USOO6636796B2 (12) United States Patent (10) Patent No.: US 6,636,796 B2 Kolmanovsky et al. (45) Date of Patent: Oct. 21, 2003 (54) METHOD AND SYSTEM FOR ENGINE AIR M. Jankovic et al., “Air-charge Estimation and Prediction in CHARGE ESTIMATION Spark Ignition Internal Combustion Engines', Proceedings (75) Inventors: Ilya V Kolmanovsky, Ypsilanti, MI of 1999 American Control Conference, San Diego, CA. (US); Alexander Anatoljevich Stotsky, Y.-W. Kim et al., “Automotive Engine Diagnosis and Con Gothenburg (SE) trol Via Nonlinear Estimation”, IEEE Control Systems Magazine, Oct. 1998, pp. 84–99. (73) Assignee: Ford Global Technologies, Inc., Dearborn, MI (US) T-C. Tseng et al., “An Adaptive Air-Fuel Ratio Controller for SI Engine Throttle Transients”, SAE Paper (*) Notice: Subject to any disclaimer, the term of this 1999-01-0552. patent is extended or adjusted under 35 U.S.C. 154(b) by 241 days. Hendricks, E. et al., “Alternative Observers for SI Engine Air/Fuel Ratio Control", Proceedings of the 35". IEEE (21) Appl. No.: 09/769,800 Conference on Decision and Control, Kobe, Japan, Dec. 11-13, 1996, Dec. 11, 1996, pp. 2806-2811, IEEE, New (22) Filed: Jan. 25, 2001 York, NY, USA. (65) Prior Publication Data US 2002/0133286 A1 Sep. 19, 2002 * cited by examiner (51) Int. Cl." ................................................ F02D 41/18 (52) U.S. Cl. ................ 701/104; 73/118.2; 123/480 Primary Examiner Andrew M. Dolinar (58) Field of Search ................................. 701/102, 104, (74) Attorney, Agent, or Firm Julia Voutyras; Allen J. 701/114, 115; 123/480, 488; 73/118.2 Lippa (56) References Cited (57) ABSTRACT U.S. PATENT DOCUMENTS The air flow into an engine is estimated via a speed-density 5,497.329 A * 3/1996 Tang .......................... 701/104 calculation wherein the Volumetric efficiency is estimated 5,555,870 A 9/1996 Asano ........................ 123/480 on-line. There are three interconnected observers in the 5,889.204 A 3/1999 Scherer et al. estimation Scheme. The first observer estimates the flow 6,363,316 B1 3/2002 Soliman et al. ............. 701/104 through the throttle based on the Signal from a mass air flow OTHER PUBLICATIONS sensor (MAF). The second observer estimates the intake J.A. Cook et al., “Engine Control”, IEEE Control Handbook, manifold pressure using the ideal gas law and the Signal CRC Press, Inc., 1996, pp. 1261–1274. from a intake manifold absolute pressure sensor (MAP). The J.W. Grizzle et al., “Improved Cylinder Air Charge Estima third observer estimates the Volumetric efficiency and pro tion For Transient Air Fuel Ratio Control', Proceedings of vides an estimate of the air flow into the engine. 1994 American Control Conference, Baltimore, Md., Jun. 1994, pp. 1568–1573. 26 Claims, 3 Drawing Sheets 90 OBSERVER FOR THE FLOW VIA THE THROTTLE OBSERVER FOR THE FLOW INTO THE ENGINE OBSERVER FOR INTAKE - MANIFOLD PRESSURE 94 U.S. Patent Oct. 21, 2003 Sheet 1 of 3 US 6,636,796 B2 S S CSd -- s S H e 2 A: FirA ZaaZYa 2. Zaayaaaaa 24, s t 3. z - S. N U.S. Patent Oct. 21, 2003 Sheet 2 of 3 US 6,636,796 B2 OBSERVER FOR INTAKE - MANFOLD PRESSURE 94 1727, 2 START 100 GET NOMINALESTIMATE OF AIRCHARGE 102 DETERMINE NOMINAL AMOUNT OFFUELTO BE INJECTED FOR STOICHOMETRIC A/F 104 CORRECT NOMINAL AMOUNT OF FUE BASED ON FEEDBACK FROM DOWNSTREAMEGO SENSOR DATA 106 NJECT FUEL CREAD 77, -7 U.S. Patent Oct. 21, 2003 Sheet 3 of 3 US 6,636,796 B2 START 110 GET SENSOR DATA AND CURRENT ESTIMATE OF NOMINAL VOLUMETRICEFFICIENCY Nykto 112 ESTIMATE THROTTLE FLOW 114 UPDATEFILTER VARIABLEEF) 116 UPDATE MAPESTIMATE Packi) f 18 ESTIMATE FLOW INTO ENGINEme) 120 ESTIMATE VOLUMETRICEFFICIENCYNy) 122 UPDATE FILTER VARIABLE E(k+1) RETURN US 6,636,796 B2 1 2 METHOD AND SYSTEM FOR ENGINE AIR model in Equation (1) even if MAP sensor is available CHARGE ESTIMATION because useful information can be extracted from the error between the modeled pressure P and the measured pres Sure p. BACKGROUND OF THE INVENTION More elaborate Schemes used in Spark-ignition (SI) engines perform the following functions: compensate for the 1. Field of the Invention dynamic lag in the MAF sensor with a lead filter, see for This invention relates to fuel control Systems and, more example J. A. Cook, J. W. Grizzle, J. Sun, “Engine Control', particularly, to an improved method of estimating the air in IEEE CONTROL HANDBOOK, CRC Press, Inc. 1996, flow into an engine. pp. 1261-1274; and J. W. Grizzle, J. Cook, W. Milam, 2. Background Art “Improved Cylinder Air Charge Estimation for Transient Air An air-charge estimation algorithm is an important part of Fuel Ratio Control, PROCEEDINGS OF 1994 AMERI a Spark-ignition engine management System. The estimate of CAN CONTROL CONFERENCE, Baltimore, Md., June the air flow into the engine is used to calculate the amount 1994, pp. 1568–1573; filter out the noise in the pressure and of fuel that needs to be injected so that the air-to-fuel ratio 15 throttle flow measurements and adapt on-line the Volumetric is kept close to the Stoichiometric value for optimum Three efficiency from the deviation between the actual preSSure Way Catalyst (TWC) performance. measurement and modeled pressure, See for example Y. W. In diesel engines, the air-to-fuel ratio must be maintained Kim, G. Rizzoni, and V. Utkin, “Automotive Engine Diag above a specified threshold to avoid the generation of visible nosis and Control via Nonlinear Estimation', IEEE CON Smoke. At tip-ins, the EGR valve is typically closed and the TROL SYSTEMS MAGAZINE, October 1998, pp. 84–99; control System calculates the amount of fuel that can be and T. C. Tseng, and W. K. Cheng, “An Adaptive Air-Fuel injected So that the air-to-fuel ratio stays at the threshold Ratio Controller for SI Engine Throttle Transients”, SAE value. Inaccurate air-to-fuel ratio estimation in transients PAPER 1999-01-0552. The adaptation is needed to com may result in either visible Smoke emissions or detrimental pensate for engine aging as well as for other uncertainties (in consequences for torque response (increased turbo-lag). 25 transient operation). For engines without an electronic throttle, an estimate of the flow into the engine needs to be Abasic air-charge estimation algorithm relies on a Speed known Several events in advance. In these cases, a predictive density equation that for a four cylinder engine has the form, algorithm for the throttle position may be employed. See, for example, M. Jankovic, S. Magner, "Air-Charge Estimation m = n.fie Var,P and Prediction in Spark Ignition Internal Combustion Engines”, PROCEEDINGS OF 1999 AMERICAN CON TROL CONFERENCE, San Diego, Calif. where: In a typical embodiment of the Schemes in the prior art, m is the mean-Value of the flow into the engine, n is the two low pass filters, on intake manifold preSSure and throttle engine speed (in rps), m is the volumetric efficiency, p 35 flow, may be employed to filter out the noise and periodic is the intake manifold preSSure, V is the total displaced Signal oscillation at the engine firing frequency. One cylinder Volume, T is the intake manifold temperature, dynamic filter would be used as a lead filter to Speed up the and R is the gas constant. dynamics of the MAF sensor. One dynamic filter would be The Volumetric efficiency map is typically calibrated on used for the intake manifold pressure model and one inte an engine dynamometer and Stored in lookup tables as a 40 grator would be utilized to adjust the estimate of the volu function of engine operating conditions. In a conventional metric efficiency as an integral of the error between the approach for a Variable Valve Timing (VVT) engine, m measured and estimated intake manifold pressure. This is a would be a function of valve timing, obtained as a result of total of five filters. elaborate calibration. The intake manifold pressure may be either measured by a pressure sensor (MAP) or, if there is no 45 SUMMARY OF THE INVENTION MAP sensor, estimated based on the intake manifold iso It is an object of the present invention to provide an thermic equation: improved air-charge estimation algorithm. RT It is another object of the present invention to provide an p = (mth - m), improved air-charge estimation algorithm that enables 50 tighter air-to-fuel ratio control in SI engines. It is a further object of the present invention is to provide where m, is the flow through the engine throttle (measured an improved air-charge estimation algorithm that enables by a MAF sensor) and V is the intake manifold Volume. least turbo-lag to be achieved without generating visible This continuous time equation needs to be discretized for the 55 Smoke. implementation as follows: In accordance with the present invention, a method and System for estimating air flow into an engine is proposed that pa(k+1) = pa (k) + AT RT (min(k)-m-(k)), (1) accomplishes the above Steps of MAF Sensor Speedup, noise i filtering and on-line Volumetric efficiency estimation but 60 uses only three dynamic filters. This reduces the implemen where AT, is the sampling rate, m(k) is the measured or tation complexity of the air charge algorithm. estimated throttle flow and m(k) is the estimate of the flow The mechanism for on-line Volumetric efficiency estima into the engine based on the current measurement or esti tion provided in the present invention is of differential type mate of the intake manifold pressure p(k). The variable as opposed to the integral type algorithms employed in Kim p may be referred to as the modeled, estimated, or 65 and Tseng.