Stick-slip detection system and method

Abstract

To easily reflect knowledge of an expert with respect to a diagnosis object such a valve.SOLUTION: A stick-slip detection system comprises: an operation data accumulation unit 1 that accumulates a stick-slip index being a ratio of a first state quantity which is based on a valve stem displacement of a diagnosis-object valve and a second state quantity which is based on the displacement; an abnormality diagnosis unit 3 that determines whether a stick-slip phenomenon occurs in the diagnosis object on the basis of the stick-slip index; and a diagnosis operation control unit 42 that causes the abnormality diagnosis unit 3 to stop a determination operation when detecting a step-like change in a control command value at an intermediate opening of the diagnosis-object valve.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a stick-slip detection system and method for detecting stick-slip in a diagnosis target such as a valve, and more particularly to a technique for suppressing erroneous detection of stick-slip. [Background technology]

[0002] Valve stick-slip is a phenomenon in which the valve stem repeatedly stops (sticks) and slides (slips). One method for detecting stick-slip is disclosed in Patent Document 1. In the method disclosed in Patent Document 1, the valve stem displacement x i The average value X of the absolute value of the valve stem speed and the square root Y of the root mean square of the valve stem speed are calculated using equations (1) and (2) (N is the number of displacement data used to calculate the state quantity), and the value SSpv is calculated by dividing Y by X.

[0003]

number

[0004] The SSpv has the characteristic that it increases as the stick-slip phenomenon of the valve increases. In the method disclosed in Patent Document 1, when the stick-slip indicator SSpv is equal to or greater than a threshold value, it is determined that stick-slip has occurred. However, with the method disclosed in Patent Document 1, even if no abnormality has occurred in the valve, when the control command value for the valve stem displacement itself changes significantly, the behavior of the measured value of the valve stem displacement may become similar to that of a stick-slip state, and the valve may be erroneously determined to be in a stick-slip state.

[0005] Therefore, a method for suppressing erroneous detection of stick-slip has been proposed (see Patent Document 2). In the method disclosed in Patent Document 2, the average value X of the absolute value of the valve stem speed and the square root Y of the root mean square of not only the measured value of the valve stem displacement but also the control command value of the valve stem displacement are calculated using equations (1) and (2), and a value SSsp is calculated by dividing Y by X. Then, only when the stick-slip index SSpv of the measured value of the valve stem displacement and the stick-slip index SSsp of the control command value satisfy equation (3), it is determined whether or not the stick-slip phenomenon has occurred, thereby suppressing erroneous detection of stick-slip. SSpv>SSsp ····(3)

[0006] Furthermore, with respect to the above-described method for suppressing erroneous stick-slip detection, a method has been proposed in which, rather than making a uniform judgment based on SSpv and SSsp, the range of SSpv for judgment is set by introducing setting parameters α and β into equation (3) as in equation (4) (see Patent Document 3). SSpv>α SSsp+β (4)

[0007] As described above, it is possible to set the range for judgment using the setting parameters α and β in equation (4). However, because the stick-slip indicators SSpv and SSsp are values ​​obtained after complex calculations, it is not easy to reflect the knowledge of experts on the valve in equation (4), such as excluding data when a certain specific operation is performed from the judgment. For this reason, there is a demand for a method of suppressing erroneous stick-slip detection that can easily reflect the knowledge of experts. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 3254624 Public Relations [Patent Document 2] Patent No. 5571346 Public Relations [Patent Document 3] Patent No. 5824333 Public Relations Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been made to solve the above-mentioned problems, and has an object to provide a stick-slip detection system and method that are capable of easily reflecting the knowledge of experts on diagnostic targets such as valves. [Means for solving the problem]

[0010] The stick-slip detection system of the present invention includes an accumulation unit configured to accumulate a stick-slip index, which is a ratio between a first state quantity based on the displacement of a movable part having a contact-sliding part in a diagnosis object, and a second state quantity based on the displacement, an abnormality diagnosis unit configured to determine whether or not a stick-slip phenomenon is occurring in the diagnosis object based on the stick-slip index, and a diagnosis operation control unit configured to stop the determination operation of the abnormality diagnosis unit when a step change in a signal for controlling the position of the movable part is detected. The diagnostic operation control unit stops the determination operation of the abnormality diagnosing unit when the movable part moves to an upper limit position, when the movable part moves to a lower limit position, when the movable part starts to move from the upper limit position in a direction toward the lower limit position, or when the movable part starts to move from the lower limit position in a direction toward the upper limit position. It is characterized by 。

[0011] Also In one configuration example of the stick-slip detection system of the present invention, the diagnosis target is a valve, the movable part is a valve stem, and the system further comprises a full open / close determination unit configured to determine whether the movable part moves to an upper limit position, when the movable part moves to a lower limit position, when the movable part starts to move from the upper limit position in a direction toward the lower limit position, or when the movable part starts to move from the lower limit position in a direction toward the upper limit position, based on a control signal output by a positioner that controls an opening of the valve to an electro-pneumatic converter. Moreover, one configuration example of the stick-slip detection system of the present invention is characterized in that it further includes a full open / close determination unit configured to determine, on the basis of a control command value for controlling the position of the movable part, whether the movable part moves to an upper limit position, the movable part moves to a lower limit position, the movable part starts to move from the upper limit position in the direction toward the lower limit position, or the movable part starts to move from the lower limit position in the direction toward the upper limit position.

[0012] Moreover, one configuration example of the stick-slip detection system of the present invention is characterized in that it further comprises a stick-slip indicator calculation unit configured to calculate the stick-slip indicator. Moreover, in one configuration example of the stick-slip detection system of the present invention, the first state quantity is an average of absolute values ​​of first-order difference values ​​of the displacement of the movable part, and the second state quantity is a square root of the mean square of the first-order difference values ​​of the displacement of the movable part.

[0013] Moreover, a stick-slip detection method of the present invention includes a first step of accumulating a stick-slip index, which is a ratio between a first state quantity based on a displacement of a movable part having a contact-sliding part in a diagnosis target, and a second state quantity based on the displacement, a second step of judging whether or not the stick-slip phenomenon is occurring in the diagnosis target based on the stick-slip index, and a third step of stopping the judgment operation of the second step when a step change in a signal for controlling the position of the movable part is detected. the third step includes a step of stopping the determination operation of the second step when the movable part moves to an upper limit position, when the movable part moves to a lower limit position, when the movable part starts to move from the upper limit position in a direction toward the lower limit position, or when the movable part starts to move from the lower limit position in a direction toward the upper limit position. It is characterized by 。

[0014] AlsoIn one configuration example of the stick-slip detection method of the present invention, the diagnosis target is a valve, the movable part is a valve stem, and the third step includes a step of determining whether the movable part moves to an upper limit position, the movable part moves to a lower limit position, the movable part starts to move from the upper limit position in a direction toward the lower limit position, or the movable part starts to move from the lower limit position in a direction toward the upper limit position, based on a control signal output to an electro-pneumatic converter by a positioner that controls an opening of the valve. Moreover, in one configuration example of the stick-slip detection method of the present invention, the third step is characterized by including a step of determining, on the basis of a control command value for controlling a position of the movable part, whether the movable part moves to an upper limit position, the movable part moves to a lower limit position, the movable part starts to move from the upper limit position in a direction toward the lower limit position, or the movable part starts to move from the lower limit position in a direction toward the upper limit position.

[0015] Moreover, one configuration example of the stick-slip detection method of the present invention is characterized in that it further includes a fourth step of calculating the stick-slip indicator. Moreover, in one configuration example of the stick-slip detection method of the present invention, the first state quantity is an average of absolute values ​​of first-order difference values ​​of the displacement of the movable part, and the second state quantity is a square root of the mean square of the first-order difference values ​​of the displacement of the movable part. Effect of the Invention

[0016] According to the present invention, the knowledge of experts on the diagnosis target can be easily reflected in the stick-slip detection method. Also, the present invention makes it possible to exclude data that corresponds to the aging of the diagnosis target caused by long-term use, and enables comparison and judgment using the same standard over the long term. [Brief description of the drawings]

[0017] [Figure 1]FIG. 1 is a block diagram showing a configuration of a stick-slip detection system according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a flowchart illustrating the operation of the stick-slip detection system according to the embodiment of the present invention. [Diagram 3] FIG. 3 is a flowchart illustrating the operation of the stick-slip detection system according to an embodiment of the present invention. [Figure 4] FIG. 4 is a diagram showing an example of a control command value, a measured valve opening, and a control signal when the valve is in a fully closed operation and when it starts to open from a fully closed state. [Diagram 5] FIG. 5 is a diagram showing an example of a control command value, a measured valve opening, and a control signal when the valve is fully open and when it starts to close from a fully open state. [Figure 6] FIG. 6 is a diagram illustrating the determination operation of the change amount determination unit of the stick-slip detection system according to the embodiment of the present invention. [Figure 7] FIG. 7 is a diagram showing an example in which the control command value changes stepwise when the valve is at an intermediate opening. [Figure 8] FIG. 8 is a diagram showing the relationship between the amount of change in the control command value and the stick-slip index when the control command value changes stepwise at an intermediate valve opening. [Figure 9] FIG. 9 is a block diagram showing an example of the configuration of a computer that realizes the stick-slip detection system according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] [Principle of the invention] When determining whether or not stick-slip is occurring in a valve, experienced maintenance personnel have the knowledge that they often make an erroneous judgment when the control command value itself changes significantly. A significant change in the control command value can be confirmed from a measurement value. Based on the knowledge of maintenance personnel, the present invention presents a method for determining whether or not stick-slip is occurring, after removing data that may cause an erroneous judgment of the stick-slip phenomenon, based on information about the amount of change in the control command value.

[0019] Examples of data with a large change in the control command value that may cause an erroneous determination of the stick-slip phenomenon include data when the valve is fully open to the fully open position, when the valve is fully closed to the fully closed position, when the valve starts to close from the fully open state, and when the valve starts to open from the fully closed state. At these times, the control command value changes in a stepwise manner, so the displacement of the valve stem also changes in a stepwise manner, and the stick-slip indicator SSpv is calculated to have a large value. The fully open operation, the fully closed operation, when the valve starts to close from the fully open state, and when the valve starts to open from the fully closed state can be detected by using the control amount output to the electro-pneumatic converter by a positioner installed in the valve. Therefore, if the range in which the stick-slip indicator SSpv is calculated includes these times, the target stick-slip indicator SSpv is excluded from the determination of stick-slip.

[0020] Even at an intermediate opening, a change in the control command value can cause a step-like change in the displacement of the valve stem, resulting in a large calculated value for the stick-slip index SSpv. Step-like changes at an intermediate opening are detected using the amount of change in the control command value in a small section. If a small section with an amount of change exceeding a set threshold is included within the calculation section of the stick-slip index SSpv, the target stick-slip index SSpv is excluded from the judgment. In addition, the threshold value set here is a value for the control command value whose change can be confirmed visually, so that it is easy to set a threshold value that reflects the operating status of the valve. With the above-described method, a method for suppressing erroneous stick-slip detection that can easily reflect valve knowledge has been achieved.

[0021] [Example] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings, in which: Fig. 1 is a block diagram showing the configuration of a stick-slip detection system according to an embodiment of the present invention. The stick-slip detection system includes an operation data storage unit 1 that stores data of a diagnosis target (e.g., a valve) having a movable part (e.g., a valve stem) with a contact sliding part, a stick-slip index calculation unit 2 that calculates a stick-slip index which is a ratio between a first state quantity based on the displacement of the movable part (valve stem displacement) and a second state quantity based on the displacement of the movable part, an abnormality diagnosis unit 3 that determines whether or not a stick-slip phenomenon is occurring in the diagnosis target based on the stick-slip index stored in the operation data storage unit 1, and an exclusion determination unit 4 that stops the determination operation of the abnormality diagnosis unit 3 when the movable part is in an intermediate position (intermediate opening) between an upper limit position (fully open) and a lower limit position (fully closed) and a control command value for controlling the movable part changes in a step manner, when the movable part moves to the upper limit position, when the movable part moves to the lower limit position, when the movable part starts to move from the upper limit position in the direction toward the lower limit position, or when the movable part starts to move from the lower limit position in the direction toward the upper limit position, a diagnosis result output unit 5 that outputs a diagnosis result, and a data acquisition unit 6 that acquires data of the diagnosis target from an external positioner or the like.

[0022] The exclusion determination section 4 is made up of a full open / close determination section 40, a change amount determination section 41, and a diagnostic operation control section .

[0023] In this embodiment, an example will be described in which the first state quantity calculation unit 7 that calculates the first state quantity, the second state quantity calculation unit 8 that calculates the second state quantity, and the stick-slip index calculation unit 2 that calculates the stick-slip index are provided in a device external to the stick-slip detection system (for example, a positioner that controls the opening of a valve to be diagnosed), but the first state quantity calculation unit 7, the second state quantity calculation unit 8, and the stick-slip index calculation unit 2 may be provided in a device in which the operation data accumulation unit 1, the abnormality diagnosis unit 3, the exclusion determination unit 4, and the diagnosis result output unit 5 are provided.

[0024] 2 and 3 are flow charts illustrating the operation of the stick-slip detection system of this embodiment. The first state quantity calculation unit 7 calculates a valve stem displacement x of the valve to be diagnosed, which is detected by a positioner (not shown). i The average X (equation (1)) of the absolute values ​​of the first-order difference values ​​of is calculated as the first state quantity (Step S100 in FIG. 2).

[0025] The second state quantity calculation unit 8 calculates the valve shaft displacement x i The square root Y (equation (2)) of the first-order difference value of is calculated as the second state quantity (step S101 in FIG. 2). The first state quantity calculation unit 7 and the second state quantity calculation unit 8 calculate the first state quantity X and the second state quantity Y based on the valve shaft displacement x i This is done for each sampling.

[0026] The stick-slip indicator calculation unit 2 calculates a stick-slip indicator SSpv by dividing the second state quantity Y by the first state quantity X at the same time as the second state quantity Y (FIG. 2, step S102). The stick-slip indicator calculation unit 2 performs such a calculation for each sampling of the first state quantity X and the second state quantity Y. SSpv = Y / X (5)

[0027] The data acquisition unit 6 acquires a first state quantity X, a second state quantity Y, a stick-slip index SSpv, a control command value (set opening) SP of the valve opening given to the positioner, and a valve stem displacement x detected by the positioner.i The control data acquisition unit 1 acquires time series data of the control signal MV (EPM drive signal) output by the positioner to the electro-pneumatic converter and stores it in the operation data accumulation unit 1 (step S103 in FIG. 2). As is well known, the positioner outputs a control signal MV corresponding to a control command value SP to the electro-pneumatic converter, the electro-pneumatic converter converts the control signal MV into air pressure and outputs it to the actuator, and the actuator drives the valve. The first state quantity X, the second state quantity Y, the control command value SP, the valve stem displacement x i , time information is added to each data of the control signal MV. The time information may be added on the positioner side or by the data acquisition unit 6.

[0028] On the other hand, the full open / close determination section 40 of the exclusion determination section 4 determines whether the valve to be diagnosed is in a full open operation to the full open position, a full closed operation to the full closed position, starting to close from a fully open state, or starting to open from a fully closed state, based on the data stored in the operation data storage section 1 (step S104 in FIG. 3). Whether the valve to be diagnosed is in a full open operation, a full closed operation, starting to close from a fully open state, or starting to open from a fully closed state can be determined based on the control signal MV output by the positioner to the electro-pneumatic converter. When the valve is in a fully open state or a fully closed state, the control signal MV is a value that swings out to 100% or more or 0% or less. Also, when the valve is in an intermediate opening degree, the control signal MV is a value close to 50%. The full open / close determination section 40 performs the above-mentioned determination for each sampling of the control signal MV.

[0029] When the full open / close determination unit 40 determines that the valve to be diagnosed is in any one of the states of fully open operation, fully closed operation, starting to close from a fully open state, or starting to open from a fully closed state (YES in step S104), the diagnostic operation control unit 42 of the exclusion determination unit 4 instructs the abnormality diagnosis unit 3 not to make a determination using the stick-slip index SSpv whose calculation range includes a time range of any one of these states. In response to the instruction from the diagnostic operation control unit 42, the abnormality diagnosis unit 3 does not perform a determination, which will be described later (step S105 in FIG. 3).

[0030] Figures 4(A) and 4(B) are diagrams showing examples of the control command value SP, the measured valve opening degree PV, and the control signal MV when the valve is fully closed and when it starts to open from a fully closed state. Figures 5(A) and 5(B) are diagrams showing examples of the control command value SP, the measured valve opening degree PV, and the control signal MV when the valve is fully open and when it starts to close from a fully open state.

[0031] Meanwhile, the change amount determination unit 41 of the exclusion determination unit 4 determines whether the control command value SP changes stepwise at an intermediate opening of the valve to be diagnosed (step S106 in FIG. 3). An intermediate opening refers to fully closed and all openings other than fully closed. Whether the control command value SP changes stepwise at an intermediate opening can be determined by whether the amount of change in the control command value SP per certain time (certain number of samplings) exceeds a predetermined change amount threshold.

[0032] 6 is a diagram for explaining the determination operation of the change amount determination unit 41. The change amount determination unit 41 extracts a section of a certain number of samples of continuous data of the control command value SP, and calculates the amount of change in the control command value SP in that section. In this embodiment, the section width is set to 5 samples, and the change amount threshold is set to 10. Also, the difference between the maximum and minimum values ​​of the control command value SP in a section of the certain number of samples is set to the amount of change in that section. Note that in this embodiment, the section width is set to 5 samples, and the change amount threshold is set to 10, but these are merely examples, and it goes without saying that other values ​​may be set.

[0033] 6, the amount of change in the control command value SP in sections t1 and t2 is smaller than the change amount threshold (=10). On the other hand, in section t3, the difference between the maximum value SPmax and the minimum value SPmin of the control command value SP becomes larger than the change amount threshold, so the change amount determination unit 41 determines that the control command value SP is changing in a stepwise manner. The change amount determination unit 41 performs the above determination for each sampling of the control command value SP. Although the amount of change in the control command value SP is defined above, the calculation of the amount of change can be changed to another calculation method (for example, the sum of the SP differences for each sample for five samples).

[0034] The change amount threshold is a value for the control command value SP whose change can be visually confirmed, and therefore can be easily set to reflect the operating status of the valve, compared to the setting parameters α and β of the conventional technology.

[0035] When the change amount determination unit 41 determines that the control command value SP is in a state where it changes stepwise at an intermediate opening of the valve to be diagnosed (YES in step S106), the diagnostic operation control unit 42 of the exclusion determination unit 4 instructs the abnormality diagnosing unit 3 not to make a determination using the stick-slip index SSpv whose calculation range includes the time range of this state. In response to the instruction from the diagnostic operation control unit 42, the abnormality diagnosing unit 3 does not perform a determination, which will be described later (step S105 in FIG. 3).

[0036] Fig. 7 is a diagram showing an example in which the control command value SP changes stepwise when the valve is at an intermediate opening. Fig. 8 is a diagram showing the relationship between the amount of change in the control command value SP and the stick-slip indicator SSpv when the control command value SP changes stepwise as in the section shown in Fig. 7. The point indicated by 700 in Fig. 8 is the value corresponding to the section shown in Fig. 7.

[0037] Next, the abnormality diagnosis unit 3 performs an abnormality diagnosis on the valve to be diagnosed by comparing the stick-slip index SSpv calculated by the stick-slip index calculation unit 2 with a predetermined index threshold Th (Step S107 in FIG. 3). When the stick-slip index SSpv is larger than the index threshold Th, the abnormality diagnosis unit 3 determines that the stick-slip phenomenon is occurring in the valve to be diagnosed, and when the stick-slip index SSpv is equal to or smaller than the index threshold Th, it determines that the stick-slip phenomenon is not occurring in the valve to be diagnosed. The abnormality diagnosis unit 3 performs such a determination for each sampling of the stick-slip index SSpv.

[0038] In this embodiment, the abnormality diagnosing unit 3 performs abnormality diagnosis of the valve to be diagnosed by comparing the stick-slip index SSpv with the index threshold value Th, but the present invention is not limited to this. It is also possible to calculate another index from the stick-slip index SSpv and perform abnormality diagnosis of the valve on the basis of this index.

[0039] The diagnosis result output unit 5 outputs the diagnosis result of the abnormality diagnosis unit 3 (Step S108 in FIG. 3). The output method may be to display the diagnosis result or to transmit information indicating the diagnosis result to the outside.

[0040] As described above, the abnormality diagnosis unit 3 stops the determination operation when instructed by the diagnosis operation control unit 42 of the exclusion determination unit 4. The abnormality diagnosis unit 3 calculates the N valve stem displacements x i When the time (the calculation range of the stick-slip indicator SSpv) includes at least a part of a time when the valve is fully opening, fully closing, starting to close from a fully open state, or starting to open from a fully closed state, the abnormality diagnosing unit 3 stops the determining operation in response to an instruction from the diagnosing operation control unit 42. Similarly, when the calculation range of the stick-slip indicator SSpv includes at least a part of a time in a section where the amount of change in the control command value SP exceeds the change amount threshold, the abnormality diagnosing unit 3 stops the determining operation in response to an instruction from the diagnosing operation control unit 42.

[0041] In this way, in this embodiment, the knowledge of valve experts can be easily reflected in the stick-slip detection method. Also, in this embodiment, the index threshold and the change amount threshold can be flexibly changed, so it is possible to exclude data that corresponds to aging caused by long-term valve use, and it is possible to make comparisons and judgments using the same standards over the long term.

[0042] The full open / close determination unit 40 may determine, based on the control command value SP, whether the valve to be diagnosed is in a fully open operation, a fully closed operation, starting to close from a fully open state, or starting to open from a fully closed state.

[0043] The operation data storage unit 1, the abnormality diagnosis unit 3, the exclusion determination unit 4, the diagnosis result output unit 5, and the data acquisition unit 6 described in this embodiment can be realized by a computer equipped with a CPU (Central Processing Unit), a storage device, and an interface, and a program that controls these hardware resources. An example of the configuration of this computer is shown in FIG.

[0044] The computer includes a CPU 200, a storage device 201, and an interface device (I / F) 202. The I / F 202 is connected to the hardware of the diagnosis result output unit 5, a positioner, etc. A program for implementing the stick-slip detection method of the present invention is stored in the storage device 201. The CPU 200 executes the processing described in this embodiment in accordance with the program stored in the storage device 201.

[0045] As described above, the first state quantity calculation unit 7, the second state quantity calculation unit 8, and the stick-slip index calculation unit 2 may be realized by the same computer as the driving data accumulation unit 1, the abnormality diagnosis unit 3, the exclusion determination unit 4, the diagnosis result output unit 5, and the data acquisition unit 6, or may be realized by a different computer (for example, a microcomputer of a positioner). [Industrial Applicability]

[0046] The present invention can be applied to a technique for detecting stick-slip of a valve. [Explanation of symbols]

[0047] 1...operation data accumulation unit, 2...stick-slip index calculation unit, 3...abnormality diagnosis unit, 4...exclusion determination unit, 5...diagnosis result output unit, 6...data acquisition unit, 7...first state quantity calculation unit, 8...second state quantity calculation unit, 40...full open / close determination unit, 41...change amount determination unit, 42...diagnosis operation control unit.

Claims

1. an accumulation unit configured to accumulate a stick-slip indicator, the stick-slip indicator being a ratio between a first state quantity based on a displacement of a movable part having a contact-sliding part in a diagnosis target, and a second state quantity based on the displacement; an abnormality diagnosis unit configured to determine whether or not a stick-slip phenomenon is occurring in the diagnosis target based on the stick-slip index; a diagnostic operation control unit configured to stop a determination operation of the abnormality diagnosing unit when a step change in a signal for controlling a position of the movable unit is detected, the diagnostic operation control unit stops the determination operation of the abnormality diagnosing unit when the movable part moves to an upper limit position, when the movable part moves to a lower limit position, when the movable part starts to move from the upper limit position in a direction toward the lower limit position, or when the movable part starts to move from the lower limit position in a direction toward the upper limit position.

2. 2. The stick-slip detection system according to claim 1, the diagnostic target is a valve, the movable part is a valve stem, a full open / close determination unit configured to determine whether the movable part moves to an upper limit position, when the movable part moves to a lower limit position, when the movable part starts to move from the upper limit position in a direction toward the lower limit position, or when the movable part starts to move from the lower limit position in a direction toward the upper limit position, based on a control signal output by a positioner that controls an opening of the valve to an electro-pneumatic converter.

3. 2. The stick-slip detection system according to claim 1, a full open / close determination unit configured to determine, based on a control command value for controlling a position of the movable part, whether the movable part moves to an upper limit position, the movable part moves to a lower limit position, the movable part starts to move from the upper limit position in a direction toward the lower limit position, or the movable part starts to move from the lower limit position in a direction toward the upper limit position.

4. The stick-slip detection system according to any one of claims 1 to 3, 13. A stick-slip detection system, comprising: a stick-slip indicator calculation unit configured to calculate the stick-slip indicator.

5. 5. The stick-slip detection system according to claim 1, the first state quantity is an average of absolute values ​​of first-order difference values ​​of the displacement of the movable part, a second state quantity being a root mean square of a first-order difference value of a displacement of the movable part;

6. a first step of accumulating a stick-slip indicator, the stick-slip indicator being a ratio between a first state quantity based on a displacement of a movable part having a contact-sliding part in a diagnosis target, and a second state quantity based on the displacement; a second step of determining whether or not the stick-slip phenomenon is occurring in the diagnostic object based on the stick-slip indicator; a third step of stopping the determination operation of the second step when a step change in a signal for controlling a position of the movable part is detected, a third step of stopping the determination operation of the second step when the movable part moves to an upper limit position, when the movable part moves to a lower limit position, when the movable part starts to move from the upper limit position in a direction toward the lower limit position, or when the movable part starts to move from the lower limit position in a direction toward the upper limit position.

7. 7. The stick-slip detection method according to claim 6, the diagnostic target is a valve, the movable part is a valve stem, the third step includes a step of determining whether the movable part moves to an upper limit position, the movable part moves to a lower limit position, the movable part starts to move from the upper limit position in a direction toward the lower limit position, or the movable part starts to move from the lower limit position in a direction toward the upper limit position, based on a control signal output to an electro-pneumatic converter by a positioner that controls an opening of the valve.

8. 7. The stick-slip detection method according to claim 6, a third step of determining, based on a control command value for controlling a position of the movable part, whether the movable part moves to an upper limit position, the movable part moves to a lower limit position, the movable part starts to move from the upper limit position in a direction toward the lower limit position, or the movable part starts to move from the lower limit position in a direction toward the upper limit position.

9. The stick-slip detection method according to any one of claims 6 to 8, 4. The stick-slip detection method according to claim 1, further comprising a fourth step of calculating the stick-slip indicator.

10. The stick-slip detection method according to any one of claims 6 to 9, the first state quantity is an average of absolute values ​​of first-order difference values ​​of the displacement of the movable part, a second state quantity being a root mean square of a first-order difference value of the displacement of the movable part;

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