Gas flow detection and control method based on self-adaptive model

Abstract

The invention provides a gas flow detection and control method based on a self-adaptive model, and the method comprises the steps: building a self-adaptive model of a gas flow detection system based on a least square curve fitting method according to a welding protection gas flow online detection and automatic control principle; the invention relates to a welding shielding gas flow online detection method based on a self-adaptive model and a welding shielding gas flow accurate control method based on an expert PID (Proportion Integration Differentiation) control algorithm. Due to the fact that a molten pool is oxidized or bubbles exist in a welding bead when the gas flow is improper, and the welding quality is affected, online detection and automatic control over the welding protection gas flow can be achieved when the working condition changes, the welding seam is formed attractively, the welding quality is improved, in addition, the method is not affected by gas types and the environment, and the method is suitable for large-scale popularization and application. And the method can also be applied to detection and control of gas flow under other working conditions, is wide in application range and has great practical application value.

Description

Technical Field

[0001] The present invention relates to the technical field of gas flow detection, and in particular to a gas flow detection and control method based on an adaptive model. Background Art

[0002] Gas flow is an important industrial parameter that has a significant impact on production and life. Taking the gas shielded welding process as an example, if the gas flow is too small, the welding pool will be oxidized by air, reducing the welding quality. If the gas flow is too large, there will be bubbles in the welding pool, which will also reduce the reliability of the welded parts. Therefore, it is necessary to invent a method for online detection and automatic control of gas flow, and this method is required to be applicable to different types of gases and different working conditions, ultimately improving the quality of welding and serving production and life. Summary of the invention

[0003] The purpose of the present invention is to provide a gas flow detection and control method based on an adaptive model. The established adaptive model can adapt to different types of gases and ambient temperatures, and then online detection of gas flow can be achieved based on the model. With precise gas flow as input, automatic control of gas flow can be achieved, which can improve the quality of machine welding and manual welding.

[0004] The present invention provides a gas flow detection and control method based on an adaptive model, the method comprising:

[0005] Obtaining the actual gas flow rate Q(j), and converting the actual gas flow rate Q(j) into a digital value AD(j) of an actual gas pressure signal;

[0006] According to the adaptive model, the target gas flow Q0(j) is converted into the digital value AD0(j) of the target gas pressure signal, and the gas pressure signal error E is obtained according to the digital value AD(j) of the actual gas pressure signal and the digital value AD0(j) of the target gas pressure signal. AD (j) and gas pressure signal error E AD (j) The rate of change EC AD (j);

[0007] The gas pressure signal error E AD (j) and the rate of change EC AD (j) is the input, and the three parameters Kp, Ki and Kd of PID are adjusted by expert control, and an improved PID control is designed to control the initial pulse number P1(j) of the stepper motor rotation as the output;

[0008] The preliminary pulse number P1(j) is combined with the preliminary pulse number P0(j) output by the expert control to output the final pulse number P2(j) for controlling the rotation of the stepper motor;

[0009] Taking the valve opening θ1(j) detected by the encoder as input, the expert control rule is used to output the speed v1(j) of the stepper motor. Combined with the final pulse number P2(j) of the stepper motor rotation, the stepper motor is rotated at an angle θ(j).

[0010] Furthermore, an adaptive model is constructed according to the following formula:

[0011]

[0012] Among them, a2, a1 and a0 are the coefficients of the adaptive model.

[0013] Furthermore, the step of obtaining the digital value AD(j) of the actual gas pressure signal includes:

[0014] Continuously collect the digital quantities of the gas pressure signals output by n A / D modules, remove the maximum and minimum values, and take the arithmetic mean of the remaining n-2 signals as the digital quantity AD(j) of the actual gas pressure signal;

[0015] The digital value AD(j) of the actual gas pressure signal is calculated according to the following formula:

[0016]

[0017] Wherein, n is the number of actual gas pressure signals, and b[k] is the kth signal among the n-2 actual gas pressure signals remaining after removing the maximum value and the minimum value.

[0018] Furthermore, the least squares curve fitting method is used to determine the adaptive model parameters a2, a1 and a0, and the sum of squared errors is used as the loss function to find the optimal solution of the model;

[0019] The loss function satisfies the following formula:

[0020]

[0021] Where m is the number of experimental data (Q(j), AD(j));

[0022] The loss function J(a2,a1,a0) takes partial derivatives of the three model parameters respectively, and we can get:

[0023]

[0024] In order to minimize the loss function J(a2,a1,a0), the partial derivatives of the loss function are all 0. After simplification, we can get:

[0025]

[0026] Substituting the collected m groups of experimental data (Q(j), AD(j)), we can obtain the parameters a2, a1 and a0.

[0027] Furthermore, the gas pressure signal error E is obtained according to the digital value AD(j) of the actual gas pressure signal and the digital value AD0(j) of the target gas pressure signal. AD (j) and gas pressure signal error E AD (j) The rate of change EC AD The steps of (j) include:

[0028] The gas pressure signal error E is calculated according to the following formula AD (j) and its rate of change EC AD (j):

[0029]

[0030] Wherein, AD0(j) is the digital value of the j-th target gas pressure signal, and AD(j) is the digital value of the actual gas pressure signal detected for the j-th time.

[0031] Furthermore, the gas pressure signal error E AD (j) and the rate of change EC AD (j) as input, the three parameters Kp, Ki and Kd of PID are adjusted by expert control, and the improved PID control is designed to control the initial pulse number P1(j) of the stepper motor as output, the steps include:

[0032] The preliminary pulse number P1(j) is calculated according to the following formula:

[0033]

[0034] Among them, E AD (j) is the jth error of the gas pressure signal, EC AD (j) is the j-th error change rate of the gas pressure signal, abs(·) is the function for calculating the absolute value, kp2 and kp3 are proportional coefficients, satisfying kp3=2kp2=0.5; ki1 and ki2 are integral coefficients, satisfying ki2=2ki1=0.4; kd2 and kd3 are differential coefficients, satisfying kd3=2kd2=0.01; m1 and m2 satisfy m1=100 and m2=1000.

[0035] Furthermore, the method further comprises:

[0036] If the expert control has an output value, the output value of the expert control is used as the final pulse number P2(j) for controlling the rotation of the stepper motor; otherwise, the output value of the improved PID is used as the final pulse number P2(j) for controlling the rotation of the stepper motor.

[0037] Furthermore, the method further comprises:

[0038] After the system is powered on, the motor that controls the opening of the gas valve is reversed by 45°. If the encoder detects that the actual rotation angle of the motor is greater than 40°, the motor that controls the opening of the gas valve is repeatedly reversed by 45°.

[0039] If the encoder detects that the actual rotation angle of the motor is less than or equal to 40°, it is determined that the air valve rotates to the fully closed position and its vicinity, and the air valve opening is lower than the first preset opening threshold. At this time, the initial value of the control air valve opening θ1(j) is 720°;

[0040] When the air valve is in the fully closed position or near it, and the air valve opening needs to be increased, the final pulse number P2(j) for controlling the rotation of the stepper motor is equal to the constant M;

[0041] When the air valve is at or near the fully open position and the air valve opening needs to be reduced, the final pulse number P2(j) for controlling the rotation of the stepper motor is equal to the constant M.

[0042] Furthermore, the method further comprises:

[0043] When the detected gas pressure signal error E AD When (j) is greater than 2000, the final pulse number P2(j) for controlling the stepper motor to rotate is 800;

[0044] When the detected gas pressure signal error E AD When (j) is less than 20, the final pulse number P2(j) is set to 0.

[0045] Furthermore, the method further comprises:

[0046] The relationship between the motor rotation speed v1(j) and the valve opening θ1(j) satisfies:

[0047]

[0048] Among them, v max is the maximum speed of the motor, v min is the minimum speed of the motor, v max =2.5r / s and v min =0.5r / s; θ1(j) is the actual opening of the gas valve, E AD (j) is the detected gas pressure signal error; when the motor runs to the fully closed position of the gas valve, the gas valve opening is 0°, in addition, θ2=90°, θ3=180°, θ4=3960° and θ5=4050°; when the motor runs to the fully open position of the gas valve, the gas valve opening is θ6, which satisfies θ6=4680°.

[0049] In summary, according to the above-mentioned gas flow detection and control method based on the adaptive model, it includes the principle of online detection and automatic control of welding shielding gas flow, the adaptive model of the gas flow detection system is established based on the least squares curve fitting method, the online detection method of welding shielding gas flow based on the adaptive model, and the precise control method of welding shielding gas flow based on the expert PID control algorithm; through the content of the present invention, the online detection of welding shielding gas flow at different types of gases and different ambient temperatures can be realized, and the precise control of welding shielding gas flow can be realized, so that the weld formation is beautiful and the quality and efficiency of welding can be improved. In addition, the method of the present invention can also be applied to the online detection and precise control of gas flow in other industries. The method of the present invention has a wide range of applications and great practical application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is a schematic diagram of gas flow detection and control based on an adaptive model in one embodiment of the present invention;

[0051] Figure 2 is a relationship diagram between the air valve opening and the motor rotation speed in one embodiment of the present invention;

[0052] Figure 3 1 is a curve showing the change of actual and target welding shielding gas flow rates during welding in one embodiment of the present invention.

[0053] The following specific implementation manner will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein should be understood by people with general skills in the field to which the present invention belongs. "Including" and similar words used in this article mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects.

[0055] An embodiment of the present invention provides a gas flow detection and control method based on an adaptive model, which mainly includes four parts: an online detection and automatic control principle of welding shielding gas flow, an adaptive model of a gas flow detection system based on a least squares curve fitting method, an online detection method of welding shielding gas flow based on an adaptive model, and an accurate control method of welding shielding gas flow based on an expert PID control algorithm, wherein:

[0056] 1. Principle of online detection and automatic control of welding shielding gas flow

[0057] like Figure 1 As shown, the actual gas flow Q(j) is converted into the actual gas pressure signal by using a pressure sensor, and then the analog value V(j) of the gas pressure signal is converted into the digital value AD(j) of the gas pressure signal by using an A / D module. On the other hand, the target gas flow Q0(j) can be converted into the digital value AD0(j) of the target gas pressure signal by using the established adaptive model of the gas flow detection system. The actual gas pressure signal AD(j) is compared with the target gas pressure signal AD0(j), and the error E of the gas pressure signal is calculated. AD (j) and the rate of change of error EC AD (j), with E AD (j) and EC AD (j) is used as input, and the three parameters Kp, Ki and Kd of PID are automatically adjusted by expert control. The improved PID control is designed to control the initial pulse number P1(j) of the stepper motor as output, which is combined with the initial pulse number P0(j) output by the expert control to output the final pulse number P2(j) of the stepper motor. The valve opening θ1(j) detected by the encoder is used as input, and the expert control rule is used to output the speed v1(j) of the stepper motor. Combined with the final pulse number P2(j) of the stepper motor, the stepper motor rotates by an angle θ(j), realizing the automatic adjustment of the valve opening, so that the actual gas flow rate is adjusted to the target gas flow rate.

[0058] 2. Establishing an adaptive model of gas flow detection system based on least squares curve fitting method

[0059] Since the relationship between gas flow and gas pressure signal changes under different working conditions, it is necessary to study Figure 1 The adaptive model of the gas flow detection system in the paper. After theoretical analysis and experimental results, it can be seen that the actual model structure of the gas flow detection system is a quadratic function, which satisfies the following formula:

[0060]

[0061] Where AD(j) is the digital value of the gas pressure signal output by the A / D module, Q(j) is the actual gas flow rate, and a2, a1, and a0 are the coefficients of the gas flow detection system model.

[0062] Continuously collect the digital quantities of the gas pressure signals output by n A / D modules, remove the maximum and minimum values, and take the arithmetic mean of the remaining n-2 signals as the final gas pressure signal AD(j), which satisfies the following formula:

[0063]

[0064] Wherein, n is the number of gas pressure signals, and b[k] is the kth signal among the n-2 gas pressure signals remaining after removing the maximum value and the minimum value.

[0065] The least squares curve fitting method is used to determine the model parameters a2, a1 and a0 in formula (1), and the error square sum is used as the loss function to find the optimal solution of the model. The loss function J (a2, a1, a0) of the gas flow detection system model in formula (1) satisfies the following formula:

[0066]

[0067] Where a2, a1 and a0 are the parameters to be solved, m is the number of experimental data (Q(j), AD(j)), and the meanings of AD(j) and Q(j) have been introduced in formula (1).

[0068] The loss function J(a2, a1, a0) is derived from the three model parameters separately, and we can get:

[0069]

[0070] To minimize the loss function J(a2,a1,a0), the partial derivatives of the loss function are all 0. After simplification, we can get:

[0071]

[0072] In formula (4-5), the meaning of each physical quantity has been introduced in formula (3).

[0073] By substituting the collected m groups of experimental data (Q(j), AD(j)) into formula (5), and substituting the identified parameters a2, a1 and a0 into formula (1), an adaptive model of the gas flow detection system that can adapt to different working conditions can be quickly established.

[0074] In order to improve the accuracy of the model, 15 actual gas flow rates Q(j) were input online, and the identified parameters were a2=5.68, a1=55.53 and a0=537.77. The adaptive model of the established gas flow detection system satisfies the following formula:

[0075] AD(j)=5.68Q(j) 2 +55.53Q(j)+537.77 (6)

[0076] Where AD(j) is the digital value of the gas pressure signal output by the A / D module, and Q(j) is the actual gas flow rate.

[0077] 3. Online detection method of welding shielding gas flow based on adaptive model

[0078] The gas flow detection system model of formula (1) can be transformed into the following equation:

[0079] a2·Q(j) 2 +a1·Q(j)+a0-AD(j)=0 (7)

[0080] Combining equation (6), and the actual gas flow rate is greater than 0, solving equation (7) can calculate the actual gas flow rate Q(j),

[0081]

[0082] In formula (7-8), AD(j) is the digital value of the gas pressure signal output by the A / D module, Q(j) is the actual gas flow rate, and a2, a1 and a0 are the coefficients of the gas flow detection system model.

[0083] Therefore, as long as the digital value AD(j) of the gas pressure signal output by the A / D module is substituted into formula (8), the actual gas flow rate Q(j) can be detected. In addition, the error E of the gas pressure signal can also be calculated. AD (j) and error change rate EC AD (j), as shown below:

[0084]

[0085] Wherein, AD0(j) is the digital value of the j-th target gas pressure signal, and AD(j) is the digital value of the actual gas pressure signal detected for the j-th time.

[0086] 4. Precise control method of welding shielding gas flow based on expert PID control algorithm

[0087] The parameters of the PID controller are automatically adjusted by expert control so that the preliminary pulse number P1(j) output by the improved PID control algorithm for controlling the rotation of the stepper motor satisfies the following formula:

[0088]

[0089] In the formula, E AD(j) is the jth error of the gas pressure signal, EC AD (j) is the jth error change rate of the gas pressure signal, and abs() is a function for calculating the absolute value. kp2 and kp3 are proportional coefficients, which satisfy kp3=2kp2=0.5; ki1 and ki2 are integral coefficients, which satisfy ki2=2ki1=0.4; kd2 and kd3 are differential coefficients, which satisfy kd3=2kd2=0.01. m1 and m2 satisfy m1=100 and m2=1000.

[0090] like Figure 1 As shown, the following four expert control rules can be used to further control the angle and speed of the stepper motor. If the expert control has an output value, the output value of the expert control is used as the final pulse number P2(j) for controlling the rotation of the stepper motor. Otherwise, the output value of the improved PID is used as the final pulse number P2(j) for controlling the rotation of the stepper motor.

[0091] Rule 1: Identification and search method of the initial position of the valve opening when the system starts

[0092] After the system is powered on, the motor that controls the valve opening is reversed by 45°. If the encoder detects that the actual rotation angle of the motor is greater than 40°, the above steps are continuously repeated. Otherwise, the valve is rotated to a position close to full closing, and the valve opening is close to 0°. Then, the initial value of the valve opening θ1(j) is set to 720°.

[0093] Rule 2: Methods to overcome the resistance to rotation of the valve when it is in the fully open or fully closed position

[0094] When the air valve is near the fully closed position and the air valve opening needs to be increased, the final pulse number P2(j) for controlling the rotation of the stepper motor is equal to a larger constant M. When the air valve is near the fully open position and the air valve opening needs to be reduced, the final pulse number P2(j) for controlling the rotation of the stepper motor is also equal to a larger constant M, where M satisfies M=800.

[0095] Rule 3: How to quickly reduce errors and avoid oscillations during operation

[0096] When the detected gas pressure signal error E AD (j) is greater than 2000, the final pulse number P2(j) for controlling the stepper motor to rotate is 800; when the detected gas pressure signal error E AD When (j) is less than 20, the final pulse number P2(j) is set to 0.

[0097] Rule 4: Motor rotation speed control method for adjusting valve opening

[0098] In this system, the knob for controlling the valve opening can be rotated 13 times in total. In order to avoid valve jam and to quickly adjust the gas flow to the target value, a threshold-based motor speed adjustment method was studied. Figure 2 This is the relationship diagram between the valve opening and the motor rotation speed.

[0099] Therefore, the relationship between the motor rotation speed v1(j) and the valve opening θ1(j) satisfies the following equation:

[0100]

[0101] In the formula, v max is the maximum speed of the motor, v min is the minimum speed of the motor, v max =2.5r / s and v min =0.5r / s. θ1(j) is the actual opening of the valve, E AD (j) is the detected gas pressure signal error. When the motor runs to the fully closed position of the gas valve, the gas valve opening is 0°. In addition, θ2 = 90°, θ3 = 180°, θ4 = 3960° and θ5 = 4050°. When the motor runs to the fully open position of the gas valve, the gas valve opening is θ6, which satisfies θ6 = 4680°.

[0102] Therefore, by using the expert PID control algorithm studied, the motor rotation angle and speed can be controlled, the valve opening can be changed, and ultimately the actual gas flow rate can accurately reach the target value.

[0103] Figure 3 The curves of actual and target welding shielding gas flow rates are shown below. Figure 3 The ae segment in the figure indicates that the welding shielding gas flow rate is 0L / min at the beginning. Then, at the 49th sampling point, the corresponding Figure 3 At point i in the figure, the target welding shielding gas flow rate is set to 15L / min, and then the method of the present invention is used to make the actual gas flow rate approximately equal to the target value at the 58th sampling point. At this time, the accuracy of welding shielding gas flow rate detection and control is 99.9%. Therefore, through the invented gas flow rate online detection and automatic control method, the actual gas flow rate can quickly and accurately reach the target value, so that the weld is beautifully formed, and the efficiency and quality of welding can be improved.

[0104] In summary, since an inappropriate gas flow rate may cause the molten pool to be oxidized or bubbles to exist in the weld, affecting the welding quality, the present invention can realize online detection and automatic control of the welding shielding gas flow rate when the working conditions change, so that the weld formation is beautiful and the welding quality is improved. In addition, the method of the present invention is not affected by the gas type and environment, and can also be applied to the detection and control of gas flow in other working conditions. It has a wide range of applications and great practical application value.

[0105] Although the embodiments of the present invention are described in detail above, it is obvious to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations are within the scope and spirit of the present invention as described in the claims. Moreover, the present invention described herein may have other embodiments and may be implemented or realized in a variety of ways.

Claims

1. A gas flow detection and control method based on an adaptive model, characterized in that: The method comprises: Obtaining the actual gas flow rate Q(j), and converting the actual gas flow rate Q(j) into a digital value AD(j) of an actual gas pressure signal; According to the adaptive model, the target gas flow Q0(j) is converted into the digital value AD0(j) of the target gas pressure signal, and the gas pressure signal error E is obtained according to the digital value AD(j) of the actual gas pressure signal and the digital value AD0(j) of the target gas pressure signal. AD (j) and gas pressure signal error E AD (j) The rate of change EC AD (j); The gas pressure signal error E AD (j) and the rate of change EC AD (j) is the input, and the three parameters Kp, Ki and Kd of PID are adjusted by expert control, and an improved PID control is designed to control the initial pulse number P1(j) of the stepper motor rotation as the output; The preliminary pulse number P1(j) is combined with the preliminary pulse number P0(j) output by the expert control to output the final pulse number P2(j) for controlling the rotation of the stepper motor; Taking the valve opening θ1(j) detected by the encoder as input, the expert control rule is used to output the speed v1(j) of the stepper motor. Combined with the final pulse number P2(j) of the stepper motor rotation, the stepper motor is rotated at an angle θ(j).

2. The gas flow detection and control method based on the adaptive model according to claim 1, characterized in that: The adaptive model is constructed according to the following formula: Among them, a2, a1 and a0 are the coefficients of the adaptive model.

3. The gas flow detection and control method based on the adaptive model according to claim 2 is characterized in that: The steps of obtaining the digital value AD(j) of the actual gas pressure signal include: Continuously collect the digital quantities of the gas pressure signals output by n A / D modules, remove the maximum and minimum values, and take the arithmetic mean of the remaining n-2 signals as the digital quantity AD(j) of the actual gas pressure signal; The digital value AD(j) of the actual gas pressure signal is calculated according to the following formula: Wherein, n is the number of actual gas pressure signals, and b[k] is the kth signal among the n-2 actual gas pressure signals remaining after removing the maximum value and the minimum value.

4. The gas flow detection and control method based on the adaptive model according to claim 3 is characterized in that: The least squares curve fitting method is used to determine the adaptive model parameters a2, a1 and a0, and the sum of squared errors is used as the loss function to find the optimal solution of the model; The loss function satisfies the following formula: Where m is the number of experimental data (Q(j), AD(j)); The loss function J(a2,a1,a0) takes partial derivatives of the three model parameters respectively, and we can get: In order to minimize the loss function J(a2,a1,a0), the partial derivatives of the loss function are all 0. After simplification, we can get: Substituting the collected m groups of experimental data (Q(j), AD(j)), we can obtain the parameters a2, a1 and a0.

5. The gas flow detection and control method based on the adaptive model according to claim 4 is characterized in that: The gas pressure signal error E is obtained according to the digital value AD(j) of the actual gas pressure signal and the digital value AD0(j) of the target gas pressure signal. AD (j) and gas pressure signal error E AD (j) The rate of change EC AD The steps of (j) include: The gas pressure signal error E is calculated according to the following formula AD (j) and its rate of change EC AD (j): Wherein, AD0(j) is the digital value of the j-th target gas pressure signal, and AD(j) is the digital value of the actual gas pressure signal detected for the j-th time.

6. The gas flow detection and control method based on the adaptive model according to claim 5 is characterized in that: The gas pressure signal error E AD (j) and the rate of change EC AD (j) as input, the three parameters Kp, Ki and Kd of PID are adjusted by expert control, and the improved PID control is designed to control the initial pulse number P1(j) of the stepper motor as output, the steps include: The preliminary pulse number P1(j) is calculated according to the following formula: Among them, E AD (j) is the jth error of the gas pressure signal, EC AD (j) is the j-th error change rate of the gas pressure signal, abs(·) is the function for calculating the absolute value, kp2 and kp3 are proportional coefficients, satisfying kp3=2kp2=0.5; ki1 and ki2 are integral coefficients, satisfying ki2=2ki1=0.4; kd2 and kd3 are differential coefficients, satisfying kd3=2kd2=0.01; m1 and m2 satisfy m1=100 and m2=1000.

7. The gas flow detection and control method based on the adaptive model according to claim 6 is characterized in that: The method further comprises: If the expert control has an output value, the output value of the expert control is used as the final pulse number P2(j) for controlling the rotation of the stepper motor; otherwise, the output value of the improved PID is used as the final pulse number P2(j) for controlling the rotation of the stepper motor.

8. The gas flow detection and control method based on the adaptive model according to claim 6, characterized in that: The method further comprises: After the system is powered on, the motor that controls the opening of the gas valve is reversed by 45°. If the encoder detects that the actual rotation angle of the motor is greater than 40°, the motor that controls the opening of the gas valve is repeatedly reversed by 45°. If the encoder detects that the actual rotation angle of the motor is less than or equal to 40°, it is determined that the air valve rotates to the fully closed position and its vicinity, and the air valve opening is lower than the first preset opening threshold. At this time, the initial value of the control air valve opening θ1(j) is 720°; When the air valve is in the fully closed position or near it, and the air valve opening needs to be increased, the final pulse number P2(j) for controlling the rotation of the stepper motor is equal to the constant M; When the air valve is at or near the fully open position and the air valve opening needs to be reduced, the final pulse number P2(j) for controlling the rotation of the stepper motor is equal to the constant M.

9. The gas flow detection and control method based on the adaptive model according to claim 6, characterized in that: The method further comprises: When the detected gas pressure signal error E AD When (j) is greater than 2000, the final pulse number P2(j) for controlling the stepper motor to rotate is 800; When the detected gas pressure signal error E AD When (j) is less than 20, the final pulse number P2(j) is set to 0.

10. The gas flow detection and control method based on the adaptive model according to claim 6, characterized in that: The method further comprises: The relationship between the motor rotation speed v1(j) and the valve opening θ1(j) satisfies: Among them, v max is the maximum speed of the motor, v min is the minimum speed of the motor, v max =2.5r / s and v min =0.5r / s; θ1(j) is the actual opening of the gas valve, E AD (j) is the detected gas pressure signal error; when the motor runs to the fully closed position of the gas valve, the gas valve opening is 0°, in addition, θ2=90°, θ3=180°, θ4=3960° and θ5=4050°; when the motor runs to the fully open position of the gas valve, the gas valve opening is θ6, which satisfies θ6=4680°.

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