Patent Publication Number: US-2022225918-A1

Title: Information processing device, state determination system, energy calculation system, information processing method, and storage medium

Description:
TECHNICAL FIELD 
     The present invention relates to an information processing device, a state determination system, an energy calculation system, an information processing method, and a storage medium. 
     BACKGROUND ART 
     Patent Literature 1 discloses a device for determining a pose using an acceleration sensor mounted on a human body. The device of the Patent Literature 1 determines whether the person is walking, running, lying, sitting, or standing based on the three axial acceleration acquired by the acceleration sensor. 
     CITATION LIST 
     Patent Literature 
     
         
         PTL 1: Japanese Patent Application Laid-open No. 2010-125239 
       
    
     Non Patent Literature 
     
         
         NPL 1: Sebastian O. H. Madgwick, Andrew J. L. Harrison, and Ravi Vaidyanathan, “Estimation of IMU and MARG orientation using a gradient descent algorithm”, 2011 IEEE International Conference on Rehabilitation Robotics, pp. 179-185, 2011. 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     The acceleration acquired by the acceleration sensor may include noise. When the pose determination method using acceleration as disclosed in Patent Literature 1 is applied to determination of a state of a user riding a bicycle, this noise may decrease determination accuracy. 
     The present invention intends to provide an information processing device, a state determination system, an energy calculation system, an information processing method, and a storage medium which can determine a state of a user with high accuracy. 
     Solution to Problem 
     According to one example aspect of the invention, provided is an information processing device including an acquisition unit configured to acquire motion information of a foot of a user measured by a motion measurement device and a determination unit configured to determine whether or not the user is in a pedaling state in which the user pedals a bicycle based on an angle between a sole and a ground generated from the motion information. 
     According to another example aspect of the invention, provided is an information processing method including acquiring motion information of a foot of a user measured by a motion measurement device and determining whether or not the user is in a pedaling state in which the user pedals a bicycle based on an angle between a sole and a ground generated from the motion information. 
     According to another example aspect of the invention, provided is a storage medium storing a program that causes a computer to perform acquiring motion information of a foot of a user measured by a motion measurement device and determining whether or not the user is in a pedaling state in which the user pedals a bicycle based on an angle between a sole and a ground generated from the motion information. 
     Advantageous Effects of Invention 
     According to the present invention, an information processing device, a state determination system, an energy calculation system, an information processing method, and a storage medium which can determine a state of a user with high accuracy can be provided. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic diagram illustrating a general configuration of a state determination system according to a first example embodiment. 
         FIG. 2  is a block diagram illustrating a hardware configuration of a state determination device according to the first example embodiment. 
         FIG. 3  is a block diagram illustrating a hardware configuration of an information communication terminal according to the first example embodiment. 
         FIG. 4  is a functional block diagram of an information processing device according to the first example embodiment. 
         FIG. 5  is a flowchart illustrating an example of a state determination process performed by the state determination device according to the first example embodiment. 
         FIG. 6  is a flowchart illustrating an example of a pedaling state determination process. 
         FIG. 7  is a graph illustrating an example of time series data of acceleration in a pedaling state. 
         FIG. 8  is a graph illustrating an example of time series data of an angle between a sole and ground in the pedaling state. 
         FIG. 9  is a graph illustrating an example of time series data of the acceleration and time series data of the angle when a user is walking. 
         FIG. 10  is a graph illustrating an example of frequency spectrum of the acceleration and frequency spectrum of the angle when the user is walking. 
         FIG. 11  is a graph illustrating an example of time series data of the acceleration and time series data of the angle in the pedaling state. 
         FIG. 12  is a graph illustrating an example of frequency spectrum of the acceleration and frequency spectrum of the angle in the pedaling state. 
         FIG. 13  is a functional block diagram of an information processing device according to a second example embodiment. 
         FIG. 14  is a flowchart illustrating an example of an energy calculation process performed by the energy calculation unit according to the second example embodiment. 
         FIG. 15  is a functional block diagram of an information processing device according to a third example embodiment. 
     
    
    
     Exemplary embodiments of the present invention are described below with reference to the drawings. Throughout the drawings, the same components or corresponding components are labeled with same references, and the description thereof may be omitted or simplified. 
     FIRST EXAMPLE EMBODIMENT 
     A state determination system according to the present example embodiment is described. The state determination system of the present example embodiment is a system for measuring and analyzing a state of a user including determination of the state of the user riding the bicycle. As a part of health management, there is a need to acquire a log related to exercise such as daily walking time, bicycle riding time, and the like. In order to acquire the log of the bicycle riding time of the user, a function of determining the state of the user riding the bicycle is required. Accordingly, the present example embodiment provides a state determination system capable of determining the state of the user riding the bicycle with high accuracy. 
     The state of the user riding the bicycle typically includes a pedaling state in which the user is pedaling the bicycle. In other words, the state determination system of the present example embodiment can determine whether or not the user is pedaling. 
     Even when the user is on the bicycle, a state in which the user is not pedaling is not included in the pedaling state. Such a state in which the user is not pedaling is called a non-pedaling state. In recent years, a bicycle which is commercially available has been provided with a freewheel mechanism so that the bicycle can be traveled by inertia without turning a pedal. In such riding of the bicycle, a state in which the bicycle is traveling with inertia without pedaling by the user is included in the non-pedaling state. Further, the non-pedaling state includes a state in which the user is not pedaling in the operation of a bicycle equipped with a motor, which is provided with both a pedal and a motor such as a moped and is capable of traveling with human power. 
     In this specification, the number of wheels included in the bicycle is not particularly limited, and the “bicycle” may include not only a two-wheel bicycle but also a three-wheel bicycle, a bicycle with an auxiliary wheel, and the like. Further, even a vehicle equipped with a motor such as an electrically assisted bicycle or a bicycle with a motor is included in “bicycle” as long as it is provided with a mechanism capable of being driven by a pedal with human power. Further, the “bicycle” includes a stationary bicycle such as a bicycle for indoor training having a pedal like a two-wheel bicycle. 
       FIG. 1  is a schematic diagram illustrating a general configuration of a state determination system according to the present example embodiment. The state determination system includes a state determination device  1 , an information communication terminal  2 , and a server  3  which can be connected to each other by wireless communication. 
     The state determination device  1  is provided to be close to the sole of a shoe  5  worn by a user  4 , for example. The state determination device  1  is an electronic apparatus having a sensing function for measuring a motion of the foot of the user  4 , an information processing function for analyzing the measured motion information, a communication function with the information communication terminal  2 , and the like. It is desirable that the state determination device  1  be provided at a position corresponding to the arch of the foot such as just below the arch of the foot. In this case, the state determination device  1  can measure acceleration and angular velocity of the center of the foot of the user  4 . Since the center of the foot is a position showing the feature of the motion of the foot well, it is suitable for extracting features indicating the state of the user. 
     Note that, the state determination device  1  may be provided in the insole of the shoe  5 , may be provided in the outsole of the shoe  5 , or may be embedded in the shoe  5 . The state determination device  1  may be detachably attached to the shoe  5  or may be non-detachably fixed to the shoe  5 . The state determination device  1  may be provided at a portion other than the shoe  5  as long as the state determination device  1  can measure the motion of the foot. For example, the state determination device  1  may be provided in a sock which the user  4  is wearing, provided in a decoration, directly attached to the foot of the user  4 , or embedded in the foot of the user  4 . Although  FIG. 1  illustrates an example in which one state determination device  1  is provided on one foot of the user  4 , one state determination device  1  may be provided on each of both feet of the user  4 . In this case, the motion information of both feet can be acquired in parallel, and more information can be acquired. 
     In this specification, the “foot” means a body part below an ankle of the user  4 . In addition, in this specification, the “user” means a person who is an object of a determination of the state using the state determination device  1 . Whether or not the user corresponds to the “user” is unrelated to whether or not the user is a user of a device other than the state determination device  1  constituting the state determination system, whether or not the user receives a service provided by the state determination system, or the like. 
     The information communication terminal  2  is a terminal device carried by the user  4 , such as a cellular phone, a smartphone, or a smart watch. Application software for analyzing a state is installed in advance in the information communication terminal  2 , and processing based on the application software is performed. The information communication terminal  2  acquires data such as the state determination result acquired by the state determination device  1  from the state determination device  1  and performs information processing using the data. The result of the information processing may be notified to the user  4  or may be transmitted to the server  3 . The information communication terminal  2  may have a function of providing software such as a control program of the state determination device  1  or a data analysis program to the state determination device  1 . 
     The server  3  provides application software for analyzing states to the information communication terminal  2  and updates the application software. The server  3  may store data acquired from the information communication terminal  2  and perform information processing using the data. 
     Note that, the general configuration is an example, and for example, the state determination device  1  may be directly connected to the server  3 . Further, the state determination device  1  and the information communication terminal  2  may be configured as an integrated device, and another device such as an edge server or a relay device may be further included in the state determination system. 
       FIG. 2  is a block diagram illustrating a hardware configuration example of the state determination device  1 . The state determination device  1  includes an information processing device  11 , an inertial measurement unit (IMU)  12 , and a battery  13 . 
     The information processing device  11  is, for example, a microcomputer or a microcontroller that performs a control and data processing of the entire state determination device  1 . The information processing device  11  includes a central processing unit (CPU)  111 , a random access memory (RAM)  112 , a read only memory (ROM)  113 , a flash memory  114 , a communication interface (I/F)  115 , and an IMU control device  116 . Each unit in the information processing device  11 , the IMU  12 , and the battery  13  is connected each other via a bus, wiring, a driving device, or the like. 
     The CPU  111  is a processor that performs predetermined calculation in accordance with a program stored in the ROM  113 , the flash memory  114 , or the like, and also has a function of controlling each unit of the information processing device  11 . The RAM  112  is composed of a volatile storage medium and provides a temporary memory area required for the operation of the CPU  111 . The ROM  113  is composed of a non-volatile storage medium and stores necessary information such as a program used for the operation of the information processing device  11 . The flash memory  114  is a storage device composed of a non-volatile storage medium and temporarily storing data, storing an operation program of the information processing device  11 , or the like. 
     The communication I/F  115  is a communication interface based on standards such as Bluetooth (registered trademark) or Wi-Fi (registered trademark), and is a module for performing communication with the information communication terminal  2 . 
     The IMU  12  is a motion measurement device including an angular velocity sensor that measures angular velocity in three axial directions and an acceleration sensor that measures acceleration in three directions. The angular velocity sensor may be any sensor as long as it can acquire the angular velocity as time series data, and any type of sensor such as a vibration type sensor or a capacitance type sensor may be used. The acceleration sensor may be any type of sensor as long as it can acquire acceleration as time series data, and any type of sensor such as a piezoelectric type sensor, a piezoresistance type sensor, or a capacitance type sensor may be used. In the present example embodiment, the interval between the data points of the acquired time series data may be constant or may not be constant. 
     The IMU control device  116  is a control device that controls the IMU  12  to measure angular velocity and acceleration and acquires angular velocity and acceleration acquired by the IMU  12 . The acquired angular velocity and acceleration are stored in the flash memory  114  as digital data. Note that analog-to-digital (AD) conversion for converting an analog signal measured by the IMU  12  into digital data may be performed in the IMU  12  or may be performed by the IMU control device  116 . 
     The battery  13  is, for example, a secondary battery, and supplies power necessary for the operations of the information processing device  11  and the IMU  12 . Since the battery  13  is built in the state determination device  1 , the state determination device can operate wirelessly without connecting to an external power source by wire. 
     Note that the hardware configuration illustrated in  FIG. 2  is an example, and other devices may be added or some devices may not be provided. Further, some devices may be replaced by other devices having similar functions. For example, the information processing device  11  may further include an input device such as a button so that an operation by the user  4  can be accepted, and may further include an output device such as a display, a display lamp, and a speaker for providing information to the user  4 . Thus, the hardware configuration illustrated in  FIG. 2  can be changed appropriately. 
       FIG. 3  is a block diagram illustrating a hardware configuration example of the information communication terminal  2 . The information communication terminal  2  includes a CPU  201 , a RAM  202 , a ROM  203 , and a flash memory  204 . The information communication terminal  2  also includes a communication I/F  205 , an input device  206 , and an output device  207 . Each unit of the information communication terminal  2  is connected to each other via a bus, wiring, a driving device, or the like. 
     In  FIG. 3 , each unit constituting the information communication terminal  2  is illustrated as an integrated device, but a part of these functions may be provided by an external device. For example, the input device  206  and the output device  207  may be external devices different from those constituting the functions of the computer including the CPU  201  or the like. 
     The CPU  201  is a processor that performs predetermined calculation in accordance with a program stored in the ROM  203 , the flash memory  204 , or the like, and also has a function of controlling each unit of the information communication terminal  2 . The RAM  202  is composed of a volatile storage medium and provides a temporary memory area required for the operation of the CPU  201 . The ROM  203  is composed of a non-volatile storage medium and stores necessary information such as a program used for the operation of the information communication terminal  2 . The flash memory  204  is a storage device composed of a non-volatile storage medium for storing data transmitted and received to and from the state determination device and for storing a program for operating the information communication terminal  2 . 
     The communication I/F  205  is a communication interface based on standards such as Bluetooth (registered trademark), Wi-Fi (registered trademark), or 4G and is a module for performing communication with other devices. 
     The input device  206  is a user interface used by the user  4  to operate the information communication terminal  2 . Examples of the input device  206  include a mouse, a trackball, a touch panel, a pen tablet, a button, or the like. 
     The output device  207  is, for example, a display device. The display device is a liquid crystal display, an organic light emitting diode (OLED) display, or the like, and is used for displaying information, displaying a graphical user interface (GUI) for operation input, or the like. The input device  206  and the output device  207  may be integrally formed as a touch panel. 
     Note that the hardware configuration illustrated in  FIG. 3  is an example, and other devices may be added or some devices may not be provided. Further, some devices may be replaced by other devices having similar functions. Further, some functions of the present example embodiment may be provided by other devices via a network, or some functions of the present example embodiment may be realized by being distributed among a plurality of devices. For example, the flash memory  204  may be replaced by a hard disk drive (HDD) or a cloud storage. Thus, the hardware configuration illustrated in  FIG. 3  can be changed appropriately. 
     The server  3  is a computer having substantially the same hardware configuration as that illustrated in  FIG. 3 . Since the hardware configuration of the server  3  is substantially the same as that of the information communication terminal  2  except that the server  3  may not be portable, a detailed description thereof is omitted. 
       FIG. 4  is a functional block diagram of the information processing device  11  according to the present example embodiment. The information processing device  11  includes an acquisition unit  120 , a determination unit  130 , a storage unit  140 , and a communication unit  150 . The determination unit  130  includes a coordinate system transforming unit  131 , an angle calculation unit  132 , a data selecting unit  133 , a data conversion unit  134 , a similarity degree calculation unit  135 , and a comparison unit  136 . 
     The CPU  111  loads a program stored in the ROM  113 , the flash memory  114 , or the like into the RAM  112  and executes the program. Thus, the CPU  111  realizes the functions of the determination unit  130 . Further, the CPU  111  realizes the function of the acquisition unit  120  by controlling the IMU control device  116  based on the program. The CPU  111  realizes the function of the storage unit  140  by controlling the flash memory  114  based on the program. Further, the CPU  111  realizes the function of the communication unit  150  by controlling the communication I/F  115  based on the program. Specific processing performed by each of these units is described later. 
     In the present example embodiment, each function of the functional blocks illustrated in  FIG. 4  is provided in the state determination device  1 , but some functions of the functional blocks illustrated in  FIG. 4  may be provided in the information communication terminal  2  or the server  3 . That is, the above-described functions may be realized by any of the state determination device  1 , the information communication terminal  2 , and the server  3 , or may be realized by cooperation of the state determination device  1 , the information communication terminal  2 , and the server  3 . 
       FIG. 5  is a flowchart illustrating an example of a state determination process performed by the state determination device  1  according to the present example embodiment. The process of  FIG. 5  is performed at predetermined time intervals, for example. Alternatively, the process of  FIG. 5  may be performed when the state determination device  1  detects that the user  4  has got on the bicycle based on a change in acceleration or the like. 
     In step S 101 , the acquisition unit  120  controls the angular velocity sensor and the acceleration sensor of the IMU  12  to acquire time series data of angular velocity in three axial directions and acceleration in three directions. Thus, the acquisition unit  120  can acquire time changes in angular velocity and acceleration based on the motion of the foot of the user  4 . The acquired time series data of angular velocity and acceleration is converted into digital data and then stored in the storage unit  140 . These angular velocity and acceleration are referred to more generally as motion information. 
     The three directions of acceleration acquired by the acquisition unit  120  may be, for example, the width direction (left/right direction), the longitudinal direction (front/back direction), and the vertical direction of the foot of the user  4  provided with the IMU  12 . These directions are referred to as x-axis, y-axis, and z-axis, respectively. The three axial directions of the angular velocity acquired by the acquisition unit  120  may be, for example, an adduction and an abduction of the foot about the z-axis (yaw), a pronation and a supination of the foot about the y-axis (pitch), and a bending and a stretching of the foot about x-axis (roll). 
     Here, in order to sufficiently acquire the feature included in the pedaling, it is desirable that the time series data of the angular velocity in the three axial directions and the acceleration in the three directions include data in a period corresponding to at least two pedaling cycles (rotation time corresponding to two cycles of the pedal). This is because the pedaling is a substantially periodic circular motion, and therefore, if at least two cycles can be extracted, it can be estimated that the same motion is repeated before and after the two cycles. 
     In step S 102 , the coordinate system transforming unit  131  performs coordinate system transformation of angular velocity in three axial directions and acceleration in three directions. A coordinate system with respect to angular velocity and acceleration output by the IMU  12  is an inertial coordinate system. The coordinate system transforming unit  131  transforms the angular velocity and acceleration coordinate system into a coordinate system with respect to the foot of the user  4 . Thus, the coordinate system of the angular velocity and the acceleration can be made suitable for calculating the angle between the sole and the ground. The transformation of the coordinate system is realized, for example, by multiplying the base vector of the inertial coordinate system by the direction cosine matrix E using the Euler angle and rotating the base vector. 
     An example of transformation of the coordinate system by the direction cosine matrix E is described more specifically. In a case where the base vector of the inertial coordinate system is [x i , y i , z i ], and the base vector of the coordinate system with respect to the foot is [x b , y b , z b ], a conversion formula between them is expressed by the following equation (1). 
     
       
         
           
             
               
                 
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     Note that the calculation method used for conversion of the coordinate system is merely an example, and other calculation methods may be used. For example, a calculation method using a quaternion may be applied. 
     In step S 103 , the angle calculation unit  132  calculates the angle between the sole of the user  4  and the ground from the angular velocity in the three axial directions and the acceleration in the three directions after being transformed into the coordinate system with respect to the foot of the user  4 . As a specific example of this process, there is a method in which angular velocity in three axial directions and acceleration in three directions are input to a Madgwick filter (Non Patent Literature 1), and a rotation angle in three axial directions of the foot is output. The rotation angles in the three axial directions acquired by the Madgwick filter are the angles of adduction or abduction of the foot, the angle of pronation or supination of the foot, and the angle of bending or stretching of the foot. Of these three angles, the angle of stretching or bending of the foot corresponds to the angle between the sole of the foot of the user  4  and the ground. 
     In step S 104 , the determination unit  130  performs a pedaling state determination process for determining whether or not the user  4  is in a pedaling state in which the user  4  is pedaling the bicycle, based on at least the above-described angle. 
       FIG. 6  is a flowchart illustrating an example of a pedaling state determination process. The process of  FIG. 6  is a subroutine corresponding to step S 104  of  FIG. 5 . This process is a loop process in which steps S 201  through S 207  are repeated for each data. In  FIG. 6 , i represents a data number of time series data of the input angle and acceleration. The process from steps S 201  through step S 207  are repeated until the data number reaches the predetermined upper limit value imax from the initial value. 
     In step S 201 , the data selecting unit  133  acquires data in the range from the (i−n)-th to the i-th of the time series data of the angle and the time series data of the acceleration. This process is for specifying a time range of time series data used for conversion into a frequency domain in step S 202  and step S 203  described later. Therefore, the process of the data selecting unit  133  corresponds to a process of multiplying the time series data by a rectangular window having a width n. Note that the process may be modified to use another window function, and for example, a Gaussian window, a Hanning window, or the like may be applied. 
     In step S 202 , the data conversion unit  134  converts the time series data of the angle Roll t  in the range acquired in step S 201  into the frequency spectrum Roll f . This process may be any process as long as it can convert time domain data into frequency domain data, and may be Fourier transform, for example. The algorithm used for the Fourier transform may be, for example, a fast Fourier transform. 
     In step S 203 , as in step S 202 , the data conversion unit  134  converts the time series data of the acceleration a t  in the range acquired in step S 201  into the frequency spectrum a f . 
     In step S 204 , the similarity degree calculation unit  135  calculates a correlation coefficient R 1  between time series data of the acceleration at and time series data of the angle Roll t . Further, the similarity degree calculation unit  135  calculates a correlation coefficient R 2  between the frequency spectrum of the acceleration a f  and the frequency spectrum of the angle Roll f . Note that the correlation coefficients R 1  and R 2  may typically be Pearson&#39;s product moment correlation coefficients. The correlation coefficients R 1  and R 2  may be referred to as a first similarity degree and a second similarity degree, respectively. 
     In step S 205 , the comparison unit  136  compares the correlation coefficients R 1  and R 2  with predetermined threshold values T 1  and T 2 . When the correlation coefficient R 1  is greater than the threshold value T 1  and the correlation coefficient R 2  is greater than the threshold value T 2  (YES in step S 205 ), the process proceeds to step S 206 . If the above condition is not satisfied (NO in step S 205 ), the process proceeds to step S 207 . The threshold values T 1  and T 2  may be more generally referred to as a first threshold value and a second threshold value, respectively. 
     In step S 206 , the determination unit  130  determines that the user  4  pedaled the bicycle at the i-th data acquisition time (that is, the user  4  was in the pedaling state). The determination result is stored in the storage unit  140  in association with the data number i or the time corresponding thereto. 
     In step S 207 , the determination unit  130  determines that the user  4  did not pedal the bicycle at the i-th data acquisition time (that is, the user  4  was not in the pedaling state). The determination result is stored in the storage unit  140  in association with the data number i or the time corresponding thereto. 
     In the above-described pedaling state determination process, the angle between the sole of the foot and the ground is used for determination. The reason why it is possible to accurately determine whether or not the user  4  is pedaling is described.  FIG. 7  is a graph illustrating an example of time series data of acceleration in a pedaling state. The horizontal axis of  FIG. 7  represents time in units of milliseconds (ms), and the vertical axis of  FIG. 7  represents acceleration in the y-axis direction, that is, in the longitudinal direction of the foot. The unit G of the vertical axis is a unit of acceleration based on the standard gravitational acceleration (about 9.8 m/s 2 ). When the user  4  is pedaling, the foot of the user  4  is rotating, so that the acceleration has a waveform close to a sine wave. As can be understood from  FIG. 7 , the acceleration includes large noise due to various factors such as vibration of the bicycle. In some cases, as in the vicinity of 23500 ms in  FIG. 7 , a large noise exceeding the amplitude of the sine wave may be generated, and if the determination of the pedaling state is performed using only the acceleration, such noise may affect the determination accuracy. 
       FIG. 8  is a graph illustrating an example of time series data of an angle between a sole and ground in a pedaling state. The horizontal axis of  FIG. 8  represents time, and the vertical axis of  FIG. 8  represents the angle between the sole of the foot and the ground. As can be understood from  FIG. 8 , the noise included in the angle is smaller than the noise included in the acceleration. Therefore, determination accuracy can be improved by performing determination of the pedaling state using an algorithm utilizing the angle. 
     In the above-described pedaling state determination process, the determination is performed using the correlation coefficient between the acceleration and the angle. The reason why whether or not the user  4  is pedaling can be determined with higher accuracy is described. First, waveforms of acceleration and angle when the user  4  is walking is described with reference to  FIG. 9  and  FIG. 10  as an example of a case where the user  4  is not pedaling (non-pedaling state).  FIG. 9  is a graph illustrating an example of time series data of acceleration and time series data of angle when the user  4  is walking. The horizontal axis of  FIG. 9  represents time, the left axis of  FIG. 9  represents acceleration in the y-axis direction, and the right axis of  FIG. 9  represents an angle between the sole of the foot and the ground. The solid line graph of  FIG. 9  indicates the acceleration of the left axis, and the broken line graph of  FIG. 9  indicates the angle of the right axis. 
       FIG. 10  is a graph illustrating an example of a frequency spectrum of acceleration and a frequency spectrum of angle when the user  4  is walking. The horizontal axis of  FIG. 10  represents the frequency in units of Hertz (Hz), and the vertical axis of  FIG. 10  represents the intensity in arbitrary units. The solid line graph of  FIG. 10  represents the frequency spectrum of the acceleration, and the broken line graph of  FIG. 10  represents the frequency spectrum of the angle. 
     As can be understood from  FIG. 9  and  FIG. 10 , when the user  4  walks, the waveform of the acceleration and the waveform of the angle are not similar to each other in both the time series data and the frequency spectrum. Therefore, when the user  4  walks, the correlation coefficient between the acceleration and the angle is a small value. 
     Next, waveforms of acceleration and angle when the user  4  is pedaling (pedaling state) is described with reference to  FIG. 11  and  FIG. 12 . The notations of the graphs are the same as those in  FIG. 9  and  FIG. 10 , and therefore the description thereof is omitted. As can be understood from  FIG. 11  and  FIG. 12 , in both the time series data and the frequency spectrum, the waveform of the acceleration and the waveform of angle are similar to each other. Therefore, in the pedaling state, the correlation coefficient between the acceleration and the angle is greater than that in the walking state. 
     As described above, in the pedaling state, the similarity degree between the acceleration and the angle is high and the correlation coefficient is large as compared with the non-pedaling state. Therefore, the correlation coefficient is calculated as an index of the similarity degree between the acceleration and the angle, and the magnitude relation between the correlation coefficient and the threshold value is used as the determination condition, whereby it is possible to determine the pedaling state with higher accuracy. An index other than the correlation coefficient may be used as long as the determination method uses the similarity degree between the acceleration and the angle. For example, covariance may be used as a determination condition. 
     Further, in this determination, by referring to both the time series data, which is the waveform in the time domain, and the frequency spectrum, which is the waveform in the frequency domain, it is possible to more reliably determine the pedaling state. However, the determination may be performed using only the time series data or using only the frequency spectrum. In this case, the process is simplified, and the amount of calculation can be reduced. 
     As described above, according to the present example embodiment, the information processing device  11  is provided that can accurately determine the state of the user  4  riding the bicycle by determining whether or not the user  4  is in the pedaling state based on the angle between the sole of the foot and the ground. 
     SECOND EXAMPLE EMBODIMENT 
     The energy calculation system of the present example embodiment is an example of utilizing the function of determining the pedaling state by the state determination system of the first example embodiment. There is a need to acquire a log of daily energy consumption (so-called consumed calories). As a part of health management, the energy calculation system is a system that can meet the above needs by calculating the energy consumed by the user  4  when the user  4  rides the bicycle. Description of portions common to those in the first example embodiment is omitted. 
       FIG. 13  is a functional block diagram of the information processing device  11  included in the energy calculation system according to the present example embodiment. The energy calculation system of the present example embodiment is acquired by adding an energy calculation unit  160  to the information processing device  11  of the state determination system of the first example embodiment. The CPU  111  realizes the function of the energy calculation unit  160  by loading a program stored in the ROM  113 , the flash memory  114 , or the like into the RAM  112  and executing the program. In  FIG. 13 , the energy calculation unit  160  is provided in the information processing device  11 , but this function may be provided in the information communication terminal  2  or the server  3 . 
       FIG. 14  is a flowchart illustrating an example of an energy calculation process performed by the energy calculation unit  160  according to the present example embodiment. The process of  FIG. 14  is performed, for example, after the end of the process according to the flowchart of  FIG. 5 . Alternatively, the process of  FIG. 14  may be performed based on an operation of energy calculation by the user  4 . 
     In step S 301 , the energy calculation unit  160  acquires the determination result of the pedaling state corresponding to each data acquisition time from the storage unit  140 . In step S 302 , the energy calculation unit  160  adds up the period in the pedaling state (pedaling period) and calculates the length of the pedaling period in the data acquisition period. 
     In step S 303 , the energy calculation unit  160  calculates the energy consumed by the user  4  due to the riding of the bicycle by the user  4 , based on the length of the pedaling period. For example, the following Equation (3) can be used as a calculation equation used for this calculation. 
       Consumed energy=exercise intensity (METs)×length of pedaling period×body weight×coefficient  (3)
 
     In Equation (3), METs, which is a unit of exercise intensity, represents how many times the energy consumption is as compared with the rest state during exercise. Depending on the speed, the inclination of the riding route, and the like, the METs of the bicycle riding is, for example, 4.0 (METs) or 6.8 (METs). The value of the exercise intensity may be input by the user  4  in advance with reference to a METs table or the like, or may be automatically set based on the speed of the bicycle or the like calculated from the acceleration acquired by the IMU  12 . In Equation (3), the coefficient is about 1.05 when the unit of the length of the pedaling period is time (hour), the unit of the body weight is kg, and the unit of the consumed energy is kcal. 
     In the pedaling state, by pedaling, the energy consumption is increased as compared with the case of the non-pedaling state. By focusing attention on the length of the pedaling period, the energy calculation unit  160  of the present example embodiment can calculate the consumed energy more accurately than the case where the consumed energy is calculated based only on the length of time during which the user  4  is on the bicycle. 
     The energy calculation system of the present example embodiment uses the information processing device  11  that can accurately determine the state of the user  4  riding the bicycle. Thus, an energy calculation system capable of accurately calculating consumed energy is provided. 
     The device or system described in the above example embodiments can also be configured as in the following third example embodiment. 
     THIRD EXAMPLE EMBODIMENT 
       FIG. 15  is a functional block diagram of the information processing device  61  according to the third example embodiment. The information processing device  61  includes an acquisition unit  611  and a determination unit  612 . The acquisition unit  611  acquires motion information of a foot of a user measured by a motion measurement device. The determination unit  612  determines whether or not the user is in a pedaling state in which the user pedals a bicycle based on an angle between a sole and a ground generated from the motion information. 
     According to the present example embodiment, the information processing device  61  capable of accurately determining the state of the user riding the bicycle is provided. 
     MODIFIED EXAMPLE EMBODIMENTS 
     The present invention is not limited to the example embodiments described above, and may be suitably modified within the scope of the present invention. For example, an example in which a part of the configuration of one example embodiment is added to another example embodiment or an example in which a part of the configuration of one example embodiment is replaced with another example embodiment is also an example embodiment of the present invention. 
     In the above-described example embodiments, the motion measurement device including the angular velocity sensor that measures the angular velocity in the three axial directions and the acceleration sensor that measures the acceleration in the three directions is used, but sensors other than these may also be used. For example, a magnetic sensor that detects geomagnetism by detecting magnetism in three directions to identify an azimuth may be further used. Even in this case, the same processing as the above-described example embodiments can be applied, and the accuracy can be further improved. Further, a global positioning system (GPS) receiver may also be used. In this case, the current position of the bicycle can be acquired, and the log of the position information and the speed information can be acquired. 
     Although the state determination process is performed inside the state determination device  1  in the above-described example embodiment, this function may be provided in the information communication terminal  2 . In this case, the information communication terminal  2  functions as a state determination device. 
     A processing method in which a program for operating the configuration of the above-described example embodiments are recorded in a storage medium so as to implement the functions of the above-described example embodiment, the program recorded in the storage medium is read as code, and the program is executed in a computer is also included in the scope of each example embodiment. That is, a computer-readable storage medium is also included in the scope of the example embodiments. Further, not only the storage medium in which the above program is recorded, but also the program itself is included in each example embodiment. In addition, one or more components included in the above-described example embodiments may be a circuit such as an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) configured to implement the functions of each component. 
     As the storage medium, for example, a floppy (registered trademark) disk, a hard disk, an optical disk, a magneto-optical disk, a compact disk (CD)-ROM, a magnetic tape, a nonvolatile memory card, or a ROM can be used. Further, the scope of each example embodiment is not limited to the case where the processing is executed by the program alone recorded in the storage medium, and a case where the processing is executed by operating on an operating system (OS) in cooperation with the functions of other software and extension board is also included in the scope of each example embodiment. 
     The service realized by the functions of the above-described example embodiments may be provided to the user in the form of a software as a service (SaaS). 
     It should be noted that the above-described example embodiments are merely examples of embodying the present invention, and the technical scope of the present invention should not be limitedly interpreted by these. That is, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof. 
     The whole or part of the example embodiments disclosed above can be described as, but not limited to, the following supplementary notes. 
     (Supplementary Note 1) 
     An information processing device comprising: an acquisition unit configured to acquire motion information of a foot of a user measured by a motion measurement device; and a determination unit configured to determine whether or not the user is in a pedaling state in which the user pedals a bicycle based on an angle between a sole and a ground generated from the motion information. 
     (Supplementary Note 2) 
     The information processing device according to supplementary note 1, wherein the motion information includes acceleration of the foot. 
     (Supplementary Note 3) 
     The information processing device according to supplementary note 2, wherein the determination unit determines whether or not the user is in the pedaling state further based on the acceleration. 
     (Supplementary Note 4) 
     The information processing device according to supplementary note 3, wherein the determination unit determines whether or not the user is in the pedaling state based on time series data of the angle and time series data of the acceleration. 
     (Supplementary Note 5) 
     The information processing device according to supplementary note 4, wherein the determination unit determines whether or not the user is in the pedaling state based on a first similarity degree between the time series data of the angle and the time series data of the acceleration. 
     (Supplementary Note 6) 
     The information processing device according to supplementary note 5, wherein the first similarity degree includes a correlation coefficient between the time series data of the angle and the time series data of the acceleration. 
     (Supplementary Note 7) 
     The information processing device according to any one of supplementary notes 4 to 6, wherein the determination unit determines whether or not the user is in the pedaling state further based on a frequency spectrum of the angle and a frequency spectrum of the acceleration acquired by transforming the time series data of the angle and the time series data of the acceleration into a frequency domain. 
     (Supplementary Note 8) 
     The information processing device according to supplementary note 7, wherein the determination unit determines whether or not the user is in the pedaling state based on a second similarity degree between the frequency spectrum of the angle and the frequency spectrum of the acceleration. 
     (Supplementary Note 9) 
     The information processing device according to supplementary note 8, wherein the second similarity degree includes a correlation coefficient between the frequency spectrum of the angle and the frequency spectrum of the acceleration. 
     (Supplementary Note 10) 
     The information processing device according to supplementary note 8 or 9, wherein the determination unit determines the user is in the pedaling state in a case where a first similarity degree between the time series data of the angle and the time series data of the acceleration is greater than a first threshold value and a second similarity degree between the frequency spectrum of the angle and the frequency spectrum of the acceleration is greater than a second threshold value. 
     (Supplementary Note 11) 
     The information processing device according to any one of supplementary notes 4 to 10, wherein the time series data includes at least two pedaling cycles. 
     (Supplementary Note 12) 
     The information processing device according to any one of supplementary notes 2 to 11, wherein the motion information further includes angular velocity of the foot. 
     (Supplementary Note 13) 
     The information processing device according to supplementary note 12, wherein the determination unit transforms a coordinate system of the acceleration and the angular velocity included in the motion information into a coordinate system with respect to the foot. 
     (Supplementary Note 14) 
     The information processing device according to supplementary note 12 or 13, wherein the determination unit calculates the angle using the acceleration and the angular velocity. 
     (Supplementary Note 15) 
     The information processing device according to supplementary note 14, wherein the determination unit calculates the angle using a Madgwick filter. 
     (Supplementary Note 16) 
     The information processing device according to any one of supplementary notes 1 to 15, wherein the motion measurement device is provided at a position corresponding to an arch of the foot. 
     (Supplementary Note 17) 
     A state determination system comprising: 
     the information processing device according to any one of supplementary notes 1 to 16; and 
     the motion measurement device. 
     (Supplementary Note 18) 
     An energy calculation system comprising an energy calculation unit configured to calculate energy consumed by the user by riding the bicycle based on a time of the pedaling state acquired by the information processing device according to any one of supplementary notes 1 to 16. 
     (Supplementary Note 19) 
     An information processing method comprising: 
     acquiring motion information of a foot of a user measured by a motion measurement device; and 
     determining whether or not the user is in a pedaling state in which the user pedals a bicycle based on an angle between a sole and a ground generated from the motion information. 
     (Supplementary Note 20) 
     A storage medium storing a program that causes a computer to perform: 
     acquiring motion information of a foot of a user measured by a motion measurement device; and 
     determining whether or not the user is in a pedaling state in which the user pedals a bicycle based on an angle between a sole and a ground generated from the motion information. 
     REFERENCE SIGNS LIST 
     
         
           1  state determination device 
           2  information communication terminal 
           3  server 
           4  user 
           5  shoe 
           11 ,  61  information processing device 
           12  IMU 
           13  battery 
           111 ,  201  CPU 
           112 ,  202  RAM 
           113 ,  203  ROM 
           114 ,  204  flash memory 
           115 ,  205  communication I/F 
           116  IMU control device 
           120 ,  611  acquisition unit 
           130 ,  612  determination unit 
           131  coordinate system transforming unit 
           132  angle calculation unit 
           133  data selecting unit 
           134  data conversion unit 
           135  similarity degree calculation unit 
           136  comparison unit 
           140  storage unit 
           150  communication unit 
           160  energy calculation unit 
           206  input device 
           207  output device