A small-capacity airbag blood pressure detection system and its precise pressure control method

Abstract

The present invention provides a small-capacity airbag blood pressure detection system and a precise pressure control method thereof. A micro air pump is connected to the air inlet of the small-capacity airbag via a pipeline. A linear proportional valve is provided on the air outlet of the small-capacity airbag to control the opening and closing of the air outlet and the flow rate of the air outlet. The micro air pump is normally open and provides a stable flow of input airflow to the small-capacity airbag. The valve opening of the linear proportional valve is changed by executing an adaptive differential constant pressure control algorithm, thereby changing the air outlet speed of the small-capacity airbag. The pressure of the small-capacity airbag is regulated by changing the inflation and deflation speed difference. The present invention can achieve rapid pressure stabilization and almost no pressure overshoot after the pressure is stabilized; achieve a pressure control accuracy of 1 mmHg for any pressure adjustment step; overcome the problem that traditional single-parameter closed-loop control cannot meet the precise control requirements of each pressure range; further reduce production costs, and improve the adaptability and popularity of the equipment in out-of-hospital scenarios.

Description

Technical Field

[0001] The present invention belongs to the technical field of blood pressure detection equipment, and in particular relates to a small-capacity air bag blood pressure detection system and a precise pressure control method thereof. Background Art

[0002] Cardiovascular disease (CVD) is one of the leading causes of death and disability worldwide, with its morbidity and mortality rates continuing to rise, posing a serious threat to public health. In this context, hypertension, a core risk factor for CVD, can significantly improve CVD prevention through blood pressure monitoring. However, blood pressure exhibits significant temporal variability, and its continuous, dynamic changes are closely associated with the occurrence of cardiovascular events. This has led to an increasing emphasis on continuous, dynamic blood pressure monitoring in clinical and public health practice.

[0003] The volume compensation method, as a non-invasive and continuous blood pressure measurement method, is suitable for application scenarios that require high-precision, continuous blood pressure measurement. Its basic principle is to apply pressure through the airbag to adjust the external pressure of the blood vessel so that the blood vessel volume remains at the blood volume corresponding to the stress-free state. At this time, the internal and external pressures of the blood vessel are consistent, and the transmural pressure of the blood vessel is 0. When the blood pressure is relatively stable, the blood pressure usually varies between 2-6 mmHg. This means that in order to maintain the consistency of the internal and external pressures of the blood vessel and continuously obtain blood pressure, an external pressure control system is required to provide a sufficiently small pressure step accuracy to ensure the accuracy of blood pressure measurement when the blood pressure changes are relatively small.

[0004] In addition, the detection part of this method is usually the finger, mainly because the detection of the finger position is more convenient to wear, and the finger part is smaller in size, which helps to reduce the size of the detection probe. And the finger, as the extremity of the limb, can minimize the impact on blood circulation and limb discomfort caused by long-term pressure during continuous testing. The pressurized air pump is usually designed for arm cuffs, and its boost step accuracy is limited. The air capacity of the finger airbag is much smaller than that of the arm cuff. Under the same pressure precision step requirement, the smaller the air capacity of the container, the more difficult it is to achieve. This has also become the core problem to be solved in the pressure control of the volume compensation method.

[0005] The traditional volume compensation pressure control solution uses a large-capacity cylinder as the gas source, and maintains sufficient gas source pressure in the cylinder through an air pump and closed-loop control. It also uses a linear proportional valve with high control accuracy as a control device to control the gas outlet speed of the cylinder by controlling the opening and closing size of the valve, thereby achieving precise pressure stepping of the airbag and overcoming the process pressure control accuracy limitations of conventional diaphragm pumps. However, this solution has high hardware complexity, high cost and large size, which makes it difficult for blood pressure detection equipment based on this method to be widely popularized and unable to meet people's blood pressure monitoring needs in many out-of-hospital scenarios. In response to this, this patent uses the dynamic collaboration and adaptive closed-loop pressure control model of the air pump and linear proportional valve to solve the problems of large hardware size and high cost while still meeting the requirements of precise constant pressure control. Summary of the Invention

[0006] In view of the problems existing in the prior art, the present invention provides the following technical solutions:

[0007] A precision pressure control method for a small-capacity airbag blood pressure detection system comprises the following steps: a micro air pump is connected to the air inlet of the small-capacity airbag via a pipeline; a linear proportional valve is arranged on the air discharge port of the small-capacity airbag to control the on / off state and flow rate of the air discharge port of the small-capacity airbag; the micro air pump is normally opened and provides a stable flow of input airflow to the small-capacity airbag; the valve opening of the linear proportional valve is changed by executing an adaptive differential constant pressure control algorithm, thereby changing the deflation speed of the air discharge port of the small-capacity airbag; and pressure regulation of the small-capacity airbag is achieved by changing the difference between the inflation and deflation speeds.

[0008] Furthermore, the adaptive differential constant voltage control algorithm includes:

[0009] S1. Initialization settings, which include:

[0010] S11. Read the target pressure value P target ;

[0011] S12, according to the target pressure value P target Calculate the adaptive differential coefficient K according to formula 1 d :

[0012] Formula 1

[0013] S13. Set fixed parameters:

[0014] Set the scale factor K p and the integral coefficient K i ;

[0015] Set the initial value of PWM duty cycle u (t- 1)=0;

[0016] Initialize the error history value: e k-1 =0, e k-2 =0;

[0017] Initialize the integral term accumulation value I sum =0;

[0018] Set the PWM limit range: u min =0%, u max =100%;

[0019] Set the control cycle Ts =50ms;

[0020] S2, real-time pressure closed-loop control cycle, sampling period Ts = 50ms, specifically including:

[0021] S21. Obtain the real-time pressure value of the small-capacity airbag measured by the air pressure sensing module P measured ;

[0022] S22. Calculate the current pressure error e according to formula 2. k :

[0023] Formula 2

[0024] S23. Calculate the three PID error parameters: proportional error increment P_error, integral error I_error, and second-order differential error D_error according to the following formula:

[0025] Formula 3

[0026] First run e k-1 , e k-2 is 0;

[0027] S24, execute integral anti-saturation

[0028] like u ( t- 1)≤ u min and e k >0: Freeze points ( I sum constant);

[0029] like u (t- 1)≥ u max and e k <0: freeze points;

[0030] Otherwise: Update I sum = I sum + K i I_error: prevents overshoot caused by accumulation of integral term when valve is saturated;

[0031] S25, calculate the PWM duty cycle increment Δ according to the following formula u ( t ):

[0032] Formula 4

[0033] S26, press the formula to update the PWM duty cycle output u ( t ):

[0034] Formula 5

[0035] And output PWM duty cycle u ( t ) is limited according to formula 6:

[0036] Formula 6;

[0037] S27, will u ( t ) acts on the pump valve drive module to adjust the opening of the linear proportional valve:

[0038] When P measured >P target , increase the opening of the linear proportional valve to accelerate the deflation and reduce the pressure of the small-capacity airbag;

[0039] When P measured <P target , reduce the opening of the linear proportional valve to slow down the deflation and thus increase the pressure of the small-capacity airbag;

[0040] S28. Update the historical status according to the following formula:

[0041] Formula 7;

[0042] S29, wait for the next control cycle T s , return to S21.

[0043] Furthermore, the target pressure valueP target Set by the user on the external interaction module;

[0044] Furthermore, the target pressure value P target The effective setting range is 30-250 mmHg. P target Outside the valid setting range of 30-250 mmHg, the values ​​at the end of the valid setting range are used.

[0045] Furthermore, in S13, the proportional coefficient is set K p and the integral coefficient K i The specific method is: use the empirical trial and error method, follow the order of adjusting parameters from P to I and then D, first set the integral coefficient and differential coefficient to 0, and only adjust the proportional coefficient K p , gradually increase until the system responds quickly but not excessively oscillatory; then introduce the integral coefficient K i To eliminate steady-state errors, and to observe whether the system is oscillating and making appropriate callbacks; finally, to set the proportional coefficient K p =0.05, integral coefficient K i =0.003.

[0046] Furthermore, the adaptive differential coefficient K d Updated only if target pressure changes.

[0047] Furthermore, the volume of the small-capacity airbag is less than or equal to 20 ml.

[0048] Furthermore, during the first run, three pressure samples are required to initialize the e k-1 , e k-2 .

[0049] The small-capacity airbag blood pressure detection system includes a main control module, a pump valve drive module, an air pressure sensing module, and an external interaction module. The main control module is respectively connected to the air pressure sensing module, the external interaction module, and the pump valve drive module. The pump valve drive module is also respectively connected to a micro air pump and a linear proportional valve.

[0050] The external interaction module is used to receive the target pressure set by the external user and transmit it to the main control module;

[0051] The air pressure sensing module collects the real-time pressure of the small-capacity airbag and sends the pressure data to the main control module for processing;

[0052] The main control module is used to execute the control method described above and output a control signal to the pump valve drive module;

[0053] The pump-valve drive module controls the opening, closing and power of the micro air pump, and the opening, closing and valve opening size of the linear proportional valve.

[0054] The present invention has the following beneficial effects and advantages:

[0055] 1. Fast pressure stabilization: In the range of 30-250mmHg, it can achieve a fast pressure stabilization time of no more than 2s, and almost no pressure overshoot occurs after the pressure stabilizes, minimizing the stabilization time of pressure control;

[0056] 2. Precision pressure stepping: Achieve 1mmHg pressure control accuracy in any pressure adjustment step, meeting the blood pressure detection needs when the blood pressure changes slightly;

[0057] 3. Adaptive: Based on the differences in closed-loop control parameters in different pressure ranges, a nonlinear closed-loop parameter model is established to overcome the problem that traditional single-parameter closed-loop control cannot meet the precise control requirements of each pressure range;

[0058] 4. The number of hardware components required has been greatly reduced, enabling such equipment to overcome the miniaturization difficulties brought about by the huge voltage control system, further reducing production costs and improving the equipment's adaptability and popularity in out-of-hospital scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] The drawings that constitute part of the present invention are used to provide further understanding of the present invention. The schematic embodiments of the present invention and their description are used to explain the present invention and do not constitute improper limitations on the present invention. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without making any creative efforts.

[0060] Figure 1 It is a structural block diagram of the control system of the present invention;

[0061] Figure 2 It is the block diagram of closed-loop control path;

[0062] Figure 3 Flowchart of the control method of the present invention. DETAILED DESCRIPTION

[0063] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0064] In the description of the embodiments of the present invention, it should be noted that the indicated orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the product of the application is conventionally placed when in use, or are the orientations or positional relationships conventionally understood by those skilled in the art. These are merely for the convenience of describing the present invention or simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed or operate in a specific orientation. Therefore, they should not be understood as limiting the present invention.

[0065] The term "plurality" used in the present invention refers to two or more (including two). The terms "first" and "second" are used only to distinguish and describe, and should not be understood as indicating or implying relative importance.

[0066] Unless otherwise clearly specified and limited, the terms "setting", "installation" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection through an intermediate medium.

[0067] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0068] like Figure 1 As shown, the small-capacity airbag blood pressure detection system of the present invention includes a main control module, a pump-valve driving module, an air pressure sensing module, and an external interaction module. The main control module is respectively connected to the air pressure sensing module, the external interaction module, and the pump-valve driving module. The pump-valve driving module is also respectively connected to a micro air pump and a linear proportional valve. The micro air pump is connected to the air inlet of the small-capacity airbag via a pipeline. The linear proportional valve is arranged on the air release port of the small-capacity airbag to control the opening and closing and flow rate of the air release port. The small-capacity airbag is also connected to the air pressure sensing module.

[0069] in,

[0070] The external interaction module is used to receive the target pressure set by the external user and transmit it to the main control module as the pressure control target pressure value of the pump-valve collaborative adaptive pressure control algorithm;

[0071] The air pressure sensing module collects the real-time pressure of the small-capacity airbag and sends the pressure data to the main control module for processing;

[0072] The main control module is used to analyze real-time pressure changes, execute the pump-valve coordinated adaptive pressure control algorithm, and output control signals to the pump-valve drive module;

[0073] The pump-valve drive module controls the opening, closing and power of the micro air pump, and the opening, closing and valve opening size of the linear proportional valve.

[0074] Of course, the pump and valve driving module may also be integrated into the main control module, and the control function of the pump and valve driving module is also undertaken by the main control module.

[0075] The core technical route of the control method of the present invention is:

[0076] A micro air pump is constantly running, providing a steady flow of input air to the small-volume airbag. A linear proportional valve on the airbag's deflation port serves as the core pressure control device. By varying the valve opening, the deflation rate is altered. When the airbag's inflation and deflation rates are consistent, dynamic constant pressure is achieved. Conversely, pressure regulation is achieved by varying the speed difference. Essentially, the system dynamically adjusts the air volume inside the airbag, thereby varying the pressure, by leveraging the difference in inflation and deflation rates.

[0077] In the control method of the present invention, the detection of the gas flow rate of charging and discharging is not performed directly. Instead, the three error parameters between the real-time pressure and the target pressure (P_error is the proportional coefficient; I_error is the cumulative coefficient; D_error is the differential coefficient) are calculated. K p 、 K i , K d is the closed-loop control coefficient of each error term), and the PWM drive duty cycle increment Δ is calculated based on the discrete real-time pressure change. u ( t ),like Figure 2 Finally, the PWM drive duty cycle increment Δ u ( t ) and the current PWM drive duty cycle u ( t ) are added together, and then the main control module applies the real-time adjusted PWM control signal to the pump valve drive module, and the closed-loop feedback control of the pressure is realized in a reciprocating cycle.

[0078] Through the dynamic cooperation strategy of pumps and valves and incremental PID, constant pressure control of small-capacity airbags is achieved, solving the pressure control problem caused by process performance such as air pump step accuracy. However, it still has major limitations in pressure stabilization response speed and stabilization time, which is unacceptable for continuous blood pressure detection.

[0079] The adaptive differential constant pressure control algorithm is based on the incremental PID mentioned above, by establishing the differential error coefficient K d In the adaptive model of each pressure range, the problem of pressure control overshoot becoming more severe as the target pressure increases is solved. The differential coefficient is mainly used to suppress overshoot and improve the dynamic stability of the system. By adjusting the differential coefficient K dThe pressure overshoot phenomenon can be eliminated. The differential coefficient is used as the optimal differential coefficient under the current pressure. However, by debugging the optimal differential coefficient under each pressure of 10mmHg step within 30-250mmHg, it is found that the differential coefficient gradually increases with the pressure. At this time, the fixed differential coefficient K d Unable to meet the pressure overshoot suppression requirements at various pressures.

[0080] To overcome this problem, this algorithm proposes an adaptive differential coefficient adjustment strategy. By constructing a nonlinear differential coefficient model based on a cubic polynomial across the entire pressure application range, the algorithm dynamically adjusts the optimal differential coefficient based on changes in the target pressure. This adaptive process effectively improves the control system's rapid response capability.

[0081] In summary, the control method of the present invention further includes:

[0082] S1. Initialization settings, which include:

[0083] S11. Read the target pressure value P target ; The target pressure value P target Set by the user on the external interaction module; unit: mmHg;

[0084] Furthermore, the target pressure value P target The effective setting range is 30-250 mmHg. P target If the valid setting range of 30-250 mmHg is exceeded, the boundary value of the valid setting range (30 or 250) is used;

[0085] S12, according to the target pressure value P target Calculate the adaptive differential coefficient K according to formula 1 d :

[0086] Formula 1

[0087] S13. Set fixed parameters:

[0088] Set the scale factor K p and the integral coefficient K i ; Use the trial and error method and follow the order of "P first, then I, then D". First, set the integral coefficient and differential coefficient to 0, and only adjust the proportional coefficient. K p , and gradually increase until the system responds quickly but not excessively oscillatory. The integral coefficient is then introduced Ki To eliminate the steady-state error, and observe whether the system is oscillating and adjust appropriately. Finally, set the proportional coefficient K p =0.05, integral coefficient K i =0.003;

[0089] Set the initial value of PWM duty cycle u ( t- 1)=0;

[0090] Initialize the error history value: e k-1 =0, e k-2 =0;

[0091] Initialize the integral term accumulation value I sum =0;

[0092] Set the PWM limit range: u min =0%, u max =100%;

[0093] Set the control cycle Ts =50ms;

[0094] Furthermore, the adaptive differential coefficient K d Update only when target pressure changes;

[0095] S2, real-time pressure closed-loop control cycle, sampling period Ts = 50ms, specifically including:

[0096] S21. Obtain the real-time pressure value of the small-capacity airbag measured by the air pressure sensing module P measured ;

[0097] S22. Calculate the current pressure error e according to formula 2. k :

[0098] Formula 2

[0099] S23. Calculate the three PID error parameters: proportional error increment P_error, integral error I_error, and second-order differential error D_error according to the following formula:

[0100] Formula 3

[0101] First run e k-1 , e k-2is 0;

[0102] S24, execute integral anti-saturation

[0103] like u ( t- 1)≤ u min and e k >0: Freeze points ( I sum constant);

[0104] like u ( t- 1)≥ u max and e k <0: freeze points;

[0105] Otherwise: Update I sum = I sum + K i I_error: prevents overshoot caused by accumulation of integral term when valve is saturated;

[0106] S25, calculate the PWM duty cycle increment Δ according to the following formula u ( t ):

[0107] Formula 4

[0108] Here I sum Included K i coefficient;

[0109] S26, press the formula to update the PWM duty cycle output u ( t ):

[0110] Formula 5

[0111] And output PWM duty cycle u ( t ) is limited according to formula 6:

[0112] Formula 6;

[0113] S27, will u ( t ) acts on the pump valve drive module to adjust the opening of the linear proportional valve:

[0114] When P measured >Ptarget , increase the opening of the linear proportional valve to accelerate the deflation and reduce the pressure of the small-capacity airbag;

[0115] When P measured <P target , reduce the opening of the linear proportional valve to slow down the deflation and thus increase the pressure of the small-capacity airbag;

[0116] S28. Update the historical status according to the following formula:

[0117] Formula 7;

[0118] S29, wait for the next control cycle T s , return to S21;

[0119] Furthermore, the volume of the small-capacity airbag is less than or equal to 20 ml.

[0120] Furthermore, the flow rate of the micro air pump pumped into the air inlet of the small-capacity air bag is a constant value; preferably, the constant flow rate is 200 ml / min;

[0121] Furthermore, during the first run, three pressure samples are required to initialize the e k-1 , e k-2 .

[0122] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A precision pressure control method for a small-volume airbag blood pressure detection system, characterized in that: The micro air pump is connected to the air inlet of the small-capacity airbag via a pipeline, and a linear proportional valve is provided on the air release port of the small-capacity airbag to control the opening and closing of the air release port and the flow rate of the small-capacity airbag. The micro air pump is normally turned on to provide a stable flow of input airflow to the small-capacity airbag. The valve opening of the linear proportional valve is changed by executing an adaptive differential constant pressure control algorithm, thereby changing the deflation speed of the air release port of the small-capacity airbag. The pressure of the small-capacity airbag is regulated by changing the difference between the inflation and deflation speeds. The adaptive differential constant voltage control algorithm includes: S1. Initialization settings, which include: S11. Read the target pressure value P target ; S12, according to the target pressure value P target Calculate the adaptive differential coefficient K according to formula 1 d : Formula 1 S13. Set fixed parameters: Set the scale factor K p and the integral coefficient K i ; Set the initial value of PWM duty cycle u ( t- 1)=0; Initialize the error history value: e k-1 =0, e k-2 =0; Initialize the integral term accumulation value I sum =0; Set the PWM limit range: u min =0%, u max =100%; Set the control cycle Ts =50ms; S2, real-time pressure closed-loop control cycle, sampling period Ts = 50ms, specifically including: S21. Obtain the real-time pressure value of the small-capacity airbag measured by the air pressure sensing module P measured ; S22. Calculate the current pressure error e according to formula 2. k : Formula 2 S23. Calculate the three PID error parameters: proportional error increment P_error, integral error I_error, and second-order differential error D_error according to the following formula: Formula 3 First run e k-1 , e k-2 is 0; S24, execute integral anti-saturation like u ( t- 1)≤ u min and e k >0: Freeze points ( I sum constant); like u ( t- 1)≥ u max and e k <0: freeze points; Otherwise: Update I sum = I sum + K i I_error: prevents overshoot caused by accumulation of integral term when valve is saturated; S25, calculate the PWM duty cycle increment Δ according to the following formula u ( t ): Formula 4 S26, press the formula to update the PWM duty cycle output u ( t ): Formula 5 And output PWM duty cycle u ( t ) is limited according to formula 6: Formula 6: S27, will u ( t ) acts on the pump valve drive module to adjust the opening of the linear proportional valve: When P measured >P target , increase the opening of the linear proportional valve to accelerate the deflation and reduce the pressure of the small-capacity airbag; When P measured <P target , reduce the opening of the linear proportional valve to slow down the deflation and thus increase the pressure of the small-capacity airbag; S28. Update the historical status according to the following formula: Formula 7: S29, wait for the next control cycle T s , return to S21; In S13, set the proportional coefficient K p and the integral coefficient K i The specific method is: use the empirical trial and error method, follow the order of adjusting parameters from P to I and then D, first set the integral coefficient and differential coefficient to 0, and only adjust the proportional coefficient K p , gradually increase until the system responds quickly but not excessively oscillatory; then introduce the integral coefficient K i To eliminate steady-state errors, and to observe whether the system is oscillating and making appropriate callbacks; finally, to set the proportional coefficient K p =0.05, integral coefficient K i =0.

003.

2. The precise pressure control method for a small-volume airbag blood pressure detection system according to claim 1, characterized in that: The target pressure value P target Set by the user on the external interaction module.

3. The precise pressure control method for a small-volume airbag blood pressure detection system according to claim 1, characterized in that: The target pressure value P target The effective setting range is 30-250 mmHg. P target Outside the valid setting range of 30-250 mmHg, the values ​​at the end of the valid setting range are used.

4. The precise pressure control method for a small-volume airbag blood pressure detection system according to claim 1, wherein: The adaptive differential coefficient K d Updated only if target pressure changes.

5. The precise pressure control method for a small-volume airbag blood pressure detection system according to claim 1, characterized in that: The volume value of the small-capacity airbag is less than or equal to 20 ml.

6. The precise pressure control method for a small-volume airbag blood pressure detection system according to claim 1, characterized in that: During the first run, three pressure samples are required for initialization. e k-1 , e k-2 .

7. Small-capacity airbag blood pressure detection system, characterized by: It includes a main control module, a pump valve drive module, an air pressure sensor module, and an external interaction module. The main control module is connected to the air pressure sensor module, the external interaction module, and the pump valve drive module respectively. The pump valve drive module is also connected to a micro air pump and a linear proportional valve respectively. The external interaction module is used to receive the target pressure set by the external user and transmit it to the main control module; The air pressure sensing module collects the real-time pressure of the small-capacity airbag and sends the pressure data to the main control module for processing; The main control module is used to execute the control method according to claim 1 and output a control signal to the pump valve drive module; The pump-valve drive module controls the opening, closing and power of the micro air pump, and the opening, closing and valve opening size of the linear proportional valve.

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