JP2016061611A - Method for estimating load value - Google Patents

Abstract

PROBLEM TO BE SOLVED: To estimate a load value when a load sensor breaks down.SOLUTION: The method for estimating a load value of a load sensor which has broken down by using a plurality of load sensors attached to a sole of a user includes the steps of: determining whether or not one load sensor breaks down (S13); and in the case where one load sensor has broken down, estimating a load value of the load sensor which has broken down by an expression of an estimated orbit of the center of pressure and a relational expression of the position and load value of the load sensor and the center of pressure (S14). In the case where one load sensor breaks down, the relational expression of the position and load value of the load sensor and the center of pressure is substituted for the expression of an estimated orbit of the center of pressure, so as to make an equation with a load value of the load sensor which has broken down as a variable. The load value of the load sensor which has broken down is estimated by solving the equation.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for estimating a load value, for example, a method for estimating a load value in a walking support device.

  2. Description of the Related Art There are walking support devices that are attached to a user's lower limb and assist walking, and are fixed to the upper thigh and the lower thigh, respectively, and drive the joint by power transmitted to the knee joint.

  In such a walking support device, the load is measured by a plurality of load sensors provided on the sole plate, the posture and motion of the wearer are estimated, and the power is controlled.

  For example, Patent Document 1 describes that one load sensor is provided on the sole plate of the walking support device, and the load sensor measures a load transmitted to the load button via a sphere.

JP2013-72729A

  However, the conventional method has a problem that the load value cannot be measured if the load sensor fails.

  The present invention has been made to solve such a problem, and an object of the present invention is to estimate a load value when a load sensor fails.

One aspect of the present invention is a method for estimating a load value of a failed load sensor using a plurality of load sensors attached to the user's sole,
Determining whether one of the load sensors has failed;
When one of the load sensors fails, it has a process of estimating the load value of the failed load sensor from the equation of the estimated trajectory of the pressure center and the relational expression between the position of the load sensor, the load value, and the pressure center. is there.

  According to the method of the present invention, when one of the load sensors fails, the failed load is calculated by substituting the relational expression between the position of the load sensor, the load value, and the pressure center into the estimated trajectory of the pressure center. By creating an equation using the sensor load value as a variable and solving this equation, the load value of the failed load sensor can be estimated.

It is a flowchart which shows the process of the method of the load value estimation which concerns on this invention. It is a right view which shows the outline of a walking assistance apparatus provided with a load sensor. It is an upper surface perspective view which shows schematic structure of the right leg | foot of a robot provided with a load sensor.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a flowchart showing processing of a load value estimation method according to the present invention. In FIG. 1, it demonstrates as an example of operation | movement when CPU of a walk assistance apparatus performs the process regarding a load sensor.

  In step S11, the CPU determines whether or not the load sensor is functioning normally. If the load sensor is functioning normally, the process proceeds to step S12. If the load sensor is not functioning normally, the process proceeds to step S13.

  In step S12, the CPU calculates the pressure center COP and the total load based on the load value measured by the load sensor, and proceeds to step S16.

  In step S13, the CPU determines whether or not there is one failed load sensor. If there is one failed load sensor, the process proceeds to step S14. If there is not one failed load sensor, that is, a plurality of load sensors, the process proceeds to step S17.

  In step S14, the CPU estimates the load value of the failed load sensor from the expression of the estimated center of the pressure center and the relational expression between the position of the load sensor, the load value, and the pressure center, and proceeds to step S15. Details of estimating the load value will be described later.

  In step S15, the CPU estimates the COP and total load based on the load value measured by the load sensor, and proceeds to step S16.

  In step S16, the CPU controls the robot based on the obtained COP and total load, presents information regarding the load to the user, and proceeds to step S18.

  In step S17, the CPU stops the control of the robot, stops presenting information regarding the load to the user, and proceeds to step S18.

  In step S18, the CPU determines whether or not to end the robot control. If the robot control is not terminated, the process returns to step S11. If the robot control is terminated, the process in FIG. 1 is terminated.

  As described above, the number of load sensors that have failed is determined, and when the number of load sensors that have failed is one, it is assumed that the load value can be estimated. The total load can be obtained.

  Next, a load value estimation method will be described. FIG. 2 is a right side view illustrating an outline of a walking support device including a load sensor. As illustrated in FIG. 2, the walking support device 20 includes a robot leg 21 that performs a walking motion, a foot 22 that is connected to an end of the robot leg via a joint configuration, and a plurality of legs disposed on one surface of the foot 22. Load sensor 23. The plurality of load sensors 23 measure the load value of the robot leg 21 with respect to the ground, and provide parameters for balance control of the robot leg 21 to a processing device (CPU).

  In order to control this balance, it is necessary to provide a plurality of load sensors at different positions on the soles of the robot legs. FIG. 3 is a top perspective view illustrating a schematic configuration of a right foot of a robot including a load sensor. In FIG. 3, the horizontal axis indicates the positions of the soles of the robot legs and the load sensors in the lateral direction with respect to the traveling direction, and the vertical axis indicates the positions of the soles of the robot legs and the load sensors in the traveling direction.

  FIG. 3 illustrates an example in which four load sensors are arranged on the sole of the robot. That is, load sensors 23fL, 23fR, 23rL, and 23rR are disposed on the back of the foot portion 22.

  In the character string consisting of the three characters in FIG. 3, the first character indicates which coordinate axis, L (Length) is added to the coordinate for the traveling direction, and W (Width) is assigned to the horizontal coordinate for the traveling direction. doing. The second character indicates the arrangement of the load sensor in the traveling direction, and f (front) is attached to the load sensor arranged in the front part, and r (rear) is attached to the load sensor arranged in the rear part. The third character indicates the arrangement of the load sensor in the lateral direction with respect to the traveling direction, and L (left) is assigned to the load sensor arranged on the left side, and R (Right) is assigned to the load sensor arranged on the right side. doing.

  When the first character is F, the load value of the load sensor is indicated. Similarly, the character string attached to the number of the load sensor is also marked with the same rules as the second and third characters of the character string.

That is, the load sensor 23fL means the load sensor 23 on the left side of the front part, and the center coordinate thereof is indicated by L _{fL in} the traveling direction and W _fL in the lateral direction. The load value applied to the load sensor 23fL is defined by _{F fL.} The coordinates of the pressure center COP are indicated by X _{COP in} the traveling direction and Y _COP in the horizontal direction.

Here, the total load F _sum is derived by the following equation (1).

Further, the coordinates of the pressure center COP are defined by the following equation (2).

Here, if any of the load sensors 23 fails, the load value F cannot be measured. For example, if the load sensor 23fL fails, the load value _{F fL} becomes unknown. The total load F _sum derived from the equation (1) cannot be derived unless the load value F _fL is determined.

  Here, the experimentally obtained knowledge that the pressure center COP (Center Of Pressure) of the foot during walking is on the line from the heel to the finger ball direction is used as an expression of the estimated trajectory of the pressure center. Applies to value estimation.

  That is, assuming that the trajectory of the pressure center COP is represented by a predetermined estimated trajectory equation, the load value is estimated by substituting Equation (2) into the estimated trajectory equation and solving the equation for the unknown load value. To do.

（α、β、γは実験的に求められる値） For example, it is assumed that the estimated trajectory is expressed by the following equation (3).

(Α, β, and γ are values obtained experimentally)

X _COP and Y _COP of formula (2) are substituted for x and y of formula (3), respectively.

すなわち、式（４）は荷重値Ｆ_ｆＬ以外の値は、定数または実験的に求められる値であり、荷重値Ｆ_ｆＬが変数である一元二次方程式となる。 Here, when the load sensor 23 _fL fails and has the load value F _fL , the equation obtained by introducing the equation (2) into the equation (3) becomes the equation (4) that is a quadratic equation regarding the load value F _fL .

That is, in the equation (4), values other than the load value F _fL are constants or values obtained experimentally, and become a one-dimensional quadratic equation in which the load value F _fL is a variable.

An unknown load value F _fL can be derived by solving the equation (4) for F _fL .

Then, by applying the derived load value F _fL to the equations (1) and (2), the coordinates of the total load and the pressure center COP are obtained.

  As described above, according to the method of the present embodiment, when one of the load sensors fails, the relational expression between the position of the load sensor, the load value, and the pressure center is substituted into the formula of the estimated trajectory of the pressure center. Thus, an equation having the load value of the failed load sensor as a variable is created, and by solving this equation, the load value of the failed load sensor can be estimated.

  Further, the coordinates of the total load and the pressure center COP can be derived using the estimated load value of the load sensor.

  Also, by applying the method of the present embodiment to the walking support device, the load value of the failed load sensor is derived, the coordinates of the total load and the pressure center COP are derived, the control of the walking support device, and the user Information presentation can be continued, and the convenience of the user of the walking support device can be improved.

  In the above embodiment, the number of load sensors is four. However, the number of load sensors is not particularly limited as long as it is plural.

Further, the following equation (5) may be used as the equation for the estimated COP trajectory.

The estimated COP trajectory may be used for each user and each patient's symptom.
Alternatively, a COP estimation trajectory approximated by a polynomial using the least square method based on data before the load sensor fails may be used. In this case, the accuracy of the estimated load value is improved when the estimated trajectory is accurate.

  Moreover, although the example of the robot imitating the right foot has been described in the above embodiment, the example of the robot imitating the left foot can be similarly applied. In the case of the left foot, estimation of the load value can be realized by performing estimation in consideration of the positional relationship symmetrical to the right foot. In the case of a robot configuration that imitates both left and right feet, it may be realized by measuring the load on the right and left feet independently, or a COP trajectory estimation is considered as the left and right targets and a common formula is applied. You may do it.

20 Walking support device 21 Robot leg 22 Foot 23, 23fL, 23fR, 23rL, 23rR Load sensor

Claims (1)

A method for estimating a load value of a faulty load sensor using a plurality of load sensors attached to a user's sole,
Determining whether one of the load sensors has failed;
A method including a step of estimating a load value of a failed load sensor from an equation of an estimated trajectory of the pressure center and a relational expression between a position of the load sensor, a load value, and a pressure center when one of the load sensors fails.

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