Pneumatic servo control device and method for breathing machine

Abstract

The invention relates to the technical field of medical equipment, and discloses a breathing machine pneumatic servo control device and method.The device comprises a circuit board, a sensor assembly and a control unit, the control unit and the sensor assembly are integrated on the circuit board, and the sensor assembly is in signal connection with the control unit; the sensor assembly comprises a differential pressure sensor and a pressure sensor, and the control unit performs double-closed-loop control based on parallel active-disturbance-rejection control based on signals collected by the differential pressure sensor and the pressure sensor so as to realize mixed control of air and oxygen while accurately controlling pressure and flow; wherein an inner ring adopts a parallel active-disturbance-rejection method to ensure that the linearity of air and oxygen flow control is good, the control is accurate, and the robustness is strong; pID control is adopted for the outer ring, fusion of air-oxygen mixed control and pressure control is achieved, and the use of control elements is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of medical equipment, and in particular to a pneumatic servo control device and method for a ventilator. Background Art

[0002] A ventilator is an important medical device used to assist patients in breathing, maintain their oxygenation function, and buy time for the treatment of primary diseases. It plays an irreplaceable role in the treatment of critically ill patients.

[0003] At present, the existing ventilators have the following shortcomings: 1) The components for air and oxygen in the ventilator are separated from the components for pressure and flow control, resulting in large equipment size, redundant components, high cost, and failure to meet the requirements of small, lightweight, modular, and low-cost medical equipment; 2) The development of the air-oxygen mixing function and the pressure and flow control functions in the ventilator is complex, time-consuming, and tedious to debug, which seriously affects the equipment development progress of medical equipment manufacturers. Summary of the invention

[0004] The purpose of the present application is to provide a pneumatic servo control device and method for a ventilator, which is based on a dual closed-loop control of parallel anti-disturbance control to achieve mixed control of air and oxygen while accurately controlling pressure and flow.

[0005] In order to achieve the above purpose, the technical solutions adopted are as follows:

[0006] In a first aspect, a pneumatic servo control device for a ventilator is provided, the device comprising a circuit board, a sensor assembly and a control unit, the control unit and the sensor assembly are integrated on the circuit board, the sensor assembly is connected to the control unit by signal, and the sensor assembly comprises a differential pressure sensor and a pressure sensor;

[0007] The control unit comprises a parallel active disturbance rejection controller, wherein the parallel active disturbance rejection controller comprises two extended state observers and a nonlinear state error feedback controller;

[0008] The extended state observer is used to expand the total disturbance into a new state variable of the system, and reconstruct all states including the original state variables of the system and the disturbance using the system input and output. Its discrete form is:

[0009]

[0010] Where h is the sampling period of the differential pressure sensor and the pressure sensor, y is the real-time pressure and flow value measured by the sensor assembly, u is the output of the extended state observer, z1, z2, and z3 are the disturbance variables of the extended state observer; β 01 , β 02 , β 03is the gain of the extended state observer, d is the coefficient of the nonlinear function, which is related to the sampling period, b is the compensation factor, and fal is a nonlinear function;

[0011] The real-time pressure and flow values ​​measured by the sensor are subtracted from the z1 of the previous moment of the extended state observer to obtain d1, and the output of the extended state observer at the current moment is further calculated, so that the state variables of the extended observer track the y of the controlled object, the differential of y and the disturbance received;

[0012] The nonlinear state error feedback controller is used to eliminate the error and includes the following nonlinear combination:

[0013]

[0014] In the formula, β1 and β2 are controller gains, d is the coefficient of the nonlinear function, u0 is the output of the nonlinear state error feedback control rate, e1 and e2 are the state errors of the system, and x1 is the tracking signal of the expected value; the control quantity u can be obtained by eliminating the disturbance variable z3, which is expressed as:

[0015]

[0016] Where b0 is the gain of the entire system.

[0017] Preferably, in the above-mentioned ventilator pneumatic servo control device, the control unit further includes a pressure outer loop controller, and the pressure outer loop controller is used to realize pressure control based on flow ratio control through the following formula:

[0018]

[0019] Where Q is the flow signal, k p is the proportional gain, e(t) is the state error, k i is the integral adjustment coefficient, d(t) is the microvariable with time t as the variable, k d is the differential adjustment coefficient, and t is the time.

[0020] Preferably, in the above-mentioned ventilator pneumatic servo control device, the device also includes a valve body structure, a pilot chamber and a three-way valve; the valve body structure is provided with a first air inlet and a second air inlet, the first air inlet and the second air inlet are used to introduce oxygen and air respectively, the valve body structure is connected to the pilot chamber to mix the oxygen and air introduced through the first air inlet and the second air inlet in the pilot chamber, the pilot chamber has a mixed gas outlet, the upper end of the valve body structure is provided with a three-way valve, the three-way valve is electrically installed on the circuit board to be electrically connected to the control unit, the three-way valve has three ports, two of which are respectively connected to the mixed gas outlet and the exhaust device air inlet through pipes, and the other port is provided with a quick-detachable exhalation structure.

[0021] Preferably, in the above-mentioned ventilator pneumatic servo control device, the circuit board also integrates a first solenoid valve and a second solenoid valve, wherein the first solenoid valve and the second solenoid valve are installed at the upper end of the valve body structure, for respectively controlling the air intake volume of the first air inlet and the second air inlet.

[0022] Preferably, in the above-mentioned ventilator pneumatic servo control device, the pressure sensor is used to collect the gas pressure in the pilot chamber.

[0023] Preferably, in the above-mentioned ventilator pneumatic servo control device, the differential pressure sensors are set to three, namely a first differential pressure sensor, a second differential pressure sensor and a third differential pressure sensor; wherein the first differential pressure sensor and the second differential pressure sensor are used to collect flow signals of the first air inlet and the second air inlet, and the third differential pressure sensor is used to collect the flow signal of the quick-detachable exhalation structure.

[0024] Preferably, in the above-mentioned ventilator pneumatic servo control device, a throttle plate is arranged at the center position of the differential pressure sensor.

[0025] Preferably, in the above-mentioned ventilator pneumatic servo control device, a sliding average filter is also integrated on the circuit board, and the sliding average filter is arranged at the signal output end of the differential pressure sensor to filter the signal collected by the differential pressure sensor.

[0026] In a second aspect, a pneumatic servo control method for a ventilator is provided, the method comprising:

[0027] Flow control is realized based on two extended state observers and a nonlinear state error feedback controller; wherein the extended state observer is used to expand the total disturbance into a new state variable of the system, and reconstruct all states including the original state variables of the system and the disturbance using the system input and output, and its discrete form is:

[0028]

[0029] Where h is the sampling period of the differential pressure sensor and the pressure sensor, y is the real-time pressure and flow value measured by the sensor assembly, u is the output of the extended state observer, z1, z2, and z3 are the disturbance variables of the extended state observer; β 01 , β 02 , β 03 is the gain of the extended state observer, d is the coefficient of the nonlinear function, which is related to the sampling period, b is the compensation factor, and fal is a nonlinear function;

[0030] The real-time pressure and flow values ​​measured by the sensor are subtracted from the z1 of the previous moment of the extended state observer to obtain d1, and the output of the extended state observer at the current moment is further calculated, so that the state variables of the extended observer track the y of the controlled object, the differential of y and the disturbance received;

[0031] The nonlinear state error feedback controller is used to eliminate the error and includes the following nonlinear combination:

[0032]

[0033] In the formula, β1 and β2 are controller gains, d is the coefficient of the nonlinear function, u0 is the output of the nonlinear state error feedback control rate, e1 and e2 are the state errors of the system, and x1 is the tracking signal of the expected value; the control quantity u can be obtained by eliminating the disturbance variable z3, which is expressed as:

[0034]

[0035] Where b0 is the gain of the entire system.

[0036] Preferably, the method further comprises:

[0037] Pressure control based on flow rate proportional control is achieved through the following formula:

[0038]

[0039] Where Q is the flow signal, k p is the proportional gain, e(t) is the state error, k i is the integral adjustment coefficient, d(t) is the microvariable with time t as the variable, k d is the differential adjustment coefficient, and t is the time.

[0040] The beneficial effects of this application are:

[0041] The present application is based on a dual closed-loop control of parallel auto-disturbance rejection control, which realizes the mixing control of air and oxygen while accurately controlling the pressure and flow rate; the inner loop adopts the parallel auto-disturbance rejection method to ensure good linearity, precise control and strong robustness of air and oxygen flow control; the outer loop adopts PID control to realize the integration of air-oxygen mixing control and pressure control, and reduce the use of control elements. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A schematic structural diagram of a pneumatic servo control device for a ventilator according to an embodiment of the present application is shown.

[0043] Figure 2 A three-dimensional representation of a pneumatic servo control device for a ventilator according to an embodiment of the present application is shown.

[0044] Figure 3 A side view of a pneumatic servo control device for a ventilator according to an embodiment of the present application is shown.

[0045] Figure 4 A stereoscopic view of a quick-detachable exhalation structure according to an embodiment of the present application is shown; wherein (a) and (b) respectively show the stereoscopic structure of the quick-detachable exhalation structure at different viewing angles.

[0046] Figure 5 A schematic diagram of a valve body structure in a pneumatic servo control device for a ventilator according to an embodiment of the present application is shown, wherein (a) is a front schematic diagram and (b) is a back schematic diagram.

[0047] Figure 6 A schematic diagram of a pressure measurement structure according to an embodiment of the present application is shown.

[0048] Figure 7 A schematic diagram of a dual closed-loop control system based on parallel active disturbance rejection control according to an embodiment of the present application is shown.

[0049] Reference numerals:

[0050] 100, circuit board; 200, sensor assembly; 210, differential pressure sensor; 220, pressure sensor; 300, control unit; 310, parallel anti-disturbance controller; 311, extended state observer; 312, nonlinear state error feedback controller; 320, pressure outer loop controller; 400, valve body structure; 410, first air inlet; 420, second air inlet; 500, pilot chamber; 600, three-way valve; 700, exhaust device; 710, exhaust device air inlet; 800, quick-detachable exhalation structure; 900, first solenoid valve; 1000, second solenoid valve. DETAILED DESCRIPTION

[0051] The following describes the embodiments of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. The present application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0052] The specific implementation of the present application is further described in detail below in conjunction with the drawings and examples.

[0053] Figure 1 The structure diagram of a pneumatic servo control device for a ventilator according to an embodiment of the present application is shown. The present application embodiment provides a pneumatic servo control device for a ventilator, such as Figure 1 As shown, the device includes a circuit board 100, a sensor assembly 200 and a control unit 300. The control unit 300 and the sensor assembly 200 are integrated on the circuit board. The sensor assembly 200 is signal-connected to the control unit 300. The sensor assembly 200 includes a differential pressure sensor 210 and a pressure sensor 220.

[0054] In this embodiment, a dual closed-loop control based on parallel active disturbance rejection control is implemented based on the control unit 300, and the mixing control of air and oxygen is realized while the pressure and flow are accurately controlled. Specifically, the control unit 300 includes a parallel active disturbance rejection controller 310, and the parallel active disturbance rejection controller 310 includes two extended state observers 311 and a nonlinear state error feedback controller 312.

[0055] In the dual closed-loop control based on parallel ADRC, flow control is used as the inner loop. The extended state observer 311 expands the total disturbance into a new state variable of the system, and then reconstructs all states including the original state variables of the system and the disturbance using the system input and output. Its discrete form is:

[0056]

[0057] Where h is the sampling period of the differential pressure sensor and the pressure sensor, y is the real-time pressure and flow value measured by the sensor assembly, u is the output of the extended state observer, z1, z2, and z3 are the disturbance variables of the extended state observer; β 01 , β 02 , β 03 is the gain of the extended state observer, d is the coefficient of the nonlinear function, which is related to the sampling period, b is the compensation factor, and fal is a nonlinear function.

[0058] The real-time pressure and flow value y measured by the sensor is subtracted from the z1 of the previous moment of the expanded state observer to obtain d1, and the output of the expanded state observer at the current moment is further calculated, so that the state variable z of the expanded observer can be i (t) Track the y of the controlled object, the differential of y, and the disturbance it receives.

[0059] The nonlinear state error feedback controller 312 is based on the nonlinear state error feedback control rate to eliminate the error. The recommended nonlinear combination has the following form:

[0060]

[0061] β1 and β2 are controller gains, d is the coefficient of the nonlinear function, u0 is the output of the nonlinear state error feedback control rate, e1 and e2 are the state errors of the system, and x1 is the tracking signal of the expected value; the control quantity u can be obtained by eliminating the disturbance variable z3, which is expressed as:

[0062]

[0063] Where b0 is the gain of the entire system.

[0064] The output u is proportional to the pressure and flow rate, achieving precise control of the flow rate.

[0065] In order to realize pressure control based on flow rate proportional control, the control unit 300 includes a pressure outer loop controller 320. In the pressure outer loop controller 320, the outer loop controller and the proportional distribution structure are considered as a flow distributor, and the output of the flow distributor is used as the input of the flow inner loop controller. The outer loop controller adopts PID control, and its principle is as follows:

[0066]

[0067] Where Q is the flow signal, k p is the proportional gain, e(t) is the state error, k i is the integral adjustment coefficient, d(t) is the microvariable with time t as the variable, k d is the differential adjustment coefficient, and t is the time.

[0068] In some embodiments, Figure 2 and Figure 3 1 is a perspective view and a side view of a pneumatic servo control device for a ventilator according to an embodiment of the present application, as shown in FIG. Figure 2 and Figure 3As shown, the pneumatic servo control device of the ventilator also includes a valve body structure 400, a pilot chamber 500 and a three-way valve 600; the valve body structure 400 is provided with a first air inlet 410 and a second air inlet 420, the first air inlet 410 and the second air inlet 420 are used to introduce oxygen and air respectively, the valve body structure 400 is communicated with the pilot chamber 500 to mix the oxygen and air introduced through the first air inlet 410 and the second air inlet 420 in the pilot chamber 500, the pilot chamber 500 has a mixed gas outlet 510, the upper end of the valve body structure 400 is provided with a three-way valve 600, the three-way valve 600 is electrically mounted on the circuit board 100 to be electrically connected to the control unit 300, the three-way valve 600 has three ports, two of which are respectively connected to the mixed gas outlet 510 and the exhaust device air inlet 710 through pipelines, and the other port is provided with a quick-detachable exhalation structure 800.

[0069] In this embodiment, the exhaust device air inlet 710 is disposed on the exhaust device 700, wherein the exhaust device 700 can be disposed on one side of the pilot chamber 500. The first air inlet 410 and the second air inlet 420 can be connected to the oxygen supply device and the air supply device through a pipeline. The structure of the quick-detachable exhalation structure 800 is as shown in FIG. Figure 4 As shown, it can be assembled on one port of the three-way valve 600 in the form of a flange, and then can be connected to the breathing duct in a threaded manner to connect the corresponding air supply device, such as an air supply mask, etc. through the breathing duct.

[0070] like Figure 4 As shown, a quick-detachable exhalation structure 800 is designed based on a pilot cavity structure, and the exhalation flow rate is detected in the pipeline of the quick-detachable exhalation structure 800 by the principle of a balanced flowmeter. The on-off control of the patient's exhalation airway and the positive end-expiratory pressure are achieved by controlling the pilot cavity pressure. The quick-detachable structure is designed to address the problem of the patient's exhaled gas carrying bacteria, so that medical staff can disinfect and clean it easily.

[0071] like Figure 2 As shown, the circuit board 100 also integrates a first solenoid valve 900 and a second solenoid valve 1000, wherein the first solenoid valve 900 and the second solenoid valve are installed at the upper end of the valve body structure to control the air intake of the first air inlet 410 and the second air inlet 420 respectively.

[0072] The following embodiment of the present application will specifically introduce the installation positions of the various sensors included in the sensor assembly 200. The pressure sensor 220 is used to collect the gas pressure in the pilot chamber 500. The differential pressure sensor 210 is set to three, namely, a first differential pressure sensor, a second differential pressure sensor and a third differential pressure sensor; wherein the first differential pressure sensor and the second differential pressure sensor are used to collect flow signals of the first air inlet 410 and the second air inlet 420, and the third differential pressure sensor is used to collect flow signals of the quick-detachable exhalation structure 800. Figure 2 and Figure 3 In FIG. 1 , A, B, C, and D are installation positions of the pressure sensor 220, the first differential pressure sensor, the second differential pressure sensor, and the third differential pressure sensor, respectively.

[0073] It should be noted that the method of integrating electronic components on the circuit board 100 mentioned herein refers to assembling the driving circuits of various electronic components on the circuit board 100 so that various electronic components establish signal connections to achieve signal transmission and processing. Among them, the electronic components include a control unit 300, a sensor assembly 200, a three-way valve 600, a first solenoid valve 900, and a second solenoid valve 1000.

[0074] Figure 5 is a schematic diagram of a valve body structure in a pneumatic servo control device for a ventilator according to an embodiment of the present application, Figure 5 In the figure, (a) is a front view, (b) is a back view, the back of the valve body structure 400 is connected to a metal quick-connect connector by a thread, and the front is connected to a measuring structure (including but not limited to a first differential pressure sensor and a second differential pressure sensor), fixed by bolts, with a sealing ring in the middle. Two proportional valves (a first solenoid valve 900 and a second solenoid valve 1000) and a three-way valve 600 can be installed on the top of the valve body 400. The two proportional valves are used to control the gas flow of the oxygen gas circuit and the air gas circuit respectively, and the two-position three-way valve is used to control the positive end-expiratory pressure in the pilot cavity.

[0075] Figure 6 This is a schematic diagram of a pressure and measurement structure of an embodiment of the present application. The pressure and measurement structure includes a circuit board 100 and a sensor assembly 200 and a control unit 300 integrated on the circuit board. The sensor assembly and circuit board 100 are installed on the top of the pipeline, and a throttle plate is arranged at the center of the differential pressure sensor. In order to reduce the impact of turbulence on flow measurement, circular holes are designed around the center circle to regularize the flow field. The final designed flow and pressure measurement structure is shown in the figure below.

[0076] In some embodiments, a sliding average filter is also integrated on the circuit board 100, and the sliding average filter is set at the signal output end of the differential pressure sensor 210 to filter the signal collected by the differential pressure sensor 210. Specifically, the sliding average filter accumulates n consecutive signals and then divides them by n to obtain the average value, thereby forming a window. Whenever a new sample enters, the first sample that enters is deleted, the new sample is added to the accumulator, and the average value is re-output. The signal average value is continuously calculated through a continuous sliding window.

[0077] In some embodiments, flow control can be achieved through a differential pressure sensor, so the differential pressure flow measurement circuit is calibrated and fitted. An air compressor is used as the air source device, and the pressure reducing valve reduces the inlet pressure to 0.2Mpa; the valve opening is adjusted by adjusting the solenoid valve control voltage to achieve different differential pressure measurements and corresponding flow measurements.

[0078] In a specific embodiment, based on Figure 2 and Figure 3 In the device structure shown, MCU is selected as the control unit 300. The installation method of the device can be: the oxygen supply device is directly connected to the first air inlet 410 of the device through a pipeline, the air supply device is directly connected to the second air inlet 420 of the device through a pipeline, and the mixed gas outlet 510 is connected to a three-way joint with a pipeline, one end of the joint is connected to the patient, and the other end is connected to the exhaust device air inlet 710 of the device.

[0079] The working process of the device is as follows:

[0080] When the ventilator needs to output gas at a set pressure or flow rate, the staff sets the ventilation and ventilation modes, and turns on the air compressor and oxygen gas source as the gas source. After being stabilized by the pressure regulating valve, the gas flows into the control device.

[0081] The first differential pressure sensor and the second differential pressure sensor in the device monitor the flow in the air path and the oxygen path in real time, and the pressure sensor monitors the gas pressure in the mixing chamber in real time, and feeds back the collected signal to the MCU. The MCU adjusts the control voltage in real time through the algorithm according to the feedback pressure and flow signals. Specifically, the pressure sensor, the first differential pressure sensor, and the second differential pressure sensor are used to collect the pressure and flow values ​​of the airflow inside the detection device, and the collected signals are transmitted to the MCU. During the patient's inhalation stage, the MCU outputs the control voltage through the dual closed-loop control algorithm based on parallel self-anti-disturbance control, changes the opening of the first solenoid valve and the second solenoid valve, and realizes the precise control of the proportion of air and oxygen and pressure and flow at the same time. The pressure sensor collects the pressure in the pilot chamber. During the patient's exhalation stage, the three-way valve controls the pressure in the pilot chamber to realize the end-expiratory positive pressure control, and the airflow flow in the quick-detachable exhalation structure is collected through the third differential pressure sensor.

[0082] Affected by the control voltage, the device outputs the set pressure and flow of gas, using MCU based on such Figure 7 The control flow shown implements high-precision control based on the auto-disturbance rejection algorithm.

[0083] In summary, the present application can realize functions such as air-oxygen mixing, pressure-controlled ventilation, and volume-controlled ventilation, and can be directly used as a core component of a manufacturer's ventilator research and development. The existing ventilators use two solenoid valves to achieve air-oxygen mixing, and a blower to achieve flow and pressure control, with a total of three control elements, and there is device redundancy. This device uses two solenoid valves to simultaneously achieve air-oxygen mixing, flow, and pressure control, reducing costs and size. Self-anti-disturbance control effectively enhances robustness and achieves a linear correspondence between the control voltage and the output pressure and flow. At the same time, for different respiratory mechanics parameters, a recursive least squares-based method is used for parameter adaptation to broaden the scope of application of the device.

[0084] The above implementation modes are only used to illustrate the present application, and are not intended to limit the present application. Ordinary technicians in the relevant technical field may make various changes and modifications without departing from the spirit and scope of the present application. Therefore, all equivalent technical solutions also belong to the scope of the present application, and the scope of patent protection of the present application shall be limited by the claims.

Claims

1. A pneumatic servo control device for a ventilator, characterized in that: The device comprises a circuit board, a sensor assembly and a control unit, wherein the control unit and the sensor assembly are integrated on the circuit board, the sensor assembly is connected to the control unit by signal, and the sensor assembly comprises a differential pressure sensor and a pressure sensor; The control unit comprises a parallel active disturbance rejection controller, wherein the parallel active disturbance rejection controller comprises two extended state observers and a nonlinear state error feedback controller; The extended state observer is used to expand the total disturbance into a new state variable of the system, and reconstruct all states including the original state variables of the system and the disturbance using the system input and output. Its discrete form is: Where h is the sampling period of the differential pressure sensor and the pressure sensor, y is the real-time pressure and flow value measured by the sensor assembly, u is the output of the extended state observer, z1, z2, and z3 are the disturbance variables of the extended state observer; β 01 , β 02 , β 03 is the gain of the extended state observer; d is the coefficient of the nonlinear function, which is related to the sampling period, b is the compensation factor, and fal is a nonlinear function; The real-time pressure and flow values ​​measured by the sensor are subtracted from the z1 of the previous moment of the extended state observer to obtain d1, and the output of the extended state observer at the current moment is further calculated, so that the state variables of the extended observer track the y of the controlled object, the differential of y and the disturbance received; The nonlinear state error feedback controller is used to eliminate the error and includes the following nonlinear combination: In the formula, β1 and β2 are controller gains, d is the coefficient of the nonlinear function, u0 is the output of the nonlinear state error feedback control rate, e1 and e2 are the state errors of the system, and x1 is the tracking signal of the expected value; the control quantity u can be obtained by eliminating the disturbance variable z3, which is expressed as: Where b0 is the gain of the entire system.

2. The pneumatic servo control device for a ventilator according to claim 1, characterized in that: The control unit also includes a pressure outer loop controller, which is used to achieve pressure control based on flow rate proportional control through the following formula: Where Q is the flow signal, k p is the proportional gain, e(t) is the state error, k i is the integral adjustment coefficient, d(t) is the microvariable with time t as the variable, k d is the differential adjustment coefficient, and t is the time.

3. The pneumatic servo control device for a ventilator according to claim 1, characterized in that: The device also includes a valve body structure, a pilot chamber and a three-way valve; the valve body structure is provided with a first air inlet and a second air inlet, the first air inlet and the second air inlet are respectively used to introduce oxygen and air, the valve body structure is communicated with the pilot chamber to mix the oxygen and air introduced through the first air inlet and the second air inlet in the pilot chamber, the pilot chamber has a mixed gas outlet, the upper end of the valve body structure is provided with a three-way valve, the three-way valve is electrically mounted on the circuit board to be electrically connected to the control unit, the three-way valve has three ports, two of which are respectively connected to the mixed gas outlet and the air inlet of the exhaust device through pipelines, and the other port is provided with a quick-detachable exhalation structure.

4. The pneumatic servo control device for a ventilator as claimed in claim 3, characterized in that: The circuit board also integrates a first solenoid valve and a second solenoid valve, wherein the first solenoid valve and the second solenoid valve are installed at the upper end of the valve body structure, and are used to control the air intake volume of the first air inlet and the second air inlet respectively.

5. The pneumatic servo control device for a ventilator as claimed in claim 3, characterized in that: The pressure sensor is used to collect the gas pressure in the pilot chamber.

6. The pneumatic servo control device for a ventilator as claimed in claim 3, characterized in that: The differential pressure sensors are set to three, namely the first differential pressure sensor, the second differential pressure sensor and the third differential pressure sensor; wherein the first differential pressure sensor and the second differential pressure sensor are used to collect flow signals of the first air inlet and the second air inlet, and the third differential pressure sensor is used to collect the flow signal of the quick-detachable exhalation structure.

7. The pneumatic servo control device for a ventilator according to claim 1, characterized in that: A throttle plate is arranged at the center of the differential pressure sensor.

8. The pneumatic servo control device for a ventilator according to claim 1, characterized in that: The circuit board is also integrated with a sliding average filter, which is arranged at the signal output end of the differential pressure sensor and is used to filter the signal collected by the differential pressure sensor.

9. A pneumatic servo control method for a ventilator, characterized in that: The method comprises: Flow control is realized based on two extended state observers and a nonlinear state error feedback controller; wherein the extended state observer is used to expand the total disturbance into a new state variable of the system, and reconstruct all states including the original state variables of the system and the disturbance using the system input and output, and its discrete form is: Where h is the sampling period of the differential pressure sensor and the pressure sensor, y is the real-time pressure and flow value measured by the sensor assembly, u is the output of the extended state observer, z1, z2, and z3 are the disturbance variables of the extended state observer; β 01 , β 02 , β 03 is the gain of the extended state observer; d is the coefficient of the nonlinear function, which is related to the sampling period, b is the compensation factor, and fal is a nonlinear function; The real-time pressure and flow values ​​measured by the sensor are subtracted from the z1 of the previous moment of the extended state observer to obtain d1, and the output of the extended state observer at the current moment is further calculated, so that the state variables of the extended observer track the y of the controlled object, the differential of y and the disturbance received; The nonlinear state error feedback controller is used to eliminate the error and includes the following nonlinear combination: In the formula, β1 and β2 are controller gains, d is the coefficient of the nonlinear function, u0 is the output of the nonlinear state error feedback control rate, e1 and e2 are the state errors of the system, and x1 is the tracking signal of the expected value; the control quantity u can be obtained by eliminating the disturbance variable z3, which is expressed as: Where b0 is the gain of the entire system.

10. The method according to claim 9, characterized in that The method further comprises: Pressure control based on flow rate proportional control is achieved through the following formula: Where Q is the flow signal, k p is the proportional gain, e(t) is the state error, k i is the integral adjustment coefficient, d(t) is the microvariable with time t as the variable, k d is the differential adjustment coefficient, and t is the time.

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