Cylinder torque estimation using crankshaft angular response measurements

• US 6,223,120 B1
• Filed: 10/26/1999
• Issued: 04/24/2001
• Est. Priority Date: 11/19/1998
• Status: Expired due to Fees

• Current Assignee: Jill Williams, Lawrence Williams
• Original Assignee: Jeremy Williams
• Inventors: Williams, Jeremy
• Primary Examiner(s): WOLFE JR, WILLIS RAY
• Application Number:
  US09/426,873
• Time in Patent Office: 546 Days
• Field of Search: 731/16, 731/172, 731/173, 123/339.2, 123/436, 701/102, 701/103, 701/110, 701/111, 701/115
• US Class Current: 701/111
• CPC Class Codes: F02D 2041/288 for performing a transformation into the frequency domain, e.g. Fourier transformation
• CPC Class Codes: F02D 2200/1004 Estimation of the output torque
• CPC Class Codes: F02D 35/024 using an estimation
• CPC Class Codes: G01M 15/11 by detecting misfire

Abstract

A method and apparatus for identifying misfiring cylinders using crankshaft angular velocity measurements. The measured angular velocity is used in conjunction with a system model to estimate the indicated torque developed by each cylinder. The method and apparatus provides accurate results for engines with overlapping firing pulses, and also under conditions in which there is large torsional deflection in the crankshaft. The method and apparatus is suitable for implementation with on-board misfire diagnostics. Experimental validation is provided using a nineteen liter, six cylinder diesel engine. The experimental data demonstrates that accurate detection and identification of misfiring cylinders is possible over the full speed and load range of the engine.

Claims

1. A method of estimating the torque produced by each cylinder in a reciprocating machine, the method comprising the steps of:

providing a system including a reciprocating machine having a plurality of cylinders;

measuring an angular response at at least one location in said system to define a measured angular response;

creating a mathematical model representing the angular dynamics of said system, said model associating angular responses with torques at various locations in said system;

parameterizing said torques as a function of at least one parameter;

assembling a set of frequency domain equations relating said measured angular response to said at least one parameter for a selected analysis frequency;

constructing simultaneously a plurality of said sets of frequency domain equations for a plurality of said selected analysis frequencies by repeating said parameterizing and assembling steps for said plurality of selected analysis frequencies;

repeating said constructing step at least until said plurality of sets of frequency domain equations are defined as over-determined; and

solving said plurality of said sets of frequency domain equations to determine said at least one parameter.

2. The method of claim 1 further comprising the step of utilizing said at least one parameter determined in said solving step to estimate said torques.

3. The method of claim 1 wherein said frequency domain equations comprise complex equations having real and imaginary parts, said assembling step further comprising the steps of:

converting said complex equations relating said at least one measured angular response to said at least one parameter into twice as many equivalent real equations; and

eliminating as unknown quantities said imaginary parts of said at least one parameter in said real equations, thereby increasing the rank of said real equations.

4. The method of claim 1 wherein said step of parameterizing comprises the steps of:

separating said torque into constituent indicated torque and inertia torque; and

defining said indicated torque as a linear function of said at least one parameter.

5. The method of claim 1 further comprising the step of calculating a plurality of harmonic frequencies of said torque for each said cylinder wherein said selected analysis frequencies are substantially equal to said harmonic frequencies.

6. The method of claim 1 wherein said parameterizing step comprises defining said torque for each said cylinder as a linear function of one or more parameters by locally linearizing a non-linear function for said torque around an initial estimate for said at least one parameter.

7. The method of claim 1 wherein said at least one parameter for each said cylinder comprises the indicated mean effective pressure (IMEP) for said cylinder.

8. The method of claim 1 wherein said at least one parameter for each said cylinder comprises the mean indicated torque (Tmean ind) for said cylinder.

9. A method of estimating the torque produced by each of a plurality of cylinders in a reciprocating machine, the method comprising the steps of:

providing a system including a reciprocating machine having a plurality of cylinders;

creating a mathematical model representing the angular dynamics of said system at a plurality of nodes, said model associating angular responses at said plurality of nodes with torques at said plurality of nodes, at least some of said plurality of nodes corresponding to said plurality of cylinders;

activating said reciprocating machine for causing said angular responses of said plurality of nodes;

measuring at a selected analysis frequency at least one of said angular responses at said plurality of nodes to define at least one measured angular response at said selected analysis frequency;

parameterizing said torque for each of said cylinders at said selected analysis frequency as a function of at least one parameter;

assembling a plurality of sets of frequency domain equations, each said set of frequency domain equations associating said at least one measured angular response with said at least one parameter for said plurality of cylinders at said selected analysis frequency, wherein said set of frequency domain equations is defined as over-determined; and

solving said set of frequency domain equations to determine said at least one parameter for each of said plurality of cylinders.

10. The method of claim 9 further comprising the step of estimating said torque for each said cylinder utilizing said at least one parameter for each of said plurality of cylinders as determined in said solving step.

11. The method of claim 9 wherein said step of assembling said plurality of sets of frequency domain equations comprises the steps of:

choosing a different said selected analysis frequency;

repeating said measuring and parameterizing steps for said different selected analysis frequency;

comparing the number of frequency domain equations in said plurality of sets to the number of unknown quantities within said frequency domain equations; and

repeating said aforesaid steps until said number of frequency domain equations in said plurality of sets exceeds said number of unknown quantities.

12. The method of claim 9 wherein said frequency domain equations comprise complex equations having real and imaginary parts, said assembling step further comprising the steps of:

converting said complex equations relating said at least one measured angular response to said at least one parameter into twice as many equivalent real equations; and

eliminating as unknown quantities said imaginary parts of said at least one parameter in said real equations, thereby increasing the rank of said real equations.

13. The method of claim 9 wherein said step of parameterizing comprises the steps of:

separating said torque into constituent indicated torque and inertia torque; and

defining said indicated torque as a linear function of said at least one parameter.

14. The method of claim 9 further comprising the step of calculating a plurality of harmonic frequencies of said torque for each said cylinder wherein each said selected analysis frequency is substantially equal to one of said harmonic frequencies.

15. The method of claim 9 wherein said parameterizing step comprises defining said torque for each said cylinder as a linear function of one or more parameters by locally linearizing a non-linear function for said torque around an initial estimate for said at least one parameter.

16. The method of claim 9 wherein said reciprocating machine is one of an internal combustion engine and a compressor.

17. The method of claim 9 wherein said system includes a drivetrain operably connected to said machine, and said mathematical model represents the angular dynamics of said machine and drivetrain.

18. The method of claim 9 wherein unknown boundary conditions to said mathematical model are treated as additional said torques which are solved simultaneously with said at least one parameter in said plurality of sets of frequency domain equations.

19. The method of claim 9 wherein unknown torques in said system other than said torques produced by said cylinders are treated as additional unknown applied system torques which are solved simultaneously with said at least one parameter in said plurality of sets of frequency domain equations.

20. The method of claim 9 wherein unknown boundary conditions and unknown torques other than said torques produced by said cylinders are parameterized as a function of said at least one parameter and are incorporated into said set of frequency domain equations for simultaneous solution with other unknowns.

21. The method of claim 9 wherein said at least one parameter for each said cylinder comprises the indicated mean effective pressure (IMEP) for said cylinder.

22. The method of claim 9 wherein said at least one parameter for each said cylinder comprises the mean indicated torque (Tmean ind) for said cylinder.

23. The method of claim 9 further comprising the steps of:

interpreting said value of said at least one parameter resulting from said solving step;

changing said at least one parameter based upon the results of said interpreting step; and

repeating said parameterizing step.

24. A method of estimating the torque produced by a cylinder in a reciprocating machine, the method comprising the steps of:

providing a system including a reciprocating machine having a plurality of cylinders;

creating a lumped property model representing the angular dynamics of said system at a plurality of nodes, said model associating angular responses at said plurality of nodes with said torques at said plurality of nodes, at least some of said plurality of nodes corresponding to said plurality of cylinders;

measuring at a selected analysis frequency an angular response of at least one of said nodes to define at least one measured angular response at said selected analysis frequency;

parameterizing said torque for each of said cylinders at said selected analysis frequency as a linear function of at least one parameter by locally linearizing a non-linear function for said torque around an initial estimate for said at least one parameter;

assembling a plurality of sets of frequency domain equations, each said set of frequency domain equations associating said at least one measured angular response with said at least one parameter for said plurality of cylinders at said selected analysis frequency, wherein said set of frequency domain equations is defined as over-determined;

solving said set of frequency domain equations to determine said at least one parameter for each of said plurality of cylinders;

locally relinearizing said non-linear function for said torque around said at least one parameter determined from said solving step and then repeating said assembling and solving steps; and

repeating said locally relinearizing step until said at least one parameter determined from said solving step has converged to a stable solution.

25. The method of claim 24 further comprising the step of estimating said torque utilizing said at least one parameter as determined from said solving step.

26. The method of claim 24 wherein said frequency domain equations comprise complex equations having real and imaginary parts, said assembling step further comprising the steps of:

converting said complex equations relating said at least one measured angular response to said at least one parameter into twice as many equivalent real equations; and

eliminating as unknown quantities said imaginary parts of said at least one parameter in said real equations, thereby increasing the rank of said real equations.

27. The method of claim 24 wherein the key parameter for each cylinder comprises the indicated mean effective pressure (IMEP) for that cylinder.

28. The method of claim 24 wherein the key parameter for each cylinder comprises the indicated mean indicated torque (Tmean ind) for that cylinder.

29. An apparatus for estimating the torque in each cylinder of a reciprocating machine defining a system, the apparatus comprising:

a set of sensors for measuring angular response of at least one location of said system and producing an output;

means for substantially defining a measured angular response based on said output from said sensors;

means for parameterizing torque for each of the cylinders at a selected analysis frequency as a function of at least one parameter;

means for relating said measured angular response to said torque for each said cylinder at said selected analysis frequency, thereby creating a set of frequency domain equations;

means for assembling an over-determined plurality of said sets of frequency domain equations associating said at least one measured angular response with said at least one parameter for said plurality of cylinders at said selected analysis frequency; and

means for solving said set of frequency domain equations to determine said at least one parameter, said estimating means including means for solving said plurality of sets of frequency domain equations for said at least one parameter.

30. The apparatus of claim 29 further comprising means for estimating said torque of each said cylinder from said at least one parameter.

31. The apparatus of claim 29 wherein said frequency domain equations comprise complex equations having real and imaginary parts, said assembling means further comprising means for converting said complex equations into twice as many equivalent real equations and means for eliminating as unknown quantities said imaginary parts of said at least one parameter in said real equations.

32. The apparatus of claim 29 wherein said at least one parameter for each said cylinder comprises the indicated mean effective pressure (IMEP) for said cylinder.

33. The apparatus of claim 29 wherein said at least one parameter for each said cylinder comprises the indicated mean torque (Tmean ind) for said cylinder.