Patent Description:
There is known a load reduction device that performs assistance of a load such as a walking motion of a user and mitigates the load of luggage carried by the user, when worn by the user. When wearable by a person, the load reduction device is sometimes called a powered suit.

Some powered suits assist walking movement by driving a link mechanism provided on the user's legs by outputting torque from an actuator to assist muscle strength. Patent Document <NUM> discloses a powered suit that smoothly supports a load with little discomfort and shock by outputting torque at the timing of transition from a swing state to a stance state. Patent Document <NUM> relates to a walking aid device that assists a user's walking motion. Patent Document <NUM> relates to a power-assisted robotic device that assists a wearer in performing forceful works. Patent Document <NUM> relates to an exoskeleton adapted to decrease energy consumption of a user. Patent Document <NUM> relates to a method of controlling a walking assist torque for assisting a walking of a pedestrian. Patent Documents <NUM> to <NUM> describe a load reduction device with torque estimation means and stance/swing determination means on the basis of loads on soles of the legs and an angle at each of the joints of the legs.

However, while in the technique described in Patent Document <NUM>, the torque is adjusted by using a correction coefficient according to the ratio of the floor reaction forces of the right leg and the left leg, in a single-leg bending and stretching motion and a single-leg jumping motion and the like, smooth switching is not possible due to being a single-leg movement. That is, it is not possible to smoothly reduce the load for every motion of the user.

Therefore, an example object of the present invention is to provide a load reduction device, a load reduction method, and a storage medium for storing a program therein that can solve the above-mentioned problems.

According to the present invention, it is possible to provide smooth load reduction for all motions of the user.

Hereinbelow, a load reduction device, a load reduction method, and a storage medium for storing a program therein according to an embodiment of the present invention will be described with reference to the drawings.

<FIG> is a diagram showing a configuration of a powered suit according to the present embodiment.

A powered suit <NUM> is one aspect of the load reduction device. The powered suit <NUM> is constituted by a skeleton portion <NUM>, a belt <NUM>, a hip actuator <NUM>, a knee actuator <NUM>, an ankle actuator <NUM>, a shoe sole plate <NUM>, a foot harness <NUM>, a foot sole load sensor <NUM>, a loading platform <NUM>, a control device <NUM>, a battery <NUM>, a hip joint sensor <NUM>, a knee joint sensor <NUM>, an ankle joint sensor <NUM>, and the like. The skeleton portion <NUM> is roughly classified into a first skeleton portion <NUM>, a second skeleton portion <NUM>, and a third skeleton portion <NUM> as an example.

As shown in <FIG>, the powered suit <NUM> is configured as follows so as to support the loading platform <NUM>, which is one aspect of the mechanism for holding luggage as an example. That is, the powered suit <NUM> is provided with the first skeleton portion <NUM>, and the left and right hip actuators <NUM> are coupled rotatable to the first skeleton portion <NUM> and the second skeleton portion <NUM>, which corresponds to the left or right thigh portion of the user wearing the powered suit <NUM>, respectively. The left and right knee actuators <NUM> couple rotatable the corresponding second skeleton portion <NUM> on the left or right side and the corresponding third skeleton portion <NUM> along the left or right lower leg portion of the user wearing the powered suit <NUM>. The ankle actuators <NUM> couple rotatable to the corresponding third skeleton portion <NUM> on the left or right side, and a corresponding shoe sole plate <NUM> provided on the back of the foot harness <NUM> on the left or right side of the user wearing the powered suit <NUM>. The actuators <NUM>, <NUM> and <NUM> are drive mechanisms that output torques that reduce the load on the user at each joint of each leg of the user.

The user who wears the powered suit <NUM> puts his/her left and right feet into the corresponding foot harnesses <NUM>, and fixes the first skeleton portion <NUM> to the waist with the belt <NUM> so that the first skeleton portion <NUM> is closely attached to the waist. The powered suit <NUM> has a structure in which most of the load of the luggage and the load of the powered suit <NUM> is released to the ground surface in contact with the soles of the feet via the skeleton portion <NUM> and the actuators <NUM>, <NUM>, and <NUM>. The user turns on the control device <NUM> of the powered suit <NUM>. The control device <NUM> controls the actuators <NUM>, <NUM>, and <NUM> so as to transmit as much of the device weight as possible, which is the sum of the load of the luggage loaded on the loading platform <NUM> and the weight of the powered suit <NUM>, to the walking surface via the skeleton portion <NUM> and the actuators <NUM>, <NUM> and <NUM>. Thereby, the powered suit <NUM> mitigates the burden such as the load of the luggage on the user who wears the powered suit <NUM> and performs various motions.

The hip joint sensor <NUM> is installed in the hip actuator <NUM>, and detects the hip joint angle, that is, the angle formed between the first skeleton portion <NUM> and the second skeleton portion <NUM>, by an encoder. The knee joint sensor <NUM> is installed in the knee actuator <NUM>, and detects the knee joint angle, that is, the angle between the second skeleton portion <NUM> and the third skeleton portion <NUM>, by the encoder. The ankle joint sensor <NUM> is installed in the ankle actuator <NUM>, and detects the ankle joint angle, that is, the angle between the third skeleton portion <NUM> and the shoe sole plate <NUM>, by the encoder. The joint sensors <NUM>, <NUM>, and <NUM> detect the angle of each joint of each leg of the user (hereinafter referred to as "joint angle").

The foot sole load sensors <NUM> detect the values of loads on the soles of the feet of each leg of the user. The foot sole load sensor <NUM> is provided so as to cover the entire sole of each foot so as to be able to measure the weight inside the foot harness <NUM> from the sole of the user. For example, the foot sole load sensor <NUM> is attached between the insole of the foot harness <NUM> and the shoe sole plate <NUM>.

As an example, the foot sole load sensor <NUM> has electrodes arranged in a matrix on the front and back of a thin sheet-like insulator, measures the electrical resistance of the lattice points of the electrodes, and outputs the measured value to the control device <NUM>. The control device <NUM> calculates the pressure applied to each lattice point and the load value on the entire surface of the sensor sheet on the basis of the electrical resistance value of each lattice point.

<FIG> is a diagram showing the hardware configuration of the control device.

As shown in this figure, the control device <NUM> is a computer provided with hardware such as a CPU (Central Processing Unit) <NUM>, a ROM (Read Only Memory) <NUM>, a RAM (Random Access Memory) <NUM>, a signal input/output device <NUM>, and a wireless communication device <NUM>.

The signal input/output device <NUM> inputs signals output from the foot sole load sensor <NUM>, the hip joint sensor <NUM>, the knee joint sensor <NUM>, and the ankle joint sensor <NUM>. The signal input/output device <NUM> outputs control signals for controlling the hip actuator <NUM>, the knee actuator <NUM>, and the ankle actuator <NUM>. The control device <NUM> operates by power supplied from the battery <NUM>.

The wireless communication device <NUM> is communicatively connected with another device.

<FIG> is a function block diagram of the control device.

The control device <NUM> is activated based on the power supplied from the battery <NUM> by turning on the power button. The control device <NUM> executes the control program after startup. As a result, the control device <NUM> is provided with at least an information acquisition unit <NUM>, an integrated control unit <NUM>, an actuator control unit <NUM>, and a power supply unit <NUM>.

The information acquisition unit <NUM> acquires sensing information from the foot sole load sensor <NUM>, the hip joint sensor <NUM>, the knee joint sensor <NUM>, and the ankle joint sensor <NUM>. The sensing information of the foot sole load sensor <NUM> is sole load information indicating the detected load value. The sensing information of the hip joint sensor <NUM>, the knee joint sensor <NUM>, and the ankle joint sensor <NUM> is joint angle information indicating the detected joint angle.

The actuator control unit <NUM> controls the hip actuator <NUM>, the knee actuator <NUM>, and the ankle actuator <NUM>.

When the power button is turned on, the power supply unit <NUM> supplies electric power from the battery <NUM> to each part of the control device <NUM>.

The integrated control unit <NUM> is provided with a torque estimation unit <NUM>, a stance/swing determination unit <NUM>, and a torque output smoothing unit <NUM>.

The torque estimation unit <NUM> calculates the stance torque output by the actuators <NUM>, <NUM> and <NUM> during a stance period and the swing torque output by the actuators <NUM>, <NUM> and <NUM> during a swing period on the basis of the values of loads on the soles of the feet of the legs and the angles of the respective joints of the legs. Specifically, the stance torque and the swing torque at each joint are calculated based on a control model in which the joints on the sagittal plane of the user are linked.

The stance/swing determination unit <NUM> determines whether the states of a user's legs are stance or swing. Specifically, the stance/swing determination unit <NUM>, based on the load value applied to the sole of the foot of one leg, determines whether the state of the leg is the stance state or the swing state. For example, the stance/swing determination unit <NUM> determines the state of the right leg on the basis of the load value applied to the sole of the foot of the right leg. The stance/swing determination unit <NUM> determines the state of the left leg on the basis of the load value applied to the sole of the foot of the left leg.

When the state of each leg of the user has switched, the torque output smoothing unit <NUM> transitions the torque output by the actuators <NUM>, <NUM>, and <NUM> based on the stance torque and the swing torque so as to become smooth according to the elapsed time. Specifically, the torque output smoothing unit <NUM> provides a switching time for switching between a period in which the actuators <NUM>, <NUM> and <NUM> output the stance torque and the period in which the actuators <NUM>, <NUM> and <NUM> output the swing torque. The torque output smoothing unit <NUM> transitions the magnitudes of the torques output by the actuators <NUM>, <NUM> and <NUM> in the switching time according to the elapsed time. For example, the torque output smoothing unit <NUM> adds the stance torque and the swing torque in accordance with a ratio according to the elapsed time to the switching time.

Subsequently, the operation of the control device <NUM> will be described in detail.

<FIG> is an operation block diagram showing the operation of the control device.

First, the torque estimation unit <NUM> calculates the stance torque and the swing torque on the basis of values of loads detected by the foot sole load sensor <NUM> of each leg and the joint angles detected by the joint sensors <NUM>, <NUM>, and <NUM> of each leg.

<FIG> is a diagram showing an example of a stance torque control model. As the control model in this embodiment, a three-link model in which the hip joint, knee joint, and ankle joint in the sagittal plane of the user are linked is adopted. For example, stance torque τ3 of the hip actuator <NUM> is a distributed load "FcosθAcosθK" in the rotational direction as seen from the upper body weight center axis. The value "F" is a floor reaction force value obtained by multiplying the weight of the user, the weight of the powered suit <NUM> and the luggage by the impact acceleration. The weight of the user, the weight of the powered suit <NUM>, and the weight of the luggage are values measured in advance before the use of the powered suit <NUM>. The impact acceleration may be estimated based on the load value detected by the foot sole load sensor <NUM>, or may be specified based on the detection result of an acceleration sensor (not shown) provided on the foot harness <NUM>.

The value "θA" is the ankle joint angle detected by the ankle joint sensor <NUM>. The value "θK" is the knee joint angle detected by the knee joint sensor <NUM>. <FIG> shows the distributed load "FcosθAsinθK" in the rotation direction seen from the hip joint axis, the distributed load "FcosθA" in the rotation direction seen from the knee joint axis, and the component force of the foot sole load sensor <NUM> (distributed load in the centripetal direction as seen from the joint axis) "FsinθA".

In the following, the direction in which the user travels is defined as the forward direction, and the direction opposite to the direction of gravity is defined as the upward direction. The XYZ coordinate system is defined with the forward direction as the X-axis direction, the upward direction orthogonal to the X-axis direction as the Z-axis direction, and the direction orthogonal to the X-axis direction and the Z-axis direction as the Y-axis direction.

Specifically, the torque estimation unit <NUM> calculates the stance torque by the following equations of motion (<NUM>) to (<NUM>). The inertial matrix M is represented by the following Equation (<NUM>).

Each element of the inertial matrix M is calculated by the following equations (<NUM>-<NUM>) to (<NUM>-<NUM>). Here, the value "m<NUM>" is the mass around the ankle joint. The value "m<NUM>" is the mass around the knee joint. The value "m<NUM>" is the mass around the hip joint. The value "l<NUM>" is the length from the foot to the knee. The value "l<NUM>" is the length from the knee to the waist. The value "l<NUM>" is the length of the upper body. The value "lg1" is the length from the ankle joint to the center of gravity of the tibia. The value "lg2" is the length from the knee joint to the center of gravity of the femur. The value "lg3" is the length from the hip joint to the upper body center of gravity. The value "I<NUM>" is the inertia around the ankle joint. The value "I<NUM>" is the inertia around the knee joint. The value "I<NUM>" is the inertia around the hip joint. The value "θ<NUM>" is the ankle joint angle. The value "θ<NUM>" is the knee joint angle. The value "θ<NUM>" is the hip joint angle.

The values of the mass m<NUM> around the ankle joint, the mass m<NUM> around the knee joint, the mass m<NUM> around the hip joint, the length l<NUM> from the foot to the knee, the length l<NUM> from the knee to the waist, the length l<NUM> of the upper body, the length lg1 from the ankle joint to the center of gravity of the tibia, the length lg2 from the knee joint to the center of gravity of the femur, the length lg3 from the hip joint to the upper body center of gravity, the inertia I<NUM> around the ankle joint, the inertia I<NUM> around the knee joint and the inertia I<NUM> around the hip joint are set in advance in the control device <NUM>. <MAT> <MAT> <MAT> <MAT> <MAT> <MAT> <MAT> <MAT> <MAT> <MAT> <MAT> <MAT> <MAT> <MAT> <MAT> <MAT> <MAT> <MAT> <MAT> <MAT> <MAT> <MAT> <MAT> <MAT> <MAT>.

The Coriolis force h is expressed by the following Equation (<NUM>).

Each element of the Coriolis force h is calculated by the following equations (<NUM>-<NUM>) to (<NUM>-<NUM>). <MAT> <MAT> <MAT> <MAT> <MAT>.

The gravity term vector g is expressed by the following Equation (<NUM>).

Each element of the gravity term vector g is calculated by the following equations (<NUM>-<NUM>) to (<NUM>-<NUM>). <MAT> <MAT> <MAT> <MAT> <MAT>.

The torque coefficient matrix D is expressed by the following Equation (<NUM>).

Further, the torque τ is expressed by the following Equation (<NUM>). The value "τ<NUM>" is the torque around the ankle joint. The value "l<NUM>" is the torque around the knee joint. The value "τ<NUM>" is the torque around the hip joint. The torque around the ankle joint is the output torque output by the ankle actuator <NUM>. The torque around the knee joint is the output torque output by the knee actuator <NUM>. The torque around the hip joint is the output torque output by the hip actuator <NUM>.

The torque τ is calculated by the following Equation (<NUM>). The generalized coordinate X is expressed by Equation (<NUM>-<NUM>). x is an X coordinate value. z is a Z coordinate value. <MAT> <MAT>.

Also, let the generalized coordinate X(k) of each joint be the following Equation (<NUM>). The value "k" indicates the kth in time series (current value). The value "x<NUM>" is the X coordinate of the ankle joint when the forward direction is positive. The value "x<NUM>" is the X coordinate of the knee joint when the forward direction is positive. The value "x<NUM>" is the X coordinate of the hip joint when the forward direction is positive. The value "zi" is the Z coordinate of the ankle joint when the upward direction is positive. The value "z<NUM>" is the Z coordinate of the knee joint when the upward direction is positive. The value "z<NUM>" is the Z coordinate of the hip joint when the upward direction is positive.

Then, X (k + <NUM>) is expressed by the following Equation (<NUM>). F is the floor reaction force value. H is the Coriolis force h. G is the gravitational term vector g.

The torque estimation unit <NUM> calculates the stance torque by sequentially calculating τ in Equation (<NUM>). By adopting the <NUM>-link model in the sagittal plane in this way, the accuracy can be improved. Since the floor reaction force value F is used in the equations of motion, the stance torque can be calculated in consideration of the impact force from the floor surface. In addition, in order to further improve the accuracy, an equation of motion in the coronal plane may be added as an extension.

The torque estimation unit <NUM> calculates the swing torque by the above-mentioned equations of motion (<NUM>) to (<NUM>). However, when calculating the swing torque, the value "m<NUM>" is the mass around the hip joint. The value "m<NUM>" is the mass around the knee joint. The value "m<NUM>" is the mass around the ankle joint. The value "l<NUM>" is the length from the crotch to the knee. The value "l<NUM>" is the length from the knee to the waist. The value "l<NUM>" is the length from the ankle to the toe.

The value "lg1" is the length from the hip joint to the center of gravity of the femur. The value "lg<NUM>" is the length from the knee joint to the center of shin. The value "lg3" is the length from the ankle joint to the center of gravity of the foot. The value "I<NUM>" is the inertia around the hip joint. The value "I<NUM>" is the inertia around the knee joint. The value "I<NUM>" is the inertia around the ankle joint. The value "θ<NUM>" is the hip joint angle. The value "θ<NUM>" is the knee joint angle. The value "θ<NUM>" is the ankle joint angle. The value "τ<NUM>" is the torque around the hip joint. The value "l<NUM>" is the torque around the knee joint. The value "τ<NUM>" is the torque around the ankle joint. The value "x<NUM>" is the X coordinate of the hip joint when the forward direction is positive. The value "x<NUM>" is the X coordinate of the knee joint when the forward direction is positive. The value "x<NUM>" is the X coordinate of the ankle joint when the forward direction is positive. The value "z<NUM>" is the Z coordinate of the hip joint when the upward direction is positive. The value "z<NUM>" is the Z coordinate of the knee joint when the upward direction is positive. The value "z<NUM>" is the Z coordinate of the ankle joint when the upward direction is positive. The torque coefficient matrix D for calculating the swing torque is the following Equation (<NUM>).

The torque estimation unit <NUM> outputs the calculated stance torque and swing torque of the actuators <NUM>, <NUM> and <NUM> of each leg to the torque output smoothing unit <NUM>.

Subsequently, the stance/swing determination unit <NUM> determines whether the state of each leg is the stance state or the swing state on the basis of the load value detected by the foot sole load sensor <NUM> attached to the leg. For example, when the load value detected by the foot sole load sensor <NUM> is large (for example, equal to or greater than a first threshold value), the stance/swing determination unit <NUM> makes a determination of a stance, and when the load value detected by the foot sole load sensor <NUM> is small (for example, equal to or less than a second threshold value), the stance/swing determination unit <NUM> makes a determination of an swing. The first threshold value is the load value when the sole of the foot is in contact with the ground. The second threshold value is the load value when the sole of the foot is not in contact with the ground.

The stance/swing determination unit <NUM> determines the state of the corresponding leg on the basis of the load value detected by the foot sole load sensor <NUM> of each leg. Therefore, it is possible to accurately make a determination of a stance or a swing for all agile movements such as running without the heel making contact with the ground, one leg movements, and irregular walking movements. For example, the stance/swing determination unit <NUM> determines the state of the right leg on the basis of only the value of the load detected by the foot sole load sensor <NUM> of the right leg, even if a one-leg movement in which only the right leg repeats the swing and the stance. For this reason, the state of the right leg can be accurately determined.

After that, the stance/swing determination unit <NUM> decides the drive modes of the actuators <NUM>, <NUM> and <NUM> of each leg. The drive modes include a stance mode that outputs stance torque and a swing mode that outputs swing torque.

<FIG> is a diagram showing the detection result of each sensor and the drive mode of each actuator according to the state of the user.

As shown in <FIG>, when the user is walking, the states of both legs stance, and one-leg stance/one-leg swing are repeated in that order. Both legs stance is a state in which both legs are being the stance. One-leg stance/one-leg swing is a state in which one leg is being the stance and the other leg is being the swing. On the other hand, when the user is running, the states of one-leg stance/one-leg swing and both legs swing are repeated in that order. Both legs swing is a state in which both legs are being the swing.

As shown in <FIG>, when both legs are being the stance, the joint sensors <NUM>, <NUM>, and <NUM> detect the joint angle from the encoder, the foot sole load sensor <NUM> detects ground contact (equal to or greater than the first threshold value) at both feet, and each of the actuators <NUM>, <NUM> and <NUM> of both legs is driven in the stance mode.

In addition, the following processing is performed during a one-leg stance/one-leg swing period. That is, each of the joint sensors <NUM>, <NUM>, and <NUM> detects the joint angle from the encoder, the foot sole load sensor <NUM> on the stance side detects ground contact, and the foot sole load sensor <NUM> on the swing side detects non-ground contact (equal to or less than the second threshold). The hip actuators <NUM> of both legs are driven in the swing mode, the knee actuator <NUM> on the stance side is driven in the stance mode, and the knee actuator <NUM> on the swing side is driven in the swing mode. The ankle actuator <NUM> on the stance side is driven in the stance mode, and the ankle actuator <NUM> on the swing side is driven in the swing mode.

Further, when both legs of the user are being the swing, the joint sensors <NUM>, <NUM>, <NUM> detect the joint angle from the encoder, the foot sole load sensor <NUM> detects that both legs are not touching the ground, and the actuators <NUM>, <NUM>, <NUM> of both legs are driven in the swing mode.

However, the control model during a stance period and the control model during a swing period differ. Therefore, when the drive modes of the actuators <NUM>, <NUM> and <NUM> are switched only based on whether or not the sole of the user's foot is in contact with the ground, at the moment of switching from the stance mode to the swing mode or the moment of switching from the swing mode to the stance mode, non-linear torque is output from the actuators <NUM>, <NUM> and <NUM>. For this reason, the difference in output torque at the time of switching is applied to the body as an excessive load, and the user feels uncomfortable as compared with the normal time, making movement difficult.

Therefore, the stance/swing determination unit <NUM> measures the elapsed time t after the drive mode is switched. Then, the stance/swing determination unit <NUM> outputs the drive mode and the elapsed time t of the actuators <NUM>, <NUM> and <NUM> of each leg to the torque output smoothing unit <NUM>.

The torque output smoothing unit <NUM> computes the output torque of the actuators <NUM>, <NUM>, <NUM> of each leg on the basis of the drive mode and elapsed time t determined by the stance/swing determination unit <NUM> and the stance torque and swing torque calculated by the torque estimation unit <NUM>. Specifically, the torque output smoothing unit <NUM> executes a smoothing process so that the transition of the torque value becomes smooth when the drive modes of the actuators <NUM>, <NUM> and <NUM> switch. That is, the torque output smoothing unit <NUM> calculates the torque so that the transition of the torque value becomes gentle when the drive mode is switched.

<FIG> is a graph showing an outline of an exemplary smoothing process.

The torque output smoothing unit <NUM> provides a switching time T1 from the stance mode to the swing mode. The torque output smoothing unit <NUM> sets output torque τ so as to smoothly transition from the stance torque τs to the swing torque τf during the switching time T1 (that is, the elapsed time t ≤ the switching time T1) after the drive mode is switched from the stance mode to the swing mode. More specifically, the output torque τ is calculated by the following Equation (<NUM>).

Further, the torque output smoothing unit <NUM> provides a switching time T2 from the swing mode to the stance mode. The torque output smoothing unit <NUM> sets the output torque τ so as to smoothly transition from the swing torque τf to the swing torque τs during the switching time T2 (that is, the elapsed time t ≤ the switching time T2) after switching from the swing mode to the stance mode. More specifically, the output torque τ is calculated by the following Equation (<NUM>).

In this way, the torque output smoothing unit <NUM> calculates the stance torque and the swing torque according to the ratio of the elapsed time t to the switching times T1 and T2. The torque output smoothing unit <NUM> calculates the output torque τ by adding the stance torque and the swing torque in accordance with the ratio.

Another example of the smoothing process executed by the torque output smoothing unit <NUM> will be described.

<FIG> is a graph showing the transition of the output torque of the actuator according to the present invention.

The horizontal axis of the graph shown in this figure is time, and the vertical axis is output torque.

The process shown in this figure differs from the smoothing process shown in <FIG> in that parameters α1, β1, α2, β2 used in the smoothing process are changed according to the rate of change of the output torque τ due to the smoothing process.

Specifically, first, the torque output smoothing unit <NUM> sets "Fmax = τs" and "Fmiddle = Fmax/<NUM>" when the drive mode is switched from the stance mode to the swing mode at time t11. Then, the torque output smoothing unit <NUM> calculates the output torque τ by the following Equation (<NUM>) during the period until time t12 when the output torque τ becomes "Fmiddle". t is the elapsed time from time t11. The switching time T1 is set in advance, and in this example is the period from time t11 to time t13. The parameter α1 and parameter β1 are parameters including time-dependent mathematical expressions.

Subsequently, the torque output smoothing unit <NUM> resets the parameter α1 and the parameter β1 so that the rate of change of the output torque τ becomes steeper or smoother according to the rate of change of the output torque τ during the period from the time t11 to the time t12. Then, the torque output smoothing unit <NUM> calculates the output torque τ by the above Equation (<NUM>) using the parameter α1 and the parameter β1 that were reset during the period from time t12 to time t13. Thereby, the output torque τ at T13, the end of the switching time T1, is the swing torque (Fmin = τf).

The solid line <NUM> shows the transition of the swing torque before the smoothing process at the switching time T1. On the other hand, the solid line <NUM> shows the transition of the output torque after the smoothing process at the switching time T1. By resetting the parameter α1 and the parameter β1 during the smoothing process in this way, it is possible to smooth the change in the output torque τ more stably than in the process shown in <FIG>. Thereby, it is possible to prevent the output torque from suddenly changing when the drive mode is switched, and to reduce the discomfort felt by the user.

Further, the torque output smoothing unit <NUM> calculates the output torque τ by the following Equation (<NUM>) during the period until time t15 when the output torque τ becomes "Fmiddle" when the drive mode is switched from the swing mode to the stance mode at time t14. t is the elapsed time from time t14. The switching time T2 is set in advance, and in this example is the period from time t14 to time t16. The parameter α2 and parameter β2 are parameters including time-dependent mathematical expressions.

Subsequently, the torque output smoothing unit <NUM> resets the parameter α2 and the parameter β2 so that the rate of change of the output torque τ becomes steeper or smoother according to the rate of change of the output torque τ during the period from the time t14 to the time t15. Then, the torque output smoothing unit <NUM> calculates the output torque τ by the above Equation (<NUM>) using the parameter α2 and the parameter β2 that were re-set, during the period from time t15 to time t16.

The solid line <NUM> shows the transition of the stance torque before the smoothing process at the switching time T2. On the other hand, the solid line <NUM> shows the transition of the output torque after the smoothing process at the switching time T2. By resetting the parameter α2 and the parameter β2 during the smoothing process in this way, it is possible to smooth the change in the output torque τ more stably than in the process shown in <FIG>. Thereby, it is possible to prevent the output torque from suddenly changing when the drive mode is switched, and to reduce the discomfort felt by the user.

Note that the torque output smoothing unit <NUM> may adaptively change the switching time T1 and the switching time T2 by machine learning. For example, the torque output smoothing unit <NUM> may change the time from when the drive mode is switched until the load value detected by the foot sole load sensor <NUM> reaches the maximum value or the minimum value, as the switching time. This makes it possible to optimally smooth the output torque at the time of switching.

The torque output smoothing unit <NUM> outputs the calculated output torque of each actuator <NUM>, <NUM> and <NUM> of each leg to the actuator control unit <NUM>.

The actuator control unit <NUM> controls the rotation angles of the actuators <NUM>, <NUM> and <NUM> with an angle controller Kci(s) on the basis of the output torque. "s" indicates the frequency domain of the control system. Subsequently, the actuator control unit <NUM> causes the actuators <NUM>, <NUM> and <NUM> of each leg to output the torque τ with a force controller Kbi(s).

Thereby, the interaction force between suits and person Dk applied by the user, the applied torque lk applied by the user, and the output torque τ in the kth of the time series (current value) become the dynamics P(s) of each actuator. Each joint sensor <NUM>, <NUM>, <NUM> detects each joint angle θk in the kth of the time series according to the dynamics G(s) of the powered suit <NUM> based on the dynamics P(s) of the actuators <NUM>, <NUM>, <NUM> and outputs the detected each joint angle θk to the torque estimation unit <NUM>. Then, the control device <NUM> repeats the above-described processing.

<FIG> is a flowchart showing the processing of the powered suit.

First, the user puts on the powered suit <NUM>. Since each foot sole load sensor <NUM> is attached between the insole of the foot harness <NUM> and the shoe sole plate <NUM>, when the user wears the foot harnesses <NUM>, the foot sole load sensors <NUM> can measure the weight applied from the soles of the user.

The user operates a power button of the control device <NUM> provided in the powered suit <NUM> to turn on the power. As a result, the control device <NUM> is started. The user walks while wearing the powered suit <NUM>. The user may load luggage on the loading platform <NUM> of the powered suit <NUM> and walk. The actuator control unit <NUM> of the control device <NUM> controls the hip actuator <NUM>, the knee actuator <NUM>, and the ankle actuator <NUM> so as to reduce the load on the user due to the weight of the luggage and the powered suit <NUM>. Thereby, the powered suit <NUM> tracks various motions of the user.

While the control device <NUM> is being driven, the information acquisition unit <NUM> acquires joint angle information from the joint sensors <NUM>, <NUM>, and <NUM> at predetermined intervals (Step S101). Further, while the control device <NUM> is being driven, the information acquisition unit <NUM> acquires the sole load information from each foot sole load sensor <NUM> at a predetermined interval (Step S102). The predetermined interval is, for example, every short time such as every <NUM> milliseconds.

The torque estimation unit <NUM> calculates the stance torque and swing torque of each actuator <NUM>, <NUM>, <NUM> of each leg based on the joint angle information and the sole load information acquired by the information acquisition unit <NUM>, and estimates the torque (Step S103). The stance/swing determination unit <NUM> determines the drive modes of the actuators <NUM>, <NUM> and <NUM> of each leg on the basis of the sole load information acquired by the information acquisition unit <NUM>. The stance/swing determination unit <NUM> measures the elapsed time after the drive mode is switched (Step S104).

The torque output smoothing unit <NUM> smooths the output torque on the basis of the drive mode and elapsed time determined by the stance/swing determination unit <NUM> and the stance torque and swing torque calculated by the torque estimation unit <NUM> (Step S105). The actuator control unit <NUM> causes the actuators <NUM>, <NUM> and <NUM> of each leg to output the torque (Step S106). After that, the process returns to the process of Step S101, and the control device <NUM> repeats the process from steps S101 to S106 until the process is completed.

According to the above processing, the accurate torque required for each joint to support the load is calculated, and the actuators <NUM>, <NUM> and <NUM> can output that torque. For this reason, even if there is a large fluctuation from low response to high response in all movement patterns of the user, such as slow walking movements and agile movements of running, it is always possible to follows the user's movements and it is possible to realize assist for load reduction in a timely and appropriate manner at each movement. For example, the torque output smoothing unit <NUM> smooths the output torque when switching between the stance and the swing. As a result, it is possible to prevent the output torque from suddenly changing, and so a sense of discomfort during motion is alleviated, and it is possible to realize an improvement in the ability to track movements of the user.

Further, even during an swing period, the torque estimation unit <NUM> calculates the swing torque and causes the actuators <NUM>, <NUM> and <NUM> to output the swing torque, thereby assisting the load of the powered suit <NUM> itself and enabling smooth movement tracking without hindering the user's motion. Therefore, agile motion is possible in the state of the powered suit <NUM> being worn.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the present invention.

For example, the foot sole load sensor <NUM> may be inserted inside the foot harness <NUM> during use by the user. The foot sole load sensor <NUM> may be provided on a side of the ground contact surface of the foot harness <NUM>.

In the above description, it was shown that the foot sole load sensor <NUM> has an area inside the foot harness <NUM> so as to cover the entire surface of the sole. However, the foot sole load sensor <NUM> should be capable of measuring the load applied to the ground contact surface from the shoe sole plate <NUM> or the foot harness <NUM> even when the position where that load is applied deviates.

The above description illustrated a case of controlling the powered suit <NUM> but is not limited thereto, and the control device <NUM> can be applied to general control of a multi-joint robot or the like (for example, a humanoid robot) having a non-linear mode transition.

Further, in the above description, the powered suit <NUM> is provided with the hip actuator <NUM>, the knee actuator <NUM>, and the ankle actuator <NUM> corresponding respectively to each joint, but is not limited thereto. The powered suit <NUM> may be provided with at least one of the actuators <NUM>, <NUM>, and <NUM>. For example, the powered suit <NUM> may be provided with only the hip actuator <NUM> and the knee actuator <NUM>, and does not have to be provided with the ankle actuator <NUM>. Alternatively, the ankle actuator <NUM> may be an actuator that does not use a control signal, such as a mechanical leaf spring. In this case, the ankle joint sensor <NUM> is an angle detection sensor that detects the bending angle of the leaf spring or a force sensor that detects the reaction force of the leaf spring. The torque estimation unit <NUM> calculates the torque around the hip joint and the torque around the knee joint by Equation (<NUM>) on the basis of the bending angle of the leaf spring or the reaction force of the leaf spring detected by the ankle joint sensor <NUM>.

<FIG> is a diagram showing the minimum configuration of the control device.

As one aspect of the load reduction device, the control device <NUM> may have at least the functions of the torque estimation unit <NUM>, the stance/swing determination unit <NUM>, and the torque output smoothing unit <NUM> described above.

The torque estimation unit <NUM> calculates the stance torque output by the actuators <NUM>, <NUM> and <NUM> during a stance period and the swing torque output by the actuators <NUM>, <NUM> and <NUM> during a swing period on the basis of the load values applied to the soles of the feet and the angle of each joint of the leg. The actuators <NUM>, <NUM> and <NUM> output torque to reduce the load on the user at the joints of the legs of the user.

The stance/swing determination unit <NUM> determines whether the leg state is the stance state or the swing state.

The torque output smoothing unit <NUM> smooths the transition of the torque output by each of the actuators <NUM>, <NUM> and <NUM> according to the elapsed time based on the stance torque and the swing torque when the leg state is switched. That is, when the state of each leg is switched, the torque output smoothing unit <NUM> calculates the torque whose transition was smoothed according to the elapsed time.

The above-mentioned control device may also be a computer provided with hardware such as the CPU (Central Processing Unit) <NUM>, the ROM (Read Only Memory) <NUM>, the RAM (Random Access Memory) <NUM>, an HDD (Hard Disk Drive) <NUM>, and the wireless communication device <NUM>.

The control device described above has a computer system inside. The process of each processing described above is stored in a computer-readable recording medium in the form of a program, with the process being performed by the computer reading and executing this program. Here, the computer-readable recording medium refers to a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like. This computer program may be distributed to a computer via a communication line, and the computer receiving the distribution may execute the program.

Further, the above-mentioned program may be for realizing some of the functions described above.

Moreover, the above-mentioned program may be a so-called differential file (differential program) that can realize the above-mentioned functions in combination with a program already recorded in the computer system.

Priority is claimed on <CIT>, the content of which is incorporated herein by reference.

Claim 1:
A load reduction device (<NUM>) comprising:
an information acquisition means (<NUM>) for acquiring, at predetermined intervals, loads on soles of the legs of a user and an angle at each of joints of the legs of the user;
a torque estimation means (<NUM>) for calculating sequentially stance torque output during a stance period and swing torque output during a swing period by a drive mechanism for outputting torque to reduce a load on the user at the joints of the legs, on the basis of values of the loads on the soles of the legs and the angle at each of the joints of the legs that are acquired at the predetermined intervals;
a stance/swing determination means (<NUM>) for determining whether each of the legs is in a stance state or a swing state; and
a torque output smoothing means (<NUM>) for smoothing, upon a switch in a state of the each of legs, a transition in the torque output by the drive mechanism in a switching time T1, in accordance with an elapsed time t on the basis of the stance torque τs and the swing torque τf that are calculated sequentially,
wherein the torque output smoothing means (<NUM>) is configured for providing the switching time T1 for switching between a period in which the drive mechanism outputs the stance torque τs and a period in which the drive mechanism outputs the swing torque τf, the switching time T1 including a first period of time until the torque to be output reaches a predetermined torque indicating half of the stance torque τs, and a second period of time after the torque to be output reached the predetermined torque, calculating the torque τ for the first period according to an equation <MAT>
a value α1 indicating a first parameter, a value β1 indicating a second parameter, a value t indicating the elapsed time in the switching time T1, a value τs indicating a torque at a beginning of the switching time T1, and a value τf indicating a torque at an end of the switching time T1,
resetting the first parameter α1 and the second parameter β1, according to a rate of change of the torque in the first period calculated by the equation, and
calculating the torque τ for the second period according to the equation using the re-set first parameter α1 and the re-set second parameter β1.