Method, program, and electronic device for determining body posture

Abstract

Provided is a method, performed by a computer, for determining the posture of a subject to which an electronic device is attached, comprising the steps of: acquiring, from the electronic device, a magnetic field value and an acceleration value based on a local coordinate system having the same three-axis directions; determining a stable state and a walking state of the subject on the basis of a variance value in a first direction having the maximum value among the magnetic field values; setting a reference coordinate system on the basis of first angles between conversion acceleration vectors and an average acceleration vector calculated in the walking state; and calculating a sagittal plane angle by converting the acceleration value acquired in the stable state into the reference coordinate system, and determining the posture of the subject on the basis of the sagittal plane angle.

Description

Methods, programs and electronic devices for assessing body posture

[0001] Embodiments of the present invention relate to a method, program, and electronic device for determining body posture. More specifically, embodiments of the present invention relate to a method, program, and electronic device for accurately determining a subject's body posture using a single inertial measurement unit (IMU) randomly and irregularly attached to the human body.

[0002] Human posture measurement plays a crucial role in diverse fields, including medicine, sports science, virtual reality, and human-robot interaction. In particular, posture measurement technology using inertial measurement units (IMUs) is widely used due to its non-invasive nature and relatively high accuracy. Existing IMU-based posture measurement technologies primarily utilize multiple sensors attached to specific parts of the human body. This method fuses the data obtained from each sensor to estimate a virtual human posture in three-dimensional space. In other words, the system estimates the movement of each joint based on data from each sensor and then synthesizes this data to reconstruct the overall posture.

[0003] More specifically, human posture measurement technology using multiple IMU sensors is a method of accurately estimating posture by attaching sensors to various parts of the body. Typically, sensors are attached to major body parts such as the head, upper body, upper arms, forearms, hands, pelvis, thighs, shins, and feet. Each sensor collects data such as acceleration, angular velocity, and direction at the corresponding location, which is sampled at regular intervals and transmitted to a central processing unit. The central processing unit then processes the collected data for noise removal and compensation, and then fuses it using an algorithm such as a Kalman filter. This process allows for accurate estimation of the direction and position of each body part.

[0004] Based on the above information, a human skeletal model is used to link the position and orientation information of each sensor. This allows the overall human posture to be reconstructed, and the angles and positions of each joint are calculated to represent the human posture in 3D space. The estimated posture data is visualized as a 3D avatar or graph, and changes in posture over time can be analyzed to identify movement patterns or abnormalities.

[0005] The advantages of this technology include high accuracy and precision, real-time measurement capability, and usability in both indoor and outdoor environments.

[0006] However, the inconvenience of having to attach multiple sensors to major body parts, the need for synchronization and calibration between sensors, and the relatively high cost are pointed out as disadvantages.

[0007] Embodiments of the present invention provide a method for determining a subject's posture, which can achieve improved accuracy and precision by randomly attaching a single IMU sensor to a part of the body.

[0008] According to one aspect of the present invention, a method for determining a posture of a subject to whom an electronic device is attached, which is performed by a computer, is provided, comprising the steps of: obtaining acceleration values ​​and magnetic field values ​​based on a local coordinate system with the same three-axis direction from the electronic device; determining a stable state and a walking state of the subject based on a variance value for a first direction having a maximum value among the magnetic field values; setting a reference coordinate system based on first angles between an average acceleration vector and a transformed acceleration vector calculated in the walking state; and converting an acceleration value obtained in the stable state into the reference coordinate system to calculate a sagittal angle, and determining the posture of the subject based on the sagittal angle.

[0009] According to an exemplary embodiment, the stable state may be characterized as being defined as a case where the dispersion value for the first direction is less than or equal to a first reference value.

[0010] According to an exemplary embodiment, the walking state may be characterized in that the non-stable state is determined when the non-stable state is repeated for a time shorter than the reference stable period.

[0011] According to an exemplary embodiment, the transformation acceleration vector may be obtained at each point in time when the variance value for the first direction is transformed from a large value to a small value based on the second reference value.

[0012] According to an exemplary embodiment, the step of setting the reference coordinate system may include a step of defining a direction of a transformation acceleration vector corresponding to a maximum value of the first angles as a first reference direction when the maximum value is 90 degrees or more, defining a direction that is perpendicular to the first reference direction and in which a magnetic field dispersion value for the first direction converges to 0 as a second reference direction, and defining a direction from which the first reference direction is derived when an outer product is performed with the second reference direction as a third reference direction.

[0013] According to an exemplary embodiment, the step of determining the subject's posture may be characterized by determining that the subject is in a supine position when the maximum value is 90 degrees or more.

[0014] According to an exemplary embodiment, the step of setting the reference coordinate system may include the steps of calculating, as a second angle, an angle formed by one of the transformation acceleration vectors corresponding to the maximum value and each of the remaining transformation acceleration vectors when the maximum value among the first angles is less than 90 degrees, the step of calculating a sagittal angle by adding (95 degrees - the maximum value) to each of the second angles, and the step of defining a direction in which the sagittal angle is 90 degrees and a variance value for the first direction converges to 0 as a first reference direction, defining a vector direction formed by cross-producting the transformation acceleration vector corresponding to the maximum value with a unit vector of the first reference direction as a third reference direction, and defining a vector direction formed by cross-producting the first reference direction and the third reference direction as a second reference direction.

[0015] According to an exemplary embodiment, the step of determining the posture of the subject may be characterized in that the opposite direction of the second reference direction is defined as a virtual supine position.

[0016] According to one aspect of the present invention, a computer-readable recording medium is provided, which is coupled to a computer and stores a program for executing a method for determining the posture of a subject.

[0017] According to one aspect of the present invention, an electronic device is provided, comprising a memory and a processor, wherein the processor causes the electronic device to obtain acceleration values ​​and magnetic field values ​​based on a local coordinate system with the same three-axis direction from the electronic device, determine a stable state and a walking state of the subject based on a variance value for a first direction having a maximum value among the magnetic field values, set a reference coordinate system based on first angles between an average acceleration vector and a transformed acceleration vector calculated in the walking state, calculate a sagittal plane angle by converting an acceleration value obtained in the stable state into the reference coordinate system, and determine a posture of the subject based on the sagittal plane angle.

[0018] Other aspects, features and advantages other than those described above will become apparent from the following detailed description, claims and drawings for carrying out the invention.

[0019] Additionally, these general and specific aspects may be implemented using any system, method, computer program, or combination of any system, method, or computer program.

[0020] As described above, according to the method for determining the subject's posture according to the embodiments of the present invention, posture determination with improved accuracy can be implemented even if a single electronic device having a geomagnetic sensor and an acceleration sensor having the same local coordinate system is randomly attached to the body.

[0021] That is, not only does it improve cost efficiency by achieving high accuracy with a single IMU, but it also simplifies the attachment and calibration process of the electronic device, increasing user convenience and ensuring longer usage time with the same capacity battery by using only the minimum system resources.

[0022] Furthermore, it enables precise posture measurement while minimizing restrictions on the wearer's movements, and allows for accurate analysis of complex posture changes. Furthermore, it enables the implementation of a flexible system suitable for both long-term monitoring in everyday life and professional motion analysis.

[0023] FIG. 1 is a drawing for explaining a local coordinate system obtainable through a communication device according to one embodiment of the present invention.

[0024] Figure 2 is a flowchart for explaining a method for determining a subject's posture according to one embodiment of the present invention.

[0025] FIG. 3 is a drawing defining a first reference direction from a supine position according to one embodiment of the present invention.

[0026] FIG. 4 is a table for defining a second reference direction using acceleration values, sagittal angles, and dispersion values ​​for the three-axis directions of a local coordinate system according to one embodiment of the present invention.

[0027] FIG. 5 is a graph showing the magnetic field dispersion value and the sagittal plane angle in the walking state among the determined stable state postures and unstable states according to one embodiment of the present invention.

[0028] FIG. 6 is a photograph showing the state of an electronic device mounted at positions A and B of a subject according to one embodiment of the present invention.

[0029] FIG. 7 is a table and graphs for explaining acceleration values ​​for three-axis directions measured in each state of being mounted at positions A and B according to one embodiment of the present invention.

[0030] FIG. 8 is a graph for explaining the angle on the sagittal plane using acceleration values ​​for the three-axis directions measured in each state of being mounted at positions A and B according to one embodiment of the present invention.

[0031] FIG. 9 is a drawing defining a first reference direction from the maximum value of the first angle according to one embodiment of the present invention.

[0032] 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.

[0033] 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."

[0034] 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.

[0035] 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.

[0036]

[0037] FIG. 1 is a drawing for explaining a local coordinate system obtainable through a communication device according to one embodiment of the present invention.

[0038] Referring to Figure 1, a communication device according to one embodiment of the present invention may be a mobile phone (or smartphone). However, this is not a limitation, and the electronic device may be any portable wireless communication device. For example, the communication device may be a wearable device such as a smartwatch or smart glasses.

[0039] A mobile phone, which is an example of a communication device, uses the same coordinate system for both the Android OS and the iOS system that runs the iPhone. That is, when the mobile phone is placed on a flat surface with the screen facing up, the direction of the display from the floor is the z-axis, and the counterclockwise rotation around the z-axis is the yaw momentum. In addition, when the mobile phone is held upright, the direction from left to right is the y-axis, and the counterclockwise rotation around the y-axis is called roll. In this case, the direction from bottom to top of the mobile phone when held upright is the z-axis, and the amount of rotation around the z-axis is defined as pitch. The direction of increase in rotational momentum 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. However, this is not limited to this, and the x-axis, y-axis, and z-axis through a communication device (e.g., a mobile phone) can of course be defined in various ways. In addition, the same axis definition can be applied to acceleration sensors, angular velocity sensors (gyro sensors), and geomagnetic sensors installed inside communication devices (e.g., mobile phones). For convenience of explanation, in the following description, 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.

[0040] Meanwhile, 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 perpendicular to the direction of gravity. The azimuth value, which indicates how much the mobile phone is rotated on the 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, GPS, etc.

[0041] Figure 2 is a flowchart for explaining a method for determining a subject's posture according to one embodiment of the present invention.

[0042] In one embodiment, the electronic device of the present invention may be an inertial measurement unit (IMU) and may include at least one of an acceleration sensor, an angular velocity sensor, and a magnetometer sensor. In addition, the acceleration sensor, the angular velocity sensor, and / or the magnetometer sensor included in the electronic device may have the same local coordinate system in three directions and may be driven at the same measurement cycle.

[0043] In one embodiment, the electronic device may include an acceleration sensor and a magnetometer sensor having the same local coordinate system in three directions. Since the three-axis directions according to the local coordinate system have been described above with reference to FIG. 1, a detailed description thereof will be omitted.

[0044] Meanwhile, in the present invention, the three-axis directions of the local coordinate system may be three-axis directions that are perpendicular to each other as shown in Fig. 1, but are not limited thereto.

[0045] An electronic device can determine the condition of a subject to which the electronic device is attached based on magnetic field values ​​and / or acceleration values ​​acquired through an acceleration sensor and / or a geomagnetic sensor included in the electronic device. Here, the condition of the subject can include a stable state and an unstable state.

[0046] A stable state may include, but is not limited to, a standing position (not walking) in which the subject's center of gravity and the direction of the gravitational field are in a straight line, a sitting position with the back straight and the waist at a right angle, a Fowler position in which the back is tilted backwards 30 to 45 degrees from the sitting position, and a semi-Fowler position with an angle intermediate between the Fowler position and the supine position.

[0047] Unsteady states may include, but are not limited to, states in which the subject is moving or exercising, such as walking or running.

[0048] The acceleration sensor and magnetometer sensor operate at the same measurement cycle. For example, the acceleration sensor and magnetometer sensor can measure acceleration and magnetometer values ​​for each of the three axes once every 0.25 seconds.

[0049] First, using the above-mentioned geomagnetic sensor, the measured magnetic field values ​​of each of the three directions are measured. In one embodiment, if the variance value (Vm) for the unit measurement time for the first measured magnetic fields in the first direction corresponding to the maximum value among the measured magnetic field values ​​is less than or equal to a preset first reference value, the state of the subject can be defined as a stable state (S110).

[0050] For example, for each of the three directions, the first direction having the maximum value among the measured magnetic field values ​​has the largest dispersion value. Therefore, if the dispersion value (Vm) for the first direction is defined as being less than or equal to the first reference value, the stability state can be evaluated more accurately.

[0051] Meanwhile, the unit measurement time can be set to, for example, 1 second. In this case, if the measurement cycle is 0.25 seconds, the variance value can be obtained as the average value for a total of four measurement data during the unit measurement time. Alternatively, the unit measurement time can be set differently.

[0052] Additionally, for example, the first reference value may be set to 10 μT. Alternatively, the first reference value may be set to a value within the range of 5 to 10 μT.

[0053] Therefore, when the variance value (Vm) for the first direction is less than or equal to the first reference value, it is defined as a stable state.

[0054] On the other hand, if the variance value (Vm) for the first direction exceeds the first reference value, the subject's condition can be defined as an unstable state.

[0055] Next, the electronic device can determine the state of the subject as a walking state based on the duration of the unstable state and the reference stability period. In one embodiment, the electronic device determines the state of the subject as a walking state if, among the unstable states that have deviated from the stable state, the duration of the unstable state is repeated less than or equal to the reference stability period (S120).

[0056] For example, a period may occur in which a stable state in which the variance value (Vm) for the first direction is less than or equal to a first reference value and an unstable state in which the variance value (Vm) for the first direction exceeds the first reference value are periodically repeated (see the dashed line area in Fig. 5). In this case, the unstable state may be defined as a walking state by repeating the maintenance time of the unstable state less than or equal to the reference stable period.

[0057] The above reference stability period can be determined by considering a typical walking speed, for example, a cadence value. For example, the reference stability period can be determined to be, for example, 1 to 5 seconds.

[0058] Meanwhile, humans change their posture throughout the day, from walking to exercising to sitting to sleeping.

[0059] Specifically, in the walking state (W), humans typically walk at a walking angle of approximately 95 degrees relative to the rearward surface, opposite the direction of travel. However, the walking angle may change depending on a person's health and aging. Therefore, if a reference coordinate system defining the walking angle as a reference direction is used, errors in posture assessment are inevitable.

[0060] Meanwhile, during sleep, humans sleep in a supine position, lying parallel to the ground and looking vertically upward. Despite the progression of a person's health and aging, the supine position rarely changes. In other words, the sagittal plane angle during supine sleep can be defined as 0.

[0061] Next, in the walking state (W), the average acceleration vector composed of the average acceleration values ​​of each of the three-axis directions and the first angles formed by each of the transformation acceleration vectors at each of the transformation points defined as points in time when the variance value changes from a large value to a small value based on the second reference value are calculated (S130).

[0062] In the above walking state (W), the average acceleration vector (W_ax, W_ay, W_az) composed of the average acceleration values ​​in each of the three-axis directions corresponds to the average acceleration value in the walking state.

[0063] Meanwhile, the transformation acceleration vectors can be determined at each of the transformation points defined as points at which the above-mentioned variance value is transformed from a large value to a small value based on the second reference value.

[0064] The above variance value means the difference from the average value of the first measured magnetic field values ​​for the entire measurement time including the steady state and the unstable state.

[0065] At this time, if the variance value has a large value relative to the second reference value, it corresponds to a relatively unstable state, whereas if the variance value has a small value relative to the second reference value, it corresponds to a relatively stable state. Therefore, the transition points defined as each point in time when the variance value changes from a large value to a small value relative to the second reference value correspond to the transition points from a relatively unstable state to a stable state.

[0066] The second reference value may be greater than or equal to the first reference value. For example, when the first and second reference values ​​are equal to each other, each of the first and second reference values ​​may be set to 10 μT. Alternatively, when the second reference value is greater than the first reference value, the first reference value may be set to 10 μT and the second reference value may be set to 10 μT.

[0067] First angles between the vectors formed by the above average acceleration vector (W_ax, W_ay, W_az) and each of the plurality of transformed acceleration vectors are calculated. One of the transformed acceleration vectors having the maximum value among the first angles indicates the subject's sleeping state.

[0068] FIG. 3 is a drawing defining a first reference direction from a supine position according to one embodiment of the present invention.

[0069] Referring to FIGS. 2 and 3, the three-axis reference directions of the reference coordinate system are defined using the maximum value among the first angles (S140).

[0070] In one embodiment of the present invention, the step of defining the three-axis directions of the reference coordinate system defines, when the maximum value is 90 degrees or greater, the direction of the transformation acceleration vector corresponding to the maximum value as the first reference direction. That is, the maximum value among the first angles between the vectors formed by the average acceleration vector (W_ax, W_ay, W_az) and each of the plurality of transformation acceleration vectors corresponds to the angle between the acceleration vectors between the upright state and the sleeping state.

[0071] Therefore, even if the gait angle changes depending on the progress of a specific person's health and aging, the direction of the translational acceleration vector in the supine sleeping state remains constant. In this case, the sagittal plane angle is defined as 0. Therefore, the direction of the translational acceleration vector with the maximum value corresponds to a sagittal plane angle of 0.

[0072] FIG. 4 is a table for defining a second reference direction using acceleration values, sagittal angles, and dispersion values ​​for the three-axis directions of a local coordinate system according to one embodiment of the present invention.

[0073] Referring to FIGS. 2 and 4, the case in which the first measured magnetic field dispersion value is perpendicular to the first direction and converges to 0 is defined as the second reference direction. The case in which the first measured magnetic field dispersion value is perpendicular to the first direction is determined as a 90-degree sagittal angle. Among the transformation acceleration vectors having the 90-degree sagittal angle, the case in which the first measured magnetic field dispersion value has a value closest to 0 is defined as the direction of the transformation acceleration vector with respect to the second reference direction as a unit vector of the second reference direction.

[0074] Referring again to Figure 2, the direction in which the first reference direction is derived when the second reference direction is cross-producted is defined as the third reference direction.

[0075] FIG. 5 is a graph showing the magnetic field dispersion value and the sagittal plane angle in the walking state among the determined stable state postures and unstable states according to one embodiment of the present invention.

[0076] Referring to FIGS. 2 and 5, the posture of the subject in the stable state is determined as an angle on the sagittal plane formed by the first and second reference directions included in the reference coordinate system using the above-described transformation acceleration value (S150).

[0077] That is, the sagittal plane angle is calculated on the sagittal plane based on the 0 degree sagittal plane angle corresponding to the first reference direction.

[0078] Referring again to Figure 5, the magnetic field dispersion value and the sagittal plane angle are shown according to the stable state that changes over time from the supine position, the left-sided position, the right-sided position, the (semi)Fowler position, the sitting position, and the standing state, and the unstable state that includes the walking state that changes from the standing state.

[0079] At this time, the posture change according to the change in the sagittal plane angle can be confirmed. The dashed-dotted line (magnetic field dispersion graph) represents the dispersion value of the z-axis signal according to the local coordinate system with the largest signal value among the geomagnetic sensor signals calculated to extract the stable posture, and the dashed-dotted line area represents the walking section with an average dispersion value of 10 μT or more, which is the second reference value.

[0080] FIG. 6 is a photograph showing the state of an electronic device mounted at positions A and B of a subject according to one embodiment of the present invention.

[0081] Referring to Figure 6, it shows a state in which an electronic device is attached to arbitrary locations A and B on the subject's upper body.

[0082] FIG. 7 is a table and graphs for explaining acceleration values ​​for three-axis directions measured in each state of being mounted at positions A and B according to one embodiment of the present invention.

[0083] Referring to Fig. 7, it can be confirmed that there is a significant difference in the measured acceleration values ​​when mounted at different locations A and B.

[0084] FIG. 8 is a graph for explaining the angle on the sagittal plane using acceleration values ​​for the three-axis directions measured in each state of being mounted at positions A and B according to one embodiment of the present invention.

[0085] Referring to Figure 8, it can be confirmed that the difference in the sagittal angle between the results measured at arbitrary locations A and B was within 8 degrees at most, and within 2 degrees in most sections.

[0086] The above results show that, regardless of the mounting position or angle of the electronic device, it is possible to accurately detect changes in the angle in the sagittal plane by arbitrarily mounting a single electronic device on the upper body above the extension of the centerline of the pelvic spherical surfaces on both sides of the pelvis.

[0087] Meanwhile, according to Statistics Korea, the average person spends 7 hours and 40 minutes sitting in their daily life. According to 2014 OECD statistics, 7 hours and 49 minutes of their time is spent lying down for sleep. The remaining 8 hours and 30 minutes are spent socializing, moving around, exercising, and other activities. If, according to the present invention, the supine position, a state of sleep, is not present within the measurement time range between the start and end times, the measurement may not be performed.

[0088] FIG. 9 is a drawing defining a first reference direction from the maximum value of the first angle according to one embodiment of the present invention.

[0089] Figure 9 illustrates a case where the maximum value is less than 90 degrees. The second angles formed by one of the transformation acceleration vectors corresponding to the maximum value and each of the remaining transformation acceleration vectors are calculated.

[0090] At this time, the sagittal angle is calculated by adding (95 degrees - maximum value) to each of the second angles. The 95 degrees correspond to the angle between the upper body angle and the ground surface in a normal standing state of a normal person.

[0091] Next, the case where the above-mentioned plane angle is 90 degrees and the first measured magnetic field dispersion value converges to 0 is defined as the first reference direction of the reference coordinate system. The vector direction formed by cross-producting the transformation acceleration vector corresponding to the maximum value with the unit vector of the first reference direction is defined as the third reference direction. In addition, the vector direction formed by cross-producting the first and third reference directions is defined as the second reference direction.

[0092] At this time, the step of determining the subject's posture may be defined such that the opposite direction of the second reference direction is a virtual supine position. That is, the opposite direction of the vector of the second reference direction is defined as a vector when the subject is in a supine position even though the subject has never laid down within the measurement section.

[0093]

[0094] A device for implementing 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. The 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 to 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.

[0095] 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.

[0096] As described above, the specific description of the present invention has been made by way of embodiments with reference to the attached drawings. However, since the above-described embodiments have only been described as preferred examples of the present invention, the present invention should not be understood as being limited to the above-described embodiments, and the scope of the present invention should be understood by the claims described below and their equivalent concepts.

Claims

1. A method for determining the posture of a subject with an electronic device attached, performed by a computer, A step of obtaining acceleration values ​​and magnetic field values ​​based on a local coordinate system with the same three-axis direction from the electronic device; A step of determining the stable state and walking state of the subject based on the dispersion value for the first direction having the maximum value among the above magnetic field values; A step of setting a reference coordinate system based on first angles between the average acceleration vector and the transformed acceleration vector calculated in the above walking state; and A step of converting the acceleration value obtained in the above stable state into the above reference coordinate system to calculate a sagittal plane angle, and determining the posture of the subject based on the sagittal plane angle; A method comprising:

2. In paragraph 1, A method characterized in that the above stable state is defined as a case where the dispersion value for the first direction is less than or equal to the first reference value.

3. In paragraph 2, A method characterized in that the above walking state is determined when a state that is not a stable state is repeated for a time shorter than a reference stable period.

4. In paragraph 1, A method characterized in that the above transformation acceleration vector is obtained at each point in time when the dispersion value for the first direction is converted from a large value to a small value based on the second reference value.

5. In paragraph 1, The step of setting the above reference coordinate system is: If the maximum value of the above first angles is 90 degrees or more, A method comprising the steps of defining the direction of the transformation acceleration vector corresponding to the maximum value as a first reference direction, defining a case where the direction is perpendicular to the first reference direction and the magnetic field dispersion value for the first direction converges to 0 as a second reference direction, and defining a direction from which the first reference direction is derived when an outer product is performed with the second reference direction as a third reference direction.

6. In paragraph 5, The step of judging the posture of the subject is as follows: A method characterized in that when the above maximum value is 90 degrees or more, it is determined to be a supine position.

7. In paragraph 1, The step of setting the above reference coordinate system is: If the maximum value of the above first angles is less than 90 degrees, A step of calculating the angle formed by one of the transformation acceleration vectors corresponding to the above maximum value and each of the remaining transformation acceleration vectors as a second angle; A step of calculating the sagittal angle by adding (95 degrees - the maximum value) to each of the second angles; and A step of defining a direction in which the above-mentioned plane angle is 90 degrees and the dispersion value for the first direction converges to 0 as a first reference direction, defining a vector direction formed by cross-producting a transformation acceleration vector corresponding to the maximum value with a unit vector of the first reference direction as a third reference direction, and defining a vector direction formed by cross-producting the first reference direction and the third reference direction as a second reference direction; A method comprising:

8. In paragraph 7, The step of judging the posture of the subject is as follows: A method characterized in that the opposite direction of the second reference direction is defined as a virtual supine position.

9. A computer program stored in a storage medium to execute the methods of claims 1 to 8 in combination with hardware.

10. In electronic devices. memory; and Contains a processor, The above processor causes the electronic device to: An electronic device that obtains acceleration values ​​and magnetic field values ​​based on a local coordinate system with the same three-axis direction from the electronic device, determines the stable state and walking state of the subject based on a variance value for a first direction having a maximum value among the magnetic field values, sets a reference coordinate system based on first angles between the average acceleration vector and the transformed acceleration vector calculated in the walking state, converts the acceleration value obtained in the stable state into the reference coordinate system to calculate a sagittal plane angle, and determines the posture of the subject based on the sagittal plane angle.

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