Method and system for engine air-charge estimation

• US 6,636,796 B2
• Filed: 01/25/2001
• Issued: 10/21/2003
• Est. Priority Date: 01/25/2001
• Status: Expired due to Fees

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Stotsky, Alexander Anatoljevich, Kolmanovsky, Ilya V
• Primary Examiner(s): Dolinar, Andrew M.
• Application Number:
  US09/769,800
• Publication Number:
  US 20020133286A1
• Time in Patent Office: 999 Days
• Field of Search: 701/102, 701/104, 701/114, 701/115, 123/480, 123/488, 731/182
• US Class Current: 701/104
• CPC Class Codes: F02D 2041/001 for engines with variable valve actuation
• CPC Class Codes: F02D 2041/1416 Observer
• CPC Class Codes: F02D 2200/0402 the parameter being determined by using a model of the engine intake or its components
• CPC Class Codes: F02D 2200/0406 Intake manifold pressure
• CPC Class Codes: F02D 2200/0411 Volumetric efficiency
• CPC Class Codes: F02D 41/1401 characterised by the control or regulation method F02D41/1473, F02D41/1477 take precedence
• CPC Class Codes: F02D 41/18 by measuring intake air flow

Abstract

The air flow into an engine is estimated via a speed-density calculation wherein the volumetric efficiency is estimated on-line. There are three interconnected observers in the estimation scheme. The first observer estimates the flow through the throttle based on the signal from a mass air flow sensor (MAF). The second observer estimates the intake manifold pressure using the ideal gas law and the signal from a intake manifold absolute pressure sensor (MAP). The third observer estimates the volumetric efficiency and provides an estimate of the air flow into the engine.

Claims

1. A method of estimating air flow into an engine comprising a sequence of the steps of:

measuring the mass air flow through the engine throttle with a mass air flow sensor (MAF);

measuring the pressure in the engine intake manifold with a pressure sensor (MAP);

estimating the flow through the throttle based on the signal from the MAF sensor and compensating for the MAF sensor dynamics;

estimating the intake manifold pressure based on the signals from the MAP and MAF sensors and filtering the noise and periodic oscillations at engine firing frequency contained in the MAP and the MAF sensor signals; and

estimating the volumetric efficiency and the air flow into the engine using a differential type algorithm based on the estimates of intake manifold pressure and throttle flow.

2. A system for estimating air flow into an engine comprising:

a mass air flow (MAF) sensor;

a first observer for estimating the flow through the throttle based on the signal from the MAF sensor and for compensating for the MAF sensor dynamics;

a manifold absolute pressure (MAP) sensor;

a second observer for estimating the intake manifold pressure based on the signal from the MAP sensor and for filtering the noise and periodic oscillations at engine firing frequency contained in the MAP sensor signal and the MAF sensor signals;

a third observer for estimating the volumetric efficiency and providing an estimate of the air flow into the engine based on the estimates provided by said first and second observers.

3. The system of claim 2 wherein the first observer include means for estimating throttle flow as a weighted sum of the MAF sensor measurement and a first filter variable.

4. The system of claim 3 wherein the first filter variable is dynamically updated using its past values and MAF sensor readings.

5. The system of claim 2 wherein the first observer is provided by a differential type algorithm derived on the basis of a MAF sensor model and known MAF sensor time constant.

6. The system of claim 2 wherein the second observer includes an intake manifold pressure model based on the ideal gas law corrected with a difference between estimated and measured pressures multiplied by a gain.

7. The system of claim 2 wherein the second observer uses estimates of the throttle flow provided by the first observer and estimates of the cylinder flow provided by the third observer.

8. The system of claim 7 wherein the third observer calculates the mass air flow into the engine based on an on-line estimation of volumetric efficiency using a differential type algorithm.

9. The system of claim 8 wherein the volumetric efficiency is modeled as a sum of an initial calibration and an estimated correction error and expressed as:

10. The system of claim 9 wherein the estimated volumetric efficiency correction is provided as a weighted sum of a second filter variable and intake manifold pressure estimate.

11. The system of claim 10 wherein the second filter variable is dynamically updated using its past value, estimate of the throttle flow and estimate of intake manifold pressure.

12. The system of claim 11 wherein the second filter variable is dynamically updated as per equation:

$\mathrm{\varepsilon <br><br>}<br><br>\left(k+1\right)=\mathrm{\varepsilon <br><br>}<br><br>\left(k\right)+\mathrm{\Delta <br><br>}·<br><br>\left(-\mathrm{\gamma <br><br>\varepsilon <br><br>}<br><br>\left(k\right)-{\mathrm{\gamma <br><br>\eta <br><br>}}_{\mathrm{vk}}<br><br>\left(k\right)<br><br>\frac{n_e<br><br>\left(k\right)}{2}<br><br>V_d<br><br>\frac{p_{\mathrm{cal}}<br><br>\left(k\right)}{V_{\mathrm{IM}}}+\mathrm{\gamma <br><br>}<br><br>\frac{R<br><br>\text{\hspace{1em}<br><br>}<br><br>T<br><br>\left(k\right)}{V_{\mathrm{IM}}}<br><br>m_{\mathrm{th}}<br><br>\left(k\right)+{\mathrm{\gamma <br><br>}}^2<br><br>p_{\mathrm{cal}}<br><br>\left(k\right)\right).$

13. The system of claim 12 wherein the engine is a spark ignition engine.

14. The system of claim 12 wherein the engine is a diesel engine.

15. The system of claim 2 wherein the first observer has the following form:

${\stackrel{.}{\mathrm{\varepsilon <br><br>}}}_f=-{\mathrm{\gamma <br><br>}}_f<br><br>{\mathrm{\varepsilon <br><br>}}_f<br><br>\frac{{\mathrm{\gamma <br><br>}}_f}{\mathrm{\tau <br><br>}}<br><br>m_{\mathrm{MAF}}+{\mathrm{\gamma <br><br>}}_f^2<br><br>m_{\mathrm{MAF}},<br><br>m_{\mathrm{th}}={\mathrm{\tau <br><br>}}_{\mathrm{MAF}}<br><br>\left({\mathrm{\gamma <br><br>}}_f<br><br>m_{\mathrm{MAF}}-{\mathrm{\varepsilon <br><br>}}_f\right).$

16. The system of claim 15 wherein the second observer has the following form:

${\stackrel{.}{p}}_{\mathrm{cal}}=\frac{R<br><br>\text{\hspace{1em}<br><br>}<br><br>T}{V_{\mathrm{IM}}}<br><br>\left(m_{\mathrm{th}}-m_e\right)-{\mathrm{\gamma <br><br>}}_p<br><br>\left(p_{\mathrm{cal}}-p_{\mathrm{MAP}}\right).$

17. The system of claim 16 wherein the third observer has the following form:

$m_e={\mathrm{\eta <br><br>}}_{\mathrm{vk}}<br><br>\frac{n_e}{2}<br><br>V_d<br><br>\frac{p_{\mathrm{cal}}}{R<br><br>\text{\hspace{1em}<br><br>}<br><br>T}+\left(\mathrm{\varepsilon <br><br>}-{\mathrm{\gamma <br><br>}}_p<br><br>p_{\mathrm{cal}}\right)<br><br>\frac{V_{\mathrm{IM}}}{R<br><br>\text{\hspace{1em}<br><br>}<br><br>T},$

where ∈

is adjusted as follows;

$\stackrel{.}{\mathrm{\varepsilon <br><br>}}=-\mathrm{\gamma <br><br>\varepsilon <br><br>}-{\mathrm{\gamma <br><br>\eta <br><br>}}_{\mathrm{vk}}<br><br>\frac{n_e}{2}<br><br>V_d<br><br>\frac{p_{\mathrm{cal}}}{V_{\mathrm{IM}}}<br><br>m_{\mathrm{th}}+{\mathrm{\gamma <br><br>}}^2<br><br>p_{\mathrm{cal}}.$

18. A system for controlling operation of a fuel control system having fuel injector means for supplying fuel to an engine, said fuel injector means being responsive to a fuel control signal based on air flow into the engine intake manifold comprising;

sensor means for sensing conditions of operation of said engine and for producing data indicative thereof, said sensor means including a mass air flow (MAF) sensor for measuring air flow into the intake manifold and a manifold absolute pressure (MAP) sensor;

observer means for generating real time estimates of air charge entering the engine based on data from said sensors;

said observer means compensating for MAF sensor dynamics, estimating the intake manifold pressure based on the ideal gas law and data from said MAP sensor and filtering noise and periodic oscillations at engine firing frequency contained in the data from said MAF and MAP sensors, and estimating the volumetric efficiency and the air flow into the engine using a speed density equation wherein the volumetric efficiency is estimated on line using a differential type algorithm.

19. An article of manufacture comprising:

a computer storage medium having a computer program encoded therein for estimating air-charge for an engine, said computer storage medium comprising code for measuring the mass air flow through the engine throttle with a mass air flow sensor (MAF);

code for measuring the pressure in the engine intake manifold with a pressure sensor (MAP);

code for estimating the flow through the throttle based on the signal from the MAF sensor and compensating for the MAF sensor dynamics;

code for estimating the intake manifold pressure based on the signal from the MAP sensor and filtering the noise, and periodic oscillations at engine firing frequency, contained in the MAP sensor signal and the MAF sensor signals; and

code for estimating the volumetric efficiency and providing an estimate of the air flow into the engine.

20. A method for estimating cylinder air-charge in an internal combustion engine, the engine having an intake manifold coupled upstream of it, the manifold having a manifold airflow (MAF) and a manifold absolute pressure (MAP) sensors disposed inside it, the method comprising:

reading a MAF sensor signal and filtering said reading to compensate for MAF sensor dynamics;

estimating air flow through the throttle based on said filtered MAF sensor reading;

reading a MAP sensor signal and filtering said reading to compensate for the noise;

estimating intake manifold pressure based on said filtered MAP sensor reading and said filtered MAF sensor reading; and

estimating cylinder air-charge based on said estimated engine airflow and said estimated intake manifold pressure.

21. The method defined in claim 20 wherein said step of estimating cylinder air-charge is further based on an on-line estimation of volumetric efficiency using a differential type algorithm.

22. The method of claim 21 wherein the volumetric efficiency is modeled as a sum of an initial calibration and an estimated correction error and expressed as:

23. The method of claim 20 wherein the air flow estimating step is represented by the following equations:

${\stackrel{.}{\mathrm{\varepsilon <br><br>}}}_f=-{\mathrm{\gamma <br><br>}}_f<br><br>{\mathrm{\varepsilon <br><br>}}_f<br><br>\frac{{\mathrm{\gamma <br><br>}}_f}{\mathrm{\tau <br><br>}}<br><br>m_{\mathrm{MAF}}+{\mathrm{\gamma <br><br>}}_f^2<br><br>m_{\mathrm{MAF}},<br><br>m_{\mathrm{th}}={\mathrm{\tau <br><br>}}_{\mathrm{MAF}}<br><br>\left({\mathrm{\gamma <br><br>}}_f<br><br>m_{\mathrm{MAF}}-{\mathrm{\varepsilon <br><br>}}_f\right).<br><br>$

24. The method of claim 23 wherein the intake manifold pressure estimating step is represented by the following equation:

${\stackrel{.}{p}}_{\mathrm{cal}}=\frac{R<br><br>\text{\hspace{1em}<br><br>}<br><br>T}{V_{\mathrm{IM}}}<br><br>\left(m_{\mathrm{th}}-m_e\right)-{\mathrm{\gamma <br><br>}}_p<br><br>\left(p_{\mathrm{cal}}-p_{\mathrm{MAP}}\right).$

25. The method of claim 24 wherein the air-charge estimating step is represented by the following equations:

$m_e={\mathrm{\eta <br><br>}}_{\mathrm{vk}}<br><br>\frac{n_e}{2}<br><br>V_d<br><br>\frac{p_{\mathrm{cal}}}{R<br><br>\text{\hspace{1em}<br><br>}<br><br>T}+\left(\mathrm{\varepsilon <br><br>}-{\mathrm{\gamma <br><br>}}_p<br><br>p_{\mathrm{cal}}\right)<br><br>\frac{V_{\mathrm{IM}}}{R<br><br>\text{\hspace{1em}<br><br>}<br><br>T}.$

where ∈

is adjusted as follows;

$\stackrel{.}{\mathrm{\varepsilon <br><br>}}=-\mathrm{\gamma <br><br>\varepsilon <br><br>}-{\mathrm{\gamma <br><br>\eta <br><br>}}_{\mathrm{vk}}<br><br>\frac{n_e}{2}<br><br>V_d<br><br>\frac{p_{\mathrm{cal}}}{V_{\mathrm{IM}}}<br><br>m_{\mathrm{th}}+{\mathrm{\gamma <br><br>}}^2<br><br>p_{\mathrm{cal}}.$

26. A system for estimating cylinder air-charge in an internal combustion engine, the system comprising:

a manifold airflow (MAF) sensor;

a manifold absolute pressure (MAP) sensor;

a controller for filtering a MAF sensor signal to obtain a first estimate of air flow into the engine, said controller further filtering a MAP sensor signal, calculating a second estimate of intake manifold pressure based on said filtered MAP sensor signal and said first estimate, and calculating a third estimate of cylinder air-charge based on said first estimate and said second estimate.