatile memory), such as at least one disk memory.

[0159] If the memory 601, the processor 602 and the communication interface 603 are implemented independently, the communication interface 603, the memory 601 and the processor 602 can be connected to each other through a bus and communicate with each other. The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component (PCI) bus or an Extended Industry Standard Architecture (EISA) bus. The bus can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, Figure 6 Only one thick line is used in the diagram, but this does not mean that there is only one bus or only one type of bus.

[0160] Optionally, in a specific implementation, if the memory 601, the processor 602 and the communication interface 603 are integrated on a chip, the memory 601, the processor 602 and the communication interface 603 can communicate with each other through an internal interface.

[0161] The processor 602 may be a central processing unit (CPU), or an application specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of the present application.

[0162] This embodiment further provides a computer-readable storage medium on which a computer program is stored. When the program is executed by a processor, the above method for controlling urea injection is implemented.

[0163] The embodiment of the present application further provides a computer program product, including a computer program, which, when executed by a processor, implements the method for controlling urea injection provided by the embodiment of the present invention.

[0164] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or N embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0165] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of this application, "N" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0166] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, fragment or portion of code comprising one or N executable instructions for implementing the steps of a custom logical function or process, and the scope of the preferred embodiments of the present application includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present application belong.

[0167] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in combination with these instruction execution systems, devices or apparatuses. For the purpose of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in combination with these instruction execution systems, devices or apparatuses. More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or N wirings (electronic devices), a portable computer disk box (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), a fiber optic device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically by optically scanning the paper or other medium and then editing, interpreting or processing in other suitable ways as necessary and then storing it in a computer memory.

[0168] It should be understood that the various parts of the present application can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiment, the N steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0169] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0170] In addition, each functional unit in each embodiment of the present application may be integrated into a processing module, or each unit may exist physically separately, or two or more units may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. If the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium.

[0171] The storage medium mentioned above may be a read-only memory, a magnetic disk or an optical disk, etc. Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present application. A person of ordinary skill in the art may change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A method for controlling urea injection, characterized in that: The following steps are involved: Obtaining ammonia content at an SCR outlet of an exhaust system of a vehicle; matching a urea injection control strategy for the vehicle based on the ammonia content; When the urea injection control strategy is the first preset leakage control strategy, the ammonia storage amount of the SCR is estimated based on the historical retained ammonia content of the SCR of the vehicle, the SCR inlet temperature and the SCR outlet temperature, and the urea injection control strategy is corrected using the ammonia storage amount to control the vehicle to perform urea injection according to the corrected urea injection control strategy.

2. The method according to claim 1, characterized in that: The urea injection control strategy for matching the vehicle based on the ammonia content includes: When the ammonia content is zero, determining that the urea injection control strategy of the vehicle is a no-leakage control strategy; When the ammonia content is less than a first preset threshold, determining that the urea injection control strategy of the vehicle is the first preset leakage control strategy, wherein the first preset threshold is obtained by an upstream NOx value and a downstream NOx value; When the ammonia content is greater than a second preset threshold, the urea injection control strategy of the vehicle is determined to be a second preset leakage control strategy, and the exhaust system is determined to be in an ammonia leakage state under the second preset leakage control strategy, wherein the second preset threshold is obtained by the NOx value at the SCR outlet and the downstream NOx value.

3. The method according to claim 2, characterized in that After matching the urea injection control strategy of the vehicle based on the ammonia content, the method further includes: In a case where the urea injection control strategy is the non-leakage control strategy, the urea injection amount is determined based on a current conversion efficiency of the SCR of the vehicle.

4. The method according to claim 2, characterized in that: After matching the urea injection control strategy of the vehicle based on the ammonia content, the method further includes: When the urea injection control strategy is the second preset leakage control strategy, the vehicle is controlled to stop the urea injection action.

5. The method according to claim 1, characterized in that The estimating the ammonia storage amount of the SCR based on the historical ammonia content of the SCR of the vehicle, the SCR inlet temperature and the SCR outlet temperature includes: Determining whether the average value of the SCR inlet temperature and the SCR outlet temperature is greater than a preset temperature threshold; If the average value is greater than the preset temperature threshold, resetting the SCR historical residual ammonia content to zero; If the average value is less than or equal to the preset temperature threshold, the ammonia limit storage amount and the ammonia limit conversion efficiency at the corresponding temperature are obtained based on the SCR inlet temperature and the SCR outlet temperature, and the ammonia limit storage amount is used as the SCR historical retained ammonia content; The ammonia storage amount of the SCR is obtained based on the historical retained ammonia content of the SCR and a pre-constructed ammonia storage calculation formula.

6. The method according to claim 5, characterized in that The estimating the ammonia storage amount of the SCR based on the historical ammonia content of the SCR of the vehicle, the SCR inlet temperature and the SCR outlet temperature also includes: Determining whether the vehicle is in an idle condition; If the vehicle is in the idle condition, the ammonia storage amount of the SCR is estimated using a pre-built fuzzy lookup table, wherein the fuzzy lookup table is obtained from the ammonia storage amount and the limiting conversion efficiency of the SCR at different temperatures and space speeds.

7. The method according to claim 1, characterized in that The method of modifying the urea injection control strategy by using the ammonia storage amount includes: matching a corresponding urea injection amount correction coefficient based on the ammonia storage amount; The urea injection amount correction coefficient is used to correct the urea injection amount in the urea injection control strategy.

8. A device for controlling urea injection, characterized in that: include: An acquisition module, used for acquiring ammonia content at an SCR outlet of an exhaust system of a vehicle; a matching module, configured to match a urea injection control strategy of the vehicle based on the ammonia content; A control module is used for estimating the ammonia storage amount of the SCR based on the historical ammonia content of the SCR, the SCR inlet temperature and the SCR outlet temperature of the vehicle when the urea injection control strategy is the first preset leakage control strategy, and correcting the urea injection control strategy by using the ammonia storage amount to control the vehicle to perform urea injection according to the corrected urea injection control strategy.

9. A vehicle, characterized in that: include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the method for controlling urea injection according to any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: The program is executed by a processor to implement the method for controlling urea injection as described in any one of claims 1 to 7.

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