Patent Publication Number: US-11375924-B2

Title: Walking state measurement device, walking state measurement system, walking state measurement method, and storage medium for storing walking state measurement program

Description:
This application is a National Stage Entry of PCT/JP2017/041408 filed on Nov. 17, 2017, which claims priority from Japanese Patent Application 2016-231395 filed on Nov. 29, 2016, the contents of all of which are incorporated herein by reference, in their entirety. 
     TECHNICAL FIELD 
     The present invention relates to a walking state measurement device, a walking state measurement system, a walking state measurement method, and a storage medium for storing a walking state measurement program, and particularly relates to a walking state measurement device, a walking state measurement system, a walking state measurement method, and a storage medium for storing a walking state measurement program that enable easy measurement of a walking state of a walker. 
     BACKGROUND ART 
     In order to support targets such as an aged person and a patient undergoing rehabilitation, a technology allowing easy measurement of a walking state of the target in daily life has been sought. 
     When measuring a walking state in the present situation of technologies, a technology of measuring, by use of a measurement device composed of a motion capture device and a force plate, a motion of a walker by the motion capture device, and three component forces of a floor reaction force (a vertical component force, a lateral component force, and a longitudinal component force) and a point of application of the floor reaction force (coordinate values on the floor surface) by the force plate, and then measuring a walking state, based on inverse dynamic calculation, is commonly used. Joint torque at a hip joint, a knee joint, an ankle joint, and the like, muscle tension and amounts of muscle activity at a hamstring, quadriceps, and the like, and in addition, a metabolic cost may be measured as the walking state. 
     However, the force plate needs to be installed on the floor surface in the aforementioned technology, and therefore it is difficult to easily measure a walking state of a target in daily life. Then, a technology of measuring a walking state of a walker by use of, for example, a sensor reacting to a floor reaction force, such as a pressure sensor, being arranged on a surface of a shoe which a walker wears and walks with, in place of the force plate is proposed. 
     “ESTIMATION SYSTEM OF LOWER LIMB JOINT MOMENT AND LOWER LIMB MUSCLE TENSION USING SOLE PRESSURE” as PTL 1 being Japanese Patent No. 4390129 describes a technology of estimating a floor reaction force, a lower limb joint moment, and lower limb muscle tension by use of a measurement value of a sensor reacting to a floor reaction force, such as a pressure sensor, being arranged on a surface of a shoe which a subject wears and walks with. 
     “LOAD MEASUREMENT DEVICE” as PTL 2 being Japanese Patent No. 4860430 describes a technology related to a sheet-shaped load measurement device independent of a load distribution. The technology in PTL 2 allows measurement of a total amount of vertical load applied to a sole surface, that is, a vertical component force of a floor reaction force, independently of a size and a shape of a foot of a user. 
     PTL 3 discloses a technology of evaluating a motion characteristic of a subject, based on pressure placed on left and right sole regions of the subject and positional transition of the sole regions. 
     PTL 4 describes a technology of calculating a moving distance of a human, a moving speed of the human, and a floor reaction force, based on signals from a plurality of attitude sensors, such as acceleration sensors, attached to the human body. 
     “Use of pressure insoles to calculate the complete ground reaction forces” by A. Forner Cordero, et al. as NPL 1 describes a technology of estimating a floor reaction force and a lower limb joint moment by use of a measurement value of a pressure sensor array arranged on a sole surface. 
     CITATION LIST 
     Patent Literature 
     
         
         PTL 1: Japanese Patent No. 4390129 
         PTL 2: Japanese Patent No. 4860430 
         PTL 3: Japanese Unexamined Patent Application Publication No. 2012-161402 
         PTL 4: Japanese Unexamined Patent Application Publication No. 2016-150193 
       
    
     Non Patent Literature 
     
         
         NPL 1: A. Forner Cordero et al., “Use of pressure insoles to calculate the complete ground reaction forces,” Journal of Biomechanics, Vol. 37, No. 9, pp. 1427 to 1432, 2004 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     However, the technology described in each of PTL 1, PTL 2, PTL 3, and NPL 1 that are related to the present invention has a problem described below. 
     First, the technology in PTL 1 requires sensors reacting to a floor reaction force, such as pressure sensors, being arranged in at least four spots or more on a shoe surface. Then, while the sensors need to be arranged in suitable positions (a heel region, an arch region, a metatarsal region, and a toe region), such suitable positions vary by a size and a shape of a foot of a target; and therefore there is a problem that adjustment for each target is required and it takes time to make the adjustment. The technology described in PTL 3 also has a similar problem. 
     On the other hand, as described above, the technology in PTL 2 allows measurement of a total amount of vertical load applied to a sole surface, that is, a vertical component force of a floor reaction force, independently of a size and a shape of a foot of a target, and therefore does not require adjustment of an arrangement position of a sensor. However, component forces of a floor reaction force other than a vertical component force and a point of application cannot be measured. In other words, a lateral component force and a longitudinal component force of a floor reaction force, and a point of application of the floor reaction force cannot be measured. Accordingly, it is difficult to measure a walking state, based on inverse dynamic calculation as described above. 
     The technology in NPL 1 uses a measurement device including an array of 86 to 99 pressure sensors. Since such a large number of pressure sensors measure a load on an entire sole surface, adjustment of positions of the sensors for each target is not required; however, there is a problem that the measurement device becomes expensive and an economic burden on a user increases. 
     As described above, it is difficult to easily measure a walking state of a target in daily life in the present situation of the technologies related to the present invention. 
     Object of Present Invention 
     The present invention has been made in view of such problems, and an object of the present invention is to provide a walking state measurement device, a walking state measurement system, a walking state measurement method, and a walking state measurement program that enable easy measurement of a walking state of a walker, regardless of a shape and a size of a foot of the walker. 
     Solution to Problem 
     In order to resolve the aforementioned problems, a walking state measurement device, a walking state measurement system, a walking state measurement method, and a walking state measurement program, according to the present invention, mainly employ characteristic configurations as follows. 
     A walking state measurement device according to an aspect of the present invention includes: 
     a floor reaction force estimation means for estimating a floor reaction force by use of at least either of motion data and lower limb vertical load data of a walker, and outputting the floor reaction force as floor reaction force data; and 
     a walking state calculation means for calculating a walking state of the walker by use of at least either of the motion data and the floor reaction force data, and outputting the walking state. 
     A walking state measurement system according to an aspect of the present invention includes: 
     a motion measurement means for acquiring motion data of a walker; 
     a lower limb vertical load measurement means for acquiring lower limb vertical load data of the walker; and 
     a walking state measurement means for calculating a walking state of the walker by use of at least either of the motion data acquired in the motion measurement means and the lower limb vertical load data acquired in the lower limb vertical load measurement means, and outputting the walking state. 
     A walking state measurement method according to an aspect of the present invention includes: 
     estimating a floor reaction force by use of at least either of motion data and lower limb vertical load data of a walker, and outputting the floor reaction force as floor reaction force data; and 
     calculating a walking state of the walker by use of at least either of the motion data and the floor reaction force data, and outputting the walking state. 
     A storage medium according to an aspect of the present invention stores a walking state measurement program causing a computer to execute 
     walking state measurement processing including: 
     floor reaction force estimation processing of estimating a floor reaction force by use of at least either of motion data and lower limb vertical load data of a walker, and outputting the floor reaction force as floor reaction force data; and 
     walking state calculation processing of calculating a walking state of the walker by use of at least either of the motion data and the floor reaction force data, and outputting the walking state. The aspect of the present invention may also be provided by the walking state measurement program stored in the aforementioned storage medium. 
     Advantageous Effects of Invention 
     A walking state measurement device, a walking state measurement system, a walking state measurement method, and a storage medium for storing a walking state measurement program, according to the present invention, provide an effect that an arrangement position of a sensor reacting to a floor reaction force, such as a pressure sensor, being arranged on a surface of a shoe which a walker wears and walks with does not need to be adjusted for each target. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a system configuration diagram illustrating a system configuration example of a walking state measurement system according to a first example embodiment of the present invention. 
         FIG. 2  is a functional block diagram illustrating a functional configuration example of a walking state measurement device in the walking state measurement system according to the first example embodiment of the present invention. 
         FIG. 3  is a flowchart illustrating an example of a flow of walking state measurement processing in the walking state measurement device in the walking state measurement system according to the first example embodiment of the present invention. 
         FIG. 4  is a system configuration diagram illustrating a system configuration example of a walking state measurement system according to a second example embodiment of the present invention. 
         FIG. 5  is a functional block diagram illustrating a functional configuration example of a lower limb motion measurement device in the walking state measurement system according to the second example embodiment of the present invention. 
         FIG. 6  is a system configuration diagram illustrating a system configuration example of a walking state measurement system according to a third example embodiment of the present invention. 
         FIG. 7  is a functional block diagram illustrating a functional configuration example of a walking state measurement device in the walking state measurement system according to the third example embodiment of the present invention. 
         FIG. 8A  is a graph illustrating an example of an output result of a floor reaction force estimation unit in an example 1 of the present invention. 
         FIG. 8B  is a graph illustrating an example of an output result of the floor reaction force estimation unit in the example 1 of the present invention. 
         FIG. 9  is a graph illustrating an example of an output result of a walking state calculation unit in the example 1 of the present invention. 
         FIG. 10  is a functional block diagram illustrating a functional configuration example of a walking state measurement device according to a fourth example embodiment of the present invention. 
         FIG. 11  is a flowchart illustrating an operation example of the walking state measurement device according to the fourth example embodiment of the present invention. 
         FIG. 12  is a block diagram illustrating a hardware configuration of a computer capable of providing the walking state measurement device, the lower limb motion measurement device, and the walking state measurement device, according to the example embodiments of the present invention. 
     
    
    
     EXAMPLE EMBODIMENT 
     Preferred example embodiments of a walking state measurement device, a walking state measurement system, a walking state measurement method, a walking state measurement program, and a storage medium for storing the walking state measurement program, according to the present invention, will be described below with reference to accompanying drawings. While a walking state measurement device, a walking state measurement system, and a walking state measurement method, according to the present invention, will be described in the following description, it goes without saying that such a walking state measurement method may be implemented as a walking state measurement program executable by a computer, or the walking state measurement program may be recorded in a computer-readable recording medium. Further, it goes without saying that reference signs given to the drawings below are given to components for convenience, as examples for facilitating understanding, and are not intended to limit the present invention to the illustrated aspects. 
     Characteristic of Present Invention 
     Prior to description of example embodiments of the present invention, first, an overview of a characteristic of the present invention will be described. A main characteristic of the present invention is to include a floor reaction force estimation means for estimating a floor reaction force by use of at least either of motion data and lower limb vertical load data of a walker, and outputting the floor reaction force as floor reaction force data, and a walking state calculation means for calculating a walking state of the walker by use of at least either of the motion data and the floor reaction force data. Thus, an arrangement position of a sensor reacting to a floor reaction force, such as a pressure sensor, arranged on a surface of a shoe which a walker wears and walks with does not need to be adjusted for each walker. 
     EXAMPLE EMBODIMENTS OF PRESENT INVENTION 
     Three (first to third) example embodiments of the present invention will be described in detail below with reference to drawings. In the drawings referred to below, a transmission direction of data or the like is not limited to a direction of an arrow. 
     First Example Embodiment 
     First, a first example embodiment of the present invention will be described with reference to drawings. 
     Description of Configuration 
     Configuration Example of Walking State Measurement System 
     A system configuration of a walking state measurement system according to the first example embodiment of the present invention will be described with reference to  FIG. 1 .  FIG. 1  is a system configuration diagram illustrating a system configuration example of the walking state measurement system according to the first example embodiment of the present invention. The walking state measurement system  1  illustrated in  FIG. 1  is a system measuring a walking state of a walker  6000 . 
     As illustrated in  FIG. 1 , the walking state measurement system  1  is configured to include at least a motion measurement device  1000 , a lower limb vertical load measurement device  2000 , a walking state measurement device  3000 , a storage device  4000 , and a display device  5000 . A connection method between the devices included in the walking state measurement system  1  is not limited to a specific connection method. For example, the devices included in the walking state measurement system  1  may be connected in a wired manner by use of a local area network (LAN) cable, a universal serial bus (USB) cable, or the like, or may be wirelessly connected by use of Bluetooth (registered trademark) or a wireless LAN. 
     The motion measurement device  1000  is a device measuring a motion of the walker  6000 . For example, a motion is information such as an angle and angular velocity of each joint, and an attitude, a position, acceleration, and angular velocity of each segment when the body of the walker  6000  is considered as a rigid body link model, but is not limited to such information, according to the first example embodiment. The motion measurement device  1000  transmits measurement data indicating the measured motion (hereinafter referred to as motion data) of the walker  6000  to the walking state measurement device  3000 . 
     An inertial measurement unit (IMU) including an accelerometer and an angular velocimeter, a smartphone, or the like may be used as an example of the motion measurement device  1000 . It is desirable that a measurement range of each of the accelerometer and the angular velocimeter in attached positions include maximum acceleration and maximum angular velocity when the walker  6000  is walking. An optical motion capture device, a goniometer, a camera, and the like may be used as another example of the motion measurement device  1000 . However, a specific device as the motion measurement device  1000  according to the first example embodiment is not limited to any of the aforementioned examples. 
     The motion measurement device  1000  may measure a plurality of motions. Accordingly, a number of motion measurement devices is not limited to one. 
     Time intervals at which the motion measurement device  1000  measures a motion of the walker  6000  are not particularly limited. However, when the time interval is too long, calculation accuracy of a walking state, to be described later, may decline; and on the other hand, when the time interval is too short, an amount of transmitted data may be too much. Accordingly, considering a walking cycle of the walker  6000 , it is desirable that the motion measurement device  1000  measure a motion at, for example, 10-millisecond intervals. 
     The lower limb vertical load measurement device  2000  is a device measuring a lower limb vertical load of the walker  6000 . A lower limb vertical load refers to a total amount of vertical load applied to a sole surface of a left lower limb or a right lower limb of the walker  6000 . The lower limb vertical load measurement device  2000  transmits measurement data indicating the measured lower limb vertical load (hereinafter referred to as lower limb vertical load data) to the walking state measurement device  3000 . 
     For example, the lower limb vertical load measurement device  2000  may be considered to be configured by use of at least one sensor having an entire sole surface as a pressure-sensitive surface. For example, as a sensor reacting to a floor reaction force, such as a pressure sensor, arranged on a surface of a shoe which the walker  6000  wears and walks with, the load measurement device described in PTL 2 or a pressure gauge such as a strain gauge type pressure gauge or a capacitance type pressure gauge may be used in order to provide a measurement function of a lower limb vertical load. It is desirable that a measurement range of the sensor include a maximum lower limb vertical load when the walker  6000  is walking. 
     The lower limb vertical load measurement device  2000  may be installed on either of a left lower limb and a right lower limb, or on each of both lower limbs, and measure a lower limb vertical load in a region where the device is installed. 
     Time intervals at which the lower limb vertical load measurement device  2000  measures a lower limb vertical load of the walker  6000  is not particularly limited. However, when the time interval is too long, calculation accuracy of a walking state, to be described later, may decline, and on the other hand, when the time interval is too short, an amount of transmitted data may be too much. Accordingly, considering a walking cycle of the walker  6000 , it is desirable that the lower limb vertical load measurement device  2000  measure a lower limb vertical load at, for example, 10-millisecond intervals. 
     The walking state measurement device  3000  receives motion data and lower limb vertical load data from the motion measurement device  1000  and the lower limb vertical load measurement device  2000 , respectively. By use of the received motion data and lower limb vertical load data, the walking state measurement device  3000  calculates a walking state of the walker  6000 . The walking state measurement device  3000  transmits calculation data indicating the calculated walking state (hereinafter referred to as walking state data) to the display device  5000 . For example, a walking state includes indicators such as joint torque, muscle tension, an amount of muscle activity, and a metabolic cost, but is not limited only to such indicators, according to the first example embodiment. A specific functional configuration of the walking state measurement device  3000  will be described separately with a separate drawing. 
     The storage device  4000  is a device storing designated data required for calculating a walking state of the walker  6000 . The storage device  4000  transmits designated data required for calculating a walking state (hereinafter referred to as required calculation data) to the walking state measurement device  3000 . While the storage device  4000  is described as a configuration separate from the walking state measurement device  3000 , according to the first example embodiment, the present invention is not limited to such a configuration, and for example, the storage device  4000  may be built into the walking state measurement device  3000 . Data stored in the storage device  4000  will be described separately with a separate drawing. 
     The display device  5000  is a device displaying walking state data received from the walking state measurement device  3000 . The display device  5000  may display at least one type of data out of motion data, lower limb vertical load data, and data related to a floor reaction force, together with the walking state data. 
     Configuration Example of Walking State Measurement Device 
     Next, a functional configuration of the walking state measurement device  3000  in the walking state measurement system  1  according to the first example embodiment will be described with reference to  FIG. 2 .  FIG. 2  is a functional block diagram illustrating functional configuration examples of the walking state measurement device  3000  and the storage device  4000  in the walking state measurement system  1  according to the first example embodiment. As illustrated in  FIG. 2 , the walking state measurement device  3000  is configured to include at least a floor reaction force estimation unit  3100  and a walking state calculation unit  3200 . 
     Floor Reaction Force Estimation Unit  3100   
     The floor reaction force estimation unit  3100  in the walking state measurement device  3000  receives motion data and lower limb vertical load data from the motion measurement device  1000  and the lower limb vertical load measurement device  2000 , respectively. Next, the floor reaction force estimation unit  3100  receiving the motion data and the lower limb vertical load data refers to a body data storage unit  4200 , to be described later, in the storage device  4000  and acquires body data of the walker  6000  stored in the body data storage unit  4200 . 
     Subsequently, the floor reaction force estimation unit  3100  refers to a floor reaction force model storage unit  4100 , to be described later, in the storage device  4000  and acquires a designated floor reaction force model (for example, a previously designated floor reaction force model) stored in the floor reaction force model storage unit  4100 . Then, in accordance with the acquired floor reaction force model, the floor reaction force estimation unit  3100  estimates a floor reaction force by use of at least either of the received motion data and the received lower limb vertical load data, and the previously acquired body data. The floor reaction force estimation unit  3100  transmits the estimated floor reaction force to the walking state calculation unit  3200  as floor reaction force data. 
     A floor reaction force refers to characteristics of a force received by a sole surface from the floor, such as three component forces (a vertical component force, a lateral component force, and a longitudinal component force) of the force received by the sole surface from the floor, a point of application of floor reaction force (coordinate values on the floor surface), and also a rotational moment indicating a rotation strength of the force. The floor reaction force estimated by the floor reaction force estimation unit  3100  is not limited to one type out of the characteristics of the force received from the floor. The floor reaction force estimation unit  3100  may estimate a plurality of types of characteristics. 
     The floor reaction force estimation unit  3100  receives, from the motion measurement device  1000 , attitude information about each segment when the body of the walker  6000  is considered as a rigid body link model, and uses the received attitude information as the motion data when estimating a floor reaction force. In such a case, the floor reaction force estimation unit  3100  may use, as the motion data, attitude information about at least one of a thigh region, a lower leg region, and a foot region of the walker  6000  in the attitude information about each segment. Alternatively, the floor reaction force estimation unit  3100  may receive, from the motion measurement device  1000 , at least either of acceleration and angular velocity of each segment when the body of the walker  6000  is considered as a rigid body link model, and use at least either of the received acceleration and the received angular velocity as the motion data when estimating a floor reaction force. 
     Walking State Calculation Unit  3200   
     The walking state calculation unit  3200  receives motion data and floor reaction force data from the motion measurement device  1000  and the floor reaction force estimation unit  3100 , respectively. Next, the walking state calculation unit  3200  refers to the body data storage unit  4200 , to be described later in the storage device  4000  and acquires body data of the walker  6000  stored in the body data storage unit  4200 . 
     Subsequently, the walking state calculation unit  3200  calculates a walking state of the walker  6000  by use of at least either of the received motion data and the received floor reaction force data, and the acquired body data. Specifically, the walking state calculation unit  3200  calculates at least either of joint torque and muscle tension as a walking state of the walker  6000 , based on inverse dynamic calculation. The walking state calculation unit  3200  supplies the calculated walking state of the walker  6000  to the display device  5000  as walking state data. 
     Configuration Example of Storage Device 
     Next, a functional configuration of the storage device  4000  in the walking state measurement system  1  according to the first example embodiment of the present invention will be described with reference to  FIG. 2 . As illustrated in  FIG. 2 , the storage device  4000  includes at least the floor reaction force model storage unit  4100 , the body data storage unit  4200 , and a measurement data storage unit  4300 . 
     Floor Reaction Force Model Storage Unit  4100   
     The floor reaction force model storage unit  4100  stores a previously designated floor reaction force model. A designated floor reaction force model refers to a model indicating a correlation between a floor reaction force, and a motion and a lower limb vertical load of the walker  6000 . For example, a physical model based on a dynamic characteristic of a body may be considered as a floor reaction force model. In addition, a table indicating a correspondence relation between a floor reaction force, and a motion and a lower limb vertical load of the walker, a regression model (such as linear regression, the k-nearest neighbors algorithm, a neural network, and support vector regression) and a coefficient thereof, and the like may be considered as a floor reaction force model. However, a floor reaction force model according to the first example embodiment is not limited to the models described above. 
     Body Data Storage Unit  4200   
     The body data storage unit  4200  stores body data of the walker  6000 . Body data include a height and a weight of the walker  6000 , a length, a weight, and a moment of inertia of each segment. 
     Measurement Data Storage Unit  4300   
     The measurement data storage unit  4300  stores at least motion data and lower limb vertical load data measured by the motion measurement device  1000  and the lower limb vertical load measurement device  2000 , respectively. 
     Description of Operation 
     Next, an example of an operation of the walking state measurement device  3000  in the walking state measurement system  1  according to the first example embodiment illustrated in  FIG. 1  will be described with reference to  FIG. 3 .  FIG. 3  is a flowchart illustrating an example of a flow of walking state measurement processing in the walking state measurement device  3000  in the walking state measurement system  1  according to the first example embodiment. 
     In the flowchart illustrated in  FIG. 3 , first, the floor reaction force estimation unit  3100  estimates a floor reaction force in accordance with a designated floor reaction force model stored in the floor reaction force model storage unit  4100 , by use of at least either of motion data transmitted from the motion measurement device  1000  and lower limb vertical load measurement data transmitted from the lower limb vertical load measurement device  2000 , and outputs the estimated floor reaction force as floor reaction force data (Step S 101 ). 
     Next, the walking state calculation unit  3200  calculates a walking state of the walker  6000  by use of at least either of the motion data transmitted from the motion measurement device  1000  and the floor reaction force data output from the floor reaction force estimation unit  3100  in Step S 101  (Step S 102 ). 
     By performing the processing Steps S 101  and S 102  described above, the walking state measurement device  3000  in the walking state measurement system  1  according to the first example embodiment can measure a walking state of the walker  6000 . 
     Description of Effect of First Example Embodiment 
     As described above, the walking state measurement system  1  according to the first example embodiment can provide an effect that adjustment of an arrangement position of a sensor reacting to a floor reaction force, such as a pressure sensor, arranged on a surface of a shoe which a walker wears and walks with becomes unnecessary. The reason is that the walking state measurement device  3000  in the walking state measurement system  1  according to the first example embodiment includes the floor reaction force estimation unit  3100  having a function of estimating a floor reaction force, based on two types of measurement data being motion data and lower limb vertical load data of a target (walker  6000 ). A lower limb vertical load may be measured independently of a size and a shape of a foot of the target (walker  6000 ) without adjusting an arrangement position of a sensor, by use of, for example, the technology described in PTL 2, or the like. 
     Furthermore, at least one sensor reacting to a floor reaction force has only to be required for measurement of the lower limb vertical load, and therefore an effect that the walking state measurement device  3000  can be provided with a simple and inexpensive configuration can be provided at the same time. 
     Second Example Embodiment 
     Next, a second example embodiment of the invention will be described with reference to drawings. For convenience of description, a component having the same function as a component included in a drawing described in the aforementioned first example embodiment is given the same sign, and overlapping description is omitted. 
     Description of Configuration 
     Configuration Example of Walking State Measurement System 
     A system configuration of a walking state measurement system according to the second example embodiment of the invention will be described with reference to  FIG. 4 .  FIG. 4  is a system configuration diagram illustrating a system configuration example of the walking state measurement system according to the second example embodiment of the invention. The walking state measurement system  2  illustrated in  FIG. 4  is a system measuring a walking state of a walker  6000 . 
     As illustrated in  FIG. 4 , the walking state measurement system  2  is configured to include at least a lower limb motion measurement device  1100 , a lower limb vertical load measurement device  2000 , a walking state measurement device  3000 , a storage device  4000 , and a display device  5000 . The difference between the walking state measurement system  1  illustrated in  FIG. 1  as the first example embodiment and the walking state measurement system  2  illustrated in  FIG. 4  as the second example embodiment is that the motion measurement device  1000  in  FIG. 1  is replaced by a lower limb motion measurement device  1100  in  FIG. 4 . 
     The lower limb motion measurement device  1100  measures attitude information about each of six segments being the left thigh, the left lower leg, the left foot region, the right thigh, the right lower leg, and the right foot region when the body of the walker  6000  is considered as a rigid body link model. Then, the lower limb motion measurement device  1100  outputs data related to the measured attitude information to the walking state measurement device  3000  as motion data. 
     Configuration Example of Lower Limb Motion Measurement Device 
     Next, a functional configuration of the lower limb motion measurement device  1100  in the walking state measurement system  1  according to the second example embodiment will be described with reference to  FIG. 5 .  FIG. 5  is a functional block diagram illustrating a functional configuration example of the lower limb motion measurement device  1100  in the walking state measurement system  2  according to the second example embodiment. As illustrated in  FIG. 5 , the lower limb motion measurement device  1100  is configured to include at least a left thigh inertial measurement unit (IMU)  1110 , a left lower leg IMU  1120 , a left foot region IMU  1130 , a right thigh IMU  1140 , a right lower leg IMU  1150 , a right foot region IMU  1160 , and a motion analysis unit  1170 . 
     The left thigh IMU  1110 , the left lower leg IMU  1120 , the left foot region IMU  1130 , the right thigh IMU  1140 , the right lower leg IMU  1150 , and the right foot region IMU  1160  measure acceleration and angular velocity at the segments being the left thigh, the left lower leg, the left foot region, the right thigh, the right lower leg, and the right foot region, respectively. 
     With regard to an attachment position of each of the left thigh IMU  1110 , the left lower leg IMU  1120 , the left foot region IMU  1130 , the right thigh IMU  1140 , the right lower leg IMU  1150 , and the right foot region IMU  1160 , it is desirable that, for example, when measurements are made in the foot regions, the left foot region IMU  1130  and the right foot region IMU  1160  are attached to the insteps of the walker  6000 , respectively. 
     As examples of attachment positions of the other IMUs, when an attitude of a thigh region or a lower leg region is to be measured, since a change in an attachment position on the thigh or the lower leg in a longitudinal direction does not affect measurement of the attitude, each of the left thigh IMU  1110 , the right thigh IMU  1140 , the left lower leg IMU  1120 , and the right lower leg IMU  1150  may be attached to any position on the thigh or the lower leg. 
     It is assumed that an attachment position of each of the left thigh IMU  1110 , the left lower leg IMU  1120 , the left foot region IMU  1130 , the right thigh IMU  1140 , the right lower leg IMU  1150 , and the right foot region IMU  1160  is thus attached in a suitable position, based on a segment where each IMU makes a measurement. 
     The motion analysis unit  1170  included in the lower limb motion measurement device  1100  receives acceleration and angular velocity at each segment from each of the left thigh IMU  1110 , the left lower leg IMU  1120 , the left foot region IMU  1130 , the right thigh IMU  1140 , the right lower leg IMU  1150 , and the right foot region IMU  1160 . 
     Next, the motion analysis unit  1170  calculates an attitude of each segment by use of the received acceleration and angular velocity. An attitude refers to a rotation matrix or a quaternion based on designated standard coordinates. A calculation method of an attitude of each segment is not particularly limited, and a common method may be used; and therefore detailed description is omitted. As a common method, for example, a method of calculating an attitude by use of gravitational acceleration and an integrated value of angular velocity is known. 
     Finally, the motion analysis unit  1170  outputs the calculation result being data indicating an attitude of each of the segments being the left thigh, the left lower leg, the left foot region, the right thigh, the right lower leg, and the right foot region to the walking state measurement device  3000  as motion data. In other words, the motion analysis unit  1170  outputs attitude information about each segment when the body of the walker  6000  is considered as a rigid body link model to the walking state measurement device  3000  as motion data. In such a case, the motion analysis unit  1170  may output attitude information about at least one of the thigh regions and the lower leg regions of the walker  6000  in the attitude information about each segment to the walking state measurement device  3000  as motion data. Alternatively, the motion analysis unit  1170  may output at least either of acceleration and angular velocity of each segment when the body of the walker  6000  is considered as a rigid body link model to the walking state measurement device  3000  as motion data. 
     Configuration Example of Walking State Measurement Device 
     Next, a functional configuration of the walking state measurement device  3000  in the walking state measurement system  2  according to the second example embodiment will be described. The walking state measurement device  3000  in the walking state measurement system  2  according to the second example embodiment has a functional configuration similar to that according to the first example embodiment illustrated in  FIG. 2  and is configured to include at least a floor reaction force estimation unit  3100  and a walking state calculation unit  3200 . 
     Floor Reaction Force Estimation Unit  3100   
     The floor reaction force estimation unit  3100  in the walking state measurement device  3000  receives motion data and lower limb vertical load data from the lower limb motion measurement device  1100  and the lower limb vertical load measurement device  2000 , respectively. Next, the floor reaction force estimation unit  3100  receiving the motion data and the lower limb vertical load data refers to a body data storage unit  4200  in the storage device  4000  illustrated in  FIG. 2  and acquires a length Lfoot of the foot region of the walker  6000  stored in the body data storage unit  4200 . 
     Subsequently, the floor reaction force estimation unit  3100  refers to a floor reaction force model storage unit  4100  in the storage device  4000  illustrated in  FIG. 2  and acquires a designated floor reaction force model (for example, a previously designated floor reaction force model) stored in the floor reaction force model storage unit  4100 . Then, in accordance with the acquired floor reaction force model, the floor reaction force estimation unit  3100  estimates a floor reaction force by use of at least either of the received motion data and the received lower limb vertical load data, and the previously acquired length Lfoot of the foot region, and transmits the estimated floor reaction force to the walking state calculation unit  3200  as floor reaction force data. 
     The floor reaction force estimation unit  3100  estimates a floor reaction force, based on a procedure as exemplified below. First, equation (1) below is an example of a floor reaction force model for calculating a three-dimensional vector GRF having three component forces (a vertical component force, a lateral component force, and a longitudinal component force) of a floor reaction force as components and coordinates CoP of a point of application of floor reaction force on the sole surface. 
     
       
         
           
             
               
                 
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           t∈Z: walking cycle (0 to 100%)   {right arrow over (GRF)}(t)∈R 3×1 : unit vector of GRF   {right arrow over (CoP)}(t)∈R 2×1 : unit vector of CoP   x(t)∈R 3×1 : attitude of thigh region   y(t)∈R 3×1 : attitude of lower leg region   α(t), β(t)∈R 3×3 ,γ(t)∈R 3×1 : partial regression coefficient   κ(t),λ(t)∈R 2×3 ,μ(t)∈R 2×1 : partial regression coefficient   
         
           
         
       
    
     The floor reaction force model indicated in equation (1) is a linear regression equation indicating a correlation between an attitude x of the thigh region, an attitude y of the lower leg region, and a unit vector of a three-dimensional vector GRF related to three component forces of a floor reaction force
 
 {right arrow over (GRF)}   [Math. 2]
 
and a unit vector of a two-dimensional vector CoP denoting coordinates of a point of application of floor reaction force on the sole surface
 
 {right arrow over (CoP)}   [Math. 3]
 
     In equation (1), a three-dimensional vector x(t) denotes an attitude of the thigh region, and a three-dimensional vector y(t) denotes an attitude of the lower leg region. Each of 3×3 matrices α(t) and β(t), a three-dimensional vector γ(t), 2×3 matrices κ(t) and λ(t), and a two-dimensional vector μ(t) denotes a partial regression coefficient. 
     Furthermore, t denotes a walking cycle and takes an integer value in a range from 0 to 100. A walking cycle is a value defined on the basis of a motion of a lower limb and indicates a time point of a cyclic operation of a walk. Typically, t is defined in such a way that t at a time point when the heel of the left lower limb (or the right lower limb) contacts the ground is set to 0, and t at a time point when the toe of the left lower limb (or the right lower limb) leaves the ground is set to 100. Typically, t is defined in such a way that t at a time point when the heel of the left lower limb (or the right lower limb) contacts the ground is set to 0, and t at a next time point when the heel of the left lower limb (or the right lower limb) contacts the ground is set to 100. A method of calculating a walking cycle t by the floor reaction force estimation unit  3100  is a common method and is not limited to a specific method. For example, the floor reaction force estimation unit  3100  may use a method of referring to the measurement data storage unit  4300 , determining a timing of the heel of the left lower limb (or the right lower limb) contacting the ground and a timing of the toe leaving the ground from past motion data and a lower limb vertical load, dividing the time between the timing of the heel contacting the ground and the timing of the toe leaving the ground into 100 equal parts, and defining the timing of the heel contacting the ground and the timing of the toe leaving the ground as a walking cycle 0 to 100. A method of determining timings of the heel of the left lower limb (or right lower limb) contacting the ground, dividing a time between adjacent timings of the heel contacting the ground into 100 equal parts, and defining the timings of the heel contacting the ground and acquired times as a walking cycle 0 to 100 may be used. 
     By substituting the attitude x of the thigh region and the attitude y of the lower leg region received as motion data into equation (1), a unit vector of the three-dimensional vector of the floor reaction force
 
 {right arrow over (GRF)}   [Math. 4]
 
and a unit vector of the coordinates CoP of the point of application of floor reaction force
 
 {right arrow over (CoP)}   [Math. 5]
 
are calculated by the floor reaction force estimation unit  3100 .
 
     Next, by substituting received lower limb vertical load measurement data Pfoot into equation (2) below, the floor reaction force estimation unit  3100  calculates the three-dimensional vector GRF having the three component forces of the floor reaction force as components. 
                   [     Math   .           ⁢   6     ]                           GRF   =         P   foot       GRF   z       ×     GRF   →               (   2   )               
where
 
GRF z : magnitude of vertical component force out of 3 component forces of floor reaction force
 
     Subsequently, by substituting the length Lfoot of the foot region of the walker  6000  into equation (3) below, the floor reaction force estimation unit  3100  calculates the two-dimensional vector CoP having coordinate components of the point of application of floor reaction force on the sole surface.
 
[Math. 7]
 
 CoP=L   foot   ×{right arrow over (CoP)}   (3)
 
     As described above, the floor reaction force estimation unit  3100  estimates a floor reaction force (a floor reaction force GRF composed of three component forces, and coordinates CoP of a point of application of floor reaction force) and transmits the estimated floor reaction force to the walking state calculation unit  3200  as floor reaction force data. 
     The walking state calculation unit  3200  receiving motion data and floor reaction force data from the lower limb motion measurement device  1100  and the floor reaction force estimation unit  3100 , respectively, calculates a walking state of the walker  6000  in accordance with a procedure similar to that according to the first example embodiment and supplies the calculated walking state to the display device  5000  as walking state data. 
     Description of Effect of Second Example Embodiment 
     As described above, the walking state measurement system  2  according to the second example embodiment can provide an effect that adjustment of an arrangement position of a sensor reacting to a floor reaction force, such as a pressure sensor, arranged on a surface of a shoe which a walker wears and walks with becomes unnecessary, similarly to the walking state measurement system  1  according to the aforementioned first example embodiment. The reason is that, similarly to the walking state measurement system  1  according to the first example embodiment, the walking state measurement device  3000  in the walking state measurement system  2  according to the second example embodiment also includes the floor reaction force estimation unit  3100  estimating a floor reaction force, based on two types of measurement data being motion data and lower limb vertical load data of a target (walker  6000 ). 
     Furthermore, the walking state measurement system  2  according to the second example embodiment also can provide an effect that, since each of the left thigh IMU  1110 , the left lower leg IMU  1120 , the left foot region IMU  1130 , the right thigh IMU  1140 , the right lower leg IMU  1150 , and the right foot region IMU  1160  in the lower limb motion measurement device  1100  may be attached in any position on a segment in a longitudinal direction, equipping becomes easy. The reason is that a change in an attachment position on each segment in a longitudinal direction does not affect measurement of an attitude. 
     Third Example Embodiment 
     Next, a third example embodiment of the present invention will be described with reference to drawings. For convenience of description, a component having the same function as a component included in a drawing described in the aforementioned first and second example embodiments is given the same sign, and overlapping description is omitted. 
     Description of Configuration 
     Configuration Example of Walking State Measurement System 
     A system configuration of a walking state measurement system according to the third example embodiment of the present invention will be described with reference to  FIG. 6 .  FIG. 6  is a system configuration diagram illustrating a system configuration example of the walking state measurement system according to the third example embodiment of the present invention. The walking state measurement system  3  illustrated in  FIG. 6  is a system measuring a walking state of a walker  6000 . 
     As illustrated in  FIG. 6 , the walking state measurement system  3  is configured to include at least a lower limb motion measurement device  1100 , a lower limb vertical load measurement device  2100 , a walking state measurement device  3000 , a storage device  4000 , and a display device  5000 . While  FIG. 6  illustrates a configuration using the lower limb motion measurement device  1100  similar to that according to the second example embodiment in  FIG. 4 , the walking state measurement system  3  may be configured by use of a motion measurement device  1000  similar to that according to the first example embodiment in  FIG. 1  in place of the lower limb motion measurement device  1100 . The difference between the walking state measurement systems  1  and  2  illustrated in  FIGS. 1 and 4  as the first and second example embodiments, and the walking state measurement system  3  illustrated in  FIG. 6  as the third example embodiment is that the lower limb vertical load measurement device  2000  in  FIGS. 1 and 2  is replaced by the lower limb vertical load measurement device  2100  including two sensors in  FIG. 6 . The lower limb vertical load measurement device  2100  also differs from the walking state measurement systems  1  and  2  illustrated in  FIGS. 1 and 2  in including a first sensor  2110  and a second sensor  2120 , and outputting two types of lower limb vertical load data to the walking state measurement device  3000 . 
     Configuration Example of Lower Limb Vertical Load Measurement Device 
     As described above, the lower limb vertical load measurement device  2100  includes at least two sensors being the first sensor  2110  and the second sensor  2120 . Each of the two sensors being the first sensor  2110  and the second sensor  2120  measures a lower limb vertical load in each area acquired by dividing an entire area of a sole surface into two areas, based on a preset designated standard. For example, a configuration of the first sensor  2110  and the second sensor  2120  measuring lower limb vertical loads in two areas being the toe side and the heel side of the sole surface, respectively, may be considered. Then, the lower limb vertical load measurement device  2100  transmits lower limb vertical loads measured by the sensors being the first sensor  2110  and the second sensor  2120  to the walking state measurement device  3000  as first lower limb vertical load data and second lower limb vertical load data, respectively. 
     Configuration Example of Walking State Measurement Device 
     Next, a functional configuration of the walking state measurement device  3000  in the walking state measurement system  3  according to the third example embodiment will be described with reference to  FIG. 7 .  FIG. 7  is a functional block diagram illustrating functional configuration examples of the walking state measurement device  3000  and the storage device  4000  in the walking state measurement system  3  according to the third example embodiment. As illustrated in  FIG. 7 , the walking state measurement device  3000  is configured to include at least a floor reaction force estimation unit  3110  and a walking state calculation unit  3200 . The walking state measurement device  3000  illustrated in  FIG. 7  is configured by use of the floor reaction force estimation unit  3110  in place of the floor reaction force estimation unit  3100  in the walking state measurement device  3000  according to the first example embodiment illustrated in  FIG. 2 . 
     Floor Reaction Force Estimation Unit  3110   
     The floor reaction force estimation unit  3110  according to the third example embodiment receives motion data, and first lower limb vertical load data and second lower limb vertical load data from the lower limb motion measurement device  1100  and the lower limb vertical load measurement device  2100 , respectively. Specifically, with regard to lower limb vertical load data from the lower limb vertical load measurement device  2100 , the floor reaction force estimation unit  3110  receives first lower limb vertical load data measured by the first sensor  2110  and second lower limb vertical load data measured by the second sensor  2120  being two types of lower limb vertical load data in respective areas acquired by dividing the sole surface into two areas. 
     Next, the floor reaction force estimation unit  3110  receiving the motion data and the two types of lower limb vertical load data calculates lower limb vertical load data Pfoot by adding the received first lower limb vertical load data to the received second lower limb vertical load data. The floor reaction force estimation unit  3110  thereafter estimates a floor reaction force GRF composed of three component forces and coordinates CoP of a point of application of floor reaction force in accordance with a procedure similar to that according to the second example embodiment. 
     Furthermore, the floor reaction force estimation unit  3110  according to the third example embodiment calculates a ratio R related to the received first lower limb vertical load data and second lower limb vertical load data. The ratio R includes information about a load balance of the sole surface. For example, the ratio R may be a ratio between the first lower limb vertical load data or the second lower limb vertical load data, and the lower limb vertical load data Pfoot. For example, R=1.0 when a load is placed on the toe side, R=0.0 when a load is placed on the heel side, and R=0.5 when a load is equally placed on the toe side and the heel side. 
     In other words, the floor reaction force estimation unit  3110  according to the third example embodiment estimates a floor reaction force by further using the ratio R related to the received first lower limb vertical load data and second lower limb vertical load data in addition to the estimation processing related to a floor reaction force by the floor reaction force estimation unit  3100  according to the second example embodiment. Subsequently, the floor reaction force estimation unit  3110  transmits the estimated floor reaction force to the walking state calculation unit  3200  as floor reaction force data. 
     The walking state calculation unit  3200  receiving motion data and floor reaction force data from the lower limb motion measurement device  1100  and the floor reaction force estimation unit  3110 , respectively, calculates a walking state of the walker  6000  in accordance with a procedure similar to that according to the first and second example embodiments and supplies the calculated walking state to the display device  5000  as walking state data. 
     Description of Effect of Third Example Embodiment 
     As described above, the walking state measurement system  3  according to the third example embodiment provides an effect that adjustment of an arrangement position of a sensor reacting to a floor reaction force, such as a pressure sensor, arranged on a surface of a shoe which a walker wears and walks with becomes unnecessary, similarly to the walking state measurement systems  1  and  2  according to the aforementioned first and second example embodiments. The reason is that the walking state measurement device  3000  in the walking state measurement system  3  according to the third example embodiment also includes the floor reaction force estimation unit  3100  having a function of estimating a floor reaction force, based on two types of measurement data being motion data and lower limb vertical load data of a target (walker  6000 ). 
     Furthermore, the walking state measurement system  3  according to the third example embodiment can also provide an effect of being able to more accurately calculate a walking state of the walker  6000 . The reason is that addition and use of information about a load balance of the sole surface (that is, information about a ratio R related to first lower limb vertical load data and second lower limb vertical load data) is enabled, and therefore estimation accuracy of a floor reaction force can be improved. 
     Specifically, for example, in a walk on a slope or a stairway, a configuration of dividing the sole surface into two areas being the toe side and the heel side is effective in terms of lower limb vertical load data. When walking on a slope or a stairway, the walker  6000  tends to adjust a balance by minutely shifting a load backward and forward on the sole surface, in order to prevent a fall. Compared with the walking state measurement device  3000  according to the first and second example embodiments, the walking state measurement device  3000  according to the third example embodiment further enables use of information about a load balance of the sole surface and therefore can more accurately estimate a floor reaction force and consequently more accurately measure a walking state. 
     Furthermore, in a case of walking in a curve, a configuration of dividing the sole surface into two areas being the outside and the inside of the body is effective in terms of lower limb vertical load data. The reason is that when walking in a curve, the walker  6000  tends to adjust a balance by minutely shifting a load leftward and rightward on the sole surface and changing directions. 
     Fourth Example Embodiment 
     Next, a fourth example embodiment of the present invention will be described with reference to drawings. 
     Description of Configuration 
       FIG. 10  is a functional block diagram illustrating a functional configuration example of a walking state measurement device  3000  according to the fourth example embodiment of the present invention. 
     As illustrated in  FIG. 10 , the walking state measurement device  3000  according to the fourth example embodiment includes a floor reaction force estimation unit  3100  and a walking state calculation unit  3200 . The floor reaction force estimation unit  3100  estimates a floor reaction force by use of at least either of motion data and lower limb vertical load data of a walker, and outputs the estimated floor reaction force as floor reaction force data. The walking state calculation unit  3200  calculates a walking state of the walker by use of at least either of motion data and floor reaction force data, and outputs the walking state. 
     Description of Operation 
       FIG. 11  is a flowchart illustrating an operation example of the walking state measurement device according to the fourth example embodiment of the present invention. 
     As indicated in  FIG. 11 , first, the floor reaction force estimation unit  3100  estimates a floor reaction force by use of at least either of motion data and lower limb vertical load data of a walker (Step S 401 ). Next, the walking state calculation unit  3200  calculates a walking state of the walker by use of at least either of the motion data and the floor reaction force data (Step S 403 ). 
     Description of Effect of Fourth Example Embodiment 
     As described above, the walking state measurement device  3000  according to the fourth example embodiment can provide an effect that adjustment of an arrangement position of a sensor reacting to a floor reaction force, such as a pressure sensor, arranged on a surface of a shoe which a walker wears and walks with becomes unnecessary. The reason is that the walking state measurement device  3000  in the walking state measurement system  1  according to the first example embodiment includes the floor reaction force estimation unit  3100  having a function of estimating a floor reaction force, based on two types of measurement data being motion data and lower limb vertical load data of the walker. For example, a lower limb vertical load may be measured without adjusting an arrangement position of a sensor and also independently of a size and a shape of a foot of the walker, by using the technology described in PTL 2 or the like. 
     OTHER EXAMPLE EMBODIMENTS 
     Each of the walking state measurement device according to the first example embodiment, the lower limb motion measurement device according to the second example embodiment, and the walking state measurement device according to the third example embodiment of the present invention may be provided by a computer operating by program control. Each of the walking state measurement device according to the first example embodiment, the lower limb motion measurement device according to the second example embodiment, and the walking state measurement device according to the third example embodiment of the present invention may also be provided by dedicated hardware such as a circuit. Each of the walking state measurement device according to the first example embodiment, the lower limb motion measurement device according to the second example embodiment, and the walking state measurement device according to the third example embodiment of the present invention may also be provided by a combination of the aforementioned computer and dedicated hardware. The aforementioned computer may be a plurality of communicably connected computers. The aforementioned dedicated hardware may be a plurality of communicably connected pieces of dedicated hardware. 
       FIG. 12  is a diagram illustrating a hardware configuration example of a computer  10000  capable of providing the devices according to the example embodiments of the present invention. Referring to  FIG. 12 , the computer  10000  includes a processor  10001 , a memory  10002 , a storage device  10003 , and an input/output (I/O) interface  10004 . Further, the computer  10000  can access a storage medium  10005 . For example, each of the memory  10002  and the storage device  10003  is a storage device such as a random access memory (RAM) or a hard disk. For example, the storage medium  10005  is a storage device such as a RAM or a hard disk, a read only memory (ROM), or a portable storage medium. The storage device  10003  may be the storage medium  10005 . The processor  10001  can read and write data and a program from and into the memory  10002  and the storage device  10003 . For example, the processor  10001  can access a display device  5000  and the like through the I/O interface  10004 . The processor  10001  can access the storage medium  10005 . For example, the aforementioned storage device  4000  may be provided by the storage device  10003 , the memory  10002 , or a combination of the storage device  10003  and the memory  10002 . 
     For example, the storage medium  10005  stores a program causing the computer  10000  to operate as the lower limb motion measurement device  1100 . The processor  10001  loads the program causing the computer  10000  to operate as the lower limb motion measurement device  1100  into the memory  10002 , the program being stored in the storage medium  10005 . Then, by the program loaded in the memory  10002  being executed by the processor  10001 , the computer  10000  operates as the lower limb motion measurement device  1100 . 
     For example, the storage medium  10005  stores a program causing the computer  10000  to operate as the walking state measurement device  3000 . The processor  10001  loads the program causing the computer  10000  to operate as the walking state measurement device  3000  into the memory  10002 , the program being stored in the storage medium  10005 . Then, by the program loaded in the memory  10002  being executed by the processor  10001 , the computer  10000  operates as the walking state measurement device  3000 . 
     For example, the motion analysis unit  1170 , the floor reaction force estimation unit  3100 , the floor reaction force estimation unit  3110 , and the walking state calculation unit  3200  may be provided by a dedicated program capable of providing the function of each unit, the program being read into the memory  10002  from the storage medium  10005  storing a program, and the processor  10001  executing the program. The floor reaction force model storage unit  4100 , the body data storage unit  4200 , and the measurement data storage unit  4300  may be provided by the memory  10002  or the storage device  10003 , such as a hard disk device, included in the computer  10000 . The motion analysis unit  1170 , the floor reaction force estimation unit  3100 , the floor reaction force estimation unit  3110 , and the walking state calculation unit  3200  may be provided in part or in whole by a dedicated circuit providing the function of each unit. The floor reaction force model storage unit  4100 , the body data storage unit  4200 , and the measurement data storage unit  4300  may also be provided in part or in whole by a dedicated circuit providing the function of each unit. 
     Example 1 
     This example 1 indicates a specific example using the aforementioned walking state measurement system  2  according to the second example embodiment and the aforementioned walking state measurement device  3000  according to second example embodiment. 
     In an experiment in this example 1, a small-sized wireless multifunctional sensor “TSND121” from ATR-Promotions, Inc. was used for each of the six IMU sensors being the left thigh IMU  1110 , the left lower leg IMU  1120 , the left foot region IMU  1130 , the right thigh IMU  1140 , the right lower leg IMU  1150 , and the right foot region IMU  1160  in the lower limb motion measurement device  1100 . Each of the IMUs for the thigh regions being the left thigh IMU  1110 , and the right thigh IMU  1140  was attached with an elastic band in a position between the hip joint and the knee joint, and at the same time in an outside position of the thigh region. Each of the IMUs for the lower leg regions being the left lower leg IMU  1120  and the right lower leg IMU  1150  was attached with an elastic band in a position between the knee joint and the ankle joint, and at the same time in an outside position of the lower leg region. Each of the IMUs for the foot regions being the left foot region IMU  1130  and the right foot region IMU  1160  was attached with an elastic band in a middle position of the third metatarsal body and at the same time in a position on the instep side. 
     A walking analyzer “STEP AID” (a shoe type load measurement device) from IMAC Co., Ltd. was used as the lower limb vertical load measurement device  2000  for measuring each lower limb vertical load on the left and right sides. 
     Furthermore, a linear regression model described in the second example embodiment was used as a floor reaction force model. Parameters of the linear regression model were determined in accordance with a least squares method using, as true values, measurement data of a true floor reaction force and motion data measured by use of a force plate and optical motion capture. A musculoskeletal model simulator “OpenSIM” was used as a walking state measurement means. 
     A walking state in a condition that a walker walks a straight distance of approximately 10 m was measured by use of a walking state measurement system with a specific configuration as described above. Ankle joint torque of the walker was measured as the walking state. 
     Next, an example of a measurement result of a walking state actually measured in this example 1 will be described.  FIGS. 8A and 8B  are graphs illustrating examples of output results of the floor reaction force estimation unit  3100  in this example 1.  FIG. 8A  illustrates estimated values (Estimated) and actual measurements (Ground Truth) of three component forces (an X-axis component [lateral component force], a Y-axis component [longitudinal component force], and a Z-axis component [vertical component force]) of floor reaction force data, and  FIG. 8B  illustrates estimated values (Estimated) and actual measurements (Ground Truth) of coordinates of a point of application of floor reaction force. As illustrated in  FIGS. 8A and 8B , it is observed that values extremely close to actual measurements (Ground Truth) are acquired as estimated values (Estimated) of floor reaction force data in the floor reaction force estimation unit  3100  in the walking state measurement device  3000  according to the second example embodiment of the present invention. 
       FIG. 9  is a graph illustrating an example of an output result of the walking state calculation unit  3200  in this example 1. The graph in  FIG. 9  illustrates a case of displaying calculated ankle joint torque (ankle_angle_1_moment) acquired by inputting the actual measurements (Ground Truth) of the floor reaction force data illustrated in  FIGS. 8A and 8B  into the walking state calculation unit  3200 , as an example of a measurement result of a walking state. 
     From the experimental results in this example 1 as described above, it is proven that the walking state measurement system according to the present invention can accurately measure a walking state of a walker  6000 . Accordingly, it is confirmed that an effect that adjustment of an arrangement position of a sensor reacting to a floor reaction force, such as a pressure sensor, arranged on a surface of a shoe which the walker  6000  wears and walks with becomes unnecessary is provided. 
     The aforementioned example embodiments may also be described in part or in whole as the following Supplementary Notes but are not limited thereto. 
     Supplementary Note 1 
     A walking state measurement device including: 
     a floor reaction force estimation means for estimating a floor reaction force by use of at least either of motion data and lower limb vertical load data of a walker, and outputting the floor reaction force as floor reaction force data; and 
     a walking state calculation means for calculating a walking state of the walker by use of at least either of the motion data and the floor reaction force data, and outputting the walking state. 
     Supplementary Note 2 
     The walking state measurement device according to Supplementary Note 1, wherein 
     the walking state calculation means outputs a result of calculating at least either of joint torque and muscle tension, based on inverse dynamic calculation, as the walking state of the walker. 
     Supplementary Note 3 
     The walking state measurement device according to Supplementary Note 1 or 2, wherein 
     the floor reaction force estimation means uses, as the motion data, attitude information about each segment when a body of the walker is considered as a rigid body link model. 
     Supplementary Note 4 
     The walking state measurement device according to Supplementary Note 3, wherein 
     the floor reaction force estimation means uses, as the motion data, attitude information about at least one of a thigh region and a lower leg region of the walker in attitude information about the each segment when a body of the walker is considered as a rigid body link model. 
     Supplementary Note 5 
     The walking state measurement device according to Supplementary Note 1 or 2, wherein 
     the floor reaction force estimation means uses, as the motion data, at least either of acceleration and angular velocity of each segment when a body of the walker is considered as a rigid body link model. 
     Supplementary Note 6 
     The walking state measurement device according to any one of Supplementary Notes 1 to 5, wherein 
     the floor reaction force estimation means uses, as the lower limb vertical load data, a result of measuring a lower limb vertical load in each area acquired by dividing a sole surface into two areas. 
     Supplementary Note 7 
     A walking state measurement system including: 
     a motion measurement means for acquiring motion data of a walker; 
     a lower limb vertical load measurement means for acquiring lower limb vertical load data of the walker; and 
     a walking state measurement means for calculating a walking state of the walker by use of at least either of the motion data acquired in the motion measurement means and the lower limb vertical load data acquired in the lower limb vertical load measurement means, and outputting the walking state. 
     Supplementary Note 8 
     The walking state measurement system according to Supplementary Note 7, wherein 
     the walking state measurement means includes: 
     a floor reaction force estimation means for estimating a floor reaction force by use of at least either of the motion data of the walker acquired by the motion measurement means and the lower limb vertical load data of the walker acquired by the lower limb vertical load measurement means, and outputting the floor reaction force as floor reaction force data; and 
     a walking state calculation means for calculating the walking state of the walker by use of at least either of the motion data and the floor reaction force data, and outputting the walking state. 
     Supplementary Note 9 
     The walking state measurement system according to Supplementary Note 8, wherein 
     the walking state calculation means outputs a result of calculating at least either of joint torque and muscle tension, based on inverse dynamic calculation, as the walking state of the walker. 
     Supplementary Note 10 
     The walking state measurement system according to Supplementary Note 8 or 9, wherein 
     the floor reaction force estimation means uses, as the motion data, attitude information about each segment when a body of the walker is considered as a rigid body link model. 
     Supplementary Note 11 
     The walking state measurement system according to Supplementary Note 10, wherein 
     the floor reaction force estimation means uses, as the motion data, attitude information about at least one of a thigh region and a lower leg region of the walker in attitude information about the each segment when a body of the walker is considered as a rigid body link model. 
     Supplementary Note 12 
     The walking state measurement system according to Supplementary Note 8 or 9, wherein 
     the floor reaction force estimation means uses, as the motion data, at least either of acceleration and angular velocity of each segment when a body of the walker is considered as a rigid body link model. 
     Supplementary Note 13 
     The walking state measurement system according to any one of Supplementary Notes 8 to 12, wherein 
     the floor reaction force estimation means uses, as the lower limb vertical load data, a result of measuring a lower limb vertical load in each area acquired by dividing a sole surface into two areas. 
     Supplementary Note 14 
     A walking state measurement method including: 
     estimating a floor reaction force by use of at least either of motion data and lower limb vertical load data of a walker, and outputting the floor reaction force as floor reaction force data; and 
     calculating a walking state of the walker by use of at least either of the motion data and the floor reaction force data, and outputting the walking state. 
     Supplementary Note 15 
     The walking state measurement method according to Supplementary Note 14, further including 
     outputting a result of calculating at least either of joint torque and muscle tension, based on inverse dynamic calculation, as the walking state of the walker. 
     Supplementary Note 16 
     The walking state measurement method according to Supplementary Note 14 or 15, further including using, as the motion data, attitude information about each segment when a body of the walker is considered as a rigid body link model. 
     Supplementary Note 17 
     The walking state measurement method according to Supplementary Note 16, further including 
     using, as the motion data, attitude information about at least one of a thigh region and a lower leg region of the walker in attitude information about the each segment when a body of the walker is considered as a rigid body link model. 
     Supplementary Note 18 
     The walking state measurement method according to Supplementary Note 14 or 15, further including 
     using, as the motion data, at least either of acceleration and angular velocity of each segment when a body of the walker is considered as a rigid body link model. 
     Supplementary Note 19 
     The walking state measurement method according to any one of Supplementary Notes 14 to 18, further including 
     using, as the lower limb vertical load data, a result of measuring a lower limb vertical load in each area acquired by dividing a sole surface into two areas. 
     Supplementary Note 20 
     A storage medium for storing a walking state measurement program, the walking state measurement program causing a computer to execute: 
     walking state measurement processing including: 
     floor reaction force estimation processing of estimating a floor reaction force by use of at least either of motion data and lower limb vertical load data of a walker, and outputting the floor reaction force as floor reaction force data; and 
     walking state calculation processing of calculating a walking state of the walker by use of at least either of the motion data and the floor reaction force data, and outputting the walking state. 
     Supplementary Note 21 
     The storage medium according to Supplementary Note 20, wherein 
     the walking state calculation processing outputs a result of calculating at least either of joint torque and muscle tension, based on inverse dynamic calculation, as the walking state of the walker. 
     Supplementary Note 22 
     The storage medium according to Supplementary Note 20 or 21, wherein 
     the floor reaction force estimation processing uses, as the motion data, attitude information about each segment when a body of the walker is considered as a rigid body link model. 
     Supplementary Note 23 
     The storage medium according to Supplementary Note 22, wherein 
     the floor reaction force estimation processing uses, as the motion data, attitude information about at least one of a thigh region and a lower leg region of the walker in attitude information about the each segment when a body of the walker is considered as a rigid body link model. 
     Supplementary Note 24 
     The storage medium according to Supplementary Note 20 or 21, wherein 
     the floor reaction force estimation processing uses, as the motion data, at least either of acceleration and angular velocity of each segment when a body of the walker is considered as a rigid body link model. 
     Supplementary Note 25 
     The storage medium according to any one of Supplementary Notes 20 to 24, wherein 
     the floor reaction force estimation processing uses, as the lower limb vertical load data, a result of measuring a lower limb vertical load in each area acquired by dividing a sole surface into two areas. 
     Configurations of preferred example embodiments of the present invention have been described above. However, it should be noted that such example embodiments are merely exemplifications of the present invention and do not limit the present invention in any way. A person skilled in the art may easily understand that various modifications and changes may be made to the present invention, based on specific application purposes, without departing from the spirit of the present invention. 
     This application claims priority based on Japanese Patent Application No. 2016-231395 filed on Nov. 29, 2016, the disclosure of which is hereby incorporated by reference thereto in its entirety. 
     INDUSTRIAL APPLICABILITY 
     For example, fields described below may be considered as utilization examples of the present invention.
     (1) Real-time diagnosis of walking in daily life   (2) An online diagnosis system presenting a risk of a fall from a walking state   (3) A service providing a doctor and a physiotherapist with a walking state of a patient after discharge from the hospital and providing continued care   

     REFERENCE SIGNS LIST 
     
         
           1  Walking state measurement system 
           2  Walking state measurement system 
           3  Walking state measurement system 
           1000  Motion measurement device 
           1100  Lower limb motion measurement device 
           1110  Left thigh IMU 
           1120  Left lower leg IMU 
           1130  Left foot region IMU 
           1140  Right thigh IMU 
           1150  Right lower leg IMU 
           1160  Right foot region IMU 
           1170  Motion analysis unit 
           2000  Lower limb vertical load measurement device 
           2100  Lower limb vertical load measurement device 
           2110  First sensor 
           2120  Second sensor 
           3000  Walking state measurement device 
           3100  Floor reaction force estimation unit 
           3110  Floor reaction force estimation unit 
           3200  Walking state calculation unit 
           4000  Storage device 
           4100  Floor reaction force model storage unit 
           4200  Body data storage unit 
           4300  Measurement data storage unit 
           5000  Display device 
           6000  Walker 
           10000  Computer 
           10001  Processor 
           10002  Memory 
           10003  Storage device 
           10004  I/O interface 
           10005  Storage medium