Parallel link mechanism and link operating device

Abstract

To provide a parallel link mechanism which has high rigidity and can calculate a tip position with high accuracy, and to provide a link operation device.SOLUTION: A parallel link mechanism 100 includes a base end link hub 10, a tip link hub 20, multiple links 30, and a beam member 40. The beam member 40 is arranged so as to pass through a first spherical surface link center point and a second spherical surface link center point. The beam member 40 includes a measured part 45 protruding from the base end link hub 10 to the opposite side of the tip link hub 20.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] In recent years, link actuators used in devices that require precise and wide operating ranges, such as medical devices or industrial devices, have attracted attention.

[0003] Japanese Patent Application Laid-Open No. 2000-94245 (Patent Document 1) discloses a working device including a parallel link mechanism for attaching a tool for machining and a work holding unit for holding a work.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Conventional parallel link mechanisms have low rigidity and the entire mechanism deforms. For this reason, the accuracy of calculating the tip position from the movement amount of the drive unit of the parallel link mechanism, such as a work holding unit, is low. Also, when detecting the tip position with a high-precision sensor, the high-precision sensor is large in size and difficult to install on the parallel link mechanism. Therefore, conventional parallel link mechanisms have had the problem of poor absolute value accuracy of the tip position.

[0006] The present disclosure discloses a parallel link mechanism and a link actuator that solve the above problems. Specifically, the present disclosure provides a parallel link mechanism and a link actuator that have high rigidity and can calculate the tip position with high accuracy.

Means for Solving the Problems

[0007] The present disclosure relates to a parallel link mechanism. The parallel link mechanism includes a base link hub, a tip link hub, a plurality of links, and a beam member. Each of the plurality of links has a first end link member, a second end link member, and an intermediate link member. The first end link member is connected to the base link hub at one end so as to be rotatable about a first rotation axis. The second end link member is connected to the tip link hub at one end so as to be rotatable about an axis between a second rotation axes. The intermediate link member is connected to the other end of the first end link member at one end so as to be rotatable about a third rotation axis, and is connected to the other end of the second end link member at the other end so as to be rotatable about a fourth rotation axis. The central axis of the base 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 second spherical link center point. 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 link hub so as to be rotatable about the central axis of the base link hub, a second connection portion connected to the tip link hub so as to be rotatable about the central axis of the tip link hub, and a measured portion protruding from the base link hub to the side opposite to the tip link hub.

Effects of the Invention

[0008] According to the parallel link mechanism of the present disclosure, the rigidity is increased and the measured portion is provided, so that the accuracy of measuring the absolute position of the tip position is improved, and the control of the absolute position of the working device becomes easy.

Brief Description of the Drawings

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Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The same components are denoted by the same reference numerals, and the description thereof will not be repeated.

[0011] <Configuration of Parallel Link Mechanism and Link Actuating Device> FIG. 1 is a perspective view of a link actuating device 400 according to the present embodiment. FIG. 2 is a front view of the link actuating device 400 shown in FIG. 1. FIG. 3 is a top view of the link actuating device 400 shown in FIG. 1. FIG. 4 is a rear view of the link actuating device 400 shown in FIG. 1. FIG. 5 is a bottom view of the link actuating device 400 shown in FIG. 1. FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 3.

[0012] As shown in FIGS. 1 to 6, the link actuating device 400 mainly includes a parallel link mechanism 100 and three drive sources 500.

[0013] 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.

[0014] The base end link hub 10 can have an arbitrary shape, for example, it is annular. As shown in FIG. 6, an opening for inserting a part of the beam member 40 is formed in the bottom surface of the base end link hub 10. On the outer periphery of the bottom surface of the base end link hub 10, side walls extending in a direction intersecting the bottom surface (toward the tip end link hub 20 side) are formed. Through holes are formed in the side walls. The through holes are formed at three locations on the side walls. The three through holes are arranged at equal intervals in 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 perpendicular to the bottom surface of the base end link hub 10 may be referred to as the central axis CL1.

[0015] The distal link hub 20 can have an arbitrary shape, for example, it can be annular or cup-shaped. In FIGS. 1 to 6, an example where the shape of the distal link hub 20 is annular is shown. As shown in FIG. 4, an opening for exposing the tip of the beam member 40 is formed on the top surface of the distal link hub 20. On the outer periphery of the top surface of the distal link hub 20, side walls extending in a direction intersecting the top surface (toward the proximal link hub 10 side) are formed. Through holes are formed in the side walls. The through holes are formed at three locations on the side walls. The three through holes are arranged at equal intervals on the annular side wall when viewed from a direction perpendicular to the top surface. Note that the arrangement of the three through holes does not have to be at equal intervals. The central axis of the distal link hub 20 perpendicular to the top surface of the distal link hub 20 may be referred to as the central axis CL2. Although not shown, a working device is attached to the distal link hub 20. As the working device, in addition to end effectors such as a suction pad and a hand, an inspection camera, a cutting tool, a fastening tool, a welding torch, a marking dispenser, etc. can be attached.

[0016] Each of the plurality of 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 plurality of links 30 is three in the illustrated example. However, the number of the plurality of links 30 may be two or four or more. Each of the plurality of links 30 preferably has the same shape as each other.

[0017] One end of the first end link member 31 is rotatably connected to the proximal 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 (see FIGS. 2 and 4) is passed through both the through hole formed at one end of the first end link member 31 and the through hole formed in the side wall of the proximal link hub 10. Thereby, the first end link member 31 is connected to the proximal link hub 10 at one end so as to be rotatable about the central axis of the shaft member 34 (hereinafter, may be referred to as the first rotation axis RA1 in FIG. 7). The first end link member 31 has, for example, an L shape.

[0018] The second end link member 32 is rotatably connected to the tip link hub 20 at one end. More specifically, a through hole (not shown) is formed at one end of the second end link member 32. A shaft member 35 (see FIGS. 2 and 4) is passed through both the through hole formed at one end of the second end link member 32 and the through hole formed in the side wall of the tip link hub 20. Thereby, the second end link member 32 is rotatably connected to the tip link hub 20 at one end about the central axis of the shaft member 35 (hereinafter, may be referred to as the second rotation axis RA2 in FIG. 7). The second end link member 32 has, for example, an L shape.

[0019] The intermediate link member 33 is rotatably connected to the other end of the first end link member 31 at one end. More specifically, an insertion hole (not shown) is formed at one end of the intermediate link member 33. A through hole (not shown) is formed at the other end of the first end link member 31. A shaft member 36 (see FIGS. 2 and 6) is passed through both the insertion hole formed at one end of the intermediate link member 33 and the through hole formed at the other end of the first end link member 31.

[0020] Thereby, the intermediate link member 33 is rotatably connected to the other end of the first end link member 31 at one end about the central axis of the shaft member 36 (hereinafter, may be referred to as the third rotation axis RA3 in FIG. 7).

[0021] The intermediate link member 33 is rotatably connected to the other end of the second end link member 32 at the other end. More specifically, an insertion hole (not shown) is formed at the other end of the intermediate link member 33. A through hole (not shown) is formed at the other end of the second end link member 32. A shaft member 37 (see FIGS. 2 and 6) is passed through both the insertion hole formed at the other end of the intermediate link member 33 and the through hole formed at the other end of the second end link member 32.

[0022] As a result, the intermediate link member 33 is connected to the other end of the second end link member 32 so as to be rotatable about the central axis of the shaft member 37 (hereinafter, may be referred to as the fourth rotation axis RA4 in FIG. 7) at the other end.

[0023] In the above description, three through holes are provided in the side walls of the base end link hub 10 and the tip end link hub 20, and the first end link member 31 and the second end link member 32 are attached thereto. However, it is not always necessary to provide through holes. Instead of the through holes, various means for rotatably coupling the first end link member 31 and the second end link member 32 to the base end link hub 10 and the tip end link hub 20 can be adopted.

[0024] FIG. 7 is a schematic diagram showing the mutual relationship between the central axis CL1, the central axis CL2, and the first rotation axis RA1 to the fourth rotation axis RA4. FIG. 7 shows the position of the working device 50 attached to the tip end link hub 20. As shown in FIG. 7, the central axis CL1, the first rotation axis RA1, and the third rotation axis RA3 intersect at one point. This point is defined 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 defined as the spherical link center point P2. A straight line connecting the spherical link center point P1 and the spherical link center point P2 is defined as the straight line CL3. The straight line CL3 intersects the central axis CL1 at the spherical link center point P1. The straight line CL3 intersects the central axis CL2 at the spherical link center point P2. The above relationship always holds regardless of the posture of the parallel link mechanism 100. In FIGS. 1 to 7, the fold angle θ, which is the angle formed by the central axis CL1 and the central axis CL2, is 0, showing a special positional relationship in which the central axis CL1, the central axis CL2, and the straight line CL3 are aligned on the same straight line. The posture of the parallel link mechanism 100 in the positional relationship shown in FIGS. 1 to 7 is defined as the origin posture of the parallel link mechanism 100. In the origin posture, the tip position P4 of the working device 50 is on the central axis CL1.

[0025] As shown in Fig. 7, the beam member 40 is arranged along a straight line CL3 so as to pass 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 postures of the base end link hub 10 and the tip end link hub 20.

[0026] As shown in Fig. 6, the beam member 40 includes a linearly extending beam portion 43, connecting portions 41 and 42, and a base end side end portion 44. The connecting portions 41 and 42 each have a constant velocity joint including a rotation axis passing through the spherical link center point P1 and the spherical link center point P2, respectively. The base end side end portion 44 protrudes outward from the opening of the base end link hub. A portion to be measured 45 is formed in the base end side end portion 44.

[0027] The constant velocity joints arranged at the connecting portions 41 and 42 of the beam member 40 are, for example, ZF type constant velocity joints. The outer ring of the constant velocity joint arranged at the connecting portion 41 is integrated with the base end link hub 10. Also, the inner ring of the constant velocity joint arranged at the connecting portion 41 is integrated with the beam portion 43 of the beam member. The center of the inner ring of the constant velocity joint arranged at the connecting portion 41 overlaps with the first spherical link center point P1 as shown in Figs. 6 and 7. The outer ring of the constant velocity joint arranged at the connecting portion 42 is integrated with the tip end link hub 20. Also, the inner ring of the constant velocity joint arranged at the connecting portion 42 is integrated with the beam portion 43 of the beam member. The center of the inner ring of the constant velocity joint arranged at the connecting portion 42 overlaps with the second spherical link center point P2 as shown in Figs. 6 and 7.

[0028] The positions and postures 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 Figs. 1 to 7, three drive sources 500 are installed in the link operating device 400. The drive source 500 is, for example, a motor capable of controlling the rotation angle.

[0029] Each drive source 500 is connected to the corresponding first end link member 31. The drive source 500 rotates the first end link member 31 around the first rotation axis RA1 shown in FIG. 7. The drive source 500 can determine the rotation angle of the first end link member 31 around the first rotation axis RA1. Thereby, the position and posture of the tip link hub 20 with respect to the base link hub 10 can be changed.

[0030] Note that the parallel link mechanism 100 constituting the link operating 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.

[0031] FIG. 8 is a perspective view for explaining the state of the link operating device 400 whose posture has changed from the origin posture. FIG. 9 is a perspective view of the link operating device 400 shown in FIG. 8 as viewed from another direction. FIG. 10 is a front view of the link operating device 400 shown in FIG. 8. FIG. 11 is a top view of the link operating device 400 shown in FIG. 8. FIG. 12 is a right side view of the link operating device 400 shown in FIG. 8. FIG. 13 is a left side view of the link operating device 400 shown in FIG. 8. FIG. 14 is a bottom view of the link operating device 400 shown in FIG. 8. FIG. 15 is a cross-sectional view taken along line XV-XV in FIG. 10. FIG. 16 is a view in which a straight line indicating the axis and the fold angle θ are added to FIG. 15.

[0032] In the postures shown in FIGS. 1 to 7, the fold angle θ = 0, and the central axis CL1 of the base link hub 10, the central axis CL2 of the tip link hub 20, and the straight line CL3 which is the axis of the beam member 40 were aligned on the same straight line. On the other hand, in the postures shown in FIGS. 11 to 16, as shown in FIG. 16, the fold angle θ which is the angle formed by the central axis CL1 of the base link hub 10 and the central axis CL2 of the tip link hub 20 is 90°, and the straight line CL3 which is the axis of the beam member 40 intersects at an angle of 45° which is half of the central axis CL1 and the fold angle θ (= 90°).

[0033] As described above, the parallel link mechanism 100 shown in this embodiment is a spherical link mechanism in which two spherical links composed of three or more link systems are connected in series. The parallel link mechanism 100 has two connecting portions 41 and 42 that connect a beam member 40 passing through two spherical link center points P1 and P2, a tip link hub 20, and a base link hub 10 rotatably with two degrees of rotational freedom by constant velocity joints at the respective spherical link center points P1 and P2.

[0034] When the spherical link center points P1 and P2 are connected by the beam member 40 which is a single rigid body, the distance between the center points P1 and P2 of the two spherical links is maintained, and the overall rigidity of the parallel link mechanism 100 is improved.

[0035] In this embodiment, further, a measured portion 45 that does not interfere with the operation of the link mechanism is disposed below the base link hub 10. The link operating device 400 further includes a measuring device 610 and a control device 600 as shown in FIGS. 1 and 12. The control device 600 includes a CPU 601 and a memory 602.

[0036] The measuring device 610 measures the position of the measured portion 45. As the measuring device 610, for example, a camera or the like can be used. By measuring the position of the measured portion 45, the position of the tip of the beam member 40 to which an end effector or the like is attached can be calculated with high precision.

[0037] Note that the structure of the connecting portions at both ends of the beam may be rotatable. Also, there may be three or more link systems. Further, the sizes of the upper and lower spherical links, that is, the spherical link of the base link hub 10 and the spherical link of the tip link hub 20 may be different. Also, the measured portion 45 and the measuring device 610 may not measure by visible light.

[0038] During operation, starting from the center point P1 of the base-end side link, the measurement target 45 to be measured rotates. In this example, the measurement target is in a cross shape, and measurement target balls are arranged at its four ends and the center. Making the measurement target in a cross shape is preferable because if the camera measures the cross shape and measures the horizontal plane projection distances (L in FIG. 12) between the central part and the four end parts of the cross shape, the inclination of the beam member 40 can be specified.

[0039] FIG. 17 is a schematic diagram (θ = 90°) for explaining the calculation of the tip position. FIG. 18 is a schematic diagram (θ = 45°) for explaining the calculation of the tip position.

[0040] Hereinafter, a working device such as an end effector 50 will be attached to the tip link hub 20 so that the tip position of the working device comes to the position of the height Lt on the central axis CL2. The point P4 shown in FIGS. 16 to 18 indicates the tip position of the working device 50. Also, the point P3 indicates the center position of the measurement target 45.

[0041] FIG. 19 is a diagram for explaining the observation of the measurement target. The coordinates C(x, y) obtained by projecting the center point P3 of the measurement target 45 onto the XY plane (measurement plane S) are measured by a measuring device such as a camera. Then, from the coordinates C(x, y), the folding angle θ and the turning angle φ are derived, and the coordinates of the tip position P4 of the working device are obtained.

[0042] In FIGS. 17 and 18, the central axis CL1 is set as the Z axis, the point P1 is set as the origin, the length between the points P1 - P2 of the beam member 40 is Lo, and the length between the points P1 - P3 is Le.

[0043] In the description of FIGS. 17 and 18, it is assumed that the turning angle φ = 0°, and the case where the point P4 is on the XZ plane (y = 0) will be considered. The turning angle φ will be considered later.

[0044] The coordinates of P2(x2, z2) are represented by the following formulas (1) and (2). x2 = Lo×sin(θ / 2) …(1) z2 = Lo×cos(θ / 2) …(2) Since the length of the line segment P2 - P4 is Lt, the increments (Δx, Δz) of the coordinates of point P4 from the coordinates of point P2 are represented by the following equations (3) and (4). Δx = Lt×sinθ …(3) Δz = Lt×cosθ …(4) Therefore, the coordinates of P4(x4, z4) are represented by the following equations (5) and (6). x4 = x2 + Δx = Lo×sin(θ / 2) + Lt×sinθ …(5) z4 = z2 + Δz = Lo×cos(θ / 2) + Lt×cosθ …(6) Next, consider the coordinates of point P4 when the turning angle φ is taken into account.

[0045] The z - coordinate of point P4 does not change even when the turning angle φ changes. Since the x and y coordinates of point P4 can be obtained by rotating the x and y coordinates (x4, 0) of point P4 when φ = 0 around the z - axis by -φ (assuming φ>0), they are obtained by the following equation (7). (x, y)=(x4×cos(-φ), x4×sin(-φ)) (x, y)=(x4×cosφ, -x4×sinφ) …(7) Therefore, when applying the above equation (7) to x4 calculated by equation (5), the coordinates of point P4(x4, y4, z4) considering the turning angle φ are obtained as follows in equations (8) - (10). x4=(Lo×sin(θ / 2)+Lt×sinθ)×cosφ …(8) y4=-(Lo×sin(θ / 2)+Lt×sinθ)×sinφ …(9) z4=Lo×cos(θ / 2)+Lt×cosθ …(10) On the other hand, the folding angle θ and the turning angle φ can be obtained from C(x, y) as follows. When the turning angle is -φ, the projected coordinates of point P3 onto the XY plane are represented by the following equations (11) and (12). x = Le×sin(θ / 2)cos(φ + π) …(11) y = Le×sin(θ / 2)sin(φ + π) …(12) By eliminating φ + π from equations (11) and (12), an equation (13) representing θ in terms of x and y can be obtained. Note that asin is the inverse function of sin, arcsine. θ = 2×asin((x 2 + y 2 ) / (Le 2 )) …(13) When Equation (12) is transformed, Equation (14) expressing φ in terms of y and θ can be obtained. φ = -asin(y / (Le×sin(θ / 2)) …(14) Therefore, the control device 600 calculates the bending angle θ from C(x, y) according to Equation (13), and further calculates the turning angle φ from C(x, y) and the bending angle θ according to Equation (14). Then, the control device 600 can calculate the coordinates P4(x4, y4, z4) of the tip position of the working device 50 from the bending angle θ and the turning angle φ according to Equations (8) to (10).

[0046] In the above description, the measurement target is the coordinates C(x, y) obtained by vertically projecting the center point P3 of the measured part 45 provided on the base end side of the beam member 40 onto the XY plane. Alternatively, instead of this, the laser beam spot or the like irradiated onto the measurement plane on the extension of the straight line CL3 from the base link center on the straight line passing through the measurement target center point P3 may be measured.

[0047] [Modification Example] In the above description, the case where the working device 50 such as an end effector is attached to the tip link hub 20 has been described. However, as shown in FIG. 1 and the like, when the tip link hub 20 has a shape that can penetrate the beam member 40, the beam member 40 may be projected toward the tip link hub 20 side and the working device 50 may be attached to the beam member 40. In this case, as shown in FIG. 20, the tip position of the working device 50 is at the point P5 on the straight line CL3.

[0048] When the distance from point P2 to point P5 is Lt as the coordinates P5(x5, y5, z5) of the tip position, the coordinates P5(x5, y5, z5) are obtained as in the following Equations (15) to (17). x5 = (Lo + Lt)sin(θ)cos(φ) …(15) y5 = (Lo + Lt)sin(θ)sin(φ) …(16) z5 = (Lo + Lt)cos(θ) …(17) If θ and φ in formulas (13) and (14) are substituted into formulas (15) to (17), the coordinates P5(x5, y5, z5) of the tip position can be obtained from c(x, y).

[0049] (Summary) Finally, referring to the drawings again, the present embodiment will be summarized.

[0050] The present disclosure relates to a parallel link mechanism. As shown in FIG. 1, the parallel link mechanism 100 includes a base link hub 10, a tip link hub 20, a plurality of links 30, and a beam member 40. Each of the plurality of links 30 has a first end link member 31, a second end link member 32, and an intermediate link member 33. As shown in FIGS. 1 to 7, the first end link member 31 is connected to the base link hub 10 at one end so as to be rotatable about a first rotation axis RA1. The second end link member 32 is connected to the tip link hub 20 at one end so as to be rotatable about a second rotation axis RA2. The intermediate link member 33 is connected to the other end of the first end link member 31 at one end so as to be rotatable about a third rotation axis RA3, and is connected to the other end of the second end link member 32 at the other end so as to be rotatable about a fourth rotation axis RA4. The central axis CL1 of the base link hub 10, the first rotation axis RA1, and the third rotation axis RA3 intersect at a first spherical link center point P1. The central axis CL2 of the tip link hub 20, the second rotation axis RA2, and the fourth rotation axis RA4 intersect at a 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 a first connection portion 41 connected to the base link hub 10 so as to be rotatable about the central axis CL1 of the base link hub 10, a second connection portion 42 connected to the tip link hub 20 so as to be rotatable about the central axis CL2 of the tip link hub 20, and a measured portion 45 protruding from the base link hub 10 to the side opposite to the tip link hub 20.

[0051] Preferably, it further includes a working device 50 attached to the tip link hub 20. The tip position of the working device 50 is the point P4 shown in FIGS. 16 to 18.

[0052] Preferably, as described in the modification example, the beam member 40 further includes a working device 50 that protrudes from the distal link hub 20 to the side opposite to the proximal link hub 10. In this case, the tip position of the working device 50 is the point P5 shown in FIG. 20.

[0053] More preferably, each of the first connection portion 41 and the second connection portion 42 includes a constant velocity joint.

[0054] In another aspect, the present disclosure relates to a link operating device 400 including any one of the parallel link mechanisms 100 described above and a measuring device 610 that measures the position of the portion to be measured.

[0055] Preferably, the link operating device 400 further includes an arithmetic device 601 that specifies the position of the working device in accordance with the output of the measuring device 610.

[0056] More preferably, for at least two of the plurality of links 30, a drive source 500 that increases or decreases the rotation angle around the first rotation axis RA1 of the first end link member 31 connected to the proximal link hub 10, and a control device 600 that controls the drive source 500 in accordance with the output of the measuring device 610 are further provided.

[0057] With the above configuration, since the beam member 40 is rotatably connected to the proximal link hub 10 and the distal link hub 20, the rigidity of the parallel link mechanism 100 can be improved. Further, since the positional accuracy of the link 30 of the parallel link mechanism 100 is improved by arranging the beam member 40, the operation of the parallel link mechanism 100 becomes smooth. Furthermore, since the portion to be measured 45 is provided on the beam member 40, it is possible to accurately detect the tip position of an end effector or the like attached to the distal end link hub 20 or the distal end portion of the beam member 40 by measuring the position of the portion to be measured 45.

Description of reference numerals

[0058] 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, 41, 42 connection part, 43 beam part, 44 base end side end part, 45 part to be measured, 50 working device, 100 parallel link mechanism, 400 link operating device, 500 drive source, 600 control device, 601 CPU, 602 memory, 610 measuring device.

Claims

1. A parallel link mechanism comprising a base link hub, a tip link hub, a plurality of links, and a beam member, each of the plurality of links having a first end link member, a second end link member, and an intermediate link member, the first end link member being connected at one end to the base link hub rotatably about a first rotation axis, the second end link member being connected at one end to the tip link hub rotatably about a second rotation axis, the intermediate link member being connected at one end to the other end of the first end link member rotatably about a third rotation axis and 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 link hub, the first rotation axis, and the third rotation axis intersecting at a first spherical link center point, the central axis of the tip link hub, the second rotation axis, and the fourth rotation axis intersecting at a second spherical link center point, the beam member being disposed so as to pass through the first spherical link center point and the second spherical link center point, the beam member including a first connection portion connected to the base link hub rotatably about the central axis of the base link hub, a second connection portion connected to the tip link hub rotatably about the central axis of the tip link hub, and a measured portion protruding from the base link hub to the side opposite the tip link hub, a parallel link mechanism.

2. The parallel link mechanism according to claim 1, further comprising a working device attached to the tip link hub.

3. The parallel link mechanism according to claim 1, wherein the beam member further comprises a working device protruding from the tip link hub to the side opposite the base link hub.

4. The parallel link mechanism according to claim 2 or 3, wherein each of the first connection portion and the second connection portion includes a constant velocity joint.

5. A link operating device comprising the parallel link mechanism according to any one of claims 2 to 4, and a measuring device for measuring the position of the measured portion.

6. The link operating device according to claim 5, further comprising an arithmetic device for specifying the position of the working device according to the output of the measuring device.

7. For at least two of the plurality of links, a drive source that increases or decreases the rotation angle of the first end link member connected to the base link hub about the first rotation axis, The link operating device according to claim 6, further comprising a control device that controls the drive source in response to an output of the measuring device.

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