WO2010074160A1

WO2010074160A1 - Walking assist device

Info

Publication number: WO2010074160A1
Application number: PCT/JP2009/071466
Authority: WO
Inventors: 一誠中島; 敬介菅; 仁司鴻巣; 周平真鍋
Original assignee: トヨタ自動車株式会社
Priority date: 2008-12-25
Filing date: 2009-12-24
Publication date: 2010-07-01
Also published as: JP2010148637A

Abstract

Provided is a walking assist device which is capable of determining a swing leg state end timing without any mistake and appropriately changing the control in accordance with user's walking. When touch of the foot of a swing leg is detected, the walking assist device continues the swing leg state mode if the relative speed of the foot of the swing leg relative to the foot of a stance leg exceeds the speed threshold value. The walking assist device switches the control mode to the stance leg state mode if the relative speed is not higher than the speed threshold value. In order to determine the swing leg state end timing, the walking assist device refers to the output of a touch sensor and the relative speed of the foot of the swing leg relative to the foot of the stance leg. Even when the touch sensor detects a touch to the ground, if the relative speed of the foot exceeds the speed threshold value, the walking assist device does not determine the timing as the swing leg state end timing. With such a configuration, the walking assist device can prevent mistaken determination of the swing leg state end timing and switch from the swing leg state mode to the stance leg state mode at an appropriate timing.

Description

Walking assist device

This application claims priority based on Japanese Patent Application No. 2008-329403 filed on Dec. 25, 2008. The entire contents of that application are incorporated herein by reference.

The present invention relates to a walking assistance device that assists a user's walking by applying torque to a leg joint. In this specification, a leg that the user can freely move is referred to as a healthy leg, and a leg that cannot be freely moved is referred to as an affected leg.

A walking assist device that assists the user's walking by applying torque to the joint of the affected leg has been studied. For example, Patent Document 1 discloses a walking assist device that applies torque to a joint of an affected leg so as to be the same as the movement of a healthy leg. The walking assistance device may be required to detect the timing when the user's leg shifts from the swinging leg state to the standing leg state. For example, the device of Patent Document 2 includes a ground sensor on the sole in order to detect such timing.

JP 2003-116893 A JP-A-7-163607

The walking assist device may switch the control mode (control law) depending on whether the user's leg is in a free leg state or a standing leg state. Therefore, it is preferable that the walking assistance device can detect the timing at which the user's leg shifts from the swinging state to the standing state. Hereinafter, the timing of transition from the swinging leg state to the standing leg state is referred to as the swinging leg state end timing. As described above, conventionally, the free leg state end timing is determined based on the output signal of the ground sensor provided on the sole.

However, the swinging leg of the swinging leg may hit the floor unintentionally by the user. When the leg of the free leg hits the floor, the ground sensor detects the ground. Since the free leg state continues even if the leg of the free leg hits the floor, it is not preferable to determine this timing as the free leg state end timing. If the free leg state end timing is determined from the information of only the ground sensor, there is a risk of erroneous determination. There is a demand for a technique that can determine the end timing of the free leg state as accurately as possible. The present specification provides a technique for suppressing erroneous determination of a swing leg state end timing, and a walking assist device that can switch the control mode appropriately according to the state of the user's leg by applying the technique.

A walking assistance device according to an embodiment of the technology disclosed in this specification includes a leg sensor, a ground sensor, an actuator, and a controller. The leg sensor detects the movement of the user's leg. The ground sensor detects the ground of the user's foot. The actuator applies torque to the user's leg. The controller is configured to be able to switch the control mode of the actuator according to the state of the user's leg. The controller is configured as follows. The controller can calculate the relative speed of the free leg's foot with respect to the leg of the standing leg based on the output of the leg sensor. The controller specifies the contact timing when the contact of the leg of the free leg is detected. The controller determines that the free leg state continues when the relative speed at the contact timing exceeds the speed threshold. The controller determines that the free leg state has ended when the relative speed at the contact timing is equal to or less than the speed threshold. That is, the controller continues the swing leg state mode when the relative speed of the free leg's foot with respect to the standing leg exceeds the speed threshold when the ground sensor of the free leg detects the ground. The controller switches the control mode from the free leg state mode to the standing state mode when the relative speed of the leg of the free leg with respect to the leg of the standing leg is equal to or less than the speed threshold when the ground sensor of the free leg detects the grounding. The speed threshold is given in advance. Here, “standing leg” may be rephrased as “rear leg”. Hereinafter, the relative speed of the leg of the free leg with respect to the leg of the standing leg may be referred to as “relative foot speed”.

The above walking assistance device refers to the relative foot speed in addition to the output of the ground sensor to determine the end timing of the swing leg state. Even if the grounding sensor detects the grounding, the walking assist device does not determine that the swinging leg state is finished when the relative foot speed exceeds the speed threshold. With such a configuration, the walking assist device described above can prevent erroneous determination of the swing leg state end timing, and can switch the control mode from the swing leg state mode to the standing state mode at an appropriate timing. In addition, when the relative speed is equal to the speed threshold value, whether to continue the swing leg state mode or to switch the control mode may be arbitrarily selected. The walking assist device is characterized in that a speed threshold value is provided for continuing the swing leg state mode even when the ground contact is detected.

If the relative position in the front-rear direction of the free leg's foot with respect to the leg of the standing leg at the timing when the ground contact sensor of the free leg detects ground contact (ground contact timing), it is possible to further determine the end timing of walking. If the timing of the end of walking can be determined, a walking assistance device that can quickly respond to the user's behavior when the user intends to stop walking can be realized. That is, in other embodiments disclosed herein, the controller is preferably configured to perform the following functions. The controller calculates the distance in the front-rear direction of both feet at the contact timing based on the output of the leg sensor. The controller switches to the first stance state mode for continuing walking when the calculated distance is equal to or greater than the distance threshold. On the other hand, the controller switches to the standing state mode for stopping walking when the calculated distance is below the distance threshold. Whether or not to switch to the stance control mode for continuing walking when the distance between the front and rear of both feet is equal to the distance threshold may be arbitrarily selected. The walking assistance device of this other embodiment is characterized in that it has a distance threshold for switching to a walking stop control mode (second stance state mode).

The technology disclosed in this specification provides a walking assist device that can determine the end timing of the swing leg state without misjudgment and can appropriately switch the control mode according to the user's walking.

The typical front view of the walk auxiliary device of an example is shown. The typical side view of the walk auxiliary device of an example is shown. The transition diagram of a walking state is shown. A block diagram of the controller is shown. The flowchart of the process which a controller performs is shown. It is a figure which shows the conditions of state transition judgment.

Referring to the drawings, the walking assistance device of the embodiment will be described. FIG. 1 shows a schematic diagram of a walking assistance device 10 worn by a user. FIG. 1A shows a front view of the walking assistance device 10, and FIG. 1B shows a side view of the walking assistance device 10. In this embodiment, it is assumed that the user cannot freely move the knee joint of the left leg. The walking assist device 10 applies an appropriate torque to the user's left knee joint to assist the user's walking motion.

The walking assist device 10 includes a right leg orthosis 12R and a left leg orthosis 12L. The right leg orthosis 12R is attached to the outside of the leg along the thigh from the user's thigh. The right leg orthosis 12R includes an upper link 14R, a lower link 16R, and a foot link 26R. The left and

right leg appliances

12R and 12L are connected by a support bar 30. The support bar 30 is disposed on the back side of the user and connects the upper end of the right leg brace 12R and the upper end of the left leg brace 12L.

The upper end of the upper link 14R is connected to the support bar 30 via a waist joint. A waist encoder 22R that detects the angle of the upper link 14R is attached to the waist joint. The lower link 16R is connected to the upper link 14R by a knee joint located outside the knee. A knee encoder 20R that detects the angle of the lower link 16R is attached to the knee joint. The foot link 26R is swingably connected to the lower link 16R by an ankle rotation joint located outside the ankle. An ankle encoder 24R that detects the angle of the foot link 26R is attached to the ankle rotation joint.

The upper link 14R is fixed to the user's thigh with a belt. The lower link 16R is fixed to the user's lower leg with a belt. The foot link 26R is fixed to the user's foot with a belt. In FIG. 1, the belt for fixing the foot link 26R is not shown.

A grounding sensor 28R is attached to the sole of the foot link 26R. That is, the ground sensor 28R is arranged on the sole of the user. The right foot grounding sensor 28R detects contact between the right foot and the ground. Similarly, the left foot contact sensor detects contact between the left foot and the ground. As shown in FIG. 1B, the ground sensors are respectively attached to the front and rear of the foot link.

Since the structure of the left leg orthosis 12L is the same as that of the right leg orthosis 12R, description thereof is omitted. However, the left leg orthosis 12L includes a motor 32. The motor 32 is provided in the knee joint of the left leg orthosis 12L, and is located outside the user's knee joint. The motor 32 can rotate the lower link 16L with respect to the upper link 14L. That is, the motor 32 can apply torque to the user's left knee joint.

The controller 40 is attached to the support bar 30. A tilt sensor 27 is provided inside the controller 40. The tilt sensor 27 detects an absolute tilt angle of the user's body. That is, the tilt sensor 27 detects the tilt angle (absolute tilt angle) of the body with respect to the vertical direction. An encoder group attached to each joint may be collectively referred to as a leg sensor 20. The ground sensor group attached to each of the left and

right foot links

26L and 26R may be collectively referred to as a ground sensor 28.

The controller 40 controls the motor 32 based on the outputs of the tilt sensor 27, the leg sensor 20, and the ground sensor 28. Specifically, the controller 40 controls the motor 32 to apply a torque in the same rotational direction as the swinging direction of the user's lower limb to the user's left knee joint when the left leg is in the free leg state. In addition, the controller 40 controls the motor 32 so as to apply torque in a direction in which the left knee is extended when the left leg is in a standing state.

Explain the state of the legs. FIG. 2 shows a leg state transition diagram. As shown in FIG. 2, the walking motion is divided into the following five states. That is, five types of gait stop state, affected leg swing leg state (healthy leg stand state), both leg stand leg state (before affected leg), affected leg stand leg state (normal leg swing leg state), and both leg stand leg state (before healthy leg) It is. The alphabetic characters in FIG. 2 indicate the state transition. The state transitions at the next timing. That is, the walking stop state shifts to the affected leg swing leg state at the timing of leaving the affected leg (transition A). Alternatively, the walking stop state shifts to the affected leg standing leg state (normal leg swing leg state) at the timing of leaving the healthy leg (transition B). The swinging leg state of the affected leg shifts to the standing state of both legs (before the affected leg) at the timing of contact of the affected leg (transition D). The both-leg stand state (before the affected leg) shifts to the affected leg stand state (normal leg swing leg state) at the timing of leaving the healthy leg (Transition E). The affected leg standing state (healthy leg swing leg state) shifts to the both leg standing leg state (before the healthy leg) at the contact timing of the healthy leg (transition F). The both-leg stand state (before the healthy leg) shifts to the affected leg swing leg state at the timing of leaving the affected leg (Transition C). The affected leg swing leg state (normal leg standing leg state) may shift to a walking stop state at the contact timing of the healthy leg (transition G). Similarly, the affected leg standing leg state (healthy leg swing leg state) may shift to a walking stop state at the contact timing of the healthy leg (transition H). The determination of whether the affected leg swing leg state shifts to the both-leg stand state or the walking stop state will be described later. The timing of transition D and transition F corresponds to the swing leg state end timing.

The controller 40 switches the control mode according to the state of the leg. FIG. 3 shows a block diagram of the controller 40. The controller 40 includes a database 42, a management module 44, and a PID module 46. The database 42 stores data on the target stride and the target walking speed. The management module 44 reads out data from the database 42 and generates a knee target angle, that is, a target value of the motor 32 based on the output signals of the leg sensor 20 and the ground sensor 28. More specifically, the target stride and the target walking speed are described as parameters of the target trajectory of the positions of both feet and the waist in the walking motion. The target trajectory may be called a walking pattern or gait data. The management module 42 determines the knee target angle for each sampling time by inverse kinematics from the foot position and the waist position for each sampling time in the walking pattern.

When the knee target angle is generated, the management module 44 determines the walking state from the outputs of the leg sensor 20 and the ground sensor 28 and switches the control mode to a control mode corresponding to the walking state. The determination of the walking state and the control mode will be described later. The PID module 46 controls the motor 32 so that the difference between the knee target angle and the actual knee angle (knee measurement angle) becomes zero. That is, the controller 40 controls the motor 32 so that the user's knee angle (knee measurement angle) follows the knee target angle.

Describes the control mode. The controller 40 stores the next control mode. That is, (1) a free leg state mode, (2) a standing leg mode, and (3) a walking stop mode. The swing leg state mode and the standing leg state mode are both control modes during the walking motion, and control in which the motor 32 follows the knee target angle that changes with time. The difference between the free leg state mode and the standing leg state mode is as follows. The angle deviation gain of the PID module in the standing state mode is larger than the angle deviation gain in the free leg state mode. Further, the motor torque upper limit value in the standing leg state mode is larger than the motor torque upper limit value in the swing leg state mode. These differences are based on the finding that a weak auxiliary torque is sufficient because the free leg can be moved freely at the user's will, while a strong auxiliary torque is necessary for the stance leg to support weight against gravity. Based on. The walking stop mode is a control mode in which the motor 32 is controlled to maintain a predetermined knee target angle. The standing state mode corresponds to an example of the first standing state mode, and the walking stop mode corresponds to an example of the second standing state mode.

The control rules of the controller 40 will be described. FIG. 4 shows a control flowchart. First, the controller 40 acquires data of various sensors (S10). Next, the controller 40 passes the acquired sensor data through a low-pass filter and removes noise (S12). Since the output of the leg sensor 20 is angle data of each joint, the controller 40 converts the angle data into the position and speed of the foot (S14). In other words, the leg sensor 20 corresponds to a sensor that detects the position and speed of the foot. The conversion from joint angle and angular velocity to foot position and velocity can be calculated using well-known robot forward kinematics algorithms. Here, at the same time, the relative position and relative speed of the leg of the free leg based on the position and speed of the leg of the standing leg are obtained. The controller 40 determines the walking state based on the relative position and speed of the foot and the output of the ground sensor (S16). When the determined walking state is different from the previous walking state (S18: YES), the controller 40 switches the control mode (S20). Next, the controller 40 acquires data on the target position of the foot (S22). The target position of the foot is stored in the database 42 in advance. Then, the controller 40 converts the target position of the foot into the knee target angle based on the inverse kinematics of the robot (S24). A command value is output to the motor so that the knee angle of the user matches the knee target angle obtained in this way (S26). The above process is repeated for each control cycle.

The walking state determination process will be described. FIG. 5 shows conditions for state transition. The letters in the left column of FIG. 5 correspond to the state transitions shown in FIG. Note that “ON” in FIG. 5 indicates that the ground sensor detects grounding, and “OFF” indicates that grounding is not detected. In other words, “ON” indicates that the foot is grounded, and “OFF” indicates that the foot is floating. Therefore, “ON → OFF” in FIG. 5 means the timing when the foot touches the ground, and “OFF → ON” means the bed leaving timing. Further, as described above, in step S14 in FIG. 4, the relative position and relative speed of the free leg's foot are obtained with reference to the position and speed of the leg of the standing leg. Hereinafter, “relative position” and “relative speed” mean the relative position and relative speed of the user in the front-rear direction. In FIG. 5, “distance between feet” indicates the relative distance between the front and back of both feet, and “free leg speed” indicates the relative speed in the front-rear direction of the leg of the free leg with respect to the leg of the standing leg (back leg). Since the speed of the leg of the standing leg is zero, the relative speed of the leg of the free leg is equal to the absolute speed. Further, the distance threshold and the speed threshold are stored in the database 42 in advance.

When the free leg position at the timing when the ground sensor 28L of the left leg (affected leg) detects leaving of the affected leg is equal to or greater than the distance threshold, the controller 40 determines the transition from the walking stop state to the affected leg free leg state. (Migration A) When the distance between the feet at the timing when the ground contact sensor 28R of the right leg (healthy leg) detects the leaving of the healthy leg is equal to or greater than the distance threshold, the controller 40 changes from the walking stop state to the affected leg standing leg state (healthy leg swing leg state). To shift to (Transition B).

If the ground sensor 28L detects that the affected leg has left the floor when the current state is the both-leg stand state, the controller 40 determines whether the affected leg swing leg from the both-leg stand state regardless of the distance between the legs or the free leg speed. Transition to the state is determined (transition C). When the distance between the feet at the contact timing when the contact sensor 28L detects the contact of the free leg (affected leg) is equal to or greater than the distance threshold and the foot speed is equal to or less than the speed threshold, the controller 40 starts from the affected leg free leg state. A transition to the state is determined (transition D). That is, the controller 40 specifies the swing leg state end timing at this time. On the other hand, if the distance between the feet at the contact timing when the contact sensor 28L detects the contact of the free leg (affected leg) is less than the distance threshold or the foot speed exceeds the speed threshold, the controller 40 It is determined that the free leg state of the affected leg continues. If the ground sensor 28R detects that the normal leg has left the floor when the current state is the both-leg stand state, the controller 40 changes from the two-leg stand state to the affected leg stand state regardless of the distance between the legs or the free leg speed. Transition to (normal leg swing leg state) is determined (transition E).

When the distance between the feet at the grounding timing when the grounding sensor 28R detects the grounding of the free leg (healthy leg) is equal to or greater than the distance threshold and the foot speed is equal to or less than the speed threshold, the controller 40 ) To a both-leg stand state (transition F). That is, the controller 40 specifies the swing leg state end timing at this time. On the other hand, if the distance between the feet at the contact timing when the contact sensor 28R detects the contact of the free leg (healthy leg) is below the distance threshold or the foot speed exceeds the speed threshold, the controller 40 It is determined that the affected leg standing state (normal leg swing leg state) continues.

When the left leg (affected leg) is in a free leg state, the distance between the feet at the contact timing when the contact sensor 28L detects the contact is below the distance threshold, and the free leg speed is equal to or less than the speed threshold. 40 determines the transition from the affected leg swing leg state (normal leg stand state) to the stopped state (transition G). When the right leg (healthy leg) is in a free leg state, the distance between the feet at the ground contact timing when the ground sensor 28R detects the ground contact is below the distance threshold, and the free leg foot speed is less than the speed threshold, the controller 40 determines a transition from the affected leg standing leg state (normal leg swing leg state) to the stopped state (transition H).

The points to be noted in the above judgment are described. The controller 40 continues the swing leg state mode when the relative speed of the free leg foot exceeds the speed threshold at the timing when the ground contact of the free leg is detected (contact timing). Such a configuration prevents the control from switching to the standing state mode when the user hits the ground unintentionally. In addition, when the ground contact of the affected leg is detected in the affected leg swing state, the controller 40 determines that the user is walking if the distance between the feet is equal to or greater than the distance threshold, and the control mode for walking (first standing state) Mode) is continued, and when the distance between the feet is below the distance threshold, the mode is switched to the stop control mode (second stance state mode).

The walking assist device of the embodiment may be expressed as follows. The walking assist device includes a leg sensor that detects the movement of the user's leg, a ground sensor disposed on the sole of the user, an actuator that applies torque to the user's leg, and whether or not the leg is in a free leg state. And a controller for switching the control mode of the actuator. The controller continues the swing leg state mode when the relative foot speed at the contact timing (relative speed of the free leg to the standing leg) exceeds the speed threshold, and the relative speed is equal to or less than the speed threshold. The control mode is switched to the standing state mode.

In the walking assistance device of the present embodiment, the determination of the state transition is performed based on the distance between the feet when the ground sensor detects the ground contact and the free leg foot speed. Therefore, the above determination is made simultaneously with the detection of the grounding by the grounding sensor. Thus, the point which can judge a state transition rapidly is also the characteristics of the walk assistance apparatus of a present Example.

Other technical features of the walking assist device of the embodiment will be described. The standing state mode is control for applying torque to support the weight to the leg. The free leg state mode is, for example, control for applying torque to the leg to assist the operation of swinging the leg forward. Therefore, in the free leg state mode, the angle gain of the angle control of the actuator is smaller than in the standing state mode. The “angle gain” corresponds to a gain for causing the joint angle of the leg to follow the target joint angle. In other words, the walking assistance device of the embodiment controls when the relative speed of the free leg's foot with respect to the leg of the standing leg (the back leg) is equal to or less than the speed threshold at the contact timing when the ground contact of the free leg is detected. The mode is switched to the stance state mode having an angle gain larger than the angle gain in the swing state mode. In short, the walking assistance device of the embodiment has a relative foot speed (relative speed of the leg of the free leg with respect to the leg of the standing leg) at the contact timing of the leg of the free leg (the timing at which the ground is detected) is equal to or less than the speed threshold. In this case, the angle gain of the actuator control is changed. In summary, the walking assistance device of the embodiment changes the gain (angle gain) for controlling the joint angle in the standing state mode and the swinging state mode. Note that the standing state mode may refer to a walking pattern different from the walking pattern (the knee angle or the trajectory of the toe position and the waist position) referred to in the swing leg control mode.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

10: Walking assist

device

12R, 12L:

Orthosis

14R, 14L:

Upper link

16R, 16L: Lower link 20R, 20L: Knee encoder 22R, 22L: Waist encoder 24R, 24L:

Ankle encoder

26R, 26L: Foot link 27:

Inclination sensor

28R, 28L: Ground sensor 30: Support bar 40: Controller 42: Database 44: Management module 46: PID module

Claims

An actuator that applies torque to the user's leg;
A leg sensor for detecting the movement of the user's leg;
A grounding sensor for detecting the grounding of the user's foot;
A controller for controlling the actuator based on the output of the leg sensor,
The controller
Based on the output of the leg sensor, calculate the relative speed of the leg of the free leg to the leg of the standing leg
If the relative speed at the contact timing at which the contact of the leg of the free leg is detected exceeds the speed threshold, it is determined that the free leg state continues,
A walking assist device configured to determine that the free leg state has ended when the relative speed at the contact timing is equal to or less than a speed threshold.
The controller
The control mode of the actuator can be switched between the swinging state mode and the standing state mode,
If it is determined that the free leg state continues, the free leg state mode is continued,
The walking assistance device according to claim 1, wherein the walking assist device is configured to switch from the free-leg state mode to the standing-leg state mode when it is determined that the free-leg state has ended.
The controller
Based on the output of the leg sensor, calculate the distance in the front-rear direction of both feet at the contact timing,
When the distance is equal to or greater than the distance threshold, the control mode is switched to the first stance state mode for continuing walking,
The walking assistance device according to claim 2, wherein the walking assistance device is configured to switch to a second stance state mode for stopping walking when the distance is below a distance threshold.