CN104188643B - A kind of pressure control circuit for blood pressure measurement and control method - Google Patents

Abstract

The invention relates to a pressure control circuit and control method for blood pressure measurement. The control circuit includes a pressure sensor, a signal conditioning circuit, a microcontroller, a PWM controller and a peristaltic pump. The pressure sensor is connected to the input end of the signal conditioning circuit, and the signal conditioning circuit The output end of the circuit is connected to the input end of the microcontroller, the output end of the microcontroller is connected to the input end of the PWM controller, and the output end of the PWM controller is connected to the peristaltic pump; the pressure sensor collects the mixed signal of pressure and pulse wave, and the signal conditioning circuit Receive the mixed signal and process it, obtain the pressure feedback signal and pulse wave signal and send it to the microcontroller. After comparison and PI adjustment, the microcontroller sends a control signal to the PWM controller, and the PWM controller sends a PWM signal with a corresponding pulse width. , to complete the control of the peristaltic pump. Compared with the prior art, the invention can effectively control the uniform pressure change during the measurement process and improve the measurement accuracy.

Description

A pressure control circuit and control method for blood pressure measurement

technical field

The invention relates to the technical field of medical devices, in particular to a pressure control circuit and control method for blood pressure measurement.

Background technique

Electronic sphygmomanometer in the blood pressure measurement process, in order to obtain accurate blood pressure measurement value, it is necessary to ensure that the pulse wave information at each pressure point is uniform, that is, the pressure changes at a uniform speed during the entire measurement process. In the traditional step-down blood pressure measuring machine measurement, the uniform deflation valve plays a key role. In the measurement of the step-up blood pressure measuring machine, the measurement method is the same as the step-down measurement principle, but in the process of step-up, if the pressure is required to change at a constant speed, the non-linear change of the speed of the inflator must be controlled. If the control is not accurate enough, the air flow will be unstable during the boosting process, the pressure change speed will be uneven, and the measurement results will easily cause deviations. At present, electronic sphygmomanometers have gradually replaced traditional mercury column sphygmomanometers, and electronic sphygmomanometers that use air pumps for pressure control have limitations in the accuracy of air pump control, and at the same time, the air pump needs to be additionally equipped with an air release valve for air release.

Therefore, it is necessary to develop a pressure control circuit and control method for high-precision blood pressure measurement. Whether it is a step-down measurement method or a step-up measurement method, it can effectively control the uniform pressure change during the entire measurement process, thereby improving measurement accuracy.

Contents of the invention

The object of the present invention is to provide a pressure control circuit and control method for blood pressure measurement in order to overcome the defects of the above-mentioned prior art, which can effectively control the uniform pressure change during the measurement process and improve the measurement accuracy.

The purpose of the present invention can be achieved through the following technical solutions:

A pressure control circuit for blood pressure measurement, including a pressure sensor, a signal conditioning circuit, a microcontroller, a PWM controller and a peristaltic pump, the output end of the pressure sensor is connected to the input end of the signal conditioning circuit, and the signal The output end of the conditioning circuit is connected to the input end of the microcontroller, the output end of the microcontroller is connected to the input end of the PWM controller, and the output end of the PWM controller is connected to the peristaltic pump;

The pressure sensor collects the mixed signal of pressure and pulse wave, the signal conditioning circuit receives the mixed signal and processes it, obtains the pressure feedback signal and pulse wave signal and sends them to the microcontroller, and the microcontroller sends the signal to the PWM controller after comparison and PI adjustment. Send a control signal, and the PWM controller sends out a PWM signal with a corresponding pulse width to complete the control of the peristaltic pump.

The signal conditioning circuit includes a pressure signal amplifier and a pulse signal extraction circuit, the input end of the pressure signal amplifier is connected to the pressure sensor, and the output end is respectively connected to the input end of the pulse signal extraction circuit and the first input end of the microcontroller, The output end of the pulse signal extraction circuit is connected to the second input end of the microcontroller, the pressure signal amplifier amplifies the mixed signal of pressure and pulse wave, and its output end outputs a pressure feedback signal. After the pulse signal extraction circuit receives the input signal , from which the pulse wave signal is extracted and output.

Described signal amplifier is AD620 chip.

The pulse signal extraction circuit includes an analog bandpass filter and an emitter follower, the input end of the analog bandpass filter is connected to the output end of the pressure signal amplifier, and the output end is connected to the input end of the emitter follower. The output end of the emitter follower is connected to the second input end of the microcontroller, and the emitter follower is an LM358 chip.

Described microcontroller is STM32f103 chip.

The pressure sensor is an MD-PSG010 chip.

The PWM controller is an L293B chip.

A pressure control method for blood pressure measurement, including a pressure control method for measuring blood pressure by lowering blood pressure or a pressure control method for measuring blood pressure by increasing blood pressure;

The specific steps of the pressure control method for measuring blood pressure by reducing blood pressure are as follows:

101: Start to detect the pressure signal and pulse wave signal, and send a quick pressurization command to the peristaltic pump. At this time, the PWM controller sends a pulse with a duty ratio of 80% to the peristaltic pump for open-loop control, and the peristaltic pump rotates forward to pressurize ;

102: When it is detected that the pressure signal reaches the preset value, it sends a uniform deflation command to the peristaltic pump, and starts to adjust the pressure reduction rate at a rate of 0.3mmHg/millisecond. At this time, the PWM controller sends a duty ratio of 30% to the peristaltic pump. The pulse is closed-loop controlled, and the peristaltic pump rotates in reverse to reduce pressure;

103: When the peak value of the pulse wave begins to decline and reaches 50% of the maximum peak value, a detection end signal is sent, and the PWM controller sends a pulse with a duty cycle of 80% to the peristaltic pump, and the peristaltic pump rotates in reverse to reduce pressure until the detected pressure signal is 0;

The specific steps of the pressure control method for measuring blood pressure by boosting blood pressure are:

S1: Start to detect the pressure signal and pulse wave signal, send a uniform pressurization command to the peristaltic pump, and start to adjust the pressure increase rate at a rate of 0.3mmHg/millisecond. At this time, the PWM controller sends 10% to 30% variable pulse width to the peristaltic pump The PWM signal is used for closed-loop control, and the peristaltic pump rotates forward for pressurization;

S2: When it is detected that the blood pressure test is completed, that is, the peak value of the pulse wave begins to decline and reaches 50% of the maximum peak value, a quick deflation command is sent to the peristaltic pump, at this time, the PWM controller sends a pulse with a duty cycle of 80% to the peristaltic pump For open-loop control, the peristaltic pump rotates in reverse until the detected pressure signal is 0.

The closed-loop control is as follows: the feedback pressure signal is compared with the preset pressure distribution curve, and if there is an error, after adjustment by the PI regulator, the PWM controller sends corresponding pulses to the peristaltic pump.

Compared with the prior art, the present invention has the following advantages:

1) In the control method of boosting blood pressure detection in the present invention, the pressure of the peristaltic pump is controlled to change at a constant speed, and the closed-loop control of the airflow is stable and accurate, making the measurement more accurate and fast;

2) In the blood pressure control method for step-down detection in the present invention, the peristaltic pump reversal (inhalation special type) is used to realize natural deflation, the traditional deflation valve can be omitted, and the pressure in the step-down process can be uniformly changed through closed-loop control, so that blood pressure measurement Faster and more accurate;

3) In the pressure control circuit of the present invention, a peristaltic pump is used instead of a traditional air pump, which has better speed regulation performance and simplifies equipment;

4) The pressure control circuit of the present invention includes a PWM controller, using pulse width modulation PWM technology, energy saving, and more convenient speed regulation;

5) The pressure control circuit of the present invention includes a microcontroller, through which the functions of comparison and PI adjustment are realized, so that the PWM control is more accurate, that is, the feedback pressure signal is compared with the preset pressure distribution curve, and if there is an error, it is adjusted by PI After adjustment, the PWM controller sends corresponding pulses to the peristaltic pump;

6) The signal processor in the pressure control circuit of the present invention includes a pressure signal amplifier and a pulse signal extraction circuit. The pressure signal amplifier is composed of a high-precision instrument amplifier AD620 to complete the amplification of the pressure signal. The pulse signal extraction circuit is composed of an analog band-pass filter and a radiation The pole follower amplifier LM358 is composed to complete the extraction of the pulse wave signal, and the pressure signal and the pulse wave signal are used as PI control parameters to facilitate accurate pressure control.

Description of drawings

Fig. 1 is the structural representation of pressure control circuit among the present invention;

Fig. 2 is a block diagram of pressure control in the present invention;

Fig. 3 is the circuit diagram of microcontroller among the present invention;

Fig. 4 is the circuit diagram of pressure sensor, signal conditioning circuit among the present invention;

Fig. 5 is the circuit diagram of PWM controller among the present invention;

Fig. 6 is a curve diagram of blood pressure measurement in the present invention;

Fig. 7 is a curve diagram of measuring blood pressure by boosting pressure in the present invention.

In the figure: 1. Pressure sensor, 2. Microcontroller, 3. PWM controller, 4. Peristaltic pump, 5. Cuff, U1, signal amplifier, U2, pulse signal extraction circuit.

detailed description

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is carried out on the premise of the technical solution of the present invention, and detailed implementation and specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments.

As shown in Figure 1, a pressure control circuit for blood pressure measurement includes a pressure sensor 1, a signal conditioning circuit, a microcontroller 2, a PWM controller 3 and a peristaltic pump 4, the output of the pressure sensor 1 is connected to the signal conditioning circuit The input terminal and the output terminal of the signal conditioning circuit are connected to the input terminal of the microcontroller 2 , the output terminal of the microcontroller 2 is connected to the input terminal of the PWM controller 3 , and the output terminal of the PWM controller 3 is connected to the peristaltic pump 4 .

As shown in Figure 2, when the feedback pressure signal has an error compared with the required pressure distribution curve, the pulse width required by the PWM can be obtained through the PI adjustment calculation of the microcontroller 2; through the PWM controller 3, the The variable pulse width PWM signal is amplified to control the forward and reverse rotation of the peristaltic pump 4; the peristaltic pump 4 controls the inflation and deflation of the cuff 5; the pressure sensor 1 is installed in the cuff 5 to complete the collection of pressure signals and pulse wave signals , amplify and transform, and feed back to the input terminal of microcontroller 2 to continue subsequent processing.

As shown in Figure 3, the signal conditioning circuit includes a pressure signal amplifier U1 and a pulse signal extraction circuit U2. The input end of the pressure signal amplifier U1 is connected to the pressure sensor 1, and the output end is respectively connected to the input end of the pulse signal extraction circuit U2 and the microcontroller 2. The input end, the output end of the pulse signal extraction circuit U2 is connected to the second input end of the microcontroller 2, the pressure signal amplifier U1 amplifies the mixed signal of pressure and pulse wave, and its output end outputs a pressure feedback signal, and the pulse signal extraction circuit U2 After receiving the input signal, extract the pulse wave signal and output it. The pulse signal extraction circuit U2 includes an analog bandpass filter and an emitter follower, the input end of the analog bandpass filter is connected to the output end of the pressure signal amplifier, the output end is connected to the input end of the emitter follower, and the output end of the emitter follower The terminal is connected to the second input terminal of the microcontroller. Among them, the signal amplifier U1 is the AD620 chip, the emitter follower is the LM358 chip, and the pressure sensor 1 is the MD-PSG010 chip. The output terminal ADC0 of the signal amplifier U1 is used as a pulse signal extraction circuit U2 by an analog bandpass filter and an emitter follower LM358, and its output terminal is marked as ADC1.

As shown in Figure 4, the microcontroller 2 is an STM32f103 chip, and the pressure distribution curve, comparator, and PI adjustment are required to be completed by the microcontroller 2, thereby realizing the corresponding control commands in Figure 2; the pins PB5 and PB6 of the STM32f103 chip are used as Connect the output end of the PWM controller 3, the pin PC0 is the second input end, connect the output end ADC1 of the pulse signal extraction circuit U2, input the pulse wave signal, the pin PC1 is the first input end, connect the output of the pressure signal amplifier U1 Port ADC0, the input pressure feedback signal, also includes the peripheral circuits that constitute the minimum system of the STM32f103 chip in Figure 4.

The peristaltic pump 4 control adopts pulse width modulation PWM technology, which greatly reduces the cost and power consumption of the control system, and makes the output smooth and easy to adjust the speed. The PWM controller 3 is shown in FIG. 5 , wherein L293B is a motor drive control chip, which serves as the PWM controller 3 . The corresponding pulse width of the PWM signal is obtained after PI adjustment by the STM32f103. The pin PB5 of the STM32f103 is connected to the pin IN1 of the L293B, the pin PB6 of the STM32f103 is connected to the pin IN2 of the L293B, and the L293B receives the output control signal of the STM32f103 to complete the PWM signal. The function of amplifying and controlling the rotation of the peristaltic pump 4, the L293B output pin OUT1 is respectively connected to the anode of D15, the cathode of D17 and the pin 1 of the peristaltic pump 4 socket SJ-DJ, and the pin OUT2 is respectively connected to the anode of D16, the cathode of D18 and The pin 2 of the peristaltic pump 4 socket SJ-DJ, the cathodes of D15 and D16 are connected to +12V power supply respectively, the anodes of D16 and D17 are respectively connected to the ground, and the diodes D15, D16, D17 and D18 constitute a protection circuit. Figure 5 also includes: the pins ENA, ENB, and VSS of the L293B are respectively connected to the +12V power supply, the pin VS is connected to the +5V power supply, and the four pins GND are respectively connected to the ground.

Based on the above-mentioned pressure control circuit, a pressure control method is adopted to realize blood pressure measurement, including a pressure control method of stepping down to measure blood pressure or a pressure control method of raising blood pressure to measure blood pressure.

As shown in Figure 6, the specific steps of the pressure control method for measuring blood pressure by reducing blood pressure are as follows:

101: Start to detect the pressure signal and pulse wave signal. After 3.06 seconds (corresponding to the 102nd point in Figure 6, the sampling speed is 33.3Hz), a fast pressurization command is sent to the peristaltic pump 4. At this time, the PWM controller 3 The peristaltic pump 4 sends pulses with a duty ratio of 80% for open-loop control, and the peristaltic pump 4 rotates forward to pressurize;

102: When it is detected that the pressure signal reaches the preset value, a uniform deflation command is sent to the peristaltic pump 4, and the pressure reduction rate is adjusted at a rate of 0.3mmHg/millisecond. At this time, the PWM controller 3 sends a duty cycle to the peristaltic pump 4 Closed-loop control for 30% pulse, peristaltic pump 4 counter-rotating step-down;

103: When the peak value of the pulse wave begins to decline and reaches 50% of the maximum peak value (corresponding to the 1300th point in Figure 6), a detection end signal is sent, and the PWM controller 3 sends a pulse with a duty cycle of 80% to the peristaltic pump 4, The peristaltic pump 4 reversely rotates to depressurize until the detected pressure signal is 0.

According to the pressure signal and pulse wave signal collected during the depressurization process, the blood pressure value is calculated and obtained.

As shown in Figure 7, the specific steps of the pressure control method for boosting blood pressure measurement are:

S1: Start to detect the pressure signal and pulse wave signal, send a uniform pressure command to the peristaltic pump 4, and start to adjust the pressure increase rate at a rate of 0.3mmHg/millisecond. At this time, the PWM controller 3 sends 10% to 30% to the peristaltic pump 4 The PWM signal with variable pulse width is used for closed-loop control, and the peristaltic pump 4 rotates in the forward direction for pressurization;

S2: When it is detected that the blood pressure test is completed, that is, the peak value of the pulse wave begins to decline and reaches 50% of the maximum peak value, a quick deflation command is sent to the peristaltic pump 4. At this time, the PWM controller 3 sends a duty cycle to the peristaltic pump 4. 80% of the pulses are under open-loop control, and the peristaltic pump 4 rotates in reverse until the detected pressure signal is 0.

According to the pressure signal and pulse wave signal collected during the pressurization process, the blood pressure value is calculated and obtained.

The closed-loop control is: compare the feedback pressure signal with the preset pressure distribution curve, if there is an error e, after adjustment by the PI regulator, the PWM controller 3 sends a corresponding pulse to the peristaltic pump 4 .

The above pressure control method can use the peristaltic pump 4 in conjunction with the inflation rate control method to form a specific inflation mode and deflation mechanism during the measurement process of the buck/boost measurement method.

Claims (7)

1. the pressure control circuit for blood pressure measurement, it is characterised in that include pressure transducer, signal Modulate circuit, microcontroller, PWM controller and peristaltic pump, described pressure transducer connects signal condition electricity The input on road, the outfan of described signal conditioning circuit connects the input of microcontroller, described microcontroller The outfan of device connects the input of PWM controller, and the outfan of described PWM controller connects peristaltic pump；

Pressure transducer gathers pressure and the mixed signal of pulse wave, and signal conditioning circuit receives mixed signal and carries out Process, it is thus achieved that pressure feedback signal and pulse wave signal also send to microcontroller, microcontroller through comparing, PI After regulation, sending control signal to PWM controller, PWM controller sends the pwm signal of corresponding pulsewidth, Complete the control to peristaltic pump；

Described signal conditioning circuit includes that pressure signal amplifier and pulse signal extract circuit, described pressure letter The input of number amplifier connects pressure transducer, outfan connect respectively pulse signal extract circuit input and The first input end of microcontroller, the second of the outfan connection microcontroller of described pulse signal extraction circuit is defeated Entering end, the mixed signal of pressure and pulse wave is amplified by pressure signal amplifier, and its outfan output pressure is anti- Feedback signal, after pulse signal extracts circuit reception input signal, therefrom extracts pulse wave signal and exports；

This pressure control circuit uses buck or the control peristaltic pump output of boost type compress control method at the uniform velocity to change Pressure；

Described buck compress control method concretely comprises the following steps:

101: microcontroller starts to receive pressure signal and the pulse wave signal of detection, and passes through PWM controller Send Quick-pressing instruction to peristaltic pump, now, PWM controller send the arteries and veins of dutycycle 80% to peristaltic pump Rushing in row opened loop control, peristaltic pump rotates forward pressurization；

102: after the pressure signal detected when microcontroller reaches preset value, microcontroller is controlled by PWM Device sends, to peristaltic pump, instruction of at the uniform velocity exitting, and the pressure starting to regulate peristaltic pump with 0.3mmHg/ millisecond speed reduces Speed, now, the pulse that PWM controller sends dutycycle 30% to peristaltic pump carries out closed loop control, peristaltic pump Reversely rotate blood pressure lowering；

103: when the pulse wave peak value that microcontroller detects begin to decline and reach peak-peak 50% time, micro- Controller sends detection end signal by PWM controller to peristaltic pump, and now, PWM controller is to wriggling Pump sends the pulse of dutycycle 80%, and peristaltic pump reversely rotates blood pressure lowering, until the pressure signal of detection is 0；

Described boost type compress control method concretely comprises the following steps:

S1: microcontroller start receive detection pressure signal and pulse wave signal, and by PWM controller to Peristaltic pump sends uniform pressurization instruction, starts to regulate the Pressure rise rates of peristaltic pump with 0.3mmHg/ millisecond speed, Now, the pwm signal that PWM controller sends 10%～30% variable impulse width to peristaltic pump carries out closed loop control, Peristaltic pump rotates forward and pressurizes；

S2: the pulse wave peak value detected when microcontroller begins to decline and reaches the 50% of peak-peak, micro-control Device processed sends Rapid degassing by PWM controller to peristaltic pump and instructs, and now, PWM controller is to peristaltic pump The pulse sending dutycycle 80% carries out opened loop control, and peristaltic pump reversely rotates, until the pressure signal of detection is 0.

A kind of pressure control circuit for blood pressure measurement the most according to claim 1, it is characterised in that Described signal amplifier is AD620 chip.

A kind of pressure control circuit for blood pressure measurement the most according to claim 1, it is characterised in that Described pulse signal extracts circuit and includes analog band-pass filter and emitter follower, described analog bandpass filtering The input of device connects the outfan of pressure signal amplifier, and outfan connects the input of emitter follower, described Emitter follower outfan connect microcontroller the second input, described emitter follower is LM358 Chip.

A kind of pressure control circuit for blood pressure measurement the most according to claim 1, it is characterised in that Described microcontroller is STM32f103 chip.

A kind of pressure control circuit for blood pressure measurement the most according to claim 1, it is characterised in that Described pressure transducer is MD-PSG010 chip.

A kind of pressure control circuit for blood pressure measurement the most according to claim 1, it is characterised in that Described PWM controller is L293B chip.

A kind of pressure control circuit for blood pressure measurement the most according to claim 1, it is characterised in that Described closed loop control is: contrasted with the pressure distribution curve preset by the pressure signal of feedback, if there being error, After being adjusted by pi regulator, PWM controller send corresponding pulses to peristaltic pump.