Parallel link mechanism and link actuator

Abstract

To provide a parallel link mechanism which has a wide operation range while achieving compactification thereof, and a link operation device.SOLUTION: In a parallel link mechanism 9, a tip side link hub 13 is connected to a base end side link hub 12 via three sets of link mechanisms 14 so as to be capable of changing a posture. Each link mechanism 14 has an end part link member 15 on a base end side, an end part link member 16 on a tip side, and a central link member 17, and forms a four-bar chain link mechanism 14 comprising four revolute pairs. In the parallel link mechanism 9, a significant point generates when a central axis QA, QB of the base end side link hub 12 or tip side link hub 13, and a central axis O2, O3, which is a rotation axis of a revolute pair part of the end part link member 15 on the base end side or end part link member 16 on the tip side and the central link member 17, are coincident with each other. An axial angle γ of the central link member 17 is regulated so as not to become a posture in which the significant point generates.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a parallel link mechanism and a link actuator used in equipment requiring high speed, high precision, and a wide operating range, such as medical equipment or industrial equipment such as an automatic deburring machine. [Background technology]

[0002] Patent Document 1 proposes a work device that has a base plate and a traveling plate connected by multiple links, and performs a specified task using a parallel link mechanism that moves the traveling plate by operating these links in coordination. Patent Document 2 proposes a link actuator that is compact yet capable of high speed, high precision, and wide operating range. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-94245 [Patent Document 2] U.S. Patent No. 5,893,296 Summary of the Invention [Problem to be solved by the invention]

[0004] In the parallel link mechanism of Patent Document 1, because the operating angle of each link is small, the link length must be increased to widen the operating range of the traveling plate. This increases the overall dimensions of the mechanism, resulting in a problem of a large device. Furthermore, increasing the link length reduces the rigidity of the entire mechanism. This also creates a problem of limiting the weight of the tool mounted on the traveling plate, i.e., the transportable weight of the traveling plate, to a small value.

[0005] In the configuration of the parallel link mechanism and link actuator shown in Patent Document 2, the singular points of the parallel link mechanism are not clear, and it is not possible to know whether singular points exist within the operating range of the parallel link mechanism and link actuator without analyzing using a 3D model or checking using an actual machine. As a result, it is not possible to achieve a movable range of a maximum bending angle of 90° or more, which is a movable range greater than that established through experience.

[0006] An object of the present invention is to provide a parallel link mechanism and a link actuator that are compact and have a wide operating range. [Means for solving the problem]

[0007] The parallel link mechanism of the present invention is a parallel link mechanism in which a tip-side link hub is connected to a base-side link hub via three or more link mechanisms so that its posture can be changed, and each of the link mechanisms has base-side and tip-side end link members, one end of which is rotatably connected to the base-side link hub and the tip-side link hub, respectively, and a central link member, both ends of which are rotatably connected to the other ends of the base-side and tip-side end link members, the central axis of the rotation pair between the end link member on the base end side and the central link member, and the central axis of the link hub on the base end side; or a central axis of a rotation pair between the tip-side end link member and the central link member, and a central axis of the tip-side link hub; When at least one of the above conditions is met, a singularity occurs, and the angle formed by the central axis of the rotational pair between the central link member and the base end link member and the central axis of the rotational pair between the central link member and the tip end link member is defined as the shaft angle γ of the central link member, and the shaft angle γ of the central link member is specified so that the central link member is not in a position where the singularity occurs.

[0008] The "singular point" refers to a structurally uncontrollable posture. In a typical vertical articulated robot, a singular point refers to a posture in which multiple arms are aligned in a straight line.

[0009] With this configuration, a base-end link hub, a tip-end link hub, and three or more sets of link mechanisms form a two-degree-of-freedom mechanism in which the tip-end link hub can rotate freely around two orthogonal axes relative to the base-end link hub. In other words, the tip-end link hub has two degrees of freedom of rotation relative to the base-end link hub, allowing for free attitude change. This two-degree-of-freedom mechanism is compact, yet allows for a wide range of movement of the tip-end link hub relative to the base-end link hub.

[0010] In this parallel link mechanism, a singularity occurs when at least one of the central axis of the rotation pair between the base-end end link member and the central link member and the central axis of the base-end link hub, or the central axis of the rotation pair between the tip-end end link member and the central link member and the central axis of the tip-end link hub, coincides. Because the orientation in which a singularity occurs is clearly defined, a parallel link mechanism with a wider operating range than conventional techniques can be realized by specifying the shaft angle γ of the central link member so that the orientation does not result in the singularity. This allows the orientation of the parallel link mechanism to be changed smoothly and quickly, similar to a human wrist. Furthermore, because the orientation in which a singularity occurs is clearly defined, the operating range of the parallel link mechanism can be freely designed to prevent singularities. In other words, a parallel link mechanism with greater design freedom than conventional techniques can be achieved.

[0011] The maximum bending angle between the central axis of the link hub on the base end side and the central axis of the link hub on the tip end side is defined as θ max Then, (γ / 2+θ max / 2)<90 may be satisfied. In this case, no singular points occur within the operating range of the parallel link mechanism, and smooth operation can be achieved within the operating range. Because there are no singular points within the operating range, the parallel link mechanism does not operate in unexpected directions and does not generate large loads during operation, improving durability.

[0012] a maximum bending angle θ, which is the maximum value of the bending angle between the central axis of the base end link hub and the central axis of the tip end link hub;max The maximum bending angle θ can be 90° or more. max By setting the angle to 90° or more, a wider operating range can be achieved without generating a singular point within the operating range.

[0013] The shaft angle γ may be 90° or less. In this case, the maximum bending angle θ max can be 90° or more.

[0014] The link actuation device of the present invention is provided with an attitude control actuator that arbitrarily controls the attitude of the distal link hub in two or more of the three or more link mechanisms in the parallel link mechanism of any of the above configurations of the present invention. Therefore, the effects described above for the parallel link mechanism of the present invention can be achieved. Furthermore, there is no need to generate an operating pattern to avoid singular points, and even an unskilled worker can easily perform teaching work, etc.

[0015] the shaft angle γ and the maximum bending angle θ of the parallel link mechanism max A rotation angle limiting means may be provided for limiting the rotation angle of the attitude control actuator in accordance with the value of . In this case, it is possible to easily avoid a singular point. [Effects of the Invention]

[0016] The parallel link mechanism and link actuation device of the present invention clarify the orientation at which a singularity occurs, thereby realizing a parallel link mechanism with a wider operating range than conventional techniques. Furthermore, since the tip-side link hub has two degrees of freedom of rotation relative to the base-side link hub, allowing for free orientation changes, the tip-side link hub can move freely relative to the base-side link hub while remaining compact, ensuring a wide range of movement for the tip-side link hub relative to the base-side link hub. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a front view of a parallel link mechanism according to a first embodiment of the present invention, with a portion thereof omitted. [Figure 2A] FIG. 2 is a partial cross-sectional view taken along line IIA-IIA in FIG. [Figure 2B] FIG. 2B is a partially enlarged view of part IIB in FIG. 2A. [Figure 3] FIG. 2 is a diagram showing one link mechanism of the parallel link mechanism represented by a straight line. [Figure 4] 10A and 10B are front views showing different positions of the parallel link mechanism. [Figure 5] FIG. 2 is a front view showing a singular point posture of the parallel link mechanism. [Figure 6] FIG. 2 is a perspective view of a 3D model showing the singular point posture of the parallel link mechanism. [Figure 7] FIG. 1 is a perspective view of a link actuator according to an embodiment of the present invention. [Figure 8] FIG. 10 is a front view of a simplified model of the link actuator in which two link mechanisms are omitted. [Figure 9A] FIG. 9 is a partial cross-sectional view taken along line IXA-IXA in FIG. 8. [Figure 9B] FIG. 9B is a partial enlarged view of part IXB in FIG. 9A. [Figure 10] 10A and 10B are diagrams showing the maximum bending angle of the link actuator and the like. [Figure 11] FIG. 10 is a front view of a parallel link mechanism according to a second embodiment of the present invention, with a portion thereof omitted. [Figure 12] FIG. 2 is a front view showing a singular point posture of the parallel link mechanism. DETAILED DESCRIPTION OF THE INVENTION

[0018] [First embodiment] A parallel link mechanism according to a first embodiment of the present invention will be described with reference to FIGS. As shown in Fig. 1, the parallel link mechanism 9 has a link hub 13 on the tip side connected to a link hub 12 on the base side so as to be able to change its posture via three sets of link mechanisms 14. The number of sets of link mechanisms 14 may be four or more. Note that Fig. 1 shows only one set of link mechanisms 14, with the remaining two link mechanisms being omitted.

[0019] Each link mechanism 14 has an end link member 15 on the base end side, an end link member 16 on the tip end side, and a central link member 17, and forms a four-bar chain link mechanism consisting of four revolute pairs. The proximal and distal end link members 15, 16 are L-shaped (FIG. 2A), with one end rotatably connected to the proximal link hub 12 and the distal link hub 13, respectively. The other ends of the proximal and distal end link members 15, 16 are rotatably connected to both ends of the central link member 17, respectively.

[0020] The parallel link mechanism 9 has a structure in which two spherical link mechanisms are combined. The central axes of the rotation pairs between the base-end link hub 12 and the base-end end link member 15, and the rotation pairs between the base-end end link member 15 and the central link member 17, intersect at the base-end spherical link center PA. Similarly, the central axes of the rotation pairs between the tip-end link hub 13 and the tip-end end link member 16, and the rotation pairs between the tip-end end link member 16 and the central link member 17, intersect at the tip-end spherical link center PB.

[0021] Furthermore, the distance between the center of the rotation pair between the base-end link hub 12 and the base-end end link member 15 and the base-end spherical link center PA is the same. The distance between the center of the rotation pair between the base-end end link member 15 and the central link member 17 and the base-end spherical link center PA is the same. Similarly, the distance between the center of the rotation pair between the tip-end link hub 13 and the tip-end end link member 16 and the tip-end spherical link center PB is the same. The distance between the center of the rotation pair between the tip-end end link member 16 and the central link member 17 and the tip-end spherical link center PB is the same. In this parallel link mechanism 9, the shaft angle γ of the central link member 17 is set to 60°. The shaft angle is the angle formed by the central axis of the rotation pair between the central link member 17 and the base-end end link member 15 and the central axis of the rotation pair between the central link member 17 and the tip-end end link member 16.

[0022] Figure 2A shows the rotation pair T1 between the base-end link hub 12 and the base-end end link member 15, and the rotation pair T2 between the base-end end link member 15 and the central link member 17. The rotation pair T3 between the tip-end end link member 16 and the central link member 17 shown in Figure 3 has the same shape as the rotation pair T2 shown enlarged in Figure 2B. The rotation pair T4 between the tip-end link hub 13 and the tip-end end link member 16 shown in Figure 3 has the same shape as the rotation pair T1 shown enlarged in Figure 2B.

[0023] 2A, the angle (arm angle) α formed by the central axis O1 of each rotation pair T1 between the base-end link hub 12 and the base-end end link member 15 and the central axis O2 of each rotation pair T2 between the base-end end link member 15 and the central link member 17 is, for example, 90°. However, the angle α may be other than 90°.

[0024] The three link mechanisms 14 have geometrically identical shapes. "Geometrically identical shapes" refers to a geometric model, as shown in FIG. 3, in which each link member 15, 16, 17 is represented by a straight line. That is, the model is represented by each rotation pair T1, T2, T3, T4 and the straight lines connecting these rotation pairs T1, T2, T3, T4. Regardless of the orientation of the model, the base end portion and the tip end portion with respect to the center of the central link member 17 are symmetrical. Note that the rotation pairs T1, T2, T3, T4 may be referred to as the rotation pairs T1, etc. in the following description. FIG. 3 shows one link mechanism 14 represented by straight lines. The parallel link mechanism 9 of this embodiment is rotationally symmetric, and the positional relationship between the base end link hub 12 and the base end end link member 15 and the tip end link hub 13 and the tip end end link member 16 is rotationally symmetrical with respect to the center line C of the central link member 17.

[0025] The base-end link hub 12, the tip-end link hub 13, and the three link mechanisms 14 form a two-degree-of-freedom mechanism in which the tip-end link hub 13 can rotate freely around two perpendicular axes relative to the base-end link hub 12. In other words, the tip-end link hub 13 can rotate with two degrees of freedom relative to the base-end link hub 12, allowing for free posture change. This two-degree-of-freedom mechanism is compact, yet allows for a wide range of movement of the tip-end link hub 13 relative to the base-end link hub 12.

[0026] Here, the straight lines passing through the base-end and tip-end spherical link centers PA and PB and perpendicularly intersecting the central axes O1 (FIG. 2A) of the base-end and tip-end link hubs 12 and 13 and the base-end and tip-end end link members 15 and 16 are defined as the central axes QA and QB of the base-end and tip-end link hubs 12 and 13. In this case, the perpendicular angle at which the central axis QB of the tip-end link hub 13 is inclined relative to the central axis QA of the base-end link hub 12 is called the bend angle θ. The maximum value of this bend angle θ is the maximum bend angle θ. max In the parallel link mechanism 9 of this embodiment, the maximum bending angle θ max is set to 90° or more, as will be described later. In addition, the rotation angle φ of the tip-side link hub 13 relative to the base-side link hub 12 can be set in the range of 0° to 360°. The rotation angle φ is the horizontal angle at which the central axis QB of the tip-side link hub 13 is inclined relative to the central axis QA of the base-side link hub 12.

[0027] The position of the tip-side link hub 13 relative to the base-side link hub 12 is changed around the intersection O of the central axis QA of the base-side link hub 12 and the central axis QB of the tip-side link hub 13, which serves as the center of rotation. Fig. 1 shows a state in which the central axis QA of the base-side link hub 12 and the central axis QB of the tip-side link hub 13 are on the same line, and Fig. 3 shows a state in which the central axis QB forms a certain operating angle (bend angle) with respect to the central axis QA. Even if the position of the tip-side link hub 13 relative to the base-side link hub 12 changes, the distance L between the base-side and tip-side spherical link centers PA and PB does not change.

[0028] As shown in FIG. 1, the parallel link mechanism 9 is in the original position (bending angle θ=0° ), the angle formed by the base end member 6, which will be described later, with respect to the base end link member 15 is γ / 2. As the bending angle θ increases, the angle formed by the base end link member 15 with respect to the base end member 6 also increases, and as shown in FIG. 4, it becomes a maximum of (γ / 2+θ / 2). When the maximum bending angle of the parallel link mechanism 9 is θ max In this case, the angle formed by the end link member 15 on the base end side with respect to the base end member 6 is (γ / 2±θ max / 2).

[0029] As shown in Figure 5, the parallel link mechanism 9 has a singularity at a position where the central axes QA and QB of the base-end or tip-end link hubs 12 and 13 coincide with the central axes O2 and O3, which are the rotation axes of the rotation pairs between the base-end or tip-end end link members 15 and 16 and the central link member 17. The singularity refers to a position that cannot be controlled structurally, and in a typical vertical articulated robot, it refers to a position where multiple arms are aligned in a straight line. The parallel link mechanism 9 cannot be structurally controlled when it reaches a singularity such as that shown in Figure 6. For example, if an attempt is made to return to the original position after reaching the singularity, the tip-end link hub 13 or the base-end link hub 12 may move in the opposite direction, destroying the symmetry of the parallel link mechanism 9.

[0030] Therefore, in the present parallel link mechanism 9, the shaft angle γ of the central link member 17 is specified so that the posture in which the singular point shown in FIG. 5 etc. occurs is not reached. The posture in which this parallel link mechanism 9 reaches the singular point is a position in which the base-end end link member 15 (or tip-end end link member 16) of one of the multiple link mechanisms 14 is at 90° with respect to the base-end member 6 (or tip-end member 40 described later), that is, a posture in which the central axis QA (QB) of the base-end link hub 12 (or tip-end link hub 13) coincides with the central axis O2 (O3), which is the rotation axis of the rotation pair between the base-end end link member 15 (or tip-end end link member 16) and the central link member 17.

[0031] Therefore, (γ / 2±θ max / 2) is less than 90°, the shaft angle γ and the maximum bending angle θ max In other words, if the parallel link mechanism 9 satisfies equation (1), it will not have a singular point. In this case, no singular points will occur within the operating range of the parallel link mechanism 9, and smooth operation can be achieved within the operating range. Because there are no singular points within the operating range, the parallel link mechanism 9 will not operate in an unexpected direction and will not generate large loads during operation, thereby improving durability. (γ / 2±θ max / 2)<90 …Equation (1) In design, the shaft angle γ and maximum bending angle θ are set with a safety factor of 10% or more. max It is preferable to determine the parallel link mechanism 9 so that it satisfies the formula (2). L1 in the formula (2) is a safety factor. This safety factor L1 is determined by either or both of a test and a simulation. (γ / 2±θ max / 2)×L1<90 …Equation (2)

[0032] In this embodiment, since γ=60°, the maximum bending angle θ max If the angle is less than 120°, no singular point occurs, and unlike previous parallel link mechanisms, the maximum bending angle θ max In design, the maximum bending angle θ can be set to 90° or more, taking into account the safety factor. max It is recommended that the angle be 103.6° or less.

[0033] As shown in Fig. 1, the base-side link hub 12 has a flat base-side member 6 and three rotary shaft connecting members 21 (Fig. 2A) that are integral with the base-side member 6. The base-side member 6 shown in Fig. 2A has a circular through-hole 6a in the center, and three rotary shaft connecting members 21 are arranged around the through-hole 6a at equal intervals in the circumferential direction. The center of the through-hole 6a is located on the central axis QA (Fig. 1) of the base-side link hub 12.

[0034] A bearing 23 is provided at each rotation pair T1, etc. As shown in FIG. 2B, at the rotation pair T1 between the base-end link hub 12 (FIG. 2A) and the base-end end link member 15, a rotation shaft 22 is rotatably connected to each rotation shaft connecting member 21 via a bearing 23. The axis of this rotation shaft 22 intersects with the central axis QA (FIG. 1) of the base-end link hub 12. One end of the base-end end link member 15 is connected to the rotation shaft 22 so as to rotate integrally with this rotation shaft 22.

[0035] The rotating shaft 22 is rotatably supported by the rotating shaft connecting member 21 via two bearings 23 at a small diameter portion in the middle of the axial direction. The two bearings 23 are set and fixed with the outer peripheral surfaces of their outer rings fitted into inner diameter grooves provided in the rotating shaft connecting member 21. The types and installation methods of the bearings provided in the other rotation pairs T2, T3, and T4 (Fig. 3) are also substantially similar.

[0036] A notch 25 is formed at one end of the base-side end link member 15, and both sides of this notch 25 form a pair of inner and outer rotating shaft support portions 27, 26. A through hole is formed in each of the pair of rotating shaft support portions 27, 26. The rotating shaft connecting member 21 is disposed in the notch 25, and the small-diameter portion of the rotating shaft 22 is inserted through the through hole and the inner peripheral surface of the inner ring of the bearing 23. A male thread formed at the axial end of the rotating shaft 22 protrudes inward (lower in FIG. 2B ) beyond the inner rotating shaft support portion 27. A nut Nt is threaded onto the male thread portion. A spacer Sp is interposed between the inner rotating shaft support portion 27 and the inner ring end face opposite the inner rotating shaft support portion 27, and a spacer Sp is interposed between the outer rotating shaft support portion 26 and the inner ring end face opposite the inner rotating shaft support portion 26. Therefore, a preload is applied to the bearing 23 when the nut Nt is threaded.

[0037] A rotating shaft 22 is connected to one end of the central link member 17 via a bearing 23 at the rotation pair T2 between the base-end side end link member 15 and the central link member 17. That is, the rotating shaft 22, which is rotatably connected to one end of the central link member 17, is connected to the other end of the base-end side end link member 15. This rotating shaft 22 is rotatably supported at its small diameter portion on one end of the central link member 17 via two bearings 23. A notch 37 is formed in the other end of the base-end side end link member 15, and both sides of this notch 37 form a pair of inner and outer rotating shaft support portions 39, 38. Each of these pair of rotating shaft support portions 39, 38 has a through hole formed therein.

[0038] One end of the central link member 17 is disposed within the cutout portion 37, and the small diameter portion is inserted through the through hole and the inner peripheral surface of the inner ring of the bearing 23. Furthermore, a nut Nt is screwed onto the male thread portion of the rotating shaft 22. Spacers Sp, Sp are interposed between the inner ring end surface of the bearing 23 and the pair of rotating shaft support portions 39, 38, and a preload is applied to the bearing 23 when the nut Nt is screwed onto it.

[0039] As shown in FIG. 1, the tip-side link hub 13 has a flat tip member 40 and three rotating shaft connecting members 41 provided at equal intervals in the circumferential direction on the bottom surface of this tip member 40. The center of the circumference on which each rotating shaft connecting member 41 is arranged is located on the central axis QB of the tip-side link hub 13. A rotating shaft 22 whose axis intersects with the central axis QB of the tip-side link hub 13 is rotatably connected to each rotating shaft connecting member 41. One end of the tip-side end link member 16 is connected to the rotating shaft 22. The other end of the tip-side end link member 16 is connected to the rotating shaft 22, which is rotatably connected to the other end of the central link member 17.

[0040] The rotary shaft 22 is rotatably connected to the rotary pair T4 (Fig. 3) between the tip-side link hub 13 and the tip-side end link member 16 via two bearings provided in each rotary shaft connecting member 41. The rotary shaft 22 is rotatably connected to the rotary pair T3 (Fig. 3) between the tip-side end link member 16 and the central link member 17 via two bearings provided at the other end of the central link member 17.

[0041] <Action and effect> According to the parallel link mechanism 9 described above, a two-degree-of-freedom mechanism is configured in which the base-end link hub 12, the tip-end link hub 13, and three or more sets of link mechanisms 14 allow the tip-end link hub 13 to rotate freely around two perpendicular axes relative to the base-end link hub 12. In other words, the tip-end link hub 13 has two degrees of freedom of rotation relative to the base-end link hub 12, making it possible to freely change its attitude. This two-degree-of-freedom mechanism is compact, yet allows a wide range of movement of the tip-end link hub 13 relative to the base-end link hub 12.

[0042] As shown in FIG. 5 , in the present parallel link mechanism 9, a singularity occurs when the central axis QA (QB) of the base-end link hub 12 (or the tip-end link hub 13) coincides with the central axis O2 (O3), which is the rotation axis of the rotation pair between the base-end end link member 15 (or the tip-end end link member 16) and the central link member 17. Because the orientation in which the singularity occurs is clearly defined, a parallel link mechanism 9 with a wider operating range than the prior art can be realized by specifying the shaft angle γ of the central link member 17 so that the orientation does not result in the singularity. This allows the orientation of the parallel link mechanism 9 to be changed smoothly and quickly, similar to a human wrist. Furthermore, because the orientation in which the singularity occurs is clearly defined, the operating range of the parallel link mechanism 9 can be freely designed so that the singularity does not occur. In other words, the parallel link mechanism 9 can be designed with greater freedom of design than the prior art.

[0043] <Link Actuator: Figures 7 to 9B> As shown in Fig. 7, a link actuation device 7 according to an embodiment of the present invention includes the parallel link mechanism 9 according to the first embodiment described above, attitude control actuators 10 that arbitrarily control the attitude of link hubs 13 at the tip ends of the parallel link mechanism 9, and a control unit Cu shown in Fig. 9A that controls the rotational drive of each attitude control actuator 10. Instead of the parallel link mechanism 9 described above, the link actuation device 7 may employ a parallel link mechanism 9A (Fig. 11) according to a second embodiment described below.

[0044] <Attitude control actuator> In this example, all three link mechanisms 14 are provided with attitude control actuators 10. Each attitude control actuator 10 is a rotary actuator equipped with a speed reduction mechanism 52 shown in FIG. 9B, and is installed coaxially with the rotation axis 22 on the surface of the base end member 6 (FIG. 8) of the base end link hub 12. The attitude control actuator 10 is provided integrally with the speed reduction mechanism 52, and the speed reduction mechanism 52 is fixed to the base end member 6 (FIG. 8) by a motor fixing member 53. If attitude control actuators 10 are provided in at least two of the three link mechanisms 14 shown in FIG. 9A, the attitude of the tip end link hub 13 (FIG. 8) relative to the base end link hub 12 can be determined.

[0045] <Control unit> A control unit Cu shown in Fig. 9A controls the rotational drive of each attitude control actuator 10, and the rotation is reduced via a speed reduction mechanism 52 shown in Fig. 9B and transmitted to the base-end end link member 15. As a result, the attitude of the tip-end link hub 13 relative to the base-end link hub 12 can be changed as desired, as shown in Fig. 10. An end effector (not shown) is attached to the tip member 40 of the tip-end link hub 13. Examples of the end effector include a hand including a gripper, a cleaning nozzle, a dispenser, a welding torch, and image processing equipment.

[0046] The control unit Cu (FIG. 9A) which is a rotation angle limiting means, is configured to limit the shaft angle γ (FIG. 8) and the maximum bending angle θ of the parallel link mechanism 9. max 9A, a soft limit function is provided that limits the rotation angles β1, β2, and β3 of the attitude control actuators 10 according to the values ​​of β1, β2, and β3. In this case, singular points can be easily avoided by using a program in the control unit Cu, which not only reduces costs but also makes it possible to make the link actuation device 7 more compact than, for example, avoiding singular points by providing a mechanical brake mechanism or the like in the attitude control actuators 10.

[0047] <Other embodiments> In the following description, parts corresponding to matters previously described in each embodiment are given the same reference numerals, and duplicated description will be omitted. When only a part of the configuration is described, the other parts of the configuration are the same as the previously described embodiment unless otherwise specified. The same configuration produces the same effects. It is possible to combine not only the parts specifically described in each embodiment, but also partially combine embodiments as long as there is no particular problem with the combination.

[0048] [Second embodiment: Figs. 11 and 12] As shown in Fig. 11, a parallel link mechanism 9A with a shaft angle γ of 90° may be used. In the case of this parallel link mechanism 9, as shown in Fig. 12, there is a singular point at the bending angle θ = 90°, and the operating range is narrower than that of the first embodiment. In other words, the smaller the shaft angle γ, the wider the operating range of the parallel link mechanism. If the shaft angle γ is set to 90° or less, the maximum bending angle θ max It is possible to realize a parallel link mechanism with an angle of 90° or more.

[0049] The attitude control actuator 10 may be equipped with a brake.

[0050] As a reference proposal example, it is also possible to make the central link member, the end link member on the base end or tip end side, the tip member, the base end member, etc. interfere with other parts before reaching the singular point, thereby preventing the singular point from being reached due to interference. The parallel link mechanism according to this reference proposal example is described as follows. A parallel link mechanism in which a tip-side link hub is connected to a base-side link hub via three or more link mechanisms so that its posture can be changed, and each of the link mechanisms has base-side and tip-side end link members, one end of which is rotatably connected to the base-side link hub and the tip-side link hub, respectively, and a central link member, both ends of which are rotatably connected to the other ends of the base-side and tip-side end link members, the central axis of the rotation pair between the end link member on the base end side and the central link member, and the central axis of the link hub on the base end side; or a central axis of a rotation pair between the tip-side end link member and the central link member, and a central axis of the tip-side link hub; a parallel link mechanism in which at least one of the central link member, the end link member on the base end side or the tip end side, the link hub on the tip end side, and the link hub on the base end side interfere with another component so as to prevent the posture from being one in which the singular point occurs when at least one of the central link member, the end link member on the base end side or the tip end side, the link hub on the tip end side, and the link hub on the base end side.

[0051] Although the embodiments of the present invention have been described above, the disclosed embodiments are illustrative in all respects and are not limiting. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0052] 7...Link actuator, 9, 9A...Parallel link mechanism, 10...Attitude control actuator, 12...Base end link hub, 13...Tip end link hub, 14...Link mechanism, 15...Base end link member, 16...Tip end link member, 17...Central link member, Cu...Control unit (rotation angle limiting means)

Claims

1. A link actuation device comprising a parallel link mechanism and an attitude control actuator, The parallel link mechanism includes: The link hub on the tip side controls the position of the link hub on the base side through three or more sets of link mechanisms. The link mechanisms are variably connected to each other, and each of the link mechanisms includes a link hub on the base end side and a link hub on the base end side. a proximal end link member and a distal end link member, one end of which is rotatably connected to a distal end link hub; and both ends are rotatably connected to the other ends of the base end side and tip end side end link members, respectively. and a central link member connected to the parallel link mechanism, The central axis of the rotation pair between the end link member on the base end side and the central link member, The center axis of the end link hub, or The center axis of the rotation pair between the tip end link member and the central link member, The center axis of the end link hub, When at least one of the above coincides, a singular point occurs, and the central link member and the front The central axis of the rotation pair with the end link member on the base end side and the central link member with the end link member on the tip end side The angle formed by the central axis of the rotation pair with the end link member is defined as the shaft angle γ of the central link member, a shaft angle γ of the central link member is specified so that the central link member does not assume a posture in which the singular point occurs; two or more sets of link mechanisms among the three or more sets of link mechanisms in the parallel link mechanism are provided with the attitude control actuator that arbitrarily controls the attitude of the link hub on the tip side, a link actuation device including a rotation angle limiting means for limiting the rotation angle of the attitude control actuator in accordance with the shaft angle γ and the value of the maximum bending angle θ max of the parallel link mechanism, thereby avoiding the singular point;

2. 2. The link actuation device according to claim 1, wherein the maximum bending angle between the central axis of the base end link hub and the central axis of the tip end link hub is θ ｍａｘ When this is the case, (γ / 2+θ ｍａｘ A link actuator in which the relational expression (x, y) < 90 holds true.

3. 3. The link actuation device according to claim 1, wherein a maximum bending angle θ is a maximum value of the bending angle between the central axis of the base end link hub and the central axis of the tip end link hub. ｍａｘ A link actuator in which the angle is 90° or more.

4. 4. The link actuation device according to claim 1, wherein the shaft angle γ is equal to or smaller than 90°.

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