Exhaust gas recirculation closed-loop control method based on multiple performance dimensions

Abstract

The invention discloses an exhaust gas recirculation closed-loop control method based on multiple performance dimensions, which comprises the following steps of: when an EGR closed-loop condition is switched from meeting to not meeting, determining a pressure ratio coefficient according to actual pressure of an outlet of a mixing valve, actual pressure of an inlet of the mixing valve, actual pressure of an outlet of a throttle valve and actual pressure of an inlet of the throttle valve; according to the engine rotating speed, the pressure ratio coefficient and the self-learning correction coefficient, a duration initial value is determined; wherein the self-learning correction coefficient is obtained through self-learning, and the duration initial value is used for keeping the target opening degree of the EGR valve unchanged; and the target opening degree of the EGR valve is transited to 0% at a certain speed after the initial value of the duration is maintained. According to the method, by limiting the EGR target opening degree after the EGR closed-loop condition exits, system fluctuation is effectively reduced, and system stability is improved.

Description

Technical Field

[0001] The present invention relates to the field of engine control, and in particular to an exhaust gas recirculation closed-loop control method based on multiple performance dimensions. Background Art

[0002] Exhaust Gas Recirculation (EGR) refers to taking exhaust gas from the exhaust into the intake system. Studies have shown that the EGR system has certain advantages in improving emissions, reducing fuel consumption and improving anti-knock capabilities.

[0003] The prior art does not provide any suggestion on how to reasonably control the EGR valve according to different operating conditions after the EGR closed loop is exited, which may cause performance deterioration during the EGR valve exit process. Summary of the invention

[0004] The object of the present invention is to provide an exhaust gas recirculation closed-loop control method based on multiple performance dimensions to optimize EGR valve control.

[0005] In order to solve the above technical problems, the present invention proposes an exhaust gas recirculation closed-loop control method based on multiple performance dimensions, including: when the EGR closed-loop condition is switched from being satisfied to being unsatisfied, according to the actual pressure at the outlet of the mixing valve, the actual pressure at the inlet of the mixing valve, the actual pressure at the outlet of the throttle valve, and the actual pressure at the inlet of the throttle valve, the pressure ratio coefficient is determined; Determine the initial value of the duration according to the engine speed, the pressure ratio coefficient, and the self-learning correction coefficient; wherein the self-learning correction coefficient is obtained through self-learning, and the initial value of the duration is used to maintain the target opening of the EGR valve unchanged; After maintaining the initial value for a certain period of time, the EGR valve target opening transitions to 0% at a certain rate.

[0006] According to the above scheme, the method for determining the pressure ratio coefficient includes: According to the actual pressure at the outlet of the mixing valve and the actual pressure at the inlet of the mixing valve, the ratio of the actual pressure at the inlet and outlet of the mixing valve is determined; According to the actual pressure at the throttle outlet and the actual pressure at the throttle inlet, determine the ratio of the actual pressure at the throttle inlet and outlet; According to the ratio of the actual pressures at the throttle inlet and outlet, determine the correction factor of the pressure ratio coefficient; The pressure ratio coefficient is determined based on the ratio of the pressure ratio coefficient correction coefficient and the actual pressures at the inlet and outlet of the mixing valve.

[0007] According to the above scheme, the method for determining the initial value of the duration includes: Determine a compression ratio-engine speed coefficient based on the compression ratio coefficient and the engine speed; Determine the self-learning correction coefficient through self-learning; The initial value of the duration is determined based on the compression ratio-engine speed coefficient and the self-learning correction coefficient.

[0008] According to the above scheme, the method for determining the self-learning correction coefficient includes: According to the current optimization conditions, the original remaining time is updated and optimized to obtain the optimized remaining time; the original remaining time is the time from the current moment to the moment when the EGR valve target opening is stopped. Adjust the self-learning correction coefficient according to the original remaining time and the remaining time after optimization.

[0009] According to the above scheme, the optimized operating conditions include: the situation where the target opening of the EGR valve remains unchanged after the EGR closed-loop enabling condition is exited; Under this optimization condition, the remaining time after optimization can be obtained by: determining a boost pressure difference change based on the boost pressure difference within a certain number of sampling periods; Determine a change in pressure at the outlet of the mixing valve based on the outlet of the mixing valve within a certain number of sampling periods; The original remaining time is updated and optimized based on the change in boost pressure difference and the change in mixing valve outlet pressure.

[0010] According to the above scheme, the optimized working conditions include: After the EGR closed-loop enabling condition is exited, the EGR valve target opening remains unchanged and knock occurs; Under this optimization condition, the remaining time after optimization can be obtained by: Get the number of knocks of different intensities; Determine a change in the outlet pressure of the mixing valve based on the outlet pressure of the mixing valve within a certain number of sampling periods; Determine the knock correction coefficient according to the number of knocks of different intensities; The original remaining time is updated and optimized according to the knock correction coefficient and the change in the outlet pressure of the mixing valve.

[0011] According to the above scheme, the optimized operating conditions include: after the EGR closed-loop enabling condition is exited, the EGR valve target opening remains unchanged, and the catalyst oxygen storage capacity coefficient and the air-fuel ratio coefficient change; Under this optimization condition, the remaining time after optimization can be obtained by: Obtaining catalyst oxygen storage capacity coefficient; Determining a change in the catalyst oxygen storage capacity coefficient based on the catalyst oxygen storage capacity coefficient within a certain number of sampling periods; Determine the air-fuel ratio coefficient according to the actual air-fuel ratio and the ideal air-fuel ratio; Determine the change of the air-fuel ratio coefficient based on the air-fuel ratio coefficient within a certain number of sampling periods; The original remaining time is updated and optimized according to the changes in the catalyst's oxygen storage capacity coefficient and the air-fuel ratio coefficient.

[0012] According to the above scheme, the self-learning includes: a. If the difference between the optimized remaining time and the original remaining time is greater than the first remaining time threshold, and only one of the different optimized working conditions has always occurred, and the number of consecutive occurrences exceeds the preset number of times, the self-learning correction coefficient is incremented by the first step, and the number of consecutive occurrences in this case is cleared; the newly learned and stored self-learning correction coefficient is used when entering this situation for judgment next time; b. If the difference between the optimized remaining time and the original remaining time is greater than the first remaining time threshold, and it is not always the case that only one of the different optimized conditions occurs, and the number of consecutive occurrences exceeds the preset number, then the self-learning correction coefficient is incremented by the second step length, and the number of consecutive occurrences in this case is cleared; the newly learned and stored self-learning correction coefficient is used the next time the judgment enters this situation. c. If the difference between the optimized remaining time and the original remaining time is not greater than the second remaining time threshold, and only one of the fixed situations in each optimization situation has always occurred, and the number of consecutive occurrences exceeds the preset number, the self-learning correction coefficient is decreased by the third step length, and the number of consecutive occurrences in this situation is cleared; the newly learned and stored learning value is used the next time the judgment of this situation is entered; d. If the difference between the optimized remaining time and the original remaining time is not greater than the second remaining time threshold, and not only one of the various optimization situations occurs all the time, and the number of consecutive occurrences exceeds the preset number, then the self-learning correction coefficient is decreased by the fourth step length, and the number of consecutive occurrences in this situation is cleared; the newly learned and stored learning value is used the next time the judgment of this situation is entered; e. If the difference between the optimized remaining time and the original remaining time is greater than the first remaining time threshold, and the difference between the optimized remaining time and the original remaining time is not greater than the second remaining time threshold, the time self-learning correction coefficient is increased by the fifth step, and the number of consecutive occurrences in this case is cleared; the newly learned and stored learning value is used the next time the judgment of this situation is entered; f. If the difference between the optimized remaining time and the original remaining time is not greater than the second remaining time threshold, and the difference between the optimized remaining time and the original remaining time last time is greater than the first remaining time threshold, the time self-learning correction coefficient is decreased by the sixth step, and the number of consecutive occurrences in this case is cleared; the newly learned and stored learning value is used the next time the judgment of this situation is entered; g. Except for the above cases a~f, the self-learning correction coefficient remains unchanged; Among them, the priorities of a~g decrease in sequence.

[0013] According to the above scheme, the method of transitioning the EGR valve target opening to 0% at a certain rate includes: Determine the rate of change of the target opening of the EGR valve according to the pre-calibration result and the engine speed; The EGR valve target opening is transitioned to 0% according to the determined change rate.

[0014] The present invention also provides an exhaust gas recirculation closed-loop control device based on multiple performance dimensions, comprising: A pressure ratio coefficient determination module, used for determining the pressure ratio coefficient according to the actual pressure at the mixing valve outlet, the actual pressure at the mixing valve inlet, the actual pressure at the throttle valve outlet, and the actual pressure at the throttle valve inlet when the EGR closed-loop condition is switched from being satisfied to being not satisfied; The duration initial value determination module is used to determine the duration initial value according to the engine speed, the pressure ratio coefficient, and the self-learning correction coefficient; wherein the self-learning correction coefficient is obtained through self-learning, and the duration initial value is used to maintain the EGR valve target opening unchanged; The EGR valve target opening transition module is used to make the EGR valve target opening transition to 0% at a certain rate after the EGR valve target opening maintains the initial value for a certain period of time.

[0015] Beneficial Effects The beneficial effects of the present invention are as follows: the present invention controls the EGR valve target opening to be maintained for a period of time after the EGR valve closed-loop control is exited, and limits its decreasing rate after being maintained for a period of time, thereby avoiding system fluctuations caused by excessively rapid changes in the EGR valve target opening after the EGR valve closed-loop control is exited, thereby optimizing engine emissions and avoiding engine knock.

[0016] Furthermore, the present invention can adjust the holding time of the target opening of the EGR valve according to the actual working conditions through the set self-learning coefficient, so that the optimization effect can be adjusted in real time according to the actual situation, further improving the optimization effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic structural diagram of an engine exhaust system with EGR according to the first embodiment of the present invention; Figure 2 It is a flow chart of the exhaust gas recirculation closed-loop control method based on multiple performance dimensions according to the first embodiment of the present invention.

[0018] In the figure: 1-air filter, 2-mixing valve, 3-compressor, 4-throttle, 5-engine, 6-turbine, 7-catalyst, 8-particulate matter collector, 9-EGR cooler, 10-EGR valve, 11-temperature sensor, 12-differential pressure sensor. DETAILED DESCRIPTION

[0019] Embodiment 1: See also Figure 1 , the engine exhaust system applicable to this embodiment includes: Air filter 1; The mixing valve 2 connected to the air filter is used to adjust the pressure at the outlet of the EGR valve 10, increase the pressure difference at both ends of the EGR valve 10, and extend two air flow paths from the mixing valve 2; A compressor 3 is connected to one of the air flow paths of the mixing valve 2; A throttle valve 4 connected to the compressor 3; The engine 5 is connected to the throttle valve 4 and is used to compress fresh air for supercharging; A turbine 6 connected to the engine 5 and used to control the opening of the wastegate valve; A catalyst 7 connected to the turbine 6; A particle collector 8 connected to the catalyst 7; The EGR cooler 9 is connected to another air flow path of the mixing valve 2 and is used to receive the exhaust gas output by the particulate matter collector 8 and cool it to increase the exhaust gas flow rate; An EGR valve 10, one end of which is connected to the EGR cooler 9 and the other end of which is connected to the mixing valve 2, is used to control the flow of exhaust gas entering the cylinder; A temperature sensor 11 is installed between the EGR valve 10 and the EGR cooler 9 and is used to detect the temperature of the exhaust gas entering the EGR valve 10; The differential pressure sensor 12 is connected to the EGR valve 10 and is used to detect the pressure at the inlet and outlet of the EGR valve 10 .

[0020] For the above engine exhaust system, this embodiment proposes an exhaust gas recirculation closed-loop control method based on multiple performance dimensions, see Figure 2 ,include: S1: When the EGR closed-loop condition switches from satisfied to not satisfied, the actual pressure at the outlet of the mixing valve , Actual pressure at the mixing valve inlet , Actual throttle outlet pressure , Actual throttle inlet pressure , determine the pressure ratio coefficient ; S2, according to the engine speed n, pressure ratio coefficient , self-learning correction coefficient , determine the initial value of the duration t; where the self-learning correction coefficient Obtained through self-learning, the initial value of duration t is used to maintain the target opening of the EGR valve constant; It should be understood that maintaining the EGR valve target opening The purpose is to stabilize the EGR valve to avoid affecting the boost inlet pressure and affecting the boost control responsiveness. Length of time, is the target opening of the EGR valve in the previous sampling cycle (i.e., the target opening of the EGR valve when the EGR closed-loop condition is met in the last sampling cycle), and the initial value of the duration t starts from the first sampling cycle when the EGR closed-loop condition is not met; S3, EGR valve target opening After maintaining the initial value t for a certain period of time, it transitions to 0% at a certain rate.

[0021] Step S1 includes: S101, according to the actual pressure of the mixing valve outlet , Actual pressure at the mixing valve inlet , determine the ratio of the actual pressures at the inlet and outlet of the mixing valve ; S102, according to the actual throttle outlet pressure , Actual throttle inlet pressure , determine the ratio of the actual throttle inlet and outlet pressures ; S103, based on the ratio of the actual pressure at the throttle inlet and outlet , determine the pressure ratio correction factor ; Ratio of actual pressure between throttle inlet and outlet Correction factor for pressure ratio The relationship is determined by a pre-calibrated table, as shown in Table 1 below: Table 1

[0022] The above calibration is based on: When the value is larger, the throttle control ability is poor, and the pressure control accuracy risk of the supercharger is greater. In order to avoid the problem of supercharger pressure control accuracy, improvements should be made; S104, correction coefficient according to pressure ratio coefficient , the ratio of the actual pressure at the inlet and outlet of the mixing valve , determine the pressure ratio coefficient ; .

[0023] Step S2 includes: S201, based on pressure ratio coefficient , engine speed n, determine the compression ratio-engine speed coefficient ; Compression ratio-engine speed coefficient Pressure ratio coefficient The relationship between the engine speed n is obtained by calibration, and the calibration basis is: from the first sampling period when the EGR closed-loop condition is not met to the end of the initial value of the time length t Within a sampling period ( depending on ), when the target boost pressure remains unchanged, the difference between the target boost pressure and the actual boost pressure The fluctuation of is within the preset range; among them, is the supercharger response time; The difference between the target boost pressure and the actual boost pressure The basis for judging whether the fluctuation of is within the preset range is: After the first sampling period from when the EGR closed-loop condition is not met to the end of the initial time value t The following conditions are satisfied within each sampling period:

[0024] represents the difference between the target boost pressure and the actual boost pressure The fluctuation of is within the preset range, among which, In this example, 0.1 is taken; in, When the target boost pressure remains unchanged, the following conditions are met:

[0025] in, is the original value of the difference between the target boost pressure and the actual boost pressure, is the original value of the difference between the target boost pressure and the actual boost pressure in the Nth sampling cycle, After first-order low-pass filtering , After first-order low-pass filtering , The original value of the difference between the target boost pressure and the actual boost pressure in the N-1th sampling period is obtained after a first-order low-pass filter, N=1,2,3…, Equal to the pressure difference at the 0th sampling period In particular, the 0th sampling period occurs when the EGR system closed loop is enabled; the sampling period interval In this example, it is 10ms; is the coefficient: , is the pressure difference filter coefficient, which is 0.2 in this example; S202, determining the self-learning correction coefficient through self-learning ; S203, according to the compression ratio-engine speed coefficient , self-learning correction coefficient , determine the initial value of duration t; .

[0026] Step S202 includes: S2021. According to the current optimization condition, the original remaining time tn is updated and optimized to obtain the optimized remaining time tn'; wherein the original remaining time is the time from the current moment to the moment when the target opening of the EGR valve is stopped to be maintained unchanged; S2022, adjust the self-learning correction coefficient according to the original remaining time tn and the optimized remaining time tn' .

[0027] In step S2021, the optimization process of the operating conditions and the updating optimization process of the original remaining time tn under each optimization operating condition includes: (1) The first optimization condition: EGR valve target opening after the EGR closed-loop enabling condition is exited The situation where the control remains unchanged (i.e. the EGR closed-loop control is exited but the control is stable); At this time, first determine the boost pressure difference change : Boost pressure difference change Take the nearest The difference between the maximum boost pressure difference and the minimum boost pressure difference before the sampling period (a single sampling period is 10ms) (if the maximum boost pressure difference occurs later than the minimum boost pressure difference, the boost pressure difference change is a positive value; if the maximum boost pressure difference occurs earlier than the minimum boost pressure difference, the boost pressure difference change is a negative value; if the time when the maximum boost pressure difference occurs is the same as the time when the minimum boost pressure difference occurs, the boost pressure difference change is 0); Then determine the mixing valve outlet pressure Change : Mixing valve outlet pressure change Take the nearest The difference between the maximum value of the mixing valve outlet pressure and the minimum value of the mixing valve outlet pressure before the sampling cycle (a single sampling cycle is 10ms) (if the time when the maximum value of the mixing valve outlet pressure occurs is later than the time when the minimum value of the mixing valve outlet pressure occurs, the mixing valve outlet pressure change is a positive value; if the time when the maximum value of the mixing valve outlet pressure occurs is earlier than the time when the minimum value of the mixing valve outlet pressure occurs, the change in the mixing valve outlet pressure is a negative value; the time when the maximum value of the mixing valve outlet pressure occurs is the same as the time when the minimum value of the mixing valve outlet pressure occurs, then the mixing valve outlet pressure change is 0); Finally, based on the boost pressure difference change and mixing valve outlet pressure change , the original remaining time t1 (i.e. tn, n=1 at this time, representing the first optimization condition) is updated and optimized to obtain t1' (the change in the outlet pressure of the mixing valve is considered because if the change is too large, it will deteriorate the trend of the boost control stability, thereby affecting the subsequent boost pressure control stability):

[0028] in and The calibration basis includes: 1) Preset time after t1' ends The difference between the target boost pressure and the actual boost pressure is ensured The fluctuation of is within the preset range; 2) Change in boost pressure difference Under the same circumstances, if the pressure ratio coefficient The smaller the The smaller the pressure, the smaller the difference between the target boost pressure and the actual boost pressure. The fluctuation of the pressure ratio coefficient is within the preset range; Under the same conditions, if the boost pressure difference changes The larger the The larger the pressure, the greater the difference between the target boost pressure and the actual boost pressure. The fluctuation is within the preset range (same as the fluctuation requirement control required above); 3) Change in boost pressure difference Under the same conditions, if the mixing valve outlet pressure Change The smaller the The smaller the pressure, the smaller the difference between the target boost pressure and the actual boost pressure. The fluctuation of the mixing valve outlet pressure is within the preset range; Change Under the same conditions, if the boost pressure difference changes The larger the The larger the pressure, the greater the difference between the target boost pressure and the actual boost pressure. The fluctuation is within the preset range (same as the fluctuation requirement control required above); (2) The second optimization condition: EGR valve target opening after EGR closed loop enabling condition exits Maintain unchanged (i.e. EGR closed-loop control exits but controls the stable state), and knock occurs; At this time, first determine the number of knocks of different intensities: Refer to the method of patent CN202010608134.7 "A method and system for self-learning of oil octane number" to obtain the knock number corresponding to the low intensity level, medium intensity level and high intensity level , , ; It should be understood that the number of knocks of each intensity is the number accumulated during the process of "EGR closed-loop control exits but the control is stable". Once this state changes, the number of knocks of each intensity is reset to zero and is counted again after re-entering the "EGR closed-loop control exits but the control is stable"; Then determine the mixing valve outlet pressure Change : Mixing valve outlet pressure change Take the nearest The difference between the maximum value of the mixing valve outlet pressure and the minimum value of the mixing valve outlet pressure before the sampling cycle (a single sampling cycle is 10ms) (if the time when the maximum value of the mixing valve outlet pressure occurs is later than the time when the minimum value of the mixing valve outlet pressure occurs, the mixing valve outlet pressure change is a positive value; if the time when the maximum value of the mixing valve outlet pressure occurs is earlier than the time when the minimum value of the mixing valve outlet pressure occurs, the change in the mixing valve outlet pressure is a negative value; the time when the maximum value of the mixing valve outlet pressure occurs is the same as the time when the minimum value of the mixing valve outlet pressure occurs, then the mixing valve outlet pressure change is 0); Then determine the knock correction coefficient according to the number of knocks of different intensities :

[0029] In the number of knocks , , Under the same condition, if the pressure ratio The smaller the value, the more the correction factor is determined based on the number of knocks. The smaller the pressure ratio Under the same circumstances, if the number of knocks , , The larger the , , The larger the value, the more likely it is to suppress the occurrence of knock; , , The calibration is based on: ending at t2' and delaying the preset time After a period of time (the engine completes 20 working cycles, 1 working cycle means that each cylinder of the engine completes 4 working strokes) ensure that the difference between the target boost pressure and the actual boost pressure The fluctuation is within the preset range, and only low-intensity knock occurs at most, and the number of low-intensity knocks does not exceed 5 times; among them, It is the time for the exhaust gas to flow from the EGR valve to the cylinder. This part is obtained through bench calibration. This part can be different engine speeds n and different actual intake air densities entering the cylinder. Under this condition, the average value of multiple sampling data is obtained by setting different EGR rates. It is determined by the engine speed n and the actual intake air density entering the cylinder Make sure to get; Finally, based on the knock correction factor and mixing valve outlet pressure change , the original remaining time t2 is updated and optimized to obtain t2' (the change in the outlet pressure of the mixing valve is considered because if the change is too large, it will deteriorate the trend of the boost control stability, thereby affecting the subsequent boost pressure control stability):

[0030] in The calibration basis includes: 1) End at t2' and delay for a preset time After a period of time (the engine completes 20 working cycles, 1 working cycle means that each cylinder of the engine completes 4 working strokes) ensure that the difference between the target boost pressure and the actual boost pressure The fluctuation of is within the preset range; 2) Only low-intensity detonation occurs at most, and the number of low-intensity detonation does not exceed 5 times; 3) Change in boost pressure difference Under the same conditions, if the mixing valve outlet pressure Change The smaller the The smaller the pressure, the smaller the difference between the target boost pressure and the actual boost pressure. The fluctuation of the mixing valve outlet pressure is within the preset range; Change Under the same conditions, if the boost pressure difference changes The larger the The larger the pressure, the greater the difference between the target boost pressure and the actual boost pressure. The fluctuation is within the preset range (same as the fluctuation requirement control required above); (3) The second optimization condition: EGR valve target opening after EGR closed loop enabling condition exits The situation where the EGR closed-loop control remains unchanged (i.e. the EGR closed-loop control is exited but the control is in a stable state), and the catalyst oxygen storage capacity coefficient and the air-fuel ratio coefficient change; At this time, first obtain the catalyst oxygen storage capacity coefficient : The current catalyst oxygen storage coefficient can be obtained by dividing the catalyst oxygen storage capacity by the maximum oxygen storage capacity. , the value range is between 0 and 1; it should be understood that the smaller the oxygen storage coefficient is, the smaller the oxygen storage capacity of the catalyst is. At this time, the EGR rate can be appropriately reduced, which has little effect on the generation of NOx; this step can refer to the method of real-time reading of the oxygen storage capacity of the catalyst in CN110259553A "A method, device and electronic device for calculating the oxygen storage capacity of a three-way catalytic converter", and the method of real-time reading of the maximum oxygen storage capacity of the catalyst in CN104594986A "A method for diagnosing engine catalyst degradation"; Then obtain the catalyst oxygen storage capacity coefficient The amount of change : Catalytic converter oxygen storage capacity coefficient change Pick Catalyst oxygen storage capacity coefficient before the sampling period (single sampling period is 10ms) Maximum value and catalyst oxygen storage capacity coefficient The difference between the minimum values ​​(if the catalyst oxygen storage capacity coefficient The maximum value occurs at a time ratio of the catalyst oxygen storage capacity coefficient The minimum value occurs later, so the change in the oxygen storage capacity coefficient of the mixed catalyst is a positive value; if the catalyst oxygen storage capacity coefficient The maximum value occurs at a time ratio of the catalyst oxygen storage capacity coefficient The earlier the minimum value occurs, the greater the change in the catalyst oxygen storage capacity coefficient. is a negative value; if the catalyst oxygen storage capacity coefficient The time when the maximum value occurs and the oxygen storage capacity coefficient of the catalyst The minimum value occurs at the same time, then the change in the catalyst oxygen storage capacity coefficient is 0); Then determine the air-fuel ratio coefficient ;in, is the actual fuel-air ratio, is the ideal fuel-air ratio (1 / 14.3 in this example); Then get the air-fuel ratio coefficient The amount of change ; Air-fuel ratio coefficient change ; Air-fuel ratio coefficient change Take the nearest The difference between the maximum value of the air-fuel ratio coefficient and the minimum value of the air-fuel ratio coefficient before the sampling period (a single sampling period is 10ms) (if the time when the maximum value of the air-fuel ratio coefficient occurs is later than the time when the minimum value of the air-fuel ratio coefficient occurs, the air-fuel ratio coefficient change amount is a positive value; if the maximum value of the air-fuel ratio coefficient occurs earlier than the minimum value of the air-fuel ratio coefficient, the change in the air-fuel ratio coefficient is a negative value; if the time when the maximum value of the air-fuel ratio coefficient occurs is the same as the time when the minimum value of the air-fuel ratio coefficient occurs, the change in the air-fuel ratio coefficient is 0); Finally, according to the change of catalyst oxygen storage capacity coefficient , Air-fuel ratio coefficient change , the original remaining time t3 is updated and optimized to obtain t3' (considering the catalyst oxygen storage capacity coefficient The change amount and air-fuel ratio change amount are because if the change amount is too large, it will cause a deterioration in the trend of boost control stability, thereby affecting the subsequent boost pressure control stability):

[0031] in, , , The calibration basis includes: 1) End at t3' and delay for a preset time ( ) Ensure the difference between target boost pressure and actual boost pressure within 100 ms The fluctuation of the catalyst oxygen storage capacity coefficient is within the preset range. Not exceeding the preset value (0.9 in this example), and the catalyst oxygen storage capacity coefficient The change does not exceed the preset value (0.2 in this example); 2) In Under the same circumstances, if the pressure ratio The smaller the The smaller the pressure ratio In the same case, if The larger the The bigger; 3) In Under the same circumstances, if the pressure ratio The smaller the The smaller the pressure ratio In the same case, if The larger the The bigger; 4) Change in boost pressure difference Under the same conditions, if the mixing valve outlet pressure Change The smaller the The smaller the mixing valve outlet pressure Change Under the same conditions, if the boost pressure difference changes The larger the The bigger.

[0032] In step S2022, the self-learning correction coefficient The adjustment process is as follows: a. If tn'-tn is greater than the preset value C1 (in this embodiment, C1 is 0.5s. This situation indicates that the ignition angle efficiency is adjusted too much, which is easy to cause ignition), and only one of the three optimized working conditions has always occurred, and the number of consecutive occurrences CNT1 (the initial value is 0, which can be saved after the vehicle is powered off) exceeds the preset value (5 in this example), indicating that the duration tn has been increasing, then the time t self-learning state is set to the upward learning state 1, that is, Need to add: ,in The self-learning correction coefficient stored for the last learning , and clear CNT1 at the same time; the newly learned and stored self-learning correction coefficient will be used the next time the situation is judged; b. If tn'-tn is greater than the preset value C1, and not only one of the three optimization situations occurs all the time, and the number of consecutive occurrences CNT2 (initial value is 0, which can be saved after the vehicle is powered off) exceeds the preset value (5 in this example), it means that the duration tn is increasing, then the time t self-learning state is changed to upward learning state 2, that is, Needs to be increased. , and clear CNT2 at the same time; the newly learned and stored learning value is used the next time the situation is judged; c. If tn'-tn is not greater than the preset value - C2 (C2 is taken as 0.3s in this example, this situation indicates that the ignition angle efficiency is too large, which is easy to cause pressure fluctuations), and only one of the three optimization situations has always occurred, and the number of consecutive occurrences CNT3 (initial value is 0, which can be saved after the vehicle is powered off) exceeds the preset value (5 in this example), indicating that the duration tn has been decreasing, then the time t self-learning state is set to downward learning state 1, that is, Needs to be lowered. ; At the same time, CNT3 is cleared; the newly learned and stored learning value is used the next time the situation is judged; d. If tn'-tn is not greater than the preset value -C2, and not only one of the three optimization situations occurs all the time, and the number of consecutive occurrences CNT4 (initial value is 0, which can be saved after the vehicle is powered off) exceeds the preset value (5 in this example), it means that the duration tn is decreasing, then the time t self-learning state is changed to downward learning state 2, that is, Needs to be lowered. ; At the same time, clear CNT4; the newly learned and stored learning value will be used the next time the situation is judged; e. If tn'-tn is greater than the preset value C1, and the last time tn'-tn occurred is not greater than the preset value -C2, then the time t self-learning state is changed to upward learning state three, that is, Need to add: ; The newly learned and stored learning value will be used the next time the situation is judged; f. If tn'-tn is not greater than the preset value -C2, and the last time tn'-tn was greater than the preset value C1, then the time t self-learning state is set to downward learning state three, that is, Need to be lowered; ; The newly learned and stored learning value will be used the next time the situation is judged; g. In cases other than a~f above, remain unchanged; Among them, the priorities of a~g decrease in sequence.

[0033] Step S3 includes: S301, determining the EGR valve target opening according to the engine speed n The rate of change k1; The corresponding relationship between the engine speed n and the change rate k1 is obtained through calibration, and the calibration results are shown in Table 2: Table 2

[0034] The calibration process is based on: making the fluctuation of the actual EGR pressure at the outlet of the EGR valve within a preset range; specifically, if the following conditions are met in the two sampling periods from the first sampling period when the EGR closed-loop condition is not met to the end of the time t:

[0035] It means that the fluctuation of the actual EGR pressure at the outlet of the EGR valve is within the preset range; In the above formula, satisfy:

[0036] In the above formula, is the original value of the actual EGR pressure at the EGR valve outlet, is the original value of the actual EGR pressure at the EGR valve outlet in the Nth sampling cycle, is the actual EGR pressure at the EGR valve outlet after first-order low-pass filtering, After first-order low-pass filtering , is the value of the original value of the actual EGR pressure at the EGR valve outlet of the N-1th sampling period after first-order low-pass filtering, N=1,2,3,...; Equal to the original value of the actual EGR pressure at the EGR valve outlet during the 0th sampling cycle In particular, the 0th sampling period occurs when the vehicle is powered on; the sampling period interval In this example, it is 10ms. is the coefficient: (The number of engine cylinders N in this example is 4, The calibrated speed is 1000rpm. The purpose of this setting is to normalize the process. Under different cylinder numbers and speeds, no special calibration is required. Only the 4-cylinder engine and the speed of 1000rpm need to be calibrated. , thereby reducing calibration testing work), is the actual EGR pressure filter coefficient at the EGR device outlet, which is 0.2 in this example; S302: Set the EGR valve target opening according to the change rate k1 Transition to 0%.

[0037] Embodiment 2: This embodiment provides an exhaust gas recirculation closed-loop control device based on multiple performance dimensions, including: A pressure ratio coefficient determination module, used for determining the pressure ratio coefficient according to the actual pressure at the mixing valve outlet, the actual pressure at the mixing valve inlet, the actual pressure at the throttle valve outlet, and the actual pressure at the throttle valve inlet when the EGR closed-loop condition is switched from being satisfied to being not satisfied; The duration initial value determination module is used to determine the duration initial value according to the engine speed, the pressure ratio coefficient, and the self-learning correction coefficient; wherein the self-learning correction coefficient is obtained through self-learning, and the duration initial value is used to maintain the EGR valve target opening unchanged; The EGR valve target opening transition module is used to make the EGR valve target opening transition to 0% at a certain rate after the EGR valve target opening maintains the initial value for a certain period of time.

[0038] Embodiment three: This embodiment provides a computer device, such as a smart phone, tablet computer, laptop computer, desktop computer, rack server, blade server, tower server or cabinet server (including an independent server or a server cluster composed of multiple servers) that can execute programs. The computer device of this embodiment includes at least but is not limited to: a memory and a processor that can communicate with each other through a system bus.

[0039] In this embodiment, the memory (i.e., readable storage medium) includes flash memory, hard disk, multimedia card, card-type memory (e.g., SD or DX memory, etc.), random access memory (RAM), static random access memory (SRAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), programmable read-only memory (PROM). The memory may also be an external storage device of a computer device, such as a plug-in hard disk, a smart memory card (SmartMedia Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (Flash Card), etc. equipped on the computer device. Of course, the memory may also include both the internal storage unit of the computer device and its external storage device. In this embodiment, the memory is generally used to store the operating system and various application software installed on the computer device, such as the program code of the exhaust gas recirculation closed-loop control device based on multiple performance dimensions in the first embodiment. In addition, the memory may also be used to temporarily store various data that have been output or are to be output.

[0040] In some embodiments, the processor may be a central processing unit (CPU), a controller, a microcontroller, a microprocessor, or other data processing chip. The processor is generally used to control the overall operation of a computer device. In this embodiment, the processor is used to run program codes stored in a memory or process data, such as an exhaust gas recirculation closed-loop control device based on multiple performance dimensions, to implement the exhaust gas recirculation closed-loop control method based on multiple performance dimensions in the first embodiment.

[0041] Embodiment 4: This embodiment provides a computer-readable storage medium, such as a flash memory, a hard disk, a multimedia card, a card-type memory (e.g., SD or DX memory, etc.), a random access memory (RAM), a static random access memory (SRAM), a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), a programmable read-only memory (PROM), a magnetic memory, a disk, an optical disk, a server, an App application store, etc., on which a computer program is stored, and the program realizes corresponding functions when executed by a processor. The computer-readable storage medium of this embodiment is used to store the program code of the exhaust gas recirculation closed-loop control device based on multiple performance dimensions, and when executed by the processor, the exhaust gas recirculation closed-loop control method based on multiple performance dimensions of the first embodiment is realized.

[0042] It should be pointed out that, according to the needs of implementation, the various steps / components described in this application can be split into more steps / components, and two or more steps / components or partial operations of steps / components can be combined into new steps / components to achieve the purpose of the present invention.

Claims

1. A closed-loop exhaust gas recirculation control method based on multiple performance dimensions, characterized in that: include: When the EGR closed-loop condition switches from being satisfied to being unsatisfied, the pressure ratio coefficient is determined according to the actual pressure at the mixing valve outlet, the actual pressure at the mixing valve inlet, the actual pressure at the throttle outlet, and the actual pressure at the throttle inlet; Determine the initial value of the duration according to the engine speed, the pressure ratio coefficient, and the self-learning correction coefficient; wherein the self-learning correction coefficient is obtained through self-learning, and the initial value of the duration is used to maintain the target opening of the EGR valve unchanged; After maintaining the initial value for a certain period of time, the EGR valve target opening transitions to 0% at a certain rate.

2. The exhaust gas recirculation closed-loop control method based on multiple performance dimensions according to claim 1, characterized in that: The method for determining the pressure ratio coefficient includes: According to the actual pressure at the outlet of the mixing valve and the actual pressure at the inlet of the mixing valve, the ratio of the actual pressure at the inlet and outlet of the mixing valve is determined; According to the actual pressure at the throttle outlet and the actual pressure at the throttle inlet, determine the ratio of the actual pressure at the throttle inlet and outlet; According to the ratio of the actual pressures at the throttle inlet and outlet, determine the correction factor of the pressure ratio coefficient; The pressure ratio coefficient is determined based on the ratio of the pressure ratio coefficient correction coefficient and the actual pressures at the inlet and outlet of the mixing valve.

3. The exhaust gas recirculation closed-loop control method based on multiple performance dimensions according to claim 1, characterized in that: The method for determining the initial value of the duration includes: Determine a compression ratio-engine speed coefficient based on the compression ratio coefficient and the engine speed; Determine the self-learning correction coefficient through self-learning; The initial value of the duration is determined based on the compression ratio-engine speed coefficient and the self-learning correction coefficient.

4. The exhaust gas recirculation closed-loop control method based on multiple performance dimensions according to claim 3, characterized in that: The method for determining the self-learning correction coefficient includes: According to the current optimization conditions, the original remaining time is updated and optimized to obtain the optimized remaining time; the original remaining time is the time from the current moment to the moment when the EGR valve target opening is stopped. Adjust the self-learning correction coefficient according to the original remaining time and the remaining time after optimization.

5. The exhaust gas recirculation closed-loop control method based on multiple performance dimensions according to claim 4 is characterized in that: The optimized operating conditions include: the situation where the EGR valve target opening remains unchanged after the EGR closed-loop enabling condition is exited; Under this optimization condition, the remaining time after optimization can be obtained by: determining a boost pressure difference change based on the boost pressure difference within a certain number of sampling periods; Determine a change in pressure at the outlet of the mixing valve based on the outlet of the mixing valve within a certain number of sampling periods; The original remaining time is updated and optimized based on the change in boost pressure difference and the change in mixing valve outlet pressure.

6. The exhaust gas recirculation closed-loop control method based on multiple performance dimensions according to claim 4 is characterized in that: Optimized conditions include: After the EGR closed-loop enabling condition is exited, the EGR valve target opening remains unchanged and knock occurs; Under this optimization condition, the remaining time after optimization can be obtained by: Get the number of knocks of different intensities; Determine a change in the outlet pressure of the mixing valve based on the outlet pressure of the mixing valve within a certain number of sampling periods; Determine the knock correction coefficient according to the number of knocks of different intensities; The original remaining time is updated and optimized according to the knock correction coefficient and the change in the outlet pressure of the mixing valve.

7. The exhaust gas recirculation closed-loop control method based on multiple performance dimensions according to claim 4 is characterized in that: The optimized operating conditions include: after the EGR closed-loop enabling condition is exited, the EGR valve target opening remains unchanged, and the catalyst oxygen storage capacity coefficient and air-fuel ratio coefficient change; Under this optimization condition, the remaining time after optimization can be obtained by: Obtaining catalyst oxygen storage capacity coefficient; Determining a change in the catalyst oxygen storage capacity coefficient based on the catalyst oxygen storage capacity coefficient within a certain number of sampling periods; Determine the air-fuel ratio coefficient according to the actual air-fuel ratio and the ideal air-fuel ratio; Determine the change of the air-fuel ratio coefficient based on the air-fuel ratio coefficient within a certain number of sampling periods; The original remaining time is updated and optimized according to the changes in the catalyst's oxygen storage capacity coefficient and the air-fuel ratio coefficient.

8. The exhaust gas recirculation closed-loop control method based on multiple performance dimensions according to claim 3 is characterized in that: The self-learning includes: a. If the difference between the optimized remaining time and the original remaining time is greater than the first remaining time threshold, and only one of the different optimized working conditions has always occurred, and the number of consecutive occurrences exceeds the preset number of times, the self-learning correction coefficient is incremented by the first step, and the number of consecutive occurrences in this case is cleared; the newly learned and stored self-learning correction coefficient is used when entering this situation for judgment next time; b. If the difference between the optimized remaining time and the original remaining time is greater than the first remaining time threshold, and it is not always the case that only one of the different optimized conditions occurs, and the number of consecutive occurrences exceeds the preset number, then the self-learning correction coefficient is incremented by the second step length, and the number of consecutive occurrences in this case is cleared; the newly learned and stored self-learning correction coefficient is used the next time the judgment enters this situation. c. If the difference between the optimized remaining time and the original remaining time is not greater than the second remaining time threshold, and only one of the fixed situations in each optimization situation has always occurred, and the number of consecutive occurrences exceeds the preset number, the self-learning correction coefficient is decreased by the third step length, and the number of consecutive occurrences in this situation is cleared; the newly learned and stored learning value is used the next time the judgment of this situation is entered; d. If the difference between the optimized remaining time and the original remaining time is not greater than the second remaining time threshold, and not only one of the various optimization situations occurs all the time, and the number of consecutive occurrences exceeds the preset number, then the self-learning correction coefficient is decreased by the fourth step length, and the number of consecutive occurrences in this situation is cleared; the newly learned and stored learning value is used the next time the judgment of this situation is entered; e. If the difference between the optimized remaining time and the original remaining time is greater than the first remaining time threshold, and the difference between the optimized remaining time and the original remaining time is not greater than the second remaining time threshold, the time self-learning correction coefficient is increased by the fifth step, and the number of consecutive occurrences in this case is cleared; the newly learned and stored learning value is used the next time the judgment of this situation is entered; f. If the difference between the optimized remaining time and the original remaining time is not greater than the second remaining time threshold, and the difference between the optimized remaining time and the original remaining time last time is greater than the first remaining time threshold, the time self-learning correction coefficient is decreased by the sixth step, and the number of consecutive occurrences in this case is cleared; the newly learned and stored learning value is used the next time the judgment of this situation is entered; g. Except for the above cases a~f, the self-learning correction coefficient remains unchanged; Among them, the priorities of a~g decrease in sequence.

9. The exhaust gas recirculation closed-loop control method based on multiple performance dimensions according to claim 1, characterized in that: Methods for transitioning the EGR valve target opening to 0% at a certain rate include: Determine the rate of change of the target opening of the EGR valve according to the pre-calibration result and the engine speed; The EGR valve target opening is transitioned to 0% according to the determined change rate.

10. An exhaust gas recirculation closed-loop control device based on multiple performance dimensions, characterized in that: include: A pressure ratio coefficient determination module, used for determining the pressure ratio coefficient according to the actual pressure at the mixing valve outlet, the actual pressure at the mixing valve inlet, the actual pressure at the throttle valve outlet, and the actual pressure at the throttle valve inlet when the EGR closed-loop condition is switched from being satisfied to being not satisfied; The duration initial value determination module is used to determine the duration initial value according to the engine speed, the pressure ratio coefficient, and the self-learning correction coefficient; wherein the self-learning correction coefficient is obtained through self-learning, and the duration initial value is used to maintain the EGR valve target opening unchanged; The EGR valve target opening transition module is used to make the EGR valve target opening transition to 0% at a certain rate after the EGR valve target opening maintains the initial value for a certain period of time.

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