KR102737818B1 - Method, device and non-transitory computer-readable recording medium for measuring photoplethysmography signal in wearable device - Google Patents

Abstract

According to one aspect of the present invention, a method for measuring a photoplethysmogram (PPG) signal in a wearable device is provided, the method including the steps of: obtaining a biosignal regarding a pulse wave measured from a body part on which the wearable device is worn; calculating a magnitude of a DC component included in the biosignal; and adjusting the DC component included in the biosignal with reference to the magnitude of the DC component and a reference value.

Description

METHOD, DEVICE AND NON-TRANSITORY COMPUTER-READABLE RECORDING MEDIUM FOR MEASURING PHOTOPLETHYSMOGRAPHY SIGNAL IN WEARABLE DEVICE

The present invention relates to a method, a device, and a non-transitory computer-readable recording medium for measuring a photoplethysmogram signal in a wearable device.

In recent years, wearable monitoring devices that continuously measure bio-signal data and help monitor the user's health status remotely have been developed and popularized, which is causing many changes not only in the medical environment but also in daily life.

When measuring biosignals within a medical institution, sensors can be directly applied to body parts (e.g., head, chest, stomach, back, fingers, toes, earlobes, etc.) where measurement accuracy or efficiency is high. However, since wearable monitoring devices must measure biosignals continuously over a long period of time, there is a constraint that biosignals must be measured within a range that does not interfere with the user's daily life.

Specifically, the photoplethysmogram (PPG) signal is a signal obtained by measuring light reflected, scattered, or transmitted from hemoglobin inside blood vessels or biological tissues, and the signal value may change according to changes in the volume of the blood vessels. Conventionally, the photoplethysmogram was measured using a sensor attached in a clamp-like shape to the tip of the finger where the capillary network is located, but this type of sensor has a limitation in that it is difficult to apply to wearable devices due to the great inconvenience felt by users in daily life. Therefore, a sensor suitable for wearable devices that can be worn all the time, such as a wristwatch, and a measurement technology using the sensor are required.

In particular, other body parts (such as the wrist) to which wearable devices can be attached often do not have capillary networks, unlike the fingertips or earlobes, and arterial blood vessels are often located relatively deeper, making it difficult to measure biosignals related to blood flow, and the intensity of the measured signals is very small. Therefore, technological means to resolve this are required.

Accordingly, the inventor(s) of the present invention propose a novel and advanced technology that prevents distortion or loss of a biosignal even when the intensity of the biosignal is amplified by controlling a direct current component included in a biosignal measured by a wearable device worn by a subject, and further enables accurate measurement of photoplethysmography (PPG).

Republic of Korea Patent Publication No. 10-2016-0147899

The present invention aims to solve all of the problems described above.

In addition, the present invention has another purpose of providing a method, a device, and a non-transitory computer-readable recording medium capable of accurately measuring a biosignal regarding a pulse wave by obtaining a biosignal regarding a pulse wave measured from a body part on which a wearable device is worn, calculating the size of a DC component included in the biosignal, and adjusting the DC component included in the biosignal with reference to the size of the DC component and a reference value.

A representative configuration of the present invention to achieve the above purpose is as follows.

According to one aspect of the present invention, a method for measuring a photoplethysmogram (PPG) signal in a wearable device is provided, the method including the steps of: obtaining a biosignal regarding a pulse wave measured from a body part on which the wearable device is worn; calculating a magnitude of a DC component included in the biosignal; and adjusting the DC component included in the biosignal with reference to the magnitude of the DC component and a reference value.

According to another aspect of the present invention, a device for measuring a photoplethysmogram (PPG) signal in a wearable device is provided, the device including a signal acquisition unit for acquiring a biosignal regarding a pulse wave measured from a body part on which the wearable device is worn, and a signal processing unit for calculating a magnitude of a DC component included in the biosignal and adjusting the DC component included in the biosignal with reference to the magnitude of the DC component and a reference value.

In addition, other methods for implementing the present invention, devices and non-transitory computer-readable recording media for recording a computer program for executing the method are further provided.

According to the present invention, since the DC component included in the biosignal measured from the body part on which the wearable device is worn can be adaptively adjusted, the effect of preventing the biosignal from being distorted or lost even when the intensity of the biosignal is amplified is achieved.

In addition, according to the present invention, since the DC component of the biosignal regarding the pulse can be adjusted in a direction that matches the level required by the wearable device, sensor, external device or server, the effect of being able to accurately measure the photoplethysmogram (PPG) signal is achieved.

In addition, according to the present invention, since a reference value that serves as a criterion for controlling a DC component included in a biosignal can be determined using a machine learning-based decision model, the effect of controlling a DC component included in a biosignal by considering various factors such as the characteristics of the subject, the measurement environment, and system requirements is achieved.

Figure 1 is a drawing schematically showing the configuration of the entire system according to the present invention.
FIG. 2 is a drawing exemplarily showing the internal configuration of a wearable device (200) according to one embodiment of the present invention.

The detailed description of the present invention set forth below refers to the accompanying drawings which illustrate specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It should be understood that the various embodiments of the present invention, while different from one another, are not necessarily mutually exclusive. For example, specific shapes, structures, and features described herein may be implemented in other embodiments without departing from the spirit and scope of the invention. It should also be understood that the positions or arrangements of individual components within each disclosed embodiment may be changed without departing from the spirit and scope of the invention. Accordingly, the following detailed description is not intended to be limiting, and the scope of the invention is defined only by the appended claims, along with the full scope of equivalents to which such claims are entitled, if any. Like reference numerals in the drawings designate the same or similar functionality throughout the several aspects.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings so that a person skilled in the art to which the present invention pertains can easily practice the present invention.

Composition of the entire system

Figure 1 is a drawing schematically showing the configuration of the entire system according to the present invention.

As illustrated in FIG. 1, the entire system according to one embodiment of the present invention may be composed of a communication network (100), a wearable device (200), and an external device or server (300).

First, a communication network (100) according to one embodiment of the present invention can be configured regardless of the communication mode, such as wired communication or wireless communication, and can be configured as various communication networks, such as a local area network (LAN), a metropolitan area network (MAN), and a wide area network (WAN).

Preferably, the communication network (100) referred to in the present specification may be a personal area network (PAN) that implements a communication method such as Bluetooth communication (more specifically, Bluetooth Low Energy (BLE)), ANT+, Zigbee, etc., at least in part.

However, the communication network (100) is not necessarily limited thereto and may include, at least in part, a known wired/wireless data communication network, a known telephone network, or a known wired/wireless television communication network. For example, the communication network (100) may be a wireless data communication network that implements, at least in part, a conventional communication method such as radio frequency (RF) communication, WiFi communication, cellular (LTE, etc.) communication, infrared communication, or ultrasonic communication.

Next, a wearable device (200) according to one embodiment of the present invention obtains a biosignal regarding a pulse wave measured from a body part on which the wearable device (200) is worn, calculates the size of a DC component included in the biosignal, and adjusts the DC component included in the biosignal by referring to the size of the DC component and a reference value, thereby performing a function of accurately measuring a photoplethysmogram signal.

A wearable device (200) according to one embodiment of the present invention is a digital device that includes a function for communicating after being connected to an external device or server (300), and any digital device having a memory means and a microprocessor and having a computing capability can be adopted as the wearable device (200) according to the present invention. The wearable device (200) may be a type of device such as a smart watch, a smart patch, a smart band, or smart glasses, but may also be a somewhat traditional device such as a smart phone, a smart pad, a desktop computer, a notebook computer, a workstation, a PDA, a web pad, or a mobile phone.

In addition, according to one embodiment of the present invention, the wearable device (200) may further include an application program for performing a function according to the present invention. Such an application may exist in the form of a program module within the wearable device (200). Here, at least a part of the application may be replaced with a hardware device or firmware device that can perform a function substantially identical to or equivalent to it, as necessary.

The functions of the wearable device (200) will be described in more detail below. Meanwhile, although the wearable device (200) has been described as above, this description is exemplary, and it is obvious to those skilled in the art that at least some of the functions or components required for the wearable device (200) may be realized within an external device or server (300) or included within an external device or server (300) as needed.

Composition of wearable devices

Below, the internal configuration of a wearable device (200) that performs important functions for implementing the present invention and the functions of each component will be examined.

FIG. 2 is a drawing exemplarily showing the internal configuration of a wearable device according to one embodiment of the present invention.

Referring to FIG. 2, a wearable device (200) according to one embodiment of the present invention may include a signal acquisition unit (210), a signal processing unit (220), a communication unit (230), and a control unit (240). According to one embodiment of the present invention, at least some of the signal acquisition unit (210), the signal processing unit (220), the communication unit (230), and the control unit (240) may be program modules that communicate with an external device or server (300). These program modules may be included in the wearable device (200) in the form of an operating system, an application program module, and other program modules, and may be physically stored on various known memory devices. In addition, these program modules may be stored in a remote memory device that can communicate with the wearable device (200). Meanwhile, these program modules include, but are not limited to, routines, subroutines, programs, objects, components, data structures, etc. that perform specific tasks or execute specific abstract data types to be described later according to the present invention.

First, according to one embodiment of the present invention, the signal acquisition unit (210) can acquire a biosignal regarding a pulse wave measured by a wearable device worn by a subject.

Specifically, according to one embodiment of the present invention, when a light source (not shown) included in a wearable device worn by a subject irradiates light to a body part of the subject (e.g., a wrist part, etc.), a sensor (not shown) included in the wearable device can sense light reflected, transmitted, or scattered from body tissue (e.g., a blood vessel, etc.) present in the body part, and a photoplethysmography (PPG) signal can be measured based on the light signal sensed in this way.

In addition, according to one embodiment of the present invention, the signal acquisition unit (210) can acquire a first biosignal measured in a situation where light is irradiated from a light source and a second biosignal measured in a situation where light is not irradiated from a light source and only an ambient light source exists, and can remove a noise component caused by the ambient light source from the first biosignal by referring to the first biosignal and the second biosignal acquired as described above.

Next, according to one embodiment of the present invention, the signal processing unit (220) can calculate the size of the DC component included in the photoplethysmography signal measured and acquired by the wearable device, and can adjust the size of the DC component included in the photoplethysmography signal with reference to the size of the DC component calculated as described above and the reference value. Here, according to one embodiment of the present invention, the size adjustment of the DC component can be achieved by adjusting the feedback current.

Specifically, according to one embodiment of the present invention, the signal processing unit (220) can reduce the size of the DC component by adjusting the feedback current in response to the size of the DC component included in the photoplethysmogram signal being greater than a first reference value (e.g., an upper limit of the reference range), and conversely, can increase the size of the DC component by adjusting the feedback current in response to the size of the DC component included in the photoplethysmogram signal being smaller than a second reference value (e.g., a lower limit of the reference range).

Furthermore, according to one embodiment of the present invention, the signal processing unit (220) can reduce the DC component by controlling the feedback current until the size of the DC component included in the photoplethysmogram signal becomes smaller than a first reference value, and conversely, can increase the DC component by controlling the feedback current until the size of the DC component included in the photoplethysmogram signal becomes larger than a second reference value.

In addition, according to one embodiment of the present invention, a reference value or reference range that serves as a reference for adjusting the size of a DC component included in a photoplethysmographic signal can be adaptively determined based on various factors.

For example, the above reference values or reference ranges can be adaptively determined based on the system requirements of a wearable device that measures photoplethysmography signals or the system requirements required by an external device or server that interfaces with the wearable device.

As another example, the above reference value or reference range can be adaptively determined based on the ratio between the magnitude of the AC component and the magnitude of the DC component included in the photoplethysmographic signal.

As another example, the above reference values or reference ranges can be adaptively determined based on information about the subject's physical characteristics (hemodynamic characteristics) or activity status.

As another example, the above reference values or reference ranges can be adaptively determined based on contextual information about the measurement environment (ambient light source, measurement time zone, measurement location, etc.).

Meanwhile, according to one embodiment of the present invention, a machine learning-based decision model may be constructed that is learned based on learning data regarding various factors including system requirements, the ratio between the magnitude of the AC component and the magnitude of the DC component, the physical characteristics or activity state of the subject, the measurement environment, and the like, and learning data regarding a reference value or reference range of the magnitude of the DC component that prevents the photoplethysmogram signal from being distorted or lost even when the signal is amplified. Accordingly, the signal processing unit (220) according to one embodiment of the present invention can dynamically adjust the magnitude of the DC component included in the photoplethysmogram signal with reference to the reference value or reference range determined by the machine learning-based decision model as described above.

Meanwhile, according to one embodiment of the present invention, the signal processing unit (220) can generate a photoplethysmogram signal having a sufficient level of intensity that can be utilized for measurement or analysis by amplifying the photoplethysmogram signal, the size of which is adjusted for the DC component as described above, without distortion or loss.

Meanwhile, the communication unit (230) according to one embodiment of the present invention performs a function that enables the wearable device (200) to communicate with an external device.

Finally, the control unit (240) according to one embodiment of the present invention performs a function of controlling the flow of data between the signal acquisition unit (210), the signal processing unit (220), and the communication unit (230). That is, the control unit (240) controls the flow of data from the outside or between each component of the wearable device (200), thereby controlling the signal acquisition unit (210), the signal processing unit (220), and the communication unit (230) to perform their respective functions.

In the above, the embodiment of controlling the DC component included in the photoplethysmographic signal has been mainly described, but it should be noted that the present invention is not necessarily limited to the above embodiment, and it is also possible to control the DC component included in other types of biosignals within the scope that can achieve the purpose of the present invention.

The embodiments of the present invention described above may be implemented in the form of program commands that can be executed through various computer components and recorded on a non-transitory computer-readable recording medium. The non-transitory computer-readable recording medium may include program commands, data files, data structures, etc., alone or in combination. The program commands recorded on the non-transitory computer-readable recording medium may be those specially designed and configured for the present invention or may be those known to and available to those skilled in the art of computer software. Examples of the non-transitory computer-readable recording medium include magnetic media such as hard disks, floppy disks, and magnetic tapes, optical recording media such as CD-ROMs and DVDs, magneto-optical media such as floptical disks, and hardware devices specially configured to store and execute program commands such as ROMs, RAMs, and flash memories. Examples of program commands include not only machine language codes generated by a compiler, but also high-level language codes that can be executed by a computer using an interpreter, etc. The above hardware device may be configured to operate as one or more software modules to perform processing according to the present invention, and vice versa.

Although the present invention has been described above with specific details such as specific components and limited examples and drawings, these have been provided only to help a more general understanding of the present invention, and the present invention is not limited to the above examples, and those with common knowledge in the technical field to which the present invention belongs can make various modifications and variations from this description.

Therefore, the idea of the present invention should not be limited to the embodiments described above, and not only the claims described below but also all modifications equivalent to or equivalent to the claims are included in the scope of the idea of the present invention.

100: Communication network
200: Wearable Devices
210: Signal acquisition unit
220: Signal Processing Unit
230: Communications Department
240: Control Unit
300: External device or server

Claims (13)

A method for measuring photoplethysmography (PPG) signals in a wearable device,
A step of obtaining a biosignal regarding pulse waves measured from a body part on which a wearable device is worn;
A step of calculating the size of the DC component included in the above biosignal, and
A step of controlling the DC component included in the biosignal by referring to the size of the DC component, the first reference value and the second reference value,
The first and second reference values are determined by a machine learning-based decision model that is learned based on data on at least one of system requirements, a ratio between the magnitude of an AC component included in a photoplethysmogram signal and the magnitude of a DC component, physical characteristics or activity state of a subject, and a measurement environment, and data on the magnitude of a DC component that allows a photoplethysmogram signal to be amplified without being distorted or lost.
In the above control step, the size of the DC component included in the biosignal is dynamically controlled by decreasing the DC component in response to the size of the DC component being greater than the first reference value, and increasing the DC component in response to the size of the DC component being smaller than the second reference value.
The step of generating a photoplethysmographic signal by amplifying the biosignal whose intensity of the direct current component is controlled is further included.
method. In the first paragraph,
In the above acquisition step, a first biosignal measured in a situation where light is irradiated from a light source and a second biosignal measured in a situation where light is not irradiated from a light source and only an ambient light source exists are acquired, and a noise component caused by the ambient light source is removed from the first biosignal by referring to the first biosignal and the second biosignal.
method. delete In the first paragraph,
In the above control step, the DC component is reduced until the size of the DC component becomes smaller than the first reference value, or the DC component is increased until the size of the DC component becomes larger than the second reference value.
method. delete delete A non-transitory computer-readable recording medium having recorded thereon a computer program for executing the method according to Article 1. A device for measuring photoplethysmography (PPG) signals in a wearable device,
A signal acquisition unit for acquiring a biosignal regarding a pulse wave measured from a body part on which a wearable device is worn, and
It includes a signal processing unit that calculates the size of the DC component included in the biosignal and adjusts the DC component included in the biosignal by referring to the size of the DC component, the first reference value, and the second reference value.
The first and second reference values are determined by a machine learning-based decision model that is learned based on data on at least one of system requirements, a ratio between the magnitude of an AC component included in a photoplethysmogram signal and the magnitude of a DC component, physical characteristics or activity state of a subject, and a measurement environment, and data on the magnitude of a DC component that allows a photoplethysmogram signal to be amplified without being distorted or lost.
The signal processing unit dynamically adjusts the size of the DC component included in the biosignal by reducing the DC component in response to the size of the DC component being greater than the first reference value and increasing the DC component in response to the size of the DC component being smaller than the second reference value.
The above signal processing unit generates a photoplethysmographic signal by amplifying the biosignal whose intensity of the direct current component is controlled.
Device. In Article 8,
The above signal acquisition unit acquires a first biosignal measured in a situation where light is irradiated from a light source and a second biosignal measured in a situation where light is not irradiated from a light source and only an ambient light source exists, and removes a noise component caused by the ambient light source from the first biosignal by referring to the first biosignal and the second biosignal.
Device. delete In Article 8,
The signal processing unit reduces the DC component until the size of the DC component becomes smaller than the first reference value, or increases the DC component until the size of the DC component becomes larger than the second reference value.
Device. delete delete