Control method for responsiveness of mixing valve in low-pressure EGR system

Abstract

The present invention discloses a method for controlling the responsiveness of a mixing valve in a low-pressure EGR system. The method comprises: detecting the responsiveness of the mixing valve using a method for detecting the responsiveness of the mixing valve; determining whether the mixing valve enters an activated or inactivated state using a method for determining the activation state of the mixing valve in a low-pressure EGR system; obtaining information on the target opening and actual opening of the mixing valve when the responsiveness of the mixing valve is not faulty and the mixing valve enters an activated state, and controlling the actual opening of the mixing valve to follow the target opening; otherwise, the mixing valve is not controlled, and the PWM duty cycle of the mixing valve execution motor is 0%. The method provided by the present invention can achieve high dynamic responsiveness and stability of the mixing valve.

Description

Technical Field

[0001] The present invention relates to the technical field of engine control, and in particular to a method for controlling the responsiveness of a mixing valve in a low-pressure EGR system. Background Art

[0002] Since low-pressure EGR (Exhaust Gas Re-circulation) can reduce fuel consumption and HC (hydrocarbon) emissions, it is a good solution for achieving National 6B standards using the RDE (Real Drive Emission) actual vehicle driving cycle. Compared to high-pressure EGR, low-pressure EGR takes air after the turbine, so there is no loss in turbine efficiency, and it can use EGR under almost all operating conditions, which is more significant in improving fuel efficiency. However, due to its low pressure difference, a large-diameter valve is required to meet the flow requirements. Under certain operating conditions, it is also necessary to control the mixing valve to improve the pressure at the EGR valve outlet, thereby increasing the pressure difference on both sides of the EGR valve and increasing the EGR rate. Since the mixing valve action is disturbed by the intake flow, it will bring difficulties to the dynamic response control of the mixing valve.

[0003] Patent application number 202311053201.3 discloses "A method for detecting the response performance of an engine mixing valve". This patent mainly focuses on the detection of the responsiveness performance of the mixing valve opening. It performs fault detection when the actual opening does not respond to the target opening, but does not propose a control method for how to make the actual opening respond to the target opening. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a control method for the responsiveness of a mixing valve of a low-pressure EGR system in response to the deficiencies of the prior art, which method can achieve high dynamic responsiveness and high stability of the mixing valve.

[0005] To achieve the above objectives, according to one aspect of the present invention, a method for controlling the responsiveness of a mixing valve in a low-pressure EGR system is provided, comprising:

[0006] Test the response performance of the mixing valve to determine whether the response performance of the mixing valve is faulty;

[0007] determining whether the mixing valve enters an activated state or an inactivated state;

[0008] When the response performance of the mixing valve does not fail and the mixing valve enters the activated state, the target opening of the mixing valve and the actual opening of the mixing valve are obtained, and the actual opening of the mixing valve is controlled to follow the target opening of the mixing valve; otherwise, the mixing valve is not controlled to operate, and the PWM duty cycle of the mixing valve execution motor is 0%.

[0009] In the above solution, the detection of the response performance of the mixing valve is specifically carried out by using an engine mixing valve response performance detection method, including any working condition mixing valve response performance detection and / or steady-state working condition mixing valve response performance detection, wherein,

[0010] Mixing valve response performance test under any working condition: Determine the mixing valve response performance test conditions, read and retain N mixing valve target openings in the most recent time, determine the initial and final values ​​of the mixing valve actual opening, compare the mixing valve actual opening with the final value of the mixing valve actual maximum opening or the final value of the mixing valve actual minimum opening, and judge the mixing valve response performance;

[0011] Steady-state mixing valve response performance test: Determine if the steady-state operating conditions are met. Perform a mixing valve response performance test based on the steady-state operating conditions. Accumulate the first opening time t1 from the target EGR rate of 0 to the start of the mixing valve opening change, and the second opening time t2 from the start of the mixing valve opening change to the fully open state. Compare t1 and t2 with their respective limits to determine whether the mixing valve is experiencing a steady-state response performance failure.

[0012] As long as any one of the mixing valve response performance test under any working condition and the mixing valve response performance test under steady-state working condition fails, it indicates that the mixing valve response performance fails; otherwise, no failure occurs.

[0013] In the above solution, the determination of whether the mixing valve enters the activated state or the inactivated state is specifically performed by a method for determining the activation state of the mixing valve of the low-pressure EGR system, which specifically includes: obtaining a target boost pressure demand value, and when the target boost pressure demand value is less than a preset boost pressure demand value and at least one of the following four conditions is met, controlling the mixing valve to enter the activated state, and the mixing valve receives a mixing valve opening control instruction;

[0014] Condition 1: EGR valve pressure difference is less than the preset EGR valve pressure difference;

[0015] Condition 2: The EGR valve opening is greater than the preset EGR valve opening, and the target EGR rate change rate is greater than the preset EGR rate change rate;

[0016] Condition 3: The throttle valve front-to-back pressure ratio is less than the preset throttle valve pressure ratio;

[0017] Condition 4: The target EGR rate is greater than the preset EGR rate.

[0018] In the above solution, the method for controlling the actual opening of the mixing valve to follow the target opening is:

[0019] A feedforward part is combined with a PID control part to obtain a mixing valve control duty cycle, and the mixing valve drive motor PWM control is controlled by the mixing valve control duty cycle.

[0020] In the above scheme, the feedforward part is Pct ValveDsrdFF =f(Pct PosDsrdToRef )×[1+f(Pct PosErr )]; where Pct PosDsrdToRef The target opening of the mixing valve is relative to the default opening (the default position is the fully open position, and the opening is 100%), that is, the target opening of the mixing valve minus the default opening. This part is mainly considered to be caused by the effect of the mixing valve return spring force when the mixing valve deviates from the default position; Pct PosErr The mixing valve opening deviation is obtained by subtracting the actual opening from the target opening of the mixing valve. This part mainly takes into account the friction caused by the valve disc of the mixing valve during operation. It is mainly used to compensate when the deviation between the target opening and the actual opening is large; f(Pct PosDsrdToRef ) by Pct PosDsrdToRef Calibration results: f(Pct PosErr ) by Pct PosErr Calibration is obtained;

[0021] In the above scheme, the PID control part is Pct ValveDsrdP +Pct ValveDsrdI +Pct ValveDsrdD ; Among them, Pct ValveDsrdP is the P item, Pct ValveDsrdI For item I, Pct ValveDsrdD It is option D.

[0022] In the above scheme, the P item

[0023] Pct ValveDsrdP =f1(Pct PosDsrdToRef , Pct PosErr )×Pct PosErr ×f1(p BoostErr ); where f1(Pct PosDsrdToRef ,

[0024] Pct PosErr ) is the P correction factor, p BoostErr is the difference between the target boost pressure and the actual boost pressure in boost control, f1(p BoostErr ) is p BoostErr Correction factors are determined to avoid interference with boost closed-loop control and enhance the robustness of boost and mixing valve linkage control. BoostErr When the absolute value is large, f1(p BoostErr ) is smaller; f1(Pct PosDsrdToRef , Pct PosErr ) by Pct PosDsrdToRef With Pct PosErr The joint calibration results are: f1(p BoostErr) by p BoostErr Calibration is obtained;

[0025] In the above scheme, the D item Pct ValveDsrdD =Pct ValveDsrdD_Base +Pct ValveDsrdD_SpeedCtrl ;

[0026] Among them, Pct ValveDsrdD-Base Pct is the reference value of the duty cycle of item D. ValveDsrdD_Base =f2(Pct PosDsrdToRef , Pct PosErr )×dPct PosErr ×f2(dp BoostErr ), where f2(Pct PosDsrdToRef , Pct PosErr ) is the D correction factor, dPct PosErr is the rate of change of the difference between the target opening of the mixing valve and the actual opening of the mixing valve, dp BoostErr is the rate of change of the difference between the target boost pressure and the actual boost pressure in boost control, f2(dp BoostErr ) is dp BoostErr Correction factor is determined to avoid interference with boost closed loop control and robustness of boost and mixing valve linkage control in dp BoostErr When the absolute value is large, f2(dp BoostErr ) is smaller; f2(Pct PosDsrdToRef , Pct PosErr ) by Pct PosDsrdToRef With Pct PosErr The joint calibration results are: f2(dp BoostErr ) by dp BoostErr Calibration is obtained;

[0027] Among them, Pct ValveDsrdD-SpeedCtrl This is the closed-loop correction value for item D, primarily intended to account for the difference between the requested rate of change and the actual rate of change. Since the mixing valve is located at the intake system inlet, close to the atmosphere and filtered by the air filter, fresh air still interferes with the responsiveness and control accuracy of the mixing valve. The opening accuracy of the mixing valve significantly impacts EGR control accuracy and supercharger inlet pressure control, necessitating optimization of conventional item D control.

[0028] Pct ValveDsrdD_SpeedCtrl =f2(dPct SpeedErr , Pct PosErr )×dPct SpeedErr ;

[0029] where dPct SpeedErr =dPct PosDsrdErr +dPct PosErr, which is the ideal opening change rate of the mixing valve dPct PosDsrdErr The actual opening rate of the mixing valve -dPct PosErr The actual opening change rate of the mixing valve is the change rate of the difference between the actual opening of the mixing valve and the target opening, dPct PosDsrdErr =max[f1(Pct PosErr ),f1(Pct PosDsrdToRef )]; where f1(Pct PosErr ) is based on the mixing valve opening deviation Pct PosErr The ideal rate of change obtained, f1(Pct PosDsrdToRef ) is the target opening of the mixing valve relative to the default opening Pct PosDsrdToRef The maximum change rate limit of the soft landing is obtained to avoid the mixing valve opening changing too fast and damaging the drive motor;

[0030] f1(Pct PosErr ) by Pct PosErr Calibration results: f1(Pct PosDsrdToRef ) by Pct PosDsrdToRef Calibration results: f2(dPct SpeedErr , Pct PosErr ) by dPct SpeedErr With Pct PosErr Joint calibration is obtained;

[0031] In the above scheme, for the I item Pct ValveDsrdI , its value is based on the following three situations, and when the vehicle is powered on, the mixing valve will enter the inactive state, the I item Pct ValveDsrdI The default value of the initial value is 0;

[0032] First case: If the response performance of the mixing valve fails, the I Pct ValveDsrdI =0;

[0033] Second case: If the mixing valve enters the inactive state, the I item Pct ValveDsrdI =Pct ValveDsrdI (z)×0.85, until Pct ValveDsrdI If the absolute value of the difference from 0 does not exceed 0.5%, then Pct ValveDsrdI Set to 0; where Pct ValveDsrdI (z) is the duty cycle calculated from the previous sampling period in periodic sampling, Pct ValveDsrdI It will be updated once in each sampling period Δt;

[0034] The third case: the I item Pct ValveDsrdI Equal to its original value Pct ValveDsrdRawSince the mixing valve is located at the inlet of the intake system, close to the atmosphere and filtered by the air filter, fresh air still interferes with the responsiveness and stability of the mixing valve. Therefore, it is necessary to optimize the conventional I control.

[0035] Pct ValveDsrdIRaw =[Pct ValveDsrdI (z)+Pct ValveDsrdI_Incre ]×f3(dPct SpeedErr , Pct PosErr );

[0036] Where f3(dPct SpeedErr , Pct PosErr ) by dPct SpeedErr With Pct PosErr Joint calibration is obtained;

[0037] Among them, Pct ValveDsrdI (z) is the duty cycle calculated in the previous sampling period in periodic sampling, and its default value is 0 when the vehicle is powered on;

[0038] Among them, Pct ValveDsrdI-Incre is the cumulative term, Pct ValveDsrdI-Incre =f2(dPct PosDrsd )×f2(Pct PosErr )×f4(dPct SpeedErr , Pct PosErr )×Δt×(Pct PosErr -K WindUpGain ×Pct SaturateOld ); where Δt is the sampling period; dPct PosDrsd is the target opening rate of the mixing valve; K WindUpGain is the anti-integral saturation correction coefficient, which is a preset value and is used to prevent integral saturation; f4(dPct SpeedErr , Pct PosErr ) is the correction factor for the cumulative term I;

[0039] Where f4(dPct SpeedErr , Pct PosErr ) by dPct SpeedErr With Pct PosErr The joint calibration results are: f2(dPct PosDrsd ) by dPct PosDrsd Calibration results: f2(Pct PosErr ) by Pct PosErr Calibration is obtained;

[0040] Among them, Pct SaturateOld is the EGR valve saturation opening of the previous sampling period in periodic sampling, which is related to K WindUpGainCooperate to avoid integral windup.

[0041] In the above scheme, obtain Pct ValveDsrdFF +Pct ValveDsrdP +Pct ValveDsrdI +Pct ValveDsrdD The minimum value Pct ValveMin and maximum value Pct ValveMax , which defines the mixing valve control duty cycle Pct that is ultimately closed-loop controlled ValveDsrdFinal At the minimum value Pct ValveMin and maximum value Pct ValveMax Between, that is, Pct ValveMin ≤Pct ValveDsrdFinal ≤Pct ValveMax ; The duty cycle Pct is controlled by the mixing valve ValveDsrdFinal Controlling the mixing valve drive motor PWM control to achieve the mixing valve actual opening following the mixing valve target opening;

[0042] Among them, Pct Saturate =Pct ValveDsrdFF +Pct ValveDsrdP +Pct ValveDsrdI -Pct ValveDsrdFinal , Pct SaturateOld Pct of the previous sampling period Saturate .

[0043] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0044] The present invention provides a method for controlling the responsiveness of a mixing valve in a low-pressure EGR system. The method optimizes the responsiveness control of the mixing valve based on the layout characteristics of the mixing valve and takes into account the influence of the mixing valve on the boost pressure control, thereby improving the responsiveness accuracy of the mixing valve. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] 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:

[0046] Figure 1 Schematic diagram of a low-pressure EGR system in an embodiment of the present invention.

[0047] Figure 2 Schematic diagram of a flow chart of a method for controlling the responsiveness of a mixing valve in a low-pressure EGR system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0048] 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.

[0049] 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.

[0050] Example 1

[0051] The EGR system on which the present invention is based comprises an air filter, a mixing valve, a supercharger compressor, a throttle, 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, 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 exhaust bypass valve of the supercharger, 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 fresh air flow entering the engine. In some solutions, the flow meter can be eliminated and the fresh air flow entering the engine can be estimated; the mixing valve is used to adjust the pressure at the EGR valve outlet to increase the EGR The pressure difference at both ends of the R valve increases the EGR rate. The mixing valve includes a valve plate actuator motor and a position sensor. The position sensor can read the current actual opening of the mixing valve according to the voltage and opening characteristics. The main purpose of the valve plate actuator motor is to control the valve position to achieve the change of the mixing valve opening; the oxygen sensor 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 to increase the exhaust gas flow and reduce the exhaust gas temperature; the EGR valve plays a throttling role 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.

[0052] According to one aspect of the present invention, an embodiment of the present application provides a method for controlling the responsiveness of a mixing valve in a low-pressure EGR system. Figure 2 ,include:

[0053] S1, testing the response performance of the mixing valve to determine whether the response performance of the mixing valve fails.

[0054] Specifically, in this embodiment, the response performance of the mixing valve is tested, specifically using an engine mixing valve response performance testing method (for details, please refer to Chinese Patent Publication No. CN117052572A), including any working condition mixing valve response performance testing and / or steady-state working condition mixing valve response performance testing, wherein:

[0055] Mixing valve response performance test under any working condition: Determine the mixing valve response performance test conditions, read and retain N mixing valve target openings in the most recent time, determine the initial and final values ​​of the mixing valve actual opening, compare the mixing valve actual opening with the final value of the mixing valve actual maximum opening or the final value of the mixing valve actual minimum opening, and judge the mixing valve response performance;

[0056] Steady-state mixing valve response performance test: Determine if the steady-state operating conditions are met. Perform a mixing valve response performance test based on the steady-state operating conditions. Accumulate the first opening time t1 from the target EGR rate of 0 to the start of the mixing valve opening change, and the second opening time t2 from the start of the mixing valve opening change to the fully open state. Compare t1 and t2 with their respective limits to determine whether the mixing valve is experiencing a steady-state response performance failure.

[0057] As long as any one of the mixing valve response performance test under any working condition and the mixing valve response performance test under steady-state working condition fails, it indicates that the mixing valve response performance fails; otherwise, no failure occurs.

[0058] S2, judging whether the mixing valve enters an activated state or an inactivated state.

[0059] Specifically, in this embodiment, the determination of whether the mixing valve enters the activated state or the inactivated state is performed by a method for determining the activation state of a mixing valve in a low-pressure EGR system (for details, please refer to Chinese Patent Publication No. CN112901377A), which specifically includes: obtaining a target boost pressure demand value; when the target boost pressure demand value is less than a preset boost pressure demand value and at least one of the following four conditions is met, controlling the mixing valve to enter the activated state, and the mixing valve receives a mixing valve opening control instruction;

[0060] Condition 1: EGR valve pressure difference is less than the preset EGR valve pressure difference;

[0061] Condition 2: The EGR valve opening is greater than the preset EGR valve opening, and the target EGR rate change rate is greater than the preset EGR rate change rate;

[0062] Condition 3: The throttle valve front-to-back pressure ratio is less than the preset throttle valve pressure ratio;

[0063] Condition 4: The target EGR rate is greater than the preset EGR rate.

[0064] S3: When the mixing valve response performance does not fail and the mixing valve enters the activated state, the target opening and actual opening information of the mixing valve are obtained, and the actual opening of the mixing valve is controlled to follow the target opening of the mixing valve; otherwise, the mixing valve is not controlled, and the PWM duty cycle of the mixing valve execution motor is 0%.

[0065] Specifically, in this embodiment, a method for determining a target opening of an EGR system mixing valve is used to determine a target opening of the mixing valve.

[0066] A method for determining the target opening of an EGR system mixing valve is adopted (for details, please refer to Chinese patent application number 202110184826.8): when the mixing valve opening control is activated, the initial opening of the mixing valve is determined according to the engine operating parameters, and then the following conditions are determined one by one in descending order of priority. If the previous condition is not met and the current condition is met, the target opening change rate of the mixing valve is determined according to the current condition;

[0067] Condition 1: If the air flow rate change rate is greater than the preset air flow rate change rate, the target opening rate change rate of the mixing valve is the first opening rate change rate;

[0068] Condition 2: If the mixing valve switches from a fully open state to a partially open state, the target opening change rate of the mixing valve is a second opening change rate;

[0069] Condition three: if the mixing valve switches from a partially open state to a fully open state, the target opening change rate of the mixing valve is the third opening change rate;

[0070] Condition 4: If the target EGR change rate is greater than the preset EGR change rate, and the throttle pressure ratio change rate is less than the preset throttle pressure ratio change rate, the mixing valve target opening change rate is the fourth opening change rate;

[0071] Condition 5: If the target EGR rate is greater than the preset EGR rate and the throttle pressure ratio is less than the preset throttle pressure ratio, the target opening change rate of the mixing valve is the fifth opening change rate;

[0072] Condition 6: If none of the above five conditions are met, the target opening change rate of the mixing valve is the sixth opening change rate;

[0073] Finally, the target opening of the mixing valve is determined according to the initial opening of the mixing valve, the change rate of the target opening of the mixing valve, and the control period of the mixing valve.

[0074] In this embodiment, the method for controlling the actual opening of the mixing valve to follow the target opening is:

[0075] The feedforward part is combined with the PID control part to obtain the mixing valve control duty cycle, and the mixing valve drive motor PWM control is controlled by the mixing valve control duty cycle.

[0076] Specifically, in this embodiment, the feedforward part is Pct ValveDsrdFF =f(Pct PosDsrdToRef )×[1+f(Pct PosErr )]; where Pct PosDsrdToRef The target opening of the mixing valve is relative to the default opening, which is obtained by subtracting the default opening from the target opening of the mixing valve; Pct PosErr is the mixing valve opening deviation, which is obtained by subtracting the actual opening from the mixing valve target opening; f(Pct PosDsrdToRef ) by Pct PosDsrdToRef Calibration results: f(Pct PosErr ) by Pct PosErr Calibration is obtained;

[0077] In this embodiment, f(Pct PosDsrdToRef ) The calibration data results are as follows:

[0078]

[0079] In this embodiment, f(Pct PosErr ) The calibration data results are as follows:

[0080]

[0081] In this embodiment, the PID control part is Pct ValveDsrdP +Pct ValveDsrdI +Pct ValveDsrdD ; Among them, Pct ValveDsrdP is the P item, Pct ValveDsrdI For item I, Pct ValveDsrdD It is option D.

[0082] Specifically, P term Pct ValveDsrdP =f1(Pct PosDsrdToRef , Pct PosErr )×Pct PosErr ×f1(p BoostErr ); where f1(Pct PosDsrdToRef , Pct PosErr ) is the P correction factor, p BoostErr is the difference between the target boost pressure and the actual boost pressure in boost control, f1(p BoostErr ) is p BoostErr Determined correction factor; f1(Pct PosDsrdToRef , Pct PosErr ) by Pct PosDsrdToRef With PctPosErr The joint calibration results are: f1(p BoostErr ) by p BoostErr Calibration is obtained;

[0083] In this embodiment, f1(Pct PosDsrdToRef , Pct PosErr ) The calibration data results are as follows:

[0084]

[0085] In this embodiment, f1(Pct BoostErr ) The calibration data results are as follows:

[0086]

[0087] Specifically, item D Pct ValveDsrdD =Pct ValveDsrdD_Base +Pct ValveDsrdD_SpeedCtrl ;

[0088] Among them, Pct ValveDsrdD-Base Pct is the reference value of the duty cycle of item D. ValveDsrdD_Base =f2(Pct PosDsrdToRef , Pct PosErr )×dPct PosErr ×f2(dp BoostErr ), where f2(Pct PosDsrdToRef , Pct PosErr ) is the D correction factor, dPct PosErr The change rate of the difference between the target opening of the mixing valve and the actual opening of the mixing valve, dp BoostErr is the rate of change of the difference between the target boost pressure and the actual boost pressure in boost control, f2(dp BoostErr ) is dp BoostErr Determined correction factor; f2(Pct PosDsrdToRef , Pct PosErr ) by Pct PosDsrdToRef With Pct PosErr The joint calibration results are: f2(dp BoostErr ) by dp BoostErr Calibration is obtained;

[0089] In this embodiment, f2(Pct PosDsrdToRef , Pct PosErr ) The calibration data results are as follows:

[0090]

[0091] In this embodiment, f2(dp BoostErr ) The calibration data results are as follows:

[0092]

[0093]

[0094] Among them, Pct ValveDsrdD-SpeedCtrl is the closed-loop correction value of item D, Pct ValveDsrdD_SpeedCtrl =f2(dPct SpeedErr , Pct PosErr )×dPct SpeedErr ;

[0095] where dPct SpeedErr =dPct PosDsrdErr +dPct PosErr , which is the ideal opening change rate of the mixing valve dPct PosDsrdErr The actual opening rate of the mixing valve -dPct PosErr The actual opening rate of the mixing valve is the rate of change of the difference between the actual opening of the mixing valve and the target opening, dPct PosDsrdErr =max[f1(Pct PosErr ),f1(Pct PosDsrdToRef )]; where f1(Pct PosErr ) is based on the mixing valve opening deviation Pct PosErr The ideal rate of change obtained, f1(Pct PosDsrdToRef ) is the target opening of the mixing valve relative to the default opening Pct PosDsrdToRef The maximum rate of change limit for obtaining a soft landing;

[0096] f1(Pct PosErr ) by Pct PosErr Calibration results: f1(Pct PosDsrdToRef ) by Pct PosDsrdToRef Calibration results: f2(dPct SpeedErr , Pct PosErr ) by dPct SpeedErr With Pct PosErr Joint calibration is obtained;

[0097] In this embodiment, f1(Pct PosErr ) The calibration data results are as follows:

[0098]

[0099] In this embodiment, f1(Pct PosDsrdToRef ) The calibration data results are as follows:

[0100]

[0101] In this embodiment, f2(dPct SpeedErr , PctPosErr ) The calibration data results are as follows:

[0102]

[0103] Specifically, for I item Pct ValveDsrdI , its value is based on the following three situations, and when the vehicle is powered on, the mixing valve will enter the inactive state, I Pct ValveDsrdI The default value of the initial value is 0;

[0104] Case 1: If the mixing valve response performance fails, the I Pct ValveDsrdI =0;

[0105] Second case: If the mixing valve enters the inactive state, I Pct ValveDsrdI =Pct ValveDsrdI (z)×0.85, until Pct ValveDsrdI If the absolute value of the difference from 0 does not exceed 0.5%, then Pct ValveDsrdI Set to 0; where Pct ValveDsrdI (z) is the duty cycle calculated from the previous sampling period in periodic sampling, Pct ValveDsrdI It will be updated once in each sampling period Δt. In this example, Δt is 10ms.

[0106] The third case: Pct. ValveDsrdI Equal to its original value Pct ValveDsrdRaw , Pct ValveDsrdIRaw =[Pct ValveDsrdI (z)+Pct ValveDsrdI_Incre ]×f3(dPct SpeedErr , Pct PosErr );

[0107] Where f3(dPct SpeedErr , Pct PosErr ) by dPct SpeedErr With Pct PosErr Joint calibration is obtained;

[0108] In this embodiment, f3(dPct SpeedErr , Pct PosErr ) The calibration data results are as follows:

[0109]

[0110] Among them, Pct ValveDsrdI (z) is the duty cycle calculated in the previous sampling period in periodic sampling, and its default value is 0 when the vehicle is powered on;

[0111] Among them, Pct ValveDsrdI-Incre is the cumulative term, PctValveDsrdI-Incre =f2(dPct PosDrsd )×f2(Pct PosErr )×f4(dPct SpeedErr , Pct PosErr )×Δt×(Pct PosErr -K WindUpGain ×Pct SaturateOld ); where Δt is the sampling period, which is 10ms in this example; dPct PosDrsd is the target opening rate of the mixing valve; K WindUpGain is the anti-integral saturation correction coefficient, which is the preset value. In this example, it is 0.002; f4(dPct SpeedErr , Pct PosErr ) is the correction factor for the cumulative term I;

[0112] Where f4(dPct SpeedErr , Pct PosErr ) by dPct SpeedErr With Pct PosErr The joint calibration results are: f2(dPct PosDrsd ) by dPct PosDrsd Calibration results: f2(Pct PosErr ) by Pct PosErr Calibration is obtained;

[0113] In this embodiment, f4(dPct SpeedErr , Pct PosErr ) The calibration data results are as follows:

[0114]

[0115] In this embodiment, f2(dPct PosDrsd ) The calibration data results are as follows:

[0116]

[0117] In this embodiment, f2(Pct PosErr ) The calibration data results are as follows:

[0118]

[0119]

[0120] Among them, Pct SaturateOld It is the EGR valve saturation opening degree of the previous sampling cycle in periodic sampling.

[0121] In this embodiment, obtain Pct ValveDsrdFF +Pct ValveDsrdP +Pct ValveDsrdI +PctValveDsrdD The minimum value Pct ValveMin (take 0 in this embodiment) and the maximum value Pct ValveMax (100% in this embodiment) to limit the mixing valve control duty cycle Pct of the final closed-loop control ValveDsrdFinal At the minimum value Pct ValveMin and maximum value Pct ValveMax Between, that is, Pct ValveMin ≤Pct ValveDsrdFinal ≤Pct ValveMax ;Control the duty cycle Pct through the mixing valve ValveDsrdFinal Control the mixing valve drive motor PWM control to ensure that the actual opening of the mixing valve follows the target opening of the mixing valve;

[0122] Among them, Pct Saturate =Pct ValveDsrdFF +Pct ValveDsrdP +Pct ValveDsrdI -Pct ValveDsrdFinal , Pct SaturateOld Pct of the previous sampling period Saturate .

[0123] In summary, the present invention provides a method for controlling the responsiveness of a mixing valve in a low-pressure EGR system, which can achieve high dynamic responsiveness and high stability of the mixing valve.

[0124] 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.

[0125] 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 controlling the responsiveness of a mixing valve in a low-pressure EGR system, characterized in that: include: Test the response performance of the mixing valve to determine whether the response performance of the mixing valve is faulty; determining whether the mixing valve enters an activated state or an inactivated state; When the response performance of the mixing valve is not faulty and the mixing valve enters an activated state, the target opening of the mixing valve and the actual opening of the mixing valve are obtained, and the actual opening of the mixing valve is controlled to follow the target opening of the mixing valve; otherwise, the mixing valve is not controlled to operate, and the PWM duty cycle of the mixing valve execution motor is 0%; The method for controlling the actual opening of the mixing valve to follow the target opening is: A feedforward part is combined with a PID control part to obtain a mixing valve control duty cycle, and the mixing valve drive motor PWM control is controlled by the mixing valve control duty cycle; The feedforward part is ;in Pct PosDsrdToRef The target opening of the mixing valve is relative to the default opening, that is, the target opening of the mixing valve is subtracted from the default opening; Pct PosErr is the mixing valve opening deviation, which is obtained by subtracting the actual opening of the mixing valve from the target opening; f ( Pct PosDsrdToRef )Depend on Pct PosDsrdToRef Calibration is obtained; f ( Pct PosErr )Depend on Pct PosErr Calibration is obtained; The PID control part is Pct ValveDsrdP + Pct ValveDsrdI + Pct ValveDsrdD ;in Pct ValveDsrdP is the P term, Pct ValveDsrdI is item I, Pct ValveDsrdD It is item D; Get Pct ValveDsrdFF + Pct ValveDsrdP + Pct ValveDsrdI + Pct ValveDsrdD Minimum value of Pct ValveMin and maximum value Pct ValveMax , which defines the mixing valve control duty cycle for the final closed-loop control Pct ValveDsrdFinal At minimum Pct ValveMin and maximum value Pct ValveMax Between, that is Pct ValveMin ≤ Pct ValveDsrdFinal ≤ Pct ValveMax ; The duty cycle is controlled by the mixing valve Pct ValveDsrdFinal The mixing valve driving motor is controlled by PWM control to achieve that the actual opening of the mixing valve follows the target opening of the mixing valve.

2. The method for controlling the responsiveness of a mixing valve in a low-pressure EGR system according to claim 1, characterized in that: The P term ;in f 1( Pct PosDsrdToRef , Pct PosErr ) is the P correction factor, p BoostErr It is the difference between the target boost pressure and the actual boost pressure in boost control. f 1( p BoostErr )for p BoostErr Determined correction factors; f 1( Pct PosDsrdToRef , Pct PosErr )Depend on Pct PosDsrdToRef and Pct PosErr Joint calibration is obtained; f 1( p BoostErr )Depend on p BoostErr Calibration obtained.

3. The method for controlling the responsiveness of a mixing valve in a low-pressure EGR system according to claim 2, characterized in that: The D item ; in Pct ValveDsrdD_Base is the reference value of the duty cycle of item D, ,in f 2( Pct PosDsrdToRef , Pct PosErr ) is the correction factor for item D, dPct PosErr is the rate of change of the difference between the target opening of the mixing valve and the actual opening of the mixing valve, dp BoostErr is the rate of change of the difference between the target boost pressure and the actual boost pressure in boost control, f 2(d p BoostErr ) is d p BoostErr Determined correction factors; f 2( Pct PosDsrdToRef , Pct PosErr )Depend on Pct PosDsrdToRef and Pct PosErr Joint calibration is obtained; f 2(d p BoostErr ) by d p BoostErr Calibration is obtained; in Pct ValveDsrdD_SpeedCtrl is the closed-loop correction value of item D, ; in , which is the ideal opening rate of the mixing valve dPct PosDsrdErr The actual opening rate of the mixing valve is − dPct PosErr The actual opening change rate of the mixing valve is the change rate of the difference between the actual opening of the mixing valve and the target opening. ;in f 1( Pct PosErr ) is based on the mixing valve opening deviation Pct PosErr Get the ideal rate of change, f 1( Pct PosDsrdToRef ) is the target opening of the mixing valve relative to the default opening Pct PosDsrdToRef The maximum rate of change limit for obtaining a soft landing; f 1( Pct PosErr )Depend on Pct PosErr Calibration is obtained; f 1( Pct PosDsrdToRef )Depend on Pct PosDsrdToRef Calibration is obtained; f 2( dPct SpeedErr , Pct PosErr )Depend on dPct SpeedErr and Pct PosErr Joint calibration is obtained.

4. The method for controlling the responsiveness of a mixing valve in a low-pressure EGR system according to claim 3, characterized in that: For the item I Pct ValveDsrdI , its value is based on the following three situations, and when the vehicle is powered on, the mixing valve will enter the inactive state, the I item Pct ValveDsrdI The default value of the initial value is 0; First case: If the response performance of the mixing valve fails, the item I Pct ValveDsrdI =0; Second situation: If the mixing valve enters the inactive state, the item I , until Pct ValveDsrdI If the absolute value of the difference from 0 does not exceed 0.5%, Pct ValveDsrdI Set to 0; Pct ValveDsrdI ( z ) is the duty cycle of item I calculated in the previous sampling period in periodic sampling, Pct ValveDsrdI In each sampling cycle Δt Update once within; The third case: the above item I Pct ValveDsrdI Equal to its original value Pct ValveDsrdIRaw , ; in f 3( dPct SpeedErr , Pct PosErr )Depend on dPct SpeedErr and Pct PosErr Joint calibration is obtained; in Pct ValveDsrdI ( z ) is the duty cycle calculated in the previous sampling period in periodic sampling, and its default value is 0 when the vehicle is powered on; in Pct ValveDsrdI_Incre is the I-term cumulative term, Pct ValveDsrdI_Incre = f 2( dPct PosDrsd )× f 2( Pct PosErr )× f 4( dPct SpeedErr , Pct PosErr )×Δ t ×( Pct PosErr - K WindUpGain × Pct SaturateOld );where Δ t is the sampling period; dPct PosDrsd is the target opening rate of the mixing valve; K WindUpGain is the anti-integral saturation correction coefficient, which is the preset value; f 4( dPct SpeedErr , Pct PosErr ) is the correction factor for the cumulative term I; in f 4( dPct SpeedErr , Pct PosErr )Depend on dPct SpeedErr and Pct PosErr Joint calibration is obtained; f 2( dPct PosDrsd )Depend on dPct PosDrsd Calibration is obtained; f 2( Pct PosErr )Depend on Pct PosErr Calibration is obtained; in Pct SaturateOld is the EGR valve saturation opening degree of the previous sampling period in periodic sampling; in , Pct SaturateOld The last sampling period Pct Saturate .

5. The method for controlling the responsiveness of a mixing valve in a low-pressure EGR system according to claim 1, characterized in that: The detection of the response performance of the mixing valve is specifically carried out by using an engine mixing valve response performance detection method, including any working condition mixing valve response performance detection and / or steady state working condition mixing valve response performance detection, wherein: Mixing valve response performance test under any working condition: Determine the mixing valve response performance test conditions, read and retain N mixing valve target openings in the most recent time, determine the initial and final values ​​of the mixing valve actual opening, compare the mixing valve actual opening with the final value of the mixing valve actual maximum opening or the final value of the mixing valve actual minimum opening, and judge the mixing valve response performance; Steady-state mixing valve response performance test: Determine if the steady-state operating conditions are met. Perform a mixing valve response performance test based on the steady-state operating conditions. Accumulate the first opening time t1 from the target EGR rate of 0 to the start of the mixing valve opening change, and the second opening time t2 from the start of the mixing valve opening change to the fully open state. Compare t1 and t2 with their respective limits to determine whether the mixing valve is experiencing a steady-state response performance failure. As long as any one of the mixing valve response performance test under any working condition and the mixing valve response performance test under steady-state working condition fails, it indicates that the mixing valve response performance fails; otherwise, no failure occurs.

6. The method for controlling the responsiveness of a mixing valve in a low-pressure EGR system according to claim 1, characterized in that: The determination of whether the mixing valve enters an activated state or an inactivated state is specifically performed by a method for determining the activation state of the mixing valve of the low-pressure EGR system, specifically including: Obtaining a target boost pressure demand value. When the target boost pressure demand value is less than a preset boost pressure demand value and at least one of the following four conditions is met, controlling the mixing valve to enter an activated state, and the mixing valve receives a mixing valve opening control instruction; Condition 1: EGR valve pressure difference is less than the preset EGR valve pressure difference; Condition 2: The EGR valve opening is greater than the preset EGR valve opening, and the target EGR rate change rate is greater than the preset EGR rate change rate; Condition 3: The throttle valve front-to-back pressure ratio is less than the preset throttle valve pressure ratio; Condition 4: The target EGR rate is greater than the preset EGR rate.

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