Diagnostics for mass flow control

• US 7,693,606 B2
• Filed: 12/21/2007
• Issued: 04/06/2010
• Est. Priority Date: 12/21/2007
• Status: Active Grant

• Current Assignee: Rosemount Incorporated (Emerson Electric Company)
• Original Assignee: Rosemount Incorporated (Emerson Electric Company)
• Inventors: Huisenga, Garrie David, Ahmad, Anis
• Primary Examiner(s): Shechtman; Sean P
• Application Number:
  US12/004,661
• Publication Number:
  US 20090164050A1
• Time in Patent Office: 837 Days
• Field of Search: 700/3, 700/9, 700/10, 700/28, 700/29, 700/32, 700/42, 700/45, 700/51, 700/79, 700/80, 700/282, 700/289, 702/45, 702183-185, 137/10, 137/87.03
• US Class Current: 700/282
• CPC Class Codes: G01F 1/6847 where sensing or heating elements are not disturbing the fluid flow, e.g. elements mounted outside the flow duct
• CPC Class Codes: G01F 1/6965 comprising means to store calibration data for flow signal calculation or correction
• CPC Class Codes: G01F 15/005 Valves valves in general F16K
• CPC Class Codes: G01F 25/10 of flowmeters
• CPC Class Codes: G01F 5/00 Measuring a proportion of the volume flow
• CPC Class Codes: G05D 7/0635 by action on throttling means G05D7/0688, G05D7/0694 take precedence
• CPC Class Codes: Y10T 137/0318 Processes
• CPC Class Codes: Y10T 137/7722 Line condition change responsive valves

Abstract

A flow control system comprises a flow sensor, a valve controller, a signal processor, a control processor and an interface. The flow sensor generates a sensor signal characterizing a flow rate. The valve controller controls the flow rate as a function of a control output. The signal processor converts the sensor signal into a flow signal characterizing the flow rate as a function of time, and the control processor generates the control output as a function of a setpoint and the flow signals. The interface receives an input representative of the setpoint, transmits a flow output representative of the flow signals, and transmits a diagnostic output directly indicative of an operational condition of the flow control system.

Claims

1. A flow control system comprising:

a flow sensor configured to generate a sensor signal characterizing a flow rate;

a valve controller configured to control the flow rate as a function of a control output;

a signal processor configured to convert the sensor signal into a flow signal characterizing the flow rate as a function of time;

a control processor configured to generate the control output as a function of a setpoint and the flow signal; and

an interface configured to receive an input representative of the setpoint and to transmit a flow output representative of the flow signal, flow diagnostic indicative of an operational condition of the flow control system and a control diagnostic indicative of an operational condition of the flow controller;

wherein the flow diagnostic is based on an inverse signal-to-noise ratio of a standard deviation of the flow signal to a mean of the flow signal, and the control diagnostic is based on a response function relating the control output to at least one of the setpoint and the flow signal.

2. The flow control system of claim 1, wherein the flow diagnostic is indicative of a flow obstruction.

3. The flow control system of claim 1, wherein the response function comprises a proportional-integral-derivative routine performed on the setpoint as compared to the flow signal.

4. The flow control system of claim 3, wherein the control diagnostic is indicative of wear and tear on the valve controller.

5. The flow control system of claim 1, wherein the flow sensor comprises a mass flow sensor.

6. The flow control system of claim 1, wherein the flow sensor comprises a Coriolis flow sensor.

7. The flow control system of claim 1, further comprising an integrated controller housing for housing the flow sensor, the valve controller, the signal processor, the control processor and the interface, and wherein the valve controller comprises one of a valve positioner, a valve actuator and a valve coil assembly.

8. The flow control system of claim 1, wherein the flow diagnostic is indicative of corrosion in the flow control system.

9. The flow control system of claim 1, wherein the control output comprise a pulse-width modulated control output and the response function comprises a ratio of the pulse-width modulated control output to the setpoint.

10. The flow control system of claim 9, wherein the control diagnostic is indicative of valve sticking or instability in the valve controller.

11. A flow controller comprising a flow sensor for generating an analog sensor signal;

an analog-to-digital converter for converting the analog sensor signal to a digital sensor signal;

a digital-to-analog converter for converting a digital control signal to an analog control output;

a valve controller for controlling a valve as a function of the analog control output;

a microprocessor for generating a flow signal as a function of the digital sensor signal, for generating the digital control signal as a function of a setpoint and the flow signal, and for generating first and second diagnostic signals indicative of an operational condition of the flow controller, wherein the first diagnostic signal is based on an inverse signal-to-noise ratio of a standard deviation of the flow signal to a mean of the flow signal and the second diagnostic signal is based on a response function relating the control output to at least one of the setpoint and the flow signal; and

an interface for receiving an input representative of the setpoint and for transmitting an output representative of the flow signal and the first and second diagnostic signals.

12. The flow controller of claim 11, wherein the operational condition comprises one or more of a flow obstruction or corrosion within the flow controller.

13. The flow controller of claim 11, wherein the operational condition comprises electromechanical deterioration within the flow controller.

14. The flow controller of claim 11, further comprising an integrated flow controller housing for housing the analog-to-digital converter, the digital-to-analog converter, the valve controller, the microprocessor and the interface.

15. The flow controller of claim 14, wherein the flow sensor comprises a thermal mass flow sensor.

16. The flow controller of claim 14, wherein the flow sensor comprises a Coriolis flow sensor.

17. The flow controller of claim 14, wherein the valve controller comprises a valve coil assembly.

18. The flow controller of claim 11, wherein the response function comprises a proportional-integral-derivative routine performed on the setpoint as compared to the flow signal.

19. The flow controller of claim 11, wherein the analog control output comprises a pulse-width modulated control output and the response function comprises a ratio of the pulse-width modulated control output to the setpoint.

20. A method of flow control, the method comprising:

generating a flow signal that characterizes a process flow rate as a function of time;

receiving an input representative of a setpoint for the process flow rate;

controlling the process flow rate as a function of a response function relating the setpoint and the flow signal;

generating a flow diagnostic signal that is indicative of an operational condition of the process flow rate, wherein the flow diagnostic signal is based on an inverse signal-to-noise ratio of a standard deviation of the flow signal to a mean of the flow signal;

generating a control diagnostic signal that is indicative of the operational condition of the process flow rate, wherein the control diagnostic signal is based on the response function; and

transmitting an output that is representative of the flow signal, the flow diagnostic signal and the control diagnostic signal.

21. The method of claim 20, wherein the response function comprises a proportional-integral-derivative routine performed on the setpoint as compared to the flow signal.

22. The method of claim 20, wherein controlling the process flow rate comprises controlling the process flow rate as a function of a pulse-width modulated control output based on the setpoint and the flow signal, and wherein the response function comprises a ratio of the pulse-width modulated control output to the setpoint.