A control method to improve the dynamic response of EGR rate

Abstract

The present invention provides a control method for improving the dynamic response of the EGR rate, comprising determining an updated basic correction coefficient and a dynamic correction coefficient; determining an initial value of a target pressure ratio across a mixing valve based on the updated basic correction coefficient and the dynamic correction coefficient; determining the target pressure ratio across the mixing valve under different EGR states based on the EGR state and the initial value of the target pressure ratio across the mixing valve; determining the effective area of ​​the mixing valve based on the target pressure ratio across the mixing valve; determining a target opening value of the mixing valve based on the effective area of ​​the mixing valve; repeatedly calculating the target pressure ratio across the mixing valve, the effective area of ​​the mixing valve, and the target opening value of the mixing valve at each sampling interval; and controlling a mixing valve drive motor based on the target opening value to ensure that the actual opening value follows the target opening value. The present invention dynamically updates the target pressure ratio of the mixing valve and stores it under steady-state conditions, thereby achieving adaptive control. Furthermore, a dynamic closed-loop method is used to control the target opening value of the mixing valve, thereby meeting EGR rate requirements.

Description

Technical Field

[0001] The present invention relates to the field of engine control, and in particular to a control method for improving the dynamic response of EGR rate. Background Art

[0002] Exhaust Gas Recirculation (EGR) draws exhaust gas from the exhaust system into the intake system. Research has shown that EGR systems offer advantages in improving emissions, reducing fuel consumption, and improving anti-knock performance. Controlling the mixing valve in low-pressure EGR systems is particularly important for improving the EGR rate.

[0003] In the existing technology, patent application number CN202011247319.6 "A method and system for calculating the target EGR rate" calculates the initial target EGR rate from the throttle opening, manifold pressure difference and minimum ignition angle. It can accurately calculate the target EGR rate, and introduce EGR control activation conditions to perform secondary corrections on the final target EGR rate, but does not consider the control accuracy of the target opening of the mixing valve; patent application number CN202110184826.8 "A method and system for controlling the target opening of an EGR mixing valve" corrects the target opening of the mixing valve according to various operating parameters, but does not consider the dynamic closed-loop control of the target opening of the mixing valve. Summary of the Invention

[0004] The main purpose of the present invention is to provide a control method for improving the dynamic response of the EGR rate, dynamically updating the target pressure ratio of the mixing valve, and storing it under steady-state conditions to achieve adaptive control of the mixing valve pressure ratio. At the same time, a dynamic closed-loop control method is used to control the target opening value of the mixing valve to achieve precise control of the target opening value, improve control accuracy, and meet the EGR rate requirements.

[0005] For this reason, the technical solution adopted in the present invention is:

[0006] Determine the updated basic correction coefficient and dynamic correction coefficient;

[0007] Determine the initial value of the target pressure ratio on both sides of the mixing valve according to the updated basic correction coefficient and dynamic correction coefficient;

[0008] Determine the target pressure ratio on both sides of the mixing valve under different EGR conditions according to the EGR state and the initial value of the target pressure ratio on both sides of the mixing valve;

[0009] Determine the effective area of ​​the mixing valve based on the target pressure ratio on both sides of the mixing valve;

[0010] Determine the target opening value of the mixing valve based on the effective area of ​​the mixing valve;

[0011] The target pressure ratio on both sides of the mixing valve, the effective area of ​​the mixing valve and the target opening value of the mixing valve are repeatedly calculated every time a sampling cycle is repeated;

[0012] According to the target opening value, the mixing valve drive motor is controlled to achieve the actual opening value following the target opening value.

[0013] According to the above scheme, the basic correction coefficient in the updated basic correction coefficient and dynamic correction coefficient is obtained specifically by the following method:

[0014] After all activation conditions are met, the basic correction coefficient enters the self-learning stabilization stage;

[0015] After the basic correction coefficient enters the self-learning stabilization stage for more than the preset time, the basic correction coefficient enters the self-learning activation stage;

[0016] The average value of the engine speed, the average value of the fresh air intake density entering the cylinder, the average value of the target EGR rate, and the average value of the atmospheric pressure for the continuous time after entering the self-learning activation phase are accumulated and read; the same engine speed, the fresh air intake density entering the cylinder, the target EGR rate, and the atmospheric pressure represent the same operating conditions;

[0017] After the continuous time is met, the basic correction coefficient enters the self-learning update stage, and the operating conditions corresponding to the average engine speed, the average fresh air intake density entering the cylinder, the target EGR rate, and the average atmospheric pressure for the continuous time after entering the self-learning activation stage, which are accumulated and read during the self-learning activation stage, are updated and stored, and the updated basic correction coefficient is calculated.

[0018] According to the above scheme, the dynamic correction coefficient in the basic correction coefficient and the dynamic correction coefficient after determination of the update is specifically obtained by the following method:

[0019] After all update conditions are met, read the continuous time that the initial value of the effective area of ​​the mixing valve is greater than its maximum value, the continuous time that the initial value of the effective area of ​​the mixing valve is less than its minimum value, the continuous time that the target opening filter value of the mixing valve is greater than the target opening of the mixing valve, and the continuous time that the target opening filter value of the mixing valve is less than the target opening of the mixing valve, and record the target pressure ratio status on both sides of the corresponding mixing valve:

[0020] If the initial value of the effective area of ​​the mixing valve is greater than its maximum value for a continuous period exceeding a preset time, the target pressure ratio state on both sides of the mixing valve is recorded as a state of excessively large target pressure ratio demand on both sides of the mixing valve;

[0021] If the initial value of the effective area of ​​the mixing valve is less than the minimum value for a continuous period exceeding a preset time, the target pressure ratio state on both sides of the mixing valve is recorded as a state where the target pressure ratio demand on both sides of the mixing valve is too small.

[0022] If the continuous time of the target opening filter value of the mixing valve being greater than the target opening of the mixing valve exceeds the preset time, the target pressure ratio state on both sides of the mixing valve is recorded as the target pressure ratio demand on both sides of the mixing valve is too large state 2;

[0023] If the continuous time when the target opening filter value of the mixing valve is less than the target opening of the mixing valve exceeds the preset time, the target pressure ratio state on both sides of the mixing valve is recorded as the target pressure ratio demand on both sides of the mixing valve is too small state 2;

[0024] The dynamic correction coefficient is updated according to the target pressure ratio status on both sides of the mixing valve.

[0025] According to the above scheme, the dynamic correction coefficient is updated according to the target pressure ratio state on both sides of the mixing valve as follows:

[0026] When it is detected that the target pressure ratio state on both sides of the mixing valve is the target pressure ratio demand on both sides of the mixing valve is too large (one state) and the target pressure ratio demand on both sides of the mixing valve is too large (two state), and it is not detected that the target pressure ratio state on both sides of the mixing valve is too small (one state) and the target pressure ratio demand on both sides of the mixing valve is not too small (two state), the dynamic correction coefficient is reduced;

[0027] When it is detected that the target pressure ratio state on both sides of the mixing valve is in the first state where the target pressure ratio demand on both sides of the mixing valve is too small and in the second state where the target pressure ratio demand on both sides of the mixing valve is too small, and it is not detected that the target pressure ratio state on both sides of the mixing valve is in the first state where the target pressure ratio demand on both sides of the mixing valve is too large and in the second state where the target pressure ratio demand on both sides of the mixing valve is too large, the dynamic correction coefficient is increased;

[0028] In other cases, the dynamic correction coefficient is equal to the dynamic correction coefficient updated when the condition for the last dynamic correction coefficient update of the engine is met.

[0029] According to the above solution, the reduced dynamic correction coefficient is the updated dynamic correction coefficient when the dynamic correction coefficient is equal to 0.95 times the condition of the last dynamic correction coefficient update of the engine is met;

[0030] The increased dynamic correction coefficient is the updated dynamic correction coefficient when the dynamic correction coefficient is equal to 1.02 times the condition for the last dynamic correction coefficient update of the engine is met.

[0031] According to the above scheme, the activation conditions are specifically as follows:

[0032] The engine speed exceeds the preset value;

[0033] Enter the mixing valve activation state;

[0034] The initial value of the target pressure ratio on both sides of the current mixing valve is within the fluctuation range;

[0035] The deviation between the target boost pressure and the actual boost pressure does not exceed the preset value, so as to avoid affecting the boost control during the adjustment of the mixing valve pressure ratio;

[0036] The engine speed fluctuation range is within a certain preset range;

[0037] The density of fresh air entering the cylinder fluctuates within a certain preset range;

[0038] The target EGR rate fluctuation range is within a certain preset range;

[0039] The actual EGR rate fluctuation range is within a certain preset range;

[0040] The difference between the target EGR rate and the actual EGR rate fluctuates within a certain preset range;

[0041] The fluctuation range of the mixing valve pressure ratio difference is within a certain preset range;

[0042] The atmospheric pressure fluctuation range does not exceed a certain preset range.

[0043] According to the above scheme, the update conditions are specifically as follows:

[0044] The engine speed exceeds the preset value;

[0045] Enter the mixing valve activation state;

[0046] The initial value of the target pressure ratio on both sides of the current mixing valve is within the fluctuation range;

[0047] The deviation between the target boost pressure and the actual boost pressure does not exceed the preset value.

[0048] According to the above scheme, the initial value of the target pressure ratio on both sides of the mixing valve is determined based on the updated basic correction coefficient and dynamic correction coefficient in the following manner:

[0049] After the basic correction coefficient is updated, when the vehicle is powered on again after being completely powered off, the new initial value of the target pressure ratio on both sides of the mixing valve is calculated under the same operating conditions as during the self-learning activation phase of the basic correction coefficient.

[0050] After the dynamic correction coefficient is updated, when the mixing valve exits the mixing valve activation state and enters the mixing valve activation state again, a new initial value of the target pressure ratio on both sides of the mixing valve is calculated, and the target pressure ratio demand on both sides of the mixing valve is updated to the target pressure ratio demand on both sides of the non-mixing valve is too large in the first state, and the target pressure ratio demand on both sides of the non-mixing valve is too large in the second state, and the target pressure ratio demand on both sides of the non-mixing valve is too small in the first state, and the target pressure ratio demand on both sides of the non-mixing valve is too small in the second state.

[0051] According to the above scheme, the target pressure ratio on both sides of the mixing valve under different EGR conditions is determined according to the EGR state and the initial value of the target pressure ratio on both sides of the mixing valve by the following method:

[0052] If the EGR state is in the default state, the target pressure ratio on both sides of the mixing valve is set to 1; the default state is the closed state; the EGR state enters the default state when the vehicle is powered on;

[0053] If the EGR state is one of the ramp closed state, the ramp open state, and the ramp open state, the target pressure ratio on both sides of the mixing valve is obtained by limiting the initial value of the target pressure ratio on both sides of the mixing valve to a range from the maximum value to the minimum value;

[0054] If the EGR state enters the closed state from one of the three states of ramp closed state, open state and ramp open state, and the delay time is less than the preset time, the target pressure ratio on both sides of the mixing valve is obtained by limiting the initial value of the target pressure ratio on both sides of the mixing valve to a range from the maximum value to the minimum value; if the EGR state enters the closed state from one of the three states of ramp closed state, open state and ramp open state, and the delay time is not less than the preset time, the target pressure ratio on both sides of the mixing valve is set to 1;

[0055] Determine the operating conditions where the EGR state is the default state, and the EGR state enters the closed state from one of the ramp closed state, the open state, and the ramp open state, and the delay time is not less than the preset time as the mixing valve control inactive state;

[0056] The operating conditions in which the EGR state is one of the ramp closing state, the opening state and the ramp opening state, and the EGR state enters the closing state from one of the ramp closing state, the opening state and the ramp opening state, and the delay time is less than the preset time are determined as the mixing valve control activation state.

[0057] According to the above solution, the effective area of ​​the mixing valve is determined specifically by the following method:

[0058] Determine the actual pressure ratio on both sides of the mixing valve;

[0059] A mixing valve pressure ratio difference and a changing rate of the mixing valve pressure ratio difference are obtained based on the target pressure ratio on both sides of the mixing valve and the actual pressure ratio on both sides of the mixing valve, and a first-order low-pass filter is performed on the mixing valve pressure ratio difference and the changing rate of the mixing valve pressure ratio difference;

[0060] Determine the target intake air mass flow rate into the cylinder;

[0061] Determine the closed-loop dynamic flow of the mixing valve according to the mixing valve pressure ratio difference and the mixing valve pressure ratio difference change rate;

[0062] Determine the total target flow of the mixing valve based on the target intake mass flow entering the cylinder and the closed-loop dynamic flow of the mixing valve;

[0063] When the mixing valve is in a control-inactivated state, the effective area of ​​the mixing valve is equal to the maximum effective area of ​​the mixing valve, and the maximum effective area of ​​the mixing valve is determined by the characteristics of the mixing valve body;

[0064] When the mixing valve is in the control activation state, the initial value of the mixing valve effective area is calculated based on the total target flow of the mixing valve, the gas temperature at the air filter outlet, and the target pressure ratio on both sides of the mixing valve. The initial value of the mixing valve effective area is limited to a range from a minimum value to a maximum value to obtain the effective area of ​​the mixing valve when the mixing valve enters the activation state.

[0065] According to the above solution, the target opening value of the mixing valve is determined specifically by the following method:

[0066] Determine the initial value of the target opening of the mixing valve;

[0067] Performing a first-order low-pass filter on the initial value of the mixing valve target opening, and outputting a filtered value of the mixing valve target opening;

[0068] The change rate of the mixing valve target opening value is limited based on the mixing valve target opening filter value to obtain a final mixing valve target opening value.

[0069] According to the above solution, the total target flow of the mixing valve is obtained by adding the closed-loop dynamic flow of the mixing valve and the target intake mass flow entering the cylinder, minus the actual exhaust flow of the EGR valve.

[0070] According to the above scheme, the first-order low-pass filtering is performed on the initial value of the target opening of the mixing valve, specifically, the difference between the initial value of the target opening of the mixing valve and the filtered value of the target opening of the mixing valve in the previous sampling period, multiplied by the ratio of the sampling period to the filtering time coefficient, and the resultant is added to the filtered value of the target opening of the mixing valve in the previous sampling period.

[0071] The beneficial effects of the present invention are: the target pressure ratio of the mixing valve is dynamically updated from the perspective of the physical characteristics and protection of the mixing valve, and the dynamic update of the target pressure of the mixing valve is stored under steady-state conditions, thereby realizing adaptive control of the mixing valve pressure ratio. In order to avoid interference with the boost pressure accuracy during the control process, the control of the mixing valve pressure ratio is optimized, and at the same time, a dynamic closed-loop control method is used to control the target opening value of the mixing valve, thereby realizing precise control of the target opening value, improving the control accuracy, and meeting the EGR rate requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 Schematic diagram of the low-pressure EGR system;

[0073] Figure 2 Flow chart of the method of the present invention.

[0074] In the figure: 1-air filter, 2-flow meter, 3-mixing valve, 4-supercharger compressor, 5-oxygen sensor, 6-throttle, 7-engine, 8-supercharger turbine, 9-catalyst, 10-particulate matter trap, 11-EGR valve, 12-differential pressure sensor, 13-temperature sensor, 14-EGR cooler. DETAILED DESCRIPTION

[0075] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to 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.

[0076] like Figure 1 As shown, the low-pressure EGR system includes an air filter, a mixing valve, a supercharger compressor, a throttle body, an engine, a supercharger turbine, a catalyst, a particulate matter trap, an EGR cooler, an EGR valve, an EGR temperature sensor, an EGR differential pressure sensor, a flow meter, and a linear oxygen sensor.

[0077] Among them, the supercharger compressor is used to compress fresh air for supercharging; the supercharger turbine controls the working efficiency of the turbine by controlling the opening of the supercharger's wastegate valve, thereby achieving different supercharging capabilities;

[0078] At the same time, compared to a non-low-pressure EGR system, the low-pressure EGR system has the following additional components: an EGR cooler, an EGR temperature sensor, an EGR valve, an EGR differential pressure sensor, a mixing valve, a flowmeter, and an oxygen sensor. The flowmeter is installed between the air filter and the mixing valve to detect the flow of fresh air entering the engine. Some engines may not have a flowmeter installed. Estimating the flow of fresh air entering the engine by estimation is not within the scope of this invention. The mixing valve is used to adjust the pressure at the EGR valve outlet, increasing the pressure differential across the EGR valve and thus increasing the EGR rate. The oxygen sensor is installed between the compressor and the throttle, close to the throttle, to detect the flow of mixed air entering the cylinder. The EGR cooler cools the exhaust gas, facilitating increased exhaust gas flow and reduced exhaust gas temperature. The EGR valve has a throttling function, controlling the flow of exhaust gas entering the cylinder. The EGR temperature sensor detects the temperature of the exhaust gas entering the EGR valve. The EGR differential pressure sensor detects the pressure at the EGR inlet and outlet.

[0079] The present invention provides a closed-loop control method based on the mixing valve pressure ratio, which is used for the above low-pressure EGR system. If there is a dynamic correction of power demand, the control method of patent application number CN202211337426.7 "Calculation method, device, terminal device and storage medium of mixing valve target opening" is adopted. The present invention is mainly a control method for the mixing valve target opening when non-power demand has dynamic correction, so as to improve the control accuracy of EGR rate, such as Figure 2 As shown, the method includes the following steps:

[0080] S1. Determine the updated basic correction coefficient and dynamic correction coefficient, including:

[0081] S11. Determine the updated basic correction coefficient r Base .

[0082] S111. After all activation conditions are met, the basic correction coefficient enters the self-learning stabilization stage.

[0083] The activation conditions are specifically:

[0084] The engine speed exceeds the preset value. The higher the engine speed, the higher the pressure ratio requirement of the mixing valve, and the more pressure ratio correction is needed. In this example, the preset value is 1000 rpm.

[0085] Enter the mixing valve activation state;

[0086] The initial value of the target pressure ratio on both sides of the current mixing valve r MGVPrDesRaw Within the fluctuation range, the fluctuation range of this example is ±0.02;

[0087] The deviation between the target boost pressure and the actual boost pressure (see patent CN201910988050.8 "Exhaust Gas Turbine Engine Boost Closed-Loop Adaptive System and Control Method") does not exceed a preset value. This is to avoid affecting boost control during the mixing valve pressure ratio adjustment process. In this example, the preset value is ±2 kPa.

[0088] The engine speed fluctuation range is within a certain preset range, in this example ±20rpm;

[0089] The density of fresh air entering the cylinder fluctuates within a certain preset range, which in this example is ±15 mgpl;

[0090] The target EGR rate fluctuation range is within a certain preset range, which is ±0.1 in this example;

[0091] The actual EGR rate fluctuation range is within a certain preset range, which is ±0.1 in this example;

[0092] The difference between the target EGR rate and the actual EGR rate fluctuates within a certain preset range, which is ±0.1 in this example;

[0093] Mixing valve pressure ratio difference r MGVPrErr The fluctuation range is within a certain preset range, in this example it is ±0.1;

[0094] The atmospheric pressure fluctuation range does not exceed a certain preset range, which is ±0.5kPa in this example.

[0095] If any of the activation conditions is not met at any stage during the self-learning process, the self-learning process is terminated and the self-learning inactive stage is entered. When the above activation conditions are met, the self-learning process can be attempted, and the self-learning stabilization stage is entered first.

[0096] When entering the self-learning stabilization phase, the purpose of the stabilization phase is to ensure that the self-learning activation conditions are stable and reliable.

[0097] S112: After the basic correction coefficient enters the self-learning stabilization stage for a period exceeding a preset time and the activation condition is met, the basic correction coefficient enters the self-learning activation stage.

[0098] In this example, the preset time is 2s. If the basic correction coefficient enters the self-learning stabilization stage for no longer than the preset time and the activation conditions are met, the system remains in the self-learning stabilization stage. If the basic correction coefficient enters the self-learning stabilization stage for no longer than the preset time and the activation conditions are not met, the system returns to the self-learning inactive stage. If the basic correction coefficient enters the self-learning stabilization stage for longer than the preset time and the activation conditions are met, the system enters the self-learning active stage.

[0099] S113. Accumulate and read the average value of the engine speed, the average value of the fresh air intake density entering the cylinder, the average value of the target EGR rate, and the average value of the atmospheric pressure for the continuous time after entering the self-learning activation phase; the same engine speed, the fresh air intake density entering the cylinder, the target EGR rate, and the atmospheric pressure represent the same operating conditions.

[0100] In this example, the continuous time after entering the self-learning activation phase is 2s.

[0101] S114. After the continuous time is met, the basic correction coefficient enters the self-learning update stage, and the operating conditions corresponding to the average engine speed value, the average fresh air intake density entering the cylinder, the target EGR rate value, and the atmospheric pressure value accumulated during the self-learning activation stage are updated and stored, and the updated basic correction coefficient is calculated.

[0102] The basic correction coefficient r for different operating conditions (the same engine speed, fresh air intake density entering the cylinder, target EGR rate, and atmospheric pressure represent the same operating conditions) Base All will be stored in the non-volatile memory EEPROM. There will be an initial default in EEPROM, which is 0, and the basic correction coefficient r Base After self-learning is completed, the stored value in EEPROM is updated.

[0103] Basic correction coefficient r Base The calculation method is:

[0104] r Base =(1-k1)×r Base (z)+k1×r Dyn

[0105] Among them, r Base (z) is the basic correction coefficient r stored in the last self-learning update Base , k1 is the update weight coefficient, which is 0.8 in this example.

[0106] Basic correction coefficient r Base It can be saved after the vehicle is powered off.

[0107] S12. Determine the updated dynamic correction coefficient r Dyn .

[0108] S121. After all update conditions are met, read the continuous time that the initial value of the effective area of ​​the mixing valve is greater than its maximum value, the continuous time that the initial value of the effective area of ​​the mixing valve is less than its minimum value, the continuous time that the target opening filter value of the mixing valve is greater than the target opening of the mixing valve, and the continuous time that the target opening filter value of the mixing valve is less than the target opening of the mixing valve, and record the target pressure ratio status on both sides of the corresponding mixing valve.

[0109] If the initial value of the effective area of ​​the mixing valve is greater than its maximum value for a continuous period exceeding a preset time, the target pressure ratio state on both sides of the mixing valve is recorded as a state of excessively large target pressure ratio demand on both sides of the mixing valve;

[0110] If the initial value of the effective area of ​​the mixing valve is less than the minimum value for a continuous period exceeding a preset time, the target pressure ratio state on both sides of the mixing valve is recorded as a state where the target pressure ratio demand on both sides of the mixing valve is too small.

[0111] If the continuous time of the target opening filter value of the mixing valve being greater than the target opening of the mixing valve exceeds the preset time, the target pressure ratio state on both sides of the mixing valve is recorded as the target pressure ratio demand on both sides of the mixing valve is too large state 2;

[0112] If the continuous time that the target opening filter value of the mixing valve is less than the target opening of the mixing valve exceeds the preset time, the target pressure ratio state on both sides of the mixing valve is recorded as the target pressure ratio demand on both sides of the mixing valve is too small state 2.

[0113] The update conditions are specifically:

[0114] The engine speed exceeds the preset value. The higher the engine speed, the higher the pressure ratio requirement of the mixing valve, and the more pressure ratio correction is needed. In this example, the preset value is 1000 rpm.

[0115] Enter the mixing valve activation state;

[0116] The initial value of the target pressure ratio on both sides of the current mixing valve r MGVPrDesRaw Within the fluctuation range, the fluctuation range of this example is ±0.02;

[0117] The deviation between the target boost pressure and the actual boost pressure does not exceed a preset value. The purpose is to avoid affecting the boost control during the adjustment of the mixing valve pressure ratio. In this example, the preset value is ±2 kPa.

[0118] S122. Update the dynamic correction coefficient according to the target pressure ratio state on both sides of the mixing valve.

[0119] When it is detected that the target pressure ratio state of both sides of the mixing valve is the target pressure ratio demand on both sides of the mixing valve is too large, the target pressure ratio demand on both sides of the mixing valve is too large, and the target pressure ratio demand on both sides of the mixing valve is not detected, the target pressure ratio state of both sides of the mixing valve is too small, and the target pressure ratio demand on both sides of the mixing valve is not detected. This means that from the perspective of the physical characteristics and protection of the mixing valve, the pressure ratio of the mixing valve needs to be appropriately reduced. At this time, the dynamic correction coefficient decreases, and r Dyn =r Dyn (z)×0.95;

[0120] When it is detected that the target pressure ratio state of both sides of the mixing valve is the target pressure ratio demand on both sides of the mixing valve is too small, the target pressure ratio demand on both sides of the mixing valve is too small, and the target pressure ratio demand on both sides of the mixing valve is not detected, the target pressure ratio demand on both sides of the mixing valve is too large, and the target pressure ratio demand on both sides of the mixing valve is not detected. This means that the pressure ratio request of the mixing valve is too small. From the perspective of the physical characteristics and protection of the mixing valve, the pressure ratio of the mixing valve needs to be appropriately increased. At this time, the dynamic correction coefficient increases, and r Dyn =r Dyn (z)×1.02;

[0121] In other cases, r Dyn =r Dyn (z).

[0122] Among them, r Dyn (z) is the engine's last dynamic correction coefficient r Dyn The updated dynamic correction coefficient r when the update conditions are met Dyn .

[0123] In each dynamic correction factor r Dyn After the update conditions are met, the first two cases are updated at most once.

[0124] If the engine is stopped, the Dyn = 0, until the engine is started again and the dynamic correction coefficient r is updated after condition judgment. Dyn .

[0125] S2. Determine the initial value of the target pressure ratio on both sides of the mixing valve based on the updated basic correction coefficient and dynamic correction coefficient.

[0126] After the basic correction coefficient is updated, when the vehicle is powered on again after being completely powered off, the new initial value of the target pressure ratio on both sides of the mixing valve is calculated under the same operating conditions as when the basic correction coefficient self-learning was activated;

[0127] After the dynamic correction coefficient is updated, when the mixing valve exits the mixing valve activation state and enters the mixing valve activation state again, a new initial value of the target pressure ratio on both sides of the mixing valve is calculated, and the target pressure ratio demand on both sides of the mixing valve is updated to the target pressure ratio demand on both sides of the non-mixing valve is too large in the first state, and the target pressure ratio demand on both sides of the non-mixing valve is too large in the second state, and the target pressure ratio demand on both sides of the non-mixing valve is too small in the first state, and the target pressure ratio demand on both sides of the non-mixing valve is too small in the second state.

[0128] When the mixing valve is in the control activation state, the initial value of the target pressure ratio on both sides of the mixing valve is calculated. MGVPrDesRaw The calculation method is:

[0129]

[0130] Among them, p AirFilter is the real-time air filter outlet pressure, p1 is the maximum pressure allowed for EGR system activation (101 kPa in this example), and p2 is the minimum pressure allowed for EGR system activation (55 kPa in this example). Des ) is the target pressure ratio on both sides of the mixing valve when the atmospheric pressure is p1, f2(n,rho Des ) is the target pressure ratio on both sides of the mixing valve when the atmospheric pressure is p2. Des ) and f2(n,rho Des The calibration method of ) is to set the minimum pressure ratio on both sides of the mixing valve (the smaller the pressure ratio on both sides of the mixing valve, the greater the EGR rate) under the premise of meeting the pressure control accuracy and charging efficiency stability of the supercharging system at the corresponding atmospheric pressures p1 and p2, so as to achieve the EGR rate. Base The basic correction coefficient, the default value is 0, which can be saved after the vehicle is powered off; r DynIt is the dynamic correction coefficient, and its default value is 0.

[0131] The boost system's pressure control accuracy is evaluated by the deviation between actual and target boost pressures. The smaller the deviation, the higher the pressure control accuracy. This deviation can be determined based on individual projects. This project, assuming the target boost pressure remains constant, ultimately ensures the difference between the actual and target boost pressures is less than ±2kPa. The charging efficiency stability evaluation metric is the stability of the fresh air intake density entering the cylinder relative to the engine's requested fresh air intake density, with fluctuations within ±2%.

[0132] S3. Determine the target pressure ratios on both sides of the mixing valve under different EGR states according to the EGR state and the initial value of the target pressure ratios on both sides of the mixing valve.

[0133] Patent application number CN202011247319.6 "A method and system for calculating a target EGR rate" shows that there are four EGR states, namely, the closed state (Off state), the ramp closed state (Ramp Off state), the open state (On state) and the ramp open state (Ramp In state). The target pressure ratio on both sides of the mixing valve in different states is:

[0134] If the EGR state is in the default state, the target pressure ratio on both sides of the mixing valve is set to 1; the default state is the closed state; the EGR state enters the default state when the vehicle is powered on;

[0135] If the EGR state is one of the ramp closed state, the ramp open state, and the ramp open state, the target pressure ratio on both sides of the mixing valve is obtained by limiting the initial value of the target pressure ratio on both sides of the mixing valve to a range from the maximum value to the minimum value;

[0136] If the EGR state enters the closed state from one of the three states of ramp closed state, open state and ramp open state, and the delay time is less than the preset time, the target pressure ratio on both sides of the mixing valve is obtained by limiting the initial value of the target pressure ratio on both sides of the mixing valve to a range from the maximum value to the minimum value; if the EGR state enters the closed state from one of the three states of ramp closed state, open state and ramp open state, and the delay time is not less than the preset time, the target pressure ratio on both sides of the mixing valve is set to 1;

[0137] Determine the operating conditions where the EGR state is the default state, and the EGR state enters the closed state from one of the ramp closed state, the open state, and the ramp open state, and the delay time is not less than the preset time as the mixing valve control inactive state;

[0138] The operating conditions in which the EGR state is one of the ramp closing state, the opening state and the ramp opening state, and the EGR state enters the closing state from one of the ramp closing state, the opening state and the ramp opening state, and the delay time is less than the preset time are determined as the mixing valve control activation state.

[0139] In this example, the maximum value of the initial target pressure ratio on both sides of the mixing valve is set to 1, and the minimum value is set to 0.93 to prevent the supercharger oil from entering the compressor and damaging the compressor.

[0140] S4. Determine the effective area of ​​the mixing valve based on the target pressure ratio on both sides of the mixing valve under different conditions, specifically including:

[0141] S41. Determine the actual pressure ratio on both sides of the mixing valve.

[0142] Actual pressure ratio r on both sides of the mixing valve MGVPrAct : where p MGVOutAct is the outlet pressure of the mixing valve, the pressure p at the outlet of the EGR valve can be used EGRValveOutlet Instead, it is detected by the EGR valve differential pressure sensor.

[0143] S42. Obtain the mixing valve pressure ratio difference and the mixing valve pressure ratio difference change rate based on the target pressure ratio on both sides of the mixing valve and the actual pressure ratio on both sides of the mixing valve, and perform first-order low-pass filtering on the mixing valve pressure ratio difference and the mixing valve pressure ratio difference change rate.

[0144] The mixing valve pressure ratio difference is obtained by subtracting the actual pressure ratio on both sides of the mixing valve from the target pressure ratio on both sides of the mixing valve. The purpose of filtering is to avoid poor control robustness due to excessive pressure ratio fluctuations.

[0145] Among them, the first-order low-pass filtering algorithm for the mixing valve pressure ratio difference and the rate of change of the mixing valve pressure ratio difference is as follows:

[0146] x Filter (N) = K x ×[x Raw (N)-x Filter (N-1)]+x Filter (N-1)

[0147] Among them, x Raw is the signal before filtering, x Raw (N) is the signal before filtering in the Nth sampling period, x Filter is the filtered signal after filtering, x Filter (N) is the filtered signal of the Nth sampling period, x Filter (N-1) is the filtered signal of the N-1th sampling period, N = 1, 2, 3..., x Filter(0) is equal to the signal before filtering when the 0th sampling period (the 0th sampling period refers to the moment when the vehicle is powered on); in this example, the sampling period interval Δt 10ms; K x The coefficient is , and the mixing valve pressure ratio difference and the rate of change of the mixing valve pressure ratio difference in this example are taken as 0.13 and 0.1 respectively (the pressure ratio difference change rate fluctuates more violently, and its filter coefficient is updated to reduce the fluctuation range of the pressure ratio difference change rate).

[0148] S43: Determine the target intake air mass flow rate entering the cylinder.

[0149] Patent application number CN202210332492.9 "Target intake density control method, device, equipment and readable storage medium" can obtain the real-time target intake density rho entering the cylinder ReqFinal , and converted into the target intake mass flow rate dm entering the cylinder ReqCyl :

[0150] dm ReqCyl =rho ReqFinal ×n eng ×V×N / 120

[0151] Among them, n eng is the current engine speed, N is the number of engine cylinders, and V is the engine displacement.

[0152] S44. Determine the closed-loop dynamic flow rate of the mixing valve according to the mixing valve pressure ratio difference and the rate of change of the mixing valve pressure ratio difference.

[0153] Closed loop dynamic flow of mixing valve dm MGVCL is based on the mixing valve pressure ratio difference r MGVPrErr It is determined that the main purpose is to adjust the dynamic flow of the mixing valve to control the mixing valve pressure ratio difference to become smaller and smaller, so as to achieve the mixing valve pressure ratio.

[0154] Closed loop dynamic flow of mixing valve dm MGVCL =dm MGVCL_P +dm MGVCL_I , that is, the closed-loop dynamic flow of the mixing valve is obtained by adding the closed-loop dynamic flow P item of the mixing valve and the closed-loop dynamic flow I item of the mixing valve.

[0155] Among them, the closed-loop dynamic flow P part of the mixing valve is dm MGVCL_P :

[0156]

[0157] f1(r MGVPrErr ) is based on the mixing valve pressure ratio difference r MGVPrErr The initial value of the closed-loop dynamic flow P of the mixing valve is obtained by calibration.MGV It is the time for fresh air to flow from the mixing valve through the compressor to the throttle valve and then into the cylinder. This part is obtained through bench calibration. This part can be different for different engine speeds n eng and the actual intake air density rho of different cylinders Act The average value of multiple sampling data under the above conditions is obtained. λ is the time constant of PI dynamic control. The larger the λ, the smaller the P and I, and the slower the dynamic closed-loop adjustment; the smaller the λ, the larger the P and I, and the faster the dynamic closed-loop adjustment. TCGain (r MGVPrErr ,dr MGVPrErr ) is based on the mixing valve pressure ratio difference r MGVPrErr and the mixing valve pressure ratio difference change rate dr MGVPrErr The correction coefficient of the time constant λ, which is the difference in the mixing valve pressure ratio r MGVPrErr Or the mixing valve pressure ratio change rate dr MGVPrErr The smaller the absolute value, the larger the value, to avoid the mixing valve in the small pressure ratio difference (or rate of change) fluctuations caused by the boost control pressure also fluctuates, from the priority of the boost pressure closed loop control adjustment and then adjust the mixing valve pressure ratio difference, to avoid the boost and mixing valve adjustment conflict, to improve the boost pressure adjustment and mixing valve pressure ratio adjustment process of the pressure and mixing valve opening vibration problem. TCGain (r MGVPrErr ,dr MGVPrErr ) In the mixing valve pressure ratio difference r MGVPrErr Not more than ±0.4 or the mixing valve pressure ratio difference change rate dr MGVPrErr Not more than ±2(s -1 ) is greater than 1, otherwise k TCGain (r MGVPrErr ,dr MGVPrErr ) is equal to 1. k TCGain (r MGVPrErr ,dr MGVPrErr ) In the mixing valve pressure ratio difference r MGVPrErr Greater than ±0.4 or the mixing valve pressure ratio difference change rate dr MGVPrErr Greater than ±2(s -1 ) is based on the premise that the boost pressure remains unchanged, and the difference between the actual boost pressure and the target boost pressure can be guaranteed to be less than ±2kPa.

[0158] Closed loop dynamic flow of mixing valve I part dm MGVCL_I , is based on the closed-loop dynamic flow I cumulative value part of the mixing valve dm MGVCL_I_Increment Continuously accumulating:

[0159] dm MGVCL_I =dm MGVCL_I_Increment +dm MGVCL_I (z),

[0160] Among them, dm MGVCL_I (z) is the closed-loop dynamic flow I part of the mixing valve in the previous sampling period, which is 0 when the vehicle is powered on. In particular, when the mixing valve enters the inactive state, the closed-loop dynamic flow I part of the mixing valve dm MGVCL_I Reset to 0.

[0161] Among them, if the last sampling period (sampling period interval Δt ) The initial value A of the effective area of ​​the mixing valve is obtained MGVRaw (z) is equal to its maximum allowed value A MGVMax (The maximum effective area of ​​the mixing valve is determined by the mixing valve hardware and provided by the supplier), or the effective area of ​​the mixing valve A obtained in the previous sampling period MGVRaw (z) is equal to its minimum allowable value (the minimum effective area of ​​the mixing valve is determined by the mixing valve hardware and provided by the supplier), then the closed-loop dynamic flow I cumulative value part dm of the mixing valve MGVCL_I_Increment =0.

[0162] In other cases, dm MGVCL_I_Increment =dm MGVCL_I_IncrementRaw .

[0163] dm MGVCL_I_IncrementRaw It is the initial value of the accumulated value of the closed-loop dynamic flow I of the mixing valve, and its calculation method is:

[0164]

[0165] Among them, f2(r MGVPrErr ) are based on the mixing valve pressure ratio difference r MGVPrErr The initial value of the closed-loop dynamic flow I of the mixing valve is also obtained by calibration.

[0166] S45. Determine a total target flow rate of the mixing valve according to the target intake air mass flow rate entering the cylinder and the closed-loop dynamic flow rate of the mixing valve.

[0167] The final total target flow rate of the mixing valve is dm MGVFinal The calculation method is:

[0168] dm MGVFinal =dm MGVCL +dm ReqCyl -dm EGRValveAct

[0169] That is, the total target flow of the mixing valve is obtained by adding the closed-loop dynamic flow of the mixing valve and the target intake mass flow entering the cylinder, minus the actual exhaust flow of the EGR valve. MGVCL +dm ReqCylIt can also be considered as the total target flow rate of the mixed gas after the EGR exhaust gas and fresh air are mixed. The exhaust gas flow rate of the EGR valve is subtracted from it to obtain the total target flow rate dm of the mixing valve. MGVFinal .

[0170] Among them, dm EGRValveAct The actual exhaust gas flow rate of the EGR valve can be obtained by referring to the calculation method in patent application number CN202110633093.1 "A Cylinder Exhaust Gas Flow Estimation Method and System":

[0171] will p ExhMan Replaced with the gas pressure p at the EGR valve outlet EGRValveInlet 、 Replaced with the actual exhaust gas flow rate dm of the EGR valve EGRValveAct 、A ValveEff Replaced with the effective area A of the mixing valve MGVDsrd That's it.

[0172] In this calculation method, K Adaption It is the learning value of the effective area of ​​the EGR control valve, which is saved after the vehicle is powered off. Valve is the gas temperature of the EGR valve, p EGRValveInlet Detected by the EGR valve differential pressure sensor, R Exh is the gas constant of the exhaust gas, which is 290 J / (kg·K) in this example. Determined by calibration.

[0173] Finally, when the mixing valve is in the control inactive state, the effective area of ​​the mixing valve is equal to the maximum effective area of ​​the mixing valve, that is, A MGVDsrd =A MGVMax , where A MGVMax The maximum effective area of ​​the mixing valve is determined by the characteristics of the mixing valve body. In this example, it is 2550m 2 ;

[0174] When the mixing valve is in the control activation state, first determine the initial value A of the effective area of ​​the mixing valve according to the formula MGVRaw :

[0175]

[0176] Among them, R Air are other constants for fresh air. In this example, we take 287 J / (kg·K), T AirFilter is the gas temperature at the air filter outlet, which is replaced by the mixing valve inlet temperature in the present invention, φ(r MGVPrDes ) The target pressure ratio r on both sides of the mixing valve MGVPrDes The specific calibration parameters are determined based on the flow estimation of the mixing valve and the corresponding flow meter calibration results. In this example, the results are as follows:

[0177] <![CDATA[r MGVPrDes ]]> 0.5283 0.55 0.6 0.65 0.7 0.75 0.775 0.8 0.833 0.867 0.9 0.925 0.95 0.975 <![CDATA[φ(r MGVPrDes )]]> 0.685 0.684 0.677 0.662 0.638 0.605 0.584 0.561 0.524 0.478 0.423 0.371 0.308 0.154

[0178] Finally, the initial value of the effective area of ​​the mixing valve A MGVRaw Limited to a minimum value A MGVMin (In this example, 2.2m 2 ) to the maximum value A MGVMax The effective area A of the mixing valve when the mixing valve is activated is obtained. MGVDsrd .

[0179] S5. Determine the target opening value of the mixing valve based on the effective area of ​​the mixing valve, specifically including:

[0180] S51. Determine an initial value of the target opening of the mixing valve.

[0181] Mixing valve target opening initial value pct MGVDsrdRaw and mixing valve effective area A MGVDsrd The corresponding relationship is determined by the characteristics of the mixing valve body. In this example, the corresponding relationship between the initial value of the mixing valve target opening and the effective area of ​​the mixing valve is as follows:

[0182]

[0183]

[0184] Based on the above, the initial value of the mixing valve target opening pct is determined MGVDsrdRaw .

[0185] S52: Perform a first-order low-pass filter on the initial value of the target opening of the mixing valve, and output a filtered value of the target opening of the mixing valve.

[0186] The purpose of performing a first-order low-pass filter on the initial value of the target opening of the mixing valve is to avoid excessive changes in the opening of the mixing valve. The calculation method is:

[0187]

[0188] Among them, pct MGVDsrdFilt (z) is the target opening filter value of the mixing valve in the previous sampling period (its initial value is 0), T Filter is the filter time coefficient, T Filter =f3(r MGVPrErr )+Δ, the calibration basis is to avoid the mixing valve outlet pressure fluctuation exceeding ±2kPa / 10ms, and to avoid the mixing valve opening fluctuation exceeding ±1.2% / 10ms.

[0189] Among them, f3(r MGVPrErr ) is based on r MGVPrErrThe determined filtering time coefficient is larger when the pressure ratio difference is small, to avoid excessively aggressive control and mixing valve vibration;

[0190] To determine the deviation Δ, when the actual pressure ratio of the mixing valve is close to 1, the opening of the mixing valve is controlled to change slowly to avoid pressure fluctuations at the mixing valve outlet. The state rule for determining the deviation Δ is:

[0191] If the actual pressure ratio on both sides of the mixing valve is r MGVPrAct When it is greater than 0.97, the state of the deviation Δ is state 1;

[0192] If the actual pressure ratio on both sides of the mixing valve is r MGVPrAct When it is less than 0.95, the state of the deviation Δ is state 2;

[0193] In other cases, the state of the deviation Δ maintains the previous state. In particular, the default state is state 2;

[0194] In state 1, Δ=f(r MGVPrDes ); In state 2, Δ=t TCMin .

[0195] Among them, f(r MGVPrDes ) is the target pressure ratio r on both sides of the mixing valve MGVPrDes The corresponding relationship of the determined deviation time coefficient is:

[0196]

[0197] Among them, t TCMin is the filter time coefficient deviation. In this example, t TCMin Take 15ms.

[0198] S53: Limiting the change rate of the mixing valve target opening value based on the mixing valve target opening filter value to obtain a final mixing valve target opening value.

[0199] The purpose of this step is to prevent the mixing valve from changing too quickly when the mixing valve is close to its maximum position (100%) and minimum position (0%), which may damage the mixing valve drive motor. Based on this, the rate of change of the target opening value of the mixing valve is limited. The calibration of this example is as follows:

[0200] When the target opening value of the mixing valve increases, the maximum allowable rate of change is as follows:

[0201]

[0202] When the target opening value of the mixing valve decreases, the absolute value of the maximum allowable rate of change is as follows:

[0203]

[0204] S6. Repeat steps S3-S5 every time a sampling cycle is passed to realize dynamic closed-loop control of the target opening value of the mixing valve.

[0205] S7. According to the target opening value, the mixing valve drive motor is controlled to achieve that the actual opening value follows the target opening value.

[0206] It should be pointed out that, according to the needs of implementation, the various steps described in this application can be split into more steps, or two or more steps or partial operations of the steps can be combined into new steps / components to achieve the purpose of the present invention.

[0207] The size of the serial numbers of the steps in the above 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.

[0208] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all such improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A control method for improving the dynamic response of EGR rate, characterized in that: The method includes: Determine the updated basic correction coefficient and dynamic correction coefficient; Determine the initial value of the target pressure ratio on both sides of the mixing valve according to the updated basic correction coefficient and dynamic correction coefficient; Determine the target pressure ratio on both sides of the mixing valve under different EGR conditions according to the EGR state and the initial value of the target pressure ratio on both sides of the mixing valve; Determine the effective area of ​​the mixing valve based on the target pressure ratio on both sides of the mixing valve; Determine the target opening value of the mixing valve based on the effective area of ​​the mixing valve; The target pressure ratio on both sides of the mixing valve, the effective area of ​​the mixing valve and the target opening value of the mixing valve are repeatedly calculated every time a sampling cycle is repeated; According to the target opening value, the mixing valve drive motor is controlled to achieve the actual opening value following the target opening value.

2. A control method for improving the dynamic response of EGR rate according to claim 1, characterized in that: The basic correction coefficient in the updated basic correction coefficient and the dynamic correction coefficient is obtained specifically by the following method: After all activation conditions are met, the basic correction coefficient enters the self-learning stabilization stage; After the basic correction coefficient enters the self-learning stabilization stage for more than the preset time, the basic correction coefficient enters the self-learning activation stage; The average value of the engine speed, the average value of the fresh air intake density entering the cylinder, the average value of the target EGR rate, and the average value of the atmospheric pressure for the continuous time after entering the self-learning activation phase are accumulated and read; when the engine speed, the fresh air intake density entering the cylinder, the target EGR rate, and the atmospheric pressure are all the same, it means that the operating conditions are the same; After the continuous time is met, the basic correction coefficient enters the self-learning update stage, and the operating conditions corresponding to the average engine speed, the average fresh air intake density entering the cylinder, the target EGR rate, and the average atmospheric pressure for the continuous time after entering the self-learning activation stage are updated and stored, and the updated basic correction coefficient is calculated.

3. A control method for improving the dynamic response of EGR rate according to claim 2, characterized in that: The updated basic correction coefficient and the dynamic correction coefficient in the dynamic correction coefficient are specifically obtained by the following method: After all update conditions are met, read the continuous time that the initial value of the effective area of ​​the mixing valve is greater than its maximum value, the continuous time that the initial value of the effective area of ​​the mixing valve is less than its minimum value, the continuous time that the target opening filter value of the mixing valve is greater than the target opening of the mixing valve, and the continuous time that the target opening filter value of the mixing valve is less than the target opening of the mixing valve, and record the target pressure ratio status on both sides of the corresponding mixing valve: If the initial value of the effective area of ​​the mixing valve is greater than its maximum value for a continuous period exceeding a preset time, the target pressure ratio state on both sides of the mixing valve is recorded as a state of excessively large target pressure ratio demand on both sides of the mixing valve; If the initial value of the effective area of ​​the mixing valve is less than the minimum value for a continuous period exceeding a preset time, the target pressure ratio state on both sides of the mixing valve is recorded as a state where the target pressure ratio demand on both sides of the mixing valve is too small. If the continuous time of the target opening filter value of the mixing valve being greater than the target opening of the mixing valve exceeds the preset time, the target pressure ratio state on both sides of the mixing valve is recorded as the target pressure ratio demand on both sides of the mixing valve is too large state 2; If the continuous time when the target opening filter value of the mixing valve is less than the target opening of the mixing valve exceeds the preset time, the target pressure ratio state on both sides of the mixing valve is recorded as the target pressure ratio demand on both sides of the mixing valve is too small state 2; The dynamic correction coefficient is updated according to the target pressure ratio status on both sides of the mixing valve.

4. The control method for improving the dynamic response of the EGR rate according to claim 3, characterized in that: The dynamic correction coefficient is updated according to the target pressure ratio state on both sides of the mixing valve as follows: When it is detected that the target pressure ratio state on both sides of the mixing valve is the target pressure ratio demand on both sides of the mixing valve is too large (one state) and the target pressure ratio demand on both sides of the mixing valve is too large (two state), and it is not detected that the target pressure ratio state on both sides of the mixing valve is too small (one state) and the target pressure ratio demand on both sides of the mixing valve is not too small (two state), the dynamic correction coefficient is reduced; When it is detected that the target pressure ratio state on both sides of the mixing valve is in the first state where the target pressure ratio demand on both sides of the mixing valve is too small and in the second state where the target pressure ratio demand on both sides of the mixing valve is too small, and it is not detected that the target pressure ratio state on both sides of the mixing valve is in the first state where the target pressure ratio demand on both sides of the mixing valve is too large and in the second state where the target pressure ratio demand on both sides of the mixing valve is too large, the dynamic correction coefficient is increased; In other cases, the dynamic correction coefficient is equal to the dynamic correction coefficient updated when the condition for the last dynamic correction coefficient update of the engine is met.

5. The control method for improving the dynamic response of the EGR rate according to claim 4, characterized in that: The reduced dynamic correction coefficient is the updated dynamic correction coefficient when the dynamic correction coefficient is equal to 0.95 times the condition of the last dynamic correction coefficient update of the engine is met; The increased dynamic correction coefficient is the updated dynamic correction coefficient when the dynamic correction coefficient is equal to 1.02 times the condition for the last dynamic correction coefficient update of the engine is met.

6. The control method for improving the dynamic response of the EGR rate according to claim 2, characterized in that: The activation conditions are specifically: The engine speed exceeds the preset value; Enter the mixing valve activation state; The initial value of the target pressure ratio on both sides of the current mixing valve is within the fluctuation range; The deviation between the target boost pressure and the actual boost pressure does not exceed the preset value, so as to avoid affecting the boost control during the adjustment of the mixing valve pressure ratio; The engine speed fluctuation range is within a certain preset range; The density of fresh air entering the cylinder fluctuates within a certain preset range; The target EGR rate fluctuation range is within a certain preset range; The actual EGR rate fluctuation range is within a certain preset range; The difference between the target EGR rate and the actual EGR rate fluctuates within a certain preset range; The fluctuation range of the mixing valve pressure ratio difference is within a certain preset range; The atmospheric pressure fluctuation range does not exceed a certain preset range.

7. The control method for improving the dynamic response of the EGR rate according to claim 3, characterized in that: The update conditions are specifically: The engine speed exceeds the preset value; Enter the mixing valve activation state; The initial value of the target pressure ratio on both sides of the current mixing valve is within the fluctuation range; The deviation between the target boost pressure and the actual boost pressure does not exceed the preset value.

8. A control method for improving the dynamic response of the EGR rate according to any one of claims 1 to 3, characterized in that: The determination of the initial value of the target pressure ratio on both sides of the mixing valve based on the updated basic correction coefficient and the dynamic correction coefficient is specifically obtained by the following method: After the basic correction coefficient is updated, when the vehicle is powered on again after being completely powered off, the new initial value of the target pressure ratio on both sides of the mixing valve is calculated under the same operating conditions as during the self-learning activation phase of the basic correction coefficient. After the dynamic correction coefficient is updated, when the mixing valve exits the mixing valve activation state and enters the mixing valve activation state again, a new initial value of the target pressure ratio on both sides of the mixing valve is calculated, and the target pressure ratio demand on both sides of the mixing valve is updated to the target pressure ratio demand on both sides of the non-mixing valve is too large in the first state, and the target pressure ratio demand on both sides of the non-mixing valve is too large in the second state, and the target pressure ratio demand on both sides of the non-mixing valve is too small in the first state, and the target pressure ratio demand on both sides of the non-mixing valve is too small in the second state.

9. The control method for improving the dynamic response of the EGR rate according to claim 1, characterized in that: The target pressure ratios on both sides of the mixing valve under different EGR conditions are determined according to the EGR condition and the initial value of the target pressure ratios on both sides of the mixing valve by the following method: If the EGR state is in the default state, the target pressure ratio on both sides of the mixing valve is set to 1; the default state is the closed state; the EGR state enters the default state when the vehicle is powered on; If the EGR state is one of the ramp closed state, the ramp open state, and the ramp open state, the target pressure ratio on both sides of the mixing valve is obtained by limiting the initial value of the target pressure ratio on both sides of the mixing valve to a range from the maximum value to the minimum value; If the EGR state enters the closed state from one of the three states of ramp closed state, open state and ramp open state, and the delay time is less than the preset time, the target pressure ratio on both sides of the mixing valve is obtained by limiting the initial value of the target pressure ratio on both sides of the mixing valve to a range from the maximum value to the minimum value; if the EGR state enters the closed state from one of the three states of ramp closed state, open state and ramp open state, and the delay time is not less than the preset time, the target pressure ratio on both sides of the mixing valve is set to 1; Determine the operating conditions where the EGR state is the default state, and the EGR state enters the closed state from one of the ramp closed state, the open state, and the ramp open state, and the delay time is not less than the preset time as the mixing valve control inactive state; The operating conditions in which the EGR state is one of the ramp closing state, the opening state and the ramp opening state, and the EGR state enters the closing state from one of the ramp closing state, the opening state and the ramp opening state, and the delay time is less than the preset time are determined as the mixing valve control activation state.

10. The control method for improving the dynamic response of the EGR rate according to claim 1, characterized in that: The effective area of ​​the mixing valve is determined specifically by the following method: Determine the actual pressure ratio on both sides of the mixing valve; A mixing valve pressure ratio difference and a changing rate of the mixing valve pressure ratio difference are obtained based on the target pressure ratio on both sides of the mixing valve and the actual pressure ratio on both sides of the mixing valve, and a first-order low-pass filter is performed on the mixing valve pressure ratio difference and the changing rate of the mixing valve pressure ratio difference; Determine the target intake air mass flow rate into the cylinder; Determine the closed-loop dynamic flow of the mixing valve according to the mixing valve pressure ratio difference and the mixing valve pressure ratio difference change rate; Determine the total target flow of the mixing valve based on the target intake mass flow entering the cylinder and the closed-loop dynamic flow of the mixing valve; When the mixing valve is in a control-inactivated state, the effective area of ​​the mixing valve is equal to the maximum effective area of ​​the mixing valve, and the maximum effective area of ​​the mixing valve is determined by the characteristics of the mixing valve body; When the mixing valve is in the control activation state, the initial value of the mixing valve effective area is calculated based on the total target flow of the mixing valve, the gas temperature at the air filter outlet, and the target pressure ratio on both sides of the mixing valve. The initial value of the mixing valve effective area is limited to a range from a minimum value to a maximum value to obtain the effective area of ​​the mixing valve when the mixing valve enters the activation state.

11. The control method for improving the dynamic response of EGR rate according to claim 1, characterized in that: The target opening value of the mixing valve is determined specifically by the following method: Determine the initial value of the target opening of the mixing valve; Performing a first-order low-pass filter on the initial value of the mixing valve target opening, and outputting a filtered value of the mixing valve target opening; The change rate of the mixing valve target opening value is limited based on the mixing valve target opening filter value to obtain a final mixing valve target opening value.

12. The control method for improving the dynamic response of the EGR rate according to claim 10, characterized in that: The total target flow of the mixing valve is obtained by adding the closed-loop dynamic flow of the mixing valve and the target intake mass flow entering the cylinder, and then subtracting the actual exhaust gas flow of the EGR valve.

13. The control method for improving the dynamic response of the EGR rate according to claim 11, characterized in that: The first-order low-pass filtering of the initial value of the target opening of the mixing valve is specifically obtained by multiplying the difference between the initial value of the target opening of the mixing valve and the filtered value of the target opening of the mixing valve in the previous sampling period by the ratio of the sampling period to the filtering time coefficient, and adding the filtered value of the target opening of the mixing valve in the previous sampling period.

Images