Patent Grant
8298164
1. Field of the Invention
The present invention relates to a motion assisting device for assisting a walking motion of a creature by applying to the creature an assisting force which assists a leg in moving with respect to a body.
2. Description of the Related Art
According to a first prior art (refer to Japanese Patent Laid-open No. 2004-073649), a periodical walking motion of a creature, such as a human whose body such as a lower limb or the like is suffering from hypofunction, is assisted by applying a periodically varying force to the creature. According to a second prior art (refer to Japanese Patent Laid-open No. 2007-061217), a periodical motion of a human can be assisted by adjusting a force applied to the human according to a second model (spring model) representing a behavior feature of a virtual elastic element so as to match a motion scale of the human to a desired motion scale thereof. According to the first and the second prior arts, the periodical motion of a creature can be assisted so as to match a motion rhythm of the creature to a desired motion rhythm thereof. Particularly, according to the second prior art adopting the spring model, the periodical motion of the creature can be assisted so as to match the motion scale of the creature to the desired motion scale thereof.
However, the first prior art and the second prior art can be further modified from the viewpoint of conducting a smooth motion of a plurality of legs of the creature.
The present invention has been accomplished in view of the aforementioned problems, and it is therefore an object of the present invention to provide a motion assisting device capable of assisting a periodical walking motion of a creature so as to conduct a smooth motion of a plurality of legs thereof.
A first aspect of the present invention provides a motion assisting device which assists a walking motion of a creature by applying to the creature an assisting force which assists a leg in moving with respect to a body comprises: a controlling device configured to control the assisting force according to an auxiliary coefficient, wherein the controlling device includes a first processing element configured to determine whether the leg is at an on-ground state or at an off-ground state, and a posture of the leg with respect to the body; and a second processing element configured to adjust the auxiliary coefficient so as to make the auxiliary coefficient in a reinforcement duration containing a part or a total of a second duration in which the leg is performing a stretch motion at an on-ground state as a second reinforcement duration greater than the auxiliary coefficient in a duration other than the reinforcement duration, on the basis of a determination result by the first processing element.
According to the motion assisting device of the first aspect of the present invention, the assisting force applied to the creature is reinforced only by an increment in the auxiliary coefficient increased in the reinforcement duration containing the second reinforcement duration. Note that it is not limited that the reinforced assisting force is stronger than the assisting force in the duration other than the reinforcement duration. The second reinforcement duration is referred to as a part or a total of the second duration in which the leg is performing a stretch motion (backward motion) at the on-ground state. Accordingly, the stretch motion of the leg at the on-ground state is assisted by a relatively stronger assisting force, and resultantly, the leg is subjected to a relatively stronger floor reaction force. The floor reaction force is transmitted to the body through the leg at the on-ground state to conduct the body to translate forward. When the leg is stretched by the assisting force at the on-ground state, there occurs a reflex (stretch reflex) to the stretch motion of the leg. As a result, the flexion motion (forward motion) of the leg at a subsequent off-ground state is induced by the stretch reflex at the previous on-ground state. According thereto, the periodical walking motion of the creature can be assisted to conduct not only a stretch motion (backward motion) of the leg of the creature at the on-ground state, but also a smooth flexion motion (forward motion) thereof at the off-ground state.
A second aspect of the motion assisting device of the present invention is dependent on the first aspect of the present invention, wherein the second processing element is configured to adjust the auxiliary coefficient so as to make the auxiliary coefficient in the reinforcement duration further containing a part or a total of a first duration in which the leg is moved from the flexion motion at the off-ground state to the stretch motion to step on the ground as a first reinforcement duration greater than the auxiliary coefficient in the duration other than the reinforcement duration.
According to the motion assisting device of the second aspect of the present invention, the assisting force applied to the creature is controlled to be stronger in the reinforcement duration containing the first reinforcement duration and the second reinforcement duration than that in the duration other than the reinforcement duration. The first reinforcement duration is referred to as a part or a total of the first duration in which the leg is moved from the flexion motion at the off-ground state to the stretch motion to step on the ground. Accordingly, the stretch motion of the leg immediately before the leg steps on the ground is assisted by a relatively stronger assisting force. When the leg is landed on the ground, it is subjected to a relatively stronger floor reaction force. As above mentioned, the floor reaction force is transmitted to the body through the leg at the on-ground state to conduct the body to translate forward and the leg to perform the flexion motion at the off-ground state. According thereto, the periodical walking motion of the creature can be assisted to conduct not only a stretch motion (backward motion) of the leg of the creature at the on-ground state, but also a smooth flexion motion (forward motion) thereof at the off-ground state.
A third aspect of the motion assisting device of the present invention is dependent on the first aspect of the present invention, wherein the controlling device includes a motion oscillator determination element configured to determine a second motion oscillator which periodically varies according to the walking motion of the creature; and a second oscillator generation element configured to generate a second oscillator as an output oscillation signal from a second model by inputting the second motion oscillator determined by the motion oscillator determination element to the second model as an input oscillation signal, in which the second model is configured to generate an output oscillation signal which periodically varies at an angular velocity defined according to a second intrinsic angular velocity on the basis of an input oscillation signal; and the controlling device controls the assisting force so that the assisting force periodically varies according to an amplitude determined according to the auxiliary coefficient and an angular velocity of the second oscillator generated by the second oscillator generation element.
According to the motion assisting device of the third aspect of the present invention, the periodical walking motion of the creature can be assisted to conduct not only a stretch motion (backward motion) of the leg of the creature at the on-ground state, but also a smooth flexion motion (forward motion) thereof at the off-ground state. Furthermore, the periodical operation of the motion assisting device can be controlled so as to maintain stable an amplitude relationship and a phase relationship between the periodical walking motion of the creature and the periodical operation of the motion assisting device.
A fourth aspect of the motion assisting device of the present invention is dependent on the third aspect of the present invention, wherein the controlling device includes a motion variable determination element configured to determine a motion variable representing a scale of the walking motion performed by the creature; the second model is defined by a simultaneous differential equation having a plurality of state variables representing a behavior state of the creature; and the second oscillator generation element corrects the second model by correcting a constant or a coefficient contained in the simultaneous differential equation so as to approximate a determination value of the motion variable obtained from the motion variable determination element to a desired value and generates the second oscillator on the basis of the state variables obtained by solving the simultaneous differential equation.
According to the motion assisting device of the fourth aspect of the present invention, the periodical walking motion of the creature can be assisted to conduct not only a stretch motion (backward motion) of the leg of the creature at the on-ground state, but also a smooth flexion motion (forward motion) thereof at the off-ground state. Furthermore, the periodical walking motion can be assisted so as to approximate the motion variable representing the scale of the walking motion performed by the creature to a desired value.
A fifth aspect of the motion assisting device of the present invention is dependent on the third aspect of the present invention and further includes an adjusting device, wherein the second model is defined by a simultaneous differential equation having a plurality of state variables representing a behavior state of the creature; the adjusting device is capable of manually adjusting a constant or a coefficient in the simultaneous differential equation; and the second oscillator generation element generates the second oscillator on the basis of the state variables obtained by solving the simultaneous differential equation.
According to the motion assisting device of the fifth aspect of the present invention, the periodical walking motion of the creature can be assisted to conduct not only a stretch motion (backward motion) of the leg of the creature at the on-ground state, but also a smooth flexion motion (forward motion) thereof at the off-ground state. Furthermore, the operation mode of the motion assisting device can be manually adjusted through the adjusting device so as to maintain stable an amplitude relationship and a phase relationship between the periodical walking motion of the creature and the periodical operation of the motion assisting device.
A sixth aspect of the motion assisting device of the present invention is dependent on the fourth aspect of the present invention, wherein the constant or the coefficient in the simultaneous differential equation adjusted by the second processing element serves as the auxiliary coefficient.
According to the motion assisting device of the sixth aspect of the present invention, the periodical walking motion of the creature can be assisted to conduct not only a stretch motion (backward motion) of the leg of the creature at the on-ground state, but also a smooth flexion motion (forward motion) thereof at the off-ground state. Furthermore, by adjusting the auxiliary coefficient for defining the assisting force applied to the creature, the motion variable representing the scale of the periodical walking motion of the creature can be made to approximate to the desired value, or the operation mode of the motion assisting device can be manually adjusted through the adjusting device to maintain stable an amplitude relationship and a phase relationship between the periodical walking motion of the creature and the periodical operation of the motion assisting device.
A seventh aspect of the motion assisting device of the present invention is dependent on the third aspect of the present invention, wherein the controlling device includes a motion variable determination element configured to determine a motion variable representing a scale of the walking motion performed by the creature; and the controlling device controls the assisting force so that the assisting force periodically varies according to an amplitude determined according to an elastic coefficient of a virtual elastic element serving as the auxiliary coefficient and an angular velocity of the second oscillator generated by the second oscillator generation element, both of which are used to approximate a determination value of the motion variable obtained from the motion variable determination element to a desired value.
According to the motion assisting device of the seventh aspect of the present invention, the periodical walking motion of the creature can be assisted to conduct not only a stretch motion (backward motion) of the leg of the creature at the on-ground state, but also a smooth flexion motion (forward motion) thereof at the off-ground state. Furthermore, the periodical walking motion can be assisted so as to approximate the motion variable representing the scale of the walking motion performed by the creature to the desired value.
An eighth aspect of the motion assisting device of the present invention is dependent on the third aspect of the present invention, wherein the motion oscillator determination element determines a first motion oscillator which periodically varies according to the walking motion of the creature; the controlling device includes a first oscillator generation element and an intrinsic angular velocity setting element, in which the first motion oscillator generation element is configured to generate a first oscillator as an output oscillation signal from a first model by inputting the first motion oscillator determined by the motion oscillator determination element to the first model as an input oscillation signal, in which the first model is configured to generate an output oscillation signal which varies at an angular velocity defined according to a first intrinsic angular velocity by entraining to an input oscillation signal; and the intrinsic angular velocity setting element is configured to set an angular velocity of a second virtual oscillator as the second intrinsic angular velocity according to a virtual model on the basis of a first phase difference between the first motion oscillator determined by the motion oscillator determination element and the first oscillator generated by the first oscillator generation element so as to approximate a second phase difference to a desired phase difference, in which the virtual model is expressed by a first virtual oscillator and the second virtual oscillator which vary periodically with the second phase difference while interacting mutually.
According to the motion assisting device of the eighth aspect of the present invention, the periodical walking motion of the creature can be assisted to conduct not only a stretch motion (backward motion) of the leg of the creature at the on-ground state, but also a smooth flexion motion (forward motion) thereof at the off-ground state. Furthermore, the periodical operation of the motion assisting device can be controlled so as to approximate the phase relationship between the periodical walking motion of the creature and the periodical operation of the motion assisting device to the desired phase relationship expressed by the desired phase difference.
An embodiment of a motion assisting device according to the present invention will be described with reference to the drawings. Hereinafter, symbols “L” and “R” are used to differentiate a left leg and a right leg or the like. However, the symbols may be omitted if there is not necessary to differentiate a left part and a right part or a vector having both of left and right components is mentioned. Moreover, symbols “+” and “−” are used to differentiate a flexion motion (forward motion) and a stretch motion (backward motion) of the leg (in particular, a thigh).
First, descriptions will be performed on a first embodiment of the present invention.
The first orthosis 1100 includes a first supporter 1110 and a first link member 1120. The first supporter 1110 is made from a combination of a rigid material such as a rigid resin and a flexible material such as a fiber and is mounted on the waist backward. The first link member 1120 is made of a rigid resin, and is fixed at the first supporter 1110 in such a way that when the first supporter 1110 is attached to the waist, the first link member 1120 is located at both sides of the waist laterally. The second orthosis 1200 includes a second supporter 1210 and a second link member 1220. Similar to the first supporter 1110, the second supporter 1210 is also made from a combination of a rigid material and a flexible material and is mounted on a front side and a back side of the thigh, respectively. The second link member 1220 is made of a rigid resin, extending vertically along outside of the thigh and formed as being forked into two downwardly and is connected to an output shaft of the actuator 15 and the second supporter 1210. Note that it is acceptable to mount a third orthosis to the human P. The third orthosis is comprised of a third supporter and a third link member. The third supporter is formed to have a shape of a slipper or a shoe which is mounted to a foot of the human P. The third link member is configured to extend vertically along the crus so as to connect the third supporter and a lower end portion of the second link member 1220 in a movable manner.
The hip joint angle sensor 11 is comprised of a rotary encoder disposed on a transverse side of the waist of the human P and outputs a signal according to the hip joint angle. The actuator 15 is comprised of a motor, including either one or both of a reduction gear and a compliance mechanism where appropriate. The battery 1000 is housed in the first orthosis 1100 (for example, fixed in multiple sheets of cloth constituting the first supporter 1110), which supplies electrical power to the actuator 15, the controlling device 100 and the like. Note that it is acceptable to attach or house the controlling device 100 and the battery 1000 in the second orthosis 1200; it is also acceptable to dispose them separately from the motion assisting device 10.
The controlling device 100 includes a computer housed in the first orthosis 1100 and a software stored in a memory or a storing device in the computer. The controlling device 100 controls an operation or an output torque T of the actuator 15 by adjusting the electrical power supplied from the battery 1000 to the actuator 15. The magnitude of an output from the actuator 15 is controlled according to the value of an auxiliary coefficient which will be described hereinafter. The controlling device 100 illustrated in
The first processing element 101 determines whether each leg of the human P is on the ground or has been raised from the ground and a posture of each with respect to the body. The second processing element 102 adjusts the auxiliary coefficient so as to make the auxiliary coefficient in a reinforcement duration greater than the auxiliary coefficient in a duration other than the reinforcement duration on the basis of the determination result by the first processing element 101.
The motion variable determination element 108 determines the value of a motion variable ζ which represents a scale of a periodical motion of the human P. The motion oscillator determination element 110 determines an angular velocity of each hip joint as a first motion oscillator φ1 and an angle thereof as a second motion oscillator φ2 on the basis of an output from the hip joint angle sensor 11. Each of the first motion oscillator φ1 and the second motion oscillator φ2 varies periodically according to the periodical motion of the human P, and a variation pattern thereof is defined by an amplitude and a phase (or an angular velocity which is a first order differentiation of the phase by time). Determination of an oscillator means to determine a periodical variation pattern of the oscillator. The first oscillator generation element 120 generates a first oscillator ξ1 as an output oscillation signal from a first model by inputting the first motion oscillator φ1 determined by the motion oscillator determination element 110 as an input oscillation signal to the first model. Generation of an oscillator means to define a periodical variation pattern for the oscillator. The “first model” is a model configured to generate an output oscillation signal which varies at an angular velocity defined according to a first intrinsic angular velocity ω1 by entraining to an input oscillation signal.
The intrinsic angular velocity setting element 130 includes a first phase difference setting element 131, a second phase difference setting element 132, a correlation coefficient setting element 133, a first angular velocity setting element 134, and a second angular velocity setting element 135. The intrinsic angular velocity setting element 130 sets a second intrinsic angular velocity ω2 so as to approximate a second phase difference δθ2 to a desired phase difference δθ0 according to a virtual model on the basis of a first phase difference δθ1. The first phase difference δθ1 is a phase difference between the first motion oscillator φ1 determined by the motion oscillator determination element 110 and the first oscillator ξ1 generated by the first oscillator generation element 120. The virtual model represents a periodical motion of the human P with a periodical variation of a first virtual oscillator φ1, a periodical operation of the motion assisting device 10 with a periodical variation of a second virtual oscillator φ2, and a phase difference between the periodical motion of the human P and the periodical operation of the motion assisting device 10 with a phase difference between the first virtual oscillator φ1 and the second virtual oscillator φ2, namely, the second phase difference δθ2, respectively.
The second oscillator generation element 140 generates a second oscillator ξ2 as an output oscillation signal from a second model by inputting the second motion oscillator φ2 determined by the motion oscillator determination element 110 as an input oscillation signal to the second model. The “second model” is a model which generates an output oscillation signal varying at an angular velocity defined according to the second intrinsic angular velocity ω2 defined by the intrinsic angular velocity setting element 130 on the basis of an input oscillation signal.
The auxiliary oscillator generation element 150, on the basis of the second oscillator ξ2 generated by the second oscillator generation element 140, generates an auxiliary oscillator η. The auxiliary oscillator η is used to define a variation pattern of the torque applied to the thigh by the actuator 15 in the motion assisting device 10.
Hereinafter, the operation of the motion assisting device 10 having the configuration mentioned in the first embodiment of the present invention will be described. The motion variable determination element 108, on the basis of the output signal from the hip joint angle sensor 11, determines the left hip joint angle and the right hip joint angle at the respective finished timing of the flexion motion and the finished timing of the stretch motion of the thigh for each walking cycle (FIG. 3/S002) (in detail, the left hip joint angle at the finished timing of the flexion motion, the left hip joint angle at the finished timing of the stretch motion, the right hip joint angle at the finished timing of the flexion motion and the right hip joint angle at the finished timing of the stretch motion of the thigh) as the motion variable ζ={ζi|i=L+, L−, R+, R−}. Note that it is acceptable to determine a footstep of the human P as the motion variable ζ. The footstep, for example, may be determined on the basis of a correlation among the hip joint angle of the human P which is determined according to the output signal from the hip joint angle sensor 11, the hip joint angle of the human P stored in memory and the foot position in the anteroposterior direction. Herein, it is possible to determine a step rate (numbers of steps every unit time) and a walking velocity of the human P, and thereafter determine the footstep on the basis of the step rate and the walking velocity. The step rate may be determined on the basis of an output signal from an acceleration sensor attached to the human P, which outputs the output signal according to an acceleration of the human P in the vertical direction. The walking velocity may be determined on the basis of an output signal from a velocity sensor disposed in a treadmill 30, which outputs the output signal according to the speed of an endless belt 32. Moreover, it is also acceptable to determine the value of a function, namely the motion variable ζ, having multiple variables containing at least one of the walking rate (=footstep/step rate), the footstep, the left hip joint angle at the finished timing of the flexion motion and the left hip joint angle at the finished timing of the stretch motion, the right hip joint angle at the finished timing of the flexion motion and the right hip joint angle at the finished timing of the stretch motion of the thigh for each walking cycle.
Further, the motion oscillator determination element 110 determines the angular velocity of each of the left and right hip joints of the human P as the first motion oscillator φ1=(φ1L, φ1R) on the basis of the output from the hip joint angle sensor 11 (FIG. 3/S011). Furthermore, the motion oscillator determination element 110 determines the left hip joint angle and the right joint angle of the human P as the second motion oscillator φ2=(φ2L, φ2R) on the basis of the output from the hip joint angle sensor 11 (FIG. 3/S012).
Note that it is acceptable to determine an arbitrary variable varying periodically according to the periodical motion of the human P by using an appropriate sensor as the first motion oscillator φ1 and the second motion oscillator φ2, respectively. For example, an angle or angular velocity of an arbitrary joint, such as the hip joint, knee joint, ankle joint, shoulder joint, elbow joint and the like, and a position of the thigh, foot, upper arm and waist (the position or the like in the anteroposterior direction or the vertical direction with the center-of-gravity of the human P as a reference), and a variation pattern of velocity or acceleration may be determined as the motion oscillator. The variation patterns of various parameters varying at a rhythm in conjunction with the walking motion rhythm, such as a sound generated when the left or right leg steps on the ground, a breathing sound, a deliberate phonation or the like, may be determined as one or both of the first motion oscillator φ1 and the second motion oscillator φ2. Moreover, it is acceptable to determine variables representing the periodical motion state of the same body part, such as the angle and the angular velocity or the like of the same joint, as the first motion oscillator φ1 and the second motion oscillator φ2, respectively; it is also acceptable to determine variables representing the periodical motion state of different body parts, such as the respective angles and the angular velocities or the like of different joints, as the first motion oscillator φ1 and the second motion oscillator φ2, respectively.
Thereafter, the first oscillator generation element 120 generates the first oscillator ξ1 as an output oscillation signal from the first model by inputting the first motion oscillator φ1 determined by the motion oscillator determination element 110 as an input oscillation signal to the first model (FIG. 3/S020). The first model represents the correlation between a plurality of first elements, such as the left and right feet or the like, and generates the output oscillation signal which varies at the angular velocity defined according to the first intrinsic angular velocity ω1=(ω1L, ω1R) by entraining to the input oscillation signal as described above. The first model, for example, may be defined by the Van der Pol equation expressed by the equation (10). Moreover, it is possible that the first oscillator generation element 120 sequentially updates the first model by adopting an updated second intrinsic angular velocity ω2 set by the intrinsic angular velocity setting element 130 as an updated first intrinsic angular velocity ω1, and generates a subsequent first oscillator ξ1 as the output oscillation signal by inputting a subsequent first motion oscillator φ1 as the input oscillation signal into the updated first model.
(d2φ1L/dt2)=A(1−ξ1L2)(dξ1L/dt)−ω1L2ξ1L+g(ξ1L−ξ1R)+K1φ1L,
(d2φ1R/dt2)=A(1−ξ1R2)(dξ1R/dt)−ω1R2ξ1R+g(ξ1R−ξ1L)+K1φ1R (10)
Wherein:
A: a positive coefficient set in such a way that a stable limit cycle may be drawn from the first oscillator ξ1 and the first order temporal differential (dξ1/dt) thereof in a plane of “ξ1−(dξ1/dt)”;
g: a first correlation coefficient for reflecting the correlation of different body parts, such as the left and right feet of the human P or the like, with the correlation of each of the left and right components of the first oscillator ξ1 (correlation of the output oscillation signals among the plurality of first elements); and
K1: a feedback coefficient with respect to the first motion oscillator φ1.
The first oscillator ξ1=(ξ1L, ξ1R) is calculated or generated according to the Runge-Kutta method. The angular velocity of each of the components ξ1L and ξ1R of the first oscillator ξ1 represents a virtual rhythm which assists the motion of the left leg and the right leg, respectively. Further, the first oscillator ξ1 has a feature to vary or oscillate periodically with an autonomous angular velocity or rhythm defined on the basis of the first intrinsic angular velocity ω1 while harmonizing with the rhythm of the first motion oscillator φ1 varying at an angular velocity or rhythm substantially the same as a rhythm of the actual walking motion, according to the “mutual entrainment” (harmonization effect) which is one of the properties of the Van del Pol equation.
In addition, the first model may be expressed by the Van der Pol equation having a different expression from that of the equation (10), or by a certain equation which generates the output oscillation signal varying periodically at the angular velocity defined on the basis of the first intrinsic angular velocity ω1, accompanied by the mutual entrainment to the input oscillation signal. Moreover, it is acceptable to increase the numbers of the first motion oscillator φ1, namely the determination object. The more numbers of the first motion oscillators φ1 are input to the first model, the motion will be more elaborately assisted by considering the motions of various body parts of the human P through the adjustment of the correlation coefficients, although the correlation members in a non-linear differential equation corresponding to the first oscillator ξ1 generated by the Van der Pol equation for defining the first model will become more accordingly.
The phase difference between the periodical motion of the human P and the periodical operation of the motion assisting device 10 defines the motion behavior of the human P with respect to the operation of the motion assisting device 10. For example, when the phase difference is positive, the human P can move in a way of leading the motion assisting device 10. On the other hand, when the phase difference is negative, the human P can move in a way of being led by the motion assisting device 10. Therefore, when the phase difference (the first phase difference) δθ1 of the first oscillator ξ1 with respect to the first motion oscillator φ1 deviates from the desired phase difference δθ0, it is very possible for the motion behavior of the human P to become unstable. Consequently, there is a high probability that the motion rhythm of the human P whose relative motions between the waist and the thigh assisted by the torque T varying periodically at an angular velocity corresponding to the auxiliary oscillator η would deviate from the desired motion rhythm.
Therefore, from the viewpoint of matching the motion rhythm of the human P with the desired motion rhythm while maintaining the mutual harmony between the first motion oscillator φ1 and the first oscillator ξ1, an appropriate second intrinsic angular velocity ω2 for defining the second oscillator ξ2 is set by the intrinsic angular velocity setting element 130. In other words, an appropriate second intrinsic angular velocity ω2 is set from the viewpoint of realizing an appropriate phase difference between an assisting rhythm of the motion assisting device 10 and the motion rhythm of the human P so that the motion rhythm of the human P is in accordance with the desired motion rhythm while harmonizing the assisting rhythm of the motion assisting device 10 with the motion rhythm of the human P.
Specifically, the first phase difference setting element 131 sets a phase difference between the first motion oscillator φ1 and the first oscillator ξ1 as the first phase difference δθ1 (FIG. 3/S031). The first phase difference δθ1 is calculated or set on the basis of a difference of time between, for example, a timing where φ1=0 and (dφ1/dt)>0 and a timing where ξ1=0 and (dξ1/dt)>0.
Thereafter, the second phase difference setting element 132 sets the second phase difference δθ2 on a condition that the first phase difference δθ1 over the recent three walking cycles is constant or the variation of the first phase difference δθ1 is within an allowable range (FIG. 3/S032). In detail, a phase difference between the first virtual oscillator φ1 (φ1L, φ1R) and the second virtual oscillator φ2 (φ2L, φ2R) which are defined in the virtual model, which is expressed by the equations (21) and (22), is set as the second phase difference δθ2 according to the equation (23). The first virtual oscillator φ1 in the virtual model virtually represents the first motion oscillator φ1; the second virtual oscillator φ2 in the virtual model represents the auxiliary oscillator η virtually.
dφ1L/dt=ω1L+εL sin(φ2L−φ1L),dφ1R/dt=ω1R+εR sin(φ2R−φ1R) (21)
dφ2L/dt=ω2L+εL sin(φ1L−φ2L,dφ2R/dt=ω2R+εR sin(φ1R−φ2R) (22)
δθ2L=arcsin {(ω1/L−ω2/L)/2εL},δθ2R=arcsin {(ω1/R−ω2/R)/2εR} (23)
Wherein, each component of “ε=(εL, εR)” stands for a correlation coefficient representing the correlation between each component of the first virtual oscillator φ1 and each component of the second virtual oscillator φ2. “ω1/=(ω1/L, ω1/R)” is the angular velocity for each component of the first virtual oscillator φ1, and “ω2/=(ω2/L, ω2/R)” is the angular velocity for each component of the second virtual oscillator φ2.
Subsequently, the correlation coefficient setting element 133 sets the correlation coefficient ε so that the deviation between the first phase difference δθ1 set by the first phase difference setting element 131 and the second phase difference 602 set by the second phase difference setting element 132 is minimum (FIG. 3/S033).
Specifically, the correlation coefficient ε(ti) at each timing tk where the first motion oscillator φ1 for each of the left and right components becomes zero is sequentially set according to the equation (24).
εL(tk+1)=εL(tk)−BL{V1L(tk+1)−V1L(tk)}/{εL(tk)−εL(tk−1)}
εR(tk+1)=εR(tk)−BR{V1R(tk+1)−V1R(tk)}/{εR(tk)−εR(tk−1)},
V1L(tk+1)≡(½){δθ1L(tk+1)−δθ2L(tk)}2,
V1R(tk+1)≡(½){δθ1R(tk+1)−δθ2R(tk)}2 (24)
Wherein, each component of “B=(BL, BR)” is a coefficient representing the stability of the potential V1=(V1L, V1R) for approximating each component of the first phase difference δθ1 to each of the left and right components of the second phase difference δθ2.
Next, the first angular velocity setting element 134 sets the angular velocity of the first virtual oscillator φ1 as the first angular velocity ω1/according to the equation (25) on the basis of the correlation coefficient ε set by the correlation coefficient setting element 133 so that the deviation between the first phase difference δθ1 and the second phase difference δθ2 for each component is minimum under the condition that the angular velocity ω2/of the second virtual oscillator φ2 is constant (FIG. 3/S034).
ω1/L(tk)=−αL∫dtq1L(t),ω1/R(tk)=−αR∫dtq1R(t)
q1L(t)=(4εL2(tk)−(ω1L(t)−ω2L(tk)))1/2×sin(arcsin [(ω1/L(t)−ω2/L(tk−1))/2εL(tk)]−δθ2L(tk)),
q1R(t)=(4εL2(tk)−(ω1/R(t)−ω2/R(tk)))1/2×sin(arcsin [(ω1/R(t)−ω2/R(tk−1))/2εR(tk)]−δθ2R(tk)) (25)
Wherein, each component of “α=(αL, αR)” is a coefficient representing the stability of the system.
The virtual model is constructed on a condition that the mutual harmony between the first motion oscillator φ1 and the first oscillator ξ1 is also maintained between the first virtual oscillator φ1 and the second virtual oscillator φ2 by setting the correlation coefficient ε and the angular velocity ω1/. In other words, the virtual model is constructed so that the first virtual oscillator φ1 representing the periodical motion of the human P and the second virtual oscillator φ2 representing the periodical operation of the motion assisting device 10 vary periodically at the second phase difference δθ2 with a mutual harmonization.
Thereafter, the second angular velocity setting element 135 set the angular velocity of the second virtual oscillator φ2 as the second angular velocity ω2/for each component on the basis of the first angular velocity ω1/set by the first angular velocity setting element 134 (FIG. 3/S035). The second angular velocity ω2/=(ω2/L, ω2/R) is set according to the equation (26) so that the second phase difference δθ2 for each of the left and right components approximates to the desired phase difference δθ0. Subsequently, the second angular velocity ω2/is set as the second intrinsic angular velocity ω2 (FIG. 3/S036).
ω2/L(tk)=βL∫dtq2L(t),ω2/R(tk)=βR∫dtq2R(t)
q2L(t)=(4εL2(tk)−(ω1/L(t)−ω2/L(tk)))1/2×sin(arcsin [(ω1/L(tk)−ω2/L(t))/2εL(tk)]−δθ0),
q2R(t)=(4εR2(tk)−(ω1/R(t)−ω2/R(tk)))1/2×sin(arcsin [(ω1/R(tk)−ω2/R(t))/2εR(tk)]−δθ0) (26)
Wherein, each component of “β=(βL, βR)” is a coefficient representing the stability of the system.
Accordingly, the second angular velocity ω2/is appropriately set from the viewpoint of approximating the phase difference between the periodical motion of the human P represented by the first virtual oscillator φ1 and the periodical operation of the motion assisting device 10 represented by the second virtual oscillator φ2 to the desired phase difference δθ0, while the mutual harmony between the first motion oscillator φ1 and the first oscillator ξ1 is maintained between the periodical motion of the human P and the periodical operation of the motion assisting device 10.
The second oscillator generation element 140 corrects the second model by appropriately correcting a coefficient c contained in the simultaneous differential equation representing the second model according to the equation (28) (FIG. 3/S004). “c={ci|i=L+, L−, R+, R−}” is a coefficient to be adjusted so that the motion variable ζ determined by the motion variable determination element 108 approximates to a desired value ζ0 or a deviation therebetween is minimum. The coefficient ci is served as the “auxiliary coefficient” and is to be corrected accordingly whether or not each leg is in the reinforcement duration, which will be explained hereinafter.
ci(tk+1)=ci(tk)−Ci{Vi(tk+1)−Vi(tk)}/{ci(tk)−ci(tk−1)},
Vi(tk+1)≡(½){ζi(tk+1)−ζi(tk)}2 (28)
Each component of “c=cL+, cL−, cR+, cR−}” is a coefficient representing the stability of a potential V2=(V2L+, V2L−, V2R+, V2R−) for approximating each component of the determination values of the motion variable ζ to each component of the desired value ζ0 thereof. “ζ0={ζ0i|i=L+, L−, R+, R−}” stands for the desired value for each of the left hip joint angle and the right hip joint angle at the finished timing of the flexion motion and at the finished timing of the stretch motion of the thigh every walking cycle, respectively. The desired value ζ0 may be calculated on the basis of a desired footstep of the human P which is stored preliminarily in the memory, according to the correlation between the left hip joint angle and the right hip joint angle at the finished timing of the flexion motion and at the finished timing of the stretch motion of the thigh every walking cycle, respectively, and a footstep between the left and right feet, which is also stored in the memory.
Thereafter, the first processing element 101 determines whether each leg of the human P is at the on-ground state or at the off-ground state, and determines a posture of each leg with respect to the body (FIG. 3/S006).
The on-ground state and the off-ground state of each leg vary periodically when the human P performs the periodical walking motion. Thereby, whether each leg is at the on-ground state or at the off-ground state can be determined on the basis of an arbitrary variable which varies periodically according to the periodical walking motion of the human P. For example, whether each leg is at the on-ground state or at the off-ground state can be determined on the basis of a periodical variation pattern of an angle or angular velocity of each of the left and right hip joints, an acceleration of each leg in the vertical direction, a floor reaction force subjected to each leg of the human P or the like determined by an appropriate sensor. As a posture of each leg with respect to the body, a value of a variable which can be used to specify the phase of the hip joint angle or the like in the walking cycle (for example, the phase is zero at the time when a flexion motion is finished, the phase at the time when a subsequent stretch motion to the flexion motion is finished is π, and the phase at the time when another flexion motion after the subsequent stretch motion is finished is 2π) is determined on the basis of the output signal from the hip joint angle sensor 11. The value of a state variable (to be described hereinafter) ui(i=L+, L−, R+, R−} for defining the second model varies periodically according to the periodical walking motion of the human P, therefore, whether each leg is at the on-ground state or at the off-ground state, or the posture of each leg with respect to the body can be determined on the basis of a periodical variation pattern of the value of the state variable ui.
Thereafter, the second processing element 102, on the basis of the determination result by the first processing element 101, adjusts the value of the auxiliary coefficient in such a way that the auxiliary coefficient in the reinforcement duration is greater than the auxiliary coefficient in the duration other than the reinforcement duration for each leg (FIG. 3/S008). The “reinforcement duration” is referred to as a duration including a second reinforcement duration, or a duration including a first reinforcement duration and a second reinforcement duration. The “first reinforcement duration” is referred to as a part or a total of the duration in which the leg is moved from the flexion motion at the off-ground state to the stretch motion to step on the ground. The “second reinforcement duration” is referred to as a part or a total of the duration in which the leg is performing a stretch motion at the on-ground state. The first reinforcement duration and the second reinforcement duration may be alternatively continuous or discontinuous in each walking cycle. Each of the first reinforcement duration and the second reinforcement duration may be continuous or discontinuous in each walking cycle, respectively. The coefficient ci is adjusted as the auxiliary coefficient. The coefficient ci is used to specify the variation feature of the state variable ui for defining the second model. The coefficient ci also serves as the correction subject adjusted on the basis of the motion variable ζ. In addition to or in place of the coefficient ci, it is also acceptable to adjust an inverse τ1i−1 of the time constant as the auxiliary coefficient.
For example, when the left leg is in a normal duration other than the reinforcement duration, the left flexion coefficient cL+ and the left stretch coefficient cL− are maintained at their former values. On the other hand, when the left leg is in the reinforcement duration, the left flexion coefficient cL+ is maintained at its former value, while the left stretch coefficient cL− is increased as (1+δ) (δ>0) times as its former value. The right leg is adjusted with the same auxiliary coefficient as the left leg. Specifically, when the right leg is in the normal duration other than the reinforcement duration, the right flexion coefficient cR+ and the right stretch coefficient cR− are maintained at their former values. On the other hand, when the right leg is in the reinforcement duration, the right flexion coefficient cR+ is maintained at its former value, while the right stretch coefficient cR− is increased as (1+δ) (δ>0) times as its former value. Note that there is no limitation on the increment of the auxiliary coefficient for the left leg and the right leg.
Subsequently, the second oscillator generation element 140 generates the second oscillator ξ2=(ξ2L+, ξ2L−, ξ2R+, ξ2R−) as an output oscillation signal from the second model, by inputting the second motion oscillator φ2 determined by the motion oscillator determination element 110 to the second model as an input oscillation signal (FIG. 3/S040). The second model represents the correlation between a plurality of second elements such as the neural elements or the like responsible for moving each leg to the flexion direction (forward direction) and the stretch direction (backward direction), and generates the output oscillation signal varying at an angular velocity defined according to the second intrinsic angular velocity ω2 set by the intrinsic angular velocity setting element 130 on the basis of the input oscillation signal as aforementioned.
The second model is defined by the simultaneous differential equation expressed by, for example, the equations (30). The simultaneous differential equation contains therein the state variable u={ui|i=L+, L−, R+, R−} representing the behavior state (specified by an amplitude and a phase) of each thigh to the flexion direction (forward direction) and the stretch direction (backward direction), respectively, and a self-inhibition factor ν={νi|i=L+, L−, R+, R−} representing compliance of each behavior state. Moreover, the simultaneous differential equation contains therein the desired value ζ0 for each of the left hip joint angle and the right hip joint angle at the finished timing of the flexion motion and at the finished timing of the stretch motion of the thigh every walking cycle, respectively, and the coefficient ci to be corrected as mentioned above. It is acceptable to increase the numbers of the second motion oscillator φ2 which is served as the determination object. The more numbers of the second motion oscillators φ2 are input to the second model, the more the correlation members in the simultaneous differential equation will become, however, it may allow an appropriate assist in the periodical motion of the human P through the adjustment of the correlation coefficients by considering the correlation between motion states of various body parts of the human P.
τ1L+(duL+/dt)=cL+ζ0L+−uL++wL+/L−ξ2L−+wL+/R+ξ2R+−λLνL++ƒ1(ω2L)+ƒ2(ω2L)K2φ2L,
τ1L−(duL−/dt)=cL−ζ0L−−uL−+wL−/L+ξ2L++wL−/R−ξ2R−−λLνL−+ƒ1(ω2L)+ƒ2(ω2L)K2φ2L,
τ1R+(duR+/dt)=cR+ζ0R+−uR++wR+/L+ξ2L++wR+/R−ξ2R+−λRνR++ƒ1(ω2R)+ƒ2(ω2R)K2φ2R,
τ1R−(duR−/dt)=cR−ζ0R−−uR−+wR−/L+ξ2L−+wR−/R+ξ2R+−λRνL++ƒ1(ω2R)+ƒ2(ω2R)K2φ2R,
τ2i(dνi/dt)=−νi+ξ2i,
ξ2i=H(ui−uth)=0(ui<uthi)or ui(ui≧uthi), or
ξ2i=ƒs(ui)=ui/(1+exp(−ui/D)) (30)
“τ1i” is a time constant for defining the variation feature of the state variable ui, and is expressed by a ω-dependant coefficient t(ω) and a constant γ=(γL, γR) according to the equation (31). The time constant τ1i varies in dependence on the second intrinsic angular velocity ω2. As aforementioned, “τ1i” may be also used as the auxiliary coefficient corrected by the second processing element 102.
τ1i=(t(ω2L)/ω2L)−γL(i=L+,L−),(t(ω2R)/ω2R)−γR(i=R+, R−) (31)
“τ2i” is a time constant for defining the variation feature of the self-inhibition factor νi. “wi/j” is a negative second correlation coefficient for representing the correlation between the state variables ui and uj which represent the motions of the left and right legs of the human P toward the flexion direction and the stretch direction as the correlation of each component of the second oscillator ξ2 (correlation between the output oscillation signals of the plurality of second elements). “λL” and “λR” are compliant coefficients. “κ2” is a feedback coefficient in relation to the second motion oscillator φ2.
“f1” is a first order function of the second intrinsic angular velocity ω2 defined by the equation (32) with a positive coefficient c. “f2” is a second order function of the second intrinsic angular velocity ω2 defined by the equation (33) with coefficients c0, c1 and c2.
ƒ1(ω)≡cω (32)
ƒ2(ω)≡c0+c1ω+c2ω2 (33)
The second oscillator ξ2i is equal to zero when the value of the state variable ui is smaller than a threshold value uth; and is equal to the value of ui when the value of the state variable ui is equal to or greater than the threshold value uth. In other words, the second oscillator ξ2i is defined by a sigmoid function fs (refer to the equations (30)). According thereto, if the state variable uL+ representing the behavior of the left thigh toward the forward direction increases, the amplitude of the left flexion component ξ2L+ of the second oscillator ξ2 becomes greater than that of the left stretch component ξ2L− if the state variable uR+ representing the behavior of the right thigh toward the forward direction increases, the amplitude of the right flexion component ξ2R+ of the second oscillator ξ2 becomes greater than that of the right stretch component ξ2R−. Further, if the state variable uL− representing the behavior of the left thigh toward the backward direction increases, the amplitude of the left stretch component ξ2L− of the second oscillator ξ2 becomes greater than that of the left flexion component ξ2L+; if the state variable uR− representing the behavior of the right thigh toward the backward direction increases, the amplitude of the right stretch component ξ2R− of the second oscillator ξ2 becomes greater than that of the right flexion component ξ2R+. The motion toward the forward or backward direction of the leg (thigh) is recognized by, for example, the polarity of the hip joint angular velocity.
Next, the auxiliary oscillator generation element 150 sets the auxiliary oscillator η=(ηL, ηR) on the basis of the second oscillator ξ2 generated by the second oscillator generation element 140 (FIG. 3/S050). Specifically, the auxiliary oscillator q is generated according to the equation (40). In other words, the left component ηL of the auxiliary oscillator η is calculated as a sum of a product of the left flexion component ξ2L+ of the second oscillator ξ2 and the coefficient χL+, and a product of the left stretch component ξ2L− of the second oscillator ξ2 and the coefficient “−χL−”. The right component ηR of the auxiliary oscillator η is calculated as a sum of a product of the right flexion component ξ2R+ of the second oscillator ξ2 and the coefficient χR+, and a product of the right stretch component ξ2R− of the second oscillator ξ2 and the coefficient “−χR−”.
ηL=χL+ξ2L+−χL−ξ2L−,ηL=χR+ξ2R+−χR−ξ2R− (40)
Thereafter, a current I=(IL, IR) supplied to each of the left and right actuators 15 from the battery 1000 is adjusted by the first controller 100 on the basis of the auxiliary oscillator η. The current I is represented by, for example, I(t)=G1*η(t) (wherein, G1 is a ratio coefficient) on the basis of the auxiliary oscillator η. Thereby, the assisting force to move each thigh (the second body part) with respect to the waist (the first body part), or the torque T=(TL, TR) around the hip joint which is applied to the human P by the motion assisting device 10 through the first orthosis 1100 and the second orthosis 1200 is adjusted (FIG. 3/S060). The torque T is represented by, for example, T(t)=G2*I(t) (wherein, G2 is a ratio coefficient) on the basis of the current I. Thereafter, the series of the aforementioned processes are performed repeatedly. Note that it is acceptable to control the motion of the motion assisting device 10 irrelative to the aforementioned control method on the condition that the thigh is appropriately moved with respect to the waist in a duration from the initiation of the walking motion of the human P to the finish of the walking motion after 2 to 3 foot steps.
According to the motion assisting device 10 which exhibits the aforementioned functions as the first embodiment of the present invention, the second orthosis 1200 is actuated to move with respect to the first orthosis 1100 by the actuator 15, as illustrated in
When the left leg is on the ground, the left stretch coefficient cL− is adjusted greater (refer to FIG. 3/S008), therefore, the left stretch component uL− of the state variable u representing the motion to the stretch direction (backward motion) of the left leg (left thigh) with respect to the body becomes greater, and the amplitude of the left stretch component ξ2L− of the second oscillator ξ2 also becomes greater (refer to the equations 30). As a result thereof, the assisting force (torque) which assists the stretch motion of the left leg is reinforced according to amplitude of the left stretch component ξ2L− of the second oscillator ξ2 (refer to the equation 40). In other words, the assisting force applied to the human P to assist the left leg (left thigh) in moving with respect to the body is reinforced only by an increment of the auxiliary coefficient increased in the reinforcement duration. Note that it is not limited that the reinforced assisting force is stronger than the assisting force in the duration other than the reinforcement duration. The same is applicable to the right leg.
The reinforcement duration includes the second reinforcement duration, namely, a part or a total of the second duration in which the leg is performing a stretch motion (backward motion) at the on-ground state. Accordingly, the stretch motion of the leg at the on-ground state is assisted by a relatively stronger assisting force, especially when the first reinforcement duration is contained in the reinforcement duration; and resultantly, the leg is subjected to a relatively stronger floor reaction force. The floor reaction force is transmitted to the body through the leg at the on-ground state to conduct the body to translate forward. When the leg is stretched by the assisting force at the on-ground state, there occurs a reflex (stretch reflex) to the stretch motion of the leg. As a result, the flexion motion of the leg at a subsequent off-ground state is induced by the stretch reflex at the previous off-ground state (refer to
In addition, the scale and the rhythm of the periodical walking motion of the human P are assisted so as to match the desired motion scale and the desired motion rhythm thereof, respectively.
The motion of the human P can be assisted by the motion assisting device 10 so as to match the motion rhythm of the human P to the desired motion rhythm thereof according to the following method. In detail, the second intrinsic angular velocity ω2 is appropriately set from the viewpoint of approximating the phase difference between the periodical motion of the human P represented by the first virtual oscillator φ1 and the periodical operation of the motion assisting device 10 represented by the second virtual oscillator φ2 to the desired phase difference δθ0, while the mutual harmony between the first motion oscillator φ1 and the first oscillator ξ1 is maintained between the periodical motion of the human P and the periodical operation of the motion assisting device 10 as mentioned above (refer to FIG. 3/S031 to S036). The second oscillator ξ2 varies periodically at an angular velocity defined according to the second intrinsic angular velocity ω2 and the output torque T is controlled on the basis of the second oscillator ξ2, therefore, the output torque T varies periodically at the same angular velocity defined according to the second intrinsic angular velocity ω2 (refer to FIG. 3/S040, S050 and S060). Accordingly, by applying the torque T to the human P, the motion rhythm of the human P and the operation rhythm of the motion assisting device 10 are harmonized; as a result thereof, the periodical walking motion of the human P is assisted so as to match the motion rhythm of the human P to the desired motion rhythm thereof.
The motion of the human P can be assisted by the motion assisting device 10 so as to match the motion scale of the human P to the desired motion scale thereof according to the following method. In detail, the second model is corrected so as to approximate the motion variable ζ (the left hip joint angle and the right hip joint angle at the finished timing of the flexion motion and at the finished timing of the stretch motion of the thigh every walking cycle, respectively) representing the motion scale of the periodical walking motion of the human P to the desired value ζ0 thereof (refer to FIG. 3/S004). Thereafter, the second oscillator ξ2 is generated according to the corrected second model and the torque T applied to the human P is controlled on the basis of the generated second oscillator ξ2 (refer to FIG. 3/S050 and S060). According thereto, in spite of the rhythm speed of the periodical motion of the human P, the periodical motion thereof can be assisted by applying an appropriate assisting force to the human P so as to match the motion scale (the footstep, the maximum hip joint angle or the like) of the human P to the desired motion scale thereof.
Subsequently, descriptions will be carried out on a second embodiment of the present invention. The motion assisting device 10 of the second embodiment of the present invention illustrated in
As illustrated in
The motion oscillator determination element 110 determines each hip joint angle as the second motion oscillator φ2 on the basis of an output from the hip joint angle sensor 11. In the second embodiment, the first motion oscillator φ1 is not determined. The second oscillator generation element 140 generates the second oscillator ξ2 as an output oscillation signal from the second model by inputting the second motion oscillator φ2 determined by the motion oscillator determination element 110 as an input oscillation signal to the second model. The second model in the second embodiment is the same as the second model in the first embodiment on a point that both of them are defined by the simultaneous differential equation (30). However, the second model in the second embodiment adjusts the coefficient c={ci|i=L+, L−, R+, R−} of the desired value ζ0={ζ0i|i=L+, L−, R+, R−} of the motion variable representing a motion scale of the human P and the time constant τ1i={τ1i|i=L+, L−, R+, R−} through the adjusting buttons 148 of the adjusting device 14; while the second model in the first embodiment corrects the coefficient c on the basis of a deviation between a determination value of the motion variable ζ and the desired value ζ0. On this point, the second model in the second embodiment differs from the second model in the first embodiment (refer to the equation (28) and FIG. 3/S004). Moreover, the second intrinsic angular velocity ω2 contained in the second model of the second embodiment is adjusted indirectly through adjusting the time constant τ1i (refer to the equation (31)); on this point, it differs from the second model of the first embodiment in which the second intrinsic angular velocity ω2 is set according to the virtual model. Similar to the first embodiment, the auxiliary oscillator generation element 150, on the basis of the second oscillator ξ2 generated by the second oscillator generation element 140, generates the auxiliary oscillator η. The auxiliary oscillator η is used to define a variation pattern of the torque applied to the thigh by the actuator 15 in the motion assisting device 10.
Hereinafter, the operation of the motion assisting device 10 having the configuration mentioned above in the second embodiment of the present invention will be described. The motion oscillator determination element 110 determines the left hip joint angle and the right hip joint angle of the human P as the second motion oscillator φ2=(φ2L, φ2R) on the basis of the output from the hip joint angle sensor 11 (FIG. 8/S110).
Thereafter, similar to that in the first embodiment, the first processing element 101 determines whether each leg of the human P is at the on-ground state or at the off-ground state, and determines a posture of each leg with respect to the body (FIG. 8/S112). Further, similar to that in the first embodiment, the second processing element 102, on the basis of the determination result by the first processing element 101, adjusts the value of the auxiliary coefficient in such a way that the auxiliary coefficient in the reinforcement duration is greater than the auxiliary coefficient in the duration other than the reinforcement duration for each leg (FIG. 8/S114).
Subsequently, the second oscillator generation element 140 generates the second oscillator ξ2={ξ2i|i=L+, L−, R+, R−} as an output oscillation signal from the second model by inputting the second motion oscillator θ2 determined by the motion oscillator determination element 110 as an input signal to the second model (FIG. 8/S120). As aforementioned, the time constant τ1i and the coefficient ci related to the desired value ζ0i of the motion variable in the simultaneous differential equation (30) can be adjusted by operating the adjusting buttons 148 in the adjusting device 14. In addition to or in place of the time constant τ1i or the coefficient ci, the time constant τ2i{τ2i|i=L+, L−, R+, R−}, the correlation coefficient wi/j or the like may be adjusted through the adjusting device 14.
Next, similar to that in the first embodiment, the auxiliary oscillator η=(ηL, ηR) is set by the auxiliary oscillator generation element 150 on the basis of the second oscillator ξ2 (FIG. 8/S130). The torque T=(TL, TR) applied to the human P from the motion assisting device 10 through the first orthosis 1100 and the second orthosis 1200 is adjusted (FIG. 8/S140). Thereafter, the series of the aforementioned processes are performed repeatedly. Note that it is acceptable to control the motion of the motion assisting device 10 irrelative to the aforementioned control method on the condition that the thigh is appropriately moved with respect to the waist in a duration from the initiation of the walking motion of the human P to the finish of the walking motion after 2 to 3 foot steps.
Similar to the motion assisting device 10 in the first embodiment of the present invention, according to the motion assisting device 10 which exhibits the aforementioned functions in the second embodiment of the present invention, the second orthosis 1200 is actuated to move with respect to the first orthosis 1100 by the actuator 15, as illustrated in
The assisting force applied to the human P to assist the leg (thigh) in moving with respect to the body is reinforced only by an increment of the auxiliary coefficient increased in the reinforcement duration. Note that it is not limited that the reinforced assisting force is stronger than the assisting force in the duration other than the reinforcement duration. The reinforcement duration includes the second reinforcement duration, namely, a part or a total of the second duration in which the leg is performing a stretch motion at the on-ground state. Accordingly, the stretch motion of the leg at the on-ground state is assisted by a relatively stronger assisting force, especially when the first reinforcement duration is contained in the reinforcement duration; and resultantly, the leg is subjected to a relatively stronger floor reaction force. The floor reaction force is transmitted to the body through the leg at the on-ground state to conduct the body to translate forward. When the leg is stretched by the assisting force at the on-ground state, there occurs a reflex (stretch reflex) to the stretch motion of the leg. As a result, the flexion motion of the leg at a subsequent off-ground state is induced by the stretch reflex at the previous off-ground state (refer to
Since no other model but the second model is used, accordingly, the computation processing load needed to generate the second oscillator ξ2 by the first controlling device 100 can be reduced. Further, the time constant τ1={τ1i|i=L+, L−, R+, R−} and the coefficient c={ci|i=L+, L−, R+, R−} contained in the simultaneous differential equation (refer to the equations (30)) for defining the second model are partially adjusted via the operations on the buttons 148 of the adjusting device 14. Thereafter, the second oscillator ξ2 is generated according to the adjusted second model and the output torque T applied to the human P is controlled to vary periodically according to the second oscillator ξ2 (refer to S130 and S140 in
In the aforementioned embodiment, it is described that the walking motion of the human P is assisted. However, it is also possible to assist the walking motion of an animal other than a human, such as a monkey (and/or ape), a dog, a horse, cattle or the like.
In the first embodiment, the amplitude and the phase of the periodical operation of the motion assisting device 10 represented by the auxiliary oscillator r are controlled on the basis of the amplitude and the phase of the periodical walking motion of the human P represented by the first motion oscillator φ1 and the second motion oscillator φ2. In the second embodiment, the amplitude and the phase of the periodical operation of the motion assisting device 10 represented by the auxiliary oscillator η are controlled on the basis of the amplitude and the phase of the periodical walking motion of the human P represented by the second motion oscillator φ2. Additionally, various algorithms can be used to control the operation of the motion assisting device 10 as long as they can apply the assisting force varying periodically so as to assist the thigh (or the leg) in moving periodically with respect to the body. For example, it is acceptable to adopt the generation method described in the first prior art or the second prior art as a generation method for the auxiliary oscillator η on the basis of the second oscillator ξ2.
In the second prior art, the first auxiliary oscillator representing a virtual elastic force which varies periodically is generated to approximate the motion variable ζ to the desired value ζ0 and the auxiliary oscillator is generated so as to contain the first auxiliary oscillator. A spring coefficient specifying the elastic force may be adjusted as the auxiliary coefficient.
In the above embodiment, the auxiliary coefficient is adjusted on the basis whether each leg of the human P is in the reinforcement duration by adjusting the coefficient ci (inverse τ1i−1 of the time constant, in addition to or in place of the coefficient ci) for specifying the behavior feature of the state variable ui for defining the second model. The magnitude of the assisted force is also adjusted according to the value of the auxiliary coefficient (refer to FIG. 3/S006 and S008, FIG. 8/S112 and S114). Additionally, the coefficient χi used in generating the auxiliary oscillator η may be adjusted as the auxiliary coefficient (refer to the equation (40)). For example, the coefficient χL− is adjusted in such a way that the coefficient χL− related to the left stretch component ξ2L− of the second oscillator ξ2 is greater when the left leg is in the reinforcement duration than that when the left leg is in the normal duration. Accordingly, the assisting force to assist the left leg (left thigh) in the stretch motion is reinforced only by the increment on the auxiliary coefficient χL− in the reinforcement duration. Similarly, the coefficient χR− is adjusted in such a way that the coefficient χR− related to the right stretch component ξ2R− of the second oscillator ξ2 when the right leg is in the reinforcement duration is greater than that when the right leg is in the normal duration. Accordingly, the assisting force to assist the right leg (right thigh) in the stretch motion is reinforced only by the increment on the auxiliary coefficient ωR− in the reinforcement duration.
The present invention is not merely limited to the motion assisting device 10 used in the walking training of the human P as illustrated in
Furthermore, a walking machine 70 as illustrated in
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-272018 | Oct 2007 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2008/002236 | 8/19/2008 | WO | 00 | 6/15/2009 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2009/050839 | 4/23/2009 | WO | A |
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| 20040158175 | Ikeuchi et al. | Aug 2004 | A1 |
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| Number | Date | Country | |
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| 20100049102 A1 | Feb 2010 | US |
