Temperature compensation system for minimizing sensor offset variations

• US 6,658,345 B2
• Filed: 05/18/2001
• Issued: 12/02/2003
• Est. Priority Date: 05/18/2001
• Status: Active Grant

• Current Assignee: Cummins Incorporated
• Original Assignee: Cummins Incorporated
• Inventors: Miller, Paul R.
• Primary Examiner(s): Vo, Hieu T.
• Application Number:
  US09/861,341
• Publication Number:
  US 20020173899A1
• Time in Patent Office: 928 Days
• Field of Search: 701/108, 701/113, 701/102, 701/115, 123/568.12, 123/568.16, 123/491, 123/480, 123/41.05, 123/41.01, 123/41.15, 123/41.31, 731/182, 731/173, 602/74, 602/84
• US Class Current: 701/108
• CPC Class Codes: F02D 2041/1433 using a model or simulation of the system
• 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 41/2474 Characteristics of sensors
• CPC Class Codes: F02D 41/28 Interface circuits
• CPC Class Codes: F02M 26/23 Layout, e.g. schematics
• CPC Class Codes: F02M 26/33 controlling the temperature of the recirculated gases
• CPC Class Codes: F02M 26/47 the characteristics being temperatures, pressures or flow rates
• CPC Class Codes: F02M 26/61 in response to exhaust pressure

Abstract

A temperature compensation system for minimizing sensor offset variations includes an engine controller having stored therein a model of sensor operating behavior over temperature. In one embodiment, the sensor is a ΔP sensor for sensing a differential pressure across a flow restriction mechanism disposed between an exhaust manifold and an intake manifold of an internal combustion engine. In this embodiment, the ΔP sensor is preferably thermally coupled to a structural component of the engine whose operating temperature is readily discernable; e.g., the engine cooling system. Alternatively, the ΔP sensor may include a temperature sensor coupled thereto. In either case, the engine controller is preferably responsive to transitions of the key switch to gather “hot” and “cold” temperature data under zero ΔP conditions. This information is then used to constantly update the ΔP sensor model.

Claims

1. A temperature compensation system for minimizing sensor offset variations, comprising:

a sensor producing a sensor signal indicative of an operating condition of an internal combustion engine;

means for determining a temperature of said sensor and producing a temperature signal corresponding thereto;

a key switch for starting and stopping said engine, said key switch having at least an on position and an off position; and

an engine controller responsive to a transition of said key switch to said on position to determine a first temperature signal value and an associated first sensor signal value, said controller responsive to a transition of said key switch to said off position to determine a second temperature signal value and an associated second sensor signal value, said controller defining an offset value associated with said sensor as a function of said first and second temperature signal values and of said first and second sensor signal values.

2. The system of claim 1 further including:

an intake manifold coupled to said engine;

an exhaust manifold coupled to said engine and configured to expel engine exhaust gas therefrom;

a conduit having one end fluidly coupled to said exhaust manifold and an opposite end fluidly coupled to said intake manifold, said conduit configured to supply engine exhaust gas from said exhaust manifold to said intake manifold; and

a flow restriction mechanism disposed in line with said conduit;

wherein said sensor is a differential pressure sensor producing a differential pressure signal indicative of a pressure difference across said flow restriction mechanism.

3. The system of claim 2 wherein said flow restriction mechanism is an exhaust gas recirculation valve defining a variable cross-sectional flow area therethrough.

4. The system of claim 2 wherein said flow restriction mechanism defines a fixed cross-sectional flow area therethrough.

5. The system of claim 2 wherein said differential pressure sensor is thermally coupled to a structural component of said engine such that an operating temperature of said differential pressure sensor is substantially identical to an operating temperature of said structural component of said engine;

and wherein said means for determining a temperature of said sensor is a temperature sensor producing said temperature signal, said temperature signal indicative of said operating temperature of said structural component of said engine.

6. The system of claim 5 wherein said structural component of said engine is an engine cooling system;

and wherein said temperature signal produced by said temperature sensor corresponds to a coolant temperature of said cooling system.

7. The system of claim 1 wherein said sensor is thermally coupled to a structural component of said engine such that an operating temperature of said sensor is substantially identical to an operating temperature of said structural component of said engine;

and wherein said means for determining a temperature of said sensor is a temperature sensor producing said temperature signal, said temperature signal indicative of said operating temperature of said structural component of said engine.

8. The system of claim 7 wherein said engine includes a cooling system;

and wherein said temperature signal produced by said temperature sensor corresponds to a coolant temperature of said cooling system.

9. The system of claim 1 wherein said engine controller is further responsive to a transition of said key switch to either of said off and said on positions to determine a third temperature signal value and an associated third sensor signal value, said controller defining said offset value further as a function of said third temperature signal value and said third sensor signal value.

10. The system of claim 1 further including a memory having stored therein a model of said operating condition of said engine, said model defining a temperature dependent offset term corresponding to said offset value associated with said sensor and a gain term.

11. The system of claim 10 wherein said engine controller is responsive to said sensor signal to determine a value of said operating condition based on said model.

12. A temperature compensation system for minimizing sensor offset variations, comprising:

a sensor producing a sensor signal indicative of an operating condition of an internal combustion engine;

a memory having stored therein a model of said operating condition, said model defining a temperature dependent offset term;

means for determining a temperature of said sensor and producing a temperature signal corresponding thereto;

a key switch for starting and stopping said engine, said key switch having at least an on position and an off position; and

an engine controller monitoring said key switch, said controller responsive to said temperature signal and said sensor signal to determine a first temperature and a first signal value associated with said sensor if said key switch switches to either of said off and on positions, said controller updating said temperature dependent offset term based on said first temperature and said first signal value.

13. The system of claim 12 wherein said model further includes a gain term, said engine controller responsive to said sensor signal to determine a value of said operating condition based on said model.

14. The system of claim 12 wherein said controller is responsive to said temperature signal and said sensor signal to determine a second temperature and a second signal value associated with said sensor if said key switch switches to the other of said off and on positions, said controller updating said temperature dependent offset term based further on said second temperature and said second signal value.

15. The system of claim 12 wherein said sensor is thermally coupled to a structural component of said engine such that an operating temperature of said sensor is substantially identical to an operating temperature of said structural component of said engine;

and wherein said means for determining a temperature of said sensor is a temperature sensor producing said temperature signal, said temperature signal indicative of said operating temperature of said structural component of said engine.

16. The system of claim 14 wherein said sensor is thermally coupled to said engine such that said operating temperature of said sensor is substantially identical to an operating temperature of said engine.

17. The system of claim 15 further wherein said engine further includes a cooling system;

and wherein said sensor is thermally coupled to said engine via said cooling system such that an operating temperature of said cooling system is substantially identical to an operating temperature of said sensor.

18. The system of claim 16 wherein said temperature sensor is a coolant temperature sensor producing a coolant temperature signal indicative of said operating temperature of said cooling system.

19. The system of claim 17 wherein said sensor is a differential pressure sensor producing a differential pressure signal indicative of a pressure difference between an exhaust manifold and an intake manifold of said engine.

20. The system of claim 12 further including:

an intake manifold coupled to said engine;

an exhaust manifold coupled to said engine and configured to expel engine exhaust gas therefrom;

a conduit having one end fluidly coupled to said exhaust manifold and an opposite end fluidly coupled to said intake manifold, said conduit configured to supply engine exhaust gas from said exhaust manifold to said intake manifold; and

a flow restriction mechanism disposed in line with said conduit;

wherein said sensor is a differential pressure sensor producing a differential pressure signal indicative of a pressure difference across said flow restriction mechanism.

21. The system of claim 19 wherein said flow restriction mechanism is an exhaust gas recirculation valve defining a variable cross-sectional flow area therethrough.

22. The system of claim 19 wherein said flow restriction mechanism defines a fixed cross-sectional flow area therethrough.

24. The method of claim 22 further including the step of determining a second operating temperature of said engine operating condition sensor and an associated second sensor value if said key switch switches to the other of an off and on position thereof;

and wherein the updating step includes updating said offset term of said model based further on said second operating temperature and said second sensor value.

25. The method of claim 22 further including the following steps if a detected switching of said key switch corresponds to a switch to said off position:

comparing said first operating temperature to a temperature threshold; and

executing said updating step only if said first operating temperature is above said temperature threshold.

26. The method of claim 22 further including the following steps if a detected switching of said key switch corresponds to a switch to said on position:

determining ambient temperature;

executing said updating step only if said first operating temperature is within a predefined temperature range of said ambient temperature.

27. The method of claim 22 including the following steps if a detected switching of said key switch corresponds to a switch to said on position:

sensing an elapsed time value of a timer; and

executing said updating step only if said elapsed time value is above a threshold time value corresponding to a predefined elapsed time since said key switch switched to said off position.

28. The method of claim 22 wherein said engine operating condition corresponds to a pressure difference across a flow restriction mechanism disposed between an exhaust manifold of said engine and an intake manifold of said engine.

23. A temperature compensation method of minimizing sensor offset variations, the method comprising the steps of:

sensing an operating condition of an internal combustion engine with an engine operating condition sensor;

computing a value of said engine operating condition based on a model defining a response of said engine operating condition sensor, said model including a temperature dependent offset term;

monitoring a key switch for starting and stopping said engine;

determining a first operating temperature of said engine operating condition sensor and an associated first sensor value if said key switch switches to either of an off and an on position thereof; and

updating said offset term of said model based on said first operating temperature and said first sensor value.