A method for exhaust gas recirculation closed-loop control based on multiple performance dimensions

Abstract

The application discloses a kind of based on the waste gas recirculation closed-loop control method under multiple performance dimensions, comprising: when EGR closed-loop condition is from satisfy switching to not satisfy, according to the actual pressure of mixed valve outlet, the actual pressure of mixed valve inlet, the actual pressure of throttle valve outlet, throttle valve inlet actual pressure, determine pressure ratio coefficient;According to engine speed, pressure ratio coefficient, self-learning correction coefficient, determine time length initial value;Wherein, self-learning correction coefficient is obtained by self-learning, and time length initial value is used to maintain EGR valve target opening unchanged;EGR valve target opening is transitioned to 0% at a certain rate after maintaining time length initial value.The method effectively reduces the system fluctuation by limiting the EGR target opening after EGR closed-loop condition exits, and improves the system stability.

Description

Technical Field

[0001] This invention relates to the field of engine control, and more specifically to a closed-loop control method for exhaust gas recirculation based on multiple performance dimensions. Background Technology

[0002] Exhaust gas recirculation (EGR) refers to the process of drawing exhaust gases from the exhaust system and introducing them into the intake system. Studies have shown that EGR systems have certain advantages in improving emissions, reducing fuel consumption, and improving anti-knock capabilities.

[0003] The existing technology does not provide guidance on how to reasonably control the EGR valve according to different operating conditions after the EGR closed loop exits, which may cause performance degradation during the EGR valve exit process. Summary of the Invention

[0004] The purpose of this invention is to provide a closed-loop control method for exhaust gas recirculation based on multiple performance dimensions to optimize EGR valve control.

[0005] To address the aforementioned technical problems, this invention proposes a closed-loop control method for exhaust gas recirculation based on multiple performance dimensions, comprising: when the EGR closed-loop condition switches from being met to not being met, determining the pressure ratio coefficient based on 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;

[0006] The initial duration is determined based on engine speed, pressure ratio coefficient, and self-learning correction coefficient; the self-learning correction coefficient is obtained through self-learning, and the initial duration is used to maintain the target opening of the EGR valve unchanged.

[0007] The target opening of the EGR valve transitions to 0% at a certain rate after maintaining the initial value for a certain duration.

[0008] The method for determining the initial value of the duration includes:

[0009] Based on the pressure ratio coefficient and engine speed, determine the pressure ratio-engine speed coefficient;

[0010] The self-learning correction coefficient is determined through self-learning.

[0011] The initial duration is determined based on the pressure ratio-engine speed coefficient and the self-learning correction coefficient.

[0012] The method for determining the self-learning correction coefficient includes:

[0013] Based on the current optimization conditions, the original remaining time is updated and optimized to obtain the optimized remaining time; where the original remaining time is the time from the current moment to the moment when the EGR valve target opening is stopped.

[0014] Adjust the self-learning correction coefficient based on the original remaining time and the optimized remaining time.

[0015] According to the above scheme, the method for determining the pressure ratio coefficient includes:

[0016] Determine the ratio of the actual pressure at the outlet of the mixing valve to the actual pressure at the inlet of the mixing valve based on the actual pressure at the outlet of the mixing valve and the actual pressure at the inlet of the mixing valve.

[0017] Determine the ratio of the actual pressure at the throttle outlet to the actual pressure at the throttle inlet;

[0018] The pressure ratio correction factor is determined based on the ratio of the actual pressure at the throttle inlet and outlet.

[0019] The pressure ratio coefficient is determined based on the pressure ratio coefficient correction factor and the ratio of the actual pressure at the inlet and outlet of the mixing valve.

[0020] According to the above scheme, the optimized operating conditions include: the situation where the target opening degree of the EGR valve remains unchanged after the EGR closed-loop enable condition is removed;

[0021] Under this optimized operating condition, the remaining time after optimization can be obtained in the following ways:

[0022] Based on the pressure difference within a certain number of sampling periods, determine the change in pressure difference;

[0023] Based on the mixing valve outlet pressure change within a certain number of sampling periods, determine the mixing valve outlet pressure change;

[0024] The original remaining time is updated and optimized based on the changes in the boost pressure difference and the changes in the mixing valve outlet pressure.

[0025] According to the above plan, the optimized operating conditions include:

[0026] After the EGR closed-loop enable condition is removed, the target opening of the EGR valve remains unchanged, and knocking occurs.

[0027] Under this optimized operating condition, the remaining time after optimization can be obtained in the following ways:

[0028] Obtain the number of detonation events of different intensities;

[0029] Based on the mixing valve outlet pressure within a certain number of sampling periods, determine the change in mixing valve outlet pressure.

[0030] Determine the detonation correction factor based on the number of detonations of different intensities;

[0031] The original remaining time is updated and optimized based on the knock correction coefficient and the change in outlet pressure of the mixing valve.

[0032] According to the above scheme, the optimized operating conditions include: the EGR valve target opening remains unchanged after the EGR closed-loop enabling condition is removed, and the catalyst oxygen storage capacity coefficient and air-fuel ratio coefficient change.

[0033] Under this optimized operating condition, the remaining time after optimization can be obtained in the following ways:

[0034] Obtain the oxygen storage capacity coefficient of the catalyst;

[0035] Based on the catalyst oxygen storage capacity coefficient within a certain number of sampling periods, determine the change in the catalyst oxygen storage capacity coefficient.

[0036] The air-fuel ratio coefficient is determined based on the actual air-fuel ratio and the ideal air-fuel ratio.

[0037] Based on the air-fuel ratio coefficient within a certain number of sampling periods, determine the change in the air-fuel ratio coefficient.

[0038] The original remaining time is updated and optimized based on the changes in the catalyst oxygen storage capacity coefficient and the air-fuel ratio coefficient.

[0039] According to the above scheme, the self-learning includes:

[0040] 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 optimization conditions occurs, and the number of consecutive occurrences exceeds the preset number, then the self-learning correction coefficient is increased by the first step length, and the number of consecutive occurrences in this case is cleared to zero; the newly learned and stored self-learning correction coefficient is used when judging this case again next time.

[0041] 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 only one of the different optimized conditions that occurs, and the number of consecutive occurrences exceeds the preset number, then the self-learning correction coefficient is increased by the second step size, and the number of consecutive occurrences in this case is cleared to zero; the newly learned and stored self-learning correction coefficient is used the next time this case is entered for judgment.

[0042] 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 fixed situation under each optimization condition occurs, and the number of consecutive occurrences exceeds the preset number, then the self-learning correction coefficient is decreased by the third step size, and the number of consecutive occurrences under this situation is cleared to zero; the newly learned self-learning correction coefficient is used when entering this situation judgment again.

[0043] d. If the difference between the optimized remaining time and the original remaining time is not greater than the second remaining time threshold, and it is not always only one of the fixed situations under various optimization conditions that occurs, and the number of consecutive occurrences exceeds the preset number, then the self-learning correction coefficient is decreased by the fourth step size, and the number of consecutive occurrences under this situation is cleared to zero; the newly learned and stored self-learning correction coefficient is used when entering this situation judgment again.

[0044] 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 in the previous occurrence was not greater than the second remaining time threshold, then the time self-learning correction coefficient is increased by the fifth step, and the number of consecutive occurrences in this case is cleared to zero; the newly learned self-learning correction coefficient is used when entering this case judgment again.

[0045] 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 was greater than the first remaining time threshold in the last occurrence, then the time self-learning correction coefficient is decreased by the sixth step, and the number of consecutive occurrences in this case is cleared to zero; the newly learned self-learning correction coefficient is used when entering this case judgment again.

[0046] g. In cases other than a to f above, the self-learning correction coefficient remains unchanged;

[0047] Among them, the priority of a to g decreases in that order.

[0048] According to the above scheme, the methods for transitioning the target opening of the EGR valve to 0% at a certain rate include:

[0049] The rate of change of the target opening of the EGR valve is determined based on the pre-calibration results and engine speed.

[0050] The EGR valve target opening is transitioned to 0% based on the determined rate of change.

[0051] The present invention also provides a closed-loop control device for exhaust gas recirculation based on multiple performance dimensions, comprising:

[0052] The pressure ratio coefficient determination module is used to determine the pressure ratio coefficient based on 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 when the EGR closed-loop condition switches from being met to not being met.

[0053] The initial duration determination module is used to determine the initial duration based on engine speed, pressure ratio coefficient, and self-learning correction coefficient; wherein, the self-learning correction coefficient is obtained through self-learning, and the initial duration is used to maintain the target opening of the EGR valve unchanged;

[0054] The EGR valve target opening transition module is used to transition the EGR valve target opening to 0% at a certain rate after the initial value of the EGR valve target opening duration is maintained.

[0055] Beneficial effects

[0056] The beneficial effects of this invention are as follows: After the EGR valve closed-loop control is disengaged, this invention controls the target opening of the EGR valve to be maintained for a period of time, and after maintaining it for a period of time, limits its rate of decline, thereby avoiding system fluctuations caused by the rapid change of the target opening of the EGR valve after the EGR valve closed-loop control is disengaged, thus optimizing engine emissions and avoiding engine knock.

[0057] Furthermore, by setting a self-learning coefficient, the present invention can adjust the maintenance time of the target opening of the EGR valve according to the actual working conditions, so that the optimization effect can be adjusted in real time according to the actual situation, thereby further improving the optimization effect. Attached Figure Description

[0058] Figure 1 This is a schematic diagram of the exhaust system structure of an engine with EGR according to Embodiment 1 of the present invention;

[0059] Figure 2 This is a flowchart of the waste gas recirculation closed-loop control method based on multiple performance dimensions according to Embodiment 1 of the present invention.

[0060] In the diagram: 1-Air filter, 2-Mix valve, 3-Compressor, 4-Throttle valve, 5-Engine, 6-Turbine, 7-Catalyst, 8-Particulate filter, 9-EGR cooler, 10-EGR valve, 11-Temperature sensor, 12-Differential pressure sensor. Detailed Implementation

[0061] Example 1:

[0062] See Figure 1 The engine exhaust system applicable to this embodiment includes:

[0063] Air filter 1;

[0064] The mixing valve 2 connected to the air filter is used to regulate the pressure at the outlet of the EGR valve 10, increase the pressure difference across the EGR valve 10, and extend two airflow passages from the mixing valve 2.

[0065] Compressor 3 is connected to one of the airflow passages of mixing valve 2;

[0066] Throttle valve 4 is connected to compressor 3;

[0067] Engine 5, connected to throttle valve 4, is used to compress fresh air for boosting;

[0068] Turbine 6, connected to engine 5, is used to control the opening of the exhaust bypass valve;

[0069] Catalyst 7 is connected to turbine 6;

[0070] Particulate matter trap 8 is connected to catalyst 7;

[0071] EGR cooler 9 is connected to another airflow passage of mixing valve 2 and is used to receive and cool the exhaust gas output from particulate matter collector 8 to increase exhaust gas flow.

[0072] EGR valve 10, one end of which is connected to EGR cooler 9 and the other end is connected to mixing valve 2, is used to control the flow rate of exhaust gas entering the cylinder.

[0073] Temperature sensor 11 is installed between EGR valve 10 and EGR cooler 9 to detect the temperature of exhaust gas entering EGR valve 10;

[0074] Differential pressure sensor 12 is connected to EGR valve 10 and is used to detect the pressure at the inlet and outlet of EGR valve 10.

[0075] For the aforementioned engine exhaust system, this embodiment proposes a closed-loop control method for exhaust gas recirculation based on multiple performance dimensions. (See [link to relevant documentation]). Figure 2 ,include:

[0076] S1. When the EGR closed-loop condition switches from being met to not being met, the actual outlet pressure p of the mixing valve is used as a reference. AfMixAct Actual pressure p at the inlet of the mixing valve BfMixAct Actual throttle outlet pressure p AfThrAct Actual throttle inlet pressure p BfMixAct Determine the pressure ratio coefficient r PreRatio ;

[0077] S2, based on engine speed n and pressure ratio coefficient r PreRatio Self-learning correction coefficient r t Determine the initial duration t; where the self-learning correction coefficient r t The initial value t, obtained through self-learning, is used to maintain the target opening degree pct of the EGR valve. EGRDsrd constant;

[0078] It should be understood that maintaining the target opening degree (pct) of the EGR valve EGRDsrd The purpose is to stabilize the EGR valve, thereby preventing it from affecting the boost inlet pressure and thus the boost control responsiveness. The initial duration is t, i.e., pct. EGRDsrd =pct EGRDsrd (z) duration, pct EGRDsrd(z) represents the target opening of the EGR valve in the previous sampling period (i.e., the target opening of the EGR valve when the EGR closed-loop condition is met in the last sampling period). The initial value of the duration t starts from the first sampling period when the EGR closed-loop condition is not met.

[0079] S3, EGR valve target opening degree pct EGRDsrd After maintaining the initial value t for a certain duration, it transitions to 0% at a certain rate.

[0080] Step S1 includes:

[0081] S101, Based on the actual outlet pressure p of the mixing valve AfMixAct Actual pressure p at the inlet of the mixing valve BfMixAct Determine the ratio of the actual pressure at the inlet and outlet of the mixing valve.

[0082] S102, Based on the actual pressure p at the throttle outlet AfThrAct Actual throttle inlet pressure p BfMixAct Determine the ratio of the actual pressure at the throttle inlet and outlet.

[0083] S103, based on the ratio of actual pressure at the throttle inlet and outlet. Determine the pressure ratio coefficient correction factor

[0084] The ratio of actual pressure at the throttle inlet and outlet With pressure ratio coefficient correction factor The relationships are determined through a pre-calibrated table, as shown in Table 1 below:

[0085] Table 1

[0086]

[0087] The above calibration is based on the following considerations: The larger the pressure, the worse the throttle control capability, and the greater the risk to the turbocharger's pressure control accuracy. To avoid turbocharger pressure control accuracy problems, improvements are needed.

[0088] S104, Correction coefficient based on pressure ratio coefficient The ratio of the actual pressure at the inlet and outlet of the mixing valve Determine the pressure ratio coefficient r PreRatio ;

[0089]

[0090] Step S2 includes:

[0091] S201, Based on pressure ratio coefficient r PreRatio Engine speed n, determine the pressure ratio - engine speed coefficient f(r)PreRatio ,n);

[0092] Pressure ratio - engine speed coefficient f(r) PreRatio (n) and pressure ratio coefficient r PreRatio The relationship between engine speed n and speed n is obtained through calibration. The calibration is based on the following: N from the first sampling period when the EGR closed-loop condition is not met to the end of the initial duration t. Boost Within each sampling period (N) Boost depending on Under the condition that the target boost pressure remains constant, the difference p between the target boost pressure and the actual boost pressure. BoostErr The fluctuation is within the preset range; where τ = τ Boost For turbocharger response time;

[0093] The difference between the target boost pressure and the actual boost pressure, p BoostErr The criteria for determining whether the fluctuation is within the preset range are:

[0094] From the first sampling period when the EGR closed-loop condition is not met until the end of the initial duration t, N Boost The following condition is met within each sampling period:

[0095] |p BoostFilter (N)-p BoostErr (N)|<min[p BoostErr (N), p BoostErrFilter (N)]×r BoostErrLim

[0096] This represents the difference p between the target boost pressure and the actual boost pressure. BoostErr The fluctuation is within the preset range, where r BoostErrLim In this example, the value is 0.1;

[0097] Where, p BoostErrFilter (N) Under the condition that the target boost pressure remains constant, the following conditions are met:

[0098] p BoostErrFilter (N)=K BoostErr ×[p BoostErr (N)-p BoostErrFilter [(N-1)]+p BoostErrFilter (N-1)

[0099] Where, p BoostErr p is the original value of the difference between the target boost pressure and the actual boost pressure. BoostErr (N) represents the original value of the difference between the target boost pressure and the actual boost pressure in the Nth sampling period, p BoostErrFilter p after first-order low-pass filtering BoostErr p BoostErrFilter(N) represents the p after first-order low-pass filtering. BoostErr (N), p BoostErrFilter (N-1) is the value obtained after first-order low-pass filtering of the original value of the difference between the target boost pressure and the actual boost pressure in the (N-1)th sampling period, where N = 1, 2, 3, ..., p BoostErrFilter (0) equals the pressure difference p during the 0th sampling period. AftThrErr (0), specifically, the 0th sampling period occurs at the EGR system closed-loop enable time; the sampling period interval Δt is 10ms in this example; K BoostErr For coefficients: k BoostErr The pressure difference filter coefficient is 0.2 in this example;

[0100] S202. Determine the self-learning correction coefficient r through self-learning. t ;

[0101] S203, Based on the pressure ratio - engine speed coefficient f(r) PreRatio ,n), self-learning correction coefficient r t Determine the initial value t for the duration;

[0102] t = f(r) PreRatio ,n)×(1+r t ).

[0103] Step S202 includes:

[0104] S2021. Based on the current optimized operating conditions, update and optimize the original remaining time tn to obtain the optimized remaining time tn'; where the original remaining time is the time from the current moment to the moment when the EGR valve target opening degree is maintained unchanged.

[0105] S2022. Adjust the self-learning correction coefficient r based on the original remaining time tn and the optimized remaining time tn'. t .

[0106] In step S2021, the optimization process for the optimized operating conditions and the original remaining time tn under each optimized operating condition includes:

[0107] (1) First optimized operating condition: After the EGR closed-loop enable condition is removed, the target opening degree pct of the EGR valve is determined. EGRDsrd The situation remains unchanged (i.e., EGR closed-loop control exits but control is in a stable state);

[0108] At this point, the change in boost pressure difference Δp should be determined first. BoostErr :

[0109] Change in boost pressure difference Δp BoostErr Take the nearest The difference between the maximum and minimum pressure difference before the next sampling period (each sampling period is 10ms) (if the maximum pressure difference occurs later than the minimum pressure difference, then the change in pressure difference Δp) BoostErr It is a positive value; if the maximum value of the boost pressure difference occurs earlier than the minimum value of the boost pressure difference, then the change in boost pressure difference Δp BoostErr It is a negative value; if the time when the maximum value of the boost pressure difference occurs is the same as the time when the minimum value of the boost pressure difference occurs, then the change in boost pressure difference Δp BoostErr (for 0);

[0110] Then determine the mixing valve outlet pressure p. AfMixAct Change Δp AfMixAct :

[0111] Change in outlet pressure Δp of mixing valve AfMixAct Take the nearest The difference between the maximum and minimum outlet pressure of the mixing valve within each sampling period (each sampling period is 10ms) (if the maximum outlet pressure occurs later than the minimum outlet pressure, then the change in outlet pressure Δp is the change in outlet pressure). AfMixAct It is a positive value; if the maximum value of the mixing valve outlet pressure occurs earlier than the minimum value of the mixing valve outlet pressure, then the change in mixing valve outlet pressure Δp is positive. AfMixAct If the value is negative; 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 change in mixing valve outlet pressure Δp is negative. AfMixAct (for 0);

[0112] Finally, based on the change in boost pressure difference Δp BoostErr and the change in outlet pressure Δp of the mixing valve AfMixAct The original remaining time t1 (i.e., tn, where n=1, representing the first optimized operating 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 have a deteriorating effect on the stability trend of the boost pressure control, thus affecting the stability of the subsequent boost pressure control):

[0113] t1'=t1×[1+f(r PreRatio Δp BoostErr )]×[1+f(Δp AfMixAct , Δp BoostErr )]

[0114] Where f(r) PreRatio , Δp BoostErr ) and f(Δp AfMixAct , Δp BoostErr The calibration basis includes:

[0115] 1) Set a preset time after t1' ends Internally ensure the difference p between the target boost pressure and the actual boost pressure. BoostErr The fluctuations are within the preset range;

[0116] 2) The change in boost pressure difference Δp BoostErr Under the same conditions, if the pressure ratio coefficient r PreRatio The smaller the value, the better f(r) PreRatio Δ EGRR atio E The smaller rr) is, the better it is to satisfy the difference p between the target boost pressure and the actual boost pressure. BoostErr The fluctuation is within the preset range; at the pressure ratio coefficient r PreRatio Under the same conditions, if the change in boost pressure difference Δp BoostErr The larger f(r) is, the better. PreRatio Δ EGRRatioErr The larger the value, the better to satisfy the difference p between the target boost pressure and the actual boost pressure. BoostErr The fluctuation is within the preset range (the same as the fluctuation control requirements mentioned above);

[0117] 3) The change in boost pressure difference Δp BoostErr Under the same conditions, if the mixing valve outlet pressure p AfMixAct Change Δp AfMixAct The smaller the value, the better f(Δp) AfMixAct , Δp BoostErr The smaller the value, the better the difference p between the target boost pressure and the actual boost pressure can be satisfied. BoostErr The fluctuation is within the preset range; at the mixing valve outlet pressure p AfMixAct Change Δp AfMixAct Under the same conditions, if the change in boost pressure difference Δp BoostErr The larger the value, the greater the value of f(Δp). AfMixAct , Δp BoostErr The larger the value, the better to satisfy the difference p between the target boost pressure and the actual boost pressure. BoostErr The fluctuation is within the preset range (the same as the fluctuation control requirements mentioned above);

[0118] (2) Second optimized operating condition:

[0119] After the EGR closed-loop enable condition is removed, the target opening degree (pct) of the EGR valve is reached. EGRDsrd The situation remains unchanged (i.e., EGR closed-loop control is out but control is in a stable state) and knocking occurs;

[0120] At this point, the number of detonation cycles for different intensities must first be determined:

[0121] Referring to the method in patent CN202010608134.7, "A Method and System for Self-Learning Octane Number of Oil Products," the knock count Cnt corresponding to low, medium, and high strength grades is obtained. LowKnock Cnt MediumKnock Cnt HighKnock It should be understood that the number of detonations for each intensity is the number accumulated during the process of "EGR closed-loop control exiting but control stabilizing". Once this state changes, the number of detonations for each intensity is reset to zero and will be counted again after re-entering the "EGR closed-loop control exiting but control stabilizing" state.

[0122] Then determine the mixing valve outlet pressure p. AfMixAct Change Δp AfMixAct :

[0123] Change in outlet pressure Δp of mixing valve AfMixAct Take the nearest The difference between the maximum and minimum outlet pressure of the mixing valve within each sampling period (each sampling period is 10ms) (if the maximum outlet pressure occurs later than the minimum outlet pressure, then the change in outlet pressure Δp is the change in outlet pressure). AfMixAct It is a positive value;

[0124] If the maximum outlet pressure of the mixing valve occurs earlier than the minimum outlet pressure, then the change in outlet pressure of the mixing valve Δp AfMixAct If the value is negative; 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 change in mixing valve outlet pressure Δp is negative. AfMixAct (for 0);

[0125] Then, the detonation correction factor k is determined based on the number of detonations of different intensities. Knock :

[0126] k Knock =f(r PreRatio Cnt LowKnock )×f(r PreRatio Cnt MediumKnock )×f(r PreRatio Cnt HighKnock )

[0127] Number of detonations (Cnt) LowKnock Cnt MediumKnock Cnt HighKnock If the pressure ratio r remains constant PreRatio The smaller the value, the better the correction coefficient k, which is determined based on the number of detonations. Knock The smaller the value, the better; in pressure ratio r PreRatio Under the same conditions, if the number of detonation events CntLowKnock Cnt MediumKnock Cnt HighKnock The larger f(r) is, the better. PreRatio Cnt LowKnock ), f(r) PreRatio Cnt MediumKnock ), f(r) PreRatio Cnt HighKnock The larger the values ​​of f(r), the more likely it is to suppress the occurrence of detonation; its f(r) PreRatio Cnt LowKnock ), f(r) PreRatio Cnt MediumKnock ), f(r) PreRatio Cnt HighKnock The calibration is based on: ending at t2' and delayed by a preset time τ. EGR For a subsequent period (after the engine completes 20 working cycles, one working cycle refers to each cylinder completing 4 working strokes), ensure that the difference p between the target boost pressure and the actual boost pressure is maintained. BoostErr The fluctuation is within the preset range, and at most only low-intensity detonation occurs, with no more than 5 instances of low-intensity detonation; where τ EGR This refers to the time it takes for exhaust gas to flow from the EGR valve to the cylinder. This part is obtained through bench calibration and can be used for different engine speeds (n) and different actual intake gas densities (rho) entering the cylinder. Act The value of τ is obtained by averaging multiple samples under different EGR rates. EGR It is determined by the engine speed n and the actual intake air density rho entering the cylinder. Act It is confirmed;

[0128] Finally, based on the knock correction factor k Knock and the change in outlet pressure Δp of the mixing valve AfMixAct 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 have a deteriorating effect on the stability trend of the boost control, thus affecting the stability of the subsequent boost pressure control):

[0129] t2'=t2×(1+k Knock )×[1+f(Δp AfMixAct , Δp BoostErr )]

[0130] Where f(Δp) AfMixAct , Δp BoostErr The calibration basis includes:

[0131] 1) End at t2' and delay for a preset time τ EGRFor a subsequent period (after the engine completes 20 working cycles, one working cycle refers to each cylinder completing 4 working strokes), ensure that the difference p between the target boost pressure and the actual boost pressure is maintained. BoostErr The fluctuations are within the preset range;

[0132] 2) At most, only low-intensity detonation will occur, and the number of low-intensity detonation events will not exceed 5.

[0133] 3) The change in boost pressure difference Δp BoostErr Under the same conditions, if the mixing valve outlet pressure p AfMixAct Change Δp AfMixAct The smaller the value, the better f(Δp) AfMixAct , Δp BoostErr The smaller the value, the better the difference p between the target boost pressure and the actual boost pressure can be satisfied. BoostErr The fluctuation is within the preset range; at the mixing valve outlet pressure p AfMixAct Change Δp AfMixAct Under the same conditions, if the change in boost pressure difference Δp BoostErr The larger the value, the greater the value of f(Δp). AfMixAct , Δp BoostErr The larger the value, the better to satisfy the difference p between the target boost pressure and the actual boost pressure. BoostErr The fluctuation is within the preset range (the same as the fluctuation control requirements mentioned above);

[0134] (3) The third optimized operating condition:

[0135] After the EGR closed-loop enable condition is removed, the target opening degree (pct) of the EGR valve is reached. EGRDsrd The situation where the EGR closed-loop control is maintained (i.e., the EGR closed-loop control is out but the control is in a stable state), and the catalyst oxygen storage capacity coefficient and air-fuel ratio coefficient change;

[0136] At this point, the oxygen storage capacity coefficient r of the catalyst is first obtained. CatalystOxygen :

[0137] The current oxygen storage capacity coefficient r of the catalyst can be obtained by dividing the current oxygen storage capacity of the catalyst by the maximum oxygen storage capacity. CatalystOxygen The value ranges from 0 to 1. It should be understood that the smaller the oxygen storage coefficient, the smaller the oxygen storage capacity of the catalyst. In this case, the EGR rate can be appropriately reduced, which has little impact on NOx production. 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 equipment for calculating the oxygen storage capacity of a three-way catalytic converter", and refer to the method of real-time reading of the maximum oxygen storage capacity of the catalyst in CN104594986A "A method for diagnosing engine catalyst degradation".

[0138] Then, the oxygen storage capacity coefficient r of the catalyst is obtained. CatalystOxygen The change ΔrCatalystOxygen :

[0139] Change in oxygen storage capacity coefficient of catalytic converter Δr CatalystOxygen Pick The catalyst oxygen storage capacity coefficient r before the next sampling period (each sampling period is 10ms) CatalystOxygen Maximum value and catalyst oxygen storage capacity coefficient r CatalystOxygen The difference in minimum values ​​(if the oxygen storage capacity coefficient of the catalyst is r) CatalystOxygen The time when the maximum value occurs is before the catalytic oxygen storage capacity coefficient r. CatalystOxygen If the minimum value occurs later, the change in the oxygen storage capacity coefficient of the mixed catalytic converter, Δr, will be greater. CatalystOxygen It is a positive value; if the oxygen storage capacity coefficient r of the catalyst is positive. CatalystOxygen The time when the maximum value occurs is before the catalytic oxygen storage capacity coefficient r. CatalystOxygen If the minimum value occurs earlier, the change in the catalytic converter's oxygen storage capacity coefficient Δr will be greater. CatalystOxygen It is a negative value; if the oxygen storage capacity coefficient r of the catalyst is negative. CatalystOxygen The timing of the maximum value is related to the catalyst oxygen storage capacity coefficient r. CatalystOxygen If the minimum values ​​occur at the same time, then the change in the catalytic converter's oxygen storage capacity coefficient Δr CatalystOxygen (for 0);

[0140] Then determine the air-fuel ratio coefficient. Where, r ActFuelAirRatio For the actual air-fuel ratio, r StadFuelAirRatio The ideal air-fuel ratio is (1 / 14.3 in this example);

[0141] Then obtain the air-fuel ratio coefficient. Change Change in air-fuel ratio Change in air-fuel ratio Take the nearest The difference between the maximum and minimum air-fuel ratio coefficients within the previous sampling period (each sampling period is 10ms). (If the maximum air-fuel ratio coefficient occurs later than the minimum air-fuel ratio coefficient, then the change in air-fuel ratio coefficient is...) It is a positive value; if the maximum value of the air-fuel ratio occurs earlier than the minimum value of the air-fuel ratio, then the change in the air-fuel ratio is positive. It is a negative value; if the maximum value of the air-fuel ratio occurs at the same time as the minimum value of the air-fuel ratio, then the change in the air-fuel ratio is negative. (for 0);

[0142] Finally, based on the change in the oxygen storage capacity coefficient of the catalyst Δr CatalystOxygen Change in air-fuel ratio The original remaining time t3 is updated and optimized to obtain t3' (considering the catalyst oxygen storage capacity coefficient r). CatalystOxygen The changes in the amount of pressure and air-fuel ratio are because excessive changes can worsen the stability trend of boost control, thereby affecting the stability of subsequent boost pressure control.

[0143]

[0144] Where, f(r) PreRatio , Δr CatalystOxygen ), f(Δp AfMixAct , Δp BoostErr The calibration basis includes:

[0145] 1) End at t3' and delay for a preset time. Internally ensure the difference p between the target boost pressure and the actual boost pressure. BoostErr The fluctuations are within the preset range, and the catalyst oxygen storage capacity coefficient r CatalystOxygen The value should not exceed the preset value (0.9 in this example), and the oxygen storage capacity coefficient r of the catalyst should also be within the preset range. CatalystOxygen The change does not exceed the preset value (0.2 in this example);

[0146] 2) In Δr CatalystOxygen Under the same conditions, if the pressure ratio r PreRatio The smaller the value, the better f(r) PreRatio , Δr CatalystOxygen The smaller the value, the better; in pressure ratio r PreRatio Under the same conditions, if Δr CatalystOxygen The larger f(r) is, the better. PreRatio , Δr CatalystOxygen The larger the number of )

[0147] 3) In Δr CatalystOxygen Under the same conditions, if the pressure ratio The smaller, the better The smaller the pressure ratio; Under the same conditions, if Δr CatalystOxygen The larger, the better The larger;

[0148] 4) The change in boost pressure difference Δp BoostErr Under the same conditions, if the mixing valve outlet pressure p AfMixAct Change Δp AfMixAct The smaller the value, the better f(Δp) AfMixAct , Δp BoostErr The smaller the value, the better; at the mixing valve outlet pressure p AfMixAct Change Δp AfMixAct Under the same conditions, if the change in boost pressure difference Δp BoostErr The larger the value, the greater the value of f(Δp).AfMixAct , Δp BoostErr The larger it is.

[0149] In step S2022, the self-learning correction coefficient r t The adjustment process is as follows:

[0150] a. If tn'-tn is greater than the preset value C1 (in this embodiment, C1 is 0.5s; if this occurs, it indicates that the ignition angle efficiency has been adjusted too much, which can easily cause ignition), and only one of the three optimized operating conditions occurs, and the number of consecutive occurrences CNT1 (initially 0, which can be saved after the vehicle is powered off) exceeds the preset value (in this example, it is 5), it indicates that the duration tn is continuously increasing. In this case, the self-learning state of time t is set to the upward learning state one, i.e., r t Need to add: r t =r t (z)+0.05, where r t (z) is the self-learning correction coefficient r stored from the previous learning session. t At the same time, CNT1 is cleared to zero; the self-learning correction coefficient stored in the new learning is used when judging the next time this situation is entered;

[0151] b. If tn'-tn is greater than the preset value C1, and it is not always only one of the three optimized operating conditions that occurs, and the number of consecutive occurrences CNT2 (initially 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 continuously increasing. In this case, the self-learning state of time t is changed to the upward learning state two, i.e., r t It needs to be added. t =r t (z)+0.03, and CNT2 is cleared to zero; the self-learning correction coefficient stored in the new learning is used when judging the next time this situation is entered;

[0152] c. If tn'-tn is not greater than the preset value -C2 (in this example, C2 is 0.3s; if this occurs, it indicates that the ignition angle efficiency is too high, which can easily cause pressure fluctuations), and only one of the three optimized operating conditions occurs, and the number of consecutive occurrences CNT3 (initially 0, which can be saved after the vehicle is powered off) exceeds the preset value (in this example, it is 5), it means that the duration tn is continuously decreasing. In this case, the time t self-learning state is set to the downward learning state one, i.e., r t It needs to be reduced. t =r t (z)-0.04; Simultaneously, CNT3 is cleared to zero; The newly learned self-learning correction coefficient is used the next time this situation is entered;

[0153] d. If tn'-tn is not greater than the preset value -C2, and it is not always only one of the three optimized operating conditions that occurs, and the number of consecutive occurrences CNT4 (initially 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 continuously decreasing. In this case, the time t is set to the self-learning state of downward learning state two, i.e., r t It needs to be reduced. t =r t (z)-0.02; simultaneously clear CNT4; the newly learned self-learning correction coefficient will be used the next time this situation is entered;

[0154] e. If tn'-tn is greater than the preset value C1, and the previous occurrence of tn'-tn was not greater than the preset value -C2, then the self-learning state of time t will be changed to the upward learning state three, i.e., r t Need to add: r t2 =r t2 (z)+0.02; The self-learning correction coefficient of the newly learned storage is used when judging the next time this situation is entered;

[0155] f. If tn'-tn is not greater than the preset value -C2, and the last occurrence of tn'-tn was greater than the preset value C1, then the self-learning state of time t will be changed to the downward learning state three, i.e., r t Need to be reduced; r t2 =r t2 (z)-0.01; The self-learning correction coefficient of the newly learned storage is used when judging the next time this situation is entered;

[0156] g. In cases other than a to f above, r t Remain unchanged;

[0157] Among them, the priority of a to g decreases in that order.

[0158] Step S3 includes:

[0159] S301. Determine the target opening degree (pct) of the EGR valve based on the engine speed (n). EGRDsrd The rate of change of k1;

[0160] The relationship between engine speed n and its rate of change k1 was obtained through calibration, and the calibration results are shown in Table 2.

[0161] Table 2

[0162]

[0163]

[0164] The calibration process is based on the following principle: ensuring that the fluctuation of the actual EGR pressure at the EGR valve outlet is within a preset range; specifically, if the conditions are met within the first sampling period after the EGR closed-loop condition is not satisfied, and for the next two sampling periods after the end of time t:

[0165] |p EGRValveOutFilter (N)-p EGRValveOut (N)||<min[p EGRValveOut (N),p EGRValveOutFilter (N)]×r EGRValveOutLim

[0166] This indicates that the fluctuation of the actual EGR pressure at the EGR valve outlet is within the preset range;

[0167] In the above formula, p EGRValveOutFilter (N) satisfies:

[0168] p EGRValveOutFilter (N)=K EGRValeOut ×[p EGRValveOut (N)-p EGRValveOutFilter (N-1]+p EGRValveOutFilter (N-1)

[0169] In the above formula, p EGRValveOut p represents the original value of the actual EGR pressure at the EGR valve outlet. EGRValveOut (N) represents the original value of the actual EGR pressure at the EGR valve outlet during the Nth sampling period, p EGRValveFilter p represents the actual EGR pressure at the EGR valve outlet after first-order low-pass filtering. EGRValveOutFilter (N) represents the p after first-order low-pass filtering. EGRValveOut (N), p EGRValveOutFilter (N-1) represents the original value of the actual EGR pressure at the EGR valve outlet during the (N-1)th sampling period, after being filtered by a first-order low-pass filter, where N = 1, 2, 3, ...; p EGRValveOutFilter (0) equals the original value p of the actual EGR pressure at the EGR valve outlet during the 0th sampling period. EGRValveOut (0), specifically, the 0th sampling period occurs at the moment the vehicle is powered on; the sampling period interval Δt is 10ms in this example. K EGRValveOut For coefficients: (In this example, the engine has 4 cylinders N, k) EGRValveOut The calibration speed is 1000 rpm. The purpose of this setting is normalization; no special calibration is needed for different numbers of cylinders and engine speeds. Only the 4-cylinder engine and the k-type engine at 1000 rpm need to be calibrated. EGRValveOut (thus reducing calibration testing work), k EGRValveOut The filter coefficient for the actual EGR pressure at the EGR outlet is 0.2 in this example;

[0170] S302, Adjust the target opening degree pct of the EGR valve according to the rate of change k1. EGRDsrd Transition to 0%.

[0171] Example 2:

[0172] This embodiment provides a closed-loop control device for exhaust gas recirculation based on multiple performance dimensions, including:

[0173] The pressure ratio coefficient determination module is used to determine the pressure ratio coefficient based on 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 when the EGR closed-loop condition switches from being met to not being met.

[0174] The initial duration determination module is used to determine the initial duration based on engine speed, pressure ratio coefficient, and self-learning correction coefficient; wherein, the self-learning correction coefficient is obtained through self-learning, and the initial duration is used to maintain the target opening of the EGR valve unchanged;

[0175] The EGR valve target opening transition module is used to transition the EGR valve target opening to 0% at a certain rate after the initial value of the EGR valve target opening duration is maintained.

[0176] Example 3:

[0177] This embodiment provides a computer device, such as a smartphone, tablet computer, laptop computer, desktop computer, rack server, blade server, tower server, or cabinet server (including standalone servers or server clusters composed of multiple servers) capable of executing programs. The computer device in this embodiment includes, but is not limited to, a memory and a processor that can be interconnected via a system bus.

[0178] In this embodiment, the memory (i.e., the readable storage medium) includes flash memory, hard disk, multimedia card, card-type memory (e.g., SD or DX memory), random access memory (RAM), static random access memory (SRAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), and programmable read-only memory (PROM). The memory can also be an external storage device of the computer device, such as a plug-in hard disk, smart media card (SMC), secure digital card (SD), flash card, etc., equipped on the computer device. Of course, the memory can also include both internal storage units and external storage devices of the computer device. In this embodiment, the memory is typically 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 Embodiment 1. Furthermore, the memory can also be used to temporarily store various types of data that have been output or will be output.

[0179] In some embodiments, the processor may be a central processing unit (CPU), a controller, a microcontroller, a microprocessor, or other data processing chip. This processor is typically used to control the overall operation of a computer device. In this embodiment, the processor is used to run program code stored in memory or process data, such as a multi-performance-dimensional exhaust gas recirculation closed-loop control device, to implement the multi-performance-dimensional exhaust gas recirculation closed-loop control method in Embodiment 1.

[0180] Example 4:

[0181] This embodiment provides a computer-readable storage medium, such as flash memory, hard disk, multimedia card, card-type memory (e.g., SD or DX memory), 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), magnetic memory, disk, optical disk, server, App store, etc., which stores a computer program. When the program is executed by a processor, it implements the corresponding function. In this embodiment, the computer-readable storage medium is used to store the program code of a closed-loop control device for exhaust gas recirculation based on multiple performance dimensions. When executed by a processor, it implements the closed-loop control method for exhaust gas recirculation based on multiple performance dimensions of Embodiment 1.

[0182] It should be noted that, depending on the implementation needs, the various steps / components described in this application can be broken down into more steps / components, or two or more steps / components or parts of the operation of steps / components can be combined into new steps / components to achieve the purpose of this invention.

Claims

1. A closed-loop control method for exhaust gas recirculation based on multiple performance dimensions, characterized in that, include: When the EGR closed-loop condition switches from being met to not being met, the pressure ratio coefficient is determined based on 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 initial duration is determined based on engine speed, pressure ratio coefficient, and self-learning correction coefficient; the self-learning correction coefficient is obtained through self-learning, and the initial duration is used to maintain the target opening of the EGR valve unchanged. The target opening of the EGR valve transitions to 0% at a certain rate after maintaining the initial value for a certain duration. The method for determining the initial value of the duration includes: Based on the pressure ratio coefficient and engine speed, determine the pressure ratio-engine speed coefficient; The self-learning correction coefficient is determined through self-learning. The initial duration is determined based on the pressure ratio-engine speed coefficient and the self-learning correction coefficient. The method for determining the self-learning correction coefficient includes: Based on the current optimization conditions, the original remaining time is updated and optimized to obtain the optimized remaining time; where 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 based on the original remaining time and the optimized remaining time.

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

3. The closed-loop control method for exhaust gas recirculation based on multiple performance dimensions as described in claim 1, characterized in that, Optimized operating conditions include: maintaining the target opening degree of the EGR valve unchanged after the EGR closed-loop enable condition is removed; Under this optimized operating condition, the remaining time after optimization can be obtained in the following ways: Based on the pressure difference within a certain number of sampling periods, determine the change in pressure difference; Based on the mixing valve outlet pressure change within a certain number of sampling periods, determine the mixing valve outlet pressure change; The original remaining time is updated and optimized based on the changes in the boost pressure difference and the changes in the mixing valve outlet pressure.

4. The closed-loop control method for exhaust gas recirculation based on multiple performance dimensions as described in claim 1, characterized in that, Optimized operating conditions include: After the EGR closed-loop enable condition is removed, the target opening of the EGR valve remains unchanged, and knocking occurs. Under this optimized operating condition, the remaining time after optimization can be obtained in the following ways: Obtain the number of detonation events of different intensities; Based on the mixing valve outlet pressure within a certain number of sampling periods, determine the change in mixing valve outlet pressure. Determine the detonation correction factor based on the number of detonations of different intensities; The original remaining time is updated and optimized based on the knock correction coefficient and the change in outlet pressure of the mixing valve.

5. The closed-loop control method for exhaust gas recirculation based on multiple performance dimensions according to claim 1, characterized in that, The optimized operating conditions include: the EGR valve target opening remains unchanged after the EGR closed-loop enabling condition is removed, and the catalyst oxygen storage capacity coefficient and air-fuel ratio coefficient change. Under this optimized operating condition, the remaining time after optimization can be obtained in the following ways: Obtain the oxygen storage capacity coefficient of the catalyst; Based on the catalyst oxygen storage capacity coefficient within a certain number of sampling periods, determine the change in the catalyst oxygen storage capacity coefficient. The air-fuel ratio coefficient is determined based on the actual air-fuel ratio and the ideal air-fuel ratio. Based on the air-fuel ratio coefficient within a certain number of sampling periods, determine the change in the air-fuel ratio coefficient. The original remaining time is updated and optimized based on the changes in the catalyst oxygen storage capacity coefficient and the air-fuel ratio coefficient.

6. The closed-loop control method for exhaust gas recirculation based on multiple performance dimensions according to claim 1, 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 optimization conditions occurs, and the number of consecutive occurrences exceeds the preset number, then the self-learning correction coefficient is increased by the first step length, and the number of consecutive occurrences in this case is cleared to zero; the newly learned and stored self-learning correction coefficient is used when judging this case again 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 only one of the fixed conditions under different optimization conditions that occurs, and the number of consecutive occurrences exceeds the preset number, then the self-learning correction coefficient is increased by the second step size, and the number of consecutive occurrences in this case is cleared to zero; the newly learned and stored self-learning correction coefficient is used when entering this case judgment again. 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 fixed situation under each optimization condition occurs, and the number of consecutive occurrences exceeds the preset number, then the self-learning correction coefficient is decreased by the third step size, and the number of consecutive occurrences under this situation is cleared to zero; the newly learned self-learning correction coefficient is used when entering this situation judgment again. d. If the difference between the optimized remaining time and the original remaining time is not greater than the second remaining time threshold, and it is not always only one of the fixed situations under various optimization conditions that occurs, and the number of consecutive occurrences exceeds the preset number, then the self-learning correction coefficient is decreased by the fourth step size, and the number of consecutive occurrences under this situation is cleared to zero; the newly learned and stored self-learning correction coefficient is used when entering this situation judgment again. 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 in the previous occurrence was not greater than the second remaining time threshold, then the time self-learning correction coefficient is increased by the fifth step, and the number of consecutive occurrences in this case is cleared to zero; the newly learned self-learning correction coefficient is used when entering this case judgment again. 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 was greater than the first remaining time threshold in the last occurrence, then the time self-learning correction coefficient is decreased by the sixth step, and the number of consecutive occurrences in this case is cleared to zero; the newly learned self-learning correction coefficient is used when entering this case judgment again. g. In cases other than a to f above, the self-learning correction coefficient remains unchanged; Among them, the priority of a to g decreases in that order.

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

8. A closed-loop control device for exhaust gas recirculation based on multiple performance dimensions, characterized in that, include: The pressure ratio coefficient determination module is used to determine the pressure ratio coefficient based on 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 when the EGR closed-loop condition switches from being met to not being met. The initial duration determination module is used to determine the initial duration based on engine speed, pressure ratio coefficient, and self-learning correction coefficient; wherein, the self-learning correction coefficient is obtained through self-learning, and the initial duration is used to maintain the target opening of the EGR valve unchanged; The EGR valve target opening transition module is used to transition the EGR valve target opening to 0% at a certain rate after the initial value of the EGR valve target opening maintenance duration. The method for determining the initial value of the duration includes: Based on the pressure ratio coefficient and engine speed, determine the pressure ratio-engine speed coefficient; The self-learning correction coefficient is determined through self-learning. The initial duration is determined based on the pressure ratio-engine speed coefficient and the self-learning correction coefficient. The method for determining the self-learning correction coefficient includes: Based on the current optimization conditions, the original remaining time is updated and optimized to obtain the optimized remaining time; where 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 based on the original remaining time and the optimized remaining time.

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