阅读说明：本技术 一种基于串级控制的层流质量流量控制系统及控制方法 (Laminar flow quality and flow control system and control method based on cascade control ) 是由 张龙娟 于 2021-09-16 设计创作，主要内容包括：一种基于串级控制的层流质量流量控制系统及控制方法,包括层流元件、集成传感器、电子控制部分、高压侧检测口、低压侧检测口、调节阀、连接管道一、副控制回路压力传感器、连接管道二、第二温度传感器。当流量设定值与检测值有偏差时,该偏差送入主控制器,主控制器经过计算输出压力设定值,该设定值与压力检测值比较后其偏差送给副控制器,副控制器经过计算输出控制信号给调节阀,使压力达到设定值。接着进一步调节流量值并检侧,流量设定值与该检测值比较后,其偏差送入主控制器进一步调节流量,如此循环往复,使流量达到设定值。本发明具有抗干扰能力强、控制精度高、稳定性好、超调小、过渡过程短、收敛速度快的特点。(A laminar flow quality and flow control system based on cascade control and a control method thereof comprise a laminar flow element, an integrated sensor, an electronic control part, a high-pressure side detection port, a low-pressure side detection port, a regulating valve, a first connecting pipeline, a secondary control loop pressure sensor, a second connecting pipeline and a second temperature sensor. When the flow set value has deviation with the detected value, the deviation is sent to the main controller, the main controller outputs the pressure set value through calculation, the deviation of the set value after being compared with the pressure detected value is sent to the sub controller, and the sub controller outputs a control signal to the regulating valve through calculation to enable the pressure to reach the set value. And then further regulating the flow value and detecting the flow value, comparing the flow set value with the detected value, and then sending the deviation to the main controller to further regulate the flow, and repeating the steps in such a way to enable the flow to reach the set value. The invention has the characteristics of strong anti-interference capability, high control precision, good stability, small overshoot, short transition process and high convergence speed.)

1. A laminar flow mass flow control system based on cascade control comprises a laminar flow element (1), an integrated sensor (2), an electronic control part (3), a high-pressure side detection port (15), a low-pressure side detection port (16), a regulating valve (12), a connecting pipeline I (14), an auxiliary control loop pressure sensor (13), a connecting pipeline II (17) and a second temperature sensor (18);

the laminar flow element (1) is provided with a low-pressure side detection port (16) and a high-pressure side detection port (15); the low-pressure side detection port (16) and the high-pressure side detection port (15) are connected with the integrated sensor (2); two ends of the laminar flow element (1) are connected with a first connecting pipeline (14) and a second connecting pipeline (17); a secondary control loop pressure sensor (13) is arranged on the connecting pipeline I (14), and the front end of the connecting pipeline I is connected with the regulating valve (12); a second temperature sensor (18) is arranged on the second connecting pipeline (17); the integrated sensor (2), the regulating valve (12), the auxiliary control loop pressure sensor (13) and the second temperature sensor (18) are communicated with the electronic control part (3).

2. The laminar flow quality flow control system based on the cascade control according to claim 1, characterized in that the electronic control part (3) comprises a main controller (4), a sub-controller (5), an A/D converter (7), a D/A converter (6), a memory (8), a communication module (10), a power supply module (9) and a display screen (11); the main controller (4) is connected with the communication module (10), the sub-controller (5), the A/D converter (7), the memory (8), the power module (9), the display screen (11) and the second temperature sensor (18); the A/D converter (7) is connected with the main controller (4), the sub-controller (5), the integrated sensor (2) and the sub-control loop pressure sensor (13); the D/A converter (6) is connected with the regulating valve (12).

3. A laminar flow quality and flow control method based on cascade control is characterized by comprising the following steps:

when the flow set value and the flow detection value have deviation, the deviation value is sent to a main controller, the main controller outputs a pressure set value after calculation, the pressure set value is compared with the pressure detection value of a secondary control loop and then the deviation is sent to a secondary controller, the secondary controller outputs a control signal to a D/A converter, a digital quantity is converted into an analog quantity voltage signal by the D/A converter and then sent to a regulating valve, the regulating valve receives the signal and regulates the pressure value by changing the opening degree of the valve and a secondary controlled object, the pressure is converted into a digital quantity by an A/D converter after being detected by a secondary control loop pressure sensor to obtain the pressure value, the pressure set value output by the main controller is compared with the pressure detection value of the secondary control loop, the deviation is sent to the secondary controller to further regulate the pressure, and the circulation is carried out, the pressure reaches a set value;

when the pressure reaches a set value, the flow value is further regulated through the main controlled object, the flow value is detected to obtain a flow detection value, after the flow set value is compared with the flow detection value, the deviation of the flow set value is sent to the main controller, the flow is further regulated through the auxiliary control loop and the main controlled object, and the circulation is repeated in such a way that the flow reaches the set value.

4. The system of claim 3, wherein the flow detection value is calculated from a detection value of the secondary circuit pressure sensor, a detection value of the second temperature sensor, a detection value of the pressure sensor in the integrated sensor, a detection value of the differential pressure sensor, and a detection value of the first temperature sensor during the cascade control.

5. The system of claim 3, wherein the sub-controller is independently configured or not configured; if the sub-controller is not arranged, the regulating valve (12) is controlled by the main controller.

6. The system of claim 3, wherein the secondary control loop pressure sensor is independently provided or not provided; if the auxiliary control loop pressure sensor is not arranged, the pressure sensor in the integrated sensor realizes the pressure detection of the integrated sensor and the pressure detection of the auxiliary control loop pressure sensor.

Technical Field

The invention relates to the technical field of flow measurement and control, in particular to a laminar flow quality and flow control system and a control method based on cascade control.

Background

Laminar flow mass flow controllers or control systems are important components in many industrial control fields, having a significant impact on the quality of many industrial products. However, since in the actual operation of the laminar flow mass flow controller or the control system, strong disturbance often occurs, for example, the pressure in the pipeline often has large fluctuation, and the like, the control accuracy, stability, and the like of the flow rate often drop significantly. Under strong interference, the laminar flow mass flow controller or the control system has the defects of low control precision and poor stability, and the laminar flow mass flow controller or the control system cannot meet the use requirements in many application places.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide a laminar flow quality and flow control system and a control method based on cascade control, and the control effect generated by the laminar flow quality and flow control system and the control method based on the cascade control has the characteristics of strong anti-interference capability, high control precision, good stability, small overshoot, short transition process and high convergence speed.

In order to achieve the purpose, the invention adopts the technical scheme that:

a laminar flow quality and flow control system based on cascade control comprises a laminar flow element (1), an integrated sensor (2), an electronic control part (3), a high-pressure side detection port (15), a low-pressure side detection port (16), a regulating valve (12), a first connecting pipeline (14), a secondary control loop pressure sensor (13), a second connecting pipeline (17) and a second temperature sensor (18).

The laminar flow element (1) is provided with a low-pressure side detection port (16) and a high-pressure side detection port (15); the low-pressure side detection port (16) and the high-pressure side detection port (15) are connected with the integrated sensor (2); two ends of the laminar flow element (1) are connected with a first connecting pipeline (14) and a second connecting pipeline (17); a secondary control loop pressure sensor (13) is arranged on the connecting pipeline I (14), and the front end of the connecting pipeline I is connected with the regulating valve (12); a second temperature sensor (18) is arranged on the second connecting pipeline (17); the integrated sensor (2), the regulating valve (12), the auxiliary control loop pressure sensor (13) and the second temperature sensor (18) are communicated with the electronic control part (3).

The electronic control part (3) comprises a main controller (4), a sub-controller (5), an A/D converter (7), a D/A converter (6), a memory (8), a communication module (10), a power supply module (9) and a display screen (11); the main controller (4) is connected with the communication module (10), the sub-controller (5), the A/D converter (7), the memory (8), the power module (9), the display screen (11) and the second temperature sensor (18); the A/D converter (7) is connected with the main controller (4), the sub-controller (5), the integrated sensor (2) and the sub-control loop pressure sensor (13); the D/A converter (6) is connected with the regulating valve (12).

The integrated sensor (2) comprises a pressure sensor, a differential pressure sensor and a first temperature sensor. The integrated sensor is connected with the high-pressure side detection port (15) and the low-pressure side detection port (16), and the integrated sensor (2) detects pressure, pressure difference and temperature signals of the high-pressure side detection port (15) and the low-pressure side detection port (16). These detection signals are sent to the main controller (4) through an A/D converter (7) of the electronic control section (3).

The fluid flows through the regulating valve (12), the first connecting pipeline (14), the laminar flow element (1) and the second connecting pipeline (17) in sequence;

an auxiliary control loop pressure sensor (13) is installed on the first connecting pipeline (14), the pressure sensor detects the pressure value at the outlet of the valve, and the signal of the auxiliary control loop pressure sensor (13) is sent to the A/D converter (7), converted by the A/D converter (7) and then sent to the auxiliary controller (5);

a second temperature sensor (18) is arranged on the second connecting pipeline (17), and signals of the second temperature sensor (18) are sent to the main controller (4);

the output signal of the sub-controller (5) is sent to the regulating valve (12) after passing through the D/A converter (6) so as to regulate the opening degree of the valve (12).

Because the pressure in the pipeline often fluctuates, the pressure fluctuation has great influence on the flow control of the fluid, and in order to improve the control performance of the fluid flow, the invention adopts a cascade control technology to control the flow of the fluid.

The cascade control system comprises a main controller, a secondary controller, a D/A converter, a regulating valve, a secondary controlled object, a main controlled object, an A/D converter, a secondary control loop pressure sensor and a flow detection component.

The auxiliary controller, the D/A converter, the regulating valve, the auxiliary controlled object, the A/D converter and the auxiliary control loop pressure sensor form an auxiliary control loop.

The main controller, the auxiliary control loop, the main controlled object and the flow detection form a main control loop.

The main function of the secondary control loop is to make the pressure reach a set value, and the main function of the main control loop is to make the flow reach a set value.

The a/D converter functions to convert an analog quantity into a digital quantity, and the D/a converter functions to convert a digital quantity into an analog quantity.

A laminar flow quality and flow control method based on cascade control is characterized by comprising the following steps:

when the flow set value and the flow detection value have deviation, the deviation value is sent to the main controller, the main controller outputs a pressure set value after calculation, the pressure set value is compared with the pressure detection value of the auxiliary control loop, the deviation is sent to the auxiliary controller, the auxiliary controller outputs a control signal to the D/A converter, the D/A converter converts a digital quantity into an analog quantity and sends the analog quantity to the regulating valve, the regulating valve receives the signal and regulates the pressure value by changing the opening degree of the valve and a sub controlled object, the pressure is converted into a digital quantity through the A/D converter after being detected by the pressure sensor of the auxiliary control loop to obtain the pressure value, the pressure set value output by the main controller is compared with the pressure detection value of the auxiliary control loop, the deviation is sent to the auxiliary controller to further regulate the pressure, and the circulation is carried out, the pressure is brought to the set value. When the pressure reaches a set value, the flow value is further regulated through the main controlled object, the flow value is detected to obtain a flow detection value, after the flow set value is compared with the flow detection value, the deviation of the flow set value is sent to the main controller, the flow is further regulated through the auxiliary control loop and the main controlled object, and the circulation is repeated in such a way that the flow reaches the set value.

In the cascade control process, the flow detection value is obtained by calculating the detection value of the auxiliary loop pressure sensor, the detection value of the second temperature sensor, the detection value of the pressure sensor in the integrated sensor, the detection value of the differential pressure sensor and the detection value of the first temperature sensor.

The sub-controller can be independently arranged or not arranged; if the sub-controller is not arranged, the regulating valve (12) is controlled by the main controller.

The auxiliary control loop pressure sensor can be independently arranged or not arranged; if the auxiliary control loop pressure sensor is not arranged, the pressure sensor in the integrated sensor realizes the pressure detection of the integrated sensor and the pressure detection of the auxiliary control loop pressure sensor.

The invention has the beneficial effects that:

the cascade control-based laminar flow quality and flow control system and the control method have the characteristics of strong anti-interference capability, high control precision, good stability, small overshoot, short transition process and high convergence rate.

Drawings

FIG. 1 is a schematic structural diagram of the present invention.

Fig. 2 is a schematic diagram of the cascade control system according to the present invention.

Wherein, 1 is a laminar flow element; 2 is an integrated sensor; 3 is an electronic control part; 4 is a main controller; 5 is a sub-controller; 6 is a D/A converter; 7 is an A/D converter; 8 is a memory; 9 is a power supply module; 10 is a communication module; 11 is a display screen; 12 is a regulating valve; 13 is a secondary control loop pressure sensor; 14 is a connecting pipeline I; 15 is a high pressure side detection port; 16 is a low pressure side detection port; 17 is a connecting pipeline II; and 18 is a second temperature sensor.

Detailed Description

The invention is further described below with reference to the accompanying drawings.

As shown in fig. 1, a laminar flow mass flow control system based on cascade control includes a laminar flow element (1), an integrated sensor (2), an electronic control portion (3), a high-pressure side detection port (15), a low-pressure side detection port (16), a regulating valve (12), a first connecting pipe (14), a secondary control loop pressure sensor (13), a second connecting pipe (17), and a second temperature sensor (18). The laminar flow element (1) is provided with a low-pressure side detection port (16) and a high-pressure side detection port (15); the low-pressure side detection port (16) and the high-pressure side detection port (15) are connected with the integrated sensor (2); two ends of the laminar flow element (1) are connected with a first connecting pipeline (14) and a second connecting pipeline (17); a secondary control loop pressure sensor (13) is arranged on the connecting pipeline I (14), and the front end of the connecting pipeline I is connected with the regulating valve (12); a second temperature sensor (18) is arranged on the second connecting pipeline (17);

the integrated sensor (2), the regulating valve (12), the auxiliary control loop pressure sensor (13) and the second temperature sensor (18) are communicated with the electronic control part (3).

The electronic control part (3) comprises a main controller (4), a sub-controller (5), an A/D converter (7), a D/A converter (6), a memory (8), a communication module (10), a power supply module (9) and a display screen (11); the main controller (4) is connected with the communication module (10), the sub-controller (5), the A/D converter (7), the memory (8), the power module (9), the display screen (11) and the second temperature sensor (18); the A/D converter (7) is connected with the main controller (4), the sub-controller (5), the integrated sensor (2) and the sub-control loop pressure sensor (13); the D/A converter (6) is connected with the regulating valve (12).

The integrated sensor (2) comprises a pressure sensor, a differential pressure sensor and a first temperature sensor. The integrated sensor is connected with the high-pressure side detection port (15) and the low-pressure side detection port (16), and the integrated sensor (2) detects pressure, pressure difference and temperature signals of the high-pressure side detection port (15) and the low-pressure side detection port (16). These detection signals are sent to the main controller (4) through an A/D converter (7) of the electronic control section (3).

The fluid flows through the regulating valve (12), the first connecting pipeline (14), the laminar flow element (1) and the second connecting pipeline (17) in sequence;

an auxiliary control loop pressure sensor (13) is installed on the first connecting pipeline (14), the pressure sensor detects the pressure value at the outlet of the valve, and the signal of the auxiliary control loop pressure sensor (13) is sent to the A/D converter (7), converted by the A/D converter (7) and then sent to the auxiliary controller (5);

a second temperature sensor (18) is arranged on the second connecting pipeline (17), and signals of the second temperature sensor (18) are sent to the main controller (4);

the output signal of the sub-controller (5) is sent to the regulating valve (12) after passing through the D/A converter (6) so as to regulate the opening degree of the valve (12).

Because the pressure in the pipeline often fluctuates, the pressure fluctuation has great influence on the flow control of the fluid, and in order to improve the control performance of the fluid flow, the invention adopts a cascade control technology to control the flow of the fluid.

The cascade control system comprises a main controller, a secondary controller, a D/A converter, a regulating valve, a secondary controlled object, a main controlled object, an A/D converter, a secondary control loop pressure sensor and flow detection.

The auxiliary controller, the D/A converter, the regulating valve, the auxiliary controlled object, the A/D converter and the auxiliary control loop pressure sensor form an auxiliary control loop.

The main controller, the auxiliary control loop, the main controlled object and the flow detection form a main control loop.

The main function of the secondary control loop is to make the pressure reach a set value, and the main function of the main control loop is to make the flow reach a set value.

The a/D converter functions to convert an analog quantity into a digital quantity, and the D/a converter functions to convert a digital quantity into an analog quantity.

The specific control process is as follows: when the flow set value is 500ml/min and the flow detection value is 490.7 ml/min, the deviation value is 9.3 ml/min and sent to the main controller, the main controller outputs 112.5 KPa through calculation, the pressure set value is compared with the pressure detection value of the sub-control loop, the deviation is 10.2 KPa and sent to the sub-controller, the sub-controller outputs control signals to the D/A converter through calculation, the D/A converter converts the digital quantity into the analog quantity voltage signal of 10.2V and then sends the analog quantity voltage signal to the regulating valve, the regulating valve receives the signals and then regulates the pressure value through the sub-controlled object by changing the valve opening, the pressure is detected by the sub-control loop pressure sensor and converted into the digital quantity through the A/D converter, the pressure value is 110.3KPa, the pressure set value output by the main controller of 112.5 KPa is compared with the pressure detection value of the sub-control loop of 110.3KPa, the deviation of the pressure is 2.2 KPa and is sent to a secondary controller, the pressure is further regulated, and the process is repeated in a circulating way, so that the pressure reaches a set value of 112.5 KPa. When the pressure reaches a set value, the flow value is further adjusted through the main controlled object, the flow value is detected, a flow detection value 498.8ml/min is obtained, after the flow set value 500ml/min is compared with the flow detection value 498.8ml/min, the deviation of the flow set value 500ml/min is 1.2 ml/min and sent to the main controller, the flow is further adjusted through the auxiliary control loop and the main controlled object, and the flow reaches the set value 500ml/min in a circulating reciprocating mode.

The flow rate units ml/min are ml/min, the pressure unit KPa is KPa, the voltage unit V is volt, and the flow rate is the flow rate under standard conditions.

Table 1 shows the final steady-state flow rate detected values obtained for different set values.

The flow rate unit ml/min in table 1 above indicates ml/min, and the flow rate refers to the flow rate in the standard condition.

As can be seen from table 1, the deviation between the flow set point and the final steady state flow measurement is very small.