Method for determining posture of measurement target

Abstract

The direction opposite to the gravity is defined as the y-axis direction. The z-axis direction is defined according to a local coordinate system of a geomagnetic sensor. One of the y-axis and z-axis, which has a small value among angles between the y-axis and z-axis, is defined as the Y-axis direction. An axis corresponding to the vector product between the X-axis direction and the Y-axis is defined as the Z-axis direction. A conversion coordinate system is defined on the basis of the above definition of axes. Acceleration values (aX, aY & aZ) are measured with regard to the X-axis direction, Y-axis direction, and Z-axis direction according to the conversion coordinate system by using an acceleration sensor. Thereafter, respective distances between the coordinates of the measured accelerations and the coordinates of posture-specific reference acceleration values (aX0, aY0 & aZ0) stored in a data storage unit, based on the conversion coordinate system, are calculated on the conversion coordinate system, and it is determined that the posture corresponding to the minimum value of the distances is the determined posture. Accordingly, the measurement target's postures can be easily determined.

Description

Method for determining the subject's body position

[0001] Embodiments of the present invention relate to a method for determining the body position of a subject. More specifically, embodiments of the present invention relate to a method for determining the body position of a subject, wherein a mobile device including a sensor is attached to the body of the subject and the body position of the subject is determined using acceleration values ​​measured from the sensor.

[0002] The two factors that determine human posture are muscles and ligaments. Ligaments transmit muscle strain to the skeletal system in the form of tension, so their elastic deformation range is relatively limited. In contrast, muscles, with their wide elastic deformation range, largely determine human posture.

[0003] The muscles mentioned above are divided into voluntary muscles and involuntary muscles. The somatic and autonomic nervous systems, which determine the contraction and relaxation of voluntary and involuntary muscles, are affected by various diseases and psychological conditions.

[0004] In daily life, the body's posture, or position, is closely related to a specific disease that affects the somatic nervous system and autonomic nervous system.

[0005] For example, a person with depression may feel low in energy and lethargic, leading them to sit more or spend long periods in bed. This may be related to a reduced activity level. Clinicians have observed a tendency to hunched over, often in a hunched posture (hereafter referred to as "slumping"), a behavior that reflects emotional distress.

[0006] Additionally, symptoms such as muscle pain and headaches can affect your posture and ability to perform daily activities. Research has also shown that certain postures can influence emotions. Positive posture can elicit positive emotions, while negative posture can amplify negative emotions.

[0007] Furthermore, arthritis is also closely related to movement and posture. Arthritis is a disease characterized by inflammation and damage to joints, which can affect movement and posture. Arthritis restricts movement due to inflammation and deformation around the joints, which tends to limit postures in high-activity areas. Arthritis patients often seek comfortable positions to relieve pain, leading to changes in posture compared to before the disease. For example, patients with knee arthritis may walk with their legs bent to reduce the load on their knees.

[0008] Meanwhile, in the medical field, it is recognized that it is important to understand human physiological functions by monitoring the correlation between disease and posture, and patients' postures and movements are analyzed in the form of posturography and actigraphy.

[0009] Actigraphy is primarily used in sleep medicine and research to study sleep patterns, circadian rhythms, and overall activity levels. Actigraphy is used to monitor and analyze a person's rest-activity cycle and sleep-wake patterns over long periods of time. It uses a small wrist-worn device (actigraph) equipped with an accelerometer to record movement patterns.

[0010] Additionally, posturography is used to assess the balance and postural stability of patients with balance disorders or vestibular problems. It is measured based on a specialized platform equipped with sensors to measure the center of pressure and sway of a person under various sensory conditions, and is used in the diagnosis and evaluation of balance disorders or spatial orientation problems.

[0011] Although actigraphy and postrography have different purposes, they have in common that they provide useful information that can help in the diagnosis and treatment of various health conditions, and in particular, both analyses require a means to closely examine the patient's posture, i.e., body position.

[0012] Meanwhile, smartphones contain a variety of sensors, including accelerometers, gyroscopes, magnetometers, Hall sensors, thermometers, hygrometers, contact-type PPG sensors, light meters, RGB sensors, microphones, proximity sensors, motion sensors, barometers, and fingerprint sensors. With recent technological advancements, smartwatches also support mobile phone functions and incorporate the same sensors found in smartphones.

[0013] Additionally, smart bracelets and rings have a limited number of built-in sensors compared to smartphones or smartwatches due to space and power constraints, but products designed to deliver optimal performance through appropriate selection according to needs are entering the market.

[0014] Meanwhile, applications that calculate calories stored in the body by storing information about the food consumed and calculate calories burned by measuring the amount of exercise based on a gyroscope or vibration sensor also use information such as body temperature, pulse, and oxygen saturation for more efficient calorie management.

[0015] Accelerometers, gyroscopes, and geomagnetic sensors, which measure momentum using information about acceleration generated from human body movements, are mostly integrated into a single IC.

[0016] Figure 1 is a photograph defining the x-axis direction, y-axis direction, and z-axis direction according to the local coordinate system of the mobile device.

[0017] Referring to Figure 1, both the Android OS and the iOS system that runs the iPhone use the same coordinate system. That is, when the phone is placed on a flat surface with the screen facing up, the direction from the floor through the display is the z-axis, and the counterclockwise rotation around the z-axis is the yaw momentum. In addition, when the phone is held upright, the direction from left to right is the x-axis, and the counterclockwise rotation around the x-axis is called the pitch. At this time, the direction from the bottom to the top of the phone when held upright is the y-axis, and the amount of rotation around the y-axis is defined as the roll. The direction in which the rotational momentum increases for each axis is the direction pointed by the remaining four fingers when the positive direction of the axis is aligned with the thumb and grasped.

[0018] Therefore, the accelerometer / gyro / magnetic sensor installed inside the mobile phone all use the same axis definition. In the following specification, the x-axis direction, y-axis direction, and z-axis direction of FIG. 1 are each defined as the local coordinate system of the sensor.

[0019] Furthermore, when there is no external force acting on the mobile phone, the sum of the three-axis acceleration vectors in the x, y, and z directions displayed by the mobile phone's accelerometer is always equal to the acceleration due to gravity. This can be used to measure how much the mobile phone is tilted with respect to the ground plane whose normal vector is the direction of gravity. The azimuth value, which indicates how much the mobile phone is rotated on a plane perpendicular to gravity, cannot be determined with the accelerometer alone, and can be obtained by using a Kalman filter, a geomagnetic sensor that provides a reference for absolute coordinates, or GPS in combination.

[0020] Meanwhile, the importance of vital signs sensors mounted on smart devices in relation to sleep environment monitoring has increased.

[0021] The above vital signs sensors are used to identify sleep stages, diagnose sleep disorders, monitor sleep posture, and monitor vital signs. The sensors primarily used to identify sleep stages include accelerometers and geomagnetic sensors. Based on the signals from these sensors, if the amplitude and frequency of body movement decrease, sleep is determined to be deep, and if there is complete cessation of movement, it is considered to be rapid eye movement (REM) sleep. If continuous physical activity that is difficult to recognize as sleep is observed at a level that prevents normal sleep time, a sleep disorder is diagnosed. Identifying these states involves various systems, ranging from direct signal processing to machine learning-based AI.

[0022] The measurement targets include vibrations generated from hand and foot movements, breathing per minute, pulse per minute, and brain waves, and smart devices can measure most signals except brain waves.

[0023] However, when measuring biosignals using the various built-in sensors of existing smart devices, it is necessary to use an external device or the smart device itself to determine whether the subject is in a stable state. However, current smart devices measure vibration data values, and when the amplitude and frequency of the vibration decrease, and the duration of this state exceeds a certain level (30 seconds to 2 minutes), the smart device assumes that a stable state has been reached, and then operates the sensor to extract biometric information. However, determining the subject's state based solely on the amplitude and frequency of movement can lead to many errors.

[0024] Meanwhile, in the case of the Korean Patent No. 10-2528684 for which the applicant applied and was granted a patent, the gravitational acceleration vector acting on the human body is measured as a 3-axis local vector of the sensor, so in order to measure the angle of the human body using this, an inverse trigonometric function had to be used to calculate the 3-axis orthogonal projection value of the gravitational acceleration vector acting on the human body that contributed to the 3-axis acceleration value measured by the sensor.

[0025] That is, in order to determine the body angle, three inverse trigonometric calculations corresponding to each axis must be performed, and then the calculated angle must be compared with the corresponding body angle range to determine the posture. To calculate the arccos(x) value for the orthogonal projection, use the following mathematical expression 1 and the calculated values ​​up to the 13th order of the approximate series for the arccos(x) value.

[0026]

[0027] Although the performance of microprocessors has improved significantly in recent years, calculating the above-mentioned series and determining the posture for three axes requires more than 200 cycles of calculation per axis, so a time resolution of the microsecond level is required to determine emergency situations such as sudden falls.

[0028] In addition, even if fast calculations are possible by applying a floating point unit (FPU) to improve calculation speed, the battery capacity is limited due to the nature of wearable devices, so if the processor performs a lot of calculations, it becomes a direct cause of shortening the product usage time.

[0029] Embodiments of the present invention provide a method for determining the body position of a subject, which can determine the body position of the subject through a simple processing process using an acceleration value measured from a sensor by attaching a mobile device including a sensor to the body of the subject.

[0030] According to embodiments of the present invention for solving the above technical problem, in a method for determining the posture of a subject using a mobile device including an acceleration sensor and a geomagnetic sensor that can be fixed to the chest area of ​​a subject in a normal standing state and have the same local coordinate system, a transformation coordinate system is defined in which a direction extending from the right shoulder to the left shoulder when the subject is in a normal standing state is defined as the X-axis direction, one of the y-axis and the z-axis having a smaller value among the angles formed between the opposite direction of gravity and the y-axis and the z-axis according to the local coordinate system of the geomagnetic sensor is defined as the Y-axis direction, and an axis generated by the vector multiplication between the X-axis direction and the Y-axis is defined as the Z-axis direction, and a measured acceleration value (a) for each of the X-axis direction, the Y-axis direction, and the Z-axis direction according to the transformation coordinate system is defined using the acceleration sensor. X , a Y & a Z ) is secured. Then, on the above transformation coordinate system, the coordinates of the measured acceleration values ​​and the reference acceleration values ​​(a) for each posture stored in the data storage unit according to the above transformation coordinate system X0 , a Y0 & a Z0 ) are calculated, and the posture corresponding to the minimum value among the distances is determined as the judgment posture.

[0031] According to the embodiments of the present invention described above, a local coordinate system is transformed into a transformed coordinate system by using a geomagnetic sensor included in a mobile device fixed to a subject, and a body position corresponding to the minimum value among distance values ​​between a measured acceleration value of an acceleration sensor according to the transformed coordinate system and a reference acceleration value for each body position can be determined and a body position can be specified.

[0032] Figure 1 is a photograph defining the x-axis direction, y-axis direction, and z-axis direction according to the local coordinate system of the mobile device.

[0033] Figure 2 is a conceptual diagram illustrating a state in which a mobile device is fixed to the chest area of ​​a subject.

[0034] FIG. 3 is a flowchart illustrating a method for determining the body position of a subject according to one embodiment of the present invention.

[0035] Fig. 4 is a graph showing the reference acceleration value and measured acceleration value for each posture in the transformed coordinate system using the method for determining the posture of the subject of Fig. 3.

[0036] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. The present invention can be modified in various ways and can take various forms, and thus specific embodiments are illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to a specific disclosed form, but it should be understood that all modifications, equivalents, and substitutes included in the spirit and technical scope of the present invention are included. In describing each drawing, similar reference numerals are used to indicate similar components. In the attached drawings, the dimensions of structures are shown larger than actual size to ensure clarity of the present invention.

[0037] While terms like "first" and "second" may be used to describe various components, these components should not be limited by these terms. These terms are used solely to distinguish one component from another. For example, without departing from the scope of the present invention, a first component could be referred to as a "second component," and similarly, a second component could also be referred to as a "first component."

[0038] The terminology used in this application is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, it should be understood that the terms "comprise" or "have" indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0039] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and will not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0040] Figure 2 is a conceptual diagram illustrating a state in which a mobile device is fixed to the chest area of ​​a subject. Figure 3 is a flowchart illustrating a method for determining the body position of a subject according to one embodiment of the present invention.

[0041] A method for determining a subject's body position according to embodiments of the present invention utilizes a mobile device that is secured to the subject's chest and includes a sensor. The local coordinate system of the mobile device has been previously described with reference to FIG. 1, and thus a detailed description thereof will be omitted. Furthermore, the local coordinate system of the sensor is identical to that of the mobile device. The sensor includes an acceleration sensor and a geomagnetic sensor.

[0042] First, a coordinate system is defined in which the direction extending from the right shoulder to the left shoulder when the subject is standing normally is converted to the X-axis direction, one of the y-axis and the z-axis having a smaller value among the angles between the y-axis and the z-axis according to the local coordinate system of the geomagnetic sensor and the direction opposite to gravity is converted to the Y-axis direction, and an axis generated by the vector multiplication between the X-axis direction and the Y-axis is converted to the Z-axis direction (S110).

[0043] Next, using the acceleration sensor, the measured acceleration values ​​(a) for each of the X-axis direction, Y-axis direction, and Z-axis direction according to the transformed coordinate system X , a Y & a Z ) is secured (S120).

[0044] Here, the acceleration in the X-axis direction, which is the above-mentioned transformation coordinate system, is α x , the acceleration in the z-axis direction, which is the transformed coordinate system, is α z is defined as . At this time, the acceleration α in the y-axis direction y satisfies mathematical equations 2 and 3 below.

[0045]

[0046]

[0047]

[0048] That is, the sensor is subjected to a gravitational acceleration of 9.8 m / s^2 toward the center of the Earth, i.e., in the direction of gravity. This is because, when the mobile device is fixed near the chest of a standing subject, and the subject is standing, an acceleration of 9.8 m / s^2 is applied in the negative direction of the Z-axis, which is opposite to the direction of gravity.

[0049] Therefore, when using an acceleration sensor, the vector sum of the gravitational acceleration values ​​of the sensor in a standing state without any shaking of the subject is always a vector with a magnitude of 1G (9.8 m / sec2) and a direction of -Z. That is, α of a stationary accelerometer x, α y,α z The magnitude of the vector sum (the square root of the sum of the squares of the three values) always converges to the value 9.8.

[0050] Afterwards, on the above transformation coordinate system, the measured acceleration values ​​and the reference acceleration values ​​for each posture stored in the data storage unit according to the above transformation coordinate system (a X0 , a Y0 & a Z0 ) are calculated for each distance (S130). The standard acceleration values ​​for each posture (a X0 , a Y0 & a Z0 ) corresponds to Table 1 below.

[0051] Posture X-axis acceleration (a X0, g) Y-axis acceleration (a) Y0, g)Z-axis acceleration (a) Z0, g) Right angle standing 00.90.38 Right angle left half-100 Right angle right half-100 Sitting 0.0150.830.485 Fowler's position 0.20.650.7 Half Fowler's position 0.10.370.91 Supine 0.12-0.090.98 Trendelberg 0.1-0.40.9 Slump position 0.040.95-0.27 Prone 0.10.7-0.8

[0052]

[0053] That is, on the above transformation coordinate system, the measured acceleration values ​​and the reference acceleration values ​​for each posture stored in the data storage unit according to the above transformation coordinate system (a X0 , a Y0 & a Z0 ) are calculated for each distance between them. For example, in the first case, the second case, and the third case, the measured acceleration values ​​(a X , a Y & a Z ) can be represented in the transformed coordinate system as coordinates of (0.14, 0.37, 0.9), (0.15, -0.13,0.97), and (0.14,0.59,0.78).

[0054] Meanwhile, the sum of the orthogonal projections of the vector values ​​of the acceleration in each direction for the absolute coordinate system to the Z-axis direction of the existing measured acceleration values ​​is the acceleration value in the Z-axis direction (a Z ), the sum of the orthogonal projections on the Y-axis is the acceleration value in the Y-axis direction (a Y ), the sum of the orthogonal projections on the X-axis is the acceleration value in the X-axis direction (a X ) is defined. At this time, the absolute coordinate system is defined as the Z-axis direction with the opposite direction of gravity, the direction extending from the right shoulder to the left shoulder when the subject is standing normally as the X-axis direction, and the direction from which the Z-axis direction is derived when vector multiplying the X-axis direction is the Y-axis direction. To this end, in order to calculate the arccos(x) value for the orthogonal projection, it is required to calculate the values ​​up to the 13th order of the approximate series for the arccos(x) value and the above mathematical expression 1.

[0055] On the other hand, in the case of the posture determination method according to the embodiments of the present invention, in the transformation coordinate system, the measured acceleration values ​​and the posture-specific reference acceleration values ​​(a) stored in the data storage unit according to the transformation coordinate system X0 , a Y0 & a Z0 ) can measure the respective distances between them.

[0056] At this time, on the above transformation coordinate system, the standard acceleration values ​​for each posture (a X0 , a Y0 & a Z0 ) is shown in Fig. 4.

[0057] Fig. 4 is a graph showing the reference acceleration value and measured acceleration value for each posture in the transformed coordinate system using the method for determining the posture of the subject of Fig. 3.

[0058] Referring to Figure 4, the standard acceleration values ​​for each posture (a X0 , a Y0 & a Z0 ) has already been entered into the data storage.

[0059] Meanwhile, in the first, second and third cases, the measured acceleration values ​​(aX, aY & aZ) are expressed as coordinates of (0.14, 0.37, 0.9), (0.15, -0.13,0.97) and (0.14, 0.59,0.78) on the transformed coordinate system and the corresponding posture-specific reference acceleration values ​​(a X0 , a Y0 & a Z0 ) The distance between coordinates is calculated in Table 2 below.

[0060] Distance from (0.14, 0.37, 0.9) to each posture coordinate (case 1) Distance from (0.15, -0.13, 0.97) to each posture coordinate (case 2) Distance from (0.14, 0.59, 0.78) to each posture coordinate (case 3) Right angle Standing 0.57091.42590.2757 Right angle Left half 2.24651.71472.2561 Right angle Right hemisphere 1.68652.23471.6961 Left hemisphere 0.399451.177850.16025 Fowler's hemisphere 0.1220.79020.0136 Anti-Fowler's hemisphere 0.00170.30650.0669 Supine 0.21840.06420.5028 Trendelberg 0.59450.13070.9961 Slump sphere 1.71532.73291.2421 Abdominal sphere 3.00053.87472.5101

[0061] Thereafter, the posture corresponding to the minimum value among the above distances is determined as the judgment posture (S140). That is, referring to Table 2, in the first case, the posture corresponding to the minimum value (0.0017) is the semi-Fowler's position, in the second case, the posture corresponding to the minimum value (0.0642) is the supine position, and in the third case, the posture corresponding to the minimum value (0.0136) is the Fowler's position.

[0062] A device according to embodiments of the present invention may include a processor, a memory for storing and executing program data, permanent storage such as a disk drive, a communication port for communicating with an external device, a user interface device such as a touch panel, a key, a button, etc. Methods implemented as software modules or algorithms may be stored on a computer-readable recording medium as computer-readable codes or program instructions executable on the processor. Here, the computer-readable recording medium includes a magnetic storage medium (e.g., read-only memory (ROM), random-access memory (RAM), floppy disk, hard disk, etc.) and an optical reading medium (e.g., CD-ROM, DVD: Digital Versatile Disc)). The computer-readable recording medium may be distributed to computer systems connected through a network, so that the computer-readable code may be stored and executed in a distributed manner. The medium may be readable by a computer, stored in a memory, and executed by a processor.

[0063] Embodiments of the present invention may be represented by functional block configurations and various processing steps. These functional blocks may be implemented by various hardware and / or software components that perform specific functions. For example, embodiments may employ integrated circuit components, such as memory, processing, logic, and look-up tables, that may perform various functions under the control of one or more microprocessors or other control devices. Similarly, embodiments may be implemented in a programming or scripting language, such as C, C++, Java, or an assembler, including various algorithms implemented as a combination of data structures, processes, routines, or other programming components. Functional aspects may be implemented as algorithms that execute on one or more processors. Furthermore, embodiments may employ conventional techniques for electronic configuration, signal processing, and / or data processing. Terms such as "mechanism," "element," "means," and "composition" can be used broadly and are not limited to mechanical or physical structures. These terms can also encompass a series of software routines, such as those associated with a processor.

[0064] The specific implementations described in the embodiments are merely exemplary and do not limit the scope of the embodiments in any way. For the sake of brevity of the specification, descriptions of conventional electronic components, control systems, software, and other functional aspects of the systems may be omitted. In addition, the lines connecting or connecting members between components illustrated in the drawings are merely exemplary functional connections and / or physical or circuit connections, and may be replaced or represented as various additional functional connections, physical connections, or circuit connections in an actual device. In addition, unless specifically mentioned as "essential," "important," etc., a component may not be absolutely necessary for the application of the present invention.

[0065] A method for determining a body position of a subject according to embodiments of the present invention can determine the body position of the subject by attaching a mobile device including a sensor to the body of the subject and using an acceleration value measured from the sensor.

Claims

1. A method for determining the posture of a subject using a mobile device that can be fixed to the chest area of ​​a subject in a normal standing state and includes an acceleration sensor and a geomagnetic sensor that have the same local coordinate system. A step for defining a coordinate system in which the direction extended from the right shoulder to the left shoulder when the subject is standing normally is transformed into the X-axis direction, one of the y-axis and the z-axis having a smaller value among the angles formed between the y-axis and the z-axis according to the local coordinate system of the geomagnetic sensor and the direction opposite to gravity is transformed into the Y-axis direction, and the axis generated by the vector multiplication between the X-axis direction and the Y-axis direction is transformed into the Z-axis direction; Using the above acceleration sensor, the measured acceleration values ​​(a) for each of the X-axis direction, Y-axis direction, and Z-axis direction according to the above transformation coordinate system X , a Y & a Z ) to secure; On the above transformation coordinate system, the coordinates of the measured acceleration values ​​and the reference acceleration values ​​(a) for each posture stored in the data storage unit according to the above transformation coordinate system X0 , a Y0 & a Z0 ) calculating the respective distances between the coordinates; and A step of determining a posture corresponding to the minimum value among the above distances as the judgment posture; A method for determining a subject's posture, characterized by including a .

2. In the first paragraph, the standard angular velocity values ​​for each posture (a) X0 , a Y0 & a Z0 ) is a method for judging the posture of a subject, characterized by the characteristics corresponding to Table 3 below. Posture X-axis acceleration (a X0, g) Y-axis acceleration (a Y0, g)Z-axis acceleration (a Z0, g) Right angle standing 00. 90.38 Right angle left half-100 Right angle right half100 Left half0.0150.830.485 Fowler's side0.20.650.7 Half Fowler's side0.10.370.91 Supine side0.12-0.090.98 Trendelberg side0.1-0.40.9 Slump side0.040.95-0.27 Abdominal side0.10.7-0.8

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