Mass flow controller and flow control method thereof

Abstract

The invention provides a mass flow controller and a flow control method thereof. The flow control method comprises the following steps: receiving a set flow point; obtaining the measured value of the pressure of the air inlet end of the mass flow controller under the actual working condition; determining a standard value of a driving parameter corresponding to a set flow point according to a first preset relational expression between the set flow point calibrated when the pressure of the air inlet end is at the standard pressure value and the driving parameter of a regulating valve of the mass flow controller; and selectively performing pressure compensation on the standard value of the driving parameter according to the comparison relationship between the measured value and the standard pressure value, determining a selective compensation output value of the driving parameter, and transmitting the selective compensation output value to the regulating valve so as to control the opening degree of the regulating valve to be regulated from 0% to the opening degree corresponding to the selective compensation output value of the driving parameter. By adopting the mass flow controller, the consistency of the response duration of the mass flow controller is high and the response speed is high under different set flow points and different air inlet end pressures, so that the control precision of the mass flow controller is improved.

Description

Technical Field

[0001] The present invention 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 commonly use a proportional-integral-derivative (PID) method for flow control. After entering a set flow point, if the set flow point is non-zero, the actual flow rate is compared with the set flow point to obtain a deviation. PID calculation is then applied to this deviation to determine the opening control signal output to the mass flow controller's regulating valve. The regulating valve then moves from zero to maintain 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 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, and the gas in the gas channel of the mass flow controller shows obvious flow. Then, the opening of the regulating valve is adjusted according to the results of the PID calculation, so that the flow in the gas channel of the mass flow controller reaches 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 invention 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 invention provides a flow control method for a mass flow controller, comprising:

[0008] Receive the set flow point;

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

[0010] A standard value of the driving parameter corresponding to the set flow point is determined based on a first preset relationship between the set flow point obtained by calibrating the inlet end pressure at the standard pressure value and the driving parameter of the regulating valve of the mass flow controller, and the standard value of the driving parameter is selectively pressure-compensated based on a comparison relationship between the measured value and the standard pressure value, and a selectively compensated output value of the driving parameter is determined and transmitted to the regulating valve to control the opening of the regulating valve from 0% 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 invention, 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, no pressure compensation is performed on the standard value of the driving parameter or the compensation amount of the pressure compensation on 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;

[0014] The lower limit value of the preset range is smaller than the standard pressure value, and the upper limit value is larger than the standard pressure value, and the absolute value of the difference between the lower limit value and the upper limit value and the standard pressure value is 5psi.

[0015] In an implementation of the first aspect of the present invention, determining a standard value of the driving parameter corresponding to the set flow point based on a first preset relationship between the set flow point obtained by calibrating the inlet end pressure at 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 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:

[0016] Inputting the set flow point into the first preset relationship to determine the standard value of the driving parameter, and inputting the set flow point, the standard value of the driving parameter, the measured value, and the standard pressure value into a compensation formula to determine the selective compensation output value of the driving parameter;

[0017] The compensation formula is determined based on the first-order derivative formula of the first preset relationship and the second preset relationship between the set flow point and the standard flow value; the standard flow value is the flow 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 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 at the standard pressure value is the set flow point.

[0018] In an implementation of the first aspect of the present invention, after inputting the set flow point into the first preset relationship to determine the standard value of the driving parameter, the method further includes:

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

[0020] If not, inputting 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 invention, the first preset relationship is: V(Q)=A+B×Q+C×Q 2 ; Where Q is 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 invention, the first preset relationship between 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 at a standard pressure value specifically includes:

[0026] The air inlet pressure of the mass flow controller is set to a standard pressure value;

[0027] Selecting a plurality of set flow points of the mass flow controller, and sequentially performing a calibration process on each 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 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 set flow points;

[0029] According to the relationship curve, a first preset relationship expression for representing 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 invention, performing calibration processing on each of the plurality of set flow points specifically includes:

[0031] Setting the driving parameter corresponding to the set flow point to a test value;

[0032] 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;

[0033] If not, return to the step of setting 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 invention, the standard pressure value is greater than or equal to the measured value.

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

[0037] In a second aspect, the present invention provides a mass flow controller, which includes a regulating valve, and the mass flow controller also includes: a controller, the controller including at least one processor and at least one memory, the memory storing a computer program, and the processor executing the computer program to execute any one of the flow control methods provided in the first aspect of the present invention.

[0038] The present invention has the following beneficial effects:

[0039] The flow control method of the mass flow controller provided by the present invention can selectively perform pressure compensation on the standard value of the driving parameter, which is beneficial to eliminating the influence of the change of the inlet end pressure on the gas flow in the gas channel, thereby reducing the adverse effect of the change of the inlet end 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] Figure 1 Schematic diagram comparing the flow curves of the mass flow controller in two control modes;

[0041] Figure 2 A schematic diagram of the principle of a mass flow controller provided for related technology;

[0042] Figure 3 A schematic structural diagram of a mass flow controller provided in one embodiment of the present application;

[0043] Figure 4 A flow chart of a flow control method for a mass flow controller provided in one embodiment of the present application;

[0044] Figure 5 A schematic diagram of the pressure compensation principle in a flow control method of a 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 was first sent to the control valve, and the control valve was adjusted 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 would flow significantly, so that the PID calculation could respond quickly, and the opening of the control valve was close to the opening corresponding to the set flow point, which reduced the stroke of the control valve, thereby speeding up the response speed of the mass flow controller. Figure 1 The diagram shows the flow curve of the mass flow controller, where line A represents the control mode of the mass flow controller, which is PID control followed by regulating the opening of the regulating valve, and line B represents the control mode of the mass flow controller, which is regulating the regulating valve to open to the opening corresponding to the standard value of the driving parameter before PID control. Figure 1 , when the mass flow controller's control mode is to pre-open the regulating valve to the opening corresponding to the standard value of the drive parameter before PID control, the time it takes for the regulating valve to open until the gas flow in the gas channel reaches the set flow point is t1. When the mass flow controller's control mode is to pre-open the regulating valve to the opening corresponding to the standard value of the drive parameter before PID control, the time it takes for the regulating valve to open until the gas flow in the gas channel reaches the set flow point is t2, and t2>t1. This shows that adjusting the regulating valve to the opening corresponding to the standard value of the drive parameter before PID calculation can effectively shorten the response time of the mass flow controller.

[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 with the inlet pressure of the mass flow controller at a standard pressure value. Furthermore, 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 closed-loop control after the mass flow controller's regulating valve opening is adjusted from 0% to the opening corresponding to the standard value of the driving parameter, and the overshoot value is within the desired range. Thus, for different set flow points, the response time of the closed-loop control after the regulating valve opening is adjusted from 0% to the opening corresponding to the standard value of the driving parameter is within the designed range.

[0048] However, see Figure 2 The gas channel 180a of the mass flow controller is provided with a flow-limiting hole, and the gas at the inlet end flows through the flow-limiting hole to the outlet end (at Figure 2(as indicated by the dashed arrow in the figure). Due to the presence of the restrictor, the pressure at the inlet and outlet differs, creating a pressure differential between the two ends. The greater the inlet pressure, the greater the pressure differential, which causes the gas to flow faster through the restrictor, resulting in a higher output flow rate. The smaller the inlet pressure, the smaller the pressure differential, which causes the gas to flow slower through the restrictor, resulting in a lower output flow rate. In other words, changes in inlet pressure 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 pressure at the inlet end 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 is adjusted from 0% to Y, and then closed-loop control is implemented to adjust the opening of the regulating valve 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 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 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 present invention provides 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 invention, the mass flow controller and the flow control method thereof provided by the present invention 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 Figure 3The mass flow controller shown. The mass flow controller includes a gas channel, an input module 130, a flow sensor 140, a regulating valve 150 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, a soft keyboard (also called 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 this 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, the input module 130, the flow sensor 140, and the regulating valve 150 via the system bus 170. It should be understood that the processor 110 can be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), etc. The general-purpose processor can be a microprocessor or the processor 110 can be any conventional processor, etc. The aforementioned memory 120 includes an internal memory and various storage media that can store computer programs. The storage medium 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 Figure 3 The mass flow controller shown in the figure is used as an example to illustrate. Figure 4 As shown, the flow control method includes the following steps:

[0055] S110, receiving a set flow point.

[0056] The user may input a 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] like Figure 3As shown, 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, determining a standard value of the driving parameter corresponding to the set flow point based on a first preset relationship between the set flow point obtained by calibrating the intake end pressure at the 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, determining a selectively compensated output value of the driving parameter and transmitting it to the regulating valve to control the opening of the regulating valve from 0% to an opening corresponding to the selectively compensated 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 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 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 set flow point.

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

[0063] It can be understood that, using the flow control method of this embodiment, taking 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 set flow point.

[0064] Based on the above description, the flow control method provided in this embodiment controls the opening of the regulating valve from 0% to the opening corresponding to the selective compensation output value of the drive parameter, and then controls the opening of the regulating valve through PID calculation to ensure that the gas flow in the gas channel remains consistent with 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, the response time of the regulating valve from 0% to the opening corresponding to the selective compensation output value of the drive parameter and then implementing 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 inlet pressure at the standard pressure value to obtain the first preset relationship between the set flow point and the driving parameter. The process of determining the first preset relationship between the set flow point and the driving parameter includes the following steps.

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

[0069] In this step, the mass flow controller can be set in the gas circuit on the semiconductor process equipment to adjust the pressure of the gas inlet end of the mass flow controller on the gas circuit. 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 each of the multiple set flow points in turn 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 set flow points based on the plurality of set flow points and the standard values ​​of the plurality of 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 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 predetermined relationship is calibrated under standard operating conditions with the inlet pressure at a standard value. That is, when determining the first predetermined relationship between the set flow point and the drive 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 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 points is preferably greater than or equal to 5. For example, as an optional embodiment of the present invention, the number of set flow 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 for each of the multiple set flow points in sequence until standard values ​​of multiple driving parameters corresponding to the multiple set flow points are obtained" in the above step S220 may include S221 to S224.

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

[0080] S222: Determine whether calibration processing is completed for multiple set flow points.

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

[0082] S224: If not, return to S221 and perform calibration on 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 no set flow point is missed in the calibration, so that the standard values ​​of multiple driving parameters corresponding to multiple set flow points can be obtained.

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

[0085] Step 1: Set the driving parameters 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; 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 an optional example, the implementation process of the above step 2 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 expressed as an array (t, f); based on the array (t, f), it is judged whether the test value meets the preset conditions. Specifically, the maximum flow value in the array can be screened out, the maximum flow value is subtracted from the set flow point and the absolute value is taken, the overshoot value can be calculated, and then it is judged 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 extreme point is used as the response time to judge whether the response time meets the preset expectations.

[0088] In another optional 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 flow value f corresponding to the inflection point and the overshoot point is determined in the flow curve 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 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 the present 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.

[0092] V(Q)=A+B×Q+C×Q 2 Formula (1)

[0093] In one embodiment, the step S130 of "selectively performing pressure compensation on the standard value of the driving parameter according to the comparison relationship between the measured value and the standard pressure value, and determining a selectively compensated output value of the driving parameter" includes the following steps.

[0094] 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.

[0095] 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.

[0096] 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 Ps , 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).

[0097] 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.

[0098] 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 is pressure compensated.

[0099] Specifically, if the measured value is less than the lower limit of the preset range, pressure compensation is used to increase the selective compensation output value of the drive parameter to a value greater than the standard value of the drive parameter. For example, when the measured value is less than the lower limit of the preset range, the gas flow rate under the current operating condition is less than the gas flow rate under the standard operating condition. In this embodiment, by increasing the selective compensation output value of the drive parameter to a value 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. This means that the control valve's starting opening is larger before closed-loop control, preventing the flow rate in the gas channel from decreasing due to a decrease in flow rate. This ensures that the response time for adjusting the control valve's opening from 0% to Y' and then to X is equal to Ts.

[0100] If the measured value is greater than the upper limit of the preset range, pressure compensation is used to reduce the selective compensation output value of the drive parameter to less than the standard value of the drive parameter. For example, when the measured value is greater than the upper limit of the preset range, the gas flow rate under the current operating condition is greater than the gas flow rate under the standard operating condition. This embodiment reduces the selective compensation output value of the drive parameter to less than the standard value of the drive parameter, and the corresponding opening Y' is less than the opening Y corresponding to the standard value of the drive parameter. This means that the starting opening of the control valve before closed-loop control is smaller, preventing the flow rate in the gas channel from increasing due to the increased flow rate. This ensures that the response time for adjusting the control valve opening from 0% to Y' and then to X is equal to Ts.

[0101] 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.

[0102] It should be noted that possible implementations of the above step S130 include but are not limited to the following implementations.

[0103] In one feasible manner, the specific implementation process of step S130 includes steps S131 to S133.

[0104] S131: Substitute the set flow point into a first preset relationship to determine a standard value of the driving parameter.

[0105] 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 S133.

[0106] S133, inputting the set flow point, the standard value of the driving parameter, the measured value and the standard pressure value into the compensation formula to determine 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.

[0107] The compensation formula is determined based on the first-order derivative of the first preset relationship and the second preset relationship between the set flow point 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 drive 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 drive 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 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 under standard operating conditions.

[0108] 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.

[0109] Where V(Q)' = d[V(Q)] / d(Q), that is, d[V(Q)] / d(Q) = B+2×C×Q, and d[V(Q)] = (B+2×C×Q)×d(Q). Based on this, the following formula (2) can be obtained.

[0110] ΔV(Q)=(B+2×C×Q)×ΔQFormula (2)

[0111] 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 respectively the set flow point and the standard flow value Q bc , then set the flow point and standard flow value Q bc The second preset relationship between is the following formula (3).

[0112] Q bc =Q×(P c / P s )Formula (3)

[0113] 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 driving parameter corresponding to the standard working condition.

[0114] V c (Q) = [(B + 2 × C × Q) × Q × (1-P c / P s )]+V s (Q) Formula (4)

[0115] 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 Vc (Q)=V s (Q), that is, the compensation amount is zero.

[0116] 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.

[0117] 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.

[0118] In this embodiment, the principle of pressure compensation for the standard value of the driving parameter can be referred to Figure 5 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.

[0119] In another feasible method, 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.

[0120] Combining the above formula (1) and formula (4), the preset formula can be obtained as the following formula (5).

[0121] V c (Q) = [(B + 2 × C × Q) × Q × (1-P c / P s )]+(A+B×Q+C×Q 2 )Formula (5)

[0122] 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.

[0123] Compared with the previous feasible method, in this embodiment, the measured value and the standard pressure value are not compared first, but 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.

[0124] In another feasible embodiment, the specific implementation process of step S130 includes steps S134 to S136.

[0125] S134, determine whether the measured value is within a preset range; if so, execute step S135; if not, execute step S136.

[0126] 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, the measured value is within the preset range. That is, in this embodiment, the comparison relationship between the measured value and the standard pressure value can refer to the difference between the two.

[0127] S135 , substituting 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.

[0128] S136, substituting the set flow point, 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.

[0129] In this embodiment, when executing 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.

[0130] 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 sA larger value is selected, that is, the inlet pressure under standard working conditions is high pressure. s ≥P c , therefore, P c / P s ≤1, then 1-P c / 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.

[0131] The standard pressure value P mentioned in this application s The mass flow controller can be designed based on the empirical values ​​of the application field. 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.

[0132] 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.

[0133] It will be understood that the above embodiments are merely exemplary embodiments for illustrating the principles of the present invention, and the present invention is not limited thereto. Those skilled in the art will appreciate that various modifications and improvements can be made without departing from the spirit and substance of the present invention, and such modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A flow control method for a mass flow controller, characterized in that: The flow control method comprises: Receive the set flow point; Obtaining a measured value of the inlet pressure of the mass flow controller under actual working conditions; A standard value of the driving parameter corresponding to the set flow point is determined based on a first preset relationship between the set flow point obtained by calibrating the inlet end pressure at the standard pressure value and the driving parameter of the regulating valve of the mass flow controller, and the standard value of the driving parameter is selectively pressure-compensated based on a comparison relationship between the measured value and the standard pressure value, and a selectively compensated output value of the driving parameter is determined and transmitted to the regulating valve to control the opening of the regulating valve from 0% 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: 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: 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, no pressure compensation is performed on the standard value of the driving parameter or the compensation amount of the pressure compensation on 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; The lower limit value of the preset range is smaller than the standard pressure value, and the upper limit value is larger than the standard pressure value, and the absolute value of the difference between the lower limit value and the upper limit value and the standard pressure value is 5psi.

3. The flow control method according to claim 2, characterized in that: The method further comprises: determining a standard value of the driving parameter corresponding to the set flow point according to a first preset relationship between the set flow point obtained by calibrating the inlet end pressure at 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: Inputting the set flow point into the first preset relationship to determine the standard value of the driving parameter, and inputting the set flow point, the standard value of the driving parameter, the measured value, and the standard pressure value into a compensation formula to determine the selective compensation output value of the driving parameter; The compensation formula is determined based on the first-order derivative formula of the first preset relationship and the second preset relationship between the set flow point and the standard flow value; the standard flow value is the flow 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 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 at the standard pressure value is the set flow point.

4. The flow control method according to claim 3, characterized in that: After inputting the set flow point into the first preset relationship to determine the standard value of the driving parameter, the method further includes: Determining whether the measured value is within a preset range; If not, inputting 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 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 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 at a standard pressure value specifically includes: The air inlet pressure of the mass flow controller is set to a standard pressure value; Selecting a plurality of set flow points of the mass flow controller, and sequentially performing a calibration process on each 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 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 set flow points; According to the relationship curve, a first preset relationship expression for representing 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 performing of the calibration process for each of the plurality of set flow points specifically includes: Setting the driving parameter corresponding to the set flow point to 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 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 regulating valve, and the mass flow controller further includes: a controller, The controller includes at least one processor and at least one memory, wherein the memory stores a computer program, and the processor executes the computer program to perform the flow control method according to any one of claims 1 to 9.

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