Valve control device, valve control method, valve control program, and fluid control device

Abstract

The present invention improves the response performance of valve control in a fluid control device, while reducing the influence of a nozzle. The present invention is a valve control method for controlling a valve 3 in a fluid control device 100, wherein an input flow-rate setting value Qset is multiplied by a target response transfer function F to generate a target response function Y(Qset), the target response function Y(Qset) is corrected for non-linearity between the driving voltage and the flow rate of a valve 2 to generate a target voltage function Y(Vset), the target voltage function Y(Vset) is corrected for the delay characteristics of the valve 3 to generate a feedforward voltage signal VFF, a feedback voltage signal VFB is generated by a feedback contrller 4d1 from the deviation between the target response function Y(Qset) and a measured flow-rate value Qmeas of a flow-rate sensor 2, a corrected instruction voltage signal VCMD is generatedby using the feedforward voltage signal VFF and the feedback voltage signal VFB, and the valve 3 is controlled according to the corrected instruction voltage signal VCMD.

Description

Valve control device, valve control method, valve control program, and fluid control device

[0001] The present invention relates to a valve control device, a valve control method, a valve control program, and a fluid control device.

[0002] As shown in Patent Document 1, a conventional fluid control device (also called a mass flow controller) includes a flow sensor that measures the flow rate of a fluid flowing through a flow path, a valve provided in the flow path, and a flow rate control unit that controls the flow rate using the valve based on the flow rate measurement value obtained by the flow rate sensor and a flow rate set value.

[0003] This mass flow controller focuses on the time delay of the flow rate measurement value measured by the flow sensor and is configured to prevent problems such as overshoot caused by that time delay. Specifically, the flow rate control unit has a sensor model storage unit that stores a sensor model that simulates the response characteristics of the flow rate sensor, a flow rate simulated value output unit that outputs a flow rate simulated value calculated based on the flow rate set value and the sensor model, a feedback control unit that outputs a flow rate feedback value based on the deviation between the flow rate measurement value and the flow rate simulated value, and a valve control unit that controls the valve based on the flow rate feedforward value and flow rate feedback value calculated from the flow rate set value.

[0004] Patent No. 6423792

[0005] However, even if the time delay in the flow rate measured by the flow sensor is eliminated as described above, it is difficult to improve response performance due to the delay characteristics of the valve drive circuit. Also, noise is superimposed on the flow rate measurement, and in order to reduce the influence of this noise and perform feedback control, it is possible to slow down the PID controller by inserting a low-pass filter, etc., but this will deteriorate step response performance.

[0006] Therefore, the present invention has been made in consideration of the above-mentioned problems, and its main object is to improve response performance while reducing the influence of noise in valve control of a fluid control device.

[0007] That is, the valve control device according to the present invention is a valve control device that controls a valve of a fluid control device, and is characterized by comprising: a target voltage function generation unit that generates a target voltage function by correcting nonlinearity between the drive voltage and flow rate of the valve for an input flow rate set value or a target response function generated by multiplying the flow rate set value by a target response transfer function; a feedforward voltage signal generation unit that generates a feedforward voltage signal by correcting delay characteristics of the valve from the target voltage function; a feedback voltage signal generation unit that generates a feedback voltage signal by a feedback controller from the deviation between the target response function and the flow rate measured by a flow sensor; and a voltage command value output unit that generates a corrected command voltage signal using the feedforward voltage signal and the feedback voltage signal, and outputs the voltage command value to a drive circuit of the valve.

[0008] This valve control device generates a target voltage function by correcting the nonlinearity between the valve drive voltage and the flow rate for the target response function generated by multiplying the flow rate setpoint or the flow rate setpoint by the target response transfer function, and then generates a feedforward voltage signal by correcting the valve delay characteristics from the target voltage function, thereby improving step response performance. In other words, the order of "generating target response function" → "correcting valve nonlinearity" → "correcting valve delay" is the exact inversion of the functional blocks of a real system, allowing for accurate correction of how the behavior of delay elements changes due to nonlinearity, thereby improving step response performance. Here, the present invention is configured to generate a feedforward voltage signal by correcting the valve delay characteristics from the target voltage function, and is configured not to correct the valve delay characteristics in the feedback control loop by the feedback controller, thereby reducing the effects of noise superimposed on the flow rate measurement. Furthermore, because the feedback controller generates a feedback voltage signal based on the deviation between the flow rate setpoint or the target response function generated by multiplying the flow rate setpoint by the target response transfer function and the flow rate measurement by the flow sensor, the flow rate control accuracy is not impaired. Furthermore, the target response transfer function and the feedback transfer function of the feedback controller can be adjusted individually, thereby improving the response performance of the step response in valve control.

[0009] Preferably, the valve control device of the present invention further comprises a target response function generating unit that generates the target response function by multiplying the flow rate setting value by a target response transfer function.

[0010] As a specific embodiment of the feedback controller, it is desirable to have an integral controller.

[0011] Furthermore, a valve control method according to the present invention is a valve control method for controlling a valve of a fluid control device, which comprises: generating a target voltage function by correcting nonlinearity between the drive voltage of the valve and a flow rate for an input flow rate set value or a value generated by multiplying the flow rate set value by a target response transfer function; generating a feedforward voltage signal by correcting delay characteristics of the valve from the target voltage function; generating a feedback voltage signal by a feedback controller from a deviation between the target response function and a flow rate measured by a flow sensor; generating a corrected command voltage signal using the feedforward voltage signal and the feedback voltage signal; and controlling the valve using the corrected command voltage signal.

[0012] Furthermore, the fluid control device according to the present invention is characterized by comprising a flow sensor that measures the flow rate of a fluid flowing through a flow path, a flow control valve that is provided upstream or downstream of the flow sensor, and the above-mentioned valve control device that controls the flow control valve.

[0013] In order to improve the fluid control performance of the fluid control device, it is desirable that two flow rate control valves be provided in the flow path.

[0014] Here, in order to make the effect of the present invention more pronounced, it is desirable that the flow rate sensor be a pressure type flow rate sensor.

[0015] Furthermore, the valve control program according to the present invention is a valve control program for controlling a valve of a fluid control device, and is characterized in that it causes a computer to perform the functions of: correcting the nonlinearity between the drive voltage and flow rate of the valve for an input flow rate set value or a target response function generated by multiplying the flow rate set value by a target response transfer function to generate a target voltage function; correcting the delay characteristics of the valve from the target voltage function to generate a feedforward voltage signal; generating a feedback voltage signal using a feedback transfer function from the deviation between the target response function and the flow rate measured by a flow sensor; generating a corrected command voltage signal using the feedforward voltage signal and the feedback voltage signal; and controlling the valve using the corrected command voltage signal.

[0016] According to the present invention as described above, it is possible to improve the response performance while reducing the influence of noise in the valve control of a fluid control device.

[0017] Fig. 1 is an overall schematic diagram of a fluid control system according to an embodiment of the present invention; Fig. 2 is a control block diagram of a valve control device of the same embodiment; Fig. 3 is a graph showing the control amount of the present embodiment in a step response; Fig. 4 is a graph showing the control amount of a conventional configuration in a step response; Fig. 5 is an overall schematic diagram of a fluid control system according to a modified embodiment;

[0018] A fluid control device according to an embodiment of the present invention will be described below with reference to the drawings.

[0019] <1. System Configuration> The fluid control device 100 of this embodiment is used, for example, in a semiconductor manufacturing process, and as shown in FIG. 1 , includes a flow sensor 2 that measures the flow rate of a fluid flowing through a flow path R formed in a block B, a flow control valve 3 that is provided upstream or downstream of the flow sensor 2, and a valve control device 4 that controls the flow control valve 3.

[0020] Here, the flow sensor 2 is a differential pressure type flow sensor. Specifically, the flow sensor 2 includes an upstream pressure sensor 21 provided upstream of a resistance element 5 such as a restrictor or orifice provided in the flow path R, a downstream pressure sensor 22 provided downstream of the resistance element 5, and a flow rate calculation unit 23 that calculates the flow rate from the differential pressure between the two pressure sensors 21, 22. The flow rate calculation unit 23 may be built into the valve control device 4.

[0021] In this example, the fluid control valve 3 is provided upstream of the differential pressure flow sensor 2. Specifically, the fluid control valve 3 controls the flow rate by moving a valve element back and forth relative to a valve seat using a piezoelectric actuator. The drive voltage applied to the piezoelectric actuator is adjusted by a valve drive circuit 6.

[0022] 2. Valve Control Device 4 The valve control device 4 controls the valve opening of the fluid control valve 3 based on the flow rate measurement value of the flow rate sensor 2 and the flow rate setting value.

[0023] This valve control device 4 can be configured using a computer having a CPU, internal memory, input / output interface, AD converter, etc., and as shown in FIG. 2 , the CPU and peripheral devices work together based on a control program stored in the internal memory, thereby fulfilling the functions of a target response function generator 4a, a target voltage function generator 4b, a feedforward voltage signal generator 4c, a feedback voltage signal generator 4d, and a voltage command value output unit 4e.

[0024] The target response function generator 4a calculates the flow rate setting value Q ｓｅｔ is multiplied by the target response transfer function F to obtain the target response function Y(Q ｓｅｔ Here, the target response transfer function F is a transfer function that models the fluid control valve 3 that is the control target, and in this embodiment, is a transfer function that models the valve drive circuit 6 of the fluid control valve 3.

[0025] The target voltage function generator 4b calculates the target response function Y(Q ｓｅｔ ) is corrected for the nonlinearity of the drive voltage and flow rate of the flow control valve 3 to obtain the target voltage function Y(V ｓｅｔ Here, "correcting the nonlinearity between the drive voltage and flow rate of the flow control valve 3" means that the target response function Y(Q) is generated by inverse search using relational data (which may be in the form of a look-up table or an equation) that indicates the relationship between the drive voltage and flow rate of the flow control valve 3. ｓｅｔ ) corresponding to the target voltage function Y(V ｓｅｔ ) to generate the

[0026] The feedforward voltage signal generator 4c calculates the target voltage function Y(V ｓｅｔ ) to correct the delay characteristic of the flow control valve 3 and generate a feedforward voltage signal V ＦＦ The feedforward voltage signal generator 4c of this embodiment is configured using a low-pass filter, and corrects the delay characteristic, which is a linear dynamic characteristic of the valve drive circuit 5. In other words, the feedforward voltage signal generator 4c generates a target voltage function Y(V ｓｅｔ ) is added a lead characteristic (1+a×df / dt) corresponding to the delay characteristic of the valve drive circuit 6.

[0027] The feedback voltage signal generator 4d calculates the target response function Y(Q ｓｅｔ ) and the flow rate measurement value Q of the flow rate sensor 2 ｍｅａｓ The feedback controller 4d1 generates a feedback voltage signal V ＦＢ The feedback controller 4d1 of this embodiment has at least an integral controller (feedback transfer function k).

[0028] The voltage command value output unit 4e outputs a feedforward voltage signal V ＦＦ and the feedback voltage signal V ＦＢ and the corrected command voltage signal V ＣＭＤ and outputs the voltage command value to the valve drive circuit 6. In this embodiment, the feedforward voltage signal V ＦＦ and the feedback voltage signal V ＦＢ and the corrected command voltage signal V ＣＭＤ is generated.

[0029] In addition, if there is a large response delay or a large overshoot due to aging of the fluid control valve 3, the feedforward voltage signal V ＦＦ and the feedback voltage signal V ＦＢ and the corrected command voltage signal V ＣＭＤ This configuration can improve response and reduce overshoot. ＦＦ and the feedback voltage signal V ＦＢ and is added to obtain the corrected command voltage signal V ＣＭＤ and a feedforward voltage signal V ＦＦ and the feedback voltage signal V ＦＢ and the corrected command voltage signal V ＣＭＤ This allows flexible response to various events.

[0030] The valve control method by the valve control device 4 configured in this way is to control the valves in accordance with the input flow rate setting value Q ｓｅｔis multiplied by the target response transfer function F to obtain the target response function Y(Q ｓｅｔ ) and generate the target response function Y(Q ｓｅｔ ) to correct the nonlinearity of the drive voltage and flow rate of the fluid control valve 3 to obtain the target voltage function Y(V ｓｅｔ ) and generate a target voltage function Y(V ｓｅｔ ) to correct the delay characteristic of the fluid control valve 3 and generate a feedforward voltage signal V ＦＦ and generate the target response function Y(Q ｓｅｔ ) and the flow rate measurement value Q of the flow rate sensor 2 ｍｅａｓ The feedback controller 4d1 generates a feedback voltage signal V ＦＢ and generates a feedforward voltage signal V ＦＦ and the feedback voltage signal V ＦＢ and the corrected command voltage signal V ＣＭＤ and generates the corrected command voltage signal V ＣＭＤ The fluid control valve 3 is controlled by the

[0031] FIG. 3 shows the response performance when the flow rate setting value is input as a step using the valve control device 4 configured as described above. In this simulation, the full scale is 40 sccm, the upstream pressure is 450 kPaA, and the downstream pressure is 0 kPaA. From FIG. 3, the flow rate measurement value Q ｍｅａｓ is the target response function Y(Q ｓｅｔ ) and the response performance of the step response has improved.

[0032] On the other hand, Fig. 4 shows the response performance when the flow rate setting value is input as a step in a conventional valve control device. The conventional valve control device has a configuration in which the target response function generator 4a and the target voltage function generator 4b of this embodiment are interchanged. From Fig. 4, it can be seen that the flow rate measurement value Q ｍｅａｓ It can be seen that a large overshoot occurs and the response performance of the step response is poor.

[0033] <3. Effects of this embodiment> With the fluid control device 100 of this embodiment configured as described above, the flow rate setting value Q ｓｅｔ The target response function Y(Q ｓｅｔ) is corrected for the nonlinearity of the drive voltage and flow rate of the fluid control valve 3 to obtain the target voltage function Y(V ｓｅｔ ) and generate a target voltage function Y(V ｓｅｔ ) to correct the delay characteristic of the fluid control valve 3 and generate a feedforward voltage signal V ＦＦ Since the target response function Y(Q ｓｅｔ The order of "generation of target voltage function Y(V)" → "correction of nonlinearity of valve 3" → "correction of delay of valve drive circuit 6" is the exact inversion of the functional blocks of the actual system, and it is possible to correctly correct the way in which the behavior of delay elements changes due to nonlinearity, thereby improving the response performance of the step response. Here, in this embodiment, ｓｅｔ ) to correct the delay characteristic of the fluid control valve 3 and generate a feedforward voltage signal V ＦＦ The flow rate setting value Q is generated, and the feedback control loop by the feedback controller 4d1 is configured not to correct the delay characteristics of the fluid control valve 3, so that the influence of noise superimposed on the flow rate measurement value can be reduced. ｓｅｔ The target response function Y(Q ｓｅｔ ) and the flow rate measurement value Q of the flow rate sensor 2 ｍｅａｓ The feedback controller 4d1 generates a feedback voltage signal V ＦＢ Furthermore, the target response transfer function F and the feedback transfer function k of the feedback controller 4d1 can be adjusted individually, thereby improving the response performance of the step response in valve control.

[0034] 4. Other Embodiments For example, in the above embodiment, the flow rate sensor is a pressure type flow rate sensor, but it may also be a thermal type flow rate sensor.

[0035] Furthermore, although the feedback controller in the above embodiment is an integral controller, a configuration having a proportional controller or a differential controller may be used instead of or in addition to the integral controller.

[0036] Furthermore, in the above embodiment, the configuration includes the target response function generator 4a, but the configuration may not include the target response function generator 4a, that is, the target voltage function generator 4b may generate a target voltage function by correcting the nonlinearity between the valve drive voltage and flow rate for the input flow rate setting value.

[0037] 5, a configuration having two fluid control valves 3A and 3B may be used. In this case, the valve control device 4 can control the flow rate of both of the two fluid control valves 3A and 3B in the same manner as in the above embodiment, or can control the flow rate of the upstream fluid control valve 3A in the same manner as in the above embodiment, and control the pressure of the downstream fluid control valve 3B so that the downstream pressure obtained by the downstream pressure sensor 22 approaches a predetermined pressure target value.

[0038] In addition, various modifications and combinations of the embodiments may be made as long as they do not go against the spirit of the present invention.

[0039] The present invention can improve response performance while reducing the influence of nozzles in valve control of a fluid control device.

[0040] 100: Fluid control device 2: Flow rate sensor (pressure type flow rate sensor) 3: Flow rate control valve 4: Valve control device 4a: Target response function generating unit 4b: Target voltage function generating unit 4c: Feedforward voltage signal generating unit 4d: Feedback voltage signal generating unit 4d1: Feedback controller (integral controller) 4e: Voltage command value output unit 5: Resistance element 6: Valve drive circuit

Claims

1. A valve control device that controls a valve of a fluid control device, a target voltage function generating unit that generates a target voltage function by correcting nonlinearity between the drive voltage and the flow rate of the valve for an input flow rate set value or a target response function generated by multiplying the flow rate set value by a target response transfer function; a feedforward voltage signal generating unit that generates a feedforward voltage signal by correcting a delay characteristic of the valve from the target voltage function; a feedback voltage signal generating unit that generates a feedback voltage signal by a feedback controller based on a deviation between the target response function and a flow rate measurement value of the flow rate sensor; a voltage command value output unit that generates a corrected command voltage signal using the feedforward voltage signal and the feedback voltage signal, and outputs the voltage command value to a drive circuit of the valve.

2. The valve control device according to claim 1 , further comprising a target response function generating unit that generates the target response function by multiplying the flow rate set value by a target response transfer function.

3. The valve control device according to claim 1 or 2, wherein the feedback controller comprises an integral controller.

4. A valve control method for controlling a valve of a fluid control device, comprising: A target voltage function is generated by correcting the nonlinearity between the drive voltage and the flow rate of the valve for the input flow rate set value or a target response function generated by multiplying the flow rate set value by a target response transfer function; generating a feedforward voltage signal by correcting a delay characteristic of the valve from the target voltage function; generating a feedback voltage signal by a feedback controller based on a deviation between the target response function and the flow rate measurement value of the flow rate sensor; A valve control method comprising: generating a corrected command voltage signal using the feedforward voltage signal and the feedback voltage signal; and controlling a valve using the corrected command voltage signal.

5. A valve control program for controlling a valve of a fluid control device, A target voltage function is generated by correcting the nonlinearity between the drive voltage and the flow rate of the valve for the input flow rate set value or a target response function generated by multiplying the flow rate set value by a target response transfer function; generating a feedforward voltage signal by correcting a delay characteristic of the valve from the target voltage function; generating a feedback voltage signal based on a feedback transfer function from a deviation between the target response function and the flow rate measurement value of the flow rate sensor; A valve control program that causes a computer to perform a function of generating a corrected command voltage signal using the feedforward voltage signal and the feedback voltage signal, and controlling a valve using the corrected command voltage signal.

6. a flow sensor for measuring a flow rate of a fluid flowing through a flow path; a flow control valve provided on the upstream side or downstream side of the flow sensor; A fluid control device comprising: a valve control device according to claim 1 that controls the flow rate control valve.

7. The fluid control device according to claim 6 , wherein two of the flow control valves are provided in the flow passage.

8. The fluid control device according to claim 6 , wherein the flow sensor is a pressure type flow sensor.