Mass flow controller and flow control method therefor

Abstract

A mass flow controller and a flow control method therefor. The method comprises: receiving the value of a set flow point (S110); acquiring a measured value of the gas inlet pressure of a mass flow controller under an actual operation condition (S120); and on the basis of a first preset relational expression between the value of the set flow point that is calibrated when the gas inlet pressure is a standard pressure value and a driving parameter of a regulation valve of the mass flow controller, obtaining a standard value of the driving parameter that corresponds to the value of the set flow point, and on the basis of a comparative relationship between the measured value and the standard pressure value, selectively performing pressure compensation on the standard value of the driving parameter to obtain a selective compensation output value of the driving parameter and accordingly control the regulation valve, so as to adjust the opening degree of the regulation valve to an opening degree corresponding to the selective compensation output value of the driving parameter (S130). By using the method, a mass flow controller exhibits high consistency in response time under different set flow points and different gas inlet pressures, and has a fast response speed, thereby improving the control accuracy of the mass flow controller.

Description

Mass flow controller and flow control method thereof Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular, to a mass flow controller and a flow control method thereof. Background Art

[0002] A mass flow controller (MFC) is a commonly used device for precise measurement and control of mass flow. It is widely used in a variety of fields, including semiconductor processing equipment, integrated circuit technology, specialty materials, the chemical industry, the petroleum industry, medicine, and environmental protection. In the field of semiconductor processing equipment, it is used to accurately measure and control the flow rate of process gases introduced into the process chamber.

[0003] Mass flow controllers generally use a proportional-integral-derivative (PID) method for flow control. After inputting a set flow point value, if the set flow point value is non-zero, the actual flow value detected is compared with the set flow point value to obtain a deviation. PID calculation is then performed on the deviation to determine the opening control signal, which is output to the mass flow controller's regulating valve. The regulating valve then moves from its zero position to a position that maintains the flow at the set flow point, achieving closed-loop control. This method results in a longer response time for the mass flow controller.

[0004] In order to solve this technical problem, usually after receiving the value of the set flow point, the standard value of the driving parameter corresponding to the set flow point is first determined and sent to the regulating valve, so that the regulating valve is adjusted to the opening corresponding to the standard value of the driving parameter. After the gas in the gas channel of the mass flow controller shows obvious flow, the opening of the regulating valve is adjusted according to the result of the PID calculation, so that the flow in the gas channel of the mass flow controller reaches the value of the set flow point.

[0005] However, using this method, the control accuracy of the mass flow controller is low in practical applications. Summary of the Invention

[0006] The present application aims to solve at least one of the technical problems existing in the prior art, and proposes a mass flow controller and a flow control method thereof.

[0007] In a first aspect, the present application provides a flow control method for a mass flow controller, comprising:

[0008] Receive the value of the set flow point;

[0009] Obtaining a measured value of the inlet pressure of the mass flow controller under actual working conditions;

[0010] According to a first preset relationship between the value of the set flow point calibrated when the pressure at the inlet end is a standard pressure value and the driving parameter of the regulating valve of the mass flow controller, a standard value of the driving parameter corresponding to the value of the set flow point is determined, and according to a comparison relationship between the measured value and the standard pressure value, the standard value of the driving parameter is selectively pressure compensated to obtain a selectively compensated output value of the driving parameter and the regulating valve is controlled accordingly to adjust the opening of the regulating valve to an opening corresponding to the selectively compensated output value of the driving parameter.

[0011] In an implementation of the first aspect of the present application, selectively performing pressure compensation on the standard value of the driving parameter based on a comparison relationship between the measured value and the standard pressure value to determine a selectively compensated output value of the driving parameter includes:

[0012] If the measured value exceeds a preset range, pressure compensation is performed on the standard value of the driving parameter to obtain an output value of the compensated driving parameter, and the output value of the compensated driving parameter is used as the selective compensation output value of the driving parameter;

[0013] If the measured value is within the preset range, using the standard value of the driving parameter as the selective compensation output value of the driving parameter;

[0014] The lower limit value of the preset range is less than the standard pressure value, and the upper limit value is greater than the standard pressure value.

[0015] In an implementation of the first aspect of the present application, obtaining a standard value of the driving parameter corresponding to the set flow point value based on a first preset relationship between the set flow point value calibrated when the inlet end pressure is a standard pressure value and the driving parameter of the regulating valve of the mass flow controller, and selectively performing pressure compensation on the standard value of the driving parameter based on a comparison relationship between the measured value and the standard pressure value to determine a selectively compensated output value of the driving parameter, including:

[0016] Obtaining a standard value of the driving parameter according to the value of the set flow point and the first preset relationship, and obtaining a selective compensation output value of the driving parameter according to the value of the set flow point, the standard value of the driving parameter, the measured value, the standard pressure value, and a compensation formula;

[0017] Wherein: the compensation formula is obtained according to the first-order derivative formula of the first preset relationship and the second preset relationship between the value of the set flow point and the standard flow value; the standard flow value is the flow rate output when the opening of the regulating valve is adjusted from 0% to the opening corresponding to the standard value of the driving parameter and then to the standard target opening under actual working conditions, and the flow rate output when the opening of the regulating valve is adjusted from 0% to the opening corresponding to the standard value of the driving parameter and then to the standard target opening when the intake end pressure is the standard pressure value is the value of the set flow point.

[0018] In an implementation of the first aspect of the present application, after obtaining the standard value of the driving parameter according to the value of the set flow point and the first preset relationship, the method further includes:

[0019] Determining whether the measured value is within a preset range;

[0020] If not, inputting the value of the set flow point, the standard value of the driving parameter, the measured value and the standard pressure value into a compensation formula;

[0021] If so, the standard value of the driving parameter is used as the selective compensation output value of the driving parameter.

[0022] In an implementation of the first aspect of the present application, the first preset relationship is: V(Q)=A+B×Q+C×Q 2 ; Where Q is the value of the set flow point, V(Q) is the driving parameter, and A, B, and C are constants;

[0023] The second preset relationship is: bc =Q×(P c / P s ); where Q bc is the standard flow value, P c is the measured value, P s is the standard pressure value;

[0024] The compensation formula is: V c (Q) = [(B + 2 × C × Q) × Q × (1-P c / P s )]+V s (Q); where V s (Q) is the standard value of the drive parameter, V c (Q) is the output value of the drive parameter after compensation.

[0025] In an implementation of the first aspect of the present application, a first preset relationship between the value of the set flow point and the driving parameter of the regulating valve of the mass flow controller obtained by calibration when the inlet end pressure is a standard pressure value specifically includes:

[0026] Maintaining the pressure at the inlet end of the mass flow controller at a standard pressure value;

[0027] Selecting a plurality of set flow points of the mass flow controller, and sequentially performing calibration processing on the values ​​of the plurality of set flow points until standard values ​​of a plurality of driving parameters corresponding one-to-one to the plurality of set flow points are obtained; the standard values ​​of the driving parameters satisfy preset conditions, the preset conditions at least including that the opening of the regulating valve is adjusted from 0% to the opening corresponding to the standard value of the driving parameter, the response time of the closed-loop control is within a design range, and the overshoot value is within an expected range;

[0028] According to the values ​​of the plurality of set flow points and the standard values ​​of the plurality of driving parameters corresponding thereto, a relationship curve is fitted to represent the corresponding relationship between the driving parameters and the values ​​of the set flow points;

[0029] According to the relationship curve, a first preset relationship expression for representing the value of the set flow point and the driving parameter is obtained, and the first preset relationship expression is a polynomial function.

[0030] In an implementation of the first aspect of the present application, the sequentially performing calibration processing on the values ​​of the plurality of set flow points specifically includes:

[0031] The driving parameter corresponding to the set flow point is set as a test value;

[0032] determining whether the test value satisfies the preset condition based on operating data collected in real time during the period of closed-loop control when the opening of the regulating valve is adjusted to the opening corresponding to the test value; the operating data being related to the opening of the regulating valve;

[0033] If not, return to the step of setting the value of the driving parameter corresponding to the set flow point to the test value and modify the test value;

[0034] If so, the test value is determined as the standard value of the driving parameter.

[0035] In an implementation of the first aspect of the present application, the standard pressure value is greater than or equal to the measured value.

[0036] In an implementation of the first aspect of the present application, the standard pressure value is greater than or equal to 0.1 MPa and less than or equal to 0.4 MPa.

[0037] In the second aspect, the present application provides a mass flow controller, which includes a gas channel, an input module, a flow sensor, a regulating valve and a pressure sensor, wherein the input module is used to receive the value of a set flow point; the flow sensor is used to detect the gas flow value in the gas channel; the regulating valve is arranged on the downstream side of the flow sensor to adjust the gas flow in the gas channel; the pressure sensor is used to detect the inlet end pressure of the gas channel; the mass flow controller also includes: a controller, the controller includes at least one processor and at least one memory, the at least one processor is electrically connected to the at least one memory, the input module, the flow sensor, the regulating valve and the pressure sensor; wherein the memory stores a computer program, and the processor executes the computer program to execute any one of the flow control methods provided in the first aspect of the present application.

[0038] This application has the following beneficial effects:

[0039] The flow control method of a mass flow controller provided in the present application adjusts the opening of a regulating valve to an opening corresponding to a selectively compensated output value of a driving parameter, and then controls the opening of the regulating valve through PID calculation so that the gas flow in the gas channel is consistent with the value of a set flow point. Because the selectively compensated output value of the driving parameter is obtained by selectively performing pressure compensation on a standard value of the driving parameter, the selectively compensated output value of the driving parameter also satisfies a preset condition. That is, when the opening of the regulating valve is adjusted to an opening corresponding to the selectively compensated output value of the driving parameter and the closed-loop control is then implemented, the response time is within the designed range, and the overshoot value is within the expected range. Furthermore, the method helps to eliminate the influence of changes in the inlet pressure on the gas flow in the gas channel, thereby reducing the adverse effects of changes in the inlet pressure on the response time of the mass flow controller, further improving the consistency of the response time of the mass flow controller, and thus improving the control accuracy of the mass flow controller. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] FIG1 is a schematic diagram showing a comparison of flow curves of a mass flow controller under two control modes;

[0041] FIG2 is a schematic diagram of the principle of a mass flow controller provided by the related art;

[0042] FIG3 is a schematic structural diagram of a mass flow controller provided in one embodiment of the present application;

[0043] FIG4 is a flow chart of a flow control method of a mass flow controller provided in one embodiment of the present application;

[0044] FIG5 is a schematic diagram of the pressure compensation principle in the flow control method of the mass flow controller provided in one embodiment of the present application. DETAILED DESCRIPTION

[0045] In practical applications, when the regulating valve of a mass flow controller is at the zero position (i.e., the opening of the regulating valve is 0%) and the received set flow point is a non-zero value, the main reasons for the long response time of the mass flow controller are: on the one hand, it takes a long time for the regulating valve to move to cause obvious flow of gas in the gas channel of the mass flow controller, resulting in PID calculation delay; on the other hand, after the PID calculation, the regulating valve is controlled accordingly, the stroke of the regulating valve is large, and the time consumed in the position adjustment process of the regulating valve is long.

[0046] After research, it was found that before the PID calculation, the standard value of the driving parameter corresponding to the set flow point is sent to the regulating valve to adjust the regulating valve to the opening corresponding to the standard value of the driving parameter, so that the gas in the gas channel of the mass flow controller appears to flow significantly, and the opening of the regulating valve is close to the opening corresponding to the set flow point. Therefore, during PID control, the PID calculation can respond quickly, reducing the stroke of the regulating valve, thereby speeding up the response speed of the mass flow controller. Figure 1 shows a schematic diagram of the flow curve of the mass flow controller, wherein curve A represents the control mode of the mass flow controller is to adjust the opening of the regulating valve after PID control, and curve B represents the control mode of the mass flow controller is to adjust the regulating valve to the opening corresponding to the standard value of the driving parameter before PID control. The vertical axis of Figure 1 represents the percentage of gas flow, and the horizontal axis of Figure 1 represents time, and the unit of time can be, for example, seconds (seconds). Referring to Figure 1, when the control mode of the mass flow controller is to adjust the regulating valve to the opening corresponding to the standard value of the driving parameter before PID control, the opening of the regulating valve is adjusted to the time t1 when the gas flow in the gas channel reaches the set flow point. When the mass flow controller's control mode is set to PID control and then the control valve opening is adjusted, the time it takes for the gas flow in the gas channel to reach the set flow point is t2, and t2 > t1. This shows that adjusting the control valve to the opening corresponding to the standard value of the drive parameter before PID calculation can effectively shorten the mass flow controller's response time.

[0047] It is worth noting that the standard value of the driving parameter corresponding to the set flow point is determined based on the corresponding relationship between the set flow point and the driving parameter. This corresponding relationship is typically determined when the inlet pressure of the mass flow controller is at a standard pressure value, and the standard value of the driving parameter corresponding to the set flow point obtained based on the corresponding relationship satisfies a preset condition. The preset condition includes at least the response time of the mass flow controller's regulating valve from 0% to the opening corresponding to the standard value of the driving parameter and then closed-loop control (e.g., PID control) falling within the design range, and the overshoot value falling within the expected range. Thus, for different set flow points, the response time of the regulating valve from 0% to the opening corresponding to the standard value of the driving parameter and then closed-loop control can all fall within the design range.

[0048] However, referring to Figure 2, a flow limiting hole is provided on the gas channel 180a of the mass flow controller, and the gas at the air inlet end flows to the air outlet end through the flow limiting hole (as shown by the dotted arrow in Figure 2). The gas channel 180a is connected to the regulating valve 10, and the opening of the regulating valve 10 is adjusted by the controller 20. Due to the presence of the flow limiting hole, the pressure at the air inlet end is different from the pressure at the air outlet end, that is, there is a pressure difference between the air inlet end and the air outlet end. The greater the pressure at the air inlet end, the greater the pressure difference, the faster the gas flows through the flow limiting hole, and the output flow rate is greater. The smaller the pressure at the air inlet end, the smaller the pressure difference, the slower the gas flows through the flow limiting hole, and the smaller the output flow rate. In other words, changes in the air inlet end pressure will affect the gas flow rate output by the mass flow controller.

[0049] In this way, for the same set flow point (for example, A%), assuming that the inlet pressure of the mass flow controller is the standard pressure value and the opening corresponding to the standard value of the driving parameter corresponding to the set flow point A% is Y, the opening of the regulating valve 10 is adjusted from 0% to Y, and then closed-loop control is implemented to adjust the opening of the regulating valve 10 to X, so that the flow value in the gas channel 180a reaches the set flow point A%, and the response time is the standard time Ts.

[0050] If the pressure at the inlet end of the mass flow controller is greater than the standard pressure value, when the opening of the regulating valve 10 is adjusted from 0% to Y and then to X, the gas flow rate actually output by the mass flow controller is greater than the set flow point A%, then the response time of the mass flow controller is less than the standard time Ts, and the response speed becomes faster. If the pressure at the inlet end of the mass flow controller is less than the standard pressure value, when the opening of the regulating valve 10 is adjusted from 0% to Y and then to X, the gas flow rate actually output by the mass flow controller is less than the set flow point A%, then the response time of the mass flow controller is greater than the standard time Ts, and the response speed becomes slower. Based on the above content, it can be seen that when the pressure at the inlet end is different, the consistency of the response time of the working process of the flow in the gas channel 180a of the mass flow controller reaching the same set flow point is low, which in turn affects the control accuracy of the mass flow controller.

[0051] In view of this, the embodiments of the present application provide a mass flow controller and a flow control method thereof. To enable those skilled in the art to better understand the technical solution of the present application, the mass flow controller and the flow control method provided by the present application are described in detail below with reference to the accompanying drawings.

[0052] The flow control method of the mass flow controller provided in the embodiment of the present application can be applied to the mass flow controller shown in Figure 3. The mass flow controller includes a gas channel, an input module 130, a flow sensor 140, a regulating valve 150, a pressure sensor 160 and a controller. Among them, the input module 130 is used to receive the set flow point, and the input module 130 can be, for example, a physical keyboard or a soft keyboard (also known as a virtual keyboard). The flow sensor 140 is used to detect the gas flow value in the gas channel. The regulating valve 150 is arranged on the downstream side of the flow sensor 140 to adjust the gas flow in the gas channel. It should be understood that the regulating valve 150 mentioned in the present application can be a solenoid valve or a piezoelectric valve. The controller includes at least one memory 120 and at least one processor 110, the memory 120 stores a computer program, and the processor 110 executes the computer program to perform the steps of the following method embodiment.

[0053] The processor 110 is connected to the memory 120, input module 130, flow sensor 140, regulating valve 150, and pressure sensor 160 via a system bus 170. In other words, the processor 110 is electrically connected to the memory 120, input module 130, flow sensor 140, regulating valve 150, and pressure sensor 160. It should be understood that the processor 110 can be a central processing unit (CPU), or other general-purpose processor, digital signal processor (DSP), application-specific integrated circuit (ASIC), etc. A general-purpose processor can be a microprocessor, or the processor 110 can be any conventional processor. The aforementioned memory 120 includes internal memory and various storage media that can store computer programs. The storage media can be a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk, etc. The internal memory provides an environment for the operation of the operating system and computer programs in the storage medium.

[0054] The flow control method of the mass flow controller provided in the embodiment of the present application is applied to the mass flow controller shown in FIG3 as an example for description. As shown in FIG4 , the flow control method includes the following steps:

[0055] S110, receiving the value of the set flow point.

[0056] The user may input the value of the set flow point through the input module 130 .

[0057] S120, obtaining a measured value of the inlet pressure of the mass flow controller under actual working conditions.

[0058] As shown in FIG3 , the mass flow controller may further include a pressure sensor 160 connected to the processor 110 via a system bus 170 . The pressure sensor 160 is used to detect the pressure at the inlet end of the gas channel. The processor 110 can receive the measurement value detected by the pressure sensor 160 .

[0059] S130, based on a first preset relationship between the value of the set flow point obtained by calibration when the pressure at the inlet end is a standard pressure value and the driving parameter of the regulating valve of the mass flow controller, determine the standard value of the driving parameter corresponding to the value of the set flow point, and based on the comparison relationship between the measured value and the standard pressure value, selectively perform pressure compensation on the standard value of the driving parameter to obtain a selective compensation output value of the driving parameter and control the regulating valve accordingly to adjust the opening of the regulating valve to an opening corresponding to the selective compensation output value of the driving parameter.

[0060] The first preset relationship may be pre-stored in memory 120, and the standard value of the driving parameter corresponding to the value at the set flow point, determined based on the first preset relationship, satisfies the preset condition. Depending on the type of control valve, the driving parameter is not limited to a voltage signal but may also be a current signal or other parameter that can be used to control the opening of the control valve. The following description uses a voltage signal as a representative example.

[0061] S140, controlling the opening of the regulating valve so that the gas flow in the gas channel remains consistent with the value of the set flow point.

[0062] In this step, the gas flow value detected by the flow sensor 140 can be compared with the value of the set flow point to obtain a deviation, and then PID calculation can be performed on the deviation. According to the calculation result, the opening control signal is determined and output to the regulating valve, so that the opening of the regulating valve is adjusted to a corresponding value to keep the gas flow in the gas channel consistent with the value of the set flow point.

[0063] It can be understood that, using the flow control method of this embodiment, taking the value of the set flow point as A% as an example, when the opening of the regulating valve is adjusted from 0% to the opening corresponding to the selective compensation output value of the drive parameter, and then adjusted to X, the flow in the gas channel can be kept consistent with the value of the set flow point.

[0064] Based on the above description, the flow control method provided in this embodiment adjusts the opening of the regulating valve to an opening corresponding to the selective compensation output value of the drive parameter, and then controls the opening of the regulating valve through PID calculation, so that the gas flow in the gas channel is consistent with the value of the set flow point. Because the selective compensation output value of the drive parameter is obtained by selectively performing pressure compensation on the standard value of the drive parameter, the selective compensation output value of the drive parameter also meets the preset conditions. That is, when the opening of the regulating valve is adjusted to the opening corresponding to the selective compensation output value of the drive parameter, the response time of the closed-loop control is within the design range, and the overshoot value is within the expected range. Moreover, it is helpful to eliminate the impact of changes in the inlet pressure on the gas flow in the gas channel, thereby reducing the adverse effects of changes in the inlet pressure on the response time of the mass flow controller, further improving the consistency of the response time of the mass flow controller, and thus improving the control accuracy of the mass flow controller.

[0065] In summary, by adopting the flow control method of this embodiment, at different set flow points and different inlet pressures, the response time of the mass flow controller can meet the design range, the response time is consistent, the response speed is fast, and there is no overshoot phenomenon, thereby improving the control accuracy of the mass flow controller.

[0066] The design range can be designed based on empirical values ​​in the field of application of the mass flow controller, for example, the design range is 100ms to 250ms. The expected range can also be designed based on empirical values ​​in the field of application of the mass flow controller, for example, the expected range is 1% to 10%.

[0067] The following describes in detail the specific process of calibrating the first preset relationship between the value of the set flow point and the driving parameter when the inlet pressure is the standard pressure value. The process of determining the first preset relationship between the value of the set flow point and the driving parameter includes the following steps:

[0068] S210, maintaining the pressure at the inlet end of the mass flow controller at a standard pressure value.

[0069] In this step, the mass flow controller can be set in the gas circuit on the semiconductor process equipment, and the pressure at the gas inlet end of the mass flow controller on the gas circuit can be adjusted. Alternatively, the gas circuit can be pre-built and the mass flow controller can be set in the built gas circuit.

[0070] S220, selecting multiple set flow points of the mass flow controller, and performing calibration processing on the values ​​of the multiple set flow points in sequence until standard values ​​of multiple driving parameters corresponding to the multiple set flow points are obtained; the standard values ​​of the driving parameters meet preset conditions, and the preset conditions at least include that the opening of the regulating valve is adjusted from 0% to the opening corresponding to the standard value of the driving parameter, and then the response time of the closed-loop control is within the design range and the overshoot value is within the expected range.

[0071] That is, the calibration process is performed multiple times, and each calibration process can calibrate a standard value of the driving parameter corresponding to a set flow point.

[0072] S230 , fitting a relationship curve for representing the corresponding relationship between the driving parameters and the values ​​of the set flow points based on the values ​​of the multiple set flow points and the standard values ​​of the multiple driving parameters corresponding thereto.

[0073] The embodiment of the present application does not specifically limit the method of fitting the relationship curve. For example, in some embodiments, step S230 can specifically obtain the relationship curve by performing fitting calculation using the least squares method, which is simple and stable.

[0074] S240 , obtaining a first preset relationship expression for representing the value of the set flow point and the driving parameter according to the relationship curve, where the first preset relationship expression is a polynomial function.

[0075] It is understood that the first preset relationship is calibrated under standard operating conditions with the inlet pressure at a standard value. That is, when determining the first preset relationship between the set flow point value and the driving parameter, the inlet pressure is used as the quantitative value, and the effect of changes in the inlet pressure on the gas flow rate is not considered.

[0076] In step S220, a plurality of set flow rate points may be selected based on different proportions of the full-scale flow rate of the mass flow controller. To ensure the reliability of the fitted relationship curve, the number of set flow rate points is preferably greater than or equal to 5. For example, in some embodiments, the number of set flow rate points may be 6, representing 2%, 10%, 25%, 50%, 75%, and 100% of the full-scale flow rate of the mass flow controller, respectively.

[0077] In some embodiments, the preset conditions may further include adjusting the opening of the regulating valve from 0% to an opening corresponding to a standard value of the driving parameter, and then implementing closed-loop control, and the smoothness of the flow curve of the mass flow controller is within a set range.

[0078] The specific implementation process of "performing calibration processing on the values ​​of the multiple set flow points in sequence until the standard values ​​of the multiple driving parameters corresponding to the multiple set flow points are obtained" in the above step S220 may include the following steps S221 to S224:

[0079] S221 , performing a calibration process on the value of one set flow point among the plurality of set flow points to obtain a standard value of the driving parameter corresponding to the set flow point.

[0080] S222: Determine whether the calibration process for the values ​​of the multiple set flow points has been completed.

[0081] S223, if yes, go to step S230.

[0082] S224: If not, return to step S221 and calibrate the value of the next set flow point.

[0083] In general, after each calibration process is performed, it is determined whether the standard values ​​of the driving parameters corresponding to all set flow points have been calibrated. This method is beneficial to ensure that the calibration of the value of any set flow point is not missed, so that the standard values ​​of multiple driving parameters corresponding to multiple set flow points can be obtained.

[0084] It is understood that, as disclosed herein, the specific implementation process of the "calibration process" in step S221 includes but is not limited to the following steps:

[0085] Step 1: Set the driving parameter value corresponding to the set flow point to the test value.

[0086] Step 2: Determine whether the test value meets the preset conditions based on the operating data collected in real time during the operation of adjusting the opening of the control valve from 0% to the opening corresponding to the test value and then implementing closed-loop control; wherein the operating data is related to the opening of the control valve; if not, return to step 1 and modify the test value; if so, go to step 3.

[0087] In one example, the implementation process of step 2 above can be as follows: based on the real-time collected operating data, the operating time t and the flow value f (unit: %) in the gas channel can be represented as an array (t, f); based on the array (t, f), it is determined whether the test value meets the preset conditions. Specifically, the array containing the maximum flow value can be screened out, and the maximum flow value is subtracted from the value of the set flow point and the absolute value is taken to calculate the overshoot value, and then determine whether the overshoot value meets the expected range. At the same time, the extreme point where the flow value no longer changes can be determined, and the operating time of the array where the extreme point is located is used as the response time to determine whether the response time meets the preset expectations.

[0088] In another example, the implementation process of the above step 2 can also be: fitting the operating data collected in real time to obtain a flow curve; the flow curve is used to represent the corresponding relationship between the operating time and the flow value f in the gas channel; based on the flow curve, it is judged whether the test value meets the preset conditions. Among them, the operating time can be specifically the horizontal coordinate of the flow curve, and the flow value f in the gas channel is the vertical coordinate of the flow curve. Specifically, the inflection point where the flow value f in the gas channel changes to a stable state and the overshoot point where the flow value f reaches the maximum can be determined on the flow curve, and the operating time corresponding to the inflection point is determined in the flow curve as the response time, and it is judged whether the response time meets the preset expectations; at the same time, the difference between the inflection point and the set flow point in the flow curve is determined as the overshoot value, and it is judged whether the overshoot value meets the expected range. In this way, the flow curve can be obtained by fitting calculation using the least squares method.

[0089] Step 3: Determine the test value as the standard value of the driving parameter.

[0090] According to the method of this embodiment, the test value is continuously modified and tested by simulating the operation process of the mass flow controller until the test value can meet the preset conditions, that is, at least the response time of the mass flow controller is guaranteed to be within the design range and the overshoot value is within the expected range.

[0091] Taking the driving parameter as a voltage signal as an example, in a specific example of this application, the first preset relationship is the following formula (1), where Q is the set flow point, V(Q) is the driving parameter, and A, B, and C are constants. V(Q) = A + B × Q + C × Q 2 Formula (1)

[0092] In some embodiments, in step S130, "selectively performing pressure compensation on the standard value of the driving parameter based on the comparison relationship between the measured value and the standard pressure value to determine a selectively compensated output value of the driving parameter" includes the following steps:

[0093] S131 , if the measured value exceeds a preset range, pressure compensation is performed on the standard value of the driving parameter to obtain an output value of the compensated driving parameter, and the output value of the compensated driving parameter is used as a selective compensation output value of the driving parameter.

[0094] S132: If the measured value is within the preset range, no pressure compensation is performed on the standard value of the driving parameter or the pressure compensation amount of the standard value of the driving parameter is zero, and the standard value of the driving parameter is used as the selective compensation output value of the driving parameter.

[0095] The lower limit of the above preset range is less than the standard pressure value P s , the upper limit value is greater than the standard pressure value P s, and the lower limit and upper limit are consistent with the standard pressure value P s The absolute value of the difference is 5psi. That is, the preset range is (P s -5psi, P s +5psi).

[0096] That is to say, when the measured value is within the preset range, that is, when the inlet pressure is almost equal to the standard pressure value under actual working conditions, the change of the inlet pressure from the standard pressure value to the measured value has little effect on the gas flow value of the gas channel of the mass flow controller, then the standard value of the driving parameter can be used as the selective compensation output value of the driving parameter.

[0097] However, when the measured value exceeds the preset range, that is, the difference between the inlet pressure and the standard pressure value under actual working conditions is large, the change of the inlet pressure from the standard pressure value to the measured value has a great impact on the gas flow value of the gas channel of the mass flow controller, and the standard value of the driving parameter needs to be pressure compensated.

[0098] Specifically, if the measured value is less than the lower limit of the preset range, pressure compensation is used to make the selective compensation output value of the drive parameter greater than the standard value of the drive parameter. Taking the set flow point as A% as an example, when the measured value is less than the lower limit of the preset range, the gas flow rate under the current working condition is less than the gas flow rate under the standard working condition. In this embodiment, by making the selective compensation output value of the drive parameter greater than the standard value of the drive parameter, the opening Y' corresponding to the selective compensation output value of the drive parameter is greater than the opening Y corresponding to the standard value of the drive parameter, that is, the starting opening of the control valve before closed-loop control is larger to prevent the flow in the gas channel from decreasing due to the decrease in flow rate. In this way, the response time of the process of adjusting the opening of the control valve from 0% to Y' and then to X is close to T s .

[0099] If the measured value is greater than the upper limit of the preset range, the selective compensation output value of the drive parameter is made smaller than the standard value of the drive parameter through pressure compensation. Taking the set flow point as A% as an example, when the measured value is greater than the upper limit of the preset range, the gas flow rate under the current working condition is greater than the gas flow rate under the standard working condition. In this embodiment, by making the selective compensation output value of the drive parameter smaller than the standard value of the drive parameter, the opening Y' corresponding to the selective compensation output value of the drive parameter is smaller than the opening Y corresponding to the standard value of the drive parameter, that is, the starting opening of the control valve before closed-loop control is smaller, to prevent the flow in the gas channel from increasing due to the increase in flow rate. In this way, the response time of the process of adjusting the opening of the control valve from 0% to Y' and then to X is equal to T s .

[0100] It can be understood that, compared with performing pressure compensation on the standard value of the driving parameter when the measured value is not equal to the standard pressure value, this embodiment is designed so that when the pressure at the inlet end of the gas channel is equal to the standard pressure value under actual working conditions, there is no need to perform pressure compensation on the standard value of the driving parameter when the error of the measured value is between -5psi and +5psi, thereby reducing the accuracy requirements of the pressure sensor 160.

[0101] It should be noted that possible implementations of the above step S130 include but are not limited to the following implementations.

[0102] In one feasible manner, the specific implementation process of step S130 includes the following steps S131 to S133:

[0103] S131, substituting the value of the set flow point into the first preset relationship to obtain the standard value of the driving parameter.

[0104] S132, determine whether the measured value is within a preset range; if so, use the standard value of the driving parameter as the selective compensation output value of the driving parameter; if not, go to step S133.

[0105] S133, inputting the set flow point value, the standard value of the driving parameter, the measured value and the standard pressure value into the compensation formula to obtain the output value of the compensated driving parameter, and using the output value of the compensated driving parameter as the selective compensation output value of the driving parameter.

[0106] The compensation formula is derived from the first-order derivative of the first preset relationship and the second preset relationship between the set flow point value and the standard flow value. The standard flow value is the flow rate output when the control valve opening is adjusted from 0% to the opening corresponding to the standard value of the driving parameter and then to the standard target opening under actual operating conditions. The set flow point is the flow rate output when the control valve opening is adjusted from 0% to the opening corresponding to the standard value of the driving parameter and then to the standard target opening when the inlet pressure is at the standard pressure value. In other words, under actual operating conditions, the control valve adjustment process is the same as the control valve adjustment process under standard operating conditions. Since the inlet pressure changes from the standard pressure value to the measured value, the flow rate in the gas channel changes from the set flow point value to the standard flow value. The standard target opening refers to the opening of the control valve corresponding to the flow rate in the gas channel being consistent with the set flow point value under standard operating conditions.

[0107] The first preset relationship is V(Q)=A+B×Q+C×Q 2 For example, the first derivative formula of the first preset relationship is V(Q)'=B+2×C×Q.

[0108] Where V(Q)' = d[V(Q)] / d(Q), that is, d[V(Q)] / d(Q) = B+2×C×Q, so d[V(Q)] = (B+2×C×Q)×d(Q). Based on this, the following formula (2) can be obtained. ΔV(Q) = (B+2×C×Q)×ΔQ Formula (2)

[0109] It can be understood that according to fluid mechanics, if the inlet pressure changes from P1 to P2 and the gas temperature changes from T1 to T2, the gas flow in the gas channel will change from Q1 to Q2 accordingly. Q1 and Q2 satisfy: Q1 = Q2 × (P1 / P2) × sqrt (T2 / T1). From this, it can be deduced that, assuming that the gas temperature and other conditions remain unchanged, for the same set flow point, under standard operating conditions (i.e., the inlet pressure is the standard pressure value P s ) and in actual working conditions (i.e. the inlet pressure is the measured value P c ), when the opening of the regulating valve is adjusted from 0% to the standard value of the driving parameter (determined according to the first preset relationship obtained by calibration under standard working conditions) and the corresponding opening is then adjusted to the standard target opening, the actual flow rate in the gas channel is the value of the set flow point and the standard flow value Q bc , then set the flow point value and standard flow value Q bc The second preset relationship between is the following formula (3). bc =Q×(P c / P s ) Formula (3)

[0110] Thus, combining equations (2) and (3), and ΔV(Q)=V c (Q)-V s (Q), correspondingly, ΔQ=QQ bc , the compensation formula can be obtained as formula (4). Among them, V c (Q) is the output value of the compensated drive parameter corresponding to the current working condition, V s (Q) is the standard value of the drive parameter corresponding to the standard working condition. c (Q) = [(B + 2 × C × Q) × Q × (1-P c / P s )]+V s (Q) Formula (4)

[0111] It can be seen from formula (4) that if the measured value P c Equal to the standard pressure value P s , then 1-P c / P s =0, then V c (Q)=V s (Q), that is, the compensation amount is zero.

[0112] If the measured value P c Less than the standard pressure value P s , that is, when the inlet pressure under the current working condition is lower than the inlet pressure under the standard working condition, P c / P s <1, then 1-P c / P s >0, then V c (Q)>V s (Q). If the measured value P c Greater than the standard pressure value P s , that is, when the inlet pressure under the current working condition is higher than the inlet pressure under the standard working condition, P c / P s >1, then 1-P c / P s <0, then V c (Q) <V s (Q). In other words, the lower the inlet pressure under actual operating conditions compared to the standard pressure value, the more positive compensation is applied to the standard value of the drive parameter, resulting in a larger start-up opening of the regulating valve before closed-loop control. The higher the inlet pressure under actual operating conditions, the more negative compensation is applied to the standard value of the drive parameter, resulting in a smaller start-up opening of the regulating valve before closed-loop control.

[0113] In addition, it can be seen from formula (4) that the comparison relationship between the measured value and the standard pressure value in this embodiment refers to the ratio between the two.

[0114] In this embodiment, the principle of pressure compensation for the standard value of the driving parameter can be referred to as shown in FIG5. It is understandable that since the inlet pressure changes from the standard pressure value to the measured value, it will affect the gas flow rate. Therefore, the difference in flow rate caused by the inlet pressure (i.e., QQ bc ) is compensated to the standard flow value, so that under actual working conditions, the opening of the control valve is adjusted from 0% to the opening corresponding to the selective compensation output value of the drive parameter and then to the standard target opening to reach the set flow point.

[0115] In another feasible method, the value of the set flow point, the measured value and the standard pressure value are substituted into a preset formula to obtain the output value of the compensated driving parameter, and the output value of the compensated driving parameter is used as the selective compensation output value of the driving parameter; wherein the preset formula is used to characterize the relationship between the change of the intake end pressure from the standard pressure value to the measured value, the standard value of the driving parameter corresponding to the set flow point and the output value of the compensated driving parameter.

[0116] Combining the above formula (1) and formula (4), the preset formula can be obtained as the following formula (5). c (Q) = [(B + 2 × C × Q) × Q × (1-P c / P s)]+(A+B×Q+C×Q 2 ) Formula (5)

[0117] It can also be seen from formula (5) that the comparison relationship between the measured value and the standard pressure value in this embodiment also refers to the ratio between the two.

[0118] Compared with the previous feasible method, in this embodiment, the measured value and the standard pressure value are not compared first. Instead, the value of the set flow point, the measured value and the standard pressure value are directly substituted into the preset formula. Since the preset formula includes the first preset relationship, the standard value of the driving parameter is calculated in the preset formula and the standard value of the driving parameter is selectively pressure compensated based on the comparison relationship between the measured value and the standard pressure value.

[0119] In another feasible manner, the specific implementation process of step S130 includes the following steps S134 to S136:

[0120] S134, determine whether the measured value is within a preset range; if so, execute step S135; if not, execute step S136.

[0121] In this step, the measured value can be subtracted from the standard pressure value to determine whether the absolute value of the difference between the two is no greater than 5 psi. If so, it indicates that the measured value is within the preset range. In other words, in this embodiment, the comparison relationship between the measured value and the standard pressure value can refer to the difference between the two.

[0122] S135 , substituting the value of the set flow point into the first preset relationship to determine a standard value of the driving parameter, and using the standard value of the driving parameter as a selective compensation output value of the driving parameter.

[0123] S136, substituting the set flow point value, the measured value and the standard pressure value into a preset formula to obtain the output value of the compensated driving parameter, and using the output value of the compensated driving parameter as the selective compensation output value of the driving parameter.

[0124] In this embodiment, when executing step S134 , the comparison relationship between the measured value and the standard pressure value is first determined, and then a corresponding formula is selected for calculation according to the comparison result.

[0125] In any of the above embodiments, the standard pressure value P s Can be greater than or equal to the measured value P c That is, according to the experience value of the application field of mass flow controller, the standard pressure value P s Select a larger value, that is, the standard working condition intake pressure is high pressure. With this design, due to P s ≥P c , therefore, P c / P s ≤1, then 1-Pc / P s ≥0, when pressure compensation is performed on the standard value of the driving parameter, it is positive compensation. Compared with negative compensation on the standard value of the driving parameter, the risk during operation is smaller, which is conducive to ensuring that the compensation is correct, thereby helping to ensure the control accuracy of the mass flow controller.

[0126] The standard pressure value Ps mentioned in this application can be designed based on the empirical value of the application field of the mass flow controller. s Specifically, any value between 0.1 MPa and 0.4 MPa can be selected, preferably 0.1 MPa, 0.3 MPa or 0.4 MPa.

[0127] It should be understood that the various forms of the processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this application can be performed in parallel, sequentially, or in a different order, as long as the desired results of the technical solutions disclosed in this application can be achieved. This is not a limitation herein.

[0128] It is understood that the above embodiments are merely exemplary embodiments for illustrating the principles of the present application, and the present application is not limited thereto. Those skilled in the art may make various modifications and improvements without departing from the spirit and substance of the present application, and such modifications and improvements are also considered to be within the scope of protection of the present application.

Claims

1. A flow control method for a mass flow controller, characterized in that: The flow control method comprises: Receive the value of the set flow point; Obtaining a measured value of the inlet pressure of the mass flow controller under actual working conditions; According to a first preset relationship between the value of the set flow point calibrated when the pressure at the inlet end is a standard pressure value and the driving parameter of the regulating valve of the mass flow controller, a standard value of the driving parameter corresponding to the value of the set flow point is determined, and according to a comparison relationship between the measured value and the standard pressure value, the standard value of the driving parameter is selectively pressure compensated to obtain a selectively compensated output value of the driving parameter and the regulating valve is controlled accordingly to adjust the opening of the regulating valve to an opening corresponding to the selectively compensated output value of the driving parameter.

2. The flow control method according to claim 1, characterized in that: According to the comparison relationship between the measured value and the standard pressure value, selectively performing pressure compensation on the standard value of the driving parameter to determine a selectively compensated output value of the driving parameter, including: If the measured value exceeds a preset range, pressure compensation is performed on the standard value of the driving parameter to obtain an output value of the compensated driving parameter, and the output value of the compensated driving parameter is used as the selective compensation output value of the driving parameter; If the measured value is within the preset range, using the standard value of the driving parameter as the selective compensation output value of the driving parameter; The lower limit value of the preset range is less than the standard pressure value, and the upper limit value is greater than the standard pressure value.

3. The flow control method according to claim 2, characterized in that: Obtaining a standard value of the driving parameter corresponding to the value of the set flow point according to a first preset relationship between the value of the set flow point obtained by calibration when the pressure at the inlet end is a standard pressure value and a driving parameter of the regulating valve of the mass flow controller, and selectively performing pressure compensation on the standard value of the driving parameter according to a comparison relationship between the measured value and the standard pressure value to determine a selectively compensated output value of the driving parameter, including: Obtaining a standard value of the driving parameter according to the value of the set flow point and the first preset relationship, and obtaining a selective compensation output value of the driving parameter according to the value of the set flow point, the standard value of the driving parameter, the measured value, the standard pressure value, and a compensation formula; Wherein: the compensation formula is obtained according to the first-order derivative formula of the first preset relationship and the second preset relationship between the value of the set flow point and the standard flow value; the standard flow value is the flow rate output when the opening of the regulating valve is adjusted from 0% to the opening corresponding to the standard value of the driving parameter and then to the standard target opening under actual working conditions, and the flow rate output when the opening of the regulating valve is adjusted from 0% to the opening corresponding to the standard value of the driving parameter and then to the standard target opening when the intake end pressure is the standard pressure value is the value of the set flow point.

4. The flow control method according to claim 3, characterized in that: After obtaining the standard value of the driving parameter according to the value of the set flow point and the first preset relationship, the method further includes: Determining whether the measured value is within a preset range; If not, inputting the value of the set flow point, the standard value of the driving parameter, the measured value and the standard pressure value into a compensation formula; If so, the standard value of the driving parameter is used as the selective compensation output value of the driving parameter.

5. The flow control method according to claim 3, characterized in that: The first preset relationship is: V(Q)=A+B×Q+C×Q 2 ; Where Q is the value of the set flow point, V(Q) is the driving parameter, and A, B, and C are constants; The second preset relationship is: bc =Q×(P c / P s ); where Q bc is the standard flow value, P c is the measured value, P s is the standard pressure value; The compensation formula is: V c (Q) = [(B + 2 × C × Q) × Q × (1-P c / P s )]+V s (Q); where V s (Q) is the standard value of the drive parameter, V c (Q) is the output value of the drive parameter after compensation.

6. The flow control method according to any one of claims 1 to 5, characterized in that: The first preset relationship between the value of the set flow point and the driving parameter of the regulating valve of the mass flow controller obtained by calibration when the pressure at the inlet end is a standard pressure value specifically includes: Maintaining the pressure at the inlet end of the mass flow controller at a standard pressure value; Selecting a plurality of set flow points of the mass flow controller, and sequentially performing calibration processing on the values ​​of the plurality of set flow points until standard values ​​of a plurality of driving parameters corresponding one-to-one to the plurality of set flow points are obtained; the standard values ​​of the driving parameters satisfy preset conditions, the preset conditions at least including that the opening of the regulating valve is adjusted from 0% to the opening corresponding to the standard value of the driving parameter, the response time of the closed-loop control is within a design range, and the overshoot value is within an expected range; According to the values ​​of the plurality of set flow points and the standard values ​​of the plurality of driving parameters corresponding thereto, a relationship curve is fitted to represent the corresponding relationship between the driving parameters and the values ​​of the set flow points; According to the relationship curve, a first preset relationship expression for representing the value of the set flow point and the driving parameter is obtained, and the first preset relationship expression is a polynomial function.

7. The flow control method according to claim 6, characterized in that: The step of sequentially performing calibration on the values ​​of the plurality of set flow points specifically includes: The driving parameter corresponding to the set flow point is set as a test value; determining whether the test value satisfies the preset condition based on operating data collected in real time during the period when the opening of the regulating valve is adjusted from 0% to the opening corresponding to the test value and then closed-loop controlled; the operating data being related to the opening of the regulating valve; If not, return to the step of setting the value of the driving parameter corresponding to the set flow point to the test value and modify the test value; If so, the test value is determined as the standard value of the driving parameter.

8. The flow control method according to any one of claims 1 to 5, characterized in that: The standard pressure value is greater than or equal to the measured value.

9. The flow control method according to claim 8, characterized in that: The standard pressure value is greater than or equal to 0.1 MPa and less than or equal to 0.4 MPa.

10. A mass flow controller, characterized in that: The mass flow controller includes a gas channel, an input module, a flow sensor, a regulating valve and a pressure sensor, wherein the input module is used to receive the value of a set flow point; the flow sensor is used to detect the gas flow value in the gas channel; the regulating valve is arranged on the downstream side of the flow sensor to adjust the gas flow in the gas channel; the pressure sensor is used to detect the pressure at the inlet end of the gas channel; the mass flow controller also includes: a controller, The controller includes at least one processor and at least one memory, and the at least one processor is electrically connected to the at least one memory, the input module, the flow sensor, the regulating valve and the pressure sensor; wherein the memory stores a computer program, and the processor executes the computer program to execute the flow control method described in any one of claims 1 to 9.

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