Flow control method and mass flow controller

Abstract

The invention provides a flow control method and a mass flow controller, and the method comprises the steps: obtaining the current environment temperature of the mass flow controller, and determining a temperature sensitivity coefficient according to the current environment temperature; a control parameter corresponding to the current environment temperature is obtained according to the temperature sensitivity coefficient and a preset control parameter, and the opening degree of a control valve is adjusted according to the fluid flow value detected by a flow sensor based on the control parameter, so that the fluid flow value approaches the flow set value. The temperature sensitivity coefficient is determined according to the temperature of the current environment where the mass flow controller is located, so that the control parameters in the process of feeding back and adjusting the fluid flow according to the flow set value are changed in real time, and the control valve adjusting quantity change caused by temperature change can be compensated; therefore, the problems of overshoot and delay caused by too large or too small adjusting amount are avoided, the adaptive capacity of the mass flow controller to different environment temperatures is improved, and the precision and stability of the mass flow controller for controlling fluid flow are guaranteed.

Description

Technical Field

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

[0002] Mass Flow Controller (MFC) is a device used to precisely measure and control the mass flow of gas. It has important applications in the research and production of semiconductor and integrated circuit technology, special materials, chemical industry, petroleum industry, medicine, environmental protection and vacuum. Its typical application scenarios include: microelectronic process equipment (such as diffusion, oxidation, epitaxy, chemical vapor deposition (Chemical Vapor Deposition)

[0003] Deposition, PECVD), plasma etching, sputtering, ion implantation) and coating equipment, optical fiber melting, micro-reaction device, gas mixing and distribution system, gas sampling, capillary measurement, gas chromatograph and other analytical instruments.

[0004] The mass flow controller consists of a flow sensor, a control valve, and a controller. The flow analog signal of the flow sensor is converted into a digital value acceptable to the central processor through signal amplification and conditioning on the circuit board and A / D conversion. The controller uses the proportional integral differential (PID) control algorithm to control the opening of the control valve according to the flow value set by the user to achieve the purpose of accurately controlling the gas flow. However, existing mass flow controllers often have overshoot or delay problems, making it difficult to accurately control the fluid flow. Summary of the invention

[0005] The present invention aims to provide a flow control method and a mass flow controller. The flow control method can adapt to different temperatures and ensure the flow control accuracy.

[0006] To achieve the above object, as one aspect of the present invention, a flow control method is provided, the flow control method comprising:

[0007] Acquiring the current ambient temperature of the mass flow controller, and determining a temperature sensitivity coefficient according to the current ambient temperature;

[0008] According to the temperature sensitivity coefficient and the preset control parameters, a control parameter corresponding to the current ambient temperature is obtained, and based on the control parameter, the opening of the control valve is adjusted according to the fluid flow value detected by the flow sensor so that the fluid flow value approaches the flow setting value.

[0009] Optionally, obtaining a control parameter corresponding to the current ambient temperature according to the temperature sensitivity coefficient and a preset control parameter includes:

[0010] At least one of the preset control parameters is multiplied by the temperature sensitivity coefficient to obtain a control parameter corresponding to the current ambient temperature.

[0011] Optionally, the control parameter includes a proportional control parameter, an integral control parameter and a differential control parameter, and obtaining the control parameter corresponding to the current ambient temperature according to the temperature sensitivity coefficient and the preset control parameter includes:

[0012] The preset integral control parameter is multiplied by the temperature sensitivity coefficient to obtain an integral control parameter corresponding to the current ambient temperature.

[0013] Optionally, the control valve is a solenoid valve, and adjusting the opening of the control valve according to the fluid flow value detected by the flow sensor based on the control parameter so that the fluid flow value approaches a flow setting value includes:

[0014] The opening control signal is determined based on the calculation formula U=V+k1*Kp*E+Ki*I+Kd*(E-E1), wherein U is the opening control signal, V is a constant, k1 is the temperature sensitivity coefficient, k1*Kp is the integral control parameter, Ki is the integral control parameter, Kd is the differential control parameter, E is the deviation between the fluid flow value detected by the flow sensor in the current control cycle and the fluid flow value detected in the previous control cycle, E1 is the deviation in the previous control cycle, I is the integral value, and V is the opening voltage required for the solenoid valve to open at a preset normal temperature.

[0015] Optionally, determining the temperature sensitivity coefficient according to the current ambient temperature includes:

[0016] Based on the calculation formula k1=(1+(T1-T0)×B)×(1+(T1-T0)×B), the temperature sensitivity coefficient is determined according to the current ambient temperature, wherein k1 is the temperature sensitivity coefficient, T1 is the current ambient temperature, T0 is the preset normal temperature, and B is the preset temperature coefficient.

[0017] Optionally, determining the temperature sensitivity coefficient according to the current ambient temperature includes:

[0018] Based on the correspondence between the ambient temperature and the temperature sensitivity coefficient obtained in advance by calibration, the temperature sensitivity coefficient corresponding to the current ambient temperature is determined.

[0019] Optionally, the flow control method further includes:

[0020] Acquiring a front-end fluid pressure of a control valve of the mass flow controller, and determining a pressure sensitivity coefficient according to the front-end fluid pressure;

[0021] The obtaining, according to the temperature sensitivity coefficient and the preset control parameter, a control parameter corresponding to the current ambient temperature includes:

[0022] According to the temperature sensitivity coefficient, the pressure sensitivity coefficient and the preset control parameter, a control parameter corresponding to the current ambient temperature and the front-end fluid pressure is obtained.

[0023] Optionally, obtaining the control parameter corresponding to the current ambient temperature and the front-end fluid pressure according to the temperature sensitivity coefficient, the pressure sensitivity coefficient and the preset control parameter includes:

[0024] At least one of the preset control parameters is multiplied by the temperature sensitivity coefficient and the pressure sensitivity coefficient to obtain a control parameter corresponding to the current ambient temperature and the front-end fluid pressure.

[0025] Optionally, determining the pressure sensitivity coefficient according to the front-end fluid pressure includes:

[0026] Based on the calculation formula k2=a×P+b, the pressure sensitivity coefficient is determined according to the front-end fluid pressure, wherein k2 is the pressure sensitivity coefficient, P is the front-end fluid pressure, and a and b are preset constants.

[0027] As a second aspect of the present invention, a mass flow controller is provided, comprising a controller, a fluid passage, a flow sensor and a control valve, wherein the controller comprises a processor and a memory, wherein a computer program is stored in the memory, and when the computer program is executed by the processor, the flow control method described above is implemented.

[0028] Optionally, the mass flow controller further comprises a pressure sensor, wherein the pressure sensor is used to detect the fluid pressure at the inlet end of the fluid passage, and the controller is further used to determine a preset control parameter according to the fluid pressure.

[0029] Optionally, the flow sensor is a thermal flow sensor.

[0030] Optionally, the control valve is a solenoid valve.

[0031] As a third aspect of the present invention, a calibration method for a mass flow controller is provided, the calibration method for the mass flow controller comprising:

[0032] The temperature calibration steps include:

[0033] Adjusting the proportional control parameter at different ambient temperatures so that the response speed of the mass flow controller meets the requirements, and determining the ratio between the proportional control parameter that meets the requirements and the preset control parameter corresponding to the preset normal temperature as the temperature sensitivity coefficient corresponding to the current ambient temperature;

[0034] Based on the temperature sensitivity coefficients corresponding to different current ambient temperatures, a corresponding relationship between the current ambient temperature and the temperature sensitivity coefficient is obtained.

[0035] As an optional embodiment of the present invention, the calibration of the mass flow controller

[0036] The method also includes:

[0037] The pressure calibration steps include:

[0038] Adjusting the proportional control parameter under different front-end fluid pressure conditions so that the response speed of the mass flow controller meets the requirements, and determining the ratio between the proportional control parameter that meets the requirements and the preset control parameter as the pressure sensitivity coefficient corresponding to the current front-end fluid pressure;

[0039] Based on the pressure sensitivity coefficients corresponding to different front-end fluid pressures, a corresponding relationship between the front-end fluid pressure and the pressure sensitivity coefficient is obtained.

[0040] As an optional implementation manner of the present invention, obtaining the corresponding relationship between the front-end fluid pressure and the pressure sensitivity coefficient based on the pressure sensitivity coefficient corresponding to different front-end fluid pressures includes:

[0041] Substitute the two sets of front-end fluid pressures and the corresponding pressure sensitivity coefficients into the calculation formula k2=a×P+b, and obtain the values ​​of constants a and b in the calculation formula, where k2 is the pressure sensitivity coefficient and P is the front-end fluid pressure.

[0042] In the flow control method and mass flow controller provided by the present invention, the controller can determine the temperature sensitivity coefficient in real time according to the current ambient temperature of the flow controller, thereby changing the control parameters of the fluid flow process according to the flow setting value feedback in real time, and then being able to compensate for the change in the control valve adjustment amount caused by the temperature change, thereby avoiding overshoot and delay problems caused by excessive or insufficient adjustment amount, improving the adaptability of the mass flow controller to different ambient temperatures, and ensuring the accuracy and stability of the mass flow controller in controlling the fluid flow. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings:

[0044] Figure 1 It is a schematic diagram of a flow control curve of a mass flow controller at different temperatures in the related art;

[0045] Figure 2 is a flow chart of a flow control method provided by an embodiment of the present invention;

[0046] Figure 3 is a schematic structural diagram of a mass flow controller provided by an embodiment of the present invention;

[0047] Figure 4 It is a schematic diagram of the principle of controlling fluid flow by the flow control method provided by the present invention;

[0048] Figure 5 is a schematic diagram of a flow control curve of a mass flow controller at different temperatures provided by an embodiment of the present invention;

[0049] Figure 6 is a flow chart of a flow control method provided by an embodiment of the present invention;

[0050] Figure 7 It is a schematic diagram of a flow control curve of a mass flow controller under different front-end fluid pressures in the related art;

[0051] Figure 8 Schematic diagram of a flow control curve of a mass flow controller provided by an embodiment of the present invention under different front-end fluid pressures. DETAILED DESCRIPTION

[0052] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0053] In the related art, the control valve of the mass flow controller usually adopts a solenoid valve, and its operating temperature range is generally 0℃~50℃. The factory PID control parameter adjustment generally uses room temperature (e.g. 25℃) for parameter adjustment. The PID control parameter is generally fixed to a fixed value. This will cause the current ambient temperature to be relatively low (e.g. 10℃), the solenoid valve coil resistance to become smaller, the electromagnetic force to become larger, the required drive current to become smaller, causing overshoot (overshoot greater than 1% FS). When the current ambient temperature is relatively high (e.g. 40℃), the response time is greater than 1 second, resulting in control delays, such as Figure 1The figure shows the flow control curve of the mass flow controller at different temperatures in the related art. It can be seen from the figure that the existing mass flow controller has poor automatic temperature adaptability, resulting in low fluid flow control accuracy.

[0054] Therefore, how to provide a mass flow controller and a flow control method with strong temperature adaptability has become a technical problem to be solved urgently in this field.

[0055] To achieve the above object, as one aspect of the present invention, a flow control method is provided. The flow control method is applied to a mass flow controller. The mass flow controller includes a fluid passage, a flow sensor and a control valve. The control valve is used to adjust the fluid flow (e.g., gas flow) flowing through the fluid passage. Figure 1 As shown, the flow control method includes:

[0056] Step S1, obtaining the current ambient temperature of the mass flow controller, and determining the temperature sensitivity coefficient according to the current ambient temperature;

[0057] Step S2, according to the temperature sensitivity coefficient and the preset control parameters, obtain the control parameters corresponding to the current ambient temperature, and adjust the opening of the control valve according to the fluid flow value detected by the flow sensor based on the control parameters, so that the fluid flow value approaches the flow setting value (that is, adjust the fluid flow according to the flow setting value through feedback regulation (such as PID regulation)).

[0058] The flow control method provided by the present invention determines the temperature sensitivity coefficient in real time according to the current ambient temperature of the mass flow controller, thereby changing the control parameters of the fluid flow rate adjustment process according to the flow setting value feedback in real time, thereby being able to compensate for the change in the control valve adjustment amount caused by the temperature change, thereby avoiding overshoot and delay problems caused by excessive or insufficient adjustment amount, improving the adaptability of the mass flow controller to different ambient temperatures, and ensuring the accuracy and stability of the mass flow controller in controlling the fluid flow.

[0059] As an optional implementation manner of the present invention, obtaining a control parameter corresponding to the current ambient temperature according to the temperature sensitivity coefficient and the preset control parameter may specifically include:

[0060] At least one of the preset control parameters is multiplied by the temperature sensitivity coefficient to obtain a control parameter corresponding to the current ambient temperature.

[0061] As an optional implementation of the present invention, the control parameters include proportional control parameters, integral control parameters and differential control parameters, that is, the embodiment of the present invention adjusts the opening of the control valve by proportional integral differential (PID) adjustment.

[0062] As an optional implementation manner of the present invention, determining the temperature sensitivity coefficient according to the current ambient temperature includes:

[0063] Based on the calculation formula k1=(1+(T1-T0)×B)×(1+(T1-T0)×B), the temperature sensitivity coefficient is determined according to the current ambient temperature, where k1 is the temperature sensitivity coefficient, T1 is the current ambient temperature, T0 is the preset normal temperature, and B is the preset temperature coefficient.

[0064] Specifically, the electromagnetic force of the solenoid valve is related to the magnitude of the valve current, and its calculation formula is:

[0065] F=e×S×(N×I)×(N×I) / (2×K×f×f×L×L), where F is the electromagnetic force, e is the vacuum magnetic permeability, S is the cross-sectional area of ​​the magnetic path (in square meters), K×f is the leakage coefficient, L is the gap length, N is the number of coil turns, and I is the current.

[0066] The resistance value at different temperatures can be calculated based on the temperature coefficient of the coil. For example, at 25°C, the coil resistance value is R0, and the temperature coefficient is B. The calculation formula for the current resistance R is:

[0067] R=R0×(1+(T1–T0)×B), where R is the coil resistance, R0: resistance at room temperature, B is the preset temperature coefficient, T0 is the preset room temperature, and T1 is the current ambient temperature.

[0068] According to the above two calculation formulas, when the valve voltage U is consistent, let the ratio of the electromagnetic force generated by the control valve at the preset normal temperature T0 and the current ambient temperature T1 be k1, then:

[0069] F0=e×S×(N×U / R0)×(N×U / R0) / (2×K×f×f×L×L);

[0070] F1=e×S×(N×U / (R0×(1+(T1–T0)×B)))×(N×U / (R0×(1+(T1–

[0071] T0)×B))) / (2×K×f×f×L×L);

[0072] k1=F0 / F1=(1+(T1–T0)×B)×(1+(T1–T0)×B).

[0073] It can be concluded that the temperature sensitivity coefficient k1 is only related to the current ambient temperature T1, the preset normal temperature T0 and the preset temperature coefficient B (and increases with the increase of the current ambient temperature T1). The preset normal temperature T0 and the preset temperature coefficient B can be pre-calibrated and pre-stored in the mass flow controller (external storage unit). During the use of the mass flow controller, it is only necessary to obtain the current ambient temperature T1 to determine the temperature sensitivity coefficient k1 corresponding to different temperatures.

[0074] Considering that the proportional term has the most obvious regulating effect on the response time in PID regulation, in order to simplify the calculation amount of PID regulation, as a preferred embodiment of the present invention, the control parameters corresponding to the current ambient temperature are obtained according to the temperature sensitivity coefficient and the preset control parameters, including:

[0075] The preset integral control parameter is multiplied by the temperature sensitivity coefficient to obtain the integral control parameter corresponding to the current ambient temperature.

[0076] As an optional embodiment of the present invention, the control valve is a solenoid valve, and the opening of the control valve is adjusted according to the fluid flow value detected by the flow sensor based on the control parameter so that the fluid flow value approaches the flow setting value, including:

[0077] The opening control signal is determined based on the calculation formula U=V+k1*Kp*E+Ki*I+Kd*(E–E1), where U is the opening control signal, V is a constant, k1 is the temperature sensitivity coefficient, k1*Kp is the integral control parameter, Ki is the integral control parameter, Kd is the differential control parameter, E is the deviation between the fluid flow value detected by the flow sensor in the current control cycle and the fluid flow value detected in the previous control cycle, E1 is the deviation of the previous control cycle, I is the integral value, and V is the opening voltage required for the solenoid valve to open at a preset normal temperature (for example, 25°C).

[0078] That is, the original proportional-integral-differential adjustment formula is U=V+Kp*E+Ki*I+Kd*(E–E1). In the embodiment of the present invention, the preset integral control parameter Kp is multiplied by the temperature sensitivity coefficient k1 determined in real time to obtain the integral control parameter k1*Kp used in the embodiment of the present invention, and the integral control parameter Ki and the differential control parameter Kd remain unchanged.

[0079] like Figure 4 The figure shows the principle schematic diagram of the flow control method provided by the present invention for controlling the flow of a fluid. The mass flow controller receives a setting signal to determine the flow setting value. The signal of the temperature sensor is received to determine the temperature sensitivity coefficient k1, and the control parameter is determined according to the temperature sensitivity coefficient k1. The opening of the control valve (solenoid valve) is adjusted in real time according to the fluid flow value detected by the flow sensor based on the PID adjustment algorithm including the opening voltage V, so that the fluid flow value approaches the flow setting value.

[0080] As an optional implementation of the present invention, step S1 of determining the temperature sensitivity coefficient according to the current ambient temperature includes:

[0081] Based on the correspondence between the ambient temperature and the temperature sensitivity coefficient obtained in advance, the temperature sensitivity coefficient corresponding to the current ambient temperature is determined.

[0082] In an embodiment of the present invention, the temperature sensitivity coefficient can also be determined by pre-calibration, that is, the control parameters of the PID adjustment algorithm are changed in advance at different ambient temperatures so that the adjustment effect of the mass flow controller meets the requirements, so as to determine the control parameters corresponding to different ambient temperatures, and then obtain the temperature sensitivity coefficients corresponding to different ambient temperatures. When the mass flow controller is put into use, the controller (central control unit) can determine the corresponding temperature sensitivity coefficient in real time according to the current ambient temperature based on the correspondence between the pre-stored ambient temperature and the temperature sensitivity coefficient, and then adjust the corresponding control parameters.

[0083] The inventors of the present invention also found in their research that another reason for the low accuracy of fluid flow control in the related art is that the front-end pressure of the mass flow controller is unstable. Specifically, in the related art, the fluid pressure range of the front end (i.e., the part of the fluid passage located on the upstream side of the control valve) is generally 0.1MPa to 0.3MPa, and when the factory PID control parameters are adjusted, the control parameters are generally adjusted to a fixed value based on the intermediate pressure (e.g., 0.2MPa). This will cause an overshoot greater than 1% FS when the front-end pressure is relatively large (e.g., 0.3MPa), and a response time greater than 1 second when the front-end pressure is relatively small (e.g., 0.1MPa). The mass flow controller has poor automatic adaptability to the front-end pressure, such as Figure 7 The figure shows the flow control curve of the mass flow controller under different front-end pressures in the related art. It can be seen from the figure that the existing mass flow controller has poor automatic temperature adaptability, resulting in low fluid flow control accuracy.

[0084] In order to solve the above technical problems, as a preferred implementation of the present invention, as Figure 6 As shown, the flow control method also includes:

[0085] Step S01, obtaining the front-end fluid pressure of the control valve of the mass flow controller, and determining the pressure sensitivity coefficient according to the front-end fluid pressure;

[0086] In step S2, the control parameters corresponding to the current ambient temperature are obtained according to the temperature sensitivity coefficient and the preset control parameters, which specifically include:

[0087] According to the temperature sensitivity coefficient, the pressure sensitivity coefficient and the preset control parameters, the control parameters corresponding to the current ambient temperature and the front-end fluid pressure are obtained.

[0088] In the flow control method provided in the embodiment of the present invention, the mass flow controller can determine the temperature sensitivity coefficient and the pressure sensitivity coefficient in real time according to the current ambient temperature of the mass flow controller and the front-end fluid pressure, thereby changing the control parameters of the fluid flow rate adjustment process according to the flow setting value feedback in real time, and then can simultaneously compensate for the changes in the control valve adjustment amount caused by the changes in temperature and the front-end fluid pressure, thereby avoiding overshoot and delay problems caused by excessive or too small adjustment amount, improving the adaptability of the mass flow controller to different ambient temperatures and front-end fluid pressures, and ensuring the accuracy and stability of the mass flow controller in controlling the fluid flow.

[0089] As an optional implementation of the present invention, according to the temperature sensitivity coefficient, the pressure sensitivity coefficient and the preset control parameters, the control parameters corresponding to the current ambient temperature and the front-end fluid pressure are obtained, including:

[0090] At least one of the preset control parameters is multiplied by the temperature sensitivity coefficient and the pressure sensitivity coefficient to obtain a control parameter corresponding to the current ambient temperature and the front-end fluid pressure.

[0091] As an optional embodiment of the present invention, the control valve is a solenoid valve, and the opening of the control valve is adjusted according to the fluid flow value detected by the flow sensor based on the control parameter so that the fluid flow value approaches the flow setting value, including:

[0092] The opening control signal is determined based on the calculation formula U=V+k1*k2*Kp*E+Ki*I+Kd*(E–E1), where U is the opening control signal, V is a constant, k1 is the temperature sensitivity coefficient, k2 is the pressure sensitivity coefficient, k1*k2*Kp is the integral control parameter, Ki is the integral control parameter, Kd is the differential control parameter, E is the deviation between the fluid flow value detected by the flow sensor in the current control cycle and the fluid flow value detected in the previous control cycle, E1 is the deviation of the previous control cycle, I is the integral value, and V is the opening voltage required for the solenoid valve to open at a preset normal temperature (for example, 25°C).

[0093] That is, the original proportional-integral-differential adjustment formula is U=V+Kp*E+Ki*I+Kd*(E–E1). In the embodiment of the present invention, the preset integral control parameter Kp is multiplied by the temperature sensitivity coefficient k1 and the pressure sensitivity coefficient k2 determined in real time to obtain the integral control parameter k1*k2*Kp used in the embodiment of the present invention, and the integral control parameter Ki and the differential control parameter Kd remain unchanged.

[0094] As an optional implementation of the present invention, determining the pressure sensitivity coefficient according to the front-end fluid pressure includes:

[0095] Based on the calculation formula k2=a×P+b, the pressure sensitivity coefficient is determined according to the front-end fluid pressure, where k2 is the pressure sensitivity coefficient, P is the front-end fluid pressure, and a and b are preset constants.

[0096] As a second aspect of the present invention, a mass flow controller is provided, such as Figure 3 As shown, the mass flow controller includes a controller (central control unit), a fluid passage, a flow sensor and a control valve. The controller includes a processor and a memory. The memory stores a computer program. When the computer program is executed by the processor, the flow control method of any one of claims 1 to 9 is implemented.

[0097] In the mass flow controller provided by the present invention, the controller can determine the temperature sensitivity coefficient in real time according to the current ambient temperature of the flow controller, thereby changing the control parameters of the fluid flow process according to the flow setting value feedback in real time, and then being able to compensate for the change in the control valve adjustment amount caused by the temperature change, thereby avoiding overshoot and delay problems caused by excessive or insufficient adjustment amount, improving the adaptability of the mass flow controller to different ambient temperatures, and ensuring the accuracy and stability of the mass flow controller in controlling the fluid flow.

[0098] As an optional embodiment of the present invention, Figure 3 As shown, the controller receives the current ambient temperature fed back by the temperature sensor through the A / D conversion circuit.

[0099] As an optional embodiment of the present invention, the mass flow controller further includes a pressure sensor, which is used to detect the fluid pressure at the inlet end of the fluid passage, and the controller is further used to determine the preset control parameters according to the fluid pressure.

[0100] As an optional embodiment of the present invention, Figure 3 As shown, the controller receives the fluid pressure fed back by the pressure sensor through the A / D conversion circuit.

[0101] As an optional embodiment of the present invention, Figure 3 As shown, the flow sensor is a thermal flow sensor.

[0102] As an optional embodiment of the present invention, Figure 3 As shown, the mass flow controller also includes a thermal flow sensor driving circuit. The controller supplies power to the thermal flow sensor through the thermal flow sensor driving circuit and collects sensor signals through the A / D conversion circuit.

[0103] As an optional embodiment of the present invention, Figure 3 As shown, the control valve is a solenoid valve.

[0104] As an optional embodiment of the present invention, Figure 3 As shown, the mass flow controller also includes a solenoid valve drive circuit. The controller is connected to the solenoid valve control unit through the solenoid valve drive circuit and sends a corresponding control signal to the solenoid valve control unit to drive the solenoid valve to change its opening through the solenoid valve drive circuit. At the same time, the drive voltage feedback of the solenoid valve is collected through the A / D conversion circuit (analog-to-digital conversion circuit).

[0105] like Figure 5 FIG. 1 shows the flow control curve of the mass flow controller provided by the embodiment of the present invention at different temperatures (the vertical axis is the percentage of the fluid flow rate in the maximum range, in %). Figure 5 It can be seen that, given the same flow setting value, the mass flow controller provided by the embodiment of the present invention has basically the same response time at different temperatures and no overshoot phenomenon, has strong adaptability to different ambient temperatures, and has high accuracy in controlling fluid flow.

[0106] like Figure 8 The flow control curve of the mass flow controller provided by the embodiment of the present invention under different front-end fluid pressures is shown. Figure 8 It can be seen that, given the same flow setting value, the response time of the mass flow controller provided by the embodiment of the present invention under different front-end fluid pressures is basically the same and there is no overshoot phenomenon, it has strong adaptability to different front-end fluid pressures and high accuracy in controlling fluid flow.

[0107] As a third aspect of the present invention, a calibration method for a mass flow controller is provided, the calibration method for a mass flow controller comprising:

[0108] The temperature calibration steps include:

[0109] Adjust the proportional control parameter at different ambient temperatures so that the response speed of the mass flow controller meets the requirements (for example, the response time is required to be less than 1 second, and the overshoot is controlled within 1% FS), and determine the ratio between the proportional control parameter that meets the requirements and the preset control parameter corresponding to the preset normal temperature as the temperature sensitivity coefficient corresponding to the current ambient temperature;

[0110] Based on the temperature sensitivity coefficients corresponding to different current ambient temperatures, a corresponding relationship between the current ambient temperature and the temperature sensitivity coefficient is obtained.

[0111] As an optional embodiment of the present invention, the calibration method of the mass flow controller also includes:

[0112] The pressure calibration steps include:

[0113] Adjusting the proportional control parameter under different front-end fluid pressure conditions so that the response speed of the mass flow controller meets the requirements, and determining the ratio between the proportional control parameter that meets the requirements and the preset control parameter as the pressure sensitivity coefficient corresponding to the current front-end fluid pressure;

[0114] Based on the pressure sensitivity coefficients corresponding to different front-end fluid pressures, a corresponding relationship between the front-end fluid pressure and the pressure sensitivity coefficient is obtained.

[0115] As an optional implementation of the present invention, based on the pressure sensitivity coefficients corresponding to different front-end fluid pressures, the corresponding relationship between the front-end fluid pressure and the pressure sensitivity coefficient is obtained, including:

[0116] Substitute the two sets of front-end fluid pressures and the corresponding pressure sensitivity coefficients into the calculation formula k2=a×P+b, and obtain the values ​​of constants a and b in the calculation formula, where k2 is the pressure sensitivity coefficient and P is the front-end fluid pressure. That is, the solution of the linear equation k2=a×P+b is determined by the coordinate values ​​of the two points.

[0117] In other embodiments of the present invention, multiple sets of front-end fluid pressures and corresponding pressure sensitivity coefficients may be collected, and the values ​​of constants a and b in the calculation formula k2=a×P+b may be determined by fitting.

[0118] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A flow control method, It is characterized in that The flow control method comprises: Acquiring the current ambient temperature of the mass flow controller, and determining a temperature sensitivity coefficient according to the current ambient temperature; According to the temperature sensitivity coefficient and the preset control parameters, a control parameter corresponding to the current ambient temperature is obtained, and based on the control parameter, the opening of the control valve is adjusted according to the fluid flow value detected by the flow sensor so that the fluid flow value approaches the flow setting value.

2. The flow control method according to claim 1, It is characterized in that The obtaining, according to the temperature sensitivity coefficient and the preset control parameter, a control parameter corresponding to the current ambient temperature includes: At least one of the preset control parameters is multiplied by the temperature sensitivity coefficient to obtain a control parameter corresponding to the current ambient temperature.

3. The flow control method according to claim 2, It is characterized in that The control parameters include proportional control parameters, integral control parameters and differential control parameters. The control parameters corresponding to the current ambient temperature are obtained according to the temperature sensitivity coefficient and the preset control parameters, including: The preset integral control parameter is multiplied by the temperature sensitivity coefficient to obtain an integral control parameter corresponding to the current ambient temperature.

4. The flow control method according to claim 3, It is characterized in that The control valve is a solenoid valve, and the opening of the control valve is adjusted according to the fluid flow value detected by the flow sensor based on the control parameter so that the fluid flow value approaches the flow setting value, including: The opening control signal is determined based on the calculation formula U=V+k1*Kp*E+Ki*I+Kd*(E-E1), wherein U is the opening control signal, V is a constant, k1 is the temperature sensitivity coefficient, k1*Kp is the integral control parameter, Ki is the integral control parameter, Kd is the differential control parameter, E is the deviation between the fluid flow value detected by the flow sensor in the current control cycle and the fluid flow value detected in the previous control cycle, E1 is the deviation in the previous control cycle, I is the integral value, and V is the opening voltage required for the solenoid valve to open at a preset normal temperature.

5. The flow control method according to any one of claims 1 to 4, It is characterized in that The determining of the temperature sensitivity coefficient according to the current ambient temperature includes: Based on the calculation formula k1=(1+(T1-T0)×B)×(1+(T1-T0)×B), the temperature sensitivity coefficient is determined according to the current ambient temperature, wherein k1 is the temperature sensitivity coefficient, T1 is the current ambient temperature, T0 is the preset normal temperature, and B is the preset temperature coefficient.

6. The flow control method according to any one of claims 1 to 4, It is characterized in that The determining of the temperature sensitivity coefficient according to the current ambient temperature includes: Based on the correspondence between the ambient temperature and the temperature sensitivity coefficient obtained in advance by calibration, the temperature sensitivity coefficient corresponding to the current ambient temperature is determined.

7. The flow control method according to any one of claims 1 to 4, It is characterized in that The flow control method further comprises: Acquiring a front-end fluid pressure of a control valve of the mass flow controller, and determining a pressure sensitivity coefficient according to the front-end fluid pressure; The obtaining, according to the temperature sensitivity coefficient and the preset control parameter, a control parameter corresponding to the current ambient temperature includes: According to the temperature sensitivity coefficient, the pressure sensitivity coefficient and the preset control parameter, a control parameter corresponding to the current ambient temperature and the front-end fluid pressure is obtained.

8. The flow control method according to claim 7, It is characterized in that The obtaining of the control parameter corresponding to the current ambient temperature and the front-end fluid pressure according to the temperature sensitivity coefficient, the pressure sensitivity coefficient and the preset control parameter comprises: At least one of the preset control parameters is multiplied by the temperature sensitivity coefficient and the pressure sensitivity coefficient to obtain a control parameter corresponding to the current ambient temperature and the front-end fluid pressure.

9. The flow control method according to claim 7, It is characterized in that Determining the pressure sensitivity coefficient according to the front end fluid pressure includes: Based on the calculation formula k2=a×P+b, the pressure sensitivity coefficient is determined according to the front-end fluid pressure, wherein k2 is the pressure sensitivity coefficient, P is the front-end fluid pressure, and a and b are preset constants.

10. A mass flow controller, comprising a controller, a fluid passage, a flow sensor and a control valve, wherein the controller comprises a processor and a memory, wherein a computer program is stored in the memory, and when the computer program is executed by the processor, the flow control method according to any one of claims 1 to 9 is implemented.

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