Method and system for verifying virtual sensors

• US 20080154811A1
• Filed: 12/21/2006
• Published: 06/26/2008
• Est. Priority Date: 12/21/2006
• Status: Abandoned Application

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Grichnik, Anthony J., Seskin, Michael
• Application Number:
  US11/642,913
• Publication Number:
  US 20080154811A1
• Time in Patent Office: Days
• US Class Current: 706/13
• CPC Class Codes: G06N 3/084 Backpropagation, e.g. using gradient descent
• CPC Class Codes: G06N 3/126 Evolutionary algorithms, e.g. genetic algorithms or genetic programming

Abstract

A method is provided for a virtual sensor system. The method may include starting at least one established virtual sensor process model indicative of interrelationships between a plurality of input parameters and a plurality of output parameters and retrieving calibration data associated with the virtual sensor process model. The method may also include obtaining a set of values of the plurality of input parameters and calculating corresponding values of the plurality of output parameters simultaneously based upon the set of values of the plurality of input parameters and the virtual sensor process model. Further, the method may include determining whether the set of values of input parameters are qualified for the virtual sensor process model to generate the values of the plurality of output parameters with desired accuracy based on the calibration data.

Claims

1. A method for a virtual sensor system, comprising:

starting at least one established virtual sensor process model indicative of interrelationships between a plurality of input parameters and a plurality of output parameters;

retrieving calibration data associated with the virtual sensor process model;

obtaining a set of values of the plurality of input parameters;

calculating corresponding values of the plurality of output parameters simultaneously based upon the set of values of the plurality of input parameters and the virtual sensor process model; and

determining whether the set of values of input parameters are qualified for the virtual sensor process model to generate the values of the plurality of output parameters with desired accuracy based on the calibration data.

2. The method according to claim 1, wherein determining further includes:

obtaining respective ranges of the plurality of input parameters based on the calibration data;

determining whether the value of at least one of the input parameters is within the obtained range of the at least one of the input parameters; and

determining that the set of values of input parameters are not qualified if the value of the at least one of the input parameters is not within the obtained range.

3. The method according to claim 1, wherein determining further includes:

calculating a confidence index of the set of values of the plurality of input parameters based on the calibration data;

comparing the confidence index with a predetermined threshold; and

determining that the set of values of the input parameters are not qualified if the confidence index is beyond the predetermined threshold.

4. The method according to claim 3, wherein calculating further includes:

calculating a mahalanobis distance of the set of values of the input parameters based on the calibration data; and

deriving the confidence index from the mahalanobis distance.

5. The method according to claim 3, further including:

if the confidence index is not beyond the predetermined threshold, providing the values of the output parameters and the confidence index to a control system.

6. The method according to claim 1, further including:

if it is determined that the set of values of input parameters are not qualified, notifying an undesired operational condition to a control system; and

discarding the values of output parameters.

7. The method according to claim 6, further including:

calculating at least one indication parameter corresponding to a degree to which the set of values of input parameters are not qualified based on the values of output parameters; and

indicating that the virtual sensor process model 304 is unqualified when provided with the set of values of input parameters and the output parameters based on the indication parameter.

8. The method according to claim 7, further including:

continuing using a last qualified set of values of the input parameters until it is determined that a new set of values of the input parameters are qualified.

9. The method according to claim 1, wherein the plurality of input parameters include one or more of engine speed, fuel rate, injection timing, intake manifold temperature, intake manifold pressure, inlet valve actuation end of current, and injection pressure.

10. The method according to claim 1, wherein the plurality of output parameters include one or more of NO_x emission level, soot emission level, HC emission level, soot oxidation rate, soot passive regeneration rate, exhaust manifold temperature, air system pressure and temperature estimations, gas-to-brick temperature offset estimation, auxiliary regeneration flame detection temperature, sound emission levels, heat rejection levels, and vibration levels.

11. The method according to claim 1, wherein the process model is established by:

obtaining data records associated with one or more input variables and the plurality of output parameters;

selecting the plurality of input parameters from the one or more input variables;

generating a computational model indicative of the interrelationships between the plurality of input parameters and the plurality of output parameters;

determining desired statistical distributions of the plurality of input parameters of the computational model;

defining a desired input space based on the desired statistical distributions; and

storing data used and created during the establishment of the process model as the calibration data associated with the process model.

12. The method according to claim 11, wherein selecting further includes:

pre-processing the data records; and

using a genetic algorithm to select the plurality of input parameters from the one or more input variables based on a mahalanobis distance between a normal data set and an abnormal data set of the data records.

13. The method according to claim 11, wherein generating further includes:

creating a neural network computational model;

training the neural network computational model using the data records; and

validating the neural network computation model using the data records.

14. The method according to claim 11, wherein determining further includes:

determining a candidate set of values the input parameters with a maximum zeta statistic using a genetic algorithm; and

determining the desired distributions of the input parameters based on the candidate set,

wherein the zeta statistic ζ

is represented by;

15. The method according to claim 1, wherein the at least one established virtual sensor process model includes a network of virtual sensor process models with interrelated relationships.

15-1. A system for a virtual sensor process model, comprising:

a database configured to store information relevant to the virtual sensor process model and calibration data associated with the virtual sensor process model; and

a processor configured to;

start the virtual sensor process model indicative of interrelationships between a plurality of input parameters and a plurality of output parameters;

retrieve calibration data associated with the virtual sensor process model;

obtain a set of values of the plurality of input parameters;

calculate corresponding values of the plurality of output parameters simultaneously based upon the set of values of the plurality of input parameters and the virtual sensor process model; and

determine whether the set of values of input parameters are qualified for the virtual sensor process model to generate the values of the plurality of output parameters with desired accuracy based on the calibration data.

17. The system according to claim 16, wherein, to determine whether the set of values of input parameters are qualified, the processor is further configured to:

obtain respective ranges of the plurality of input parameters based on the calibration data;

determine whether the value of at least one of the input parameters is within the obtained range of the at least one of the input parameters; and

determine that the set of values of input parameters are not qualified if the value of the at least one of the input parameters is not within the obtained range.

18. The system according to claim 16, wherein, to determine whether the set of values of input parameters are qualified, the processor is further configured to:

calculate a confidence index of the set of values of the plurality of input parameters based on the calibration data;

compare the confidence index with a predetermined threshold; and

determine that the set of values of the input parameters are not qualified if the confidence index is beyond the predetermined threshold.

19. The system according to claim 18, wherein, to calculate the confidence index, the processor is further configured to:

calculate a mahalanobis distance of the set of values of the input parameters based on the calibration data; and

derive the confidence index from the mahalanobis distance.

20. The system according to claim 18, wherein the processor is further configured to:

provide the values of the output parameters and the confidence index to a control system, if the confidence index is not beyond the predetermined threshold.

21. The system according to claim 16, wherein the processor is further configured to:

notify an undesired operational condition to a control system, if it is determined that the set of values of input parameters are not qualified;

discard the values of output parameters;

calculate at least one indication parameter corresponding to a degree to which the set of values of input parameters are not qualified based on the values of output parameters; and

indicate that the virtual sensor process model 304 is unqualified when provided with the set of values of input parameters and the output parameters based on the indication parameter.

22. A computer-readable medium for use on a computer system configured to establish at least one virtual sensor process model, the computer-readable medium having computer-executable instructions for performing a method comprising:

obtaining data records associated with one or more input variables and a plurality of output parameters;

selecting the plurality of input parameters from the one or more input variables;

generating a computational model indicative of the interrelationships between the plurality of input parameters and the plurality of output parameters;

determining desired statistical distributions of the plurality of input parameters of the computational model;

defining a desired input space based on the desired statistical distributions; and

storing data used and created during the establishment of the process model as the calibration data associated with the process model.

23. The computer-readable medium according to claim 22, wherein the at least one virtual sensor process model includes a network of virtual sensor process models with interrelated relationships.

24. The computer-readable medium according to claim 22, wherein the selecting further includes:

pre-processing the data records; and

using a genetic algorithm to select the plurality of input parameters from the one or more input variables based on a mahalanobis distance between a normal data set and an abnormal data set of the data records.

25. The computer-readable medium according to claim 22, wherein generating further includes:

creating a neural network computational model;

training the neural network computational model using the data records; and

validating the neural network computation model using the data records.

26. The computer-readable medium according to claim 22, wherein determining further includes:

determining a candidate set of values the input parameters with a maximum zeta statistic using a genetic algorithm; and

determining the desired distributions of the input parameters based on the candidate set,

wherein the zeta statistic ζ

is represented by;