JP5796365B2 - Walking assist device - Google Patents

Description

  The present invention relates to an apparatus for assisting a user's walking motion. In particular, the present invention relates to a walking assist device suitable for rehabilitation of walking motion.

  Devices that assist the user's walking motion have been studied. One type of such device includes an actuator that can be worn on the user's leg and generates torque about the knee joint axis of rotation. The technique disclosed in the present specification also relates to such a type of walking assist device, and an example thereof is disclosed in Patent Document 1.

JP 2007-20672 A

  The above-described type of walking assistance device can be used both for the purpose of powering up a healthy person and for the purpose of walking assistance (including rehabilitation) of a non-healthy person. However, healthy users and non-healthy people have different assumed user abilities (physical strength, muscle strength, agility, etc.). For example, certain illnesses may leave an obstacle below the knee. Many non-healthy people with such disabilities rehabilitate using long leg braces. Such an unhealthy person may collapse without being able to support his weight by himself. Hereinafter, in order to simplify the description, the fact that the user collapses without supporting his / her weight is expressed as “knee break”. As functional recovery progresses through rehabilitation, the unhealthy person shifts the auxiliary device to be used from the long leg brace to the short leg brace. The transition period from long leg braces to short leg braces is a particularly unstable period for non-healthy people, and caregivers should always be on the side, and non-healthy people need to cope in case of loss of balance. For example, the burden is imposed on both non-healthy people and caregivers. On the other hand, in the long leg brace, since the knee is fixed in the extended state, the user relies on the brace to prevent the knee from being broken, and the function recovery for supporting the weight with his / her own force may be insufficient.

  As described above, when a non-healthy person is assumed to be an assumed user, it is desirable that the walking assist device take into account that the user may collapse without being able to support his / her own weight. If there is no such consideration, if the aim is to rehabilitate a user who is unable to walk, sufficient aiming will not be achieved unless sufficient assisting force is applied. Does not achieve the purpose of rehabilitation. The present specification provides a walking assistance device suitable for rehabilitation of a non-healthy person who is unable to walk. However, it should be noted that the technique disclosed in this specification is effective not only for rehabilitation purposes but also for assisting walking in the normal life of non-healthy persons.

  As described above, one type of walking assist device includes an actuator that generates a torque around the user's knee joint rotation axis and a controller that controls the actuator. The walking assist device disclosed in this specification also includes the actuator and the controller. One embodiment of the walking assistance device disclosed in the present specification includes a sensor that detects the swinging direction of the lower leg. Further, the controller controls the actuator so as to output an assist torque in a direction in which the knee is extended while the user's lower leg swings in the knee bending direction with respect to the standing leg during the walking motion. On the other hand, the controller controls the actuator so that the assist torque is not output with respect to the standing leg while the user's lower leg swings in the knee extension direction.

  The walking assist device outputs assist torque only when the lower leg swings in the knee flexion direction. While the lower leg swings in the knee extension direction, the user can support his / her body weight by himself / herself, and thus no assist torque is output during that period. While the lower leg swings in the knee flexion direction, the assist torque acts in a direction that prevents the knee flexion swing. If the swing of the lower leg in the flexion direction stops, the assist torque becomes zero. Note that the swing in the knee flexion direction may not stop even with the assist torque, but at least the swing speed in the knee flexion direction becomes slow. Since it takes a long time to break the knee, an assistant may assist during that time. That is, the walking assistance device disclosed in the present specification can allow the user to use the muscular strength as much as possible while applying assist torque to the knee break.

  In order to determine whether the leg to be assisted is a standing leg or a free leg, for example, a touch sensor (or load sensor) may be provided on the sole of the leg. In order to detect the swinging direction of the lower leg, one method is to take the time difference of the measurement values of the sensor that detects the swinging angle of the lower leg. When the walking assist device has a multi-link mechanism having a thigh link and a lower leg link, it is also preferable to obtain the lower leg swing angle (and the swing direction) from the relative angle of the lower leg link and the thigh link. Of course, the swinging direction of the lower leg may be directly sensed by installing a gyro.

  In one embodiment of the walking assistance device disclosed in this specification, the controller applies an assist torque according to the swinging angular velocity (swinging speed) of the lower leg while the lower leg of the user is swinging in the knee bending direction. It is preferable to control the actuator to output. When the rocking angular velocity is fast, there is a high possibility that it will collapse as it is (it is highly possible that the knee will break), so it is preferable to output a large assist torque.

  In another embodiment disclosed in the present specification, the controller controls the knee regardless of the swinging direction of the lower leg when the swinging angle of the user's lower leg in the bending direction exceeds a predetermined limit angle. It is preferable to control the actuator so as to generate an assist torque in the direction in which the torque is extended and according to the difference between the limit angle and the swing angle. The limit angle is set to the maximum value of the angle estimated that the user will be able to support the dead weight by himself. In other words, the limit angle is set to an angle that is estimated to be highly likely to cause a knee break if the knee bends further. By forcibly returning the knee swing angle to the limit angle when the user's knee swing angle exceeds the limit angle, the walking assistance device acts to continue the walking motion as much as possible while preventing the knee from being folded.

  An example of the limit angle is about 20 degrees. In the description of the present specification, a measurement standard in which the state where the lower leg is stretched is set to the swing angle = 0 and the knee bending direction is the positive direction of the swing angle is employed. However, this measurement standard is for convenience of explanation. Which angle is set to zero or which rotation direction is set to the positive direction is arbitrary, and is based on the technique disclosed in this specification. Note that it has essentially no effect.

It is a schematic diagram of a walking assistance device. 1A shows a front view, and FIG. 1B shows a side view. It is a figure explaining the definition of the value of a rocking angle and torque used in this specification. It is a block diagram of a walking assistance device. It is a control flowchart figure of the walk auxiliary device of the 1st example. It is a graph which shows the relationship between the rocking | fluctuation angle and assist torque in 2nd Example. It is a control flowchart figure of the walking assistance apparatus of 2nd Example.

  (First Embodiment) FIG. 1 schematically shows a walking assist device 2 of the embodiment. FIG. 1 shows the walking assist device 2 in a state worn by the user. The walking assist device 2 is a so-called wearable device that is worn along a user's leg. The walking assist device 2 is mechanically mainly composed of a thigh link 5, a lower leg link 9, a foot link 11, a knee joint 7 that connects the thigh link 5 and the lower leg link 9, and an ankle joint that connects the lower leg link 9 and the foot link 11. 10 multi-link multi-joint mechanism. The thigh link 5 is fixed to the user's thigh with a belt, and the lower leg link 9 is fixed to the user's lower leg with a belt. Although not shown, the foot link 11 includes shoes, and the foot link 11 is fixed to the user when the user wears the shoes. When the user wears the walking assist device 2, the knee joint 7 is positioned substantially coaxially with the rotation axis of the user's knee joint, and the ankle joint 10 is rotated about the rotation axis (rotation around the pitch axis) of the user's ankle joint. The axis).

  With reference to FIG. 2, the measurement standard (definition of zero point and positive value direction) of the swing angle and assist torque used in this specification will be described. As shown in FIG. 2, the crus swing angle Ag is defined as an angle formed by a straight line L <b> 1 extending in the longitudinal direction of the thigh link 5 and the crus link 9. Therefore, the state where the thigh link 5 and the lower leg link 9 are aligned, that is, the state where the user has extended the lower leg corresponds to the swing angle Ag = 0. The positive direction of the swing angle Ag is defined as the direction in which the user bends the knee. The assist torque Tq is defined as a positive value in the direction in which the knee is extended from the bent state (the direction in which the lower leg link swings forward). That is, the positive assist torque acts against the user's knee breakage.

  Returning to FIG. 1, the description of the walking assist device 2 will be continued. In addition, since the block diagram of the walk assistance apparatus 2 is shown in FIG. 3, please refer to it simultaneously. The knee joint 7 incorporates a motor 8 (actuator) and an angle sensor 6. A load sensor 12 is built in the sole of the foot link 11. Data of each sensor is sent to the controller 20 fixed to the thigh link 5. The controller 20 outputs a command value to the motor 8 based on the sensor data.

  The lower leg link 9 swings relative to the thigh link 5 by the driving force of the motor 8. Since the thigh link 5 and the lower leg link 9 are fixed to the user's thigh and lower leg, respectively, the driving force of the motor 8 is a force that causes the user's lower leg to swing. That is, the motor 8 gives a torque around the rotation axis of the user's knee joint. As will be described later, the controller 20 (walking assisting device 2) generates torque so as to assist (assist) the user's walking motion. Therefore, in this specification, the torque output from the motor 8 (walking assisting device 2) is referred to as assist torque. As shown in FIG. 1, in this embodiment, the walking assistance device 2 is attached to the left leg of the user and assists the movement of the left leg.

  The angle sensor 6 is an encoder and measures an angle formed by the thigh link 5 and the crus link 9. This angle is an angle formed by the user's thigh and lower leg, and corresponds to the swing angle Ag described above. The load sensor 12 measures the floor reaction force applied to the leg of the leg (the left leg in the example) to which the walking assist device 2 is attached. The magnitude of the floor reaction force measured by the load sensor 12 is used by the controller 20 to determine whether or not the leg of the leg wearing the walking assist device 2 is in contact with the ground.

  As illustrated in FIG. 3, the walking assist device 2 includes an input device 22 and a storage device 23 in addition to the controller 20. In FIG. 1, the input device 22 and the storage device 23 are not shown. The input device 22 includes a switch for instructing activation and stop of the walking assist device 2 and a switch for inputting various parameters used for a control algorithm (described later) executed by the controller 20. Various parameters are input by the user of the walking assistance device 2 or a person who assists the user's rehabilitation (therapist or the like). The input parameters are stored in the storage device 23.

  A process (control) executed by the controller 20 will be described with reference to the flowchart of FIG. The controller 20 acquires the sensor data of the load sensor 12, and further acquires the sensor data of the angle sensor 6 (steps S2 and S3). The sensor data of the angle sensor 6 corresponds to the swing angle Ag. The controller 20 calculates the swing angular velocity dAg by taking the difference between the swing angle value acquired this time and the swing angle value acquired in the past (step S4). As the difference method, in addition to the simple Euler method, there are many well-known methods such as a central difference method, a backward difference method, and a second-order difference method, and any of them may be used.

  Next, the controller 20 determines whether or not the leg on which the walking assistance device 2 is mounted is in a standing state (step S5). This determination is based on the sensor data of the load sensor 12. Specifically, when the sensor data of the load sensor 12 is zero or a value close to zero, the controller 4 determines that the leg is not in the standing state (that is, in the free leg state). If it is determined that the leg on which the walking assistance device 2 is mounted is not in the standing state, the process is terminated without outputting the assist torque (step S5: NO).

  When the leg on which the walking assistance device 2 is mounted is in the standing state (step S5: YES), the controller 20 sets a command value for the assist torque Tq based on the following formula (1). As described with reference to FIG. 2, it should be noted that the swing angle Ag has a positive value in the knee bending direction, but the assist torque Tq has a positive value that acts in the direction of extending the knee.

  In (Equation 1), ka is a proportional gain, and kd is a differential gain. Both ka and kd are constant values and are input by the user (or therapist) by the input device 22 described above. In accordance with (Equation 1), the controller 20 sets Tq1 as the torque command value Tq when the swing angle Ag is larger than the limit angle AgH (steps S6: YES, S7). The set torque command value Tq is output to the motor 8 (step S14). The motor 8 outputs the commanded assist torque.

  Tq = T1 is the magnitude of the assist torque (command value) when the swing angle Ag is larger than the limit angle AgH. The limit angle AgH is, for example, 20 degrees, and is set to an angle at which there is a high possibility that the knee will bend when the knee is bent beyond this angle. In other words, the limit angle is set to a value that is estimated that the user will be able to support the weight by himself / herself up to that angle. The limit angle AgH is preferably determined by a therapist in charge of rehabilitation by observing the state of the user.

  As shown in (Expression 1), Tq1 acts to return the swing angle Ag exceeding the limit angle AgH to the limit angle AgH. Tq1 is set so that the swing angle is forcibly returned to an angle (that is, a limit angle AgH) that is estimated to be able to support the weight of the user by himself / herself when the knee is bent to such a degree that the knee may be broken. Works.

  When the swing angle Ag is equal to or smaller than the limit angle AgH (step S6: NO) and the angular velocity dAg is greater than zero (step S8: YES), the controller 20 sets the torque command value Tq = Tq2 (step S12). ). The set torque command value Tq is output to the motor 8 (step S14). The motor 8 outputs the commanded assist torque.

  Tq2 is proportional to the swinging angular velocity of the lower leg. Furthermore, Tq2 is given only while the lower leg swings in the knee flexion direction (that is, while dAg> 0). When the lower leg is swinging in the extension direction or not swinging (that is, dAg ≦ 0), the torque command value Tq = 0 is set (steps S8: NO, S13). That is, at this time, the assist torque is not output.

  Tq2 is given in a magnitude proportional to the swing angular velocity only while the user's lower leg swings in the knee flexion direction. In other words, it acts to assist the user only while there is a concern about knee bending. In the case of dAg ≦ 0, that is, when the lower leg is swinging in the extending direction or not swinging, it indicates that the user is supporting the weight by his / her own force. Is not added to the user. Thereby, the walking assist device 2 promotes the user's muscle strength recovery (that is, rehabilitation).

  Even if the assist torque Tq2 is output, the swing in the knee flexion direction may not stop. However, even in that case, at least the swing speed in the knee flexion direction is slow. Since it takes a long time to break the knee, an assistant may assist during that time. The walking assist device 2 promotes the user to use muscle strength as much as possible while applying assist torque to resist knee bending.

  Note that the condition “Ag> AgH] of Tq1 in (Equation 1) may be“ Ag ≧ AgH ”. Similarly, it should be noted that the condition “dAg> 0” of Tq2 in (Equation 1) may be “dAg ≧ 0”. The important point is that the limit angle AgH is provided, and the assist torque does not depend on the swing angle Ag but depends on the swing angular velocity dAg while the swing angle Ag is equal to or less than the limit angle AgH (or less than the limit angle AgH). Is output, and when the swing angle Ag is larger than the limit angle (or when the swing angle Ag is equal to or greater than the limit angle), an assist torque for forcibly returning the swing angle Ag to the limit angle AgH is generated. It is at the point to be output.

  (Second Embodiment) Next, a walking assist device of the second embodiment will be described. Since the configuration of the walking assist device of the second embodiment is the same as that of the walking assist device 2 of the first embodiment, description thereof is omitted. Therefore, the same reference numerals as those used in the first embodiment are used for the components of the walking assist device of the second embodiment. The walking assist device of the second embodiment is different from that of the first embodiment in the control algorithm executed by the controller 20.

  The controller of the walking assist device of the second embodiment sets the assist torque Tq based on the following formula (2).

  In (Expression 2), the swing angles AgL and AgH are constants. In (Expression 2), TqA and TqB are constant values. The size of TqA is set to a size sufficient to support the weight of the user with only the walking assistance device. TqB is set to a small value. Further, in (Equation 2), Flag is set to “1” when the swing angle Ag exceeds the limit angle AgH, and when the swing angle Ag returns to zero (or has shifted to the swing phase). To 0). The technical meaning of Flag will be described with reference to the flowchart of FIG.

  FIG. 5 is a graph showing the torque command value Tq of (Equation 2). As shown in FIG. 5, in the case of the second embodiment, the assist torque Tq depends on the swing angle. When the swing angle Ag is equal to or smaller than the first angle AgL, the controller 20 sets a constant value Tq1 (first assist torque) = TqB as an assist torque command. When the swing angle Ag is between the first angle AgL and the second angle AgH, the controller 20 sets a torque command value Tq2 (second assist torque) proportional to the swing angle Ag. When the swing angle Ag is larger than the second angle AgH, the controller 20 sets the constant value Tq3 (third assist torque) = TqA as the torque command value. As shown in FIG. 5, the third assist torque Tq3 is set to a value larger than the second assist torque Tq2 when the swing angle Ag is equal to the second angle AgH. Although not shown in the graph of FIG. 5, as indicated by (Equation 2), the controller 20 returns the swing angle Ag to zero once the swing angle Ag exceeds the second angle AgH. Until, the torque command value is fixed at the third assist torque Tq3 = TqA.

  Since the motor 8 outputs torque according to the assist torque command value output from the controller 20, the torque command value = the assist torque that is actually output.

  FIG. 6 shows a control flowchart for realizing the assist torque output of the graph of FIG. Hereinafter, the processing of the controller 20 will be described with reference to the flowchart of FIG.

  The controller 20 acquires the sensor data of the load sensor 12, and further acquires the sensor data of the angle sensor 6 (steps S22 and S23). Then, the controller 20 determines whether or not the leg on which the walking assistance device is mounted is a standing leg based on the sensor data of the load sensor (step S24). The processing so far is the same as in the first embodiment. When the leg on which the walking assistance device is mounted is not in the standing state (that is, in the swinging state), the controller 20 sets Flag to zero and ends the process (step S25). Setting zero to Flag in step S25 corresponds to a so-called reset. When the leg on which the walking assistance device is mounted is a standing leg (step S24: YES), the process proceeds to step S26.

  Flag is set to “1” when the swing angle Ag exceeds the second angle AgH (step S26: YES, S27). The flag set to “1” is reset to zero when the swing angle Ag returns to zero (steps S32: YES, S33). That is, Flag is set to “1” when the swing angle Ag exceeds the second angle AgH, and thereafter maintained at “1” until the swing angle returns to zero, and when the swing angle Ag returns to zero. Reset to zero. While the flag is “1”, Tq3 = TqA is set as the torque command value Tq (step S28). That is, the controller 20 controls the motor 8 to output the third assist torque Tq3 when the swing angle Ag is larger than the second angle AgH. Here, the third assist torque Tq3 is a constant value larger than the second assist torque Tq2 when the swing angle Ag is equal to the second angle AgH. Furthermore, once the swing angle Ag exceeds the second angle AgH, the controller 20 controls the motor 8 so as to continue outputting the third assist torque Tq3 until the swing angle Ag returns to zero.

  When the flag is not “1” and the swing angle Ag is equal to or smaller than the second angle AgH, the controller 20 compares the swing angle Ag with the first angle AgL (step S34). When the swing angle Ag is larger than the first angle AgL, the controller 20 sets the second assist torque Tq2 to the torque command value Tq (step S35). When the swing angle Ag is between zero and the first angle AgL, the controller 20 sets the first assist torque Tq1 to the torque command value Tq (step S36). The set torque command value Tq is output to the motor 8 (step S37). As described above, since the motor 8 outputs torque according to the command value, torque command value = assist torque to be output.

  The second angle AgH may be the same size as the limit angle AgH of the first embodiment. In other words, the second angle AgH is set to an angle that is estimated to have a high possibility of bending the knee when the knee is further bent. A specific example of the second angle AgH is 20 degrees. The first angle AgL is set to an angle at which it is estimated that the user will be able to support his / her weight sufficiently. A specific example of the first angle AgL is about 10 degrees, which is half of the second angle Ag. The first angle AgL and the second angle AgH may be determined by observing the state of the user by a therapist who supervises the user's rehabilitation.

  As is apparent from FIGS. 5 and 6, the walking assist device of the second embodiment outputs the first assist torque Tq <b> 1 that is a small constant value while the swing angle Ag is small, and the swing angle is slightly higher. When it becomes larger (AgL <Ag <AgH), the second assist torque Tq2 proportional to the swing angle Ag is output. Since the second assist torque Tq2 increases as the swing angle Ag increases, the user can flex the knee with peace of mind. Furthermore, when the swing angle Ag exceeds the second angle AgH, this walking assist device outputs a constant third assist torque Tq3 sufficient to support the weight of the user. Once the swing angle Ag exceeds the second angle AgH, the walking assist device continues to output the third assist torque until the swing angle Ag returns to zero. The swing angle Ag = 0 is equivalent to a state where the user stands upright. That is, once the possibility of knee breakage is increased (Ag> AgH), the walking assistance device returns the user's leg to an upright state and reliably returns it to a stable posture. With the above algorithm, the user can perform rehabilitation (walking training) with peace of mind.

  Points to be noted regarding the walking assistance device of the embodiment will be described. “The assist torque is not output while the user's lower leg is swinging in the knee extension direction” means that a slight torque is output in the knee extension direction and the mechanical resistance of the device worn along the user's leg ( For example, the case of canceling the rotation resistance of the joint between the lower leg link and the thigh link) is included. When the rotational resistance between the lower leg link and the lower leg link is very small, the power supply to the actuator may be simply cut. For example, when the actuator that swings the crus link is a direct drive system in which a motor having a small rotational inertia moment is directly connected to the rotation shaft of the crus link, the power supply to the motor may be cut off.

  The walking assistance device of the embodiment employs a motor as an actuator, but the actuator is not limited to a motor. An actuator using hydraulic pressure, water pressure, or air pressure may be used.

  The walking assistance apparatus of an Example makes a non-healthy person who cannot perform a walking operation | movement smoothly an object user. The walking assist device is attached to the user when such a user performs rehabilitation of walking motion. The walking assistance device attached to the user outputs a large assist torque when the user is about to break the knee, preventing the user from collapsing. On the other hand, the walking assist device of the first embodiment does not output assist torque while swinging in the knee extension direction, and the walking assist device of the second embodiment is small as long as the swing angle is small. It is configured to output assist torque, and consideration is given so as not to hinder the user's recovery of muscle strength as much as possible. The walking assistance device disclosed in this specification is suitable for rehabilitation of a non-healthy person who is unable to walk. However, the walking assist device disclosed in the present specification is effective even when applied to an elderly person, and is effective even when used by a healthy person, for example, when carrying heavy objects.

  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.

2: Walking assist device 4: Controller 5: Thigh link 6: Angle sensor 7: Knee joint 8: Motor 9: Lower leg link 10: Ankle joint 11: Foot link 12: Load sensor 20: Controller 22: Input device 23: Storage device

Claims (3)

A walking assistance device to be worn on the user's leg,
An actuator that generates torque about the user's knee joint rotation axis;
A sensor for detecting the swinging direction of the lower leg;
A controller that controls the actuator;
The controller is equipped with
When the user's lower leg swings in the knee flexion direction with respect to the standing leg while walking, the assist torque is in the direction of extending the knee and the assist torque corresponding to the swinging angular velocity of the lower leg is output. A walking assist device that controls the actuator and controls the actuator so that assist torque is not output while the user's lower leg swings in the knee extension direction. When the swing angle of the user's lower leg flexion direction exceeds a predetermined limit angle, the controller is an assist torque in the direction of extending the knee regardless of the lower leg swing direction, walking assist apparatus according to claim 1, characterized in that for controlling the actuator so as to generate an assist torque corresponding to the difference between the angle and the swing angle.   A walking assistance device to be worn on the user's leg,
  An actuator that generates torque about the user's knee joint rotation axis;
  A sensor for detecting the swinging direction of the lower leg;
  A controller that controls the actuator;
The controller is equipped with
  While the user's lower leg swings in the knee flexion direction with respect to the standing leg during walking, the actuator is controlled to output an assist torque in the direction of extending the knee, and the user's lower leg is in the knee extension direction. Control the actuator not to output the assist torque while swinging
  When the swing angle in the flexion direction of the user's lower leg exceeds a predetermined limit angle, the assist torque is in the direction in which the knee is extended regardless of the swing direction of the lower leg. A walking assist device that controls an actuator to generate an assist torque according to a difference in dynamic angle.

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