JP5728952B2 - Walking support device - Google Patents

Description

  The present invention relates to a device for assisting movement of a user's leg. In particular, the present invention relates to a walking support device that assists walking motion.

  In recent years, a walking support device that actively assists the movement of a user's leg by an actuator has been studied. In such a walking support device, the thigh link attached to the user's thigh and the crus link attached to the lower leg are connected so as to be able to swing, and the actuator swings the lower leg link. Examples of such walking support devices are disclosed in Patent Literature 1 and Patent Literature 2.

  Note that the walking assist device disclosed in Patent Document 2 is unique in that a four-link mechanism is employed as a speed reduction mechanism that amplifies the torque of a motor (actuator) and transmits the amplified torque to a lower leg link. The walking support device comprises a four-link closed link mechanism in which a thigh link and a crus link are connected by two auxiliary links. It is known that the 4-link closed link mechanism functions as a reduction gear when the length of each link is appropriately selected. For example, when the shortest link rotates once, the longest link rotates 1/4, the torque amplification factor at this time is about four times. As will be described later, since the present invention is also a walking support device adopting a four-link mechanism, Patent Document 2 is cited as a related prior art.

  Hereinafter, for the sake of simplicity, the “walking support device” may be simply referred to as “support device”. Furthermore, some terms used in this specification will be explained. The pitch axis is a term well known in the technical field of robots, and means an axis extending in the left-right direction (side) of the robot (in this specification, a user wearing a support device). Further, “front” and “rear” used in the following description mean front and rear when the user takes an upright posture. The “longitudinal centerline of the leg” means a straight line connecting the hip rotation center and the knee rotation center for the thigh when the user is observed from the side, and the knee rotation center and the ankle joint for the lower leg. This means a straight line connecting the centers of rotation.

JP 2002-301124 A JP 2008-23234 A

  The walking support device must prevent the knee joint from bending when the leg (wearing leg) wearing the device cannot support the weight with its own muscle strength. The fact that the knee joint is bent due to the inability to support weight is commonly referred to as “knee break”. Hereinafter, since the explanation is easy to understand, the term “knee break” is also used in this specification. The walking assist device is required to prevent knee breakage. Typically, when assisting the walking motion, the walking assist device needs to output a torque that maintains the angle of the lower leg link so that the knee does not break when the attached leg is a standing leg. At this time, if the output torque required for the actuator can be reduced, the energy saving of the support device can be achieved. Alternatively, since the maximum torque required for the actuator is reduced, a small (small output) actuator can be employed.

  As a method to prevent knee breakage without relying on the torque of the actuator, there may be a method of braking the rotation of the lower leg link when the attached leg is a standing leg, but in that case the brake is turned on in accordance with the predetermined timing of walking It is necessary to switch off / on. The present specification provides a walking assist device that can prevent knee breakage of a standing leg by a mechanical device without using a brake and without requiring a large output torque from an actuator.

  The walking support device disclosed in this specification employs a four-link closed link mechanism in which a thigh link and a lower leg link are connected by two auxiliary links, like the walking support device of Patent Document 2. One feature of the technology disclosed in this specification is that the closed link structure is defined so as to satisfy specific geometric conditions, so that not only the brake but also the torque of the actuator is not required. The purpose is to prevent knee breakage of the stance.

  One mode of the support device disclosed in this specification will be described. The support device includes a thigh link, a crus link, a first auxiliary link, a second auxiliary link, and an actuator. The thigh link and the crus link are rotatably connected to each other, and are respectively attached to the user's thigh and crus. The rotation axis between the thigh link and the crus link substantially coincides with the rotation axis of the knee joint when the user wears the support device. The first auxiliary link is connected to the thigh link so as to be rotatable around the pitch axis, and the second auxiliary link is connected to the crus link so as to be rotatable around the pitch axis. The tip of the first auxiliary link is rotatably connected to the tip of the second auxiliary link. The actuator rotates the lower leg link with respect to the thigh link.

  In the support device disclosed in this specification, the thigh link, the lower thigh link, the first and second auxiliary links constitute a four-link closed link structure (closed four-link structure). This is the same as the support device of Patent Document 2. The feature of the support device disclosed in this specification is that the closed four-link structure is configured to satisfy the following two geometrical conditions. The first geometric condition is that the user wearing the support device observes from the side when the knee is stretched, and the rotation center of the connecting portion between the thigh link and the first auxiliary link, the first auxiliary link and the second The condition is that the three points of the rotation center of the connecting portion of the auxiliary link and the rotation center of the connecting portion of the lower leg link and the second auxiliary link are arranged in a straight line. Hereinafter, this condition will be referred to as a knee lock condition. The reason will be described later.

  The second geometric condition is that at least one of the rotation center of the connecting portion of the thigh link and the first auxiliary link and the rotation center of the connecting portion of the lower leg link and the second auxiliary link is when the user wears the support device. When observed from the side, it is located behind the center line in the longitudinal direction of the leg passing through the rotation axis of the knee joint. Hereinafter, this condition is referred to as a bending condition. The bending condition is a condition necessary for the thigh link and the crus link to bend in the knee bending direction while satisfying the knee lock condition. When the user stretches the leg, if both the first and second auxiliary links are completely positioned forward of the longitudinal center line of the leg (when the bending condition is not satisfied), the first and second links are It can be easily imagined that the thigh link and the crus link cannot rotate in the knee flexion direction because they are pulled together.

  The technical meaning of the knee lock condition will be described with reference to FIG. FIG. 5 schematically shows a view of the support device 100 worn by the user observed from the side. FIG. 5A shows a state where the user has stretched the knee, and FIG. 5B shows a state where the user has bent the knee. Reference numerals 10, 20, 30, and 40 denote a thigh link, a crus link, a first auxiliary link, and a second auxiliary link, respectively. The thigh link 10 and the crus link 20 are connected by a joint 51. The rotation axis of the joint 51 substantially coincides with the rotation axis of the user's knee. One end of the first auxiliary link 30 is connected to the thigh link 10 by a joint 52. One end of the second auxiliary link 40 is connected to the crus link 20 by a joint 54. The other end of the second auxiliary link 40 is connected to the other end of the first auxiliary link 30 by a joint 53. A motor 55 for rotating the first auxiliary link 30 is attached to the thigh link 10 (joint 52). “Joint” corresponds to “connecting portion”.

  As shown in FIG. 5A, when the user stretches the knee, the three rotation centers of the joints 52, 53, and 54 are aligned in a straight line as observed from the side. That is, the knee lock condition is satisfied. Even if external force torque in the knee flexion direction acts on the joint 51 in this state, the first auxiliary link 30 and the second auxiliary link 40 are along the longitudinal direction (the straight line connecting the joints 52, 53, and 54). Because force acts, it does not rotate. In other words, since the axial force acts on the first auxiliary link 30 and the second auxiliary link 40 but the moment does not act, they do not rotate. That is, when the knee lock condition is satisfied, the lower leg link 20 does not rotate even when an external force torque in the bending direction (torque that rotates the lower leg link 20 in the arrow Tf direction) acts on the knee joint. That is, the rotation of the knee is locked. This is the technical significance of the “knee lock condition”.

  Note that at least one of the bending conditions, that is, the rotation center of the joint 52 of the thigh link 10 and the first auxiliary link 30 and the rotation center of the joint 54 of the crus link 20 and the second auxiliary link 40, the user uses the support device 100. If the condition of locating behind the longitudinal center line (straight lines L1 and L2) passing through the knee joint rotation axis (joint 51) is not observed, the crus link 20 will be The inability to rotate in the bending direction will be apparent from FIG.

  Even if external force torque is applied around the joint 51, the crus link 20 does not rotate (although the knee remains locked), but when torque is applied to the first auxiliary link 30 around the joint 52, the first auxiliary link 30 is applied. Rotates easily, and as a result, the lower leg link 20 rotates. That is, if the motor 55 outputs a torque for rotating the first auxiliary link 30, the knee lock is released (FIG. 5B).

  As described above, when the knee lock condition is satisfied when the user extends the knee, even if the external force torque acts on the knee, the rotation of the lower leg link can be prohibited without the motor 55 outputting the torque. That is, knee breakage can be prevented without requiring the output torque of the motor 55. Note that the rotation centers of the joints 52, 53, and 54 do not have to be strictly aligned. It suffices if it is almost a straight line. Specifically, the angle formed by the straight line L3 connecting the rotation center of the joint 52 and the rotation center of the joint 53 and the straight line L4 connecting the rotation center of the joint 53 and the rotation center of the joint 54 is within about 180 ± 5 degrees. That's fine. This is because, within such a range, the output torque required for the motor 55 to prohibit the rotation of the first auxiliary link 30 when an external force torque acts on the joint 51 is very small. This is because the torque (moment) generated in the first auxiliary link 30 due to the external force torque acting on the joint 51 is very small.

  The support device observes from the side direction so that the angle formed by the first auxiliary link and the second auxiliary link that is 180 degrees or less when the knee is bent does not exceed 180 degrees at the maximum. It is preferable to provide a limiting stopper. In the example of FIG. 5, it is preferable to include a stopper that limits the angle Ag so that it does not exceed 180 degrees at the maximum. More precisely, a stopper is provided that restricts the angle formed by the first auxiliary link and the second auxiliary link to be 180 degrees or less when the knee is bent so that the angle does not exceed 180 degrees + a minute angle. It is preferable. Here, the minute angle is approximately 5 degrees or less. As is apparent from FIG. 5, when the angle Ag formed by the first auxiliary link 30 and the second auxiliary link 40 is 180 degrees + a small angle, the external force torque acting in the bending direction on the knee joint further increases the angle Ag. Acts in the direction of Therefore, the stopper that limits the angle Ag to 180 degrees + a minute angle resists external force torque acting on the extended knee joint in the bending direction, and prevents knee bending.

  In the above support apparatus, it is preferable that the first auxiliary link is shorter than the second auxiliary link, and the actuator is attached to the thigh link and rotationally drives the first auxiliary link. The load on the user's leg is less when the actuator is attached to the thigh link than to the lower leg link. Furthermore, the shorter the first auxiliary link that the actuator rotates, the shorter the torque (input torque) that the actuator applies to the first auxiliary link and the torque (output torque) that occurs in the lower leg link due to that torque ( That is, the torque ratio as a speed reduction mechanism is increased. To shorten the first auxiliary link, the second auxiliary link must be lengthened. Therefore, qualitatively, the torque ratio can be increased when the first auxiliary link is shorter than the second auxiliary link. That is, with such a configuration, the actuator can be small and the support device can be reduced in weight. Or when employ | adopting the actuator of the same size, the torque which rotates a leg link can be enlarged, so that a 1st auxiliary link is short.

  ADVANTAGE OF THE INVENTION According to this invention, the walk assistance apparatus which can prevent the knee break of a standing leg can be implement | achieved, without using a brake and without request | requiring a big torque for an actuator.

It is an external view of a walking assistance device. It is an enlarged side view of the connection part of a thigh link and a crus link. It is an expanded side view of the connection part of a thigh link and a leg link corresponding to the state where the user extended the knee. It is an expanded side view of the connection part of a thigh link and a leg link corresponding to the state where the user bent the knee. It is a typical side view of a walk assistance device.

  In FIG. 1, the external view of the assistance apparatus 100 (walking assistance apparatus) of an Example is shown. In this embodiment, the support device 100 is worn on the user's left leg. The support device 100 includes a motor 55 (actuator), and applies torque to the knee joint of the left leg to support walking motion. The support device 100 includes an angle sensor that measures the rotation angle (knee angle) of the lower leg and a grounding sensor that detects the grounding of the leg, and a controller that controls the motor 55 based on the measurement results of these sensors. ing. Various sensors and controllers are not shown.

  A coordinate system used in the drawings will be described. The X axis indicates the front-rear direction of the user, and the positive direction of the X axis corresponds to “front” and the negative direction corresponds to “rear”. The Y axis in the drawing indicates the left-right direction (side) of the user. The Y axis is also called the pitch axis. The Z axis indicates the vertical direction. These coordinate systems are commonly used in the technical field of robots.

  The support device 100 supports not only the walking motion but also the movement of the knee joint (lower leg motion) during the standing-up motion and the seating motion by changing the algorithm for controlling the motor 55 in various ways. Since the technology disclosed in this specification is characterized by the mechanism of the support device, description of the control algorithm for walking support and standing up support is omitted.

  The mechanical structure of the support device 100 will be described. The support device 100 has a leg brace structure in which a thigh link 10 attached to a user's thigh and a crus link 20 attached to a crus are connected by a joint 52. A foot link 25 is connected to the lower end of the lower leg link 20 via a joint 24. The foot link 25 is attached to the user's foot. “Joint” corresponds to “connecting part”.

  The thigh link 10 has frames extending on both sides of the thigh, and the frames on both sides are connected by thigh pads 12. The crus link 20 has frames extending on both sides of the crus, and the frames on both sides are connected by knee pads 22.

  The thigh link 10 and the crus link 20 are connected to each other by a pair of joints 52 so as to be rotatable. The pair of joints 52 are located on both sides of the knee when worn by the user, and the rotation axis thereof substantially coincides with the rotation axis of the knee joint (rotation axis around the pitch axis). One joint 52 is equipped with a motor 55. The motor 55 is fixed to the thigh link 10. The motor 55 rotates the first auxiliary link 30 described later.

  A portion surrounded by a broken line in FIG. 1 shows a connecting portion of the thigh link 10 and the crus link 20, and an enlarged view of the connecting portion is shown in FIG. 3 and 4 show side views of the connecting portion. 2 to 4, only a part of the frames of the thigh link 10 and the crus link 20 are shown. As shown in these drawings, two auxiliary links 30 and 40 are connected between the thigh link 10 and the crus link 20, and the thigh link 10, the crus link 20, the first auxiliary link 30, The second auxiliary link 40 constitutes a closed 4-link mechanism.

  The structure of the closed 4-link mechanism will be described in detail. One end of the first auxiliary link 30 is connected to the thigh link 10 via a joint 52. One end of the second auxiliary link 40 is connected to the crus link 20 via a joint 54. The other end of the first auxiliary link 30 and the other end of the second auxiliary link 40 are connected via a joint 53. Each of the joints 51, 52, 53, and 54 has a rotation axis extending in the pitch axis (Y-axis in the drawing) direction. That is, any link can rotate around the pitch axis around the joint.

  A straight line L1 in FIGS. 3 and 4 indicates a center line in the longitudinal direction of the thigh, and L2 indicates a center line in the longitudinal direction of the lower leg. L1 and L2 are collectively referred to as the longitudinal center line of the leg. The center line means a line segment that connects the centers of joints at both ends of each part of the limb (such as the thigh and the lower leg). FIG. 4 shows a form of a closed four-link mechanism when the user takes an upright posture. The rotation center of the joint 52 connecting the thigh link 10 and the first auxiliary link 30 is the knee joint rotation center (joint 51). The center line L1 in the longitudinal direction of the leg passing through the center of rotation). The rotation center of the joint 54 that connects the lower leg link 20 and the second auxiliary link 40 is also located behind the center line L2 in the leg longitudinal direction passing through the knee joint rotation center. It should be noted that at least one of the joints 52 and 54 only needs to be positioned behind the center lines L1 and L2 in the longitudinal direction of the leg passing through the knee joint rotation center. This geometric condition corresponds to the bending condition described above. As described above, the bending condition is only a condition for ensuring that the lower leg link 20 rotates to the bending side.

  FIG. 3A shows a side view of the closed four-link mechanism when the user takes an upright posture. FIG. 3B is a diagram schematically showing the form of the first auxiliary link 30 and the second auxiliary link 40 in FIG. As shown in FIG. 3, when the user takes an upright posture, the rotation center of the joint 52 that connects the thigh link 10 and the first auxiliary link 30 and the first auxiliary link are observed from the side (pitch axis direction). The rotation center of the joint 53 connecting the 30 and the second auxiliary link 40 and the rotation center of the joint 54 connecting the lower leg link 20 and the second auxiliary link 40 are configured to be substantially aligned. . That is, the knee lock condition described above is satisfied. In other words, when the user takes an upright posture, the angle Ag formed by the straight line L3 connecting the rotation centers of the joints 52 and 53 and the straight line L4 connecting the rotation centers of the joints 53 and 54 is approximately 180 degrees. Strictly speaking, as shown in FIG. 3B, the angle Ag is 180 + a minute angle.

  As shown in FIG. 3, the crus link 20 is provided with a mechanical stopper 21. The mechanical stopper 21 limits the angle Ag so that it does not exceed 180 degrees + a minute angle. To be precise, the angle Ag is an angle formed by the first auxiliary link 30 and the second auxiliary link 40 when observed from the side direction, which is 180 ° or less when the knee is bent. is there. As indicated by a symbol Ag in FIG. 4, the first auxiliary link 30 and the second auxiliary link 40 have an angle of 180 or less on the side close to the crus link 20 when the user bends the knee.

  As apparent from FIG. 3, when the user stretches the knee, the knee lock condition is satisfied, and thus the thigh link 10 and the crus link 20 do not rotate. More specifically, even if an external force torque in the knee bending direction acts on the thigh link 10 or the crus link 20, the longitudinal direction L3 of the first auxiliary link 30 and the longitudinal direction L4 of the second auxiliary link 40 are substantially straight. Therefore, these auxiliary links resist external force torque and prevent rotation of the lower leg link 20. That is, the two auxiliary links arranged in a straight line prevent the knee from being bent. Strictly speaking, the external force torque acts in a direction to increase the angle Ag, but the crus link 20 does not rotate because the mechanical stopper 21 limits the angle Ag to 180 degrees + a minute angle at the maximum. Even if the motor 55 does not output torque for preventing knee breakage, the two auxiliary links prevent knee breakage.

  When the motor 55 rotates the first auxiliary link 30, the knee lock is released, and when the motor 55 further rotates, the lower leg link 20 is rotated as shown in FIG. The motor 55 has a function of releasing the knee lock and a function of swinging the crus link 20. Here, as shown in FIG. 3B, the length H1 of the first auxiliary link 30 that the motor 55 rotates is shorter than the length H2 of the second auxiliary link 40. Accordingly, since the motor rotationally drives the shorter auxiliary link (first auxiliary link 30), the torque generated in the lower leg link 20 than when the longer auxiliary link (second auxiliary link 40) is rotationally driven. (Ie, output torque) increases. Further, since the motor 55 is fixed to the thigh link 10, the burden on the user can be reduced as compared with the case where the motor 55 is fixed to the thigh link 20.

  A modification of the support device 100 according to the embodiment will be described. The support device may include an auxiliary actuator that releases the knee lock in addition to the actuator that swings the lower leg link. For example, the auxiliary actuator may extend the mechanical stopper 21 shown in FIG. 2 backward. In this case, when the mechanical stopper 21 extends rearward and the second auxiliary link 40 is rotated in the clockwise direction, the joints 52, 53, and 54 are not aligned in a straight line, and the knee lock is released.

  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: Thigh link 20: Lower leg link 21: Mechanical stopper 24: Joint 25: Foot link 30: First auxiliary link 40: Second auxiliary link 51, 52, 53, 54: Joint 55: Motor 100: Walking support device

Claims (3)

A thigh link attached to the user's thigh;
A thigh link connected to the thigh link so as to be rotatable about the pitch axis,
A first auxiliary link coupled to the thigh link for rotation about the pitch axis;
A second auxiliary link that is connected to the lower leg link so as to be rotatable around the pitch axis, and whose tip is rotatably connected to the tip of the first auxiliary link;
An actuator for rotating the lower leg link with respect to the thigh link;
With
At least one of the rotation center of the connection part of the thigh link and the first auxiliary link and the rotation center of the connection part of the lower leg link and the second auxiliary link is behind the longitudinal center line of the leg passing through the knee joint rotation center. Located
Observing from the side when the user stretches the knee, the rotation center of the connecting portion of the thigh link and the first auxiliary link, the rotation center of the connecting portion of the first auxiliary link and the second auxiliary link, and the lower leg link A walking support device, characterized in that the rotation centers of the connecting portions of the second auxiliary link are arranged in a straight line.   A stopper is provided to limit the angle formed by the first auxiliary link and the second auxiliary link, which is an angle formed by the first auxiliary link and the second auxiliary link, and which does not exceed 180 degrees when the knee is bent. The walking support device according to claim 1. The first auxiliary link is shorter than the second auxiliary link,
The walking support device according to claim 1 or 2, wherein the actuator is attached to the thigh link and rotationally drives the first auxiliary link.

Images