A method and system for predicting transient gas volume in engine cylinder

Abstract

The present invention provides a method and system for predicting the transient gas volume in an engine cylinder, belonging to the technical field of engine control. The method comprises: establishing a differential pressure expression of the differential of the estimated intake manifold pressure, wherein the differential pressure expression uses the throttle upstream pressure and the intake manifold pressure to express the differential of the estimated intake manifold pressure; solving the differential pressure expression m times according to the initial value P0(K) of the intake manifold pressure of the Kth sampling period and the Euler formula with exponents, so as to obtain the intake manifold pressure P of the mth order model of the Kth sampling period. m (K), where, when K=1, P0(K) is taken as the set value; when K>1, P0(K)=P m (K‑1); according to P of each sampling period m (K), the ideal gas state equation and the delay angle of the gas volume required for executing the engine fuel injection calculate the in-cylinder predicted gas volume used for executing the engine fuel injection in each sampling period. The present invention can effectively improve the prediction accuracy of the in-cylinder predicted gas volume.

Description

Technical Field

[0001] The invention belongs to the technical field of engine control, and in particular relates to a method and system for predicting transient gas volume in an engine cylinder. Background Art

[0002] With the implementation of the National VI emission regulations, the emission calibration of carbon monoxide, nitrogen oxides and particulate matter is more stringent than that of the National V emission regulations. In order to meet the requirements of the regulations, the current engine electronic control technology adopts electronic fuel injection as the feature, combined with air-fuel ratio closed-loop control, and uses a three-way catalytic converter and a GPF particulate filter for exhaust gas purification. Among them, the engine air-fuel ratio is an important factor affecting fuel economy and exhaust emissions. The amount of engine fuel injection depends on the real-time gas volume entering the cylinder. For most gasoline engines, in order to achieve better fuel atomization effect and fully and evenly mix air and gasoline, the injection time of the circulating fuel must be prior to the time when the engine intake volume is completed, which means that the gasoline engine needs to predict the amount of gas entering the cylinder in advance before injecting fuel. Since the air flow entering the cylinder is not easy to obtain directly in real time through the sensor, especially at the transient operating point, the transmission delay of the air flow, the retention in the pipe, the pump air loss and other effects make the measurement more difficult. Therefore, in order to achieve precise closed-loop control, it is necessary to accurately estimate the cylinder gas volume in real time.

[0003] The existing technology for transient estimation of cylinder intake air volume mainly involves algorithms based on intake pressure change gradient and algorithms based on model segmentation of the intake port to cylinder path. However, the above algorithms have the problem that the cylinder air volume estimation model does not converge in actual application after being discretized, and the prediction accuracy is low. Summary of the invention

[0004] An object of the first aspect of the present invention is to provide a method for predicting the transient gas volume in an engine cylinder, which can solve the problem that the in-cylinder gas volume estimation model does not converge and has low prediction accuracy in practical applications after being discretized.

[0005] A further object of the present invention is to improve computing efficiency and reduce the computational load of the controller.

[0006] An object of the second aspect of the present invention is to provide a system for predicting the transient gas volume in an engine cylinder.

[0007] In particular, the present invention provides a method for predicting the transient gas volume in an engine cylinder, comprising:

[0008] Establishing a pressure differential expression of the differential of the estimated intake manifold pressure, wherein the pressure differential expression expresses the differential of the estimated intake manifold pressure using the throttle upstream pressure and the intake manifold pressure;

[0009] According to the initial value P0(K) of the intake manifold pressure of the Kth sampling period and the exponential Euler formula, the pressure differential expression is iterated and solved m times to obtain the intake manifold pressure P of the m-order model of the Kth sampling period. m (K), where, when K=1, P0(K) is taken as the set value; when K>1, P0(K)=P m (K-1), P m (K-1) is the intake manifold pressure of the m-order model in the K-1th sampling period, and the exponential Euler formula is:

[0010]

[0011] Where y0 is the value of the previous sampling period, y1 is the value of the current sampling period, h is the sampling period, f(y0) is the corresponding function, and f′(y0) is the derivative of f(y0);

[0012] According to the P of each sampling period m (K), the ideal gas state equation and the delay angle of the gas volume required to perform engine injection are used to calculate the predicted in-cylinder gas volume used to perform engine injection in each sampling period.

[0013] Optionally, when m is greater than 2, according to Newton's iteration method and using P m-1 (K) and p m-2 (K) Calculate P m (K) expression.

[0014] Optionally, the step of establishing a differential pressure expression of the differential of the estimated intake manifold pressure comprises:

[0015] According to the nozzle model of one-dimensional compressible fluid, the throttle air flow M is obtained. thr The expression is:

[0016]

[0017]

[0018] A thr =table(X thr )

[0019]

[0020] Where k is the adiabatic index, pDs is the intake manifold pressure, pUs is the throttle upstream pressure, R thr is the gas constant, T thr is the throttle upstream temperature, X thr is the throttle opening, A thr is the throttle area, table(X thr) is based on X thr The throttle area value obtained by querying the one-dimensional calibration table, the one-dimensional calibration table calibrates X thr and A thr The corresponding relationship, Cd thr is the throttle flow coefficient, Based on X thr The throttle flow coefficient value obtained by querying the two-dimensional calibration table, the two-dimensional calibration table calibrates X thr with cd thr The corresponding relationship, is the pressure ratio function;

[0021] According to the ideal gas state equation of the engine and the speed density method principle, the mean air flow rate M of the cylinder intake port is obtained. cyl The expression is:

[0022]

[0023] Among them, V d is the engine displacement, η u is the engine charging efficiency, n is the engine speed, and T is the temperature of the intake manifold;

[0024] Replace M with the transient intake manifold pressure p thr The expression and M cyl The pDs in the expression of are respectively used to obtain the transient predicted throttle flow M thr (p) and the predicted flow rate M in the engine cylinder cyl The expression of (p) is:

[0025]

[0026]

[0027] According to the mass conservation principle of the air flow in the intake manifold, the transient air flow M in the intake manifold is obtained. man The expression of (p) is:

[0028] M man (p) = M thr (p)-M cyl (p)

[0029] Using the ideal gas state equation to express M man (p)

[0030]

[0031] Wherein, V is the volume of the pipeline from the throttle to the engine intake port;

[0032] According to the above two M man The expression of (p) gives the differential of the estimated intake manifold pressure The pressure differential expression is:

[0033]

[0034] Optionally, the pressure differential expression is iterated m times according to the initial value P0(K) of the intake manifold pressure of the Kth sampling period and the exponential Euler formula to obtain the intake manifold pressure P of the m-order model of the Kth sampling period. m The steps of (K) include:

[0035] P i-1 (K) Substitute into the pressure differential expression to obtain the Pd i-1 The expression of (K):

[0036]

[0037] Where, i = 1, ..., m, when i is greater than 1, P i-1 (K) intake manifold pressure of the i-1 order model at the Kth sampling period;

[0038] For the Pd i-1 (K) in P i-1 (K) is derived to obtain the derivative DPd i-1 The expression of (K):

[0039]

[0040] DPd i-1 The expression of (K) is simplified;

[0041] Using P i-1 (K) and the Euler formula with index for the simplified DPd i-1 (K) Perform m iterations to obtain P m (K).

[0042] Optionally, the pair DPd i-1 The steps to simplify the expression of (K) include:

[0043] P i-1 (K) Substitute into the M cyl The expression of (p) is transformed to obtain the DPd i-1 In the expression of (K) The expression is:

[0044]

[0045] Determined based on the curve of intake manifold pressure and throttle flow The expression is:

[0046]

[0047] Will The expression and Substitute the expression of DPd into i-1 After the expression of (K) is obtained:

[0048]

[0049] Optionally, the use of P i-1 (K) and the Euler formula with index for the simplified DPd i-1 (K) Iterate and solve in turn to obtain P m (K) The steps include:

[0050] P i-1 (K) and DPd i-1 (K) Substitute the exponential Euler formula and iterate to obtain P i (K) expression, and for P i The expression of (K) includes Pd i-1 The term (K) is given the adjustment coefficient fac(i):

[0051]

[0052] The adjustment coefficient fac(i) is a value between 0 and 1 and is determined through a calibration experiment.

[0053] Optionally, the P according to each sampling period m (K), the step of calculating the predicted in-cylinder gas volume used for executing the engine fuel injection in each sampling period using the ideal gas state equation and the delay angle of the gas volume required for executing the engine fuel injection comprises:

[0054] According to P m (K) and the ideal gas state equation to calculate the predicted gas volume M in the cylinder during the Kth sampling period cyl Pred(K):

[0055]

[0056] The corresponding delay time tDly is calculated based on the delay angle of the required amount of gas for engine injection:

[0057]

[0058] Among them, Ag1 is the advance angle of the intake variable valve in the Kth sampling period, and Ag3 is the angle of the crankshaft from the actual injection time to the closing time of the engine intake valve in the Kth sampling period;

[0059] Convert the delay time tDly into the number of sampling cycles and substitute it into M cyl Pred(K) gets the correction value M of the predicted gas volume in the cylinder during the Kth sampling period cyl InjPred(K):

[0060]

[0061] Accumulate the M in each adoption cycle within the target time period cyl InjPred(K) is used to obtain the corresponding predicted in-cylinder gas volume.

[0062] Optionally, the set value is 100 and m is 3.

[0063] In particular, the present invention also provides a prediction system for the transient gas volume in an engine cylinder, comprising a control device, the control device comprising a memory and a processor, the memory storing a control program, and the control program, when executed by the processor, is used to implement any of the above-mentioned methods for predicting the transient gas volume in the engine cylinder.

[0064] The present invention addresses the defects of the traditional discrete algorithm by introducing an exponential to the gradient compensation coefficient of the Euler method, i.e., the Euler formula with exponent in the above text, which can effectively solve the problem of non-convergence of the intake manifold pressure model estimation and improve the accuracy of the real-time estimated intake manifold pressure value.

[0065] Furthermore, the present invention uses the Newton iteration method in the last-order calculation process to accelerate the acquisition of the intake manifold pressure, thereby avoiding excessive iteration times in the calculation process, improving calculation efficiency, and reducing the calculation load of the controller.

[0066] Based on the following detailed description of specific embodiments of the present invention in conjunction with the accompanying drawings, those skilled in the art will become more aware of the above and other objects, advantages and features of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Hereinafter, some specific embodiments of the present invention will be described in detail in an exemplary and non-limiting manner with reference to the accompanying drawings. The same reference numerals in the accompanying drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale. In the accompanying drawings:

[0068] Figure 1 It is a structural diagram of the engine intake system and exhaust system;

[0069] Figure 2 is a flow chart of a method for predicting transient gas volume in an engine cylinder according to one embodiment of the present invention;

[0070] Figure 3 It is a graph of the relationship between throttle air flow and intake manifold pressure;

[0071] Figure 4 It is a curve comparison diagram of the data estimated by the method for predicting the transient gas volume in the engine cylinder according to one embodiment of the present invention and the measured data.

[0072] Reference numerals:

[0073] 1-throttle body, 2-intake manifold pressure sensor, 3-intake manifold pipeline, 4-injector assembly, 5-ignition assembly, 6-oxygen sensor, 7-exhaust manifold, 8-catalyst, 9-muffler, 10-cylinder, 11-throttle pre-pressure temperature sensor DETAILED DESCRIPTION

[0074] Figure 1 It is a structural diagram of the engine intake system and exhaust system. Figure 1 As shown, the intake and exhaust process of the engine is roughly as follows: the air enters the intake manifold 3 pipeline from the intake pipe through the throttle body 1, and then enters the cylinder 10 of the engine. The cylinder 10 is also provided with an injector assembly 4 and an ignition assembly 5 for injecting fuel. The exhaust gas discharged from the engine is discharged from the exhaust manifold 7, and the exhaust manifold 7 is provided with an oxygen sensor 6, a catalyst 8 and a muffler 9. The pre-throttle pressure and temperature sensor 11 and the intake manifold pressure sensor 2 are respectively provided upstream and downstream of the throttle body 1. Both sensors integrate a pressure sensing module and a temperature sensing module, and can detect pressure and temperature. The intake manifold pressure sensor 2 measures the pressure downstream of the throttle body 1, that is, the intake manifold pressure.

[0075] Figure 2 FIG. 1 is a flow chart of a method for predicting the transient gas volume in an engine cylinder according to an embodiment of the present invention. Figure 2 As shown, in one embodiment, the method for predicting the transient gas volume in the engine cylinder of the present invention includes:

[0076] Step S100, establishing a pressure differential expression of the differential of the estimated intake manifold pressure, wherein the pressure differential expression uses the throttle upstream pressure and the intake manifold pressure to express the differential of the estimated intake manifold pressure.

[0077] In one embodiment, the pressure differential expression can be obtained according to the following steps:

[0078] According to the nozzle model of one-dimensional compressible fluid, the throttle air flow M is obtained. thr The expression is:

[0079]

[0080]

[0081] A thr =table(X thr ) (3)

[0082]

[0083] Where, k is the adiabatic index (k = 1.4), pDs is the intake manifold pressure, pUs is the throttle upstream pressure, R thr is the gas constant (R thr =287), T thr is the throttle upstream temperature, X thr is the throttle opening, A thr is the throttle area, table(X thr ) is based on X thr The throttle area value is obtained by querying the one-dimensional calibration table. The one-dimensional calibration table calibrates X thr and A thr The corresponding relationship, Cd thr is the throttle flow coefficient, Based on X thr The throttle flow coefficient value is obtained by querying the two-dimensional calibration table. The two-dimensional calibration table calibrates X thr with cd thr The corresponding relationship, is the pressure ratio function.

[0084] According to the ideal gas state equation of the engine and the speed density method principle, the mean air flow rate M of the cylinder intake port is obtained. cyl The expression is:

[0085]

[0086] Among them, V d is the engine displacement, η v is the engine charging efficiency, n is the engine speed, and T is the temperature of the intake manifold.

[0087] Replace M with the transient intake manifold pressure p thr The expression and M cyl The pDs in the expression of are respectively used to obtain the transient predicted throttle flow M thr (p) and the predicted flow rate M in the engine cylinder cyl The expression of (p) is:

[0088]

[0089]

[0090] According to the mass conservation principle of the air flow in the intake manifold, the transient air flow M in the intake manifold is obtained. man The expression of (p) is:

[0091] M man (p) = M tnr (p)-M cyl (p) (8)

[0092] Using the ideal gas state equation to express M man (p)

[0093]

[0094] Wherein, V is the volume of the pipeline from the throttle valve to the engine intake port.

[0095] According to the above two M man The expression of (p), that is, equations (8) and (9) give the estimated differential of the intake manifold pressure The pressure differential expression is:

[0096]

[0097] Step S200, performing m iterations to solve the pressure differential expression according to the initial value P0(K) of the intake manifold pressure of the Kth sampling period and the exponential Euler formula, so as to obtain the intake manifold pressure P of the m-order model of the Kth sampling period. m (K), where K = 1, P0 (K) is taken as a set value, which can be 100; when K> 1, P0 (K) = P m (K-1), P m (K-1) is the intake manifold pressure of the m-order model in the K-1th sampling period.

[0098] Euler's formula with exponents is:

[0099]

[0100] Among them, y0 is the value of the previous sampling period, y1 is the value of the current sampling period, h is the sampling period, f(y0) is the corresponding function, and f′(y0) is the derivative of f(y0).

[0101] Euler's formula with exponents can be used to obtain y1 based on y0 and f(y0). When combined with this case, when P0(K) is a known set value and the pressure differential expression is known, P0(K) is substituted for y0 in formula (11), and the pressure differential expression about P0(K) is substituted for f(y0) in formula (11), and P1(K) can be obtained. After obtaining P1(K), the above steps are repeated to obtain P2(K). P can be obtained by iteration. m (K).

[0102] Step S300, according to P of each sampling period m (K), the ideal gas state equation and the delay angle of the gas volume required to perform engine injection calculate the predicted in-cylinder gas volume used to perform engine injection within the target time period.

[0103] In one embodiment, step S300 includes the following steps:

[0104] According to P m (K) and the ideal gas state equation to calculate the predicted gas volume M in the cylinder during the Kth sampling period cyl Pred(K):

[0105]

[0106] The corresponding delay time tDly is calculated based on the delay angle of the required amount of gas for engine injection:

[0107]

[0108] Among them, Ag1 is the advance angle of the intake variable valve in the Kth sampling period, and Ag3 is the angle of the crankshaft from the actual injection time to the closing time of the engine intake valve in the Kth sampling period;

[0109] Convert the delay time tDly into the number of sampling cycles and substitute it into M cyl Pred(K) gets the correction value M of the predicted gas volume in the cylinder during the Kth sampling period cyl InjPred(K):

[0110]

[0111] If a traditional discrete algorithm (such as the finite element method) is used to solve equation (10) for the intake manifold pressure P i (K), errors are introduced after discretization, and the accumulation of errors poses a risk of algorithm non-convergence.

[0112] In view of the defects of the above-mentioned discrete algorithm, this embodiment introduces an exponential gradient compensation coefficient to the Euler method, that is, the Euler formula with exponent in the above text, which can effectively solve the problem of non-convergence of the intake manifold pressure model estimation and improve the accuracy of the real-time estimated intake manifold pressure value.

[0113] In one embodiment, step S200 includes:

[0114] Step S202: P i-1 Substituting (K) into the pressure differential expression, we get Pd i-1 The expression of (K):

[0115]

[0116] Where, i = 1, ..., m, when i is greater than 1, P i-1 (K) Intake manifold pressure of the i-1 order model at the Kth sampling period.

[0117] Step S204, Pd i-1( K) in P i-1 (K) is derived to obtain the derivative DPd i-1 The expression of (K):

[0118]

[0119] Step S206, DPd i-1 In one embodiment, the expression of (K) can be simplified by following the steps below:

[0120] P i-1 (K) Substitute into M cyl (p) and transform it to get DPd i-1 In the expression of (K) The expression is:

[0121]

[0122]

[0123] Determined based on the curve of intake manifold pressure and throttle flow The expression is:

[0124]

[0125] Figure 3 It is a graph showing the relationship between throttle air flow and intake manifold pressure. Figure 3 The horizontal axis is the intake manifold pressure, and the vertical axis is the throttle air flow. The graph can be drawn according to formula (1). Figure 3Point A in the middle represents that the mass flow rate is 0 and the pressure ratio The corresponding maximum intake manifold pressure is P max ; Point B represents the critical sound velocity point, pressure ratio Corresponding critical intake manifold pressure P cr BC section (i.e. pressure ratio ) From the mechanical condition, the airflow reaches the speed of sound, the geometric shape of the throttle limits the expansion of the airflow, and the throttle flow is stable at the maximum value M thr (max), at this time

[0126]

[0127] AB section (i.e. pressure ratio ) is the throttle flow change curve segment, It can be approximately described as the slope of the AD line, that is:

[0128]

[0129] In formula (20), P max is the maximum intake manifold pressure, which can be replaced by the throttle upstream pressure sensor test value pUs, then formula (20) can be described as:

[0130]

[0131] Will The expression and Substitute the expression of DPd into i-1 The expression of (K), that is, formula (16), is obtained:

[0132]

[0133] Step S208, using P i-1 (K) and Euler's formula with exponent for the simplified DPd i-1 (K) (i.e., formula (22)) is solved m times in turn to obtain P m (K).

[0134] In this step, in order to consider the influence of each order model, an adjustment coefficient related to the order is also added, that is, a calibrable adjustment coefficient is added to the gradient part of each order model to facilitate calibration preset.

[0135] Specifically, P i-1 (K) and DPd i-1 (K) Substitute the exponential Euler formula and iterate to get P i (K) expression, and for P i The expression of (K) includes Pd i-1The term (K) is given the adjustment coefficient fac(i):

[0136]

[0137] The adjustment coefficient fac(i) is a value between 0 and 1 and is determined through calibration experiments.

[0138] In order to better illustrate the process of multi-order iterative solution, m=2 is taken as an example below.

[0139] For the Kth sampling period: when i=1, substitute P0(K) into formula (22) to obtain the expression of DPd0(K), that is:

[0140]

[0141] Substituting P0(K) into formula (23) yields P1(K):

[0142]

[0143] Substituting formula (24) into formula (25) can obtain the value of P1(K), which is the intake manifold pressure P1(K) of the first-order model in the Kth sampling period.

[0144] After obtaining P1(K), substitute P1(K) into (22) to obtain the expression of DPd1(K), that is:

[0145]

[0146] Substituting P1(K) into formula (23) yields P2(K):

[0147]

[0148] In this embodiment, m is 2, and the intake manifold pressure P of the m-order model in the Kth cycle is m (K) is P2(K).

[0149] When K=1, P0(K) is taken as a set value, assuming it is 100, and P2(1) can be solved by substituting it into formulas (26) and (27).

[0150] When K>1, P0(K)=P m (K-1), for example, when K=2, P2(1) can be substituted into formulas (26) and (27) to obtain P2(2). Similarly, the same solution can be obtained for other cases where K>1.

[0151] The above m is generally not greater than 5, preferably 2 or 3. In one embodiment, when m is greater than 2, the Newton iteration method is used to obtain the value of P m-1 (K) and Pm-2 (K) Calculate P m (K) expression.

[0152] The formula corresponding to Newton's iteration method is as follows:

[0153]

[0154] Among them, x n is the value of the previous sampling period, x n+1 is the value of the current sampling period, f(x n ) is the corresponding function, f′(x n ) is f(x n ) is the derivative of .

[0155] In specific applications, Pd1(K) and Pd2(K) can be obtained according to formula (15), and P0(K), P1(K), and P2(K) can be obtained according to formula (23). Based on this, the first-order model deviation equation F1(P1(K)) and the second-order model deviation equation F2(P2(K)) of the Kth sampling period can be constructed:

[0156] F1(P1(K))=P1(K)-P0(K)-Pd1(K)·h (29)

[0157] F2(P2(K))=P2(K)-P0(K)-Pd2(K)·h (30)

[0158] The Newton iteration method based on formula (28) can quickly obtain the intake manifold pressure P3(K) of the m-order model in the Kth sampling period:

[0159]

[0160] This embodiment uses the Newton iteration method in the last-order calculation process to accelerate the acquisition of the intake manifold pressure, thereby avoiding excessive iteration times in the calculation process, improving the calculation efficiency, and reducing the calculation load of the controller.

[0161] Figure 4 It is a curve comparison diagram of the data estimated by the method for predicting the transient gas volume in the engine cylinder according to one embodiment of the present invention and the measured data. Figure 4The solid line 1 is the actual cylinder air volume calculated by the mean model of the air flow rate at the cylinder intake port, the dotted line 2 is the cylinder air volume calculated based on the prediction method, the solid line 3 is the measured intake manifold pressure, the dotted line 4 is the predicted intake manifold pressure, and the solid line 5 is the excess air coefficient. For the embodiment with m=3, each adjustment coefficient satisfies the following rule: fac(1)+fac(2)=1, and the adjustment of fac(3) is an acceleration algorithm, which is increased or decreased appropriately according to demand. The general principle is to ensure that the excess air coefficient corresponding to the predicted value meets the transient control requirements under the premise of speed increase. Figure 4 In the corresponding embodiment, m is taken as 3, fac(1), fac(2), and fac(3) are calibrated as 0.6, 0.4, and 0.001, respectively, and P3(K) is calculated using the Newton iteration method when m=3. The engine speed is controlled at 2000 rpm, the adjustment coefficient is adjusted, and the engine request load is manually adjusted from 150 mg / stroke to 400 mg / stroke, and the corresponding actual intake manifold pressure changes from 70 kPa to 105 kPa. From the load comparison, it can be seen that the predicted gas volume is ahead of the actual gas volume in the cylinder. After entering the steady state, the predicted gas volume converges to the actual gas volume, both of which are about 400 mg per stroke, and the error is controlled within 5%; from the manifold pressure comparison, it can be seen that the predicted manifold pressure is ahead of the actual pressure. After entering the steady state, the predicted manifold pressure converges to the actual pressure, and the error is controlled within 5%. The measured excess air coefficient is controlled between 0.95-1.05, and the absolute deviation of the air-fuel ratio under transient operating conditions is controlled within 5%, meeting the air-fuel ratio control standard requirements.

[0162] The present invention also provides a prediction system for the transient gas volume in an engine cylinder, including a control device, the control device including a memory and a processor, the memory storing a control program, and the control program is used to implement the prediction method for the transient gas volume in the engine cylinder in any of the above embodiments when executed by the processor. The processor can be a central processing unit (CPU), or a digital processing unit, etc. The processor sends and receives data through a communication interface. The memory is used to store the program executed by the processor. The memory is any medium that can be used to carry or store the desired program code in the form of instructions or data structures and can be accessed by a computer, and can also be a combination of multiple memories. The above-mentioned calculation program can be downloaded from a computer-readable storage medium to a corresponding calculation / processing device or downloaded to a computer or an external storage device via a network (such as the Internet, a local area network, a wide area network and / or a wireless network).

[0163] At this point, those skilled in the art should recognize that, although multiple exemplary embodiments of the present invention have been shown and described in detail herein, many other variations or modifications that conform to the principles of the present invention can still be directly determined or derived based on the content disclosed in the present invention without departing from the spirit and scope of the present invention. Therefore, the scope of the present invention should be understood and recognized as covering all these other variations or modifications.

Claims

1. A method for predicting the transient gas volume in an engine cylinder, characterized in that: include: Establishing a pressure differential expression of the differential of the estimated intake manifold pressure, wherein the pressure differential expression expresses the differential of the estimated intake manifold pressure using the throttle upstream pressure and the intake manifold pressure; According to the initial value P0(K) of the intake manifold pressure of the Kth sampling period and the exponential Euler formula, the pressure differential expression is iterated and solved m times to obtain the intake manifold pressure P of the m-order model of the Kth sampling period. m (K), where, when K=1, P0(K) is taken as the set value; when K>1, P0(K)=P m (K-1), P m (K-1) is the intake manifold pressure of the m-order model in the K-1th sampling period, and the exponential Euler formula is: Where y0 is the value of the previous sampling period, y1 is the value of the current sampling period, h is the sampling period, f(y0) is the corresponding function, and f′(y0) is the derivative of f(y0); According to the P of each sampling period m (K), the ideal gas state equation and the delay angle of the gas volume required to perform the engine fuel injection calculate the predicted in-cylinder gas volume used to perform the engine fuel injection in each sampling period; The P of each sampling period m (K), the step of calculating the predicted in-cylinder gas volume used for executing the engine fuel injection in each sampling period using the ideal gas state equation and the delay angle of the gas volume required for executing the engine fuel injection comprises: According to P m (K) and the ideal gas state equation to calculate the predicted gas volume M in the cylinder during the Kth sampling period cyl Pred(K): Among them, V d is the engine displacement, η υ is the engine charging efficiency, T is the temperature of the intake manifold, Rthr is the gas constant, The corresponding delay time tDly is calculated based on the delay angle of the required amount of gas for engine injection: Wherein, Ag1 is the advance angle of the intake variable valve in the Kth sampling period, Ag3 is the angle of the crankshaft from the actual injection time to the closing time of the engine intake valve in the Kth sampling period, and n is the engine speed; Convert the delay time tDly into the number of sampling cycles and substitute it into M cyl Pred(K) gets the correction value M of the predicted gas volume in the cylinder during the Kth sampling period cyl InjPred(K):

2. The method for predicting the transient gas volume in the engine cylinder according to claim 1, characterized in that: When m is greater than 2, according to Newton's iteration method and using P m-1 (K) and P m-2 (K) Calculate P m (K) expression.

3. The method for predicting the transient gas volume in the engine cylinder according to claim 1 or 2, characterized in that: The step of establishing a differential pressure expression of the differential of the estimated intake manifold pressure comprises: According to the nozzle model of one-dimensional compressible fluid, the throttle air flow M is obtained. thr The expression is: A thr =table(X thr ) Where k is the adiabatic index, pDs is the intake manifold pressure, pUs is the throttle upstream pressure, T thr is the throttle upstream temperature, X thr is the throttle opening, A thr is the throttle area, table(X thr ) is based on X thr The throttle area value obtained by querying the one-dimensional calibration table, the one-dimensional calibration table calibrates X thr and A thr The corresponding relationship, Cd thr is the throttle flow coefficient, Based on X thr The throttle flow coefficient value obtained by querying the two-dimensional calibration table, the two-dimensional calibration table calibrates X thr with cd thr The corresponding relationship, is the pressure ratio function; According to the ideal gas state equation of the engine and the speed density method principle, the mean air flow rate M of the cylinder intake port is obtained. cyl The expression is: Replace M with the transient intake manifold pressure p thr The expression and M cyl The pDs in the expression of are respectively used to obtain the transient predicted throttle flow M thr (p) and the predicted flow rate M in the engine cylinder cyl The expression of (p) is: According to the mass conservation principle of the air flow in the intake manifold, the transient air flow M in the intake manifold is obtained. man The expression of (p) is: M man (p)=M thr (p)-M cyl (p) Using the ideal gas state equation to express M man (p) Wherein, V is the volume of the pipeline from the throttle to the engine intake port; According to the above two M man The expression of (p) gives the differential of the estimated intake manifold pressure The pressure differential expression is:

4. The method for predicting the transient gas volume in the engine cylinder according to claim 3, characterized in that: The pressure differential expression is iterated m times according to the initial value P0(K) of the intake manifold pressure of the Kth sampling period and the exponential Euler formula to obtain the intake manifold pressure P of the m-order model of the Kth sampling period. m The steps of (K) include: P i-1 (K) Substitute into the pressure differential expression to obtain the Pd i-1 The expression of (K): Where, i = 1, ..., m, when i is greater than 1, P i-1 (K) intake manifold pressure of the i-1 order model at the Kth sampling period; For the Pd i-1 (K) in P i-1 (K) is derived to obtain the derivative DPd i-1 The expression of (K): DPd i-1 The expression of (K) is simplified; Using P i-1 (K) and the Euler formula with index for the simplified DPd i-1 (K) Perform m iterations to obtain P m (K).

5. The method for predicting the transient gas volume in the engine cylinder according to claim 4, characterized in that: The DPd i-1 The steps to simplify the expression of (K) include: P i-1 (K) Substitute into the M cyl The expression of (p) is transformed to obtain the DPd i-1 In the expression of (K) The expression is: Determined based on the curve of intake manifold pressure and throttle flow The expression is: Will The expression and Substitute the expression of DPd into i-1 After the expression of (K) is obtained:

6. The method for predicting the transient gas volume in the engine cylinder according to claim 5, characterized in that: The use of P i-1 (K) and the Euler formula with index for the simplified DPd i-1 (K) Iterate and solve in turn to obtain P m (k) The steps include: P i-1 (K) and DPd i-1 (K) Substitute the exponential Euler formula and iterate to obtain P i (K) expression, and for P i The expression of (K) includes Pd i-1 The term (K) is given the adjustment coefficient fac(i): The adjustment coefficient fac(i) is a value between 0 and 1 and is determined through a calibration experiment.

7. The method for predicting the transient gas volume in an engine cylinder according to any one of claims 1 to 6, characterized in that: The set value is 100, and m is 3.

8. A prediction system for transient gas volume in an engine cylinder, comprising a control device, characterized in that: The control device includes a memory and a processor, wherein a control program is stored in the memory, and when the control program is executed by the processor, it is used to implement the method for predicting the transient gas volume in the engine cylinder according to any one of claims 1 to 7.

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