Title:

Generated torque control method for leg body exercise assistive apparatus

Document Type and Number:

United States Patent 7278954

Abstract:

A generated torque control method for a leg body exercise assistive apparatus enabling a person to make a leg motion in such a feeling that the person is not wearing the leg body exercise assistive apparatus as much as possible by reducing the weight of the leg body exercise assistive apparatus attached to the person acting on the person. On the assumption that a person (A) not wearing the assistive apparatus (1) is making the same motion as a leg motion of the person (A) wearing the leg body exercise assistive apparatus (1) during the leg motion of the person (A), an estimation is made for a person-side joint moment to be generated in each joint of the leg of the person (A), and on the assumption that the assistive apparatus (1) is independently making the same motion as the leg motion, an estimation is made for an apparatus-side joint moment to be generated in the joint regions (4), (6), and (10) of the leg sections of the assistive apparatus (1). The estimated value of the apparatus-side joint moment is considered as a reference torque for torque generation means (18), (19), and (20), and a torque formed by adding a torque according to the estimated value of the person-side joint moment to the reference torque is generated in the torque generation means (18), (19), and (20).

Inventors:

Kawai, Masakazu (Wako, JP)
Ikeuchi, Yasushi (Wako, JP)

Plaque It!

FIELD OF THE INVENTION

The present invention relates to a generated torque control method for a leg body exercise assistive apparatus, which is attached to the legs of a person.

BACKGROUND ART

Conventionally, as this type of assistive apparatus, there is an already known apparatus disclosed in Japanese Patent Laid-Open No. 2003-220102 (hereinafter, referred to as “patent document 1”). The assistive apparatus of the patent document 1 includes moment generators on the hip joint, the knee joint, and the ankle joint of each leg of a person, with the moment generators connected to a foot supporting portion for supporting the foot of the person via beams. Moreover, it includes a sensor for detecting a force and moment acting between the foot supporting portion and the ground, a sensor for detecting a tilt angle of a beam, a sensor for detecting a force acting between the assistive apparatus and the person. On the basis of detected outputs of these sensors, a force to be generated by the each portion of the person is calculated when no support force (support torque) is applied by each moment generator, thereby causing each moment generator to generate a support force obtained by multiplying the calculated force by a certain reduction ratio. Thereby, the total load on the person is borne by the person and the assistive apparatus at a roughly predetermined ratio, so that the load on the person is reduced.

The apparatus of the patent document 1, however, calculates a force to be generated in each portion such as a joint of each leg by using the detected value of a force acting on the foot supporting portion of a landing leg when calculating a force to be generated in each portion of the person. Therefore, the calculated force is to be a force for supporting the total load of the person including the assistive apparatus. Therefore, even if the moment generator is caused to generate a certain rate of the calculated force as described above, the person makes a leg motion with being aware of the weight of the assistive apparatus attached to the person in a lot of situations during walking of the person. Consequently, the assistive apparatus easily causes a difference between an actual leg motion pattern and the motion pattern assumed by the person. Furthermore, it leads to causing an awkward leg motion or to making it hard for each moment generator to effectively generate a support torque, which enables a smooth leg motion.

As techniques for estimating joint moments to be generated in the joints of the legs during human walking, there have been known ones suggested by the present applicant, for example, in Japanese Patent Laid-Open No. 2003-89083 and Japanese Patent Laid-Open No. 2003-112893. The joint moments estimated using the techniques are necessary to support the total load of the person and the apparatus attached thereto. Therefore, even if the moment generators on the respective joints are caused to generate the predetermined rate of the joint moments calculated in these techniques, the same problem as the patent document 1 occurs.

DISCLOSURE OF THE INVENTION

In view of the above background, the present invention has been provided. Therefore, it is an object of the present invention to provide a generated torque control method for a leg body exercise assistive apparatus enabling a person to make a leg motion in such a feeling that the person is not wearing the leg body exercise assistive apparatus as much as possible by reducing the weight of the leg body exercise assistive apparatus attached to the person acting on the person.

To achieve the above object, according to a first feature of the present invention, there is provided a generated torque control method for a leg body exercise assistive apparatus of controlling generated torques of respective torque generation means in the leg body exercise assistive apparatus, which includes leg sections attached to both legs of a person so as to be movable integrally with the legs, with the leg sections each having a foot orthosis portion, which is disposed on the bottom side of the foot of each leg so as to be landing with the foot put on the foot orthosis portion during the landing period, being connected with joint regions corresponding to an ankle joint, a knee joint, and a hip joint of each leg, respectively, along the leg, and the torque generation means capable of generating support torques applied to at least the joint regions corresponding to the knee joint and the hip joint of the leg, the method comprising: a moment estimation step of sequentially estimating person-side joint moments, which are moments to be generated at least in the knee joint and the hip joint of each leg, in a situation where the person wearing the leg body exercise assistive apparatus is making a motion of his or her both legs, on the assumption that the person is making almost the same motion as the motion of the legs with the leg body exercise assistive apparatus removed from the person, and of sequentially estimating apparatus-side joint moments, which are moments to be generated in the joint regions of the leg body exercise assistive apparatus corresponding to at least the knee joint and the hip joint of each leg, respectively, on the assumption that the leg body exercise assistive apparatus is independently making almost the same motion as the motion of the person's legs; and a torque control step of controlling the torque generation means so as to generate a torque, as the support torque, which is obtained by adding the torque determined according to an estimated value of the person-side joint moment corresponding to the joint region concerned to a reference torque, assuming that an estimated value of the apparatus-side joint moment of each joint region corresponding to each of the knee joint and the hip joint of the leg is the reference torque to be generated by the torque generation means corresponding to the joint region concerned.

According to a second feature of the present invention, there is provided a method of controlling generated torques of respective torque generation means in the leg body exercise assistive apparatus, which includes leg sections attached to both legs of a person so as to be movable integrally with the legs, with the leg sections each having a foot orthosis portion, which is disposed on the bottom side of the foot of each leg so as to be landing with the foot put on the foot orthosis portion during the landing period, being connected with joint regions corresponding to an ankle joint, a knee joint, and a hip joint of each leg, respectively, along the leg, and the torque generation means capable of generating a support torque applied to the joint regions corresponding to the ankle joint, the knee joint, and the hip joint of the leg, respectively, the method comprising: a moment estimation step of sequentially estimating person-side joint moments, which are moments to be generated in the ankle joint, the knee joint, and the hip joint of each leg, in a situation where the person wearing the leg body exercise assistive apparatus is making a motion of his or her both legs, on the assumption that the person is making almost the same motion as the motion of the legs with the leg body exercise assistive apparatus removed from the person, and of sequentially estimating apparatus-side joint moments, which are moments to be generated in the joint regions of the leg body exercise assistive apparatus corresponding to the ankle joint, the knee joint, and the hip joint of each leg, respectively, on the assumption that the leg body exercise assistive apparatus is independently making almost the same motion as the motion of the person's legs; and a torque control step of controlling the torque generation means so as to generate a torque, as the support torque, which is obtained by adding a torque determined according to the estimated value of the person-side joint moment corresponding to the joint region concerned to a reference torque, assuming that an estimated value of the apparatus-side joint moment of each joint region corresponding to each of the ankle joint, the knee joint, and the hip joint is the reference torque to be generated by the torque generation means corresponding to the joint region concerned.

In the first and second features of the present invention, the moment estimation step includes the sequential estimation of person-side joint moments to be generated in the respective joints (at least the knee joint and the hip joint in the first feature of the invention, and the ankle joint, the knee joint, and the hip joint in the second feature of the invention) of each leg, in the situation where the person wearing the leg body exercise assistive apparatus is making the motion of his or her legs, on the assumption that the person is making almost the same motion as the motion of the legs with the leg body exercise assistive apparatus removed from the person. In other words, on the assumption that the person not wearing the leg body exercise assistive apparatus is independently making almost the same motion as the motion of the legs actually being made by the person wearing the leg body exercise assistive apparatus, the person-side joint moments to be generated in the joints of each leg are sequentially estimated. Therefore, the person-side joint moments estimated here are joint moments necessary for the person to make almost the same motion as the motion of the legs while supporting the person's own weight without help (more specifically, joint moments necessary for satisfying a dynamic balance relation between an inertia force generated by the motion of the person not wearing the leg body exercise assistive apparatus and a gravity and floor reaction forces acting on the person).

Moreover, the moment estimation step includes sequential estimation of the apparatus-side joint moments to be generated in the joint regions of the leg body exercise assistive apparatus, on the assumption that the leg body exercise assistive apparatus is independently (without help) making almost the same motion as the motion of the legs. Therefore, the apparatus-side joint moment estimated here are joint moments necessary for the leg body exercise assistive apparatus to make the same motion as the motion of the legs as if the leg body exercise assistive apparatus were supporting its own weight without help (more specifically, joint moments necessary for satisfying a dynamic balance relation between an inertia force generated by the independent motion of the leg body exercise assistive apparatus and a gravity and floor reaction forces acting on the leg body exercise assistive apparatus).

More specifically, in the moment estimation step, estimation is made for the person-side joint moment for making the leg motion while the person is supporting his or her own weight and the apparatus-side joint moment for making almost the same motion as the leg motion while the leg body exercise assistive apparatus is supporting its own weight separately from each other.

Furthermore, in the first and second features of the present invention, the torque control step includes generating torque obtained by adding a torque according to the estimated value of the person-side joint moment (for example, a torque of a predetermined rate of the person-side joint moment) corresponding to each joint region to a reference torque, assuming that the estimated value of the apparatus-side joint moment of the joint region concerned is the reference torque to be generated by the torque generation means corresponding to the joint region concerned. Therefore, the torque generation means generates the torque enabling the leg body exercise assistive apparatus to make the same motion as the person's leg motion without help as far as possible and at the same time supplementarily generates a torque for a part of the person-side joint moments to be generated by the respective joints of the person's legs. In this instance, reaction forces are necessary for generating the torque of the torque generation means, and many of the reaction forces are covered with floor reaction forces applied to the foot orthosis portion on the leg side during the landing period by the floor directly (without passing through the person).

Therefore, according to the first and second features of the present invention, it becomes possible to reduce the empty weight of the leg body exercise assistive apparatus, which is attached to the person, acting on the person, whereby the person can make the leg motion in such a feeling that the person is not wearing the leg body exercise assistive apparatus as far as possible.

Incidentally, in the first feature of the present invention, the torque generation means for applying the support torque to the ankle joint of each leg is not necessarily required. In this case, while the person incurs more percentage of the empty weight of the leg body exercise assistive apparatus in comparison with the second feature of the present invention, it is possible to reduce the percentage of the empty weight of the leg body exercise assistive apparatus incurred by the person to a relatively low level by applying the torque from the torque generation means to the joint regions corresponding to the hip joint and the knee joint of the leg body exercise assistive apparatus as described above. In order to minimize the percentage of the empty weight of the leg body exercise assistive apparatus that the person incurs, however, preferably the torque generation means applies the torque to the joint regions corresponding to the ankle joint, the knee joint, and the hip joint of each leg as described in the second feature of the present invention.

In the first and second features of the present invention, the person-side joint moment and the apparatus-side joint moment estimated in the moment estimation step may naturally be a moment around three axes (moment as a three-dimensional vector quantity) and may also be, for example, a moment around one axis viewed on the sagittal plane (the plane formed by the axis in the forward/backward direction of the person and the axis in the vertical direction) (moment around the axis perpendicular to the sagittal plane). In this case, in order to minimize the percentage of the empty weight of the leg body exercise assistive apparatus that the person incurs, it is thought to be preferable that the person-side joint moment and the apparatus-side joint moment estimated in the moment estimation step are moments around three axes (moments as three-dimensional vector quantities) and the torque that can be generated by the torque generation means are also three-dimensional quantities in principle. This, however, generally complicates or enlarges the structure of the leg body exercise assistive apparatus, thus inhibiting a smooth motion of the person's legs, instead.

The motion of each leg during human walking is mainly a bending and stretching motion. The bending and stretching motion is made by rotating the hip joints, the knee joints, and the ankle joints of the legs each around the axis substantially perpendicular to the plane passing through the respective joints. Therefore, according to the third feature of the present invention, the person-side joint moment and the apparatus-side joint moment estimated in the moment estimation step are considered as moments around the axis substantially perpendicular to a leg plane as a plane passing through the hip joint, the knee joint, and the ankle joint of each leg of the person. In this case, the support torque generated by the torque generation means is a torque around the axis substantially perpendicular to the leg plane.

According to the third feature of the present invention, the estimated person-side joint moment and apparatus-side joint moment may be components around one axis and the torque generated by the torque generation means may also be a torque around one axis. Therefore, the structure of the leg body exercise assistive apparatus can be compact and simple. At the same time, the torque generated by the torque generation means is controlled by estimating the person-side joint moment and the apparatus-side joint moment related to the bending and stretching motion, which is the main human leg motion, thereby achieving an effective reduction of the load on the person applied by the empty weight of the leg body exercise assistive apparatus.

Moreover, in the first or second feature of the present invention, there may be a wide variety of techniques (modes of the moment estimation step) for estimating the person-side joint moment and the apparatus-side joint moment. Preferably, however, the moment estimation step includes: a first step of sequentially grasping an acceleration of a predetermined region of the person or the leg body exercise assistive apparatus; a second step of sequentially grasping displacements of the hip joint, the knee joint, and the ankle joint of each leg of the person; a third step of sequentially estimating floor reaction forces acting on the person and the application point thereof, on the assumption that almost the same motion as the motion of both legs of the person is being made with the leg body exercise assistive apparatus removed from the person; a fourth step of sequentially estimating floor reaction forces acting on the leg body exercise assistive apparatus and the application point thereof, on the assumption that the leg body exercise assistive apparatus is independently making almost the same motion as the motion of both legs of the person; a fifth step of estimating the person-side joint moment by inverse dynamics calculation processing by using the acceleration grasped in the first step, the displacements grasped in the second step, the floor reaction forces and the application point thereof estimated in the third step, and a person-side rigid link model which represents the person as a link body formed of a plurality of rigid elements and joint elements; and a sixth step of estimating the apparatus-side joint moment by using the acceleration grasped in the first step, the displacements grasped in the second step, the floor reaction forces and the application point thereof estimated in the fourth step, and an apparatus-side rigid link model which represents the leg body exercise assistive apparatus as a link body formed of a plurality of rigid elements and joint elements (a fourth feature of the present invention).

More specifically, relative positional relations and dynamic relations (relations between force and motion) of the person's respective portions (the regions corresponding to the elements of the person-side rigid link model) are determined by grasping the acceleration of the predetermined region of the person or the leg body exercise assistive apparatus and the displacements of the hip joint, the knee joint, and the ankle joint of each leg of the person, estimating the floor reaction forces acting on the person and the application point thereof on the assumption that almost the same motion as the motion of both legs of the person is being made with the leg body exercise assistive apparatus removed from the person, and using the grasped or estimated physical quantities and the person-side rigid link model. Therefore, the person-side joint moment can be estimated by so-called inverse dynamics calculation processing. Generally speaking, the inverse dynamics calculation is arithmetic processing of estimating a reaction force or a moment, which are internal forces of the object, on the assumption that the external forces acting on the object and positional information are already known (with the external forces and the positional information as input parameters). In this case, the floor reaction force is already known as an external force acting on each leg and therefore the person-side joint moments can be estimated in order from a joint relatively close to the floor (in the order of the ankle joint, the knee joint, and the hip joint) by the inverse dynamics calculation.

Similarly, the relative positional relations and the dynamic relations (relations between force and motion) of the respective portions of the leg body exercise assistive apparatus (the regions corresponding to the elements of the apparatus-side rigid link model) are determined by using the grasped acceleration and displacements, the floor reaction forces and the application point thereof estimated in the fourth step, and the apparatus-side rigid link model. Therefore, the apparatus-side joint moment can be estimated by the inverse dynamics calculation processing.

Incidentally, the acceleration and the displacements can be grasped by using an acceleration sensor, a rotation angle sensor, or the like. The floor reaction forces and the application point thereof can be estimated by using the grasped acceleration and joint displacements, the person-side and apparatus-side rigid link models, and the like.

In the fourth feature of the present invention, similarly to the third feature of the present invention, preferably, in cases where the person-side joint moment estimated in the fifth step and the apparatus-side joint moment estimated in the sixth step are moments around an axis substantially perpendicular to a leg plane as a plane passing through the hip joint, the knee joint, and the ankle joint of each leg of the person, where the acceleration grasped in the first step, the floor reaction forces and the application point thereof estimated in the third step, and the floor reaction forces and the application point thereof estimated in the fourth step are all three-dimensional quantities, and where the displacements of the hip joint, the knee joint, and the ankle joint of each leg grasped in the second step each include an amount of rotation around an axis substantially perpendicular to the leg plane of the leg and the displacement of the hip joint is a three-dimensional quantity, the generated torque control method further includes: a seventh step of sequentially grasping an acceleration of a predetermined reference point fixed to a person's predetermined region as a three-dimensional quantity by using at least the acceleration grasped in the first step; an eighth step of sequentially grasping the positions and postures on the leg plane of the elements of each leg section of the person-side rigid link model by using at least the displacements grasped in the second step and the person-side rigid link model; a ninth step of grasping the positions and postures on the leg plane of the elements of each leg section of the apparatus-side rigid link model by using at least the displacements grasped in the second step and the apparatus-side rigid link model, wherein the fifth step includes estimating the person-side joint moment by using a two-dimensional quantity, which is obtained by projecting the acceleration of the predetermined reference point grasped in the seventh step and the floor reaction forces and the application point thereof estimated in the third step onto the leg plane corresponding to each leg according to the displacement of the hip joint, and the positions and postures grasped in the eighth step and wherein the sixth step includes estimating the apparatus-side joint moment by using a two-dimensional quantity, which is obtained by projecting the acceleration of the predetermined reference point grasped in the seventh step and the floor reaction forces and the application point thereof estimated in the fourth step onto the leg plane corresponding to each leg according to the displacement of the hip joint, and the positions and postures grasped in the ninth step (a fifth feature of the present invention).

In this regard, the amount of rotation around the axis substantially perpendicular to the leg plane of the hip joint, the knee joint, and the ankle joint of each leg grasped in the second step can be grasped relatively accurately by using a rotation angle sensor such as a potentiometer or a rotary encoder. Then, according to the fifth feature of the present invention, even if the motion of each leg of the person is a three-dimensional motion, which includes a motion (abduction, external rotation, adduction, internal rotation, or the like) other than the two-dimensional motion on the leg plane, it is possible to grasp the positions and postures on the leg plane of the person-side rigid link model and the positions and postures on the leg plane of the apparatus-side rigid link model relatively accurately in the eighth step and the ninth step. Moreover, in consideration of a spatial (three-dimensional) motion of the person and the leg body exercise assistive apparatus attached thereto, the acceleration of the reference point, the floor reaction forces acting on the person and the position of the application point thereof, and the floor reaction forces acting on the leg body exercise assistive apparatus and the position of the application point thereof are grasped as three-dimensional quantities (vector quantities expressed in a certain three-dimensional coordinate system) in the seventh step, the third step, and the fourth step. Then, they are projected onto the leg plane related to the leg according to the displacement (a three-dimensional quantity) of the hip joint of the leg, thereby making it possible to obtain two-dimensional quantities on the leg plane (more specifically, components on the plane parallel to the leg plane) of the acceleration of the reference point, the floor reaction forces acting on the person, and the application point thereof, and the floor reaction forces acting on the leg body exercise assistive apparatus and the application point thereof. In the fifth step, the person-side joint moment is then estimated in the inverse dynamics calculation processing on the leg plane by using the two-dimensional quantities on the leg plane of the acceleration of the reference point, the floor reaction forces acting on the person, and the application point thereof, and the positions and postures on the leg plane of the elements of the person-side rigid link model grasped in the eighth step. Similarly, the apparatus-side joint moment is estimated in the inverse dynamics calculation processing on the leg plane by using the two-dimensional quantities on the leg plane of the acceleration of the reference point, the floor reaction forces acting on the leg body exercise assistive apparatus, and the application point thereof and the positions and postures on the leg plane of the elements of the apparatus-side rigid link model grasped in the ninth step. By estimating the person-side joint moment and the apparatus-side joint moment and the apparatus-side joint moment around the axis substantially perpendicular to the leg plane in this manner, it becomes possible to estimate the components around the axis substantially perpendicular to the leg plane of each of the joint moments with sufficient estimation accuracy and to prevent excessive changes in the components. Consequently, the torque generated by the respective torque generation means can be made suitable for stably reducing the load on the person generated by the empty weight of the leg body exercise assistive apparatus.

Moreover, in the fourth or fifth feature of the present invention, preferably the third step includes estimating the floor reaction forces acting on the person and the application point thereof by using at least the acceleration grasped in the first step, the displacements grasped in the second step, and the person-side rigid link model and the fourth step includes estimating the floor reaction forces acting on the leg body exercise assistive apparatus and the application point thereof by using at least the acceleration grasped in the first step, the displacements grasped in the second step, and the apparatus-side rigid link model (a sixth feature of the present invention).

The motion state (eventually, the inertia force) of each part of the person can be known by using the acceleration of a predetermined region of the person or the leg body exercise assistive apparatus, the displacements of the joints of each leg of the person, and the person-side rigid link model, thereby allowing an estimation of the floor reaction forces acting on the person by his or her own weight and the application point thereof by a dynamic or geometric calculation. Similarly, by using the acceleration of a predetermined region of the person or the leg body exercise assistive apparatus, the displacements of the joints of each leg of the person, and the apparatus-side rigid link model, it is possible to estimate the floor reaction forces acting on the leg body exercise assistive apparatus by its own weight and the application point thereof. As mentioned above, the leg body exercise assistive apparatus can be downsized by reducing the sensors or the like to be attached to the person by using the acceleration or the like in the predetermined region to estimate the floor reaction forces and the application point thereof. Moreover, in this case, the acceleration sensor necessary for grasping the acceleration is only required to be attached to the region corresponding to a rigid element of either the person-side rigid link model or the apparatus-side rigid link model, thus providing a high degree of freedom in the place where it is attached. Thereby, it is possible to prevent an attachment of a sensor in a place interfering with the leg motion of the person as much as possible.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a lateral view showing a person wearing a leg body exercise assistive apparatus according to a first embodiment;

FIG. 2 is a front view showing a lower part of the body of the person wearing the leg body exercise assistive apparatus shown in FIG. 1;

FIG. 3 is a block diagram showing an internal configuration of a sensor box of the leg body exercise assistive apparatus shown in FIG. 1;

FIG. 4 is a diagram showing a structure of a person-side rigid link model and an apparatus-side rigid link model for use in control processing of the leg body exercise assistive apparatus shown in FIG. 1;

FIG. 5 is a diagram showing a structure of a foot of the apparatus-side rigid link model;

FIG. 6 is a block diagram showing an outline of a processing function of an arithmetic processing unit shown in FIG. 3;

FIG. 7 is a block diagram showing detailed functions of person-side joint moment estimation means shown in FIG. 6;

FIG. 8 is a block diagram showing detailed functions of apparatus-side joint moment estimation means shown in FIG. 6;

FIG. 9 is a diagram for explaining a position and a posture of a leg on the leg plane;

FIG. 10 is a diagram for explaining floor reaction force estimation processing of the person in a single support state;

FIGS. 11(a), (b) are diagrams each for explaining floor reaction force estimation processing of the person in a double support state;

FIGS. 12(a) to (c) are diagrams for explaining estimation processing of a floor reaction force application point on a sagittal plane of the person;

FIG. 13 is a diagram for explaining estimation processing of the floor reaction force application point on a horizontal plane of the person;

FIG. 14 is a diagram for explaining projection of a physical quantity to the leg plane for estimating a joint moment of the person;

FIG. 15 is a diagram for explaining estimation processing of a joint moment of the person using an inverse dynamics model;

FIG. 16 is a diagram for explaining floor reaction force estimation processing of the leg body exercise assistive apparatus in the single support state;

FIGS. 17(a), (b) are diagrams for explaining floor reaction force estimation processing of the leg body exercise assistive apparatus in the double support state;

FIGS. 18(a) to (c) are diagrams for explaining estimation processing of the floor reaction force application point on a sagittal plane of the leg body exercise assistive apparatus;

FIG. 19 is a diagram for explaining estimation processing of the floor reaction force application point on a horizontal plane of the leg body exercise assistive apparatus;

FIG. 20 is a diagram for explaining a structure of a foot of a leg body exercise assistive apparatus according to a third embodiment;

FIG. 21 is a graph for explaining an effect of the present invention;

FIG. 22 is a graph for explaining an effect of the present invention;

FIG. 23 is a graph for explaining an effect of the present invention; and

FIG. 24 is a graph for explaining an effect of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment (a first embodiment) of the present invention will be described below by using FIG. 1 to FIG. 19. This embodiment is intended for the first and second features of the present invention. FIG. 1 shows a state where a person A is wearing a leg body exercise assistive apparatus 1 according to this embodiment, by means of a lateral view. FIG. 2 shows a lower part of the body of the person A wearing the leg body exercise assistive apparatus 1, by means of a front view. In FIG. 2, the hip joint, the knee joint, and the ankle joint of each leg of the person A are illustrated in chain-and-dash line circles, respectively, for purposes of the description.

In these FIG. 1 and FIG. 2, the leg body exercise assistive apparatus 1 (hereinafter, simply referred to as the assistive apparatus 1) includes a sensor box 2 attached to the back of the waist of the person A, a waist link member 3 extended from the sensor box 2 to the place of the hip joint of each leg of the person A, a thigh link member 5 extended from the waist link member 3 to the place of the knee joint along the thigh of each leg via the hip joint region 4, a first crus link member 7 extended from the thigh link member 5 along the crus of each leg via the knee joint region 6 and then connected to the crus annular member 8 externally inserted in the lower part of the crus (on the upper side of the ankle joint) of the leg, a second crus link member 9 extended from the crus annular member 8 to the place of the ankle joint of each leg, and a foot link member 11 extended from the second crus link member 9 toward the bottom face of the foot of each leg via the ankle joint region 10 and connected to the foot orthosis portion 12 in the form of flat plate abutted against the bottom face of the foot. The sensor box 2 is fixed to the waist via the belt 13 or the like, the thigh link member 5 is fixed to the thigh of each leg via belts 14, 15 or the like, the crus link member 7 is fixed to the crus of each leg via a belt 16 or the like, and the foot orthosis portion 12 is fixed to the foot of each leg via a belt 17 or the like.

The hip joint region 4, the knee joint region 6, and the ankle joint region 10 are located in the positions corresponding to the hip joint, the knee joint, and the ankle joint of each leg of the person A, respectively, and they are assumed to be rotatable with the bending and stretching motion of the leg (capable of making a rotary motion around an axis generally perpendicular to the surface of the page showing FIG. 1 (more specifically, around an axis substantially perpendicular to the leg plane described later)). Moreover, the waist link member 3 has a portion 3a relatively close to the sensor box 2 being formed by a hard rigid member and a portion 3b relatively close to the hip joint region 4 being formed by an elastic material such as rubber. The elastic portion 3b is deformed, thereby allowing an abduction or adduction motion of the leg of the person A (a motion of rotating the thigh of the leg around the hip joint in the horizontal direction of the person A) or a swinging motion (a motion of rotating the thigh of the leg relative to the waist around the central axis substantially in the vertical direction). Moreover, the second crus link member 9 is attached to the crus annular member 8 in such a way as to be capable of making a swinging motion relative to the first crus link member 7, thereby allowing a swinging motion around the ankle joint of the foot (a motion of rotating the foot around the central axis of the crus).

A lower part from each hip joint region 4 down (including the hip joint region 4) of the assistive apparatus 1 having the above structure is a leg section corresponding to each leg of the person A.

The assistive apparatus 1 has electric motors 18, 19, and 20 as torque generation means, which are located in the hip joint region 4, the knee joint region 6, and the ankle joint region 10 of each leg and apply torques to the respective joint regions. These electric motors 18 to 20 are disposed on the lateral surfaces (the right side surface of the right leg and the left side surface of the left leg). In this case, the electric motor 18 can generate a torque for rotating the thigh link member 5 around the rotation axis of the hip joint region 4 relative to the waist link member 3, the electric motor 19 can generate torque for rotating the first and second crus link members 7, 9 around the rotation axis of the knee joint region 6 relative to the thigh link member 5, and the electric motor 20 can generate a torque for rotating the foot link member 11 and the foot orthosis portion 12 around the rotation axis of the ankle joint region 10 relative to the first and second crus link members 7, 9. Incidentally, the torque generation means may use, for example, a pneumatic actuator, instead of an electric motor.

As shown in the block diagram of FIG. 3, the sensor box 2 contains an acceleration sensor 21 for detecting 3-axis acceleration (translation acceleration), a gyro sensor 22 for detecting a 3-axis angular velocity, an arithmetic processing unit 23 configured using a microcomputer, an light emitter/receiver 26 for emitting a light to be introduced to optical fibers 24, 25 described later or receiving a feedback light, a motor drive circuit 27 for controlling generated torque of the electric motors 18 to 20 upon receiving a command of the arithmetic processing unit 23, and a battery 28 as a power supply for each electrical equipment such as the arithmetic processing unit 23. Detected outputs of the light emitter/receiver 26, the acceleration sensor 21, and the gyro sensor 22 are input to the arithmetic processing unit 23. The acceleration sensor 21 and the gyro sensor 22 are fixed to the waist via the sensor box 2 and the band 13 in such a way as to move integrally with the waist.

The assistive apparatus 1 has a sensing structure as described below, in addition to the acceleration sensor 21 and the gyro sensor 22.

Specifically, as shown in FIG. 2, the hip joint region 4, the knee joint region 6, and the ankle joint region 10 are provided with the joint displacement sensors 29, 30, and 31 for detecting displacements (rotation angles) of the hip joint, the knee joint, and the ankle joint of the person A, respectively. Detected outputs of the joint displacement sensors 29 to 31 are input to the arithmetic processing unit 23 of the sensor box 2 via signal lines, not shown. The displacement detected by the joint displacement sensor 29 of the hip joint region 4 among the joint displacement sensors 29 to 31 is a 3-axis rotation angle of (a three-dimensional quantity made of a combination of rotation angles around three axes) of the hip joint of the person A, the displacement detected by the joint displacement sensor 30 of the knee joint region 6 is a single-axis rotation angle of the knee joint of the person A, and the displacement detected by the joint displacement sensor 31 of the ankle joint region 10 is a single-axis rotation angle of the ankle joint of the person A. In this case, the rotation axis of one of the rotation angles detected by the joint displacement sensor 29 and the rotation axes of the rotation angles detected by the joint displacement sensors 30, 31 are, as shown in FIG. 2, axes a29, a30, and a31 substantially perpendicular to the leg plane PL (a plane perpendicular to the surface of the page of FIG. 2) as a plane passing through substantially the center of the hip joint, the knee joint, and the ankle joint of the leg corresponding to the joint displacement sensors 29 to 31, respectively. These axes a29, a30, and a31 are rotation axes of the hip joint region 4, the knee joint region 6, and the ankle joint region 10, respectively. The joint displacement sensors 29 to 31 are configured so as to detect the rotation angles around the rotation axes a29, a30, and a31 of the hip joint, the knee joint, and the ankle joint, respectively, by using a potentiometer or a rotary encoder.

In this regard, the leg plane PL is supplementarily described. On the leg plane PL, there are the center points of the hip joint, the knee joint, and the ankle joint of the leg when the person A bends and stretches the corresponding leg by bending the leg at the knee joint. In other words, each leg is bent and stretched with the center points of the hip joint, the knee joint, and the ankle joint positioned substantially on the leg plane PL. In addition, for example, if the left leg is abducted by a motion of the hip joint like the left leg shown in FIG. 2, the leg plane PL corresponding to the left leg inclines relative to the vertical direction.

Rotation angles around other two axes detected by the joint displacement sensor 29 of the hip joint region 4 are those around two axes parallel to the leg plane PL of the corresponding leg, but not parallel to each other. Moreover, the rotation angles are detected by using a strain sensor for detecting a volume of deformation of the elastic portion 3b of the waist link member 3 or a sensor using optical fibers described later.

As shown in FIG. 1, two optical fibers 24, 25 introduced from the sensor box 2 are extended upward along the back face (back) of the body of the person A and their points are fixed to the back face of the abdomen and the back face of the chest of the person A, respectively, via a band or other member not shown. The optical fibers 24, 25 are components of detection means for detecting tilt angles (tilt angles on the sagittal plane) of the abdomen and the chest relative to the waist. The tilt angles of the abdomen and the chest are measured using the optical fibers 24, 25 in the method described below. The method of measuring the tilt angle of the abdomen using the optical fiber 24 will now be typically described. A light having a predetermined intensity is introduced from the light emitter/receiver 26 in the sensor box 2 into the optical fiber 24 and the introduced light is reflected on the end of the optical fiber 24 and returns to the sensor box 2 side. The light emitter/receiver 26 then detects the feedback amount of the light (the intensity of the feedback light). The optical fiber 24 is provided with a plurality of notches (not shown) allowing subtle light leakage disposed at intervals in the longitudinal direction. Therefore, light of the amount according to the tilt angle of the abdomen relative to the waist leaks from the optical fiber 24 via the notches, out of the light introduced into the optical fiber 24. Therefore, the feedback amount of the light to the sensor box 2 side depends upon the tilt angle of the abdomen and the tilt angle of the abdomen relative to the waist is measured by detecting the feedback amount. In other words, a detected output of the light emitter/receiver 26 according to the feedback amount of the light of the optical fiber 24 depends upon the tilt angle of the abdomen relative to the waist and it is input to the arithmetic processing unit 23 as a signal indicating the tilt angle. The same applies to the method of measuring the tilt angle of the chest using the optical fiber 25.

Incidentally, the rotation angles of the hip joint, the knee joint, and the ankle joint detected by the joint displacement sensors 29 to 31 are measured with reference (zero point) to a state where the person A stands upright with both feet directed forward in parallel (hereinafter, referred to as the reference posture condition). The same applies to the tilt angles of the abdomen and the chest detected by using the optical fibers 25, 26.

Moreover, as shown in FIG. 1 the assistive apparatus 1 has two landing sensors 32, 33 on the bottom face of each foot orthosis portion 12. Regarding the landing sensors 32, 33, the landing sensor 32 is disposed in the part (heel) just under the ankle joint and the landing sensor 33 is disposed in the part (toe) just under the metatarsophalangeal joint of the foot (a joint at the root of the big toe of the foot). These landing sensors 32, 33 output ON/OFF signals indicating whether the parts where they are disposed are in contact with the ground. Incidentally, detected outputs of the landing sensors 32, 33 are input to the arithmetic processing unit 23 of the sensor box 2 via signal lines (not shown).

The configuration of the assistive apparatus 1 has been described hereinabove. In this type of assistive apparatus 1, the foot orthosis portion 12 is brought into contact with the ground with the foot of the leg placed on the foot orthosis portion 12. In this case, for example, in a state where the person A stands upright, almost the entire weight of the assistive apparatus 1 acts on the floor (ground) via both foot orthosis portions 12, 12 while not acting on the person A almost at all.

The following describes a rigid link model (geometric model) of the person A, a rigid link model (geometric model) of the assistive apparatus 1, and coordinate systems used in this embodiment. Referring to FIG. 4, there is shown a structure and a coordinate system for the rigid link model S1 of the person A. As described later, the basic structure of the rigid link model of the assistive apparatus 1 is assumed to be the same as that of the rigid link model S1 of the person A in this embodiment. Therefore, FIG. 4 shows the structure of the rigid link model of the assistive apparatus 1, too. Accordingly, the reference symbol S1′ indicating the rigid link model of the assistive apparatus 1 is put in parentheses in FIG. 4.

As shown in FIG. 4, the rigid link model S1 of the person A is represented as a link body formed of nine rigid elements and eight joint elements in this embodiment. In FIG. 4, each rigid element is represented by a line segment and each joint element is represented by a circle (except one indicated by the reference character J4). More specifically, the rigid link model S1 is roughly composed of a pair of leg sections S2, S2 corresponding to the legs of the person and an upper body section S3 corresponding to the upper part of the body (the upper part from the waist) of the person. The upper body section S3 is configured as a link body wherein a rigid element S4 corresponding to the waist of the person is coupled to a rigid element S5 corresponding to the abdomen via a joint element JU1 and further the rigid element S5 is coupled to a rigid element S6 corresponding to the chest via a joint element JU2. Hereinafter, the rigid elements S4 to S6 are respectively referred to as the waist element S4, the abdomen element S5, and the chest element S6 in some cases, and the joint elements JU1 and JU2 are respectively referred to as the lower joint of the upper body JU1 and the upper joint of the upper body JU2 in some cases.

In this case, the lower joint of the upper body JU1 is disposed at the upper end of the waist element S4 and a pair of joint elements J1, J1 corresponding to a pair of hip joints (hereinafter, simply referred to as the hip joint J1 in some cases) of the person A are disposed at right and left both ends of the lower part of the waist element S4. Moreover, the lower joint of the upper body JU1 corresponds to a joint supposed on the backbone of the person A in the vicinity of the border between the waist and the abdomen of the person A, and the upper joint of the upper body JU2 corresponds to a joint supposed on the backbone of the person A in the vicinity of the border between the abdomen and the chest. In the rigid link model S1, the bending motion of the upper body section S3 corresponding to the bending motion of the body of the person A is made by two joint elements of the lower joint of the upper body JU1 and the upper joint of the upper body JU2.

Each leg section S2 of the rigid link model S1 is configured as a link body wherein a thigh element S7 as a rigid element corresponding to the thigh of the person is coupled to the waist element S4 via the hip joint J1, a crus element S8 as a rigid element corresponding to the crus is coupled via a joint element J2 corresponding to the knee joint, and a foot element S9 as a rigid element corresponding to the foot is coupled via a joint element J3 corresponding to the ankle joint. Hereinafter, the rigid elements S7 to S9 are simply referred to as the thigh element S7, the crus element S8, and the foot element S9 and the joint elements J2, J3 are simply referred to as the knee joint J2 and the ankle joint J3, respectively, in some cases.

In FIG. 4, the part indicated by the reference character J4 at the tip of the foot element S9 corresponds to the metatarsophalangeal joint (hereinafter, referred to as the MP joint), which is a joint at the root of the big toe of the foot of the person. In the rigid link model S1, the part J4 does not have a function of a joint, but hereinafter the part J4 is referred to as the MP joint for convenience.

The rigid elements and the joint elements of the rigid link model S1 of the person A configured as described above are capable of making a motion in such a way that the mutual positional relationship and posture relationship (directional relationship) of the elements are coincident with the mutual positional relationship and posture relationship of the respective portions of the person corresponding to the rigid elements and the joint elements by means of the rotary motions of the joint elements. In this case, the lower joint of the upper body JU1 and the upper joint of the upper body JU2 are assumed to be rotatable around three axes. By using one of the three axes as a measurement axis, a rotation around the measurement axis (arrows (rotation arrows) corresponding to the joint elements JU1, JU2 shown in FIG. 4) is measured. In this embodiment, the measurement axis is parallel to a line segment connecting the centers of the pair of hip joints J1, J1. In addition, the hip joint J1 of the each leg section S2 is assumed to be rotatable around three axes as indicated by arrows (rotation arrows) typically shown in FIG. 4 regarding the hip joint J1 of the left leg section S2. Moreover, the knee joint J2 and the ankle joint J3 of the each leg section S2 are assumed to be rotatable around a single axis as indicated by the arrows (rotation arrows) typically shown in FIG. 4 regarding the joint elements J2, J3 of the left leg section S2, respectively. The rotation axis of the knee joint J2 and that of the ankle joint J3 are perpendicular to the leg plane PL (not shown for the left leg section S2 in FIG. 4) passing through the centers of the hip joint J1, the knee joint J2, and the ankle joint J3. The rotating motion of the hip joint J1, the knee joint J2, and the ankle joint J3 of the right leg section S2 is the same as in the left leg section S2. In this case, the each rotation axis (a single axis) of the knee joint J2 and the ankle joint J3 of the right leg section S2 is perpendicular to the leg plane PL shown correspondingly to the right leg section S2. The each hip joint J1 can rotate around the three axes regarding both leg sections S2 and therefore can rotate around the axis perpendicular to the leg plane PL corresponding to each leg section S2.

In the rigid link model S1, the weight, the length (the length in the segment direction in FIG. 4) of the each rigid element and the center of gravity location of the each rigid element (the position in the element coordinate system fixed to the each rigid element described later) are predetermined and stored in a memory, not shown, in the arithmetic processing unit 23. Black dots G6, G5, G4, G7, G8, and G9 shown in FIG. 4 illustratively indicate the centers of gravity of the chest element S6, the abdomen element S5, the waist element S4, the thigh element S7, the crus element S8, and the foot element S9, respectively. As supplementary information, the waist element S6 is coupled to the three joint elements JU1, J1, and J1 and therefore the length of the waist element S6 includes the length of a line segment between both hip joints J1, J1 and the length of a line segment between the midpoint of the above line segment and the lower joint of the upper body JU1. Instead of the length of the each rigid element, the positions of the endpoints of the rigid element in the element coordinate system fixed to the rigid element concerned may be previously stored in the arithmetic processing unit 23.

The weight, the length, and the center of gravity location of each rigid element of the rigid link model S1 are basically set so as to be substantially coincident with the weight, the length, and the center of gravity location of the region (rigid equivalent part) of the person corresponding to each rigid element. For example, the weight, the length, and the center of gravity location of the thigh element S7 are substantially the same as the actual weight, the length, and the center of gravity location of the thigh of the person. The weight, the length, and the center of gravity location of each rigid element of the rigid link model S1 are the weight, the length, and the center of gravity location in a state where the person A is not wearing the assistive apparatus 1. Moreover, the weight and the center of gravity location of the chest element S6 are the weight and the center of gravity location of the chest, and both arms, and the head of the person included. As supplementary information, the change in the center of gravity location of the chest element S6 accompanying the motion of both arms (the motion of swinging the arms back and forth) of the person during walking is relatively small and therefore the center of gravity location is maintained at a substantially fixed position of the chest element S6.

While the weight, the length, and the center of gravity location of each rigid element of the rigid link model S1 may be basically determined based on the actual measurements of the size or the weight of each part of the person, it is also possible to estimate them on the basis of average statistical data of a human being from the height and the weight of the person. In general, the center of gravity location, the weight, and the length of the rigid equivalent part of the person corresponding to each rigid element have a correlation with the height and the weight (the entire weight) of a human being, and it is possible to estimate the center of gravity location, the weight, and the length of the rigid equivalent part of the person corresponding to each rigid element relatively accurately from measurement data of the height and the weight of the person on the basis of the correlation.

Although the centers of gravity G4 to G9 are located on the central axes of the rigid elements corresponding to them respectively (on the shown line segments) in FIG. 4 for convenience, they are not necessarily located on the central axes, but can exist in the positions deviating from the central axes, respectively.

In this embodiment, a coordinate system as described below is preset for the rigid link model S1. More specifically, as shown in FIG. 4, a body coordinate system BC is set so as to be fixed to the waist element S4. The body coordinate system BC is established as a three-dimensional coordinate system (XYZ coordinate system) whose origin is defined as being the midpoint of a line segment between the centers of the pair of hip joints J1, J1, whose Y axis is defined as being in the direction of the line segment, whose Z axis is defined as being in the direction from the origin toward the center of the lower joint of the upper body JU1, and whose X axis is defined as being in the direction perpendicular to the Y axis and the Z axis. In the reference posture condition of the person A, the X axis, the Y axis, and the Z axis of the body coordinate system BC are oriented in the forward/backward direction, the right/left direction, and the up/down direction (vertical direction) of the person A, respectively, and the XY plane is a horizontal plane. In this embodiment, the origin of the body coordinate system BC corresponds to the reference point in the present invention.

A leg coordinate system LC is fixed and set to the leg plane PL corresponding to each leg section S2. In FIG. 4, only the leg coordinate system LC corresponding to the leg plane Pl of the right leg section S2 is typically shown for convenience. The leg coordinate system LC is a three-dimensional coordinate system (XYZ coordinate system) whose origin is the center of the hip joint J1 on the leg plane PL, with the Y axis in the direction perpendicular to the leg plane PL, with the Z axis in the direction parallel to the axis obtained by projecting the Z axis of the body coordinate system BC onto the leg plane PL, and with the X axis in the direction perpendicular to the Y axis and the Z axis. Incidentally, the XZ plane of the leg coordinate system LC is coincident with the leg plane PL.

Moreover, an element coordinate system is fixedly set at each rigid element as indicated by reference characters C4 to C9, for example. In this embodiment, the element coordinate system C4 of the waist element S4 is defined as being coincident with the body coordinate system BC. Moreover, the element coordinate systems C6, C5, C7, C8, and C9 of the chest element S6, the abdomen element S5, each thigh element S7, each crus element S8, and each foot element S9 are defined as being three-dimensional coordinate systems (XYZ coordinate systems) whose origins are at the center of the upper joint of the upper body JU2, the lower joint of the upper body JU1, the knee joint J2, the ankle joint J3, and the MP joint J4, respectively.

The element coordinate systems C4 to C9 can be established with settings of an arbitrary origin or arbitrary directions of axes as long as they are fixed to the corresponding rigid element.

Subsequently, the rigid link model of the assistive apparatus 1 is described below. In this embodiment, the coupling structure of the rigid link model of the assistive apparatus 1 is the same as that of the rigid link model S1 of the person (hereinafter, referred to as the person rigid link model S1), having the structure shown in FIG. 4. Therefore, the rigid link model of the assistive apparatus 1 is described by using FIG. 4. Hereinafter, the rigid link model of the assistive apparatus 1 is represented by a reference character S1′ with parentheses as shown in FIG. 4 and referred to as the apparatus rigid link model S1′.

In this case, the joint elements J1 to J3 of each leg section S2 of the apparatus rigid link model S1′ correspond to the hip joint region 4, the knee joint region 6, and the ankle joint region 10 of the assistive apparatus 1, respectively. Moreover, the joint elements JU1 and JU2 of the upper body section S3 correspond to joints supposed on the backbone of the person A in the same manner as for the person A. In this embodiment, the joint elements J1 to J3, JU1, and JU2 of the apparatus rigid link model S1′ are assumed to be in the same positions as the joint elements J1 to J3, JU1, and JU2 of the person rigid link model S1, respectively, and the rotations that can be made by the joint elements J1 to J3, JU1, and JU2 of the apparatus rigid link model S1′ are the same as those of the person rigid link model S1.

The rigid elements S4 to S9 of the apparatus rigid link model S1′ correspond to portions attached to the regions of the person corresponding to the rigid elements in the assistive apparatus 1. For example, the thigh element S5 of the apparatus rigid link model S1′ corresponds to a portion between the center of the hip joint region 4 and the center of the knee joint region 6 of the assistive apparatus 1 (the thigh link member 5 and the bands 14, 15 and half bodies of the hip joint region 4, the knee joint region 6, the electric motors 18, 19, and the joint displacement sensors 29, 30). Then, the weights and the center of gravity locations (the positions in the element coordinate system fixed to the rigid elements, respectively) of the rigid elements S4 to S9 of the apparatus rigid link model S1′ are previously stored in the memory of the arithmetic processing unit 23. The weights and the center of gravity locations of the rigid elements S3 to S9 of the apparatus rigid link model S1′ are those of the assistive apparatus 1 only (the assistive apparatus 1 detached from the person A).

Since the positions of the joint elements of the apparatus rigid link model S1′ are the same as those of the person rigid link model S1 of the person A in this embodiment, the lengths of the rigid elements S4 to S8 except the foot element S9 are assumed to be the same as those of the person rigid link model S1. In addition, the body coordinate system BC, the leg coordinate system LC, and the element coordinate systems C4 to C9 are also assumed to be the same in both of the rigid link models S1 and S1′.

Additionally, the foot element S9 in the apparatus rigid link model S1′ is assumed to have a structure shown in FIG. 5 in this embodiment. In other words, a base S9c substantially in the form of flat plate is coupled to the ankle joint J3 and support members S9a, S9b in contact with the floor are respectively provided on the under surface of the front part (the part relatively close to the toe) and the rear part (the part relatively close to the heel) of the base S9c. Moreover, regarding the foot element S9 of the apparatus rigid link model S1′, the positions of the support members S9a, S9b (the positions of the bottom edges of the support members S9a, S9b) in the element coordinate system C9 of the foot element S9 are stored in the memory of the arithmetic processing unit 23, instead of the length.

In this embodiment, the weights of the portions of the assistive apparatus 1 corresponding to the abdomen and the chest of the person A are sufficiently low in comparison with the weights of other portions so as to be substantially zero. Therefore, the upper elements than the waist element S4 of the apparatus rigid link model S1′ or the lower joint of the upper body JU1, the abdomen element S5, the upper joint of the upper body JU2, and the chest element S6 may be omitted.

The following describes an outline of processing functions of the arithmetic processing unit 23. FIG. 6 is a block diagram schematically showing the entire processing functions of the arithmetic processing unit 23. FIG. 7 and FIG. 8 are block diagrams showing processing functions of the essential parts of the arithmetic processing unit 23.

The processing functions of the arithmetic processing unit 23 can be roughly classified into as follows: person-side joint moment estimation means 41 for sequentially estimating joint moments generated at the joints (the ankle joint, the knee joint, and the hip joint) of each leg of the person A; apparatus-side joint moment estimation means 42 for sequentially estimating joint moments generated at the joint regions 4, 6, 10 of the assistive apparatus 1; apparatus generated torque determination means 43 for determining torque (support torque) to be generated at the electric motors 18 to 20 of the assistive apparatus 1 on the basis of the joint moments estimated by these estimation means 41 and 42; and motor control means 44 for controlling the electric motors 18 to 20 to generate the determined torque via the motor drive circuit 27.

As shown in FIG. 7, the person-side joint moment estimation means 41 includes: transformation tensor generation means 51 for generating a transformation tensor for use in a coordinate transformation described later on the basis of detected outputs of the joint displacement sensor 29 and the light emitter/receiver 26 in the hip joint region 4; two-dimensional leg posture and element center-of-gravity location calculation means 52 for calculating positions of the joint elements, postures (tilt angles) of the rigid elements, and the center of gravity locations of the rigid elements on the leg plane PL of the each leg section S2 of the person rigid link model S1 on the basis of detected outputs of the joint displacement sensors 29, 30, and 31; three-dimensional joint and element center-of-gravity location calculation means 53 for calculating three-dimensional position vector values (coordinate component values) in the body coordinate system BC of the joint elements and the centers of gravity of the rigid elements of the person rigid link model S1 by using the transformation tensor generated by the transformation tensor generation means 51 and the positions and postures calculated by the two-dimensional leg posture and element center-of-gravity location calculation means 52; body coordinate system acceleration and angular velocity calculation means 54 for calculating values of an acceleration vector (translation acceleration) and the angular velocity vector of the origin of the body coordinate system BC (coordinate component values in the body coordinate system BC) on the basis of detected outputs of the acceleration sensor 21 and the gyro sensor 22; and body coordinate system tilt angle calculation means 55 for calculating a tilt angle relative to the vertical direction of the body coordinate system BC on the basis of detected outputs of the acceleration sensor 21 and the gyro sensor 22. The position vector calculated by the three-dimensional joint and element center-of-gravity location calculation means 53 includes a position vector in the body coordinate system BC of the MP joint J4 of the foot element S9 of the person rigid link model S1.

Moreover, the person-side joint moment estimation means 41 includes entire center-of-gravity location calculation means 56 for calculating a value of the position vector of the entire center of gravity (the entire center of gravity of the person A) of the person rigid link model S1 in the body coordinate system BC by using the position vectors of the centers of gravity of the rigid elements calculated by the three-dimensional joint and element center-of-gravity location calculation means 53.

Moreover, the person-side joint moment estimation means 41 includes: floor reaction force estimation means 57 for estimating a value in the body coordinate system BC (a coordinate component value) of a floor reaction force vector (a translation floor reaction force) acting on each leg of the person A by using the position vector value of each ankle joint J3 calculated by the three-dimensional joint and element center-of-gravity location calculation means 53, the position vector value of the entire center of gravity calculated by the entire center-of-gravity location calculation means 56, the acceleration vector value of the origin of the body coordinate system BC calculated by the body coordinate system acceleration and angular velocity calculation means 54, and the detected outputs of the landing sensors 32, 33; and floor reaction force application point estimation means 58 for estimating a value in the body coordinate system BC of the position vector of the application point of the floor reaction vector (hereinafter, simply referred to as the floor reaction force application point) acting on each leg by using the position vector values of each ankle joint J3 and each MP joint J4 calculated by the three-dimensional joint and element center-of-gravity location calculation means 53, the tilt angle of the body coordinate system BC calculated by the body coordinate system tilt angle calculation means 55, the position vector value of the entire center of gravity calculated by the entire center-of-gravity location calculation means 56, and the detected outputs of the landing sensors 32, 33.

Furthermore, the person-side joint moment estimation unit 41 includes: leg plane projection means 59 for projecting the floor reaction force vector value estimated by the floor reaction force estimation means 57, the position vector value of the floor reaction force application point estimated by the floor reaction force application point estimation means 58, and the acceleration vector and angular velocity vector values calculated by the body coordinate system acceleration and angular velocity calculation means 54 onto the leg plane PL corresponding to each leg by using the transformation tensor generated by the transformation tensor generation means 51; and a joint moment calculation means 60 for calculating estimated values of the joint moments acting on the ankle joint, the knee joint, and the hip joint of each leg of the person A by using the values obtained by the projection (two-dimensional quantities) and the locations and the postures calculated by the two-dimensional leg posture and element center-of-gravity location calculation means 52.

Although the details will be described later, the person-side joint moment estimation means 41 sequentially performs the arithmetic processing of the aforementioned means 51 to 60 each in a predetermined arithmetic processing period and sequentially calculates the estimated values of the joint moments finally by using the joint moment calculation means 60 in each arithmetic processing period. The estimated values of the joint moments calculated here are moments generated at the respective joints of each leg of the person A on the assumption that the person A makes a required motion of each leg by himself without wearing the assistive apparatus 1.

On the other hand, the apparatus-side joint moment estimation means 42 includes: two-dimensional element center-of-gravity location calculation means 61 for calculating the center of gravity locations of the rigid elements of each leg section S2 of the apparatus rigid link model S1′ on the leg plane PL on the basis of the positions of the joint elements of each leg section S2 on the leg plane PL calculated by the two-dimensional leg posture and element center-of-gravity location calculation means 52 of the person-side joint moment estimation means 41; three-dimensional element center-of-gravity location calculation means 62 for calculating three-dimensional position vector values in the body coordinate system BC of the centers of gravity of the rigid elements of the apparatus rigid link model S1′ by using the center of gravity locations of the rigid elements calculated by the two-dimensional element center-of-gravity location calculation means 61 and the transformation tensor generated by the transformation tensor generation means 51 of the person-side joint moment estimation means 41; and entire center-of-gravity location calculation means 63 for calculating a value of the position vector of the entire center of gravity (the entire center of gravity of the assistive apparatus 1) of the apparatus rigid link model S1′ in the body coordinate system BC by using the position vector values of the centers of gravity of the rigid elements calculated by the three-dimensional element center-of-gravity location calculation means 62. The position vectors calculated by the three-dimensional element center-of-gravity location calculation means 62 include position vectors of the support members S9a, S9b of the each foot element S9 of the apparatus rigid link model S1′ (See FIG. 5).

Moreover, the apparatus-side joint moment estimation means 42 includes: floor reaction force estimation means 64 for estimating a value in the body coordinate system BC (a coordinate component value) of a floor reaction force vector (a translation floor reaction force) acting on the each leg section of the assistive apparatus 1 by using the position vector values of each ankle joint J3 calculated by the three-dimensional joint and element center-of-gravity location calculation means 53 of the person-side joint moment estimation means 41, the position vector value of the entire center of gravity of the assistive apparatus 1 calculated by the entire center-of-gravity location calculation means 63, the acceleration vector values of the origin of the body coordinate system BC calculated by the body coordinate system acceleration and angular velocity calculation means 54 of the person-side joint moment estimation means 41, and detected outputs of the landing sensors 32, 33; and floor reaction force application point estimation means 65 for estimating a value in the body coordinate system BC of the position vector of the application point of a floor reaction force vector (the floor reaction force application point) acting on the each leg section of the assistive apparatus 1 by using the position vector values of the support members S9a, S9b of the each foot element S9 of the apparatus rigid link model S1′ calculated by the three-dimensional element center-of-gravity location calculation means 62, the position vector value of the entire center of gravity calculated by the entire center-of-gravity location calculation means 63, and detected outputs of the landing sensors 32, 33.

Furthermore, the apparatus-side joint moment estimation means 42 includes: leg plane projection means 66 for projecting the floor reaction force vector value estimated by the floor reaction force estimation means 64 and the position vector value of the floor reaction force application point estimated by the floor reaction force application point estimation means 65 onto the leg plane PL corresponding to each leg by using the transformation tensor generated by the transformation tensor generation means 51; and joint moment calculation means 67 for calculating estimated values of joint moments to be generated at the joint regions 4, 6, and 10 of the assistive apparatus 1 by using the values (two-dimensional quantities) obtained by the projection and the position vectors (which correspond to the position vectors of the joint elements of the each leg section S2 of the apparatus rigid link model S1′ in this embodiment) in the leg coordinate system LC of the hip joint J1, the knee joint J2, and the ankle joint J3 of the each leg section S2 of the person rigid link model S1 calculated by the two-dimensional leg posture and element center-of-gravity location calculation means 52.

Although the details will be described later, the apparatus-side joint moment estimation means 42 sequentially performs arithmetic processing of the aforementioned means 61 to 67 each in a predetermined arithmetic processing period in parallel with the processing of the person-side joint moment estimation means 41 and sequentially calculates the estimated values of the joint moments finally by using the joint moment calculation means 67 in each arithmetic processing period. The estimated values of the joint moments calculated here are moments generated at the joint regions 4, 6, and 10 of the assistive apparatus 1 on the assumption that the assistive apparatus 1 makes the same motion as the required motion of each leg of the person by itself.

The following describes the operation of the apparatus of this embodiment in conjunction with the detailed arithmetic processing of the respective means of the arithmetic processing unit 23. In the following description, generally the transformation tensor for coordinate-converting a vector quantity from a certain coordinate system Ca to another coordinate system Cb, namely a tensor for converting a vector quantity represented by a component value of the coordinate system Ca to a vector quantity represented by a component value of the coordinate system Cb is denoted by R(Ca→Cb). Furthermore, a position vector of a point P or a region P viewed in the coordinate system Ca is denoted by U(P/Ca). Still further, a vector A of an applied force, an acceleration, or other physical quantity of an object Q or a region Q, which is represented by a coordinate component value of a certain coordinate system Ca is denoted by A(Q/Ca). In this case, when representing a coordinate component value in the coordinate system Ca of the position vector U(P/Ca) or the physical quantity vector A(Q/Ca), the name of each coordinate axis x, y, or z is added in the denotation. For example, the X coordinate component of the position vector U(P/Ca) is denoted by U(P/Ca)x.

Moreover, the element coordinate systems C4 to C9 are sometimes referred to as C_waist, C_abdomen, C_chest, C_thigh, C_crus, and C_foot by using the names of the regions of the person A corresponding to C4 to C9, respectively. It is assumed that the same applies to the rigid elements S4 to S9 of the person rigid link model S1 and the centers of gravity G4 to G9 of the rigid elements S4 to S9. For example, the waist element S4 of the person rigid link model S1 and its center of gravity G4 are sometimes denoted by S_waist and G_waist, respectively.

Furthermore, the rigid elements S4 to S9 of the apparatus rigid link model S1′ are sometimes referred to as S_waist apparatus, S_abdomen apparatus, S_chest apparatus, S_thigh apparatus, S_crus apparatus, and S_foot apparatus, respectively, by using the names of the corresponding regions of the person A. It is assumed that the same applies to the centers of gravity of the rigid elements S4 to S9 of the apparatus rigid link model S1′. For example, the center of gravity G4 of the waist element S4 of the apparatus rigid link model S1′ is sometimes denoted by G_waist apparatus.

Regarding denotations related to the leg of the person A or related to the leg section of the assistive apparatus 1, “right” or “left” is added in the denotation if the difference between right and left need be indicated. For example, the right thigh element S7 is sometimes referred to as an S_right thigh or S_right thigh apparatus.

Moreover, the hip joint J1, the knee joint J2, the ankle joint J3, and the MP joint J4 are sometimes referred to as J_hip, J_knee, J_ankle, and J_MP, respectively. Again, if there is a need for indicating the difference between right and left, the term “right” or “left” is added in the denotation similarly to the above.

The arithmetic processing unit 23 accepts detected outputs of the joint displacement sensors 29, 30, and 31, the light emitter/receiver 26, the acceleration sensor 21, and the gyro sensor 22 via an A/D converter, which is not shown, and accepts detected outputs (ON/OFF signals) of the landing sensors 32, 33 each in a predetermined arithmetic processing period. It then performs the arithmetic processing of the person-side joint moment estimation means 41 and the apparatus-side joint moment estimation means 42 in parallel, first.

The arithmetic processing of the person-side joint moment estimation means 41 is described in detail below. First, the arithmetic processing operations of the transformation tensor generation means 51, the two-dimensional leg posture and element center-of-gravity location calculation means 52, and the three-dimensional joint and element center-of-gravity location calculation means 53 are sequentially performed. A rigid element is assumed to mean a rigid element of the person rigid link model S1, unless otherwise specified, hereinafter until the description of the person joint moment estimation means 41 is completed.

The arithmetic processing of the transformation tensor generation means 51 includes generating a transformation tensor R(LC→BC) for performing a coordinate transformation of a vector quantity between the leg coordinate system LC corresponding to each leg plane PL and the body coordinate system BC, and transformation tensors R(C_abdomen→BC) and R(C_chest→BC) for performing a coordinate transformation of a vector quantity between each of the element coordinate system C5 of the abdomen element S5 and the element coordinate system C6 of the chest element S6 and the body coordinate system BC.

The transformation tensor R(LC→BC) is determined from rotation angles around two axes except the rotation angle around a rotation axis a29 perpendicular to the leg plane PL among the rotation angles around three axes of the hip joint detected by the joint displacement sensor 29 of the hip joint region 4. In this embodiment, if the rotation angles of the hip joint around two axes except the rotation axis a29 perpendicular to the leg plane PL (rotation angles accompanying an abduction or adduction and a slewing motion of the leg) are determined, the posture relationship between the leg coordinate system LC and the body coordinate system BC is integrally determined. Therefore, the transformation tensor R(LC→BC) can be obtained from the detected values of the rotation angles around two axes except the rotation angle around the rotation axis a29 perpendicular to the leg plane PL out of the rotation angles around three axes of the hip joint. Incidentally, the transformation tensor R(LC→BC) is obtained for each of the right and left legs.

The transformation tensors R(C_abdomen→BC) and the R(C_chest→BC) are generated as described below. First, tilt angles of the abdomen element S5 and the chest element S6 relative to the waist element S4 of the person rigid link model S1 (more specifically, the tilt angles on the sagittal plane (XZ plane) relative to the Z axis direction of the body coordinate system BC) are grasped based on the detected outputs of the light emitter/receiver 26. Then, the transformation tensor R(C_abdomen→BC) is determined as one having the coordinate system C_abdomen tilting on the sagittal plane relative to the body coordinate system BC by the tilt angle of the abdomen element S5 relative to the waist element S4. Similarly, the transformation tensor R(C_abdomen→BC) is determined as one having the coordinate system C_chest tilting on the sagittal plane relative to the body coordinate system BC by the tilt angle of the chest element S6 relative to the waist element S4.

More specifically, although measurement has been made only for the tilt angles relative to the waist element S4 of the abdomen element S5 and the chest element S6 caused by the rotation around a single axis (around the Y axis of the C_abdomen and C_chest) of the lower joint of the upper body JU1 and the upper joint of the upper body JU2 of the person rigid link model S1 in this embodiment, it is also possible to measure tilt angles around two axes of the abdomen element S5 and the chest element S6, supposing that the lower joint of the upper body JU1 and the upper joint of the upper body JU2 can rotate, for example, around two axes (for example, around two axes of the Y axis and the X axis of the C_abdomen and the C_chest). Then, the transformation tensors R(C_abdomen→BC) and R(C_chest→BC) may be calculated based on the tilt angles around these two axes.

Incidentally, the transpositions of the aforementioned transformation tensors R(LC→BC), R(C_abdomen→BC), and R(C_chest→BC) are transformation tensors for performing inverse transformations therefor. Therefore, R(BC→LC)=R(LC→BC)^T, R(BC→C_abdomen)=R(C_abdomen→BC)^T, R(BC→C_chest)=R(C_chest→BC)^T(T designates a transposition).

In the arithmetic processing of the two-dimensional leg posture and element center-of-gravity location calculation means 52, first, tilt angles θ_thigh, θ_crus, and θ_foot of the thigh element S7, the crus element S8, and the foot element S9 of the person rigid link model S1 are respectively calculated from rotation angles around axes (rotation axes a29, a30, and a31 in FIG. 2) perpendicular to the leg plane PL of the hip joint, the knee j, and the ankle joint of the leg, which are grasped from the detected outputs of the joint displacement sensors 29 to 31 of each leg. Note here that the tilt angles θ_thigh, θ_crus, and θ_foot are those relative to the Z axis direction of the leg coordinate system LC related to the leg plane PL. The θ_thigh, θ_crus, and θ_foot are also tilt angles of the thigh element S7, the crus element S8, and the foot element S9 of the apparatus rigid link model S1′, respectively.

Specifically, as shown in FIG. 9, supposing that the detected rotation angles of the hip joint, the knee joint, and the ankle joint (the rotation angles around the axis perpendicular to the leg plane PL (=the XZ plane of the leg coordinate LC) from the reference posture condition) are θ_hip, θ_knee, and θ_ankle, the θ_thigh, θ_crus, and θ_foot are calculated in order by the following formulas (1a) to (1c), respectively:
θ_thigh=−θ_hip (1a)
θ_crus=θ_thigh+θ_knee (1b)
θ_foot=θ_crus−θ_ankle+90° (1c)
where θ_hip>0, θ_knee>0, and θ_ankle>0, while θ_thigh<0, θ_crus>0, and θ_foot<0. In addition, the calculations of θ_thigh, θ_crus, and θ_foot are performed for each of the leg sections individually.

The tilt angles θ_thigh, θ_crus, and θ_foot calculated as described above are assumed to indicate the posture on the leg plane PL corresponding to the leg section S2 of the rigid elements of each of the leg sections S2 of the person-side and apparatus-side rigid link models S1, S1′.

Subsequently the positions on the XZ plane of the leg coordinate system LC, in other words, on the leg plane PL of the joint elements of the each leg section S2 are calculated by using θ_thigh, θ_crus, and θ_foot calculated as described above and the lengths of the rigid elements of the each leg section S2 of the person rigid link model S1 previously stored in the memory of the arithmetic processing unit 23. Specifically, the position vectors U(J_hip/LC), U(J_knee/LC), U(J_ankle/LC), and U(J_MP/LC) in the leg coordinate system LC of the joint elements J_hip (J1), J_knee (J2), J_ankle (J3), and J_MP (J4) of the each leg section S2 are sequentially calculated in order by the formulas (2a) to (2d) shown below, respectively. In this condition, all of the positions of J_hip, J_knee, J_ankle, and J_MP in the Y-axis direction of the leg coordinate system LC (in the direction of a normal line of the leg plane PL), namely, the Y coordinate components in the leg coordinate system LC of J_hip, J_knee, J_ankle, and J_MP are assumed to be zero. In other words, all of J_hip, J_knee, J_ankle, and J_MP are assumed to be movable only on the leg plane PL in this embodiment.
U(J_hip/LC)=(0, 0, 0)^T (2a)
U(J_knee/LC)=U(J< /i>_hip/LC)+(−L7×sin(θ_thigh), 0, −L7×cos(θ_thigh))^T (2b)
U(J_ankle/LC)=U(J _knee/LC)+(−L8×sin(θ_crus), 0, −L8×cos(θ_thigh))^T (2c)
U(J_—MP/LC)= U(J_ankle/LC)+(−L9×sin(θ_foot), 0, −L9×cos(θ_foot))^T (2d)

In the above, L7, L8, and L9 in the formulas (2b), (2c), and (2d) are the lengths of the thigh element S7, the crus element S8, and the foot element S9 and they are previously stored in the memory of the arithmetic processing unit 23 as described above. The vectors of the second term in the right-hand side of the formulas (2b) to (2d) mean the position vector of the knee joint J2 viewed from the hip joint J1, the position vector of the ankle joint J3 viewed from the knee joint J2, and the position vector of the MP joint J4 viewed from the ankle joint J3, respectively. In this regard, a pair of the X coordinate component and the Z coo

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