CN116603142A - Oxygen concentration control method for breathing machine and breathing machine - Google Patents
Oxygen concentration control method for breathing machine and breathing machine Download PDFInfo
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- CN116603142A CN116603142A CN202310593811.6A CN202310593811A CN116603142A CN 116603142 A CN116603142 A CN 116603142A CN 202310593811 A CN202310593811 A CN 202310593811A CN 116603142 A CN116603142 A CN 116603142A
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- 239000001301 oxygen Substances 0.000 title claims abstract description 267
- 229910052760 oxygen Inorganic materials 0.000 title claims abstract description 267
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 title claims abstract description 266
- 238000000034 method Methods 0.000 title claims abstract description 44
- 230000029058 respiratory gaseous exchange Effects 0.000 title description 11
- 230000001105 regulatory effect Effects 0.000 claims abstract description 46
- 239000007789 gas Substances 0.000 claims abstract description 43
- 238000012546 transfer Methods 0.000 claims description 20
- 238000012545 processing Methods 0.000 claims description 8
- 230000000241 respiratory effect Effects 0.000 claims description 8
- 238000009423 ventilation Methods 0.000 claims description 6
- 230000004069 differentiation Effects 0.000 claims description 3
- 238000005070 sampling Methods 0.000 claims description 3
- 230000008859 change Effects 0.000 abstract description 5
- 230000008569 process Effects 0.000 description 18
- 230000033228 biological regulation Effects 0.000 description 8
- 238000010586 diagram Methods 0.000 description 7
- 238000012544 monitoring process Methods 0.000 description 7
- 238000004364 calculation method Methods 0.000 description 3
- 230000001276 controlling effect Effects 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 230000007774 longterm Effects 0.000 description 2
- 210000004072 lung Anatomy 0.000 description 2
- 230000005298 paramagnetic effect Effects 0.000 description 2
- 206010021143 Hypoxia Diseases 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 239000008280 blood Substances 0.000 description 1
- 210000004369 blood Anatomy 0.000 description 1
- 238000011088 calibration curve Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000007954 hypoxia Effects 0.000 description 1
- 238000013178 mathematical model Methods 0.000 description 1
- 230000004060 metabolic process Effects 0.000 description 1
- 238000006213 oxygenation reaction Methods 0.000 description 1
- 231100000572 poisoning Toxicity 0.000 description 1
- 230000000607 poisoning effect Effects 0.000 description 1
- 208000023504 respiratory system disease Diseases 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 238000011144 upstream manufacturing Methods 0.000 description 1
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
- A61M16/0003—Accessories therefor, e.g. sensors, vibrators, negative pressure
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
- A61M16/021—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes operated by electrical means
- A61M16/022—Control means therefor
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
- A61M16/021—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes operated by electrical means
- A61M16/022—Control means therefor
- A61M16/024—Control means therefor including calculation means, e.g. using a processor
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
- A61M16/10—Preparation of respiratory gases or vapours
- A61M16/1005—Preparation of respiratory gases or vapours with O2 features or with parameter measurement
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
- A61M16/10—Preparation of respiratory gases or vapours
- A61M16/12—Preparation of respiratory gases or vapours by mixing different gases
- A61M16/122—Preparation of respiratory gases or vapours by mixing different gases with dilution
- A61M16/125—Diluting primary gas with ambient air
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
- A61M16/20—Valves specially adapted to medical respiratory devices
- A61M16/201—Controlled valves
- A61M16/202—Controlled valves electrically actuated
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
- A61M16/0003—Accessories therefor, e.g. sensors, vibrators, negative pressure
- A61M2016/0027—Accessories therefor, e.g. sensors, vibrators, negative pressure pressure meter
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
- A61M16/0003—Accessories therefor, e.g. sensors, vibrators, negative pressure
- A61M2016/003—Accessories therefor, e.g. sensors, vibrators, negative pressure with a flowmeter
- A61M2016/0033—Accessories therefor, e.g. sensors, vibrators, negative pressure with a flowmeter electrical
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- A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
- A61M16/10—Preparation of respiratory gases or vapours
- A61M16/1005—Preparation of respiratory gases or vapours with O2 features or with parameter measurement
- A61M2016/102—Measuring a parameter of the content of the delivered gas
- A61M2016/1025—Measuring a parameter of the content of the delivered gas the O2 concentration
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- A—HUMAN NECESSITIES
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- A61M2205/00—General characteristics of the apparatus
- A61M2205/33—Controlling, regulating or measuring
- A61M2205/3375—Acoustical, e.g. ultrasonic, measuring means
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]
- Y02B30/70—Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating
Abstract
Embodiments of the present disclosure provide an oxygen concentration control method for a ventilator and a ventilator. An oxygen concentration control method for a ventilator includes setting an oxygen concentration value; detecting a current oxygen concentration value in a mixed gas of air and oxygen; calculating a feedback value based on a control signal sent to the oxygen flow regulating device and a model of an estimated gas path delay link; obtaining an oxygen concentration deviation at least according to the detected current oxygen concentration value and the set oxygen concentration value; and adjusting a control signal sent to the oxygen flow adjusting device according to the oxygen concentration deviation and the calculated feedback value. According to the embodiment of the disclosure, the delay characteristic of oxygen concentration change in the gas path is considered, a control algorithm aiming at a delay link is set to eliminate interference of the delay characteristic on oxygen concentration adjustment as much as possible, and the rapidity and stability of oxygen concentration adjustment and the accuracy of oxygen concentration control are improved.
Description
Technical Field
The disclosure relates to the technical field of respirators, in particular to an oxygen concentration control method of a respirator and the respirator using the method.
Background
The oxygen concentration of the breathing machine can be controlled by adopting a calibration curve to look up a table, so that the voltage of the oxygen flow valve can be obtained for adjustment, and the PID can be used for controlling the oxygen flow valve for adjustment. However, because the change of the oxygen concentration has a certain delay characteristic due to the air path factor, a stable value can be reached only after a period of time, so that the oxygen concentration is easy to control to fluctuate in the adjusting process, and the problems of long time required for adjusting to a stable state, limited control precision and the like exist.
In addition, current ventilators typically employ oxygen cell sensors or paramagnetic oxygen sensors for oxygen concentration monitoring and control. The oxygen battery sensor is a consumable equipment element, the accuracy of monitoring the oxygen concentration can be obviously reduced along with the consumption of the battery, the oxygen battery sensor needs to be replaced regularly, and in the adjustment process, the condition that the oxygen concentration is unstable and the accuracy is inaccurate easily occurs due to slower data monitoring reaction. Paramagnetic oxygen sensors are susceptible to vibration, position, etc., causing increased failure rates, and this type of sensor is expensive and costly to produce and maintain.
For the above reasons, there is therefore a need for an oxygen concentration control method that can reduce fluctuations in the oxygen concentration control process so that the control of the oxygen concentration is more stable and faster, on the one hand, and on the other hand, find a sensor for oxygen concentration monitoring of a ventilator that is lower in cost and longer in service life.
Disclosure of Invention
The present disclosure provides an oxygen concentration control method for a ventilator and a ventilator using the same, which solve one or more of the above-mentioned technical problems.
To solve at least one of the above technical problems, an embodiment according to a first aspect of the present disclosure provides an oxygen concentration control method for a ventilator, including setting an oxygen concentration value; detecting a current oxygen concentration value in a mixed gas of air and oxygen; calculating a feedback value based on a control signal sent to the oxygen flow regulating device and a model of an estimated gas path delay link; obtaining an oxygen concentration deviation at least according to the detected current oxygen concentration value and the set oxygen concentration value; and adjusting a control signal sent to the oxygen flow adjusting device according to the oxygen concentration deviation and the calculated feedback value.
According to the embodiment of the disclosure, the delay characteristic of oxygen concentration change in the gas path is considered, the control algorithm aiming at the delay link is set to eliminate the interference of the delay characteristic on the oxygen concentration adjustment as much as possible, and the rapidity, the stability and the accuracy of the oxygen concentration adjustment are improved.
Optionally, according to an embodiment of the first aspect of the disclosure, the model of the estimated gas path delay element includes a discretization model of the transfer function of the estimated oxygen flow regulating device and a discretization model of the transfer function of the estimated oxygen flow regulating device including the gas path delay element, and the calculating the feedback value includes calculating the feedback value of the control signal via the discretization model of the transfer function of the estimated oxygen flow regulating device and the discretization model of the transfer function of the estimated oxygen flow regulating device including the gas path delay element, respectively.
The above-mentioned embodiment of the present disclosure uses two feedback loops, and the feedback loop of the estimation model including the gas path delay link can implement moving the delay link to the outside of the control loop, so that the rapidity of the adjustment process is improved, and the feedback loop of the estimation model not including the gas path delay link can compensate errors caused by inaccurate model or occurrence of other disturbances.
Optionally, according to an embodiment of the first aspect of the 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:
Gp(s)＝Go(s)*e -τs
wherein e -τs Is a transfer function of the gas path delay link.
Optionally, according to an embodiment of the first aspect of the disclosure, adjusting the control signal sent to the oxygen flow regulating device according to the oxygen concentration deviation and the calculated feedback value includes calculating a deviation signal e 2 (k) Wherein
e 2 (k)＝e 1 (k)-x m (k)+y m (k)＝r(k)-y(k)-x m (k)+y m (k)
Wherein e 1 (k) In order to provide the deviation of the oxygen concentration,x m (k) Y, the output of the discretization model of the control signal through the transfer function of the estimated oxygen flow regulating device m (k) And r (k) is the set oxygen concentration value, and y (k) is the current oxygen concentration value, wherein the control signal is output through the pre-estimated discretization model of the transfer function of the oxygen flow regulating device comprising the gas path delay link.
Optionally, according to an embodiment of the first aspect of the disclosure, the obtaining the oxygen concentration deviation at least according to the detected current oxygen concentration value and the set oxygen concentration value includes calculating a difference between the current oxygen concentration value and the set oxygen concentration value as the oxygen concentration deviation e 1 (k)。
Optionally, according to an embodiment of the first aspect of the disclosure, the deriving the oxygen concentration deviation at least from the detected current oxygen concentration value and the set oxygen concentration value includes calculating the oxygen concentration deviation e according to the following equation 1 (k)：
D 0 (k)＝y m (k)/y(k)
D 1 (k)＝D 0 (k)+T d *[D 0 (k)-D 0 (k-1)]/T s ，T d ＝τ
D 2 (k)＝x m (k)*D 1 (k)
e 1 (k)＝r(k)-D 2 (k)
Wherein D is 0 (k) Is y m (k) Ratio to y (k), D 1 (k) Is D 0 (k) The value calculated after first-order differentiation, D 2 (k) Is D 1 (k) And x m (k) Product of T s Is the sampling period.
Optionally, according to an embodiment of the first aspect of the disclosure, the oxygen concentration control method for a ventilator further includes calculating a ratio of oxygen to air flow and an oxygen flow value according to the set oxygen concentration value and ventilation total flow, and obtaining an initial control signal of the oxygen flow regulating device according to the oxygen flow value.
Optionally, according to an embodiment of the first aspect of the present 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 so, the current control signal is maintained unchanged.
Optionally, according to an embodiment of the first aspect of the disclosure, adjusting the control signal sent to the oxygen flow regulating device according to the oxygen concentration deviation and the calculated feedback value includes adjusting the control signal using any one of PI adjustment, PID adjustment, and PD adjustment.
Alternatively, in accordance with an embodiment of the first aspect of the present disclosure, an ultrasonic oxygen sensor is used to detect a current oxygen concentration value in the mixed gas.
The embodiment of the disclosure can select an ultrasonic oxygen sensor which is a non-consumable element, so that the stability and high precision of monitoring data can be ensured, the cost can be reduced, and the long-term stable operation of the breathing machine can be ensured.
According to a second aspect of the present disclosure, embodiments of the present disclosure provide a ventilator that may use the above-described oxygen concentration control method for a ventilator, the ventilator including an oxygen flow regulating device for regulating a flow of oxygen into the ventilator; an oxygen flow sensor for detecting an oxygen flow; the power device is positioned at the downstream of the oxygen flow regulating device and is used for introducing mixed gas of air and oxygen; an oxygen concentration sensor, which is positioned at the downstream of the power device and is used for detecting the oxygen concentration value in the mixed gas of air and oxygen; the respiratory processing unit is used for calculating a feedback value based on a control signal sent to the oxygen flow regulating device and a model of an estimated gas path delay link; obtaining an oxygen concentration deviation at least according to the detected current oxygen concentration value and the set oxygen concentration value; and adjusting a control signal sent to the oxygen flow regulating device according to the oxygen concentration deviation and the calculated feedback value.
Optionally, according to an embodiment of the second aspect of the disclosure, the oxygen concentration sensor is an ultrasonic oxygen sensor.
The ventilator of the above embodiment of the present disclosure can achieve rapid, accurate, stable oxygen concentration control during operation.
Not all of the advantages described above need be achieved at the same time in practicing any one of the devices of the present disclosure. Additional features and advantages of the disclosure will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the disclosure. The objects and advantages of the disclosed embodiments may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings of the embodiments will be briefly described below, and it is apparent that the drawings in the following description relate only to some embodiments of the present disclosure, not to limit the present disclosure.
FIG. 1 is a general block diagram of a system for ventilator regulation of oxygen concentration in accordance with one embodiment of the present disclosure;
FIG. 2 is a schematic block diagram of an oxygen concentration control system according to one embodiment of the present disclosure;
FIG. 3 is a schematic block diagram of an oxygen concentration control system including a digital predictor according to an embodiment of the present disclosure;
FIG. 4 is a flow chart of an oxygen concentration regulation and control method according to one embodiment of the present disclosure;
FIG. 5 is a schematic block diagram of an oxygen concentration control system including a digital predictor according to another embodiment of the present disclosure;
FIG. 6 is a flow chart of an oxygen concentration regulation and control method according to another embodiment of the present disclosure;
fig. 7A and 7B are respectively example curves of oxygen concentration variation processes obtained using an existing oxygen concentration control system and an oxygen concentration control system according to the above-described embodiment of the present disclosure.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present disclosure more apparent, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present disclosure. It will be apparent that the described embodiments are some, but not all, of the embodiments of the present disclosure. Various embodiments may be combined with one another to form further embodiments not shown in the following description. All other embodiments, which can be made by one of ordinary skill in the art without the need for inventive faculty, are within the scope of the present disclosure, based on the described embodiments of the present disclosure.
Unless defined otherwise, technical or scientific terms used herein should be given the ordinary meaning as understood by one of ordinary skill in the art to which this disclosure belongs. The terms "first," "second," and the like in the description and in the claims, do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. Likewise, the terms "a" or "an" and the like do not necessarily denote a limitation of quantity. The word "comprising" or "comprises", and the like, means that elements or items preceding the word are included in the element or item listed after the word and equivalents thereof, but does not exclude other elements or items. The terms "connected" or "connected," and the like, are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", etc. are used merely to indicate relative positional relationships, which may also be changed when the absolute position of the object to be described is changed.
The monitoring and regulation of the oxygen concentration of the breathing machine are important components of the function of the breathing machine, and the main functions of the breathing machine are that the breathing machine corrects the problem of insufficient oxygen required in the metabolism of the body of the patient in the process of providing support ventilation for the patient, improves the oxygen partial pressure in arterial blood of the human body, treats respiratory diseases which cause the hypoxia of the body due to various reasons and improves the oxygenation of the patient.
Fig. 1 illustrates a general block diagram of a system 100 for ventilator regulation of oxygen concentration in accordance with one embodiment of the present disclosure. The system 100 includes an oxygen concentration sensor 101, a total flow sensor 102, a power plant 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 exhalation valve 106 and a proximal respiratory flow and/or pressure sensor 107.
The oxygen concentration sensor 101 may be located downstream of the mixed gas circuit for detecting the oxygen concentration of the mixed gas, and may be located near the outlet of the ventilator, that is, detecting the oxygen concentration of the mixed gas near the inhalation end of the patient, and feeding back the detected value to the control system, so as to ensure that the patient is supplied with oxygen in accordance with the preset oxygen concentration, and avoid oxygen poisoning caused by long-time high-concentration oxygen inhalation or life hazard caused by too low oxygen concentration. The oxygen concentration sensor 101 can adopt an ultrasonic oxygen sensor, has long service life and low cost, and is not easy to damage and fail due to interference factors. The oxygen concentration sensor 101 may be implemented using other suitable oxygen sensors.
The total flow sensor 102 is configured to detect a total flow of the mixed gas, and is disposed downstream of the mixed gas path, and may be located upstream of the oxygen concentration sensor 101. The total flow sensor 102 may send the detection to the respiratory processing unit. The respiratory processing unit ensures the stabilization of the ventilation total flow and obtains the flow value of oxygen according to the set oxygen concentration value.
The power unit 103 serves as the primary power source for the ventilator and is located downstream of the air and oxygen inlets. The power plant may employ a turbo fan and/or a flow valve. The air inlet and the oxygen inlet may be configured to provide air-oxygen mixing at the front end of the power plant inlet. After the ventilator is started to ventilate, in the inspiration phase, the power device 103 is powered up to a certain rotation speed, the oxygen flow regulating device 105 is simultaneously powered up to control the oxygen flow, and the oxygen flow sensor 104 is arranged downstream of the oxygen flow regulating device 105 to detect the oxygen flow. The oxygen and air are mixed according to the ratio calculated by the set oxygen concentration, and then are conveyed to the air path at the rear end by the power device 103, and finally enter the lung. Upon exhalation, the power unit 103 rotates at a reduced speed, and the exhalation valve 106 opens to expel the gas from the lungs. The oxygen flow regulating means 105 may be realized by an oxygen flow valve.
The functionality of the respiratory processing unit may be implemented in whole or in part by program software, for example by embedded system software in a Microcontroller (MCU), which may send control signals to the relevant components or may obtain the required data from the relevant components.
The positions of the total flow sensor, the oxygen concentration sensor and the oxygen flow sensor can be adjusted as required.
A proximal respiratory flow and/or pressure sensor 107 may be used to measure the flow and/or pressure of the gas inhaled and exhaled by the patient, which may be located downstream of the oxygen concentration sensor, near the patient's side.
In addition to the system 100 for regulating oxygen concentration described above, the ventilator may include tubing, a gas source, a humidifier, etc., and may include more or fewer components than shown, or may be combined with or separated from certain components, or may be constructed in a different arrangement of components. The ventilator may include one or more processing units, which may be stand-alone devices, or may be integrated into one or more processors, which may include, but are not limited to, one or more of a Microcontroller (MCU), a Central Processing Unit (CPU), a Digital Signal Processor (DSP), a Field Programmable Gate Array (FPGA).
In the oxygen concentration control system of the ventilator, main components for adjusting the oxygen concentration include an oxygen flow rate adjustment device 105, an oxygen flow rate sensor 104, and an oxygen concentration sensor 101. The control link may be described in terms of a single-loop control system, and fig. 2 shows a system block diagram of the oxygen concentration control link.
In FIG. 2, R is the set oxygen concentration, Y is the oxygen concentration detected by the oxygen concentration sensor, G c (s) is a controller which can be realized by using software and is used for giving a regulating signal according to the oxygen concentration deviation value, G 0 And(s) is a controlled object. In the gas circuit, because the change of the oxygen concentration has obvious delay links, if the oxygen flow regulating device is regulated according to the deviation of the set oxygen concentration and the feedback oxygen concentration, the condition that the oxygen concentration is overshot can be caused, and the unstable phenomenon can occur under the influence of interference factors. Therefore, the design of the system considers the delay link of the gas path in the oxygen concentration adjusting process, namely, the controlled object comprises the oxygen flow adjusting device 105 and the delay link of the gas path. Thereby, the transmission of the controlled objectThe transfer function can be expressed as:
G P (s)＝G 0 (s)*e -τs (1)
e -τs is the transfer function of the delay element. In order to eliminate the interference of the delay link, a model of the gas path delay link can be estimated in advance, and the deviation value of the oxygen concentration can be corrected according to the model so as to avoid the possible problems of overshoot or instability. One embodiment of the present disclosure designs a control algorithm for a digital predictor for a delay element. As shown in FIG. 3, G P (z) and G 0 (z) discretized G respectively P (s) and G 0 (s)，G HP (z) is a controlled object G with delay links P (z) estimation model, G H0 (z) is the controlled object G without delay links 0 An estimation model of (z).
Two estimation models G HP (z) and G H0 The relationship between (z) can be expressed by the following equation:
G HP (z)＝G HO (z)*z -k (2)
wherein z is -k Representing a delay operator that will take the signal k sample periods later.
The estimation model is predetermined according to the structures of all parts of the equipment, the gas path structure and the like; x is X m Is a first feedback loop according to G H0 (z) a calculation to compensate for errors due to model inaccuracies or disturbances; y is Y m Is a second feedback loop according to G HP (z) calculating to move the delay element outside the control loop to improve the rapidity of the adjustment process; u is a control signal sent by the controller to the controlled object. X is X m And Y m Can be calculated according to the following equations, respectively:
x m (z)＝G H0 (z)*u(z) (3)
y m (z)＝G HP (z)*u(z) (4)
as is available from the digital predictor shown in fig. 3, controller G c The inputs for (z) are:
e 2 (k)＝e 1 (k)-x m (k)+y m (k)＝r(k)-y(k)-x m (k)+y m (k) (5)
bringing the results of the calculations of equations (3), (4) into equation (5), calculating to obtain E 2 . Controller G c (z) upon receipt of E 2 Thereafter, a control algorithm (e.g., PI control algorithm) is used to send a control signal to the oxygen flow control device 105.
The model estimates the controlled object under the two conditions of the delay link and the non-delay link, and moves the delay link to the outside of the control loop, so that the adjusting process can be faster and smoother.
The specific steps of the above-described control process are explained below with reference to fig. 4. FIG. 4 illustrates a flow chart of a method 400 for oxygen concentration adjustment and control based on the digital predictor shown in FIG. 3.
In step 401, the user sets necessary parameters such as an oxygen concentration value and starts ventilation.
In step 402, the controller calculates a proportional relationship between oxygen flow and air flow from the set oxygen concentration value and the total ventilation flow.
In step 403, the controller controls the oxygen flow regulating device 105 (e.g., the oxygen flow valve may be adjusted to a specified opening) based on the calculated oxygen flow value.
In step 404, a model G is estimated by a digital estimator based on the output of the controller and the estimated model G H0 (z) and G HP (z) calculating the output signals X respectively m And Y m 。
In step 405, the current oxygen concentration is obtained from the oxygen concentration sensor, and the deviation E between the current oxygen concentration and the set oxygen concentration value is obtained using the current oxygen concentration as a feedback value 1 The deviation may be the difference between the two.
In step 406, E is calculated according to equation (5) 1 、X m And Y m To calculate the controller G c Input deviation signal E of (z) 2 。
In step 407, based on E obtained by taking into account the delay element 2 Controller G c (z) toward the oxygen flow control device 105And outputting a control signal to adjust the oxygen concentration. Controller G c (z) may be adjusted using various adjustment algorithms, such as the PI (proportional integral) control algorithm described above, or PD (proportional derivative) control algorithm, PID (proportional integral derivative) control algorithm, or the like. The PI algorithm can be used as a preferable scheme for the embodiment of the disclosure, and mainly because the control accuracy is relatively good, and errors can be effectively reduced and eliminated; secondly, the rapidity can be improved by combining the scheme, so that the oxygen concentration reaches the target value faster; thirdly, the anti-interference capability is strong, and the influence of high-frequency noise on a system can be avoided.
In step 408, the set oxygen concentration value is compared with the detected current oxygen concentration value, if the set oxygen concentration value and the detected current oxygen concentration value are consistent, the current control signal is kept unchanged, if the set oxygen concentration value and the detected current oxygen concentration value are inconsistent, the process returns to step 404, steps 404-408 are repeatedly executed, and adjustment is continued.
FIG. 5 shows a schematic block diagram of an oxygen concentration control system including a digital predictor according to another embodiment of the present disclosure. The difference between fig. 5 and fig. 3 is that a compensation link for the predictor error is added, and the rest is identical to fig. 3, so that a detailed description is omitted. Since there may be some error in the mathematical model of the control process and the actual process characteristics and the error may accumulate over time, the sensitivity of the error to process characteristic changes is high. In order to improve the problem, a compensation link can be added on the basis of the digital predictor so as to compensate errors generated between the actual process and the digital predictor. As shown in FIG. 5, the output value Y (i.e., the oxygen concentration detected by the oxygen concentration sensor) is first compared with the model G HP Output value Y of (z) m Dividing to obtain a ratio D 0 It passes through a first-order differential link T d * S+1 to give D 1 ，D 1 And model G H0 Output value X of (z) m Multiplication, output result D 2 Comparing the feedback value with a set value R to obtain a deviation E 1 . As available from the digital predictor shown in FIG. 5, E 1 The calculation can be performed by the following procedure:
D 0 (k)＝y m (k)/y(k) (6)
D 1 (k)＝D 0 (k)+T d *[D 0 (k)-D 0 (k-1)]/T s ，T d ＝τ (7)
D 2 (k)＝x m (k)*D 1 (k) (8)
e 1 (k)＝r(k)-D 2 (k) (9)
through the compensation link, a feedback signal for correcting errors of the digital predictor is provided, so that the control process is more accurate and stable.
FIG. 6 is a flow chart of a method of regulating and controlling the oxygen concentration control system according to the embodiment shown in FIG. 5. The main difference between the flowcharts shown in FIG. 6 and FIG. 4 is the point of the flowchart shown in FIG. E 1 The computational steps are improved, i.e. the pair E is increased 1 Is used (see step 605). The same parts as the flow in fig. 4 will not be described again. In step 605, the current oxygen concentration Y, signal X m Sum signal Y m Calculating the compensation signal D of the predictor based on the above equations (6) - (8), respectively 0 、D 1 、D 2 I.e. output value Y and signal Y m Ratio D of (2) 0 Obtaining D after first-order differentiation 1 ，D 1 And signal X m Multiplying to obtain D 2 Finally D is provided 2 Comparing with the set oxygen concentration value to obtain deviation E 1 Wherein T is s Is the sampling period. E is calculated to obtain 1 Then calculate E according to equation (5) 2 。
Fig. 7A and 7B show graphs of oxygen concentration change processes obtained by the existing oxygen concentration control system and the oxygen concentration control system according to the above-described embodiment of the present disclosure. As can be seen from fig. 7A, the oxygen concentration fluctuates up and down with a relatively large amplitude during the adjustment to be smooth, whereas the above-described embodiment of the present disclosure has no significant fluctuation in the oxygen concentration during the adjustment, and reaches a steady state at a faster speed, showing a relatively good effect in stability, adjustment accuracy, and adjustment speed, as shown in fig. 7B. In the embodiment of the disclosure, the control system with the predictor is constructed by considering the delay characteristic of the oxygen concentration, so that the problems of unstable regulation result, low regulation speed and low accuracy caused by overshoot and the like in the regulation process are avoided. In addition, the oxygen concentration sensor of the embodiment can adopt an ultrasonic oxygen sensor, ensures the stability and high precision of monitoring data, belongs to a non-vulnerable original, can reduce cost and ensures long-term stable operation of the breathing machine.
The foregoing is merely exemplary embodiments of the present disclosure and is not intended to limit the scope of the disclosure, which is defined by the appended claims.
Claims (10)
1. An oxygen concentration control method for a ventilator, comprising:
setting an oxygen concentration value;
detecting a current oxygen concentration value in a mixed gas of air and oxygen;
calculating a feedback value based on a control signal sent to the oxygen flow regulating device and a model of an estimated gas path delay link;
obtaining an oxygen concentration deviation at least according to the detected current oxygen concentration value and the set oxygen concentration value;
and adjusting a control signal sent to the oxygen flow regulating device according to the oxygen concentration deviation and the calculated feedback value.
2. The oxygen concentration control method for a ventilator of claim 1, wherein the model of the estimated gas circuit delay element comprises 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 circuit delay element, and the calculating the feedback values comprises calculating feedback values 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 circuit delay element, respectively.
3. The oxygen concentration control method for a ventilator according to claim 1 or 2, wherein 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 section have the following relationship:
Gp(s)＝Go(s)*e -τs
wherein e -τs Is a transfer function of the gas path delay link.
4. The oxygen concentration control method for a ventilator according to claim 2, wherein the adjusting the control signal sent to the oxygen flow regulating device according to the oxygen concentration deviation and the calculated feedback value includes calculating a deviation signal e 2 (k) Wherein
e 2 (k)＝e 1 (k)-x m (k)+y m (k)＝r(k)-y(k)-x m (k)+y m (k)
Wherein e 1 (k) For the oxygen concentration deviation, x m (k) Y, the output of the discretization model of the control signal through the transfer function of the estimated oxygen flow regulating device m (k) And r (k) is the set oxygen concentration value, and y (k) is the current oxygen concentration value, wherein the control signal is output through the pre-estimated discretization model of the transfer function of the oxygen flow regulating device comprising the gas path delay link.
5. The oxygen concentration control method for a ventilator according to claim 4, wherein the deriving the oxygen concentration deviation from at least the detected current oxygen concentration value and the set oxygen concentration value includes calculating the oxygen concentration deviation e according to the following equation 1 (k):
D 0 (k)＝y m (k)/y(k)
D 1 (k)＝D 0 (k)+T d *[D 0 (k)-D 0 (k-1)]/T s ，T d ＝τ
D 2 (k)＝x m (k)*D 1 (k)
e 1 (k)＝r(k)-D 2 (k)
Wherein D is 0 (k) Is y m (k) And y is(k) Ratio of D 1 (k) Is D 0 (k) Value after first-order differentiation, D 2 (k) Is D1 and x m (k) Product of T s Is the sampling period.
6. The oxygen concentration control method for a ventilator according to claim 1, further comprising calculating a ratio of oxygen to air flow and an oxygen flow value from the set oxygen concentration value and ventilation total flow, and obtaining an initial control signal of the oxygen flow regulating device from the oxygen flow value.
7. The oxygen concentration control method for a ventilator of claim 4, wherein adjusting the control signal sent to the oxygen flow regulating device according to the oxygen concentration deviation and the calculated feedback value includes adjusting the control signal using any one of PI adjustment, PID adjustment, and PD adjustment.
8. The oxygen concentration control method for a ventilator according to claim 1, wherein the current oxygen concentration value in the mixed gas is detected using an ultrasonic oxygen sensor.
9. A ventilator using the oxygen concentration control method for a ventilator according to any one of claims 1 to 7, the ventilator comprising
An oxygen flow regulating device for regulating the flow of oxygen into the ventilator;
an oxygen flow sensor for detecting an oxygen flow;
the power device is positioned at the downstream of the oxygen flow regulating device and is used for introducing mixed gas of air and oxygen;
an oxygen concentration sensor, which is positioned at the downstream of the power device and is used for detecting the oxygen concentration value in the mixed gas of air and oxygen;
the respiratory processing unit is used for calculating a feedback value based on a control signal sent to the oxygen flow regulating device and a model of an estimated gas path delay link; obtaining an oxygen concentration deviation at least according to the detected current oxygen concentration value and the set oxygen concentration value; and adjusting a control signal sent to the oxygen flow regulating device according to the oxygen concentration deviation and the calculated feedback value.
10. The ventilator of claim 9, wherein the oxygen concentration sensor is an ultrasonic oxygen sensor.
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