Control method, controller, and vehicle for low-pressure egr system

Abstract

A control method, controller, and vehicle for a low-pressure EGR system are disclosed. The low-pressure EGR system includes an air filter and an exhaust gas recirculation (EGR) valve arranged sequentially along an intake manifold. The method includes: acquiring the current EGR opening of the EGR valve, and acquiring the pressure and temperature before the air filter, the pressure after the air filter, and the pressure and temperature before the EGR valve; obtaining a first current EGR rate based on the current EGR opening, the pressure and temperature before the air filter, the pressure after the air filter, and the pressure and temperature before the EGR valve. This improves the estimation accuracy of the first current EGR rate.

Description

Technical Field

[0001] This disclosure relates to the field of vehicle technology, and in particular to a control method, controller, and vehicle for a low-pressure EGR system. Background Technology

[0002] In EGR (Exhaust Gas Recirculation) control, it is necessary to estimate the EGR flow rate. Related technologies first obtain the pressures before and after the EGR valve and the temperature before the EGR valve, then obtain the standard flow rates at various EGR opening degrees obtained from calibration, and finally obtain the EGR flow rate based on these parameters.

[0003] However, while the aforementioned techniques provide relatively accurate EGR flow estimation when the pressure ratio before and after the EGR valve is less than 0.95, slight changes in the pressure ratio can lead to significant changes in flow rate when the pressure ratio is greater than 0.95. Since turbocharged engines typically use low-pressure EGR valves, whose pressure ratios are mostly greater than 0.95, even small changes in the pressure ratio can cause significant valve fluctuations, resulting in decreased accuracy in EGR flow rate estimation. Summary of the Invention

[0004] A control method, controller, and vehicle for a low-pressure EGR system are disclosed. This disclosure uses a first current EGR rate estimation method (i.e., an EGR rate estimation method for a low-pressure EGR system without an intake mixing valve) and a second current EGR rate estimation method (i.e., an EGR rate estimation method for a low-pressure EGR system with an intake mixing valve). Since this disclosure is applicable to cases where the EGR pressure ratio is greater than 0.528, it improves the estimation accuracy of the EGR rate for the low-pressure EGR system. In a low-pressure EGR system without an intake mixing valve, this disclosure controls the EGR valve using the aforementioned first target EGR opening degree. In a low-pressure EGR system with an intake mixing valve, it controls the EGR valve using the second target EGR opening degree and controls the intake mixing valve using the target DPT opening degree, thereby improving the control accuracy of the EGR valve and the intake mixing valve in the low-pressure EGR system.

[0005] In a first aspect, this disclosure proposes a control method for a low-pressure EGR system, the low-pressure EGR system comprising an air filter and an exhaust gas recirculation (EGR) valve arranged sequentially along an intake pipe, the method comprising: acquiring the current EGR opening of the EGR valve, and acquiring the pressure and temperature before the air filter, the pressure after the air filter, and the pressure and temperature before the EGR valve; and obtaining a first current EGR rate based on the current EGR opening, the pressure and temperature before the air filter, the pressure after the air filter, and the pressure and temperature before the EGR valve.

[0006] According to the control method of the low-pressure EGR system of the present disclosure, a first current EGR rate is obtained by considering the current EGR opening, the pressure and temperature before the air filter, the pressure after the air filter, and the pressure and temperature before the EGR valve, thereby improving the estimation accuracy of the first current EGR rate.

[0007] Secondly, this disclosure proposes a controller, including a memory, a processor, and a computer program stored in the memory, wherein when the computer program is executed by the processor, it implements the control method of the low-voltage EGR system.

[0008] According to the controller of this disclosure, when the computer program corresponding to the control method of the low-pressure EGR system stored thereon is executed by the processor, the estimation accuracy of the EGR rate of the low-pressure EGR system is improved, and the control accuracy of the EGR valve in the low-pressure EGR system is improved.

[0009] Thirdly, this disclosure proposes a vehicle including the aforementioned controller.

[0010] The vehicle of this embodiment improves the estimation accuracy of the EGR rate of the low-pressure EGR system and the control accuracy of the EGR valve in the low-pressure EGR system through the controller described above.

[0011] Additional aspects and advantages of this disclosure will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this disclosure. Attached Figure Description

[0012] Figure 1 This is a flowchart illustrating the control method of a low-voltage EGR system according to the first embodiment of this disclosure;

[0013] Figure 2 This is a flowchart of the EGR rate estimation strategy for a low-pressure EGR system without an intake mixing valve according to the first embodiment of this disclosure;

[0014] Figure 3 This is a flowchart of the EGR valve opening control strategy for a low-pressure EGR system without an intake mixing valve according to the first embodiment of this disclosure;

[0015] Figure 4 This is a flowchart illustrating the control method of a low-voltage EGR system according to the second embodiment of this disclosure;

[0016] Figure 5 This is a flowchart of the EGR rate estimation strategy for a low-pressure EGR system with an intake mixing valve according to the second embodiment of this disclosure;

[0017] Figure 6 This is a flowchart of the intake mixing valve opening control strategy for a low-pressure EGR system with an intake mixing valve according to the first embodiment of this disclosure;

[0018] Figure 7 This is a flowchart of the EGR rate estimation strategy for a low-pressure EGR system with an intake mixing valve according to the second embodiment of this disclosure;

[0019] Figure 8 This is a schematic diagram of the structure of a controller according to an embodiment of the present disclosure;

[0020] Figure 9 This is a schematic diagram of the structure of a vehicle according to an embodiment of the present disclosure. Detailed Implementation

[0021] Embodiments of this disclosure are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this disclosure, and should not be construed as limiting this disclosure.

[0022] The following is a reference appendix. Figure 1-9 This disclosure describes a control method, controller, and vehicle for a low-pressure EGR system according to embodiments of the present disclosure.

[0023] Figure 1 This is a flowchart illustrating the control method of a low-pressure EGR system. The low-pressure EGR system includes an air filter and an exhaust gas recirculation (EGR) valve arranged sequentially along the intake manifold. Figure 1 As shown, the control method for a low-pressure EGR system includes the following steps:

[0024] S101. Obtain the current EGR opening of the EGR valve, and obtain the pressure and temperature before the air filter, the pressure after the air filter, and the pressure and temperature before the EGR valve.

[0025] Specifically, the current EGR opening of the EGR valve can be obtained through an opening detection device, and the pressure and temperature before the air filter, the pressure after the air filter, and the pressure and temperature before the EGR valve can be obtained through a pressure gauge and a temperature sensor.

[0026] S102. Based on the current EGR opening, the pressure and temperature before the air filter, the pressure after the air filter, and the pressure and temperature before the EGR valve, obtain the first current EGR rate.

[0027] Specifically, step S102 may include: obtaining a first ratio based on the current EGR opening; obtaining a second ratio between the mass flow rate of EGR gas in the intake manifold and the mass flow rate of fresh gas based on the first ratio, the pressure and temperature before the air filter, the pressure after the air filter, and the pressure and temperature before the EGR valve; and obtaining a first current EGR rate based on the second ratio.

[0028] Specifically, different EGR opening degrees and K can be obtained experimentally. EGR / K AirFilter The relational MAP table (i.e., the C_EGR_1D table), given the current EGR opening degree (the opening degree of EGR_Position, i.e., K), EGR Under the premise of ), the first ratio (i.e., K) is obtained by looking up table C_EGR_1D. EGR / K AirFilter The result is then used to obtain the second ratio (i.e., the mass flow rate q of the EGR gas in the intake pipe) through the following formula. EGR The mass flow rate q of the fresh gas in the intake manifold 空气 The ratio between them:

[0029]

[0030] Where, q EGR / q 空气 For the second ratio, K EGR / K AirFilter p is the first ratio. Air p is the pressure before the air filter (i.e., atmospheric pressure). AirFilter_out p is the pressure after the air filter. EGR_in T is the pressure before the EGR valve. Air T represents the temperature before the air filter (i.e., the ambient temperature). EGR_in The temperature before the EGR valve is given. The first current EGR rate is finally obtained using the following formula (see...). Figure 2 ):

[0031] q EGR / q 空气 =EGR_Rate / (1-EGR_Rate),

[0032] Where EGR_Rate is the first current EGR rate, q EGR / q 空气 The second ratio, q EGR q is the mass flow rate of EGR gas in the intake manifold. 空气 This is the mass flow rate of fresh gas in the intake manifold.

[0033] It should be noted that this disclosure mainly uses the differential pressure model rather than the pressure ratio model for EGR control and estimation. Since the differential pressure model is suitable for situations with a large pressure ratio, this disclosure is suitable for situations where the EGR pressure ratio is greater than 0.528. This model is not applicable to situations where the pressure ratio is too small.

[0034] Furthermore, this disclosure primarily addresses the estimation of the EGR rate, rather than the direct calculation of the EGR flow rate. The EGR flow rate can be indirectly calculated from the fresh air flow rate and the EGR rate, while the pressure ratio model can directly yield the EGR flow rate. The advantage of this approach is that the low-pressure EGR differential is very small, and the corresponding DPT differential is also very small; these two values ​​are essentially of the same order of magnitude, and using their ratio yields a larger value.

[0035] Therefore, based on the current EGR opening, the pressure and temperature before the air filter, the pressure after the air filter, and the pressure and temperature before the EGR valve, the first current EGR rate is obtained, which improves the estimation accuracy of the first current EGR rate.

[0036] As a first example, the control method for a low-pressure EGR system may also include: obtaining a target EGR rate; obtaining a first target EGR opening based on the target EGR rate, the pressure and temperature before the air filter, the pressure after the air filter, and the pressure and temperature before the EGR valve; and controlling the EGR valve based on the first target EGR opening.

[0037] Specifically, see Figure 3 According to the target EGR rate Desired_EGRRate (i.e., EGR_Rate in the following formula) 需求 ), the pressure p before the air filter Air and temperature T Air Pressure p after the air filter AirFilteｒ_out The pressure p before the EGR valve ＥGR_in and temperature T EGR_in The required K is calculated using the following formula. EGR / K AirFilte需求r :

[0038] (q EGＲ / q 空气 ) 需求 =EGR_Rate 需求 / (1-EGR_Rate 需求 )

[0039]

[0040] Since the air filter's flow characteristics are fixed, K EGR / K AirFilter需求 It is only related to the EGR opening, therefore, the relationship between different EGR openings and K can be obtained experimentally. EGR / K airFilter需求 The relational MAP table (i.e., the C_EGR_C_1D table), given K EGR / K AirFilter需求Under the premise of this, the required EGR opening (i.e., the unfiltered first target EGR opening) can be obtained by looking up this MAP table in reverse. Finally, the unfiltered first target EGR opening is filtered by a filter to obtain the final first target EGR opening Desired_EGRPosition. Then, the EGR valve is controlled according to the first target EGR opening Desired_EGRPosition.

[0041] Therefore, based on the target EGR rate, the pressure and temperature before the air filter, the pressure after the air filter, and the pressure and temperature before the EGR valve, the first target EGR opening is obtained; and the EGR valve is controlled according to the first target EGR opening.

[0042] Figure 4 This is a schematic flowchart illustrating the control method of a low-pressure EGR system according to a second embodiment of this disclosure. It should be noted that this low-pressure EGR system also includes an intake mixing valve, which is located after the air filter and before the connection between the EGR valve outlet and the post-air filter piping. Figure 4 As shown, a low-voltage EGR system may also include the following steps:

[0043] S201. Obtain the current EGR opening of the EGR valve and the current DPT opening of the intake mixing valve.

[0044] Specifically, the current EGR opening of the EGR valve and the current DPT opening of the intake mixing valve can be obtained through the opening detection device.

[0045] S202. Based on the current EGR opening, current DPT opening, pressure and temperature before the intake mixing valve, pressure after the intake mixing valve, and pressure and temperature before the EGR valve, obtain the second current EGR rate.

[0046] Specifically, different DPT opening and EGR opening ratios can be obtained experimentally in relation to K. EGR / K DPT The relational MAP table (i.e., the F_EGR_2D table) is used when the current EGR opening degree K is known. EGR and the current DPT opening degree K DPT Under the premise that K is obtained by looking up table F_EGR_2D EGR / K DPT As a result, since the target value K of the intake mixing valve opening coefficient is only related to the structure of the valve body itself, when the valve body structure is fixed, K is only related to the opening of the valve body, and the flow rate through the intake mixing valve is the flow rate of fresh air, the ratio q between the mass flow rate of EGR gas in the intake pipe and the mass flow rate of fresh gas in the intake mixing valve can be obtained by the following formula. EGR / q DPT :

[0047]

[0048] Where, p DPT_in p is the absolute pressure after the air filter (also the pressure before the intake mixing valve). DPT_out p is the pressure at the EGR outlet mixing point. EGR_in T is the absolute pressure before the EGR valve. DPT_in T is the temperature after the air filter (K) (also the temperature before the intake mixing valve). EGR_in The temperature (K) before the EGR valve is given. The second current EGR rate is finally obtained using the following formula (see...). Figure 5 ):

[0049] q EGR / q DPT =EGR_Rate2 / (1-EGR_Rate2),

[0050] Where EGR_Rate2 is the second current EGR rate, q EGR q is the mass flow rate of EGR gas in the intake manifold. DPT This is the mass flow rate of fresh gas in the intake mixing valve.

[0051] It should be noted that the main function of the intake mixing valve is to increase the negative pressure after DPT, thereby increasing the pressure difference across the EGR. Consequently, it can improve the estimation accuracy of the second current EGR rate. Experiments have shown that when the EGR pressure difference is greater than a certain value, the estimation accuracy of the second current EGR rate will be relatively high. This value is the calibration value. For ease of explanation, this value is defined as 2 kPa in this disclosure. Therefore, the control of the intake mixing valve mainly revolves around how to ensure that the pressure difference across the EGR is greater than or equal to 2 kPa.

[0052] Therefore, by obtaining the second current EGR rate based on the current EGR opening, the current DPT opening, the pressure and temperature before the intake mixing valve, the pressure after the intake mixing valve, and the pressure and temperature before the EGR valve, the estimation accuracy of the second current EGR rate is improved.

[0053] As a second example, the control method for a low-pressure EGR system may also include: acquiring the temperature before the intake mixing valve and the pressure after the intake mixing valve; obtaining a second target EGR opening based on the target EGR rate, the pressure after the air filter (i.e., the pressure before the intake mixing valve), the temperature before the intake mixing valve, the pressure after the intake mixing valve, and the pressure and temperature before the EGR valve; and controlling the EGR valve based on the second target EGR opening.

[0054] Specifically, see Figure 6 And based on the target EGR rate Desired_EGRRate (i.e., EGR_Rate in the following formula)需求 The pressure after the air filter (i.e., the pressure p before the intake mixing valve) DPT_in Temperature T before the intake mixing valve DPT_in The pressure p after the intake mixing valve DPT_in ), the pressure p before the EGR valve EGR_in and temperature T EGR_in K is obtained by calculating the following formula. EGR / K DPT需求 ;

[0055] (q EGR / q 空气 ) 需求 =EGR_Rate 需求 / (1-EGR_Rate 需求 )

[0056]

[0057] Different DPT and EGR openings and K can be obtained experimentally. EGR / K DPT需求 The relational MAP table (i.e., the F_EGR_C_2D table), given the DPT opening degree and K... EGR / K DPT需求 Under the premise of this, the required EGR opening (i.e., the unfiltered second target EGR opening) can be obtained by looking up this MAP table in reverse. Finally, the unfiltered second target EGR opening is filtered by a filter to obtain the final second target EGR opening, Desired_EGRPosition. Then, the EGR valve is controlled according to the filtered second target EGR opening, Desired_EGRPosition.

[0058] Therefore, based on the target EGR rate, the pressure and temperature before the air filter, the pressure after the air filter, and the pressure and temperature before the EGR valve, the first target EGR opening is obtained; and the EGR valve is controlled according to the first target EGR opening.

[0059] As a third example, the control method for a low-pressure EGR system may further include: acquiring a target airflow rate; obtaining a target value for the opening coefficient of the intake mixing valve based on the target airflow rate, the temperature before the intake mixing valve, the pressure after the air filter, and the pressure before the EGR valve; obtaining the required DPT opening based on the target opening coefficient value, and obtaining the minimum DPT opening based on the target airflow rate; taking the larger of the required DPT opening and the minimum DPT opening as the target DPT opening, and controlling the intake mixing valve based on the target DPT opening.

[0060] Specifically, see Figure 7The target value of the intake mixing valve opening coefficient can be obtained using the following formula:

[0061]

[0062] Where, q m The target airflow rate is a demand value, K is the target value of the intake mixing valve opening coefficient, and ρ1 = p AirFilter_out / (R*T DPT_in ), where R is the gas density in the upstream section of the intake mixing valve, R = 287 J / (kg*K), Δp = Max[(p AirFilter_out -(p EGR_in -2)), 2], is the pressure difference (here, to avoid the intake mixing valve pressure difference being too small, which would cause DPT control problems, a minimum pressure difference limit of 2 kPa is required, from which the target value K of the intake mixing valve opening coefficient is calculated), p AirFilter_out T is the pressure after the air filter. DPT_in p is the temperature before the intake mixing valve. EGR_in The pressure before the EGR valve is denoted as . It should be noted that, using formula (1), the table lookup value of C_DPT_1D under different DPT opening degrees can be obtained based on experimental data.

[0063] Specifically, for subsonic flow (pressure ratio greater than 0.528) in pipelines such as orifice / butterfly valves, the relationship between pressure difference and gas flow rate can be established as follows:

[0064] Where, q m Let be the gas mass flow rate, C be the flow coefficient, β be the diameter ratio d / D, ε be the expansion coefficient, d be the orifice diameter, D be the pipe diameter, Δp be the pressure difference, and ρ1 be the gas density of the upstream pipe section. Let The relationship between pressure difference and flow rate can then be simplified as follows:

[0065] Then, the original required DPT opening can be obtained by looking up the target opening coefficient K in the C_DPT_1D table. Subsequently, since insufficient closure of the intake mixing valve can lead to problems such as insufficient intake volume and low compressor inlet negative pressure causing oil leakage, it is necessary to impose a minimum limit on the final DPT opening to avoid problems such as instantaneous changes in DPT opening due to abnormal reasons during the target intake mixing valve calculation process. This limit is obtained by looking up the minimum DPT opening in the C_DPT_Min table based on the target airflow. Finally, the larger value between the required DPT opening and the minimum DPT opening is taken as the target DPT opening, and the intake mixing valve is controlled according to the target DPT opening.

[0066] Therefore, based on the target airflow, the temperature before the intake mixing valve, the pressure after the air filter, and the pressure before the EGR valve, the target value of the intake mixing valve opening coefficient is obtained; the required DPT opening is obtained based on the target opening coefficient, and the minimum DPT opening is obtained based on the target airflow; the larger of the required DPT opening and the minimum DPT opening is taken as the target DPT opening, and the intake mixing valve is controlled based on the target DPT opening.

[0067] In summary, this disclosure improves the estimation accuracy of the EGR rate of low-pressure EGR systems by using the aforementioned first current EGR rate estimation method (i.e., the EGR rate estimation method for low-pressure EGR systems without an intake mixing valve) and the second current EGR rate estimation method (i.e., the EGR rate estimation method for low-pressure EGR systems with an intake mixing valve). Furthermore, since this disclosure is applicable to cases where the EGR pressure ratio is greater than 0.528, it improves the control accuracy of the EGR rate of low-pressure EGR systems. In low-pressure EGR systems without an intake mixing valve, this disclosure controls the EGR valve using the aforementioned first target EGR opening degree; in low-pressure EGR systems with an intake mixing valve, it controls the EGR valve using the second target EGR opening degree and the intake mixing valve using the target DPT opening degree.

[0068] Figure 8 This is a schematic diagram of the structure of a controller according to an embodiment of this disclosure. Figure 8 As shown, the controller 100 includes a memory 110, a processor 120, and a computer program stored in the memory 120. When the computer program is executed by the processor 120, it implements the control method of the low-voltage EGR system described above.

[0069] When the computer program corresponding to the control method of the low-pressure EGR system stored on the controller of this embodiment is executed by the processor, the estimation accuracy of the EGR rate of the low-pressure EGR system is improved, and the control accuracy of the EGR valve in the low-pressure EGR system is improved.

[0070] Figure 9 This is a schematic diagram of the structure of a vehicle according to an embodiment of this disclosure. Figure 9 As shown, vehicle 200 includes the aforementioned controller 100.

[0071] The vehicle of this embodiment improves the estimation accuracy of the EGR rate of the low-pressure EGR system and the control accuracy of the EGR valve in the low-pressure EGR system through the controller described above.

[0072] It should be noted that the logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0073] It should be understood that various parts of this disclosure can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0074] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this disclosure. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0075] In the description of this disclosure, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this disclosure and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this disclosure.

[0076] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this disclosure, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0077] In this disclosure, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this disclosure according to the specific circumstances.

[0078] In this disclosure, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0079] Although embodiments of the present disclosure have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present disclosure. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present disclosure.

Claims

1. A control method for a low-pressure EGR system, characterized in that, The low-pressure EGR system includes an air filter and an exhaust gas recirculation (EGR) valve arranged sequentially along the intake manifold, and the method includes: Obtain the current EGR opening of the EGR valve, and obtain the pressure and temperature before the air filter, the pressure after the air filter, and the pressure and temperature before the EGR valve; The first current EGR rate is obtained based on the current EGR opening, the pressure and temperature before the air filter, the pressure after the air filter, and the pressure and temperature before the EGR valve.

2. The control method for a low-voltage EGR system according to claim 1, characterized in that, The method further includes: Obtain the target EGR rate; The first target EGR opening is obtained based on the target EGR rate, the pressure and temperature before the air filter, the pressure after the air filter, and the pressure and temperature before the EGR valve. The EGR valve is controlled according to the first target EGR opening.

3. The control method for a low-voltage EGR system according to claim 2, characterized in that, The step of obtaining the first current EGR rate based on the current EGR opening, the pressure and temperature before the air filter, the pressure after the air filter, and the pressure and temperature before the EGR valve includes: The first ratio is obtained based on the current EGR opening. Based on the first ratio, the pressure and temperature before the air filter, the pressure after the air filter, and the pressure and temperature before the EGR valve, a second ratio between the mass flow rate of EGR gas and the mass flow rate of fresh gas in the intake pipe is obtained. The first current EGR rate is obtained based on the second ratio.

4. The control method for a low-pressure EGR system according to claim 3, characterized in that, The second ratio is obtained using the following formula: Where, q EGR / q 空气 The second ratio, q EGR q is the mass flow rate of EGR gas in the intake manifold. 空气 K is the mass flow rate of fresh gas in the intake manifold. EGR / K AirFilter For the first ratio, K EGR p is the current EGR opening. Air p is the pressure before the air filter. AirFilter_out p is the pressure after the air filter. EGR_in T is the pressure before the EGR valve. Air T is the temperature before the air filter. EGR_in The temperature before the EGR valve is [temperature value missing].

5. The control method for a low-voltage EGR system according to claim 3, characterized in that, The first current EGR rate is obtained using the following formula: q EGR / q 空气 =EGR_Rate / (1-EGR_Rate), Where EGR_Rate is the first current EGR rate, q EGR / q 空气 The second ratio, q EGR q is the mass flow rate of EGR gas in the intake pipe. 空气 The mass flow rate of the fresh gas in the intake pipe is given.

6. The control method for a low-voltage EGR system according to claim 2, characterized in that, The low-pressure EGR system further includes an intake mixing valve, which is arranged after the air filter and before the connection between the EGR valve outlet and the air filter downstream pipeline. The method further includes: The temperature before the intake mixing valve and the pressure after the intake mixing valve are obtained. The second target EGR opening is obtained based on the target EGR rate, the pressure after the air filter, the temperature before the intake mixing valve, the pressure after the intake mixing valve, and the pressure and temperature before the EGR valve. The EGR valve is controlled according to the second target EGR opening.

7. The control method for a low-voltage EGR system according to claim 6, characterized in that, The method further includes: Obtain the current EGR opening of the EGR valve and the current DPT opening of the intake mixing valve; The second current EGR rate is obtained based on the current EGR opening, the current DPT opening, the pressure and temperature before the intake mixing valve, the pressure after the intake mixing valve, and the pressure and temperature before the EGR valve.

8. The control method for a low-voltage EGR system according to claim 6, characterized in that, The method further includes: Obtain the target airflow rate; The target value of the opening coefficient of the intake mixing valve is obtained based on the target air flow rate, the temperature before the intake mixing valve, the pressure after the air filter, and the pressure before the EGR valve. The required DPT opening is obtained based on the target value of the opening coefficient, and the minimum DPT opening is obtained based on the target airflow. The larger of the required DPT opening and the minimum DPT opening is taken as the target DPT opening, and the intake mixing valve is controlled according to the target DPT opening.

9. The control method for a low-voltage EGR system according to claim 8, characterized in that, The target value of the opening coefficient of the intake mixing valve is obtained by the following formula: , Where, q m The target airflow rate is given by K, where K is the target value of the opening coefficient of the intake mixing valve, and ρ1 = p AirFilter_out / (R*T DPT_in ), where R is the gas density in the upstream pipe section of the intake mixing valve, R = 287 J / (kg*K). , where p is the pressure difference. AirFilter_out T is the pressure after the air filter. DPT_in p is the temperature before the intake mixing valve. EGR_in The pressure before the EGR valve is [value].

10. The control method for a low-pressure EGR system according to claim 8, characterized in that, The step of controlling the EGR valve according to the second target EGR opening includes: filtering the second target EGR opening, and controlling the EGR valve according to the filtered second target EGR opening; The step of controlling the intake mixing valve according to the target DPT opening includes: filtering the target DPT opening and controlling the intake mixing valve according to the filtered target DPT opening.

11. A controller, characterized in that, The system includes a memory, a processor, and a computer program stored in the memory, wherein when the computer program is executed by the processor, it implements a control method for a low-voltage EGR system according to any one of claims 1-10.

12. A vehicle, characterized in that, Includes the controller according to claim 11.

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