Gait change determination device

1. A gait change determination device comprising:

a main body arranged to be worn by a user in a predetermined area;

an accelerometer that detects an acceleration of the main body; and

a control unit that is arranged and programmed to determine a change in a gait of the user; wherein

the control unit includes:

a specification unit that is arranged and programmed to, based on the acceleration detected by the accelerometer, specify a trajectory of the predetermined area on which the main body is worn during walking;

a first calculation unit that is arranged and programmed to calculate a temporal change in the trajectory specified by the specification unit; and

a determination unit that is arranged and programmed to, based on the temporal change calculated by the first calculation unit, determine a degree of change that is the degree of the temporal change.

2. The gait change determination device according to claim 1 , wherein

the control unit includes an acceptance unit that is arranged and programmed to accept an input of a level of fatigue when the user is walking;

the determination unit is arranged and programmed to determine the degree of change when the degree of change has been accepted by the acceptance unit;

the control unit further includes a storage unit that is arranged and programmed to store the level of fatigue accepted by the acceptance unit and the degree of change determined by the determination unit in association with each other in the storage unit; and

the determination unit is arranged and programmed to determine the level of fatigue that corresponds to the degree of change determined by the determination unit based on the level of fatigue and the degree of change stored in the storage unit.

3. The gait change determination device according to claim 2 , further comprising an alert unit, wherein the control unit includes an alert control unit that is arranged and programmed to communicate the level of fatigue determined by the determination unit using the alert unit.

4. The gait change determination device according to claim 1 , wherein

the trajectory is a three-dimensional trajectory from which a movement component in an advancement direction in which the predetermined area on which the main body is worn advances during walking has been removed, and a pattern of the trajectory includes a plurality of characteristic points that define characteristics of the pattern;

the specification unit is arranged and programmed to specify positions of the characteristic points in the trajectory projected, with the movement component in the advancement direction removed, onto planes perpendicular to each of three axial directions, including a vertical direction, the advancement direction, and a horizontal direction, based on the acceleration calculated by the accelerometer;

the first calculation unit includes:

a second calculation unit that is arranged and programmed to calculate values of characteristic factors of the trajectory based on the positions specified by the specification unit;

a third calculation unit that is arranged and programmed to, in accordance with a correlation relationship, determined in advance, between the values of the characteristic factors and the value of an index indicating the gait, calculate a value of the index, based on the values of the characteristic factors calculated by the second calculation unit; and

a fourth calculation unit that is arranged and programmed to calculate a temporal change amount of the index based on the value of the index calculated by the third calculation unit; and

the determination unit is arranged and programmed to determine the degree of change based on the temporal change amount calculated by the fourth calculation unit.

5. The gait change determination device according to claim 4 , wherein

the temporal change amount includes a temporal change amount of a gait posture;

the control unit includes a gait posture determination unit that determines the gait posture based on the value of the index calculated by the third calculation unit;

the fourth calculation unit is arranged and programmed to calculate the temporal change amount of the gait posture determined by the gait posture determination unit; and

the determination unit is arranged and programmed to determine the degree of change, including a posture change degree in the temporal change of the gait posture, based on the temporal change amount calculated by the fourth calculation unit.

6. The gait change determination device according to claim 4 , wherein the correlation relationship is indicated by a multi regression formula that is a relational expression between the values of the characteristic factors serving as a response variable and the value of the index serving as an explaining variable, obtained through a multi regression analysis.

7. The gait change determination device according to claim 6 ,

wherein the characteristic points include a first characteristic point when a first foot touches the ground, a second characteristic point when the trajectory reaches the highest position while the user is standing on the first foot, a third characteristic point when a second foot touches the ground, and a fourth characteristic point when the trajectory reaches the highest position while the user is standing on the second foot;

the characteristic factors include a first characteristic factor that is a distance between the first characteristic point and the second characteristic point in the vertical direction in the trajectory projected onto the plane that is perpendicular to the advancement direction, and a second characteristic factor that is calculated from a distance between the first characteristic point and the second characteristic point and a distance between the third characteristic point and the fourth characteristic point in the trajectory projected onto the plane that is perpendicular to the horizontal direction;

the index includes a step size; and

the multi regression formula is a formula (Length=α×Hr+β×StShi+γ) that calculates the sum of the product of a first partial regression coefficient (α) obtained through the multi regression analysis and the first characteristic factor, the product of a second partial regression coefficient (β) obtained through the multi regression analysis and the second characteristic factor, and a third partial regression coefficient (γ).

8. The gait change determination device according to claim 6 , wherein the characteristic points include a first characteristic point when a first foot touches the ground, a second characteristic point when the trajectory reaches the highest position while the user is standing on the first foot, a third characteristic point furthest to the right in the trajectory, a fourth characteristic point furthest to the left in the trajectory, a fifth characteristic point furthest forward on the right side in the trajectory, a sixth characteristic point furthest forward on the left side in the trajectory, a seventh characteristic point furthest rearward on the right side in the trajectory, and an eighth characteristic point furthest rearward on the left side in the trajectory;

the characteristic factors include a first characteristic factor that is a quotient obtained by dividing a distance between the first characteristic point and the second characteristic point in the vertical direction in the trajectory projected onto the plane that is perpendicular to the advancement direction, by a distance between the third characteristic point and the fourth characteristic point in the horizontal direction, and a second characteristic factor that is a quotient obtained by dividing a distance between the fifth characteristic point and the sixth characteristic point in the horizontal direction in the trajectory projected onto the plane that is perpendicular to the vertical direction, by a distance between the seventh characteristic point and the eighth characteristic point in the horizontal direction;

the index includes a step spacing; and

the multi regression formula is a formula (Width=δ×Hr/W+ε×WuSu/WdSu+ζ) that calculates the sum of the product of a first partial regression coefficient (δ) obtained through the multi regression analysis and the first characteristic factor, the product of a second partial regression coefficient (ε) obtained through the multi regression analysis and the second characteristic factor, and a third partial regression coefficient (ζ).