A method for optimizing control of target boost pressure

Abstract

The present invention discloses a method for optimizing and controlling target boost pressure, comprising: entering boost closed-loop enablement when boost closed-loop enablement conditions are met, obtaining a filtered EGR rate characteristic coefficient after first-order low-pass filtering based on a filtering time and an EGR rate characteristic coefficient; calculating a target boost pressure that has not been dynamically optimized based on the currently disclosed target boost pressure, the EGR rate characteristic coefficient, and the filtered EGR rate characteristic coefficient; dynamically optimizing the target boost pressure that has not been dynamically optimized based on the actual boost pressure read in real time to obtain a dynamically optimized target boost pressure; and controlling a boost actuator based on the dynamically optimized target boost pressure. The method provided by the present invention can achieve optimized control of the target boost pressure, further improving boost closed-loop control stability and EGR response accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of engine control, and in particular to a method for optimizing control of a target boost pressure. Background Art

[0002] To respond to engine intake boost and torque requests, the boost system must be controlled to maximize exhaust energy and achieve boost pressure. Boost control also determines engine performance and fuel economy. Closed-loop boost control actively controls the action of the boost actuator to ensure that actual boost pressure tracks the target boost pressure. In non-closed-loop boost control, the boost actuator opening is not actively controlled. Therefore, research is needed to optimize the control of target boost pressure. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for optimizing the control of the target boost pressure, which can achieve optimized control of the target boost pressure and further improve the boost closed-loop control stability and EGR response accuracy.

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

[0005] Entering the boost closed-loop enablement state when the boost closed-loop enablement condition is met, obtaining a filtered EGR rate characteristic coefficient after first-order low-pass filtering based on the filtering time and the EGR rate characteristic coefficient; calculating a target boost pressure that has not been dynamically optimized based on the currently disclosed target boost pressure, the EGR rate characteristic coefficient, and the filtered EGR rate characteristic coefficient; this step optimizes the target boost pressure based on the EGR rate to ensure that after the EGR function is activated, an overshoot of the target boost pressure due to the dynamic change of the EGR rate due to the hysteresis of the actual EGR rate response occurs, thereby optimizing the target boost pressure;

[0006] dynamically optimizing the target boost pressure that has not been dynamically optimized according to the actual boost pressure read in real time to obtain a dynamically optimized target boost pressure;

[0007] The boost actuator is controlled according to the dynamically optimized target boost pressure.

[0008] In the above scheme, the specific method for obtaining the filtered EGR rate characteristic coefficient after first-order low-pass filtering according to the filtering time and the EGR rate characteristic coefficient is:

[0009]

[0010] Wherein, T is the filtering time, which is obtained by calibration; Δt is the sampling period; is the EGR rate characteristic coefficient; is the characteristic coefficient of the filtered EGR rate after the first-order low-pass filter in the Nth sampling period, is the characteristic coefficient of the filtered EGR rate after the first-order low-pass filter in the N-1th sampling period, N = 1, 2, 3, ..., where is the characteristic coefficient of the filtered EGR rate when the engine is just started, and

[0011] In the above solution, based on the currently disclosed target boost pressure, the EGR rate characteristic coefficient, and the filtered EGR rate characteristic coefficient, a specific method for calculating the target boost pressure without dynamic optimization is:

[0012]

[0013] Where p BoostReqUnDyn is the target boost pressure without dynamic optimization, p BoostReqRaw is the target boost pressure disclosed so far.

[0014] In the above solution, the method for obtaining the filtering time T is:

[0015] T=f(dm CylAir )

[0016] Where T is the filtering time, dm CylAir is the mass flow of fresh air entering the cylinder. The filter time T is obtained by a calibration method, specifically: when different engine speeds and different fresh air intake densities entering the cylinder are fixed, by adjusting the target EGR rate, the target boost pressure finally obtained is read when the overshoot under the stable working condition does not exceed the preset value. CylAir The time is taken as the filtering time T.

[0017] In the above solution, the target boost pressure that has not been dynamically optimized is dynamically optimized according to the actual boost pressure read in real time. The method of obtaining the dynamically optimized target boost pressure is specifically shown in the following three cases:

[0018] The first case: If the actual boost pressure p read in real time during this sampling period BoostAct The target boost pressure p after dynamic optimization of the previous sampling period is BoostReqDyn The absolute value of the difference does not exceed the preset value p1, p1>0, then the target boost pressure p after dynamic optimization BoostReqDyn In this sampling period, the target boost pressure p is updated without dynamic optimization. BoostReqUnDyn ;

[0019] Second case: During this sampling period, the actual boost pressure p is read in real time. BoostAct The target boost pressure p after dynamic optimization of the previous sampling period is BoostReqDyn The absolute value of the difference exceeds the preset value p1; the actual boost pressure p read in real time BoostAct Compared with the target boost pressure p without dynamic optimization BoostReqUnDyn The absolute value of the difference exceeds the preset value p2, and p2 is greater than p1. If the actual boost pressure p BoostAct Less than the target boost pressure p without dynamic optimization BoostReqUnDyn , then the target boost pressure p that is not dynamically optimized is BoostReqUnDyn -p2+C1 is the target boost pressure p after dynamic optimization BoostReqDyn , where C1 is the preset value; if the actual boost pressure p BoostAct Greater than the target boost pressure p without dynamic optimization BoostReqUnDyn , then the target boost pressure p that is not dynamically optimized is BoostReqUnDyn +p2-C1 is the target boost pressure p after dynamic optimization BoostReqDyn ;

[0020] The third case: In other cases, the target boost pressure p after dynamic optimization BoostReqDyn It is equal to the target boost pressure after dynamic optimization in the previous sampling period plus C2, where C2 is equal to the deviation Δ×k2, where k2 is the coefficient of variation and can be continuously updated and saved after the vehicle is powered off; the deviation Δ is equal to the target boost pressure p after dynamic optimization in the previous sampling period BoostReqDyn The actual boost pressure p read in real time BoostAct difference.

[0021] In the above solution, the updating method of the variation coefficient k2 is:

[0022] When the variation coefficient judgment condition is met, the counter CNT2 corresponding to the variation coefficient k2 is incremented by 1, and the default value of the counter CNT2 is 0;

[0023] If CNT2≤m2, then k2=k2(z), where m2 is a preset value and k2(z) is the coefficient of variation learned in the previous sampling period; in other cases, k2=k2(z)-0.03, and the counter CNT2 is cleared; this is to limit the boost pressure control from being too fast and thus accelerating the boost pressure deviation.

[0024] If the boost closed-loop enabling condition of the engine speed being greater than the preset value and the electronic pressure relief valve of the supercharger assembly not being open are not simultaneously met during consecutive driving cycles with CNT3 ≥ m3, then k2 = k2(z) + 0.01, and CNT3 is immediately cleared; where m3 is the preset value.

[0025] In the above solution, the variation coefficient k2 satisfies: 0.02≤k2≤0.8.

[0026] In the above scheme, the variation coefficient judgment condition is:

[0027] (1) Boost control is in closed-loop enabled state;

[0028] (2) The difference between the target EGR rate and the actual EGR rate exceeds the preset value;

[0029] (3) The difference between the target boost pressure and the actual boost pressure exceeds a preset value;

[0030] (4) There was no malfunction in the supercharging system and EGR system.

[0031] In the above scheme, the boost closed loop enabling condition is:

[0032] (1) The target pressure at the compressor outlet of the supercharger assembly is greater than the minimum boost pressure;

[0033] (2) The engine speed is greater than the preset value;

[0034] (3) The electronic pressure relief valve of the supercharger assembly is not open.

[0035] In the above solution, the compressor outlet target pressure of the supercharger assembly is calculated based on the target boost pressure, the gas temperature at the compressor inlet on the supercharger intake side, and the gas pressure and temperature before the throttle valve.

[0036] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0037] The present invention provides a method for optimizing the control of a target boost pressure. The method optimizes the boost closed-loop control in order to improve the pressure control stability when the boost enters the closed-loop and improve the boost responsiveness and EGR system responsiveness. Specifically, the target boost pressure is optimized, and learning parameters are continuously updated in the subsequent control process to further improve the boost closed-loop control stability and EGR response accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present invention. Throughout the drawings, the same reference figures denote the same components. In the drawings:

[0039] Figure 1 Schematic diagram of a low-pressure EGR system in an embodiment of the present invention.

[0040] Figure 2 Schematic diagram of the flow of the target boost pressure optimization control method in an embodiment of the present invention. DETAILED DESCRIPTION

[0041] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining 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 may be combined with each other as long as they do not conflict with each other.

[0042] It should be understood that the size of the serial numbers of the steps in the embodiment 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 embodiment of the present application.

[0043] Example 1

[0044] The system structure with low-pressure EGR system and exhaust gas turbocharging system based on the present invention includes air filter, mixing valve, supercharger compressor, throttle, engine, supercharger turbine, catalyst, particulate matter trap, EGR cooler, EGR valve, EGR temperature sensor, EGR pressure difference sensor, flow meter and linear oxygen sensor, such as Figure 1 As shown. 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 exhaust bypass valve, thereby achieving different supercharging capabilities; the low-pressure EGR system has the following additional components compared to the non-low-pressure EGR system: EGR cooler, EGR temperature sensor, EGR valve, EGR pressure difference sensor, mixing valve, flow meter and oxygen sensor; the flow meter is installed between the air filter and the mixing valve to detect the flow of fresh air entering the engine. The flow meter is an optional accessory and can be installed according to the vehicle model. It is optional. Select, if not selected, the estimation method will be used to obtain the corresponding information; the mixing valve is used to adjust the pressure at the EGR valve outlet, increase the pressure difference at both ends of the EGR valve, and increase the EGR rate; the oxygen sensor, which is also an optional accessory, is installed between the compressor and the throttle, close to the throttle, and is used to detect the mixture flow entering the cylinder; the EGR cooler is used to cool the exhaust gas, which is convenient for increasing the exhaust gas flow and reducing the exhaust gas temperature; the EGR valve acts as a throttling device to control the exhaust gas flow entering the cylinder; the EGR temperature sensor is used to detect the exhaust gas temperature entering the EGR valve; the EGR pressure difference sensor is used to detect the pressure at the EGR inlet and outlet.

[0045] According to one aspect of the present invention, an embodiment of the present application provides a method for optimizing and controlling a target boost pressure. Figure 2 ,include:

[0046] S1, enters the boost closed-loop enablement when the boost closed-loop enablement conditions are met, obtains the filtered EGR rate characteristic coefficient after first-order low-pass filtering based on the filtering time and the EGR rate characteristic coefficient; calculates the target boost pressure without dynamic optimization based on the currently disclosed target boost pressure, EGR rate characteristic coefficient and filtered EGR rate characteristic coefficient.

[0047] Specifically, in this embodiment, the boost closed-loop enabling condition and boost closed-loop enabling can be specifically referred to Chinese Patent Publication No. CN110748409A, wherein the boost closed-loop enabling condition is specifically:

[0048] (1) The target pressure at the compressor outlet of the supercharger assembly is greater than the minimum boost pressure;

[0049] (2) The engine speed is greater than a preset value; the preset value used in this embodiment is 1000 rpm;

[0050] (3) The electronic pressure relief valve of the supercharger assembly is not open.

[0051] When the above conditions (1) to (3) are met at the same time, the boost closed loop is enabled.

[0052] In this embodiment, the specific method for obtaining the filtered EGR rate characteristic coefficient after first-order low-pass filtering according to the filtering time and the EGR rate characteristic coefficient is:

[0053]

[0054] Wherein, T is the filtering time, which is obtained by calibration; Δt is the sampling period, which is 10ms in this embodiment; is the EGR rate characteristic coefficient; is the characteristic coefficient of the filtered EGR rate after the first-order low-pass filter in the Nth sampling period, is the characteristic coefficient of the filtered EGR rate after the first-order low-pass filter in the N-1th sampling period, N = 1, 2, 3, ..., where is the characteristic coefficient of the filtered EGR rate when the engine is just started, and

[0055] Specifically, the method for obtaining the filtering time T is:

[0056] T=f(dm CylAir )

[0057] Where T is the filtering time, dm CylAiris the fresh air mass flow entering the cylinder. The filter time T is obtained by a calibration method, specifically: when different engine speeds and different fresh air intake densities entering the cylinder are fixed, by adjusting the target EGR rate, the target boost pressure finally obtained is read when the overshoot under the stable working condition does not exceed the preset value (in this embodiment, ±3kPa), and the corresponding fresh air mass flow dm entering the cylinder is read. CylAir The time is taken as the filtering time T.

[0058] In this embodiment, based on the currently disclosed target boost pressure, EGR rate characteristic coefficient, and filtered EGR rate characteristic coefficient, a specific method for calculating the target boost pressure without dynamic optimization is as follows:

[0059]

[0060] Where p BoostReqUnDyn is the target boost pressure without dynamic optimization, p BoostReqRaw This is the currently disclosed target boost pressure.

[0061] S2, dynamically optimizing the target boost pressure that has not been dynamically optimized according to the actual boost pressure read in real time, to obtain a dynamically optimized target boost pressure.

[0062] Specifically, in this embodiment, the target boost pressure that has not been dynamically optimized is dynamically optimized according to the actual boost pressure read in real time. The method for obtaining the dynamically optimized target boost pressure is specifically as shown in the following three cases:

[0063] The first case: If the actual boost pressure p read in real time during this sampling period BoostAct The target boost pressure p after dynamic optimization of the previous sampling period is BoostReqDyn The absolute value of the difference does not exceed the preset value p1. In this embodiment, p1 is 3 kPa. The target boost pressure p after dynamic optimization is BoostReqDyn In this sampling period, the target boost pressure p is updated without dynamic optimization. BoostReqUnDyn ;

[0064] Second case: During this sampling period, the actual boost pressure p is read in real time. BoostAct The target boost pressure p after dynamic optimization of the previous sampling period is BoostReqDyn The absolute value of the difference exceeds the preset value p1; the actual boost pressure p read in real time BoostAct Compared with the target boost pressure p without dynamic optimization BoostReqUnDyn The absolute value of the difference exceeds the preset value p2. In this embodiment, p2 is 10 kPa. If the actual boost pressure p BoostAct Less than the target boost pressure p without dynamic optimizationBoostReqUnDyn , then the target boost pressure p that is not dynamically optimized is BoostReqUnDyn -p2+C1 is the target boost pressure p after dynamic optimization BoostReqDyn , where C1 is a preset value. In this embodiment, C1 is 3kPa. If the actual boost pressure p BoostAct Greater than the target boost pressure p without dynamic optimization BoostReqUnDyn , then the target boost pressure p that is not dynamically optimized is BoostReqUnDyn +p2-C1 is the target boost pressure p after dynamic optimization BoostReqDyn ;

[0065] The third case: In other cases, the target boost pressure p after dynamic optimization BoostReqDyn =Equal to the dynamically optimized target boost pressure in the previous sampling period plus C2, where C2 is equal to the deviation Δ×k2, where k2 is the coefficient of variation. In this embodiment, the default value of k2 is 0.35 and can be continuously updated and saved after the vehicle is powered off; the deviation Δ is equal to the dynamically optimized target boost pressure p in the previous sampling period. BoostReqDyn The actual boost pressure p read in real time BoostAct difference.

[0066] Specifically, the updating method of the variation coefficient k2 is:

[0067] When the variation coefficient judgment condition is met, the counter CNT2 corresponding to the variation coefficient k2 is incremented by 1, and the default value of the counter CNT2 is 0;

[0068] In this embodiment, the variation coefficient determination condition is:

[0069] (1) Boost control is in closed-loop enabled state;

[0070] (2) The difference between the target EGR rate and the actual EGR rate exceeds a preset value, which in this embodiment is ±0.2;

[0071] (3) The difference between the target boost pressure and the actual boost pressure exceeds a preset value, which in this embodiment is ±5 kPa;

[0072] (4) There was no malfunction in the supercharging system and EGR system.

[0073] If CNT2≤m2, then k2=k2(z), where m2 is a preset value. In this embodiment, the preset value m2 is 500, and k2(z) is the coefficient of variation learned in the previous sampling period. In other cases, k2=k2(z)-0.03, and the counter CNT2 is cleared.

[0074] If the boost closed-loop enabling condition of the engine speed being greater than the preset value and the electronic pressure relief valve of the supercharger assembly not being open are not simultaneously met during consecutive driving cycles with CNT3 ≥ m3, then k2 = k2(z) + 0.01, and CNT3 is immediately reset; where m3 is a preset value, which in this embodiment is 200.

[0075] In particular, the coefficient of variation k2 satisfies: 0.02≤k2≤0.8.

[0076] S3, controlling the boost actuator according to the dynamically optimized target boost pressure.

[0077] Specifically, in this embodiment, after the dynamically optimized target boost pressure is obtained, the action of the boost actuator is actively controlled to achieve tracking of the actual boost pressure with the target boost pressure.

[0078] In summary, the present invention provides a method for optimizing the control of a target boost pressure, which can achieve optimized control of the target boost pressure and further improve the boost closed-loop control stability and EGR response accuracy.

[0079] 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 to achieve the purpose of the present invention.

[0080] It will be easily understood by those skilled in the art that the above description is merely 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 scope of protection of the present invention.

Claims

1. A method for optimizing and controlling target boost pressure, characterized in that: include: When the boost closed loop enabling condition is met, the boost closed loop is enabled, and the filtered EGR rate characteristic coefficient after the first-order low-pass filter is obtained according to the filtering time and the EGR rate characteristic coefficient; Calculating a target boost pressure that is not dynamically optimized based on the currently disclosed target boost pressure, the EGR rate characteristic coefficient, and the filtered EGR rate characteristic coefficient; dynamically optimizing the target boost pressure that has not been dynamically optimized according to the actual boost pressure read in real time to obtain a dynamically optimized target boost pressure; controlling the boost actuator according to the dynamically optimized target boost pressure; The method of dynamically optimizing the target boost pressure that has not been dynamically optimized according to the actual boost pressure read in real time to obtain the dynamically optimized target boost pressure is specifically shown in the following three cases: The first case: If the actual boost pressure p read in real time during this sampling period BoostAct The target boost pressure p after dynamic optimization of the previous sampling period is BoostReqDyn The absolute value of the difference does not exceed the preset value p1, p1>0, then the target boost pressure p after dynamic optimization BoostReqDyn In this sampling period, the target boost pressure p is updated without dynamic optimization. BoostReqUnDyn ; Second case: During this sampling period, the actual boost pressure p is read in real time. BoostAct The target boost pressure p after dynamic optimization of the previous sampling period is BoostReqDyn The absolute value of the difference exceeds the preset value p1; the actual boost pressure p read in real time BoostAct Compared with the target boost pressure p without dynamic optimization BoostReqUnDyn The absolute value of the difference exceeds the preset value p2, and p2 is greater than p1. If the actual boost pressure p BoostAct Less than the target boost pressure p without dynamic optimization BoostReqUnDyn , then the target boost pressure p that is not dynamically optimized is BoostReqUnDyn -p2+C1 is the target boost pressure p after dynamic optimization BoostReqDyn , where C1 is the preset value; if the actual boost pressure p BoostAct Greater than the target boost pressure p without dynamic optimization BoostReqUnDyn , then the target boost pressure p that is not dynamically optimized is BoostReqUnDyn +p2-C1 is the target boost pressure p after dynamic optimization BoostReqDyn ; The third case: In other cases, the target boost pressure p after dynamic optimization BoostReqDyn It is equal to the target boost pressure after dynamic optimization in the previous sampling period plus C2, where C2 is equal to the deviation Δ×k2, where k2 is the coefficient of variation and can be continuously updated and saved after the vehicle is powered off; the deviation Δ is equal to the target boost pressure p after dynamic optimization in the previous sampling period BoostReqDyn The actual boost pressure p read in real time BoostAct difference.

2. The method for optimizing and controlling target boost pressure according to claim 1, characterized in that: The specific method for obtaining the filtered EGR rate characteristic coefficient after first-order low-pass filtering based on the filtering time and EGR rate characteristic coefficient is: Wherein, T is the filtering time, which is obtained by calibration; Δt is the sampling period; is the EGR rate characteristic coefficient; is the characteristic coefficient of the filtered EGR rate after the first-order low-pass filter in the Nth sampling period, is the characteristic coefficient of the filtered EGR rate after the first-order low-pass filter in the N-1th sampling period, N = 1, 2, 3, ..., where is the characteristic coefficient of the filtered EGR rate when the engine is just started, and 3. The method for optimizing and controlling target boost pressure according to claim 2, characterized in that: According to the currently disclosed target boost pressure, the EGR rate characteristic coefficient, and the filtered EGR rate characteristic coefficient, a specific method for calculating the target boost pressure without dynamic optimization is as follows: Where p BoostReqUnDyn is the target boost pressure without dynamic optimization, p BoostReqRaw is the target boost pressure disclosed so far.

4. The method for optimizing and controlling target boost pressure according to claim 2, wherein: The method for obtaining the filtering time T is: T=f(dm CylAir ) Where T is the filtering time, dm CylAir is the mass flow of fresh air entering the cylinder. The filter time T is obtained by a calibration method, specifically: when different engine speeds and different fresh air intake densities entering the cylinder are fixed, by adjusting the target EGR rate, the target boost pressure finally obtained is read when the overshoot under the stable working condition does not exceed the preset value. CylAir The time is taken as the filtering time T.

5. The method for optimizing and controlling target boost pressure according to claim 4, characterized in that: The updating method of the variation coefficient k2 is: When the variation coefficient judgment condition is met, the counter CNT2 corresponding to the variation coefficient k2 is incremented by 1, and the default value of the counter CNT2 is 0; If CNT2≤m2, then k2=k2(z), where m2 is a preset value and k2(z) is the coefficient of change learned in the previous sampling period; otherwise, k2=k2(z)-0.03, and the counter CNT2 is cleared; If the boost closed-loop enabling condition of the engine speed being greater than the preset value and the supercharger assembly's electronic pressure relief valve not being open are not met simultaneously during consecutive driving cycles with CNT2 ≥ m3, then k2 = k2(z) + 0.01 and CNT3 is immediately cleared; Where m3 is the preset value.

6. The method for optimizing and controlling target boost pressure according to claim 5, characterized in that: The variation coefficient k2 satisfies: 0.02≤k2≤0.

8.

7. The method for optimizing and controlling target boost pressure according to claim 5, characterized in that: The variation coefficient judgment condition is: (1) Boost control is in closed-loop enabled state; (2) The difference between the target EGR rate and the actual EGR rate exceeds the preset value; (3) The difference between the target boost pressure and the actual boost pressure exceeds a preset value; (4) There was no malfunction in the supercharging system and EGR system.

8. The method for optimizing and controlling target boost pressure according to claim 1, characterized in that: The boost closed loop enabling condition is: (1) The target pressure at the compressor outlet of the supercharger assembly is greater than the minimum boost pressure; (2) The engine speed is greater than the preset value; (3) The electronic pressure relief valve of the supercharger assembly is not open.

9. The method for optimizing and controlling target boost pressure according to claim 8, characterized in that: The target pressure at the compressor outlet of the supercharger assembly is calculated based on the target boost pressure, the gas temperature at the compressor inlet on the supercharger intake side, and the gas pressure and temperature before the throttle valve.

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