Multi-mode control algorithm

• US 7,640,078 B2
• Filed: 07/05/2006
• Issued: 12/29/2009
• Est. Priority Date: 07/05/2006
• Status: Active Grant

• Current Assignee: Hitachi Metals (Thailand) Ltd.
• Original Assignee: Advanced Energy Industries Incorporated
• Inventors: Smirnov, Alexei V.
• Primary Examiner(s): Von Buhr; Maria N.
• Application Number:
  US11/481,228
• Publication Number:
  US 20080009978A1
• Time in Patent Office: 1,273 Days
• Field of Search: 700/28, 700 32- 34, 700 40- 46, 700 75- 77, 700282-285, 137 2- 12, 137/14, 73/10.1, 73/11.6, 73/13.5, 73/15.7
• US Class Current: 700/282
• CPC Class Codes: G05D 7/0635 by action on throttling means G05D7/0688, G05D7/0694 take precedence
• CPC Class Codes: Y10T 137/0379 By fluid pressure

Abstract

A system and method for controlling a flow of a fluid using a multi-mode control algorithm is described. One embodiment includes a method for changing the multi-mode control algorithm from a closed-loop mode to an open-loop mode. The method includes receiving at least one sensor indicator generated by a sensor. The multi-mode control algorithm is modified from the closed-loop mode to the open-loop mode when, based on the at least one sensor indicator, the threshold condition is satisfied. The multi-mode control algorithm is used by a flow controller to control a flow of a fluid according to a set point.

Claims

1. A method, comprising:

receiving a pressure measurement of a fluid generated by a pressure sensor;

disengaging a feedback control loop responsive to a pressure change rate of the fluid satisfying a threshold condition;

initiating a timer when the feedback control loop is disengaged;

calculating a valve position to produce a fluid flow according to a specified fluid flow set point, the calculation of the valve position being based on the pressure measurement, and the calculated valve position being used to control a flow of the fluid while the feedback control loop is disengaged; and

re-engaging the feedback control loop when a time period of the timer expires, the time period is defined based on the pressure change rate.

2. The method of claim 1, wherein the feedback control loop is configured to control the flow of the fluid according to the set point and based on a characteristic of the flow as provided by a sensor.

3. The method of claim 1, wherein the feedback control loop is configured to control the flow of the fluid using a flow sensor that senses the flow of the fluid, the threshold condition is defined based on a characteristic of the flow sensor.

4. The method of claim 1, wherein the feedback control loop is configured to control the flow of the fluid using a flow sensor that senses the flow of the fluid, the threshold condition is defined based on an operating range of the flow sensor.

5. The method of claim 1, wherein the calculating includes calculating the valve position based on at least one of calibration data or characterization data.

6. The method of claim 1, further comprising re-engaging the feedback control loop when at least one of the time period of the timer expires or the threshold condition changes from being satisfied to unsatisfied.

7. The method of claim 1, further comprising re-engaging the feedback control loop when the time period of the timer expires, the time period is defined based on a magnitude of the pressure change.

8. The method of claim 1, wherein the pressure change rate is calculated using at least two measurements each with a corresponding measurement time.

9. The method of claim 1, wherein the pressure measurement is a second pressure measurement at a second time,

the method, further comprising detecting the pressure change of the fluid, the pressure change is a difference between a first pressure measurement at a first time and the second pressure measurement, the second time is after the first time.

10. The method of claim 1, including extending the time period responsive to the pressure change rate of the fluid satisfying the threshold condition during the time period.

11. A method, comprising:

receiving at least one sensor indicator generated by a fluid flow characteristic sensor;

modifying a multi-mode control algorithm from a closed-loop mode to an open-loop mode when, based on the at least one sensor indicator, a threshold condition is satisfied, the multi-mode control algorithm is used by a flow controller to control a flow of a fluid according to a set point;

initiating a timer when the threshold condition is satisfied;

calculating a valve position of a valve so as to deliver the fluid according to the set point when operating in the open-loop mode; and

modifying the multi-mode control algorithm from the open-loop mode to the closed loop mode when a time period of the timer expires.

12. The method of claim 11, wherein calculating the valve position of a valve comprises, using the open-loop mode and using the at least one sensor indicator.

13. The method of claim 11, wherein calculating the valve position comprises using (i) the open-loop-control algorithm, (ii) the at least one sensor indicator, and (iii) a mathematical relationship.

14. The method of claim 11, wherein the fluid flow characteristic sensor is a pressure sensor, the at least one sensor indicator is a pressure sensor indicator.

15. The method of claim 11, wherein the fluid flow characteristic sensor is at least one of a flow sensor, a timer, a pressure sensor or a temperature sensor.

16. The method of claim 11, further comprising detecting a change in the sensor indicator, the threshold condition is satisfied by the change.

17. The method of claim 11, wherein the sensor indicator indicates a characteristic associated with the fluid.

18. The method of claim 11, wherein the closed-loop mode is configured to control the flow of the fluid using a flow sensor that senses the flow of the fluid, the threshold condition is defined based on at least one of a characteristic of the flow sensor or an operating range of the flow sensor.

19. The method of claim 11, further comprising modifying the control algorithm from the open-loop mode to the closed-loop mode when the threshold condition associated with the sensor indicator changes from being satisfied to unsatisfied.

20. The method of claim 11, wherein the threshold condition is a first threshold condition, the at least one sensor indicator is received at a first time;

and

the method further comprising modifying the control algorithm from the open-loop mode to the closed-loop mode when, based on a second sensor indicator received at a second time from the sensor, a second threshold condition is satisfied.

21. The method of claim 11, wherein the open-loop mode is selected from a set of open-loop modes in response to the threshold condition being satisfied.

22. An apparatus, comprising:

a processor configured to calculate a valve position based on a pressure measurement when a feedback control loop has been disengaged, the feedback control loop being disengaged when a pressure change of a fluid satisfies a threshold condition, a valve controls a flow of the fluid in response to the valve position, and the processor is configured to re-engage the feedback control loop when a time period after the threshold condition was satisfied expires; and

a memory configured to store a mathematical relationship between the valve position, the flow of the fluid, and the pressure measurement, the mathematical relationship is used by the processor to calculate the valve position.

23. The apparatus of claim 22, further comprising a memory that is configured to store the threshold condition, the processor is configured to access the threshold condition from the memory.

24. The apparatus of claim 22, wherein the feedback control loop is configured to control the flow of the fluid according to a set point and using a flow sensor that senses the flow of the fluid, the threshold condition is defined based on an operating range of the flow sensor.

25. The apparatus of claim 22, wherein the feedback control loop is re-engaged when at least one of a time period of a timer expires or the threshold condition changes from being satisfied to unsatisfied.