Patent Publication Number: US-2020289034-A1

Title: Control device of motion support device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority of Japan patent application serial no. 2019-043699, filed on Mar. 11, 2019. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. 
     BACKGROUND 
     Technical Field 
     The disclosure relates to a control device of a motion support device that supports a predetermined motion of a user. 
     Description of Related Art 
     A motion estimation method disclosed in Patent Document 1 (Japanese Laid-open No. 2018-15023) is known in the related art. In this motion estimation method, a user wears one mobile terminal on his or her thigh, and a motion of the user is estimated on the basis of a detection signal of an acceleration sensor installed in the mobile terminal. Specifically, accelerations in directions of three axes (directions of x, y, and z axes) are calculated on the basis of detection signals of the acceleration sensor, and whether a user has transitioned a posture from a “standing posture” or one of a “sitting posture” and a “crouching posture” is estimated on the basis of change in a magnitude relation of the absolute values of the accelerations. 
     According to the motion estimation method of the related art, one acceleration sensor is used to estimate transition of a motion of the user. However, according to the related art, it is not possible to estimate the start of the motion as long as a posture of the user does not significant 1 y change and the magnitude relation of the absolute values of accelerations in the directions of the three axes does not significant 1 y change. That is, it takes time to estimate the start of the motion of the user. 
     Thus, in a case where the motion estimation method is applied to a control device of a motion support device that supports a walking motion of a user and the like, it takes time to estimate a start of a motion of the user, it is thus difficult to quickly support the motion, and thus the motion support device is actually likely to hinder the motion of the user. 
     SUMMARY 
     An embodiment of the disclosure is for a control device  10  of a motion support device (walking assist device  1 ) worn by a user M to support a motion of at least the lower body of the user M, the control device including a first motion sensor (left foot motion sensor  26 ) capable of detecting a motion of a left sole part of the user M, a second motion sensor (right foot motion sensor  27 ) capable of detecting a motion of a right sole part of the user M, a third motion sensor (waist motion sensor  28 ) capable of detecting a motion of a waist part of the user M, a standing state estimation part (assist controller  11 , STEPS  7  and  8 ) estimating whether the user M is in a standing state in accordance with a detection signal of the first to third motion sensors, a waist movement state parameter calculation part (assist controller  11 ) calculating a waist movement state parameter (an x-axis speed of the waist part V_Wx, the absolute value of the x-axis speed of the waist part VA_Wx, or the absolute value of a y-axis speed of the waist part VA_Wy) indicating a movement state of the waist part of the user M in accordance with the detection signal of the third motion sensor, a motion estimation part (assist controller  11 , STEPS  40  to  43 ) estimating that the user M has started a predetermined motion from the standing state if the waist movement state parameter has a value in a predetermined range indicating a movement of the waist part of the user M in one of a backward direction and a lateral direction in a case where the user M is estimated to be in the standing state, and a control part (assist controller  11 , STEPS  90  to  96 ) controlling the motion support device such that the predetermined motion is supported in a case where the user M is estimated to have started the predetermined motion. 
     In an embodiment of the disclosure, if the waist movement state parameter has a value in the predetermined range indicating a movement of the waist part of the user M in the backward direction (YES in STEPS  55  and  56 ), the motion estimation part may estimate that the user M has started a crouching motion as the predetermined motion from the standing state (STEP  41 ), and the control part may control the motion support device such that the crouching motion is supported (STEPS  93  to  94 ) in a case where the user M is estimated to have started the crouching motion from the standing state. 
     In an embodiment of the disclosure, a fourth motion sensor (head motion sensor  29 ) capable of detecting a motion of a head part of the user M and a forward tilt angle calculation part (assist controller  11 ) calculating a forward tilt angle of the head part of the user M Ahead in accordance with a detection signal of the fourth motion sensor are further provided, and if the waist movement state parameter has a value in the predetermined range and the forward tilt angle of the head part of the user M Ahead has a value in a second predetermined range (YES in STEPS  51 ,  55  to  56 ) in the case where the user M is estimated to be in the standing state, the motion estimation part may estimate that the user M has started the crouching motion from the standing state (STEP  58 ). 
     In an embodiment of the disclosure, if the waist movement state parameter has a value in the predetermined range indicating a movement of the waist part in the lateral direction (YES in STEP  71 ) in a case where the user M is estimated to be in the standing state, the motion estimation part may estimate that the user M has started a walking motion as the predetermined motion from the standing state (STEP  73 ), and the control part may control the motion support device such that the walking motion is supported in a case where the user M is estimated to have started the walking motion from the standing state (STEPS  91  and  92 ). 
     In an embodiment of the disclosure, if the waist movement state parameter has a value in the predetermined range indicating the movement of the waist part in the lateral direction and a value in a third predetermined range indicating a movement of the waist part in a forward direction (YES in STEPS  70  and  71 ) in a case where the user M is estimated to be in the standing state, the motion estimation part may estimate that the user M has started the walking motion from the standing state. 
     Another embodiment of the disclosure is for a control device  10  of a motion support device (walking assist device  1 ) worn by a user M to support a motion of at least the lower body of the user M, the control device including a first motion sensor (left foot motion sensor  26 ) capable of detecting a motion of a left sole part of the user M, a second motion sensor (right foot motion sensor  27 ) capable of detecting a motion of a right sole part of the user M, a third motion sensor (waist motion sensor  28 ) capable of detecting a motion of a waist part of the user M, a fourth motion sensor (head motion sensor  29 ) capable of detecting a motion of a head part of the user M, a sitting state estimation part (assist controller  11 , STEPS  5  and  6 ) estimating whether the user M is in a sitting state in accordance with a detection signal of the first to third motion sensors, a forward tilt state parameter calculation part (assist controller  11 ) calculating a forward tilt state parameter (forward tilt angle of the upper body θupper) indicating a forward tilt state of an upper body of the user M in accordance with the detection signal of the third motion sensor and the fourth motion sensor, a motion estimation part (assist controller  11 , STEPS  85  and  87 ) estimating that the user M has started a standing-up motion from the sitting state if the forward tilt state parameter has a value in a fourth predetermined range indicating a forward tilt of the upper body of the user M in a case where the user M is estimated to be in the sitting state, and a control part (assist controller  11 , STEPS  95  and  96 ) controlling the motion support device such that the standing-up motion is supported in a case where the user M is estimated to have started the standing-up motion. 
     According to another embodiment of the disclosure, a forward tilt angle calculation part (assist controller  11 ) calculating a forward tilt angle of the head part of the user M Ahead in accordance with the detection signal of the fourth motion sensor (head motion sensor  29 ) is further provided, and if the forward tilt state parameter has the value in the fourth predetermined range and the forward tilt angle of the head part has a value in a fifth predetermined range (YES in STEPS  81  and  85 ) in the case where the user M is estimated to be in the sitting state, the motion estimation part may estimate that the user M has started the standing-up motion from the sitting state (STEP  87 ). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view schematically illustrating a configuration of a control device according to an embodiment of the disclosure and a walking assist device to which the control device is applied. 
         FIG. 2  is a side view of the walking assist device. 
         FIG. 3  is a block diagram illustrating an electrical configuration of the control device. 
         FIG. 4  is a diagram illustrating posture change of a subject when he or she performs a crouching motion. 
         FIG. 5  is a diagram illustrating posture change of a subject when he or she performs a standing-up motion. 
         FIG. 6  is a diagram illustrating posture change of a subject when he or she performs a walking motion. 
         FIG. 7  is an overhead view of a side tilt posture C 2  of  FIG. 6 . 
         FIG. 8  is a flowchart showing a motion state estimation process. 
         FIG. 9  is a flowchart showing a walking estimation process. 
         FIG. 10  is a flowchart showing a motion start estimation process. 
         FIG. 11  is a flowchart showing a crouching start estimation process. 
         FIG. 12  is a flowchart showing a walking start estimation process. 
         FIG. 13  is a flowchart showing a standing start estimation process. 
         FIG. 14  is a flowchart showing an assist control process. 
         FIG. 15  is a timing flowchart showing transitions of various parameters when a crouching motion is started. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     The embodiments of the disclosure provide a control device of a motion support device that can quickly and appropriately support a predetermined motion of a user when the user wearing the motion support device performs the predetermined motion. 
     According to the control device of the motion support device, whether the user is in a standing state is estimated in accordance with detection signals of the first to third motion sensors. In this case, since the first to third motion sensors can detect each of motions of the left sole part, the right sole part, and the waist part, whether the user is in the standing state can be accurately estimated from positional relations of the left sole part and the right sole part with the waist part. In addition, in a case where the waist movement state parameter indicating a movement state of the waist part of the user is calculated and the user is estimated to be in the standing state in accordance with a detection signal of the third motion state, if the waist movement state parameter has a value in the predetermined range indicating a movement of the waist part of the user in one of the backward direction and the lateral direction, the user is estimated to have started the predetermined motion from the standing state. 
     In this case, the present applicants have ascertained through testing that, when a human starts a predetermined motion (e.g., a crouching motion or a walking motion) from a standing state, a motion of the waist part moving in the backward direction or the lateral direction is performed first (see  FIGS. 4, 6, and 7  which will be described below). Therefore, whether the user has started a predetermined motion from a standing state can be accurately estimated under the condition that the waist movement state parameter has a value in the predetermined range indicating a movement of the waist part of the user in one of the backward direction or the lateral direction. Furthermore, since the motion support device is controlled such that the predetermined motion is supported in the case where the user is accurately estimated to have started the predetermined motion from the standing state as described above, the motion support device can quickly and appropriately support the predetermined motion of the user. 
     The present applicants have ascertained through testing that, when the user starts the crouching motion from the standing state, a motion of the waist part moving in the backward direction is performed first as described above (see  FIG. 4  which will be described below). Therefore, according to the control device of the motion support device, since the user is estimated to have started the crouching motion as the predetermined motion from the standing state if the waist movement state parameter has a value in the predetermined range indicating a movement of the waist part of the user in the backward direction, the estimation can be accurately performed. Furthermore, since the motion support device is controlled such that the crouching motion is supported in the case where the user is accurately estimated to have started the crouching motion as described above, the motion support device can quickly and appropriately support the crouching motion when the user starts the crouching motion (further, “crouching motion” in the present specification means a series of motions of the user performed from a standing state to be in a completely crouching state). 
     According to the control device of the motion support device, the user is estimated to have started the crouching motion from the standing-up motion if the waist movement state parameter has a value in the predetermined range and the forward tilt angle of the head part of the user has a value in the second predetermined range in the case where the user is estimated to be in the standing state. In this case, the present applicants have ascertained through testing that, when a human starts a crouching motion from a standing state, a forward tilt motion of the head part of the user accompanies a motion of the waist part of the user moving in the backward direction as described above (see  FIG. 4  which will be described below). Therefore, since a start of the crouching motion from the standing state is estimated under the condition of a forward tilt motion of the head part in addition to a motion of the waist part of the user moving in the backward direction as described above, the estimation accuracy can be further improved. Thus, control accuracy of the motion support device can be further improved. 
     The present applicants have ascertained through testing that, when a human starts a walking motion from a standing state, a motion of the waist moving in the lateral direction is performed first as described above (see  FIGS. 6 and 7  which will be described below). Therefore, according to the control device of the motion support device, since the user is estimated to have started the walking motion as a predetermined motion from the standing state if the waist movement state parameter has a value in the predetermined range indicating a movement of the waist part in the lateral direction, the estimation can be accurately performed. Furthermore, since the motion support device is controlled such that the walking motion is supported in a case where the user is accurately estimated to have started the walking motion as described above, the motion support device can quickly and appropriately support the walking motion when the user starts the walking motion (further, “walking motion” in the present specification means a series of motions of the user performed from a standing state to be in a completely walking state). 
     The present applicants have ascertained through testing that, when a human starts a walking motion from a standing state, a movement of the waist part in the forward direction is performed first in addition to a movement of the waist part in the lateral direction as described above (see  FIG. 7  which will be described below). Therefore, according to the control device of the motion support device, since the user is estimated to have started the walking motion from the standing state if the waist movement state parameter has the value in the predetermined range indicating the movement of the waist part in the lateral direction and the value in the third predetermined range indicating the movement of the waist part in the forward direction, the estimation accuracy can be further improved. Accordingly, control accuracy of the motion support device can be further improved. 
     According to the control device of the motion support device, whether the user is in a sitting state is estimated in accordance with detection signals of the first to third motion sensors. In this case, since the first to third motion sensors can detect motions of the left sole part, the right sole part, and the waist part, the user can be accurately estimated to be in the sitting state from positional relations of the left sole part and the right sole part with the waist part. In addition, in a case where the forward tilt state parameter indicating a forward tilt state of the upper body of the user is calculated and the user is estimated to be in the sitting state in accordance with detection signals of the third and fourth motion state, if the forward tilt state parameter has a value in the fourth predetermined range indicating a movement of the upper body of the user tilting forward, the user is estimated to have started the standing-up motion as the predetermined motion from the sitting state. 
     In this case, the present applicants have ascertained through testing that, when a human starts a standing-up motion from a sitting state, a motion of tilting the upper body forward, that is, a motion of moving the head part and the waist part away from each other in the front-rear direction, is performed first (see  FIG. 5  which will be described below). Therefore, whether the user has started the standing-up motion from the sitting state can be accurately estimated under the condition that the forward tilt state parameter has a value in the fourth predetermined range indicating that the user is tilting his or her upper body forward. Furthermore, since the motion support device is controlled such that the standing-up motion is supported in a case where the user is accurately estimated to have started the standing-up motion, the motion support device can quickly and appropriately support the standing-up motion when the user starts the standing-up motion (further, “standing-up motion” in the present specification means a series of motions of the user performed from a sitting state to be in a completely standing state). 
     According to the control device of the motion support device, if the forward tilt state parameter has the value in the fourth predetermined range and the forward tilt angle of the head part has the value in the fifth predetermined range in the case where the user M is estimated to be in the sitting state, the user is estimated to have started the standing-up motion from the sitting state. In this case, the present applicants have ascertained through testing that, when a human starts a standing-up motion from a sitting state, a forward tilt motion of the head part of the user accompanies a forward tilt motion of the upper body of the user (see  FIG. 5  which will be described below). Therefore, since a start of the standing-up motion from the sitting state is estimated under the condition of the forward tilt motion of the head part in addition to the forward tilt motion of the upper body of the user, the estimation accuracy can be further improved. Therefore, control accuracy of the motion support device can be further improved. 
     A control device of a motion support device according to an embodiment of the disclosure will be described below with reference to the drawings. The control device  10  of the present embodiment controls states of motions of a walking assist device  1  serving as a motion support device as illustrated in  FIG. 1  and  FIG. 2 , and first, the walking assist device  1  will be described below. 
     The walking assist device  1  assists a user M with walking motions and the like and is of an active type including a drive device  9  (see  FIG. 3 ) as a power source. Further, in the following description, a front-rear direction of the walking assist device  1  and the user M who is wearing the walking assist device will be referred to as “front-rear,” a left-right direction thereof will be referred to as “left-right,” and a top-bottom direction thereof will be referred to as “top-bottom.” 
     Although the walking assist device  1  is configured similarly to, specifically, that disclosed in Japanese Patent No. 4872821, for example, and detailed description thereof will be omitted here, a seat member  2  and a pair of left and right leg link mechanisms  3  and  3  are provided. The user M is seated on the seat member  2  while wearing the walking assist device  1 . 
     In addition, each of the leg link mechanisms  3  and  3  includes a first joint  4 , a first link member  5 , a second joint  6 , and a second link member  7 . The first link member  5  is connected to the seat member  2  to be capable of freely swinging via the first joint  4 . Furthermore, the first link member  5  is connected to the second link member  7  to be capable of freely rotating via the second joint  6 . 
     In addition, a shoe-shaped grounding member  8  is connected at a lower end of the second link member  7  of each leg link mechanism  3 . When the user M wears the walking assist device  1 , the left and right sole parts of the user M are inserted into the grounding member  8 . 
     Furthermore, a drive device  9  is attached to the leg link mechanism  3 . The drive device  9  is a combination of a motor and a reduction gear mechanism (neither of which is illustrated) and is electrically connected to an assist controller  11 . The drive device  9  drives an angle between the second link member  7  and the first link member  5  to change by being controlled by the assist controller  11  as will be described below. Accordingly, an assisting force for supporting a body weight of the user M is generated and thus the user M can be assisted with walking. 
     Next, the control device  10  will be described with reference to  FIG. 3 . As illustrated in the drawing, the control device  10  includes the assist controller  11  and a battery  12 , and both the assist controller  11  and the battery  12  are built in the seat member  2 . 
     The assist controller  11  is configured as a microcomputer including a CPU, a RAM, a ROM, an I/O interface, a wireless communication circuit, various electric circuits (none of which are illustrated), and the like, and operates by receiving supply of power from the battery  12 . The ROM stores various programs for executing a motion state estimation process, and the like, which will be described below. 
     Further, in the present embodiment, the assist controller  11  corresponds to a standing state estimation part, a waist movement state parameter calculation part, a motion estimation part, a control part, a forward tilt angle calculation part, a sitting state estimation part, and a forward tilt state parameter calculation part. 
     The assist controller  11  is electrically connected to a left foot pressure sensor  20 , a right foot pressure sensor  21 , a left joint force sensor  22 , a right joint force sensor  23 , a seating force sensor  24 , a gripping force sensor  25 , a left foot motion sensor  26 , a right foot motion sensor  27 , a waist motion sensor  28 , and a head motion sensor  29 . 
     The left foot pressure sensor  20  and the right foot pressure sensor  21  are built in the bottoms of the left and right grounding members  8  and  8 , respectively, detect pressure acting on the bottoms of the left and right grounding members  8  and  8 , and output detection signals indicating the pressure to the assist controller  11 . The assist controller  11  determines the left and right sole parts of the user M to be in contact with the grounding member  8  on the basis of the detection signals of the left and right foot pressure sensors  20  and  21 . 
     In addition, the left joint force sensor  22  and right joint force sensor  23  are provided in the left and right second joints  6  and  6 , respectively, detect forces acting on the joints, and output detection signals indicating the forces to the assist controller  11 . 
     Furthermore, the seating force sensor  24  detects a force acting between the seat member  2  and the thighs of the user M and outputs a detection signal indicating the force to the assist controller  11 , and the gripping force sensor  25  detects a force acting on a grip part  2 a of the seat member  2  and outputs a detection signal indicating the force to the assist controller  11 . 
     Meanwhile, the left foot motion sensor  26  and the right foot motion sensor  27  are of an inertial measurement unit type, are provided on the sole parts of the left and right grounding members  8  and  8 , and are configured to be capable of performing wireless communication with the assist controller  11 . The left and right foot motion sensors  26  and  27  detect three-axis (x, y, and z axes) accelerations, three-axis rotation angles, and three-axis positions of the left and right grounding members  8  and  8  and output detection signals indicating the values to the assist controller  11  as radio signals. 
     The assist controller  11  computes three-axis speeds, positions, and the like of the left and right sole parts of the user M on the basis of the detection signals from the left and right foot motion sensors  26  and  27 . Further, in the present embodiment, the left foot motion sensor  26  corresponds to a first motion sensor, and the right foot motion sensor  27  corresponds to a second motion sensor. 
     In addition, the waist motion sensor  28  is of an inertial measurement unit type as well, and is configured to be worn around the waist part of the user M in the form of a belt or the like and capable of wirelessly communicating with the assist controller  11 . The waist motion sensor  28  detects a three-axis (x, y, and z axes) acceleration, a three-axis rotation angle, and a three-axis position of the waist part of the user M and outputs detection signals indicating the values to the assist controller  11  as radio signals. 
     The assist controller  11  calculates a three-axis speed, position, and the like of the waist part of the user M on the basis of the detection signals of the waist motion sensor  28 . Further, in the present embodiment, the waist motion sensor  28  corresponds to a third motion sensor. 
     Furthermore, the head motion sensor  29  is of an inertial measurement unit type as well, and is configured to be worn on the top of the head of the user M in the form of a hat or the like and capable of wirelessly communicating with the assist controller  11 . The head motion sensor  29  detects a three-axis (x, y, and z axes) acceleration, a three-axis rotation angle, and a three-axis position of the top of the head of the user M and outputs detection signals indicating the values to the assist controller  11  as radio signals. 
     The assist controller  11  calculates a tilt angle, a position, and the like of the head part of the user M on the basis of the detection signals of the head motion sensor  29 . In this case, the tilt angle of the head part of the user M is calculated to indicate a positive value in a forward tilting direction, that is, a bowing direction. Further, in the present embodiment, the head motion sensor  29  corresponds to a fourth motion sensor. 
     In addition, with respect to the four above-described motion sensors  26  to  29 , when the user M wearing the walking assist device  1  is in a standing state and the attachment positions of the sensors are set to the origin, the front-rear direction in a room coordinate system is set as an x-axis direction, the left-right direction is set as a y-axis direction, and the top-bottom direction is set as a z-axis direction. In addition, with respect to each of the sensors, a detection value forward from the origin in the x-axis direction is set as a positive value, a detection value rearward from the origin in the x-axis direction is set as a negative value, and a detection value to the left of the origin in the y-axis direction is set as a positive value and a detection value to the right of the origin in the y-axis direction is set as a negative value. Furthermore, a detection value above the origin in the z-axis direction is set as a positive value, and a detection value below the origin in the z-axis direction is set as a negative value. 
     The assist controller  11  causes a motion estimation process to be performed in accordance with detection signals of the four above-described motion sensors  26  to  29 , and as will be described below, causes an assist control process to be performed in accordance with detection signals of the ten sensors  20  to  29 . 
     Next, the principle of motion estimation by the assist controller  11  will be described. First, the principle of the method for estimating whether the user M has started a crouching motion from a standing state will be described with reference to  FIG. 4 . The drawing illustrates change in posture of a healthy subject M 2  who does not need the walking assist device  1  acquired using a motion capture method in the case where the subject repeats a crouching motion from a standing state many times to be in a crouching state and an average of the change. 
     In the drawing, COP represents an application point of a floor reaction force, and Lc represents a vertical line (i.e., a z-axis line) passing the origin of the x, y, and z axes of the waist motion sensor  28 . In addition, the arrow Art represents a movement speed of the waist part in the x-axis direction, the arrow Ar 2  represents a movement speed of the waist part in the z-axis direction, and the arrow Ar 3  extending upward from the application point of a floor reaction force COP represents a reaction force from the floor. The above-described matters also apply to  FIGS. 5 to 7 , which will be described below. 
     In a case where the subject M 2  performs a crouching motion from a standing state as illustrated in  FIG. 4 , the subject M 2  first tilts only his or her head part from the standing posture A 1 , and thereby the posture changes to a looking-down posture A 2 . Next, when the subject M 2  tilts his or her upper body forward while moving his or her waist backward from the looking-down posture A 2 , the posture transitions to the forward tilt posture A 3 . Then, when the subject M 2  drops his or her waist from the forward tilt posture A 3 , the posture transitions to a middle waist posture A 4 , and when the subject further drops his or her waist, the posture transitions to a middle waist posture A 5 . 
     In addition, when the subject M 2  further drops his or her waist from the middle waist posture A 5 , the posture of the subject finally reaches a crouching posture A 6 . Since the crouching motion is performed as described above, it is ascertained that, in a case where whether the user M has started a crouching motion from a standing state is to be estimated, it is good to determine whether a posture of the user M has transitioned from the standing posture A 1  to the forward tilt posture A 3 . Based on the above-described principle, a start of a crouching motion is estimated in the present embodiment using an estimation method which will be described below. 
     Next, the principle of a method for estimating whether the user M has started a standing-up motion from a sitting state will be described with reference to  FIG. 5 . The drawing illustrates change in posture of the above-described subject M 2  acquired using a motion capture method in the case where the subject repeats a standing-up motion performed from a sitting state many times to be in a standing state and an average of the change. 
     As illustrated in the drawing, in a case where the subject M 2  performs a standing-up motion from a sitting state, the subject M 2  first tilts only his or her head part forward from a sitting posture B 1 , and thereby the posture changes to a looking-down posture B 2 . Next, when the subject M 2  tilts his or her upper body forward from the looking-down posture B 2 , the posture transitions to a forward tilt posture B 3 . Then, when the subject M 2  moves his or her waist obliquely upward from the forward tilt posture B 3 , the posture of the subject M 2  transitions to a middle waist posture B 4 , and when the subject moves his or her waist upward from the middle waist posture B 4 , the posture transitions to a middle waist posture B 5 . 
     Then, when the subject M 2  moves his or her waist further upward from the middle waist posture B 5 , the posture of the subject M 2  finally reaches a standing posture B 6 . Since the standing-up motion is performed as described above, it is ascertained that, in a case where whether the user M has started a standing-up motion from a sitting state is to be estimated, it is good to determine whether a posture of the user M has transitioned from the sitting posture B 1  to the forward tilt posture B 3 . Based on the above-described principle, a start of a standing-up motion can be estimated in the present embodiment using the estimation method which will be described below. 
     Next, the principle of a method for estimating whether the user M has started a walking motion from a standing state will be described with reference to  FIG. 6  and  FIG. 7 .  FIG. 6  illustrates change in posture of the above-described subject M 2  acquired using a motion capture method when the subject repeats a walking start motion many times from a standing state to be in a walking state and an average of the change, and  FIG. 7  illustrates a side tilt posture C 2  of  FIG. 6  viewed from above. 
     In a case where the subject M 2  performs a walking motion from a standing state as illustrated in  FIG. 6 , when the subject M 2  first moves his or her waist part obliquely forward from a standing posture C 1  (forward and obliquely to the right in  FIG. 6  and  FIG. 7 ), the posture changes to the side tilt posture C 2 . Next, when the subject M 2  raises his or her foot on the side opposite to the direction in which the waist was moved, the posture transitions to a foot-up posture C 3 . Then, although not illustrated, when the subject M 2  moves his or her waist toward his or her foot while putting the raised foot on the floor, the subject M 2  transitions to a walking motion state. 
     Since the subject M 2  performs a walking motion as described above, it is ascertained that it is good to determine whether a posture of the user M has transitioned from the standing posture C 1  to the side tilt posture C 2 . Based on the above-described principle, a start of a walking motion is estimated in the present embodiment using the estimation method which will be described below. 
     Next, the motion state estimation process will be described with reference to  FIG. 8 . The motion state estimation process is to estimate a motion state of a user M wearing the walking assist device  1  (which will be referred to simply as a “user M” below) and is performed by the assist controller  11  on a predetermined control cycle. Further, various values calculated and set in the following description are assumed to be stored in the RAM of the assist controller  11 . 
     First, a walking estimation process is performed as shown in the drawing ( FIG. 8 /STEP  1 ). The walking estimation process is to estimate whether the user M is in a walking state, and specifically, performed as illustrated in  FIG. 9 . 
     First, whether all of VA_LFx&lt;Vlow, VA_LFy&lt;Vlow, and VA_LFz&lt;Vlow are satisfied is determined as shown in the drawing ( FIG. 9 /STEP  20 ). In this case, VA_LFx represents the absolute value of an x-axis speed of the left sole part of the user M, VA_LFy represents the absolute value of a y-axis speed of the left sole part of the user M, and VA_LFz represents the absolute value of a z-axis speed of the left sole part of the user M, and these values are calculated on the basis of detection signals of the left foot motion sensor  26 . In addition, Vlow represents a positive predetermined value satisfying Vlow≈0. 
     If the result of the determination is negative ( FIG. 9 /NO in STEP  20 ), that is, if the left sole part of the user M is in a moving state, the user M is estimated to be walking, and a walking flag F_WALK is set to “1,” and at the same time both a walking end flag F_WALK_END and a stop flag F_STOP are set to “0” to indicate the state ( FIG. 9 /STEP  21 ). Then, the process ends. 
     On the other hand, if the result of the determination is positive ( FIG. 9 /YES in STEP  20 ), that is, if the left sole part of the user M is in a stop state, it is determined whether all of VA_RFx&lt;Vlow, VA_RFy&lt;Vlow, and VA_RFz&lt;Vlow are satisfied ( FIG. 9 /STEP  22 ). In this case, VA_RFx represents the absolute value of an x-axis speed of the right sole part of the user M, VA_RFy represents the absolute value of a y-axis speed of the right sole part of the user M, and VA_RFz represents the absolute value of a z-axis speed of the right sole part of the user M, and these values are calculated on the basis of detection signals of the right foot motion sensor  27 . 
     If the result of the determination is negative ( FIG. 9 /NO in STEP  22 ), that is, if the right sole part of the user M is in a moving state, the user M is estimated to be walking, and to indicate the state, the walking flag F_WALK is set to “1,” and at the same time, both the walking end flag F_WALK_END and the stop flag F_STOP are set to “0” as described above ( FIG. 9 /STEP  21 ). Then, the present process ends. 
     On the other hand, if the result of the above-described determination is positive ( FIG. 9 /YES in STEP  22 ), that is, if both the left sole part and the right sole part of the user M are in the stop state, whether the walking end flag F_WALK_END is “1” is determined ( FIG. 9 /STEP  23 ). 
     If the result of the determination is negative ( FIG. 9 /NO in STEP  23 ), whether the stop flag F_STOP stored in the RAM is “0” is determined ( FIG. 9 /STEP  24 ). 
     If the result of the determination is positive ( FIG. 9 /YES in STEP  24 ), that is, if both the left sole part and the right sole part of the user M are in the stop state at the current control timing, the stop flag F_STOP is set to “1” to indicate the state ( FIG. 9 /STEP  25 ). Next, the previous counted value CTz of the stop counter is set to “0” ( FIG. 9 /STEP  26 ). 
     On the other hand, if the result of the determination is negative ( FIG. 9 /NO in STEP  24 ), that is, if both the left sole part and the right sole part of the user M had been in the stop state at the control timing before the previous timing, the previous counted value CTz of the stop counter is set to a current counted value CT of the stop counter stored in the RAM ( FIG. 9 /STEP  27 ). 
     As described above, after the previous counted value CTz of the stop counter is set to the value “0” or the current value “CT,” the current counted value CT of the stop counter is set to the sum of the previous value CTz and the value “1” CTz+ 1  ( FIG. 9 /STEP  28 ). That is, the current counted value CT of the stop counter is incremented by “1.” 
     Next, whether the current counted value CT of the stop counter is greater than a predetermined stop value Cstop is determined ( FIG. 9 /STEP  29 ). If the result of the determination is negative ( FIG. 9 /NO in STEP  29 ), the present process ends as it is. 
     On the other hand, if the result of the determination is positive ( FIG. 9 /YES in STEP  29 ), the user M is determined to have ended the walking, and the walking end flag F_WALK_END is set to “1” to indicate the state ( FIG. 9 /STEP  30 ). 
     If the walking end flag F_WALK_END is set to “1” as described above or the result of the above-described determination is positive ( FIG. 9 /YES in STEP  23 ), successively, the walking flag F_WALK is set to “0” and at the same time the stop flag F_STOP is reset to “0” to indicate that the user M is not walking ( FIG. 9 /STEP  31 ). Then, the present process ends. 
     Returning to  FIG. 8 , after the walking estimation process ( FIG. 8 /STEP  1 ) is performed as described above, whether the above-described walking flag F_WALK is “1” is determined ( FIG. 8 /STEP  2 ). If the result of the determination is positive ( FIG. 8 /YES in STEP  2 ), that is, if the user M is estimated to be walking, the present process ends as it is. 
     On the other hand, if the result of the determination is negative ( FIG. 8 /NO in STEP  2 ) and the user M is estimated not to be walking, whether both P_W&gt;P_LF and P_W&gt;P_RF are satisfied is determined ( FIG. 8 /STEP  3 ). In this case, P_W represents a position of the waist part of the user M and is calculated on the basis of a detection signal of the waist motion sensor  28 . In addition, P_LF represents a position of the left sole part of the user M and is calculated on the basis of a detection signal of the left foot motion sensor  26 . Furthermore, P_RF represents a position of the right sole part of the user M and is calculated on the basis of a detection signal of the right foot motion sensor  27 . 
     If the result of the determination is positive ( FIG. 8 /YES in STEP  3 ), a waist part height deviation DH is set to a deviation H_W max-H_W of a maximum waist part height H_W_max and a waist part height H_W ( FIG. 8 /STEP  4 ). The maximum waist part height H_W_max represents a height of the waist part of the user M when the user M is in a standing state and is set at the time of initialization process when the user M wears the walking assist device  1 . In addition, the waist part height H_W is a current height of the waist part of the user M and is calculated on the basis of a detection signal of the waist motion sensor  28 . 
     Next, whether the waist part height deviation DH is greater than a predetermined sitting determination value Dsit is determined ( FIG. 8 /STEP  5 ). If the result of the determination is positive ( FIG. 8 /YES in STEP  5 ), the user M is estimated to be in a sitting state and a sitting state flag F_SIT is set to “1” and a standing state flag F_STAND is set to “0” to indicate the state ( FIG. 8 /STEP  6 ). Then, the present process ends. 
     On the other hand, if the result of the determination is negative ( FIG. 8 /NO in STEP  5 ) and DH&lt;Dsit is satisfied, whether the waist part height deviation DH is greater than a predetermined standing determination value Dstand is determined ( FIG. 8 /STEP  7 ). The standing determination value Dstand is set to satisfy Dstand&lt;Dsit. 
     If the result of the determination is positive ( FIG. 8 /YES in STEP  7 ), the user M is estimated to be in a standing state, and the standing state flag F_STAND is set to “1” and the sitting state flag F_SIT is set to “0,” respectively, to indicate the state ( FIG. 8 /STEP  8 ). Then, the present process ends. 
     On the other hand, if the result of the above-described determination is negative and at least one of P_W≤P_LF and P_W≤P_RF is satisfied ( FIG. 8 /NO in STEP  3 ) or Dsit≤DH&lt;Dstand is satisfied ( FIG. 8 /NO in STEP  7 ), the user M is estimated to be in neither a sitting state nor a standing state, and both the sitting state flag F_SIT and the standing state flag F_STAND are set to “0” ( FIG. 8 /STEP  9 ) to indicate the state. Then, the present process ends. 
     As described above, if the user M is estimated to be in a walking state in the motion state estimation process, the walking flag F_WALK is set to “1,” if the user M is estimated to be in a sitting state, the sitting state flag F_SIT is set to “1,” and if the user M is estimated to be in a standing state, the standing state flag F_STAND is set to “1.” 
     Next, a motion start estimation process will be described with reference to  FIG. 10 . The motion start estimation process is to estimate a start of a motion of a user M wearing the walking assist device  1  (which will be referred to simply as a “user M” below) using a method based on the above-described estimation principle and is performed by the assist controller  11  on a predetermined control cycle. 
     First, whether the above-described standing state flag F_STAND is “1” is determined as shown in the drawing ( FIG. 10 /STEP  40 ). If the result of the determination is positive ( FIG. 8 /YES in STEP  40 ), that is, if the user M is estimated to be in a standing state, a crouching start estimation process is performed ( FIG. 10 /STEP  41 ). 
     The crouching start estimation process is to estimate whether the user M, who is in a standing state, has started a crouching motion and is performed specifically as shown in  FIG. 11 . First, whether a head part forward tilt flag F_HEAD_DWN is “1” is determined as shown in the drawing ( FIG. 11 /STEP  50 ). 
     If the result of the determination is negative ( FIG. 11 /NO in STEP  50 ), whether θhead&gt;θjud is satisfied is determined ( FIG. 11 /STEP  51 ). Ahead represents a forward tilt angle of the head part of the user M and is calculated on the basis of a detection signal of the head motion sensor  29 . In addition, θjud is a determination value for determining whether the user M looks down in a forward direction. 
     If the result of the determination is negative ( FIG. 11 /NO in STEP  51 ) and the user M is not looking down in the forward direction, the head part forward tilt flag F_HEAD_DWN is set to “0” to indicate the state ( FIG. 11 /STEP  52 ). Next, the user M is estimated not to be starting a crouching motion and a crouching start flag F_SIT_ST is set to “0” to indicate the state ( FIG. 11 /STEP  53 ). Then, the present process ends. 
     On the other hand, if the result of the determination is positive ( FIG. 11 /YES in STEP  51 ) and θhead&gt;θjud is satisfied, the user M is estimated to be looking down in the forward direction and the head part forward tilt flag F_HEAD_DWN is set to “1” to indicate the state ( FIG. 11 /STEP  54 ). 
     If the head part forward tilt flag F_HEAD_DWN is set to “1” or if the result of the above-described determination is positive ( FIG. 11 /YES in STEP  50 ) and the head part forward tilt flag F_HEAD_DWN is set to “1” at the timing prior to the previous timing as described above, whether V_Wx&lt;0 is satisfied is successively determined ( FIG. 11 /STEP  55 ). V_Wx is an x-axis speed of the waist part of the user M and is calculated on the basis of a detection signal of the waist motion sensor  28 . 
     If the result of the determination is negative ( FIG. 11 /NO in STEP  55 ), the crouching start flag F_SIT_ST is set to “0” as described above ( FIG. 11 /STEP  53 ), and then the present process ends. 
     On the other hand, if the result of the determination is positive ( FIG. 11 /YES in STEP  55 ), that is, the user M is estimated to be moving his or her waist part backward, whether VA_Wx&gt;Vjud 1  is satisfied is determined ( FIG. 11 /STEP  56 ). VA_Wx is the absolute value of the x-axis speed of the waist part of the user M, and Vjud 1  represents a predetermined determination value for determining whether the user M is actually moving his or her waist part backward. Further in the present embodiment, the x-axis speed V_Wx and the absolute value VA_Wx of the waist part correspond to waist movement state parameters. 
     If the result of the determination is negative ( FIG. 11 /NO in STEP  56 ), the crouching start flag F_SIT ST is set to “0” as described above ( FIG. 11 /STEP  53 ), and then the present process ends. 
     On the other hand, if the result of the determination is positive ( FIG. 11 /YES in STEP  56 ), that is, if the user M is estimated to be actually moving his or her waist part backward, whether TMsit&gt;Tjud 1  is satisfied is determined ( FIG. 11 /STEP  57 ). TMsit represents a time elapsed in a state in which V_Wx&lt;0 and VA_Wx&gt;Vjud 1  are satisfied, and Tjud 1  represents a predetermined determination value for determining whether the user M is actually moving his or her waist part backward. 
     If the result of the determination is negative ( FIG. 11 /NO in STEP  57 ), the crouching start flag F_SIT_ST is set to “0” as described above ( FIG. 11 /STEP  53 ), and then the present process ends. 
     On the other hand, if the result of the determination is positive ( FIG. 11 /YES in STEP  57 ), the user M is estimated to have started a crouching motion, and the crouching start flag F_SIT_ST is set to “1,” and at the same time, the head part forward tilt flag F_HEAD_DWN is reset to “0” to indicate the state ( FIG. 11 /STEP  58 ). Then, the present process ends. 
     Returning to  FIG. 10 , after the crouching start estimation process ( FIG. 10 /STEP  41 ) is performed as described above, whether the above-described crouching start flag F_SIT_ST is “1” is determined ( FIG. 10 /STEP  42 ). If the result of the determination is positive ( FIG. 10 /YES in STEP  42 ) and the user M is estimated to have started the crouching motion, the present process ends as it is. 
     On the other hand, if the result of the determination is negative ( FIG. 10 /NO in STEP  42 ), a walking start estimation process is performed ( FIG. 10 /STEP  43 ). This walking start estimation process is to estimate whether the user M who is in a standing state has started a walking motion and is performed specifically as shown in  FIG. 12 . 
     First, whether V_Wx&gt;Vjud 2  is satisfied is determined as shown in the drawing ( FIG. 12 /STEP  70 ). Vjud 2  is a determination value for determining whether the waist part of the user M is actually moving forward. 
     If the result of the determination is negative ( FIG. 12 /NO in STEP  70 ), that is, if the waist part of the user M is estimated not to be moving forward, the user M is estimated not to have started a walking motion, and a walking start flag F_WALK_ST is set to “0” to indicate the state ( FIG. 12 /STEP  74 ). Then, the present process ends. 
     On the other hand, if the result of the determination is positive ( FIG. 12 /YES in STEP  70 ), whether VA_Wy&gt;Vjud 3  is satisfied is determined ( FIG. 12 /STEP  71 ). VA_Wy represents the absolute value of a y-axis speed of the waist part of the user M, and Vjud 3  represents a predetermined determination value for determining whether the user M is actually moving his or her waist part in the left-right direction. Further, in the present embodiment, the absolute value of the y-axis speed of the waist part VA_Wy corresponds to a waist movement state parameter. 
     If the result of the determination is negative ( FIG. 12 /NO in STEP  71 ), the walking start flag F_WALK_ST is set to “0” ( FIG. 12 /STEP  74 ) as described above, and then the present process ends. 
     On the other hand, if the result of the determination is positive ( FIG. 12 /YES in STEP  71 ), and if the user M is estimated to be actually moving his or her waist part in the left-right direction, whether TMwlk&gt;Tjud 2  is satisfied is determined ( FIG. 12 /STEP  72 ). TMwlk represents a time elapsed in a state in which V_Wx&gt;Vjud 2  and VA_Wy&gt;Vjud 3  are satisfied, and Tjud 2  represents a predetermined determination value for determining whether the user M is actually moving his or her waist part obliquely forward. 
     If the result of the determination is negative ( FIG. 11 /NO in STEP  72 ), the walking start flag F_WALK_ST is set to “0” ( FIG. 12 /STEP  74 ) as described above, and then the present process ends. 
     On the other hand, if the result of the determination is positive ( FIG. 11 /YES in STEP  72 ), the user M is estimated to have started a walking motion, and the walking start flag F_WALK_ST is set to “1” to indicate the state ( FIG. 12 /STEP  73 ). Then, the present process ends. 
     Returning to  FIG. 10 , after the walking start estimation process ( FIG. 10 /STEP  43 ) is performed as described above, the motion start estimation process ends. 
     On the other hand, if the result of the above-described determination is negative ( FIG. 10 /NO in STEP  40 ), that is, the standing state flag F_STAND is “0,” whether the above-described sitting state flag F_SIT is “1” is determined ( FIG. 10 /STEP  44 ). If the result of the determination is negative ( FIG. 10 /NO in STEP  44 ), that is, the user M is neither in a standing state nor a sitting state, the present process ends. 
     On the other hand, if the result of the determination is positive ( FIG. 10 /YES in STEP  44 ) and the user M is in a sitting state, a standing-up start estimation process is performed ( FIG. 10 /STEP  45 ). The standing-up start estimation process is to estimate whether the user M who is in the sitting state has started a standing-up motion and is performed specifically as shown in  FIG. 13 . 
     First, whether the head part forward tilt flag F_HEAD_DWN is “1” is determined ( FIG. 13 /STEP  80 ) as shown in the drawing. 
     If the result of the determination is negative ( FIG. 13 /NO in STEP  80 ), whether θhead&gt;θjud is satisfied is determined ( FIG. 13 /STEP  81 ). If the result of the determination is negative ( FIG. 13 /NO in STEP  81 ) and the user M is not looking down in the forward direction, the head part forward tilt flag F_HEAD_DWN is set to “0” ( FIG. 13 /STEP  82 ). 
     Next, the user M is estimated not to have started a standing-up motion, a standing-up start flag F_STA_ST is set to “0” to indicate the state ( FIG. 13 /STEP  83 ). Then, the present process ends. 
     On the other hand, if the result of the determination is positive ( FIG. 13 /YES in STEP  81 ) and θhead&gt;θjud is satisfied, the user M is estimated to be looking down in the forward direction and the head part forward tilt flag F_HEAD_DWN is set to “1” to indicate the state ( FIG. 13 /STEP  84 ). 
     If the head part forward tilt flag F_HEAD_DWN is set to “1” as described above or if the result of the determination is positive ( FIG. 13 /YES in STEP  80 ) and the head part forward tilt flag F_HEAD_DWN is set to “1” at the timing before the previous timing, whether θupper&gt;θjud 2  is satisfied is determined ( FIG. 13 /STEP  85 ). 
     θupper represents a forward tilt angle of the upper body of the user M and is calculated on the basis of detection signals of the waist motion sensor  28  and the head motion sensor  29 . In addition, θjud 2  represents a predetermined determination value for determining whether the user M has started a standing-up motion. Further, in the present embodiment, the forward tilt angle of the upper body θupper corresponds to a forward tilt state parameter. 
     If the result of the determination is negative ( FIG. 13 /NO in STEP  85 ), the standing-up start flag F_STA_ST is set to “0” as described above ( FIG. 13 /STEP  83 ), and then the present process ends. 
     On the other hand, if the result of the determination is positive ( FIG. 13 /YES in STEP  85 ), that is, if the user M is estimated to have his or her upper body tilt forward, whether TMsta&gt;Tjud 2  is satisfied is determined ( FIG. 13 /STEP  86 ). TMsta represents a time elapsed in a state in which θupper&gt;θjud 2  is satisfied, and Tjud 2  represents a predetermined determination value for determining whether the user M is actually tilting his or her upper body forward. 
     If the result of the determination is negative ( FIG. 13 /NO in STEP  86 ), the standing-up start flag F_STA_ST is set to “0” as described above ( FIG. 13 /STEP  83 ), and then the present process ends. 
     On the other hand, if the result of the determination is positive ( FIG. 13 /YES in STEP  86 ), the user M is estimated to have started a standing-up motion, the standing-up start flag F_STA_ST is set to “1” to indicate the state, and at the same time, the head part forward tilt flag F_HEAD_DWN is reset to “0” ( FIG. 13 /STEP  87 ). Then, the present process ends. 
     Returning to  FIG. 10 , after the standing-up start estimation process ( FIG. 10 /STEP  45 ) is performed as described above, the motion start estimation process ends. In the motion start estimation process of  FIG. 10 , a start of a walking motion, a start of a standing-up motion, a start of a crouching motion, and the like are estimated as described above. 
     Next, an assist control process will be described with reference to  FIG. 14 . The assist control process is to control the walking assist device  1  according to a motion state of the user M and is performed by the assist controller  11  on a predetermined control cycle. 
     First, whether the above-described walking flag F_WALK is “1” is determined ( FIG. 14 /STEP  90 ) as shown in the drawing. If the result of the determination is positive ( FIG. 14 /YES in STEP  90 ) and the user M is walking, a walking time control process is performed ( FIG. 14 /STEP  91 ). 
     In the walking time control process, the drive device  9  is controlled such that an assisting force for helping and/or supporting a walking motion of the user M is generated in accordance with detection signals of the above-described various sensors  20  to  29 . After the walking time control process is performed as described above, the present process ends. 
     On the other hand, if the result of the above-described determination is negative ( FIG. 14 /NO in STEP  90 ) and the user M is not walking, whether the above-described walking start flag F_WALK_ST is “1” is determined ( FIG. 14 /STEP  92 ). 
     If the result of the determination is positive ( FIG. 14 /YES in STEP  92 ) and the user M has started a walking motion, the walking time control process is performed as described above ( FIG. 14 /STEP  91 ), and then the present process ends. 
     On the other hand, if the result of the above-described determination is negative ( FIG. 14 /NO in STEP  92 ), whether the above-described crouching start flag F_SIT_ST is “1” is determined ( FIG. 14 /STEP  93 ). If the result of the determination is positive ( FIG. 14 /YES in STEP  93 ) and the user M has started a crouching motion, a crouching time control process is performed ( FIG. 14 /STEP  94 ). 
     In the crouching time control process, the drive device  9  is controlled such that an assisting force for helping and/or supporting a crouching motion of the user M is generated in accordance with detection signals of the above-described various sensors  20  to  29 . After the crouching time control process is performed as described above, the present process ends. 
     On the other hand, if the result of the above-described determination is negative ( FIG. 14 /NO in STEP  93 ), whether the above-described standing-up start flag F_STA_ST is “1” is determined ( FIG. 14 /STEP  95 ). If the result of the determination is positive ( FIG. 14 /YES in STEP  95 ) and the user M has started a standing-up motion, a standing-up time control process is performed ( FIG. 14 /STEP  96 ). 
     In the standing-up time control process, the drive device  9  is controlled such that an assisting force for helping and/or supporting a standing-up motion of the user M is generated in accordance with detection signals of the above-described various sensors  20  to  29 . After the standing-up time control process is performed as described above, the present process ends. 
     On the other hand, if the result of the above-described determination is negative ( FIG. 14 /NO in STEP  95 ), a normal control process is performed ( FIG. 14 /STEP  97 ). In this normal control process, when it is necessary to help and/or support a motion of the user M, the drive device  9  is controlled such that an assisting force is generated in accordance with detection signals of the above-described various sensors  20  to  29 . After the normal control process is performed as described above, the present process ends. 
     Next, transition of each parameter when the user M performs a crouching motion from a standing state and the like will be described with reference to  FIG. 15 . Further, VA_Wz in the drawing represents the absolute value of a z-axis speed of the waist part of the user M, and Vjusz represents a predetermined determination value for determining whether the user M has actually started to sit down. 
     As the user M starts the crouching motion at time t 1 , the forward tilt angle of the head part of the user M  0 head starts increasing as illustrated in the drawing. Then, the head part forward tilt flag F_HEAD_ DWN is set to “1” at the timing at which θhead&gt;θjud is satisfied (time t 1 ). 
     Then, when the user M moves his or her waist part backward, VA_Wx&gt;Vjud 1  is satisfied (time t 2 ). Then, when the user M is estimated to have started the crouching motion at the timing when a time corresponding to a determination value Tjud 1  has elapsed from the timing at which VA_Wx&gt;Vjud 1  was satisfied (time t 3 ), the crouching start flag F_SIT_ST is set to “1,” and at the same time, the head part forward tilt flag F_HEAD_DWN is set to “0.” 
     Accordingly, the crouching motion of the user M is helped and/or supported due to the crouching time control process performed from the time t 3 . In this case, for example, if the walking assist device  1  starts control at the timing at which VA_Wz&gt;Vjudz is satisfied and the user M actually starts lowering his or her waist part (time t 4 ), the walking assist device  1  is likely to obstruct the crouching motion of the user M until the walking assist device  1  actually generates an assisting force. 
     In order to solve this problem, according to the control device  10  of the present embodiment, since the crouching time control process is performed at an earlier timing (time t 3 ) than the timing at which the user M actually starts lowering his or her waist part (time t 4 ), it is ascertained that the crouching motion of the user M can be appropriately supported and/or helped without the above-described problem. 
     According to the control device  10  of the present embodiment, whether the user M is in a standing state is estimated and whether the user M is in a sitting state is estimated in accordance with detection signals of the left and right foot motion sensors  26  and  27  and the waist motion sensor  28  as described above. In this case, whether the user M is in a standing state can be accurately estimated and whether the user M is in a sitting state can also be accurately estimated using positional relations of the left and right sole parts with the waist part and with a height of the waist part. 
     In addition, the x-axis speed V_Wx and the absolute value VA_Wx of the waist part are calculated in accordance with a detection signal of the third motion sensor  28 , and the forward tilt angle of the head part  0 head is calculated in accordance with a detection signal of the fourth motion sensor  29 . In addition, if both θhead&gt;θjud, and V_Wx&lt;0 and VA_Wx&gt;Vjud 1  are satisfied in a case where the user M is estimated to be in a standing state, the user M is estimated to have started a crouching motion from the standing state. 
     In this case, when a human starts a crouching motion from a standing state, a looking-down motion of the head part and a motion of the waist part moving backward are performed first as described above, and thus whether the user has started a crouching motion from a standing state can be accurately estimated assuming that the above-described conditions (θhead&gt;θjud, V_Wx&lt;0, and VA_Wx&gt;Vjud 1 ) are satisfied. 
     Then, in a case where the user M is estimated to have started the crouching motion, the walking assist device  1  is controlled such that the crouching motion is supported, and thus the crouching motion of the user M can be quickly and appropriately supported by the walking assist device  1 . 
     In addition, if both V_Wx&gt;Vjud 2  and VA_Wy&gt;Vjud 3  are satisfied in a case where the user M is estimated to be in a standing state, the user M is estimated to have started a walking motion from the standing state. Since a movement of the waist part in a lateral direction is performed first in addition to a movement of the waist part forward when a human starts a walking motion from a standing state as described above, whether the user M has started the walking motion from the standing state can be accurately estimated assuming that the above-described conditions (V_Wx&gt;Vjud 2  and VA_Wy&gt;Vjud 3 ) are satisfied. 
     Then, in a case where the user M is estimated to have started the walking motion, the walking assist device  1  is controlled such that the walking motion is supported, and thus the walking motion of the user M can be quickly and appropriately supported by the walking assist device  1 . 
     Furthermore, if both θhead&gt;θjud and θupper&gt;θjud 2  are satisfied in a case where a forward tilt angle of the upper body θupper is calculated and the user M is estimated to be in a sitting state in accordance with detection signals of the third motion sensor  28  and the fourth motion sensor  29 , the user M is estimated to have started a standing-up motion from the sitting state. 
     In this case, since a looking-down motion of the head part and a forward tilting motion of the upper body are performed first when a human starts a standing-up motion from a sitting state as described above, whether the user M has started the standing-up motion from the sitting state can be accurately estimated assuming that the above-described conditions (θhead&gt;θjud and θupper&gt;θjud 2 ) are satisfied. 
     Then, in a case where the user M is estimated to have started the standing-up motion, the walking assist device  1  is controlled such that the standing-up motion is supported, and thus the standing-up motion of the user M can be quickly and appropriately supported by the walking assist device  1 . 
     Further, in the crouching start estimation process of the embodiment in  FIG. 11 , the processes of STEPS  50  to  52  and  54  may be omitted, and the determination value Vjud 1  of STEP  56  may be set to a greater value than that of  FIG. 11 . The reason for this operation is that, since there are cases of transition from the standing posture A 1  to the forward tilt posture A 3  with the head part of the user M in the looking-down posture A 2  tilting at a smaller angle, a start of a crouching motion can be accurately estimated even if determination of whether a posture has changed from the standing posture A 1  to the looking-down posture A 2  is omitted. 
     Furthermore, the crouching start estimation process of the embodiment in  FIG. 11 , whether the tilt angle of the upper body of the user M exceeds a predetermined value may be determined or whether a tilt angle speed of the upper body of the user M exceeds a predetermined value may be determined instead of performing the determination processes of STEP  55  and  56 , and if the result of the determination is positive, the process of STEP  57  may be performed. Even with the above-described configuration, a start of a crouching motion can be accurately estimated. 
     On the other hand, in the walking start estimation process of the embodiment in  FIG. 12 , the process of STEP  70  may be omitted, and the determination value Vjud 3  of STEP  71  may be set to a greater value than that of  FIG. 12 . The reason for this operation is that, since there are cases where the user M has a small forward movement amount when he or she transitions from the standing posture C 1  to the side tilt posture C 2 , a start of a walking motion can be accurately estimated even if determination of whether the user M has moved forward is omitted. 
     In addition, in the standing-up start estimation process of the embodiment in  FIG. 13 , the processes of STEPS  80  to  82  and  84  may be omitted, and the determination value θjud 2  of STEP  85  may be set to a greater value than that of  FIG. 13 . The reason for this operation is that, since there are cases of transition from the sitting posture B 1  to the forward tilt posture B 3  with the head part of the user M in the looking-down posture B 2  tilting at a smaller angle, a start of a standing-up motion can be accurately estimated even if determination of whether a posture has changed from the sitting posture B 1  to the forward tilt posture B 3  is omitted. 
     On the other hand, although the embodiment includes an example in which the x-axis speed of the waist part V_Wx, the absolute value of the x-axis speed of the waist part VA_Wx, and the absolute value of the y-axis speed of the waist part VA_Wy are used as waist movement state parameters, waist movement state parameters of one or some exemplary embodiments of the disclosure are not limited thereto, and any value indicating a movement state of the waist part of the user may be used. For example, an x-axis acceleration and a y-axis speed of the waist part, and the absolute values thereof may be used as waist movement state parameters. 
     In addition, although the embodiment includes an example in which the forward tilt angle θupper of the upper body is used as a forward tilt state parameter, a forward tilt state parameter of one or some exemplary embodiments of the disclosure is not limited thereto, and any value indicating a forward tilt state of the upper body of the user M may be used. For example, a forward tilt angular speed (or forward tilt angular acceleration) of the upper body may be used as a forward tilt state parameter, and in this case, whether a forward tilt angular speed (or forward tilt angular acceleration) of the upper body of the user M exceeds a predetermined value may be determined, instead of performing the determination process of STEP  85  in the standing-up start estimation process of the embodiment in  FIG. 13 . 
     Furthermore, a positional relation of a center position of the head part in the upper body of the user M with a center position of the waist part of the user M may be used as a forward tilt state parameter, and in this case, whether the center position of the head part in the upper body is positioned forward from the center position of the waist part by a predetermined value may be determined, instead of performing the determination process of STEP  85  in the standing-up start estimation process of the embodiment in  FIG. 13 . 
     In addition, although the embodiment includes an example in which the active-type walking assist device  1  is used as a motion support device, a motion support device of one or some exemplary embodiments of the disclosure is not limited thereto, and any device that supports motions of at least the lower body of a human is possible. For example, an active-type assist device that supports motions of the upper body as well as the lower body of a human may be used as a motion support device. Furthermore, a passive-type walking assist device without a power source may be used as a motion support device. 
     On the other hand, although the embodiment includes an example in which the left foot motion sensor  26  is used as the first motion sensor, the first motion sensor of one or some exemplary embodiments of the disclosure is not limited thereto, and a sensor that detects motions of the left sole part may be used. For example, an acceleration sensor, a gyro sensor, or the like may be used as the first motion sensor. In addition, the left foot motion sensor  26  may be mounted direct 1 y on the left sole part of the user. 
     In addition, although the embodiment includes an example in which the right foot motion sensor  27  is used as the second motion sensor, the second motion sensor of one or some exemplary embodiments of the disclosure is not limited thereto, and a sensor that detects motions of the right sole part may be used. For example, an acceleration sensor, a gyro sensor, or the like may be used as the second motion sensor. In addition, the right foot motion sensor  27  may be mounted direct 1 y on the right sole part of the user. 
     In addition, although the embodiment includes an example in which the waist motion sensor  28  is used as the third motion sensor, the third motion sensor of one or some exemplary embodiments of the disclosure is not limited thereto, and a sensor that detects motions of the waist part may be used. For example, an acceleration sensor, a gyro sensor, or the like may be used as the third motion sensor. In addition, the waist motion sensor  28  may be provided in the seat member  2  of the walking assist device  1 . 
     On the other hand, although the embodiment includes an example in which the head motion sensor  29  is used as the fourth motion sensor, the fourth motion sensor of one or some exemplary embodiments of the disclosure is not limited thereto, and a sensor that detects motions of the head part may be used. For example, an acceleration sensor, a gyro sensor, or the like may be used as the fourth motion sensor.