CN114154377A - Prediction method and system for transient gas quantity in engine cylinder - Google Patents

Prediction method and system for transient gas quantity in engine cylinder Download PDF

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CN114154377A
CN114154377A CN202111455218.2A CN202111455218A CN114154377A CN 114154377 A CN114154377 A CN 114154377A CN 202111455218 A CN202111455218 A CN 202111455218A CN 114154377 A CN114154377 A CN 114154377A
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intake manifold
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李宁
钱鹏飞
刘义强
赵福成
王瑞平
肖逸阁
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Zhejiang Geely Holding Group Co Ltd
Ningbo Geely Royal Engine Components Co Ltd
Aurobay Technology Co Ltd
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Ningbo Geely Royal Engine Components Co Ltd
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Abstract

The invention provides a method and a system for predicting transient gas quantity in an engine cylinder, and belongs to the technical field of engine control. The method comprises the following steps: establishing a pressure differential expression of the estimated differential of the pressure of the intake manifold, wherein the pressure differential expression utilizes the upstream pressure of the throttle valve and the pressure of the intake manifold to achieve the estimated differential of the pressure of the intake manifold; intake manifold pressure initial value P according to Kth sampling period0(K) And solving the pressure differential expression m times by using an Euler formula with index to obtain the pressure P of the intake manifold of the m-order model of the Kth sampling periodm(K) Wherein, when K is 1, P0(K) Taking the value as a set value; when K > 1, P0(K)＝Pm(K-1); root of herbaceous plantAccording to P of each sampling periodm(K) The ideal gas state equation and the delay angle of the gas quantity required by the fuel injection of the engine are calculated, and the in-cylinder prediction gas quantity used for the fuel injection of the engine is calculated in each sampling period. The method can effectively improve the prediction accuracy of the in-cylinder prediction air quantity.

Description

Prediction method and system for transient gas quantity in engine cylinder
Technical Field
The invention belongs to the technical field of engine control, and particularly relates to a method and a system for predicting transient gas quantity in an engine cylinder.
Background
As the national six emission regulations are pursued, emission calibration for carbon monoxide, nitrogen oxides and particulate matter is more rigorous than the national five emission regulations. In order to meet the requirements of regulations, the existing engine electric control technology is realized by adopting an electric control fuel injection as a characteristic, combining air-fuel ratio closed-loop control and adopting a three-way catalyst and a GPF particle catcher to purify tail gas. Which is an important factor affecting fuel economy and exhaust emissions. And the fuel injection quantity of the engine depends on the real-time gas quantity entering the cylinder. For most gasoline engines, in order to achieve a better fuel atomization effect and sufficiently and uniformly mix air and gasoline, the injection time of circulating fuel needs to be prior to the time when the air inflow of the engine is completed, which means that the air quantity entering a cylinder needs to be predicted in advance before the gasoline engine injects fuel. Because the air flow entering the air cylinder is difficult to directly obtain in real time through the sensor, especially at the transient operating point, the influence such as the transmission delay of air flow, the retention in the pipe, the pumping loss, etc. causes the measuring difficulty more. Therefore, in order to realize accurate closed-loop control, the air quantity of the air cylinder needs to be accurately estimated in real time.
In the prior art, transient estimation aiming at air inflow in a cylinder mainly relates to an algorithm for subdividing a path from an air inlet to the cylinder based on an air inlet pressure change gradient algorithm and a model. However, the algorithm has the problems that after the in-cylinder air quantity estimation model is dispersed, the in-cylinder air quantity estimation model is not converged in practical application, and the prediction accuracy is low.
Disclosure of Invention
The invention aims to provide a method for predicting transient gas quantity in an engine cylinder, which can solve the problems of unconvergence and low prediction accuracy in practical application after a prediction model of the gas quantity in the cylinder is dispersed.
It is a further object of the present invention to improve the calculation efficiency and reduce the calculation load of the controller.
It is an object of a second aspect of the present invention to provide a system for predicting an amount of transient gas in an engine cylinder.
Particularly, the invention provides a method for predicting an in-cylinder transient air quantity of an engine, which comprises the following steps:
establishing a differential pressure expression of the estimated differential of the pressure of the intake manifold, wherein the differential pressure expression utilizes the upstream pressure of a throttle valve and the pressure of the intake manifold to achieve the estimated differential of the pressure of the intake manifold;
intake manifold pressure initial value P according to Kth sampling period0(K) And carrying out m times of iterative solution on the pressure differential expression by using an Euler formula with index to obtain the pressure P of the intake manifold of the m-order model of the Kth sampling periodm(K) Wherein, when K is 1, P0(K) Taking the value as a set value; when K > 1, P0(K)＝Pm(K-1)，Pm(K-1) is the intake manifold pressure of the m-th order model of the K-1 sampling period, and the Euler formula with index is as follows:
Figure BDA0003387475790000021
wherein, y0Is the value of the last sampling period, y1Is the value of the current sampling period, h is the sampling period, f (y)0) As a corresponding function, f' (y)0) Is f (y)0) A derivative of (a);
according to P of each sampling periodm(K) The ideal gas state equation and the delay angle of the gas quantity required by the fuel injection of the engine are calculated, and the in-cylinder prediction gas quantity used for the fuel injection of the engine is calculated in each sampling period.
Alternatively, when m is greater than 2, according to Newton's iteration and using Pm-1(K) And pm-2(K) Estimate Pm(K) Is described in (1).
Optionally, the step of establishing a pressure differential expression that is a differential of the estimated intake manifold pressure comprises:
obtaining air flow M of throttle valve according to nozzle model of one-dimensional compressible fluidthrExpression (c):
Figure BDA0003387475790000022
Figure BDA0003387475790000023
Athr＝table(Xthr)
Figure BDA0003387475790000024
where k is the adiabatic exponent, pDs is intake manifold pressure, pUs is throttle upstream pressure, RthrIs a gas constant, TthrIs throttle upstream temperature, XthrIs throttle opening degree, AthrIs throttle area, table (X)thr) Is according to XthrQuerying a one-dimensional calibration table for calibrating X to obtain an area value of the throttle valvethrAnd AthrCorresponding relation of (1), CdthrIs a flow coefficient of the throttle valve,
Figure BDA0003387475790000025
is based on
Figure BDA0003387475790000026
XthrThe throttle valve flow coefficient value obtained by inquiring a two-dimensional calibration table, which calibrates
Figure BDA0003387475790000031
XthrWith CdthrThe corresponding relationship of (a) to (b),
Figure BDA0003387475790000032
is a pressure ratio function;
obtaining the average value M of the air flow of the air inlet in the cylinder according to the ideal gas state equation of the engine and the principle of a speed density methodcylExpression (c):
Figure BDA0003387475790000033
wherein, VdIs the engine displacement, ηuThe engine charging efficiency is given, n is the engine speed, and T is the temperature of the intake manifold;
substituting transient intake manifold pressure p for MthrIs expressed bycylpDs in the expression of (1) respectively obtain transient predicted throttle flows Mthr(p) and the predicted in-cylinder flow rate M of the enginecyl(p) expression:
Figure BDA0003387475790000034
Figure BDA0003387475790000035
obtaining the transient air flow M in the intake manifold according to the mass conservation principle of the air flow in the intake manifoldman(p) expression:
Mman(p)＝Mthr(p)-Mcyl(p)
expression of M by ideal gas state equationman(p)
Figure BDA0003387475790000036
Wherein V is the volume of a pipeline from a throttle valve to an air inlet door of the engine;
according to the two Mman(p) deriving a derivative of said estimated intake manifold pressure
Figure BDA0003387475790000039
The pressure differential expression of (1):
Figure BDA0003387475790000037
optionally, the initial value of intake manifold pressure P according to the Kth sampling period0(K) And carrying out m times of iterative solution on the pressure differential expression by using an Euler formula with index to obtain the pressure P of the intake manifold of the m-order model of the Kth sampling periodm(K) Comprises the following steps:
will Pi-1(K) Substituting the pressure differential expression to obtain the Pdi-1(K) Expression (c):
Figure BDA0003387475790000038
wherein, when i is 1i-1(K) Intake manifold pressure for the i-1 th order model for the Kth sampling period;
for the Pdi-1(K) At Pi-1(K) Is derived to obtain a derivative DPdi-1(K) Expression (c):
Figure BDA0003387475790000041
pair DPdi-1(K) Is given by the expressionSimplifying the rows;
by Pi-1(K) And said Euler formula pair with index is reduced to DPdi-1(K) Sequentially carrying out m times of iterative solution to obtain Pm(K)。
Optionally, the pair DPdi-1(K) The step of simplifying the expression of (a) includes:
will Pi-1(K) Substituting said Mcyl(p) and deforming to obtain said DPdi-1(K) In the expression of
Figure BDA0003387475790000042
Expression (c):
Figure BDA0003387475790000043
curve determination based on intake manifold pressure and throttle flow
Figure BDA0003387475790000044
Expression (c):
Figure BDA0003387475790000045
will be provided with
Figure BDA0003387475790000046
Is expressed by
Figure BDA0003387475790000047
Substitution of expression into DPdi-1(K) Is then obtained:
Figure BDA0003387475790000048
optionally, said utilizing Pi-1(K) And said Euler formula pair with index is reduced to DPdi-1(K) Iterative solution is carried out in sequence to obtain Pm(K) The method comprises the following steps:
will Pi-1(K) And DPdi-1(K) Substituting the Euler formula with the index into the Euler formula to sequentially solve the Euler formula with the index in an iterative manner to obtain Pi(K) Is given to Pi(K) Is expressed by including Pdi-1(K) Term (ii) gives the adjustment coefficient fac (i):
Figure BDA0003387475790000049
wherein the adjustment coefficient fac (i) is a value between 0 and 1 and is determined by calibration experiments.
Optionally, said P according to each sampling periodm(K) The steps of calculating the in-cylinder predicted gas quantity used for executing the fuel injection of the engine in each sampling period by the ideal gas state equation and the delay angle of the gas quantity required for executing the fuel injection of the engine comprise the following steps:
according to Pm(K) Calculating the predicted gas quantity M in the cylinder in the Kth sampling period by using the ideal gas state equationcylPred(K)：
Figure BDA0003387475790000051
And (3) converting corresponding delay time tDly according to the delay angle of the gas amount required by executing the fuel injection of the engine:
Figure BDA0003387475790000052
ag1 is the advance angle of the intake variable valve in the Kth sampling period, and Ag3 is the angle of crankshaft rotation from the actual oil injection time to the closing time of the intake valve of the engine in the Kth sampling period;
converting the delay time tDly into the number of sampling cycles and substituting into McylPred (K) obtaining a correction value M of the predicted gas quantity in the cylinder in the Kth sampling periodcylInjPred(K)：
Figure BDA0003387475790000053
Accumulating M in each adoption period in the target time periodcylInjpred (k) to obtain a corresponding in-cylinder predicted gas amount.
Optionally, the set value is taken as 100, and m is taken as 3.
Particularly, the invention further provides a system for predicting the transient air quantity in the cylinder of the engine, which comprises a control device and a processor, wherein the control device comprises a memory and the processor, the memory stores a control program, and the control program is used for realizing the method for predicting the transient air quantity in the cylinder of the engine when being executed by the processor.
In the invention, for the defects of the traditional discrete algorithm, an index-to-gradient compensation coefficient, namely the Euler formula with the index in the euler method is introduced, so that the problem of non-convergence of the estimation of the pressure model of the intake manifold can be effectively solved, and the accuracy of the real-time estimated pressure value of the intake manifold is improved.
Furthermore, the method adopts the Newton iteration method in the last-order calculation process to accelerate the acquisition of the pressure of the intake manifold, so that the excessive iteration times in the calculation process can be avoided, the calculation efficiency is improved, and the calculation load of the controller is also reduced.
The above and other objects, advantages and features of the present invention will become more apparent to those skilled in the art from the following detailed description of specific embodiments thereof, taken in conjunction with the accompanying drawings.
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Some specific embodiments of the invention will be described in detail hereinafter, by way of illustration and not limitation, with reference to the accompanying drawings. The same reference numbers in the drawings identify the same or similar elements or components. Those skilled in the art will appreciate that the drawings are not necessarily drawn to scale. In the drawings:
FIG. 1 is a schematic block diagram of an engine intake system and exhaust system;
FIG. 2 is a flowchart of a method for predicting an amount of transient air in an engine cylinder according to an embodiment of the present disclosure;
FIG. 3 is a graph of throttle air flow versus intake manifold pressure;
FIG. 4 is a graph comparing predicted data and measured data of a prediction method of an in-cylinder transient state air quantity of an engine according to an embodiment of the invention.
Reference numerals:
1-throttle body, 2-intake manifold pressure sensor, 3-intake manifold pipeline, 4-fuel injector assembly, 5-ignition assembly, 6-oxygen sensor, 7-exhaust manifold, 8-catalyst, 9-silencer, 10-cylinder and 11-throttle front pressure and temperature sensor
Detailed Description
Fig. 1 is a schematic structural view of an engine intake system and an exhaust system. As shown in fig. 1, the intake and exhaust processes of the engine are substantially as follows: air enters a pipeline of an intake manifold 3 from an intake pipeline through a throttle body 1 and then enters a cylinder 10 of the engine, and a fuel injector assembly 4 and an ignition assembly 5 for injecting fuel are further arranged at the cylinder 10. Exhaust gas discharged from the engine is discharged from an exhaust manifold 7, and an oxygen sensor 6, a catalyst 8, and a muffler 9 are provided on the exhaust manifold 7. The upstream and the downstream of the throttle body 1 are respectively provided with a throttle front pressure and temperature sensor 11 and an intake manifold pressure sensor 2, and the two sensors are integrated with a pressure sensing module and a temperature sensing module and can detect pressure and temperature. The intake manifold pressure sensor 2 measures a pressure downstream of the throttle body 1, that is, an intake manifold pressure.
FIG. 2 is a flowchart of a method for predicting an amount of transient air in an engine cylinder according to an embodiment of the present disclosure. In one embodiment, as shown in fig. 2, the method for predicting the transient air amount in the cylinder of the engine according to the present invention includes:
step S100, establishing a pressure differential expression of the estimated differential of the intake manifold pressure, wherein the pressure differential expression utilizes the upstream pressure of the throttle valve and the pressure of the intake manifold to reach the estimated differential of the intake manifold pressure.
In one embodiment, the pressure differential expression may be obtained according to the following steps:
obtaining air flow M of throttle valve according to nozzle model of one-dimensional compressible fluidthrExpression (c):
Figure BDA0003387475790000061
Figure BDA0003387475790000062
Athr＝table(Xthr) (3)
Figure BDA0003387475790000063
where k is the adiabatic exponent (k 1.4), pDs is the intake manifold pressure, pUs is the throttle upstream pressure, R is the throttle upstream pressurethrIs a gas constant (R)thr＝287)，TthrIs throttle upstream temperature, XthrIs throttle opening degree, AthrIs throttle area, table (X)thr) Is according to XthrThe area value of the throttle valve obtained by the one-dimensional calibration table is inquired, and the one-dimensional calibration table calibrates XthrAnd AthrCorresponding relation of (1), CdthrIs a flow coefficient of the throttle valve,
Figure BDA0003387475790000071
is based on
Figure BDA0003387475790000072
XthrThe throttle valve flow coefficient value obtained by inquiring the two-dimensional calibration table, the two-dimensional calibration table calibrates
Figure BDA0003387475790000073
XthrWith CdthrThe corresponding relationship of (a) to (b),
Figure BDA0003387475790000074
as a function of the pressure ratio.
Obtaining the average value M of the air flow of the air inlet in the cylinder according to the ideal gas state equation of the engine and the principle of a speed density methodcylExpression (c):
Figure BDA0003387475790000075
wherein, VdIs the engine displacement, ηvFor engine charging efficiency, n is engine speed and T is intake manifold temperature.
Substituting transient intake manifold pressure p for MthrIs expressed bycylpDs in the expression of (1) respectively obtain transient predicted throttle flows Mthr(p) and the predicted in-cylinder flow rate M of the enginecyl(p) expression:
Figure BDA0003387475790000076
Figure BDA0003387475790000077
obtaining the transient air flow M in the intake manifold according to the mass conservation principle of the air flow in the intake manifoldman(p) expression:
Mman(p)＝Mtnr(p)-Mcyl(p) (8)
expression of M by ideal gas state equationman(p)
Figure BDA0003387475790000078
Where V is the volume of the conduit from the throttle to the engine intake port.
According to the two MmanThe expression of (p), equations (8) and (9), yields the differential of the estimated intake manifold pressure
Figure BDA0003387475790000079
The pressure differential expression of (1):
Figure BDA00033874757900000710
step S200, according to the initial value P of the pressure of the intake manifold in the Kth sampling period0(K) And performing m times of iterative solution on the pressure differential expression by using an Euler formula with index to obtain the pressure P of the intake manifold of the m-order model of the Kth sampling periodm(K) Wherein, when K is 1, P0(K) Taken as a set value, which may be 100; when K > 1, P0(K)＝Pm(K-1)，Pm(K-1) is the intake manifold pressure of the m-th order model for the K-1 sample period.
The euler formula with index is:
Figure BDA0003387475790000081
wherein, y0Is the value of the last sampling period, y1Is the value of the current sampling period, h is the sampling period, f (y)0) As a corresponding function, f' (y)0) Is f (y)0) The derivative of (c).
Euler's formula with index, which can be based on y0And f (y)0) Result in y1When combined with the scheme, when P is0(K) For a known set value and a known differential expression of pressure, P will be0(K) Instead of y in equation (11)0Will be referred to P0(K) Is substituted for f (y) in the formula (11)0) Then P can be obtained1(K) In that respect Then obtaining P1(K) Then the above steps are repeated to obtain P2(K) Thus, P can be obtained by iterationm(K)。
Step S300, according to P of each sampling periodm(K) The ideal gas state equation and the delay angle of the gas amount required for executing the fuel injection of the engine calculate the in-cylinder predicted gas amount used for executing the fuel injection of the engine in the target time period.
In one embodiment, step S300 includes the steps of:
according to Pm(K) And the ideal gas state equation calculates the KthSampling period in-cylinder prediction gas quantity McylPred(K)：
Figure BDA0003387475790000082
And (3) converting corresponding delay time tDly according to the delay angle of the gas amount required by executing the fuel injection of the engine:
Figure BDA0003387475790000083
ag1 is the advance angle of the intake variable valve in the Kth sampling period, and Ag3 is the angle of crankshaft rotation from the actual oil injection time to the closing time of the intake valve of the engine in the Kth sampling period;
the delay time tDly is converted into the number of sampling cycles and substituted into McylPred (K) obtaining a correction value M of the predicted gas quantity in the cylinder in the Kth sampling periodcylInjPred(K)：
Figure BDA0003387475790000084
Solving for intake manifold pressure P if conventional discrete algorithms (e.g., finite element method) are used for equation (10)i(K) Errors are introduced after discretization, and the risk of non-convergence of the algorithm exists in the accumulation of the errors.
Aiming at the defects of the discrete algorithm, the method introduces an index-to-gradient compensation coefficient, namely the above euler formula with the index, into the euler method, so that the problem of non-convergence of the estimation of the intake manifold pressure model can be effectively solved, and the accuracy of the real-time estimated intake manifold pressure value is improved.
In one embodiment, step S200 includes:
step S202, adding Pi-1(K) Substituting pressure differential expression to obtain Pdi-1(K) Expression (c):
Figure BDA0003387475790000085
wherein, when i is 1i-1(K) Intake manifold pressure for the i-1 th order model for the Kth sampling period.
Step S204, for Pdi-1(K) At Pi-1(K) Is derived to obtain a derivative DPdi-1(K) Expression (c):
Figure BDA0003387475790000091
step S206, pair DPdi-1(K) The expression of (c) is simplified. In one embodiment, the simplification can be made as follows:
will Pi-1(K) Substitution into Mcyl(p) and modified to DPdi-1(K) In the expression of
Figure BDA0003387475790000092
Expression (c):
Figure BDA0003387475790000093
Figure BDA0003387475790000094
curve determination based on intake manifold pressure and throttle flow
Figure BDA0003387475790000095
Expression (c):
Figure BDA0003387475790000096
FIG. 3 is a graph of throttle airflow versus intake manifold pressure. The abscissa in fig. 3 is the intake manifold pressure and the ordinate is the throttle air flow rate, which can be plotted according to equation (1). Point a in fig. 3 characterizes thisMass flow rate of 0 and pressure ratio
Figure BDA0003387475790000097
Corresponding to maximum intake manifold pressure Pmax(ii) a Point B represents critical sonic velocity point, pressure ratio
Figure BDA0003387475790000098
Corresponding critical intake manifold pressure Pcr(ii) a BC section (i.e. pressure ratio)
Figure BDA0003387475790000099
) The air flow reaches the sound velocity under the mechanical condition, the expansion of the air flow is limited by the geometric shape of the throttle valve, and the flow of the throttle valve is stabilized at the maximum value Mthr(max) at this time
Figure BDA00033874757900000910
AB section (i.e. pressure ratio)
Figure BDA00033874757900000911
) Is a throttle flow change curve segment,
Figure BDA00033874757900000912
can be approximately described as the slope of the AD line, i.e.:
Figure BDA00033874757900000913
in the formula (20), PmaxFor maximum intake manifold pressure, which may be replaced with the throttle upstream pressure sensor test value pUs, equation (20) may be described as:
Figure BDA0003387475790000101
will be provided with
Figure BDA0003387475790000102
Is expressed by
Figure BDA0003387475790000103
Substitution of expression into DPdi-1(K) The expression of (c), equation (16), is obtained:
Figure BDA0003387475790000104
step S208, using Pi-1(K) And Euler's formula with index versus reduced DPdi-1(K) (equation (22)) are solved m times in order to obtain Pm(K)。
In order to consider the influence of each order model, an adjustment coefficient related to the order is added, namely, a calibratable adjustment coefficient is added to the gradient part of each order model, so that calibration and presetting are facilitated.
Specifically, P isi-1(K) And DPdi-1(K) Substituting into Euler formula with index, and sequentially and iteratively solving to obtain Pi(K) Is given to Pi(K) Is expressed by including Pdi-1(K) Term (ii) gives the adjustment coefficient fac (i):
Figure BDA0003387475790000105
the adjustment coefficient fac (i) is a value between 0 and 1 and is determined by calibration experiments.
To better illustrate the process of multi-step iterative solution, m is 2 as an example.
For the Kth sampling period: when i is 1, adding P0(K) Substitution of the formula (22) results in DPd0(K) The expression of (c), namely:
Figure BDA0003387475790000106
will P0(K) Substituting into formula (23) to obtain P1(K)：
Figure BDA0003387475790000107
Substituting equation (24) into equation (25) yields P1(K) Is the intake manifold pressure P of the 1 st order model of the Kth sampling period1(K)。
When P is obtained1(K) Then P is1(K) Substitution (22) gives DPd1(K) The expression of (c), namely:
Figure BDA0003387475790000111
will P1(K) Substituting into formula (23) to obtain P2(K)：
Figure BDA0003387475790000112
In this embodiment, m is 2, intake manifold pressure P of the Kth cycle m-order modelm(K) Is P2(K)。
When K is 1, P0(K) Assuming that the set value is 100, P can be obtained by substituting equations (26) and (27)2(1)。
When K > 1, P0(K)＝Pm(K-1), e.g. when K is 2, the P already solved is2(1) By substituting equations (26) and (27), P can be solved2(2). Likewise, this is true for other cases where K > 1.
The value of m is generally not more than 5, preferably 2 or 3. In one embodiment, when m is greater than 2, P is utilized according to Newton's iteration methodm-1(K) And Pm-2(K) Estimate Pm(K) Is described in (1).
The newton iteration method corresponds to the following formula:
Figure BDA0003387475790000113
wherein x isnIs the value of the last sampling period, xn+1Is the value of the current sampling period, f (x)n) As a corresponding function, f' (x)n) Is f (x)n) The derivative of (c).
In specific applications, Pd can be obtained according to the formula (15)1(K)、Pd2(K) P can be obtained from the formula (23)0(K)、P1(K)、P2(K) From this, a 1 st order model deviation equation F for the Kth sampling period can be constructed1(P1(K) And 2 model deviation equation F2(P2(K))：
F1(P1(K))＝P1(K)-P0(K)-Pd1(K)·h (29)
F2(P2(K))＝P2(K)-P0(K)-Pd2(K)·h (30)
The intake manifold pressure P of the m-order model of the Kth sampling period can be quickly obtained by the Newton iteration method based on the formula (28)3(K)：
Figure BDA0003387475790000114
According to the embodiment, the Newton iteration method is adopted in the last-stage calculation process to accelerate the acquisition of the pressure of the intake manifold, so that the excessive iteration times in the calculation process can be avoided, the calculation efficiency is improved, and the calculation load of the controller is also reduced.
FIG. 4 is a graph comparing predicted data and measured data of a prediction method of an in-cylinder transient state air quantity of an engine according to an embodiment of the invention. In fig. 4, a solid line 1 is an in-cylinder intake air flow average value model to calculate an actual in-cylinder air amount, a dotted line 2 is an in-cylinder air amount calculated based on the prediction method, a solid line 3 is an actually measured intake manifold pressure, a dotted line 4 is a predicted intake manifold pressure, and a solid line 5 is an excess air coefficient. For the embodiment with m-3, each adjustment coefficient satisfies the following rule: fac (1) + fac (2) is equal to 1, fac (3) is adjusted by an acceleration algorithm, and is increased or decreased in a proper amount according to requirements, and the general principle is to ensure that the predicted value corresponds to the predicted value on the premise of accelerating speedThe excess air factor meets the transient control demand. In the example corresponding to fig. 4, when m is 3, fac (1), fac (2), and fac (3) are respectively designated as 0.6, 0.4, and 0.001, and m is 3, P is estimated by the newton iteration method3(K) In that respect The engine speed was controlled at 2000rpm, the adjustment factor was adjusted, and the engine load request was manually adjusted from 150 mg per stroke to 400 mg per stroke, corresponding to a change in actual intake manifold pressure from 70kPa to 105 kPa. The load comparison shows that the predicted air volume is ahead of the actual air volume in the cylinder, and after the air volume enters the steady state, the predicted air volume converges on the actual air volume, wherein the predicted air volume is about 400 mg per stroke, and the error is controlled within 5 percent; as can be seen from the comparison of the manifold pressures, the predicted manifold pressure is advanced from the actual pressure, and after the manifold pressure enters the steady state, the predicted manifold pressure is converged to the actual pressure, the error is controlled within 5%, the actually measured excess air coefficient is controlled within 0.95-1.05, and the absolute deviation of the air-fuel ratio under the transient working condition is controlled within 5%, so that the air-fuel ratio control standard requirement is met.
The invention also provides a system for predicting the transient gas quantity in the cylinder of the engine, which comprises a control device and a processor, wherein the control device comprises a memory and the processor, the memory stores a control program, and the control program is used for realizing the method for predicting the transient gas quantity in the cylinder of the engine in any embodiment when being executed by the processor. The processor may be a Central Processing Unit (CPU), a digital processing unit, or the like. The processor receives and transmits data through the communication interface. The memory is used for storing programs executed by the processor. The memory is any medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by the computer, or a combination of memories. The above-described computing program may be downloaded from a computer-readable storage medium to a corresponding computing/processing device or to a computer or external storage device via a network (e.g., the internet, a local area network, a wide area network, and/or a wireless network).
Thus, it should be appreciated by those skilled in the art that while a number of exemplary embodiments of the invention have been illustrated and described in detail herein, many other variations or modifications consistent with the principles of the invention may be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Accordingly, the scope of the invention should be understood and interpreted to cover all such other variations or modifications.

Claims (9)

1. A method for predicting an in-cylinder transient air quantity of an engine is characterized by comprising the following steps:
establishing a differential pressure expression of the estimated differential of the pressure of the intake manifold, wherein the differential pressure expression utilizes the upstream pressure of a throttle valve and the pressure of the intake manifold to achieve the estimated differential of the pressure of the intake manifold;
intake manifold pressure initial value P according to Kth sampling period0(K) And carrying out m times of iterative solution on the pressure differential expression by using an Euler formula with index to obtain the pressure P of the intake manifold of the m-order model of the Kth sampling periodm(K) Wherein, when K is 1, P0(K) Taking the value as a set value; when K > 1, P0(K)＝Pm(K-1)，Pm(K-1) is the intake manifold pressure of the m-th order model of the K-1 sampling period, and the Euler formula with index is as follows:
Figure FDA0003387475780000011
wherein, y0Is the value of the last sampling period, y1Is the value of the current sampling period, h is the sampling period, f (y)0) As a corresponding function, f' (y)0) Is f (y)0) A derivative of (a);
according to P of each sampling periodm(K) The ideal gas state equation and the delay angle of the gas quantity required by the fuel injection of the engine are calculated, and the in-cylinder prediction gas quantity used for the fuel injection of the engine is calculated in each sampling period.
2. The method of predicting an in-cylinder transient amount of an engine according to claim 1,
when m is greater than 2, according to Newton's iteration and using Pm-1(K) And Pm-2(K) Estimate Pm(K) Is described in (1).
3. The method for predicting the amount of transient air in an engine cylinder according to claim 1 or 2, wherein the step of establishing a pressure differential expression that is a differential of the estimated intake manifold pressure includes:
obtaining air flow M of throttle valve according to nozzle model of one-dimensional compressible fluidthrExpression (c):
Figure FDA0003387475780000012
Figure FDA0003387475780000013
Athr＝table(Xthr)
Figure FDA0003387475780000021
where k is the adiabatic exponent, pDs is intake manifold pressure, pUs is throttle upstream pressure, RthrIs a gas constant, TthrIs throttle upstream temperature, XthrIs throttle opening degree, AthrIs throttle area, table (X)thr) Is according to XthrQuerying a one-dimensional calibration table for calibrating X to obtain an area value of the throttle valvethrAnd AthrCorresponding relation of (1), CdthrIs a flow coefficient of the throttle valve,
Figure FDA0003387475780000022
is based on
Figure FDA0003387475780000023
XthrThe throttle valve flow coefficient value obtained by inquiring a two-dimensional calibration table, which calibrates
Figure FDA0003387475780000024
XthrWith CdthrThe corresponding relationship of (a) to (b),
Figure FDA0003387475780000025
is a pressure ratio function;
obtaining the average value M of the air flow of the air inlet in the cylinder according to the ideal gas state equation of the engine and the principle of a speed density methodcylExpression (c):
Figure FDA0003387475780000026
wherein, VdIs the engine displacement, ηυThe engine charging efficiency is given, n is the engine speed, and T is the temperature of the intake manifold;
substituting transient intake manifold pressure p for MthrIs expressed bycylpDs in the expression of (1) respectively obtain transient predicted throttle flows Mthr(p) and the predicted in-cylinder flow rate M of the enginecyl(p) expression:
Figure FDA0003387475780000027
Figure FDA0003387475780000028
obtaining the transient air flow M in the intake manifold according to the mass conservation principle of the air flow in the intake manifoldman(p) expression:
Mman(p)＝Mthr(p)-Mcyl(p)
expression of M by ideal gas state equationman(p)
Figure FDA0003387475780000029
Wherein V is the volume of a pipeline from a throttle valve to an air inlet door of the engine;
according to the two Mman(p) deriving a derivative of said estimated intake manifold pressure
Figure FDA00033874757800000210
The pressure differential expression of (1):
Figure FDA00033874757800000211
4. the method for predicting the transient gas amount in the cylinder of the engine according to claim 3, wherein the initial value P of the pressure of the intake manifold according to the Kth sampling period0(K) And carrying out m times of iterative solution on the pressure differential expression by using an Euler formula with index to obtain the pressure P of the intake manifold of the m-order model of the Kth sampling periodm(K) Comprises the following steps:
will Pi-1(K) Substituting the pressure differential expression to obtain the Pdi-1(K) Expression (c):
Figure FDA0003387475780000031
wherein, when i is 1i-1(K) Intake manifold pressure for the i-1 th order model for the Kth sampling period;
for the Pdi-1(K) At Pi-1(K) Is derived to obtain a derivative DPdi-1(K) Expression (c):
Figure FDA0003387475780000032
pair DPdi-1(K) The expression of (2) is simplified;
by Pi-1(K) And said Euler formula pair with index is reduced to DPdi-1(K) Sequentially carrying out m times of iterative solution to obtain Pm(K)。
5. The method for predicting the amount of transient gas in an engine cylinder according to claim 4, wherein said pair DPdi-1(K) The step of simplifying the expression of (a) includes:
will Pi-1(K) Substituting said Mcyl(p) and deforming to obtain said DPdi-1(K) In the expression of
Figure FDA0003387475780000033
Expression (c):
Figure FDA0003387475780000034
curve determination based on intake manifold pressure and throttle flow
Figure FDA0003387475780000035
Expression (c):
Figure FDA0003387475780000036
will be provided with
Figure FDA0003387475780000037
Is expressed by
Figure FDA0003387475780000038
Substituting the expression of (A) into the expression of DPdi-1(K) to obtain:
Figure FDA0003387475780000039
6. the method for predicting the amount of transient gas in an engine cylinder according to claim 5, wherein said utilizing Pi-1(K) And said Euler formula pair with index is reduced to DPdi-1(K) Iterative solution is carried out in sequence to obtain Pm(K) The method comprises the following steps:
will Pi-1(K) And DPdi-1(K) Substituting the Euler formula with the index into the Euler formula to sequentially solve the Euler formula with the index in an iterative manner to obtain Pi(K) Is given to Pi(K) Is expressed by including Pdi-1(K) Term (ii) gives the adjustment coefficient fac (i):
Figure FDA0003387475780000041
wherein the adjustment coefficient fac (i) is a value between 0 and 1 and is determined by calibration experiments.
7. The method for predicting the amount of transient gas in an engine cylinder according to claim 6, wherein P is determined according to each sampling periodm(K) The steps of calculating the in-cylinder predicted gas quantity used for executing the fuel injection of the engine in each sampling period by the ideal gas state equation and the delay angle of the gas quantity required for executing the fuel injection of the engine comprise the following steps:
according to Pm(K) Calculating the predicted gas quantity M in the cylinder in the Kth sampling period by using the ideal gas state equationcylPred(K)：
Figure FDA0003387475780000042
And (3) converting corresponding delay time tDly according to the delay angle of the gas amount required by executing the fuel injection of the engine:
Figure FDA0003387475780000043
ag1 is the advance angle of the intake variable valve in the Kth sampling period, and Ag3 is the angle of crankshaft rotation from the actual oil injection time to the closing time of the intake valve of the engine in the Kth sampling period;
converting the delay time tDly into the number of sampling cycles and substituting into McylPred (K) obtaining a correction value M of the predicted gas quantity in the cylinder in the Kth sampling periodcylInjPred(K)：
Figure FDA0003387475780000044
8. The method for predicting the amount of transient gas in an engine cylinder according to any one of claims 1 to 7, wherein the set value is 100 and m is 3.
9. A prediction system of an in-cylinder transient air quantity of an engine, comprising a control device, characterized in that the control device comprises a memory and a processor, the memory stores a control program, and the control program is used for implementing the prediction method of the in-cylinder transient air quantity of the engine according to any one of claims 1 to 8 when being executed by the processor.
CN202111455218.2A 2021-12-01 2021-12-01 Prediction method and system for transient gas quantity in engine cylinder Pending CN114154377A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114718746A (en) * 2022-03-31 2022-07-08 东风汽车集团股份有限公司 Model optimization method, device and equipment for intake pressure and readable storage medium
CN117852318A (en) * 2024-03-07 2024-04-09 中汽研汽车检验中心(昆明)有限公司 Performance simulation method and system for coupling system of automobile exhaust purification device

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114718746A (en) * 2022-03-31 2022-07-08 东风汽车集团股份有限公司 Model optimization method, device and equipment for intake pressure and readable storage medium
CN114718746B (en) * 2022-03-31 2022-12-27 东风汽车集团股份有限公司 Model optimization method, device and equipment for intake pressure and readable storage medium
CN117852318A (en) * 2024-03-07 2024-04-09 中汽研汽车检验中心(昆明)有限公司 Performance simulation method and system for coupling system of automobile exhaust purification device

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