CN107536605B - PWM circuit duty ratio adjusting method, controller and blood pressure measuring device - Google Patents
PWM circuit duty ratio adjusting method, controller and blood pressure measuring device Download PDFInfo
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- CN107536605B CN107536605B CN201710790446.2A CN201710790446A CN107536605B CN 107536605 B CN107536605 B CN 107536605B CN 201710790446 A CN201710790446 A CN 201710790446A CN 107536605 B CN107536605 B CN 107536605B
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Abstract
The application provides a PWM circuit duty ratio adjusting method, a controller and a blood pressure measuring device. The application provides a PWM circuit duty cycle adjusting method, which comprises 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; calculating a first coefficient in a functional relation between the driving energy and the air pressure when the air pressure in the cuff exceeds a first preset value for the first time; after the air pressure in the cuff exceeds a 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 based on 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 further instructing a PWM circuit to generate a PWM signal with the duty ratio equal to the driving duty ratio. The PWM circuit duty ratio adjusting method, the controller and the blood pressure measuring device can adapt to wider driving voltage.
Description
Technical Field
The application relates to the technical field of electronics, in particular to a PWM circuit duty ratio adjusting method, a controller and a blood pressure measuring device.
Background
When the blood pressure measuring device is operated, after the air pressure in the cuff of the blood pressure measuring device is higher than the normal blood pressure (20mmHg) of the human body, in order to improve the accuracy of the measurement result, the pressure increasing speed of the air pressure in the cuff is generally required to be kept constant. In order to realize constant-speed pressurization, the control of the air pump is particularly important, a Pulse Width Modulation (PWM) circuit is generally adopted as a driving circuit of the air pump, and the pumping power of the air pump can be adjusted by adjusting the duty ratio of a PWM signal, so as to realize constant-speed pressurization.
The existing PWM circuit duty ratio adjusting method comprises the following steps: acquiring real-time air pressure in the cuff in the blood pressure measuring process; calculating the duty ratio of a PWM circuit in the blood pressure measuring device according to the real-time air pressure and a duty ratio and air pressure relation model, wherein the duty ratio and air pressure relation model represents the functional relation between the duty ratio and the air pressure when the rising speed of the air pressure in the cuff is constant; and adjusting the working duty ratio of the PWM circuit according to the duty ratio.
However, when the duty ratio of the PWM circuit is adjusted by the above method, and the pumping power of the air pump is adjusted by the duty ratio, the constant-speed pressurization is realized. Because the pressure increasing speed of the air pressure in the cuff is also related to the magnitude of the driving voltage of the air pump, and the blood pressure measuring device is generally powered by the battery, under the condition of a certain duty ratio, when the output voltage of the battery (namely the driving voltage of the air pump) is lower, the corresponding inflating power is lower, and the pressure increasing speed of the air pressure in the cuff is lower; when the output voltage of the battery is larger, the corresponding pumping power is higher, and the pressure boosting speed of the air pressure in the cuff is higher, so that the method in the prior art cannot adapt to a wider driving voltage (namely, when the driving voltage is lower or higher, constant-speed pressurization cannot be ensured).
Disclosure of Invention
In view of this, the present application provides a PWM circuit duty ratio adjusting method, a controller and a blood pressure measuring device, so as to solve the problem that the existing adjusting method cannot adapt to a wider driving voltage.
The application provides a PWM circuit duty ratio adjusting method in a first aspect, which includes:
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 cycle;
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.
Further, the functional relation between the driving energy and the air pressure is as follows:
wherein 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; the calculating a first coefficient in the determined functional relation between the driving energy and the air pressure specifically includes:
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.
Further, 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.
Further, before the 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 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.
Further, the method further comprises:
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.
Further, 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 method further includes:
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.
Further, the constant a and the constant b in the functional relation between the driving energy and the air pressure are obtained by the following steps:
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.
A second aspect of the present application provides 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 cycle;
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.
Further, the functional relation between the driving energy and the air pressure is as follows:
wherein 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;
the processing module is specifically configured to determine an initial value of the fine tuning coefficient 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 processing module is further 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 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.
Further, the processing module 200 is further configured to calculate a boosting speed at the current moment after the air pressure in the cuff exceeds the first preset value for the first time;
the processing module is further configured to update the fine tuning coefficient according to the following formula:
wherein S is the boosting speed at the current moment;
the processing module 200 is further configured to update the determined driving energy to be multiplied by the updated fine tuning coefficient before determining the driving duty ratio of the current time according to the determined driving energy and the driving voltage of the current time.
Further, the processing module 200 is further specifically configured to, before updating the determined driving energy to the determined driving energy multiplied by the updated fine tuning coefficient, determine whether the updated fine tuning coefficient is within a preset fine tuning coefficient interval; when the updated fine tuning coefficient is judged to be larger than the upper limit value of the fine tuning coefficient interval, setting the updated fine tuning coefficient as the upper limit value; and when the updated fine tuning coefficient is judged to be smaller than the lower limit value of the fine tuning coefficient interval, setting the updated fine tuning coefficient 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, after determining the driving duty ratio of the current time according to the determined driving energy and the driving voltage of the current time, update the driving duty ratio of the current time according to a formula D [ i ] ═ nD [ i-1] + (1-n) D, where D is the driving duty ratio of the current time determined according to the determined driving energy and the driving voltage value of the current time, D [ i ] is the updated driving duty ratio of the current time, and D [ i-1] is the duty ratio of the PWM signal generated by the PWM circuit at the time before the current time.
Further, the processing module is further configured to perform filtering processing on the acquired air pressure in the cuff to filter out a high-frequency signal.
Further, the constant a and the constant b in the functional relation between the driving energy and the air pressure are obtained by the following steps:
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.
A third aspect of the present application provides a blood pressure measuring device including: the device comprises an air pressure acquisition device, a driving voltage acquisition device, a PWM circuit, an air pump, a cuff and any one controller provided by the second aspect of the application; the blood pressure measuring device adopts an auxiliary power supply for power supply; wherein the content of the first and second substances,
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.
According to the PWM circuit duty ratio adjusting method, the controller and the blood pressure measuring device, when the blood pressure measuring device works, the air pressure in the cuff and the driving voltage of the air pump are obtained in real time, when the air pressure in the cuff exceeds a first preset value for the first time, a first coefficient in a function relation between determined driving energy and the air pressure is calculated 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, after the air pressure in the cuff exceeds the first preset value, the driving energy at the current time is determined according to the air pressure at the current time and the function relation between the driving energy and the air pressure based on the calculated first coefficient, and the driving duty ratio at the current time is determined according to the determined driving energy and the driving voltage at the current time, and further instructs the PWM circuit to generate a PWM signal having a duty ratio equal to the above-described drive duty ratio, wherein the drive energy is equal to a product of the drive voltage and the drive duty ratio. Therefore, when the duty ratio is adjusted, firstly, the driving energy is determined according to the functional relation, and then the driving duty ratio at the current moment is determined by combining the driving voltage at the current moment, so that under the condition that the determined driving energy is certain, if the driving voltage at the current moment is high, the determined driving duty ratio is low, and the problem that the boosting speed is too high due to the high driving voltage cannot be caused; correspondingly, if the driving voltage at the current moment is low, the determined driving duty ratio is high, and the problem of low boosting speed caused by low driving voltage is not caused.
Drawings
FIG. 1 is a flowchart of a first embodiment of a PWM circuit duty cycle adjustment method of the present application;
FIG. 2 is a schematic diagram of the driving energy as a function of the gas pressure obtained during the test with the test vessel;
FIG. 3 is a schematic diagram of the driving energy as a function of air pressure obtained during a test using a cuff;
FIG. 4 is a flowchart of a second embodiment of a PWM circuit duty cycle adjustment method of the present application;
FIG. 5 is a schematic diagram of the duty cycle of the actual output of the PWM circuit after the duty cycle is adjusted according to the method provided by the present application;
FIG. 6 is a schematic diagram of real-time cuff pressure-increasing speed after the air pump is controlled according to the PWM signal with the duty ratio shown in FIG. 5;
FIG. 7 is a schematic diagram of an embodiment of a controller according to the present application;
fig. 8 is a schematic structural diagram of a blood pressure measuring device according to a first embodiment of the present application.
Detailed Description
Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present application, as detailed in the appended claims.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this application and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.
It is to be understood that although the terms first, second, third, etc. may be used herein to describe various information, such information should not be limited to these terms. These terms are only used to distinguish one type of information from another. For example, first information may also be referred to as second information, and similarly, second information may also be referred to as first information, without departing from the scope of the present application. The word "if" as used herein may be interpreted as "at … …" or "when … …" or "in response to a determination", depending on the context.
The application provides a PWM circuit duty ratio adjusting method, a controller and a blood pressure measuring device, which aim to solve the problem that the existing adjusting method cannot adapt to a wider driving voltage.
The technical solution of the present application will be described in detail below with specific examples. The following several specific embodiments may be combined with each other, and details of the same or similar concepts or processes may not be repeated in some embodiments.
Fig. 1 is a flowchart of a first embodiment of a PWM circuit duty cycle adjustment method according to the present application. The execution subject of the present embodiment is a controller provided in the blood pressure measurement apparatus. Referring to fig. 1, the method for adjusting the duty ratio of the PWM circuit provided in the present embodiment may include the following steps:
s101, 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.
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 for collecting air pressure in the cuff according to a preset sampling frequency, and the driving voltage collecting device is used for collecting driving voltage of the air pump according to a preset sampling precision (for example, in one embodiment, the air pressure collecting device may be a pressure sensor, and the preset sampling frequency may be 100 Hz; and the driving voltage collecting device may be a voltage sensor, and the preset sampling precision may be 0.001V). Correspondingly, in the step, when the blood pressure measuring device works, the controller can acquire the air pressure in the cuff from the air pressure acquisition device in real time and acquire the driving voltage of the air pump from the driving voltage acquisition device in real time; or the controller acquires the air pressure in the cuff and the driving voltage of the air pump in real time based on the data transmission of the air pressure acquisition device and the driving circuit acquisition device.
S102, 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 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.
Specifically, when the pressure in the cuff is lower than the normal blood pressure (20mmHg) of the human body, the pressure increase speed of the pressure in the cuff does not affect the measurement result of the blood pressure measurement device, and therefore, in order to improve the accuracy of the measurement result, the pressure increase speed of the pressure in the cuff is kept constant by adjusting the duty ratio of the PWM circuit only after the pressure in the cuff is higher than the normal blood pressure (20mmHg) of the human body. Therefore, the first preset value is 20 mmHg. When the 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 does not affect the measurement result of the blood pressure measurement device, and therefore, the PWM circuit needs only to be instructed to generate the PWM signal having the duty ratio equal to the constant c until the air pressure in the cuff is lower than 20 mmHg. The constant c is set according to actual needs, and for example, the constant c may be 70% or 50%, and the following description will be given taking the constant c as 50%.
Further, the determined functional relationship between the driving energy and the air pressure is shown in formula (1):
wherein 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.
It should be noted that, the formula (1) is determined according to a previous experiment, and a specific determination process related to the formula (1) will be described below and will not be described herein again. Further, in the determined functional relationship between the driving energy and the air pressure (i.e., in the formula (1)), the first coefficient a is an unknown number, and other coefficients are known (determined in the previous experiment). In addition, in the formula (1), when the preset pressure increasing speed is 6mmHg/s, the second preset value P1 is 75mmHg, a is 0.0095, and b is 0.25.
Further, in this step, the first coefficient a may be calculated as follows, the method including the steps of:
(1) determining an initial value of the fine tuning coefficient according to equation (2):
wherein m is a fine tuning coefficient; q is a constant; s0 is a preset boost speed; s1 is the pressure increase speed when the air pressure first exceeds the first preset value.
When the predetermined pressure increasing rate was 6mmHg/s, q was 0.6. Further, the boosting speed when the air pressure first exceeds the first preset value can be calculated by a least square method according to N sampling points (including the sampling points when the air pressure first exceeds the first preset value) before the air pressure first exceeds the first preset value. For example, in one embodiment, the N sampling points are: (t1, P1), (t2, P2), … …, and (tn Pn), where tn is the time when the air pressure first exceeds the first preset value, and at this time, the boost speed can be calculated according to equation (3):
further, when the pressure increase speed S1 at which the air pressure first exceeds the first preset value is calculated, the initial value of the trimming coefficient m is determined according to the formula (2). For example, in one embodiment, the boosting speed when the air pressure first exceeds the first preset value is calculated to be 7mmHg/s, and at this time, the initial value of the fine tuning coefficient m is determined to be 1.
(2) Calculating a first coefficient according to equation (4):
A＝(c*U0/m0-(a*75+b))/(P0-75)^2 (4)
wherein 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.
For example, in one embodiment, the driving voltage is 4.0V when the air pressure first exceeds the first preset value, and the air pressure is 22mmHg when the air pressure first exceeds the first preset value. Combining the above example (c equals 50%, m0 equals 1), the first coefficient a can be calculated at this time.
It should be noted that, when the blood pressure measuring apparatus is operated, the first coefficient in the determined functional relationship between the driving energy and the air pressure is calculated through this step. Thus, no unknown number exists in the determined functional relation between the driving energy and the air pressure, and at this time, the duty ratio of the PWM circuit can be adjusted based on the determined functional relation between the driving energy and the air pressure based on the calculated first coefficient.
And S103, 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 the functional relation between the driving energy and the air pressure based on the calculated first coefficient.
For example, in an embodiment, the air pressure at the current time is 55mmHg (less than 75mmHg), and at this time, based on the calculated first coefficient, the driving energy at the current time may be determined according to E ═ a (P-P1) ^2+ a × P1+ b. For another example, in another embodiment, the air pressure at the current time is 90mmHg (greater than 75mmHg), and at this time, the driving energy at the current time may be determined according to E ═ aP + b.
And S104, determining the driving duty ratio of the current moment according to the determined driving energy and the driving voltage of the current moment, and instructing a PWM circuit to generate a PWM signal with the duty ratio equal to the driving duty ratio.
Specifically, after the driving energy at the current time is determined in step S103, in this step, the driving duty at the current time may be calculated according to the determined driving energy and the driving voltage at the current time, where the driving duty at the current time is equal to the determined driving energy divided by the driving voltage at the current time. Further, after the driving duty ratio at the current moment is determined, the PWM circuit is instructed to generate a PWM signal with the duty ratio equal to the driving duty ratio, and the purpose of adjusting the duty ratio of the PWM circuit is achieved.
The determination of the functional relationship between the driving energy and the air pressure is briefly described below.
Specifically, in order to achieve that the PWM circuit duty ratio adjustment is related to the drive voltage of the air pump at the present moment, a concept of drive energy is first defined, wherein the drive energy is equal to the product of the drive voltage and the drive duty ratio.
Further, the model parameters are determined by experiment. The cuff is an elastic container, and the air volume (the air volume is the volume of the cuff capable of containing air) of the elastic container changes within a certain range according to the inflation state. Therefore, when the functional relation between the driving energy and the air pressure is determined, a stable test environment is constructed. The test was first conducted using a non-elastic container as the test container. For example, the test vessel is a 500ml steel cylinder. Further, after the experimental container is determined, the steel cylinder is charged under certain experimental conditions (under different driving voltages and different driving duty ratios), for example, when the driving duty ratios are 25%, 30%, 35%, 40%, 45%, 50%, 55%, and 60% respectively when the driving voltages are 3.4V, 3.6V, 3.8V, 4.0V, and 4.2V, the 500mL steel cylinder is charged (i.e., 40 sets of experiments are performed under different driving voltages and different driving duty ratios), the air pressure of the experimental container is obtained in real time during each charging process, and the boosting speed of the experimental container is calculated in real time (the boosting speed is calculated according to equation (3) by using a least square method). Further, when the pressure increasing speed of the experimental container is determined to be equal to the preset pressure increasing speed (6mmHg/s), the air pressure of the experimental container is tested, the driving energy is calculated (that is, when the pressure increasing speed of the experimental container is equal to 6mmHg/s, the corresponding air pressure and driving energy of the experimental container are obtained, that is, 40 discrete points are obtained), and finally, according to the air pressure of the experimental container determined in the process of inflating the experimental container each time and the calculated driving energy, a functional relation between the driving energy and the air pressure of the experimental container is obtained by fitting, as shown in fig. 2 (fig. 2 is a schematic diagram of a functional relation between the driving energy and the air pressure obtained when the experimental container is used for testing:
as can be seen from fig. 2, when the pressure increase rate is constant (6mmHg/S), the air pressure P at the present time and the drive energy E satisfy a linear relationship.
Further, to verify the accuracy, the actual cuff was attached to the arm, and data acquisition was performed in the same manner, so as to obtain the curve shown in fig. 3 (fig. 3 is a schematic diagram of the functional relationship between the driving energy and the air pressure obtained in the experiment using the cuff). As can be seen from fig. 3, the actual situation is consistent with the ideal steel cylinder when the cuff pressure is greater than 75 mmHg. When the air pressure of the cuff is less than 75mmHg, the air pressure and the driving energy approximately satisfy a quadratic function relation. Therefore, based on the above experimental study, the functional relationship between the driving energy and the air pressure was determined as:
wherein 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 the steel cylinder experimental fitting. And the vertex of the functional relationship when the air pressure in the cuff is less than P1 is the point (P1 aP1+ b), so that the functional relationship when the air pressure in the cuff is less than P1 is also determined, wherein a is an unknown number and can be calculated in the process of actual adjustment.
Further, when the constants a and b are determined by fitting the steel cylinder experiment as described above, they are determined according to the following formula:
wherein:
it should be noted that Pji represents the air pressure of the experimental container when the determined pressure increase speed of the experimental container is equal to the preset pressure increase speed when the driving voltage is j and the duty ratio is i; pji shows the calculated drive energy when the drive voltage is j and the duty ratio is i.
In the method provided by this embodiment, when the blood pressure measuring apparatus is in operation, by acquiring the air pressure in the cuff and the driving voltage of the air pump in real time, and when the air pressure in the cuff first exceeds a first preset value, calculating a first coefficient in the determined functional relationship between the driving energy and the air pressure according to a preset boosting speed, the air pressure when the air pressure first exceeds the first preset value, the boosting speed when the air pressure first exceeds the first preset value, and the driving voltage when the air pressure first exceeds the first preset value, and then after the air pressure in the cuff exceeds the first preset value, determining the driving energy at the current time according to the air pressure at the current time and the functional relationship between the driving energy and the air pressure based on the calculated first coefficient, and determining the driving duty ratio at the current time according to the determined driving energy and the driving voltage at the current time, and further instructing the PWM circuit to generate a PWM signal having a duty ratio equal to the driving duty ratio, wherein the driving energy is equal to the product of the driving voltage and the driving duty ratio. Therefore, when the duty ratio is adjusted, firstly, the driving energy is determined according to the functional relation, and then the driving duty ratio at the current moment is determined by combining the driving voltage at the current moment, so that under the condition that the determined driving energy is certain, if the driving voltage at the current moment is high, the determined driving duty ratio is low, and the problem that the boosting speed is too high due to the high driving voltage cannot be caused; accordingly, if the driving voltage at the present moment is low, the determined driving duty ratio is high, and the problem of low boosting speed due to low driving voltage is not caused. In addition, according to the method provided by the embodiment, when the blood pressure measuring device works, the pressure boosting speed of the cuff is stable, the noise introduced by the air pump is small, and the measuring result is accurate. Further, according to the method provided by the embodiment, when the blood pressure measuring device works, the pressure increasing speed of the cuff is stable, and the experience of the measured person is more comfortable.
Further, when the blood pressure measuring device is operated, the cuff is tied to the arm of the subject, and the volume of the cuff varies depending on the thickness of the arm or the tightness of the cuff. Therefore, in the test stage, in order to further verify the rationality of the duty ratio adjustment, the influence of the gas capacity on the driving energy is further studied. In order to study the influence of gas capacity on driving energy, a 1000ml cylinder was charged by the same method as the above method, and the functional relationship between driving energy and gas pressure was obtained as follows: e ═ d ═ (aP + b). Where d is a constant related to its capacity. From the above experiment, it can be seen that the change of the air volume affects the driving energy, and further affects the pressure increase rate, and the actual pressure increase rate (the actual pressure increase rate can be kept stable) is smaller than or larger than the preset pressure increase rate, and further affects the measurement time (that is, when measuring different objects, the air volume of the cuff is different due to the different arm thicknesses of the objects to be measured or the different tightness of the cuff band, at this time, the actual pressure increase rate of the cuff can be kept constant, but the actual pressure increase rate of the cuff cannot reach the preset pressure increase rate, so the actual pressure increase rate of different objects to be measured is different, and thus, the measurement time is different for different objects to be measured). Therefore, in the actual adjustment process, in order to make the actual boosting speeds of different objects to be measured the same (all the actual boosting speeds can reach the preset boosting speed), and further make the measurement time of the different objects to be measured constant, the determined driving energy can be further finely adjusted. A more specific embodiment is provided below for explaining the PWM circuit duty ratio adjustment method provided in the present application in detail.
Fig. 4 is a diagram illustrating the whole process of the second embodiment of the PWM circuit duty cycle adjusting method of the present application. Referring to fig. 4, the method provided in this embodiment may include the following steps:
s201, 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.
Specifically, the specific implementation process and implementation principle of this step may refer to the description of step S101 in the embodiment, and are not described herein again.
S202, filtering the acquired air pressure in the cuff to filter out high-frequency signals.
Specifically, in this step, the acquired air pressure in the cuff may be low-pass filtered. For a specific implementation principle and implementation procedure of the filtering process, reference may be made to descriptions in the prior art, and details are not described here.
It should be noted that, according to 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 the high-frequency signal can be filtered out, and an accurate air pressure value can be obtained.
And S203, when the air pressure in the cuff is lower than a first preset value, instructing the PWM circuit to generate a PWM signal with the duty ratio equal to a constant c.
In conjunction with the foregoing, the first preset value is 20 mmHg. Before the air pressure in the cuff is lower than the normal blood pressure (20mmHg) of the human body, the pressure increasing speed of the air pressure in the cuff does not influence the measurement result of the blood pressure measuring device, so that the PWM circuit is only required to be instructed to generate a PWM signal with the duty ratio equal to the constant c before the air pressure in the cuff is lower than 20 mmHg.
S204, when the air pressure in the cuff exceeds a first preset value for the first time, calculating the boosting speed when the air pressure exceeds the first preset value for the first time, determining the initial value of the fine tuning coefficient according to the preset boosting speed, the boosting speed when the air pressure exceeds the first preset value for the first time and the formula (2), and calculating a first coefficient in the determined functional relation between the driving energy and the air pressure 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, the driving voltage when the air pressure exceeds the first preset value for the first time and the formula (4).
Specifically, the specific implementation process and implementation principle of this step may refer to the description of step S102 in the embodiment, and are not described herein again. It should be noted that, after this step, each coefficient in the determined functional relationship between the driving energy and the air pressure is known.
And S205, 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 the functional relation between the driving energy and the air pressure based on the calculated first coefficient.
Specifically, the specific implementation process and implementation principle of this step may refer to the description of step S103 in the embodiment, and are not described herein again.
And S206, calculating the boosting speed at the current moment, and updating the fine adjustment coefficient according to the formula (5).
Specifically, the boosting speed at the current time is calculated by using N sampling points before the current time according to a least square method, that is, according to formula (3).
Further, equation (5) is:
wherein S is the boosting speed at the current time.
Specifically, in this step, after the step-up speed at the current time is calculated, the fine adjustment coefficient may be updated according to the calculated step-up speed at the current time, the preset step-up speed, and the formula (5). With reference to the description of the first embodiment (the initial value m1 of the fine tuning coefficient m is equal to 1). For example, in this embodiment, the current time is the next time after the air pressure first exceeds the first preset value, and the boosting speed at the current time is calculated to be 7.2; at this time, the fine adjustment coefficient is updated according to the formula (5), and the updated fine adjustment coefficient is-0.44 (where-0.44 ═ 1- (6-7.2) ^ 2).
And S207, judging whether the updated fine tuning coefficient is in a preset fine tuning coefficient interval, 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.
In particular, to prevent abrupt changes in duty cycle. Therefore, the fine adjustment coefficient section 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 6mmHg/s, the preset fine tuning coefficient interval is: [0.91.6]. For example, in the example above, when the updated fine adjustment coefficient is-0.44, and at this time, the updated fine adjustment coefficient is smaller than the lower limit value (0.9) of the fine adjustment coefficient section, the updated fine adjustment coefficient is set to the lower limit value in this step.
And S208, updating the determined driving energy into the mode that the determined driving energy is multiplied by the updated fine adjustment coefficient.
Specifically, for example, the determined driving energy is E1, and the updated fine adjustment coefficient is m 2. In this step, the determined driving energy is updated to E1 × m2, and in combination with the above example, the updated fine adjustment coefficient is 0.9, and at this time, the determined driving energy is updated to 0.9E 1.
And S209, determining the driving duty ratio of the current moment according to the determined driving energy and the driving voltage of the current moment, and instructing a PWM circuit to generate a PWM signal with the duty ratio equal to the driving duty ratio.
Specifically, the specific implementation process and implementation principle of this step may refer to the description of step S104 in an embodiment, and are not described herein again.
Further, fig. 5 is a schematic diagram of the duty ratio actually output by the PWM circuit after the duty ratio is adjusted according to the method provided in the present application; FIG. 6 is a schematic diagram of real-time cuff pressure-increasing speed after the air pump is controlled by the PWM signal with the duty ratio shown in FIG. 5. As can be seen from fig. 5 and 6, after the duty ratio is adjusted by the method provided by the present application, after the air pressure in the cuff is greater than the normal blood pressure of the human body, the cuff can be ensured to be pressurized at a stable pressurization speed, and the pressurization speed of the cuff can be ensured to be a preset pressurization speed, so that the measurement time is constant.
According to the method provided by the embodiment, after the air pressure in the cuff is obtained, the obtained air pressure in the cuff is filtered, so that a high-frequency signal can be filtered, an accurate air pressure value is obtained, and the accuracy of a measurement result is improved. In addition, according to the method provided by this embodiment, before the driving duty ratio at the current time is determined according to the determined driving energy and the driving voltage at the current time, the voltage boosting speed at the current time is calculated, and the fine adjustment coefficient is updated, so that the determined driving energy is updated to be the determined driving energy multiplied by the updated fine adjustment coefficient. Therefore, the adjusting method can adapt to different air volumes, and the adjustment rationality is further improved, so that when different objects to be measured are measured, although the air volumes of the cuffs are different, the air volumes do not influence the pressure increasing speed, the measuring time can be constant, and the accuracy of the measuring result is further improved. Further, in the method provided in this embodiment, after the fine tuning coefficient is updated, by determining whether the updated fine tuning coefficient is within a preset fine tuning coefficient interval, if the updated fine tuning coefficient is greater than an upper limit value of the fine tuning coefficient interval, the updated fine tuning coefficient is set to the upper limit value, and if the updated fine tuning coefficient is less than a lower limit value of the fine tuning coefficient interval, the updated fine tuning coefficient is set to the lower limit value, so that abrupt duty change can be prevented.
Further, in a possible implementation manner, 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 includes:
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.
N is a constant and n is determined according to actual needs, and for example, n may be 0.2 or 0.1, and the following description will be given by taking n as 0.2 as an example. For example, in one embodiment, the driving duty ratio D at the present time determined from the determined driving energy and the driving voltage value at the present time is 35%, and the duty ratio of the PWM signal generated by the PWM circuit at the time immediately before the present time is 32%, so that the updated driving duty ratio at the present time is 34.4% (where 34.4% + 0.8% + 35%).
In the method provided by this embodiment, after the driving duty ratio at the current time is determined according to the determined driving energy and the driving voltage at the current time, the determined driving duty ratio at the current time is updated according to the duty ratio of the PWM signal generated by the PWM circuit at the time before the current time. Therefore, the duty ratio can be correspondingly adjusted according to the working state of the PWM circuit at the previous moment, and the reasonability of duty ratio adjustment can be further improved.
Fig. 7 is a schematic structural diagram of a controller according to a first embodiment of the present application. The controller can be implemented by software, hardware or a combination of software and hardware. The controller is applied to 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 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 200 is configured to calculate a first coefficient in a function relation between determined driving energy and air pressure according to a preset boosting speed, the air pressure when the air pressure first exceeds a first preset value, the boosting speed when the air pressure first exceeds the first preset value, and a driving voltage when the air pressure first exceeds the first preset value; wherein the driving energy is equal to the product of the driving voltage and the driving duty cycle;
the processing module 200 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 200 is further configured to determine a driving duty ratio of the current time according to the determined driving energy and the driving voltage of the current time, and instruct the PWM circuit to generate a PWM signal with a duty ratio equal to the driving duty ratio.
The controller of this embodiment may be configured to execute the technical solution of the method embodiment shown in fig. 1, and the implementation principle and the technical effect are similar, which are not described herein again.
In a possible implementation manner, the functional relation between the driving energy and the air pressure is as follows:
wherein 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;
the processing module 200 is specifically configured to determine an initial value of the fine tuning coefficient 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 processing module 200 is further 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 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.
Further, the processing module 200 is further configured to calculate a boosting speed at the current moment after the air pressure in the cuff exceeds the first preset value for the first time;
the processing module 200 is further configured to perform the followingThe formula updates the fine tuning coefficients:
wherein S is the boosting speed at the current moment;
the processing module 200 is further configured to update the determined driving energy to be multiplied by the updated fine tuning coefficient before determining the driving duty ratio of the current time according to the determined driving energy and the driving voltage of the current time.
Further, the processing module 200 is further specifically configured to, before updating the determined driving energy to the determined driving energy multiplied by the updated fine tuning coefficient, determine whether the updated fine tuning coefficient is within a preset fine tuning coefficient interval; when the updated fine tuning coefficient is judged to be larger than the upper limit value of the fine tuning coefficient interval, setting the updated fine tuning coefficient as the upper limit value; and when the updated fine tuning coefficient is judged to be smaller than the lower limit value of the fine tuning coefficient interval, setting the updated fine tuning coefficient 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, after determining the driving duty ratio of the current time according to the determined driving energy and the driving voltage of the current time, update the driving duty ratio of the current time according to a formula D [ i ] ═ nD [ i-1] + (1-n) D, where D is the driving duty ratio of the current time determined according to the determined driving energy and the driving voltage value of the current time, D [ i ] is the updated driving duty ratio of the current time, and D [ i-1] is the duty ratio of the PWM signal generated by the PWM circuit at the time before the current time.
Further, the processing module 200 is further configured to perform filtering processing on the acquired air pressure in the cuff to filter out a high-frequency signal.
Further, the constant a and the constant b in the functional relation between the driving energy and the air pressure are obtained by the following steps:
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.
Fig. 8 is a schematic structural diagram of a blood pressure measuring device according to the present application. Referring to fig. 8, the blood pressure measuring device provided in this embodiment includes: the device comprises an air pressure acquisition device, a driving voltage acquisition device, a PWM circuit, an air pump, a cuff and any one controller provided by the second aspect of the application; the blood pressure measuring device adopts an auxiliary power supply for power supply; wherein the content of the first and second substances,
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.
Specifically, the blood pressure measuring device is powered by an auxiliary power supply, which may 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 will understand that: all or a portion of the steps of implementing the above-described method embodiments may be performed by hardware associated with program instructions. The program may be stored in a computer-readable storage medium. When executed, the program performs steps comprising the method embodiments described above; and the aforementioned storage medium includes: various media that can store program codes, such as ROM, RAM, magnetic or optical disks.
Finally, it should be noted that: the above embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present application.
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 content of the first and second substances,
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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