Engine out NOx virtual sensor using cylinder pressure sensor

• US 8,301,356 B2
• Filed: 10/06/2008
• Issued: 10/30/2012
• Est. Priority Date: 10/06/2008
• Status: Expired due to Fees

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations LLC (General Motors Company)
• Inventors: Wang, Yue-Yun, He, Yongsheng
• Primary Examiner(s): MOULIS, THOMAS N
• Application Number:
  US12/245,828
• Publication Number:
  US 20100083640A1
• Time in Patent Office: 1,485 Days
• Field of Search: 701/102, 701/106, 701/115, 602/76, 602/77, 602/85, 602/86, 731/141.6, 731/141.7, 123/435, 123/703
• US Class Current: 701/102
• CPC Class Codes: F01N 2900/14 said parameters being related to the exhaust gas
• CPC Class Codes: F02D 2041/288 for performing a transformation into the frequency domain, e.g. Fourier transformation
• CPC Class Codes: F02D 35/026 using an estimation
• CPC Class Codes: F02D 41/1405 Neural network control
• CPC Class Codes: F02D 41/1462 with determination means using an estimation

Abstract

A Method for estimating NOx creation in a combustion process of a four-stroke internal combustion engine includes monitoring engine sensor inputs, modeling parameters descriptive of said combustion process based upon said engine sensor inputs, and estimating NOx creation with an artificial neural network based upon said parameters.

Claims

1. Method for estimating NOx creation in a combustion process of a four-stroke internal combustion engine including a variable volume combustion chamber defined by a piston reciprocating within a cylinder between top-dead center and bottom-dead center points, intake and exhaust passages, and intake and exhaust valves controlled during repetitive, sequential exhaust, intake, compression and expansion strokes of said piston, comprising:

monitoring engine sensor inputs comprising a cylinder pressure within the combustion chamber;

modeling a mass fraction burn value for combustion within the combustion chamber based upon said engine sensor inputs, wherein said mass fraction burn value indexes a crank angle at which a selected percentage of injected fuel is burned in a combustion cycle;

estimating a state of combustion within the combustion chamber based upon the mass fraction burn value, the state of combustion comprising a combustion phasing and a combustion strength; and

estimating NOx creation within the combustion chamber with an artificial neural network based upon said state of combustion.

2. The method of claim 1, further comprising controlling aftertreatment devices based upon said estimating NOx creation.

3. The method of claim 1, wherein said modeling said mass fraction burn value comprises calculating a total heat released for a given crank angle based upon said cylinder pressure.

4. The method of claim 1, wherein said modeling said mass fraction burn value includes analyzing said cylinder pressure through spectral analysis comprising a Fast Fourier Transform.

5. The method of claim 1, further comprising modifying a result of said estimating NOx creation based upon a dynamic engine factor.

6. The method of claim 5, wherein said dynamic engine factor comprises a filter discriminating NOx estimates generated during transitory engine operation.

7. The method of claim 5, wherein said dynamic engine factor comprises a NOx creation rate estimate utilized to estimate effects of transitory engine operation.

8. The method of claim 1, wherein estimating said NOx creation is further based upon:

a crank angle wherein a predetermined percentage of a fractional pressure rise in said combustion chamber is achieved;

a maximum pressure achieved within said combustion chamber;

a crank angle wherein said maximum pressure is achieved;

an air-fuel ratio; and

a percentage of cylinder intake comprising exhaust gas recirculation flow.

9. The method of claim 1, wherein estimating said NOx creation is further based upon:

an estimated temperature of burned charge within said cylinder;

a crank angle wherein a predetermined percentage of a fractional pressure rise in said combustion chamber is achieved;

a percentage of intake comprising exhaust gas recirculation flow;

an air-fuel ratio; and

a fuel rail pressure.

10. The method of claim 1, wherein estimating said NOx creation is further based upon:

an estimated average temperature within said combustion chamber;

a crank angle wherein a predetermined percentage of a fractional pressure rise in said combustion chamber is achieved;

a percentage of intake comprising exhaust gas recirculation flow;

an air-fuel ratio; and

a fuel rail pressure.

11. The method of claim 1, wherein estimating said NOx creation is further based upon:

an estimated average temperature within said combustion chamber;

a crank angle wherein a predetermined percentage of a fractional pressure rise in said combustion chamber is achieved;

an engine speed;

a fuel energy content;

an oxygen sensor measurement; and

a fuel rail pressure.

12. The method of claim 1, wherein estimating said NOx creation is further based upon:

an estimated average temperature within said combustion chamber;

a crank angle wherein a predetermined percentage of a fractional pressure rise in said combustion chamber is achieved;

an engine speed;

a fuel energy content;

an oxygen sensor measurement; and

a start of fuel injection crank angle.

17. The method of claim 1, further comprising:

monitoring an average temperature within said combustion chamber; and

wherein estimating said NOx creation is further based upon said average temperature.

18. The method of claim 17, wherein monitoring said average temperature comprises:

monitoring a maximum pressure achieved within said combustion chamber;

monitoring a volume of the cylinder at an instant said maximum pressure is achieved;

monitoring a charge flow into said cylinder; and

determining said average temperature based upon said maximum pressure, said volume, and said charge flow.

13. Apparatus for estimating NOx creation in a combustion process of a four-stroke internal combustion engine including a variable volume combustion chamber defined by a piston reciprocating within a cylinder between top-dead center and bottom-dead center points, intake and exhaust passages, and intake and exhaust valves controlled during repetitive, sequential exhaust, intake, compression and expansion strokes of said piston, said apparatus comprising:

a pressure sensor generating pressure sensor readings describing conditions within said combustion chamber;

a NOx estimation module including logic operations comprising;

monitoring said pressure sensor readings;

modeling a mass fraction burn value for combustion within the combustion chamber based upon said pressure sensor readings, wherein said mass fraction burn value indexes a crank angle at which a selected percentage of injected fuel is burned in a combustion cycle;

estimating a state of combustion within the combustion chamber based upon the mass fraction burn value, the state of combustion comprising a combustion phasing and a combustion strength; and

and

estimating NOx creation with an artificial neural network based upon said state of combustion; and

an aftertreatment system receiving an exhaust gas flow from said engine and modulating aftertreatment based upon said NOx creation estimate.

14. The apparatus of claim 13, wherein said logic operations further comprise a dynamic engine filter modulating NOx estimates based upon transient operation of said engine.

15. The apparatus of claim 13, wherein said aftertreatment system comprises a lean NOx trap;

and wherein said modulating aftertreatment comprises scheduling regeneration events.

16. The apparatus of claim 13, wherein said aftertreatment system comprises a selective catalytic reduction device;

and wherein said modulating aftertreatment comprises dosing urea injection based upon said NOx creation estimation.