A three-degree-of-freedom parallel mechanism

Abstract

The present invention discloses a three-degree-of-freedom parallel mechanism, which relates to the technical field of parallel mechanisms and includes: a fixed platform, a moving platform, and a first kinematic branch, a second kinematic branch, a third kinematic branch, and a fourth kinematic branch located between the fixed platform and the moving platform. The third kinematic branch and the fourth kinematic branch are located in a first plane. The first and second kinematic branches have the same structure and are symmetrical about the first plane. The first, second, and fourth kinematic branches are all located in a second plane perpendicular to the first plane. The first and second kinematic branches are connected to the fixed platform and the moving platform via Hooke's joints at their ends, respectively. The upper ends of the third and fourth kinematic branches are connected to the fixed platform via ball joints, and the lower ends are connected to the moving platform via revolute joints, respectively. Each kinematic branch has a moving joint. The present invention has the advantages of good stiffness performance, high stiffness, large rotation angle, high flexibility, and a large working space.

Description

Technical Field

[0001] The present invention relates to the technical field of parallel mechanisms, and more particularly to a three-degree-of-freedom parallel mechanism. Background Art

[0002] Compared to traditional serial robots, three-DOF parallel mechanisms offer advantages such as superior rigidity, high precision, and greater load-bearing capacity. Compared to six-DOF parallel mechanisms, three-DOF parallel mechanisms offer advantages such as low coupling and ease of modularization. Therefore, three-DOF parallel mechanisms, particularly those with two rotational and one translational mechanisms, have become the backbone of high-end manufacturing equipment and are widely used in aerospace, automotive, and other fields.

[0003] Some three-degree-of-freedom parallel structures have been disclosed in the relevant technology. For example, the Z3 spindle head (US6431802) is a 3-PRS mechanism. Each branch chain provides a constraint force. The three branches jointly limit the two movements and one rotation of the dynamic platform, but its working space is small and there is accompanying motion. The Chinese invention patent CN201510379982.4 discloses a 2SPR-UPU parallel mechanism. The three active branches each generate a constraint on the dynamic platform to achieve the two rotations and one movement of the dynamic platform. A parallel motion machine (WO2006054935) adopts a 2UPR-SPR parallel configuration, and the Chinese patent application CN201910059217.2 uses 2UPU-SP as a parallel mechanism. Both use three active branches to form an over-constrained two-rotation-one-shift three-degree-of-freedom parallel mechanism. The above are all three-branch two-rotation-one-shift parallel configurations. Compared with the four-branch configuration, they are insufficient in stiffness and load-bearing capacity.

[0004] The four-chain two-turn and one-shift parallel configuration, such as Tricept (US4732525), is composed of three UPS branches and one UP branch. The UP branch provides two-movement and one-rotation constraints for the dynamic platform and only the UP branch participates in the force resistance of the dynamic platform. TriMule (CN201520494616.9) is composed of four branches, the UPS branch is located at the rear, and the other three branches are in the front plane. Two of the branches can be UPR, UPS and other configurations, and are symmetrically arranged about the middle UP branch. The load-bearing of this configuration mainly depends on the three branches on the front plane, which is a cantilever state. Therefore, compared with the two-turn and one-shift configuration in which four branches in space participate in load resistance at the same time, the parallel configuration of Tricept and TriMule is still lacking in uniform force and overall stiffness.

[0005] In addition, many research units and scientific research institutions have constructed a variety of three-degree-of-freedom parallel mechanisms with two rotations and one translation, but each branch provides a constraint. There are relatively few over-constrained four-branch parallel mechanisms with high stiffness, balanced load, simple structure, low manufacturing cost and high degree of modularity. Summary of the Invention

[0006] In view of this, the present invention provides a three-degree-of-freedom parallel mechanism, which aims to solve the problems in the above-mentioned background technology, so as to realize a three-degree-of-freedom parallel mechanism with good stiffness performance, high stiffness, large rotation angle, high flexibility, large working space and other advantages.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A three-degree-of-freedom parallel mechanism comprises: a fixed platform, a movable platform, and a first kinematic branch, a second kinematic branch, a third kinematic branch, and a fourth kinematic branch located between the fixed platform and the movable platform, wherein the third kinematic branch and the fourth kinematic branch are located in a first plane, the first kinematic branch and the second kinematic branch have identical structures and are symmetrical about the first plane, and the first kinematic branch, the second kinematic branch, and the fourth kinematic branch are all located in a second plane, and the second plane is perpendicular to the first plane.

[0009] Two ends of the first motion branch chain and two ends of the second motion branch chain are respectively connected to the fixed platform and the moving platform through Hooke's joints;

[0010] The upper ends of the third and fourth kinematic branches are connected to the fixed platform via ball joints, respectively. The lower ends of the third and fourth kinematic branches are connected to the movable platform via revolute joints, respectively. The axis of the revolute joint at the lower end of the third kinematic branch is perpendicular to the axis of the revolute joint at the lower end of the fourth kinematic branch.

[0011] The first motion branch, the second motion branch, the third motion branch and the fourth motion branch each have a moving pair.

[0012] According to the three-degree-of-freedom parallel mechanism provided by the present invention, the first kinematic branch chain includes a first rotation axis of a Hooke's pair, a second rotation axis of a Hooke's pair, a first moving pair, a third rotation axis of a Hooke's pair, and a fourth rotation axis of a Hooke's pair;

[0013] The first rotating shaft of the Hooke's pair is rotationally connected to the fixed platform, and the third rotating shaft of the Hooke's pair is rotationally connected to the movable platform; the second rotating shaft of the Hooke's pair is rotationally connected to the first rotating shaft of the Hooke's pair, and the fourth rotating shaft of the Hooke's pair is rotationally connected to the third rotating shaft of the Hooke's pair; the second rotating shaft of the Hooke's pair is connected to the fourth rotating shaft of the Hooke's pair through the first moving pair; the axis of the first moving pair is perpendicular to the axis of the second rotating shaft of the Hooke's pair and the axis of the fourth rotating shaft of the Hooke's pair, respectively.

[0014] According to the three-degree-of-freedom parallel mechanism provided by the present invention, the second kinematic branch chain includes a fifth rotation axis of a Hooke's pair, a sixth rotation axis of a Hooke's pair, a second moving pair, a seventh rotation axis of a Hooke's pair, and an eighth rotation axis of a Hooke's pair;

[0015] The fifth rotating shaft of the Hooke's pair is rotationally connected to the fixed platform, and the seventh rotating shaft of the Hooke's pair is rotationally connected to the movable platform; the sixth rotating shaft of the Hooke's pair is rotationally connected to the fifth rotating shaft of the Hooke's pair, and the eighth rotating shaft of the Hooke's pair is rotationally connected to the seventh rotating shaft of the Hooke's pair; the sixth rotating shaft of the Hooke's pair is connected to the eighth rotating shaft of the Hooke's pair through a second moving pair; the axis of the second moving pair is perpendicular to the axis of the sixth rotating shaft of the Hooke's pair and the axis of the eighth rotating shaft of the Hooke's pair, respectively.

[0016] According to the three-degree-of-freedom parallel mechanism provided by the present invention, the third kinematic branch comprises a first ball pair, a third translation pair and a first rotation pair;

[0017] The first ball pair is connected to the fixed platform, the first rotation pair is connected to the movable platform, the first ball pair is connected to the first rotation pair through the third moving pair, and the axis of the third moving pair is perpendicular to the axis of the first rotation pair.

[0018] According to the three-degree-of-freedom parallel mechanism provided by the present invention, the fourth kinematic branch comprises a second ball pair, a fourth translation pair and a second rotation pair;

[0019] The second ball pair is connected to the fixed platform, the second rotation pair is connected to the movable platform, the second ball pair is connected to the second rotation pair through the fourth movable pair, and the axis of the fourth movable pair is perpendicular to the axis of the second rotation pair.

[0020] According to the three-degree-of-freedom parallel mechanism provided by the present invention, the axis of the first rotating shaft of the Hooke's pair, the axis of the fifth rotating shaft of the Hooke's pair, and the center of the second ball pair are located on the same straight line; the line connecting the center of the first ball pair and the center of the second ball pair is perpendicular to the axis of the first rotating shaft of the Hooke's pair; the axis of the third rotating shaft of the Hooke's pair coincides with the axis of the seventh rotating shaft of the Hooke's pair; the axis of the first rotating pair and the axis of the second rotating pair intersect perpendicularly, and the axis of the first rotating pair, the axis of the second rotating pair and the axis of the third rotating shaft of the Hooke's pair are coplanar; the axis of the second rotating pair coincides with or is perpendicular to the axis of the third rotating shaft of the Hooke's pair.

[0021] According to the three-degree-of-freedom parallel mechanism provided by the present invention, the first moving pair, the second moving pair, and the third moving pair are driving pairs, and the fourth moving pair is a driven pair;

[0022] Or the first moving pair, the second moving pair, the third moving pair and the fourth moving pair are all drive pairs, forming a redundant drive.

[0023] It can be seen from the above technical solution that compared with the prior art, the present invention discloses a three-degree-of-freedom parallel mechanism, which is provided with four motion branches between the fixed platform and the movable platform, and a 2UPU-2SPR configuration of a three-degree-of-freedom parallel mechanism with two rotations and one movement is formed through a Hooke pair, a rotation pair and a translation pair. Each motion branch of the parallel mechanism provides a constraint, and the four motion branches jointly participate in load resistance, so the load-bearing is more balanced and has good stiffness performance. At the same time, the parallel mechanism is an over-constrained mechanism with the advantages of high stiffness, large rotation angle, high flexibility and large working space, and can be used for the processing and manufacturing of complex parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0025] Figure 1 A schematic structural diagram of a three-degree-of-freedom parallel mechanism provided in Example 1 of the present invention;

[0026] Figure 2 This is a structural diagram of a three-degree-of-freedom parallel mechanism provided in Example 2 of the present invention.

[0027] Among them: 1 is the first kinematic branch; 11 is the first rotation axis of the Hooke's pair; 12 is the second rotation axis of the Hooke's pair; 13 is the third rotation axis of the Hooke's pair; 14 is the fourth rotation axis of the Hooke's pair; 15 is the first moving pair; 2 is the second kinematic branch; 21 is the fifth rotation axis of the Hooke's pair; 22 is the sixth rotation axis of the Hooke's pair; 23 is the seventh rotation axis of the Hooke's pair; 24 is the eighth rotation axis of the Hooke's pair; 25 is the second moving pair; 3 is the third kinematic branch; 31 is the first ball pair; 32 is the first rotation pair; 33 is the third moving pair; 4 is the fourth kinematic branch; 41 is the second ball pair; 42 is the second rotation pair; 43 is the fourth moving pair; 5 is the moving platform; 6 is the fixed platform. DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] Example 1

[0030] See also Figure 1 The embodiment of the present invention discloses a three-degree-of-freedom parallel mechanism, including: a fixed platform 6, a movable platform 5, and a first motion branch 1, a second motion branch 2, a third motion branch 3, and a fourth motion branch 4 located between the fixed platform 6 and the movable platform 5, wherein the third motion branch 3 and the fourth motion branch 4 are located in a first plane, the first motion branch 1 and the second motion branch 2 have the same structure and are symmetrical about the first plane, and the first motion branch 1, the second motion branch 2, and the fourth motion branch 4 are all located in a second plane, and the second plane is perpendicular to the first plane;

[0031] The two ends of the first motion branch chain 1 and the two ends of the second motion branch chain 2 are respectively connected to the fixed platform 6 and the moving platform 5 through Hooke's joints;

[0032] The upper ends of the third kinematic branch chain 3 and the upper ends of the fourth kinematic branch chain 4 are respectively connected to the fixed platform 6 via ball joints, and the lower ends of the third kinematic branch chain 3 and the lower ends of the fourth kinematic branch chain 4 are respectively connected to the moving platform 5 via revolute joints, and the axis of the revolute joint at the lower end of the third kinematic branch chain 3 is perpendicular to the axis of the revolute joint at the lower end of the fourth kinematic branch chain 4;

[0033] The first kinematic branch 1 , the second kinematic branch 2 , the third kinematic branch 3 and the fourth kinematic branch 4 each have a moving pair.

[0034] It should be noted that: in this embodiment, the fixed platform 6 and the movable platform 5 have similar shapes, and the area of ​​the fixed platform 6 is larger than the area of ​​the movable platform 5, so that the ends of the first moving branch 1, the second moving branch 2, the third moving branch 3 and the fourth moving branch 4 close to the movable platform 5 are respectively in a structure that converges toward the center position of the movable platform 5.

[0035] By connecting the fixed platform 6 and the moving platform 5 through four kinematic branches, namely the first kinematic branch 1, the second kinematic branch 2, the third kinematic branch 3 and the fourth kinematic branch 4, a 2UPU-2SPR parallel mechanism with three degrees of freedom, two rotations and one movement, is formed by using Hooke's pairs, rotation pairs and translation pairs. Each kinematic branch of the parallel mechanism provides a constraint, and the four kinematic branches jointly participate in load resistance, so the load bearing is more balanced and has good stiffness performance. At the same time, the parallel mechanism is an over-constrained mechanism with the advantages of high stiffness, large rotation angle, high flexibility and large working space, and can be used for the processing and manufacturing of complex parts.

[0036] According to the three-degree-of-freedom parallel mechanism provided by the present invention, the first kinematic branch 1 includes a Hooke's pair first rotation axis 11, a Hooke's pair second rotation axis 12, a first moving pair 15, a Hooke's pair third rotation axis 13 and a Hooke's pair fourth rotation axis 14;

[0037] The first rotating shaft 11 of the Hooke's pair is rotationally connected to the fixed platform 6, and the third rotating shaft 13 of the Hooke's pair is rotationally connected to the movable platform 5; the second rotating shaft 12 of the Hooke's pair is rotationally connected to the first rotating shaft 11 of the Hooke's pair, and the fourth rotating shaft 14 of the Hooke's pair is rotationally connected to the third rotating shaft 13 of the Hooke's pair; the second rotating shaft 12 of the Hooke's pair is connected to the fourth rotating shaft 14 of the Hooke's pair through the first moving pair 15; the axis of the first moving pair 15 is perpendicular to the axis of the second rotating shaft 12 of the Hooke's pair and the axis of the fourth rotating shaft 14 of the Hooke's pair, respectively.

[0038] According to the three-degree-of-freedom parallel mechanism provided by the present invention, the second kinematic branch 2 includes a Hooke's pair fifth rotation axis 21, a Hooke's pair sixth rotation axis 22, a second moving pair 25, a Hooke's pair seventh rotation axis 23 and a Hooke's pair eighth rotation axis 24;

[0039] The fifth rotating shaft 21 of the Hooke's pair is rotationally connected to the fixed platform 6, and the seventh rotating shaft 23 of the Hooke's pair is rotationally connected to the movable platform 5; the sixth rotating shaft 22 of the Hooke's pair is rotationally connected to the fifth rotating shaft 21, and the eighth rotating shaft 24 of the Hooke's pair is rotationally connected to the seventh rotating shaft 23; the sixth rotating shaft 22 of the Hooke's pair is connected to the eighth rotating shaft 24 of the Hooke's pair through the second moving pair 25; the axis of the second moving pair 25 is perpendicular to the axis of the sixth rotating shaft 22 and the axis of the eighth rotating shaft 24 of the Hooke's pair.

[0040] According to the three-degree-of-freedom parallel mechanism provided by the present invention, the third kinematic branch 3 includes a first ball pair 31, a third moving pair 33 and a first rotation pair 32;

[0041] The first ball pair 31 is connected to the fixed platform 6 , the first rotation pair 32 is connected to the movable platform 5 , and the first ball pair 31 is connected to the first rotation pair 32 through the third movement pair 33 , and the axis of the third movement pair 33 is perpendicular to the axis of the first rotation pair 32 .

[0042] According to the three-degree-of-freedom parallel mechanism provided by the present invention, preferably, the fourth kinematic branch 4 includes a second ball pair 41, a fourth moving pair 43 and a second rotation pair 42;

[0043] The second ball pair 41 is connected to the fixed platform 6 , the second rotation pair 42 is connected to the movable platform 5 , and the second ball pair 41 is connected to the second rotation pair 42 through the fourth movement pair 43 , and the axis of the fourth movement pair 43 is perpendicular to the axis of the second rotation pair 42 .

[0044] According to the three-degree-of-freedom parallel mechanism provided by the present invention, the axis of the first rotation axis 11 of the Hooke's pair, the axis of the fifth rotation axis 21 of the Hooke's pair, and the center of the second ball pair 41 are located on the same straight line; the line connecting the center of the first ball pair 31 and the center of the second ball pair 41 is perpendicular to the axis of the first rotation axis 11 of the Hooke's pair; the axis of the third rotation axis 13 of the Hooke's pair coincides with the axis of the seventh rotation axis 23 of the Hooke's pair; the axis of the first rotation pair 32 and the axis of the second rotation pair 42 intersect perpendicularly, and the axis of the first rotation pair 32, the axis of the second rotation pair 42, and the axis of the third rotation axis 13 of the Hooke's pair are coplanar; the axis of the second rotation pair 42 is perpendicular to the axis of the third rotation axis 13 of the Hooke's pair. That is, in this embodiment, the axis of the first rotation pair 32 is parallel to the axis of the third rotation axis 13 of the Hooke's pair, and the axis of the second rotation pair 42 and the axis of the first rotation pair 32 intersect at the center of the axis of the first rotation pair 32.

[0045] According to the three-degree-of-freedom parallel mechanism provided by the present invention, the first moving pair 15, the second moving pair 25, and the third moving pair 33 are driving pairs, and the fourth moving pair 43 is a driven pair;

[0046] Or the first moving pair 15 , the second moving pair 25 , the third moving pair 33 and the fourth moving pair 43 are all drive pairs, forming a redundant drive.

[0047] Example 2

[0048] See also Figure 2 This embodiment differs from Embodiment 1 in that the axis of the first rotational pair 32 and the axial direction of the second rotational pair 42 are arranged in different directions. Specifically, the axis of the second rotational pair 42 coincides with the axis of the third rotational axis 13 of the Hooke's pair. That is, in this embodiment, the axis of the first rotational pair 32 is perpendicular to the axis of the third rotational axis 13 of the Hooke's pair, and the axis of the first rotational pair 32 and the axial direction of the second rotational pair 42 intersect at the center of the axis of the second rotational pair 42.

[0049] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0050] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A three-degree-of-freedom parallel mechanism, characterized in that: include: a fixed platform, a movable platform, and a first motion branch, a second motion branch, a third motion branch, and a fourth motion branch located between the fixed platform and the movable platform, wherein the third motion branch and the fourth motion branch are located in a first plane, the first motion branch and the second motion branch have the same structure and are symmetrical about the first plane, and the first motion branch, the second motion branch, and the fourth motion branch are all located in a second plane, and the second plane is perpendicular to the first plane; Two ends of the first motion branch chain and two ends of the second motion branch chain are respectively connected to the fixed platform and the moving platform through Hooke's joints; The upper ends of the third and fourth kinematic branches are connected to the fixed platform via ball joints, respectively. The lower ends of the third and fourth kinematic branches are connected to the movable platform via revolute joints, respectively. The axis of the revolute joint at the lower end of the third kinematic branch is perpendicular to the axis of the revolute joint at the lower end of the fourth kinematic branch. The first motion branch, the second motion branch, the third motion branch and the fourth motion branch each have a moving pair; The branch configurations of the first and second motion branches are UPU, and the branch configurations of the third and fourth motion branches are SPR.

2. The three-degree-of-freedom parallel mechanism according to claim 1, characterized in that: The first kinematic branch chain includes a first rotation axis of a Hooke's pair, a second rotation axis of a Hooke's pair, a first moving pair, a third rotation axis of a Hooke's pair, and a fourth rotation axis of a Hooke's pair; The first rotating shaft of the Hooke's pair is rotationally connected to the fixed platform, and the third rotating shaft of the Hooke's pair is rotationally connected to the movable platform; the second rotating shaft of the Hooke's pair is rotationally connected to the first rotating shaft of the Hooke's pair, and the fourth rotating shaft of the Hooke's pair is rotationally connected to the third rotating shaft of the Hooke's pair; the second rotating shaft of the Hooke's pair is connected to the fourth rotating shaft of the Hooke's pair through the first moving pair; the axis of the first moving pair is perpendicular to the axis of the second rotating shaft of the Hooke's pair and the axis of the fourth rotating shaft of the Hooke's pair, respectively.

3. The three-degree-of-freedom parallel mechanism according to claim 2, characterized in that: The second kinematic branch chain includes a fifth rotation axis of a Hooke's pair, a sixth rotation axis of a Hooke's pair, a second moving pair, a seventh rotation axis of a Hooke's pair, and an eighth rotation axis of a Hooke's pair; The fifth rotating shaft of the Hooke's pair is rotationally connected to the fixed platform, and the seventh rotating shaft of the Hooke's pair is rotationally connected to the movable platform; the sixth rotating shaft of the Hooke's pair is rotationally connected to the fifth rotating shaft of the Hooke's pair, and the eighth rotating shaft of the Hooke's pair is rotationally connected to the seventh rotating shaft of the Hooke's pair; the sixth rotating shaft of the Hooke's pair is connected to the eighth rotating shaft of the Hooke's pair through a second moving pair; the axis of the second moving pair is perpendicular to the axis of the sixth rotating shaft of the Hooke's pair and the axis of the eighth rotating shaft of the Hooke's pair, respectively.

4. The three-degree-of-freedom parallel mechanism according to claim 3, characterized in that: The third kinematic branch chain includes a first ball pair, a third translation pair and a first rotation pair; The first ball pair is connected to the fixed platform, the first rotation pair is connected to the movable platform, the first ball pair is connected to the first rotation pair through the third moving pair, and the axis of the third moving pair is perpendicular to the axis of the first rotation pair.

5. The three-degree-of-freedom parallel mechanism according to claim 4, characterized in that: The fourth kinematic branch chain includes a second ball pair, a fourth translation pair and a second rotation pair; The second ball pair is connected to the fixed platform, the second rotation pair is connected to the movable platform, the second ball pair is connected to the second rotation pair through the fourth movable pair, and the axis of the fourth movable pair is perpendicular to the axis of the second rotation pair.

6. The three-degree-of-freedom parallel mechanism according to claim 5, characterized in that: The axis of the first rotating shaft of the Hooke's pair, the axis of the fifth rotating shaft of the Hooke's pair, and the center of the second ball pair are located on the same straight line; the line connecting the center of the first ball pair and the center of the second ball pair is perpendicular to the axis of the first rotating shaft of the Hooke's pair; the axis of the third rotating shaft of the Hooke's pair coincides with the axis of the seventh rotating shaft of the Hooke's pair; the axis of the first rotating pair and the axis of the second rotating pair intersect perpendicularly, and the axis of the first rotating pair, the axis of the second rotating pair and the axis of the third rotating shaft of the Hooke's pair are coplanar; the axis of the second rotating pair coincides with or is perpendicular to the axis of the third rotating shaft of the Hooke's pair.

7. The three-degree-of-freedom parallel mechanism according to claim 6, characterized in that: The first moving pair, the second moving pair, and the third moving pair are driving pairs, and the fourth moving pair is a driven pair; Or the first moving pair, the second moving pair, the third moving pair and the fourth moving pair are all drive pairs, forming a redundant drive.

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