CN113417776B - Flow measuring method and controller - Google Patents

Abstract

The invention discloses a flow measuring method and a controller, wherein the flow measuring method comprises the following steps: when the engine runs, if the mass flow sensor has measurement deviation, judging whether the set working condition parameters reach the specified working condition point; if the working condition parameters reach the working condition points, taking the numerical values corresponding to the working condition parameters as input, and calculating the reference flow corresponding to the current working condition points through a flow model; calibrating a flow measurement curve of the mass flow sensor by a reference flow; wherein the flow measurement curve is used to determine the flow. The flow measurement method provided by the invention adopts the flow calculated by the flow model as the reference flow, does not need to close the EGR valve in the process of flow measurement curve calibration, and does not need to adopt the total intake air quantity obtained after closing the EGR valve as the reference flow, thereby ensuring that the emission control of the normal operation of the engine is not interfered.

Description

A flow measurement method and controller

technical field

Embodiments of the present invention relate to measurement control technologies, and in particular, to a flow measurement method and controller.

Background technique

With the escalation of emission regulations, the engine aftertreatment system needs to strictly comply with regulations to deal with harmful emissions such as NOx and HC.

The original engine emission control is the basis for dealing with harmful emissions. Especially, for the engine with EGR system, the real, reasonable and effective EGR rate control is an important guarantee for the original engine emission control. The control of the EGR rate depends on the measurement accuracy of the fresh air volume or the EGR flow rate. If the above-mentioned gas flow rate is inaccurately measured, deviations in the control of the EGR rate are likely to occur.

In the prior art, a mass flow sensor is usually used to measure the above-mentioned gas flow, but the mass flow sensor is affected by the installation pipeline, the cleanliness of the sensor and the zero drift of the sensor itself, and a certain degree of measurement deviation usually occurs during use.

SUMMARY OF THE INVENTION

The invention provides a flow measurement method and a controller, so as to achieve the purpose of ensuring that the mass flow sensor always outputs a relatively accurate flow (mass) measurement value without disturbing the emission control of the normal operation of the engine.

In a first aspect, an embodiment of the present invention provides a flow measurement method, including: when an engine is running, if a measurement deviation occurs in a mass flow sensor, determining whether a set operating condition parameter reaches a specified operating point;

If the working condition parameter reaches the working condition point, the value corresponding to the working condition parameter is used as the input, and the reference flow rate corresponding to the current working condition point is calculated through the flow model;

Calibrate the flow measurement curve of the mass flow sensor by the reference flow;

Wherein, the flow measurement curve is used to determine the flow.

Further, judging whether the engine runs through all the specified operating points, and if so, calibrates the flow measurement curve of the mass flow sensor through all the reference flows;

Wherein, all the reference flow rates are in one-to-one correspondence with all the specified operating points.

Further, judging whether the mass flow sensor has a measurement deviation includes:

Comparing the flow measured by the mass flow sensor and the flow calculated by the flow model, and if the difference between the two exceeds the set flow difference, it is determined that the mass flow sensor has a measurement deviation.

Further, it also includes:

Control the EGR valve to close;

Determine whether the difference between the flow rate measured by the mass flow sensor and the total intake air exceeds the set difference value;

If before the EGR valve is closed, the difference between the flow measured by the mass flow sensor and the flow calculated by the flow model exceeds the set flow difference, after the EGR valve is closed, the flow measured by the mass flow sensor and the total intake air If the difference of the quantity exceeds the set difference, it is determined that the mass flow sensor has a measurement deviation;

Control the EGR valve to open.

Further, the flow difference value is associated with the engine speed and the engine fuel injection amount;

The flow difference value is determined from the first MAP map.

Further, the difference is associated with engine speed and ambient pressure;

The difference is determined from the second MAP map.

Further, when the engine enters the reverse phase, the EGR valve is controlled to be closed.

Further, the traffic model adopts a neural network model.

Further, the difference between the actual flow rates corresponding to two adjacent operating points is the same.

In a second aspect, an embodiment of the present invention further provides a controller that stores an executable program, where the executable program is used to implement the flow measurement method described in the embodiment.

Compared with the prior art, the beneficial effects of the present invention are:

1. The flow measurement method proposed by the present invention constructs a flow model that is separated from the input parameters of the mass flow sensor, determines the reference flow under the specified operating point through the flow model, and calibrates the flow measurement curve of the mass flow sensor through the flow model. The input parameters have nothing to do with the input parameters of the mass flow sensor, and the accuracy of the reference flow calculated by the flow model at the specified operating point is high. Therefore, the accuracy of the flow measurement curve calibrated based on the reference flow is high, which can ensure that the mass flow sensor is always Outputs a more accurate flow (mass) measurement.

2. The flow calculated by the flow model is used as the reference flow. In the process of calibrating the flow measurement curve, there is no need to close the EGR valve, and there is no need to use the total intake air obtained after closing the EGR valve as the reference flow, so as to ensure that it will not interfere with the normal operation of the engine. Operational emission control.

Description of drawings

1 is a schematic structural diagram of an engine intake and exhaust pipeline in an embodiment;

Fig. 2 is the flow chart of the mass flow sensor calibration method in the embodiment;

3 is a flowchart of another mass flow sensor calibration method in an embodiment;

FIG. 4 is a flowchart of another mass flow sensor calibration method in the embodiment.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention. In addition, it should be noted that, for the convenience of description, the drawings only show some but not all structures related to the present invention.

Example 1

This embodiment proposes a flow measurement method, which is used to measure the flow (mass) of fresh air entering an engine cylinder. FIG. 1 is a schematic structural diagram of an engine intake and exhaust pipeline in the embodiment. The pipeline may include filter 1, mass flow sensor 2, compressor 3, turbine 4, throttle valve 5, EGR valve 6, EGR cooler 7, pressure sensor P22.

Exemplarily, the filter 1, the mass flow sensor 2, the compressor 3, and the throttle valve 5 are connected in sequence to form an intake pipeline, and the air enters the cylinder of the engine through the intake pipeline; the turbine 4 is placed on the exhaust manifold, and the waste passes through The exhaust manifold is discharged; the EGR cooler 7 and the EGR valve 6 are located between the engine intake port and the exhaust port, and a part of the gas discharged from the exhaust port as EGR gas passes through the EGR cooler 7 and the EGR valve 6 and returns to the engine in the cylinder.

Exemplarily, in this embodiment, the flow measurement method is used to measure the air flow (mass) passing through the filter 1 , that is, the flow (mass) of fresh air.

Exemplarily, the pressure sensor P22 is used to measure the total amount of intake air entering the engine cylinders, where the total intake air includes fresh air flow and EGR gas flow.

Illustratively, when the EGR valve is closed, the fresh air flow is the same as the total intake air.

Exemplarily, in this embodiment, the mass flow sensor 2 may be an HFM sensor or a MAF sensor, and the air flow (mass) measurement is implemented based on the mass flow sensor 2 .

Exemplarily, during the use of the mass flow sensor 2, a deviation between the measured value and the actual value may occur due to zero point drift and use loss. In order to enable the mass flow sensor to output an accurate flow measurement value, when the mass flow sensor has a measurement deviation , the mass flow sensor needs to be calibrated.

In this embodiment, the flow measurement method includes: determining the air flow through the flow measurement curve of the mass flow sensor, wherein if the measurement deviation of the mass flow sensor occurs, the flow measurement curve of the mass flow sensor is calibrated.

Fig. 2 is the flow chart of the mass flow sensor calibration method in the embodiment, with reference to Fig. 2, the flow measurement curve calibration method includes:

S101. Determine whether the set working condition parameters reach the specified working condition point.

Exemplarily, the operating state of the engine is related to the intake air amount of the engine. In this embodiment, the operating condition parameters mainly include factors that can reflect the operating state of the engine.

Exemplarily, an engine operating parameter that is closely related to the intake air amount and can be obtained directly may be determined through a calibration test, and the above-mentioned engine operating parameter may be used as a working condition parameter.

Exemplarily, the operating condition parameters may include engine speed, rail pressure measurement, boost pressure, intake air pressure, intake air temperature, engine outlet water temperature, SCR upstream temperature, main injection advance angle, main injection set advance angle, Fuel injection volume, total fuel injection volume, NOx emissions, etc.

Exemplarily, in this embodiment, the above-mentioned operating condition parameters are used to represent the operating conditions of the engine, and one operating condition point includes values corresponding to all the operating condition parameters at a certain moment. Among them, for the same working point, the value corresponding to each working condition parameter can fluctuate up and down within a certain range.

Exemplarily, in this embodiment, the operating point used in the calibration process of the flow measurement curve is the set value, and the strategy for selecting the operating point may be:

Determine the current intake flow range of the engine, select several intake flow values within the intake flow range randomly or according to a fixed step size, and determine the operating condition parameter value corresponding to the selected intake flow value through a calibration test. A set of working condition parameter values corresponding to the intake air flow value is taken as a working condition point;

Within the achievable working conditions of the engine, several sets of working condition parameter values are randomly selected, and a set of working condition parameter values is regarded as a working condition point.

Exemplarily, in this embodiment, when multiple operating points are included, if the value corresponding to the operating condition parameter is the same as that corresponding to one of the operating points, it is determined that the set operating condition parameter reaches the specified operating point.

S102. If the working condition parameter reaches the working condition point, use the value corresponding to the working condition parameter as the input, and calculate the reference flow rate corresponding to the current working condition point through the flow model.

Exemplarily, in this embodiment, the flow model is used to calculate the intake air flow corresponding to a certain operating point, and the flow model may be a nonlinear mathematical model such as a neural network model or a Kriging model.

S103. Calibrate the flow measurement curve of the mass flow sensor by the reference flow.

Exemplarily, thermal mode measurement is a common measurement principle for mass flow sensors, on the basis of which the calibration procedure is described.

Exemplarily, the thermal mode mass flow sensor works as follows: the flow rate (mass) of the fluid is determined by the heat inside the sensor (the heated body) taken away when the fluid flows. If the thermal power of the mass flow sensor remains unchanged, it can be The mass flow of the fluid is determined by the temperature difference of the mass flow sensor.

Exemplarily, the temperature difference has a certain functional relationship with mass flow, and the flow measurement curve can be a function curve representing temperature difference-mass flow, wherein the initial flow measurement curve configured in the mass flow sensor can be determined by calibration.

Exemplarily, when the engine is running, the mass flow sensor also works, therefore, each operating point also corresponds to a temperature difference determined by the mass flow sensor.

Exemplarily, in this embodiment, the intake air flow rate calculated by the flow model is used as the reference flow rate, and the temperature difference corresponding to one operating point and the reference flow rate are used as a calibration coordinate point.

Exemplarily, after obtaining a calibration coordinate point, the flow measurement curve can be re-fitted by using the calibration coordinate point and the sampling point of the original flow measurement curve, and the flow measurement curve can be calibrated in real time.

Exemplarily, the flow measurement curve may also be re-fitted by using all the calibration coordinate points, or the flow measurement curve may be re-fitted by using all the calibration coordinate points and the sampling points of the original flow measurement curve.

Exemplarily, the output signal of the mass flow sensor is usually an analog voltage, and the analog voltage is used to represent the measured mass flow. The flow measurement curve can also be a temperature difference-analog voltage curve. The calibration method of the temperature difference-analog voltage curve is related to the temperature difference. - The mass flow curve is calibrated in the same way.

Exemplarily, if the mass flow sensor is based on other measurement principles, the calibration method of the corresponding flow measurement curve is similar to the above-mentioned calibration method, that is, the independent variable of the mass flow sensor in the measurement process is determined, which will be corresponding to a working point. The independent variable and the reference flow are used as a calibration point, and the flow measurement curve is calibrated based on the calibration point.

Exemplarily, the flow measurement curve is re-fitted by using the reference flow rate calculated by the flow rate model and the sampling points of the original flow rate measurement curve under the specified operating point, instead of using all the reference flow rates calculated by the flow model to perform the flow rate measurement curve. The re-fitting can reduce the problem of reducing the measurement accuracy of the mass flow sensor due to the limited data samples used in the construction of the flow model, resulting in a low accuracy of the reference flow calculated by the flow model under non-specified operating points. .

The flow measurement method proposed in this embodiment constructs a flow model that is separated from the input parameters of the mass flow sensor, determines the reference flow at a specified operating point through the flow model, and calibrates the flow measurement curve of the mass flow sensor through the parameter flow. The parameters have nothing to do with the input parameters of the mass flow sensor, and the accuracy of the reference flow rate calculated by the flow model at the specified operating point is high. Therefore, the accuracy of the flow measurement curve calibrated based on the reference flow rate is high, which can ensure that the mass flow sensor always outputs A more accurate flow (mass) measurement.

In addition, since the flow calculated by the flow model is used as the reference flow, in the process of calibrating the flow measurement curve, there is no need to close the EGR valve, and there is no need to use the total intake air obtained after closing the EGR valve as the reference flow, so as to ensure that there will be no interference Emission control for normal engine operation.

Fig. 3 is another kind of mass flow sensor calibration method flow chart in the embodiment, with reference to Fig. 3, the flow measurement curve calibration method can also be:

S201. Determine whether a measurement deviation occurs in the mass flow sensor through the flow rate calculated by the flow rate model.

Exemplarily, in this solution, the traffic model adopts a neural network model, and the training process of the neural network model is the same as that in the prior art.

In particular, in this solution, the sample data set used in training the neural network model is a data set formed based on the specified operating point and the corresponding intake air flow.

For example, the working condition parameter is recorded as x _i , if the value corresponding to x _i in a specified working condition point is K _i , then for this working condition point, a set of random generation can be generated within a certain range around the value of K _i data, bind the set of data with the intake air flow corresponding to the operating point to form a data unit, and the bound data unit will be included in the sample data set.

Exemplarily, when the operating condition parameters include a variety of engine operating parameters, if in a specified operating point, the values of the various engine operating parameters are (K ₁ . . . K _n ), and the corresponding intake air flow rate is L, the data In a unit, a piece of sample data can be in the form of {random(K ₁ ), random(K ₂ )...random(K _n ), L}. Among them, random(K _i ) represents a random value near _Ki within a certain range.

Exemplarily, the final sample data set includes data units corresponding to all selected operating points.

In this solution, the flow measured by the mass flow sensor and the flow calculated by the flow model are compared, and if the difference between the two exceeds the set flow difference, it is determined that the mass flow sensor has a measurement deviation.

Exemplarily, in this solution, the flow difference value may be a nominal measurement error value of the mass flow sensor or a measurement deviation threshold value determined through a calibration experiment.

As an embodiment, the measurement deviation threshold determined by the calibration test is used as the flow difference value, wherein, during the calibration test, the corresponding relationship between the selected parameters (such as engine speed, engine fuel injection amount) and the measurement deviation threshold is determined, A first MAP map is made of the corresponding relationship between the above-mentioned selected parameters and the measured deviation value threshold.

Exemplarily, when the engine is running, the first MAP map is used to determine the flow difference value used for judging whether the mass flow sensor has a measurement deviation under the current operating condition.

S202. Determine whether the set working condition parameters reach the specified working condition point.

Exemplarily, in this solution, the strategy for selecting a working point may be:

Determine the range of engine intake air flow. Within this range, select a number of intake air flow values according to a fixed step size, and determine the operating condition parameter value corresponding to the selected intake air flow value through a calibration test. A corresponding set of parameter values of operating conditions is regarded as a operating point.

For example, if the range of the intake air flow is 0 to 1000, take 100 as a step, select 10 intake air flow values, and take a set of operating condition parameter values corresponding to each intake air flow value as a working point .

S203. If the working condition parameter reaches the working condition point, use the value corresponding to the working condition parameter as the input, and calculate the reference flow rate corresponding to the current working condition point through the flow model.

S204. Calibrate the flow measurement curve of the mass flow sensor through all the reference flows.

Exemplarily, in this solution, it is judged whether the engine runs through all the specified operating points, and if so, the flow measurement curve of the mass flow sensor is calibrated through all the reference flows.

Exemplarily, if the number of selected operating points is 10, after calculating the parameter flow corresponding to all operating points through the flow model, the flow measurement curve of the mass flow sensor is calibrated through the reference flow.

Exemplarily, in this solution, the flow measurement curve is re-fitted by using all the calibration coordinate points and the sampling points of the original flow measurement curve, so as to realize the calibration of the measurement measurement curve.

On the basis of the beneficial effects of the scheme shown in Figure 2, in this scheme, the flow rate calculated by the flow model is used to determine whether the mass flow sensor has a measurement deviation. A MAP map determines the flow difference value used to judge whether the mass flow sensor has measurement deviation, which can avoid the accuracy of the reference flow calculated by the flow model under non-specified operating points due to the limited data samples used in the training of the flow model. is lower, which in turn leads to the problem of inability to accurately determine whether the mass flow sensor has measurement deviation.

Fig. 4 is another kind of mass flow sensor calibration method flow chart in the embodiment, with reference to Fig. 4, the flow measurement curve calibration method can also be:

S301. Determine whether the mass flow sensor has a measurement deviation through the flow calculated by the flow model.

Exemplarily, in this solution, the manner of judging whether a measurement deviation occurs in the mass flow sensor is the same as that described in step S201.

S302. Control the EGR valve to close, determine whether the difference between the flow measured by the mass flow sensor and the total intake air exceeds a set difference, and control the EGR valve to open.

1, when it is determined that the mass flow sensor has a measurement deviation, the EGR valve 6 is controlled to be closed. Since the EGR pipeline is closed, the gas flow through the mass flow sensor 2 is the same as the gas flow into the engine cylinder.

Referring to FIG. 1 , in this solution, the flow rate measured by the mass flow sensor and the flow rate determined by the pressure sensor P22 are compared, and it is determined whether the difference between the two exceeds the set difference value.

When the gas flow rate after closing the EGR valve 6, that is, the total amount of intake air is determined by the pressure sensor P22, the EGR valve 6 is controlled to open.

Exemplarily, in this solution, if the difference between the flow measured by the mass flow sensor and the flow calculated by the flow model exceeds the set flow difference before the EGR valve is closed, the flow measured by the mass flow sensor after the EGR valve is closed. If the difference with the total intake air exceeds the set difference, it is determined that the mass flow sensor is abnormal.

Exemplarily, the intake and exhaust pipes of the engine are coupled by multiple components, and there are various reasons for the measurement deviation of the mass flow sensor. Generally, when the non-intake pipeline fails, even if the mass flow sensor itself is not abnormal. , the flow measured by the mass flow sensor will also have a certain deviation compared with the flow calculated by the flow model. Since the purpose of calibrating the flow measurement curve is to compensate the measurement error of the mass flow sensor itself, it needs to appear in the mass flow sensor itself. When abnormal, calibrate the flow measurement curve.

As an embodiment, the deviation threshold determined by the calibration test is used as the difference value, wherein, when the calibration test is performed, the corresponding relationship between the selected parameters (such as engine speed, ambient pressure) and the deviation threshold is determined, and the above selected parameters are used as the difference. The correspondence with the deviation value threshold is made into a second MAP map.

Exemplarily, when the engine is running, the second MAP map is used to determine the difference used to determine whether the mass flow sensor itself is abnormal under the current operating conditions.

As a possible implementation, when the engine enters the reverse phase, the EGR valve is controlled to be closed.

Exemplarily, when the engine is running normally, the EGR valve needs to be kept open. If the EGR valve is closed during this period, the NOx emission will increase, and in severe cases, the emission will exceed the standard.

In this solution, the EGR valve is closed when the engine is in the reverse towing condition. In the reverse towing condition, the vehicle moves by inertia, and there is no combustion in the engine cylinder, so there is no NOx emission problem. When the EGR valve is closed and the total amount of intake air is determined, the EGR valve is then controlled to open according to normal requirements to ensure the exhaust state of the engine during normal operation.

S303. Determine whether the set working condition parameters reach the specified working condition point.

S304. If the working condition parameter reaches the working condition point, take the value corresponding to the working condition parameter as the input, and calculate the reference flow rate corresponding to the current working condition point through the flow model.

S305. Calibrate the flow measurement curve of the mass flow sensor through all reference flows.

Exemplarily, in this solution, the implementation manners of steps S303 to S305 are the same as those described in steps S202 to S204.

On the basis of the beneficial effects of the scheme shown in Figure 3, in this scheme, when it is determined that the mass flow sensor has a measurement deviation through the reference flow calculated by the flow model, after further closing the EGR valve, the flow measured by the mass flow sensor is different from the intake air. The difference of the total amount determines whether the mass flow sensor itself is abnormal. When the mass flow sensor itself is abnormal, the flow measurement curve is recalibrated to avoid unnecessary calculation processes.

Embodiment 2

Exemplarily, the flow measurement method proposed in the first embodiment can be implemented by software. This embodiment proposes a controller. The controller is configured in a vehicle and stores an executable program. The executable program is used to implement the embodiment. Any of the flow measurement methods described.

Exemplarily, in this embodiment, the beneficial effects that can be achieved based on the controller are the same as those correspondingly described in the first embodiment.

Note that the above are only preferred embodiments of the present invention and applied technical principles. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and can also include more other equivalent embodiments without departing from the concept of the present invention. The scope is determined by the scope of the appended claims.

Claims (8)

1. A flow measurement method, comprising: when the engine runs, if the mass flow sensor has measurement deviation, judging whether the set working condition parameters reach the specified working condition point;

if the working condition parameters reach the working condition points, taking the values corresponding to the working condition parameters as input, and calculating the reference flow corresponding to the current working condition points through a flow model;

calibrating a flow measurement curve of the mass flow sensor with the reference flow;

wherein the flow measurement curve is used to determine a flow;

the flow measuring method is used for measuring the flow of fresh air entering an engine cylinder;

judging whether the mass flow sensor has measurement deviation comprises the following steps:

comparing the flow measured by the mass flow sensor with the flow calculated by the flow model, and if the difference between the flow measured by the mass flow sensor and the flow calculated by the flow model exceeds a set flow difference, judging that the mass flow sensor has measurement deviation;

controlling the EGR valve to close;

judging whether the difference between the flow measured by the mass flow sensor and the total intake air exceeds a set difference or not;

if the difference between the flow measured by the mass flow sensor and the flow calculated by the flow model exceeds the set flow difference before the EGR valve is closed, and the difference between the flow measured by the mass flow sensor and the total intake air amount exceeds the set difference after the EGR valve is closed, determining that the mass flow sensor has measurement deviation;

and controlling the EGR valve to open.

2. The flow measuring method of claim 1, wherein it is determined whether all of the specified operating points are experienced while the engine is running, and if so, a flow measurement curve of the mass flow sensor is calibrated by all of the reference flows;

and all the reference flow rates correspond to all the specified working condition points one to one.

3. The flow measuring method of claim 1, wherein the flow difference is associated with an engine speed and an engine fuel injection quantity;

the flow rate difference is determined from the first MAP.

4. The flow rate measurement method according to claim 1, wherein the set difference is associated with an engine speed and an ambient pressure;

the set difference is determined from the second MAP.

5. The flow measuring method of claim 1, wherein the EGR valve is controlled to close after the engine enters a motoring phase.

6. The flow measurement method of claim 1, wherein the flow model employs a neural network model.

7. The flow measuring method of claim 2, wherein the difference between the actual flow rates corresponding to two adjacent operating points is the same.

8. A controller characterized by storing an executable program for implementing the flow rate measurement method according to any one of claims 1 to 7.

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