Passive model-based EGR diagnostic

• US 6,763,708 B2
• Filed: 07/31/2001
• Issued: 07/20/2004
• Est. Priority Date: 07/31/2001
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Inventors: Van Gilder, John F., Ting, Thomas L.
• Primary Examiner(s): Lefkowitz, Edward
• Assistant Examiner(s): STEVENS, MAURICE E
• Application Number:
  US09/919,489
• Publication Number:
  US 20030029233A1
• Time in Patent Office: 1,085 Days
• Field of Search: 731/181, 731/173
• US Class Current: 73/114.74
• 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 2200/0408 Estimation of intake manifold pressure
• CPC Class Codes: F02D 2200/703 Atmospheric pressure
• CPC Class Codes: F02D 41/0072 Estimating, calculating or determining the EGR rate, amount or flow sensors in EGR systems F02M26/45
• CPC Class Codes: F02D 41/145 with determination means using an estimation
• CPC Class Codes: F02D 41/187 using a hot wire flow sensor
• CPC Class Codes: F02D 41/221 relating to the failure of actuators or electrically driven elements
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A process for computer based, wholly passive, diagnosis of an automotive vehicle exhaust gas recirculation system is disclosed. Use is made of any suitable math model of the vehicle'"'"'s air intake system to estimate the absolute pressure in the intake manifold, MAP, assuming both a healthy EGR system, MAP_HE, and a faulty EGR valve, MAP_FE. Both estimated values are compared with the actual normally measured manifold pressure, MAPmeas. Both comparisons are repeated over many calculations and the differences analyzed to reliably determine whether there is a real restriction to recirculated exhaust flow. A preferred math model of the intake system uses as input variables: mass air flow, barometric pressure, the position command for the EGR valve and engine speed.

Claims

1. A method for diagnosis of a gas flow restriction in the exhaust gas recirculation (EGR) system of an automotive vehicle;

said vehicle comprising an engine with an intake manifold and an exhaust gas manifold, a pressure sensor for measuring the pressure of air and any exhaust gas in said intake manifold, a sensor for measuring mass air flow rate in said manifold, a sensor for determining the speed of said engine, an exhaust gas recirculation (EGR) valve and passage system for diverting engine exhaust gas from said exhaust manifold to said intake manifold, and a computer for receiving data from said sensors and controlling the flow position of said EGR valve, said method being carried out on said computer and comprising

repeatedly measuring said pressure in said intake manifold, as MAPmeas, during an EGR valve diagnosis period of time,

repeatedly estimating the absolute pressure in said intake manifold during said diagnosis period assuming no restriction in the flow of exhaust gas with respect to said control position, said estimates being MAP_HE,

repeatedly estimating the absolute pressure in said intake manifold during said diagnosis period assuming a restriction in the flow of exhaust gas through said EGR valve amounting to a defect in said EGR system, said estimates being MAP_FE, and

comparing the differences between values of MAPmeas taken during said diagnosis period with both of corresponding values of MAP_HE and MAP_FE as a passive computational basis for determining whether there is a defective restriction in said EGR system.

2. A method for diagnosis of a gas flow restriction in an EGR system as recited in claim 1 comprising

repeatedly estimating the absolute pressure in said intake manifold using input data comprising engine speed, measured or estimated barometric pressure, mass rate of intake air flow in said intake manifold and the present control command position of said EGR valve over said diagnosis period and assuming no restriction in the flow of exhaust gas with respect to said command position, said estimates being MAP_HE,

repeatedly estimating the absolute pressure in said intake manifold using input data comprising engine speed, measured or estimated barometric pressure, and mass rate of intake air flow in said intake manifold over said diagnosis period and assuming a restriction in the flow of exhaust gas through said EGR valve amounting to a defect in said EGR system, said estimates being MAP_FE.

3. A method for diagnosis of a gas flow restriction in an EGR system as recited in claim 2 comprising

comparing the differences between values of MAPmeas taken during said diagnosis period with both of corresponding values of MAP_HE and MAP_FE as a passive computational basis for determining whether there is a defective restriction in said EGR system and

further comparing said passive computational basis with experimental MAP data obtained on EGR systems of the same engineering specifications with a range of artificially introduced flow impediments as a further basis for determining whether there is a defective restriction in said EGR system.

4. A method for diagnosis of a gas flow restriction in an EGR system as recited in claim 3 in which said range of artificially introduced flow impediments include impediments which amount to EGR system defects and impediments that do not amount to EGR system defects.

5. A method as recited in claim 2 in which said passive computational basis comprises a comparison of errors in the form:

Error 1=MAPmeas−

MAP_HE,

Error 2=MAP_FE−

MAP_HE, and

Error 3=MAP_FE−

MAPmeas, and further comprises using successive and corresponding time values of said errors to calculate an error metric J₃=J₁+|1−

J₂| by calculation procedures described in this specification.

6. A method for diagnosis of a gas flow restriction in an EGR system as recited in claim 1 comprising

comparing the differences between values of MAPmeas taken during said diagnosis period with both of corresponding values of MAP_HE and MAP_FE as a passive computational basis for determining whether there is a defective restriction in said EGR system and

further comparing said passive computational basis with experimental MAP data obtained on EGR systems of the same engineering specifications with a range of artificially introduced flow impediments as a further basis for determining whether there is a defective restriction in said EGR system.

7. A method for diagnosis of a gas flow restriction in an EGR system as recited in claim 6 in which said range of artificially introduced flow impediments include impediments which amount to EGR system defects and impediments that do not amount to EGR system defects.

8. A method as recited in claim 7 in which said passive computational basis comprises a comparison of errors in the form:

Error 1=MAPmeas−

MAP_HE,

Error 2=MAP_FE−

MAP_HE, and

Error 3=MAP_FE−

MAPmeas, and further comprises using successive and corresponding time values of said errors to calculate an error metric J₃=J₁+|1−

J₂| by calculation procedures described in this specification.

9. A method as recited in claim 6 in which said passive computational basis comprises a comparison of errors in the form:

Error 1=MAPmeas−

MAP_HE,

Error 2=MAP_FE−

MAP_HE, and

Error 3=MAP_FE−

MAPmeas, and further comprises using successive and corresponding time values of said errors to calculate an error metric J₃=J₁+|1−

J₂| by calculation procedures described in this specification.

10. A method as recited in claim 1 in which said passive computational basis comprises a comparison of errors in the form:

Error 1=MAPmeas−

MAP_HE,

Error 2=MAP_FE−

MAP_HE, and

Error 3=MAP_FE−

MAPmeas, and further comprises using successive and corresponding time values of said errors to calculate an error metric J₃=J₁+|1−

J₂| by calculation procedures described in this specification.