Positioner

Abstract

The measured operation time of a setting/operating device is corrected using a first corrected value table and a second corrected value table and the size of the setting/operating device is defined based on the corrected operation time. The first corrected value table defines, as a first corrected value, the corrected value corresponding to the operation time region defined so as to correspond to the size of the setting/operating device and the sliding resistance region defined by dividing the range taken by the sliding resistance (friction) of the valve stem of a regulating valve and the second corrected value table defines, as a second corrected value, the corrected value corresponding to the operation time region defined so as to correspond to the size of the setting/operating device and the supply air pressure region defined by dividing the range taken by a supply air pressure.

Claims

1. A positioner comprising a controller outputting, as a control output, an electric signal according to a difference between a valve opening setting value sent from a higher-level device and an actual opening value fed back from a regulating valve and an electric-pneumatic converter converting the control output from the controlling portion to an air pressure and outputting the air pressure to a setting/operating device of the regulating valve, the positioner further comprising: a control parameter non-transitory storage storing, for each size of the setting/operating device used in the regulating valve, a correspondence between a level of a sliding resistance of the valve stem of the regulating valve and a control parameter used to control a valve opening of the regulating valve; a setting/operating device size/operation time non=transitory storage storing a correspondence between a size of the setting/operating device and an operation time for each size of the setting/operating device used in the regulating valve; a first corrected value non-transitory storage storing, as a first corrected value, a corrected value defined so as to correspond to an operation time region defined so as to correspond to the size of the setting/operating device used in the regulating valve and a sliding resistance region defined by dividing a range taken by the sliding resistance of the valve stem of the regulating valve; a second corrected value non-transitory storage storing, as a second corrected value, a corrected value defined so as to correspond to the operation time region defined so as to correspond to the size of the setting/operating device used in the regulating valve and a supply air pressure region defined by dividing an area taken by a pressure of instrumentation air to be supplied to the electric-pneumatic converting portion; an operation time measurer measuring an operation time of the setting/operating device used in the regulating valve by actually driving the regulating valve; a sliding resistance measurer measuring a sliding resistance of the valve stem of the regulating valve by actually driving the regulating valve; a supply air pressure measurement portion measuring the pressure of the instrumentation air supplied to the electric-pneumatic converting portion as a supply air pressure; a first corrected value acquirer acquiring a first corrected value corresponding to the operation time measured by the operation time measurer and the sliding resistance measured by the sliding resistance measurer from the first corrected value non-transitory storage; a second corrected value acquirer acquiring a second corrected value corresponding to the operation time measured by the operation time measurer and the supply air pressure measured by the supply air pressure measurer from the second corrected value storing portion; an operation time corrector correcting the operation time measured by the operation time measurer using the first corrected value acquired by the first corrected value acquirer and the second corrected value acquired by the second corrected value acquirer; a setting/operating device size acquirer acquiring the size of the setting/operating device corresponding to the operation time corrected by the operation time corrector from the setting/operating device size/operation time storing portion; and a control parameter selector selecting the control parameter corresponding to the size of the setting/operating device acquired by the setting/operating device size acquirer and the sliding resistance measured by the sliding resistance measurer from the control parameter non-transitory storage, wherein the controller controls the valve opening of the regulating valve using the control parameter selected by the control parameter selector.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates the main part of a positioner according to an example of the invention.

(2) FIG. 2 is a functional block diagram illustrating the main part of a controlling portion of the positioner.

(3) FIG. 3 illustrates a control parameter table to be stored in a control parameter storing portion of the positioner.

(4) FIG. 4 illustrates a setting/operating device size/operation time table to be stored in a setting/operating device size/operation time storing portion of the positioner.

(5) FIG. 5 illustrates a first corrected value table to be stored in a first corrected value storing portion of the positioner.

(6) FIG. 6 illustrates the relationship between the friction and the change amount of operation time obtained for each size of the setting/operating device.

(7) FIG. 7 illustrates a second corrected value table to be stored in a second corrected value storing portion of the positioner.

(8) FIG. 8 illustrates the relationship between the supply air pressure and the change amount of operation time obtained for each size of the setting/operating device.

(9) FIG. 9 illustrates the structure of the main part of a conventional positioner.

(10) FIG. 10 illustrates the structure of the main part of a regulating valve.

(11) FIG. 11 is a flowchart illustrating automatic tuning in a conventional positioner.

DETAILED DESCRIPTION

(12) An example of the invention will be described in detail below with reference to the drawings.

(13) FIG. 1 illustrates the main part of a positioner according to an example of the invention. In this drawing, the same reference numerals as in FIG. 9 indicate the same or similar components described with reference to FIG. 9 and descriptions are omitted.

(14) The positioner 1 according to the example is provided with a supply air pressure measurement portion 15 measuring the pressure of instrumentation air for the electric-pneumatic converting portion 14 of the positioner 1 as a supply air pressure Pspv and the supply air pressure Pspv measured by the supply air pressure measurement portion 15 is given to the controlling portion 11.

(15) In the positioner 1, as a function specific to the example, the controlling portion 11 has a control parameter selecting and setting function F1 for selecting and setting the optimum control parameters used to control the valve opening of the regulating valve 2 by correcting the operation time in determining the size of a setting/operating device.

(16) The positioner 1 in the example is denoted below as the positioner 1A to distinguish it from the conventional positioner 1 (1B) illustrated in FIG. 9. In addition, the controlling portion 11 in the example is denoted as the controlling portion 11A to distinguish it from the controlling portion 11 (11B) in the conventional positioner 1B illustrated in FIG. 9. The controlling portion 11A is configured by hardware including a processor and memory device and a program achieving various types of functions in corporation with the hardware.

(17) FIG. 2 is a functional block diagram illustrating the main part of the controlling portion 11A. To achieve the control parameter selecting and setting function F1, the controlling portion 11A includes a control parameter storing portion 16, a setting/operating device size/operation time storing portion 17, a first corrected value storing portion 18, a second corrected value storing portion 19, an operation time measurement portion 20, a sliding resistance measurement portion 21, a first corrected value acquisition portion 22, a second corrected value acquisition portion 23, an operation time correction portion 24, a setting/operating device size acquisition portion 25, a control parameter selecting portion 26, and a control parameter setting portion 27.

(18) The control parameter storing portion 16 stores the control parameter table TA (see FIG. 3) defining the correspondence between the hysteresis level (HYS) and the control parameters (KP, TI, TD, GE, GKP, GTI, and GTD) for each size of a setting/operating device used in the regulating valve 2 by assuming that the level of the sliding resistance of the valve stem of the regulating valve in the invention is to be the hysteresis level (HYS). In the example, the hysteresis level (HYS) is classified into three stages (H, M, and L) and the control parameters corresponding to each of the three stages of the hysteresis level (HYS) are defined.

(19) The setting/operating device size/operation time storing portion 17 stores a setting/operating device size/operation time table TB (see FIG. 4) defining the correspondence between the operation time and the size of the setting/operating device used in the regulating valve 2. In the example, the range (operation time region) taken by the operation time of a setting/operating device X is defined as a to b, the range (operation time region) taken by the operation time of a setting/operating device Y is defined as b to c, and the range (operation time region) taken by the operation time of the setting/operating device Z is defined as about c and beyond.

(20) The first corrected value storing portion 18 stores a first corrected value table TC (see FIG. 5) defining, as a first corrected value 1, the corrected value corresponding to the operation time regions defined so as to correspond to the sizes of the setting/operating device used in the regulating valve 2 and the sliding resistance regions defined by dividing the range taken by the sliding resistance (friction) of the valve stem 2d of the regulating valve 2. By obtaining the relationship between the friction and the change amount (the difference from the operation time when the friction is 0) of operation time for each size of the setting/operating device (see FIG. 6), the first corrected value 1 is defined as, for example, the average value of the change amounts of the operation time in the individual divisions of the friction.

(21) The second corrected value storing portion 19 stores the second corrected value table TD (see FIG. 7) defining, as a second corrected value 2, the corrected value corresponding to the operation time regions so as to correspond to the sizes of the setting/operating device used in the regulating valve 2 and the supply air pressure regions defined by dividing the range taken by the pressure (supply air pressure) Ps of instrumentation air supplied to the electric-pneumatic converting portion 14. By obtaining the relationship between the supply air pressure Ps and the change amounts (the difference from the operation time when the supply air pressure Ps is the reference value (for example, 200 kPa)) of operation time for each size of the setting/operating device (see FIG. 8), the second corrected value 2 is defined as, for example, the average value of the change amounts of the operation time in the individual divisions of the supply air pressure Ps.

(22) The functions of the operation time measurement portion 20, the sliding resistance measurement portion 21, the first corrected value acquisition portion 22, the second corrected value acquisition portion 23, the operation time correction portion 24, the setting/operating device size acquisition portion 25, the control parameter selecting portion 26, and the control parameter setting portion 27 in the controlling portion 11A illustrated in FIG. 2 will be described together with their operation.

(23) When receiving an automatic tuning instruction, the controlling portion 11A obtains, as the operation time S1 of a setting/operating device 2a, the response time when the valve opening of the regulating valve 2 continuously shifts from, for example, the 10% position to the 90% position by actually driving the regulating valve 2. This operation time S1 is obtained by the operation time measurement portion 20. In the example, the operation time measurement portion 20 measures, as the operation time S1, the average value of the reciprocating response time when the valve opening continuously shifts from the 10% position to the 90% position. Note that the reciprocating response time may be a one-way response time.

(24) In addition, when receiving an automatic tuning instruction, the controlling portion 11A obtains the sliding resistance (stem reciprocating motion resistance) of the valve stem 2d of the regulating valve 2 as the friction F by actually driving the regulating valve 2. This friction F is obtained by the sliding resistance measurement portion 21. In the example, the sliding resistance measurement portion 21 measures the friction F based on a step response from, for example, the 40% position to the 60% position of the valve opening position of the regulating valve 2.

(25) The operation time S1 of the setting/operating device 2a measured by the operation time measurement portion 20 is sent to the first corrected value acquisition portion 22, the second corrected value acquisition portion 23, and the operation time correction portion 24 and the friction F measured by the sliding resistance measurement portion 21 is sent to the first corrected value acquisition portion 22 and the control parameter selecting portion 26.

(26) The first corrected value acquisition portion 22 receives the operation time S1 measured by the operation time measurement portion 20 and the friction F measured by the sliding resistance measurement portion 21 and acquires the first corrected value 1 corresponding to the operation time S1 and the friction F from the first corrected value table TC stored in the first corrected value storing portion 18. The first corrected value 1 acquired by the first corrected value acquisition portion 22 is sent to the operation time correction portion 24.

(27) The second corrected value acquisition portion 23 receives the operation time S1 measured by the operation time measurement portion 20 and the supply air pressure Pspv measured by the supply air pressure measurement portion 15 and acquires the second corrected value 2 corresponding to the operation time S1 and the supply air pressure Pspv from the second corrected value table TD stored in the second corrected value storing portion 19. The second corrected value 2 acquired by the second corrected value acquisition portion 23 is sent to the operation time correction portion 24.

(28) The operation time correction portion 24 receives the operation time S1 measured by the operation time measurement portion 20, the first corrected value 1 acquired by the first corrected value acquisition portion 22, and the second corrected value 2 acquired by the second corrected value acquisition portion 23 and corrects the operation time S1 measured by the operation time measurement portion 20 using the first corrected value 1 acquired by the first corrected value acquisition portion 22 and the second corrected value 2 acquired by the second corrected value acquisition portion 23. In this case, since the operation time S1 is thought to be long when the friction F is large, the first corrected value 1 is subtracted from the operation time S1. In addition, since the operation time S1 is thought to be short when the supply air pressure Pspv is high, the second corrected value 2 is added to the operation time S. The operation time S1 corrected by the operation time correction portion 24 is sent to the setting/operating device size acquisition portion 25 as an operation time S1.

(29) The setting/operating device size acquisition portion acquires the size of the setting/operating device corresponding to the operation time S1 corrected by the operation time correction portion 24 from the setting/operating device size/operation time table TB stored in the setting/operating device size/operation time storing portion 17. In this case, since the operation time S1 is corrected by the operation time correction portion using the first corrected value 1 and the second corrected value 2, the correct size of the setting/operating device is acquired. The size of the setting/operating device acquired by the setting/operating device size acquisition portion 25 is sent to the control parameter selecting portion 26.

(30) The control parameter selecting portion 26 receives the size of the setting/operating device acquired by the setting/operating device size acquisition portion 25 and the friction F measured by the sliding resistance measurement portion 21 and selects the control parameters corresponding to the received size of the setting/operating device and the hysteresis level (HYS) to which the received friction F belongs from the control parameter table TA stored in the control parameter storing portion 16. The control parameters selected by the control parameter selecting portion 26 are sent to the control parameter setting portion 27.

(31) When receiving the control parameters from the parameter selecting portion 26, the control parameter setting portion 27 sets these control parameters as the control parameters used to control the opening of the regulating valve 2. Since the correct size of the setting/operating device is acquired by the setting/operating device size acquisition portion 25, the control parameters are set as an appropriate control pattern. As described above, according to the example, even when the operation time S of the setting/operating device 2a changes due to the supply air pressure Ps or the friction F, the optimum control parameters are selected and set.

(32) Although the invention has been described above with reference to an example, the invention is not limited to the above example. Various changes understandable to those skilled in the art can be made to the structure and details of the invention within the technical spirit of the invention. In addition, examples can be practiced in any combination without occurrence of a contradiction.