US00756.5236B2

(12) United States Patent (10) Patent No.: US 7.565,236 B2 Turin et al. (45) Date of Patent: Jul. 21, 2009

(54) AIRFLOWESTIMATION METHOD AND 5,845,627 A 12/1998 Olin APPARATUS FOR INTERNAL COMBUSTION 6,016,460 A 1, 2000 Olin ENGINE 6,651,492 B2 * 1 1/2003 Kolmanovsky et al. .. 73/114.37 (75) Inventors: Raymond Claude Turin, Grosse Pointe 6,820,589 B2 * 1 1/2004 Okubo et al...... 123,339.19 Park, MI (US); Rong Zhang, Troy, MI 6,851,304 B2 * 2/2005 Cullen et al...... T3,114.32 (US); Man-Feng Chang, Troy, MI (US) 2005/0229884 A1* 10, 2005 Kunz et al. ... 123.90.17 2006/0054134 A1 3/2006 Hennet al...... 123,325 (73) Assignee: GM Global Technology Operations, Inc., Detroit, MI (US) (*) Notice: Subject to any disclaimer, the term of this OTHER PUBLICATIONS patent is extended or adjusted under 35 U.S.C. 154(b) by 191 days. R. C. Turin and H. P. Geering, "On-Line Identification of Air-Fuel Dynamics in a Sequentially Injected SI Engine'. SAE 930857, Mar. (21) Appl. No.: 11/780,508 1993. (22) Filed: Jul. 20, 2007 * cited by examiner (65) Prior Publication Data Primary Examiner Willis R Wolfe, Jr. US 2009/OO243OO A1 Jan. 22, 2009 (57) ABSTRACT (51) Int. Cl. SO 3.08: A method of estimating an air charge in at least one combus (52) U.S. Cl 701/103. 701f1 15: 73/114.32 tion cylinder of an internal combustion engine includes cal Oa ------s 73/1433 culating cylinder mass air flow based upon a modified Volu (58) Field of Classification Search 701f101 103 metric efficiency parameter, and calculating the intake 701f1 10, 111 115. 73/1 14,311 14.35: 702.50. throttle mass air flow based upon a throttle airflow discharge s u u us . . a- s 123,479,480,494 parameter and a fuel enrichment factor. Three models includ See application file for complete search history. ing a mean-value cylinder flow model, a manifold dynamics model, and a throttle flow model are provided to estimate the (56) References Cited air charge in the at least one combustion cylinder and to U.S. PATENT DOCUMENTS control delivery of fuel to the fuel delivery system. 5,714,683 A 2/1998 Maloney 5,753,805 A 5/1998 Maloney 19 Claims, 4 Drawing Sheets

As

aszaars U.S. Patent Jul. 21, 2009 Sheet 1 of 4 US 7.565,236 B2

5-N

g &N ws s g & & X s X s (s ass

's

U.S. Patent Jul. 21, 2009 Sheet 3 of 4 US 7.565,236 B2

?ºzzzzzzZ) |38 U.S. Patent Jul. 21, 2009 Sheet 4 of 4 US 7.565,236 B2

Coooooooooooooooor XXX XXXX XXX XXXX-XXX XXX XXXb XXX XXXX XXXX-XXXX XXX-XXX XXX XXXB ENGINE toob. EXHAUS

30,58,6264,70,74,8284.85 AFIG. af

US 7,565,236 B2 1. 2 ARFLOWESTIMATION METHOD AND FIG. 1 is a schematic model of a spark ignited internal APPARATUS FOR INTERNAL COMBUSTION combustion engine system; ENGINE FIG. 2 illustrates a methodofestimating cylinder air charge without a mass air flow sensor, TECHNICAL FIELD FIG.3 is an illustration of the flow of air from atmosphere to a cylinder within the combustion engine system shown in The present invention is related to the field of engine con FIG. 1: trols for internal combustion engines and more particularly is FIG. 4 is a block diagram showing the flow of the signals directed towardestimation of throttle mass airflow as used in produced in the spark ignited internal combustion engine Such controls. 10 system shown in FIG. 1; and FIG. 5 is a correction look-up table used to determine the BACKGROUND OF THE INVENTION correction of the throttle discharge coefficient. The basic objective for fuel metering in most gasoline DESCRIPTION OF THE PREFERRED engine applications is to track the amount of airin the cylinder 15 EMBODIMENT with a predefined stoichiometric ratio. Therefore, precise air charge assessment is a critical precondition for any viable Turning now to FIG. 1, a schematic model of a spark open loop fuel control policy in Such engine applications. As ignited internal combustion engine system (System) 20 is the air charge cannot be measured directly its assessment, in illustrated. The System 20, in the most general sense, com one way or another, depends on sensing information involv prises all engine associated apparatus affecting or affected by ing a pressure sensor for the intake manifold, a mass air flow gas mass flow and includes the operating environment or sensor upstream of the throttle plate, or both. The choice of a atmosphere from which and to which gas mass flows. The particular sensor configuration reflects a compromise internal combustion engine includes a naturally aspirated or a between ultimate system cost and minimum performance boosted internal combustion engine. The atmosphere 66 is requirements. Currently, high cost Solutions involving both 25 shown entering the system at the fresh air inlet 22. sensors are found in markets with Stringent emission stan The System includes a variety of pneumatic elements, each dards while low cost solutions, mostly involving just a pres generally characterized by at least a pair of ports through Sure sensor, are targeting less demanding developing markets. which gas mass flows. For example, air induction including Speed-density methods of computing the mass airflow at fresh air inlet 22, air cleaner 24, and intake duct 26 is a first 30 general pneumatic element having ports generally corre the engine intake are known in the art. However, employing the speed-density methods in conjunction with more complex sponding to the air inlet 22 at one end and another port engine applications such as cam-phasing and/or variable generally corresponding to the intake duct 26 at the other end. valve lift capability has not been practical or economically Another example of a pneumatic element is intake manifold feasible. 36 having ports interfacing with intake duct 34 and intake 35 runner 38. Other general examples of pneumatic elements in Therefore, what is needed is a method for providing a low the System include: intake air throttle orifice 86 including cost air charge estimator without the use of a mass air flow throttle body 28 and throttle plate 32; crankcase 50: combus sensor that provides cylinder air estimation to satisfy devel tion cylinder 46 including combustion chamber 48 and intake oping market needs. valve 40 and cam 72: exhaust including exhaust duct 52, and 40 exhaust outlet 54. SUMMARY OF THE INVENTION The various elements shown in FIG. 1 are exemplary and the present invention is by no means restricted only to those An internal combustion engine system includes a control specifically called out. Generally, an element in accordance ler in signal communication with the engine and with a fuel with the present invention may take the form of a simple delivery system, a combustion cylinder and piston recipro 45 conduit or orifice (e.g. exhaust), variable geometry valve (e.g. cating therein, an intake manifold directing flow of air into the throttle orifice) 86, pressure regulator valve (e.g. PCV valve), at least one combustion cylinder, and an air throttle having a major Volumes (e.g. intake and exhaust manifolds)36.44, or throttle orifice directing flow of air mass into the intake mani pneumatic pump (e.g. combustion cylinder) 46. fold. A method of estimating an air charge in at least one In illustration of the interrelatedness of the various ele combustion cylinder of the engine includes: calculating cyl 50 ments and flow paths in the internal combustion engine sys inder mass air flow based upon a modified volumetric effi tem 20, a gas mass (gas) at atmospheric pressure enters ciency parameter, calculating the intake throttle mass airflow through fresh air inlet 22, passing an intake air temperature based upon a throttle air flow discharge parameter and a fuel sensor 58, and then passing through air cleaner 24. Gas flows enrichment factor, and using the cylinder mass air flow and from intake duct 26 through throttle body 28. For a given throttle mass air flow to estimate the air charge within the at 55 engine speed, the position of throttle plate 32, as detected by least one combustion cylinder. Three models including a a throttle position sensor 30, is one parameter determining the mean-value cylinder flow model, a manifold dynamics amount of gas ingested through the throttle body and into the model, and a throttle flow model are provided to estimate the intake duct 34. From intake duct 34, gas enters an intake air charge in the at least one combustion cylinder and to manifold 36, whereat individual intake runners 38 route gas control delivery of fuel to the fuel delivery system. 60 into individual combustion cylinders 46. Gas is drawn through cam actuated intake valve 40 into combustion cylin BRIEF DESCRIPTION OF THE DRAWINGS der 46 during piston downstroke and exhausted therefrom through exhaust runner 42 during piston upstroke. These The invention may take physical form in certain parts and intake and exhaust events are of course separated by com arrangement of parts, the preferred embodiment of which will 65 pression and combustion events in full four-cycle operation, be described in detail and illustrated in the drawings incor causing rotation of a crankshaft 60, creating an engine speed porated hereinafter, wherein: that is detected by an engine speed sensor 62. Gas continues US 7,565,236 B2 3 4 through exhaust manifold 44, past the exhaust temperature operating condition and is based on an air flow estimation sensor 64, and finally through exhaust outlet 54 to atmosphere error metric that is derived from the stoichiometric offset of a 66. closed-loop fuel factor. In one embodiment of the invention, fuel 68 is mixed with FIG. 2 is a flow diagram of cylinder air estimation without the gas by a fuel injector 56 as the gas passes through indi a mass air flow sensor. FIG. 2 shows a block flow diagram vidual intake runners 38. In other embodiments of the inven representing three physical models, including a mean-value tion, fuel 68 may be mixed with the gas at other points. cylinder flow model 76, a manifold dynamics model 78, and In accordance with an embodiment of the invention, Vari ous relatively substantial volumetric regions of the internal a throttle flow model 80. By measuring common engine sig combustion engine system are designated as pneumatic Vol 10 nals except the mass airflow, the system uses the three physi ume nodes at which respective pneumatic states are desirably cal models, two adaptation loops 90.92 modifying volumet estimated. The pneumatic states are utilized in determination ric efficiency and throttle airflow efficiency, and information of gas mass flows that are of particular interest in the control from a known production closed-loop air to fuel ratio control functions of an internal combustion engine. For example, algorithm, to calculate the cylinder mass air flow and the mass airflow through the intake system is desirably known for 15 throttle mass air flow. development of appropriate fueling commands by well The invention requires common engine measurement known fueling controls. inputs that include: throttle position sensor 30, manifold air In accordance with an embodiment of the invention, the pressure sensor (MAP) 84, engine speed sensor (RPM) 62. system may include a coolant temperature sensor 70 for sens barometric sensor or key-on barometric reading of MAPsen ing the temperature of the coolant. Sor 84, variable cam phaser position (intake and exhaust) if In accordance with an embodiment of the invention includ applicable 85, variable cam lift position 82 (intake and ing variable cam phasing, the angular positioning of the cam exhaust) if applicable, intake air temperature sensor (IAT) 58, 72 providing the actuation of the cam actuated intake valve 40 coolant temperature sensor 70, and exhaust temperature sen may be determined by a cam position sensor 85. sor 64. In another embodiment of the invention including variable 25 FIG. 3 illustrates the flow of air 102 through the throttle cam lifting, the amount of lift provided by the cam 72 pro orifice 86 and the intake manifold 36 as the air moves from viding the actuation of the cam actuated intake valve 40 may atmosphere to the cylinder 46. be determined by a variable cam lift position sensor 82. FIG. 4 generally illustrates the flow of the signals 98 pro Turning now to FIG. 2, a method of estimating cylinder air 30 duced by the preceding elements and shows the interrelated charge without a mass air flow sensor 96 in accordance with ness of the various components by depicting the information an embodiment of the invention is illustrated. FIG. 2 shows a exchanged between them. block diagram of a mean-value cylinder flow model 76, a The manifold dynamics model 78 uses both the mean manifold dynamics model 78, and a throttle flow model 80. value cylinder air flow and the throttle air flow to determine A method of cylinder air charge estimation for internal 35 manifold pressure error. The throttle airflow is determined by combustion engines without using a mass air flow (MAF) the throttle flow model 80. The accuracy of the throttle flow sensor 96, which satisfies the need of low cost engine control model 80 is improved by correcting the throttle discharge systems for markets with moderate emission standards is coefficient through use of fuel correction information derived provided. The method estimates the cylinder air charge using from air to fuel ratio close-loop fuel control algorithms a speed-density approach. The approach includes physics 40 known in the art. The correction of the throttle discharge based models for the intake manifold dynamics and the air coefficient defines the second adaptation loop 92. mass flow through the throttle orifice 86, and involves adap tive schemes to adjust the throttle air flow discharge param Transient effects of gas mass stored in a Substantial Volume eter and the volumetric efficiency parameter. The method is in a pneumatic capacitance element, such as an intake mani applicable to engines with variable valve timing and/or vari fold 36, are generally modeled in the present invention in 45 accordance with the net gas mass in the fixed Volume of Such able valve lift. The method also adjusts for variations of fuel pneumatic capacitance element. At any given instant, the properties. finite gas mass M contained in the pneumatic capacitance The method does not require a mass airflow sensor (MAF) element of interest may be expressed in terms of the well and does not directly use the measurement of an oxygen known ideal gas law: sensor (O2) or a wide-range air-fuel ratio sensor (WAFR). 50 However, a closed-loop fuel control algorithm known in the & (1) art that corrects the fuel injection amount based on O2 or WAFR measurements is used. where P is the average pressure in the volume, V is the Volume of the pneumatic capacitance element, R is the uni A mean-value model that models the manifold pressure Versal gas constant for air, and T is the average temperature of dynamics and the gas flow through the throttle orifice 86 is 55 shown in FIG. 2. Nominal static models for the volumetric the gas in the volume. The manifold pressure is related to the efficiency coefficient of the engine (m) and for the throttle manifold mass (m) through the gas equation (1): discharge coefficient (C) are corrected with correction fac tors that are adjusted by a controller 94, as shown in FIG. 4. (2) The update of the volumetric efficiency correction is per 60 formed through methods known in the art. In one embodi ment of the invention, a Kalman filter which uses the differ ence between the measured and modeled manifold pressure Differentiation of equation (2) with respect to time yields as an error metric may be used. mean-value mass conservation defining a difference between Correction of the throttle discharge coefficient is made 65 the air mass flow through the throttle and into the manifold ( using a correction look-up table 100, illustrated in FIG. 5. The rin) the air mass flow out of the manifold and into the correction look-up table 100 evolves as a function of the cylinder (rin) for the manifold volume V: US 7,565,236 B2

d (3) Pn. Va (8) - in mair = 1 cit = main - mair eff RTi

Hence Substituting equation (2) into equation (3) yields the wherein p is the intake manifold pressure, T is the mani relationship between the manifold mass flow (m) and pres fold air temperature, R is the gas constant of the gas mixture Sure rate of change p. at the manifold intake, V is the total cylinder volume dis placement, m is a volumetric efficiency coefficient that 10 relates the actual fresh air charge mass to the fresh air mass d ( p.m Vn Vn Pin Vn (4) that could occupy the cylinder 46 if the entire displaced dt (1)A RT = p, RTH-T, RT: volume (V) were completely replaced with fresh air under manifold conditions. The value of the volumetric efficiency . Vin mm Tin coefficient (m) depends on the thermodynamic conditions - PRI. - T. 15 during the ingestion process and on the valve timing and the = main - mair. lift profile. The volumetric efficiency coefficient (m) may be deter mined from a look-up table or from an analytical function The principle of energy balance applied to the intake mani based on physics. fold volume yields: A speed density equation that provides a basis for fuel metering calculations defines a mean-value cylinder flow ( rin) that may be derived from equation (9) as follows: (m,ncy.T.) = imney.T., + mney Tin (5)5 25 Filair, CpTih - filair CpTin pin Vd in (9) thair = 1eff RT, 2

wherein C, and C are the isochoric and isobaric heat wherein n is the engine speed and in is the mass flow out capacities for air, and T is the gas temperature at the throttle 30 of the manifold 36 and into the cylinder 46. The Symbols p. orifice. Combining (2) and (5) yields equation (6): and T are the ambient and manifold pressures and tempera tures, respectively, R is the specific gas constant and the T,m, -manairti, (KT-T,)-man (K-1)T, (6) isentropic exponent of air, V, the cylinder displacement Vol

Substituting equation (6) into equation (4) defines the 35 ume, in the engine speed, and m is the volumetric efficiency manifold pressure rate of change p. of the engine. Pumping effects of a flow source on intake air mass flow, for example due to the engine and effecting the air mass flow at the intake manifold, may be approximated by the RK. (7) well known speed-density equation. Pn = i (mair, Tin -inair. Tn) The engine and manifold pressure parameters are split into 40 a known nominal part (SuperScript 0) and into an unknown correction part (prescript A). The nominal parts of the Volu The mean-value cylinder flow model 76 includes the cal metric efficiency and of the throttle discharge coefficient are culation of a nominal volumetric efficiency me using the either calculated from static engine mapping data (look-up measured inputs. The mean-value cylinder flow model also 45 table approach) or via regression functions. includes a volumetric efficiency correction based on the dif The dynamics of the manifold pressure are described ference between the estimated manifold pressure (as obtained according to methods known in the art using a non-minimum from the manifold dynamics model) 78 and the measured order model representation as follows: manifold pressure, obtained from measurements made by the MAP sensor 84. The volumetric efficiency correction is made 50 using a first adaptation loop. do1 = -(no.e +k),V ?o2 - V 2 p. (10) Volumetric efficiency is corrected through the use of a O V in RK manifold pressure error metric determined from a difference d2 = -(nit + k, xvi. so t Wimair, Th in actual measured manifold pressure and estimated manifold 55 p = (ks - Anei )() + (or pressure and is input into the mean-value cylinder flow model 76. The parameter k is an arbitrary design parameter which is The mean-value cylinder flow is the average mass air flow used to obtain desirable transient properties for the non-mini rate out of the intake manifold 36 into all the cylinders 46 and 60 mum order model is derived from the cylinder air charge. The accumulated The non-minimum representation model for the manifold cylinder air charge per cycle (m) is a function of the pres pressure dynamics is used to design a state estimator accord sure and the temperature conditions across the intake valve 40 ing to the principles of an extended Kalman-filter for the during the time between intake valve opening (IVO) and unknown state 6-k-Am based on the known inputs and intake valve closing (IVC). More specifically, accumulated 65 outputs rh, and p, respectively, where mair, is the mass air cylinder air charge per cycle (m) may be expressed as flow through the throttle 28 into the manifold 36. The Kal follows: C3 man-filter state estimator equations are given below: US 7,565,236 B2 7 8 Estimator extrapolation step: sented in terms of a known nominal (C) and unknown 6.--0g, portion (AC) as defined in equation (18): C=C+AC (18) XI-X-1+9. (11) Substituting equation (18) into equation (16), the throttle Estimator update step: air mass flow in may be expressed as specified in equation 6-61-I-K-(p-fi, ) (19): th K-S-101.012-101*.S.' 10 mair,. -= Ash (C + ACd) V."Pa i? PmE} (19) X-II-K-01-XI-1 (12) The symbol X denotes the state covariance matrix, K the Kalman gain and Q and S are filter design parameters, respec With AC, as the estimate of AC, a throttle mass flow tively. While the filter design parameters Q and S signify in 15 estimate rh, i. is derived from (19) as follows: principle the state and the output noise covariance (and are hence determined by the statistical properties of the underly ing process signals) they are typically chosen arbitrarily in filair,- F Aih (C. -- AC4)r Pa Pn (20)20 such a way that desired filter performance is established. The V. v. ) Kalman filter provides an accurate estimate of the parameter 0 provided that the throttle flow input is accurate. The volu Assuming that the nominal value of the throttle discharge metric efficiency correction Amis calculated from the esti coefficient is erroneous, an accurate estimate of the throttle mate 0 as follows: mass flow may be obtained if the correction term AC may be An-k-6 (13) determined. To determine the correction term AC initially, 25 An estimate of the volumetric efficiency can be calculated the normalized air-fuel (A/F) ratio v is defined as follows: from a nominal Volumetric efficiency parameter ma?' and the Volumetric efficiency correction parameter Am k-0 as fol = fair (21) lows: Filmf in ne?t Any (14) 30 An estimate of the cylinder air charge (8) and of the cylin The normalized A/F-ratio W is given as the ratio between der air flow (9) can be calculated using the estimate for the the amount of cylinder air (m) and the amount of fuel (m) volumetric efficiency as follows, respectively: in the cylinder scaled by the fuel's stoichiometry factor (F). 35 The normalized A/F-ratio (w) assumes a value of one under stoichiometric mixture conditions. The fuel is typically r Pn. Va (15) metered as a function of an estimate for the air charge (m) maire Fleif PT i and a fuel enrichment factor (f) and may be expressed as s pin Vd in follows: mair - if RT 2 40

1 (22)

The air mass flow into the intake manifold 36 through the mf = S fair. throttle orifice 86 (th) may be expressed in terms of the compressible flow equation (16) as follows: 45 Substituting (22) into (21) yields the normalized A/F-ratio (w): filair, F Ath Cd (16) = fair (23) 50 filair. wherein A is the throttle orifice area, C is the throttle dis charge coefficient, p, and T are the ambient pressure and Assuming that the fuel enrichment factor (f) is adjusted by temperature, respectively, and up is the dimensionless com existing closed-loop A/F ratio control algorithms such that pressible flow coefficient expressed as follows: 55 the engine is running at a stoichiometric mixture ratio at all times, expression (23) may be expressed as: (17) fair fair (24) 60 fair fair

Thus, the fuel enrichment factor (f) describes the ratio between the actual amount of air in the cylinder 46 (or the air wherein K is the isentropic coefficient for air. 65 flow into the cylinder 46) and an estimate of amount of air in Similar to the representation of the volumetric efficiency the cylinder 46 (or the air flow into the cylinder 46). Hence, parameter, the throttle discharge coefficient (C) is repre deviations of the enrichment factor (f) from a value of one US 7,565,236 B2 10 precisely characterizes the air flow (or air charge) estimation constant but a function of both the throttleposition C, and the errors (e) defined by equation (25): throttle pressure drop r, the adaptation is implemented in the form of a block learn scheme. A block learn table for throttle discharge correction 100 is m = main -itair - (f - liair. (25) 5 defined according to FIG. 5. Per the nomenclature introduced in FIG. 5 and the adaptation scheme incorporated in equation (30), the update of the block-learn table evolves as follows: Under steady state conditions, the mass flow through the 1) Calculate the incremental correction for the current throttle orifice 86 operating point according to equation (31): 10

(hair) dACdk = kcd(f(t)-liair, (t) (31)

15 2) Identify the four grid points that surround the current and the mass flow through the engine operating point and calculate weighting factors for each grid point as follows: (iair.) ii C. C. : f = i. , fi = th (32) are equivalent: gii = (1-fi) (1 - fi), gi+1 = f(1 - fi), hair, = fair (26) 25 gi. 1 = (1 - fi) fi, filair, Friair gi+1.j+1 = fif

Hence, Substituting equation (26) into equation (25) yields: wherein C, is the angle of the throttleplate 32, r is the ratio 30 of manifold pressure to ambient pressure. 3) Update the table value in each of the four current grid en = mair - fair - (f - 1)fair, (27) points according to

Subtracting (20) from (19) leads to equation (28): 35 In the absence of a mass flow sensor, accuracy of this signal is established gradually by using an adaptive scheme for the s r Pa , f Pm (28) unknown discharge correction as follows: hair,air - hair,fair... = (ACd( d - ACd)Ata) Vief) 40 so that (27) finally becomes ACdk = AC +ked (f - liair. (34) Here the symbol f, stands for the closed-loop fuel correc en = (f - 1)iair,i - -= (AC - ACd)Athr Vief)Pa , Pm (29) 45 tion factor and k is the adaptation gain. This gain is a discretionary parameter and is selected to be small enough to establish stable adaptation and yet large enough to achieve a Thus, the air flow estimation error (e) is eliminated for sensible adaptation response time. Because the adaptation arbitrary throttle and pressure conditions if the estimate of the bandwidth is rather small, the update law described in equa discharge correction parameter AC equals the actual value 50 tion (3) is used along with a look-up table 100 for the dis AC. A discrete-time adaptation scheme for the unknown charge correction. The use of look-up tables accounts for the throttle air flow discharge parameter AC is readily derived fact that the discharge erroris typically not constant across the from equation (29) as follows: entire engine operating envelope but rather a function of the throttle position and of the pressure conditions across the 55 throttle orifice 86. The look-up table is updated in the four neighboring grid-points of the actual operating point (in dACdk = kodem =ked (f(t)-liair, (t) (30) terms of throttle position C, and pressure ratio It, across the ACdk = AC4-1 + dACas throttle plate 32). Hence, 60 A more Sophisticated adaptation policy involving an adjustable gain is not favored for two reasons: 1) With the ACdk = AC-1 m + gn, k.d(fix -liair, v me [i, i+1), (35) assumptions and modeling errors associated with equation in ei, i + 1 (30) together with a need to separate the adaptation rates of the Volumetric efficiency correction and the discharge correc 65 tion, only a very low adaptation bandwidth would function The indices i and denote the ith grid point on the throttle well, and 2) since the discharge error AC is probably not position axis and the jth grid point on the pressure ratio axis, US 7,565,236 B2 11 12 respectively. The parameterg, is a weighting factor associ include all Such modifications and alterations insofar as they ated with the update of the grid point with indices (m, n) that come within the scope of the invention. accounts for the distance of the actual operating point from The invention claimed is: that particular grid point (the weighting factors of all four grid 1. Method of estimating an air charge in at least one com points add up to a Sum of one). bustion cylinder of an internal combustion engine including a The continuously updated look-up table is then used to controller in signal communication with the engine and with calculate the discharge correction term AC applied in (19). a fuel delivery system, a combustion cylinder and piston With the notation introduced above, the mathematical formal reciprocating therein, an intake manifold directing flow of air ism to describe this step is given as follows: into the at least one combustion cylinder, and an air throttle 10 having a throttle orifice directing flow of air mass into the intake manifold, wherein the engine has cam-phasing and (36) variable valve lift capability, the method comprising: ACdk = X. X. gm.nacan, calculating cylinder mass airflow based upon a Volumetric efficiency parameter; 15 calculating the intake throttle mass air flow based upon a For the slow adaptation loop 92 of throttle flow model 80, throttle air flow discharge parameter and a fuel enrich active closed-loop fuel control, precise knowledge of the ment factor; Stoichiometric factor F, and accurate fuel metering are using a first cylinder air mass flow adaptation loop to assumed. In cases when these assumptions are not true, the update the Volumetric efficiency parameter, throttle flow adaptation loop 92 needs to be disabled by turn using a second throttle mass flow adaptation loop to update ing off switch SW, 88 in FIG.2. Examples of these circum the throttle air flow discharge parameter; and stances include, but are not limited to, a fuel property change using each of the first cylinder air mass flow adaptation as detected by a refuel event, a fuel injector fault as detected loops and the second throttle mass flow adaptation loop by fuel injector diagnostics, and an oxygen sensor fault as to estimate the air charge within the at least one com detected by emission diagnostics. 25 bustion cylinder. During the time when the throttle model adaptation is 2. Method of estimating an air charge in at least one com disabled, the F value is based on existing fuel type detection bustion cylinder of an internal combustion engine including a algorithms. Meanwhile, the throttle flow model 80 uses the controller in signal communication with the engine and with a fuel delivery system, a combustion cylinder and piston nominal value of the discharge coefficient C. 30 The correction of the discharge coefficient constitutes the reciprocating therein, an intake manifold directing flow of air second adaptation loop 92. into the at least one combustion cylinder, and an air throttle having a throttle orifice directing flow of air mass into the Under high load conditions when the pressure ratio across intake manifold, the method comprising: the throttle plate approaches a value of one the compressible calculating cylinder mass airflow based upon a Volumetric flow equation becomes increasingly inappropriate to charac 35 efficiency parameter; terize the mass flow through the throttle orifice. For this calculating the intake throttle mass air flow based upon a purpose the calculation of the throttle flow equation (20) is throttle air flow discharge parameter and a fuel enrich modified for high load conditions as follows: ment factor; and using the cylinder mass air flow and throttle mass air flow 40 (37) to estimate the air charge within the at least one com hairm = A, (C+ AC) V fiRt. {E} bustion cylinder. o Pn Van 3. The method of claim 2, wherein the internal combustion hairne, (1 -- AC) left RT, 2 engine comprises a naturally aspirated or a boosted internal 45 combustion engine. 'airthp if. Pmits p, 4. The method of claim 2, further comprising: s Pia mair, F s s . Pm using a first adaptation loop to correct the Volumetric effi karbhair + (1 - ki.) 'airsh if >p r ciency parameter; and Pa F. using a second adaptation loop to correct the throttle air 50 flow discharge parameter. More particularly, when the pressure ratio exceeds a cer 5. The method of claim 4, further comprising: tain threshold p, the throttle mass flow is calculated as the disabling the second adaptation loop when a stoichiometric weighted average of a mass flow value in which is based fuel enrichment factor and accuratefuel metering are not on a compressible flow equation approach and a mass flow known. value rin. The mass flow value rh is based on a speed 55 6. The method of claim 2, further comprising: density equation approach. The arbitration factorkeO1 is using a set of engine measurement parameters input into a a calibration parameter and is implemented in terms of a mean-value cylinder flow model to calculate a nominal lookup table with respect to pressure ratio. The calculation of Volumetric efficiency parameter. the discharge correction estimate AC is independent of the 7. The method of claim 6, further comprising: load case and remains as described in equation (36). Simi 60 using a manifold dynamic model to estimate a manifold larly, the update of the discharge error lookup table is inde pressure; pendent of the load case and remains as described in equation comparing a measured manifold pressure with the esti (35). mated manifold pressure to determine a manifold pres The invention has been described with specific reference to Sure error metric; and the exemplary embodiments and modifications thereto. Fur 65 updating the nominal Volumetric efficiency parameter with ther modifications and alterations may occur to others upon a corrected Volumetric efficiency parameter using the reading and understanding the specification. It is intended to manifold pressure error metric. US 7,565,236 B2 13 14 8. The method of claim 7, further comprising: 14. The method of claim 13, wherein the corrected throttle correcting the Volumetric efficiency parameter using the air flow discharge parameter is a function of the air intake manifold pressure error metric; and throttle position and of pressure across the throttle orifice. inputting the corrected Volumetric efficiency parameter 15. The method of claim 12, further comprising: into the mean-value cylinder flow model. estimating air flow through the throttle orifice; and 9. The method of claim 8, further comprising: adjusting the air flow through the throttle orifice in accor determining a mean-value cylinder flow, wherein the dance with the corrected throttle air flow discharge mean-value cylinderflow is an average mass airflow rate parameter. out of the intake manifold into each combustion cylinder 16. The method of claim 15, further comprising: within the internal combustion engine. 10 correcting the throttle airflow discharge parameter using a 10. The method of claim 9, further comprising: normalized air-fuel ratio, wherein the normalized air using a speed density calculation to determine the mean fuel ratio is the ratio of an amount of combustion cylin value cylinder flow. der air and an amount of fuel in the at least one combus 11. The method of claim 9, further comprising: tion cylinder scaled by a stoichiometric fuel enrichment using the mean-value cylinder air flow and the intake 15 factor associated with the fuel. throttle mass airflow to determine the manifold pressure error metric. 17. The method of claim 16, further comprising: 12. The method of claim 2, further comprising: determining a fuel enrichment factor, wherein the fuel inputting throttle position measurements into a throttle enrichment factor is a ratio of an actual amount of air in flow model; the combustion cylinder and an estimate of an amount of calculating a nominal throttle airflow discharge parameter air in the combustion cylinder. associated with the throttle flow model; 18. The method of claim 17, further comprising: deriving an airflow estimation error metric from a stoichio determining the air flow estimation error metric of the fuel metric offset of a closed-loop fuel enrichment factor; enrichment factor when the fuel enrichment factor does and 25 not equal a value of 1. updating the nominal throttle airflow discharge parameter 19. The method of claim 18, further comprising: with a corrected throttle air flow discharge parameter eliminating the airflow estimation error when an estimated based on the air flow estimation error metric. throttle air flow discharge parameter equals an actual 13. The method of claim 12, further comprising: value of the throttle air flow discharge parameter. using a block look-up table to determine the corrected 30 throttle air flow discharge correction parameter.