Optimization control method for target EGR rate

Abstract

The invention discloses an optimization control method for a target EGR rate, which comprises the following steps: entering EGR closed-loop enabling under the condition of meeting the closed-loop enabling of an EGR system, determining a filtering time coefficient of the target EGR rate according to the response time of a supercharger and the time of exhaust gas flowing from an EGR valve to an EGR exhaust gas convergence point, and calculating the change rate of the filtering time coefficient of the target EGR rate; obtaining filtering time according to a filtering time learning coefficient and the change rate of the filtering time coefficient of the target EGR rate; according to the filtering time and the target EGR rate, the filtered target EGR rate is obtained; and an EGR valve is controlled according to the filtered target EGR rate. According to the method provided by the invention, the target EGR rate can be optimized, the influence on engine knock deterioration when EGR enters is improved, and meanwhile, the supercharging control stability and the emission performance of the engine are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of engine control, and in particular to an optimization control method for a target EGR rate. Background Art

[0002] The exhaust gas recirculation (EGR) system takes the exhaust gas from the engine and re-enters the intake system. Studies have shown that the EGR system has certain advantages in improving emissions, reducing fuel consumption and improving anti-knock capabilities. The control of the mixing valve in the low-pressure EGR system is particularly important as it improves the effect of the EGR rate. Optimizing the target EGR rate and improving control stability and emissions are still areas that need to be studied. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide an optimization control method for the target EGR rate in view of the shortcomings of the prior art. The method can optimize the target EGR rate, improve the influence of EGR entry on the deterioration of engine knock, and improve the engine boost control stability and emission performance.

[0004] To achieve the above object, according to one aspect of the present invention, a method for optimizing and controlling a target EGR rate is provided, comprising:

[0005] Entering EGR closed-loop enabling when the EGR system closed-loop enabling conditions are met, determining a filter time coefficient of a target EGR rate according to a supercharger response time and a time for exhaust gas to flow from an EGR valve to an EGR exhaust gas confluence point, and calculating a change rate of the filter time coefficient of the target EGR rate;

[0006] Acquire the filtering time according to the filtering time learning coefficient and the change rate of the filtering time coefficient of the target EGR rate;

[0007] Obtaining a filtered target EGR rate according to the filtering time and the target EGR rate;

[0008] controlling the EGR valve according to the filtered target EGR rate;

[0009] The filter time learning coefficient has an initial value, and after operation, it is calculated and updated based on the target boost pressure, actual boost pressure, target air-fuel ratio, actual air-fuel ratio, target EGR rate, actual EGR rate, the updated filtered target EGR rate, the cumulative number of high-intensity knocks occurring in the engine, and the catalyst oxygen storage capacity coefficient.

[0010] In the above scheme, the supercharger response time τ Boost is the time for the mixed gas to flow from the supercharger compressor to the throttle outlet; the supercharger response time τ Boost It is obtained through bench calibration. The specific method is: at different engine speeds neng and different actual intake air density rho Act Under different EGR rates, the average value of the time it takes for the mixture to flow from the supercharger compressor to the throttle outlet is obtained through multiple sampling.

[0011] In the above scheme, the time τ for the exhaust gas to flow from the EGR valve to the EGR exhaust gas confluence point is EGR It is obtained through bench calibration. The specific method is: at different engine speeds n eng and different actual intake air density rho Act Under different EGR rates, the average value of the time it takes for the exhaust gas to flow from the EGR valve to the EGR exhaust gas confluence point is obtained through multiple sampling; the EGR exhaust gas confluence point refers to the place where the EGR exhaust gas and the fresh air converge.

[0012] In the above scheme, according to the supercharger response time τ Boost and the time τ for exhaust gas to flow from the EGR valve to the EGR exhaust gas confluence point EGR Determine the filter time coefficient k of the target EGR rate T The method is:

[0013]

[0014] Among them, k T is the filter time coefficient of the target EGR rate, τ Boost is the supercharger response time, τ EGR The time for the exhaust gas to flow from the EGR valve to the EGR exhaust gas confluence point. Boost and the time τ for exhaust gas to flow from the EGR valve to the EGR exhaust gas confluence point EGR Determine the filter time coefficient k of the target EGR rate T The purpose is to consider the boost response characteristics and EGR response characteristics while optimizing the target EGR rate, so as to improve the robustness of EGR rate control.

[0015] In the above scheme, the filter time coefficient k of the target EGR rate is calculated as T The rate of change dk T The method is:

[0016]

[0017] Where Δt is the sampling time, dk T (z) is the filter time coefficient k of the target EGR rate in the previous sampling cycle T The rate of change dk T , k T (z) is the filter time coefficient k of the previous sampling periodT , the initial k T (z) occurs when the EGR closed loop is enabled, and its default value is 1. The dk at the initial moment T (z) occurs when the EGR closed loop is enabled, and its default value is 0, t c The purpose of calculating the filter time coefficient change rate in the present invention is to avoid the target EGR rate filter time T from fluctuating too fast due to the change rate changing too fast, thereby affecting the target EGR rate changing too fast.

[0018] In the above scheme, the learning coefficient r is calculated based on the filtering time. T and the filtering time coefficient k of the target EGR rate T The rate of change dk T The method to obtain the filter time is:

[0019] T=f(dk T )×(1+r T );

[0020] Where T is the filtering time; r T is the filter time learning coefficient, which can be saved after the vehicle is powered off and can be continuously learned and updated during the vehicle's driving. Its default value is 0; f(dk T ) is the default time of the filtering time T, f(dk T ) is determined by the filter time coefficient k of the target EGR rate T The rate of change dk T Decision, specifically: When dk T When <-200, f(dk T )=0.15s; when dk T When >200, f(dk T )=0.18s; when -200≤dk T When <-100, f(dk T )=0.12s; when -100≤dk T When <-50, f(dk T )=0.1s; when -50≤dk T When <-10, f(dk T )=0.05s; when -10≤dk T When f(dk T )=0.01s; when 0≤dk T When <10, f(dk T )=0.05s; when 10≤dk T When <50, f(dk T )=0.12s; when 50≤dk T When <100, f(dkT )=0.16s; when 100≤dk T When <200, f(dk T )=0.18s.

[0021] In the above scheme, the filter time learning coefficient has an initial value, and after operation, the specific method of calculating and updating according to the target boost pressure, the actual boost pressure, the target air-fuel ratio, the actual air-fuel ratio, the target EGR rate, the actual EGR rate, the updated filtered target EGR rate, the cumulative number of high-intensity knocks of the engine, and the catalyst oxygen storage capacity coefficient is: when the time for satisfying the filter time learning coefficient judgment condition exceeds the preset time t1, read the average value p of the difference between the target boost pressure and the actual boost pressure within the time t1 BoostErrAvg ; The average value of the difference between the target air-fuel ratio and the actual air-fuel ratio r AFRErrAvg ; The average value of the difference between the updated filtered target EGR rate and the actual EGR rate r EGRErrAvg ; The average value of the target EGR rate after filtering r EGRDsrdFilterAvg ; Target EGR rate average value r EGRDsrdRawAvg ; The cumulative number of high-intensity knocks that occur in the engine Cnt Knock ; Catalyst oxygen storage capacity coefficient r CatalystOxygen ; The target EGR rate acquisition method described herein refers to the patent publication number CN112459910A "A method and system for calculating the target EGR rate"; wherein the cumulative number of high-intensity knocks occurring in the engine Cnt Knock For the method of obtaining , please refer to the patent with publication number CN111878279A "A method and system for self-learning of oil octane number", for the method of reading the oxygen storage capacity of the catalyst, please refer to the patent with publication number CN110259553A "A method, device and electronic device for calculating the oxygen storage capacity of a three-way catalyst", and for the method of reading the maximum oxygen storage capacity of the catalyst, please refer to the patent with publication number CN104594986A "A method for diagnosing engine catalyst degradation";

[0022] Get the filtering time learning coefficient r T The specific methods are as follows:

[0023] Case 1: If the updated filtered target EGR rate average value r EGRDsrdFilterAvg Greater than the target EGR rate average value r EGRDsrdRawAvg If the value exceeds the preset value, it means that the EGR rate is decreasing. Then the following first condition, second condition, third condition, fourth condition and fifth condition are judged in sequence to adjust the filter time learning coefficient r T Calculate and update:

[0024] The first condition: If the cumulative number of high-intensity knocks CntKnock ≥CNT1, where CNT1 is the preset value, and |p BoostErrAvg |≥p1, and |r EGRErrAvg |≤0.01, where p1 is the preset value, then r T =r T (z)+0.02, and Cnt Knock Clear and restart counting, where r T (z) is the filter time learning coefficient r stored in the last learning update T Learning value;

[0025] Second condition: If the cumulative number of high-intensity knocks Cnt occurs Knock ≥CNT1, where CNT1 is the preset value, and |r EGRErrAvg |≤0.01, then r T =r T (z)+0.01, where r T (z) is the filter time learning coefficient r stored in the last learning update T Learning value;

[0026] The third condition: If |r AFRErrAvg |≤0.01, and |p BoostErrAvg |≤p2, where p2 is a preset value, and |r EGRErrAvg |≤0.01, and r CatalystOxygen ≤r C , where r C If r is the default value T =r T (z)-0.03, where r T (z) is the filter time learning coefficient r stored in the last learning update T Learning value;

[0027] Fourth condition: If |r AFRErrAvg |≤0.01, and |p BoostErrAvg |≤p2, where p2 is a preset value, and |r EGRErrAvg |≤0.01, then r T =r T (z)-0.01, where r T (z) is the filter time learning coefficient r stored in the last learning update T Learning value;

[0028] Fifth condition: In other cases, r T =r T (z), where r T (z) is the filter time learning coefficient r stored in the last learning update T Learning value;

[0029] The priorities of the first condition, the second condition, the third condition, the fourth condition, and the fifth condition are getting lower and lower, that is, if the previous conditions are met, only the previous update results are executed; for example, when the first condition is met, only the update results of the first condition are executed, and the update results of the following conditions are not executed;

[0030] Second case: If the target EGR rate average value r EGRDsrdRawAvg Greater than the updated filtered target EGR rate average r EGRDsrdFilterAvg If the value exceeds the preset value, it means that the EGR rate is increasing. Then the following sixth condition, seventh condition, eighth condition, ninth condition and tenth condition are judged in sequence to adjust the filter time learning coefficient r T Calculate and update:

[0031] Sixth condition: If the cumulative number of high-intensity knocks Cnt Knock ≥CNT1, where CNT1 is the preset value, and |p BoostErrAvg |≥p1, and |r EGRErrAvg |≤0.01, where p1 is the preset value, then r T =r T (z)+0.03, and Cnt Knock Clear and restart counting, where r T (z) is the filter time learning coefficient r stored in the last learning update T Learning value;

[0032] Seventh condition: If the cumulative number of high-intensity knocks Cnt Knock ≥CNT1, where CNT1 is the preset value, and |r EGRErrAvg |≤0.01, then r T =r T (z)+0.01, where r T (z) is the filter time learning coefficient r stored in the last learning update T Learning value;

[0033] Condition 8: If |r AFRErrAvg |≤0.01, and |p BoostErrAvg |≤p2, where p2 is a preset value, and |r EGRErrAvg |≤0.01, and r CatalystOxygen ≤r C , where r C If r is the default value T =r T (z)-0.02, where r T (z) is the filter time learning coefficient r stored in the last learning update T Learning value;

[0034] Ninth condition: If |r AFRErrAvg |≤0.01, and |p BoostErrAvg |≤p2, where p2 is a preset value, and |r EGRErrAvg |≤0.01, then r T =r T (z)-0.01, where r T (z) is the filter time learning coefficient r stored in the last learning update T Learning value;

[0035] Tenth Condition: In other cases, r T =r T (z), where r T (z) is the filter time learning coefficient r stored in the last learning update T Learning value;

[0036] The priorities of the sixth, seventh, eighth, ninth and tenth conditions above are getting lower and lower, that is, if the previous conditions are met, only the previous update results are executed; for example, when the sixth condition is met, only the update method of the sixth condition is executed, and the update methods of the following conditions are not executed;

[0037] Third case: In other cases where neither the first case nor the second case is satisfied, r T =r T (z), where r T (z) is the filter time learning coefficient r stored in the last learning update T Learning value.

[0038] In the above scheme, the filtered target EGR rate r is obtained according to the filtering time and the target EGR rate. EGRDsrdFilter The method is:

[0039]

[0040] Among them, r EGRDsrdFilter (N) is the target EGR rate after filtering in the Nth sampling period r EGRDsrdFilter , r EGRDsrdFilter (N-1) is the target EGR rate after filtering in the N-1th sampling period. EGRDsrdFilter , Δt is the sampling time, N = 1, 2, 3..., where r EGRDsrdFilter (0) is equal to 0, which occurs when the vehicle is powered on, r EGRDsrdRaw is the target EGR rate, r EGRDsrdRaw (N) is the target EGR rate of the Nth sampling cycle, and T is the filtering time.

[0041] In the above scheme, the filter time learning coefficient judgment condition is:

[0042] (1) The engine speed fluctuation does not exceed the preset value;

[0043] (2) The actual intake air density fluctuation does not exceed the preset value;

[0044] (3) EGR system closed loop enable;

[0045] (4) The difference between the target boost pressure and the system maximum boost pressure or the system minimum boost pressure exceeds the preset value;

[0046] (5) The difference between the system maximum boost pressure and the target boost pressure exceeds the preset value;

[0047] (6) The engine water temperature does not exceed the preset value;

[0048] (7) The engine intake temperature does not exceed the preset value.

[0049] In the above scheme, the EGR system closed-loop enabling condition is:

[0050] (1) There are no related faults in the EGR system components;

[0051] (2) No fuel cut request occurs or the fuel cut recovery time exceeds the preset time;

[0052] (3) the updated filtered target EGR rate is not less than the minimum EGR rate; the method for obtaining the minimum EGR rate refers to the patent publication number CN115585070A "minimum EGR rate adjustment method, device, equipment and storage medium";

[0053] (4) The engine speed is within the preset speed range;

[0054] (5) The intake air temperature is within the preset range;

[0055] (6) The engine water temperature is within the preset range;

[0056] (7) The atmospheric temperature is within the preset range;

[0057] (8) When the atmospheric pressure exceeds 66 kPa, the EGR closed-loop enabling condition is allowed; when the atmospheric temperature is lower than 64 kPa, the EGR closed-loop enabling condition needs to be exited.

[0058] In the above scheme, the intake air temperature within the preset range specifically includes: if the current state is that the EGR closed-loop is not enabled, then entering the EGR closed-loop state, it is necessary to ensure that the intake air temperature is not lower than the minimum intake air temperature of 10°C; if the current state is the EGR closed-loop enabled state, then exiting the EGR system closed-loop enabled state requires ensuring that the intake air temperature is lower than the minimum intake air temperature of 7°C; if the current state is that the EGR closed-loop is not enabled, then entering the EGR closed-loop state, it is necessary to ensure that the maximum intake air temperature does not exceed 60°C; if the current state is the EGR closed-loop enabled state, then exiting the EGR system closed-loop enabled state requires ensuring that the maximum intake air temperature exceeds 65°C.

[0059] In the above scheme, the engine water temperature within the preset range specifically includes: if the current state is that the EGR closed loop is not enabled, then entering the EGR closed loop state, it is necessary to ensure that the water temperature is not lower than the minimum water temperature of 60°C; if the current state is the EGR closed loop enabled state, then exiting the EGR system closed loop enabled state requires to ensure that the water temperature is lower than the minimum water temperature of 55°C; if the current state is that the EGR closed loop is not enabled, then entering the EGR closed loop state, it is necessary to ensure that the maximum water temperature does not exceed 115°C; if the current state is the EGR closed loop enabled state, then exiting the EGR system closed loop enabled state requires to ensure that the water temperature exceeds the maximum water temperature of 120°C.

[0060] In the above scheme, the atmospheric temperature within the preset range specifically includes: if the current state is that the EGR closed-loop is not enabled, then entering the EGR closed-loop state, it is necessary to ensure that the atmospheric temperature is not lower than the minimum atmospheric temperature of 5°C; if the current state is the EGR closed-loop enabled state, then exiting the EGR system closed-loop enabled state requires to ensure that the atmospheric temperature is lower than the minimum atmospheric temperature of 3°C; if the current state is that the EGR closed-loop is not enabled, then entering the EGR closed-loop state, it is necessary to ensure that the atmospheric temperature does not exceed the maximum atmospheric temperature of 55°C; if the current state is the EGR closed-loop enabled state, then exiting the EGR system closed-loop enabled state requires to ensure that the atmospheric temperature exceeds the maximum atmospheric temperature of 60°C.

[0061] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0062] The present invention provides a method for optimizing control of a target EGR rate, which optimizes the target EGR rate, improves the effect of EGR entry on engine knock deterioration and engine supercharging stability, and improves the effect on emission deterioration. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Also, throughout the accompanying drawings, the same reference figures are used to represent the same components. In the drawings:

[0064] Figure 1 Schematic diagram of the system structure with EGR in an embodiment of the present invention.

[0065] Figure 2 Schematic diagram of the flow chart of the method for optimizing the control of the target EGR rate in an embodiment of the present invention.

[0066] Reference numerals

[0067] 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

[0068] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0069] It should be understood that the size of the serial numbers of the steps in the embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0070] Example 1

[0071] The system structure with EGR based on the present invention is as follows Figure 1 As shown, it includes: an air filter 1; a mixing valve 2 connected to the air filter, 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 connected to one of the air flow paths of the mixing valve 2; a throttle 4 connected to the compressor 3; an engine 5 connected to the throttle 4, used to compress fresh air for supercharging; a turbine 6 connected to the engine 5, used to control the opening of the exhaust bypass valve; a catalyst 7 connected to the turbine 6; a particulate matter collector 8 connected to the catalyst 7; and an installation The EGR cooler 9 on the other air flow path of the mixing valve 2 is used to receive the exhaust gas output by the particulate collector 8 and cool it to increase the exhaust gas flow rate; one end is connected to the EGR cooler 9, and the other end is connected to the EGR valve 10 of the mixing valve 2, which is used to control the exhaust gas flow entering the cylinder; the temperature sensor 11 installed between the EGR valve 10 and the EGR cooler 9 is used to detect the exhaust gas temperature entering the EGR valve 10; the pressure difference sensor 12 connected to the EGR valve 10 is used to detect the pressure at the inlet and outlet of the EGR valve 10.

[0072] According to one aspect of the present invention, an embodiment of the present application provides a method for optimizing and controlling a target EGR rate. Figure 2 ,include:

[0073] S1, enters EGR closed-loop enablement when the EGR system closed-loop enablement conditions are met, determines the target EGR rate filter time coefficient based on the supercharger response time and the time for the exhaust gas to flow from the EGR valve to the EGR exhaust gas confluence point, and calculates the change rate of the target EGR rate filter time coefficient.

[0074] Specifically, in this embodiment, the EGR system closed-loop enabling condition is:

[0075] (1) There are no related faults in the EGR system components;

[0076] (2) No fuel cut-off request occurs or the fuel cut-off recovery time exceeds the preset time. In this embodiment, the preset time is 0.3s;

[0077] (3) the updated filtered target EGR rate is not less than the minimum EGR rate;

[0078] (4) The engine speed is within a preset speed range. In this embodiment, the preset speed range is 750 rpm to 5500 rpm.

[0079] (5) The intake air temperature is within the preset range; if the current state is that the EGR closed loop is not enabled, then the EGR closed loop state is entered, and the minimum intake air temperature must be no less than 10°C; if the current state is the EGR closed loop enabled state, then the EGR system closed loop enabled state must be exited and the minimum intake air temperature must be 7°C lower; if the current state is that the EGR closed loop is not enabled, then the EGR closed loop state is entered, and the maximum intake air temperature must be no more than 60°C; if the current state is the EGR closed loop enabled state, then the EGR system closed loop enabled state must be exited and the maximum intake air temperature must be exceeded by 65°C;

[0080] (6) The engine water temperature is within the preset range; if the current state is that the EGR closed loop is not enabled, then the engine enters the EGR closed loop state, and the minimum water temperature must be no less than 60°C; if the current state is that the EGR closed loop is enabled, then the engine exits the EGR system closed loop enabled state and the minimum water temperature must be no less than 55°C; if the current state is that the EGR closed loop is not enabled, then the engine enters the EGR closed loop state and the maximum water temperature must be no more than 115°C; if the current state is that the EGR closed loop is enabled, then the engine exits the EGR system closed loop enabled state and the maximum water temperature must be no more than 120°C;

[0081] (7) The atmospheric temperature is within the preset range; if the current state is that the EGR closed loop is not enabled, then the EGR closed loop state is entered, and the minimum atmospheric temperature must be no less than 5°C; if the current state is that the EGR closed loop is enabled, then the EGR system closed loop enabled state must be exited, and the minimum atmospheric temperature must be 3°C lower than the minimum atmospheric temperature; if the current state is that the EGR closed loop is not enabled, then the EGR closed loop state is entered, and the maximum atmospheric temperature must be no more than 55°C; if the current state is that the EGR closed loop is enabled, then the EGR system closed loop enabled state must be exited, and the maximum atmospheric temperature must be exceeded by 60°C;

[0082] (8) When the atmospheric pressure exceeds 66 kPa, the EGR closed-loop enabling condition is allowed; when the atmospheric temperature is lower than 64 kPa, the EGR closed-loop enabling condition needs to be exited.

[0083] When the above conditions are met at the same time, the EGR system closed loop is enabled.

[0084] In this embodiment, the supercharger response time τ Boost It is the time for the mixture to flow from the supercharger compressor to the throttle outlet; supercharger response time τ Boost It is obtained through bench calibration. The specific method is: at different engine speeds n eng and different actual intake air density rho Act Under different EGR rates, the average value of the time it takes for the mixture to flow from the supercharger compressor to the throttle outlet is obtained through multiple sampling.

[0085] In this embodiment, the time τ for exhaust gas to flow from the EGR valve to the EGR exhaust gas confluence point is EGR It is obtained through bench calibration. The specific method is: at different engine speeds n eng and different actual intake air density rho Act Under different EGR rates, the average time of exhaust gas flowing from the EGR valve to the EGR exhaust gas confluence point is obtained through multiple sampling; the EGR exhaust gas confluence point refers to the place where the EGR exhaust gas and the fresh air converge. For details, see Figure 1 In this embodiment, the EGR exhaust gas confluence point refers to the location where the EGR exhaust gas and the fresh air converge at the outlet of the mixing valve 2.

[0086] Specifically, in this embodiment, according to the supercharger response time τ Boost and the time τ for exhaust gas to flow from the EGR valve to the EGR exhaust gas confluence point EGR Determine the filter time coefficient k of the target EGR rate T The method is:

[0087]

[0088] Among them, k T is the filter time coefficient of the target EGR rate, τ Boost is the supercharger response time, τ EGR It is the time for exhaust gas to flow from the EGR valve to the EGR exhaust gas confluence point.

[0089] Furthermore, in this embodiment, according to the filtering time coefficient k of the target EGR rate T Calculate the filter time coefficient k of the target EGR rate T The rate of change dk T The method is:

[0090]

[0091] Wherein, Δt is the sampling time. In this embodiment, Δt is 10ms. T (z) is the filter time coefficient k of the target EGR rate in the previous sampling cycle T The rate of change dk T , k T (z) is the filter time coefficient k of the previous sampling period T , the initial k T (z) occurs when the EGR closed loop is enabled, and its default value is 1. The dk at the initial moment T (z) occurs when the EGR closed loop is enabled, and its default value is 0, t c is a preset time constant. In this embodiment, t c Take 0.03s.

[0092] S2, obtaining the filtering time according to the filtering time learning coefficient and the change rate of the filtering time coefficient of the target EGR rate.

[0093] Specifically, in this embodiment, according to the filtering time learning coefficient r T and the filter time coefficient k of the target EGR rate T The rate of change dk T The method to obtain the filter time is:

[0094] T=f(dk T )×(1+r T );

[0095] Where T is the filtering time; r T is the filter time learning coefficient, which can be saved after the vehicle is powered off and can be continuously learned and updated during the vehicle's driving. Its default value is 0; f(dk T ) is the default filter time T, f(dk T ) is determined by the filter time coefficient k of the target EGR rate T The rate of change dkT Decision, see the table below:

[0096]

[0097] Specifically: when dk T When <-200, f(dk T )=0.15s; when dk T When >200, f(dk T )=0.18s; when -200≤dk T When <-100, f(dk T )=0.12s; when -100≤dk T When <-50, f(dk T )=0.1s; when -50≤dk T When <-10, f(dk T )=0.05s; when -10≤dk T When f(dk T )=0.01s; when 0≤dk T When <10, f(dk T )=0.05s; when 10≤dk T When <50, f(dk T )=0.12s; when 50≤dk T When <100, f(dk T )=0.16s; when 100≤dk T When <200, f(dk T )=0.18s.

[0098] Specifically, in this embodiment, the filter time learning coefficient judgment condition is:

[0099] (1) The engine speed fluctuation does not exceed a preset value, which in this embodiment is ±15 rpm;

[0100] (2) The actual intake air density fluctuation does not exceed a preset value, which is ±20 mgpl in this embodiment;

[0101] (3) EGR system closed loop enable;

[0102] (4) The difference between the target boost pressure and the system maximum boost pressure and the system minimum boost pressure exceeds a preset value, which is 10 kPa in this embodiment;

[0103] (5) The difference between the maximum system boost pressure and the target boost pressure exceeds a preset value, which is 10 kPa in this embodiment;

[0104] (6) The engine water temperature does not exceed a preset value, which is 100° C. in this embodiment;

[0105] (7) The engine intake temperature does not exceed a preset value, which is 65°C in this embodiment.

[0106] It can be understood that in this embodiment, the filter time learning coefficient has an initial value of 0. After operation, the specific method of calculating and updating according to the target boost pressure, the actual boost pressure, the target air-fuel ratio, the actual air-fuel ratio, the target EGR rate, the actual EGR rate, the updated filtered target EGR rate, the cumulative number of high-intensity knocks of the engine, and the catalyst oxygen storage capacity coefficient is as follows: when the time for satisfying the filter time learning coefficient judgment condition exceeds the preset time t1, read the average value p of the difference between the target boost pressure and the actual boost pressure within the time t1: BoostErrAvg ; The average value of the difference between the target air-fuel ratio and the actual air-fuel ratio r AFRErrAvg ; The average value of the difference between the updated filtered target EGR rate and the actual EGR rate r EGRErrAvg ; The average value of the target EGR rate after filtering r EGRDsrdFilterAvg ; Target EGR rate average value r EGRDsrdRawAvg ; The cumulative number of high-intensity knocks that occur in the engine Cnt Knock ; Catalyst oxygen storage capacity coefficient r CatalystOxygen ; The target EGR rate acquisition method is referred to the patent publication number CN112459910A "A Target EGR Rate Calculation Method and System"; The actual EGR rate acquisition method is the prior art; The cumulative number of high-intensity knocks in the engine Cnt Knock For the method of obtaining , please refer to the patent with publication number CN111878279A "A method and system for self-learning of oil octane number", for the method of reading the oxygen storage capacity of the catalyst, please refer to the patent with publication number CN110259553A "A method, device and electronic device for calculating the oxygen storage capacity of a three-way catalyst", and for the method of reading the maximum oxygen storage capacity of the catalyst, please refer to the patent with publication number CN104594986A "A method for diagnosing engine catalyst degradation";

[0107] Get the filter time learning coefficient r T The specific methods are as follows:

[0108] Case 1: If the updated filtered target EGR rate average value r EGRDsrdFilterAvg Greater than the target EGR rate average value r EGRDsrdRawAvg The value of exceeds the preset value, which is 0.05 in this embodiment, indicating that the EGR rate is decreasing. Then, the following first condition, second condition, third condition, fourth condition, and fifth condition are judged in sequence to adjust the filter time learning coefficient r T Calculate and update:

[0109] The first condition: If the cumulative number of high-intensity knocks CntKnock ≥CNT1, where CNT1 is a preset value. In this embodiment, CNT1 is 5, and |p BoostErrAvg |≥p1, and |r EGRErrAvg |≤0.01, where p1 is a preset value. In this embodiment, p1 is 4 kPa, then r T =r T (z)+0.02, and Cnt Knock Clear and restart counting, where r T (z) is the filter time learning coefficient r stored in the last learning update T Learning value;

[0110] Second condition: If the cumulative number of high-intensity knocks Cnt occurs Knock ≥CNT1, where CNT1 is a preset value. In this embodiment, CNT1 is 5, and |r EGRErrAvg |≤0.01, then r T =r T (z)+0.01, where r T (z) is the filter time learning coefficient r stored in the last learning update T Learning value;

[0111] The third condition: If |r AFRErrAvg |≤0.01, and |p BoostErrAvg |≤p2, where p2 is a preset value. In this embodiment, p2 is 2 kPa, and |r EGRErrAvg |≤0.01, and r CatalystOxygen ≤r C , where r C is a preset value. In this embodiment, C Take 0.2, then r T =r T (z)-0.03, where r T (z) is the filter time learning coefficient r stored in the last learning update T Learning value;

[0112] Fourth condition: If |r AFRErrAvg |≤0.01, and |p BoostErrAvg |≤p2, where p2 is a preset value. In this embodiment, p2 is 2 kPa, and |r EGRErrAvg |≤0.01, then r T =r T (z)-0.01, where r T (z) is the filter time learning coefficient r stored in the last learning update T Learning value;

[0113] Fifth condition: In other cases, r T =rT (z), where r T (z) is the filter time learning coefficient r stored in the last learning update T Learning value;

[0114] In particular, it should be noted that the priorities of the first condition, the second condition, the third condition, the fourth condition, and the fifth condition are lower and lower, that is, if the previous conditions are met, only the previous update results are executed; for example, when the first condition is met, only the update results of the first condition are executed, and the update results of the following conditions are not executed;

[0115] Second case: If the target EGR rate average value r EGRDsrdRawAvg Greater than the average value of the target EGR rate after filtering r EGRDsrdFilterAvg The value of exceeds the preset value, which is 0.05 in this embodiment, indicating that the EGR rate is increasing. Then, the following sixth condition, seventh condition, eighth condition, ninth condition, and tenth condition are judged in sequence to adjust the filter time learning coefficient r T Calculate and update:

[0116] Sixth condition: If the cumulative number of high-intensity knocks Cnt Knock ≥CNT1, where CNT1 is a preset value. In this embodiment, CNT1 is 5, and |p BoostErrAvg |≥p1, and |r EGRErrAvg |≤0.01, where p1 is a preset value. In this embodiment, p1 is 4 kPa, then r T =r T (z)+0.03, and Cnt Knock Clear and restart counting, where r T (z) is the filter time learning coefficient r stored in the last learning update T Learning value;

[0117] Seventh condition: If the cumulative number of high-intensity knocks Cnt Knock ≥CNT1, where CNT1 is a preset value. In this embodiment, CNT1 is 5, and |r EGRErrAvg |≤0.01, then r T =r T (z)+0.01, where r T (z) is the filter time learning coefficient r stored in the last learning update T Learning value;

[0118] Condition 8: If |r AFRErrAvg |≤0.01, and |p BoostErrAvg |≤p2, where p2 is a preset value. In this embodiment, p2 is 2 kPa, and |r EGRErrAvg |≤0.01, and rCatalystOxygen ≤r C , where r C is a preset value. In this embodiment, C Take 0.2, then r T =r T (z)-0.02, where r T (z) is the filter time learning coefficient r stored in the last learning update T Learning value;

[0119] Ninth condition: If |r AFRErrAvg |≤0.01, and |p BoostErrAvg |≤p2, where p2 is a preset value. In this embodiment, p2 is 2 kPa, and |r EGRErrAvg |≤0.01, then r T =r T (z)-0.01, where r T (z) is the filter time learning coefficient r stored in the last learning update T Learning value;

[0120] Tenth Condition: In other cases, r T =r T (z), where r T (z) is the filter time learning coefficient r stored in the last learning update T Learning value;

[0121] In particular, it should be noted that the priorities of the sixth condition, the seventh condition, the eighth condition, the ninth condition, and the tenth condition are getting lower and lower, that is, if the previous conditions are met, only the previous update results are executed; for example, when the sixth condition is met, only the update results of the sixth condition are executed, and the update results of the following conditions are not executed;

[0122] The third case: In other cases that neither the first nor the second case is satisfied, r T =r T (z), where r T (z) is the filter time learning coefficient r stored in the last learning update T Learning value.

[0123] S3, obtaining the filtered target EGR rate according to the filtering time and the target EGR rate.

[0124] Specifically, in this embodiment, the filtered target EGR rate r is obtained according to the filtering time and the target EGR rate. EGRDsrdFilter The method is:

[0125]

[0126] Among them, rEGRDsrdFilter (N) is the target EGR rate after filtering in the Nth sampling period r EGRDsrdFilter , r EGRDsrdFilter (N-1) is the target EGR rate after filtering in the N-1th sampling period. EGRDsrdFilter , Δt is the sampling time. In this embodiment, Δt is 10ms, N=1, 2, 3…, where r EGRDsrdFilter (0) is equal to 0, which occurs when the vehicle is powered on, r EGRDsrdRaw is the target EGR rate, r EGRDsrdRaw (N) is the target EGR rate of the Nth sampling cycle, and T is the filtering time.

[0127] S4: Control the EGR valve according to the filtered target EGR rate.

[0128] Specifically, in this embodiment, after the filtered target EGR rate is obtained, the EGR valve is actively controlled to achieve that the actual EGR pressure follows the target EGR pressure.

[0129] In summary, the target EGR rate optimization control method provided by the present invention can optimize the target EGR rate, improve the effect of EGR entry on the deterioration of engine knock, and improve the engine boost control stability and emission performance.

[0130] It should be pointed out that, according to the needs of implementation, the various steps described in this application can be divided into more steps, or two or more steps or partial operations of the steps can be combined into a new step to achieve the purpose of the present invention.

[0131] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for optimizing the control of a target EGR rate, characterized in that: include: Entering EGR closed-loop enabling when the EGR system closed-loop enabling conditions are met, determining a filter time coefficient of a target EGR rate according to a supercharger response time and a time for exhaust gas to flow from an EGR valve to an EGR exhaust gas confluence point, and calculating a change rate of the filter time coefficient of the target EGR rate; Acquire the filtering time according to the filtering time learning coefficient and the change rate of the filtering time coefficient of the target EGR rate; Obtaining a filtered target EGR rate according to the filtering time and the target EGR rate; controlling the EGR valve according to the filtered target EGR rate; The filter time learning coefficient has an initial value, and after operation, it is calculated and updated based on the target boost pressure, actual boost pressure, target air-fuel ratio, actual air-fuel ratio, target EGR rate, actual EGR rate, the updated filtered target EGR rate, the cumulative number of high-intensity knocks occurring in the engine, and the catalyst oxygen storage capacity coefficient.

2. The method for optimizing the target EGR rate according to claim 1, characterized in that: The supercharger response time τ Boost is the time for the mixed gas to flow from the supercharger compressor to the throttle outlet; the supercharger response time τ Boost It is obtained through bench calibration. The specific method is: at different engine speeds n eng and different actual intake air density rho Act Under different EGR rates, the average value of the time it takes for the mixture to flow from the supercharger compressor to the throttle outlet is obtained through multiple sampling.

3. The method for optimizing the target EGR rate according to claim 2, characterized in that: The time τ for the exhaust gas to flow from the EGR valve to the EGR exhaust gas confluence point EGR It is obtained through bench calibration. The specific method is: at different engine speeds n eng and different actual intake air density rho Act Under different EGR rates, the average value of the time it takes for the exhaust gas to flow from the EGR valve to the EGR exhaust gas confluence point is obtained through multiple sampling; the EGR exhaust gas confluence point refers to the place where the EGR exhaust gas and the fresh air converge.

4. The method for optimizing the target EGR rate according to claim 3, characterized in that: According to the supercharger response time τ Boost and the time τ for exhaust gas to flow from the EGR valve to the EGR exhaust gas confluence point EGR Determine the filter time coefficient k of the target EGR rate T The method is: Among them, k T is the filter time coefficient of the target EGR rate, τ Boost is the supercharger response time, τ EGR It is the time for exhaust gas to flow from the EGR valve to the EGR exhaust gas confluence point.

5. The method for optimizing and controlling a target EGR rate according to claim 4, characterized in that: Calculate the filter time coefficient k of the target EGR rate T The rate of change dk T The method is: Where Δt is the sampling time, dk T (z) is the filter time coefficient k of the target EGR rate in the previous sampling cycle T The rate of change dk T , k T (z) is the filter time coefficient k of the previous sampling period T , the initial k T (z) occurs when the EGR closed loop is enabled, and its default value is 1. The dk at the initial moment T (z) occurs when the EGR closed loop is enabled, and its default value is 0, t c is the preset time constant.

6. The method for optimizing and controlling a target EGR rate according to claim 5, characterized in that: Learning coefficient r according to filter time T and the filtering time coefficient k of the target EGR rate T The rate of change dk T The method to obtain the filter time is: T=f(dk T )×(1+r T ); Where T is the filtering time; r T is the filter time learning coefficient, which can be saved after the vehicle is powered off and can be continuously learned and updated during the vehicle's driving. Its default value is 0; f(dk T ) is the default time of the filtering time T, f(dk T ) is determined by the filter time coefficient k of the target EGR rate T The rate of change dk T Decision, specifically: When dk T When <-200, f(dk T )=0.15s; when dk T When >200, f(dk T )=0.18s; when -200≤dk T When <-100, f(dk T )=0.12s; when -100≤dk T When <-50, f(dk T )=0.1s; when -50≤dk T When <-10, f(dk T )=0.05s; when -10≤dk T When f(dk T )=0.01s; when 0≤dk T When <10, f(dk T )=0.05s; when 10≤dk T When <50, f(dk T )=0.12s; when 50≤dk T When <100, f(dk T )=0.16s; when 100≤dk T When <200, f(dk T )=0.18s.

7. The method for optimizing and controlling a target EGR rate according to claim 6, characterized in that: The filter time learning coefficient has an initial value, and after operation, the specific method of calculating and updating according to the target boost pressure, the actual boost pressure, the target air-fuel ratio, the actual air-fuel ratio, the target EGR rate, the actual EGR rate, the updated filtered target EGR rate, the cumulative number of high-intensity knocks of the engine, and the catalyst oxygen storage capacity coefficient is as follows: when the time for satisfying the filter time learning coefficient judgment condition exceeds the preset time t1, read the average value p of the difference between the target boost pressure and the actual boost pressure within the time t1 BoostErrAvg ; The average value of the difference between the target air-fuel ratio and the actual air-fuel ratio r AFRErrAvg ; The average value of the difference between the updated filtered target EGR rate and the actual EGR rate r EGRErrAvg ; The average value of the target EGR rate after filtering r EGRDsrdFilterAvg ; Target EGR rate average value r EGRDsrdRawAvg ; The cumulative number of high-intensity knocks that occur in the engine Cnt Knock ; Catalyst oxygen storage capacity coefficient r CatalystOxygen ; Get the filtering time learning coefficient r T The specific methods are as follows: Case 1: If the updated filtered target EGR rate average value r EGRDsrdFilterAvg Greater than the target EGR rate average value r EGRDsrdRawAvg If the value exceeds the preset value, it means that the EGR rate is decreasing. Then the following first condition, second condition, third condition, fourth condition and fifth condition are judged in sequence to adjust the filter time learning coefficient r T Calculate and update: The first condition: If the cumulative number of high-intensity knocks Cnt Knock ≥CNT1, where CNT1 is the preset value, and |p BoostErrAvg |≥p1, and |r EGRErrAvg |≤0.01, where p1 is the preset value, then r T =r T (z)+0.02, and Cnt Knock Clear and restart counting, where r T (z) is the filter time learning coefficient r stored in the last learning update T Learning value; Second condition: If the cumulative number of high-intensity knocks Cnt occurs Knock ≥CNT1, where CNT1 is the preset value, and |r EGRErrAvg |≤0.01, then r T =r T (z)+0.01, where r T (z) is the filter time learning coefficient r stored in the last learning update T Learning value; The third condition: If |r AFRErrAvg |≤0.01, and |p BoostErrAvg |≤p2, where p2 is a preset value, and |r EGRErrAvg |≤0.01, and r CatalystOxygen ≤r C , where r C If r is the default value T =r T (z)-0.03, where r T (z) is the filter time learning coefficient r stored in the last learning update T Learning value; Fourth condition: If |r AFRErrAvg |≤0.01, and |p BoostErrAvg |≤p2, where p2 is a preset value, and |r EGRErrAvg |≤0.01, then r T =r T (z)-0.01, where r T (z) is the filter time learning coefficient r stored in the last learning update T Learning value; Fifth condition: In other cases, r T =r T (z), where r T (z) is the filter time learning coefficient r stored in the last learning update T Learning value; The priority of the first condition, the second condition, the third condition, the fourth condition, and the fifth condition is getting lower and lower, that is, if the previous condition is met, only the previous update result is executed; Case 2: If the target EGR rate average value r EGRDsrdRawAvg Greater than the updated filtered target EGR rate average r EGRDsrdFilterAvg If the value exceeds the preset value, it means that the EGR rate is increasing. Then the following sixth condition, seventh condition, eighth condition, ninth condition and tenth condition are judged in sequence to adjust the filter time learning coefficient r T Calculate and update: Sixth condition: If the cumulative number of high-intensity knocks Cnt Knock ≥CNT1, where CNT1 is the preset value, and |p BoostErrAvg |≥p1, and |r EGRErrAvg |≤0.01, where p1 is the preset value, then r T =r T (z)+0.03, and Cnt Knock Clear and restart counting, where r T (z) is the filter time learning coefficient r stored in the last learning update T Learning value; Seventh condition: If the cumulative number of high-intensity knocks Cnt Knock ≥CNT1, where CNT1 is the preset value, and |r EGRErrAvg |≤0.01, then r T =r T (z)+0.01, where r T (z) is the filter time learning coefficient r stored in the last learning update T Learning value; Eighth condition: If |r AFRErrAvg |≤0.01, and |p BoostErrAvg |≤p2, where p2 is a preset value, and |r EGRErrAvg |≤0.01, and r CatalystOxygen ≤r C , where r C If r is the default value T =r T (z)-0.02, where r T (z) is the filter time learning coefficient r stored in the last learning update T Learning value; Ninth condition: If |r AFRErrAvg |≤0.01, and |p BoostErrAvg |≤p2, where p2 is a preset value, and |r EGRErrAvg |≤0.01, then r T =r T (z)-0.01, where r T (z) is the filter time learning coefficient r stored in the last learning update T Learning value; Tenth Condition: In other cases, r T =r T (z), where r T (z) is the filter time learning coefficient r stored in the last learning update T Learning value; The priorities of the sixth, seventh, eighth, ninth and tenth conditions above are getting lower and lower, that is, if the previous conditions are met, only the previous update results are executed; Third case: In other cases where neither the first case nor the second case is satisfied, r T =r T (z), where r T (z) is the filter time learning coefficient r stored in the last learning update T Learning value.

8. The method for optimizing and controlling a target EGR rate according to claim 7, characterized in that: Obtain the filtered target EGR rate r according to the filtering time and the target EGR rate EGRDsrdFilter The method is: Among them, r EGRDsrdFilter (N) is the target EGR rate after filtering in the Nth sampling period r EGRDsrdFilter , r EGRDsrdFilter (N-1) is the target EGR rate after filtering in the N-1th sampling period. EGRDsrdFilter , Δt is the sampling time, N = 1, 2, 3..., where r EGRDsrdFilter (0) is equal to 0, which occurs when the vehicle is powered on, r EGRDsrdRaw is the target EGR rate, r EGRDsrdRaw (N) is the target EGR rate of the Nth sampling cycle, and T is the filtering time.

9. The method for optimizing and controlling a target EGR rate according to claim 7, characterized in that: The filter time learning coefficient judgment condition is: (1) The engine speed fluctuation does not exceed the preset value; (2) The actual intake air density fluctuation does not exceed the preset value; (3) EGR system closed loop enable; (4) The difference between the target boost pressure and the system maximum boost pressure or the system minimum boost pressure exceeds the preset value; (5) The difference between the system maximum boost pressure and the target boost pressure exceeds the preset value; (6) The engine water temperature does not exceed the preset value; (7) The engine intake temperature does not exceed the preset value.

10. The method for optimizing and controlling a target EGR rate according to claim 1, characterized in that: The EGR system closed-loop enabling condition is: (1) There are no related faults in the EGR system parts; (2) No fuel cut request occurs or the fuel cut recovery time exceeds the preset time; (3) the updated filtered target EGR rate is not less than the minimum EGR rate; (4) The engine speed is within the preset speed range; (5) The intake air temperature is within the preset range; (6) The engine water temperature is within the preset range; (7) The atmospheric temperature is within the preset range; (8) When the atmospheric pressure exceeds 66 kPa, the EGR closed-loop enabling condition is allowed; when the atmospheric temperature is lower than 64 kPa, the EGR closed-loop enabling condition needs to be exited.

11. The method for optimizing and controlling a target EGR rate according to claim 10, characterized in that: The intake air temperature within the preset range specifically includes: if the current state is that the EGR closed-loop is not enabled, then entering the EGR closed-loop state, it is necessary to ensure that the intake air temperature is not lower than the minimum intake air temperature of 10°C; if the current state is the EGR closed-loop enabled state, then exiting the EGR system closed-loop enabled state requires ensuring that the intake air temperature is lower than the minimum intake air temperature of 7°C; if the current state is that the EGR closed-loop is not enabled, then entering the EGR closed-loop state, it is necessary to ensure that the maximum intake air temperature does not exceed 60°C; if the current state is the EGR closed-loop enabled state, then exiting the EGR system closed-loop enabled state requires ensuring that the maximum intake air temperature exceeds 65°C.

12. The method for optimizing and controlling a target EGR rate according to claim 10, characterized in that: The engine water temperature within the preset range specifically includes: if the current state is that the EGR closed loop is not enabled, then entering the EGR closed loop state, it is necessary to ensure that the water temperature is not lower than the minimum water temperature of 60°C; if the current state is the EGR closed loop enabled state, then exiting the EGR system closed loop enabled state requires to ensure that the water temperature is lower than the minimum water temperature of 55°C; if the current state is that the EGR closed loop is not enabled, then entering the EGR closed loop state, it is necessary to ensure that the water temperature does not exceed the maximum water temperature of 115°C; if the current state is the EGR closed loop enabled state, then exiting the EGR system closed loop enabled state requires to ensure that the water temperature exceeds the maximum water temperature of 120°C.

13. The method for optimizing and controlling a target EGR rate according to claim 10, characterized in that: The atmospheric temperature within the preset range specifically includes: if the current state is that the EGR closed-loop is not enabled, then entering the EGR closed-loop state, it is necessary to ensure that the atmospheric temperature is not lower than the minimum atmospheric temperature of 5°C; if the current state is the EGR closed-loop enabled state, then exiting the EGR system closed-loop enabled state requires to ensure that the atmospheric temperature is lower than the minimum atmospheric temperature of 3°C; if the current state is that the EGR closed-loop is not enabled, then entering the EGR closed-loop state, it is necessary to ensure that the atmospheric temperature does not exceed the maximum atmospheric temperature of 55°C; if the current state is the EGR closed-loop enabled state, then exiting the EGR system closed-loop enabled state requires to ensure that the atmospheric temperature exceeds the maximum atmospheric temperature of 60°C.

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