JP6382775B2 - Step counting device, step counting method, and program - Google Patents

Description

  The present invention relates to a step count measuring apparatus, a step count measuring method, and a program for measuring the number of steps due to walking or running of a person.

  2. Description of the Related Art Conventionally, as a biological information measuring device for measuring human biological information, a step count measuring device for measuring the number of steps by walking or running of a worn person is known. Many of the step counting devices include three-axis acceleration sensors orthogonal to each other, detect the walking or running of a person wearing the acceleration sensor, and measure the number of steps by walking or running.

  For example, in Non-Patent Document 1, a piezoresistive three-axis acceleration sensor detects accelerations in the X-axis, Y-axis, and Z-axis directions, and a value obtained by combining the detected three-axis accelerations (three-axis A technique of counting the number of steps is considered that the occurrence of walking is that the combined value of (1) becomes higher than 1G after being lower than 1G. Non-Patent Document 2 discloses a system configuration diagram of a conventional step count measuring device that counts the number of steps based on a composite value of three axes and displays the counted number of steps on a display device.

"Triaxial acceleration sensor application note piezoresistive type triaxial acceleration sensor HAAM-326B pedometer", 1st edition, Hokuriku Electric Industry Co., Ltd., February 2007. “Low-Power Pedometer Using an MSP430TM MCU”, Dennis Lehman, Application Report, SLAA599, TEXAS INSTRUMENT, May 2013.

  It has been clarified by the inventors of the present application that the conventional step counting technique disclosed in Non-Patent Document 1 and Non-Patent Document 2 may erroneously detect human walking. Details will be described below.

  In the conventional step count measurement techniques disclosed in Non-Patent Document 1 and Non-Patent Document 2, a triaxial composite value is calculated by (Equation 1).

In equation (1), a _[n] is a composite value of triaxial acceleration, and ax _[n] , _{ay [n]} , and _{az [n]} are measured by a triaxial acceleration sensor. The measured values of acceleration in the directions of the nth (n is an integer of 1 or more) th axis from the start of step count measurement.

  As can be understood from the above equation (1), the combined value of the three-axis accelerations is always “0” or more. Therefore, even if the acceleration values in the respective axis directions are all “negative” values, the combined value of the three axes is positive.

  In general, when a person walks or runs (hereinafter referred to as “walking motion”), the ground contact period in which one of the left foot and the right foot is in contact with the floor, and both the left foot and the right foot are not floating. There is a grounding period. In the ground contact period, due to the impact of one foot on the ground, a large force is instantaneously applied from the ground to the pedestrian's body vertically upward (vertically upward). Since the pedestrian's body is stagnant during the non-contact period, the force applied to the body generates only a gravitational acceleration that is vertically downward (vertically downward) with respect to the ground.

For example, during a walking motion in which the wearer's body movement is large, a ground contact period and a non-ground contact period are alternately repeated, and acceleration vibration in a direction perpendicular to the ground occurs in the pedestrian's body. This time change of acceleration vibration is considered to be a sinusoidal periodic waveform.
In other words, the composite value of the acceleration calculated by the above formula (1) has a characteristic that it is convex during the ground contact period and concave during the non-ground contact period. Therefore, the number of steps can be counted by detecting the occurrence of the peak of the composite value of acceleration.

  However, in the conventional method for measuring the number of steps, in a walking operation in which the grounding period and the non-grounding period are alternately repeated, such as running where the wearer's body movement is large, acceleration is performed not only during the grounding period but also during the grounding period. The combined value of may increase. An example is shown in FIG.

FIG. 10 is a diagram illustrating a step count calculation result by a step count measuring apparatus including a conventional triaxial acceleration sensor.
FIG. 10 shows, as an example of a motion during walking or running of a person (hereinafter referred to as “walking motion”), a characteristic 1001 of a composite value of triaxial acceleration during a walking motion with a large body motion of the wearer. And the number of steps 1002 measured based on the composite value.

  The step count 1002 shown in FIG. 10 is measured by the step count detection algorithm of the conventional step count measurement device described in “Step Count Measurement Method” and “Table 1” of Non-Patent Document 1. Specifically, the number of steps 1002 first detects that the combined value of the three axes is lower than the threshold “0.9G” as the first step, and then within a certain time (1 second) as the second step. If it is detected that the composite value of the three axes is higher than the threshold value “1.1G” and the difference from the previous composite value of the three axes is greater than or equal to the threshold value “0.2G”, the number of steps is counted. This is the result obtained by the step count detection algorithm that returns to the first step again when is established or not established.

  As shown in FIG. 10, in the walking motion in which the wearer's body movement is large, the contact period and the non-contact period are alternately repeated, and the composite value of the acceleration becomes convex in the contact period, and the composite value of the acceleration in the non-contact period Becomes concave.

  However, as indicated by reference numeral 1003 in FIG. 10, the combined acceleration value may increase even in the non-ground period. The increase in the composite value is such that at least one of the measured values of the three axes becomes a large “negative” value, and when the composite value of the three axes is calculated according to the above equation (1), the large “negative” value is squared. This is considered to be because the sign is inverted and a large “positive” peak value is obtained. When the generation of the positive peak of the composite value resulting from the sign inversion satisfies the conditions for detecting the number of steps, an erroneous detection of the number of steps occurs as shown in FIG.

  If there is such an erroneous detection of the number of steps, an error occurs between the actual number of steps and the detected number of steps, and the error is accumulated, so that the accuracy as the step counting device is significantly lowered. As a result, wrong information is presented to the wearer of the pedometer, and there is a risk that the quality of life of the wearer who is keeping good health will be significantly impaired.

  The present invention has been made in view of the above problems, and an object of the present invention is to reduce the occurrence of erroneous detection of the number of steps due to walking or running of a person.

  The step count measuring apparatus according to the present invention combines a measurement value of acceleration of each measurement axis (xa, ya, za) measured by an acceleration sensor (101) having a plurality of measurement axes to calculate a combined value. A wearer who wears the acceleration sensor based on the inclination calculation unit (12), the inclination calculation unit (13) that calculates the inclination of the acceleration sensor with respect to the vertical direction based on the measurement values of the acceleration of the respective measurement axes A vibration direction determination unit (14) that determines the direction of vibration in the vertical direction, a composite value correction unit (15) that corrects a composite value based on the vibration direction determined by the vibration direction determination unit, and a composite value And a step number calculating unit (16) for calculating the number of steps by walking or running by the wearer of the acceleration sensor based on the composite value corrected by the correcting unit.

  In the step counting device, the inclination calculating unit (13) receives the combined value calculated by the combined value calculating unit, and extracts a vector quantity (a [n] ′) based on gravitational acceleration, and a low-pass filter (131). An angle calculation unit (132) that calculates an angle between the vector amount based on the gravitational acceleration and each measurement axis of the acceleration sensor may be included.

  In the step counting device, the vibration direction determination unit is configured to determine the vibration direction in the vertical direction of the wearer wearing the acceleration sensor based on the sign of the acceleration measurement value of the measurement axis with the smallest angle calculated by the angle calculation unit. May be determined.

  In the step count measuring apparatus, the composite value correction unit, when the vibration direction determination unit determines that the vibration of the wearer wearing the acceleration sensor is vertically upward, indicates a sign of the composite value calculated by the composite value calculation unit. If the vibration direction determination unit determines that the vibration of the wearer wearing the acceleration sensor is vertically downward, the sign of the composite value calculated by the composite value calculation unit may be negative.

  In the step count measuring apparatus, a sensor unit (10) having an acceleration sensor, an output unit (103) for outputting a measurement value of acceleration for each measurement axis measured by the acceleration sensor, and each measurement axis output from the output unit And a storage unit (11) for storing a measured value of acceleration of the sensor. The sensor unit and the output unit are formed in the first terminal (3), and the storage unit, the composite value calculation unit, the inclination calculation unit, the vibration direction The determination unit, the composite value correction unit, and the step count calculation unit may be formed in a second terminal (4) different from the first terminal.

  In the above description, as an example, constituent elements on the drawing corresponding to the constituent elements of the invention are represented by reference numerals with parentheses.

  According to the present invention, it is possible to reduce the occurrence of erroneous detection of the number of steps due to walking or running of a person.

FIG. 1 is a diagram showing a configuration of a step count measuring apparatus according to the first embodiment. FIG. 2 is a diagram showing an outline of the step count measurement process of the step count measuring apparatus according to the first embodiment. FIG. 3 is a diagram illustrating the flow of the inclination calculation process performed by the inclination calculation unit. FIG. 4 is a diagram illustrating an example of an internal configuration of the inclination calculation unit. FIG. 5 is a diagram for explaining a process for calculating the inclination of each measurement axis of the acceleration sensor with respect to the gravitational acceleration. FIG. 6 is a diagram illustrating a flow of determination processing of the direction of vibration in the vertical direction by the vibration direction determination unit. FIG. 7 is a diagram illustrating a step count measurement result of the step count measuring apparatus according to the first embodiment. FIG. 8 is a diagram showing a configuration of the step count measuring apparatus according to the second embodiment. FIG. 9 is a diagram illustrating a specific implementation example of the step count measuring apparatus according to the second embodiment. FIG. 10 is a diagram illustrating a step count calculation result of a step count measuring apparatus including a conventional triaxial acceleration sensor.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<< Embodiment 1 >>
<Configuration of Step Counting Apparatus 1 According to Embodiment 1>
FIG. 1 is a diagram showing a configuration of a step count measuring apparatus according to the first embodiment.
A step count measuring apparatus 1 shown in FIG. 1 is mounted on a living body represented by a person, for example, and measures the number of steps by walking or running of the mounted living body (wearer) based on the detection result of acceleration by an acceleration sensor. It is. The step count measuring apparatus 1 has a function of detecting an appropriate number of steps in consideration of acceleration vibration in a direction perpendicular to the ground during the wearer's walking motion.
Hereinafter, a specific configuration of the step count measuring apparatus 1 will be described.

  As shown in FIG. 1, the step count measuring apparatus 1 includes a sensor unit 10, a storage unit 11, a composite value calculation unit 12, an inclination calculation unit 13, a vibration method determination unit 14, a composite value correction unit 15, a step calculation unit 16, and A display unit 17 is included.

  The sensor unit 10 is a functional unit that reads biological information generated by the movement of the wearer's body and gravity. The sensor unit 10 includes, for example, an acceleration sensor 101 having a plurality of measurement axes and an A / D converter 102.

  The acceleration sensor 101 is a triaxial acceleration sensor having three measurement axes, for example, an X axis, a Y axis, and a Z axis, and measures the acceleration of each measurement axis of the X axis, the Y axis, and the Z axis.

The A / D converter 102 converts the measured values of the analog axes measured by the acceleration sensor 101 into digital signals at a predetermined conversion period, and measures the measured values of acceleration in the X-axis direction (X-axis acceleration) a. _{x [n]} , Y-axis direction acceleration measurement value (Y-axis acceleration) a _{y [n]} , and Z-axis direction acceleration measurement value (Z-axis acceleration) a _{z [n]} are output. Here, as described above, n is an integer equal to or greater than 1, and the order from the start of measurement (for example, the order in which A / D conversion processing is performed or the calculation order of the composite value of acceleration described later). Represents.

  The storage unit 11 is a functional unit for storing measured values of acceleration of each axis output from the sensor unit 10. Examples of the storage unit 11 include a rewritable nonvolatile memory such as a flash memory, a RAM (Random Access Memory), and the like.

  The composite value calculation unit 12, the inclination calculation unit 13, the vibration method determination unit 14, the composite value correction unit 15, and the step count calculation unit 16 are realized by program processing executed by a program processing device such as an MCU (Memory Control Unit), for example. Is done.

  The composite value calculation unit 12 calculates the composite value by combining the acceleration measurement values of the respective measurement axes stored in the storage unit 11.

  The inclination calculation unit 13 is a functional unit for detecting the attachment angle of the acceleration sensor 101 when the step count measuring device 1 is worn on a living body. Specifically, the inclination calculation unit 13 calculates an inclination (inclination) with respect to a direction (vertical direction) perpendicular to the ground of the acceleration sensor 101 based on the acceleration measurement value of each measurement axis stored in the storage unit 11. calculate.

  The vibration direction determination unit 14 is a functional unit that determines the vibration direction (phase) of the wearer wearing the acceleration sensor 101 in the vertical direction based on the inclination calculated by the inclination calculation unit 13.

  The composite value correction unit 15 is a functional unit for correcting the composite value of acceleration according to the vertical movement of the wearer of the acceleration sensor 101. Specifically, the composite value correction unit 15 corrects the composite value calculated by the composite value calculation unit 12 based on the vibration direction of the wearer in the vertical direction determined by the vibration direction determination unit 14.

  The step count calculation unit 16 is a functional unit that calculates the number of steps by walking or running by the wearer based on the corrected composite value corrected by the composite value correction unit 15. Specifically, the step count calculation unit 16 detects a change in the composite value of the corrected acceleration that satisfies the step count detection condition, and calculates the number of steps based on the number of detections.

  Here, the step count detection condition is a condition for determining the presence or absence of walking or running on the basis of a change in the composite value of the corrected acceleration with time. Details of the step count detection condition will be described later.

  The display unit 17 is a functional unit for visually providing information on the number of steps calculated by the step number calculating unit 16 to users including the wearer. Examples of the display unit 17 include display devices such as a liquid crystal display and an organic EL display.

<Step Counting Process by Step Counting Apparatus 1 According to Embodiment 1>
Next, the step count measurement process by the step count measuring apparatus 1 will be described.
FIG. 2 is a diagram showing an outline of the step count measurement process by the step count measuring apparatus according to the first embodiment.

  First, the step count measuring apparatus 1 synthesizes the measured values of triaxial acceleration by the acceleration sensor 101 stored in the storage unit 11, and calculates a combined value of acceleration (S1). Next, the step count measuring apparatus 1 calculates the inclination of the acceleration sensor 101 with respect to the vertical direction based on the measurement value of the acceleration of each measurement axis (S2). Next, the step counting device 1 determines the direction of vibration in the vertical direction of the wearer of the acceleration sensor 101 based on the inclination calculated in step S2 (S3). Next, the step count measuring apparatus 1 corrects the combined acceleration value of each measurement axis calculated in step S1 based on the vibration direction determined in step S3 (S4). Thereafter, the step count measuring apparatus 1 calculates the number of steps due to walking or running of the wearer based on the corrected composite value obtained in step S4 by the step count calculating unit 16 (S5).

  Thereafter, the information on the calculated number of steps is displayed on the display unit 17. Note that the information on the number of steps is not only displayed on the display unit 17 but may be stored in the storage unit 11 or may be transmitted to an external device wirelessly or by wire.

  Next, each step in the step count measurement process shown in FIG. 2 will be described in detail.

(1) Step S1 (calculation process of acceleration synthesized value a [n])
In step S _< b _> 1, the composite value calculation unit 12 performs triaxial acceleration based on the acceleration measurement values (ax _[n] , _{ay [n]} , and _{az [n]} ) stored in the storage unit 11. The composite value a _[n] is calculated. Specifically, the composite value calculation unit 12 calculates the composite value a _[n] of the triaxial acceleration by performing the calculation of the above-described equation (1).

(2) Step S2 (inclination calculation process)
In step S <b> 2, the inclination calculation unit 13 calculates the inclination of the acceleration sensor 101 with respect to the vertical direction.

FIG. 3 is a diagram illustrating the flow of the tilt calculation process performed by the tilt calculation unit 13.
As shown in FIG. 3, the inclination calculating unit 13 first extracts a vector amount based on gravitational acceleration by removing high-frequency components from the combined value a _{[n] of the} triaxial acceleration (S31). Next, the inclination calculation unit 13 calculates the inclination of each measurement axis of the acceleration sensor 101 with respect to the gravitational acceleration based on the extracted vector amount based on the gravitational acceleration (S32). Hereinafter, the processes of steps S31 and S32 will be described in detail.

FIG. 4 is a diagram illustrating an example of an internal configuration of the inclination calculation unit 13.
As shown in FIG. 4, the inclination calculation unit 13 includes a low-pass filter 131 and an angle calculation unit 132.

The low-pass filter 131 is a functional unit for realizing the process of step S31. The X-axis acceleration a _{x [n]} , Y-axis acceleration a _{y [n]} , and Z-axis acceleration stored in the storage unit 11 are stored in the storage unit 11. Band limiting processing is performed on the acceleration a _{z [n]} and the combined value a _{[n] of the} three-axis acceleration.
In the present embodiment, the low-pass filter 131 will be described using a filter that performs the band limiting process represented by Expression (2) as an example.

In equation (2), β _[n] represents the input of the low-pass filter 131, and any of the above-described a _{x [n]} , a _{y [n]} , a _{z [n]} , and a _[n] is substituted. The β ′ _[n] represents the output of the low-pass filter 131. Further, h is an arbitrary filter coefficient and is a value in the range of 0 to 1. The closer h is to “1”, the stronger the band limiting effect of the low-pass filter 131 and the wider the frequency band to be removed.

  In equation (2), for example, when h = 0.9, it means that 90% of the acceleration measured in the previous measurement cycle is taken over by the acceleration measured in the next measurement cycle. By setting the filter coefficient h to about 0.9 (for example, h = 0.85 to 0.95), only the occurrence of sharp irregularities can be removed by means of continuation of the previous measurement value.

  As described above, when acceleration data is input to the low-pass filter 131, high-frequency components included in the acceleration data, that is, sharp irregularities are removed, so that the change in acceleration (acceleration characteristics) with the passage of time becomes a sine wave. Close shape.

In step S21 described above, by inputting the resultant value a of the acceleration to a low-pass filter 131 [n], high frequency components are removed, combined value includes only low frequency components _a'[n] is calculated. Thereby, the acceleration component due to the body movement of the wearer of the acceleration sensor 101 is removed, and the vector amount a ′ _[n] in which the gravitational acceleration component is dominant can be obtained. Hereinafter, the vector quantity _a'[n], referred to as vector quantity _a'[n] based on the gravitational acceleration.

By referring to the vector quantity a ′ _[n] based on the gravitational acceleration, it is possible to determine the direction of the gravitational acceleration. Further, according to the low-pass filter 131 represented by Expression (2), acceleration data measured in the next measurement cycle by the two items “(1-h) β [n]” on the right side in Expression (2). Is updated (in the case of h = 0.9, 10% of the acceleration data of the next measurement cycle), it is possible to follow a rough change in the posture of the wearer.

In general, an acceleration sensor measures not the gravitational acceleration itself but the reaction force as a reaction, and thus the vector amount a ′ _[n] based on the gravitational acceleration represents the reaction of the gravitational acceleration.

  The angle calculation unit 132 is a functional unit for realizing the process of step S22, and calculates the inclination of each measurement axis of the acceleration sensor 101 with respect to the gravitational acceleration.

FIG. 5 is a diagram for explaining processing for calculating the inclination of each measurement axis of the acceleration sensor 101 with respect to the gravitational acceleration.
In FIG. 5, the Z axis is an axis in a direction perpendicular to the ground (vertical direction). The X axis and the Y axis are orthogonal to each other and also orthogonal to the Z axis. Further, the xa axis, the ya axis, and the za axis are measurement axes of the acceleration sensor 101.

  The directions of the measurement axes of the acceleration sensor 101, the xa axis, the ya axis, and the za axis, depend on the angle at which the acceleration sensor 101 is attached to the wearer's body, and therefore are not necessarily the xa axis, ya axis, and za axis. Neither is an axis perpendicular to the ground. Therefore, the angle calculation unit 202 determines the inclination (deviation) of the xa axis, the ya axis, and the za axis with respect to the Z axis perpendicular to the ground as an angle between the reaction of gravity acceleration and each measurement axis of the acceleration sensor 101. Calculate as

Specifically, as shown in FIG. 5, the angle calculation unit 132 performs the acceleration a ′ _{x [n] on} the xa axis after passing through the low-pass filter 131 with respect to the vector amount a ′ _[n] based on the gravitational acceleration. Information on the angle between the ya-axis acceleration a ′ _{y [n]} and the za-axis acceleration a ′ _{z [n]} is calculated. More specifically, by solving the following equations (3), (4), and (5), information on the angles of the xa axis, the ya axis, and the za axis with respect to the vector quantity a ′ _[n] based on the gravitational acceleration. sin θx [n], sin θy [n], and sin θz [n] are calculated.

(3) Step S3 (Vertical vibration direction determination process)
In step S3, the vibration direction determination unit 14 determines the vibration direction of the wearer of the acceleration sensor 101 in the vertical direction based on the inclination calculated in step S2.

FIG. 6 is a diagram illustrating a flow of the determination process of the vibration direction in the vertical direction by the vibration direction determination unit 14.
As shown in FIG. 6, first, the vibration direction determination unit 14, the measurement axes x _a of the acceleration sensor 101, y _a, and among the z _a, the closest outermost vertical axis in the vertical direction axis (Z axis) Determine (S31). Specifically, the vibration direction determination unit 14 uses the angle information sin θ _{x [n]} , sin θ _{y [n]} , sin θ _{z [} calculated by the angle calculation unit 132 based on the above formulas (3) to (5) _{. n]} are compared, and the measurement axis having the smallest information of the angle is set as the most vertical axis.

For example, when | sin θ _{x [n]} | ≦ | sin θ _{y [n]} | and | sin θ _{x [n]} | ≦ | sin θ _{z [n]} |, the x _a axis of the acceleration sensor 101 becomes the most vertical axis. . _{Moreover, | sinθ y [n] |} ≦ | sinθ x [n] |, and _{| sinθ y [n] | ≦} | sinθ z [n] | When, y _a-axis of the acceleration sensor 101 is uppermost vertical axis . Further, when | sin θ _{z [n]} | ≦ | sin θ _{x [n]} | and | sin θ _{z [n]} | ≦ | sin θ _{y [n]} |, the z _a axis of the acceleration sensor 101 is the most vertical axis. .

  Next, the vibration direction determination unit 14 determines the orientation of the vertical axis with respect to the ground determined in step S31 (S32). Specifically, the vibration direction determination unit 14 determines whether the most vertical axis is upward (vertically upward) or downward from the sign of the acceleration value of the most vertical axis after passing through the low-pass filter 131. It is determined whether it is (vertically downward).

For example, if x _a-axis is the most vertical axis, if the acceleration a'x _[n] ≧ 0 for x _a-axis after passing through the low-pass filter 131, x _a-axis which is the uppermost vertical axis vertically upward is determined to be, if a'x _[n] <0, it is determined that x _a-axis which is the uppermost vertical axis is vertically downward. For example, when y _a-axis is the most vertical axis, if the acceleration a'y _[n] ≧ 0 for y _a-axis after passing through the low-pass filter 131, y _a-axis which is the uppermost vertical axis it is determined to be vertically upward, if ay' _[n] <0, it is determined that y _a-axis which is the uppermost vertical axis is vertically downward. For example, when z _a-axis is the most vertical axis, if the acceleration a'z _[n] ≧ 0 of z _a-axis after passing through the low-pass filter 131, z _a-axis which is the uppermost vertical axis If it is determined to be vertically upward and a ′ _{z [n]} <0, it is determined that the z _a axis that is the most vertical axis is vertically downward.

Next, the vibration direction determination unit 14 determines the direction of vibration in the vertical direction of the wearer of the acceleration sensor 101 (S33). Specifically, the phase of the combined value a _[n] with respect to the most vertical axis is determined based on the measured value of the acceleration of the most vertical axis and the direction of the most vertical axis determined in step S32.

For example, when the x _a axis that is the most vertical axis is vertically upward, and the acceleration a _{x [n]} ≧ 0 of the x _a axis before passing through the low-pass filter 131, the combined value a _[n] is the most vertical axis. It is determined that the vibration in the vertical direction of the wearer of the acceleration sensor 101 is vertically upward. On the other hand, if the acceleration a _{x [n]} <0 of the x _a axis, the composite value a _[n] is in an opposite phase to the most vertical axis, and the vibration in the vertical direction of the wearer of the acceleration sensor 101 is vertically downward. Judge that there is.

For example, when y _a-axis which is the uppermost vertical axis is vertically upward, if the acceleration a _{y [n]} ≧ 0 for y _a-axis before passing the low-pass filter 131, the combined value a _[n] is the outermost It is determined that the vibration in the wearer's vertical direction of the acceleration sensor 101 is vertically upward with respect to the vertical axis. On the other hand, if the acceleration a _{y [n]} <0 for x _a-axis, the combined value a _[n] is the opposite phase to the uppermost vertical axis, vibration in the vertical direction of the wearer of the acceleration sensor 101 in vertically downward Judge that there is.

Also, for example, when the z _a axis that is the most vertical axis is vertically upward, and the acceleration az [n] ≧ 0 of the z _a axis before passing through the low-pass filter 131, the combined value a _[n] is the most vertical. It is determined that the vibration is in the vertical direction of the wearer of the acceleration sensor 101 and is vertically upward with respect to the axis. On the other hand, if the acceleration a _{z [n]} <0 of the z _a axis, the composite value a _[n] is in an opposite phase to the most vertical axis, and the vibration in the vertical direction of the wearer of the acceleration sensor 101 is vertically downward. Judge that there is.

(4) Step S4 (Correction process of acceleration composite value)
In step S4, the composite value correction unit 15 corrects the composite value of the acceleration of each measurement axis based on the vibration direction of the wearer in the vertical direction determined in step S3.
Specifically, if it is determined in step S3 that the wearer's vertical vibration is vertically upward, the sign of the composite value a _[n] calculated by the composite value calculator 12 is “positive”. When the wearer's vertical vibration is determined to be vertically downward, the sign of the composite value a _[n] calculated by the composite value calculation unit 12 is set to “negative”.

That is, the corrected acceleration composite value A _[n] is expressed by Equation (6) when it is determined that the wearer's vertical vibration is vertically upward, and the wearer's vertical vibration is Is determined to be vertically downward, it is expressed by equation (7).

  Thereby, a composite value having a vector having the same sign as the vibration direction of the wearer in the vertical direction can be obtained.

(5) Step S5 (step count calculation process)
In step S5, the number-of-steps calculation unit 16 counts the number of times that the variation with time of the corrected acceleration composite value A _[n] calculated in step S4 satisfies the number of steps detection condition, and the number of times is used as the number of steps. calculate.

Here, as an example, the step count calculation unit 16 employs the same number of step detection conditions as the conventional step count measuring apparatus shown in FIG. That is, the step count calculating unit 16 calculates the corrected acceleration within a certain time (for example, 1 second) after the combined value A _[n] of the corrected acceleration becomes lower than the first threshold (for example, 0.9 G). The composite value A _[n] is higher than the second threshold (for example, 1.1 G), and the difference from the composite value A _[n] of the acceleration after the previous correction is not less than the third threshold (for example, 0.2 G). This is the step count detection condition.

When the corrected composite value A _[n] satisfies the above-described step count detection condition, the step count calculation unit 16 determines that there has been a walk or a run and counts up the number of steps. On the other hand, if the corrected composite value A _[n] does not satisfy the above step count detection condition, the step count is not counted up.

<Effects of the step counting device 1 according to Embodiment 1>
FIG. 7 is a diagram showing a step count measurement result by the step count measuring apparatus 1 according to the first embodiment.
FIG. 7 shows the characteristic 2001 of the composite value A _[n] after correction by the step count measuring apparatus 1 and the number of steps 2002 obtained based on the composite value A _[n] after correction.

Further, the characteristic 2001 and the number of steps 2002 of the corrected composite value A _[n] shown in FIG. 7 are the same as those of the conventional step counting device shown in FIG. 10 with respect to the step counting device 1 according to the first embodiment. This is a result obtained by applying the same step count calculation algorithm to the step count calculation unit 16 using the acceleration data of each measurement axis.

As understood from FIG. 7, according to the step count measuring apparatus 1, the corrected composite value A _[n] is a value considering the wearer's vertical vibration direction. Unlike a measuring device, it is a positive or negative value.

As a result, even if at least one of the measured values of the three axes becomes a large “negative” value during the non-ground period, the corrected composite value A _[n] is inverted as in the conventional case. Therefore, it is possible to prevent erroneous detection of the number of steps due to the convex peak of the composite value during the non-contact period, which is seen in the measurement result of the conventional step counting device shown in FIG. it can.

  As described above, according to the step count measuring apparatus 1 according to the first embodiment, the direction of vibration in the vertical direction of the wearer wearing the acceleration sensor 101 is determined based on the inclination of each measurement axis of the acceleration sensor 101 with respect to the vertical direction. In addition, the combined value of the acceleration of each measurement axis of the acceleration sensor 101 is corrected according to the determined vertical vibration direction, and the number of steps is detected based on the corrected combined value. It is possible to prevent erroneous detection of the number of steps during the non-ground period that occurs during operation.

  Thereby, compared with the conventional step counting device, it is possible to reduce the occurrence of erroneous detection of the step number, and it is possible to present more accurate step number information to the wearer of the step counting device.

  Further, according to the step count measuring apparatus 1, a vector amount based on the gravitational acceleration is extracted by passing a combined value of accelerations of the respective measurement axes of the acceleration sensor 101 through a low-pass filter, and the vector amount based on the extracted gravitational acceleration and the acceleration sensor are extracted. By calculating the angle of each measurement axis 101, the inclination of the measurement axis of the acceleration sensor 101 with respect to the vertical direction can be easily calculated.

  In addition, according to the step count measuring apparatus 1, the measurement axis with the smallest angle information calculated by the angle calculation unit is set as the most vertical axis closest to the vertical axis (Z axis), and the acceleration of the vertical axis is measured. By determining the sign of the value, the direction of vibration in the vertical direction of the wearer wearing the acceleration sensor 101 can be easily determined.

  Further, according to the step count measuring apparatus 1, when the vibration direction determination unit 14 determines that the wearer's vibration is vertically upward, the sign of the composite value of acceleration is positive, and the wearer's vibration is determined to be vertically downward. In this case, by performing a correction that makes the sign of the composite value of acceleration negative, it is possible to easily calculate the composite value in consideration of the wearer's vertical vibration.

<< Embodiment 2 >>
FIG. 8 is a diagram showing a configuration of the step count measuring apparatus according to the second embodiment.
The step count measuring apparatus 2 according to the second embodiment is such that the sensor unit 10 including the acceleration sensor 101 and the signal processing unit for calculating the number of steps such as the composite value correction unit 15 are formed in separate terminals. This is different from the step counting device 1 according to the first embodiment.

  In the step count measuring apparatus 2 according to the second embodiment, the same components as those in the step count measuring apparatus 1 according to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

Specifically, the step count measuring device 2 includes a sensor terminal 3 and a child terminal 4.
The sensor terminal 3 includes a sensor unit 10 and an output unit that outputs measurement values (ax _[n] , _{ay [n]} , and _{az [n]} ) of acceleration of each measurement axis measured by the sensor unit 10. 103 is a wearable device.

  The child terminal 4 includes a sensor unit 10, a storage unit 11, a composite value calculation unit 12, an inclination calculation unit 13, a vibration method determination unit 14, a composite value correction unit 15, a step count calculation unit 16, a display unit 17, and a data acquisition unit 18. have.

  The data acquisition unit 18 acquires the measurement value of the acceleration of each measurement axis output from the sensor terminal 3 and stores it in the storage unit 11. The composite value calculation unit 12, the inclination calculation unit 13, the vibration method determination unit 14, the composite value correction unit 15, and the step count calculation unit 16 are for calculating the number of steps as in the step count measuring apparatus 1 according to the first embodiment. Perform various signal processing.

FIG. 9 is a diagram illustrating a specific implementation example of the step count measuring apparatus according to the second embodiment.
As shown in FIG. 9, the sensor terminal 3 is attached to a garment 5 or the like that can be worn by a user (living body). In FIG. 9, a shirt is illustrated as the garment 5, but the garment 5 may be anything that can be worn by the user, and may be, for example, a pant, a belly, a supporter, a band, or the like.

  The sensor terminal 3 and the child terminal 4 can communicate with each other by wire or wireless. Specifically, the child terminal 4 is connected to the sensor terminal 3 by low-power radio such as Bluetooth (registered trademark), for example, and receives a measured value of acceleration output from the sensor terminal 3. The child terminal 4 is an information processing terminal such as a mobile phone, a smartphone, or a tablet terminal.

  The child terminal 4 calculates the number of steps based on the acceleration measurement value received from the sensor terminal 3 by the same method as the step count measuring apparatus 1 according to the first embodiment, and displays the calculated step number information on the display unit 11. To do. The child terminal 4 is connected to a communication network by wireless communication such as a cellular method or a wireless LAN method. For example, the calculated number of steps and the position information of the child terminal 4 are transmitted to the server or the like via the communication network. May be.

  As described above, according to the step count measuring apparatus 2 according to the second embodiment, the sensor unit 10 and the other signal processing units are separated from each other, and the sensor terminal 3 and the child terminal 4 are configured separately. The terminal 3 can be reduced in size and can be kept out of the way for the user to carry. In addition, since the power saving of the sensor terminal 3 is possible, the sensor terminal 3 can be operated for a long time, and the user can be saved from the trouble of charging.

  Although the invention made by the present inventors has been specifically described based on the embodiments, it is needless to say that the present invention is not limited thereto and can be variously modified without departing from the gist thereof. Yes.

  For example, although the case where the acceleration sensor 101 is a triaxial acceleration sensor has been described as an example in the above embodiment, the present invention is not limited to this. For example, the acceleration sensor 101 may be an acceleration sensor having two measurement axes, or may be an acceleration sensor having four or more measurement axes. Similarly, when the acceleration sensor is other than three axes, the most vertical axis closest to the vertical axis (Z axis) is found from the plurality of measurement axes, and the composite value is calculated based on the sign of the acceleration of the most vertical axis. If corrected, the same effect as the above embodiment can be expected.

  In the above embodiment, in the step count calculation algorithm by the step count calculation unit 16, the corrected acceleration composite value becomes higher than the second threshold value after the corrected acceleration composite value becomes lower than the first threshold value. Although the case where this is used as the step count detection condition is illustrated, it is not limited to this. For example, the step count detection condition may be that the composite value of the corrected acceleration becomes lower than the first threshold value after the composite value of the corrected acceleration becomes higher than the second threshold value. The step count detection condition may be that the corrected combined value becomes higher than the second threshold without detecting that the value has decreased below the first threshold.

  In general, when walking occurs, the acceleration sensor first swings upward, so that it is possible to detect the number of steps quickly in time by giving priority to the detection of the fluctuation of the composite value in the positive direction (upward) as described above. .

In the step count measuring apparatuses 1 and 2, the acceleration measurement values (ax _[n] , _{ay [n]} , _{az [n]} ) and the composite value a _[n] of each measurement axis of the acceleration sensor 101 are used. When performing signal processing, it is possible to appropriately limit the bandwidth. For example, a high-frequency noise component may be removed by using a low-pass filter, a band-pass filter, or the like before or after performing various signal processing. For example, when the sampling rate is very fine and the noise of high frequency components is noticeable, the band limiting filtering may be performed a plurality of times before and after the calculation of the synthesized value of acceleration.

  Moreover, in the step count measuring apparatus 2 according to the second embodiment, the case where the composite value calculation unit 12 is provided in the child terminal 4 is illustrated, but the composite value calculation unit 12 is built in the sensor terminal 3 and each measurement is performed from the sensor terminal 3. You may make it output the measured value of the acceleration of an axis | shaft, and the synthesized value calculated by the synthesized value calculation part 12 to the child terminal 4. FIG.

  Moreover, although the case where the composite value calculation unit 12, the inclination calculation unit 13, the vibration method determination unit 14, the composite value correction unit 15, and the step count calculation unit 16 are realized by a program process is illustrated, It may be realized by a dedicated hardware circuit.

  DESCRIPTION OF SYMBOLS 1, 2 ... Step counting device, 3 ... Sensor terminal, 4 ... Child terminal, 5 ... Clothing, 10 ... Sensor part, 11 ... Memory | storage part, 12 ... Composite value calculation part, 13 ... Inclination calculation part, 14 ... Vibration direction determination Reference numeral 15: Composite value correction unit 16: Step count calculation unit 17: Display unit 18: Data acquisition unit 101: Acceleration sensor 102: A / D converter 131: Low pass filter 132: Angle calculation unit

Claims (8)

A synthesized value calculation unit that calculates a synthesized value by synthesizing the measured values of acceleration of the respective measuring axes measured by an acceleration sensor having a plurality of measuring axes;
An inclination calculation unit for calculating an inclination of the acceleration sensor with respect to a vertical direction based on a measured value of acceleration of each of the measurement axes;
Based on the inclination, a vibration direction determination unit that determines the direction of vibration in the vertical direction of the wearer wearing the acceleration sensor;
A composite value correction unit that corrects the composite value based on the vibration direction determined by the vibration direction determination unit;
A step count measuring device comprising: a step number calculating unit that calculates a step number by walking or running by a wearer of the acceleration sensor based on the combined value corrected by the combined value correcting unit. In the step counting device according to claim 1,
The inclination calculation unit
A low-pass filter that inputs the composite value calculated by the composite value calculator and extracts a vector quantity based on gravitational acceleration;
An angle calculation unit that calculates an angle between the vector amount based on the gravitational acceleration and each measurement axis of the acceleration sensor;
A step count measuring device characterized by comprising: In the step counting device according to claim 2,
The vibration direction determination unit
The number of steps is characterized by determining the direction of vibration in the vertical direction of the wearer wearing the acceleration sensor based on the sign of the acceleration measurement value of the measurement axis with the smallest angle calculated by the angle calculation unit. Measuring device. In the step counting device according to claim 3,
The composite value correction unit corrects the sign of the composite value calculated by the composite value calculation unit when the vibration direction determination unit determines that the vibration of the wearer wearing the acceleration sensor is vertically upward. When the vibration of the wearer wearing the acceleration sensor is determined to be vertically downward by the vibration direction determination unit, the sign of the composite value calculated by the composite value calculation unit is negative.
A step counting device characterized by that. In the step counting device as described in any one of Claims 1 thru | or 4,
A sensor unit having the acceleration sensor;
An output unit that outputs a measured value of acceleration for each measurement axis measured by the acceleration sensor;
A storage unit that stores a measurement value of acceleration for each measurement axis output from the output unit;
The sensor unit and the output unit are formed in the first terminal,
The storage unit, the composite value calculation unit, the inclination calculation unit, the vibration direction determination unit, the composite value correction unit, and the step count calculation unit are formed in a second terminal different from the first terminal. A step count measuring device. A first step of calculating a combined value by combining measured values of acceleration for each of the measurement axes measured by an acceleration sensor having a plurality of measurement axes;
A second step of calculating an inclination of the acceleration sensor with respect to a vertical direction based on a measured value of acceleration of the measurement axis;
Based on the inclination calculated in the second step, a third step of determining the direction of vibration in the vertical direction of the wearer wearing the acceleration sensor;
A fourth step of correcting the composite value in the first step based on the vibration direction determined in the third step;
Based on the composite value corrected in the fourth step, a fifth step of calculating the number of steps by walking or running by the wearer;
Step counting method including. In the step count measuring method of Claim 6,
The second step includes
A sixth step of extracting a vector quantity based on gravitational acceleration from the composite value calculated in the first step;
A seventh step of calculating an angle between the vector amount based on the gravitational acceleration extracted in the sixth step and each of the measurement axes of the acceleration sensor;
The third step includes
Determining the direction of vibration in the vertical direction of the wearer wearing the acceleration sensor, based on the sign of the acceleration measurement value of the measurement axis having the smallest angle calculated in the seventh step,
The fourth step includes
If the vibration of the wearer wearing the acceleration sensor is determined to be vertically upward in the third step, the sign of the composite value calculated in the first step is made positive, and the acceleration is determined in the third step. A step count measuring method comprising the step of making the sign of the composite value calculated in the first step negative when the vibration of the wearer wearing the sensor is determined to be vertically downward.   The program for making a computer perform each step in the step counting method of Claim 6 or 7.