CN113482785A - Engine intake flow estimation method and system - Google Patents
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Abstract
The application relates to an engine intake air flow estimation method and system, which comprises the following steps: obtaining the air flow discharged by the manifold and entering the cylinder in the current time period and the previous time period based on the air flow of the mixture entering the cylinder in the current time period and the previous time period, and performing difference on the air flow and the air flow to obtain a first difference value; obtaining an air flow estimated value of the air flow entering a manifold of the next time period throttle valve based on the flow of the expected throttle valve in the current time period and the flow of the throttle valve under the opening degree of the throttle valve in the current time period; and obtaining the air inflow in the cylinder in the next time period based on the first difference value, the air flow estimated value and the air flow discharged from the manifold and entering the cylinder in the current time period. Therefore, the flow of the fresh air filled in the air inlet manifold under the dynamic working condition is estimated based on the flow of the expected throttle valve, and the aim of accurately estimating the dynamic air inlet flow of the single-point injection engine is fulfilled.
Description
Technical Field
The application relates to the technical field of engine control, in particular to an engine intake air flow estimation method and system.
Background
The gas entering a cylinder of a general air inlet channel injection engine is a mixed gas of oil and air, the fuel injection time is prior to the air intake quantity completion time (for premixing, the fuel injection is generally injected into an air intake manifold in advance), namely the fuel injection is completed before the air intake is completed at the bottom dead center of an air intake stroke. The fuel concentration can be accurately ensured if the engine is operated under steady-state conditions. However, if the engine is in a transient operating condition with a sharp change, the next cylinder intake air amount must be estimated approximately before the oil amount calculation, and then the target oil amount calculation is performed based on the intake air amount. Only in this way, the air-fuel ratio of the next time period can be better ensured, otherwise, the phenomena of 'lean acceleration and over-rich deceleration' of the engine are easily caused, the torque responsiveness is poor under the transient working condition, the emission is deteriorated, and therefore the air inflow in the cylinder needs to be estimated.
In some related technologies, a dynamic intake air flow estimation scheme adopted by a current single-point injection engine is the same as that of an air inlet multi-point injection engine, that is, based on manifold pressures of a current time period and a previous time period, manifold pressure of a next time period is estimated through an interpolation method, and then the estimated intake air flow is calculated by using a speed-density method, but the following problems exist:
(1) for a single-point injection engine, fuel oil (or fuel gas) is injected at the front end of an intake manifold, and the fuel oil (or fuel gas) enters a cylinder for combustion after oil and gas are mixed in the intake manifold, so expected fuel injection quantity is calculated based on fresh air flow in the intake manifold, dynamic intake air flow estimation of the single-point injection engine is carried out by adopting dynamic intake air flow estimation of a multi-point injection engine, and fresh air flow filled in the intake manifold under a dynamic working condition is not estimated, so that estimation of the intake air quantity of the engine in the next time period has deviation.
(2) When the dynamic intake air flow is estimated, the expected throttle opening degree is not considered, the expected throttle opening degree requirements under different states are different, and when the expected throttle opening degree changes, the deviation between the estimated intake air flow and the actual flow is large.
Disclosure of Invention
The embodiment of the application provides an engine intake air flow estimation method and system, which aim to solve the problem that the estimation of the engine intake air amount in the next time period has deviation because the dynamic intake air flow of a single-point injection engine in the related technology is estimated and the fresh air flow filled in an intake manifold under the dynamic working condition is not estimated.
In a first aspect, an engine intake air flow estimation method is provided, which includes the steps of:
obtaining the air flow discharged by the manifold and entering the cylinder in the current time period and the previous time period based on the air flow of the mixture entering the cylinder in the current time period and the previous time period, and performing difference on the air flow and the air flow to obtain a first difference value;
obtaining an air flow estimated value of the air flow entering a manifold of the next time period throttle valve based on the flow of the expected throttle valve in the current time period and the flow of the throttle valve under the opening degree of the throttle valve in the current time period;
and obtaining the air inflow in the cylinder of the next time period based on the first difference value, the air flow estimated value and the air flow discharged from the manifold and entering the cylinder of the current time period.
The method comprises the steps of obtaining whether a manifold corresponding to the next time period of the engine is in an air charging process or an air discharging process and the air charging or air discharging amount, adding the air charging or air discharging amount to the air flow discharged by the manifold and entering a cylinder in the current time period, and obtaining the value which is the air intake amount in the cylinder in the next time period
In some embodiments, the air flow exiting the manifold and into the cylinder for the current time period is calculated according to a first formula, wherein the first formula comprises:
wherein ,
air flow rate into the cylinder from the manifold for the current time period, ratioEGRIn order to expect the EGR rate,
the flow rate of the mixture entering the cylinder for the current time period;
calculating an air flow rate out of the manifold and into the cylinder for a period of time according to a second equation, wherein the second equation comprises:
wherein ,
air flow rate into the cylinder from manifold exhaust for the last period of time, ratioEGR-oldThe desired EGR rate, the desired EGR rate for the previous time period,
the flow rate of the mixture entering the cylinder in the previous time period.
In some embodiments, the engine intake air flow estimation method further comprises calculating
A step of calculating the
The method comprises the following steps:
establishing a manifold pressure model and obtaining a current time period manifold pressure sensor measurement to estimate a current time period manifold pressure model value MAPest；
Based on the MAPestCalculating the flow of the mixture entering the cylinder through the intake valve in the current time period by using a speed-density method
In some embodiments, obtaining an estimated value of air flow entering the manifold through the throttle valve in the next time period based on the desired throttle flow in the current time period and the throttle flow at the throttle opening in the current time period comprises the following steps:
the flow of the throttle valve in the current time period is subtracted from the flow of the throttle valve in the current time period under the opening degree of the throttle valve to obtain a second difference value;
and carrying out attenuation processing on the second difference value to obtain an estimated value of the air flow entering the manifold from the throttle valve in the next time period.
In some embodiments, attenuating the second difference to obtain an estimated throttle air flow into the manifold for a next time period comprises:
performing attenuation processing on the second difference value once to obtain an attenuation value;
judging whether the flow of the throttle valve expected in the current time period changes or not;
if the attenuation value is not changed, taking the attenuation value as an air flow prediction value of the throttle valve entering the manifold in the next time period;
and if the air flow rate is changed, subtracting the air throttle flow rate after the change of the current time period from the air throttle flow rate under the opening degree of the air throttle in the current time period, adding the attenuation value to obtain an updated second difference value, carrying out attenuation treatment on the updated second difference value once to obtain a new attenuation value, and taking the new attenuation value as an air flow rate estimated value of the air throttle entering the manifold in the next time period.
In some embodiments, the second difference is attenuated by filtering.
In some embodiments, deriving an in-cylinder intake air amount for a next time period based on the first difference, the predicted airflow value, and the current time period airflow discharged from the manifold and entering the cylinder comprises:
subtracting the air flow estimated value from the first difference value to obtain a third difference value;
and adding the third difference value with the air flow discharged from the manifold and entering the cylinder in the current time period to obtain the air inflow in the cylinder in the next time period.
In some embodiments, after obtaining the third difference, before adding the third difference to the air flow exiting the manifold and entering the cylinder for the current time period, the method further comprises the steps of:
and correcting the third difference value by using a correction coefficient.
In some embodiments, the throttle flow at the throttle opening is calculated according to a third formula
Wherein the third formula comprises:
wherein ,PinFor throttle front pressure, PoutFor throttle back pressure, TinFor the temperature before the throttle valve, AeffIs an effective cross-sectional area related to the opening of the throttle valve, R is a gas constant, P0 and T0Pressure and temperature under standard conditions, P0＝101.3kPa，T0＝20℃。
In a second aspect, an engine intake air flow estimation system is provided, comprising:
the first module is used for obtaining the air flow discharged by the manifolds and entering the cylinder in the current time period and the previous time period based on the mixed air flow entering the cylinder in the current time period and the previous time period, and obtaining a first difference value by subtracting the air flow discharged by the manifolds and entering the cylinder in the current time period and the previous time period;
the second module is used for obtaining an air flow estimated value of the air flow entering the manifold of the throttle valve in the next time period based on the expected throttle flow in the current time period and the throttle flow under the throttle opening in the current time period;
a third module obtains an in-cylinder intake air amount for a next time period based on the first difference, the predicted airflow value, and an airflow discharged from the manifold and into the cylinder for a current time period.
The beneficial effect that technical scheme that this application provided brought includes:
the embodiment of the application provides a method and a system for estimating the intake air flow of an engine, the operation of the engine is divided into a plurality of operation time periods, the flow of mixed air entering a cylinder in the current time period and the previous time period is calculated, the flow of an expected throttle valve in the current time period and the flow of the throttle valve under the throttle opening degree in the current time period are calculated, then a predicted value of the air flow entering a manifold in the next time period and the difference value of the air flow discharged from the manifold in the current time period and the previous time period and entering the cylinder are obtained respectively, then the difference value and the predicted value of the air flow entering the manifold are differed to obtain whether the manifold in the next time period of the engine is in an inflation process or an exhaust process and the amount of inflation or exhaust, the amount of the inflation or exhaust is added with the air flow discharged from the manifold in the current time period and entering the cylinder, and the air flow in the cylinder in the next time period is the intake air amount in the cylinder in the next time period, therefore, the air intake flow in the cylinder in the next time period is estimated according to the air intake amount in the manifold under different working conditions by the mode, and the purpose of accurately estimating the dynamic air intake flow of the single-point injection engine is achieved.
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In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a flow chart of a method for estimating motive intake air flow according to an embodiment of the present disclosure;
FIG. 2 is a flow chart of the damping to obtain the predicted air flow into the manifold for the next time period when the desired throttle flow changes as provided by the embodiments of the present application.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
The embodiment of the application provides an engine intake flow estimation method and system, which aim to solve the problem that the estimation of the engine intake air amount in the next time period has deviation because the dynamic intake flow of a single-point injection engine in the related technology is estimated and the fresh air flow filled in an intake manifold under the dynamic working condition is not estimated.
The inventors have found the following on the basis of the principle of the influence of the filling action of the intake manifold on the in-cylinder dynamic intake air flow rate:
for a single-point injection engine, since fuel (or gas) is injected at the front end of the intake manifold and combusted in the cylinder after the mixture of fuel and gas in the intake manifold, the expected fuel injection amount should be calculated based on the air flow newly charged into the intake manifold. Regarding the intake manifold as an open system, the pressure change equation in the intake manifold can be obtained according to the ideal gas state equation, and the following formula is specifically shown in the specification:
According to the formula, when the engine is in a steady state working condition, the air inlet flow flowing into the air inlet manifold
Flow out of the intake manifold
At this time, the air flow rate in the intake manifold
Air flow through the throttle
Air flow through the inlet valve
When the engine is in a transition working condition, the throttle valve is quickly opened, the air inlet manifold carries out an air charging process, and the air inlet flow flowing into the air inlet manifold
Flow out of the intake manifold
Whereby the pressure in the manifold varies
When the throttle valve is closed quickly, the intake manifold is an exhaust process, and the flow of intake air flowing into the intake manifold
< flow out of intake manifold
Whereby the pressure in the manifold varies
At this time, the intake air flow rate into the intake manifold is calculated from the compressible gas equation
Or the air inlet flow into the engine cylinder calculated by a speed-density method is not equal to the fresh air flow in the air inlet manifold
Resulting in inaccurate calculation of the desired fuel flow. Therefore, the following method for estimating the intake air flow of the engine is provided.
Referring to fig. 1, a method for estimating an intake air flow of an engine includes the following steps:
101. calculating the flow of the mixture gas entering the cylinder in the current time period and the flow of the mixture gas entering the cylinder in the previous time period, and obtaining the flow of the air discharged by the manifold and entering the cylinder in the current time period based on the flow of the mixture gas entering the cylinder in the current time period and the flow of the mixture gas entering the cylinder in the previous time period
And the air flow discharged from the manifold and entering the cylinder during the previous period
Then, the difference is made to obtain the first difference value
That is, the first difference is obtained according to the following formula
102. Calculating the expected throttle flow in the current time period
And throttle flow rate at throttle opening for the current time period
Desired throttle flow based on current time period
And throttle flow rate at throttle opening for the current time period
Obtaining an estimated value of air flow into the manifold of the throttle valve in the next time period
103. Based on the first difference
Air flow prediction value
And the air flow discharged from the manifold and into the cylinder during the current time period
Obtaining the air inflow in the cylinder in the next time period according to the following formula
The formula is as follows:
By the above steps, the operation of the engine is divided into a plurality of operation periods, and the air flow discharged from the manifold and introduced into the cylinder is firstly performed in the current period
And the air flow discharged from the manifold and entering the cylinder during the previous period
And the desired throttle flow for the current time period
And throttle flow rate at throttle opening for the current time period
Then, respectively obtaining the predicted values of the air flow entering the manifold from the throttle valve in the next time period
And the difference between the air flow discharged from the manifold and entering the cylinder in the current time period and the previous time period, i.e. the first difference
Then the first difference value is compared
And an estimate of intake air flow to the manifold
Making a difference to obtain whether the manifold is in the charging process or the exhausting process in the next time period of the corresponding engine and the charging or exhausting amount, adding the charging or exhausting amount to the air flow discharged by the manifold and entering the cylinder in the current time period to obtain the value which is the air inflow in the cylinder in the next time period, and therefore, the air inflow is based on the expected throttle flow in the above mode
The method has the advantages that different conditions of air inflow in the manifold under different working conditions of the engine are considered, so that the air inflow in the cylinder in the next time period is estimated, errors caused by an air inflow estimation method of a multipoint injection engine are avoided, and the purpose of accurately estimating the dynamic air inflow of the single-point injection engine is achieved.
In some preferred embodiments, the desired throttle flow is calculated for the current time period
And throttle flow rate at throttle opening for the current time period
The method comprises the following steps:
calculating an air flow rate discharged from the manifold and into the cylinder for a current time period according to a first formula, wherein the first formula comprises:
wherein ,
air flow rate into the cylinder from the manifold for the current time period, ratioEGRIn order to expect the EGR rate,
the flow rate of the mixture entering the cylinder for the current time period;
calculating an air flow rate out of the manifold and into the cylinder for a period of time according to a second equation, wherein the second equation comprises:
wherein ,
air flow rate into the cylinder from manifold exhaust for the last period of time, ratioEGR-oldFor the period of time in which the EGR rate is desired,
the flow rate of the mixture entering the cylinder in the previous time period.
Further, the method for estimating the intake air flow of the engine further comprises calculating
A step of calculating the
The method comprises the following steps:
establishing a manifold pressure model and obtaining a current time period manifold pressure sensor measurement to estimate a current time period manifold pressure model value MAPest；
Based on MAPestCalculating the flow of the mixture entering the cylinder through the intake valve in the current time period by using a speed-density method
In some preferred embodiments, throttle flow is desired based on the current time period
And throttle flow rate at throttle opening for the current time period
Obtaining an estimated value of air flow into the manifold of the throttle valve in the next time period
The method comprises the following steps:
desired throttle flow for current time period
And throttle flow rate at throttle opening for the current time period
Making a difference to obtain a second difference value
For the second difference
Performing attenuation processing to obtain the predicted value of the air flow entering the manifold from the throttle valve in the next time period
Further, the calculation is effected in consideration of the fact that the throttle is expected to change in the subsequent period, and therefore the second difference is applied thereto
The method comprises the following specific steps:
201. desired throttle flow for current time period
And throttle flow rate at throttle opening for the current time period
Making a difference to obtain a second difference value
202. For the second difference
Performing attenuation treatment once to obtain attenuation value
203. Determining the desired throttle flow for the current time period
Whether a change has occurred;
206. if no change occurs, the attenuation value is adjusted
As an estimate of air flow into the manifold for the next period of time
204. If the air throttle opening degree changes, acquiring the expected throttle flow after the current time period changes and the air throttle flow under the throttle opening degree after the expected throttle flow changes, then subtracting the two to obtain a difference value, and comparing the difference value with the attenuation value
Adding to obtain a new second difference value;
205. using the new attenuation value as the predicted value of the air flow entering the manifold of the throttle valve in the next time period
Wherein the predicted amount of air flow into the manifold is calculated every period of time during the dynamic to steady state transition due to the engine transitioning from dynamic to steady state
Is attenuated once, and when the attenuation value is 0, the steady state is proved, and the change gradient value of the next time period and the current time period is proved to be a steady state
Air flow out of manifold and into cylinder during current time period
The difference in (a) is the air flow rate discharged from the manifold and into the cylinder during the next period
An example is given below for illustration:
Further, the second difference value is filtered
Attenuation is performed.
In some preferred embodiments, the throttle flow rate at the throttle opening degree is calculated according to the third formula
Wherein the third formula comprises:
wherein ,PinFor throttle front pressure, PoutFor throttle back pressure, TinFor the temperature before the throttle valve, AeffEffective cross-sectional area, P, related to throttle opening0 and T0R is the gas constant, P in this example, for the pressure and temperature under standard conditions0＝101.3kPa，T0＝20℃。
In some preferred embodiments, to ensure the accuracy of the calculation under different engine operating conditions, the third difference is calibrated and corrected by the following formula for the air flow discharged from the manifold and entering the cylinder during the next time period
There is also provided an engine intake air flow estimation system, comprising:
a first module for calculating the flow of the mixture gas entering the cylinder in the current time period and the flow of the mixture gas entering the cylinder in the previous time period, and obtaining the flow of the air discharged from the manifold and entering the cylinder in the current time period based on the flow of the mixture gas entering the cylinder in the current time period and the flow of the mixture gas entering the cylinder in the previous time period
And the air flow discharged from the manifold and entering the cylinder during the previous period
Then, the difference is made to obtain the first difference value
A second module to calculate a desired throttle flow for a current time period
And throttle flow rate at throttle opening for the current time period
Desired throttle flow based on current time period
And throttle flow rate at throttle opening for the current time period
Obtaining an estimated value of air flow into the manifold of the throttle valve in the next time period
A third module for basing the first difference value
Air flow prediction value
And the air flow discharged from the manifold and into the cylinder during the current time period
Obtaining the air input in the cylinder in the next time period
A storage medium is also proposed, which includes a stored program, wherein the apparatus on which the storage medium is controlled when the program is executed performs the above-described engine intake air flow estimation method.
The principle of the application is as follows:
(1) dividing engine operation into multiple operation periods, and introducing air flow discharged from manifold into cylinder in the current period
And the air flow discharged from the manifold and entering the cylinder during the previous period
And the desired throttle flow for the current time period
And throttle flow rate at throttle opening for the current time period
Then, respectively obtaining the predicted values of the air flow entering the manifold from the throttle valve in the next time period
And the difference between the air flow discharged from the manifold and entering the cylinder in the current time period and the previous time period, i.e. the first difference
Then the first one isDifference value
And an estimate of intake air flow to the manifold
Making a difference to obtain whether the manifold is in the charging process or the exhausting process in the next time period of the corresponding engine and the charging or exhausting amount, adding the charging or exhausting amount to the air flow discharged by the manifold and entering the cylinder in the current time period to obtain the value which is the air inflow in the cylinder in the next time period, and therefore, the air inflow is based on the expected throttle flow in the above mode
The method has the advantages that different conditions of air inflow in the manifold under different working conditions of the engine are considered, so that the air inflow in the cylinder in the next time period is estimated, errors caused by an air inflow estimation method of a multipoint injection engine are avoided, and the purpose of accurately estimating the dynamic air inflow of the single-point injection engine is achieved.
(2) The change of the expected throttle valve is considered, and the air flow entering the manifold dynamically of the engine is matched for calculation, so that the accuracy of the estimated dynamic intake air flow is further improved.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks. In a typical configuration, a device includes one or more processors, memories, and buses. May include input/output interfaces, network interfaces, etc. The memory may include volatile memory in a computer readable medium, random access memory, and/or nonvolatile memory, such as read only memory or flash memory, and the memory includes at least one memory chip. The memory is an example of a computer-readable medium. Computer-readable media, including both non-transitory and non-transitory, removable and non-removable media, may implement information storage by any method or technology. The information may be computer readable instructions, data structures, modules of a program, or other data. Examples of computer storage media include, but are not limited to, phase change memory, static random access memory, dynamic random access memory, other types of random access memory, read only memory, electrically erasable programmable read only memory, flash memory or other memory technology, compact disc read only memory, digital versatile discs or other optical storage, magnetic cassettes, magnetic tape disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information that can be accessed by a computing device. As defined herein, computer readable media does not include transitory computer readable media such as modulated data signals and carrier waves.
In the description of the present application, it should be noted that the terms "upper", "lower", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, which are only for convenience in describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and operate, and thus, should not be construed as limiting the present application. Unless expressly stated or limited otherwise, the terms "mounted," "connected," and "connected" are intended to be inclusive and mean, for example, that they may be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as appropriate.
It is noted that, in the present application, relational terms such as "first" and "second", and the like, are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
The above description is merely exemplary of the present application and is presented to enable those skilled in the art to understand and practice the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. An engine intake air flow estimation method is characterized by comprising the following steps:
obtaining the air flow discharged by the manifold and entering the cylinder in the current time period and the previous time period based on the air flow of the mixture entering the cylinder in the current time period and the previous time period, and performing difference on the air flow and the air flow to obtain a first difference value;
obtaining an air flow estimated value of the air flow entering a manifold of the next time period throttle valve based on the flow of the expected throttle valve in the current time period and the flow of the throttle valve under the opening degree of the throttle valve in the current time period;
and obtaining the air inflow in the cylinder of the next time period based on the first difference value, the air flow estimated value and the air flow discharged from the manifold and entering the cylinder of the current time period.
2. The engine intake air flow estimation method as claimed in claim 1, wherein:
calculating an air flow rate discharged from the manifold and into the cylinder for a current time period according to a first formula, wherein the first formula comprises:
wherein ,
air flow rate into the cylinder from the manifold for the current time period, ratioEGRIn order to expect the EGR rate,
the flow rate of the mixture entering the cylinder for the current time period;
calculating an air flow rate out of the manifold and into the cylinder for a period of time according to a second equation, wherein the second equation comprises:
wherein ,
air flow rate into the cylinder from manifold exhaust for the last period of time, ratioEGR-oldThe desired EGR rate, the desired EGR rate for the previous time period,
the flow rate of the mixture entering the cylinder in the previous time period.
3. The engine intake air flow estimation method of claim 2, further comprising calculating the engine intake air flow estimation method
A step of calculating the
The method comprises the following steps:
establishing a manifold pressure model and obtaining a current time period manifold pressure sensor measurement to estimate a current time period manifold pressure model value MAPest；
Based on the MAPestCalculating the flow of the mixture entering the cylinder through the intake valve in the current time period by using a speed-density method
4. The engine intake air flow estimation method according to claim 1, wherein the predicted value of the air flow into the manifold for the next period of time for the throttle valve is obtained based on the desired throttle flow for the current period of time and the throttle flow at the throttle opening for the current period of time, and specifically comprises the steps of:
the flow of the throttle valve in the current time period is subtracted from the flow of the throttle valve in the current time period under the opening degree of the throttle valve to obtain a second difference value;
and carrying out attenuation processing on the second difference value to obtain an estimated value of the air flow entering the manifold from the throttle valve in the next time period.
5. The method of estimating intake air flow of an engine of claim 4, wherein attenuating the second difference to obtain an estimate of air flow into the manifold for the next time period, comprises:
performing attenuation processing on the second difference value once to obtain an attenuation value;
judging whether the flow of the throttle valve expected in the current time period changes or not;
if the attenuation value is not changed, taking the attenuation value as an air flow prediction value of the throttle valve entering the manifold in the next time period;
and if the air flow rate is changed, subtracting the air throttle flow rate after the change of the current time period from the air throttle flow rate under the opening degree of the air throttle in the current time period, adding the attenuation value to obtain an updated second difference value, carrying out attenuation treatment on the updated second difference value once to obtain a new attenuation value, and taking the new attenuation value as an air flow rate estimated value of the air throttle entering the manifold in the next time period.
6. The engine intake air flow estimation method according to claim 4, wherein:
attenuating the second difference by filtering.
7. The engine intake air flow estimation method of claim 1, wherein obtaining an in-cylinder intake air amount for a next time period based on the first difference, the air flow estimate, and an air flow discharged from a manifold and entering a cylinder for a current time period comprises:
subtracting the air flow estimated value from the first difference value to obtain a third difference value;
and adding the third difference value with the air flow discharged from the manifold and entering the cylinder in the current time period to obtain the air inflow in the cylinder in the next time period.
8. The engine intake air flow estimation method of claim 6, wherein after obtaining a third difference, before adding the third difference to the air flow exiting the manifold and entering the cylinder for the current time period, further comprising the steps of:
and correcting the third difference value by using a correction coefficient.
9. The engine intake air flow estimation method as claimed in claim 1, wherein:
according to a third formula, calculating the throttle flow under the throttle opening
Wherein the third formula comprises:
wherein ,PinFor throttle front pressure, PoutFor throttle back pressure, TinFor the temperature before the throttle valve, AeffIs an effective cross-sectional area related to the opening of the throttle valve, R is a gas constant, P0 and T0Pressure and temperature under standard conditions, P0＝101.3kPa，T0＝20℃。
10. An engine intake air flow estimation system as defined in any one of claims 1 to 9, comprising:
the first module is used for obtaining the air flow discharged by the manifolds and entering the cylinder in the current time period and the previous time period based on the mixed air flow entering the cylinder in the current time period and the previous time period, and obtaining a first difference value by subtracting the air flow discharged by the manifolds and entering the cylinder in the current time period and the previous time period;
the second module is used for obtaining an air flow estimated value of the air flow entering the manifold of the throttle valve in the next time period based on the expected throttle flow in the current time period and the throttle flow under the throttle opening in the current time period;
a third module obtains an in-cylinder intake air amount for a next time period based on the first difference, the predicted airflow value, and an airflow discharged from the manifold and into the cylinder for a current time period.
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