NORMALIZED PROCESS DYNAMICS

• US 20150088279A1
• Filed: 09/23/2013
• Published: 03/26/2015
• Est. Priority Date: 09/23/2013
• Status: Active Grant

• Current Assignee: Rosemount Incorporated (Emerson Electric Company)
• Original Assignee: Rosemount Incorporated (Emerson Electric Company)
• Inventors: Miller, John Philip, Hedtke, Robert Carl
• Granted Patent: US 9,551,599 B2
• Time in Patent Office: Days
• US Class Current: 700/55
• CPC Class Codes: G01D 18/00 Testing or calibrating apparatus or arrangements provided for in groups G01D1/00 - G01D15/00
• CPC Class Codes: G01K 7/00 Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat giving results other than momentary value of temperature G01K3/00 ; Power supply therefor, e.g. using thermoelectric elements
• CPC Class Codes: G05B 15/02 electric
• CPC Class Codes: G05B 23/0221 Preprocessing measurements, e.g. data collection rate adjustment; Standardization of measurements; Time series or signal analysis, e.g. frequency analysis or wavelets; Trustworthiness of measurements; Indexes therefor; Measurements using easily measured parameters to estimate parameters difficult to measure; Virtual sensor creation; De-noising; Sensor fusion; Unconventional preprocessing inherently present in specific fault detection methods like PCA-based methods
• CPC Class Codes: Y02P 90/02 Total factory control, e.g. smart factories, flexible manufacturing systems [FMS] or integrated manufacturing systems [IMS]

Abstract

A sensing system includes a filter construction module that constructs a high pass filter for filtering sensor values indicative of a process variable, the filter construction module setting values for parameters of the filter based on a temperature value indicative of a temperature of the sensor that produced the sensor values.

Claims

1. A process field device comprising:

a sensor providing a signal indicative of a process variable;

a temperature sensor providing a signal indicative of a temperature of the sensor;

converter circuitry for converting the sensor signal into sensor values and the temperature sensor signal into temperature values;

a processor implementing a digital filter that filters the sensor values to produce filtered sensor values and executing statistical process monitoring instructions that compute a statistical value from the filtered sensor values, wherein the digital filter is temperature-dependent such that the filter changes as the temperature values change.

2. The process field device of claim 1 wherein the processor constructs the digital filter by applying a temperature value to an equation determined by fitting a curve to parameter values determined for filters constructed for a plurality of temperature values.

3. The process field device of claim 2 wherein the filters constructed for a plurality of temperature values are each constructed to produce a target frequency response.

4. The process field device of claim 3 wherein the target frequency response comprises a frequency response of a standard deviation of filtered sensor values.

5. The process field device of claim 3 wherein the target frequency response comprises a frequency response associated with a model sensor operating in a different range from the sensor and at a selected temperature.

6. The process field device of claim 3 wherein the target frequency response comprises a frequency response of a model sensor with a constant frequency response at all temperatures.

7. A sensing system comprising a filter construction module constructing a filter for filtering sensor values indicative of a process variable, the filter construction module setting values for parameters of the filter based on a temperature value indicative of a temperature of the sensor that produced the sensor values.

8. The sensing system of claim 7 wherein the filter construction module sets a value for a parameter by applying the temperature value to an equation determined by fitting a curve to parameter values determined for filters constructed for a plurality of temperature values.

9. The sensing system of claim 8 wherein the filters constructed for a plurality of temperature values are each constructed to produce a target frequency response.

10. The sensing system of claim 9 wherein the target frequency response comprises a frequency response of a standard deviation of a filtered sensor signal wherein the sensor signal is produced by a model sensor operating at a same range as the sensor and at a selected temperature.

11. The sensing system of claim 9 wherein the target frequency response comprises a frequency response of a standard deviation of a filtered sensor signal wherein the sensor signal is produced by a model sensor operating in a different range from the sensor and at a selected temperature.

12. The sensing system of claim 9 wherein the target frequency response comprises a frequency response of a standard deviation of a filtered sensor signal wherein the sensor signal is produced by a model sensor with a constant frequency response at all temperatures.

13. A control system comprising:

a filter that filters a series of sensor values to produce filtered values; and

a statistical process monitoring unit that determines a statistical value from the filtered values and that issues an alert when the statistical value crosses a threshold, wherein the filter filters the sensor values to achieve a desired frequency response in the statistical value that matches a frequency response in the statistical value produced from sensor values generated by a sensor operating in a selected range.

14. The control system of claim 13 wherein the filter comprises a temperature-dependent filter that is constructed by applying the temperature value to respective equations that each define a separate parameter of the filter.

15. The control system of claim 14 wherein each equation is constructed by fitting a curve to values of a filter parameter determined at different temperatures.

16. The control system of claim 13 wherein the desired frequency response of the statistical value further matches a frequency response in the statistical value produced from sensor values generated by the sensor operating at a selected temperature.

17. The control system of claim 13 wherein the desired frequency response of the statistical value comprises a frequency response produced at least in part by a sensor operating in a different range from a sensor that produced the series of sensor values.

18. The control system of claim 13 wherein the desired frequency response of the statistical value comprises a frequency response produced at least in part by a sensor that was manufactured differently from a sensor that produced the series of sensor values.

19. A method comprising:

training coefficients for temperature-dependent filter parameters;

receiving a sensor signal and a temperature signal;

constructing a filter using the temperature-dependent filter parameters and the temperature signal;

applying the sensor signal to the filter to produce a filtered signal;

generating a statistical value from the filtered signal; and

activating an alarm when the statistical value crosses a threshold.

20. The method of claim 19 wherein training coefficients for temperature-dependent filter parameters comprises:

selecting a model frequency response for the statistical value;

for each of a plurality of temperatures, selecting filter parameter values that produce a frequency response for the statistical value that matches the model frequency response for the statistical value; and

for each filter parameter, fitting a curve that is a function of temperature to the values of the filter parameter at the plurality of temperatures to produce coefficients for the filter parameters.

21. The method of claim 20 wherein the model frequency response comprises a frequency response produced at least in part by a sensor operating at a selected temperature.

22. The method of claim 21 wherein the sensor is operating at a selected operating range.

23. The method of claim 20 wherein the temperature signal represents a temperature of an impulse line connected to a sensor that generates the sensor signal.

24. The method of claim 23 wherein the impulse line is further connected near a valve and the sensor senses cavitation at the valve.