Analysis device and analysis method

Abstract

To provide an analysis device capable of calculating a point of application of force acting on a ball during pitching without giving a sense of incongruity to a subject.SOLUTION: An analysis device includes an acquisition unit for acquiring motion information of a ball detected by a sensor built in the ball, a time calculation unit for calculating a release time when the ball is released from a subject's fingers based on the motion information, a first calculation unit for calculating a force vector acting on the ball from the subject's fingers and a torque vector acting on the ball during a period before the release time based on the motion information and specification information of the ball, and a second calculation unit for calculating a point of application of the force on a surface of the ball based on the force vector, the torque vector, and the specification information of the ball.SELECTED DRAWING: Figure 10

Description

[Technical field]

[0001] The present disclosure relates to an analysis device and an analysis method. [Background technology]

[0002] There are known devices for measuring the swing motion of golf, bat, etc., which are tools operated using both hands. For example, Japanese Patent No. 6886650 (Patent Document 1) discloses a motion measuring device that independently measures six-axis forces, i.e., each acting force and each acting torque of multiple hands, such as the left and right. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6886650 Summary of the Invention [Problem to be solved by the invention]

[0004] The device according to Patent Document 1 is configured to use a golf club equipped with a force sensor to measure (calculate) the point of application of each force acting on the grip of the golf club. In this way, by providing a force sensor on an object (here, a golf club), the point of application of the force acting on the object can be calculated. However, there are cases where providing a force sensor on an object is not preferable. For example, when pitching a ball such as a baseball, if it is desired to calculate the point of application of the force acting on the ball from the fingers, a configuration in which a force sensor is arranged on the surface of the ball is conceivable. However, with this configuration, the inertial characteristics of the ball are different from those of a normal ball, and the pitcher may feel uncomfortable when pitching the ball.

[0005] An object in one aspect of the present disclosure is to provide an analysis device and analysis method that are capable of calculating the point of application of force acting on a ball when it is pitched, without causing discomfort to the subject. [Means for solving the problem]

[0006] An analysis device according to one embodiment includes an acquisition unit that acquires ball motion information detected by a sensor built into the ball; a time calculation unit that calculates the release time at which the ball is released from the subject's fingers based on the motion information; a first calculation unit that calculates a force vector acting from the subject's fingers on the ball and a torque vector acting on the ball during a period prior to the release time based on the motion information and ball specification information; and a second calculation unit that calculates the point of application of the force on the surface of the ball based on the force vector, torque vector, and ball specification information.

[0007] An analysis method according to another embodiment includes the steps of acquiring ball motion information detected by a sensor built into the ball, calculating the release time at which the ball is released from the subject's fingers based on the motion information, calculating a force vector acting from the subject's fingers on the ball and a torque vector acting on the ball during a period prior to the release time based on the motion information and ball specification information, and calculating the point of application of the force on the surface of the ball based on the force vector, torque vector, and ball specification information. Effect of the Invention

[0008] According to the present disclosure, it is possible to calculate the point of application of the force acting on the ball when pitching it, without causing any discomfort to the subject. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram for explaining an overall configuration of an analysis device. [Diagram 2] FIG. 2 is a block diagram showing a hardware configuration of the terminal device. [Diagram 3] FIG. 2 is a block diagram showing a hardware configuration of a sensor device. [Figure 4] 10 is a flowchart illustrating an example of the operation of the analysis device. [Diagram 5] FIG. 2 is a diagram for explaining a dynamic model according to the present embodiment. [Figure 6] FIG. 2 is a diagram showing the position of a force application point. [Figure 7] FIG. 13 is a diagram showing the plot results of force vectors and points of action on a three-dimensional sphere. [Figure 8] FIG. 13 is a diagram showing plot results of force vectors and points of action on each plane. [Figure 9] FIG. 2 is a diagram showing the distance traveled and the distance rotated by the ball. [Figure 10] 3 is a block diagram showing an example of a functional configuration of a sensor device; FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the present embodiment will be described with reference to the drawings. In the following description, the same components are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

[0011] <Overall composition> Fig. 1 is a diagram for explaining the overall configuration of analysis device 1000. With reference to Fig. 1, analysis device 1000 is a device for analyzing the point of application of force acting from the fingers of subject 5 on ball 2 when subject 5 makes a pitching motion of ball 2.

[0012] The analysis device 1000 includes a terminal device 10 and a ball 2 incorporating a sensor device 20. In this embodiment, the sensor device 20 has a function of analyzing the point of application of a force acting on the ball 2, and the terminal device 10 has a function of displaying the analysis results by the sensor device 20.

[0013] The appearance of the ball 2 is the same as that of a typical hard ball. The ball 2 has a leather outer shell and is configured so that the stitching can be seen. The sensor device 20 is fixed in place with a polycarbonate capsule and silicone gel, and has excellent impact resistance.

[0014] The terminal device 10 is configured as a smartphone. However, the terminal device 10 can be realized as any device regardless of the type. For example, the terminal device 10 may be a laptop personal computer (PC), a tablet terminal, a desktop PC, etc.

[0015] The terminal device 10 communicates with the sensor device 20 by a wireless communication method. For example, BLE (Bluetooth (registered trademark) low energy) is adopted as the wireless communication method. However, the terminal device 10 may adopt other wireless communication methods such as Bluetooth (registered trademark), wireless LAN (local area network), etc.

[0016] The sensor device 20 detects acceleration, angular velocity, and geomagnetism in a sensor coordinate system (i.e., a local coordinate system) at each predetermined sampling period. Specifically, the sensor device 20 includes an acceleration sensor, an angular velocity sensor, and a geomagnetic sensor. The acceleration sensor detects accelerations ax, ay, and az (hereinafter, also simply referred to as "three-axis acceleration") in three mutually orthogonal axial directions (X-axis, Y-axis, and Z-axis). That is, the acceleration sensor detects an acceleration vector (ax, ay, and az) indicating the acceleration in the three axial directions. The angular velocity sensor detects angular velocities ωx, ωy, and ωz (hereinafter, also simply referred to as "three-axis angular velocity") around the three axes (X-axis, Y-axis, and Z-axis). That is, the acceleration sensor detects an angular velocity vector (ωx, ωy, and ωz) indicating the angular velocity around the three axes. The geomagnetic sensor detects geomagnetism (hereinafter, also simply referred to as "three-axis geomagnetism") indicating the magnetic field (magnetic flux density) in the three axial directions (X-axis, Y-axis, and Z-axis). That is, the geomagnetic sensor detects a geomagnetic vector that indicates a magnetic field in three axial directions. For example, a magnet resistive (MR) element, a magnet impedance (MI) element, a Hall element, or the like is used as the geomagnetic sensor.

[0017] The sensor device 20 executes a predetermined process based on the detected sensor data (for example, time-series data of acceleration and angular velocity) to calculate the point of action of the force acting on the ball 2. The terminal device 10 receives the calculation result from the sensor device 20 and displays the calculation result on the display.

[0018] <Hardware configuration> (Terminal device 10) Fig. 2 is a block diagram showing a hardware configuration of the terminal device 10. Referring to Fig. 2, the terminal device 10 includes, as main components, a processor (Central Processing Unit) 102, a memory 104, a touch panel 106, a wireless communication unit 108, a communication antenna 110, a display 112, and a communication interface (I / F) 114.

[0019] The processor 102 controls the operation of each part of the terminal device 10 by reading and executing a program stored in the memory 104. The processor 102 is typically an arithmetic processing unit such as a CPU (Central Processing Unit) or an MPU (Multi Processing Unit). The memory 104 is realized by a RAM (Random Access Memory), a ROM (Read-Only Memory), a flash memory, or the like. The memory 104 stores the program executed by the processor 102, data used by the processor 102, and the like.

[0020] The touch panel 106 is provided on a display 112 that functions as a display unit. The wireless communication unit 108 connects to a mobile communication network via a communication antenna 110 and transmits and receives signals for wireless communication.

[0021] The communication interface (I / F) 114 is, for example, a communication interface for transmitting and receiving data between the terminal device 10 and the sensor device 20. The communication method is, for example, wireless communication using BLE, wireless LAN, or the like.

[0022] The terminal device 10 may include a speaker that outputs sound based on instructions from the processor 102, a microphone that accepts speech to the terminal device 10, an input / output interface (I / F) for transmitting and receiving data to and from an external recording medium, and the like.

[0023] (Sensor device 20) Fig. 3 is a block diagram showing a hardware configuration of the sensor device 20. Referring to Fig. 3, the sensor device 20 includes, as main components, a processor 202 for executing various processes, a memory 204 for storing programs and data executed by the processor 202, an acceleration sensor 205, an angular velocity sensor 206, a geomagnetic sensor 208, a communication interface (I / F) 210 for communicating with the terminal device 10, and a storage battery 212 for supplying power to the various components of the sensor device 20.

[0024] <Example of operation> Fig. 4 is a flowchart for explaining an example of the operation of analysis device 1000. Typically, among the steps shown in Fig. 4, the steps performed by terminal device 10 are realized by processor 102, and the steps performed by sensor device 20 are realized by processor 202. Here, a flow will be explained in which analysis device 1000 analyzes sensor data detected by a sensor built into ball 2 thrown by subject 5, and displays the results such as the point of application of force acting on ball 2.

[0025] The sensor device 20 (processor 202) acquires a time series of three-axis acceleration detected by the acceleration sensor 205 and a time series of three-axis angular velocity detected by the angular velocity sensor 206 (step S10). The acquired three-axis acceleration and three-axis angular velocity are data in the sensor coordinate system.

[0026] The sensor device 20 calculates the release time tr, which indicates the time when the ball 2 is released (released) from the fingers of the subject 5 (step S20). For example, the sensor device 20 calculates the time when the resultant acceleration A of the accelerations in the three axial directions becomes equal to or greater than a threshold value Ka1, as the release time tr. The sensor device 20 may calculate, for each of the accelerations in the three axial directions, the difference between the acceleration at the previous time and the acceleration at the current time, and calculate the time when any of the difference values ​​becomes equal to or greater than a threshold value J1, as the release time tr. Typically, the resultant acceleration A is calculated by taking the square root of the sum of the squares of the accelerations in the three axial directions (i.e., A=(ax 2 +ay 2 +az 2 ) 1 / 2 ).

[0027] Furthermore, the sensor device 20 may calculate the time when the composite angular velocity Sω of the angular velocities around the three axes becomes constant as the release time tr. Typically, the composite angular velocity Sω is the square root of the sum of the squares of the angular velocities around the three axes (i.e., Sω=(ωx 2 +ωy 2 +ωz 2 ) 1 / 2 The time when the resultant angular velocity Sω becomes constant is, for example, the time when the sum of squares E of the differences between the angular velocity vector (ωx, ωy, ωz) at the previous time (t-1) and the angular velocity vector at the current time t becomes less than a threshold value J2. Note that "E={ωx(t-1)-ωx(t)} 2 +{ωy(t-1)-ωy(t)} 2 +{ωz(t-1)-ωz(t)} 2 " is.

[0028] The sensor device 20 calculates the time a predetermined time (e.g., 200 ms) before the release time tr as the time t1 when the subject 5 starts the pitching motion of throwing the ball 2 (hereinafter also referred to as the "motion start time") (step S30). The sensor device 20 may calculate the time when the resultant acceleration A becomes equal to or greater than a threshold value Ka2 as the motion start time t1. However, the threshold value Ka2 is assumed to be smaller than the threshold value Ka1.

[0029] The sensor device 20 uses a low-pass filter having a predetermined cutoff frequency to filter the time-series three-axis acceleration and three-axis angular velocity acquired in step S10 to remove high-frequency noise components (step S40). The sensor device 20 performs this filtering on the time-series three-axis acceleration and three-axis angular velocity during the period from the operation start time t1 to the release time tr, for example. Note that the sensor device 20 may be configured not to perform the filtering in step S40.

[0030] The sensor device 20 calculates the time t2 when the fingers of the subject 5 start to rotate the ball 2 (step S50). For example, the sensor device 20 calculates the time when the resultant acceleration A is maximum as the time t2. Alternatively, the sensor device 20 may calculate the angular acceleration around the three axes by differentiating the angular velocities around the three axes with respect to time (hereinafter referred to as "time differentiation"), and calculate the time when the resultant angular acceleration obtained by combining the angular accelerations around the three axes becomes equal to or greater than the threshold value H as the time t2. Typically, the resultant angular acceleration is the square root of the sum of the squares of the angular accelerations around the three axes.

[0031] Based on the three-axis acceleration, three-axis angular velocity, and specification information of ball 2, sensor device 20 calculates a force vector acting on the ball from the fingers of subject 5 (hereinafter also referred to as "force vector F") and a torque vector acting on the ball (hereinafter also referred to as "torque vector N") during a predetermined period (step S60). The predetermined period is, for example, the period from time t2 to release time tr (or immediately before). However, the predetermined period may also be the period from motion start time t1 to release time tr (or immediately before). The specification information of ball 2 includes the radius, mass, and moment of inertia of ball 2, etc.

[0032] The sensor device 20 calculates a point of action xb of the force on the surface of the ball 2 based on the force vector F and torque vector N acting on the ball 2 and the specification information of the ball 2 (step S70). The method of calculating the point of action xb will be described in detail later.

[0033] The terminal device 10 displays the force application point xb and the force vector (direction and magnitude) calculated by the sensor device 20 on the display 112 (step S80). Typically, the terminal device 10 receives the calculation results of the force application point xb and the force vector F for a predetermined period from the sensor device 20 and displays the calculation results on the display 112.

[0034] <Calculation method for point of action> Just before the ball is released in a pitching motion, the fingers rotate the ball and then it is completely released. Therefore, focusing on the phase just before the ball is released, in which the fingers rotate the ball, a calculation method for calculating the point of action xb using the acceleration and angular velocity of the ball 2 will be described.

[0035] FIG. 5 is a diagram for explaining a dynamics model according to the present embodiment. The dynamics model of the ball is defined as shown in FIG. 5. If the center of ball 2 is "O", the vector of the force (action force) acting on ball 2 is "F", the vector of the torque (action torque) acting on ball 2 is "N", and the position vector of the ball surface is xbn, then the torque vector N can be expressed by the following equation (1). In equation (1), "×" indicates a cross product, and "τ" indicates a torque vector acting on a point located on the line of action 50 of the force. Note that in equation (1), x is used as the x axis in order to simplify the display. bn For example, "x in a formula" should be written in subscript form. bn " is the same as "xbn in the text." This also applies to equations (8), (9) and (10) described below.

[0036]

number

[0037] In equation (1), the torque vector N is converted to the equivalent sum of "xbn×F" and the torque vector τ. The force vector F passes through xbn on the ball surface and penetrates the ball 2 in the direction of the arrow shown in Figure 5. A constant force moment "xbn×F" is applied to the ball 2 on the straight line in that direction. In addition, in the phase of rotating the ball 2, the ball 2 is not grasped at multiple dispersed positions, but the force vector is considered to act at a position where one or multiple fingertips are gathered, and the representative point where the force vector acts is considered to be the point of application of the force. Therefore, the point of application of the force is calculated as a problem of finding the intersection point between the straight line facing the direction of the force vector F and the sphere. If the ball 2 is assumed to be spherically symmetric, the moment of inertia of the ball 2 is "I", and the angular velocity vector of the ball 2 is "ω", the torque vector N is calculated from equation (2), which is the equation of motion for the rotational motion of the ball 2.

[0038]

number

[0039] In equation (2), “ω·” represents the angular acceleration vector of the ball 2. The angular acceleration vector can be calculated by differentiating the angular velocity vector with respect to time. “ω·” refers to the letter ω with a dot on top.

[0040] If the mass of ball 2 is "m", the gravitational acceleration vector is "g", and the acceleration vector of ball 2 is "x··", the force vector F acting on ball 2 is calculated by the following formula (3). Note that "x··" means the letter x with two dots above it.

[0041]

number

[0042] Here, if we define the force vector F as in equation (4), then the skew-symmetric matrix "F~" is expressed as in equation (5). The skew-symmetric matrix describes the cross product operation by multiplying this matrix with a vector. "F~" means the letter F with the symbol "~" above it.

[0043]

number

[0044] [F1F2F3] in equation (4) T The "T" in the above expression stands for transposed matrix.

[0045] Point of application xb of the force acting on the surface of ball 2 is located on line of action 50 of the force, and can be calculated by minimizing torque vector τ. Here, point p, which is located on line of action 50 of the force, minimizes torque vector τ acting on said point, and has a minimum distance from center O, is calculated by the following formula (6) using force vector F, torque vector N, and a skew-symmetric matrix.

[0046]

number

[0047] In equation (6), "||F||" indicates the norm of the force vector F. The distance d from point p to the point of application xb on the ball surface is calculated by equation (7), where "R" is the radius of ball 2.

[0048]

number

[0049] From equation (7), two solutions can be obtained for the distance d, which means that a straight line passing through the point of application of the force (for example, line of action 50) intersects at two points on the ball's surface. There are tensile and compressive forces acting on ball 2, and a compressive force acts on the ball during the throw. Therefore, the point of application xb on the ball's surface is calculated using the following equation (8).

[0050]

number

[0051] This allows the force application point xb in the sensor coordinate system to be calculated three-dimensionally.

[0052] <Example> An example in which a subject was made to throw a changeup will be described. In this example, the subject was made to hold the ball 2 so that the Z axis of the ball 2 was aligned in the direction of the long axis of the second and third fingers of the subject's throwing arm, and the X axis of the ball 2 was aligned approximately in the direction connecting the metacarpophalangeal joint of the third finger to the metacarpophalangeal joint of the second finger, and the ball 2 was made to be thrown approximately in the Y axis direction.

[0053] Fig. 6 is a diagram showing the position of the force application point in the sensor coordinate system. In the example of Fig. 6, the three-axis position information (x, y, z) of the application point xb during a predetermined period from time t2 (corresponding to "-12 ms" in the figure) when the finger starts to rotate the ball 2 to 2 ms before the release time tr (corresponding to "-2" in the figure) is shown. The release time tr is set to 0 ms.

[0054] 6, it can be seen that, among the three axes of the sensor coordinate system, the position of the action point xb on the Z axis in particular changes upward. This is thought to be a reflection of the result of the action point xb moving to the vicinity of the fingertip on the top of the ball due to the rotation of the ball 2.

[0055] Fig. 7 is a diagram showing plot results of force vectors and points of action on a three-dimensional sphere. Fig. 8 is a diagram showing plot results of force vectors and points of action on each plane. Specifically, Fig. 8(a) shows plot results on the XZ plane, and Fig. 8(b) shows plot results on the XY plane.

[0056] 7 and 8, it can be seen that the force vector is directed toward the center of the ball, and as the point of application xb moves, the magnitude of the force vector gradually decreases. This is thought to be because, in the case of a changeup, which is a pitch with a low spin rate, control is exercised to suppress the spin rate by directing the force vector toward the center of the ball.

[0057] 9 is a diagram showing the moving distance and the rotating distance of the ball. Referring to FIG. 9, the diagram shows the time change of the moving distance ΔIb of the point of action xb on the spherical surface and the rotating distance Δl of the ball 2 during a predetermined period from the time t2 when the fingers start to rotate the ball 2 to 2 ms before the release time tr.

[0058] Since the moving distance ΔIb in a specified period of time is considered to reflect the rotational distance Δl of the ball 2 rolling on the fingers, the rotational distance Δl was calculated from the angular velocity detected by the angular velocity sensor 206 mounted on the ball 2 using the following equation (9).

[0059]

number

[0060] ωt indicates the resultant angular velocity at time t, and Δt indicates the sampling interval of the angular velocity sensor 206. Based on the position coordinates of the action point xb for a predetermined period, the movement distance Δlb on the spherical surface is expressed by the following equation (10).

[0061]

number

[0062] Δθt represents the angle between the center O of the ball 2 and the point of action xb at time (t-1) and between times t. Error evaluation was performed using the root mean squared error (RMSE) between the moving distance Δlb and the rotating distance Δl. Furthermore, the intraclass correlation coefficients (ICC) between the rotating distance Δl and the moving distance on the sphere Δlb were calculated to evaluate the degree of agreement.

[0063] According to the time series data in Figure 9, the RMSE of the moving distance Δlb is 0.001m, which is a small error, and the ICC(3,1) between the rotation distance Δl and the moving distance Δlb is “0.70”, which is a high value. This result is considered to reflect the rotation of the ball 2.

[0064] The results shown in FIGS. 6 to 9 suggest the possibility that the force acting on the ball from the subject's fingers and the point of application of the force can be estimated by using ball 2 equipped with various sensors.

[0065] <Functional configuration> Fig. 10 is a block diagram showing an example of a functional configuration of the sensor device 20. Referring to Fig. 10, the sensor device 20 includes an acquisition unit 250, a time calculation unit 252, a first calculation unit 254, a second calculation unit 256, and an output control unit 258. These are basically realized by the processor 202 of the sensor device 20, etc. Note that some or all of these functional configurations may be realized by hardware.

[0066] Acquisition unit 250 acquires motion information of ball 2 detected by sensors (e.g., acceleration sensor 205, angular velocity sensor 206) built into ball 2. The motion information includes time series data of three-axis acceleration and three-axis angular velocity of ball 2. Acquisition unit 250 may further acquire time series data of three-axis geomagnetism detected by geomagnetic sensor 208.

[0067] Based on the motion information, the time calculation unit 252 calculates the release time tr at which the ball 2 is released from the fingers of the subject 5. Specifically, the time calculation unit 252 calculates, as the release time tr, the time at which the resultant acceleration A obtained by combining the accelerations in the three axial directions becomes equal to or greater than the threshold value Ka1, or the time at which the resultant angular velocity Sω obtained by combining the angular velocities about the three axes becomes constant.

[0068] The time calculation unit 252 calculates the time when the resultant acceleration A becomes maximum or the time when the resultant angular acceleration obtained by combining the angular accelerations around the three axes becomes equal to or greater than the threshold value H as the time t2 when the fingers of the subject 5 start to rotate the ball 2.

[0069] The first calculation unit 254 calculates a force vector acting on the ball 2 from the fingers of the subject 5 (i.e., force vector F) and a torque vector acting on the ball 2 (i.e., torque vector N) during a period before the release time tr, based on the motion information and specification information of the ball 2. This period is, for example, a period (for example, the above-mentioned predetermined period) whose start time is time t2 and whose end time is just before (for example, 2 ms before) the release time tr.

[0070] Specifically, the first calculation unit 254 calculates a force vector F based on an acceleration vector indicating the mass and three-axis acceleration of the ball 2. The first calculation unit 254 calculates a torque vector N based on the moment of inertia of the ball 2 and an angular acceleration vector obtained by time-differentiating an angular velocity vector indicating the angular velocity about the three axes. In particular, the first calculation unit 254 calculates the torque vector N using equation (2), and calculates the force vector F using equation (3).

[0071] The second calculation unit 256 calculates a point of action xb of the force on the surface of the ball 2 based on the force vector F, the torque vector N, and the specification information of the ball 2. Specifically, the second calculation unit 256 calculates a point (for example, point p) located on the line of action 50 of the force, which minimizes the torque vector τ acting on the point, and which has a minimum distance d from the center of the ball 2. Next, the second calculation unit 256 calculates the point of action xb based on the point p, the radius R of the ball 2, and the force vector F. Furthermore, the second calculation unit 256 calculates the distance d between the point p and the point of action xb based on the radius R of the ball 2. In detail, the second calculation unit 256 calculates the point p using equation (6), calculates the distance d using equation (7), and calculates the point of action xb using equation (8).

[0072] The output control unit 258 outputs the calculation results (e.g., force vector F, torque vector N, and point of action xb) of the first calculation unit 254 and the second calculation unit 256. Specifically, the output control unit 258 transmits the calculation results to the terminal device 10. The terminal device 10 includes a display control unit that displays the calculation results. Typically, the display control unit displays the force vector F and point of action xb for a predetermined period (e.g., the period from time t2 to immediately before the release time tr) on the display 112. For example, the display control unit displays the results shown in FIGS. 6 to 9.

[0073] <Advantages> According to this embodiment, by using a ball with a built-in sensor, it is possible to easily calculate the point of application of the force acting on the ball when the subject throws it, without giving the subject any discomfort. This makes it possible to know at what point on the surface of the ball the force is being applied and in what direction before the ball is released. In addition, by combining the result of the force application point with the results of the number of rotations and axis of rotation that are calculated separately, it is possible to analyze what kind of force is being applied at what point, generating the rotation of the pitched ball.

[0074] <Other embodiments> (1) In the above embodiment, the ball 2 with the built-in sensor is a baseball ball, but the present invention is not limited to this configuration. For example, the present invention is also applicable to a case where the ball 2 is a softball.

[0075] (2) In the above-described embodiment, the terminal device 10 may have some of the functions of the sensor device 20. For example, the terminal device 10 may have the functions of the sensor device 20 in Fig. 10. In this case, an acquisition unit of the terminal device 10 receives sensor data (e.g., acceleration, angular velocity, geomagnetism, etc.) detected by a sensor of the sensor device 20. Other functional configurations (e.g., a time calculation unit, a first calculation unit, a second calculation unit, an output control unit) are similar to the functional configurations described above.

[0076] (3) It is also possible to provide a program that causes a computer to function and execute the control as described in the above embodiment. Such a program can be recorded on a non-transitory computer-readable recording medium such as a flexible disk, ROM, RAM, or memory card that is attached to the computer and provided as a program product. Alternatively, the program can be recorded on a recording medium such as a hard disk built into the computer and provided. The program can also be provided by downloading it over a network.

[0077] (4) The configurations exemplified as the above-mentioned embodiments are merely examples of the configurations of the present invention, and may be combined with other known technologies. The present invention may also be modified, for example by omitting some parts, without departing from the gist of the present invention.

[0078] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0079] 2 ball, 5 subject, 10 terminal device, 20 sensor device, 102, 202 processor, 104, 204 memory, 106 touch panel, 108 wireless communication unit, 110 communication antenna, 112 display, 205 acceleration sensor, 206 angular velocity sensor, 208 geomagnetic sensor, 212 storage battery, 250 acquisition unit, 252 time calculation unit, 254 first calculation unit, 256 second calculation unit, 258 output control unit, 1000 analysis device.

Claims

1. an acquisition unit that acquires motion information of the ball detected by a sensor built into the ball; a time calculation unit that calculates a release time at which the ball is released from the subject's fingers based on the motion information; a first calculation unit that calculates a force vector acting from the subject's fingers to the ball and a torque vector acting on the ball during a period prior to the release time based on the motion information and specification information of the ball; a second calculation unit that calculates a point of application of the force on a surface of the ball based on the force vector, the torque vector, and specification information of the ball.

2. the ball specification information includes a radius of the ball; The second calculation unit is calculating a first point located on the line of action of the force, the first point minimizing a torque vector acting on the first point and having a minimum distance from the center of the ball; The analysis device according to claim 1 , wherein the point of action is calculated based on the first point, a radius of the ball, and the force vector.

3. The analysis device according to claim 2 , wherein the second calculation unit calculates the distance between the first point and the point of action based on a radius of the ball.

4. the motion information includes an acceleration of the ball in three axial directions and an angular velocity of the ball about three axes; the specification information includes a mass of the ball and a moment of inertia of the ball; The first calculation unit is Calculating the force vector based on an acceleration vector indicating the acceleration in the three axial directions and the mass; 4. The analysis device according to claim 1, wherein the torque vector is calculated based on an angular acceleration vector obtained by time-differentiating an angular velocity vector indicating angular velocities about the three axes and the moment of inertia.

5. The analysis device according to claim 4 , wherein the time calculation unit calculates, as the release time, a time when a resultant acceleration obtained by combining the accelerations in the three axial directions becomes equal to or greater than a first threshold value, or a time when a resultant angular velocity obtained by combining the angular velocities about the three axes becomes constant.

6. the start time of the period is the first time that the subject's fingers start to rotate the ball; The analysis device according to claim 4, wherein the time calculation unit calculates as the first time a time when a resultant acceleration obtained by combining accelerations in the three axial directions becomes maximum, or a time when a resultant angular acceleration obtained by combining angular accelerations around the three axes obtained by time-differentiating angular velocities around the three axes becomes equal to or greater than a second threshold value.

7. The analysis device according to claim 6 , further comprising a display control unit that displays the force vector and the point of action during the period.

8. The analysis device according to claim 4 , wherein the sensor includes an acceleration sensor that detects acceleration in the three axial directions, and an angular velocity sensor that detects angular velocity about the three axes.

9. acquiring motion information of the ball detected by a sensor built into the ball; calculating a release time when the ball is released from the subject's fingers based on the motion information; calculating a force vector acting on the ball from the subject's fingers and a torque vector acting on the ball during a period prior to the release time based on the motion information and specification information of the ball; and calculating a point of application of the force on a surface of the ball based on the force vector, the torque vector, and specification information of the ball.

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