Patent Publication Number: US-2023157579-A1

Title: Detection system, walking exercise system, detection method and storage medium

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Japanese Patent Application No. 2021-188343 filed on Nov. 19, 2021, incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a detection system, a walking exercise system, a detection method and a storage medium. 
     2. Description of Related Art 
     There has been developed a walking exercise system in which a rehabilitation patient performs exercise for walking action. In the walking exercise system, the load distribution of an exerciser is measured by a load distribution sensor installed in a treadmill. For example, WO2006/106714 discloses a pressure distribution detection device including two kinds of loop electrode groups, elastic bodies on the loop electrode groups, and conductive substances on the elastic bodies. The walking exercise system measures the walking state of the exerciser based on a load value that is obtained from a measurement result, and aids the motion of the joint of the exerciser. 
     SUMMARY 
     For example, in the case where the load value exceeds a control determination value and then falls below the control determination value again, the walking exercise system detects a state where the exerciser has started to weaken stepping force, and aids the extension of the joint of the exerciser. However, in the case where the pressure distribution detection device described in WO2006/106714 is used in the walking exercise system, stress is gradually transmitted in an elastic member, so that there is a gap between the output of the load distribution sensor and the actually applied load. Thereby, there is a problem in that the state where the exerciser has started to weaken the stepping force can be falsely detected. 
     The present disclosure has been made for solving this problem, and provides a detection system, a walking exercise system, a detection method and a storage medium that improve the detection accuracy of the action state of the leg. 
     A detection system according to an aspect of the present disclosure includes an acquisition unit, a calculation unit, a determination unit and a correction unit. The acquisition unit acquires measurement information from a load distribution sensor, the load distribution sensor detecting a distribution of a load that is received from a sole of a subject. The calculation unit calculates a total load value of a sole region based on the measurement information, the sole region corresponding to the position of a sole of one leg of the subject. The determination unit determines an action state of the one leg based on the total load value. The correction unit starts to offset the total load value using an offset filter, in response to a determination that the action state is a first action state, the offset filter decreasing an offset amount with time elapse, the first action state being a state where the total load value tends to increase and is equal to or larger than a preset determination value. Thereby, the detection system can improve the detection accuracy of the action state of the leg. Further, the determination unit may determine that the action state is a second action state, in a case where the offset total load value tends to decrease and is smaller than the determination value. Thereby, it is possible to avoid of the false detection of the state where the exerciser has started to weaken the stepping force. 
     The correction unit may generate the offset filter, based on an output characteristic of the load distribution sensor to an input load and an attribute of the subject. Thereby, it is possible to reflect the output characteristic of the load distribution sensor that corresponds to a pattern of the input load that is estimated from the attribute of the subject, in the offset amount. 
     Particularly, the correction unit may generate the offset filter, based on the output characteristic of the load distribution sensor to the input load and the body weight of the subject. By estimating the input load from the body weight value, it is possible to generate the offset filter easily and accurately. 
     Further, the correction unit may generate the offset filter, based on a state of the sole of the subject when the sole begins to be grounded, in a case where it is determined that the action state is the first action state. Thereby, the correction unit can execute an offset correction appropriate for the walking state of the exerciser. 
     The determination unit may determine that the action sate is the first action state, in a case where the area of the sole region is equal to or larger than a predetermined area threshold. 
     A walking exercise system according to an aspect of the present disclosure includes: a control device configured to control extension of a leg robot worn on at least one leg of a subject, based on an action state of the leg of the subject; a load distribution sensor configured to detect a distribution of a load that is received from a sole of the subject; and a detection device. The detection device includes an acquisition unit, a calculation unit, a determination unit and a correction unit. The acquisition unit acquires measurement information from the load distribution sensor. The calculation unit calculates a total load value of a sole region based on the measurement information, the sole region corresponding to the position of a sole of one leg of the subject. The determination unit determines an action state of the one leg based on the total load value. The correction unit starts to offset the total load value using an offset filter, in response to a determination that the action state is a first action state, the offset filter decreasing an offset amount with time elapse, the first action state being a state where the total load value tends to increase and is equal to or larger than a preset determination value. Thereby, the walking exercise system can improve the detection accuracy of the action state of the leg. Further, the determination unit may determine that the action state is a second action state, in a case where the offset total load value tends to decrease and is smaller than the determination value. Thereby, it is possible to avoid of the false detection of the state where the exerciser has started to weaken the stepping force. 
     The control device may control the extension of the leg robot in response to a detection of the second action state. 
     A detection method according to an aspect of the present disclosure includes: a step of acquiring measurement information from a load distribution sensor, the load distribution sensor detecting a distribution of a load that is received from a sole of a subject; a step of calculating a total load value of a sole region based on the measurement information, the sole region corresponding to the position of a sole of one leg of the subject; a step of determining an action state of the one leg based on the total load value; and a step of starting to offset the total load value using an offset filter, in response to a determination that the action state is a first action state, the offset filter decreasing an offset amount with time elapse, the first action state being a state where the total load value tends to increase and is equal to or larger than a preset determination value. Thereby, it is possible to improve the detection accuracy of the action state of the leg. 
     A storage medium storing a program according to an aspect of the present disclosure causes a computer to execute a detection method. The detection method includes: a step of acquiring measurement information from a load distribution sensor, the load distribution sensor detecting a distribution of a load that is received from a sole of a subject; a step of calculating a total load value of a sole region based on the measurement information, the sole region corresponding to the position of a sole of one leg of the subject; a step of determining an action state of the one leg based on the total load value; and a step of starting to offset the total load value using an offset filter, in response to a determination that the action state is a first action state, the offset filter decreasing an offset amount with time elapse, the first action state being a state where the total load value tends to increase and is equal to or larger than a preset determination value. Thereby, it is possible to improve the detection accuracy of the action state of the leg. 
     The present disclosure can provide a detection system, a walking exercise system, a detection method and a storage medium that improve the detection accuracy of the action state of the leg. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features, advantages, and technical and industrial significance of exemplary embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like signs denote like elements, and wherein: 
         FIG.  1    is a schematic perspective view of a walking exercise system according to an embodiment; 
         FIG.  2    is a schematic perspective view showing an exemplary configuration of a walking exercise device; 
         FIG.  3    shows a lateral view and top view of a treadmill according to the embodiment; 
         FIG.  4    is a diagram showing an example of the output characteristic of a load distribution sensor to an input load; 
         FIG.  5    is a diagram showing an example of the output characteristic of the load distribution sensor when a load is received from the sole of one leg of an exerciser during walking; 
         FIG.  6    is a diagram for describing an example of an offset amount according to the embodiment; 
         FIG.  7    is a block diagram showing a schematic configuration of a detection device according to the embodiment; 
         FIG.  8    is a flowchart showing a procedure of a detection method according to the embodiment; 
         FIG.  9    is a diagram showing an example of an offset filter according to the embodiment; 
         FIG.  10    is a diagram showing another example of the offset filter according to the embodiment; 
         FIG.  11    is a diagram for describing an estimation process for a sole region according to the embodiment; and 
         FIG.  12    is a schematic configuration diagram of a computer that is used as the detection device and a system control unit according to the embodiment. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     The present disclosure will be described below with an embodiment. The disclosure according to the claims is not limited to the embodiment described below. Further, all configurations described in the embodiment are not essential as means for solving the problem. For clear explanations, in the following description and the drawings, omission and simplification are performed when appropriate. 
       FIG.  1    is a schematic perspective view of a walking exercise system  1  according to the embodiment. The walking exercise system  1  is an example of a system to which a detection device (also referred to as a detection system) according to the embodiment can be applied. The walking exercise system  1  is a system in which walking exercise is performed by an exerciser  900  that is a hemiplegia patient suffering the paralysis of one leg. The exerciser  900  is also referred to as a subject. The up-down direction, right-left direction and front-rear direction in the following description are directions on the basis of the orientation of the exerciser  900 . 
     The walking exercise system  1  mainly includes a control panel  133  that is attached to a frame  130  forming a whole skeleton, a treadmill  131  on which the exerciser  900  walks, and a walking aid device  120  that is worn on at least one leg of the exerciser  900 . In the embodiment, the at least one leg is an affected leg that is a leg portion on the paralysis side of the exerciser  900 . 
     The frame  130  is provided so as to stand on the treadmill  131  that is installed on a floor surface. The treadmill  131  rotates a ring-shaped belt  132  by an unillustrated motor. Thereby, the belt  132  runs along an orbit. The treadmill  131  is a device that encourages the walking of the exerciser  900 . When performing walking exercise, the exerciser  900  gets on the belt  132 , and tries walking action on a walking surface formed on the belt  132 . 
     The frame  130  supports the control panel  133 , an exercise monitor  138  and a voice output unit  139 . The control panel  133  contains a detection device  100  and a system control unit  200 . The detection device  100  is a computer device that detects the action state of the leg of the exerciser  900  walking on the walking surface, from a measurement result of a sensor. The system control unit  200 , which is also referred to as a control device, is a computer device that controls the sensor and the motor. For example, the system control unit  200  controls the extension of the walking aid device  120 , based on the action state of the leg of the exerciser  900  that is detected by the detection device  100 . 
     The exercise monitor  138  is a display device that presents information relevant to the exercise and the measurement, to the exerciser  900 . For example, the exercise monitor  138  is a liquid crystal panel. The exercise monitor  138  is installed such that the exerciser  900  can visually recognize the exercise monitor  138  while walking on the belt  132  of the treadmill  131 . 
     The voice output unit  139  outputs information relevant to the exercise and the measurement, by voice, and informs the exerciser  900 . For example, the voice output unit  139  is a speaker. The voice output unit  139  is installed at such a position that the exerciser  900  can hear the voice while walking on the belt  132  of the treadmill  131 . 
     Further, the frame  130  supports a front-side pulling unit  135  near a head upper front portion of the exerciser  900 , supports a harness pulling unit  112  near a head upper portion of the exerciser  900 , and supports a rear-side pulling unit  137  near a head upper rear portion of the exerciser  900 . Further, the frame  130  may include a rail  130   a  that is grasped by the exerciser  900 . 
     A camera  140  is a front camera unit that picks up the image of the exerciser  900  at a field angle that makes it possible to recognize the gait of the exerciser  900  from the front. The camera  140  may include a side camera unit that picks up the image of the exerciser  900  at a field angle that makes it possible to recognize the gait of the exerciser  900  from a side. The camera  140  in the embodiment includes a set of a lens and an image pickup element. The lens has a field angle that makes it possible to capture the whole body including a head portion of the exerciser  900  that stands on the belt  132 . The image pickup element is a CMOS image sensor, for example, and converts an optical image formed on an image forming surface, into an image signal. The camera  140  is installed at the vicinity of the exercise monitor  138 , so as to be oriented to the exerciser  900 . In the case where the camera  140  includes the side camera unit, the side camera unit may be installed on the rail  130   a,  so as to capture the exerciser  900  from the side. 
     One end of a front-side wire  134  is joined to a wind-up mechanism of the front-side pulling unit  135 , and the other end is joined to the walking aid device  120 . The wind-up mechanism of the front-side pulling unit  135  turns an unillustrated motor on or off in accordance with an instruction from the system control unit  200 , and thereby winds up or pays out the front-side wire  134  depending on the motion of the affected leg. Similarly, one end of a rear-side wire  136  is joined to a wind-up mechanism of the rear-side pulling unit  137 , and the other end is joined to the walking aid device  120 . The wind-up mechanism of the rear-side pulling unit  137  turns an unillustrated motor on or off in accordance with an instruction from the system control unit  200 , and thereby winds up or pays out the rear-side wire  136  depending on the motion of the affected leg. By such a cooperative action of the front-side pulling unit  135  and the rear-side pulling unit  137 , the load from the walking aid device  120  is cancelled such that the load does not become a burden on the affected leg, and further a motion start action of the affected leg is assisted depending on the level of setting. 
     An operator  910  that is an exerciser aid person sets the assist level to a high level, for an exerciser that suffers a severe paralysis. The operator  910  is a physical therapist or doctor that has the authority to select, alter and add setting items for the walking exercise system  1 . When the assist level is set to a high level, the front-side pulling unit  135  winds up the front-side wire  134  with a relatively great force, at the same timing as the start of the motion of the affected leg. When the exercise advances and the assist becomes unnecessary, the operator sets the assist level to the lowest level. When the assist level is set to the lowest level, the front-side pulling unit  135  winds up the front-side wire  134  with a force allowing the self-weight of the walking aid device  120  to be cancelled, at the same timing as the start of the motion of the affected leg. 
     The walking exercise system  1  includes a safety device that has a safety outfit  110 , a harness wire  111  and the harness pulling unit  112  as main constituent elements. The safety outfit  110  is a belt that is wound around an abdominal portion of the exerciser  900 , and is fixed to a lumbar portion by a hook-and-loop fastener, for example. The harness wire  111  is a wire that has one end joined to the safety outfit  110  and that has the other end joined to a wind-up mechanism of the harness pulling unit  112 . The wind-up mechanism of the harness pulling unit  112  turns an unillustrated motor on or off, and thereby winds up or pays out the harness wire  111 . By this configuration, in the case where the posture of exerciser  900  is greatly lost, the safety device winds up the harness wire  111  in accordance with an instruction from the system control unit  200  that detects the motion, and thereby supports the upper body of the exerciser  900  with the safety outfit  110 . 
     The management monitor  141  is a display device that is attached to the frame  130  and that is monitored and operated by the operator  910 . The management monitor  141  is a liquid crystal panel, for example, and a touch panel is superposed on a surface of the management monitor  141 , as an example of an input unit  142 . The management monitor  141  presents various menu items relevant to setting for the exercise and the measurement, various parameter values at times of the exercise and the measurement, measurement results at the time of the exercise. The input unit  142  may be a keyboard or the like, instead of the touch panel. Further, the operator  910  selects, alters or adds setting items through the input unit  142 . Further, the management monitor  141  is installed at such a position that the exerciser  900  cannot visually recognize the display on the management monitor  141  at an exercise trial position on the treadmill  131 . A support unit that supports the management monitor  141  may include a rotation mechanism that inverts the display surface. In this case, the operator  910  can purposely cause the exerciser  900  to see the display screen. 
     The walking aid device  120  is worn on the affected leg of the exerciser  900 , and aids the walking of the exerciser  900  by reducing the load for extension and flexion at the knee joint of the affected leg. The walking aid device  120  sends data that is relevant to leg movement and that is obtained by walking exercise, to the system control unit  200 , and drives a joint portion in accordance with an instruction from the system control unit  200 . The walking aid device  120  may be connected with a hip joint (a connection member including a rotation portion) attached to the safety outfit  110  that is a part of a fall prevention harness device, through a wire or the like. 
       FIG.  2    is a schematic perspective view showing an exemplary configuration of the walking aid device  120 . The walking aid device  120  mainly includes a control unit  121  and a plurality of frames that supports portions of the affected leg. The walking aid device  120  is also referred to as a leg robot. 
     The control unit  121  includes an aid control unit  220  that controls the walking aid device  120 , and includes an unillustrated motor that generates a drive force for aiding the extension movement and flexion movement of the knee joint. The frames that supports the portions of the affected leg includes an upper leg frame  122 , and lower leg frames  123  pivotally joined to the upper leg frame  122 . Further, the frames include a flat foot frame  124  pivotally joined to the lower leg frames  123 , a front-side joining frame  127  for joining the front-side wire  134 , and a rear-side joining frame  128  for joining the rear-side wire  136 . 
     The upper leg frame  122  and the lower leg frames  123  relatively pivot around an illustrated hinge shaft Ha. The motor of the control unit  121  rotates in accordance with an instruction from the aid control unit  220 , and gives force such that the upper leg frame  122  and the lower leg frames  123  are relatively opened around the hinge shaft Ha or gives force such that the upper leg frame  122  and the lower leg frames  123  are relatively closed around the hinge shaft Ha. An angle sensor  223  contained in the control unit  121  is a rotary encoder, for example, and detects the angle between the upper leg frame  122  and the lower leg frames  123  around the hinge shaft Ha. The lower leg frames  123  and the flat foot frame  124  relatively pivot around an illustrated hinge shaft Hb. The angle range of the relative pivoting is adjusted by an adjustment mechanism  126  in advance. 
     The front-side joining frame  127  is provided so as to extend in the right-left direction on the front side of the upper leg and to connect both ends to the upper leg frame  122 . Further, on the front-side joining frame  127 , a joining hook  127   a  for joining the front-side wire  134  is provided near the center in the right-left direction. The rear-side joining frame  128  is provided so as to extend in the right-left direction on the rear side of the lower leg and to connect both ends to the lower leg frames  123  each of which extends in the up-down direction. Further, on the rear-side joining frame  128 , a joining hook  128   a  for joining the rear-side wire  136  is provided near the center in the right-left direction. 
     The upper leg frame  122  includes an upper leg belt  129 . The upper leg belt  129  is a belt provided integrally with the upper leg frame, and fixes the upper leg frame  122  to an upper leg portion of the affected leg while being wound around the upper leg portion. Thereby, the whole of the walking aid device  120  is prevented from deviating from the leg portion of the exerciser  900 . 
       FIG.  3    shows a lateral view and top view of the treadmill according to the embodiment. The treadmill  131  includes at least the ring-shaped belt  132 , pulleys  151  and an unillustrated motor. 
     Further, a load distribution sensor  150  is disposed on the inside of the belt  132 , that is, on the opposite side of the surface of the belt  132  on which the exerciser  900  gets. The load distribution sensor  150  is fixed to the treadmill  131 , so as not to be moved by the movement of the belt  132 . 
     The load distribution sensor  150  is a load distribution sensor sheet that has a plurality of pressure detection points. The plurality of pressure detection points is disposed in a matrix manner, parallel to a walking surface W (placement surface) that supports the sole of the exerciser  900  in the standing state. Further, the load distribution sensor  150  is disposed at a center portion of the walking surface W in the right-left direction orthogonal to a walking front-rear direction. The walking front-rear direction is a direction that is parallel to the running direction of the belt  132 . The load distribution sensor  150  can detect the magnitudes and distribution of vertical loads that are received from the sole of the exerciser  900 , by using output values of the plurality of pressure detection points. Thereby, through the belt  132 , the load distribution sensor  150  detects the position of a grounding region (sole region) SL of the sole of the exerciser  900  in the standing state, and the distribution of loads that are received from the sole of the exerciser  900 . The position of the sole region SL is also referred to as a standing position or stepping position of the exerciser  900 . 
     The load distribution sensor  150  is connected to the detection device  100 . The detection device  100  acquires load distribution information from the load distribution sensor  150 , as measurement information, and measures the action state of the leg of the exerciser  900  based on the load distribution information. For example, the action state of the leg is a state where the stepping is started, a state where the stepping is maximized, or a state where the force starts to be weakened. The detection device  100  is connected to the system control unit  200  by wire or by wireless, and outputs the measured action state to the system control unit  200 . 
     The system control unit  200  controls various drive units, based on the action state of the leg that is acquired from the detection device  100 . For example, the system control unit  200  is connected to a treadmill drive unit  211 , a pulling drive unit  214 , a harness drive unit  215 , and the aid control unit  220  of the walking aid device  120 , by wire or by wireless. The system control unit  200  sends drive signals to the treadmill drive unit  211 , the pulling drive unit  214  and the harness drive unit  215 , and sends a control signal to the aid control unit  220 . 
     The treadmill drive unit  211  includes the above-described motor that rotates the belt  132  of the treadmill  131 , and a drive circuit for the motor. The system control unit  200  executes the rotation control of the belt  132 , by sending the drive signal to the treadmill drive unit  211 . For example, the system control unit  200  adjusts the rotation speed of the belt  132 , depending on the walking speed set by the operator  910 . Alternatively, the system control unit  200  adjusts the rotation speed of the belt  132 , depending on the action state of the leg of the exerciser  900  that is output from the detection device  100 . 
     The pulling drive unit  214  includes a motor that is provided in the front-side pulling unit  135  and that pulls the front-side wire  134 , and a drive circuit for the motor, and includes a motor that is provided in the rear-side pulling unit  137  and that pulls the rear-side wire  136 , and a drive circuit for the motor. The system control unit  200  controls each of the wind-up of the front-side wire  134  and the wind-up of the rear-side wire  136 , by sending the drive signal to the pulling drive unit  214 . Further, in addition to the wind-up action, the system control unit  200  controls the pulling force of each wire, by controlling the drive torque of the motor. Furthermore, for example, the system control unit  200  assists the action of the affected leg, by identifying the timing of the switching of the affected leg from a leg standing state to a leg idling state based on the action state of the leg of the exerciser  900  that is output from the detection device  100  and increasing or decreasing the pulling force of each wire in synchronization with the timing. 
     The harness drive unit  215  includes a motor that is provided in the harness pulling unit  112  and that pulls the harness wire  111 , and a drive circuit for the motor. The system control unit  200  controls the wind-up of the harness wire  111  and the pulling force of the harness wire  111 , by sending the drive signal to the harness drive unit  215 . For example, in the case where the fall of the exerciser  900  is predicted, the system control unit  200  prevents the fall of the exerciser  900  by winding up the harness wire  111  by a certain amount. 
     The aid control unit  220  is a microprocessor unit (MPU), for example, and executes the control of the walking aid device  120  by executing a control program that is given from the system control unit  200 . Further, the aid control unit  220  gives notice of the state of the walking aid device  120 , to the system control unit  200 . Further, the aid control unit  220  executes the control of the walking aid device  120 , as exemplified by the activation and stop of the walking aid device  120 , in response to a command from the system control unit  200 . 
     The aid control unit  220  sends a drive signal to a joint drive unit that includes the motor of the control unit  121  and a drive circuit for the motor, and thereby gives force such that the upper leg frame  122  and the lower leg frames  123  are relatively opened around the hinge shaft Ha or gives force such that the upper leg frame  122  and the lower leg frames  123  are relatively closed around the hinge shaft Ha. By this action, the extension action and flexion action of the knee are assisted, and a buckling is prevented. The aid control unit  220  receives a detection signal from an angle sensor (not illustrated) that detects the angle between the upper leg frame  122  and the lower leg frames  123  around the hinge shaft Ha, and computes the opening angle of the knee joint. 
     In the load distribution sensor  150 , an elastic sheet  150   c  is inserted between two electrode sheets  150   a,    150   b  that face each other. The elastic sheet  150   c  is an elastic member composed of silicon sponge sheet, urethane foam or the like. The elastic sheet  150   c  has a property of slowly transmitting stress and gradually deforming when an external force is given, because of influence of viscosity. 
       FIG.  4    is a diagram showing an example of the output characteristic of the load distribution sensor  150  to the input load. The figure shows a temporal change in the output value of the load distribution sensor  150  when an external force (input load) having a certain load value p 1  (kPa) is continuously applied to the load distribution sensor  150 . As shown in the figure, at a time point when the external force begins to be applied, the output value of the load distribution sensor  150  is lower than the load value of the external force that is actually being applied. This is because the stress is transmitted in the load distribution sensor  150  with a delay due to the existence of the elastic sheet  150   c  included in the load distribution sensor  150 , so that the output of the load distribution sensor  150  is delayed. However, the output value of the load distribution sensor  150  asymptotically becomes closer to the load value pi of the external force that is being applied, with time elapse. That is, the difference between the output value of the load distribution sensor  150  and the load value p 1  of the external force becomes smaller with time elapse. Then, after a predetermined time elapses from the start of the application of the external force, the output value of the load distribution sensor  150  is stabilized at a value comparable to the load value p 1  that is being applied. 
       FIG.  5    is a diagram showing an example of the output characteristic of the load distribution sensor  150  when a load is received from the sole of one leg of the exerciser  900  during walking. In the embodiment, the one leg is an affected leg. In the figure, the ordinate indicates the load value (kPa) that is received from the sole of the leg during a leg standing period, and the abscissa indicates time (s). 
     A broken line indicates a load value that is actually applied to the load distribution sensor  150  from the sole of the leg of the exerciser  900  during the leg standing period from landing to departing (“actual load”). In the “actual load”, the load value gradually increase from the start of the stepping, and the load value reaches the maximum at a certain time point. At this time point, the total body weight is supported by the leg during the leg standing period, and therefore the maximum value of the load value is nearly equal to the body weight of the exerciser  900 . Thereafter, in a leg standing latter period, the exerciser  900  starts to gradually weaken the force, and therefore the load value gradually decreases. Then, the exerciser  900  causes the leg to depart from the ground, resulting in the transition to a leg idling period. 
     A solid line indicates a load value that is received from the sole of the leg during the leg standing period of the exerciser  900  and that is calculated based on the output of the load distribution sensor  150  (“sensor output”). The “sensor output” is obtained by extracting the load value that is received from the sole of the leg during the leg standing period, from the output of the load distribution sensor  150 . Specifically, the “sensor output” is obtained by calculating the sum of the load values output from the pressure detection points within the sole region SL of the leg during the leg standing period. 
     The “sensor output” increases in a leg standing beginning period, and when the “sensor output” exceeds a first determination value (point P 1 ), the detection device  100  detects a first action state. The first action state is a state where the stepping is started. Then, when the “sensor output” reaches the maximum (point P M ), the detection device  100  detects a maximum state. The maximum state is a state where the stepping is maximized. Further, a second determination value is a value that is larger than the first determination value and smaller than the body weight value of the exerciser  900 . After the point PM, the “sensor output” gradually decreases, and when the “sensor output” falls below the second determination value (point P 2 ), the detection device  100  detects a second action state. The second action state is a state where the force starts to be weakened. In response to the detection of the second action state, the system control unit  200  sends the control signal to the aid control unit  220 , and controls the extension of the walking aid device  120 . Alternatively, in response to the detection of the second action state, the system control unit  200  sends the drive signal to the pulling drive unit  214 , and assists the action of the affected leg. 
     The value of the “sensor output” is lower than the load value that is actually applied, until the output becomes stable, because of the influence of the above-described output characteristic of the load distribution sensor  150 . Accordingly, there is a gap between the “sensor output” and the “actual load”. This causes the false detection of the second action state. For solving this problem, in the embodiment, the detection device  100  offsets the “sensor output” by a predetermined amount, from the detection of the first action state. Hereinafter, “offsetting” is sometimes referred to as “correcting” or “performing offset correction”. 
       FIG.  6    is a diagram for describing an example of an offset amount according to the embodiment. For example, the detection device  100  offsets the “sensor output”, by adding an offset amount (broken lint) that monotonically decreases with time elapse, to the “sensor output” (thin solid line). In the figure, the “sensor output after offset” is indicated by a thick solid line. The method for deciding the offset amount will be described later. Specifically, in response to the detection of the first action state, the detection device  100  starts the offset of the “sensor output” (point P 1 ′). Thereby, the “sensor output after offset” becomes closer to the “actual load”, compared to the “sensor output (before offset)”. Accordingly, the error of the detection timing of the second action state (point P 2 ′) of the “sensor output after offset” is smaller than that of the detection timing of the second action state (point P 2 ) of the “sensor output (before offset)”. Accordingly, it is possible to avoid the false detection of the second action state, and to improve the detection accuracy. 
     In the embodiment, the offset amount becomes zero after the elapsed of a predetermined time and therefore the detection device  100  does not need to terminate (end) the offset after the start of the offset. However, the detection device  100  may terminate the offset when the offset amount becomes equal to or smaller than a predetermined value. The predetermined value may be zero, or may be a larger value than zero. 
       FIG.  7    is a block diagram showing a schematic configuration of the detection device  100  according to the embodiment. The detection device  100  includes an acquisition unit  101 , a calculation unit  102 , a determination unit  103 , a correction unit  104 , an output unit  105 , and a storage unit  106 . The constituent elements of the detection device  100  are connected with each other. 
     The acquisition unit  101  acquires the load distribution information from the load distribution sensor  150 , as the measurement information. For example, the acquisition unit  101  is connected to the load distribution sensor  150 , and acquires the load distribution information from the load distribution sensor  150 . Then, the acquisition unit  101  supplies the load distribution information of the load distribution sensor  150  to the calculation unit  102 . 
     Further, the acquisition unit  101  is connected to the input unit  142 , and acquires basic information for generating an offset filter. The basic information is input from the input unit  142 . The offset filter is a filter for deciding an offset amount that is applied at a predetermined time point. In the embodiment, the offset filter has a characteristic in which the offset amount decrease with time elapse. The basic information for generating the offset filter includes at least information indicating the output characteristic of the load distribution sensor  150  to the input load. For example, the information indicating the output characteristic may include a time function for the output value to the input load. Further, the information indicating the output characteristic may include the elastic modulus of the elastic sheet  150   c  included in the load distribution sensor  150 , the viscosity coefficient of the elastic sheet  150   c,  and the thickness of the elastic sheet  150   c.  Further, the basic information for generating the offset filter includes attribute information about the exerciser  900 , for example, information about the body weight value of the exerciser  900 . In addition to or instead of this, the basic information may include other attribute information such as the sex, age, foot length information and rehabilitation stage level of the exerciser  900 . Further, the acquisition unit  101  supplies the basic information received from the input unit  142 , to the correction unit  104 . 
     Based on the load distribution information, the calculation unit  102  calculates a total load value of the sole region SL corresponding to the position of the sole of one leg of the exerciser  900 . Specifically, first, the calculation unit  102  extracts the load values of the pressure detection points within the sole region SL of one leg of the exerciser  900 , from the load distribution information. Then, based on the extracted load values, the calculation unit  102  calculates a total load value that is the sum of the loads in the sole region SL. One leg is a leg that is an object of the measurement of the action state, and is also referred to as an object leg. The object leg may be an affected leg. The calculation unit  102  supplies information about the calculated total load value, to the determination unit  103 . 
     The determination unit  103  detects various action states of the object leg of the exerciser  900 , based on at least one of the total load value calculated by the calculation unit  102  and a later-described total load value after the offset by the correction unit  104 . For example, in the case where the total load value calculated by the calculation unit  102  tends to increase and is equal to or larger than the first determination value, the determination unit  103  determines that the action state of the object leg is the first action state. It may be determined that the total load value tends to increase, when the change amount of total load values based on outputs of the load distribution sensor  150  at consecutive measurement timings has a positive value, or when total load values based on outputs of the load distribution sensor  150  in a predetermined time have a positive correlation. Instead of this, in the case where the area of the sole region SL of the object leg is equal to or larger than a predetermined area threshold, the determination unit  103  may determine that the action state of the object leg is the first action state. That is, in the case where the area of the sole region tends to increase and is equal to or larger than the predetermined area threshold, the determination unit  103  may determine that the action state of the object leg is the first action state. It may be determined that the area of the sole region SL tends to increase, when the change amount of areas of the sole region SL of the object leg at consecutive measurement timings has a positive value, or when areas of the sole region SL of the object leg in a predetermined time have a positive correlation. Needless to say, in the first action state, the total load value calculated by the calculation unit  102  is smaller than the second determination value. 
     In the case where the total load value calculated by the calculation unit  102  reaches the maximum, the determination unit  103  determines that the action state of the object leg is the maximum state. For example, in the case where the tendency of the total load value calculated in the calculation unit  102  changes from an increasing tendency to a decreasing tendency, the determination unit  103  may determine that the total load value calculated by the calculation unit  102  has reached the maximum. 
     Further, for example, in the case where the total load value after the offset correction by the correction unit  104  tends to decrease and is smaller than the second determination value, the determination unit  103  determines that the action state of the object leg is the second action state. The total load value after the offset correction by the correction unit  104  is equal to the offset total load value in the case where the offset correction by the correction unit  104  is performed, and is equal to the total load value calculated by the calculation unit  102  in the case where the offset correction by the correction unit  104  is terminated. It may be determined that the total load value tends to decrease, when the change amount of total load values based on outputs of the load distribution sensor  150  at consecutive measurement timings has a negative value, or when total load values based on outputs of the load distribution sensor  150  in a predetermined time have a negative correlation. The determination unit  103  supplies a determination result (detection result) to the output unit  105 . 
     The correction unit  104  generates the offset filter based on the basic information for generating the offset filter. For example, the correction unit  104  generates the offset filter based on the information indicating the output characteristic of the load distribution sensor  150  to the input load and the attribute information about the exerciser  900 . The output characteristic of the load distribution sensor  150  changes depending on the pattern of the input load. Accordingly, by this configuration, it is possible to reflect the output characteristic of the load distribution sensor  150  depending on the pattern of the input load that is estimated from the attribute of the exerciser  900 , in the offset amount. In the embodiment, the correction unit  104  generates the offset filter based on the information indicating the output characteristic of the load distribution sensor  150  to the input load and the body weight value of the exerciser  900 . By estimating the input load from the body weight value, the correction unit  104  can generate the offset filter easily and accurately. 
     Then, the correction unit  104  offsets the total load value, using the generated offset filter. Specifically, in response to the determination that the action state of the object leg is the first action state, the correction unit  104  starts the offset for the total load value calculated by the calculation unit  102 , using the offset filter. Thereby, it is possible to cause the total load value to be close to the actual load, and therefore, for example, it is possible to avoid the false detection of the second action state where the force starts to be weakened, so that it is possible to improve the detection accuracy of the action state. 
     The output unit  105  outputs the control signal based on the detection result supplied from the determination unit  103 , to the system control unit  200 . In the embodiment, in the case where the second action state is detected, the output unit  105  outputs a control signal indicating the detection of the second action state, to the system control unit  200 . However, without being limited to this, also in the case where the first action state or the maximum state is detected, the output unit  105  may output a control signal corresponding to the action state, to the system control unit  200 . 
     The storage unit  106  is a storage medium in which information necessary for processing in the detection device  100  and generated information are stored. 
       FIG.  8    is a flowchart showing a procedure of a detection method according to the embodiment. First, the acquisition unit  101  acquires the basic information from the exerciser  900  or the operator  910  through the input unit  142  (step S 10 ). Then, the correction unit  104  generates the offset filter based on the basic information (step S 11 ). 
       FIG.  9    is a diagram showing an example of the offset filter according to the embodiment. An offset filter f(t) shown in  FIG.  9    is a function for time t about the offset amount. The offset filter f(t) may be a filter in which the initial value of the offset amount is o 1  (&gt;0 kPa), in which the offset amount decreases with time elapse, and in which the offset amount becomes zero (kPa) at a preset time t 1 . The correction unit  104  may generate the offset filter f(t) by deciding the initial value o 1 , the time t 1  and the slope based on the basic information. In the case where the offset filter is a function for time t about the offset amount, the correction unit  104  may execute the offset correction, by adding the value of the offset filter at the current time point, to the total load value. 
       FIG.  10    is a diagram showing another example of the offset filter according to the embodiment. An offset filter g(t) shown in  FIG.  10    is a function for time t about an offset coefficient. The offset filter g(t) may be a function in which the initial value of the offset coefficient is o 2  (&gt;1), in which the offset coefficient decreases with time elapse, and in which the offset coefficient becomes 1 (kPa) at a preset time t 2 . The correction unit  104  may generate the offset filter g(t) by deciding the initial value o 2 , the time t 2  and the slope based on the basic information. In the case where the offset filter is a function for time t about the offset coefficient, the correction unit  104  may execute the offset correction, by multiplying the total load value by the value of the offset filter. 
     Back to  FIG.  8   , the description will be continued. The detection device  100  determines whether the measurement is started (step S 12 ). The measurement is started, for example, in the case where the exercise with the walking exercise system  1  is started, or in the case where the detection process with the detection device  100  is started by an operation from the operator  910 . The detection device  100  repeats the process shown in step S 12 , until it is determined that the measurement is started, and in the case where it is determined that the measurement is started (YES in step S 12 ), the detection device  100  causes the process to proceed to step S 13 . 
     The acquisition unit  101  acquires the load distribution information from the load distribution sensor  150 , as the measurement information (step S 13 ). The load distribution information includes information indicating load values respectively corresponding to pressure detection points at different positions from each other. Then, the acquisition unit  101  supplies the load distribution information to the calculation unit  102 . Next, the calculation unit  102  estimates the sole region SL of the object leg based on the load distribution information (step S 14 ), and extracts the load values in the sole region SL of the object leg. Then, the calculation unit  102  calculates the total load value that is the sum of the extracted load values in the sole region SL of the object leg (step S 15 ). 
       FIG.  11    is a diagram for describing an estimation process for the sole region SL according to the embodiment. For example, the calculation unit  102  generates a load distribution map shown in  FIG.  11   , based on position information about the pressure detection points and the load values detected from the pressure detection points. The calculation unit  102  may generate the load distribution map, by extracting position information about load values equal to or larger than a detection threshold, from the load values detected from the pressure detection points. Then, the calculation unit  102  detects the sole region SL based on the load distribution map. Here, suppose that the object leg is the right leg. The calculation unit  102  determines whether the sole region SL is a region of the object leg, based on the position of the sole region SL with respect to a central axis D 1  of the load distribution sensor  150  in the right-left direction. For example, the calculation unit  102  calculates the position of the barycenter of the sole region SL, and in the case where the position of the barycenter is on the right side of the center axis D 1 , the calculation unit  102  determines that the sole region SL is the sole region SL of the object leg. Then, the calculation unit  102  calculates the sum of the load values included in the sole region SL, as the total load value. The region in which load values are extracted is not limited to the sole region SL, and may be a predetermined region A 1  that contains the sole region SL. 
     Further, the calculation unit  102  may determine whether the detected sole region SL is the sole region SL of the object leg, based on a photographed image generated by photographing the gait of the exerciser  900  with the camera  140  that is the front camera unit and the side camera unit. For example, in the case where the photographed image shows that the exerciser  900  moves the right leg forward, or in the case where the photographed image shows that the exerciser  900  causes the right leg to be grounded, the calculation unit  102  determines that the detected sole region SL is the sole region SL of the object leg. 
     The case where the calculation unit  102  detects one sole region SL, that is, the case where the sole of one leg is grounded was described above. However, in the case where the calculation unit  102  detects two sole regions SL, that is, in the case where the soles of both legs are grounded, the calculation unit  102  may estimate the sole region SL of the object leg, based on the relative positions of the two sole regions SL. For example, the calculation unit  102  may set the sole region SL that is of the two sole regions SL and that is on the right side, as the sole region SL of the object leg. Also in this case, the calculation unit  102  may estimate the sole region SL of the object leg based on the photographed image. 
     Further, since the exerciser  900  walks while the sole of the right leg and the sole of the left leg are alternately grounded, the calculation unit  102  may estimate the sole region SL of the object leg, depending on a walking cycle. 
     Back to  FIG.  8   , the description will be continued. In step S 16 , the determination unit  103  determines whether the total load value tends to increase. In the case where the correction unit  104  is not performing the offset correction, that is, in the case where the offset amount is zero, the total load value is the total load value calculated by the calculation unit  102 . Further, in the case where the correction unit  104  is performing the offset correction, that is, in the case where the offset amount is not zero, the total load value is the total load value after the offset. In the case where the determination unit  103  determines that the total load value tends to increase (YES in step S 16 ), the determination unit  103  determines whether the total load value has become equal to or larger than the first determination value for the first time in a first object period (step S 17 ). 
     The first object period is a period that is in the current walking cycle and during which the total load value tends to increase. In the case where the determination unit  103  determines that the total load value has not yet become equal to or larger than the first determination value in the first object period or that the total load value has become equal to or larger than the first determination value in the first object period in the past (NO is step S 17 ), the determination unit  103  causes the process to proceed to step S 23 . On the other hand, in the case where the determination unit  103  determines that the total load value has become equal to or larger than the first determination value for the first time in the first object period (YES in step S 17 ), the determination unit  103  determines that the action state of the object leg is the first action state (step S 18 ). Then, the correction unit  104  starts the offset correction for the total load value, using the offset filter (step S 19 ), and causes the process to proceed to step S 23 . 
     In the case where the determination unit  103  determines that the total load value does not tend to increase (NO in step S 16 ), the determination unit  103  determines whether the total load value has become smaller than the second determination value for the first time in a second object period (step S 20 ). The second object period is a period that is in the current walking cycle and during which the total load value tends to decrease. In the case where the determination unit  103  determines that the total load value has not yet become smaller than the second determination value in the second object period or that the total load value has become smaller than the second determination value in the second object period in the past (NO in step S 20 ), the determination unit  103  causes the process to proceed to step S 23 . On the other hand, in the case where the determination unit  103  determines that the total load value has become smaller than the second determination value for the first time in the second object period (YES in step S 20 ), the determination unit  103  determines that the action state of the object leg is the second action state (step S 21 ). Then, the output unit  105  outputs the control signal indicating the detection of the second action state, to the system control unit  200  (step S 22 ), and causes the process to proceed to step S 23 . 
     In step S 23 , the detection device  100  determines whether the measurement is ended. The measurement is ended, for example, in the case where the exercise with the walking exercise system  1  is ended, or in the case where the detection process with the detection device  100  is ended by an operation from the operator  910 . The detection device  100  repeats the processes shown in steps S 13  to S 23 , until it is determined that the measurement is ended. 
       FIG.  8    shows a flow in the case where the detection device  100  does not terminate the offset correction. However, in the case where the detection device  100  terminates the offset correction, the detection device  100  may execute the following process, just before step S 23  (in step S 19 , in step S 22 , or after step S 17  in the case of NO in step S 17 ), for example. In the case where the offset amount is equal to or smaller than a predetermined value, the correction unit  104  of the detection device  100  may terminate the offset correction, and may cause the process to proceed to step S 23 . On the other hand, in the case where the offset amount is larger than a predetermined value, the correction unit  104  may continue to execute the offset correction, and may cause the process to proceed to step S 23 . 
     In this way, with the embodiment, the detection device  100  can improve the detection accuracy of the action state of the leg that is measured, and particularly, can improve the detection accuracy of the timing when the force starts to be weakened. 
     In the above description, the correction unit  104  generates the offset filter based on the basic information, in step S 11  of  FIG.  8    before the start of the measurement. However, instead of or in addition to this, the correction unit  104  may generate the offset filter during the measurement. For example, the correction unit  104  may generate the offset filter based on the state of the sole of the exerciser  900  when the sole begins to be grounded, in a period between step S 15  and step S 16  before it is determined that the action state of the object leg is the first action state. Then, the correction unit  104  may execute the offset correction using the generated offset filter. The state of the sole when the sole begins to be grounded may be a “heel grounding state” in the case where the heel is grounded earlier or a “toe grounding state” in the case where the toe is grounded earlier. The state of the sole when the sole begins to be grounded may be determined by the calculation unit  102 , and the information about the state of the sole when the sole begins to be grounded may be supplied from the calculation unit  102  to the correction unit  104 . For example, in the case where the calculation unit  102  determines that the sole region SL has expanded in the rearward direction of the walking with time after the detection based on the temporal change in the area of the sole region SL and the running speed of the treadmill  131 , the calculation unit  102  may determine that the state of the sole when the sole begins to be grounded is the “toe grounding state”. On the other hand, in the case where the sole region SL has expanded in the forward direction of the walking with time after the detection, the calculation unit  102  may determine that the state of the sole when the sole begins to be grounded is the “heel grounding state”. Offset filters corresponding to the “toe grounding state” and the “heel grounding state” may be different from each other in at least one of the initial value, the slope and the time. Thereby, the correction unit  104  can execute the offset correction appropriate for the walking state of the exerciser  900 . 
       FIG.  12    is a schematic configuration diagram of a computer that is used as the detection device and the system control unit  200  according to the embodiment. A computer  1900  includes a processor  1000 , a read only memory (ROM)  1010 , a random access memory (RAM)  1020 , and an interface (IF) unit  1030 , as primary hardware constituents. The processor  1000 , the ROM  1010 , the RAM  1020  and the interface unit  1030  are connected with each other through a data bus and the like. 
     The processor  1000  has a function as an arithmetic device that performs control processing, arithmetic processing and the like. The processor  1000  may be a central processing unit (CPU), a graphics processing unit (GPU), a field-programmable gate array (FPGA), a digital signal processor (DSP), an application specific integrated circuit (ASIC) or a combination of them. The ROM  1010  has a function to store control programs, arithmetic programs and the like that are executed by the processor  1000 . The RAM  1020  has a function to temporarily store processing data and the like. The interface unit  1030  exchanges signals with the exterior by wire or by wireless. Further, the interface unit  1030  accepts user&#39;s operation to input data, and displays information to the user. For example, the interface unit  1030  communicates with the load distribution sensor  150 , the input unit  142  and the system control unit  200 . 
     In the above-described example, the programs include commands (or software codes) that causes a computer to execute one or more functions described in the embodiment when being read by the computer. The programs may be stored in various non-transitory computer-readable media, each of which is an example of the ROM  1010 , or tangible storage media. Although not limited, examples of the computer-readable media or the tangible storage media include memory technologies such as a random-access memory (RAM), a read-only memory (ROM), a flash memory, a solid-state drive (SSD), optical disk storages such as a CD-ROM, a digital versatile disc (DVD) and a Blu-ray (registered trademark) disk, and magnetic storage devices such as a magnetic cassette, a magnetic tape and a magnetic disk storage. The programs may be sent through transitory computer-readable media or communication media. Although not limited, examples of the transitory computer-readable media or the communication media include an electric propagation signal, an optical propagation signal, an acoustic propagation signal, and another type of propagation signal. 
     In the above-described embodiment, the computer  1900  is configured by a computer system including a personal computer, a word processor and the like. However, without being limited to this, the computer  1900  can be configured by a server in a local area network (LAN), a host for computer (PC) communication, a computer system connected to the internet, and the like. Further, function distribution may be performed among devices on a network, and the computer  1900  may be configured by the whole of the network. Accordingly, constituent elements of the detection device may be distributed among different devices from each other. 
     The present disclosure is not limited to the above embodiment, and modifications can be made without departing from the spirit, when appropriate. For example, in the above-described embodiment, the detection device  100  detects the action state of the affected leg as the object leg. However, the detection device  100  may detect the action state of a normal leg. Further, the detection device  100  may detect the action state of each of the right and left legs. In this case, for each leg, the processes shown in steps S 13  to S 23  of  FIG.  8    are executed. 
     Further, in the above embodiment, the second determination value is larger than the first determination value. However, the second determination value may be equal to the first determination value. 
     Further, the exerciser  900  may wear the walking aid device  120  on both legs, and may perform exercise. Alternatively, the exerciser  900  does not need to wear the walking aid device  120  on any leg.