Biosafety cabinet quality detector and automatic correction method thereof

Abstract

The invention discloses a biosafety cabinet quality detector and an automatic correction method thereof, and belongs to the technical field of detection. Comprising a pressure detection unit A, a pressure detection unit B, a pressure detection unit C, a pressure detection unit D, a pressure detection unit E, a wind speed detection unit A, a wind speed detection unit B, a wind speed detection unit C, a wind speed detection unit D, a wind speed detection unit E, a fan control circuit, a main controller, a butterfly valve driving circuit A, a butterfly valve driving circuit B, a butterfly valve driving circuit C, a butterfly valve driving circuit D and a touch screen. The technical problem of automatically adjusting the flow of the four branch air ducts is solved, a control strategy can be automatically optimized according to different operation states, the response capability and the adjusting precision of the system are effectively improved, and the nonlinear and dynamic characteristics of the system can be effectively compensated, so that the environment change and interference can be better coped with.

Description

Technical Field

[0001] The invention belongs to the field of detection technology, and in particular relates to a biosafety cabinet quality detector and an automatic calibration method thereof. Background Art

[0002] As an important laboratory equipment, biological safety cabinet (BSC) is widely used in the operation and research of biological, chemical and other hazardous substances. The detection device for testing the quality of biological safety cabinets is an important measuring instrument to ensure the safe use of biological safety cabinets.

[0003] At present, most of the biosafety cabinet quality detectors on the market use the microbiological method or the potassium iodide method to detect the biosafety cabinet. The potassium iodide method is to first place a potassium iodide aerosol generator in the biosafety cabinet to generate potassium iodide aerosol in the biosafety cabinet, and then place the biosafety cabinet quality detector directly in front of the biosafety cabinet. By generating negative pressure in the main air duct in the measuring unit, the four branch air ducts are driven to inhale air, so that the four filter papers installed at the branch air duct openings can inhale the air in the space in front of the biosafety cabinet and adsorb the potassium iodide aerosol in the air. Finally, remove the four filter papers and drip palladium chloride solution on them to make the adsorbed potassium iodide change color. By checking the number of potassium iodide spots, it is determined whether the quality of the biosafety cabinet meets the standards.

[0004] In the process of testing the quality of the biological safety cabinet, it is necessary to compare the number of potassium iodide spots on four filter papers at a time. This requires that the number of potassium iodide spots on the four filter papers cannot have too large an error. To achieve this, it is necessary to control the air intake flow of the four branch air ducts to remain consistent before testing.

[0005] At present, the traditional practice is to manually adjust the butterfly valves of the four branch air ducts multiple times so that the flow rates of the four branch air ducts are finally kept consistent. The adjustment process is cumbersome and time-consuming. Summary of the invention

[0006] The purpose of the present invention is to provide a biosafety cabinet quality detector and an automatic correction method thereof, which solves the technical problem of automatically adjusting the flow rates of four branch air ducts.

[0007] To achieve the above purpose, the present invention adopts the following technical inventions: A biosafety cabinet quality detector, comprising a pressure detection unit A, a pressure detection unit B, a pressure detection unit C, a pressure detection unit D, a pressure detection unit E, a wind speed detection unit A, a wind speed detection unit B, a wind speed detection unit C, a wind speed detection unit D, a wind speed detection unit E, a fan control circuit, a main controller, a butterfly valve drive circuit A, a butterfly valve drive circuit B, a butterfly valve drive circuit C, a butterfly valve drive circuit D, a touch screen, a communication module and a power module, the pressure detection unit A, the pressure detection unit B, the pressure detection unit C and the pressure detection unit D are all connected to the main controller through a first I2C bus, the pressure detection unit E is connected to the main controller through a second I2C bus, the wind speed detection unit A, the wind speed detection unit B, the wind speed detection unit C and the wind speed detection unit D are all connected to the main controller through a third I2C bus, and the wind speed detection unit E is connected to the main controller through a fourth I2C bus; The fan control circuit is a 3.3V to 12V level drive circuit composed of field effect tube Q1 and field effect tube Q2. The G pole of field effect tube Q1 is connected to an IO port of the main controller, and the S pole of field effect tube Q1 drives field effect tube Q2. Field effect tube Q2 is used to control the opening or closing of the fan. The butterfly valve driving circuit A comprises an isolation driving circuit A and a motor driver A, wherein the input end of the isolation driving circuit A is respectively connected to a group of IO ports of the main controller, and the output end drives the input end of the motor driver, and the output end of the motor driver is connected to and drives an external first driving motor for controlling the opening or closing of the first butterfly valve; The circuit principles of butterfly valve drive circuit B, butterfly valve drive circuit C and butterfly valve drive circuit D are the same as those of butterfly valve drive circuit A. Butterfly valve drive circuit B, butterfly valve drive circuit C and butterfly valve drive circuit D are respectively connected to different IO ports of the main controller, and respectively drive the second drive motor for controlling the second butterfly valve, the third drive motor for controlling the third butterfly valve, and the fourth drive motor for controlling the fourth butterfly valve; the touch screen and the communication module are both connected to the main controller; The power module supplies power to all pressure detection units, all wind speed detection units, fan control circuits, main controllers, touch screens, communication modules and all butterfly valve drive circuits.

[0008] Preferably, the power supply module includes a 12V voltage stabilizing module, a 5V voltage stabilizing module and a 3.3V voltage stabilizing module, the input end of the 12V voltage stabilizing module is connected to the mains, and the output end outputs a 12V power supply, the input end of the 5V voltage stabilizing module is connected to the 12V power supply, and the output end outputs a 5V power supply, and the input end of the 3.3V voltage stabilizing module is connected to the 5V power supply, and the output end outputs a 3.3V power supply; The model of the 12V voltage regulator module is LRS-35-12 switching power supply; the model of the 5V voltage regulator module is LM7805; and the model of the 3.3V voltage regulator module is AM1117.

[0009] Preferably, the pressure detection unit A includes an interface J1, a capacitor C1, a resistor R1 and a resistor R5, the interface J1 is connected to an external first pressure sensor, specifically, pin 4 of the interface J1 is connected to a power supply end of the first pressure sensor, pin 2 is connected to an SCL end of the first pressure sensor, pin 1 is connected to an SDA end of the first pressure sensor, and pin 3 is connected to a ground wire; Pin 4 of the interface J1 is also connected to a 3.3V power supply, a filter capacitor C1 is connected between pins 3 and 4, pins 2 and 1 are connected to a 3.3V power supply through resistors R1 and R5 respectively, and pins 2 and 1 of the interface J1 are respectively the SCL1 interface and SDA1 interface of the first I2C bus, which are respectively connected to a group of IO ports of the main controller; The circuit principles of the pressure detection unit B, the pressure detection unit C and the pressure detection unit D are the same as those of the pressure detection unit A, and are connected to the first I2C bus together with the pressure detection unit A; the pressure detection unit B, the pressure detection unit C and the pressure detection unit D are respectively connected to the external second pressure sensor, the third pressure sensor and the fourth pressure sensor; The circuit principle of the pressure detection unit E is the same as that of the pressure detection unit A. The pressure detection unit E is connected to the second I2C bus and a group of IO ports of the main controller; the pressure detection unit E is connected to an external fifth pressure sensor; The wind speed detection unit A includes an interface J5, a capacitor C5, a resistor R9 and a resistor R13. The interface J5 is connected to an external first wind speed sensor, specifically, the 4th pin of the interface 5 is connected to the power supply end of the first wind speed sensor, the 2nd pin is connected to the SCL end of the first wind speed sensor, the 1st pin is connected to the SDA end of the first wind speed sensor, and the 3rd pin is connected to the ground wire; Pin 4 of interface J5 is also connected to a 3.3V power supply, a filter capacitor C5 is connected between pins 3 and 4, pins 2 and 1 are connected to a 3.3V power supply through resistors R9 and R13 respectively, and pins 2 and 1 of interface J5 are respectively the SCL3 interface and SDA3 interface of the third I2C bus, which are respectively connected to a group of IO ports of the main controller; The circuit principles of the wind speed detection unit B, the wind speed detection unit C and the wind speed detection unit D are the same as those of the wind speed detection unit A, and are connected to the third I2C bus together with the wind speed detection unit A; the wind speed detection unit B, the wind speed detection unit C and the wind speed detection unit D are respectively connected to the external second wind speed sensor, the third wind speed sensor and the fourth wind speed sensor; The circuit principle of the wind speed detection unit E is the same as that of the wind speed detection unit A. The wind speed detection unit E is connected to the fourth I2C bus and a group of IO ports of the main controller; the wind speed detection unit E is connected to an external fifth wind speed sensor.

[0010] The first wind speed sensor, the second wind speed sensor, the third wind speed sensor, the fourth wind speed sensor and the fifth wind speed sensor are all AWM720P1 digital wind speed sensors; the first pressure sensor, the second pressure sensor, the third pressure sensor, the fourth pressure sensor and the fifth pressure sensor are all BMP180 digital pressure sensors.

[0011] Preferably, the motor driver A includes a driving chip IC1, a diode D1, a diode D2, a diode D3, a diode D4, a diode D5, a diode D6, a diode D7, a diode D8, a capacitor C12 and an interface J9; The isolation driving circuit A includes a 6-way photoelectric isolation circuit consisting of an optical coupler U20, an optical coupler U21, an optical coupler U22, an optical coupler U23, an optical coupler U24 and an optical coupler U25 and their corresponding peripheral circuits; The IN1 terminal, IN2 terminal, IN3 terminal, IN4 terminal, ENA terminal and ENB terminal of the driver chip IC1 are respectively connected to different IO ports of the main controller through optical coupler U20, optical coupler U21, optical coupler U22, optical coupler U23, optical coupler U24 and optical coupler U25; The OUT1, OUT2, OUT3 and OUT4 terminals of the driver chip IC1 are connected to the 5th, 4th, 3rd, 2nd and 1st pins of the interface J9 respectively, the 6th pin of the interface J9 is connected to the 12V power supply, and the 1st pin is connected to the ground wire; the ISENA, ISENB and GND terminals of the driver chip IC1 are all connected to the ground wire; The positive electrode of the diode D1 is connected to the OUT4 terminal of the driver chip IC1, and the negative electrode is connected to the 12V power supply. The negative electrode of the diode D2 is connected to the OUT4 terminal of the driver chip IC1, and the positive electrode is connected to the ground wire. The positive electrode of the diode D3 is connected to the OUT3 terminal of the driver chip IC1, and the negative electrode is connected to the 12V power supply. The negative electrode of the diode D4 is connected to the OUT3 terminal of the driver chip IC1, and the positive electrode is connected to the ground wire. The positive electrode of the diode D5 is connected to the OUT2 terminal of the driver chip IC1, and the negative electrode is connected to the 12V power supply. The negative electrode of the diode D6 is connected to the OUT2 terminal of the driver chip IC1, and the positive electrode is connected to the ground wire. The positive electrode of the diode D7 is connected to the OUT1 terminal of the driver chip IC1, and the negative electrode is connected to the 12V power supply. The negative electrode of the diode D8 is connected to the OUT1 terminal of the driver chip IC1, and the positive electrode is connected to the ground wire. The VSS terminal of the driver chip IC1 is connected to a 5V power supply, the VS terminal is connected to a 12V power supply, and the capacitor C12 is a ground capacitor of the VSS terminal of the driver chip IC1; The model of the driving chip IC1 is L298N DC motor driver, and the models of the first driving motor, the second driving motor, the third driving motor and the fourth driving motor are all N20 micro DC motors.

[0012] Preferably, the fan control circuit specifically includes a field effect tube Q1, a field effect tube Q2, a resistor R21, a resistor R22, a resistor R35, a diode D9 and an interface J12, the G pole of the field effect tube Q1 is connected to an IO port of the main controller through the resistor R22, the S pole is connected to the G pole of the field effect tube Q2 through the resistor R35, and the D pole is connected to a 3.3V power supply, one end of the resistor R21 is connected to the 3.3V power supply, and the other end is connected to the G pole of the field effect tube Q1 through the resistor R22, the S pole of the field effect tube Q2 is connected to the ground wire, the D pole is connected to the positive pole of the diode D9, and the negative pole of the diode D9 is connected to the 12V power supply, and the 1st and 2nd pins of the interface J12 are connected to the negative pole of the diode D9, and the 3rd and 4th pins are connected to the positive pole of the diode D9; Interface J12 is connected to the fan; The model of the main controller is STM32F407, and the model of the communication module is RS485.

[0013] A method for automatically calibrating a biosafety cabinet quality detector comprises the following steps: Step 1: Place the biosafety cabinet quality detector in the detection space, power on the biosafety cabinet quality detector, select the correction mode through the touch screen, and the main controller controls the biosafety cabinet quality detector to enter the correction mode; The specific process of the correction mode is as follows: Step 1-1: Initialization phase: Start the system: the main controller first starts the fan set in the main air duct through the fan control circuit, collects data from the fifth wind speed sensor set in the main air duct through the wind speed detection unit E, thereby obtaining the wind speed in the main air duct; at the same time, collects data from the fifth pressure sensor set in the main air duct through the pressure detection unit E, thereby obtaining the pressure value in the main air duct; Similarly, the main controller obtains the wind speeds in the four branch air ducts respectively through the first wind speed sensor, the second wind speed sensor, the third wind speed sensor, and the fourth wind speed sensor; The main controller obtains the pressure values ​​in the four branch air ducts respectively through the first pressure sensor, the second pressure sensor, the third pressure sensor, and the fourth pressure sensor; According to the obtained wind speed, calculate the flow rate in each air duct: Q i = A i × v i ; Wherein, Q is the flow rate; A is the cross-sectional area of ​​the air duct, which is a preset value; v is the wind speed; i represents the number of the air duct, i=1,2,3,4,5, where i=5 represents the main air duct; Record the initial flow of each branch air duct: Q1, Q2, Q3, Q4; Step 1-2: The main controller calculates the error between the current flow rate and the target flow rate of each branch duct, where the target flow rate is the expected flow rate: e i (0) = Q i (0) − Q target ; Among them, e i (0) is the calculated initial error, Q i (0) indicates the initial flow rate; Q target The target flow is: Q target = Q5÷4; Q5 represents the flow rate of the main air duct; Step 1-3: The main controller designs a PID controller for each branch air duct, the goal is to adjust the butterfly valve opening θ j Make the flow rate of each branch duct Q j Always keep near the set target value, and the values ​​of j and i are consistent: The control equation of the PID controller is as follows: Among them, e j (t) = Q j (t) − Q target , represents the current flow error of air duct j; K p , K i , K d are proportional, integral and differential gains respectively; Δu m (t) is the correction value calculated by the dynamic model of the air duct and fan, which is used to compensate for the nonlinear or dynamic characteristics of the system response; Δu c (t) is the adjustment calculated by disturbance compensation; Δu m (t) = α × (Q pred1 (t) − Q measured (t)); Among them, α is a coefficient used to adjust the influence of the model correction on the air valve opening; Q pred1 (t) is the predicted flow rate obtained based on dynamic modeling; Q measured (t) is the actual measured flow rate; Δu c (t) = β×(Q pred2(t) − Q measured (t)); Among them, β is a coefficient used to adjust the intensity of interference compensation, Q pred2 (t) is the predicted flow obtained by the flow prediction model; Q measured (t) is the actual measured flow rate; Step 1-4: Update the butterfly valve opening θ of each branch air duct according to the adjustment amount calculated by PID i (t): θ i (t) = θ prev + Δθ i (t); Among them, θ prev is the previous butterfly valve opening, Δθ i (t) is the adjustment amount calculated by the PID controller; Step 1-5: When executing steps 1-1 to 1-4, you need to wait for the airflow to stabilize, that is, wait for a certain time t after each adjustment of the butterfly valve. wait To ensure stable airflow, t wait Estimate by duct length and gas sound velocity: ; Where L2 is the length of the branch air duct, which is the preset value; v sound is the sound speed of the gas, fixed at 343 m / s; τ is the inertial time constant of the system; Waiting for wait After a certain time, re-measure the flow rate of each branch duct and calculate the error: e i (t new ) = Q i (t new ) − Q target ; E i (t new ) and the preset error tolerance threshold ϵ threshold For comparison, if e i (t new ) at the threshold ϵ threshold Inside, that is, e i (t new ) ≤ ϵ threshold , it means that the branch air duct i has reached the expected level; Step 1-6: Repeat the process from step 1-1 to step 1-5, and continue to iterate and adjust until the flow of all branch ducts is within the set threshold, that is, the condition Q is met. i In Q target ± ϵ threshold Within, the adjustment process is considered complete; Step 1-7: Record the final butterfly valve opening of each branch air duct as the default adjustment strategy and save it as the system default configuration; Step 2: In actual use, it is preferred to call the default adjustment strategy for adjustment. If the adjustment fails to meet the condition Q i In Q target ± ϵ threshold If the value is within the range, the correction mode method in step 1 is called to readjust.

[0014] Preferably, when performing steps 1-3, K p , K i , K d The value of is adaptively adjusted according to the flow error, specifically: Use the initial preset PID parameter K pbase , K ibase , K dbase Start the PID controller and adjust the flow error e j (t), adjust PID parameters in real time: K p = K pbase ×(1+λ×|e j (t)∣); K i = K ibase ×(1+λ×|e j (t)∣); K d = K dbase ×(1+λ×|e j (t)∣); Among them, λ is the adjustment coefficient.

[0015] Preferably, the predicted flow Q obtained by dynamic modeling pred1 The calculation formula of (t) is as follows: Q pred1 (t) = C × N(t) × A; Wherein, C is the constant coefficient between the fan and the air duct, which is the factory preset value; A is the cross-sectional area of ​​the air duct; N(t) is the speed of the fan; N(t) = k1× ΔP(t) + k2; Wherein, ΔP(t) is the pressure value change measured by the fifth pressure sensor, and k1 and k2 are both preset constants; The predicted flow Q obtained by the flow prediction model pred2 The calculation formula of (t) is as follows: Q pred2 (t) = a × θ(t) + b; Among them, a and b are coefficients obtained by fitting historical data, a and b are factory preset values, and θ(t) is the current butterfly valve opening.

[0016] Preferably, the main controller monitors the stability of the working state of the biosafety cabinet quality detector according to the change in the pressure value in the four branch air ducts, generates a stability report, and uploads it to the host computer through the communication module.

[0017] The biosafety cabinet quality detector and its automatic correction method described in the present invention solve the technical problem of automatically adjusting the flow of four branch air ducts. The present invention introduces an adaptive PID control method, which can adjust the control parameters according to the real-time flow error. By adaptively adjusting the PID gain parameters, the control strategy can be automatically optimized according to different operating states, effectively improving the system's responsiveness and adjustment accuracy, and reducing manual intervention. By establishing a dynamic model of the air duct and the fan, the flow can be predicted in real time, and correction can be made based on the deviation between the predicted value of the model and the actual flow. Dynamic modeling can not only improve the accuracy of flow regulation, but also effectively compensate for the nonlinearity and dynamic characteristics of the system, so as to better cope with environmental changes and interference. High-precision pressure and wind speed sensors are used, combined with multi-channel The I2C bus communication ensures the real-time and accuracy of multi-point data collection. By calculating the flow of each air duct and comparing it with the target flow, the butterfly valve can be adjusted efficiently to ensure that the flow of all branch air ducts is equal and meets the set standards. When the system cannot meet the set flow accuracy, it can automatically enter the correction mode and readjust the flow of each air duct by dynamically adjusting the butterfly valve to ensure long-term stable operation of the system. The automatic correction function reduces the need for manual operation and improves the self-repair ability of the system. By accurately calculating the stabilization time of the airflow and predicting the flow, it can make more precise adjustments, and can provide real-time feedback and optimization according to environmental changes. The influence of interference factors such as fan speed and pressure fluctuations is minimized, thereby ensuring the stability of the system and precise control of the flow. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic block diagram of the present invention; Figure 2 It is a schematic diagram of the external interface of the present invention; Figure 3 It is a circuit diagram of the I2C bus of the present invention; Figure 4 is a circuit diagram of a butterfly valve driving circuit A of the present invention; Figure 5 is a circuit diagram of a fan control circuit of the present invention; Figure 6 It is the main flow chart of the present invention. DETAILED DESCRIPTION

[0019] Embodiment 1: Depend on Figure 1-Figure 5 A biosafety cabinet quality detector shown includes a pressure detection unit A, a pressure detection unit B, a pressure detection unit C, a pressure detection unit D, a pressure detection unit E, a wind speed detection unit A, a wind speed detection unit B, a wind speed detection unit C, a wind speed detection unit D, a wind speed detection unit E, a fan control circuit, a main controller, a butterfly valve drive circuit A, a butterfly valve drive circuit B, a butterfly valve drive circuit C, a butterfly valve drive circuit D, a touch screen, a communication module and a power module, and the power module supplies power to all pressure detection units, all wind speed detection units, the fan control circuit, the main controller, the touch screen, the communication module and all butterfly valve drive circuits.

[0020] The power supply module includes a 12V voltage stabilizing module, a 5V voltage stabilizing module and a 3.3V voltage stabilizing module. The input end of the 12V voltage stabilizing module is connected to the mains power supply, and the output end outputs a 12V power supply. The input end of the 5V voltage stabilizing module is connected to the 12V power supply, and the output end outputs a 5V power supply. The input end of the 3.3V voltage stabilizing module is connected to the 5V power supply, and the output end outputs a 3.3V power supply. The model of the 12V voltage regulator module is LRS-35-12 switching power supply; the model of the 5V voltage regulator module is LM7805; and the model of the 3.3V voltage regulator module is AM1117.

[0021] The pressure detection unit A, the pressure detection unit B, the pressure detection unit C and the pressure detection unit D are all connected to the main controller through the first I2C bus, the pressure detection unit E is connected to the main controller through the second I2C bus, the wind speed detection unit A, the wind speed detection unit B, the wind speed detection unit C and the wind speed detection unit D are all connected to the main controller through the third I2C bus, and the wind speed detection unit E is connected to the main controller through the fourth I2C bus; The pressure detection unit A includes an interface J1, a capacitor C1, a resistor R1 and a resistor R5, the interface J1 is connected to an external first pressure sensor, specifically, the 4th pin of the interface J1 is connected to the power supply end of the first pressure sensor, the 2nd pin is connected to the SCL end of the first pressure sensor, the 1st pin is connected to the SDA end of the first pressure sensor, and the 3rd pin is connected to the ground wire; Pin 4 of the interface J1 is also connected to a 3.3V power supply, a filter capacitor C1 is connected between pins 3 and 4, pins 2 and 1 are connected to a 3.3V power supply through resistors R1 and R5 respectively, and pins 2 and 1 of the interface J1 are respectively the SCL1 interface and SDA1 interface of the first I2C bus, which are respectively connected to a group of IO ports of the main controller; The circuit principles of the pressure detection unit B, the pressure detection unit C and the pressure detection unit D are the same as those of the pressure detection unit A, and are connected to the first I2C bus together with the pressure detection unit A; the pressure detection unit B, the pressure detection unit C and the pressure detection unit D are respectively connected to the external second pressure sensor, the third pressure sensor and the fourth pressure sensor; The circuit principle of the pressure detection unit E is the same as that of the pressure detection unit A. The pressure detection unit E is connected to the second I2C bus and a group of IO ports of the main controller; the pressure detection unit E is connected to an external fifth pressure sensor; The wind speed detection unit A includes an interface J5, a capacitor C5, a resistor R9 and a resistor R13. The interface J5 is connected to an external first wind speed sensor, specifically, the 4th pin of the interface 5 is connected to the power supply end of the first wind speed sensor, the 2nd pin is connected to the SCL end of the first wind speed sensor, the 1st pin is connected to the SDA end of the first wind speed sensor, and the 3rd pin is connected to the ground wire; Pin 4 of interface J5 is also connected to a 3.3V power supply, a filter capacitor C5 is connected between pins 3 and 4, pins 2 and 1 are connected to a 3.3V power supply through resistors R9 and R13 respectively, and pins 2 and 1 of interface J5 are respectively the SCL3 interface and SDA3 interface of the third I2C bus, which are respectively connected to a group of IO ports of the main controller; The circuit principles of the wind speed detection unit B, the wind speed detection unit C and the wind speed detection unit D are the same as those of the wind speed detection unit A, and are connected to the third I2C bus together with the wind speed detection unit A; the wind speed detection unit B, the wind speed detection unit C and the wind speed detection unit D are respectively connected to the external second wind speed sensor, the third wind speed sensor and the fourth wind speed sensor; The circuit principle of the wind speed detection unit E is the same as that of the wind speed detection unit A. The wind speed detection unit E is connected to the fourth I2C bus and a group of IO ports of the main controller; the wind speed detection unit E is connected to an external fifth wind speed sensor.

[0022] The first wind speed sensor, the second wind speed sensor, the third wind speed sensor, the fourth wind speed sensor and the fifth wind speed sensor are all AWM720P1 digital wind speed sensors; the first pressure sensor, the second pressure sensor, the third pressure sensor, the fourth pressure sensor and the fifth pressure sensor are all BMP180 digital pressure sensors.

[0023] The fan control circuit is a 3.3V to 12V level drive circuit composed of field effect tube Q1 and field effect tube Q2. The G pole of field effect tube Q1 is connected to an IO port of the main controller, and the S pole of field effect tube Q1 drives field effect tube Q2. Field effect tube Q2 is used to control the opening or closing of the fan. The fan control circuit specifically includes a field effect tube Q1, a field effect tube Q2, a resistor R21, a resistor R22, a resistor R35, a diode D9 and an interface J12, the G pole of the field effect tube Q1 is connected to an IO port of the main controller through the resistor R22, the S pole is connected to the G pole of the field effect tube Q2 through the resistor R35, and the D pole is connected to a 3.3V power supply, one end of the resistor R21 is connected to the 3.3V power supply, and the other end is connected to the G pole of the field effect tube Q1 through the resistor R22, the S pole of the field effect tube Q2 is connected to the ground wire, the D pole is connected to the positive pole of the diode D9, and the negative pole of the diode D9 is connected to the 12V power supply, and the 1st and 2nd pins of the interface J12 are connected to the negative pole of the diode D9, and the 3rd and 4th pins are connected to the positive pole of the diode D9; Interface J12 is connected to the fan; The model of the main controller is STM32F407, and the model of the communication module is RS485.

[0024] The butterfly valve driving circuit A comprises an isolation driving circuit A and a motor driver A, wherein the input end of the isolation driving circuit A is respectively connected to a group of IO ports of the main controller, and the output end drives the input end of the motor driver, and the output end of the motor driver is connected to and drives an external first driving motor for controlling the opening or closing of the first butterfly valve; The circuit principles of butterfly valve drive circuit B, butterfly valve drive circuit C and butterfly valve drive circuit D are the same as those of butterfly valve drive circuit A. Butterfly valve drive circuit B, butterfly valve drive circuit C and butterfly valve drive circuit D are respectively connected to different IO ports of the main controller, and respectively drive the second drive motor for controlling the second butterfly valve, the third drive motor for controlling the third butterfly valve, and the fourth drive motor for controlling the fourth butterfly valve; the touch screen and the communication module are both connected to the main controller; The motor driver A includes a driving chip IC1, a diode D1, a diode D2, a diode D3, a diode D4, a diode D5, a diode D6, a diode D7, a diode D8, a capacitor C12 and an interface J9; The isolation driving circuit A includes a 6-way photoelectric isolation circuit consisting of an optical coupler U20, an optical coupler U21, an optical coupler U22, an optical coupler U23, an optical coupler U24 and an optical coupler U25 and their corresponding peripheral circuits; The IN1 terminal, IN2 terminal, IN3 terminal, IN4 terminal, ENA terminal and ENB terminal of the driver chip IC1 are respectively connected to different IO ports of the main controller through optical coupler U20, optical coupler U21, optical coupler U22, optical coupler U23, optical coupler U24 and optical coupler U25; The OUT1, OUT2, OUT3 and OUT4 terminals of the driver chip IC1 are connected to the 5th, 4th, 3rd, 2nd and 1st pins of the interface J9 respectively, the 6th pin of the interface J9 is connected to the 12V power supply, and the 1st pin is connected to the ground wire; the ISENA, ISENB and GND terminals of the driver chip IC1 are all connected to the ground wire; The positive electrode of the diode D1 is connected to the OUT4 terminal of the driver chip IC1, and the negative electrode is connected to the 12V power supply. The negative electrode of the diode D2 is connected to the OUT4 terminal of the driver chip IC1, and the positive electrode is connected to the ground wire. The positive electrode of the diode D3 is connected to the OUT3 terminal of the driver chip IC1, and the negative electrode is connected to the 12V power supply. The negative electrode of the diode D4 is connected to the OUT3 terminal of the driver chip IC1, and the positive electrode is connected to the ground wire. The positive electrode of the diode D5 is connected to the OUT2 terminal of the driver chip IC1, and the negative electrode is connected to the 12V power supply. The negative electrode of the diode D6 is connected to the OUT2 terminal of the driver chip IC1, and the positive electrode is connected to the ground wire. The positive electrode of the diode D7 is connected to the OUT1 terminal of the driver chip IC1, and the negative electrode is connected to the 12V power supply. The negative electrode of the diode D8 is connected to the OUT1 terminal of the driver chip IC1, and the positive electrode is connected to the ground wire. The VSS terminal of the driver chip IC1 is connected to a 5V power supply, the VS terminal is connected to a 12V power supply, and the capacitor C12 is a ground capacitor of the VSS terminal of the driver chip IC1; The model of the driving chip IC1 is L298N DC motor driver, and the models of the first driving motor, the second driving motor, the third driving motor and the fourth driving motor are all N20 micro DC motors.

[0025] In this embodiment, the butterfly valve driving circuit B, the butterfly valve driving circuit C and the butterfly valve driving circuit D are respectively provided with a driving chip IC2, a driving chip IC3, a driving chip IC4 and a driving chip IC5, and the model of each is L298N DC motor driver.

[0026] Embodiment 2: like Figure 6 As shown, the automatic calibration method of a biosafety cabinet quality detector described in Example 2 is implemented on the basis of the biosafety cabinet quality detector described in Example 1, and includes the following steps: Step 1: Place the biosafety cabinet quality detector in the detection space, power on the biosafety cabinet quality detector, select the correction mode through the touch screen, and the main controller controls the biosafety cabinet quality detector to enter the correction mode; The specific process of the correction mode is as follows: Step 1-1: Initialization phase: Start the system: the main controller first starts the fan set in the main air duct through the fan control circuit, collects data from the fifth wind speed sensor set in the main air duct through the wind speed detection unit E, thereby obtaining the wind speed in the main air duct; at the same time, collects data from the fifth pressure sensor set in the main air duct through the pressure detection unit E, thereby obtaining the pressure value in the main air duct; Similarly, the main controller obtains the wind speeds in the four branch air ducts respectively through the first wind speed sensor, the second wind speed sensor, the third wind speed sensor, and the fourth wind speed sensor; The main controller obtains the pressure values ​​in the four branch air ducts respectively through the first pressure sensor, the second pressure sensor, the third pressure sensor, and the fourth pressure sensor; According to the obtained wind speed, calculate the flow rate in each air duct: Q i = A i × v i ; Wherein, Q is the flow rate; A is the cross-sectional area of ​​the air duct, which is a preset value; v is the wind speed; i represents the number of the air duct, i=1,2,3,4,5, where i=5 represents the main air duct; Record the initial flow of each branch air duct: Q1, Q2, Q3, Q4; Step 1-2: The main controller calculates the error between the current flow rate and the target flow rate of each branch duct, where the target flow rate is the expected flow rate: e i (0) = Q i (0) − Q target ; Among them, e i (0) is the calculated initial error, Q i (0) indicates the initial flow rate; Q target The target flow is: Q target = Q5÷4; Q5 represents the flow rate of the main air duct; Step 1-3: The main controller designs a PID controller for each branch air duct, the goal is to adjust the butterfly valve opening θ j Make the flow rate of each branch duct Q j Always keep near the set target value, and the values ​​of j and i are consistent: The control equation of the PID controller is as follows: Among them, e j (t) = Q j (t) − Q target , represents the current flow error of air duct j; K p, K i , K d are proportional, integral and derivative gains respectively; K p , K i , K d The value of is adaptively adjusted according to the flow error, specifically: Use the initial preset PID parameter K pbase , K ibase , K dbase Start the PID controller and adjust the flow error e j (t), adjust PID parameters in real time: K p = K pbase ×(1+λ×|e j (t)∣); K i = K ibase ×(1+λ×|e j (t)∣); K d = K dbase ×(1+λ×|e j (t)∣); Among them, λ is the adjustment coefficient.

[0027] Δu m (t) is the correction value calculated by the dynamic model of the air duct and fan, which is used to compensate for the nonlinear or dynamic characteristics of the system response; Δu c (t) is the adjustment calculated by disturbance compensation; Δu m (t) = α×(Q pred1 (t) − Q measured (t)); Among them, α is a coefficient used to adjust the influence of the model correction on the air valve opening; Q pred1 (t) is the predicted flow rate obtained based on dynamic modeling; Q measured (t) is the actual measured flow rate; Δu c (t) = β×(Q pred2 (t) − Q measured (t)); Among them, β is a coefficient used to adjust the intensity of interference compensation, Q pred2 (t) is the predicted flow obtained by the flow prediction model; Q measured (t) is the actual measured flow rate; According to the predicted flow Q obtained by dynamic modeling pred1 The calculation formula of (t) is as follows: Qpred1 (t) = C × N(t) × A; Wherein, C is the constant coefficient between the fan and the air duct, which is the factory preset value; A is the cross-sectional area of ​​the air duct; N(t) is the speed of the fan; N(t) = k1× ΔP(t) + k2; Wherein, ΔP(t) is the pressure value change measured by the fifth pressure sensor, and k1 and k2 are both preset constants; In this embodiment, the fan speed N(t) is estimated based on the pressure change in the air duct, and compensation is performed based on the relationship between wind speed and pressure. The predicted flow rate Q is calculated by combining the estimated value of the fan speed and the cross-sectional area of ​​the air duct. pred1 (t), which provides a more accurate input for the PID control algorithm, making flow control more precise.

[0028] The predicted flow Q obtained by the flow prediction model pred2 The calculation formula of (t) is as follows: Q pred2 (t) = a × θ(t) + b; Among them, a and b are coefficients obtained by fitting historical data, a and b are factory preset values, and θ(t) is the current butterfly valve opening.

[0029] Step 1-4: Update the butterfly valve opening θ of each branch air duct according to the adjustment amount calculated by PID i (t): θ i (t) = θ prev + Δθ i (t); Among them, θ prev is the previous butterfly valve opening, Δθ i (t) is the adjustment amount calculated by the PID controller; Step 1-5: When executing steps 1-1 to 1-4, you need to wait for the airflow to stabilize, that is, wait for a certain time t after each adjustment of the butterfly valve. wait To ensure stable airflow, t wait Estimate by duct length and gas sound velocity: ; Where L2 is the length of the branch air duct, which is the preset value; v sound is the sound speed of the gas, fixed at 343 m / s; τ is the inertial time constant of the system; Waiting for wait After a certain time, re-measure the flow rate of each branch duct and calculate the error: e i (t new) = Q i (t new ) − Q target ; E i (t new ) and the preset error tolerance threshold ϵ threshold For comparison, if e i (t new ) at the threshold ϵ threshold Inside, that is, e i (t new ) ≤ ϵ threshold , it means that the branch air duct i has reached the expected level; Step 1-6: Repeat the process from step 1-1 to step 1-5, and continue to iterate and adjust until the flow of all branch ducts is within the set threshold, that is, the condition Q is met. i In Q target ± ϵ threshold Within, the adjustment process is considered complete; Step 1-7: Record the final butterfly valve opening of each branch air duct as the default adjustment strategy and save it as the system default configuration; Step 2: In actual use, it is preferred to call the default adjustment strategy for adjustment. If the adjustment fails to meet the condition Q i In Q target ± ϵ threshold If the value is within the range, the correction mode method in step 1 is called to readjust.

[0030] The main controller monitors the stability of the working state of the biosafety cabinet quality detector according to the changes in the pressure values ​​in the four branch air ducts, generates a stability report, and uploads it to the host computer through the communication module.

[0031] The biosafety cabinet quality detector and its automatic correction method described in the present invention solve the technical problem of automatically adjusting the flow of four branch air ducts. The present invention introduces an adaptive PID control method, which can adjust the control parameters according to the real-time flow error. By adaptively adjusting the PID gain parameters, the control strategy can be automatically optimized according to different operating states, effectively improving the system's responsiveness and adjustment accuracy, and reducing manual intervention. By establishing a dynamic model of the air duct and the fan, the flow can be predicted in real time, and correction can be made based on the deviation between the predicted value of the model and the actual flow. Dynamic modeling can not only improve the accuracy of flow regulation, but also effectively compensate for the nonlinearity and dynamic characteristics of the system, so as to better cope with environmental changes and interference. High-precision pressure and wind speed sensors are used, combined with multi-channel The I2C bus communication ensures the real-time and accuracy of multi-point data collection. By calculating the flow of each air duct and comparing it with the target flow, the butterfly valve can be adjusted efficiently to ensure that the flow of all branch air ducts is equal and meets the set standards. When the system cannot meet the set flow accuracy, it can automatically enter the correction mode and readjust the flow of each air duct by dynamically adjusting the butterfly valve to ensure long-term stable operation of the system. The automatic correction function reduces the need for manual operation and improves the self-repair ability of the system. By accurately calculating the stabilization time of the airflow and predicting the flow, it can make more precise adjustments, and can provide real-time feedback and optimization according to environmental changes. The influence of interference factors such as fan speed and pressure fluctuations is minimized, thereby ensuring the stability of the system and precise control of the flow.

Claims

1. A biosafety cabinet quality detector, characterized in that: It includes a pressure detection unit A, a pressure detection unit B, a pressure detection unit C, a pressure detection unit D, a pressure detection unit E, a wind speed detection unit A, a wind speed detection unit B, a wind speed detection unit C, a wind speed detection unit D, a wind speed detection unit E, a fan control circuit, a main controller, a butterfly valve drive circuit A, a butterfly valve drive circuit B, a butterfly valve drive circuit C, a butterfly valve drive circuit D, a touch screen, a communication module and a power module, the pressure detection unit A, the pressure detection unit B, the pressure detection unit C and the pressure detection unit D are all connected to the main controller through a first I2C bus, the pressure detection unit E is connected to the main controller through a second I2C bus, the wind speed detection unit A, the wind speed detection unit B, the wind speed detection unit C and the wind speed detection unit D are all connected to the main controller through a third I2C bus, and the wind speed detection unit E is connected to the main controller through a fourth I2C bus; The fan control circuit is a 3.3V to 12V level drive circuit composed of field effect tube Q1 and field effect tube Q2. The G pole of field effect tube Q1 is connected to an IO port of the main controller, and the S pole of field effect tube Q1 drives field effect tube Q2. Field effect tube Q2 is used to control the opening or closing of the fan. The butterfly valve driving circuit A comprises an isolation driving circuit A and a motor driver A, wherein the input end of the isolation driving circuit A is respectively connected to a group of IO ports of the main controller, and the output end drives the input end of the motor driver, and the output end of the motor driver is connected to and drives an external first driving motor for controlling the opening or closing of the first butterfly valve; The circuit principles of butterfly valve drive circuit B, butterfly valve drive circuit C and butterfly valve drive circuit D are the same as those of butterfly valve drive circuit A. Butterfly valve drive circuit B, butterfly valve drive circuit C and butterfly valve drive circuit D are respectively connected to different IO ports of the main controller, and respectively drive the second drive motor for controlling the second butterfly valve, the third drive motor for controlling the third butterfly valve, and the fourth drive motor for controlling the fourth butterfly valve; the touch screen and the communication module are both connected to the main controller; The power module supplies power to all pressure detection units, all wind speed detection units, fan control circuits, main controllers, touch screens, communication modules and all butterfly valve drive circuits.

2. A biosafety cabinet quality detector as claimed in claim 1, characterized in that: The power supply module includes a 12V voltage stabilizing module, a 5V voltage stabilizing module and a 3.3V voltage stabilizing module. The input end of the 12V voltage stabilizing module is connected to the mains power supply, and the output end outputs a 12V power supply. The input end of the 5V voltage stabilizing module is connected to the 12V power supply, and the output end outputs a 5V power supply. The input end of the 3.3V voltage stabilizing module is connected to the 5V power supply, and the output end outputs a 3.3V power supply. The model of the 12V voltage regulator module is LRS-35-12 switching power supply; the model of the 5V voltage regulator module is LM7805; and the model of the 3.3V voltage regulator module is AM1117.

3. A biosafety cabinet quality detector as claimed in claim 2, characterized in that: The pressure detection unit A includes an interface J1, a capacitor C1, a resistor R1 and a resistor R5, the interface J1 is connected to an external first pressure sensor, specifically, the 4th pin of the interface J1 is connected to the power supply end of the first pressure sensor, the 2nd pin is connected to the SCL end of the first pressure sensor, the 1st pin is connected to the SDA end of the first pressure sensor, and the 3rd pin is connected to the ground wire; Pin 4 of the interface J1 is also connected to a 3.3V power supply, a filter capacitor C1 is connected between pins 3 and 4, pins 2 and 1 are connected to a 3.3V power supply through resistors R1 and R5 respectively, and pins 2 and 1 of the interface J1 are respectively the SCL1 interface and SDA1 interface of the first I2C bus, which are respectively connected to a group of IO ports of the main controller; The circuit principles of the pressure detection unit B, the pressure detection unit C and the pressure detection unit D are the same as those of the pressure detection unit A, and are connected to the first I2C bus together with the pressure detection unit A; the pressure detection unit B, the pressure detection unit C and the pressure detection unit D are respectively connected to the external second pressure sensor, the third pressure sensor and the fourth pressure sensor; The circuit principle of the pressure detection unit E is the same as that of the pressure detection unit A. The pressure detection unit E is connected to the second I2C bus and a group of IO ports of the main controller; the pressure detection unit E is connected to an external fifth pressure sensor; The wind speed detection unit A includes an interface J5, a capacitor C5, a resistor R9 and a resistor R13. The interface J5 is connected to an external first wind speed sensor, specifically, the 4th pin of the interface 5 is connected to the power supply end of the first wind speed sensor, the 2nd pin is connected to the SCL end of the first wind speed sensor, the 1st pin is connected to the SDA end of the first wind speed sensor, and the 3rd pin is connected to the ground wire; Pin 4 of interface J5 is also connected to a 3.3V power supply, a filter capacitor C5 is connected between pins 3 and 4, pins 2 and 1 are connected to a 3.3V power supply through resistors R9 and R13 respectively, and pins 2 and 1 of interface J5 are respectively the SCL3 interface and SDA3 interface of the third I2C bus, which are respectively connected to a group of IO ports of the main controller; The circuit principles of the wind speed detection unit B, the wind speed detection unit C and the wind speed detection unit D are the same as those of the wind speed detection unit A, and are connected to the third I2C bus together with the wind speed detection unit A; the wind speed detection unit B, the wind speed detection unit C and the wind speed detection unit D are respectively connected to the external second wind speed sensor, the third wind speed sensor and the fourth wind speed sensor; The circuit principle of the wind speed detection unit E is the same as that of the wind speed detection unit A. The wind speed detection unit E is connected to the fourth I2C bus and a group of IO ports of the main controller; the wind speed detection unit E is connected to an external fifth wind speed sensor; The first wind speed sensor, the second wind speed sensor, the third wind speed sensor, the fourth wind speed sensor and the fifth wind speed sensor are all AWM720P1 digital wind speed sensors; the first pressure sensor, the second pressure sensor, the third pressure sensor, the fourth pressure sensor and the fifth pressure sensor are all BMP180 digital pressure sensors.

4. A biosafety cabinet quality detector as claimed in claim 2, characterized in that: The motor driver A includes a driving chip IC1, a diode D1, a diode D2, a diode D3, a diode D4, a diode D5, a diode D6, a diode D7, a diode D8, a capacitor C12 and an interface J9; The isolation driving circuit A includes a 6-way photoelectric isolation circuit consisting of an optical coupler U20, an optical coupler U21, an optical coupler U22, an optical coupler U23, an optical coupler U24 and an optical coupler U25 and their corresponding peripheral circuits; The IN1 terminal, IN2 terminal, IN3 terminal, IN4 terminal, ENA terminal and ENB terminal of the driver chip IC1 are respectively connected to different IO ports of the main controller through optical coupler U20, optical coupler U21, optical coupler U22, optical coupler U23, optical coupler U24 and optical coupler U25; The OUT1, OUT2, OUT3 and OUT4 terminals of the driver chip IC1 are connected to the 5th, 4th, 3rd, 2nd and 1st pins of the interface J9 respectively, the 6th pin of the interface J9 is connected to the 12V power supply, and the 1st pin is connected to the ground wire; The ISENA, ISENB and GND terminals of the driver chip IC1 are all connected to the ground wire; The positive electrode of the diode D1 is connected to the OUT4 terminal of the driver chip IC1, and the negative electrode is connected to the 12V power supply. The negative electrode of the diode D2 is connected to the OUT4 terminal of the driver chip IC1, and the positive electrode is connected to the ground wire. The positive electrode of the diode D3 is connected to the OUT3 terminal of the driver chip IC1, and the negative electrode is connected to the 12V power supply. The negative electrode of the diode D4 is connected to the OUT3 terminal of the driver chip IC1, and the positive electrode is connected to the ground wire. The positive electrode of the diode D5 is connected to the OUT2 terminal of the driver chip IC1, and the negative electrode is connected to the 12V power supply. The negative electrode of the diode D6 is connected to the OUT2 terminal of the driver chip IC1, and the positive electrode is connected to the ground wire. The positive electrode of the diode D7 is connected to the OUT1 terminal of the driver chip IC1, and the negative electrode is connected to the 12V power supply. The negative electrode of the diode D8 is connected to the OUT1 terminal of the driver chip IC1, and the positive electrode is connected to the ground wire. The VSS terminal of the driver chip IC1 is connected to a 5V power supply, the VS terminal is connected to a 12V power supply, and the capacitor C12 is a ground capacitor of the VSS terminal of the driver chip IC1; The model of the driving chip IC1 is L298N DC motor driver, and the models of the first driving motor, the second driving motor, the third driving motor and the fourth driving motor are all N20 micro DC motors.

5. A biosafety cabinet quality detector as claimed in claim 2, characterized in that: The fan control circuit specifically includes a field effect tube Q1, a field effect tube Q2, a resistor R21, a resistor R22, a resistor R35, a diode D9 and an interface J12, the G pole of the field effect tube Q1 is connected to an IO port of the main controller through the resistor R22, the S pole is connected to the G pole of the field effect tube Q2 through the resistor R35, and the D pole is connected to a 3.3V power supply, one end of the resistor R21 is connected to the 3.3V power supply, and the other end is connected to the G pole of the field effect tube Q1 through the resistor R22, the S pole of the field effect tube Q2 is connected to the ground wire, the D pole is connected to the positive pole of the diode D9, and the negative pole of the diode D9 is connected to the 12V power supply, and the 1st and 2nd pins of the interface J12 are connected to the negative pole of the diode D9, and the 3rd and 4th pins are connected to the positive pole of the diode D9; Interface J12 is connected to the fan; The model of the main controller is STM32F407, and the model of the communication module is RS485.

6. An automatic calibration method for a biosafety cabinet quality detector, applied to the biosafety cabinet quality detector according to any one of claims 1 to 5, characterized in that: The steps include: Step 1: Place the biosafety cabinet quality detector in the detection space, power on the biosafety cabinet quality detector, select the correction mode through the touch screen, and the main controller controls the biosafety cabinet quality detector to enter the correction mode; The specific process of the correction mode is as follows: Step 1-1: Initialization phase: Start the system: the main controller first starts the fan set in the main air duct through the fan control circuit, collects data from the fifth wind speed sensor set in the main air duct through the wind speed detection unit E, thereby obtaining the wind speed in the main air duct; at the same time, collects data from the fifth pressure sensor set in the main air duct through the pressure detection unit E, thereby obtaining the pressure value in the main air duct; Similarly, the main controller obtains the wind speeds in the four branch air ducts respectively through the first wind speed sensor, the second wind speed sensor, the third wind speed sensor, and the fourth wind speed sensor; The main controller obtains the pressure values ​​in the four branch air ducts respectively through the first pressure sensor, the second pressure sensor, the third pressure sensor, and the fourth pressure sensor; According to the obtained wind speed, calculate the flow rate in each air duct: Q i = A i × v i ; Wherein, Q is the flow rate; A is the cross-sectional area of ​​the air duct, which is a preset value; v is the wind speed; i represents the number of the air duct, i=1,2,3,4,5, where i=5 represents the main air duct; Record the initial flow of each branch air duct: Q1, Q2, Q3, Q4; Step 1-2: The main controller calculates the error between the current flow rate and the target flow rate of each branch duct, where the target flow rate is the expected flow rate: e i (0) = Q i (0) − Q target ; Among them, e i (0) is the calculated initial error, Q i (0) indicates the initial flow rate; Q target The target flow is: Q target = Q5 ÷ 4; Q5 represents the flow rate of the main air duct; Step 1-3: The main controller designs a PID controller for each branch air duct, the goal is to adjust the butterfly valve opening θ j Make the flow rate of each branch duct Q j Always keep near the set target value, and the values ​​of j and i are consistent: The control equation of the PID controller is as follows: Among them, e j (t) = Q j (t) − Q target , represents the current flow error of air duct j; K p , K i , K d are proportional, integral and differential gains respectively; Δu m (t) is the correction value calculated by the dynamic model of the air duct and fan, which is used to compensate for the nonlinear or dynamic characteristics of the system response; Δu c (t) is the adjustment calculated by disturbance compensation; Δu m (t)= α×( Q pred1 (t) − Q measured (t)); Among them, α is a coefficient used to adjust the influence of the model correction on the air valve opening; Q pred1 (t) is the predicted flow rate obtained based on dynamic modeling; Q measured (t) is the actual measured flow rate; Δu c (t)= β×( Q pred2 (t) − Q measured (t)); Among them, β is a coefficient used to adjust the intensity of interference compensation, Q pred2 (t) is the predicted flow obtained by the flow prediction model; Q measured (t) is the actual measured flow rate; Step 1-4: Update the butterfly valve opening θ of each branch air duct according to the adjustment amount calculated by PID i (t): i i (t) = θ prev + Dth i (t); Among them, θ prev is the previous butterfly valve opening, Δθ i (t) is the adjustment amount calculated by the PID controller; Step 1-5: When executing steps 1-1 to 1-4, you need to wait for the airflow to stabilize, that is, wait for a certain time t after each adjustment of the butterfly valve. wait To ensure stable airflow, t wait Estimate by duct length and gas sound velocity: ； Where L2 is the length of the branch air duct, which is the preset value; v sound is the sound speed of the gas, fixed at 343 m / s; τ is the inertial time constant of the system; Waiting for wait After a certain time, re-measure the flow rate of each branch duct and calculate the error: e i (t new ) = Q i (t new ) − Q target ; E i (t new ) and the preset error tolerance threshold ϵ threshold For comparison, if e i (t new ) at the threshold ϵ threshold Inside, that is, e i (t new ) ≤ ϵ threshold , it means that the branch air duct i has reached the expected level; Step 1-6: Repeat the process from step 1-1 to step 1-5, and continue to iterate and adjust until the flow of all branch ducts is within the set threshold, that is, the condition Q is met. i In Q target ± ϵ threshold Within, the adjustment process is considered complete; Step 1-7: Record the final butterfly valve opening of each branch air duct as the default adjustment strategy and save it as the system default configuration; Step 2: In actual use, it is preferred to call the default adjustment strategy for adjustment. If the adjustment fails to meet the condition Q i In Q target ± ϵ threshold If the value is within the range, the correction mode method in step 1 is called to readjust.

7. The automatic calibration method of a biosafety cabinet quality detector according to claim 6, characterized in that: When executing steps 1-3, K p , K i , K d The value of is adaptively adjusted according to the flow error, specifically: Use the initial preset PID parameter K pbase , K ibase , K dbase Start the PID controller and adjust the flow error e j (t), adjust PID parameters in real time: K p = K pbase ×(1+λ×∣e j (t)∣); K i = K ibase ×(1+λ×∣e j (t)∣); K d = K dbase ×(1+λ×∣e j (t)∣); Among them, λ is the adjustment coefficient.

8. The automatic calibration method of a biosafety cabinet quality detector according to claim 6, characterized in that: According to the predicted flow Q obtained by dynamic modeling pred1 The calculation formula of (t) is as follows: Q pred1 (t) = C × N(t) × A; Wherein, C is the constant coefficient between the fan and the air duct, which is the factory preset value; A is the cross-sectional area of ​​the air duct; N(t) is the speed of the fan; N(t) = k1 × ΔP(t) + k2; Wherein, ΔP(t) is the pressure value change measured by the fifth pressure sensor, and k1 and k2 are both preset constants; The predicted flow Q obtained by the flow prediction model pred2 The calculation formula of (t) is as follows: Q pred2 (t) = a × θ(t) + b; Among them, a and b are coefficients obtained by fitting historical data, a and b are factory preset values, and θ(t) is the current butterfly valve opening.

9. The automatic calibration method of a biosafety cabinet quality detector according to claim 6, characterized in that: The main controller monitors the stability of the working state of the biosafety cabinet quality detector according to the changes in the pressure values ​​in the four branch air ducts, generates a stability report, and uploads it to the host computer through the communication module.

Images