JP2015087175A - Forward motion acceleration calculation method, apparatus and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately determine acceleration caused by forward movement of a person without attaching hardware except an acceleration sensor to the person.SOLUTION: From an acceleration sensor which is attached to a person and the posture of which changes with the forward movement of the person, the z-axis direction acceleration component Aand the y-axis direction acceleration component Aduring the forward movement are obtained, a waveform representing the time change of the physical quantity specified by the A, A, and a gravitational acceleration g is determined, and a vertical acceleration component acaused by the person's forward movement is calculated as the vibrational component of the waveform. For example, based on a relational expression ∫(A+A-g)dt=∫(a+a)dt-2 g∫adt, the (left side) which continues to increase with vibration with respect to time t is determined from the output, etc. from the acceleration sensor, the (first term of right side) which continues to increase with respect to the time t is extracted from the (left side), the (second term of -right side) which vibrates with respect to the time t is determined by subtracting the (left side) from the (first term of right side), and ais determined by time-differentiating the (second term of -right side)/2 g.

Description

  The present invention relates to a technique for determining an acceleration generated by a forward movement of a person based on an output of an acceleration sensor attached to the person in order to evaluate the forward movement of the person.

  Conventionally, rehabilitation for patients with gait disorders has been performed in medical facilities, nursing homes, and the like. In this rehabilitation, an instructor, such as a physical therapist, generally creates a gait training program (program) that is appropriate for the patient and understands the patient's recovery level. Is repeatedly evaluated.

  In recent years, an acceleration sensor is attached to the patient so that the patient's walking state can be objectively and quantitatively evaluated, and the acceleration in each direction caused by the patient's walking is measured from the output of the acceleration sensor during the patient's walking. Various methods for imaging and displaying the acceleration have been proposed.

  As the acceleration sensor, a triaxial acceleration sensor is usually used. A general three-axis acceleration sensor measures acceleration in each of the three axis directions of x, y, and z in a three-dimensional orthogonal coordinate system with the sensor body as a reference, and outputs the acceleration data (data). The acceleration in the left-right direction, horizontal traveling direction (front-rear direction), and vertical direction (up-down direction) of the patient in the real space three-dimensional orthogonal coordinate system is obtained based on the acceleration data in the three-axis directions.

  By the way, in principle, the acceleration sensor measures all accelerations acting on the acceleration sensor. That is, the acceleration sensor measures not only the acceleration caused by the patient's own walking or the like but also the acceleration obtained by combining the acceleration caused by gravity (gravity acceleration). Therefore, when the acceleration due to walking is obtained based on the acceleration data output from the acceleration sensor, if the gravity acceleration is not taken into consideration and subtracted, an error that cannot be ignored is included in the obtained acceleration. When the instructor refers to the acceleration including the error in this way, there is a possibility that it may lead to grasping or instructing the patient's erroneous motion. For this reason, when obtaining the acceleration caused by walking of the patient, it is desirable to subtract the gravitational acceleration component from the acceleration directly obtained by the acceleration sensor.

  The gravitational acceleration is an acceleration of a certain magnitude in the vertical direction. On the other hand, the posture of the acceleration sensor body changes as needed depending on the walking motion of the patient. Therefore, in the coordinate system based on the acceleration sensor body, the direction in which the gravitational acceleration acts on the acceleration sensor also changes as needed. In other words, the acceleration data output from the acceleration sensor always includes a gravitational acceleration component whose direction changes from time to time, and the gravitational acceleration component can be accurately subtracted from the acceleration directly obtained by the acceleration sensor. difficult.

  Therefore, in general, an acceleration sensor and an angular velocity sensor (gyro sensor) are attached to the patient, and the components of gravitational acceleration at each time in the coordinate system of the acceleration sensor are specified from the output of these sensors, and the acceleration is performed. It is conceivable to use a method of subtracting the specified gravitational acceleration component from the acceleration obtained based on the sensor output (see Patent Document 1, Abstract, etc.).

JP 2005-114537 A

  However, in the above method, since another sensor is required in addition to the acceleration sensor, the cost is high. In addition, the sensors attached to the patient increase in size, increasing the physical burden on the patient, and complicating the attaching work of the sensors.

  Under such circumstances, there is a demand for a technology that can accurately determine acceleration due to a person's forward movement without attaching hardware other than the acceleration sensor to the person.

The invention of the first aspect
The x-axis in the Cartesian coordinate system with reference to the acceleration sensor is attached to the person so that it substantially coincides with the left-right direction of the person, and is output from the acceleration sensor whose posture changes as the person moves forward. and step (step) for acquiring acceleration component a _y of the acceleration component in the z-axis direction in the forward movement a _z and y-axis direction that,
A waveform representing a time change of a physical quantity specified by the acquired acceleration components A _z and A _y and gravitational acceleration g is obtained, and a vertical acceleration component a _z generated by the forward movement of the person is obtained as a vibration component of the waveform. A forward motion acceleration calculating method comprising: a calculating step;

に基づいて、前記鉛直方向の加速度成分ａ_zを求める、上記第１の観点の前進運動加速度算出方法を提供する。 The invention of the second aspect is
The vertical acceleration component a _z and the horizontal acceleration component a _y generated by the forward movement of the person, the gravitational acceleration g, and the z-axis acceleration components A _z and y-axis directions obtained from the acceleration sensor. The following first mathematical expression representing the relationship with the acceleration component A _{y of}

Based on the above, there is provided a forward motion acceleration calculation method according to the first aspect, wherein the vertical acceleration component a _z is obtained.

The invention of the third aspect is
A first step of obtaining a left side of the first mathematical expression representing a waveform increasing while oscillating with respect to time t;
A second step of obtaining a first term on the right side of the first mathematical expression representing a component increasing with respect to time t based on the left side of the first mathematical expression obtained in the first step; ,
Subtracting the left side of the first mathematical formula obtained in the first step from the first term on the right side of the first mathematical formula obtained in the second step, the first representing the vibration component A third step for obtaining the second term on the right-hand side of the formula of 1;
A fourth step for obtaining the vertical acceleration component a _z by dividing the second term on the right side of the first mathematical formula obtained in the third step by 2 g and then differentiating it by time t; A forward motion acceleration calculation method according to the second aspect is provided.

The invention of the fourth aspect is
The x-axis in the Cartesian coordinate system with reference to the acceleration sensor is attached to the person so that it substantially coincides with the left-right direction of the person, and is output from the acceleration sensor whose posture changes as the person moves forward. wherein the z-axis direction acceleration component a _z and y-axis direction obtaining means for obtaining an acceleration component a _y of in forward motion that,
A waveform representing a temporal change of a physical quantity specified by the acceleration components A _z and A _y and the gravitational acceleration g acquired by the acquisition means is obtained, and vertical acceleration generated by the forward movement of the person as a vibration component of the waveform There is provided a forward motion acceleration calculating device including a calculating means for calculating a component a _z .

に基づいて、前記鉛直方向の加速度成分ａ_zを求める、上記第４の観点の前進運動加速度算出装置を提供する。 The invention of the fifth aspect is
The calculating means is
The vertical acceleration component a _z and the horizontal acceleration component a _y generated by the forward movement of the person, the gravitational acceleration g, and the z-axis acceleration components A _z and y-axis directions obtained from the acceleration sensor. The following first mathematical expression representing the relationship with the acceleration component A _{y of}

The forward motion acceleration calculating apparatus according to the fourth aspect is provided that calculates the vertical acceleration component a _z based on the above.

The invention of the sixth aspect is
The calculating means is
A first step of obtaining a left side of the first mathematical expression representing a waveform increasing while oscillating with respect to time t;
A second step of obtaining a first term on the right side of the first mathematical expression representing a component increasing with respect to time t based on the left side of the first mathematical expression obtained in the first step; ,
Subtracting the left side of the first mathematical formula obtained in the first step from the first term on the right side of the first mathematical formula obtained in the second step, the first representing the vibration component A third step for obtaining the second term on the right-hand side of the formula of 1;
A fourth step for obtaining the vertical acceleration component a _z by dividing the second term on the right side of the first mathematical formula obtained in the third step by 2 g and then differentiating it by time t; The forward motion acceleration calculating apparatus according to the fifth aspect is provided.

The invention of the seventh aspect
In the second step, a least square method is applied to the plot of the left side of the first mathematical expression at each time, and a straight line or curve that approximates the plot is obtained as the first term on the right side of the first mathematical expression. The forward motion acceleration calculating apparatus according to the sixth aspect, which is a step for obtaining, is provided.

The invention of the eighth aspect
The second step performs frequency analysis processing on the left side plot of the first mathematical expression at each time, and the first term on the right side of the first mathematical expression represents a straight line representing a low frequency component of the plot or The forward motion acceleration calculating apparatus according to the sixth aspect, which is a step of obtaining a curve, is provided.

The invention of the ninth aspect is
The second step performs a smoothing process on the plot of the left side of the first mathematical expression at each time, and approximates the plot as the first term on the right side of the first mathematical expression. The forward motion acceleration calculating apparatus according to the sixth aspect, which is a step of obtaining a straight line or a curve, is provided.

The invention of the tenth aspect is
Provided is a forward motion acceleration calculating device according to any one of the fourth to ninth aspects, further comprising generating means for generating a graph representing a temporal change in the acceleration component a _{z in} the vertical direction. To do.

に、前記ｚ軸方向の加速度成分Ａ_z及びｙ軸方向の加速度成分Ａ_yと、前記重力加速度ｇと、前記第４のステップにて求められた前記鉛直方向の加速度成分ａ_zとを代入して、前記水平進行方向の加速度成分ａ_yを求める第５のステップをさらに実行する、上記第６の観点から第９の観点のいずれか一つの観点の前進運動加速度算出装置を提供する。 The invention of the eleventh aspect is
The calculation unit calculates the following second formula representing the relationship:

To, substituted and acceleration component A _y of the acceleration component A _z and y-axis direction of the z-axis direction, and the gravitational acceleration g, the acceleration component a _z of the fourth of the vertical direction obtained in step Thus, the forward motion acceleration calculating apparatus according to any one of the sixth to ninth aspects is provided, which further executes a fifth step of obtaining the acceleration component a _y in the horizontal traveling direction.

The invention of the twelfth aspect is
The acquisition unit obtains an acceleration component A _x in the x-axis direction from the acceleration sensor as a lateral acceleration a _x generated by the forward movement,
Wherein further comprising a generating means for generating a two-dimensional map representing the lateral direction of the acceleration a _x and the frequency or the locus of the acceleration component a _y in the horizontal travel direction, to provide a forward motion acceleration calculation device of the eleventh aspect.

The invention of the thirteenth aspect is
Provided is a forward motion acceleration calculating device according to any one of the fourth to twelfth aspects, wherein the forward movement is walking.

The invention of the fourteenth aspect is
Provided is a forward motion acceleration calculating device according to any one of the fourth to twelfth aspects, wherein the forward movement is traveling.

The invention of the fifteenth aspect is
A program for causing a computer to function as the forward motion acceleration calculating device according to any one of the fourth to fourteenth aspects is provided.

According to the invention of the above aspect, the acceleration component A _y of the acceleration component A _z and y-axis direction of the z-axis direction in the forward movement is output from the acceleration sensor mounted on the person performing the forward movement and the gravitational acceleration g Since a waveform representing a time change of the specified physical quantity is obtained and a vertical acceleration component a _z generated by a person's forward movement is calculated as a vibration component of this waveform, even if the posture of the acceleration sensor is unknown, The acceleration due to the forward movement can be theoretically derived, and the acceleration due to the forward movement of the person can be obtained with high accuracy without mounting hardware other than the acceleration sensor on the person.

It is a figure which shows roughly the structure of a walking state display system (system). 4 is a diagram illustrating a relationship between acceleration generated by a walking of a subject expressed in an orthogonal coordinate system in real space and an acceleration sensor output expressed in an orthogonal coordinate system of an acceleration sensor 2. FIG. It is the graph obtained by calculating | requiring the left side of Formula (4) in each time, using the output of the acceleration sensor with which the said person's waist | hip | lumbar part was mounted | worn during a person's walk, and plotting them. It is a figure which shows the curve or the straight line corresponding to each term in (4 ') Formula. It is a figure which shows the flow of the algorithm (algorithm) for calculating | requiring the acceleration component _az of the perpendicular direction produced by the subject's 10 walk. It is a figure which shows an example of the result of having applied this algorithm to the output of the acceleration sensor 2 with which the said person's waist | hip | lumbar part was mounted | worn during a person's walk. It is a figure which shows an example of the comparison result with the case where this algorithm is not applied to the output of the acceleration sensor 2 with which the said person's waist | hip | lumbar part was mounted | worn during a person's walk. It is a flow figure showing a flow of processing in a walking state display system.

  Embodiments of the invention will be described below. The invention is not limited thereby.

  FIG. 1 is a diagram schematically showing a configuration of a walking state display system.

  As shown in FIG. 1, the walking state display system 1 includes an acceleration sensor 2 and a walking state display device 3. The walking state display device 3 is an example of a forward motion acceleration calculation device in the invention.

  The acceleration sensor 2 is attached to the center of the lower back of the subject 10 or the like. The acceleration sensor 2 is a three-axis acceleration sensor, and measures acceleration in each of the x, y, and z axes in a three-dimensional orthogonal coordinate system based on the sensor body at a predetermined sampling frequency, for example, 128 Hz. . Here, the acceleration sensor 2 has an RL (Right-Left) direction, an AP (Anterior-Posterior) direction, and an SI (Superior-Direction) direction of the subject 10 respectively in the x-axis direction, the y-axis direction, and the z-axis direction of the sensor body. (Inferior) It is attached to match the direction. The RL direction, AP direction, and SI direction are also referred to as a sagittal direction, a coronal direction, and an axial direction, respectively. Since the posture of the subject person 10 is changed by the movement of the subject person 10, the posture of the acceleration sensor 2 is also changed during the movement of the subject person 10. Here, it is assumed that the posture (inclination) of the acceleration sensor 2 changes in the front-rear direction but does not change in the left-right direction while the subject 10 is walking.

The acceleration sensor 2 has a transmission unit 21. The transmission unit 21 transmits acceleration data representing the measured acceleration wirelessly in almost real time. The acceleration sensor 2 outputs acceleration data at a scale of 1 g (gravity acceleration) = 9.8 m / s ² = acceleration data value 128, for example. Here, the positive / negative acceleration is positive on the right side, front side, and upper side.

The walking state display device 3 is, for example, a smartphone (smart
This is realized by causing a computer terminal such as a phone), a tablet computer, or a notebook PC to execute a predetermined program.

  The walking state display device 3 includes an operation unit 31, a display unit 32, a reception unit 33, a walking acceleration calculation unit 34, a graph / map generation unit 35, and a display control unit 37. have. The reception unit 33 is an example of an acquisition unit in the invention, the walking acceleration calculation unit 34 is an example of a calculation unit in the invention, and the graph / map generation unit 35 is an example of a generation unit in the invention.

  The operation unit 31 receives an operator's operation. The operation unit 31 includes, for example, a touch panel, a touch pad, a keyboard, a mouse, and the like. The operator is an instructor such as a physical therapist, for example.

  The display unit 32 displays an image. The display unit 32 includes a liquid crystal panel, an organic EL panel, and the like.

  The receiving unit 33 wirelessly receives acceleration data transmitted from the transmitting unit 21 of the acceleration sensor 2. Note that standards such as Bluetooth (registered trademark) can be used for wireless communication between the transmission unit 21 and the reception unit 33, for example.

  The walking acceleration calculation unit 34 calculates the acceleration component in the vertical direction (vertical direction) of the target person 10 in consideration of the gravitational acceleration based on the acquired acceleration data. The algorithm for calculating the acceleration component will be described in detail later.

  Based on the acceleration data received by the receiving unit 33, the graph / map generating unit 35 calculates the time change of the vertical acceleration in a two-dimensional coordinate space with the time and the vertical acceleration of the subject 10 as two axes. Generate a graph to represent. This graph is referred to, for example, to evaluate the walking cycle, landing and crossing timings of the subject person 10, the strength of the walking motion, and the stability thereof. In addition, the graph / map generation unit 35, based on the received acceleration data, in the two-dimensional coordinate space with the left and right accelerations in the subject 10 and the acceleration in the horizontal traveling direction as two axes, in the horizontal and horizontal traveling directions. A two-dimensional map such as a two-dimensional histogram representing the frequency of acceleration is generated. This two-dimensional map evaluates, for example, the width of the moving range, left-right symmetry, balance in the front-rear direction, movement pattern, balance position of weight, etc., regarding the weight movement in the horizontal direction while the subject 10 is walking. To be referenced.

  The display control unit 37 causes the display unit 32 to display the graph and the two-dimensional map.

  An algorithm for calculating the acceleration in the vertical direction (vertical direction) in the subject 10 from the acceleration data in consideration of the gravitational acceleration g will be described.

  FIG. 2 is a diagram illustrating the relationship between the acceleration generated by the walking of the subject 10 expressed in the orthogonal coordinate system of the real space and the acceleration sensor output expressed in the orthogonal coordinate system of the acceleration sensor 2.

Now, assume that the acceleration sensor 2 is attached to the waist of the subject 10 and the patient 10 walks. Here, as shown in FIG. 2, it is assumed that the y-axis direction and the z-axis direction of the acceleration sensor 2 coincide with the AP direction (Coronal direction) and the SI direction (Axial direction) of the subject 10, respectively. . In this case, the output of the acceleration sensor 2 can be described as follows using the acceleration of the subject 10 and the gravitational acceleration.

Here, A _z and A _y are outputs of the acceleration sensor 2 in the z-axis direction and the y-axis direction, respectively, and both include the influence of the gravitational acceleration g. Further, a _z and a _y are accelerations due to walking that should be observed, and are an acceleration component in the vertical direction (vertical direction) and an acceleration component in the horizontal traveling direction (front-rear direction), respectively. θ is an angle formed by the SI direction of the subject 10, that is, the z axis of the acceleration sensor 2 and the horizontal ground on which the subject 10 walks, and represents the posture of the subject 10. Therefore, when the subject 10 is upright and stationary, θ = 90 °.

  As can be seen from the equations (1) and (2), although the gravitational acceleration g itself is a constant, the influence of the gravitational acceleration g changes as the posture θ of the subject 10 changes.

Next, when (1) and (2) are squared and the sum is taken, the following (3) is obtained.

  Equation (3) does not include a trigonometric function of the angle θ representing the attitude of the acceleration sensor 2. Therefore, the expression (3) is configured such that each term can be specified even if the angle θ itself is unknown.

Next, g ² is subtracted from both sides of the expression (3) and integrated over the entire time, thereby obtaining the expression (4).

  In the equation (4), since the gravitational acceleration g is a constant, the left side of the equation (4) can be calculated using the actual output of the acceleration sensor 2.

  FIG. 3 is a graph obtained by obtaining the left side of equation (4) at each time using the output of the acceleration sensor attached to the waist of the person while walking and plotting them. From this graph, it can be seen that the left side of equation (4) gradually increases while vibrating at a constant period.

Here, since the first term on the right side of the equation (4) is the sum of the squares of the real numbers, it is always positive and keeps increasing according to the length of the integration time. In walking, it is rarely experienced that both the acceleration component a _z in the vertical direction and the acceleration component a _{y in} the horizontal traveling direction are close to 0 or close to the peak at the same time. I know. Therefore, the first term on the right side of the equation (4) tends to increase while maintaining a certain degree of linearity, that is, without having a large vibration component.

On the other hand, the second term on the right side of equation (4) is obtained by integrating and multiplying the vertical acceleration _az by walking. Since the vertical acceleration _az during walking has a peak at the landing and level crossing of the foot, it vibrates at a constant period, and it is thought that it vibrates at the same period as the second term on the right side of equation (4), which is the integral. . Each item can be explained as follows when compared with the curve of the graph of FIG.

  FIG. 4 is a diagram showing curves or straight lines corresponding to the terms in the expression (4) ′.

  Next, the first term on the right side of equation (4), which is a component that continues to increase, is generally expressed using a plot on the left side of equation (4) that is composed of constant gravitational acceleration g and the output of acceleration sensor 2. It can be obtained by a technique. For example, a mathematical method such as a least square method is applied to the plot on the left side of the equation (4) to obtain a straight line approximate to the plot or a smooth curve close to the straight line. Further, for example, an analytical method such as frequency analysis is applied to the plot on the left side of equation (4) to obtain a direct current component or a low frequency component close to direct current. Further, for example, smoothing processing is performed on the plot on the left side of equation (4) to obtain a smooth curve close to a straight line.

Thus, the first term on the left side and the right side of equation (4) can be obtained from the output of the acceleration sensor 2 and the gravitational acceleration g which is a constant. As a result, equation (4) can be expressed as follows.

If the parts that can be calculated are collectively F (t), they can be expressed as follows.

That is, the vertical acceleration _az at the time of walking can be calculated | required by dividing | segmenting the part F (t) which can be calculated by the constant 2g, and differentiating with time t. That is, by following the above-described process, the influence of the gravitational acceleration g that changes with the attitude of the acceleration sensor 2 can be greatly suppressed, and only the acceleration in the vertical direction during walking can be extracted and observed with high accuracy.

  The flow of this algorithm is summarized as follows.

FIG. 5 is a diagram showing a flow of an algorithm for obtaining the vertical acceleration component a _z generated by the walking of the subject 10.

In step T1, the value of the left side of equation (4) is obtained based on the outputs A _z and A _y of the acceleration sensor 2 and the gravitational acceleration g at each time t _i .

  In step T2, low frequency components that continue to increase are obtained based on the value on the left side of equation (4) obtained in step T1.

  In step T3, F (t) is obtained by subtracting the left side of equation (4) obtained in step T1 from the low frequency component obtained in step T2.

  In step T4, F (t) obtained in step T3 is divided by a constant 2g to obtain F (t) / 2g.

In step T5, F (t) / 2g obtained in step T4 is time-differentiated to obtain vertical acceleration _az .

In step T6, the acceleration a _y in the horizontal traveling direction is obtained by substituting the vertical acceleration a _z obtained in step T5 into equation (3).

  FIG. 6 is a diagram illustrating an example of a result of applying this algorithm to the output of the acceleration sensor 2 attached to the waist of the person while walking. In the waveform of this figure, two peaks due to landing and level crossing are seen in one cycle.

  FIG. 7 is a diagram illustrating an example of a comparison result between the case where the present algorithm is not applied and the case where the present algorithm is not applied to the output of the acceleration sensor 2 attached to the waist of the person while walking. When this algorithm is not applied, the gravitational acceleration subtraction process is performed on the assumption that the gravitational acceleration always acts in the same direction in the three-dimensional orthogonal coordinate system of the acceleration sensor. Note that the positive / negative of the vertical axis in the graph of FIG. 7 is opposite to the graph of FIG. 6 for various reasons.

Originally, when the subject 10 is moving horizontally such as walking, the total value of the vertical acceleration _az at each time in the subject 10 is theoretically considered when viewed in sufficient observation time. Takes a value close to zero. In the example of FIG. 7, in a _z sampling number i = 1000 to 2000, a sum Σa _z = 6.53 × 10 ³ of a _z in front the algorithm applied, the sum of a _z in after the algorithm applied Σa _z = 1.05 × 10 ⁻¹² . From this comparison result, it can be confirmed that the total value of the output of the same acceleration sensor 2 is closer to 0 after application compared to before application of the present algorithm. That is, it can be seen that the vertical acceleration _az of the subject 10 is calculated with higher accuracy after application than before application of the present algorithm.

  Hereafter, the flow of processing in the walking state display system will be described.

  FIG. 8 is a flowchart showing the flow of processing in the walking state display system.

In step S1, acceleration data at each time t _i during the walking of the subject 10 is acquired. Here, the acceleration sensor 2 is attached to the waist of the subject 10. Then, the subject 10 is made to walk at a standard walking speed for about 10 to 30 seconds, or about 10 to 20 steps. The acceleration sensor 2 samples and measures accelerations A _x , A _y , and A _z in the x-axis direction, the y-axis direction, and the z-axis direction while the subject 10 is walking. The transmission unit 21 transmits acceleration data representing the measured acceleration almost in real time. The walking state display device 3 receives and acquires the acceleration data transmitted from the transmission unit 21 using the reception unit 33.

In step S <b _> 2, the walking acceleration calculation unit 34 uses the above algorithm in consideration of the gravitational acceleration g based on the acquired acceleration data, and the acceleration a _z in the vertical direction (vertical direction) at each time in the subject 10, An acceleration a _{y in the} horizontal traveling direction (front-rear direction) is calculated. As the acceleration a _{x in the} left-right direction, the acceleration A _x in the x-axis direction represented by the acquired acceleration data is used as it is.

In step S3, the graph / map generator 35 generates a graph representing the temporal change of the vertical acceleration _az obtained in step S2. For example, in the two-dimensional coordinate space with the vertical acceleration a _z and the time t _i in the subject 10 as two axes, the data point [a corresponding to the vertical acceleration a _z (i) at each time t _{i z} (i), t _i ] are plotted, and a line graph is generated. Note that i is a sampling number, and time t _i is the time at which acceleration is sampled or the elapsed time from the start of data acquisition.

A graph map generation unit 35 generates a two-dimensional map representing the measured frequency or the trajectory of the acceleration a _y of the acceleration a _x and the horizontal moving direction of the horizontal direction obtained in step S2 (longitudinal direction) . For example, in a two-dimensional coordinate space in which the subject 10 has a left-right acceleration a _x and a horizontal traveling acceleration a _y as two axes, the horizontal acceleration a _x and the horizontal traveling acceleration at each time t _i. data points corresponding to a _y (i) integrated with each plotting _{[a x (i), a} y (i)], to produce a 2-dimensional histogram representing the frequency of each data point as a two-dimensional map.

  In step S4, the display control unit 37 causes the display unit 2 to display the graph generated in step S3 and the two-dimensional map.

According to the present embodiment, gait during walking output from the acceleration sensor 2 mounted on the subject 10 z-axis direction acceleration component acceleration component of A _z and y-axis direction A _y and the gravitational acceleration g Is obtained, and the acceleration component a _z in the vertical direction generated by the walking of the subject 10 is calculated as the vibration component of the waveform, so that the posture of the acceleration sensor 2 is unknown. In addition, the acceleration due to walking of the subject 10 can be theoretically derived, and the acceleration due to walking of the subject 10 can be obtained with high accuracy without attaching hardware other than the acceleration sensor 2 to the subject 10. .

In addition, according to the present embodiment, the acceleration component a _{z in the} vertical direction and the acceleration component a _{y in the} horizontal traveling direction, the gravitational acceleration g, and the acceleration in the z-axis direction obtained from the acceleration sensor 2 caused by the walking of the subject 10. In equation (4) representing the relationship between the component A _z and the acceleration component A _{y in the} y-axis direction, the left side having a value that continues to increase while oscillating with respect to time t is obtained using the output of the acceleration sensor 2 and obtained. By executing the process of obtaining the first term on the right side having a value that continues to increase with respect to time t from the left side and obtaining the second term on the right side including the vertical acceleration component a _z of the remaining subject 10 A vertical acceleration component a _z of the person 10 is obtained. Therefore, the vertical acceleration component a _z can be obtained without performing a huge amount of complicated calculations, and the burden on the calculation unit of the apparatus can be suppressed. As a result, a small mobile terminal such as a smartphone can be actively used as a walking state display device, and convenience in performing walking evaluation of the instructor is improved. For example, while walking the target person 10, a smartphone that is a walking state display device is put in a pocket, paying attention to the safety of the target person 10, and displayed on the walking state display device on the spot after walking. An acceleration graph or a two-dimensional map can be shown to the target person 10 to explain the result of the walking evaluation.

In addition, according to the present embodiment, not only the vertical acceleration component a _z of the subject 10 but also the acceleration component a _y in the horizontal traveling direction is highly accurate by an algorithm that does not require the posture of the acceleration sensor 2 to be specified. It is possible to provide the instructor with information that enables more appropriate and extensive gait evaluation.

  The invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the invention.

For example, in this embodiment, the time and graphs showing changes, in the horizontal direction by the walking of the subject 10 acceleration a _x and the horizontal traveling direction (longitudinal acceleration a _z in the vertical direction by the walking of the subject 10 (vertical direction) ) And a two-dimensional map representing the measured frequency or trajectory of the acceleration a _y is generated and displayed. However, for example, a graph representing the temporal change of the acceleration a _{y in} the horizontal traveling direction (front-rear direction) or the acceleration a _{x in} the left-right direction of the subject 10 and the measured frequency or trajectory of the acceleration in the other biaxial directions. A two-dimensional map may be generated and displayed.

  Further, for example, the present embodiment is an example in which the invention is applied to acceleration caused by a person's walking, but can also be applied to acceleration caused by other forward movements of a person, for example, acceleration caused by a person's running. .

  Further, for example, the present embodiment is a device that obtains the acceleration generated by the forward movement of the person from the output of the acceleration sensor worn on the person with high accuracy using the above algorithm, but for causing the computer to function as such a device. A program is also one embodiment of the invention.

DESCRIPTION OF SYMBOLS 1 Walking state display system 2 Acceleration sensor 3 Walking state display apparatus 10 Target person 21 Transmission part 31 Operation part 32 Display part 33 Reception part 34 Walking acceleration calculation part 35 Graph / map generation part 37 Display control part

Claims (15)

An acceleration sensor, which is attached to the person so that the x-axis in the Cartesian coordinate system with reference to the acceleration sensor substantially coincides with the left-right direction of the person, and the posture changes as the person moves forward and obtaining an acceleration component a _y of the acceleration component in the z-axis direction in the forward movement output from the acceleration sensor a _z and y-axis direction,
A waveform representing a temporal change of a physical quantity specified by the acceleration components A _z and A _y and the gravitational acceleration g acquired by the acquisition means is obtained, and vertical acceleration generated by the forward movement of the person as a vibration component of the waveform A step of calculating a component a _z , and a forward motion acceleration calculation method. The vertical acceleration component a _z and the horizontal acceleration component a _y generated by the forward movement of the person, the gravitational acceleration g, and the z-axis acceleration components A _z and y-axis directions obtained from the acceleration sensor. The following first mathematical expression representing the relationship with the acceleration component A _{y of}

The forward motion acceleration calculation method according to claim 1, wherein the vertical acceleration component a _z is obtained based on A first step of obtaining a left side of the first mathematical expression representing a waveform increasing while oscillating with respect to time t;
A second step of obtaining a first term on the right side of the first mathematical expression representing a component increasing with respect to time t based on the left side of the first mathematical expression obtained in the first step; ,
Subtracting the left side of the first mathematical formula obtained in the first step from the first term on the right side of the first mathematical formula obtained in the second step, the first representing the vibration component A third step for obtaining the second term on the right-hand side of the formula of 1;
A fourth step for obtaining the vertical acceleration component a _z by dividing the second term on the right side of the first mathematical formula obtained in the third step by 2 g and then differentiating it by time t; The forward motion acceleration calculation method according to claim 2, comprising: An acceleration sensor, which is attached to the person so that the x-axis in the Cartesian coordinate system with reference to the acceleration sensor substantially coincides with the left-right direction of the person, and the posture changes as the person moves forward and obtaining means for obtaining an acceleration component a _y of the z-axis direction acceleration component a _z and y-axis direction in the forward movement which is output from the acceleration sensor,
A waveform representing a temporal change of a physical quantity specified by the acceleration components A _z and A _y and the gravitational acceleration g acquired by the acquisition means is obtained, and vertical acceleration generated by the forward movement of the person as a vibration component of the waveform A forward motion acceleration calculating device comprising: calculating means for calculating a component a _z . The calculating means includes
The vertical acceleration component a _z and the horizontal acceleration component a _y generated by the forward movement of the person, the gravitational acceleration g, and the z-axis acceleration components A _z and y-axis directions obtained from the acceleration sensor. The following first mathematical expression representing the relationship with the acceleration component A _{y of}

The forward motion acceleration calculating apparatus according to claim 4, wherein the vertical acceleration component a _z is obtained based on The calculating means includes
A first step of obtaining a left side of the first mathematical expression representing a waveform increasing while oscillating with respect to time t;
A second step of obtaining a first term on the right side of the first mathematical expression representing a component increasing with respect to time t based on the left side of the first mathematical expression obtained in the first step; ,
Subtracting the left side of the first mathematical formula obtained in the first step from the first term on the right side of the first mathematical formula obtained in the second step, the first representing the vibration component A third step for obtaining the second term on the right-hand side of the formula of 1;
A fourth step for obtaining the vertical acceleration component a _z by dividing the second term on the right side of the first mathematical formula obtained in the third step by 2 g and then differentiating it by time t; The forward motion acceleration calculating apparatus according to claim 5, wherein:   In the second step, a least square method is applied to the plot of the left side of the first formula at each time, and a straight line or a curve that approximates the plot is obtained as the first term on the right side of the first formula. The forward motion acceleration calculating device according to claim 6, wherein the forward motion acceleration calculating device is a step of obtaining.   The second step performs a frequency analysis process on the left side plot of the first mathematical expression at each time, and as a first term on the right side of the first mathematical expression, a straight line representing a low frequency component of the plot or The forward motion acceleration calculating apparatus according to claim 6, which is a step of obtaining a curve.   The second step is a step of performing a smoothing process on a plot of the left side of the first mathematical expression at each time and obtaining a straight line or a curve that approximates the plot as the first term on the right side of the first mathematical expression The forward motion acceleration calculating apparatus according to claim 6, wherein The forward motion acceleration calculation apparatus according to any one of claims 4 to 9, further comprising a generation unit that generates a graph representing a temporal change in the acceleration component a _{z in} the vertical direction. The calculating means is the following second mathematical expression representing the relationship.

To, substituted and acceleration component A _y of the acceleration component A _z and y-axis direction of the z-axis direction, and the gravitational acceleration g, the acceleration component a _z of the fourth of the vertical direction obtained in step The forward motion acceleration calculating apparatus according to any one of claims 6 to 9, further executing a fifth step of obtaining the acceleration component _ay in the horizontal traveling direction. The acquisition means obtains an acceleration component A _x in the x-axis direction from the acceleration sensor as a lateral acceleration a _x generated by the forward movement,
Wherein further comprising a generating means for generating a two-dimensional map representing the lateral direction of the acceleration a _x and the frequency or the locus of the acceleration component a _y in the horizontal direction of travel, forward motion acceleration calculating apparatus according to claim 11.   The forward motion acceleration calculating device according to any one of claims 4 to 12, wherein the forward motion is walking.   The forward motion acceleration calculating apparatus according to any one of claims 4 to 12, wherein the forward motion is traveling. The program for functioning a computer as a forward movement acceleration calculation apparatus as described in any one of Claims 4-14.

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