Flow control system

Abstract

To automatically set a low flow cut threshold for a flow rate control device.SOLUTION: A flow rate control system includes: a data retaining unit 16 that stores data on a flow rate measured value of the flow rate control device 1; a communicating unit 40 that reads the data in the data retaining unit 16; and a threshold setting unit 43 that sets, based on the fluctuation width around a zero point of the flow rate measured value read by the communicating unit 40, a low flow cut threshold for the flow rate control device 1.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This invention relates to a flow control system that can automatically configure the settings of a flow control device. [Background technology]

[0002] Generally, flow control devices (mass flow controllers) are used to control the flow rate of a fluid. A flow control device controls the flow rate by comparing the fluid flow rate detected by a flow sensor with a set flow rate, and then outputting a drive current to a valve based on the result. In such flow control devices, for example, the PID constants of the controller that controls the valve are automatically set to improve responsiveness in the low flow rate range (see Patent Document 1), or the controller gain is automatically set for accurate control of the valve (see Patent Document 2).

[0003] However, conventional technologies did not automatically set the low-flow cut threshold of the flow control device or the time constant of the PV filter that smooths and outputs the instantaneous flow rate (PV) measured by the flow sensor. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-149502 [Patent Document 2] Special Publication No. 2018-528550 [Overview of the project] [Problems that the invention aims to solve]

[0005] The present invention was made to solve the above problems and aims to provide a flow control system that can automatically set the low-flow cut threshold of a flow control device. Furthermore, the present invention aims to provide a flow control system that can automatically set the time constant of the PV filter of a flow control device. [Means for solving the problem]

[0006] The flow control system of the present invention is characterized by comprising: a data holding unit configured to store data of flow measurement values ​​of a flow control device; a communication unit configured to read data from the data holding unit; and a threshold setting unit configured to set a low flow cut threshold of the flow control device based on the fluctuation width near the zero point of the flow measurement value read by the communication unit. Furthermore, the flow rate control system of the present invention is characterized by comprising: a data holding unit configured to store flow rate measurement data of a flow rate control device; a PV filter configured to smooth and output the flow rate measurement data; a communication unit configured to read the data from the data holding unit; and a time constant setting unit configured to set the time constant of the PV filter based on the fluctuation width near the zero point of the flow rate measurement data read by the communication unit.

[0007] Furthermore, in one example of the flow rate control system of the present invention, the communication unit is characterized in that it reads data from the data holding unit when the zero point of the flow rate control device is adjusted. Furthermore, one example of the flow rate control system of the present invention is characterized by further comprising a data recording unit configured to record the flow rate measurement data in the data holding unit. Furthermore, one example of the flow rate control system of the present invention further includes a flow rate control unit configured to control the opening degree of a valve by calculating an operating amount such that the flow rate measurement value and the flow rate setting value match and outputting it to a valve installed in the piping of the flow rate control device, and the data recording unit is characterized in that it records the data of the operating amount in addition to the flow rate measurement value in the data holding unit.

[0008] Furthermore, in one example of the flow rate control system of the present invention, the data recording unit is characterized in that it starts recording the flow rate measurement value and the manipulated amount to the data holding unit when the user gives an instruction to start recording, when the user gives an instruction to start flow rate control, when the user gives an instruction to change the flow rate setting value, or when the user gives an instruction to perform zero point adjustment. Furthermore, in one example configuration of the flow rate control system of the present invention, the data recording unit is characterized in that, when the user gives an instruction to stop recording, it stops recording the flow rate measurement value and the manipulated amount to the data holding unit. Furthermore, in one example of the flow rate control system of the present invention, the data recording unit is characterized in that when it has recorded a specific number of data points from the start of recording, it stops recording the flow rate measurement value and the manipulated amount to the data holding unit. Furthermore, one example of the flow rate control system of the present invention further includes an abnormality determination unit configured to determine whether or not there is an abnormality in the flow rate control device, and the data recording unit is characterized in that when the abnormality determination unit determines that there is an abnormality in the flow rate control device, it stops recording the flow rate measurement value and the manipulated amount to the data holding unit. [Effects of the Invention]

[0009] According to the present invention, by providing a data holding unit, a communication unit, and a threshold setting unit, a low-flow cut threshold can be automatically set so that there is virtually no possibility of a non-zero flow rate measurement value being erroneously output due to noise or the like when the flow rate is zero.

[0010] Furthermore, in this invention, by providing a data holding unit, a communication unit, and a time constant setting unit, the time constant of the PV filter can be automatically set to an appropriate value. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is an external view of a flow rate control system according to the first embodiment of the present invention. [Figure 2]FIG. 2 is a block diagram showing the configuration of a flow rate control system according to a first embodiment of the present invention. [Figure 3] FIG. 3 is a flowchart for explaining the operation of a flow rate control device according to a first embodiment of the present invention. [Figure 4] FIG. 4 is a flowchart for explaining the operation of a terminal according to a first embodiment of the present invention. [Figure 5] FIG. 5 is a diagram showing an example of data display of a flow rate measurement value and an operation amount. [Figure 6] FIG. 6 is a diagram showing another example of data display of a flow rate measurement value and an operation amount. [Figure 7] FIG. 7 is a block diagram showing the configuration of a flow rate control system according to a second embodiment of the present invention. [Figure 8] FIG. 8 is a flowchart for explaining the operation of a flow rate control device according to a second embodiment of the present invention. [Figure 9] FIG. 9 is a block diagram showing the configuration of a flow rate control system according to a third embodiment of the present invention. [Figure 10] FIG. 10 is a flowchart for explaining the operation of a flow rate control device according to a third embodiment of the present invention. [Figure 11] FIG. 11 is a block diagram showing the configuration of a flow rate control system according to a fourth embodiment of the present invention. [Figure 12] FIG. 12 is a flowchart for explaining the operation of a flow rate control device according to a fourth embodiment of the present invention. [Figure 13] FIG. 13 is a block diagram showing the configuration of a flow rate control system according to a fifth embodiment of the present invention. [Figure 14] FIG. 14 is a flowchart for explaining the operation of a flow rate control device according to a fifth embodiment of the present invention. [Figure 15] FIG. 15 is a block diagram showing a configuration example of a computer that realizes a flow rate control device and a terminal according to the first to fifth embodiments of the present invention.

MODE FOR CARRYING OUT THE INVENTION

[0012] [First Embodiment] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Figure 1 is an external view of a flow control system according to a first embodiment of the present invention. The flow control system consists of a flow control device 1 and a terminal 2 connected to the flow control device 1 via a communication cable 3.

[0013] Figure 2 is a block diagram showing the configuration of the flow control system according to this embodiment. The flow control device 1 includes a pipe 10 through which the fluid to be flow controlled flows, a sensor package 11 installed in the pipe 10, a valve 12 installed in the pipe 10, a flow measurement unit 14 that converts the output value of a flow sensor 13 mounted on the sensor package 11 into a flow measurement value PV, a flow control unit 15 that controls the opening degree of the valve 12 by outputting an operation amount MV to the valve 12 so that the flow measurement value PV and the flow setting value SP match, a data holding unit 16 that stores data of the flow measurement value PV and the operation amount MV, a data recording unit 17 that records data of the flow measurement value PV and the operation amount MV in the data holding unit 16, a PV filter 18 that smooths the flow measurement value PV, a PV output unit 19 that outputs the smoothed flow measurement value PV to the outside, a zero point adjustment unit 20 that calculates a zero point correction value during zero point adjustment, and a communication unit 21 for communicating with the terminal 2.

[0014] In Figure 2, 31 is the inlet opening of the pipe 10, and 32 is the outlet opening of the pipe 10. The fluid (gas) flows into the pipe 10 from opening 31, passes through valve 12, and is discharged from opening 32. The flow sensor 13 is mounted in a sensor package 11 and attached to the pipe 10 so as to be exposed to the fluid to be measured.

[0015] Terminal 2 includes a communication unit 40 for communicating with the flow rate control device 1, a display unit 41 for displaying data, an operation unit 42 for the user to give instructions to Terminal 2, a threshold setting unit 43 for setting a low flow cut threshold of the flow rate control device 1 based on the fluctuation range near the zero point of the flow rate measurement value PV read by the communication unit 40, and a time constant setting unit 44 for setting the time constant of the PV filter 18 based on the fluctuation range near the zero point of the flow rate measurement value PV read by the communication unit 40.

[0016] Figure 3 is a flowchart illustrating the operation of the flow control device 1, and Figure 4 is a flowchart illustrating the operation of terminal 2. The user connects the flow control device 1 and the terminal 2 via the communication cable 3 when setting up or performing maintenance on the flow control device 1.

[0017] The flow sensor 13 of the flow control device 1 outputs a signal with a value corresponding to the flow rate of the fluid flowing through the pipe 10. The flow measurement unit 14 converts the output value of the flow sensor 13 into a flow measurement value Q (Figure 3, step S100). Specifically, if the output value of the flow sensor 13 (actually the value obtained by A / D conversion of the output of the flow sensor 13) is X, the conversion formula for the flow measurement value Q is as shown in equation (1). Q = AX + C ... (1)

[0018] In equation (1), A and C are known characteristic coefficients for each individual unit, determined at the time of shipment of the flow control device 1. The flow measurement unit 14 then measures the flow offset value OFS at the time of zero-point adjustment performed at the time of shipment of the flow control device 1. ref The value obtained by subtracting this from the flow rate measurement value Q is output as the corrected flow rate measurement value PV. PV = Q - OFS ref ...(2)

[0019] Flow rate offset value OFS refThis is a representative value of the flow rate measurement value Q when the flow rate is set to zero at the time of shipment. This representative value is, for example, the average value of the flow rate measurement value Q. Furthermore, when the corrected flow rate measurement value PV is within a predetermined low flow cut threshold C, the flow rate measurement unit 14 performs a low flow cut process to set the flow rate measurement value PV to zero and outputs it. The low flow cut threshold C at this time is set to an initial value.

[0020] The flow control unit 15 of the flow control device 1 takes the flow measurement value PV and the flow setting value SP output from the flow measurement unit 14 as input and calculates the manipulated variable MV by PID control calculation so that the flow measurement value PV and the flow setting value SP match (Figure 3, step S101). The flow control unit 15 outputs the calculated manipulated variable MV to the valve 12 and controls the flow rate of the fluid flowing through the piping 10 by adjusting the opening degree of the valve 12 (Figure 3, step S102).

[0021] The data recording unit 17 of the flow rate control device 1 records the flow rate measurement value PV output from the flow rate measurement unit 14 and the manipulated variable MV output from the flow rate control unit 15 in the data holding unit 16 (Figure 3, step S103).

[0022] The data storage unit 16 has a capacity to store a specific number of data points (for example, 1000 points) of flow rate measurement value PV and manipulated variable MV. The data recording unit 17 stores data sequentially from the first address of the data storage unit 16, and stores data up to the last address of the data storage unit 16. When it has finished storing the specific number of data points of flow rate measurement value PV and manipulated variable MV, it updates the data by overwriting the oldest stored data in order.

[0023] Next, the PV filter 18 of the flow rate control device 1 smooths the flow rate measurement value PV output from the flow rate measurement unit 14 (Figure 3, step S104). For example, the smoothing process can be a first-order lag low-pass filter. PV' = PV / (1+K) t s) ···(3)

[0024] In equation (3), PV' is the smoothed flow rate measurement value PV, K t is the time constant, and s is the Laplace operator. The smoothed flow rate measurement value PV' is output from the PV output unit 19 to the outside of the flow rate control device 1 (Figure 3, step S105).

[0025] When the communication unit 21 of the flow rate control device 1 receives a data read request from the terminal 2 (YES in step S106 of Figure 3), it first copies the flow rate measurement value PV and manipulated variable MV data recorded in the data holding unit 16 to an internal communication buffer (not shown) (step S107 of Figure 3), and then transfers the data stored in the communication buffer to the terminal 2 (step S108 of Figure 3).

[0026] Furthermore, when the communication unit 21 receives a zero-point adjustment instruction signal transmitted from the terminal 2 (YES in step S109 of Figure 3), as described later, it forwards this instruction signal to the zero-point adjustment unit 20.

[0027] The zero-point adjustment unit 20 calculates a representative value of the flow rate measurement value PV during a predetermined zero-point adjustment time (e.g., 3 seconds) from the start of adjustment after receiving an instruction signal as the zero-point correction value OFS (Figure 3, step S110). The representative value at this time is, for example, the average value of the flow rate measurement value PV. The zero-point adjustment unit 20 sets the zero-point correction value OFS for the flow rate measurement unit 14 (Figure 2, step S111). Thereafter, the flow rate measurement unit 14 calculates the flow rate offset value OFS from the flow rate measurement value Q calculated by equation (1). ref The value obtained by subtracting the zero-point correction value OFS is output as the corrected flow rate measurement value PV. PV = Q - OFS ref -OFS ···(4)

[0028] Also, when the communication unit 21 receives

[0029] the low-flow cut-off threshold C transmitted from the terminal 2 as described later (YES in step S112 of FIG. 3), it transfers this low-flow cut-off threshold C to the flow rate measurement unit 14. The flow rate measurement unit 14 updates the low-flow cut-off threshold C set in itself with the low-flow cut-off threshold C transferred from the communication unit 21 (step S113 of FIG. 3). Thereafter, the flow rate measurement unit 14 performs low-flow cut-off processing on the flow rate measurement value PV using the updated low-flow cut-off threshold C.

[0030] On the other hand, the communication unit 40 of the terminal 2 makes a data read request to the flow control device 1 (step S200 of FIG. 4). The communication unit 40 may make a read request at regular intervals, or may make a read request in response to an instruction from the user.

[0031] The communication unit 40 receives the data of the flow rate measurement value PV and the manipulated variable MV transferred from the communication unit 21 of the flow control device 1 (step S201 of FIG. 4). The display unit 41 of the terminal 2 displays at least one of the data of the flow rate measurement value PV and the manipulated variable MV received by the communication unit 40 (step S202 of FIG. 4).

[0032] t を受信すると(図3ステップS114においてYES)、この時定数K t をPVフィルタ18に転送することにより、PVフィルタ18に設定されている時定数K t を端末2から受信した時定数K t に更新する(図3ステップS115)。以後、PVフィルタ18は、更新後の時定数K t を用いて式(3)の平滑化処理を行う。流量制御装置1は、以上のような図3の処理を制御周期(例えば1.5ms)毎に行う。 さらに、通信部21は、後述のように端末2から送信された時定数K を受信すると(図3ステップS114においてYES)、この時定数K をPVフィルタ18に転送することにより、PVフィルタ18に設定されている時定数K を端末2から受信した時定数K を用いて式(3)の平滑化処理を行う。流量制御装置1は、以上のような図3の処理を制御周期(例えば1.5ms)毎に行う。 t t を用いて式(3)の平滑化処理を行う。流量制御装置1は、以上のような図3の処理を制御周期(例えば1.5ms)毎に行う。 通信部40は、流量制御装置1の通信部21から転送された流量計測値PVと操作量MVのデータを受信する(図4ステップS201)。 端末2の表示部41は、通信部40が受信した流量計測値PVと操作量MVのデータのうち少なくとも一方を表示する(図4ステップS202)。Figure 5 shows an example of data display for the flow rate measurement value PV and the manipulated variable MV. The example in Figure 5 shows an example of the control response when the flow rate setting value SP is changed from 50%FS to 80%FS. The screen 410 of the display unit 41 displays the flow rate measurement value PV and the manipulated variable MV data in a graph.

[0033] By viewing the changes in the flow rate measurement value PV on a graph, users can reliably detect overshoots in the flow rate measurement value PV (part 411 in Figure 5) that cannot be detected by numerical display alone. In the example in Figure 5, the 98% response of the flow rate measurement value PV to the set value SP, which was changed from 50%FS to 80%FS at time 0, is approximately 100ms.

[0034] According to Figure 5, the time from when the flow rate measurement value PV overshoots during its rise to when it returns to 80% FS is approximately 20 ms. The magnitude of this overshoot varies depending on the individual valve 12. By accurately observing the overshoot, the user can suppress it by taking measures such as tuning the PID constants (proportional gain, integral time, derivative time) of the flow rate control unit 15.

[0035] If the user determines that a change in the PID constant is necessary, they operate the control unit 42 of terminal 2 to input the PID constant to be changed. This allows the PID constant of the flow control unit 15 to be set and changed via the communication unit 40 of terminal 2 and the communication unit 21 of the flow control device 1.

[0036] Furthermore, by viewing the changes in the flow rate measurement value PV on a graph, the user can accurately observe the range and period of fine fluctuations in the flow rate measurement value PV during its settling (part 412 in Figure 5). This allows the user to appropriately determine the PID constants of the flow control unit 15.

[0037] Figure 6 shows another example of data display for the flow rate measurement value PV and the manipulated variable MV. In the example in Figure 6, hunting occurs in the flow rate measurement value PV. When hunting occurs, if the manipulated variable MV also fluctuates with the same period as the flow rate measurement value PV, it can be inferred that the cause is an over-response of valve 12, and countermeasures such as reducing the proportional gain of the flow control unit 15 can be considered. On the other hand, if the oscillation period of the manipulated variable MV does not match the oscillation period of the flow rate measurement value PV, it can be inferred that the cause is fluctuations in upstream pressure due to disturbances or a first-order lag in downstream pressure. In that case, countermeasures such as changing the proportional gain or control period of the flow control unit 15, or reducing the integration time can be considered.

[0038] Next, when performing zero-point adjustment on the flow control device 1, the user closes the valves (not shown) located before and after the flow control device 1 to reduce the fluid flow rate to zero, and then operates the control unit 42 of terminal 2 to instruct the zero-point adjustment to be performed. Alternatively, instead of closing the valve located behind the flow control device 1, the valve 12 of the flow control device 1 may be closed.

[0039] When the communication unit 40 of terminal 2 receives an instruction from the user to perform zero-point adjustment (YES in step S203 of Figure 4), it transmits a zero-point adjustment instruction signal to the flow rate control device 1 (step S204 of Figure 4).

[0040] Next, the communication unit 40 requests the flow rate control device 1 to read data after a predetermined time has elapsed (for example, after a few seconds) since the user has given an instruction to perform zero-point adjustment (Figure 4, step S205). The processing in steps S206 and S207 in Figure 4 is the same as in steps S201 and S202.

[0041] The threshold setting unit 43 of terminal 2 calculates the low-flow cut threshold C of the flow rate control device 1 based on the fluctuation range of the flow rate measurement value PV data received by the communication unit 40 in response to the read request in step S205 (Figure 4, step S208). Specifically, the threshold setting unit 43 calculates the low-flow cut threshold C as shown in equation (5), assuming that σ0 is the standard deviation of the flow rate measurement value PV received by the communication unit 40 when the flow rate is zero. C = α × σ₀···(5)

[0042] The coefficient α is a predetermined positive number; for example, it can be 10, but it goes without saying that other values ​​are also acceptable. Furthermore, if the value calculated in equation (3) is less than, for example, 3σ0+n (where n is a predetermined positive number), a lower bound processing may be performed by setting the low flow cut threshold C to 3σ0+n.

[0043] The threshold setting unit 43 transmits the calculated low-flow cut threshold C to the flow rate control device 1 via the communication unit 40 (Figure 4, step S209). As a result, the low-flow cut threshold C set in the flow rate measurement unit 14 of the flow rate control device 1 as described above is updated.

[0044] Thus, in this embodiment, the low-flow cut threshold C can be automatically set to an appropriate value when zero-point adjustment is performed, and the low-flow cut threshold C can be set so that there is virtually no possibility of a non-zero flow rate measurement value PV being erroneously output due to noise or the like when the flow rate is zero.

[0045] Meanwhile, the time constant setting unit 44 of terminal 2 sets the time constant K of the PV filter 18 of the flow rate control device 1 based on the fluctuation range of the flow rate measurement value PV data received by the communication unit 40 in response to the read request in step S205. t The following is calculated (Figure 4, step S210). The standard deviation of the flow rate measurement value PV received by the communication unit 40 when the flow rate is zero is σ0, and the standard deviation of the flow rate measurement value PV is σ ref The ideal time constant at this time is K. ref Therefore, the time constant K t This can be calculated using equation (6). K t =(σ0 / σ ref ) 2 K ref ...(6)

[0046] Equation (6) is based on the fact that, under ideal conditions where the flow rate measurement PV consists only of white noise, the standard deviation of the flow rate measurement PV is approximately inversely proportional to the square root of the low-pass filter time constant. Time constant K refFor a certain type of flow control device, the standard deviation of the flow rate measurement value PV when the flow rate is zero is σ ref The ideal time constant of the PV filter 18 was determined experimentally under these conditions.

[0047] The time constant setting unit 44 sets the time constant K calculated by equation (6). t This is transmitted to the flow rate control device 1 via the communication unit 40 (Figure 4, step S211). This transmits the time constant K set in the PV filter 18 of the flow rate control device 1 as described above. t It will be updated. Thus, in this embodiment, the time constant K of the PV filter 18 is used when zero-point adjustment is performed. t It can be automatically set to an appropriate value.

[0048] Furthermore, in this embodiment, the flow rate measurement value PV and the manipulated variable MV data are temporarily stored in the data holding unit 16, and the data stored in the data holding unit 16 can be read by the terminal 2. As described above, the control period of the flow rate control device 1 is, for example, 1.5 ms, but the sampling period of serial communication between the flow rate control device 1 and the terminal 2 has limitations in terms of speed due to constraints such as the processing time and transmission time of the respective CPUs (Central Processing Units) of the flow rate control device 1 and the terminal 2. The sampling period for serial communication is usually about 100 ms for the two data points, the flow rate measurement value PV and the manipulated variable MV. Therefore, if data for the flow rate measurement value PV and the manipulated variable MV is to be collected by normal communication, the data can only be collected at a speed slower than the process response of the flow rate control, and it will not be possible to collect enough data to correctly analyze the control phenomenon.

[0049] Therefore, in this embodiment, data is temporarily recorded in the data storage unit 16 during the control cycle of the flow rate control device 1, and the data stored in the data storage unit 16 is read out by the terminal 2. This makes it possible to acquire data with a faster sampling cycle than data acquisition by normal communication, and to obtain data suitable for analyzing control phenomena.

[0050] [Second Example] Next, a second embodiment of the present invention will be described. Figure 7 is a block diagram showing the configuration of the flow rate control system according to this embodiment. The flow rate control system of this embodiment consists of a flow rate control device 1a and a terminal 2.

[0051] The flow control device 1a comprises a pipe 10, a sensor package 11, a valve 12, a flow sensor 13, a flow measurement unit 14, a flow control unit 15, a data recording unit 17a, a PV filter 18, a PV output unit 19, a zero point adjustment unit 20, and a communication unit 21.

[0052] Figure 8 is a flowchart illustrating the operation of the flow rate control device 1a. The processes in steps S100-102 and S104-S115 of Figure 8 are as described in the first embodiment. The data recording unit 17a starts recording the flow rate measurement value PV and the manipulated amount MV to the data holding unit 16 (Figure 8, step S117) when, for example, the user instructs the flow rate control device 1a to start flow rate control, or when the user instructs the user to change the flow rate set value SP, or when the terminal 2 receives an instruction signal to execute zero point adjustment (YES in step S116 of Figure 8). Instructions from the user to the flow rate control device 1a can be made by operating a key provided on the flow rate control device 1a, sending a command from the terminal 2, or inputting a digital input (DI) signal.

[0053] Furthermore, when the data recording unit 17a has recorded a specific number of data points (for example, 1000 points) from the start of recording in step S117 (YES in step S118 in Figure 8), it stops recording to the data holding unit 16 (step S119 in Figure 8). The configuration and operation of terminal 2 are the same as in the first embodiment.

[0054] Thus, in this embodiment, recording of flow rate measurement value PV and manipulated variable MV data is started when flow rate control is initiated, when the flow rate setpoint SP is changed, or when zero point adjustment is performed, and recording can be automatically stopped when a specific number of data points have been recorded from the start of recording. As described above, in the first embodiment, if the number of data points recorded from the start of recording exceeds a specific number, data overwriting occurs, but in this embodiment, overwriting does not occur.

[0055] [Third embodiment] Next, a third embodiment of the present invention will be described. Figure 9 is a block diagram showing the configuration of the flow rate control system according to this embodiment. The flow rate control system of this embodiment consists of a flow rate control device 1b and a terminal 2.

[0056] The flow control device 1b comprises a pipe 10, a sensor package 11, a valve 12, a flow sensor 13, a flow measurement unit 14, a flow control unit 15, a data recording unit 17b, a PV filter 18, a PV output unit 19, a zero point adjustment unit 20, and a communication unit 21.

[0057] Figure 10 is a flowchart illustrating the operation of the flow rate control device 1b. The processes in steps S100-102 and S104-S115 of Figure 10 are as described in the first embodiment. When the user gives an instruction to start data recording, or when the terminal 2 gives an instruction signal to perform zero-point adjustment (YES in step S120 of Figure 10), the data recording unit 17b starts recording the flow rate measurement value PV and the manipulated amount MV to the data holding unit 16 (step S121 of Figure 10). Instructions from the user to the flow rate control device 1b can be given by operating a key provided on the flow rate control device 1b, sending a command from the terminal 2, or inputting a DI signal.

[0058] Furthermore, when the data recording unit 17b has recorded a specific number of data points (for example, 1000 points) from the start of recording in step S121 (YES in step S122 of Figure 10), it stops recording to the data holding unit 16 (step S123 of Figure 10). The configuration and operation of terminal 2 are the same as in the first embodiment.

[0059] Thus, in this embodiment, when the user gives an instruction to start data recording, or when zero-point adjustment is performed, the recording of flow rate measurement value PV and manipulated variable MV data can be started, and recording can be automatically stopped when a specific number of data points have been recorded from the start of recording.

[0060] [Fourth embodiment] Next, a fourth embodiment of the present invention will be described. Figure 11 is a block diagram showing the configuration of the flow rate control system according to this embodiment. The flow rate control system of this embodiment consists of a flow rate control device 1c and a terminal 2.

[0061] The flow control device 1c comprises a pipe 10, a sensor package 11, a valve 12, a flow sensor 13, a flow measurement unit 14, a flow control unit 15, a data recording unit 17c, a PV filter 18, a PV output unit 19, a zero point adjustment unit 20, and a communication unit 21.

[0062] Figure 12 is a flowchart illustrating the operation of the flow rate control device 1c. The processes in steps S100 to S115 of Figure 12 are as described in the first embodiment. When the user instructs the data recording unit 17c to stop recording the flow rate measurement value PV and the manipulated amount MV to the data holding unit 16 (Figure 12, step S125), the data recording unit 17c stops recording the data (Figure 12, step S125). Instructions from the user to the flow rate control device 1c can be made by operating a key provided on the flow rate control device 1c, sending a command from terminal 2, or inputting a DI signal.

[0063] The configuration and operation of terminal 2 are the same as in the first embodiment. Thus, in this embodiment, data is recorded continuously, as in the first embodiment, and recording can be stopped when instructed to stop by the user.

[0064] [Fifth Example] Next, a fifth embodiment of the present invention will be described. Figure 13 is a block diagram showing the configuration of the flow rate control system according to this embodiment. The flow rate control system of this embodiment consists of a flow rate control device 1d and a terminal 2.

[0065] The flow control device 1d includes a pipe 10, a sensor package 11, a valve 12, a flow sensor 13, a flow measurement unit 14, a flow control unit 15, a data recording unit 17d, a PV filter 18, a PV output unit 19, a zero-point adjustment unit 20, a communication unit 21, and an abnormality determination unit 22 that determines whether there is an abnormality in the flow control device 1d.

[0066] Figure 14 is a flowchart illustrating the operation of the flow rate control device 1d. The processes in steps S100 to S115 of Figure 14 are as described in the first embodiment. The abnormality detection unit 22 outputs an alarm when it determines that an abnormality has occurred in the flow rate control device 1d. For example, the abnormality detection unit 22 determines that the system is normal if the flow rate measurement value PV is within the range of SP±β (where β is the allowable range), and determines that it is abnormal and outputs an alarm if the flow rate measurement value PV is outside the range of SP±β. The occurrence of an alarm is notified to the user by a digital output (DO) signal or by the illumination of an LED provided on the flow rate control device 1d.

[0067] When the abnormality determination unit 22 determines that there is an abnormality and outputs an alarm (YES in step S126 of Figure 14), the data recording unit 17d stops recording the flow rate measurement value PV and the manipulated amount MV to the data holding unit 16 (step S127 of Figure 12). The configuration and operation of terminal 2 are the same as in the first embodiment.

[0068] The flow control device is equipped with a function that outputs an alarm if the flow rate cannot be controlled according to the flow rate setpoint SP, and the deviation between the flow rate setpoint SP and the flow rate measured value PV is not zero but exceeds a certain value. It is thought that stopping the recording of the flow rate measured value PV and the manipulated variable MV when such an alarm is output will be helpful in alarm analysis.

[0069] For example, when a user recognizes the occurrence of an alarm due to a change in the state of the DO signal, they operate terminal 2 to request data retrieval from the flow control device 1d. This allows the data of the flow measurement value PV and the manipulated amount MV to be displayed graphically on terminal 2, as shown in the example in Figure 5.

[0070] A user viewing the graph can see, for example, that if the manipulated variable MV increases immediately before an alarm occurs, it indicates that the upstream pressure is decreasing, and because the upstream pressure is insufficient, the set flow rate cannot be maintained, causing valve 12 to gradually open. In this case, it can be determined that a problem such as a gas leak or a drop in the supply pressure of the gas cylinder has occurred upstream.

[0071] The flow rate measurement unit 14, flow rate control unit 15, data recording units 17, 17a to 17d, PV filter 18, zero point adjustment unit 20, communication unit 21, and abnormality detection unit 22 of the flow rate control devices 1, 1a to 1d described in the first to fifth embodiments can be realized by a computer equipped with a CPU, storage device, and interface, and a program that controls these hardware resources. Furthermore, the communication unit 40, threshold setting unit 43, and time constant setting unit 44 of terminal 2 can also be realized by a computer. An example of the configuration of these computers is shown in Figure 15.

[0072] The computer comprises a CPU 100, a storage device 101, and an interface device (I / F) 102. In the case of flow rate control devices 1, 1a to 1d, hardware such as a valve 12, a flow sensor 13, a PV output unit 19, and a communication unit 21 are connected to the I / F 102. In the case of terminal 2, hardware such as an operation unit 42, a display unit 41, and a communication unit 40 are connected to the I / F 102. In such a computer, the program for realizing the flow rate control method of the present invention is stored in the storage device 101. The CPU 100 of each device executes the processing described in the first to fifth embodiments according to the program stored in the storage device 101. [Industrial applicability]

[0073] This invention can be applied to techniques for setting a flow control device from an external source. [Explanation of Symbols]

[0074] 1, 1a~1d...Flow control device, 2...Terminal, 3...Communication cable, 10...Piping, 11...Sensor package, 12...Valve, 13...Flow sensor, 14...Flow measurement unit, 15...Flow control unit, 16...Data holding unit, 17, 17a~17d...Data recording unit, 18...PV filter, 19...PV output unit, 20...Zero point adjustment unit, 21, 40...Communication unit, 22...Anomaly detection unit, 41...Display unit, 42...Operation unit, 43...Threshold setting unit, 44...Time constant setting unit.

Claims

1. A data holding unit configured to store flow rate measurement data from a flow control device, A PV filter configured to smooth and output the aforementioned flow rate measurement values, A communication unit configured to read data from the data storage unit, A flow rate control system characterized by comprising a time constant setting unit configured to set the time constant of the PV filter based on the fluctuation range near the zero point of the flow rate measurement value read out by the communication unit.

2. In the flow rate control system according to Claim 1, A flow rate control system characterized by comprising a threshold setting unit configured to set a low flow cut threshold of the flow rate control device based on the fluctuation range near the zero point of the flow rate measurement value read out by the communication unit.

3. In the flow control system according to claim 1 or 2, The flow rate control system is characterized in that the communication unit reads data from the data holding unit when the zero point of the flow rate control device is adjusted.

4. In the flow control system according to claim 1 or 2, A flow rate control system further comprising a data recording unit configured to record the flow rate measurement data in the data holding unit.

5. In the flow rate control system according to claim 4, The flow control unit is further configured to control the opening degree of a valve by calculating an operating amount such that the measured flow rate value and the set flow rate value match and outputting this amount to a valve installed in the piping of the flow control device. The flow rate control system is characterized in that the data recording unit records the data of the manipulated quantity in addition to the flow rate measurement value in the data holding unit.

6. In the flow rate control system according to claim 5, The flow control system is characterized in that the data recording unit starts recording the flow rate measurement value and the manipulated variable to the data holding unit when the user gives an instruction to start recording, when the user gives an instruction to start flow rate control, when the user gives an instruction to change the flow rate setting value, or when the user gives an instruction to perform zero point adjustment.

7. In the flow rate control system according to claim 5, The flow rate control system is characterized in that the data recording unit stops recording the flow rate measurement value and the manipulated amount to the data holding unit when the user gives an instruction to stop recording.

8. In the flow rate control system according to claim 5, The flow rate control system is characterized in that the data recording unit stops recording the flow rate measurement value and the manipulated amount to the data holding unit when it has recorded a specific number of data points from the start of recording.

9. In the flow rate control system according to claim 5, The flow rate control device further comprises an abnormality determination unit configured to determine whether or not there is an abnormality in the flow rate control device, The flow rate control system is characterized in that the data recording unit stops recording the flow rate measurement value and the manipulated amount to the data holding unit when the abnormality determination unit determines that there is an abnormality in the flow rate control device.

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