Parallel link mechanism and link actuator

Abstract

To provide a parallel link mechanism and a link operation device that can transmit sufficient rotative power to a tip link hub, and have high rigidity.SOLUTION: A parallel link mechanism 100 comprises a base end link hub 10, a tip link hub 20, a plurality of links 30, and a beam member 40. A center axis line, a first rotation axis, a third rotation axis of the base end link hub 10 intersect at a first spherical link center point P1. A center axis line, a second rotation axis, a fourth rotation axis of the tip link hub 20 intersect at a second spherical link center point P2. The beam member 40 is arranged so as to pass through the first spherical link center point P1 and the second spherical link center point P2. The beam member 40 includes a first connection part 41 and a second connection part 42 rotatably connected to the base end link hub 10 and the tip link hub 20 respectively. The first connection part 41 and the second connection part 42 comprise at least one of a universal joint and a constant velocity joint.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present disclosure relates to a parallel link mechanism and a link actuator. [Background technology]

[0002] For example, Patent Document 1 (JP 2014-224564 A) discloses a link actuation device. The link actuation device described in Patent Document 1 includes a base end link hub, a tip end link hub, multiple link mechanisms, and a wire rod as a rotational power transmission mechanism independent of the link mechanisms. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-224564 Summary of the Invention [Problem to be solved by the invention]

[0004] The above-mentioned link actuation device uses a flexible wire as the rotational power transmission mechanism, which results in a small transmission torque and limits the types of work that can be done. Furthermore, the above-mentioned link actuation device lacks the rigidity of the entire device, which means that the link actuation device may deform due to the work load, which could reduce positional accuracy and operability.

[0005] The present disclosure has been made to solve the above-mentioned problems. Specifically, the present disclosure provides a parallel link mechanism and a link actuator that are capable of transmitting sufficient rotational power to the tip link hub and have high rigidity. [Means for solving the problem]

[0006] A parallel link mechanism according to the present disclosure includes a base end link hub, a tip end link hub, a plurality of links, and a beam member. Each of the plurality of links includes a first end link member, a second end end link member, and an intermediate link member. The first end link member is connected at one end to the base end link hub rotatably about a first rotation axis. The second end link member is connected at one end to the tip end link hub rotatably about a second rotation axis. The intermediate link member is connected at one end to the other end of the first end link member rotatably about a third rotation axis. The intermediate link member is connected at the other end to the other end of the second end link member rotatably about a fourth rotation axis. The central axis of the base end link hub, the first rotation axis, and the third rotation axis intersect at a center point of the first spherical link. The central axis of the tip link hub, the second rotation axis, and the fourth rotation axis intersect at a center point of the second spherical link. The beam member is arranged to pass through the center point of the first spherical link and the center point of the second spherical link. The beam member includes a first connection portion and a second connection portion. The first connection portion is connected to the base end link hub so as to be rotatable about the central axis of the base end link hub. The second connection portion is connected to the tip end link hub so as to be rotatable about the central axis of the tip end link hub. The first connection portion and the second connection portion have at least one of a universal joint and a constant velocity joint.

[0007] A link actuation device according to the present disclosure includes the parallel link mechanism and at least two or more drive sources, and the positions and orientations of the base end link hub and the tip end link hub are determined by the at least two or more drive sources. [Effects of the Invention]

[0008] According to the above, a parallel link mechanism and a link actuator device that can transmit sufficient rotational power to the tip link hub and have high rigidity can be obtained. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic perspective view of a link actuation device according to a first embodiment. FIG. [Figure 2]FIG. 2 is a schematic front view of the link actuator shown in FIG. [Figure 3] FIG. 2 is a schematic top view of the link actuator shown in FIG. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 2. [Figure 5] FIG. 3 is a cross-sectional view taken along line VV in FIG. 2. [Figure 6] 3 is a schematic diagram showing the relationship between the central axis CL1, the central axis CL2, and the first to fourth rotation axes RA1 to RA4. FIG. [Figure 7] 2 is a schematic perspective view for explaining the operating state of the link actuation device shown in FIG. 1. FIG. [Figure 8] 2 is a partial cross-sectional schematic view for explaining the operating state of the link actuation device shown in FIG. 1. FIG. [Figure 9] FIG. 10 is a schematic perspective view of a link actuation device according to a second embodiment. [Figure 10] FIG. 10 is a schematic front view of the link actuator shown in FIG. 9. [Figure 11] FIG. 10 is a schematic top view of the link actuator shown in FIG. 9. [Figure 12] FIG. 12 is a cross-sectional view taken along line XII-XII in FIG. [Figure 13] 10 is a cross-sectional view illustrating an operating state of the link actuator shown in FIG. 9. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described. Note that the same reference numerals are used to designate the same components, and the description thereof will not be repeated.

[0011] (Embodiment 1) The parallel link mechanism 100 and the link actuation device 400 according to the first embodiment will be described below.

[0012] <Configuration of the parallel link mechanism and link actuator> FIG. 1 is a schematic perspective view of a link actuation device 400 according to the first embodiment. FIG. 2 is a schematic front view of the link actuation device 400 shown in FIG. 1. FIG. 3 is a schematic top view of the link actuation device 400 shown in FIG. 1. FIG. 4 is a schematic cross-sectional view taken along line IV-IV in FIG. 2. FIG. 5 is a schematic cross-sectional view taken along line VV in FIG. 2. FIG. 6 is a schematic diagram showing the relationship between the central axis CL1, the central axis CL2, and the first to fourth rotation axes RA1 to RA4. FIG. 7 is a schematic perspective view illustrating the operating state of the link actuation device 400 shown in FIG. 1. FIG. 8 is a partial cross-sectional view illustrating the operating state of the link actuation device 400 shown in FIG. 1.

[0013] As shown in FIGS. 1 to 8, the link actuation device 400 mainly includes the parallel link mechanism 100, three drive sources 500, and a beam member drive source 501.

[0014] The parallel link mechanism 100 includes a base end link hub 10, a tip end link hub 20, a plurality of links 30, and a beam member 40.

[0015] The base end link hub 10 can have any shape, for example, a cup shape. An opening is formed in the bottom surface of the base end link hub 10 for inserting a portion of the beam member 40, as shown in FIG. 4. A side wall is formed on the outer periphery of the bottom surface of the base end link hub 10, extending in a direction intersecting the bottom surface (toward the tip link hub 20). Through holes are formed in the side wall. The through holes are formed in three locations on the side wall. The three through holes are arranged at equal intervals on the annular side wall when viewed from a direction perpendicular to the bottom surface. Note that the arrangement of the three through holes does not have to be at equal intervals. The central axis of the base end link hub 10 may be referred to as the central axis line CL1.

[0016] The tip link hub 20 can have any shape, for example, a cup shape. An opening is formed in the top surface of the tip link hub 20 for inserting a portion of the beam member 40, as shown in FIG. 4 . A side wall is formed on the outer periphery of the top surface of the tip link hub 20, extending in a direction intersecting the top surface (toward the base link hub 10). Through holes are formed in the side wall. The through holes are formed in three locations on the side wall. The three through holes are arranged at equal intervals on the annular side wall when viewed from a direction perpendicular to the top surface. The three through holes do not have to be arranged at equal intervals. The central axis of the tip link hub 20 may be referred to as the central axis CL2. Although not shown, an end effector is attached to the end of the beam member 40 protruding from the tip link hub 20.

[0017] Each of the multiple links 30 has a first end link member 31, a second end link member 32, and an intermediate link member 33. The number of the multiple links 30 is, for example, three. However, the number of the multiple links 30 may be two or four or more. It is preferable that each of the multiple links 30 have the same shape as each other.

[0018] The first end link member 31 is rotatably connected at one end to the base end link hub 10. More specifically, a through hole (not shown) is formed at one end of the first end link member 31. A shaft member 34 is passed through both the through hole formed at one end of the first end link member 31 and a through hole formed in the side wall of the base end link hub 10. As a result, the first end link member 31 is rotatably connected at one end to the base end link hub 10 around the central axis of the shaft member 34 (hereinafter, sometimes referred to as a first rotation axis RA1). The first end link member 31 has, for example, an L-shape.

[0019] The second end link member 32 is rotatably connected at one end to the tip link hub 20. More specifically, a through hole (not shown) is formed at one end of the second end link member 32. A shaft member 35 is passed through both the through hole formed at one end of the second end link member 32 and a through hole formed in the side wall of the tip link hub 20. As a result, the second end link member 32 is rotatably connected at one end to the tip link hub 20 around the central axis of the shaft member 35 (hereinafter, sometimes referred to as the second rotation axis RA2). The second end link member 32 has, for example, an L-shape.

[0020] One end of the intermediate link member 33 is rotatably connected to the other end of the first end link member 31. More specifically, an insertion hole (not shown) is formed in one end of the intermediate link member 33. A through hole (not shown) is formed in the other end of the first end link member 31. A shaft member 36 is passed through both the insertion hole formed in one end of the intermediate link member 33 and the through hole formed in the other end of the first end link member 31.

[0021] As a result, the intermediate link member 33 is connected at one end to the other end of the first end link member 31 so as to be rotatable around the central axis of the shaft member 36 (hereinafter sometimes referred to as the third rotation axis RA3).

[0022] The other end of the intermediate link member 33 is rotatably connected to the other end of the second end link member 32. More specifically, an insertion hole (not shown) is formed in the other end of the intermediate link member 33. A through hole (not shown) is formed in the other end of the second end link member 32. A shaft member 37 is passed through both the insertion hole formed in the other end of the intermediate link member 33 and the through hole formed in the other end of the second end link member 32.

[0023] As a result, the intermediate link member 33 is connected at its other end to the other end of the second end link member 32 so as to be rotatable around the central axis of the shaft member 37 (hereinafter sometimes referred to as the fourth rotation axis RA4).

[0024] FIG. 6 is a schematic diagram showing the relationship between the central axis CL1, the central axis CL2, and the first to fourth rotation axes RA1 to RA4. As shown in FIG. 6, the central axis CL1, the first rotation axis RA1, and the third rotation axis RA3 intersect at one point. This point is designated as the spherical link center point P1. The central axis CL2, the second rotation axis RA2, and the fourth rotation axis RA4 intersect at one point. This point is designated as the spherical link center point P2. A line connecting the spherical link center point P1 and the spherical link center point P2 is designated as a line RA5. The line RA5 intersects with the central axis CL1 at the spherical link center point P1. The line RA5 intersects with the central axis CL2 at the spherical link center point P2. This relationship always holds regardless of the orientation of the parallel link mechanism 100. Note that FIG. 6 shows a unique positional relationship in which the central axis CL1, the central axis CL2, and the line RA5 are aligned on the same straight line. The posture of the parallel link mechanism 100 that is in the positional relationship shown in FIG.

[0025] 8, the beam member 40 is disposed along a straight line RA5 that passes through the first spherical link center point P1 and the second spherical link center point P2. This relationship always holds regardless of the positions and orientations of the base end link hub 10 and the tip end link hub 20.

[0026] As shown in FIG. 4, the beam member 40 includes a linearly extending beam portion 43, connecting portions 41 and 42, a base end portion 44, and a tip end portion 45. The connecting portion 41, which serves as a first connecting portion, is connected to the base end link hub 10 so as to be rotatable about the central axis CL1 of the base end link hub 10 (see FIG. 6). The connecting portion 42, which serves as a second connecting portion, is connected to the tip link hub 20 so as to be rotatable about the central axis CL2 of the tip link hub 20. The connecting portions 41 and 42 have universal joints including rotation axes passing through the spherical link center points P1 and P2, respectively. The base end portion 44 protrudes outward from an opening in the base end link hub. A beam member drive source 501 is connected to the base end portion 44. The tip end portion 45 protrudes outward from an opening in the tip link hub. The beam portion 43 includes a hollow portion 40a. In other words, the beam portion 43 is a cylindrical body with a hollow interior.

[0027] The beam member 40 can be rotated by the beam member drive source 501 around the line RA5 as the rotation axis. The connection portions 41, 42 of the beam member 40 are connected to the base end link hub 10 or the tip end link hub 20 via a rotational resistance reducing member such as a bearing (not shown). Furthermore, because the connection portions 41, 42 have universal joints, the tip end portion 45 can be easily rotated by rotating the base end portion 44, even when the tip link hub 20 is disposed at various angles relative to the base end link hub 10 as shown in FIGS. 7 and 8.

[0028] The universal joints included in the connecting portions 41 and 42 may be, for example, Cardan joints that include two rotation axes that extend in different directions intersecting the extension direction of the beam member 40. Any configuration may be used for the joints arranged in the connecting portions 41 and 42 as long as they are bendable in the extension direction of the beam member 40 and can transmit rotation of the beam member 40 around the straight line RA5.

[0029] The positions and orientations of the base end link hub 10 and the tip end link hub 20 may be determined by at least two or more drive sources 500. As shown in Figures 1 to 3, three drive sources 500 are installed in the link actuator 400. The drive sources 500 are, for example, motors.

[0030] Each drive source 500 is connected to the first end link member 31. The drive source 500 rotates the first end link member 31 around a first rotation axis RA1 shown in FIG. 6. The drive source 500 can determine the rotation angle of the first end link member 31 around the first rotation axis RA1. This can change the position and orientation of the distal link hub 20 relative to the proximal link hub 10. Although not shown, each of the multiple drive sources 500 can rotate the second end link member 32 of each of the multiple links 30 around a second rotation axis RA2. This can change the position and orientation of the proximal link hub 10 relative to the distal link hub 20.

[0031] The parallel link mechanism 100 constituting the link actuation device 400 may include three or more links 30. In this case, the number of the plurality of drive sources 500 may be less than the number of the plurality of links 30.

[0032] <Action and effect> A parallel link mechanism 100 according to the present disclosure includes a base end link hub 10, a tip end link hub 20, a plurality of links 30, and a beam member 40. Each of the plurality of links 30 includes a first end link member 31, a second end link member 32, and an intermediate link member 33. The first end link member 31 is connected at one end to the base end link hub 10 so as to be rotatable about a first rotation axis RA1. The second end link member 32 is connected at one end to the tip end link hub 20 so as to be rotatable about a second rotation axis RA2. The intermediate link member 33 is connected at one end to the other end of the first end link member 31 so as to be rotatable about a third rotation axis RA3. The intermediate link member 33 is connected at the other end to the other end of the second end link member 32 so as to be rotatable about a fourth rotation axis RA4. The central axis CL1, first rotation axis RA1, and third rotation axis RA3 of the base link hub 10 intersect at the first spherical link center point P1. The central axis CL2, second rotation axis RA2, and fourth rotation axis RA4 of the tip link hub 20 intersect at the second spherical link center point P2. The beam member 40 is disposed so as to pass through the first spherical link center point P1 and the second spherical link center point P2. The beam member 40 includes connection portions 41 and 42 rotatably connected to the base link hub 10 and the tip link hub 20, respectively. The connection portions 41 and 42 include at least one of a universal joint and a constant velocity joint.

[0033] In this way, the beam member 40 is rotatably connected to the base end link hub 10 and the tip end link hub 20, thereby improving the rigidity of the parallel link mechanism 100. Furthermore, the positioning accuracy of the links 30 of the parallel link mechanism 100 is improved by arranging the beam member 40, which results in smoother operation of the parallel link mechanism 100. Furthermore, because the beam member 40 can rotate independently of the operation of the links 30, the parallel link mechanism 100 as a whole can be realized with three degrees of freedom of rotation.

[0034] Furthermore, because the rotational force is transmitted to the tip link hub 20 side via the beam member 40, the base link hub 10 can be fixed to the fixed end, unlike when the entire parallel link mechanism 100 is rotated. Therefore, the link 30 and other components do not need to bear the rotational force, and the configuration of the link 30 and other components can be simplified and made smaller.

[0035] Furthermore, since the beam member 40 is used to transmit the rotational force, the transmitted torque can be increased compared to when a flexible tube or the like is used.

[0036] In the parallel link mechanism 100, the beam member 40 may include a hollow portion 40a extending from the base end link hub 10 side to the tip end link hub 20 side. The universal joints included in the connecting portions 41, 42 of the beam member 40 may also include through-holes. In this case, when attaching a mechanical device (end effector) or the like to the tip end link hub 20, wiring for the mechanical device can be arranged in the hollow portion 40a and through-holes. In this way, the wiring can be arranged so as not to interfere with the operation of the link 30.

[0037] The link actuation device 400 according to the present disclosure includes the parallel link mechanism 100 and at least two or more drive sources 500. The positions and attitudes of the base end link hub 10 and the tip end link hub 20 are determined by the at least two or more drive sources 500. In this case, the relative attitude of the tip end link hub 20 with respect to the base end link hub 10 can be determined by the drive sources 500. Furthermore, since the parallel link mechanism 100 including the beam member 40 is used, the rigidity of the parallel link mechanism 100 is high, and as a result, the link actuation device 400 can operate at high speed and with high precision.

[0038] In the above-described link actuation device 400, each of the at least two or more drive sources 500 may rotate the first end link member 31 of each of the plurality of links 30 about the first rotation axis RA1. In this case, the drive source 500 is disposed on the base end link hub 10 side, so the moment of inertia of the tip link hub 20 can be made smaller than when the drive source 500 is disposed closer to the tip link hub 20. This allows the operation of the link actuation device 400 to be made faster and more accurate.

[0039] The link actuation device 400 may include a beam member drive source 501 that rotates the beam member 40 relative to the base end link hub 10 and the tip end link hub 20. The beam member drive source 501 may be connected to the base end side end 44, which is the end of the beam member 40 on the base end link hub 10 side. In this case, the beam member 40 can be rotated by the beam member drive source 501. Furthermore, because the beam member 40 is rotatably connected to the base end link hub 10 and the tip end link hub 20 by the connection portions 41, 42, the beam member 40 can be rotated regardless of the attitude of the parallel link mechanism 100.

[0040] (Embodiment 2) <Configuration of the parallel link mechanism and link actuator> Fig. 9 is a schematic perspective view of a link actuation device 400 according to embodiment 2. Fig. 10 is a schematic front view of the link actuation device 400 shown in Fig. 9. Fig. 11 is a schematic top view of the link actuation device 400 shown in Fig. 9. Fig. 12 is a schematic cross-sectional view taken along line XII-XII in Fig. 11. Fig. 13 is a schematic cross-sectional view for explaining the operating state of the link actuation device 400 shown in Fig. 9.

[0041] 9 to 13 has a configuration basically similar to that of the link actuation device 400 shown in Figures 1 to 8, but the configuration of the beam member 40 differs from that of the link actuation device 400 shown in Figures 1 to 8. That is, the link actuation device 400 shown in Figures 9 to 13 differs from the link actuation device 400 shown in Figures 1 to 8 in that the connection portions 41 and 42 of the beam member 40 are equipped with constant velocity joints and that the beam portion 43 includes a damper portion 48.

[0042] The constant velocity joints arranged at the connection portions 41, 42 of the beam member 40 are, for example, Rzeppa-type constant velocity joints. The outer rings of the constant velocity joints arranged at the connection portions 41, 42 are integral with the base end portion 44 or the tip end portion 45. As shown in FIG. 12 , the outer rings of the constant velocity joints are rotatably connected to the base end link hub 10 or the tip end link hub 20 via a rotational resistance reduction member 50 such as a bearing. The rotational resistance reduction member 50 can be configured in any manner, such as a bearing in which rolling elements are arranged between the outer ring and the inner ring, or a sliding bearing.

[0043] The centers of the inner rings of the two constant velocity joints overlap with the first spherical link center point P1 or the second spherical link center point P2, respectively, as shown in Figure 13. As a result, the beam member 40 can move smoothly even when the attitude of the tip link hub 20 relative to the base link hub 10 is changed, as shown in Figure 13. As a result, even when the link actuator 400 is in any attitude, the beam member 40 can reliably transmit rotational force from the base link hub 10 side to the tip link hub 20 side.

[0044] The connecting portion 41 and the connecting portion 42 are connected via connecting shaft portions 43a and 43b and a damper portion 48. The connecting shaft portion 43a is connected to one end of the damper portion 48. The connecting shaft portion 43a connects the damper portion 48 to the connecting portion 41. The connecting shaft portion 43b is connected to the other end of the damper portion 48. The connecting shaft portion 43b connects the damper portion 48 to the connecting portion 42. The damper portion 48 may have any configuration as long as it can dampen vibrations transmitted from the connecting shaft portion 43a or the connecting shaft portion 43b. For example, the damper portion 48 may be a device including a cylinder filled with oil and air and a damper piston with an orifice disposed in the cylinder.

[0045] <Action and effect> In the above-described link actuation device 400 or parallel link mechanism 100, the connecting portions 41, 42 have constant velocity joints, so that the same effects as those of the link actuation device 400 or parallel link mechanism 100 shown in FIGS. 1 to 8 can be obtained. Furthermore, by using constant velocity joints in the connecting portions 41, 42, constant velocity is achieved, with no speed change during rotation. This constant velocity improves quietness. Furthermore, the load of the connecting portions 41, 42 is borne by multiple rolling elements, such as steel balls, arranged between the inner and outer rings of the constant velocity joints, so the durability and reliability of the link actuation device 400 and the parallel link mechanism 100 are improved.

[0046] Furthermore, the above-described link actuation device 400 or parallel link mechanism 100 may further include a rotational resistance reduction member 50 that rotatably connects the base end link hub 10 or the tip end link hub 20 to the beam member 40. In this case, the beam member 40 can be reliably rotated while being supported by the base end link hub 10 and the tip end link hub 20.

[0047] In the parallel link mechanism 100, the beam member may include a damper portion 48. In this case, transmission of vibration between the base end link hub 10 side and the tip end link hub 20 side can be suppressed.

[0048] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. Unless there is a contradiction, at least two of the embodiments disclosed herein may be combined. The basic scope of the present disclosure is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope equivalent to the claims. [Explanation of symbols]

[0049] 10 base end link hub, 20 tip end link hub, 30 link, 31 first end link member, 32 second end link member, 33 intermediate link member, 34, 35, 36, 37 shaft member, 40 beam member, 40a hollow portion, 41, 42 connection portion, 43 beam portion, 43a, 43b connection shaft portion, 44 base end side end portion, 45 tip end side end portion, 48 damper portion, 50 rotational resistance reduction member, 100 parallel link mechanism, 400 link actuator, 500 drive source, 501 beam member drive source, CL1, CL2 central axis, P1 first spherical link center point, P2 second spherical link center point, RA1 first rotation axis, RA2 second rotation axis, RA3 third rotation axis, RA4 fourth rotation axis, RA5 straight line.

Claims

1. a proximal link hub; A tip link hub; Multiple links and a beam member; Each of the plurality of links includes a first end link member, a second end link member, and an intermediate link member; the first end link member is connected at one end to the base end link hub so as to be rotatable about a first rotation axis; The second end link member is connected at one end to the tip link hub so as to be rotatable about a second rotation axis, the intermediate link member is connected at one end to the other end of the first end link member so as to be rotatable about a third rotation axis, and is connected at the other end to the other end of the second end link member so as to be rotatable about a fourth rotation axis, the central axis of the base end link hub, the first rotation axis, and the third rotation axis intersect at a first spherical link center point, the central axis of the tip link hub, the second rotation axis, and the fourth rotation axis intersect at a center point of a second spherical link, the beam member is disposed so as to pass through the first spherical link center point and the second spherical link center point, the beam member includes a first connection portion connected to the base end link hub so as to be rotatable about the central axis of the base end link hub, and a second connection portion connected to the tip end link hub so as to be rotatable about the central axis of the tip end link hub, the first connecting portion and the second connecting portion include at least one of a universal joint and a constant velocity joint; An end effector can be attached to the end of the beam member on the tip link hub side.

2. The parallel link mechanism according to claim 1 , further comprising a rotational resistance reducing member that rotatably connects the base end link hub or the tip end link hub to the beam member.

3. The parallel link mechanism according to claim 1 or 2, wherein the beam member includes a damper portion.

4. 3. The parallel link mechanism according to claim 1, wherein the beam member includes a hollow portion extending from the base end link hub side to the tip end link hub side.

5. The parallel link mechanism according to any one of claims 1 to 4; At least two drive sources; A link actuator, wherein the positions and orientations of the base end link hub and the tip end link hub are determined by the at least two drive sources.

6. The link actuation device according to claim 5 , wherein each of the at least two or more drive sources rotates the first end link member of each of the plurality of links about the first rotation axis.

7. The link actuator according to claim 5 or 6, further comprising a beam member drive source that rotates the beam member relative to the base end link hub and the tip end link hub.

Images