Symmetrical two-revolute-one-prismatic full-redundant actuated parallel mechanism with compound spherical hinge

Abstract

The application provides a symmetrical two-rotation-one-translation full-redundant driving parallel mechanism containing a composite spherical hinge, which comprises a fixed platform, a movable platform and a motion branch, the movable platform is connected with the fixed platform through six motion branches, the motion branches are the same and are in RPS configuration, each motion branch comprises a driving rod and a spherical hinge opening, the first end of the driving rod is rotationally connected with the fixed platform through a rotary pair, two connecting rods in the driving rod are slidingly connected through a moving pair, interfaces for rotationally connecting the driving rod are arranged on both sides of the spherical hinge opening, and the second end of the driving rod is rotationally connected with the movable platform through the spherical hinge opening.The linear driving of the driving rod in the motion branch drives the mechanism to move, a redundant driving over-constrained parallel mechanism is formed, the rotation of the movable platform around the X axis and the Y axis and the movement of the movable platform in the Z axis direction are realized, and the application has the advantages of high bearing capacity, high stability, high rigidity, convenient control, simple mechanical installation interface and the like, and is applied to machining occasions with high precision, high rigidity and large load.

Description

TECHNICAL FIELD

[0001] The present application relates to parallel mechanism, belongs to the field of robot, especially relates to a symmetrical two-rotation one-translation full-redundant drive parallel mechanism containing composite spherical hinge. BACKGROUND

[0002] Two-rotation one-translation parallel mechanism belongs to a typical class of parallel mechanism with few degrees of freedom. Due to its simple structure and easy control, it has attracted wide attention in academic and industrial fields. There is a class of mechanisms with different structures but the same kinematic characteristics in the field of parallel mechanism with few degrees of freedom. This kind of mechanism is called kinematically equivalent mechanism. The parallel mechanism of the current widely used parallel machine tool body mostly adopts this kind of two-rotation one-translation mechanism, such as Tricept mechanism (us4732525), 3-PRS mechanism of parallel body of Z3 power drill (WO2000025976), 2-UPR+SPR mechanism of parallel body of Exechon machine tool (WO2006054935).

[0003] Dr. K.E. Neumann, the inventor of Tricept mechanism, pointed out that the geometric error, clearance and other problems of the joint are the main source of the accuracy problem of parallel machine tool (Adaptive in-jig high load Exechon machining & assembly technology. SAE Internation, 08AMT-0044). Although the parallel machine tool with few joints often has over-constraint, which increases the difficulty of manufacturing and assembly of the machine tool, from the perspective of improving the accuracy and stiffness of the mechanism, the parallel machine tool with few joints and few invalid degrees of freedom is still a good choice. Based on this, Dr. K.E. Neumann proposed the Exechon mechanism widely adopted in the industry at present, which contains two over-constraints and has two joints. The Chinese invention patent with patent number CN202113388268.3 discloses a two-rotation one-translation parallel mechanism with few joints and multiple redundant drives, which includes a fixed platform, a moving platform and five branch chains connecting the moving platform and the fixed platform. The first branch chain and the third branch chain have the same structure of RPU. The parallel mechanism has the advantages of few joints, simple structure, high stiffness, motion decoupling, easy control and the like, and can realize the motion mode of two-rotation one-translation. SUMMARY

[0004] In view of the problems in the prior art, the present application provides a symmetrical two-rotation one-translation full-redundant driving parallel mechanism containing a composite spherical hinge, the driving rod of a motion branch is used to drive the mechanism to move by extension and contraction, the equipment driving force is optimally distributed by adding a redundant driving branch or joint, the demand for the mechanical strength of the equipment branch and the load capacity of the driving unit is reduced, the equipment is lightweight and high-reliability, and the symmetrical two-rotation one-translation full-redundant driving parallel mechanism containing a composite spherical hinge has the advantages of high bearing capacity, high stability, high rigidity, convenient control, simple mechanical installation interface and the like.

[0005] The present application provides a symmetrical two-rotation one-translation full-redundant driving parallel mechanism containing a composite spherical hinge, the full-symmetrical driving parallel mechanism comprising a fixed platform, a movable platform and a motion branch, the movable platform being connected with the fixed platform through six motion branches, each motion branch being of the same structure and being of an RPS configuration, each motion branch comprising a driving rod and a spherical hinge opening, the first end of the driving rod being rotatably connected with the fixed platform through a rotary joint, two connecting rods in the driving rod being slidably connected through a moving joint, the spherical hinge opening being provided with an interface on both sides for rotatably connecting the driving rod, the second end of the driving rod being rotatably connected with the movable platform through the spherical hinge opening, the full-symmetrical motion branch comprising a first branch, a second branch, a third branch, a fourth branch, a fifth branch and a sixth branch, the first branch, the second branch and the third branch being located at the triangular position of the fixed platform, the fourth branch, the fifth branch and the sixth branch being located in the fixed platform, the axis of the first rotary joint being at an angle of 30° with the X axis, the axis of the second rotary joint being at an angle of 30° with the X axis, the axis of the third rotary joint being perpendicular to the X axis, and the motion branch being arranged in a full-symmetrical connection mode; all the rotary joints are located in the same plane, the axis of the first rotary joint being parallel to the axis of the fourth rotary joint, the axis of the second rotary joint being parallel to the axis of the fifth rotary joint, and the axis of the third rotary joint being parallel to the axis of the sixth rotary joint.

[0006] Preferably, the semi-symmetrical driving parallel mechanism comprises a fixed platform, a moving platform and motion branches, the moving platform is connected with the fixed platform through six motion branches, each motion branch is of RPS configuration and is identical in structure, each motion branch comprises a driving rod and a spherical hinge, a first end of the driving rod is rotatably connected with the fixed platform through a rotary joint, two links in the driving rod are slidably connected through a moving joint, spherical hinge interfaces for rotatably connecting the driving rod are arranged on both sides of the spherical hinge, a second end of the driving rod is rotatably connected with the moving platform through the spherical hinge, the semi-symmetrical motion branches comprise a first branch, a second branch, a third branch, a fourth branch, a fifth branch and a sixth branch, the first branch, the second branch, the third branch, the fourth branch and the fifth branch are located on the periphery of the fixed platform, and the sixth branch is located in the fixed platform, an axis of the first rotary joint is perpendicular to the X-axis, an axis of the second rotary joint is parallel to the X-axis, an axis of the third rotary joint is perpendicular to the X-axis, and the motion branches are arranged in a semi-symmetrical connection mode; all rotary joints are located in the same plane, the axis of the first rotary joint is parallel to the axis of the fourth rotary joint, the axis of the second rotary joint is parallel to the axis of the fifth rotary joint, and the axis of the third rotary joint is parallel to the axis of the sixth rotary joint.

[0007] Preferably, the fixed platform and the moving platform are both equilateral triangular structures, and the centers of the fixed platform and the moving platform are located on the same vertical line.

[0008] Preferably, the first branch and the fourth branch are connected with the moving platform through a shared first spherical joint, the second branch and the fifth branch are connected with the moving platform through a shared second spherical joint, and the third branch and the sixth branch are connected with the moving platform through a shared third spherical joint.

[0009] Preferably, the first branch, the fourth branch and the fixed platform form an isosceles triangle, wherein the first branch and the fourth branch are the two equal sides; the second branch, the fifth branch and the fixed platform form an isosceles triangle, wherein the second branch and the fifth branch are the two equal sides; and the third branch, the sixth branch and the fixed platform form an isosceles triangle, wherein the third branch and the sixth branch are the two equal sides.

[0010] Preferably, when the moving platform is parallel to the fixed platform, a projection of the first spherical joint on the fixed platform is a point on a line connecting the first rotary joint and the fourth rotary joint, a projection of the second spherical joint on the fixed platform is a point on a line connecting the second rotary joint and the fifth rotary joint, and a projection of the third spherical joint on the fixed platform is a point on a line connecting the third rotary joint and the fourth rotary joint.

[0011] Preferably, all moving joints are driving joints, and all rotary joints and spherical joints are passive joints.

[0012] It can be preferred that the motion branch chains are divided into full-symmetrical motion branch chains and half-symmetrical motion branch chains according to the arrangement of the motion branch chains on the fixed platform, in the full-symmetrical type, the motion branch chains connected with the fixed platform are arranged in an equilateral triangle, three motion branch chains are located at the three corners of the fixed platform, and the remaining three motion branch chains are located at the inner three corners of the fixed platform; in the half-symmetrical type, five motion branch chains are located at the edge corners of the fixed platform, and the remaining one is located in the fixed platform, and the connection modes of the full-symmetrical motion branch chains and the half-symmetrical motion branch chains with the moving platform are completely same.

[0013] The two-rotation-one-translation full-redundant driving parallel mechanism of the application is calculated by the degree of freedom G-K formula:

[0014]

[0015] Wherein, the order of the mechanism λ = 6, the number of components including the rack n = 14, the number of motion pairs g = 18, f i The degree of freedom of the i-th motion pair is represented, the number of degrees of freedom of the moving pair, the rotating pair and the ball pair in the mechanism is 30, the over-constraint number v = 6, the above parameters are sequentially brought into the formula, F represents the degree of freedom of the mechanism, and F = 3 is calculated. The driving number of the whole mechanism is 6, and the degree of freedom is 3. Since the driving number is greater than the degree of freedom, a redundant driving parallel mechanism is formed, the redundant driving parallel mechanism improves the stress characteristics of the mechanism, and singular positions of the mechanism can be avoided. Meanwhile, the over-constrained parallel mechanism greatly improves the stiffness and load capacity of the mechanism.

[0016] Compared with the prior art, the application has the following advantages:

[0017] 1. The symmetrical two-rotation-one-translation full-redundant driving parallel mechanism with a composite spherical hinge of the application drives the mechanism to move by the extension and contraction of the driving rods in the motion branch chains, forms a redundant driving over-constrained parallel mechanism, and through the mutual coordination of the multiple redundant driving branch chains, the motion or stress adjustment performance of the mechanism is better, and the multi-angle optimization of the performance of the mechanism is realized.

[0018] 2. The symmetrical two-rotation-one-translation full-redundant driving parallel mechanism with a composite spherical hinge of the application realizes the optimal distribution of the driving force of the equipment by increasing the redundant driving branch chains or joints, reduces the demand for the mechanical strength of the equipment branch chain and the load capacity of the driving unit, and realizes the lightweight and high-reliability design of the equipment.

[0019] 3. The symmetrical two-rotation-one-translation full-redundant driving parallel mechanism with a composite spherical hinge of the application has less degree of freedom for each motion branch chain, and the branch chain structures are the same, so that the machining and manufacturing of the equipment are facilitated, the advantages of the passive over-constrained parallel mechanism and the redundant driving parallel mechanism are combined, and the mechanism has the characteristics of large load capacity and good isotropy. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is the overall structure schematic diagram of the full-symmetrical connection type full-redundant driving parallel mechanism of the present application;

[0021] Figure 2 is the top view schematic diagram of the full-symmetrical connection type full-redundant driving parallel mechanism of the present application;

[0022] Figure 3 is the principle schematic diagram of the full-symmetrical connection type full-redundant driving parallel mechanism of the present application;

[0023] Figure 4 is the overall structure schematic diagram of the half-symmetrical connection type full-redundant driving parallel mechanism of the present application;

[0024] Figure 5 is the top view schematic diagram of the half-symmetrical connection type full-redundant driving parallel mechanism of the present application;

[0025] Figure 6 is the principle schematic diagram of the half-symmetrical connection type full-redundant driving parallel mechanism of the present application.

[0026] Main reference signs:

[0027] fixed platform 1, moving platform 2, first branch chain 3, second branch chain 4, third branch chain 5, fourth branch chain 6, fifth branch chain 7, sixth branch chain 8, first rotary pair 31, second rotary pair 41, third rotary pair 51, fourth rotary pair 61, fifth rotary pair 71, sixth rotary pair 81, first moving pair 32, second moving pair 42, third moving pair 52, fourth moving pair 62, fifth moving pair 72, sixth moving pair 82, first spherical pair 33, second spherical pair 43, third spherical pair 53. DETAILED DESCRIPTION

[0028] To make the technical content, structural features, achieved purposes and effects of the present application clear, the following will be described in detail in combination with the drawings of the specification.

[0029] The symmetrical two-rotation-one-moving full-redundant driving parallel mechanism of the present application containing composite spherical hinge is like Figure 1As shown, the full-symmetry type driving parallel mechanism includes a fixed platform 1, a moving platform 2 and a motion branch, the moving platform 2 is connected with the fixed platform 1 through six motion branches, each motion branch has the same structure of RPS configuration, each motion branch includes a driving rod and a spherical hinge, the first end of the driving rod is rotatably connected with the fixed platform 1 through a rotary joint, two connecting rods in the driving rod are slidably connected through a moving joint, the spherical hinge is provided with an interface on both sides for rotatably connecting the driving rod, the second end of the driving rod is rotatably connected with the moving platform 2 through the spherical hinge, the full-symmetry type motion branch includes a first branch 3, a second branch 4, a third branch 5, a fourth branch 6, a fifth branch 7 and a sixth branch 8, the first branch 3, the second branch 4 and the third branch 5 are located at the triangular position of the fixed platform 1, the fourth branch 6, the fifth branch 7 and the sixth branch 8 are located in the fixed platform 1, the axis of the first rotary joint 31 is at an angle of 30° with the X axis, the axis of the second rotary joint 41 is at an angle of 30° with the X axis, and the axis of the third rotary joint 51 is perpendicular to the X axis. All rotary joints are located in the same plane, the axis of the first rotary joint 31 is parallel to the axis of the fourth rotary joint 61, the axis of the second rotary joint 41 is parallel to the axis of the fifth rotary joint 71, and the axis of the third rotary joint 51 is parallel to the axis of the sixth rotary joint 81. The axis of the first moving joint 32 intersects with the axis of the fourth moving joint 62 at the first spherical joint 33, the axis of the second moving joint 42 intersects with the axis of the fifth moving joint 72 at the second spherical joint 43, and the axis of the third moving joint 52 intersects with the axis of the sixth moving joint 82 at the third spherical joint 53.

[0030] As shown, Figure 4 the semi-symmetry type driving parallel mechanism includes a fixed platform 1, a moving platform 2 and a motion branch, the moving platform 2 is connected with the fixed platform 1 through six motion branches, each motion branch has the same structure of RPS configuration, each motion branch includes a driving rod and a spherical hinge, the first end of the driving rod is rotatably connected with the fixed platform 1 through a rotary joint, two connecting rods in the driving rod are slidably connected through a moving joint, the spherical hinge is provided with an interface on both sides for rotatably connecting the driving rod, the second end of the driving rod is rotatably connected with the moving platform 2 through the spherical hinge, the semi-symmetry type motion branch includes a first branch 3, a second branch 4, a third branch 5, a fourth branch 6, a fifth branch 7 and a sixth branch 8, the first branch 3, the second branch 4, the third branch 5, the fourth branch 6 and the fifth branch 7 are located on the peripheral side of the fixed platform 1, and the sixth branch 8 is located in the fixed platform 1, the axis of the first rotary joint 31 is perpendicular to the X axis, the axis of the second rotary joint 41 is parallel to the X axis, and the axis of the third rotary joint 51 is perpendicular to the X axis. All rotary joints are located in the same plane, the axis of the first rotary joint 31 is parallel to the axis of the fourth rotary joint 61, the axis of the second rotary joint 41 is parallel to the axis of the fifth rotary joint 71, and the axis of the third rotary joint 51 is parallel to the axis of the sixth rotary joint 81.

[0031] In combination with Figure 1 and Figure 4As shown, the first branch chain 3 and the fourth branch chain 6 are connected with the movable platform 2 through the first ball joint 33, the second branch chain 4 and the fifth branch chain 7 are connected with the movable platform 2 through the second ball joint 43, and the third branch chain 5 and the sixth branch chain 6 are connected with the movable platform 2 through the third ball joint 53. The first branch chain 3, the fourth branch chain 6 and the fixed platform 1 form an isosceles triangle, and the first branch chain 3 and the fourth branch chain 6 are the two sides of the isosceles triangle. The second branch chain 4, the fifth branch chain 7 and the fixed platform 1 form an isosceles triangle, and the second branch chain 4 and the fifth branch chain 7 are the two sides of the isosceles triangle. The third branch chain 5, the sixth branch chain 8 and the fixed platform 1 form an isosceles triangle, and the third branch chain 5 and the sixth branch chain 8 are the two sides of the isosceles triangle. All the moving pairs are linear driving pairs, and all the rotating pairs and ball pairs are passive pairs.

[0032] As shown in Figure 2 and Figure 5 , the fixed platform 1 and the movable platform 2 are both equilateral triangle structures, and the centers of the fixed platform 1 and the movable platform 2 are located on the same vertical line. When the movable platform 2 is parallel to the fixed platform 1, the projection of the first ball joint 33 on the fixed platform 1 is a point on the line connecting the first rotating pair 31 and the fourth rotating pair 61, the projection of the second ball joint 43 on the fixed platform 1 is a point on the line connecting the second rotating pair 41 and the fifth rotating pair 71, and the projection of the third ball joint 53 on the fixed platform 1 is a point on the line connecting the third rotating pair 51 and the fourth rotating pair 81. According to the arrangement of the motion branch chains on the fixed platform 1, they can be divided into full-symmetrical motion branch chains and half-symmetrical motion branch chains. In the full-symmetrical type, the motion branch chains connected with the fixed platform 1 are arranged in an equilateral triangle, and the three motion branch chains are located at the three corners of the fixed platform 1, and the remaining three motion branch chains are located at the inner triangle of the fixed platform 1. In the half-symmetrical type, five motion branch chains are located at the corners of the fixed platform 1, and the remaining one is located inside the fixed platform 1. The connection modes of the full-symmetrical motion branch chains and the half-symmetrical motion branch chains with the movable platform 2 are completely the same.

[0033] As shown in Figure 3 and Figure 6 , the two-rotation-one-motion full-redundant driving parallel mechanism of the application is calculated by the degree of freedom G-K formula:

[0034]

[0035] Wherein, the order of the mechanism λ = 6, the number of components including the rack n = 14, the number of motion pairs g = 18, f i represents the degree of freedom of the i-th motion pair, the number of degrees of freedom of the moving pair, the rotating pair and the ball pair in the mechanism is 30, the over constraint number v = 6, the above parameters are sequentially brought into the formula, F represents the degree of freedom of the mechanism, and F = 3 is calculated. The driving number of the whole mechanism is 6, and the degree of freedom is 3. Since the driving number is greater than the degree of freedom, a redundant driving parallel mechanism is formed, which improves the stress characteristics of the mechanism, avoids the singular position of the mechanism, and at the same time, the over-constrained parallel mechanism greatly improves the stiffness and carrying capacity of the mechanism.

[0036] The following description, in conjunction with embodiments, further illustrates the symmetrical two-rotation-one-transfer fully redundant drive parallel mechanism containing a composite ball joint according to the present invention:

[0037] like Figure 3 and Figure 6 As shown, the fixed coordinate system O-XYZ is on fixed platform 1, and the moving coordinate system o-xyz is on moving platform 2. Triangles A1A2A3 and A4A5A6 are both equilateral triangles. The origin O is the center of equilateral triangle A1A2A3, and the X-axis is perpendicular to the line connecting A1A2. Triangle B1B2B3 is also an equilateral triangle, with the origin O being the center of B1B2B3, and the X-axis is perpendicular to the line connecting B1B2. Let OA... i =R1(i=1,2,3),oB i =r(i=1,2,3),OA i =R2(i=4,5,6), where points A1, A2, A3, A4, A5, A6, B1, B2 and B3 represent the hinge points 31, 41, 51, 61, 71, 81, 33, 43, and 53 of the first ball joint, respectively.

[0038] In the fixed coordinate system O-XYZ, the degrees of freedom of the general configuration of this mechanism are analyzed, and the results obtained are more generally applicable. Therefore, the coordinates of points B1, B2, and B3 are represented as (x1 y1 z1), (x2 y2 z2), and (x3 y3 z3), respectively, and the direction cosines of the sliding joints in branches A1B1, A2B2, A3B3, A4B4, A5B5, and A6B6 are represented as (d1 m1 n1), (d2 m2 n2), (d3 m3 n3), (d4 m4 n4), (d5 m5 n5), and (d6 m6 n6), respectively.

[0039] Branch A1B1 is an RPS branch, and the motion spiral system of this branch is represented as follows:

[0040]

[0041] The anti-helical system of this helical system (1.1) is:

[0042]

[0043] Similarly, we can obtain branch A. i B i The anti-spiral system of (i = 2, 3, 4, 5, 6) is:

[0044]

[0045] Simplify the screw system of formula (1.2), formula (1.3), obtain:

[0046]

[0047] From formula (1.4), three constraint forces are linearly independent, and three degrees of freedom of the moving platform 2 are constrained, the constrained motion includes two movements of the moving platform 2 and rotation around the normal line of the moving platform 2. Therefore, the mechanism is a three-degree-of-freedom parallel mechanism with two rotations and one movement, and can realize rotation of the moving platform 2 in the X-axis and Y-axis directions and movement in the Z-axis direction.

[0048] The above-described embodiments are only to describe the preferred embodiments of the present application, and do not limit the scope of the present application, and various modifications and improvements of the technical solutions of the present application made by those skilled in the art without departing from the design spirit of the present application shall fall within the protection scope determined by the claims of the present application.

Claims

1. A symmetrical, two-rotation, one-transfer, fully redundant drive parallel mechanism containing a composite ball joint, characterized in that, The fully symmetrical parallel drive mechanism includes a fixed platform, a moving platform, and kinematic chains. The moving platform is connected to the fixed platform through six kinematic chains, each with an identical RPS configuration. Each motion chain includes a drive rod and a ball joint. The first end of the drive rod is rotatably connected to the fixed platform via a revolute joint. The two connecting rods in the drive rod are slidably connected via a prismatic joint. Interfaces for rotatable connection of the drive rod are provided on both sides of the ball joint. The second end of the drive rod is rotatably connected to the moving platform via the ball joint. The six kinematic branches include a first branch, a second branch, a third branch, a fourth branch, a fifth branch, and a sixth branch. The first branch, the second branch, and the third branch are located at the triangular position of the fixed platform, and the fourth branch, the fifth branch, and the sixth branch are located within the fixed platform. The axis of the revolute joint of the first branch makes an angle of 30° with the X-axis, the axis of the revolute joint of the second branch makes an angle of 30° with the X-axis, and the axis of the revolute joint of the third branch is perpendicular to the X-axis. All revolute joints are located in the same plane. The axis of the revolute joint of the first branch is parallel to the axis of the revolute joint of the fourth branch, the axis of the revolute joint of the second branch is parallel to the axis of the revolute joint of the fifth branch, and the axis of the revolute joint of the third branch is parallel to the axis of the revolute joint of the sixth branch.

2. A symmetrical, two-rotation, one-transfer, fully redundant drive parallel mechanism containing a composite ball joint, characterized in that, The semi-symmetrical parallel drive mechanism includes a fixed platform, a moving platform, and kinematic chains. The moving platform is connected to the fixed platform via six kinematic chains, each with an identical RPS configuration. Each motion chain includes a drive rod and a ball joint. The first end of the drive rod is rotatably connected to the fixed platform via a revolute joint. The two connecting rods in the drive rod are slidably connected via a prismatic joint. Interfaces for rotatable connection of the drive rod are provided on both sides of the ball joint. The second end of the drive rod is rotatably connected to the moving platform via the ball joint. The six kinematic branches include a first branch, a second branch, a third branch, a fourth branch, a fifth branch, and a sixth branch. The first branch, the second branch, the third branch, the fourth branch, and the fifth branch are all located on the outer periphery of the fixed platform, and the sixth branch is located inside the fixed platform. The axis of the revolute joint of the first branch is perpendicular to the X-axis, the axis of the revolute joint of the second branch is parallel to the X-axis, and the axis of the revolute joint of the third branch is perpendicular to the X-axis. All revolute joints are located in the same plane. The axis of the revolute joint of the first branch is parallel to the axis of the revolute joint of the fourth branch, the axis of the revolute joint of the second branch is parallel to the axis of the revolute joint of the fifth branch, and the axis of the revolute joint of the third branch is parallel to the axis of the revolute joint of the sixth branch.

3. The symmetrical two-rotation-one-transfer fully redundant drive parallel mechanism with composite ball joint as described in claim 1 or 2, characterized in that, Both the fixed platform and the moving platform are equilateral triangular structures, and the centroids of the fixed platform and the moving platform are located on the same vertical line.

4. The symmetrical two-rotation-one-transfer fully redundant drive parallel mechanism with composite ball joint as described in claim 1 or 2, characterized in that, The first and fourth branches are connected to the moving platform via a shared first ball joint, the second and fifth branches are connected to the moving platform via a shared second ball joint, and the third and sixth branches are connected to the moving platform via a shared third ball joint.

5. The symmetrical two-rotation-one-transfer fully redundant drive parallel mechanism with composite ball joint as described in claim 4, characterized in that, The first branch, the fourth branch, and the fixed platform form an isosceles triangle, with the first branch and the fourth branch being the legs; the second branch, the fifth branch, and the fixed platform form an isosceles triangle, with the second branch and the fifth branch being the legs; the third branch, the sixth branch, and the fixed platform form an isosceles triangle, with the third branch and the sixth branch being the legs.

6. The symmetrical two-rotation-one-transfer fully redundant drive parallel mechanism with composite ball joint as described in claim 4, characterized in that, When the moving platform is parallel to the fixed platform, the projection of the first ball joint on the fixed platform is a point on the line connecting the revolute joint of the first branch and the revolute joint of the fourth branch; the projection of the second ball joint on the fixed platform is a point on the line connecting the revolute joint of the second branch and the revolute joint of the fifth branch; and the projection of the third ball joint on the fixed platform is a point on the line connecting the revolute joint of the third branch and the revolute joint of the fourth branch.

7. The symmetrical two-rotation-one-transfer fully redundant drive parallel mechanism with composite ball joint as described in claim 6, characterized in that, All sliding joints are linearly driven driving joints, while all revolute and ball joints are passive joints.

8. The symmetrical two-rotation-one-transfer fully redundant drive parallel mechanism with composite ball joint as described in claim 1 or 2, characterized in that, Based on the arrangement of the motion branches on the fixed platform, they are divided into fully symmetrical motion branches and semi-symmetrical motion branches. In the fully symmetrical type, the motion branches connected to the fixed platform are arranged in an equilateral triangle, with three motion branches located at the triangular part of the fixed platform and the other three motion branches located at the inner triangle of the fixed platform. In the semi-symmetrical type, five motion branches are located at the corners of the fixed platform, and the remaining one is located inside the fixed platform. The connection method between the fully symmetrical motion branches and the semi-symmetrical motion branches and the moving platform is exactly the same.

9. The symmetrical two-rotation-one-transfer fully redundant drive parallel mechanism with composite ball joint as described in claim 1 or 2, characterized in that, The formula for calculating its degrees of freedom GK is: ； Among them, the order of the mechanism Number of components including the frame The number of kinematic pairs , This represents the degree of freedom of the i-th kinematic pair. The mechanism has a total of 30 degrees of freedom across its prismatic, revolute, and ball joints. The number of over-constraints... Substituting the above parameters into the formula in sequence, M represents the degree of freedom of the mechanism, and we get M=3; the number of drives of the mechanism is 6 and the degree of freedom is 3. Since the number of drives is greater than the number of degrees of freedom, it constitutes a redundant drive parallel mechanism.

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