CN107536605B - PWM circuit duty ratio adjusting method, controller and blood pressure measuring device - Google Patents

Abstract

The present application provides a PWM circuit duty cycle adjustment method, controller and blood pressure measurement device. The method for adjusting the duty cycle of a PWM circuit provided by the present application includes: when the blood pressure measuring device is working, acquiring the air pressure in the cuff and the driving voltage of the air pump in real time; when the air pressure in the cuff exceeds a first preset value for the first time, calculating The first coefficient in the functional relationship between driving energy and air pressure; after the air pressure in the cuff exceeds the first preset value, based on the calculated first coefficient, according to the current air pressure and the difference between the driving energy and air pressure Determine the driving energy at the current moment according to the functional relationship of . The method for adjusting the duty cycle of the PWM circuit, the controller and the blood pressure measuring device provided by the present application can adapt to a wider driving voltage.

Description

A PWM circuit duty cycle adjustment method, controller and blood pressure measurement device

technical field

The present application relates to the field of electronic technology, and in particular, to a PWM circuit duty cycle adjustment method, a controller and a blood pressure measurement device.

Background technique

When the blood pressure measuring device is working, when the air pressure in the cuff of the blood pressure measuring device is greater than the normal blood pressure (20 mmHg) of the human body, in order to improve the accuracy of the measurement results, it is usually necessary to keep the increasing speed of the air pressure in the cuff constant. In order to achieve constant-speed pressurization, the control of the air pump is particularly important. The drive circuit of the air pump generally adopts a pulse width modulation (Pulse Width Modulation, referred to as PWM) circuit. Rapid pressurization.

The existing PWM circuit duty cycle adjustment method includes the following steps: in the blood pressure measurement process, obtain the real-time air pressure in the cuff; Duty ratio, wherein, the above duty ratio and air pressure relationship model represents the functional relationship between the duty ratio and the air pressure when the air pressure in the cuff is rising at a constant speed; the duty ratio of the PWM circuit is adjusted according to the above duty ratio.

However, when the above method is used to adjust the duty cycle of the PWM circuit, and then adjust the pumping power of the air pump through the duty cycle to achieve constant-speed pressurization. Since the boosting speed of the air pressure in the cuff is also related to the driving voltage of the air pump, and the blood pressure measurement device is generally powered by a battery, in this way, under the condition of a certain duty cycle, the output voltage of the battery (that is, the output voltage of the air pump When the driving voltage) is lower, the corresponding pumping power is lower, and the boosting speed of the air pressure in the cuff is lower; when the output voltage of the battery is higher, the corresponding pumping power is higher, and the boosting speed of the air pressure in the cuff is faster. Therefore, the methods in the prior art cannot adapt to a wider driving voltage (ie, when the driving voltage is lower or the driving voltage is higher, the constant-speed pressurization cannot be guaranteed).

SUMMARY OF THE INVENTION

In view of this, the present application provides a PWM circuit duty cycle adjustment method, a controller and a blood pressure measurement device to solve the problem that the existing adjustment method cannot adapt to a wide driving voltage.

A first aspect of the present application provides a method for adjusting the duty cycle of a PWM circuit, including:

When the blood pressure measuring device is working, obtain the air pressure in the cuff and the driving voltage of the air pump in real time;

When the air pressure in the cuff exceeds the first preset value for the first time, according to the preset pressure increase speed, the air pressure when the air pressure exceeds the first preset value for the first time, the pressure increase speed and the air pressure when the air pressure exceeds the first preset value for the first time For the driving voltage when the first preset value is exceeded for the first time, the first coefficient in the functional relationship between the determined driving energy and the air pressure is calculated; wherein, the driving energy is equal to the product of the driving voltage and the driving duty cycle;

After the air pressure in the cuff exceeds the first preset value, based on the calculated first coefficient, determine the driving energy at the current moment according to the air pressure at the current moment and the functional relationship between the driving energy and the air pressure;

The driving duty ratio at the current moment is determined according to the determined driving energy and the driving voltage at the current moment, and the PWM circuit is instructed to generate a PWM signal whose duty ratio is equal to the driving duty ratio.

其中，E为驱动能量；P为袖带内的气压；a、b为常数；P1为第二预设值；A为第一系数；所述计算已确定的驱动能量与气压之间的函数关系式中的第一系数，具体包括：Further, the functional relationship between the driving energy and air pressure is:

Wherein, E is the driving energy; P is the air pressure in the cuff; a and b are constants; P1 is the second preset value; A is the first coefficient; the functional relationship between the driving energy and air pressure determined by the calculation The first coefficient in the formula specifically includes:

其中，m为微调系数；q为常数；S0为预设的升压速度；S1为气压首次超过第一预设值时的升压速度；Determine the initial value of the fine-tuning coefficient according to the following formula:

Wherein, m is the fine-tuning coefficient; q is a constant; S0 is the preset boosting speed; S1 is the boosting speed when the air pressure exceeds the first preset value for the first time;

Calculate the first coefficient according to the following formula: A=(c*U0/m0-(a*75+b))/(P0-75)^2, where m0 is the determined initial value of the fine-tuning coefficient; U0 is the air pressure The driving voltage when it exceeds the first preset value for the first time; P0 is the air pressure when the air pressure exceeds the first preset value for the first time; c is a constant.

Further, after the air pressure in the cuff exceeds the first preset value for the first time, the method further includes:

Calculate the boost speed at the current moment;

其中，S为当前时刻的升压速度；The fine-tuning coefficients are updated according to the following formula:

Among them, S is the boost speed at the current moment;

Before determining the driving duty ratio at the current moment according to the determined driving energy and the driving voltage at the current moment, the method further includes:

The determined driving energy is updated by multiplying the determined driving energy by the updated fine-tuning coefficient.

Further, before updating the determined driving energy to the determined driving energy multiplied by the updated fine-tuning coefficient, the method further includes:

judging whether the updated fine-tuning coefficient is within a preset fine-tuning coefficient interval;

If the updated fine-tuning coefficient is greater than the upper limit value of the fine-tuning coefficient interval, setting the updated fine-tuning coefficient as the upper limit value;

If the updated fine-tuning coefficient is smaller than the lower limit value of the fine-tuning coefficient interval, the updated fine-tuning coefficient is set as the lower limit value.

Further, the method also includes:

When the air pressure in the cuff is lower than the first preset value, the PWM circuit is instructed to generate a PWM signal with a duty cycle equal to the constant c.

Further, after the driving duty ratio at the current moment is determined according to the determined driving energy and the driving voltage at the current moment, the method further includes:

The driving duty ratio at the current moment is updated according to the formula D[i]=nD[i-1]+(1-n)D, where D is the current driving energy determined according to the determined driving energy and the driving voltage value at the current moment The driving duty ratio at the moment, D[i] is the driving duty ratio updated at the current moment, and D[i-1] is the duty ratio of the PWM signal generated by the PWM circuit at the previous moment at the current moment.

Further, the constant a and the constant b in the functional relationship between the driving energy and the air pressure are obtained through the following steps:

Under different driving voltages, the PWM circuit is controlled to generate PWM signals with a duty cycle equal to different preset values, so as to drive the air pump to inflate the experimental container;

In the process of inflating the experimental container each time, the air pressure of the experimental container is obtained in real time, and the pressure increase speed of the experimental container is calculated in real time;

Determine the air pressure of the experimental container when the pressure increasing speed of the experimental container is equal to the preset pressure increasing speed, and calculate the driving energy according to the determined air pressure of the experimental container and the current driving voltage;

According to the air pressure of the experimental container and the calculated driving energy determined in the process of inflating the experimental container each time, the constant a and the constant b in the functional relationship between the driving energy and the air pressure are obtained by fitting.

A second aspect of the present application provides a controller, comprising: an acquisition module and a processing module, wherein,

The acquisition module is used to acquire the air pressure in the cuff and the driving voltage of the air pump in real time when the blood pressure measurement device is working;

The processing module is used for, when the air pressure in the cuff exceeds the first preset value for the first time, according to the preset boosting speed, the air pressure when the air pressure exceeds the first preset value for the first time, and the air pressure when the air pressure exceeds the first preset value for the first time When the boosting speed and the driving voltage when the air pressure exceeds the first preset value for the first time, the first coefficient in the functional relationship between the determined driving energy and the air pressure is calculated; wherein, the driving energy is equal to the driving voltage and the driving duty product of ratios;

The processing module is further configured to, after the air pressure in the cuff exceeds the first preset value, based on the calculated first coefficient, according to the air pressure at the current moment and the functional relationship between the driving energy and the air pressure Determine the driving energy at the current moment;

The processing module is further configured to determine the drive duty cycle at the current moment according to the determined drive energy and the drive voltage at the current moment, and instruct the PWM circuit to generate a PWM signal with a duty cycle equal to the drive duty cycle.

其中，E为驱动能量；P为袖带内的气压；a、b为常数；P1为第二预设值；A为第一系数；Further, the functional relationship between the driving energy and air pressure is:

Among them, E is the driving energy; P is the air pressure in the cuff; a and b are constants; P1 is the second preset value; A is the first coefficient;

其中，m为微调系数；q为常数；S0为预设的升压速度；S1为气压首次超过第一预设值时的升压速度；The processing module is specifically used to determine the initial value of the fine-tuning coefficient according to the following formula:

Wherein, m is the fine-tuning coefficient; q is a constant; S0 is the preset boosting speed; S1 is the boosting speed when the air pressure exceeds the first preset value for the first time;

The processing module is also specifically configured to calculate the first coefficient according to the following formula: A=(c*U0/m0-(a*75+b))/(P0-75)^2, where m0 is determined The initial value of the fine-tuning coefficient; U0 is the driving voltage when the air pressure exceeds the first preset value for the first time; P0 is the air pressure when the air pressure exceeds the first preset value for the first time; c is a constant.

Further, the processing module 200 is further configured to calculate the pressure boosting speed at the current moment after the air pressure in the cuff exceeds the first preset value for the first time;

其中，S为当前时刻的升压速度；The processing mode is also used to update the fine-tuning coefficient according to the following formula:

Among them, S is the boost speed at the current moment;

The processing module 200 is further configured to update the determined driving energy by multiplying the determined driving energy by the updated Fine-tuning coefficients.

Further, the processing module 200 is further specifically configured to determine whether the updated fine-tuning coefficient is within a preset fine-tuning coefficient before updating the determined driving energy to the determined driving energy multiplied by the updated fine-tuning coefficient. and when judging that the updated fine-tuning coefficient is greater than the upper limit value of the fine-tuning coefficient interval, set the updated fine-tuning coefficient as the upper limit value; when judging that the updated fine-tuning coefficient is When the fine-tuning coefficient is smaller than the lower limit value of the fine-tuning coefficient interval, the updated fine-tuning coefficient is set as the lower limit value.

Further, the processing module is further configured to instruct the PWM circuit to generate a PWM signal with a duty cycle equal to a constant c when the air pressure in the cuff is lower than the first preset value.

Further, the processing module is further configured to determine the driving duty ratio at the current moment according to the determined driving energy and the driving voltage at the current moment, according to the formula D[i]=nD[i-1]+(1 -n) D updates the driving duty ratio at the current moment, where D is the driving duty ratio at the current moment determined according to the determined driving energy and the driving voltage value at the current moment, and D[i] is the updated driving duty ratio at the current moment The driving duty ratio of , D[i-1] is the duty ratio of the PWM signal generated by the PWM circuit at the previous moment of the current moment.

Further, the processing module is further configured to filter the acquired air pressure in the cuff to filter out high-frequency signals.

Further, the constant a and the constant b in the functional relationship between the driving energy and the air pressure are obtained through the following steps:

Under different driving voltages, the PWM circuit is controlled to generate PWM signals with a duty cycle equal to different preset values, so as to drive the air pump to inflate the experimental container;

In the process of inflating the experimental container each time, the air pressure of the experimental container is obtained in real time, and the pressure increase speed of the experimental container is calculated in real time;

Determine the air pressure of the experimental container when the pressure increasing speed of the experimental container is equal to the preset pressure increasing speed, and calculate the driving energy according to the determined air pressure of the experimental container and the current driving voltage;

According to the air pressure of the experimental container and the calculated driving energy determined in the process of inflating the experimental container each time, the constant a and the constant b in the functional relationship between the driving energy and the air pressure are obtained by fitting.

A third aspect of the present application provides a blood pressure measuring device, comprising: an air pressure collecting device, a driving voltage collecting device, a PWM circuit, an air pump, a cuff, and any controller provided in the second aspect of the present application; the blood pressure measuring device adopts an auxiliary power supply; where,

the air pressure collecting device, used for collecting the air pressure in the cuff according to a preset sampling frequency;

The driving voltage acquisition device is used to acquire the driving voltage of the air pump according to a preset sampling precision;

the PWM circuit for generating a PWM signal under the instruction of the controller;

The air pump is used to inflate the cuff under the control of the PWM circuit.

The PWM circuit duty cycle adjustment method, controller and blood pressure measurement device provided by the present application, when the blood pressure measurement device is working, the air pressure in the cuff and the driving voltage of the air pump are obtained in real time, and the air pressure in the cuff exceeds the first At a preset value, according to the preset boosting speed, the air pressure when the air pressure exceeds the first preset value for the first time, the boosting speed when the air pressure exceeds the first preset value for the first time, and the pressure when the air pressure exceeds the first preset value for the first time Drive voltage, calculate the first coefficient in the functional relationship between the determined drive energy and air pressure, and then after the air pressure in the cuff exceeds the first preset value, based on the calculated first coefficient, according to the current moment. The functional relationship between the air pressure and the above-mentioned driving energy and air pressure determines the driving energy at the current moment, and determines the driving duty ratio at the current moment according to the determined driving energy and the driving voltage at the current moment, and then instructs the PWM circuit to generate a duty cycle. A PWM signal equal to the above-mentioned drive duty cycle, wherein the drive energy is equal to the product of the drive voltage and the drive duty cycle. In this way, when adjusting the duty ratio, the driving energy is first determined according to the functional relationship, and then the driving duty ratio at the current moment is determined in combination with the driving voltage at the current moment. In this way, under the condition that the determined driving energy is constant , if the driving voltage at the current moment is high, the determined driving duty ratio will be low, which will not cause the problem of too fast boost speed due to high driving voltage; correspondingly, if the driving voltage at the current moment is low, the determined driving The higher the duty cycle is, the lower the boosting speed will not be caused by the low driving voltage. Therefore, the PWM circuit duty cycle adjustment method, controller and blood pressure measuring device provided by the present application can adapt to a wider driving voltage.

Description of drawings

1 is a flowchart of Embodiment 1 of a method for adjusting a duty cycle of a PWM circuit of the present application;

Fig. 2 is a schematic diagram of the functional relationship between the driving energy and the air pressure obtained when the experiment container is used for testing;

Figure 3 is a schematic diagram of the functional relationship between the driving energy and the air pressure obtained when the cuff is used for the test;

4 is a flowchart of Embodiment 2 of a method for adjusting a duty cycle of a PWM circuit of the present application;

5 is a schematic diagram of the duty ratio actually output by the PWM circuit after the duty cycle is adjusted according to the method provided by the present application;

6 is a schematic diagram of the real-time boosting speed of the cuff after the air pump is controlled by the PWM signal of the duty cycle shown in FIG. 5;

FIG. 7 is a schematic structural diagram of the first implementation of the controller of the present application;

FIG. 8 is a schematic structural diagram of Embodiment 1 of the blood pressure measurement device of the present application.

Detailed ways

Exemplary embodiments will be described in detail herein, examples of which are illustrated in the accompanying drawings. Where the following description refers to the drawings, the same numerals in different drawings refer to the same or similar elements unless otherwise indicated. The implementations described in the illustrative examples below are not intended to represent all implementations consistent with this application. Rather, they are merely examples of apparatus and methods consistent with some aspects of the present application as recited in the appended claims.

The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit the application. As used in this application and the appended claims, the singular forms "a," "the," and "the" are intended to include the plural forms as well, unless the context clearly dictates otherwise. It will also be understood that the term "and/or" as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

It should be understood that although the terms first, second, third, etc. may be used in this application to describe various information, such information should not be limited by these terms. These terms are only used to distinguish the same type of information from each other. For example, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information without departing from the scope of the present application. Depending on the context, the word "if" as used herein can be interpreted as "at the time of" or "when" or "in response to determining."

The present application provides a duty cycle adjustment method, a controller and a blood pressure measurement device of a PWM circuit, so as to solve the problem that the existing adjustment method cannot adapt to a wider driving voltage.

The technical solutions of the present application will be described in detail below with specific examples. The following specific embodiments may be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments.

FIG. 1 is a flowchart of Embodiment 1 of a method for adjusting a duty cycle of a PWM circuit of the present application. The execution subject of this embodiment is a controller provided in the blood pressure measurement device. Referring to FIG. 1 , the method for adjusting the duty ratio of a PWM circuit provided in this embodiment may include the following steps:

S101. When the blood pressure measuring device is working, acquire the air pressure in the cuff and the driving voltage of the air pump in real time.

Specifically, the blood pressure measuring device is provided with an air pressure collecting device and a driving voltage collecting device, wherein the air pressure collecting device is used to collect the air pressure in the cuff according to the preset sampling frequency, and the driving voltage collecting device is used to collect the air pressure according to the preset sampling frequency. The sampling accuracy collects the driving voltage of the air pump (for example, in one embodiment, the air pressure collection device may be a pressure sensor, and the preset sampling frequency may be 100 Hz; the driving voltage collection device may be a voltage sensor, and the preset collection accuracy may be is 0.001V). Correspondingly, in this step, when the blood pressure measuring device is working, the controller can obtain the air pressure in the cuff in real time from the air pressure collecting device, and obtain the driving voltage of the air pump in real time from the driving voltage collecting device; The driving voltage acquisition device transmits the collected data to the controller in real time. Based on the data transmission of the air pressure acquisition device and the driving circuit acquisition device, the controller acquires the air pressure in the cuff and the driving voltage of the air pump in real time.

S102. When the air pressure in the cuff exceeds the first preset value for the first time, according to the preset pressure increasing speed, the air pressure when the air pressure exceeds the first preset value for the first time, and the pressure increasing speed when the air pressure exceeds the first preset value for the first time and the driving voltage when the air pressure exceeds the first preset value for the first time, calculate the first coefficient in the functional relationship between the determined driving energy and the air pressure; wherein, the driving energy is equal to the product of the driving voltage and the driving duty cycle.

Specifically, when the air pressure in the cuff is lower than the normal blood pressure (20mmHg) of the human body, the pressure increase speed of the air pressure in the cuff will not affect the measurement results of the blood pressure measuring device. Therefore, in order to improve the accuracy of the measurement results, After the air pressure in the cuff is greater than the normal blood pressure (20mmHg) of the human body, the boosting speed of the air pressure in the cuff can be kept constant by adjusting the duty ratio of the PWM circuit. Therefore, the first preset value is 20mmHg. It should be noted that when the air pressure in the cuff is lower than the normal blood pressure of the human body (20mmHg), the increase rate of the air pressure in the cuff will not affect the measurement results of the blood pressure measuring device. Therefore, the air pressure in the cuff Before it is lower than 20mmHg, it is only necessary to instruct the PWM circuit to generate a PWM signal with a duty cycle equal to a constant c. The constant c is set according to actual needs. For example, the constant c may be 70% or 50%. The following description will be given by taking the constant c as 50% as an example.

Further, the functional relationship between the determined driving energy and air pressure is shown in formula (1):

Among them, E is the driving energy; P is the air pressure in the cuff; a and b are constants; P1 is the second preset value; A is the first coefficient.

It should be noted that the formula (1) is determined according to the preliminary test, and the specific determination process of the formula (1) will be introduced below, and will not be repeated here. Further, in the functional relationship between the determined driving energy and air pressure (ie, in formula (1)), the first coefficient A is an unknown, and the other coefficients are known (determined by previous experiments). In addition, in formula (1), when the preset boosting speed is 6 mmHg/s, the second preset value P1 is 75 mmHg, a is 0.0095, and b is 0.25.

Further, in this step, the first coefficient A can be calculated according to the following method, and the method includes the following steps:

(1) Determine the initial value of the fine-tuning coefficient according to formula (2):

Wherein, m is the fine-tuning coefficient; q is a constant; S0 is the preset boosting speed; S1 is the boosting speed when the air pressure exceeds the first preset value for the first time.

It should be noted that when the preset boosting speed is 6 mmHg/s, q is 0.6. Further, the boosting speed when the air pressure exceeds the first preset value for the first time may adopt the minimum value according to the N sampling points before the air pressure exceeds the first preset value for the first time (including the sampling points when the air pressure exceeds the first preset value for the first time). Calculated by the square method. For example, in an embodiment, the N sampling points are: (t1, P1), (t2, P2), ..., (tn Pn), where tn is the time corresponding to when the air pressure exceeds the first preset value for the first time , at this time, the boost speed can be calculated according to formula (3):

Further, when the boosting speed S1 when the air pressure exceeds the first preset value for the first time is calculated, at this time, the initial value of the fine-tuning coefficient m is determined according to formula (2). For example, in one embodiment, after calculation, it is determined that the boosting speed when the air pressure exceeds the first preset value for the first time is 7 mmHg/s. At this time, the initial value of the fine-tuning coefficient m is determined to be 1.

(2) Calculate the first coefficient according to formula (4):

A=(c*U0/m0-(a*75+b))/(P0-75)^2 (4)

Wherein, m0 is the determined initial value of the fine-tuning coefficient; U0 is the driving voltage when the air pressure exceeds the first preset value for the first time; P0 is the air pressure when the air pressure exceeds the first preset value for the first time; c is a constant.

For example, in one embodiment, the driving voltage when the air pressure exceeds the first preset value for the first time is 4.0V, and the air pressure when the air pressure exceeds the first preset value for the first time is 22 mmHg. Combined with the above example (c is equal to 50%, m0=1), at this time, the first coefficient A can be calculated.

It should be noted that, when the blood pressure measuring device is in operation, after this step, the first coefficient in the functional relationship between the determined driving energy and the air pressure can be calculated. In this way, there is no unknown in the functional relationship between the determined driving energy and air pressure. At this time, based on the calculated first coefficient, it can be adjusted according to the determined functional relationship between the driving energy and air pressure. The duty cycle of the PWM circuit.

S103. After the air pressure in the cuff exceeds the first preset value, based on the calculated first coefficient, determine the driving energy at the current moment according to the air pressure at the current moment and the functional relationship between the driving energy and the air pressure.

For example, in an embodiment, the air pressure at the current moment is 55 mmHg (less than 75 mmHg). At this time, based on the calculated first coefficient, the current air pressure can be determined according to E=A(P-P1)^2+a*P1+b Momentary driving energy. For another example, in another embodiment, the air pressure at the current moment is 90 mmHg (greater than 75 mmHg). In this case, the driving energy at the current moment can be determined according to E=aP+b.

S104. Determine the driving duty ratio at the current moment according to the determined driving energy and the driving voltage at the current moment, and instruct the PWM circuit to generate a PWM signal with a duty ratio equal to the above driving duty ratio.

Specifically, after the driving energy at the current moment is determined through step S103, in this step, the driving duty ratio at the current moment can be calculated according to the determined driving energy and the driving voltage at the current moment, wherein the driving power at the current moment The duty cycle is equal to the determined driving energy divided by the current driving voltage. Further, when the driving duty ratio at the current moment is determined, the PWM circuit is instructed to generate a PWM signal whose duty ratio is equal to the above driving duty ratio, so as to realize the purpose of adjusting the duty ratio of the PWM circuit.

The following is a brief introduction to the determination process of the functional relationship between the driving energy and the air pressure.

Specifically, in order to achieve that the duty cycle adjustment of the PWM circuit is related to the driving voltage of the air pump at the current moment, the concept of driving energy is first defined, wherein the driving energy is equal to the product of the driving voltage and the driving duty cycle.

Further, the model parameters are determined through experiments. It should be noted that the cuff is an elastic container, and its air capacity (the air capacity is the volume of air that the cuff can hold) changes within a certain range with the inflation state. Therefore, when determining the functional relationship between driving energy and air pressure, in order to build a relatively stable test environment. Firstly, an inelastic container is selected as the experimental container for testing. For example, the experimental container is a 500ml steel cylinder. Further, when the experimental container is determined, the above-mentioned steel cylinder is inflated under certain experimental conditions (under different driving voltages and different driving duty ratios), for example, when the driving voltage is 3.4V, 3.6V, At 3.8V, 4.0V, and 4.2V, when the drive duty cycle is 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, inflate the 500mL cylinder (that is, at different 40 sets of experiments were carried out under the driving voltage and different driving duty ratios), and in the process of each inflation, the air pressure of the experimental container was obtained in real time, and the pressure-boosting speed of the experimental container was calculated in real time (the least-squares method was used for the pressure-boosting speed, according to Equation (3) is calculated). Then determine the pressure of the experimental container when the boosting speed of the experimental container is equal to the preset boosting speed (6mmHg/s), and calculate the driving energy (that is, when the boosting speed of the experimental container is equal to 6mmHg/s, the corresponding experimental container Finally, according to the air pressure and the calculated driving energy of the experimental container determined in the process of inflating the experimental container each time, the driving energy and air pressure of the experimental container are obtained by fitting. The functional relationship of , as shown in Figure 2 (Figure 2 is a schematic diagram of the functional relationship between the driving energy and air pressure obtained when the experimental container is used for testing):

It can be seen from FIG. 2 that when the boosting speed is constant (6 mmHg/S), the current air pressure P and the driving energy E satisfy a linear relationship.

其中，袖带内的气压大于P1时的函数关系中的常数a和常数b，采用前面所说的钢瓶实验拟合确定。而袖带内的气压小于P1时的函数关系的顶点为(P1 aP1+b)点，这样，袖带内的气压小于P1时的函数关系也确定了，其中，A为未知数，可在实际调节的过程中计算出。Further, in order to verify the accuracy, the actual cuff is used to bind the arm, and the data is collected in the same way to obtain the curve shown in Figure 3 (Figure 3 is the driving energy and air pressure obtained when the cuff is used for the test. Schematic diagram of the functional relationship between). It can be seen from Figure 3 that when the air pressure of the cuff is greater than 75mmHg, the actual situation is consistent with the ideal cylinder. When the air pressure of the cuff is less than 75mmHg, the air pressure and the driving energy approximately satisfy the quadratic function relationship. Therefore, based on the above experimental research, the functional relationship between the driving energy and air pressure is determined as:

Among them, the constant a and the constant b in the functional relationship when the air pressure in the cuff is greater than P1 are determined by fitting with the aforementioned cylinder experiment. The vertex of the functional relationship when the air pressure in the cuff is less than P1 is the point (P1 aP1+b). In this way, the functional relationship when the air pressure in the cuff is less than P1 is also determined. Among them, A is an unknown number, which can be adjusted in practice. calculated in the process.

Further, when the constant a and the constant b are determined by fitting the aforementioned steel cylinder experiment, they are determined according to the following formula:

in:

It should be noted that Pji represents the air pressure of the experimental container when the driving voltage is j and the duty cycle is i, and the determined boosting speed of the experimental container is equal to the preset boosting speed; Pji represents that when the driving voltage is j, The calculated drive energy when the duty cycle is i.

In the method provided in this embodiment, when the blood pressure measuring device is working, the air pressure in the cuff and the driving voltage of the air pump are obtained in real time, and when the air pressure in the cuff exceeds the first preset value for the first time, the pressure is increased according to the preset pressure The speed, the air pressure when the air pressure exceeds the first preset value for the first time, the boosting speed when the air pressure exceeds the first preset value for the first time, and the driving voltage when the air pressure exceeds the first preset value for the first time, calculate the difference between the determined driving energy and the air pressure. After the air pressure in the cuff exceeds the first preset value, based on the calculated first coefficient, according to the current air pressure and the functional relationship between the driving energy and air pressure The driving energy at the current moment is determined by the formula, and the driving duty ratio at the current moment is determined according to the determined driving energy and the driving voltage at the current moment, and then the PWM circuit is instructed to generate a PWM signal whose duty ratio is equal to the above driving duty ratio, wherein, The drive energy is equal to the product of the drive voltage and the drive duty cycle. In this way, when adjusting the duty ratio, the driving energy is first determined according to the functional relationship, and then the driving duty ratio at the current moment is determined in combination with the driving voltage at the current moment. In this way, under the condition that the determined driving energy is constant , if the driving voltage at the current moment is high, the determined driving duty ratio will be low, which will not cause the problem of too fast boost speed due to high driving voltage; correspondingly, if the driving voltage at the current moment is low, the determined driving The higher the duty cycle is, the lower the boosting speed will not be caused by the low driving voltage. Therefore, the method provided in this embodiment can adapt to a wider driving voltage. In addition, with the method provided in this embodiment, when the blood pressure measuring device is working, the pressure increasing speed of the cuff is stable, the noise introduced by the air pump is small, and the measurement result is accurate. Further, according to the method provided in this embodiment, when the blood pressure measuring device is working, the pressure increasing speed of the cuff is stable, and the subject experience is more comfortable.

Further, when the blood pressure measuring device is working, the cuff is tied on the arm of the subject to be measured, and the gas capacity of the cuff will vary with the thickness of the arm or the tightness of the binding. Therefore, in the experimental stage, in order to further verify the rationality of the duty cycle adjustment, the effect of the gas capacity on the driving energy was further studied. It should be noted that, in order to study the influence of gas capacity on driving energy, the sampling method is the same as the method mentioned above, and a 1000ml steel cylinder is inflated, and the functional relationship between driving energy and air pressure is obtained as: E=d*(aP+ b). Among them, d is a constant related to its capacity. From the above experiments, it can be seen that the change of gas capacity will affect the driving energy, which will affect the boosting speed, which will make the actual boosting speed (the actual boosting speed can be kept stable) less than or greater than the preset boosting speed, which will affect the measurement time. (That is, when measuring different measured objects, the air capacity of the cuff is different due to the difference in the thickness of the measured object’s arm or the tightness of the cuff. At this time, the actual boosting speed of the cuff can be maintained constant. However, the actual boosting speed of the cuff cannot reach the preset boosting speed. In this way, since the actual boosting speed of different measured objects is different, the measurement time is also different for different measured objects). Therefore, in the actual adjustment process, in order to make the actual boosting speed of different measured objects the same (all can reach the preset boosting speed), and then make the measurement time of different measured objects constant, it is also possible to further determine the The output drive energy can be fine-tuned. A more specific embodiment is given below to describe in detail the method for adjusting the duty cycle of the PWM circuit provided by the present application.

FIG. 4 is the whole process of the second embodiment of the duty cycle adjustment method of the PWM circuit of the present application. This embodiment involves the entire process of adjusting the duty cycle. Please refer to FIG. 4 . The method provided by this embodiment may include the following steps:

S201. When the blood pressure measuring device is working, acquire the air pressure in the cuff and the driving voltage of the air pump in real time.

Specifically, for the specific implementation process and implementation principle of this step, reference may be made to the description of step S101 in the first embodiment, which will not be repeated here.

S202. Perform filtering processing on the acquired air pressure in the cuff to filter out high-frequency signals.

Specifically, in this step, low-pass filtering may be performed on the acquired air pressure in the cuff. For the specific implementation principle and implementation process of the filtering process, reference may be made to the description in the prior art, and details are not repeated here.

It should be noted that, in the method provided in this embodiment, after the air pressure in the cuff is obtained, the obtained air pressure in the cuff is filtered, so that high-frequency signals can be filtered out and an accurate air pressure value can be obtained .

S203. When the air pressure in the cuff is lower than the first preset value, instruct the PWM circuit to generate a PWM signal with a duty cycle equal to a constant c.

Combined with the previous introduction, the first preset value is 20mmHg. When the air pressure in the cuff is lower than the normal blood pressure (20mmHg) of the human body, the increase rate of the air pressure in the cuff will not affect the measurement results of the blood pressure measuring device. Therefore, before the air pressure in the cuff is lower than 20mmHg, It is only necessary to instruct the PWM circuit to generate a PWM signal with a duty cycle equal to the constant c.

S204. When the air pressure in the cuff exceeds the first preset value for the first time, calculate the pressure increase speed when the air pressure exceeds the first preset value for the first time, and according to the preset pressure increase speed, when the air pressure exceeds the first preset value for the first time and formula (2) to determine the initial value of the fine-tuning coefficient, and according to the determined initial value of the fine-tuning coefficient, the air pressure when the air pressure exceeds the first preset value for the first time, and the drive when the air pressure exceeds the first preset value for the first time Voltage and equation (4), calculate the first coefficient in the functional relationship between the determined driving energy and air pressure.

Specifically, for the specific implementation process and implementation principle of this step, reference may be made to the description of step S102 in the first embodiment, which will not be repeated here. It should be noted that, after this step, each coefficient in the functional relationship between the determined driving energy and the air pressure is known.

S205. After the air pressure in the cuff exceeds the first preset value, based on the calculated first coefficient, determine the driving energy at the current moment according to the air pressure at the current moment and the functional relationship between the driving energy and the air pressure.

Specifically, for the specific implementation process and implementation principle of this step, reference may be made to the description of step S103 in the first embodiment, which will not be repeated here.

S206: Calculate the boost speed at the current moment, and update the fine-tuning coefficient according to formula (5).

Specifically, the boosting speed at the current moment is calculated by using N sampling points before the current moment according to the least square method, that is, calculated according to formula (3).

Further, formula (5) is:

Among them, S is the boost speed at the current moment.

Specifically, in this step, after the boosting speed at the current moment is calculated, the fine-tuning coefficient can be updated according to the calculated boosting speed at the current moment, the preset boosting speed and formula (5). With reference to the introduction in the first embodiment (the initial value m1 of the fine-tuning coefficient m is equal to 1). For example, in this embodiment, the current moment is the next moment after the air pressure exceeds the first preset value for the first time, and the boosting speed at the current moment is calculated to be 7.2; at this time, the fine-tuning coefficient is updated according to formula (5), and after the update The fine-tuning coefficient of is -0.44 (where, -0.44=1-(6-7.2)^2).

S207. Determine whether the updated fine-tuning coefficient is within the preset fine-tuning coefficient interval. If the updated fine-tuning coefficient is greater than the upper limit of the fine-tuning coefficient interval, set the updated fine-tuning coefficient to the above-mentioned upper limit. The fine-tuning coefficient is less than the lower limit of the fine-tuning coefficient interval, and the updated fine-tuning coefficient is set to the above-mentioned lower limit.

Specifically, in order to prevent the duty cycle from changing abruptly. Therefore, the trimming coefficient interval is set in advance. Specifically, the preset fine-tuning coefficient interval is set according to actual needs. For example, when the preset boosting speed is 6 mmHg/s, the preset fine-tuning coefficient interval is: [0.9 1.6]. For example, in combination with the above example, when the updated fine-tuning coefficient is -0.44, at this time, the updated fine-tuning coefficient is less than the lower limit (0.9) of the fine-tuning coefficient interval. In this step, the updated fine-tuning coefficient is set is the lower limit.

S208. Update the determined driving energy to the determined driving energy multiplied by the updated fine-tuning coefficient.

Specifically, for example, the determined driving energy is E1, and the updated fine-tuning coefficient is m2. In this step, the determined driving energy is updated to E1*m2. In combination with the above example, the updated fine-tuning coefficient is 0.9. At this time, the determined driving energy is updated to 0.9E1.

S209: Determine the driving duty ratio at the current moment according to the determined driving energy and the driving voltage at the current moment, and instruct the PWM circuit to generate a PWM signal whose duty ratio is equal to the above driving duty ratio.

Specifically, for the specific implementation process and implementation principle of this step, reference may be made to the description of step S104 in the embodiment, which will not be repeated here.

Further, Fig. 5 is a schematic diagram of the duty ratio of the actual output of the PWM circuit after adjusting the duty cycle according to the method provided by the application; Fig. 6 is a real-time boost of the cuff after the PWM signal of the duty cycle shown in Fig. 5 controls the air pump. Schematic diagram of speed. It can be seen from FIG. 5 and FIG. 6 that after the method provided by the present application is used to adjust the duty cycle, after the air pressure of the cuff is greater than the normal blood pressure of the human body, the cuff can be guaranteed to be boosted at a stable pressure-boosting speed, and the cuff can be ensured. The boosting speed is the preset boosting speed, so that the measurement time is constant.

In the method provided in this embodiment, after the air pressure in the cuff is obtained, the obtained air pressure in the cuff is filtered, so that high-frequency signals can be filtered out, an accurate air pressure value can be obtained, and the accuracy of the measurement result can be improved. accuracy. In addition, in the method provided in this embodiment, before determining the driving duty ratio at the current moment according to the determined driving energy and the driving voltage at the current moment, the step-up speed at the current moment is calculated and the fine-tuning coefficient is updated, and then the determined The driving energy of is updated by multiplying the determined driving energy by the updated fine-tuning coefficient. In this way, the adjustment method can be adapted to different air volumes, and the rationality of adjustment is further improved. In this way, when different measured objects are measured, although the air volumes of the cuffs are different, the air volume will not affect the increase in air volume. The influence of the pressure speed can make the measurement time constant and further improve the accuracy of the measurement results. Further, in the method provided by this embodiment, after the fine-tuning coefficient is updated, it is judged whether the updated fine-tuning coefficient is within the preset fine-tuning coefficient interval, and if the updated fine-tuning coefficient is greater than the upper limit of the fine-tuning coefficient interval, update the fine-tuning coefficient. The updated fine-tuning coefficient is set to the above upper limit value. If the updated fine-tuning coefficient is smaller than the lower limit value of the fine-tuning coefficient interval, the updated fine-tuning coefficient is set to the above-mentioned lower limit value, which can prevent the duty cycle from abruptly changing.

Further, in a possible implementation manner, after the driving duty ratio at the current moment is determined according to the determined driving energy and the driving voltage at the current moment, the method further includes:

The driving duty ratio at the current moment is updated according to the formula D[i]=nD[i-1]+(1-n)D, where D is the current driving energy determined according to the determined driving energy and the driving voltage value at the current moment The driving duty ratio at the moment, D[i] is the driving duty ratio updated at the current moment, and D[i-1] is the duty ratio of the PWM signal generated by the PWM circuit at the previous moment at the current moment.

It should be noted that n is a constant, and n is determined according to actual needs. For example, n may be 0.2 or 0.1, etc. The following description will be given by taking n being 0.2 as an example. For example, in an embodiment, the driving duty ratio D at the current moment determined according to the determined driving energy and the driving voltage value at the current moment is 35%, and the duty ratio of the PWM signal generated by the PWM circuit at the previous moment at the current moment is 35%. The duty ratio is 32%, so the updated driving duty ratio at the current moment is 34.4% (wherein, 34.4%=0.2*32%+0.8*35%).

In the method provided by this embodiment, after determining the driving duty ratio at the current moment according to the determined driving energy and the driving voltage at the current moment, the determination is further updated according to the duty ratio of the PWM signal generated by the PWM circuit at the previous moment at the current moment. The drive duty cycle at the current moment is output. In this way, the duty ratio can be adjusted correspondingly according to the working state of the PWM circuit at the previous moment, which can further improve the rationality of the duty ratio adjustment.

FIG. 7 is a schematic structural diagram of Embodiment 1 of the controller of the present application. The controller can be implemented by software, hardware or a combination of software and hardware. The controller is used in a blood pressure measuring device. Referring to FIG. 7 , the controller provided in this embodiment may include: an acquisition module 100 and a processing module 200, wherein,

The acquisition module 100 is used to acquire the air pressure in the cuff and the driving voltage of the air pump in real time when the blood pressure measurement device is working;

The processing module 200 is used for, when the air pressure in the cuff exceeds the first preset value for the first time, according to the preset boosting speed, the air pressure when the air pressure exceeds the first preset value for the first time, and the air pressure when the air pressure exceeds the first preset value for the first time. The boost speed and the driving voltage when the air pressure exceeds the first preset value for the first time, calculate the first coefficient in the functional relationship between the determined driving energy and the air pressure; wherein, the driving energy is equal to the driving voltage and the driving occupation. The product of the empty ratio;

The processing module 200 is further configured to, after the air pressure in the cuff exceeds the first preset value, based on the calculated first coefficient, according to the air pressure at the current moment and the functional relationship between the driving energy and the air pressure The formula determines the driving energy at the current moment;

The processing module 200 is further configured to determine the drive duty cycle at the current moment according to the determined drive energy and the drive voltage at the current moment, and instruct the PWM circuit to generate a PWM signal with a duty cycle equal to the drive duty cycle.

The controller in this embodiment may be used to execute the technical solution of the method embodiment shown in FIG. 1 , and the implementation principle and technical effect thereof are similar, and are not described herein again.

其中，E为驱动能量；P为袖带内的气压；a、b为常数；P1为第二预设值；A为第一系数；In a possible implementation manner, the functional relationship between the driving energy and the air pressure is:

Among them, E is the driving energy; P is the air pressure in the cuff; a and b are constants; P1 is the second preset value; A is the first coefficient;

其中，m为微调系数；q为常数；S0为预设的升压速度；S1为气压首次超过第一预设值时的升压速度；The processing module 200 is specifically configured to determine the initial value of the fine-tuning coefficient according to the following formula:

Wherein, m is the fine-tuning coefficient; q is a constant; S0 is the preset boosting speed; S1 is the boosting speed when the air pressure exceeds the first preset value for the first time;

The processing module 200 is also specifically configured to calculate the first coefficient according to the following formula: A=(c*U0/m0-(a*75+b))/(P0-75)^2, where m0 is the determined The initial value of the fine-tuning coefficient; U0 is the driving voltage when the air pressure exceeds the first preset value for the first time; P0 is the air pressure when the air pressure exceeds the first preset value for the first time; c is a constant.

Further, the processing module 200 is further configured to calculate the pressure boosting speed at the current moment after the air pressure in the cuff exceeds the first preset value for the first time;

其中，S为当前时刻的升压速度；The processing module 200 is further configured to update the fine-tuning coefficient according to the following formula:

Among them, S is the boost speed at the current moment;

The processing module 200 is further configured to update the determined driving energy by multiplying the determined driving energy by the updated Fine-tuning coefficients.

Further, the processing module 200 is further specifically configured to determine whether the updated fine-tuning coefficient is within a preset fine-tuning coefficient before updating the determined driving energy to the determined driving energy multiplied by the updated fine-tuning coefficient. and when judging that the updated fine-tuning coefficient is greater than the upper limit value of the fine-tuning coefficient interval, set the updated fine-tuning coefficient as the upper limit value; when judging that the updated fine-tuning coefficient is When the fine-tuning coefficient is smaller than the lower limit value of the fine-tuning coefficient interval, the updated fine-tuning coefficient is set as the lower limit value.

Further, the processing module 200 is further configured to instruct the PWM circuit to generate a PWM signal with a duty cycle equal to a constant c when the air pressure in the cuff is lower than the first preset value.

Further, the processing module 200 is further configured to determine the driving duty ratio at the current moment according to the determined driving energy and the driving voltage at the current moment, according to the formula D[i]=nD[i-1]+( 1-n) D updates the driving duty ratio at the current moment, where D is the driving duty ratio at the current moment determined according to the determined driving energy and the driving voltage value at the current moment, and D[i] is the current moment update The following driving duty ratio, D[i-1] is the duty ratio of the PWM signal generated by the PWM circuit at the previous moment at the current moment.

Further, the processing module 200 is further configured to filter the acquired air pressure in the cuff to filter out high frequency signals.

Further, the constant a and the constant b in the functional relationship between the driving energy and the air pressure are obtained through the following steps:

Under different driving voltages, the PWM circuit is controlled to generate PWM signals with a duty cycle equal to different preset values, so as to drive the air pump to inflate the experimental container;

In the process of inflating the experimental container each time, the air pressure of the experimental container is obtained in real time, and the pressure increase speed of the experimental container is calculated in real time;

Determine the air pressure of the experimental container when the pressure increasing speed of the experimental container is equal to the preset pressure increasing speed, and calculate the driving energy according to the determined air pressure of the experimental container and the current driving voltage;

According to the air pressure of the experimental container and the calculated driving energy determined in the process of inflating the experimental container each time, the constant a and the constant b in the functional relationship between the driving energy and the air pressure are obtained by fitting.

FIG. 8 is a schematic structural diagram of Embodiment 1 of the blood pressure measuring device of the present application. Please refer to FIG. 8 , the blood pressure measurement device provided in this embodiment includes: an air pressure collection device, a driving voltage collection device, a PWM circuit, an air pump, a cuff, and any controller provided in the second aspect of the present application; the blood pressure measurement device Use auxiliary power supply; among them,

the air pressure collecting device, used for collecting the air pressure in the cuff according to a preset sampling frequency;

The driving voltage acquisition device is used to acquire the driving voltage of the air pump according to a preset sampling precision;

the PWM circuit for generating a PWM signal under the instruction of the controller;

The air pump is used to inflate the cuff under the control of the PWM circuit.

Specifically, the blood pressure measuring device is powered by an auxiliary power source, and the auxiliary power source can be a battery. In addition, in a possible implementation manner, the air pressure collecting device may be a pressure sensor, and the driving voltage collecting device may be a voltage sensor.

Those of ordinary skill in the art can understand that all or part of the steps of implementing the above method embodiments may be completed by program instructions related to hardware. The aforementioned program can be stored in a computer-readable storage medium. When the program is executed, the steps including the above method embodiments are executed; and the foregoing storage medium includes: ROM, RAM, magnetic disk or optical disk and other media that can store program codes.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: The technical solutions described in the foregoing embodiments can still be modified, or some or all of the technical features thereof can be equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the embodiments of the present application. scope.

Claims (10)

1. A PWM circuit duty cycle adjusting method is characterized by comprising the following steps:

when the blood pressure measuring device works, the air pressure in the cuff and the driving voltage of the air pump are acquired in real time;

when the air pressure in the cuff exceeds a first preset value for the first time, calculating a first coefficient in a function relation between the determined driving energy and the air pressure according to a preset boosting speed, the air pressure when the air pressure exceeds the first preset value for the first time, the boosting speed when the air pressure exceeds the first preset value for the first time and the driving voltage when the air pressure exceeds the first preset value for the first time; wherein the driving energy is equal to the product of the driving voltage and the driving duty ratio, and the functional relation between the driving energy and the air pressure is as follows:

e is driving energy; p is the air pressure in the cuff; a. b is a constant; p1 is a second preset value; a is a first coefficient;

after the air pressure in the cuff exceeds the first preset value, determining the driving energy at the current moment according to the air pressure at the current moment and a functional relation between the driving energy and the air pressure on the basis of the calculated first coefficient;

and determining the driving duty ratio of the current moment according to the determined driving energy and the driving voltage of the current moment, and indicating a PWM circuit to generate a PWM signal with the duty ratio equal to the driving duty ratio.

2. The method according to claim 1, wherein said calculating a first coefficient in the determined functional relationship between drive energy and air pressure comprises:

the initial value of the fine tuning coefficient is determined according to the following formula:

wherein m is a fine tuning coefficient; q is a constant; s0 is a preset boost speed; s1 is the pressure increasing speed when the air pressure exceeds the first preset value for the first time;

the first coefficient is calculated according to the following formula: a ═ c × U0/m0- (a × 75+ b))/(P0-75) ^2, where m0 is the initial value of the determined fine tuning coefficient; u0 is the driving voltage when the air pressure exceeds the first preset value for the first time; p0 is the air pressure when the air pressure exceeds the first preset value for the first time; c is a constant.

3. The method of claim 2, wherein after the air pressure within the cuff first exceeds the first preset value, the method further comprises:

calculating the boosting speed at the current moment;

updating the fine tuning coefficients according to the following formula:

wherein S is the boosting speed at the current moment;

before determining the driving duty ratio at the current moment according to the determined driving energy and the determined driving voltage at the current moment, the method further includes:

and updating the determined driving energy into the determined driving energy multiplied by the updated fine adjustment coefficient.

4. A method according to claim 3, wherein before updating the determined drive energy to the determined drive energy multiplied by the updated fine tuning coefficient, the method further comprises:

judging whether the updated fine tuning coefficient is in a preset fine tuning coefficient interval or not;

if the updated fine tuning coefficient is larger than the upper limit value of the fine tuning coefficient interval, setting the updated fine tuning coefficient as the upper limit value;

and if the updated fine tuning coefficient is smaller than the lower limit value of the fine tuning coefficient interval, setting the updated fine tuning coefficient as the lower limit value.

5. The method of claim 2, further comprising:

and when the air pressure in the cuff is lower than the first preset value, the PWM circuit is instructed to generate a PWM signal with the duty ratio equal to the constant c.

6. The method of claim 1, wherein after determining the driving duty ratio at the current time according to the determined driving energy and the driving voltage at the current time, the method further comprises:

and updating the driving duty ratio of the current moment according to a formula D [ i ] - [ nD [ i-1] + (1-n) D, wherein D is the driving duty ratio of the current moment determined according to the determined driving energy and the driving voltage value of the current moment, D [ i ] is the updated driving duty ratio of the current moment, and D [ i-1] is the duty ratio of the PWM signal generated by the PWM circuit at the moment before the current moment.

7. The method according to claim 2, wherein the constants a and b in the functional relationship between the driving energy and the air pressure are obtained by:

under different driving voltages, the PWM circuit is controlled to generate PWM signals with duty ratios equal to different preset values so as to drive the air pump to inflate the experimental container;

in the process of inflating an experimental container each time, acquiring the air pressure of the experimental container in real time, and calculating the pressure-boosting speed of the experimental container in real time;

determining the pressure boosting speed of the experimental container to be equal to the preset pressure boosting speed, testing the air pressure of the container, and calculating the driving energy according to the determined air pressure of the experimental container and the current driving voltage;

and fitting to obtain a constant a and a constant b in a functional relation between the driving energy and the air pressure according to the air pressure of the experimental container determined in the process of inflating the experimental container and the calculated driving energy each time.

8. The method according to claim 3, characterized in that said first preset value is 20 mmHg; when the preset pressure increasing speed is 6mmHg/s, the second preset value is 75 mmHg; the a is 0.0025; b is 0.95; q is 0.6.

9. A controller, comprising: an acquisition module and a processing module, wherein,

the acquisition module is used for acquiring the air pressure in the cuff and the driving voltage of the air pump in real time when the blood pressure measuring device works;

the processing module is used for calculating a first coefficient in a function relation between the determined driving energy and the air pressure according to a preset boosting speed, the air pressure when the air pressure exceeds a first preset value for the first time, the boosting speed when the air pressure exceeds the first preset value for the first time and the driving voltage when the air pressure exceeds the first preset value for the first time when the air pressure in the cuff exceeds the first preset value for the first time; wherein the driving energy is equal to the product of the driving voltage and the driving duty ratio, and the functional relation between the driving energy and the air pressure is as follows:

e is driveKinetic energy; p is the air pressure in the cuff; a. b is a constant; p1 is a second preset value; a is a first coefficient;

the processing module is further configured to determine, based on the calculated first coefficient, the driving energy at the current time according to the air pressure at the current time and the functional relation between the driving energy and the air pressure after the air pressure in the cuff exceeds the first preset value;

the processing module is further configured to determine a driving duty ratio at the current moment according to the determined driving energy and the driving voltage at the current moment, and instruct the PWM circuit to generate a PWM signal having a duty ratio equal to the driving duty ratio.

10. A blood pressure measuring device, comprising: an air pressure acquisition device, a driving voltage acquisition device, a PWM circuit, an air pump, a cuff and the controller of claim 9; the blood pressure measuring device adopts an auxiliary power supply for power supply; wherein,

the air pressure acquisition device is used for acquiring air pressure in the cuff according to a preset sampling frequency;

the driving voltage acquisition device is used for acquiring the driving voltage of the air pump according to preset sampling precision;

the PWM circuit is used for generating a PWM signal under the instruction of the controller;

the air pump is used for inflating the cuff under the control of the PWM circuit.

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