Oxygen concentration control methods for ventilators and ventilators

Abstract

This disclosure provides an oxygen concentration control method and a ventilator for use in a ventilator. The oxygen concentration control method for a ventilator includes setting an oxygen concentration value; detecting the current oxygen concentration value in a mixture of air and oxygen; calculating a feedback value based on a control signal sent to an oxygen flow regulator and a model of an estimated gas path delay; obtaining an oxygen concentration deviation at least based on the detected current oxygen concentration value and the set oxygen concentration value; and adjusting the control signal sent to the oxygen flow regulator based on the oxygen concentration deviation and the calculated feedback value. Embodiments of this disclosure consider the delay characteristics of oxygen concentration changes in the gas path and set a control algorithm for the delay element to minimize the interference of delay characteristics on oxygen concentration regulation, thereby improving the speed, stability, and accuracy of oxygen concentration regulation.

Description

Technical Field

[0001] This disclosure relates to the field of ventilator technology, and more specifically, to a method for controlling oxygen concentration in a ventilator and a ventilator using the method. Background Technology

[0002] Oxygen concentration control on a ventilator can be achieved by looking up a calibration curve to obtain the voltage of the oxygen flow valve for adjustment, or by using PID control of the oxygen flow valve. However, due to gas path factors, changes in oxygen concentration have a certain delay characteristic, requiring a period of time to reach a stable value. Therefore, fluctuations in oxygen concentration control are likely to occur during adjustment, resulting in problems such as long adjustment time to a stable state and limited control accuracy.

[0003] Furthermore, current ventilators generally use oxygen cell sensors or paramagnetic oxygen sensors for oxygen concentration monitoring and control. Oxygen cell sensors are consumable components; as the battery depletes, the accuracy of oxygen concentration monitoring decreases significantly, requiring periodic replacement. Moreover, during adjustment, the slow data monitoring response can lead to instability and inaccurate oxygen concentration adjustments. Paramagnetic oxygen sensors are susceptible to vibration, position, and other factors, resulting in a higher failure rate. Additionally, this type of sensor is expensive, leading to high production and maintenance costs.

[0004] Therefore, based on the above reasons, on the one hand, there is a need for an oxygen concentration control method that can reduce fluctuations in the oxygen concentration control process, making the oxygen concentration control more stable and faster; on the other hand, there is a need to find a sensor with lower cost and longer service life for oxygen concentration monitoring in ventilators. Summary of the Invention

[0005] This disclosure provides a method for controlling oxygen concentration in a ventilator and a ventilator using the method, to solve one or more of the aforementioned technical problems.

[0006] To address at least one of the aforementioned technical problems, an embodiment of the first aspect of this disclosure provides an oxygen concentration control method for a ventilator, comprising: setting an oxygen concentration value; detecting a current oxygen concentration value in a mixture of air and oxygen; calculating a feedback value based on a control signal sent to an oxygen flow regulating device and a model of an estimated gas path delay; obtaining an oxygen concentration deviation based at least on the detected current oxygen concentration value and the set oxygen concentration value; and adjusting the control signal sent to the oxygen flow regulating device based on the oxygen concentration deviation and the calculated feedback value.

[0007] The embodiments of this disclosure take into account the delayed characteristics of oxygen concentration changes in the gas path, and set up a control algorithm for the delayed element to minimize the interference of the delayed characteristics on oxygen concentration regulation, thereby improving the speed, stability and accuracy of oxygen concentration regulation and oxygen concentration control.

[0008] Optionally, according to an embodiment of the first aspect of this disclosure, the model of the estimated gas path delay link includes a discretized model of the transfer function of the estimated oxygen flow regulating device and a discretized model of the transfer function of the estimated oxygen flow regulating device including the gas path delay link, and the calculation of the feedback value includes calculating the feedback value of the control signal via the discretized model of the transfer function of the estimated oxygen flow regulating device and the discretized model of the transfer function of the estimated oxygen flow regulating device including the gas path delay link, respectively.

[0009] The above embodiments of this disclosure use two feedback loops. The feedback loop that includes the estimation model of the gas path delay element can move the delay element outside the control loop, improving the speed of the adjustment process. The feedback loop that does not include the estimation model of the gas path delay element can compensate for errors caused by model inaccuracy or other disturbances.

[0010] Optionally, according to an embodiment of the first aspect of this disclosure, the transfer function Go(s) of the oxygen flow regulating device and the transfer function Gp(s) of the oxygen flow regulating device including the gas path delay element have the following relationship:

[0011] Gp(s) = Go(s) * e -τs

[0012] Where e -τs This is the transfer function of the gas path delay element.

[0013] Optionally, according to an embodiment of the first aspect of this disclosure, adjusting the control signal sent to the oxygen flow regulating device based on the oxygen concentration deviation and the calculated feedback value includes calculating the deviation signal e2(k), wherein...

[0014] e2(k)=e1(k)-x m (k)+y m (k)=r(k)-y(k)-x m (k)+y m (k)

[0015] Where e1(k) is the oxygen concentration deviation, x m (k) is the output of the discretized model of the control signal via the transfer function of the estimated oxygen flow regulating device, y m (k) is the output of the discretized model of the transfer function of the oxygen flow regulating device including the gas path delay link, the control signal is the set oxygen concentration value, and y(k) is the current oxygen concentration value.

[0016] Optionally, according to an embodiment of the first aspect of this disclosure, obtaining the oxygen concentration deviation based at least on the detected current oxygen concentration value and the set oxygen concentration value includes calculating the difference between the current oxygen concentration value and the set oxygen concentration value as the oxygen concentration deviation e1(k).

[0017] Optionally, according to an embodiment of the first aspect of this disclosure, obtaining the oxygen concentration deviation based at least on the detected current oxygen concentration value and the set oxygen concentration value includes calculating the oxygen concentration deviation e1(k) according to the following equation:

[0018] D0(k)=y m (k) / y(k)

[0019] D1(k)=D0(k)+T d *[D0(k)-D0(k-1)] / T s T d =τ

[0020] D2(k)=x m (k)*D1(k)

[0021] e1(k)=r(k)-D2(k)

[0022] Where D0(k) is y m The ratio of (k) to y(k), where D1(k) is the value calculated after the first derivative of D0(k), and D2(k) is the ratio of D1(k) to x. m The product of (k), T s It is the sampling period.

[0023] Optionally, according to an embodiment of the first aspect of this disclosure, the oxygen concentration control method for a ventilator further includes calculating the ratio of oxygen to air flow and an oxygen flow value based on the set oxygen concentration value and total ventilation flow, and obtaining an initial control signal for the oxygen flow regulating device based on the oxygen flow value.

[0024] Optionally, according to an embodiment of the first aspect of this disclosure, the oxygen concentration control method for a ventilator further includes determining whether the set oxygen concentration value is consistent with the current oxygen concentration value; if they are consistent, then the current control signal is maintained unchanged.

[0025] Optionally, according to an embodiment of the first aspect of this disclosure, adjusting the control signal sent to the oxygen flow regulating device based on the oxygen concentration deviation and the calculated feedback value includes adjusting the control signal using any one of PI regulation, PID regulation, and PD regulation.

[0026] Optionally, according to an embodiment of the first aspect of this disclosure, an ultrasonic oxygen sensor is used to detect the current oxygen concentration value in the gas mixture.

[0027] The embodiments of this disclosure may select an ultrasonic oxygen sensor. The ultrasonic oxygen sensor is a non-consumable component, which can ensure the stability and high accuracy of monitoring data, reduce costs, and ensure the long-term stable operation of the ventilator.

[0028] According to a second aspect of this disclosure, embodiments of this disclosure provide a ventilator that can use the above-described oxygen concentration control method for a ventilator. The ventilator includes an oxygen flow regulating device for regulating the flow rate of oxygen entering the ventilator; an oxygen flow sensor for detecting the oxygen flow rate; a power unit, located downstream of the oxygen flow regulating device, for receiving a mixture of air and oxygen; an oxygen concentration sensor, located downstream of the power unit, for detecting the oxygen concentration value in the air-oxygen mixture; a respiratory processing unit that calculates a feedback value based on a control signal sent to the oxygen flow regulating device and a model of an estimated airway delay; obtains an oxygen concentration deviation at least based on the detected current oxygen concentration value and a set oxygen concentration value; and adjusts the control signal sent to the oxygen flow regulating device based on the oxygen concentration deviation and the calculated feedback value.

[0029] Optionally, according to an embodiment of the second aspect of this disclosure, the oxygen concentration sensor is an ultrasonic oxygen sensor.

[0030] The ventilator of the above embodiments of this disclosure can achieve rapid, accurate and stable oxygen concentration control during operation.

[0031] Implementing any apparatus of this disclosure does not necessarily require achieving all of the advantages described above simultaneously. Other features and advantages of this disclosure will be set forth in the following description and will be apparent in part from the description and embodiments, or may be learned by practicing this disclosure. The objects and advantages of embodiments of this disclosure may be realized and obtained by means of the structures pointed out in the description, claims, and drawings. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings of the embodiments will be briefly introduced below. Obviously, the drawings described below only relate to some embodiments of this disclosure, and are not intended to limit this disclosure.

[0033] Figure 1 This is a general block diagram of a ventilator system for regulating oxygen concentration according to an embodiment of the present disclosure;

[0034] Figure 2 This is a schematic block diagram of an oxygen concentration control system according to an embodiment of the present disclosure;

[0035] Figure 3 This is a schematic block diagram of an oxygen concentration control system including a digital estimator according to an embodiment of the present disclosure;

[0036] Figure 4 This is a flowchart of an oxygen concentration adjustment and control method according to an embodiment of the present disclosure;

[0037] Figure 5 This is a schematic block diagram of an oxygen concentration control system including a digital estimator according to another embodiment of the present disclosure;

[0038] Figure 6 This is a flowchart of an oxygen concentration adjustment and control method according to another embodiment of the present disclosure;

[0039] Figure 7A and Figure 7B These are example curves of oxygen concentration change processes obtained using an existing oxygen concentration control system and an oxygen concentration control system according to the above embodiments of this disclosure. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. Various different embodiments can be combined with each other to constitute other embodiments not shown in the following description. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0041] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” and similar terms used in this patent application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, “an” or “a” and similar terms do not necessarily indicate a quantity limitation. Terms such as “comprising” or “including” mean that the element or object preceding the word encompasses the element or object listed following the word and its equivalents, without excluding other elements or objects. Terms such as “connected” or “linked” are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as “upper,” “lower,” “left,” and “right” are used only to indicate relative positional relationships, which may change accordingly when the absolute position of the described object changes.

[0042] Monitoring and regulating oxygen concentration in a ventilator is an important part of its function. Its main function is to correct the lack of oxygen required for the patient's metabolism during the process of providing support ventilation, increase the partial pressure of oxygen in the arterial blood, treat respiratory diseases caused by hypoxia due to various reasons, and improve the patient's oxygenation.

[0043] Figure 1 A general block diagram of a system 100 for regulating oxygen concentration in a ventilator according to an embodiment of the present disclosure is shown. The system 100 includes an oxygen concentration sensor 101, a total flow sensor 102, a power unit 103, an oxygen flow sensor 104, an oxygen flow regulating device 105, and a respiratory processing unit (not shown). The system may also include an expiratory valve 106 and a proximal respiratory flow and / or pressure sensor 107.

[0044] The oxygen concentration sensor 101 can be located downstream of the gas mixing path to detect the oxygen concentration of the mixed gas. It can be located near the ventilator outlet, i.e., detecting the oxygen concentration of the mixed gas near the patient's inspiratory end, and feeding the detected value back to the control system to ensure that the patient is receiving oxygen at a preset concentration, avoiding oxygen toxicity caused by prolonged high-concentration oxygen inhalation or life-threatening situations due to excessively low oxygen concentration. The oxygen concentration sensor 101 can be an ultrasonic oxygen sensor, which has a long lifespan, low cost, and is less prone to damage and failure due to interference. Other suitable oxygen sensors can also be used to implement the oxygen concentration sensor 101.

[0045] The total flow sensor 102 is used to detect the total flow rate of the mixed gas. It is located downstream of the mixed gas path and can also be located upstream of the oxygen concentration sensor 101. The total flow sensor 102 can send the detection result to the breathing processing unit. The breathing processing unit ensures the stability of the total ventilation flow rate and obtains the oxygen flow rate value according to the set oxygen concentration value.

[0046] The power unit 103, serving as the main power source for the ventilator, is located downstream of the air and oxygen inlets. The power unit can be a turbine fan and / or a flow valve. Air and oxygen mixing can occur upstream of the power unit inlet. After the ventilator is activated, during the inspiratory phase, the power unit 103 is powered on and reaches a certain speed. Simultaneously, the oxygen flow regulator 105 is powered on to control the oxygen flow rate, and the oxygen flow sensor 104, located downstream of the oxygen flow regulator 105, detects the oxygen flow rate. Oxygen and air are mixed according to a ratio calculated based on the set oxygen concentration and then delivered by the power unit 103 to the downstream airway, ultimately entering the lungs. During expiration, the power unit 103's speed decreases, and the expiratory valve 106 opens to expel air from the lungs. The oxygen flow regulator 105 can be implemented using an oxygen flow valve.

[0047] The functions of the breathing processing unit can be implemented entirely or partially through software, such as embedded system software in a microcontroller (MCU), which can send control signals to relevant components or obtain the required data from relevant components.

[0048] The positions of the total flow sensor, oxygen concentration sensor, and oxygen flow sensor can be adjusted as needed.

[0049] The proximal respiratory flow and / or pressure sensor 107 can be used to measure the flow and / or pressure of inhaled and exhaled gases at the patient end, and it can be positioned downstream of the oxygen concentration sensor, close to the patient side.

[0050] In addition to the oxygen concentration regulating system 100 described above, the ventilator may also include tubing, a gas source, a humidifier, etc. The ventilator may include more or fewer components than shown in the diagram, or combine some components, or separate some components, or be configured with different component arrangements. The ventilator may include one or more processing units. These processing units may be independent devices or integrated into one or more processors. The processors may include, but are not limited to, one or more of the following: microcontroller (MCU), central processing unit (CPU), digital signal processor (DSP), and field-programmable gate array (FPGA).

[0051] In the oxygen concentration control system of a ventilator, the main components for regulating oxygen concentration include an oxygen flow regulator 105, an oxygen flow sensor 104, and an oxygen concentration sensor 101. This control loop can be described as a single-loop control system. Figure 2 A system block diagram of the oxygen concentration control process is shown.

[0052] exist Figure 2 In the diagram, R represents the set oxygen concentration, Y represents the oxygen concentration detected by the oxygen concentration sensor, and G represents the oxygen concentration detected by the sensor. c (s) is the controller, which can be implemented in software. Its function is to provide an adjustment signal based on the oxygen concentration deviation. G0(s) is the controlled object. In the gas path, due to the significant delay in oxygen concentration changes, if the oxygen flow regulator is adjusted solely based on the deviation between the set oxygen concentration and the feedback oxygen concentration, overshooting may occur, potentially leading to instability under the influence of interference factors. Therefore, the design of this system considers the gas path delay in the oxygen concentration adjustment process; that is, the controlled object includes the oxygen flow regulator 105 and the gas path delay. Thus, the transfer function of the controlled object can be expressed as:

[0053] G P (s)=G0(s)*e -τs (1)

[0054] e -τsLet be the transfer function of the delay element. To eliminate interference from the delay element, a model of the gas path delay element can be pre-estimated, and the deviation value of oxygen concentration can be corrected based on this model to avoid potential overshoot or instability problems. One embodiment of this disclosure designs a control algorithm for a digital predictor for the delay element. For example... Figure 3 As shown, G P G(z) and G0(z) are the discretized G(z) and G0(z) respectively. P (s) and G0(s), G HP (z) represents the controlled object G with a delay element. P The estimation model of (z), G H0 (z) is the estimation model of the controlled object G0(z) without delay.

[0055] Two estimation models G HP (z) and G H0 The relationship between (z) can be expressed by the following equation:

[0056] G HP (z)=G HO (z)*z -k (2)

[0057] Where z -k This represents the delay operator, which will use a signal delayed by k sampling periods.

[0058] The estimation model is predetermined based on the structure of each part of the equipment and the gas path structure; X m It is the first feedback loop, which is based on G. H0 (z) Calculation, used to compensate for errors caused by model inaccuracies or disturbances; Y m It is the second feedback loop, which is based on G. HP (z) Calculation: Move the delay element to the outside of the control loop to improve the speed of the adjustment process; U is the control signal sent by the controller to the controlled object. X m and Y m The following equations can be used to calculate:

[0059] x m (z)=G H0 (z)*u(z) (3)

[0060] y m (z)=G HP (z)*u(z) (4)

[0061] Depend on Figure 3 The digital predictor shown indicates that the controller G... c The input for (z) is:

[0062] e2(k)=e1(k)-x m (k)+y m (k)=r(k)-y(k)-x m (k)+y m (k) (5)

[0063] Substituting the results from equations (3) and (4) into equation (5), we obtain E2. Controller G c (z) After receiving E2, a control signal is sent to the oxygen flow regulating device 105 using a control algorithm (e.g., PI control algorithm).

[0064] The above model estimates the controlled object in both cases with and without a delay element, and moves the delay element to the outside of the control loop, making the adjustment process faster and smoother.

[0065] The following is for reference Figure 4 The specific steps of the above control process will be explained. Figure 4 It shows the basis Figure 3 The flowchart shown is for a method 400 of adjusting and controlling oxygen concentration using a digital estimator.

[0066] In step 401, the user sets the necessary parameters such as oxygen concentration and starts ventilation.

[0067] In step 402, the controller calculates the ratio of oxygen flow rate to air flow rate based on the set oxygen concentration value and total ventilation flow rate.

[0068] In step 403, the controller controls the oxygen flow regulating device 105 according to the calculated oxygen flow value (for example, the oxygen flow valve can be adjusted to a specified opening).

[0069] In step 404, the digital predictor calculates the model G based on the controller output and the predicted model G. H0 (z) and G HP (z) Calculate the output signal X respectively m and Y m .

[0070] In step 405, the current oxygen concentration is obtained from the oxygen concentration sensor, and the current oxygen concentration is used as a feedback value to obtain the deviation E1 between it and the set oxygen concentration value. This deviation can be the difference between the two.

[0071] In step 406, according to equation (5) and the calculated E1 and X m and Y m To calculate controller G c The input deviation signal E2 of (z).

[0072] In step 407, based on E2 obtained after considering the delay, controller G... c (z) A control signal is sent to the oxygen flow regulating device 105 to regulate the oxygen concentration. Controller G c (z) Various adjustment algorithms can be used for adjustment, such as the PI (Proportional-Integral) control algorithm mentioned above, or the PD (Proportional-Derivative) control algorithm, PID (Proportional-Integral-Derivative) control algorithm, etc. The PI algorithm is preferred for use in the embodiments of this disclosure mainly because: firstly, it has good control accuracy and can effectively reduce and eliminate errors; secondly, combined with the above scheme, it can improve speed, so that the oxygen concentration can reach the target value more quickly; and thirdly, it has strong anti-interference ability and can avoid the influence of high-frequency noise on the system.

[0073] In step 408, the set oxygen concentration value is compared with the detected current oxygen concentration value. If they match, the current control signal remains unchanged. If they do not match, the process returns to step 404 and repeats steps 404-408 to continue the adjustment.

[0074] Figure 5 A schematic block diagram of an oxygen concentration control system including a digital estimator according to another embodiment of the present disclosure is shown. Figure 5 and Figure 3 The difference lies in the addition of a compensation stage for predictor errors; the rest is the same as... Figure 3 The differences are consistent and will not be elaborated further. Because there may be some error between the mathematical model of the control process and the actual process characteristics, and this error accumulates over time, the error is highly sensitive to changes in process characteristics. To improve this, a compensation stage can be added to the digital predictor to compensate for the error between the actual process and the digital predictor. For example... Figure 5 As shown, the output value Y (i.e., the oxygen concentration detected by the oxygen concentration sensor) is first compared with the model G. HP The output value Y of (z) m Dividing by this yields the proportionality value D0, which passes through a first-order differential element T. d After *s+1, we obtain D1, and D1 is related to model G. H0 The output value X of (z) m The product is multiplied, and the output D2 is used as a feedback value. This value is then compared with the set value R to obtain the deviation E1. Figure 5 As shown in the numerical estimator, E1 can be calculated through the following process:

[0075] D0(k)=y m (k) / y(k) (6)

[0076] D1(k)=D0(k)+T d*[D0(k)-D0(k-1)] / T s T d =τ (7)

[0077] D2(k)=x m (k)*D1(k) (8)

[0078] e1(k)=r(k)-D2(k) (9)

[0079] This compensation mechanism provides feedback signals to correct the errors of the digital predictor, making the control process more accurate and stable.

[0080] Figure 6 It is based on Figure 5 The flowchart illustrates the adjustment and control method of the oxygen concentration control system in the illustrated embodiment. Figure 6 and Figure 4 The main difference in the flowchart shown is the improvement to the E1 calculation steps, namely, the addition of a compensation step for E1 (see step 605). Compared with... Figure 4 The parts of the process that are the same as those in the previous steps will not be repeated. In step 605, the current oxygen concentration Y and signal X are... m and signal Y m Based on the above equations (6)-(8), calculate the values ​​of the predictor's compensation signals D0, D1, and D2 respectively, that is, the output value Y and the signal Y m The ratio D0 is obtained by first-order differentiation, and D1 is the ratio of signal X. m Multiplying them together yields D2, and finally, D2 is compared with the set oxygen concentration value to obtain the deviation E1, where T... s It is the sampling period. After calculating E1, E2 is calculated according to equation (5).

[0081] Figure 7A and Figure 7B The diagram illustrates the oxygen concentration change process curves obtained by a conventional oxygen concentration control system and an oxygen concentration control system according to the above embodiments of this disclosure. From... Figure 7A As can be seen, the oxygen concentration fluctuates considerably during the process of reaching a stable level, while... Figure 7BAs shown, the above embodiments of this disclosure exhibit no significant fluctuations in oxygen concentration during the adjustment process and reach a stable state more quickly, demonstrating good performance in terms of stability, adjustment accuracy, and adjustment speed. In the embodiments of this disclosure, a control system with a predictor is constructed by considering the delay characteristics of oxygen concentration, thereby avoiding problems such as unstable adjustment results, slow adjustment speed, and low accuracy caused by overshoot during the adjustment process. Furthermore, the oxygen concentration sensor in the above embodiments can be an ultrasonic oxygen sensor, which ensures the stability and high accuracy of the monitoring data. It is a non-consumable component, reducing costs and ensuring long-term stable operation of the ventilator.

[0082] The above description is merely an exemplary embodiment of this disclosure and is not intended to limit the scope of protection of this disclosure, which is determined by the appended claims.

Claims

1. A method for controlling oxygen concentration in a ventilator, comprising: Set the oxygen concentration value; Detects the current oxygen concentration in a mixture of air and oxygen; The feedback value is calculated based on the control signal sent to the oxygen flow regulator and the estimated gas path delay. At least the oxygen concentration deviation can be obtained based on the current oxygen concentration value detected and the set oxygen concentration value; The control signal sent to the oxygen flow regulating device is adjusted based on the oxygen concentration deviation and the calculated feedback value. The model for the estimated gas path delay element includes a discretized model of the transfer function of the estimated oxygen flow rate regulating device and a discretized model of the transfer function of the estimated oxygen flow rate regulating device including the gas path delay element. The adjustment of the control signal sent to the oxygen flow rate regulating device based on the oxygen concentration deviation and the calculated feedback value includes calculating the deviation signal. ,in Where k represents the sampling period number, The oxygen concentration deviation is mentioned above. The output of the control signal is the discretized model of the transfer function of the estimated oxygen flow rate regulator. The output of the control signal is the output of a discretized model of the estimated transfer function of the oxygen flow regulating device, which includes a gas path delay element. The oxygen concentration value set herein. The current oxygen concentration value, The determination of the oxygen concentration deviation, at least based on the detected current oxygen concentration value and the set oxygen concentration value, includes calculating the oxygen concentration deviation according to the following equation. : in yes and The ratio, yes The value after first differentiation Is D1 and The product of T s τ represents the sampling period, and τ represents the gas path delay time.

2. The oxygen concentration control method for a ventilator according to claim 1, wherein the calculated feedback value includes the feedback values ​​of calculating the control signal via a discretized model of the estimated transfer function of the oxygen flow regulating device and a discretized model of the estimated transfer function of the oxygen flow regulating device including the airway delay element.

3. The oxygen concentration control method for a ventilator according to claim 1 or 2, wherein the transfer function of the oxygen flow regulating device is... and the transfer function of the oxygen flow regulation device including the gas path delay element. The following relationship exists between them: in This is the transfer function of the gas path delay element.

4. The oxygen concentration control method for a ventilator according to claim 1, further comprising calculating the ratio of oxygen to air flow and the oxygen flow rate value based on the set oxygen concentration value and the total ventilation flow rate, and obtaining the initial control signal of the oxygen flow rate regulating device based on the oxygen flow rate value.

5. The oxygen concentration control method for a ventilator according to claim 1, wherein adjusting the control signal sent to the oxygen flow regulating device based on the oxygen concentration deviation and the calculated feedback value includes adjusting the control signal using any one of PI regulation, PID regulation, and PD regulation.

6. The oxygen concentration control method for a ventilator according to claim 1, wherein an ultrasonic oxygen sensor is used to detect the current oxygen concentration value in the mixed gas.

7. A ventilator that uses the oxygen concentration control method for a ventilator according to any one of claims 1 to 5, the ventilator comprising: An oxygen flow regulator is used to regulate the flow rate of oxygen entering the ventilator. Oxygen flow sensor, used to detect oxygen flow rate; The power unit, located downstream of the oxygen flow regulating device, is used to supply the mixture of air and oxygen. An oxygen concentration sensor, located downstream of the power unit, is used to detect the oxygen concentration in a mixture of air and oxygen. The breathing processing unit calculates a feedback value based on a control signal sent to the oxygen flow regulator and a model of the estimated gas path delay; it obtains an oxygen concentration deviation based at least on the detected current oxygen concentration value and the set oxygen concentration value; and it adjusts the control signal sent to the oxygen flow regulator based on the oxygen concentration deviation and the calculated feedback value.

8. The ventilator according to claim 7, wherein the oxygen concentration sensor is an ultrasonic oxygen sensor.

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