CN111744072A

CN111744072A - Air pressure detection system and method for electric infusion pump

Info

Publication number: CN111744072A
Application number: CN202010404001.8A
Authority: CN
Inventors: 王亚刚; 丁大民
Original assignee: University of Shanghai for Science and Technology
Current assignee: University of Shanghai for Science and Technology
Priority date: 2020-05-13
Filing date: 2020-05-13
Publication date: 2020-10-09

Abstract

The invention provides an air pressure detection system and method for an electric infusion pump, wherein the system comprises: the pressure sensor is used for monitoring the atmospheric pressure environment to be measured, the pressure sensor is connected to the ADC module through a filter circuit, the ADC module is connected to the MCU, and the filter circuit is a five-order Butterworth filter circuit. The air pressure detection method provided by the invention takes N sampling values which are continuously obtained as a queue T, the length of the queue is fixed to N, a new data which is adopted each time is put into the tail of the queue, a primary data of the original head of the queue is removed, and the N data in the queue are subjected to arithmetic mean operation to obtain a new filtering result. The air pressure detection system of the electric infusion pump based on the field of medical instruments realizes the advantages of less time lag of air pressure monitoring, accurate monitoring, capability of aiming at the rotation of a peristaltic pump and effective noise resistance.

Description

Air pressure detection system and method for electric infusion pump

Technical Field

The invention relates to the technical field of medical treatment, in particular to an air pressure detection system and method for an electric infusion pump.

Background

Nephrology, etc., renal dialysis and treatment of CRRT all require the use of electrically powered infusion pumps to precisely control infusion volume and infusion rate. In this case, a multi-electric pump linkage is often used. The device needs pressure monitoring due to direct contact with a human body, so as to monitor the working state of the device in real time and judge whether the device and a pipeline channel normally operate, in particular to an electric pump directly acting on the human body, and fig. 1 shows a bubble sensor AD1, a blood leakage sensor LD1, blood sampling pressure PACC, a heparin pump SP, arterial pressure PA, venous pressure PV, a blood leakage sensor LD2, a waste liquid pump pressure P1ST, a waste liquid pump FP, a substitution liquid pump RP, a heating plate HT, a balance cavity pressure P2ND, a balance weight WT, a bubble sensor AD2, a waste liquid bag P1 and a fluid infusion bag P2, wherein the BP pump is used for drawing blood from the human body, passing through a dialyzer and finally returning the blood to the human body. The electric pump is used for infusing medicine/liquid medicine into human body, the pressure of the contact side of the infusion pump and the human body must be monitored at any time in the two processes, such as Pacc blood pressure collection, Pa arterial pressure and Pv venous pressure interfaces in figure 1, and the domestic electric infusion pump is connected with the pressure interface of a venous pot and used for connecting a pressure sensor and pipeline consumables.

The human blood pressure itself is maintained by the blood dynamics, which can be understood as a physical quantity that changes weakly at a moment, and after the electric infusion pump/peristaltic pump is connected, the noise of the pressure value becomes larger correspondingly. The products on the market at present are analog output ports of pressure sensors, hardware first-order RC filtering is added, digital algorithms such as undifferentiated mean filtering and the like are adopted in a software part, and finally obtained values are used as pressure values which can be called and inquired when the whole equipment runs.

Fig. 2 is a current air pressure detection system, a pressure environment to be detected enters a pressure sensor through a pipeline consumable material and a protection luer head, the pressure sensor collects a pressure physical signal, generates an analog electrical signal, sends the analog electrical signal into an analog-to-digital conversion module ADC through a first-order RC filter circuit module, sends a signal after hardware filtering and conversion into a processor, and finally obtains a pressure value through software algorithm processing.

The prior art has the main defects that a first-order RC filter circuit commonly used in the industry is applied and matched with a common digital filter algorithm, and the industry-specific optimization is not performed on the electric infusion pump. Although the prior art can obtain a more stable and less-noise signal than that before filtering, the effect on the low-frequency pulse generated by the continuous rotation of the peristaltic pump and the noise generated by the continuous rotation of the peristaltic pump is not very ideal.

Disclosure of Invention

The invention aims to provide an air pressure detection system and method for an electric infusion pump, which can realize the purposes of less time lag of air pressure detection, accurate monitoring, and effective noise resistance aiming at the rotation of a peristaltic pump.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows: an air pressure detection system for an electric infusion pump, comprising: the pressure sensor is used for monitoring the atmospheric pressure environment to be measured, the pressure sensor is connected to the ADC module through a filter circuit, the ADC module is connected to the MCU, and the filter circuit is a five-order Butterworth filter circuit.

Further, the fifth order butterworth filter circuit comprises a first portion, a second portion, and a third portion; the first part comprises a first-order low-pass RC filter and is used as signal following through a 1: 1-time operational amplifier; the second and third parts are two sets of second order low-pass Sallen Key structure filters.

Further, the operational amplifier is LM358 or AD 620.

The method uses continuously obtained N sampling values as a queue T, the length of the queue is fixed to be N, new data is used each time and put into the tail of the queue, primary data of the original head of the queue is removed, and the N data in the queue are subjected to arithmetic mean operation to obtain a new filtering result.

Further, the value of N is equal to the total number of pipelines pressed by a pressure spring of the peristaltic pump within 1 s.

Further, when the rotating speed k of the peristaltic pump of the direct-current brushless motor with the diameter of 36mm is less than 3000 revolutions, the value of N is 4;

when k is more than 3000 and less than 6000, N is 5.

Compared with the prior art, the invention has the advantages that: the air pressure detection system of the electric infusion pump based on the field of medical instruments realizes the advantages of less time lag of air pressure monitoring, accurate monitoring, capability of aiming at the rotation of a peristaltic pump and effective noise resistance.

Drawings

FIG. 1 is a schematic diagram of a CRRT apparatus of the background art.

Fig. 2 is a schematic diagram of a conventional air pressure detection system in the background art.

Fig. 3 is a schematic diagram of a pressure detection system for an electric infusion pump according to an embodiment of the present invention.

FIG. 4 is a parameter diagram of a five-stage Butterworth (3-stage) circuit according to an embodiment of the present invention, and the Amplifier in FIG. 4 represents an operational Amplifier.

FIG. 5 is a diagram of an LM324 single-power four-way operational amplifier according to an embodiment of the present invention.

FIG. 6 is a graph of the response of a five-step Butterworth structure, wherein (a) is a Bode plot, (b) is a voltage magnitude response plot, and (c) is a step response plot.

Fig. 7 is a diagram of time-domain signals and signals after filtering in simulation and actual use, wherein (a) is the time-domain signal diagram, and (b) is the signal diagram after filtering by moving average filtering.

Fig. 8 is a diagram of a time-domain signal and a signal after filtering.

Detailed Description

The technical solution adopted by the present invention will be further explained with reference to the schematic drawings.

A first embodiment of the present invention provides a pressure detection system for an electric infusion pump, see fig. 3, comprising: a pressure sensor for monitoring the atmospheric pressure environment that awaits measuring, the atmospheric pressure environment that awaits measuring passes through the pipeline consumptive material, through a protection luer head, gets into pressure sensor, pressure sensor passes through filter circuit and connects in the ADC module, the ADC module is connected in MCU, and pressure sensor gathers pressure physical signal, produces the analog signal of telecommunication, through the filter circuit module, sends into analog-to-digital conversion module ADC, sends into the treater with the signal after hardware filtering and conversion, handles through software algorithm again, finally obtains the pressure value. It is worth mentioning that the filter circuit is a five-order butterworth (3-order) filter circuit.

With reference to fig. 4, the fifth order butterworth filter circuit is divided into three sections, including a first section, a second section, and a third section. The first part comprises a first-order low-pass RC filter and is used as signal following through a 1: 1-time operational amplifier, and the signal strength is ensured not to be weakened. The second and third parts are two sets of second order low-pass Sallen Key structure filters. The three parts form a fifth-order Butterworth filter together. The values of the capacitor and the resistor are shown in fig. 4, and the operational amplifier may be a commercially available signal operational amplifier, such as LM358, AD620, etc., in which case LM324 (see fig. 5) is used.

After the improvement of the hardware structure, the response curve of the fifth-order Butterworth structure used in the scheme is shown in figure 6, and the response curve shows that the low-pass passband is-3 dB and is lower than 5kHz, the stopband is higher than 20kHz, and the signal is linearly reduced in the middle of 5-20 kHz.

The second embodiment of the invention provides an air pressure detection method for an electric infusion pump, which takes continuously acquired N sampling values as a queue T, the length of the queue is fixed to N, new data is taken each time and put into the tail of the queue, primary data (first-in first-out principle) of the original head of the queue is removed, and the N data in the queue are subjected to arithmetic mean operation to obtain a new filtering result.

In the software algorithm, the traditional mean value algorithm is improved into a sliding average filtering method, the value of N is changed according to the rotation speed of the peristaltic pump, the value of N is equal to the total number of the pressure springs of the peristaltic pump pressing the pipeline within 1s, and the value of N is a dynamic change quantity. Generally, when the rotation speed of a dc brushless motor peristaltic pump (used in the present case) with phi of 36mm is less than 3000 revolutions, the reduction ratio of the speed reducer is 1: 117, N is 4; the rotating speed is higher than 3000 revolutions and lower than 6000 revolutions, and the value of N is 5.

After the software algorithm part is improved, in the simulation and actual use process, time domain signals and filtered signals are shown in fig. 7. As can be seen from fig. 8, the algorithm has a good suppression effect on periodic interference, high smoothness, and excellent performance on the time lag problem compared to the time domain signal.

The above description is only a preferred embodiment of the present invention, and does not limit the present invention in any way. It will be understood by those skilled in the art that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. An air pressure detection system for an electric infusion pump, comprising: the pressure sensor is used for monitoring the atmospheric pressure environment to be measured, the pressure sensor is connected to the ADC module through a filter circuit, the ADC module is connected to the MCU, and the pressure sensor is characterized in that the filter circuit is a five-order Butterworth filter circuit.

2. A pressure detection system for an electrical infusion pump according to claim 1, wherein said fifth order butterworth filter circuit comprises a first portion, a second portion, a third portion;

the first part comprises a first-order low-pass RC filter and is used as signal following through a 1: 1-time operational amplifier;

the second and third parts are two sets of second order low-pass Sallen Key structure filters.

3. A pressure sensing system for an electrical infusion pump according to claim 2, wherein the operational amplifier is LM358 or AD 620.

4. The air pressure detection method for the electric infusion pump is characterized in that N sampling values obtained continuously are used as a queue T, the length of the queue is fixed to be N, new data is used for each time and is placed at the tail of the queue, primary data of the original queue head is removed, and the N data in the queue are subjected to arithmetic mean operation to obtain a new filtering result.

5. The method as claimed in claim 4, wherein the value of N is equal to the total number of the compression springs of the peristaltic pump pressing the tube in 1 s.

6. The method as claimed in claim 5, wherein when the speed k of the peristaltic pump with the DC brushless motor having a diameter of 36mm is less than 3000 rpm, the value of N is 4;

when k is more than 3000 and less than 6000, N is 5.