JP7123750B2 - Analysis device and analysis system - Google Patents

Description

Application of Article 30, Paragraph 2 of the Patent Act Released at the Japan Society of Mechanical Engineers Symposium: Sports Engineering and Human Dynamics 2017

The present disclosure relates to techniques for analyzing the axis of rotation of a ball.

In recent years, there has been known a method of measuring rotational parameters such as the movement trajectory, rotational speed, and direction of the rotational axis of a baseball during pitching by using information from a sensor built into the ball. For example, Japanese Patent Laying-Open No. 2018-134153 (Patent Document 1) discloses a pitch analysis system.

A pitch analysis system according to Patent Document 1 includes a ball with a built-in sensor section and a transmission section, and an analysis device that receives and analyzes the detection value of the sensor section transmitted from the transmission section. The sensor section includes a substrate, and an acceleration sensor, a geomagnetic sensor, and a gyro sensor mounted on the substrate. The analysis device identifies and stores the initial orientation of the substrate in the global coordinate system, calculates the progressive orientation of the substrate in the global coordinate system, calculates the progressive acceleration of the ball in the global coordinate system, and Calculate the trajectory of the ball in

JP 2018-134153 A

Japanese Patent Laid-Open No. 2002-200002 discloses calculating the direction of a rotation axis using a gyro sensor. However, a gyro sensor is generally relatively large in size, and a small gyro sensor that can be built into a ball has a limited measurement area. Therefore, when the ball rotates at high speed during pitching, such as in baseball, if a gyro sensor is used, it may not be possible to obtain the angle of the rotation axis of the ball with high accuracy due to saturation.

An object of one aspect of the present disclosure is to provide an analysis device and an analysis system capable of more accurately calculating the angle of the rotation axis of the ball.

According to one embodiment, an analysis device is provided for analyzing the axis of rotation of a ball. The analysis device includes an information input unit that receives input of acceleration data and geomagnetism data detected in time series by a sensor device built into the ball, and an attitude calculator that calculates the attitude information of the ball based on the acceleration data and geomagnetism data. a rotation number calculation unit that calculates the number of rotations of the ball released by the subject based on the geomagnetic data; attitude information; the number of rotations; the geomagnetic data; and a rotation axis calculation unit that calculates the angle of the rotation axis of the ball with respect to a predetermined direction using a predetermined filter based on the value.

Preferably, the axis-of-rotation calculator calculates the angle of the axis of rotation of the ball in a predetermined period before and after the timing at which the ball is released.

Preferably, the axis-of-rotation calculator calculates the geomagnetic data, the first-order differential value, and the second-order differential value based on the attitude information, the rotation speed, the geomagnetic data, the first-order differential value, and the second-order differential value. A predetermined filter is applied to the observation equation as the observed value to calculate the angle of the rotation axis of the ball.

Preferably, the analysis device further includes a direction calculation unit that calculates the traveling direction of the ball released by the subject using a predetermined filter based on the acceleration data. The predetermined direction is the traveling direction calculated by the direction calculator.

Preferably, the direction calculation unit includes a state equation whose state value is a rotation matrix that defines the direction of travel, and an observation equation whose observation value is the maximum value of acceleration data in a predetermined period before and after the timing at which the ball is released. A rotation matrix that defines the traveling direction is calculated by applying a predetermined filter to .

Preferably, the sensor device includes a low acceleration sensor for detecting low accelerations and a high acceleration sensor for detecting high accelerations. The acceleration data includes low acceleration data detected by the low acceleration sensor and high acceleration data detected by the high acceleration sensor. The attitude calculation unit uses low acceleration data as the acceleration data when calculating the initial attitude information of the ball.

Preferably, the predetermined filter is an extended Kalman filter.
According to another embodiment, an analysis device is provided for analyzing the axis of rotation of a ball. The analysis device includes an information input unit that receives input of acceleration data and geomagnetism data detected in time series by a sensor device built into the ball, and an attitude calculator that calculates the attitude information of the ball based on the acceleration data and geomagnetism data. a rotation number calculation unit that calculates the number of rotations of the ball released by the subject based on geomagnetic data; attitude information; the number of rotations; acceleration data; and a rotation axis calculation unit that calculates the angle of the rotation axis of the ball with respect to a predetermined direction using a predetermined filter based on the value.

Preferably, the rotation axis calculation unit calculates the acceleration data, the first derivative value, and the second derivative value based on the posture information, the rotation speed, the acceleration data, the first derivative value, and the second derivative value. A predetermined filter is applied to the observation equation as the observed value to calculate the angle of the rotation axis of the ball.

An analysis system according to still another embodiment includes an analysis device for analyzing the rotation axis of the ball and a sensor device built into the ball. The analysis device includes an information input unit that receives input of acceleration data and geomagnetism data detected in time series by the sensor device, an attitude calculation unit that calculates ball attitude information based on the acceleration data and the geomagnetism data, and a geomagnetism Based on the data, a rotation speed calculation unit that calculates the rotation speed of the ball released by the subject, based on the geomagnetic data, the posture information, the rotation speed, and the first derivative value and the second derivative value of the geomagnetic data and a rotation axis calculator that calculates the angle of the rotation axis of the ball with respect to a predetermined direction using a predetermined filter.

An analysis system according to still another embodiment includes an analysis device for analyzing the rotation axis of the ball and a sensor device built into the ball. The analysis device includes an information input unit that receives input of acceleration data and geomagnetism data detected in time series by a sensor device built into the ball, and an analysis device of the ball based on the acceleration data and geomagnetism data when the ball is stationary. a posture calculation unit that calculates posture information; a rotation speed calculation unit that calculates the rotation speed of a ball released by a subject based on geomagnetic data; posture information; rotation speed; acceleration data; and a rotation axis calculation unit that calculates the angle of the rotation axis of the ball with respect to a predetermined direction using a predetermined filter based on the differential value and the second differential value.

According to the present disclosure, it is possible to more accurately calculate the angle of the rotation axis of the ball.

1 is a diagram for explaining the overall configuration of an analysis system according to Embodiment 1; FIG. FIG. 2 is a diagram for explaining a schematic configuration of a ball according to Embodiment 1; FIG. 2 is a block diagram showing the hardware configuration of the analysis device according to Embodiment 1; FIG. 2 is a block diagram showing the hardware configuration of the sensor device according to Embodiment 1; FIG. 4 is a flowchart for explaining the operation of the analysis device according to Embodiment 1; FIG. 4 is a diagram for explaining a method of calculating the number of revolutions of a ball according to Embodiment 1; FIG. 4 is a diagram showing a display example of the angle of the axis of rotation of the ball according to Embodiment 1. FIG. 2 is a block diagram showing a functional configuration example of an analysis device according to Embodiment 1; FIG. 9 is a flowchart for explaining the operation of the analysis device according to Embodiment 2; FIG. 11 is a block diagram showing an example of the functional configuration of an analysis device according to Embodiment 2;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are given the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.
[Embodiment 1]
<Overall system configuration>
FIG. 1 is a diagram for explaining the overall configuration of analysis system 1000 according to the first embodiment. Referring to FIG. 1, analysis system 1000 is a system for analyzing the axis of rotation of a baseball ball thrown by test subject 5 who is a pitcher, and displaying the analysis results. The analysis system 1000 includes an analysis device 10 and a ball 2 in which a sensor device 20 is built. In FIG. 1, three mutually orthogonal axes in the sensor coordinate system are represented by the x-axis, y-axis, and z-axis, and three mutually orthogonal axes in the absolute coordinate system are represented by the X-axis, the Y-axis, and the Z-axis. there is

The analysis device 10 is composed of a smart phone. However, the analysis device 10 can be realized as an arbitrary device regardless of the type. For example, the analysis device 10 may be a laptop PC (personal computer), a tablet terminal, a desktop PC, or the like.

The analysis device 10 communicates with the sensor device 20 using a wireless communication method. For example, BLE (Bluetooth (registered trademark) low energy) is adopted as the wireless communication method. However, the analysis device 10 may employ other wireless communication methods such as Bluetooth (registered trademark) and wireless LAN (local area network).

FIG. 2 is a diagram for explaining a schematic configuration of ball 2 according to the first embodiment. FIG. 2(a) shows the appearance of the ball 2. FIG. FIG. 2(b) shows a schematic configuration inside the ball 2. As shown in FIG.

Referring to FIG. 2(a), the appearance of ball 2 is the same as that of a general hard ball. The ball 2 has an outer skin made of leather and is configured so that seams can be visually recognized. Referring to FIG. 2(b), the ball 2 incorporates a sensor device 20 for detecting the behavior of the ball 2 at its center. The sensor device 20 is secured with a polycarbonate capsule 62 and a silicone gel 64 and has excellent impact resistance.

Again referring to FIG. 1, the sensor device 20 detects acceleration and magnetic field (magnetic flux density) in the sensor coordinate system (ie, local coordinate system). Specifically, the sensor device 20 includes two acceleration sensors for low acceleration and high acceleration, and a geomagnetic sensor. The acceleration sensor detects acceleration data indicating acceleration along three mutually orthogonal axes (x-axis, y-axis, and z-axis). A geomagnetic sensor detects geomagnetic data indicating magnetic fields (magnetic flux densities) in three mutually orthogonal axial directions. For example, an MR (Magnet resistive) element, an MI (Magnet impedance) element, a Hall element, or the like is used for the geomagnetic sensor.

<Hardware configuration>
(Analysis device 10)
FIG. 3 is a block diagram showing the hardware configuration of analysis device 10 according to the first embodiment. Referring to FIG. 3, analysis device 10 includes, as main components, CPU (Central Processing Unit) 102, memory 104, touch panel 106, button 108, display 110, wireless communication unit 112, and communication antenna. 113 , a memory interface (I/F) 114 , a speaker 116 , a microphone 118 and a communication interface (I/F) 120 . Also, the recording medium 115 is an external storage medium.

The CPU 102 reads and executes a program stored in the memory 104 to control the operation of each unit of the analysis device 10 . More specifically, the CPU 102 implements each process (step) of the analysis device 10, which will be described later, by executing the program.

The memory 104 is implemented by RAM (Random Access Memory), ROM (Read-Only Memory), flash memory, or the like. The memory 104 stores programs executed by the CPU 102, data used by the CPU 102, and the like.

The touch panel 106 is provided on a display 110 that functions as a display unit, and may be of any type such as a resistive film type or a capacitive type. A button 108 is arranged on the surface of the analysis device 10 , receives an instruction from the user, and inputs the instruction to the CPU 102 .

Wireless communication unit 112 connects to a mobile communication network via communication antenna 113 and transmits and receives signals for wireless communication. This enables the analysis device 10 to communicate with a predetermined external device via a mobile communication network such as LTE (Long Term Evolution).

A memory interface (I/F) 114 reads data from an external recording medium 115 . The CPU 102 reads data stored in the external recording medium 115 via the memory interface 114 and stores the data in the memory 104 . CPU 102 reads data from memory 104 and stores the data in external recording medium 115 via memory interface 114 .

The recording medium 115 includes CD (Compact Disc), DVD (Digital Versatile Disc), BD (Blu-ray (registered trademark) Disc), USB (Universal Serial Bus) memory, memory card, FD (Flexible Disk), Examples include a medium such as a hard disk that stores programs in a nonvolatile manner.

Speaker 116 outputs sound based on a command from CPU 102 . Microphone 118 accepts speech to analysis device 10 .

A communication interface (I/F) 120 is, for example, a communication interface for transmitting and receiving data between the analysis device 10 and the sensor device 20, and is realized by an adapter, a connector, or the like. The communication method is, for example, wireless communication using BLE, wireless LAN, or the like.

(Sensor device 20)
FIG. 4 is a block diagram showing the hardware configuration of sensor device 20 according to the first embodiment. Referring to FIG. 4, sensor device 20 includes, as main components, CPU 202 for executing various processes, memory 204 for storing programs and data executed by CPU 202, acceleration sensor 220, A geomagnetic sensor 208 that detects magnetic fields in three mutually orthogonal axial directions, a communication interface (I/F) 210 for communicating with the analysis device 10, and a storage battery 212 that supplies power to various components of the sensor device 20. including.

Acceleration sensor 220 includes a low acceleration sensor 205 and a high acceleration sensor 206 . The low acceleration sensor 205 is an acceleration sensor for detecting a low acceleration range (for example, less than 24 G), and detects acceleration in three mutually orthogonal directions. A high acceleration sensor 206 is an acceleration sensor for detecting a high acceleration range (for example, 24 G or more) that cannot be detected by a low acceleration sensor, and detects acceleration in three mutually orthogonal directions. Although the high acceleration sensor 206 can also detect a low acceleration range, the low acceleration sensor 205 has higher detection accuracy than the high acceleration sensor 206 in the low acceleration range.

<Action>
FIG. 5 is a flowchart for explaining the operation of analysis device 10 according to the first embodiment. Each of the following steps is typically implemented by CPU 102 of analysis device 10 executing a program stored in memory 104 .

The analysis device 10 is operated by, for example, a store clerk. Note that the analysis device 10 may be operated by the subject 5 himself. It is assumed that analysis device 10 constantly acquires acceleration data detected by low acceleration sensor 205 and high acceleration sensor 206 and geomagnetic data detected by geomagnetic sensor 208 .

Referring to FIG. 5, analysis device 10 performs calibration of geomagnetic sensor 208 (step S10). Specifically, the test subject 5 spins the ball 2 (for example, throws the ball 2) according to the instruction of the store clerk. The analysis device 10 sequentially plots the magnetic fields in the three axial directions detected by the geomagnetic sensor 208 . The analysis device 10 approximates the plotted data (eg, 18-point data) using an elliptical equation, and calculates the center point and radius of the ellipse. Next, the analysis device 10 calibrates the geomagnetic data so that the approximated ellipse becomes a perfect circle centered on the origin. This corrects the offset error and sensitivity error of the geomagnetic sensor. Note that the analysis device 10 may calibrate the geomagnetic sensor 208 by other known methods.

Analysis device 10 performs calibration of low acceleration sensor 205 and high acceleration sensor 206 (step S12). Specifically, the test subject 5 puts the ball 2 in a stationary state (for example, puts the ball 2 on the ground) according to the instruction of the store clerk. Analysis device 10 acquires acceleration data detected by each of low acceleration sensor 205 and high acceleration sensor 206 when ball 2 is stationary.

The analysis device 10 calculates the average acceleration for a predetermined time (for example, 1 second) for each of the accelerations in the three axial directions detected by the low acceleration sensor 205 . The analysis device 10 uses the following equation (1) to calculate a three-axis synthetic acceleration As obtained by synthesizing the average accelerations _acx , _acy , and _acz of the x-, y-, and z-axes.

Analysis device 10 performs bias correction of low acceleration sensor 205 by subtracting a value obtained by dividing synthetic acceleration As by 1000 from the acceleration in the three axial directions detected by low acceleration sensor 205 (that is, the low acceleration sensor 205 calibration).

The high acceleration sensor 206 is similarly calibrated. Specifically, the analysis device 10 calculates the average value for a predetermined time (for example, 1 second) for each of the accelerations in the three axial directions detected by the high acceleration sensor 206, and uses the above equation (1). to calculate the three-axis synthetic acceleration. Analysis device 10 performs offset correction of high acceleration sensor 206 by subtracting the value obtained by dividing the synthesized acceleration by 1000 from the acceleration in the three axial directions detected by high acceleration sensor 206 (that is, calibration).

When the calibration of the low acceleration sensor 205 and the high acceleration sensor 206 is completed, the analysis device 10 notifies the subject 5 of information prompting him to pitch (step S14). The analysis device 10 may, for example, output words such as “Throw the ball” or display the words on the display 110 . Subject 5 throws ball 2 according to the notification.

The analysis device 10 determines whether or not the acceleration data detected by the low acceleration sensor 205 is less than the threshold value J1 (step S16). Specifically, the analysis device 10 determines whether or not the acceleration in each axial direction detected by the low acceleration sensor 205 is less than the threshold value J1.

If the axial acceleration is less than the threshold value J1 (YES in step S16), the analysis device 10 adopts the axial acceleration detected by the low acceleration sensor 205 as the acceleration used in subsequent steps. (Step S18). If the axial acceleration is greater than or equal to the threshold value J1 (NO in step S16), the analysis device 10 adopts the axial acceleration detected by the high acceleration sensor 206 as the acceleration used in subsequent steps. (Step S20).

The processing of steps S16 to S20 will be described with a specific example. For example, assume that the accelerations in the x-axis direction and the y-axis direction detected by the low acceleration sensor 205 are less than the threshold value J1, and the acceleration in the z-axis direction is greater than or equal to the threshold value J1. In this case, the analysis apparatus 10 adopts the acceleration detected by the low acceleration sensor 205 as the acceleration in the x-axis direction and the y-axis direction used in the processing after step S20, and uses the high acceleration as the acceleration in the z-axis direction. The acceleration detected by the acceleration sensor 206 is used. As described above, the acceleration detected by the low acceleration sensor 205 with high detection accuracy in the low acceleration range is used for the acceleration less than the threshold value J1.

Next, the analysis device 10 calculates the attitude of the ball 2 when the ball 2 is stationary (that is, the initial attitude of the ball 2) (step S22). Specifically, based on the acceleration data detected by the sensor device 20, the analysis device 10 calculates a roll angle φ indicating the rotation angle about the x-axis and a pitch angle θ indicating the rotation angle about the y-axis. The roll angle φ is expressed by the following equation (2) using average accelerations a _cy and a _cz when the ball 2 is stationary.

The pitch angle θ is expressed by the following equation (3) using average accelerations _acx , a _cy and _acz when the ball 2 is stationary.

Since the ball 2 is stationary at this time, the acceleration data detected by the low acceleration sensor 205 is used to calculate the roll angle φ and the pitch angle θ.

Further, the analysis device 10 uses the geomagnetic data detected by the sensor device 20 (the geomagnetic sensor 208), the roll angle φ calculated using Equation (2), and the pitch angle calculated using Equation (3). Based on .theta., a yaw angle .PSI. indicating a rotation angle about the z-axis is calculated.

Specifically, the analysis device 10 corrects the tilt error of the geomagnetic data of the geomagnetic sensor 208 using a rotation matrix constructed from the roll angle φ and the pitch angle θ. Let M _xi , M _yi , and M _zi be the magnetic fields in the _x- , y-, and z-axis directions after correction. Using M _y , M _z and the rotation matrix, the following equation (4) is obtained.

Using magnetic fields M _xi , M _yi , and M _zi corrected for tilt errors, the yaw angle Ψ is expressed by the following equation (5).

As described above, the information indicating the initial posture of the ball 2 in the stationary state (that is, the roll angle φ, the pitch angle θ, and the yaw angle ψ) is calculated.

Analysis device 10 calculates a rotation matrix from the sensor coordinate system to the absolute coordinate system using roll angle φ, pitch angle θ, and yaw angle ψ (step S24). Specifically, the analysis device 10 calculates the rotation matrix ⁰ R _i from the sensor coordinate system to the absolute coordinate system when the ball 2 is in a stationary state using the following equation (6).

Next, the analysis device 10 detects the timing when the subject 5 releases the ball 2 (that is, releases the ball 2 from the hand) (step S26). Specifically, the analysis device 10 calculates the incomplete differential value D of the geomagnetic data using the following equation (7). Note that s represents the Laplacian operator and n represents a differential coefficient. The incomplete differential value D is calculated for each of the magnetic fields in the three axial directions.

The analysis device 10 detects the time when the incomplete differential value D becomes 0 as the release timing. For example, the analysis device 10 detects the time when any one of the three incomplete differential values D corresponding to the magnetic fields in the three axial directions becomes 0 as the release timing.

Note that the analysis device 10 may detect the release timing using acceleration data. In this case, the analysis device 10 detects the time when the differential value of the acceleration data detected by the high acceleration sensor 206 exceeds the threshold value J2 as the release timing. For example, the analysis device 10 detects the time when any one of the three differential values respectively corresponding to the accelerations in the three axial directions exceeds the threshold value J2 as the release timing.

Next, the analysis device 10 sets a target period for analyzing the rotation axis of the ball 2 (hereinafter, also referred to as "analysis period") (step S28). Specifically, the analysis device 10 sets a fixed period before and after the timing when the ball 2 is released as the analysis period of the rotation axis of the ball 2 . Specifically, the analysis apparatus 10 sets the analysis start timing (i.e., the start point of the analysis period) to a specified time (e.g., 100 ms) before the release timing, and after a certain time (e.g., 60 ms) has elapsed from the release timing. is set as the analysis end timing (that is, the end point of the analysis period).

The analysis device 10 applies an extended Kalman filter to the acceleration data detected by the high acceleration sensor 206 to estimate the traveling direction of the ball 2 during the analysis period (step S30). Specifically, the analysis device 10 executes the following calculations.

The analysis apparatus 10 inputs the maximum values of the acceleration in the x-axis, y-axis, and z-axis directions (sensor coordinate system) within the analysis period detected by the high acceleration sensor 206, and formulates the following nonlinear state equation (8 ) and equation (9) representing the nonlinear observation equation, the rotation matrices about the x-, y-, and z-axes are calculated.

t represents a step that is discrete time. x _t , F(x _t ), and w _t in equation (8) represent the state value at step t (time t), the linear model regarding the time transition of the system, and the system noise, respectively. y _t , H(x _t ), and v _t in Equation (9) represent an observation value at time t, an observation model that linearly maps the state space to the observation space, and observation noise, respectively. x _t , F(x _t ), y _t , and H(x _t ) in formula (8) are represented by formulas (10), (11), (12), and (13), respectively.

X _rot , Y _rot , and Z _rot in equations (10) and (11) denote rotation matrices about the x-axis, y-axis, and z-axis, respectively. From equations (8), (10), and (11), the rotation matrices X _{rot , Y rot , and Z rot at step (t+1) are obtained by adding the system noise to the rotation matrices X rot , Y rot , and} Z _rot at step t. It will be added. Here, the acceleration of the ball 2 is maximized before and after the release (that is, the acceleration is maximized during the analysis period), and the direction defined by the rotation matrix when the acceleration is maximized generally indicates the traveling direction of the ball 2 . Therefore, the traveling direction of the ball 2 is the direction defined by the rotation matrices X _rot , Y _rot , Z _rot obtained by inputting the maximum value of the acceleration in each axial direction.

Ax _max , Ay _max , and Az _max in Equation (12) indicate the maximum values of acceleration (sensor coordinate system) in the x-axis, y-axis, and z-axis directions, respectively. A _t in equation (13) is the acceleration Ax _t , Ay _t , Az _t (sensor coordinate system) in the x-axis, y-axis, and z-axis directions at time t within the analysis period detected by the high acceleration sensor 206. It shows the resultant acceleration. The synthesized acceleration A _t is the square root of the sum of the squares of the components of the accelerations Ax _t , Ay _t and Az _t .

Here, f(x _t ) obtained by partially differentiating F(x _t ) with respect to x _t is defined as in equation (14), and h(x _t ) obtained by partially differentiating H(x _t ) with respect to x _t is expressed by the equation Define as in (15).

I indicates the identity matrix. The extended Kalman filter algorithm using f(x _t ) and h(x _t ) defined in this way is given by equations (16), (17), (18) and (19) below.

The above algorithm consists of two parts: one for predicting the estimated value of the next step, and the other for updating the estimated value using the obtained observed value. Equation (16) corresponds to the former, and Equations (17) to (19) correspond to the latter. By repeatedly calculating the formulas (16) to (19) given above using an instantaneous value (here, the maximum value of acceleration in each axis direction), the state value x _t becomes the optimum value. converge. That is, by applying the extended Kalman filter to f(x _t ) represented by Equation (14) and h(x _t ) represented by Equation (15), the most probable estimate of state value x _t at time t (Here, the traveling direction of the ball 2 defined by the rotation matrix around each axis) can be calculated.

Next, the analysis device 10 calculates the rotation speed of the ball 2 based on the geomagnetism data within the analysis period detected by the geomagnetism sensor 208 (step S32).

FIG. 6 is a diagram for explaining a method of calculating the number of revolutions of ball 2 according to the first embodiment. Referring to FIG. 6, graph 602 shows output values of geomagnetic data. For example, the output value is the magnetic field in the x-axis direction. A graph 604 indicates the difference value of the output value of the geomagnetic data. For example, the difference value is a value indicating the difference between the current output value and the previous output value.

The analysis device 10 counts the points where the difference value intersects 0 (zero crossing points), and calculates a predetermined count (for example, 3 counts) as one rotation. Referring to the graph 604, the first, second, and third zero cross points are counted at times p1, p2, and p3, respectively. The analysis device 10 calculates the number of revolutions (rpm) of the ball 2 from the number of zero-crossing points counted within a unit period (for example, 0.5 seconds).

Again referring to FIG. 5, analysis device 10 applies an extended Kalman filter to the geomagnetism data within the analysis period detected by geomagnetic sensor 208 to calculate the angle of the rotation axis of ball 2 (step S34). Specifically, the analysis device 10 executes the following calculations.

The analysis apparatus 10 detects each magnetic field component (sensor coordinate system) in the x-axis, y-axis, and z-axis directions within the analysis period detected by the geomagnetic sensor 208, the first derivative of each magnetic field component, and each magnetic field component. The angle of the axis of rotation of the ball 2 is calculated by solving the nonlinear state equation (8) and the nonlinear observation equation (9) with the second derivative as input. Here, x _t and F(x _t ) in equation (8) are represented by equations (20) and (21) below.

ω indicates the rotation speed of the ball 2 and corresponds to the rotation speed calculated in step S32. φ _a and θ _a are the roll angle and pitch angle in the absolute coordinate system at time t, respectively. φ _s , θ _s , and ψ _s are the roll angle, pitch angle, and yaw angle in the sensor coordinate system at time t, respectively. Also, y _t and H(x _t ) in equation (9) are represented by equations (22) and (23), respectively.

⁰ R _s , which indicates the rotation matrix from the sensor coordinate system to the absolute coordinate system, is expressed as in Equation (24) below. Note that the initial value of the rotation matrix ⁰ R _s coincides with ⁱ R _s representing the rotation matrix from the sensor coordinate system to the absolute coordinate system when the ball 2 is stationary. That is, the initial values of the roll angle φ _s , pitch angle θ _s and yaw angle ψ _s in the sensor coordinate system match the roll angle φ, pitch angle θ and yaw angle ψ when the ball 2 is stationary.

Also, ^S R _a representing the rotation matrix from the rotation axis coordinate system to the sensor coordinate system is represented by the following equation (25).

Similar to the calculation of the traveling direction in step S30, using x _t , F(x _t ), y _t , and H(x _t ) represented by equations (20) to (23), equations (14) to By repeatedly calculating (19), the most probable estimated value of the state value xt at time _t within the analysis period can be calculated. That is, the roll angle φ _a and pitch angle θ _a of the rotation axis of the ball 2 in the absolute coordinate system, and the roll angle φ _s , pitch angle θ _s and yaw angle Ψ _s of the rotation axis of the ball in the sensor coordinate system are estimated. be. In addition, although the rotational speed ω is also included in the estimated value in the equation (20), the rotational speed ω calculated in step S32 may be used as the rotational speed ω as described above. Therefore, the configuration may be such that the rotational speed ω is not used as an estimated value.

Then, using the estimated roll angle φ _a and pitch angle θ _a , the analysis device 10 calculates the angle θ _h of the rotation axis of the ball 2 with respect to the horizontal plane (the plane perpendicular to the direction of gravity). Specifically, the analysis device 10 calculates ⁰ R _a representing the rotation matrix from the rotation axis coordinate system to the absolute coordinate system using the following equation (26).

Next, if the vector indicating the rotation axis direction of the ball 2 is defined as (p _x , p _y , p _z ), Equation (27) holds. Note that p is a constant and ⁰ R _a ^T is the transposed matrix of ⁰ R _a .

Using the vector (p _x , p _y , p _z ) obtained by equation (27), the angle θ _h is expressed by equation (28).

The analysis device 10 displays the angle θ _h of the rotation axis of the ball 2 calculated in step S36 on the display 110 (step S36).

FIG. 7 is a diagram showing a display example of the angle of the rotation axis of ball 2 according to the first embodiment. Referring to FIG. 7 , analysis device 10 displays screen 502 showing the angle of the rotation axis on display 110 . For example, the screen 502 indicates that the angle of the axis of rotation of the ball 2 is 23 degrees, and that the rotation speed of the ball 2 is 1673.4 rpm. Note that this 23 degrees is the average value of _θh calculated during the analysis period.

Further, the analysis device 10 calculates the traveling direction of the ball 2 calculated in step S30 (that is, the rotation matrix in each axis direction) and the rotation matrix ⁰ from the rotation axis coordinate system to the absolute coordinate system shown in Equation (26). R _a can also be used to calculate the angle Ψ _h of the axis of rotation with respect to the direction of travel. First, using the rotation matrices X _rot , Y _rot , and Z _rot that define the traveling direction of the ball 2, the rotation matrix ⁰ R _tr from the traveling direction coordinate system to the absolute coordinate system is expressed by the following equation (29): represented.

Next, the rotation matrix ^tr R _a from the rotation axis coordinate system to the traveling direction coordinate system is obtained by the following equation (30) using the transposed matrix ⁰ R _tr ^T of the rotation matrix ⁰ R _tr and the rotation matrix ⁰ R _a . is represented as

Using the components of the rotation matrix ^tr R _a obtained by Equation (30), the angle Ψ _h , which is the azimuth angle of the rotation axis viewed from the traveling direction coordinate system, is expressed by Equation (31).

The analysis device 10 may display the angle Ψ _h of the rotation axis of the ball 2 on the display 110 .

<Functional configuration>
FIG. 8 is a block diagram showing a functional configuration example of analysis device 10 according to the first embodiment. 8, analysis apparatus 10 includes information input unit 302, attitude calculation unit 304, analysis period setting unit 306, direction calculation unit 308, rotation speed calculation unit 310, rotation axis calculation unit 312, and , and a display control unit 314 . These functional configurations are basically realized by CPU 102 of analysis device 10 executing a program stored in memory 104 and giving commands to constituent elements of analysis device 10 .

The information input unit 302 receives input of acceleration data and geomagnetism data detected by the sensor device 20 in time series. In this embodiment, the sensor device 20 is built in the center of the ball 2 . Therefore, the information input unit 302 receives input of acceleration data of the ball 2 and geomagnetism data. Typically, information input unit 302 receives acceleration data and geomagnetism data transmitted from sensor device 20 via communication interface 120 .

The attitude calculation unit 304 calculates attitude information of the ball 2 based on the acceleration data and the geomagnetism data. Typically, the attitude calculation unit 304 calculates the rotation matrix ⁰ R _s from the sensor coordinate system to the absolute coordinate system when the ball 2 is in a stationary state as the initial attitude information of the ball 2 . In this case, when calculating the initial posture information of the ball 2, the posture calculation unit 304 adopts the acceleration data detected by the low acceleration sensor 205 as the acceleration data used for processing.

Specifically, the attitude calculation unit 304 calculates the roll angle φ and the pitch angle θ in the sensor coordinate system using the acceleration data when the ball 2 is stationary. The posture calculation unit 304 calculates the yaw angle Ψ (sensor coordinate system) using the calculated roll angle φ, pitch angle θ, and geomagnetic data when the ball 2 is in a stationary state. Posture calculation section 304 calculates a rotation matrix ⁰ R _s from the sensor coordinate system to the absolute coordinate system using the calculated roll angle φ, pitch angle θ and yaw angle ψ and equation (6).

The analysis period setting unit 306 sets a predetermined period before and after the timing at which the ball is released as an analysis period. Specifically, the analysis period setting unit 306 detects the timing (release timing) at which the subject 5 releases the ball 2 based on the amount of change in the geomagnetic data or the amount of change in the acceleration data. For example, the analysis period setting unit 306 detects the point in time when the imperfect differential value D, which indicates the amount of change in the geomagnetic data, becomes 0 using Equation (7) as the release timing. Alternatively, the analysis period setting unit 306 detects the time when the differential value of the acceleration data detected by the high acceleration sensor 206 exceeds the threshold value J2 as the release timing.

Then, the analysis period setting unit 306 sets a specified time (for example, 100 ms) before the release timing as the analysis start timing (that is, the start time of the analysis period), and after a certain time (for example, 60 ms) has passed from the release timing is set as the analysis end timing (that is, the end point of the analysis period).

The direction calculation unit 308 calculates the traveling direction of the ball 2 released from the subject 5 using an extended Kalman filter based on the acceleration data. Specifically, the direction calculation unit 308 calculates a state equation in which the state value is the rotation matrix that defines the traveling direction of the ball 2, and an observation equation in which the maximum value of the acceleration data within the analysis period is the observed value. , an extended Kalman filter is applied to calculate a rotation matrix that defines the traveling direction of the ball 2 . More specifically, the direction calculation unit 308 performs calculations using the above equations (8) to (19) to obtain the rotation matrices X _rot , Y _rot , Z _rot .

The number-of-rotations calculation unit 310 calculates the number of rotations of the ball 2 based on the geomagnetic data within the analysis period. Specifically, as described with reference to FIG. 6, the rotational speed calculation unit 310 counts the number of zero-crossing points (the number of zero-crossing points) in which the difference between the output values of the geomagnetic data becomes zero. The number of revolutions of the ball 2 is calculated from the count number.

The rotation axis calculation unit 312 calculates the orientation information calculated by the orientation calculation unit 304, the rotation speed of the ball 2 calculated by the rotation speed calculation unit 310, and the geomagnetic data detected by the geomagnetic sensor 208 within the analysis period (that is, , x-axis, y-axis, and z-axis directions), the first-order differential value of the geomagnetic data, and the second-order differential value of the geomagnetic data. Calculate (estimate) the angle of

Specifically, the rotation axis calculation unit 312 calculates the angle of the rotation axis of the ball 2 (for example, , roll φ _a , pitch angle θ _a ) as state values, and an observation equation with geomagnetic data and the first and second differential values of the geomagnetic data as observed values. is applied to calculate the angle θ _h of the axis of rotation of the ball 2 with respect to the horizontal plane. More specifically, the rotation axis calculation unit 312 calculates the angle _θh by executing calculations using the above-described equations (8), (9), (14) to (28).

In another aspect, rotation axis calculation section 312 calculates the traveling direction based on rotation matrices X _rot , Y _rot , and Z _rot about each axis and rotation matrix ⁰ R _a from the rotation axis coordinate system to the absolute coordinate system. Calculate the angle Ψ _h of the axis of rotation of the ball 2 with respect to . More specifically, the rotation axis calculation unit 312 calculates the traveling direction Calculate the angle Ψ _h indicating the azimuth angle of the axis of rotation of the ball 2 with respect to .

The display control unit 314 displays on the display 110 the angle of the rotation axis of the ball 2 calculated by the rotation axis calculation unit 312 (for example, the angles θ _h and Ψ _h ). The display control unit 314 may display the rotation speed of the ball 2 calculated by the rotation speed calculation unit 310 on the display 110 . For example, the display control unit 314 displays a screen 502 as shown in FIG.

<Advantages>
According to Embodiment 1, the angle of the rotation axis of the ball can be calculated using acceleration data and geomagnetism data. Therefore, unlike the gyro sensor, saturation does not occur, and the angle of the rotation axis of the ball can be calculated more accurately.

Note that there is also known a configuration in which both a sensor device and a terminal device (for example, a smartphone, etc.) incorporate a geomagnetic sensor for measurement. In general, there are individual differences in the performance of geomagnetic sensors, so it is necessary to perform calibration or the like. Here, when the geomagnetic sensor built in the terminal device and the geomagnetic sensor built in the ball are used in combination, the performance deteriorates because the sensitivity of each magnetic sensor is different. For example, combining a geomagnetic sensor with low sensitivity and a geomagnetic sensor with high sensitivity depends on the performance of the lower one. In addition, when the place of use is different (for example, even if it is a short distance, it is not the same place), the error elements to be detected (for example, the magnetic field of the absolute coordinate system such as inclination, sensitivity, etc.) are different, so the accuracy is reduced. .

Therefore, in order to maximize the performance of the geomagnetic sensor built into the ball, after performing calibration as in this embodiment, magnetic field information in the absolute coordinate system is obtained from the geomagnetic sensor built into the ball. It is preferable to calculate the axis of rotation using only .
[Embodiment 2]
In the first embodiment, the configuration for calculating the angle of the rotation axis using geomagnetic data has been described. In a second embodiment, a configuration for calculating the angle of the rotation axis using acceleration data will be described. <Overall configuration> and <hardware configuration> of the second embodiment are the same as those of the first embodiment, and thus detailed description thereof will not be repeated.

<Action>
FIG. 9 is a flowchart for explaining the operation of analysis device 10 according to the second embodiment. Each of the following steps is typically implemented by executing a program stored in memory 104 by CPU 102 of analysis apparatus 10 according to the second embodiment.

Referring to FIG. 9, the processing of steps S12 to S32 is as explained in FIG. Here, in FIG. 9, step S10 in FIG. 5 is omitted. In the second embodiment, since the angle of the rotation axis is calculated using the acceleration data, even if the geomagnetic sensor 208 is not calibrated, the accuracy of the angle of the rotation axis is not greatly affected. This is because it is considered that However, in the second embodiment as well, the geomagnetic sensor 208 may be calibrated as in the first embodiment.

Analysis device 10 according to the second embodiment applies an extended Kalman filter to the acceleration data within the analysis period detected by acceleration sensor 220 to calculate the angle of the rotation axis of ball 2 (step S52). Specifically, the analysis device 10 executes the following calculations.

The analysis device 10 detects each acceleration component in the x-axis, y-axis, and z-axis directions within the analysis period detected by the high acceleration sensor 206, the first derivative value of each acceleration component, and the second derivative value of each acceleration component. are input, and the angle of the rotation axis of the ball 2 is calculated by solving the nonlinear state equation (8) and the nonlinear observation equation (9). Here, x _t and F(x _t ) in equation (8) are represented by equations (20) and (21) above. Also, y _t and H(x _t ) in Equation (9) are represented by Equations (32) and (33) below.

Note that ⁰ R _s indicating the rotation matrix from the sensor coordinate system to the absolute coordinate system is represented by the above equation (24), and ^S R _a indicating the rotation matrix from the rotation axis coordinate system to the sensor coordinate system is It is represented by the above equation (25).

Similar to the calculation of the traveling direction in step S30, x _t , F(x _t ) represented by equations (20) and (21) and y _t , H(x ) represented by equations (32) and (33) _t ), the most probable estimate of the state value x _t at time t can be calculated by repeatedly calculating equations (14)-(19). That is, the roll angle φ _a and pitch angle θ _a of the rotation axis of the ball 2 in the absolute coordinate system and the roll angle φ _s , pitch angle θ _s and yaw angle ψ _s of the rotation axis of the ball in the sensor coordinate system are Presumed.

Then, using the estimated roll angle φ _a and pitch angle θ _a , the analysis device 10 calculates the angle θ _h of the rotation axis of the ball 2 with respect to the horizontal plane (the plane perpendicular to the direction of gravity). Specifically, the analysis device 10 performs calculations using the above equations (26) to (28). Further, the analysis device 10 calculates the traveling direction of the ball 2 calculated in step S30 (that is, the rotation matrix in each axis direction) and the rotation matrix ⁰ from the rotation axis coordinate system to the absolute coordinate system shown in Equation (26). R _a can also be used to calculate the angle Ψ _h of the axis of rotation with respect to the direction of travel. In this case, the analysis device 10 performs calculations using the above equations (29) to (31).

The analysis device 10 displays the angle of the rotation axis of the ball 2 (for example, angles θ _h , Ψ _h ) calculated in step S52 on the display 110 (step S54), and ends the process.

<Functional configuration>
FIG. 10 is a block diagram showing a functional configuration example of analysis device 10A according to the second embodiment. Referring to FIG. 10, analysis apparatus 10A replaces rotation axis calculation section 312 in analysis apparatus 10 in FIG. 8 with rotation axis calculation section 312A. Since other functional configurations are the same as those of analysis device 10, detailed description thereof will not be repeated.

The rotation axis calculation unit 312A calculates the orientation information calculated by the orientation calculation unit 304, the rotation speed of the ball 2 calculated by the rotation speed calculation unit 310, and the x-axis and y-axis detected by the acceleration sensor 220 within the analysis period. The angle of the rotation axis of the ball 2 with respect to a predetermined direction is calculated using an extended Kalman filter based on the acceleration in the axis and z-axis directions (sensor coordinate system), the first derivative of the acceleration, and the second derivative of the acceleration. Calculate (estimate).

Specifically, the rotation axis calculation unit 312A calculates the angle of the rotation axis of the ball 2 (for example, , roll φ _a , pitch angle θ _a ) as state values, and an observation equation with acceleration data and the first and second derivative values of the acceleration data as observed values. is applied to calculate the angle θ _h of the axis of rotation of the ball 2 with respect to the horizontal plane and the angle Ψ _h of the axis of rotation with respect to the direction of travel. More specifically, the rotation axis calculation unit 312A calculates the angle θ Calculate _h and the angle Ψ _h .

<Advantages>
According to the second embodiment, the angle of the rotation axis of the ball 2 is calculated using acceleration data without using geomagnetic data. Therefore, the angle of the rotation axis of the ball 2 can be calculated with high accuracy even in a place that is easily affected by the magnetic field.

<Other embodiments>
(1) In the analysis system 1000 according to the above embodiment, the configuration in which the ball 2 is a baseball is described as an example, but the configuration is not limited to this. For example, it can be applied to softball balls as well.

(2) In the above-described embodiment, it is also possible to provide a program that causes a computer to function and execute the control described in the flowchart above. Such a program is recorded on a non-temporary computer-readable recording medium such as a flexible disk attached to a computer, CD-ROM (Compact Disk Read Only Memory), ROM, RAM and memory card as a program product. can also be provided. Alternatively, the program can be provided by recording it in a recording medium such as a hard disk built into the computer. The program can also be provided by downloading via a network.

The program may call necessary modules at a predetermined timing among program modules provided as part of the operating system (OS) of the computer to execute processing. In that case, the program itself does not include the above module, and the process is executed in cooperation with the OS. Programs that do not include such modules may also be included in the programs according to the present embodiment.

Also, the program according to the present embodiment may be provided by being incorporated into a part of another program. Even in that case, the program itself does not include the modules included in the other program, and the processing is executed in cooperation with the other program. A program incorporated in such other program can also be included in the program according to the present embodiment.

(3) The configuration illustrated as the above embodiment is an example of the configuration of the present invention, and it is possible to combine it with another known technique, and part of it can be used without departing from the scope of the present invention. It is also possible to change and configure such as omitting.

It should be considered that the embodiments disclosed this time are illustrative in all respects and not restrictive. The scope of the present invention is indicated by the scope of the claims rather than the above description, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims.

2 ball, 5 test subject, 10, 10A analyzer, 20 sensor device, 62 capsule, 64 silicone gel, 102,202 CPU, 104,204 memory, 106 touch panel, 108 button, 110 display, 112 wireless communication unit, 113 communication antenna , 114 memory interface, 115 recording medium, 116 speaker, 118 microphone, 120 communication interface, 205 low acceleration sensor, 206 high acceleration sensor, 208 geomagnetic sensor, 212 storage battery, 220 acceleration sensor, 302 information input unit, 304 rotation matrix generation unit , 306 analysis period setting unit, 308 direction calculation unit, 310 rotation speed calculation unit, 312, 312A rotation axis calculation unit, 314 display control unit, 1000 analysis system.

Claims (11)

An analysis device for analyzing a rotation axis of a ball,
an information input unit that receives input of acceleration data and geomagnetic data detected in time series by a sensor device built into the ball;
an attitude calculation unit that calculates attitude information of the ball based on the acceleration data and the geomagnetism data;
a rotational speed calculation unit that calculates the rotational speed of the ball released by the subject based on the geomagnetic data;
Based on the attitude information, the number of rotations, the geomagnetic data, and the first and second differential values of the geomagnetic data, a predetermined filter is used to determine the angle of the rotation axis of the ball with respect to a predetermined direction. and an axis-of-rotation calculator for calculating. 2. The analysis device according to claim 1, wherein the rotation axis calculator calculates the angle of the rotation axis of the ball in a predetermined period before and after the timing at which the ball is released. The rotational axis calculator calculates the geomagnetic data, the first differential value, and the 3. The analysis apparatus according to claim 1, wherein said predetermined filter is applied to an observation equation having a second derivative as an observed value to calculate the angle of said ball's axis of rotation. further comprising a direction calculation unit that calculates a traveling direction of the ball released from the subject using the predetermined filter based on the acceleration data;
The analysis device according to any one of claims 1 to 3, wherein the predetermined direction is the traveling direction calculated by the direction calculation unit. The direction calculation unit includes a state equation whose state value is a rotation matrix that defines the direction of travel, and an observation equation whose observed value is the maximum value of the acceleration data in a predetermined period before and after the timing at which the ball is released. 5. The analysis apparatus according to claim 4, wherein said predetermined filter is applied to , to calculate a rotation matrix defining said advancing direction. The sensor device includes a low acceleration sensor for detecting low acceleration and a high acceleration sensor for detecting high acceleration,
The acceleration data includes low acceleration data detected by the low acceleration sensor and high acceleration data detected by the high acceleration sensor,
The analysis device according to any one of claims 1 to 5, wherein the attitude calculation unit adopts the low acceleration data as the acceleration data when calculating the initial attitude information of the ball. The analysis device according to any one of claims 1 to 6, wherein said predetermined filter is an extended Kalman filter. An analysis device for analyzing a rotation axis of a ball,
an information input unit that receives input of acceleration data and geomagnetic data detected in time series by a sensor device built into the ball;
an attitude calculation unit that calculates attitude information of the ball based on the acceleration data and the geomagnetism data;
a rotational speed calculation unit that calculates the rotational speed of the ball released by the subject based on the geomagnetic data;
Based on the attitude information, the number of rotations, the acceleration data, and the first and second derivative values of the acceleration data, a predetermined filter is used to determine the angle of the rotation axis of the ball with respect to a predetermined direction. and an axis-of-rotation calculator for calculating. The rotation axis calculation unit calculates the acceleration data, the first derivative, and the 9. The analysis device according to claim 8, wherein said predetermined filter is applied to an observation equation with second order differential values as observation values to calculate the angle of said ball's axis of rotation. an analysis device for analyzing the rotation axis of the ball;
and a sensor device built into the ball,
The analysis device is
an information input unit that receives input of acceleration data and geomagnetic data detected in time series by the sensor device;
an attitude calculation unit that calculates attitude information of the ball based on the acceleration data and the geomagnetism data;
a rotational speed calculation unit that calculates the rotational speed of the ball released by the subject based on the geomagnetic data;
Based on the attitude information, the number of rotations, the geomagnetic data, and the first and second differential values of the geomagnetic data, a predetermined filter is used to determine the angle of the rotation axis of the ball with respect to a predetermined direction. An analysis system, comprising: a rotational axis calculator for calculating. an analysis device for analyzing the rotation axis of the ball;
and a sensor device built into the ball,
The analysis device is
an information input unit that receives input of acceleration data and geomagnetic data detected in time series by a sensor device built into the ball;
an attitude calculation unit that calculates attitude information of the ball based on the acceleration data and the geomagnetism data;
a rotational speed calculation unit that calculates the rotational speed of the ball released by the subject based on the geomagnetic data;
Based on the posture information, the number of rotations, the acceleration data, and the first and second derivative values of the acceleration data, a predetermined filter is used to determine the angle of the rotation axis of the ball with respect to a predetermined direction. An analysis system, comprising: a rotational axis calculator for calculating.

Images