EGR (Exhaust Gas Recirculation) control method and system after fault of water temperature sensor

Abstract

The invention provides an EGR control method and system after a water temperature sensor breaks down, and belongs to the technical field of engine exhaust gas recirculation rate control. According to the method, the water temperature sensor is detected, and after it is detected that at least one fault occurs to the water temperature sensor, corrected target EGR rates of various faults are determined; and taking a minimum value of the corrected target EGR rate of each fault to obtain a final target EGR rate, limiting the final target EGR rate to be not greater than the target EGR rate before the fault, and performing EGR control according to the final target EGR rate. According to the method, different target EGR rates can be optimized according to the fault occurrence condition of the water temperature sensor, meanwhile, continuous dynamic adjustment and updating are conducted, and knocking occurrence after the fault occurs is effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of engine exhaust gas recirculation rate control, and particularly relates to an EGR control method and system after water temperature sensor failure. BACKGROUND

[0002] Exhaust gas recirculation (EGR) takes exhaust gas from the exhaust system into the intake system. Studies have shown that the EGR system has certain advantages in improving emissions, reducing fuel consumption and improving anti-knock capacity. Low-pressure EGR takes gas after the turbine, so there is no loss of turbine efficiency, and it can use EGR under almost all working conditions, which is more significant for improving fuel efficiency. However, due to the low pressure difference, a large-diameter valve is needed to meet the flow requirements. In some working conditions, the opening of the mixing valve needs to be controlled to adjust the pressure at the outlet of the EGR valve, thereby improving the pressure difference on both sides of the EGR valve and improving the EGR rate. If the water temperature sensor fails, the engine knock performance will deteriorate if the target EGR rate before failure is still controlled. SUMMARY

[0003] The present application aims to solve at least one of the technical problems existing in the prior art, and provides an EGR control method and system after water temperature sensor failure.

[0004] In a first aspect, an EGR control method after water temperature sensor failure is provided, including the following steps:

[0005] S100, detecting the water temperature sensor, and determining the corrected target EGR rate for various faults after detecting that at least one fault occurs in the water temperature sensor;

[0006] S200, taking the minimum value of the corrected target EGR rate for various faults to obtain the final target EGR rate, limiting the final target EGR rate to not exceed the target EGR rate before failure, and performing EGR control according to the final target EGR rate.

[0007] Further, in the step S100, if the water temperature sensor detects an excessively low fault, the corrected target EGR rate is as follows:

[0008]

[0009] wherein is a first speed-load correction coefficient, is a first optimization correction coefficient determined based on a transient condition coefficient, is an optimization correction coefficient determined based on the engine speed and the difference ratio of ignition efficiency, is a first target EGR rate self-learning correction coefficient.

[0010] Furthermore, if the water temperature sensor is detected as stuck, the target EGR rate is corrected. as follows:

[0011]

[0012] in is the second speed load correction coefficient, is the second optimization correction coefficient determined based on the transient operating condition coefficient, It is the second target EGR rate self-learning correction coefficient.

[0013] Furthermore, if the water temperature sensor detects other faults, the target EGR rate is corrected. .

[0014] Furthermore, if the water temperature sensor detects a low fault,

[0015] a) If , then All are reduced,

[0016] ,in The first target EGR rate self-learning correction coefficient updated in the last learning.

[0017] Furthermore, if the water temperature sensor detects a low fault,

[0018] b) If , then All increased,

[0019] .

[0020] Furthermore, if the water temperature sensor detects a low fault,

[0021] c) In other cases, .

[0022] Furthermore, if the water temperature sensor is detected as stuck,

[0023] a) If , then To reduce,

[0024] ,in They are the second target EGR rate self-learning correction coefficients updated in the last learning;

[0025] b) If , then To reduce,

[0026] ;

[0027] c) If , then are both increased, ;

[0028] d) If , then is increased,

[0029] ;

[0030] e) Otherwise, .

[0031] Further, in the case of water temperature sensor detected too low fault, case a), 1) if water temperature too low fault occurs, and , and is not greater than -0.1, and no water temperature sensor stuck fault occurs within this drive cycle, then further: ; 2) if water temperature too low fault occurs, and is not greater than -0.1, and occurs, and a water temperature sensor stuck fault occurs within this drive cycle, and is not greater than -0.1, then further , , is the second target EGR rate self-learning correction coefficient of the last learning update; 3) otherwise, remain unchanged.

[0032] Further, in the case of water temperature sensor detected too low fault, case b), 1) if water temperature too low fault occurs, and , and is greater than 0.2, and no water temperature sensor stuck fault occurs within this drive cycle, then further: ; 2) if water temperature too low fault occurs, and is greater than 0.2, and a water temperature sensor stuck fault occurs within this drive cycle, and is greater than 0.2, then further , ; 3) otherwise, remain unchanged.

[0033] Further, in the case of water temperature sensor detection as a low failure, case c), if the continuous CNT1 exceeds a preset value, CNT1 initial value is 0, the vehicle is added 1 after each driving cycle, and can be saved after the vehicle is powered off, and the vehicle mileage S1 exceeds a preset value, S1 initial value is 0, and is constantly updated according to the vehicle mileage, and can be saved after the vehicle is powered off, then 1) if ≥ 0, then , and CNT1 and S1 are cleared; 2) if < 0, then , and CNT1 and S1 are cleared; 3) otherwise, remain unchanged.

[0034] Further, in the case of water temperature sensor detection as a stuck failure, case a), 1) if the water temperature sensor stuck failure occurs, and , and is not greater than -0.1, and no water temperature low failure occurs within this driving cycle, then further ; 2) if the water temperature sensor stuck failure occurs, and is not greater than -0.1, and , and the water temperature low failure occurs within this driving cycle, and is not greater than -0.1, then further , ; 3) otherwise, remain unchanged.

[0035] Further, in the case of water temperature sensor detection as a stuck failure, case d), 1) if the water temperature sensor stuck failure occurs, and , and is greater than 0.2, and no water temperature low failure occurs within this driving cycle, then further ; 2) if the water temperature sensor stuck failure occurs, and , and is greater than 0.2, and the water temperature low failure occurs within this driving cycle, and is greater than 0.2, then further , ; 3) otherwise, remain unchanged.

[0036] Further, in the case of water temperature sensor detection as a stuck failure, case e), if the continuous CNT2 exceeds a preset value, CNT2 initial value is 0, the vehicle is added 1 after each driving cycle, and can be saved after the vehicle is powered off, and the vehicle mileage S2 exceeds a preset value, S2 initial value is 0, and is constantly updated according to the vehicle mileage, and can be saved after the vehicle is powered off, then 1) if ≥ 0, then , and CNT2 and S2 are cleared; 2) if <0, then and CNT2 and S2 are cleared; 3) everything else remains unchanged.

[0037] In a second aspect, an embodiment of the present application provides an EGR control system after water temperature sensor failure, comprising:

[0038] A determination module is configured to detect the water temperature sensor, and determine a corrected target EGR rate of various faults after detecting that at least one fault occurs in the water temperature sensor.

[0039] A control module is configured to obtain a final target EGR rate by taking a minimum value of the corrected target EGR rates of various faults, limit the final target EGR rate to not exceed a target EGR rate before the fault, and perform EGR control according to the final target EGR rate.

[0040] The EGR control method and system after water temperature sensor failure provided by the present application can detect the water temperature sensor, determine a corrected target EGR rate of various faults after detecting that at least one fault occurs in the water temperature sensor, obtain a final target EGR rate by taking a minimum value of the corrected target EGR rates of various faults, limit the final target EGR rate to not exceed a target EGR rate before the fault, and perform EGR control according to the final target EGR rate. Different target EGR rates can be optimized according to the occurrence of water temperature sensor failure, and are constantly dynamically adjusted and updated, thereby effectively improving knock occurrence after the fault occurs. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 A flowchart of an EGR control method after water temperature sensor failure provided by an embodiment of the present application is shown.

[0042] Figure 2 A structure block diagram of an EGR control system after water temperature sensor failure provided by an embodiment of the present application is shown. DETAILED DESCRIPTION

[0043] In order for those skilled in the art to better understand the technical solutions of the present application, the following describes exemplary embodiments of the present application with reference to the accompanying drawings, which include various details of the embodiments of the present application to help understanding, and should be considered only as exemplary. Therefore, those skilled in the art should recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present application. Similarly, in order to be clear and concise, the description in the following description omits the description of well-known functions and structures.

[0044] In the case of no conflict, the embodiments of the present application and the features in the embodiments can be combined with each other.

[0045] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0046] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. "Coupled" or "connected" or similar terms are not restricted to physical or mechanical connections or associations, but can also include electrical connections, whether direct or indirect.

[0047] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an overly literal or overly formal sense unless expressly so defined herein.

[0048] The present application provides an EGR control method after water temperature sensor failure. Figure 1 A flowchart of an EGR control method after water temperature sensor failure is provided for an embodiment of the present application. The method comprises the following steps:

[0049] S100, detecting the water temperature sensor, and determining the corrected target EGR rate for various faults after detecting at least one failure of the water temperature sensor.

[0050] Water temperature sensor: read the highest engine body water temperature, i.e. the coolant temperature at the water outlet. Assuming that before the failure, the pre-failure target EGR rate is It can be determined by the prior art CN202011247319.6 "A method and system for calculating target EGR rate".

[0051] In one embodiment, if the water temperature sensor detects a too low failure, i.e. the water temperature sensor cannot detect the engine cooling water temperature in a high condition, the corrected target EGR rate is As follows:

[0052]

[0053] wherein is a first speed-load correction coefficient, is a first optimization correction coefficient determined based on a transient condition coefficient, Optimization correction factor determined based on engine speed and difference ratio of ignition efficiency, First target EGR rate self-learning correction factor.

[0054] Basic correction factor determined based on engine speed n and load rho (fresh air intake density into the cylinder), the higher the engine speed and the greater the engine load, the more likely the engine is to knock, in order to ensure that the engine can avoid real knock when the knock sensor fails, the basic correction factor determined based on speed and load is smaller, so the possibility of knocking is lower. The purpose of reducing the EGR rate is to reserve space for the engine in the working condition prone to knocking, and once the real knock occurs in the working condition prone to knocking, the EGR rate can be increased to suppress the possibility of knock. First speed and load correction factor Determined by querying the corresponding values of engine speed n and load rho.

[0055] Table 1 Corresponding relationship between first speed and load correction factor and engine speed and load

[0056]

[0057] Transient condition coefficient Determined by engine speed n and intake pressure fluctuation rate , which represents the change of engine transient condition, the greater the value, the more volatile the engine condition, and the value is limited within 0-1. Take the difference between the maximum and minimum values of in the last N sampling periods (a single sampling period is 10ms). N is related to engine speed, the lower the speed, the smaller the N value, the greater the speed, the greater the N value, the main reason is that the lower the speed, the more obvious the intake pressure fluctuation, and the greater the sampling period cannot truly reflect the transient condition. The N value corresponding to different engine speeds n is as follows:

[0058] Table 2 Corresponding relationship between N value and engine speed

[0059]

[0060] Throttle outlet intake pressure, Throttle outlet intake pressure of the Nth sampling period, First-order low-pass filtered throttle outlet intake pressure, Filtered throttle outlet intake pressure of the Nth sampling period.

[0061]

[0062] Wherein, Pf is the filtered throttle outlet intake air pressure of the N-1 sampling period, N = 1, 2, 3… P0 is equal to the throttle outlet intake air pressure at the 0th sampling period T is the sampling period interval The present example is 10 ms. Pf is the throttle outlet intake air pressure coefficient, The number of cylinders of the engine in the present example is 4, The calibration speed of the engine is 1000 rpm, The purpose of such a setting is to normalize the processing, without making special calibration at different cylinder numbers and speeds, only the calibration of the 4-cylinder engine and the speed of 1000 rpm , so as to reduce the calibration test work), wherein N is the number of cylinders of the engine, n is the speed of the engine, Pf is the throttle outlet intake air pressure filtering coefficient, the present example is 0.02. The transient condition coefficient of the engine The corresponding value is determined by querying the engine speed n and the intake air pressure fluctuation rate The change rate of the transient condition coefficient is limited to not more than ±0.1 / 10 ms, and the final transient condition coefficient .

[0063] Table 3 Corresponding relationship between transient condition coefficient and engine speed and intake air pressure fluctuation rate

[0064]

[0065] The first optimization correction coefficient determined based on the transient condition coefficient The corresponding value is determined by querying the transient condition coefficient The purpose of such a setting is that, through experiments, it is shown that when the engine condition jitter is slow, the engine water temperature is less risky for knock, and when the engine condition jitter is more intense, the water temperature is more risky for knock.

[0066] Table 4 Corresponding relationship between the optimization correction coefficient determined based on the transient condition coefficient and the transient condition coefficient

[0067]

[0068] Ignition efficiency difference ratio The ignition efficiency difference ratio is determined by the ignition efficiency difference and the basic ignition efficiency , Pf is the throttle outlet intake air pressure coefficient, , is the actual ignition angle efficiency of the engine. Therefore the smaller the more likely to knock, if the engine water temperature sensor temperature too low fault occurs, the more likely to knock, the need to further increase the EGR rate, the optimal correction coefficient determined based on the engine speed and ignition efficiency difference ratio determined by the table query engine speed and ignition efficiency difference ratio corresponding value.

[0069] Table 5 correspondence between the optimal correction coefficient determined based on the engine speed and ignition efficiency difference ratio and the engine speed and ignition efficiency difference ratio

[0070]

[0071] is the target EGR rate self-learning correction coefficient after the water temperature too low fault occurs, its default value is 0, which can be continuously self-learned and updated, and can be saved after the vehicle is powered off.

[0072] In one embodiment, if the water temperature sensor detects a stuck fault, that is, the water temperature signal read by the water temperature sensor changes much more slowly than the actual situation, the corrected target EGR rate is as follows:

[0073]

[0074] wherein is the second speed and load correction coefficient, is the second optimal correction coefficient determined based on the transient condition coefficient, is the second target EGR rate self-learning correction coefficient.

[0075] wherein C1 is a first adjustment coefficient greater than 0 and not greater than 1, and in the present example C1 is 0.95.

[0076] wherein C2 is a second adjustment coefficient greater than 0 and not greater than 1, and in the present example C2 is 0.4. C2 is not greater than C1 because the water temperature is stuck fault and cannot identify the water temperature transient change.

[0077] is the target EGR rate self-learning correction coefficient after the water temperature sensor stuck fault occurs, its default value is 0, which can be continuously self-learned and updated, and can be saved after the vehicle is powered off. Since the water temperature signal is stuck or changes slowly at this time, but still in some steady state conditions can represent its true water temperature, its learning process is more specific and accurate than .

[0078] In one embodiment, if the water temperature sensor detects other faults, the post-correction target EGR rate is revised .

[0079] S200, the minimum value of the post-correction target EGR rate of various faults is obtained to obtain the final target EGR rate , and the final target EGR rate is limited to not exceed the target EGR rate before the fault, and EGR control is performed according to the final target EGR rate.

[0080] In one embodiment, in the case of the water temperature sensor detecting a too low fault,

[0081] a) If , it means that the EGR rate requirement is high, and knocking is avoided, then are all reduced, , wherein is the first target EGR rate self-learning correction coefficient of the last learning update.

[0082] In particular, if the learning value is adjusted too large, the learning pace needs to be further adjusted, and the EGR rate adjustment for the water temperature hysteresis fault is pre-controlled in advance to improve the knocking risk: 1) If the water temperature too low fault occurs, and , and is not greater than -0.1, and no water temperature sensor hysteresis fault occurs in the current driving cycle, then further ; 2) If the water temperature too low fault occurs, and is not greater than -0.1, and occurs, and the water temperature sensor hysteresis fault occurs in the current driving cycle, and is not greater than -0.1, then further , , is the second target EGR rate self-learning correction coefficient of the last learning update; 3) In other cases, it remains unchanged.

[0083] b) If , it means that the EGR rate requirement is low, and knocking is not easy to occur, then the reduction of the EGR rate needs to be slowed down, and the role of EGR in improving fuel consumption needs to be fully utilized, then are all increased, .

[0084] In particular, if the learning value is not adjusted too large, the learning pace needs to be further adjusted, and the EGR rate adjustment for the water temperature hysteresis fault is pre-controlled in advance to improve the advantage of the EGR rate: 1) If the water temperature too low fault occurs, and , and is greater than 0.2, and no water temperature sensor hysteresis fault occurs in the current driving cycle, then further ; 2) if the water temperature is too low after the occurrence of the water temperature sensor stuck fault, and > 0.2, and the water temperature sensor stuck fault occurs within this driving cycle, and > 0.2, then further , ; 3) otherwise, remain unchanged.

[0085] c) otherwise, .

[0086] In particular, since the problem of the working advantage of adjusting the EGR rate to adjust the EGR rate and the risk of improving knock have not occurred for a long time, it is necessary to gradually transition the learning value to restore the advantage of the EGR rate: if consecutive CNT1 exceeds a preset value (5000 times in this example), CNT1 is initially 0, the vehicle is incremented by 1 after each driving cycle, and can be saved after the vehicle is powered off, and the vehicle mileage S1 exceeds a preset value (5 kilometers in this example), S1 is initially 0, and is constantly updated according to the vehicle mileage, and can be saved after the vehicle is powered off, then 1) if > 0, then , and CNT1 and S1 are cleared; 2) if < 0, then , and CNT1 and S1 are cleared; 3) otherwise, remain unchanged.

[0087] In one embodiment, in the case of a stuck fault detected by the water temperature sensor,

[0088] a) if occurs, it indicates that the EGR rate is required to be higher to avoid the occurrence of knock, then is reduced, , wherein are the second target EGR rate self-learning correction coefficients of the last learning update.

[0089] In particular, if the learning value is adjusted too large, it is necessary to further adjust the learning pace and adjust the EGR rate in advance to improve the risk of knock: 1) if the water temperature sensor stuck fault occurs, and , and is not greater than -0.1, and the water temperature is too low within this driving cycle, then further ; 2) if the water temperature sensor stuck fault occurs, and is not greater than -0.1, and , and the water temperature is too low within this driving cycle, and is not greater than -0.1, then further , ; 3) otherwise, remain unchanged.

[0090] b) if occurs, it means that the EGR rate requirement is high, and the occurrence of knock is avoided, then is reduced, .

[0091] c) if occurs, it means that the EGR rate requirement is low, and the occurrence of knock is not easy, then the reduction of the EGR rate is slowed down, and the effect of EGR on improving fuel consumption is fully utilized, then are all increased, .

[0092] d) if occurs, it means that the EGR rate requirement is low, and the occurrence of knock is not easy, then the reduction of the EGR rate is slowed down, and the effect of EGR on improving fuel consumption is fully utilized, then is increased, .

[0093] In particular, if the learning value is not adjusted much, further adjustment of the learning pace is needed, and the EGR rate adjustment for the water temperature too low fault is pre-controlled to improve the advantage of the EGR rate: 1) if the water temperature sensor stuck fault occurs, and occurs, and is greater than 0.2, and the water temperature too low fault does not occur in this driving cycle, then further ; 2) if the water temperature sensor stuck fault occurs, and occurs, and is greater than 0.2, and the water temperature too low fault occurs in this driving cycle, and is greater than 0.2, then further , ; 3) in other cases, it is maintained unchanged.

[0094] e) in other cases, .

[0095] In particular, since the problem of adjusting the EGR rate to adjust the working advantage of the EGR rate and improve the risk of knock has not occurred for a long time, the learning value needs to be gradually transitioned to restore the advantage of the EGR rate: if the continuous CNT2 exceeds a preset value (5000 times in this example), the initial value of CNT2 is 0, the vehicle is increased by 1 after each driving cycle, and can be saved after the vehicle is powered off, at the same time, the vehicle mileage S2 exceeds a preset value (5 kilometers in this example), the initial value of S2 is 0, and is constantly updated according to the vehicle mileage, and can be saved after the vehicle is powered off, then 1) if ≥ 0, then , and CNT2 and S2 are cleared; 2) if < 0, then and CNT2 and S2 are cleared; 3) other remain unchanged.

[0096] The embodiment of the application can optimize different target EGR rates according to the occurrence of water temperature sensor failure, and constantly dynamically adjust and update, thereby effectively improving knock occurrence after failure.

[0097] The application further provides an EGR control system after water temperature sensor failure. Figure 2 A structure block diagram of an EGR control system after water temperature sensor failure is provided for the embodiment of the application, and the system comprises:

[0098] A determination module 11 is configured to detect the water temperature sensor, and determine the corrected target EGR rate of each failure after detecting that at least one failure of the water temperature sensor occurs;

[0099] A control module 12 is configured to obtain the final target EGR rate by taking the minimum value of the corrected target EGR rate of each failure , limit the final target EGR rate to not exceed the target EGR rate before failure, and perform EGR control according to the final target EGR rate.

[0100] Example embodiments have been disclosed herein and, although the use of specific terms is expressly used herein, they are intended in the sense only of general descriptive purpose and should not be construed as limiting. In some instances, it will be apparent to those skilled in the art that features, characteristics or / and elements described in connection with a particular embodiment can be used in conjunction with other embodiments, unless otherwise explicitly stated. Therefore, those skilled in the art will appreciate that various changes can be made in form and detail without departing from the scope of the application as set forth in the appended claims.

Claims

1. A method for controlling EGR after a water temperature sensor failure, characterized in that: The following steps are involved: S100, testing the water temperature sensor, and upon detecting at least one fault of the water temperature sensor, determining a corrected target EGR rate for each fault; S200 , taking the minimum value of the corrected target EGR rates for various faults to obtain a final target EGR rate, limiting the final target EGR rate to not exceed the pre-fault target EGR rate, and performing EGR control based on the final target EGR rate.

2. The method according to claim 1, characterized in that In step S100, if the water temperature sensor detects a low fault, the target EGR rate is corrected. as follows: in is the first speed load correction coefficient, is the first optimization correction coefficient determined based on the transient operating condition coefficient, is the optimization correction coefficient determined based on the difference ratio between engine speed and ignition efficiency, It is the first target EGR rate self-learning correction coefficient.

3. The method according to claim 2, characterized in that If the water temperature sensor is detected as stuck, the target EGR rate is corrected. as follows: in is the second speed load correction coefficient, is the second optimization correction coefficient determined based on the transient operating condition coefficient, It is the second target EGR rate self-learning correction coefficient.

4. The method according to claim 3, characterized in that If the water temperature sensor detects other faults, the target EGR rate will be corrected. .

5. The method according to claim 4, characterized in that If the water temperature sensor detects a low fault, a) If , then All are reduced, ,in The first target EGR rate self-learning correction coefficient updated in the last learning.

6. The method according to claim 5, characterized in that If the water temperature sensor detects a low fault, b) If , then All increased, 。 7. The method according to claim 6, characterized in that If the water temperature sensor detects a low fault, c) In other cases, .

8. The method according to claim 7, characterized in that If the water temperature sensor is detected as stuck, a) If , then To reduce, ,in They are the second target EGR rate self-learning correction coefficients updated in the last learning; b) If , then To reduce, ； c) If , then All increased, ; d) If , then To increase, ； e) In other cases, .

9. The method according to claim 7, characterized in that If the water temperature sensor detects a low fault, in case a), 1) if the water temperature is too low after the fault occurs, and ,and If the value is not greater than -0.1 and no water temperature sensor stuck fault occurs during this driving cycle, then: ; 2) If the water temperature is too low after the fault occurs Not greater than -0.1, and appears , and a water temperature sensor stuck fault occurred during this driving cycle, and Not greater than -0.1, then further , , The second target EGR rate self-learning correction coefficient updated in the last learning; 3) In other cases, it remains unchanged.

10. The method according to claim 7, characterized in that If the water temperature sensor detects a low fault, in case b), 1) if the water temperature is too low after the fault occurs, and ,and If the value is greater than 0.2 and no water temperature sensor stuck fault occurs during this driving cycle, then: ; 2) If the water temperature is too low after the fault occurs Greater than 0.2, and a water temperature sensor stuck fault occurred during this driving cycle, and If it is greater than 0.2, then further , ;3) In other cases, remain unchanged.

11. The method according to claim 7, characterized in that If the water temperature sensor detects a low fault, in case c), if CNT1 exceeds the preset value continuously, the initial value of CNT1 is 0, and it increases by 1 after each driving cycle of the vehicle, and can be saved after the vehicle is powered off. At the same time, the vehicle mileage S1 exceeds the preset value, the initial value of S1 is 0, and it is continuously updated according to the vehicle mileage, and can be saved after the vehicle is powered off, then 1) If ≥0, then , and clear CNT1 and S1; 2) If <0, then , and clear CNT1 and S1; 3) Others remain unchanged.

12. The method according to claim 8, characterized in that If the water temperature sensor is detected as stuck, in case a), 1) if the water temperature sensor is stuck and ,and If the value is not greater than -0.1 and no low water temperature fault occurs during this driving cycle, then: ; 2) If the water temperature sensor is stuck and the fault occurs Not greater than -0.1, and , and a low water temperature fault occurs during this driving cycle, and Not greater than -0.1, then further , ;3) In other cases, remain unchanged.

13. The method according to claim 8, characterized in that If the water temperature sensor is detected as stuck, in case d), 1) if the water temperature sensor is stuck and the ,and If the value is greater than 0.2 and no low water temperature fault occurs during this driving cycle, then: ;2) If the water temperature sensor is stuck and the , and appears Greater than 0.2, and a low water temperature fault occurs during this driving cycle, and If it is greater than 0.2, then further , ;3) In other cases, remain unchanged.

14. The method according to claim 8, characterized in that If the water temperature sensor is detected as a stuck fault, in case e), if CNT2 exceeds the preset value continuously, the initial value of CNT2 is 0, and it increases by 1 after each driving cycle of the vehicle, and can be saved after the vehicle is powered off. At the same time, the vehicle mileage S2 exceeds the preset value, the initial value of S2 is 0, and it is continuously updated according to the vehicle mileage, and can be saved after the vehicle is powered off, then 1) If ≥0, then , and clear CNT2 and S2; 2) If <0, then , and clear CNT2 and S2; 3) Others remain unchanged.

15. An EGR control system after a water temperature sensor failure, characterized in that: include: a determination module, configured to detect the water temperature sensor and, upon detecting at least one fault of the water temperature sensor, determine a corrected target EGR rate for various faults; The control module is used to obtain the minimum value of the corrected target EGR rate of various faults to obtain the final target EGR rate, limit the final target EGR rate to not exceed the target EGR rate before the fault, and perform EGR control according to the final target EGR rate.

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