Laminar flow mass flow control system and method based on feedforward compensation and cascade control

Abstract

The invention belongs to the technical field of flow measurement and control, and discloses a laminar flow mass flow control system and method based on feed-forward compensation and cascade control. In the system, a laminar flow element is provided with a low-voltage side detection port and a high-voltage side detection port; the low-pressure side detection port is connected with the low-pressure ends of the pressure sensor and the differential pressure sensor, and the high-pressure side detection port is connected with the high-pressure end of the differential pressure sensor; the laminar flow element is connected with the regulating valve; the output end of the pressure sensor is connected with the input end of the feedforward compensation module; the output end of the A / D converter is connected with the input end of the main controller and the input end of the auxiliary controller; the output end of the main controller is connected with the input end of the auxiliary controller. The output end of the feed-forward compensation module is connected with the control end of the regulating valve; the output end of the auxiliary controller is connected with the control end of the adjusting valve through the D / A converter. The feed-forward compensation and cascade control technology is adopted, the pressure feed-forward compensation module and the differential pressure pair control loop are additionally arranged, and the problem that the flow precision of a control system is not accurate due to sudden change of fluid pressure is solved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of flow measurement and control, and particularly relates to a laminar flow mass flow control system and method based on feedforward compensation and cascade control. BACKGROUND

[0002] The laminar flow mass flow controller or control system is an important component in many industrial control fields, and has an important influence on the quality of many industrial products. For example, the laminar flow mass flow controller or control system is an important component of an etching machine in the chip manufacturing field. However, in the actual operation of the laminar flow mass flow controller or control system, when the fluid pressure, particularly the gas pressure, in the pipeline suddenly changes (for example, a pressure reducing valve located at the front end of the gas path fails or is damaged), the flow control accuracy of the laminar flow mass flow control system will be inaccurate. In some occasions where the flow control accuracy of the gas is required to be high, such as the etching machine in the chip manufacturing field, the control accuracy of the gas flow is required to be high, and if the flow control accuracy is inaccurate, it will have a serious impact on the quality of chip manufacturing, thereby causing the laminar flow mass flow controller or control system to fail to meet the use requirements. Therefore, it is necessary to reduce and avoid the problem of inaccurate flow accuracy of the control system caused by sudden change of the fluid pressure, particularly the gas pressure, so as to improve the accuracy, reliability, stability and anti-interference ability of the laminar flow mass flow controller or control system. SUMMARY

[0003] The present application aims to provide a laminar flow mass flow control system and method based on feedforward compensation and cascade control, which increases a pressure feedforward compensation module and a differential pressure auxiliary control loop in the laminar flow mass flow control system by adopting feedforward compensation and cascade control technology, thereby avoiding the problem of inaccurate flow accuracy of the control system caused by sudden change of the fluid pressure, particularly the gas pressure.

[0004] To achieve the above-mentioned purpose, the present application provides the following technical scheme: In a first aspect, the present application provides a laminar flow mass flow control system based on feedforward compensation and cascade control, comprising: a main controller, a feedforward compensation module, an A / D converter, a D / A converter, an auxiliary controller, a differential pressure sensor, a pressure sensor, a laminar flow element and a regulating valve. The laminar flow element is provided with a low-pressure side detection port and a high-pressure side detection port; the low-pressure side detection port is connected to the low-pressure end of the pressure sensor and the differential pressure sensor, and the high-pressure side detection port is connected to the high-pressure end of the differential pressure sensor; and the laminar flow element is connected to the regulating valve. The output end of the pressure sensor is connected to the input end of the feedforward compensation module and the input end of the A / D converter; the output end of the differential pressure sensor is connected to the input end of the A / D converter; the output end of the A / D converter is connected to the input end of the main controller and the input end of the auxiliary controller; the output end of the main controller is connected to the input end of the auxiliary controller; The output end of the feedforward compensation module is connected to the control end of the regulating valve; and the output end of the secondary controller is connected to the control end of the regulating valve through a D / A converter.

[0005] The further improvement of the present application is that the input signal of the feedforward compensation module is a pressure mutation signal, and the output is a compensation signal, which is sent to the regulating valve to reduce or offset the influence of the fluid pressure signal, especially the gas pressure signal, on the flow when the fluid pressure signal, especially the gas pressure signal, is suddenly changed, so that the flow output value of the laminar flow mass flow control system can maintain the control accuracy to meet the use requirements. When the transfer function of the pressure mutation interference channel is , the transfer function of the regulating valve is , and the transfer function of the secondary controlled object is , the transfer function of the feedforward compensation module is : .

[0006] The further improvement of the present application is that a temperature sensor is further included; the temperature sensor is used to measure the temperature of the fluid flowing through the laminar flow element; and the output end of the temperature sensor is connected to the input end of the primary controller.

[0007] The further improvement of the present application is that a secondary controlled object is further included; the secondary controller, the D / A converter, the regulating valve, the secondary controlled object, the differential pressure sensor and the A / D converter constitute a secondary control loop.

[0008] The further improvement of the present application is that a primary controlled object is further included; the primary controller, the secondary control loop, the primary controlled object and the flow detector constitute a primary control loop.

[0009] The further improvement of the present application is that the flow detector is composed of a temperature sensor, a pressure sensor and a differential pressure sensor.

[0010] The further improvement of the present application is that the input signal of the feedforward compensation module is a pressure mutation signal from the pressure sensor, and the output is a compensation signal; and the compensation signal is sent to the regulating valve to reduce or offset the influence of the fluid pressure signal, especially the gas pressure signal, on the flow when the fluid pressure signal, especially the gas pressure signal, is suddenly changed.

[0011] The further improvement of the present application is that the compensation signal output by the feedforward compensation module is superimposed with the analog signal output by the D / A converter, and then sent to the regulating valve to adjust the differential pressure.

[0012] The further improvement of the present application is that a communication module and a memory are further included; and the primary controller is connected to the communication module and the memory.

[0013] The further improvement of the present application is that the temperature sensor is arranged at the inlet of the laminar flow element, and the adjusting valve is arranged at the outlet of the laminar flow element. Alternatively, the temperature sensor is arranged at the outlet of the laminar flow element, and the adjusting valve is arranged at the inlet of the laminar flow element. Alternatively, the temperature sensor and the adjusting valve are both arranged at the inlet of the laminar flow element. Alternatively, the temperature sensor and the adjusting valve are both arranged at the outlet of the laminar flow element.

[0014] In the second aspect, the present application provides a laminar flow mass flow control method based on feedforward compensation and cascade control, comprising: When the fluid pressure suddenly changes, resulting in the deviation of the flow set value and the flow actual detection value, the flow deviation value is sent to the main controller, the main controller calculates and outputs a pressure difference set value, the pressure difference set value is compared with the pressure difference detection value detected by the pressure difference sensor in the secondary control loop to obtain a pressure difference deviation, the pressure difference deviation is sent to the secondary controller, the secondary controller calculates and outputs a control signal to the D / A converter, the digital quantity is converted into an analog quantity by the D / A converter, and the analog quantity is superimposed with the output analog signal of the feedforward compensation module and then sent to the adjusting valve, the adjusting valve adjusts the pressure difference value by changing the valve opening degree and through the secondary controlled object, the pressure difference is superimposed with the output signal of the pressure sudden change interference channel, and the superimposed pressure difference is detected by the pressure difference sensor in the secondary control loop and then converted into a digital quantity by the A / D converter to obtain a pressure difference detection value; the pressure difference set value output by the main controller is compared with the pressure difference detection value in the secondary control loop, the deviation is sent to the secondary controller again, the secondary controller calculates and outputs a control signal to the D / A converter, the digital quantity is converted into an analog quantity by the D / A converter, and the analog quantity is superimposed with the output analog signal of the feedforward compensation module and then sent to the adjusting valve to further adjust the pressure difference, and the secondary control loop control is repeated so that the pressure difference reaches the set value. When the pressure difference reaches the set value, the flow value is further adjusted by the main controlled object, and the flow value is detected to obtain a flow actual detection value, the flow set value is compared with the flow detection value to obtain a flow deviation value, the flow deviation value is sent to the main controller, the flow is further adjusted through the secondary control loop and the main controlled object, and the circulation is repeated so that the flow reaches the set value.

[0015] The further improvement of the present application is that in the control process, the flow detection value is obtained by calculating the detection value of the pressure difference sensor in the secondary control loop, the detection value of the pressure sensor and the detection value of the temperature sensor; the specific process is as follows: The volumetric flow under standard conditions The volumetric flow under standard conditions is calculated by the following formula (1): (1) In the formula, Q is the volumetric flow under standard conditions; Q is the volumetric flow under standard conditions; temperature; pressure on the low pressure side; temperature-dependent coefficient; pressure-dependent coefficient; pressure difference between the low pressure side detection port and the high pressure side detection port.

[0016] Compared with the prior art, the present application has the following beneficial effects: the present application provides a laminar flow mass flow control system based on feedforward compensation and cascade control, comprising a main controller, a feedforward compensation module, an A / D converter, a D / A converter, a secondary controller, a pressure difference sensor, a pressure sensor, a laminar element and a regulating valve; the laminar element is provided with a low pressure side detection port and a high pressure side detection port; the low pressure side detection port is connected to the low pressure end of the pressure sensor and the pressure difference sensor, and the high pressure side detection port is connected to the high pressure end of the pressure difference sensor; the laminar element is connected to the regulating valve; the output end of the pressure sensor is connected to the input end of the feedforward compensation module and the input end of the A / D converter; the output end of the A / D converter is connected to the input end of the main controller and the input end of the secondary controller; the output end of the main controller is connected to the input end of the secondary controller; the output end of the feedforward compensation module is connected to the control end of the regulating valve; and the output end of the secondary controller is connected to the control end of the regulating valve through the D / A converter. The present application increases the pressure feedforward compensation module and the pressure difference secondary control loop in the laminar flow mass flow control system by adopting the feedforward compensation and cascade control technology, thereby avoiding the problem of inaccurate flow accuracy of the control system caused by sudden change of fluid pressure, especially gas pressure.

[0017] Further, the present application specifically increases the pressure signal feedforward compensation module and the secondary control loop with the controlled variable being the pressure difference in the laminar flow mass flow control system by adopting the feedforward compensation and cascade control technology. The pressure signal feedforward compensation module can quickly compensate the strong interference caused by sudden change of pressure, and the secondary control loop with the controlled variable being the pressure difference can quickly compensate the influence of sudden change of pressure on the pressure difference signal. By combining the feedforward compensation and cascade control technology, the problem of inaccurate flow accuracy of the control system caused by sudden change of fluid pressure, especially gas pressure, is avoided, so that the high-precision operation of the laminar flow mass flow control system can be maintained. The present application has the characteristics of strong anti-interference ability, high control precision, high reliability and good stability of the laminar flow mass flow control system. BRIEF DESCRIPTION OF DRAWINGS

[0018] The accompanying drawings, which form a part of the present application, are used to provide further understanding of the present application, and the illustrative embodiments of the present application and their description serve the purpose of explaining the present application, and do not constitute an improper limitation of the present application. In the drawings: Fig. 1 This is a schematic diagram of a laminar flow mass flow control system based on feedforward compensation and cascade control according to an embodiment of the present invention. Fig. 2 This is a schematic diagram of the flow detector according to an embodiment of the present invention; Fig. 3 This is a block diagram illustrating the operational structure of a laminar mass flow control system based on feedforward compensation and cascade control, according to an embodiment of the present invention. In the attached diagram: 1 Main controller, 2 Communication module, 3 Memory, 4 Feedforward compensation module, 5 A / D converter, 6 D / A converter, 7 Sub-controller, 8 Differential pressure sensor, 9 Pressure sensor, 10 Temperature sensor, 11 First connecting pipe, 12 Second connecting pipe, 13 High-pressure side detection port, 14 Laminar flow element, 15 Low-pressure side detection port, 16 Regulating valve. Detailed Implementation

[0019] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0020] The following detailed description is exemplary and intended to provide further detailed explanation of the invention. Unless otherwise specified, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this invention is for describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention.

[0021] Please see Figs. 1 to 3 As shown, this embodiment of the invention provides a laminar flow mass flow control system based on feedforward compensation and cascade control, including a main controller 1, a communication module 2, a memory 3, a feedforward compensation module 4, an A / D converter 5, a D / A converter 6, a secondary controller 7, a temperature sensor 10, a first connecting pipe 11, a second connecting pipe 12, a laminar flow element 14, and a regulating valve 16. The input end of the feedforward compensation module 4 is connected to the output end of the pressure sensor 9, and the output end of the feedforward compensation module 4 is connected to the control end of the regulating valve 16. The input terminal of the secondary controller 7 is connected to the output terminal of the main controller 1 and the output terminal of the A / D converter 5; the output terminal of the secondary controller 7 is connected to the control terminal of the regulating valve 16 through the D / A converter 6. The flow detector consists of a temperature sensor 10, a pressure sensor 9, and a differential pressure sensor 8. The laminar flow element 14 is provided with a low-pressure side detection port 15 and a high-pressure side detection port 13; the high-pressure side detection port 13 is close to the inlet of the laminar flow element 14; the low-pressure side detection port 15 is close to the outlet of the laminar flow element 14. The low-pressure side detection port 15 is connected to the low-pressure end of the pressure sensor 9 and the differential pressure sensor 8, and the high-pressure side detection port 13 is connected to the high-pressure end of the differential pressure sensor 8; the inlet and outlet of the laminar flow element 14 are connected to the second connecting pipeline 12 and the regulating valve 16 respectively; the inlet of the second connecting pipeline 12 is connected to the first connecting pipeline 11; the first connecting pipeline 11 is provided with the temperature sensor 10. The main controller 1 is connected to the communication module 2, the memory 3, the A / D converter 5, the temperature sensor 10, the differential pressure sensor 8 and the pressure sensor 9; the input end of the A / D converter 5 is connected to the output end of the differential pressure sensor 8 and the output end of the pressure sensor 9; the output end of the A / D converter 5 is connected to the input end of the main controller 1 and the input end of the sub-controller 7.

[0022] The fluid flows through the first connecting pipeline 11, the second connecting pipeline 12, the laminar flow element 14 and the regulating valve 16 in sequence; the temperature sensor 10 is installed on the first connecting pipeline 11, and the signal of the temperature sensor 10 is sent to the main controller 1; the output signal of the sub-controller 7 is sent to the regulating valve 16 after being converted by the D / A converter 6, so as to adjust the opening degree of the regulating valve 16.

[0023] The temperature sensor 10 and the regulating valve 16 can be interchanged.

[0024] In a specific embodiment, the first connecting pipeline 11 and the temperature sensor 10 are located in front of the second connecting pipeline 12, or between the laminar flow element 14 and the regulating valve 16.

[0025] When the fluid pressure, especially the gas pressure, changes suddenly (for example, the pressure reducing valve located at the front end of the gas path fails or is damaged), in order to reduce and avoid the inaccuracy of the laminar flow mass flow control system caused by the sudden change of the fluid pressure, especially the gas pressure, and improve the precision, stability, reliability and anti-interference ability of the laminar flow mass flow control system, the present application adds a feedforward compensation module 4 and a differential pressure sub-control loop in the laminar flow mass flow control system.

[0026] Please refer to Fig. 3 The running structure of the laminar flow mass flow control system based on feedforward compensation and cascade control according to the embodiment of the present application comprises a main controller 1, a sub-controller 7, a D / A converter 6, a regulating valve 16, a sub-controlled object, a main controlled object, an A / D converter 5, a differential pressure sensor 8, a flow detector, a pressure mutation interference channel and a feedforward compensation module 4.

[0027] The sub-controller 7, the D / A converter 6, the regulating valve 16, the sub-controlled object, the differential pressure sensor 8 and the A / D converter 5 form a sub-control loop.

[0028] The main control loop consists of the main controller 1, the secondary control loop, the main controlled object, and the flow detector.

[0029] The main function of the secondary control loop is to make the differential pressure reach the set value, while the main function of the primary control loop is to make the flow rate reach the set value.

[0030] The input signal of the feedforward compensation module 4 is the pressure change signal from the pressure sensor 9, and the output is a compensation signal. This compensation signal is sent to the regulating valve 16. Its main function is to reduce or offset the influence of sudden changes in fluid pressure, especially gas pressure signal, on the flow rate. Under the strong interference of sudden changes in fluid pressure, especially gas pressure signal, the flow output value of the laminar flow mass flow control system can maintain good control accuracy to meet the usage requirements.

[0031] When the transfer function of the pressure change disturbance channel is The transfer function of regulating valve 16 is The transfer function of the secondary controlled object is Then the transfer function of feedforward compensation module 4 for: .

[0032] The pressure change interference channel is a "two-way input" circuit. Its input signal is the pressure change detection value of pressure sensor 9, and its output signal is the change in pressure difference caused by the pressure change.

[0033] Since the transfer functions of the pressure surge interference channel, the control valve 16, and the secondary controlled object are objectively known, the transfer function of the feedforward compensation module 4 can be calculated using the above formula. .

[0034] Once the transfer function of feedforward compensation module 4 is determined... Then, based on the input signal, namely the pressure change signal from the pressure sensor 9, the output compensation signal of the feedforward compensation module 4 can be calculated.

[0035] The transfer function of the feedforward compensation module 4 reflects the characteristics of the feedforward compensation module 4. Its input signal is the pressure change signal. After passing through the transfer function, the output signal is generated, which is the compensation signal. The compensation signal is superimposed with the output signal of the D / A converter and acts on the valve together.

[0036] This invention provides a laminar flow quality flow control method based on feedforward compensation and cascade control, comprising the following steps: When a sudden change in fluid pressure, especially gas pressure, causes a deviation between the flow rate setpoint and the actual flow rate detected, this flow rate deviation is sent to the main controller 1. The main controller 1 calculates and outputs a differential pressure setpoint. This setpoint is compared with the differential pressure detected by the differential pressure sensor 8 in the secondary control loop. The resulting differential pressure deviation is sent to the secondary controller 7. The secondary controller 7 calculates and outputs a control signal to the D / A converter 6. The D / A converter 6 converts the digital signal to an analog signal, which is then superimposed on the analog signal output by the feedforward compensation module 4 and sent to the regulating valve 16. Upon receiving this signal, the regulating valve 16 changes its valve opening and, via the secondary controlled valve... The differential pressure is adjusted by superimposing the output signal of the pressure surge interference channel. The superimposed differential pressure is detected by the differential pressure sensor 8 in the secondary control loop and converted into a digital value by the A / D converter 5 to obtain the differential pressure detection value. The differential pressure setpoint output by the main controller 1 is compared with the differential pressure detection value of the secondary control loop, and the deviation is sent to the secondary controller 7. The secondary controller 7 calculates and sends its output control signal to the D / A converter 6, which converts the digital value into an analog value. This analog value is then superimposed with the output analog signal of the feedforward compensation module 4 and sent to the regulating valve 16 to further adjust the differential pressure. This process is repeated until the differential pressure reaches the set value. When the differential pressure reaches the set value, the flow rate is further adjusted by the main controlled object, and the flow rate is detected to obtain the actual flow rate value. The flow rate setpoint is compared with the flow rate detection value, and the flow rate deviation is sent to the main controller 1. Through the secondary control loop and the main controlled object, the flow rate is further adjusted. This process is repeated until the flow rate reaches the set value. This effectively reduces or avoids the impact of strong pressure fluctuations on flow accuracy when fluid pressure, especially gas pressure, changes abruptly.

[0037] In the control process described above, the flow rate detection value is calculated from the detection values ​​of differential pressure sensor 8, pressure sensor 9, and temperature sensor 10 in the secondary control loop. Specifically: Volumetric flow rate under standard conditions It is calculated using the following formula (1): (1) In the above formula, Volumetric flow rate under standard conditions; Temperature, in degrees Celsius; The pressure at the low-pressure side detection port 15 detected by pressure sensor 9, in units of ; A coefficient related to temperature; , The coefficients are related to the laminar flow channel structure, and the units are... ; The dynamic viscosity of the gas is determined by... Confirmed, unit is ; A coefficient related to pressure;

[0038] The pressure difference between the low-pressure side detection port 15 and the high-pressure side detection port 13 detected by the differential pressure sensor 8; The beneficial effects of this invention are that it enables the laminar flow mass flow control system to have strong anti-interference ability, high control accuracy, high reliability and good stability.

[0039] Example 1 This invention provides a laminar flow quality flow control system based on feedforward compensation and cascade control. During operation, the specific implementation is as follows: When the flow rate setpoint is 20 liters / minute, and the fluid is nitrogen, the steady-state flow rate is 19.9999 liters / minute. The deviation between the steady-state flow rate and the setpoint is -0.0001 liters / minute, which is extremely small. At this time, the fluid temperature... t The temperature was 25.3℃, and the pressure detected by pressure sensor 9 was [missing information]. p The actual measured differential pressure value is 301 kPa, detected by differential pressure sensor 8. The pressure is 1.0002 kPa, and the system is operating normally. When the pressure reducing valve located at the front end of the gas path malfunctions or is damaged, the pressure... pWithin one second, the pressure changes abruptly from 301 kPa to 350.12 kPa. Without the feedforward compensation and cascade control technology described in this invention, the actual flow rate would abruptly change to 18.5521 liters / minute, far below the set flow rate of 20 liters / minute. When the feedforward compensation and cascade control technology of this invention is used, when the pressure sensor 9 detects a pressure signal abruptly changing to 350.12 kPa, the main controller 1 calculates and outputs a differential pressure setpoint of 0.8616 kPa. At this time, the differential pressure detected by the differential pressure sensor 8 in the secondary control loop, 0.7992 kPa, is compared with this differential pressure setpoint, and the deviation of -0.0624 kPa is sent to the secondary controller 7. The secondary controller 7 calculates and outputs a control signal value. The digital quantity is converted into an analog voltage signal of 11.393V by the D / A converter. This value is superimposed with the analog compensation value of 0.652V from the feedforward compensation module 4, resulting in an analog voltage signal of 12.045V. The signal V is sent to the regulating valve 16. After receiving the signal, the regulating valve 16 adjusts the differential pressure value by changing the valve opening and through the secondary controlled object. The differential pressure is superimposed on the output signal of the pressure change interference channel. The superimposed differential pressure is detected by the differential pressure sensor 8 in the secondary control loop and converted into a digital quantity by the A / D converter 5, resulting in a differential pressure value of 0.8608 kPa. The differential pressure detection value of 0.8608 kPa in the secondary control loop is compared with the differential pressure set value of 0.8616 kPa output by the main controller. The deviation of -0.0008 kPa is sent to the secondary controller 7. After calculation, the secondary controller 7 outputs a control signal value. The digital quantity is converted into an analog voltage signal of 11.405V by the D / A converter 6. This value is superimposed on the analog compensation value of 0.652V from the feedforward compensation module 4, resulting in an analog voltage signal of 12.057V, which is sent to the regulating valve 16 to further adjust the differential pressure. This process is repeated until the differential pressure reaches the set value of 0.8616 kPa. When the differential pressure reaches the set value, the flow rate is further adjusted by the main controlled object, and the flow rate is measured. The measured flow rate is 19.9999 liters / minute. The deviation between this measured flow rate of 19.9999 liters / minute and the set flow rate of 20 liters / minute is very small, with a deviation of -0.0001 liters / minute. This measured flow rate of 19.9999 liters / minute is the same as the stable output flow rate of 19.9999 liters / minute before the pressure jump. It can be considered that the flow rate was not affected by the pressure jump, which shows that the flow control system has strong anti-interference ability, high control accuracy, high reliability and good stability.

[0040] The above-mentioned flow rate refers to the flow rate under standard conditions.

[0041] In one specific implementation, the primary controlled object and the secondary controlled object can each be regarded as a control system component with input and output; the input signal of the secondary controlled object is the valve opening degree, and the output signal is the pressure difference; the input signal of the primary controlled object is the pressure difference, and the output is the flow rate.

[0042] As is known from common technical knowledge, this invention can be implemented through other embodiments that do not depart from its spirit or essential characteristics. Therefore, the disclosed embodiments described above are merely illustrative in all respects and are not the only ones. All modifications within the scope of this invention or its equivalents are included in this invention.

Claims

1. A laminar flow mass flow control system based on feed forward compensation and cascade control, characterized in that, It comprises: The main controller (1), the feedforward compensation module (4), the A / D converter (5), the D / A converter (6), the sub-controller (7), the differential pressure sensor (8), the pressure sensor (9), the laminar flow element (14) and the regulating valve (16); The low pressure side detection port (15) and the high pressure side detection port (13) are arranged on the laminar flow element (14); the low pressure side detection port (15) is connected with the low pressure end of the pressure sensor (9) and the differential pressure sensor (8), and the high pressure side detection port (13) is connected with the high pressure end of the differential pressure sensor (8); the laminar flow element (14) is connected with the regulating valve (16); The output end of the pressure sensor (9) is connected with the input end of the feedforward compensation module (4) and the input end of the A / D converter (5); the output end of the differential pressure sensor (8) is connected with the input end of the A / D converter (5); the output end of the A / D converter (5) is connected with the input end of the main controller (1) and the input end of the sub-controller (7); the output end of the main controller (1) is connected with the input end of the sub-controller (7); The output end of the feedforward compensation module (4) is connected with the control end of the regulating valve; the output end of the sub-controller (7) is connected with the control end of the regulating valve through the D / A converter (6).

2. The laminar flow mass flow control system based on feed forward compensation and cascade control of claim 1, wherein, It also comprises a temperature sensor (10); the temperature sensor (10) is used for measuring the temperature of the fluid flowing through the laminar flow element (14); the output end of the temperature sensor (10) is connected with the input end of the main controller (1).

3. The laminar flow mass flow control system based on feed forward compensation and cascade control of claim 1, wherein, It also comprises a sub-controlled object; the sub-controller (7), the D / A converter (6), the regulating valve (16), the sub-controlled object, the differential pressure sensor (8) and the A / D converter (5) form a sub-control loop.

4. The laminar flow mass flow control system based on feed forward compensation and cascade control of claim 3, wherein, It also comprises a main controlled object; the main controller (1), the sub-control loop, the main controlled object and a flow detector form a main control loop.

5. The laminar flow mass flow control system based on feed forward compensation and cascade control of claim 4, wherein, The flow detector is composed of the temperature sensor (10), the pressure sensor (9) and the differential pressure sensor (8).

6. The laminar flow mass flow control system based on feed forward compensation and cascade control as claimed in claim 1, wherein, The input signal of the feedforward compensation module (4) is a pressure mutation signal from the pressure sensor (9), and the output is a compensation signal; the compensation signal is sent to the regulating valve (16) to reduce or offset the influence of the fluid pressure signal on the flow when the fluid pressure signal suddenly changes.

7. The laminar flow mass flow control system based on feed forward compensation and cascade control as claimed in claim 1, wherein, The compensation signal output by the feedforward compensation module (4) is superimposed with the analog signal output by the D / A converter (6) and then sent to the regulating valve (16) to adjust the differential pressure.

8. The laminar flow mass flow control system based on feed forward compensation and cascade control of claim 1, wherein, It also comprises a communication module (2) and a memory (3); the main controller (1) is connected with the communication module (2) and the memory (3).

9. The laminar flow mass flow control system based on feed forward compensation and cascade control according to claim 2, characterized in that, The temperature sensor (10) is arranged at the inlet of the laminar flow element (14), and the regulating valve is arranged at the outlet of the laminar flow element (14); Or, the temperature sensor (10) is arranged at the outlet of the laminar flow element (14), and the regulating valve is arranged at the inlet of the laminar flow element (14); Or, the temperature sensor (10) and the regulating valve are both arranged at the inlet of the laminar flow element (14); Or, the temperature sensor (10) and the regulating valve are both arranged at the outlet of the laminar flow element (14).

10. A laminar flow mass flow control method based on feed forward compensation and cascade control, characterized in that, The laminar flow mass flow control system based on feedforward compensation and cascade control according to any one of claims 1 to 9, comprising: When the fluid pressure mutation causes the flow deviation between the flow set value and the actual flow detection value, the flow deviation value is sent to the main controller (1), the main controller (1) calculates and outputs the pressure difference set value, compares the pressure difference set value with the pressure difference detection value detected by the pressure difference sensor (8) in the secondary control loop, obtains the pressure difference deviation, and sends the pressure difference deviation to the secondary controller (7). The secondary controller (7) calculates and outputs the control signal to the D / A converter (6), which converts the digital quantity into an analog quantity, which is superimposed with the output analog signal of the feedforward compensation module (4) and sent to the regulating valve. The regulating valve adjusts the pressure difference value by changing the valve opening and through the secondary controlled object, the superimposed pressure difference is superimposed with the output signal of the pressure difference disturbance channel, and the superimposed pressure difference is detected by the pressure difference sensor (8) in the secondary control loop and converted into a digital quantity by the A / D converter (5) to obtain the pressure difference detection value; the pressure difference set value output by the main controller (1) is compared with the pressure difference detection value of the secondary control loop, the deviation is sent to the secondary controller (7) again, the secondary controller (7) calculates and outputs the control signal to the D / A converter (6), which converts the digital quantity into an analog quantity, which is superimposed with the output analog signal of the feedforward compensation module (4) and sent to the regulating valve (16) to further adjust the pressure difference. The secondary control loop control is repeated to make the pressure difference reach the set value. When the pressure difference reaches the set value, the flow value is further adjusted by the main controlled object, and the flow value is detected to obtain the actual flow detection value. The flow set value is compared with the flow detection value to obtain the flow deviation value, which is sent to the main controller (1), which is further adjusted by the secondary control loop and the main controlled object to adjust the flow, and the cycle is repeated to make the flow reach the set value.

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