CN112847317A

CN112847317A - Three-dimensional space two-degree-of-freedom centrosome motion parallel mechanism

Info

Publication number: CN112847317A
Application number: CN202110302625.3A
Authority: CN
Inventors: 张锦平; 韩鑫; 姚进
Original assignee: Sichuan University
Current assignee: Sichuan University
Priority date: 2021-03-22
Filing date: 2021-03-22
Publication date: 2021-05-28
Anticipated expiration: 2041-03-22
Also published as: CN112847317B

Abstract

The invention relates to the technical field of parallel robots, in particular to a parallel mechanism which can realize two-degree-of-freedom remote center point motion in a three-dimensional space and has the characteristics of high rigidity and high load; comprises a frame, a main arm (2), and a plurality of groups of moving branched chains, wherein the moving branched chains can be in the forms of PS 'S, PS' RRR, PUS, PURRR, PRRS, PRRRR and the like; five groups of moving branched chains are necessary, the size of the first moving branched chain is obtained by amplifying the size of the second moving branched chain in equal proportion, the size of the third moving branched chain is obtained by amplifying the size of the fourth moving branched chain in equal proportion, the five groups of moving branched chains have two degrees of freedom, the prime mover is arranged on a moving pair formed by the moving branched chains and the frame, and the five groups of moving branched chains can constrain the main arm (2) to be constantly directed to a remote center point (0); in addition, some moving branched chains can be added to control the rotation of the main arm (2).

Description

Three-dimensional space two-degree-of-freedom centrosome motion parallel mechanism

Technical Field

The invention relates to the technical field of parallel robots, in particular to a parallel mechanism capable of realizing two-degree-of-freedom remote center point motion in a three-dimensional space.

Background

The remote center point mechanism refers to a mechanism capable of realizing remote center point movement, which is widely moved by a person in a minimally invasive surgery such as a laparoscopic surgery. The current method for realizing the movement of the remote center mainly comprises the steps of controlling multi-axis linkage by means of an algorithm, utilizing a composite parallelogram mechanism, utilizing an arc-shaped guide rail, utilizing a spherical mechanism, utilizing a passive hinge, utilizing a parallel mechanism and the like.

Chinese patent 201510243307.9 discloses a parallel mechanism capable of realizing spatial apocenter movement, which comprises a base, a movable platform, an instrument and three groups of movable branched chains, wherein the driving component of the mechanism is a moving pair on the three groups of movable branched chains, and the installation relationship of the rotating pairs among the movable branched chains, the instrument, the movable platform base and the like in the mechanism ensures that the instrument constantly passes through the apocenter. The mechanism is compact, but the rotary joint may be stressed greatly, and the prime mover is not suitable for using an electric power element such as a ball screw.

Chinese patent 202010165548.7 discloses a three-degree-of-freedom serial-parallel telecentric mechanism, which includes a double-parallelogram mechanism, a base, a first linear module, a second linear module, etc., the prime mover of the mechanism is the first linear module and the second linear module, wherein the first linear module controls the double-parallelogram mechanism to further realize the two-degree-of-freedom telecentric point motion, and the second linear module controls the end effector to linearly move. The disadvantage of this mechanism is that the stiffness of the double parallelogram mechanism may be low.

Disclosure of Invention

The invention aims to provide a parallel mechanism capable of realizing two-degree-of-freedom centrosome motion in a three-dimensional space, which is more convenient to control in a multi-axis linkage mode, has higher rigidity in a composite parallelogram mode and a spherical mechanism mode, and can solve or improve the problems of the parallel mechanism in the aspects of rigidity, stress and the like.

The invention provides a three-dimensional space two-degree-of-freedom centroclinal motion parallel mechanism which comprises a rack, a main arm and five groups of motion branched chains, wherein one ends of the five groups of motion branched chains are respectively connected with the rack, the other ends of the five groups of motion branched chains are respectively connected with the main arm, and a driving link of the mechanism is positioned on the motion branched chains; the mechanism has the functions of restraining the axis of the main arm to constantly point to the remote center point and controlling the main arm to realize the motion of the two-degree-of-freedom remote center point around the remote center point.

A three-dimensional space two-degree-of-freedom centrobaric motion parallel mechanism comprises a rack, a main arm and five groups of motion branched chains, wherein the five groups of motion branched chains comprise a first motion branched chain, a second motion branched chain, a third motion branched chain, a fourth motion branched chain and a fifth motion branched chain; the five groups of motion branched chains have similar structures, and each group of motion branched chains comprises a connecting rod, a two-degree-of-freedom rotation unit, a three-degree-of-freedom rotation unit and a moving unit; the frame, the mobile unit, the two-degree-of-freedom rotating unit, the connecting rod, the three-degree-of-freedom rotating unit and the main arm are sequentially connected; the main arm and the connecting rod can relatively rotate in three degrees of freedom in a three-dimensional space through the three-degree-of-freedom rotating unit; the two-degree-of-freedom rotation unit can be a ball pin pair, a universal joint and a serial joint formed by two rotation pairs with non-parallel axes, the three-degree-of-freedom rotation unit can be a serial joint formed by a ball pair and a rotation pair with non-coplanar three axes, and therefore the motion branched chain can be in the form of PS 'S, PS' RRR, PUS, PURRR, PRRS and PRRRRR.

The three-dimensional space two-degree-of-freedom centrobaric motion parallel mechanism has 5 degrees of freedom, each group of motion branched chains has 6 degrees of freedom, when a plurality of groups of motion branched chains are connected in parallel, each group of motion branched chains are connected in parallel, the newly added motion branched chains increase 6 degrees of freedom, but the motion branched chains can reduce 6 degrees of freedom when connected in parallel into the mechanism, so that the three-dimensional space two-degree-of-freedom centrobaric motion parallel mechanism has 6 degrees of freedom, and the rotation degree of freedom of a main arm is regarded as a local degree of freedom, so that the three-dimensional space two-degree-of-freedom centrobaric motion parallel mechanism has 5 degrees of freedom. Therefore, the moving pairs between the five groups of moving branched chains and the frame are prime moving parts, and the three-dimensional space two-degree-of-freedom centrocline motion parallel mechanism has a determined posture.

Five groups of moving branched chains form moving pairs with the frame through moving units respectively, and form ball pairs or rotating pairs with the main arm through three-degree-of-freedom rotating units respectively; the directions of the moving pairs formed by the five groups of moving branched chains and the rack point to a far center point, the directions of the moving pairs formed by the first moving branched chain, the second moving branched chain and the rack are the same, and the directions of the moving pairs formed by the third moving branched chain, the fourth moving branched chain and the rack are the same; when the three-degree-of-freedom rotating unit is a spherical pair, the central points of the spherical pairs formed by the five groups of moving branched chains and the main arm are on the same straight line, namely the axis of the main arm, and when the three-degree-of-freedom rotating unit is a serial joint formed by rotating pairs with non-coplanar axes, the directions of the axes of the rotating pairs formed by the five groups of moving branched chains and the main arm are the same and are collinear with the axis of the main arm.

The size of the first moving branched chain is obtained by amplifying the size of the second moving branched chain in equal proportion, and the proportion is equal to the proportion of the distance from the moving pair of the first moving branched chain to the far center point and the distance from the moving pair of the second moving branched chain to the far center point; the size of the third moving branched chain is obtained by amplifying the size of the fourth moving branched chain in equal proportion, and the proportion is equal to the proportion of the distance from the moving pair of the third moving branched chain to the far center point and the distance from the moving pair of the fourth moving branched chain to the far center point.

The three-dimensional space two-degree-of-freedom centrosome motion parallel mechanism meeting the relationship has the following solution: when the three-degree-of-freedom rotating unit is a spherical pair, the central points of the spherical pairs formed by the five groups of moving branched chains and the main arm are on the same straight line and are over the center of gravity; the first moving branched chain and the second moving branched chain are coplanar, and the third moving branched chain and the fourth moving branched chain are coplanar; a polygon formed by the first moving branched chain and the main arm is similar to a polygon formed by the second moving branched chain and the main arm, a polygon formed by the third moving branched chain and the main arm is similar to a polygon formed by the fourth moving branched chain and the main arm, and the distance between the main arm and a remote center point is unchanged; namely, the axis of the main arm points to the far center point, and the distance between the main arm and the far center point is unchanged; because the number of the prime movers of the three-dimensional space two-degree-of-freedom centrocentric motion parallel mechanism is equal to the degree of freedom of the mechanism, when the axis of the main arm is constantly directed to the centroidal point, the posture of the mechanism is stable.

The prime mover of the three-dimensional space two-degree-of-freedom centrocentric motion parallel mechanism is a moving pair between five groups of motion branched chains and the frame; the sliding pair is driven by a screw rod nut, a screw rod is arranged on the frame, and the nut is arranged on the moving branch chain; the sliding pair of the first moving branched chain and the sliding pair of the second moving branched chain are driven by the same motor, the motor drives two lead screws with different lead lengths to rotate at the same rotating speed, and the ratio of the lead lengths of the two lead screws is the ratio of the distance from the sliding pair of the first moving branched chain to a far center point to the distance from the sliding pair of the second moving branched chain to the far center point; the sliding pair of the third moving branched chain and the sliding pair of the fourth moving branched chain are driven by the same motor, the motor drives two lead screws with different lead lengths to rotate at the same rotating speed, and the ratio of the lead lengths of the two lead screws is the ratio of the distance from the sliding pair of the third moving branched chain to the far center point to the distance from the sliding pair of the fourth moving branched chain to the far center point; therefore, when the movable branch chain is installed at a proper initial position, the ratio of the distance from the moving pair of the first movable branch chain to the far center point to the distance from the moving pair of the second movable branch chain to the far center point is a constant value, and the ratio of the distance from the moving pair of the third movable branch chain to the far center point to the distance from the moving pair of the fourth movable branch chain to the far center point is a constant value.

Further, in order to improve the rigidity and strength of the mechanism and reduce the stress of the motion branch chain, a sixth motion branch chain can be added, and the form of the sixth motion branch chain can be PS 'S, PS' RRR, PUS, PURRR, PRRS and PRRRR; the sixth moving branch chain and the frame form a moving pair, and the sixth moving branch chain and the main arm form a rotating pair or a spherical pair; the driving part is a moving pair between the sixth moving branch chain and the frame, the moving pair is driven by a screw rod and a nut, the screw rod is arranged on the frame, and the nut is arranged on the moving branch chain; meanwhile, in order to simplify control, the size of the sixth motion branched chain is obtained by amplifying the size of the fifth motion branched chain in equal proportion, a moving pair of the fifth motion branched chain and a moving pair of the sixth motion branched chain are driven by the same motor, the motor drives two lead screws with different lead lengths to rotate at the same rotating speed, and the ratio of the lead lengths of the two lead screws is the ratio of the distance from the moving pair of the fifth motion branched chain to a far center point to the distance from the moving pair of the sixth motion branched chain to the far center point.

Furthermore, in order to control the rotation freedom degree of the main arm, a seventh kinematic branched chain can be added, and the form of the seventh kinematic branched chain can be PS 'U, PS' RR, PS 'S', PUS ', PURR, PUU, PRRU, PRRRRU and PRRS'; the seventh motion branch chain and the frame form a moving pair, and form a rotating pair, a ball pin pair or a universal joint with the main arm; the driving link is a moving pair between the seventh moving branch chain and the frame, the moving pair is driven by a screw rod and a nut, the screw rod is arranged on the frame, and the nut is arranged on the moving branch chain.

Furthermore, in order to control the rotation freedom degree of the main arm, a method of adding two motion branched chains can be adopted, the added eighth motion branched chain and the added ninth motion branched chain have the same form, and the form of the added eighth motion branched chain and the added ninth motion branched chain can be PUS, PRRS, PS 'S, PURRR, PRRRRR, PS' RRR; the eighth moving branch chain and the ninth moving branch chain form a moving pair with the frame respectively and are connected with the main arm through auxiliary parts; the direction of a moving pair formed by the eighth moving branched chain, the ninth moving branched chain and the rack points to a far center point, the axial direction of a rotating pair formed by the eighth moving branched chain, the ninth moving branched chain and the auxiliary part points to the far center point, and the included angle between the directions of the moving pair formed by the eighth moving branched chain, the ninth moving branched chain and the rack is equal to the included angle between the axial directions of the rotating pair formed by the eighth moving branched chain, the ninth moving branched chain and the auxiliary part; the distance from a moving pair formed by the eighth moving branched chain and the rack to a far center point is equal to the distance from a moving pair formed by the ninth moving branched chain and the rack to the far center point; the eighth moving branched chain and the ninth moving branched chain have the same size; the eighth moving branch and the ninth moving branch which satisfy the above conditions have the same posture, and the rotation angle of the main arm is kept constant.

Furthermore, in order to control the rotation freedom degree of the main arm, a twelfth kinematic branch chain can be added, and the form of the twelfth kinematic branch chain can be PS 'RRR, PS' S, PUS, PURRR, PRRS and PRRRRR; the twelfth motion branch chain and the frame form a moving pair and form a rotating pair or a spherical pair with the main arm; the driving part is a moving pair between the twelfth moving branch chain and the rack, the moving pair is driven by a screw rod and a nut, the screw rod is arranged on the rack, and the nut is arranged on the moving branch chain.

Furthermore, the prime mover of the three-dimensional space two-degree-of-freedom centrocentric motion parallel mechanism can not be arranged on a moving pair formed by the motion branched chain and the frame, but on the connecting rod of the motion branched chain, the posture of the mechanism is influenced by the length change of the connecting rod; the moving branched chain and the frame form a revolute pair or a universal joint, and the moving branched chain and the main arm form a revolute pair or a spherical pair; the kinematic branches may be in the form of UPS, UPRRR, RRPS, RRPRRR, S 'PS, S' PRRR; all of the aforementioned compositions, dimensional relationships, functions, and functions, still apply to this type of moving branch.

The invention has the beneficial effects that: 1) the number of the moving branched chains is large, and the rigidity, the strength and the precision of the mechanism are improved; 2) the power element of the mechanism is a screw rod nut, elements such as a screw rod, a motor and the like are arranged on the rack, and moving parts such as a moving branch chain, a main arm and the like have smaller volume, lighter weight and more compact structure; 3) the rotation of the main arm 2 can be controlled, and the rotation angle of the main arm 2 can be conveniently kept unchanged.

Drawings

Fig. 1 is a three-dimensional view of a mechanism having 5 sets of PRRRRR kinematic branches.

Fig. 2 is a three-dimensional view of the first moving branch mechanism.

Fig. 3 is a three-dimensional view of the second moving branch mechanism.

Fig. 4 is a three-dimensional view of the third moving branch mechanism.

Fig. 5 is a three-dimensional view of the fourth moving branch mechanism.

Fig. 6 is a three-dimensional view of a fifth kinematic chain mechanism.

Fig. 7 is a dimensional diagram of a mechanism having 5 sets of PRRRRR kinematic branches.

Fig. 8 is a three-dimensional view of a mechanism with 6 sets of PRRRRR kinematic branches.

Fig. 9 is a three-dimensional view of the seventh kinematic chain mechanism.

Fig. 10 is a three-dimensional view of the eighth moving branch and the ninth moving branch mechanism.

Fig. 11 is a mechanism size diagram of the eighth moving branch chain and the ninth moving branch chain.

Fig. 12 is a three-dimensional view of the mechanism of the twelfth moving branch.

Fig. 13 is a three-dimensional view of the mechanism of the tenth moving branch chain and the eleventh moving branch chain.

Fig. 14 is a mechanism size diagram of the tenth moving branch chain and the eleventh moving branch chain.

Description of the main symbols: the device comprises a frame base 1-1, a frame third boss 1-2, a frame second boss 1-3, a frame first boss 1-4, a frame fourth boss 1-6, a frame fifth boss 1-5, a frame main arm 2, a main arm auxiliary connecting part 2-1, a first moving branch chain sliding block 3-2, a first moving branch chain two-degree-of-freedom rotating unit 3-3, a first moving branch chain connecting rod 3-4, a first moving branch chain three-rotating part 3-5, a first moving branch chain three-two-rotating part 4-1, a second moving branch chain sliding block 4-2, a second moving branch chain two-rotating unit 4-3, a second moving branch chain connecting rod 4-4, a second moving branch chain three-rotating part 4-5, and a second moving branch chain three-two-rotating part 4-5, 5-1 of a sixth motion branched chain sliding block, 5-2 of a sixth motion branched chain two-degree-of-freedom rotating unit, 5-3 of a sixth motion branched chain connecting rod, 5-4 of a sixth motion branched chain three-degree-of-freedom rotating part, 5-5 of a sixth motion branched chain three-two rotating part, 6-1 of a fifth motion branched chain sliding block, 6-2 of a fifth motion branched chain two-degree-of-freedom rotating unit, 6-3 of a fifth motion branched chain connecting rod, 6-4 of a fifth motion branched chain three-degree-of-freedom rotating part, 6-5 of a fifth motion branched chain three-two rotating part, 7-1 of a third motion branched chain sliding block, 7-2 of a third motion branched chain two-degree-of freedom rotating unit, 7-3 of a third motion branched chain connecting rod, 7-4 of a third motion branched chain three-degree-of-freedom rotating part, 7-5 of a third motion branched chain three-two rotating, 8-1, a fourth moving branched chain sliding block, 8-2, a fourth moving branched chain two-degree-of-freedom rotating unit, 8-3, a fourth moving branched chain connecting rod, 8-4, a fourth moving branched chain three-rotating part, 8-5, a fourth moving branched chain three-two rotating part, 9-1, a seventh moving branched chain sliding block, 9-2, a seventh moving branched chain two-degree-of-freedom rotating unit, 9-3, a seventh moving branched chain connecting rod, 9-4, a seventh moving branched chain two-rotating part, 9-5, a seventh moving branched chain two-rotating part, 10-1, an eighth moving branched chain sliding block, 10-2, an eighth moving branched chain two-degree-of-freedom rotating unit, 10-3, an eighth moving branched chain connecting rod, 10-4, an eighth moving branched chain three-rotating part, 10-5, an eighth moving branched chain three-two-rotating part, 11-1 of a ninth motion branched chain sliding block, 11-2 of a ninth motion branched chain two-degree-of-freedom rotation unit, 11-3 of a ninth motion branched chain connecting rod, 11-4 of a ninth motion branched chain three-rotation part, 11-5 of a ninth motion branched chain three-two rotation part, 12-1 of a tenth motion branched chain fixing part, 12-2 of a tenth motion branched chain two-degree-of-freedom rotation unit, 12-3 of a tenth motion branched chain front connecting rod, 12-4 of a tenth motion branched chain rear connecting rod, 12-5 of a tenth motion branched chain three-rotation part, 12-6 of a tenth motion branched chain three-two rotation part, 13-1 of an eleventh motion branched chain fixing part, 13-2 of an eleventh motion branched chain two-degree-of freedom rotation unit, 13-3 of an eleventh motion branched chain front connecting rod, 13-4 of an eleventh motion branched chain rear connecting rod, 13-5. eleventh moving branch chain three-rotation part, 13-6. eleventh moving branch chain three-two rotation part, 14-1. twelfth moving branch chain slide block, 14-2. twelfth moving branch chain two-degree-of-freedom rotation unit, 14-3. twelfth moving branch chain connecting rod, 14-4. twelfth moving branch chain three-rotation part, 14-5. twelfth moving branch chain three-two rotation part, 14-6. twelfth moving branch chain auxiliary connecting piece, 0. remote center point, A1-2.12 line, A1-3.13 line, A1-4.14 line, A2.2 line, A3-2.32 line, A3-3.33 line, A3-4.34 line, A4-2.42 line, A4-3.43 line, A4-4.44 line, A6-2.62 line, A6-3.63 line, A7-4.64 line, A5392.62-3.72 line, A6853.73 line, A7-4.74 line, A8-2.82 line, A8-3.83 line, A8-4.84 line, A10-2.102 line, A10-3.103 line, A10-4.104 line, A10-5.105 line, A10-2.112 line, A10-10 line, A10-5.115 line, A10-2.122 line, A10-10 line, A10-3.133 line, A10-10 line, P10-1.31 point, P10-2.32 point, P10-3.33 point, P10-4.34 point, P10-1.41 point, P10-2.42 point, P72-3.43 point, P10-4.72 point, P10-3.72 point, P10-10 point, P10-3.72 point, P10-3.72 point, P10, P8-4.84, P10-1.101, P10-2.102, P10-3.103, P10-4.104, P11-1.111, P11-2.112, P11-3.113, P11-4.114, P12-1.121, P12-2.122, P12-3.123, P12-4.124, P13-1.131, P13-2.132, P13-3.133 and P13-4.134.

Detailed Description

The following detailed description of embodiments of the invention refers to the accompanying drawings.

A three-dimensional space two-degree-of-freedom centrosome motion parallel mechanism comprises a frame, a main arm 2, a first motion branch chain, a second motion branch chain, a third motion branch chain, a fourth motion branch chain and a fifth motion branch chain; each group of the moving branched chains is sequentially connected by a frame, a moving unit, a two-degree-of-freedom rotating unit, a connecting rod, a three-degree-of-freedom rotating unit and a main arm 2; the main arm and the connecting rod can relatively rotate in three degrees of freedom in a three-dimensional space through the three-degree-of-freedom rotating unit; the two-degree-of-freedom rotation unit can be a ball pin pair, a universal joint and a serial joint formed by two rotation pairs with non-parallel axes, the three-degree-of-freedom rotation unit can be a serial joint formed by a ball pair and a rotation pair with non-coplanar three axes, and therefore the motion branched chain can be in the form of PS 'S, PS' RRR, PUS, PURRR, PRRS and PRRRRR.

The figure shows a first embodiment disclosed by the invention, wherein the rack comprises a rack base 1-1, a rack third boss 1-2, a rack second boss 1-3 and a rack first boss 1-4; the machine frame third boss 1-2, the machine frame second boss 1-3 and the machine frame first boss 1-4 are fixedly connected with the machine frame base 1-1 respectively.

The first, second, third, fourth, and fifth moving branches are PRRRRR, for example.

As shown in fig. 2, the first moving branch chain comprises a first moving branch chain sliding block 3-1, a first moving branch chain two-degree-of-freedom rotating unit 3-2, a first moving branch chain connecting rod 3-3, a first moving branch chain three-rotating part 3-4 and a first moving branch chain three-two rotating part 3-5; the first boss 1-4 of the rack and the first moving branched chain sliding block 3-1 form a moving pair, and the direction of the moving pair is 14 lines A1-4 and points to a far center point 0; the first moving branch chain sliding block 3-1 and the first moving branch chain two-degree-of-freedom rotating unit 3-2 form a rotating pair; the first moving branch chain two-degree-of-freedom rotating unit 3-2 and the first moving branch chain connecting rod 3-3 form a rotating pair, the common perpendicular line between the rotating axis of the rotating pair and the 14 line A1-4 is a 32 line A3-2, the 32 line A3-2 intersects with the rotating pair at a 32 point P3-2, and the 32 line A3-2 intersects with the 14 line A1-4 at a 31 point P3-1; the first moving branch chain connecting rod 3-3 and the first moving branch chain three-rotating part 3-4 form a rotating pair; the first moving branch chain three-rotating part 3-4 and the first moving branch chain three-two-rotating part 3-5 form a rotating pair, the common perpendicular line between the rotating axis and the line 2A 2 is a line 34A 3-4, the line 34A 3-4 intersects with the rotating pair axis at a point 33P 3-3, and the line 34A 3-4 intersects with the line 2A 2 at a point 34P 3-4; the first moving branched chain three-two rotating parts 3-5 and the main arm 2 form a rotating pair, and the axis of the rotating pair is a2 line A2; the connecting line of the 32 point P3-2 and the 33 point P3-3 is a 33 line A3-3; the first moving branched chain sliding block 3-1 is a moving unit; the first motion branch chain two-degree-of-freedom rotation unit 3-2 is a two-degree-of-freedom rotation unit and is a serial joint formed by two rotation pairs with non-parallel axes; the three-rotation part 3-4 of the first moving branch chain and the three-two rotation part 3-5 of the first moving branch chain are combined into a three-degree-of-freedom rotation unit which is a serial joint formed by three rotation pairs with non-coplanar axes.

As shown in fig. 3, the second moving branch chain includes a second moving branch chain slider 4-1, a second moving branch chain two-degree-of-freedom rotation unit 4-2, a second moving branch chain connecting rod 4-3, a second moving branch chain three-rotation part 4-4, and a second moving branch chain three-two rotation part 4-5; a first boss 1-4 of the rack and a second moving branched chain sliding block 4-1 form a moving pair, and the direction of the moving pair is 14 lines A1-4 and points to a far center point 0; the second moving branch chain sliding block 4-1 and the second moving branch chain two-degree-of-freedom rotating unit 4-2 form a rotating pair; the second movement branched chain two-degree-of-freedom rotating unit 4-2 and the second movement branched chain connecting rod 4-3 form a rotating pair, the common perpendicular line between the rotating axis of the rotating pair and the 14 line A1-4 is a 42 line A4-2, the 42 line A4-2 intersects with the rotating pair at a 42 point P4-2, and the 42 line A4-2 intersects with the 14 line A1-4 at a 41 point P4-1; the second moving branch chain connecting rod 4-3 and the second moving branch chain three-rotating part 4-4 form a rotating pair; the third rotating part 4-4 of the second moving branch chain and the third rotating part 4-5 of the second moving branch chain form a rotating pair, the common perpendicular line between the rotating axis of the rotating pair and the line A2 is a line 44A 4-4, a line 44A 4-4 intersects with the rotating pair at a 43 point P4-3, and a line 44A 4-4 intersects with a line 2A 2 at a 44 point P4-4; the second moving branched chain three-two rotating parts 4-5 and the main arm 2 form a rotating pair, and the axis of the rotating pair is a2 line A2; the connection line of the point 42P 4-2 and the point 43P 4-3 is a line 43A 4-3; the second moving branched chain sliding block 4-1 is a moving unit; the second motion branched chain two-degree-of-freedom rotation unit 4-2 is a two-degree-of-freedom rotation unit and is a serial joint formed by two rotation pairs with non-parallel axes; the three-rotation part 4-4 of the second moving branch chain and the three-two rotation part 4-5 of the second moving branch chain are combined into a three-degree-of-freedom rotation unit which is a serial joint formed by three rotation pairs with non-coplanar axes.

As shown in fig. 4, the third moving branched chain includes a third moving branched chain slider 7-1, a third moving branched chain two-degree-of-freedom rotation unit 7-2, a third moving branched chain connecting rod 7-3, a third moving branched chain three-rotation part 7-4, and a third moving branched chain three-two rotation part 7-5; a third boss 1-2 of the rack and a third moving branched chain sliding block 7-1 form a moving pair, and the direction of the moving pair is a 12-line A1-2 and points to a far center point 0; the third moving branch chain sliding block 7-1 and the third moving branch chain two-degree-of-freedom rotating unit 7-2 form a rotating pair; the third moving branch chain two-degree-of-freedom rotating unit 7-2 and the third moving branch chain connecting rod 7-3 form a rotating pair, the common perpendicular line between the rotating axis of the rotating pair and the 12 line A1-2 is a 72 line A7-2, the 72 line A7-2 intersects with the rotating pair at a 72 point P7-2, and the 72 line A7-2 intersects with the 12 line A1-2 at a 71 point P7-1; the third moving branch chain connecting rod 7-3 and the third moving branch chain three-rotating part 7-4 form a rotating pair; the third moving branch chain three-rotation part 7-4 and the third moving branch chain three-two rotation part 7-5 form a rotation pair, the common perpendicular line between the rotation axis and the line 2A 2 is a line 74A 7-4, a line 74A 7-4 intersects with the rotation pair axis at a 73 point P7-3, and a line 74A 7-4 intersects with a line 2A 2 at a 74 point P7-4; the third motion branched chain three-two rotating part 7-5 and the main arm 2 form a rotating pair, and the axis of the rotating pair is a2 line A2; the connection line of the 72 point P7-2 and the 73 point P7-3 is a 73 line A7-3; the third moving branched chain sliding block 7-1 is a moving unit; the third motion branched chain two-degree-of-freedom rotation unit 7-2 is a two-degree-of-freedom rotation unit and is a serial joint formed by two rotation pairs with non-parallel axes; the third moving branch chain three-rotation part 7-4 and the third moving branch chain three-two-rotation part 7-5 are combined to form a three-degree-of-freedom rotation unit which is a serial joint formed by three rotation pairs with non-coplanar axes.

As shown in fig. 5, the fourth moving branch chain includes a fourth moving branch chain slider 8-1, a fourth moving branch chain two-degree-of-freedom rotation unit 8-2, a fourth moving branch chain connecting rod 8-3, a fourth moving branch chain three-rotation part 8-4, and a fourth moving branch chain three-two rotation part 8-5; a third boss 1-2 of the rack and a fourth moving branched chain sliding block 8-1 form a moving pair, and the direction of the moving pair is a 12-line A1-2 and points to a far center point 0; the fourth moving branch chain sliding block 8-1 and the fourth moving branch chain two-degree-of-freedom rotating unit 8-2 form a rotating pair; the fourth moving branch chain two-degree-of-freedom rotating unit 8-2 and the fourth moving branch chain connecting rod 8-3 form a rotating pair, the common perpendicular line between the rotating axis of the rotating pair and the 12 line A1-2 is 82 line A8-2, 82 line A8-2 intersects with the rotating pair at 82 point P8-2, and 82 line A8-2 intersects with 12 line A1-2 at 81 point P8-1; a fourth moving branch chain connecting rod 8-3 and a fourth moving branch chain three-rotating part 8-4 form a rotating pair; the third rotating part 8-4 of the fourth moving branch chain and the third rotating part 8-5 of the fourth moving branch chain form a rotating pair, the common perpendicular line between the rotating axis of the rotating pair and the line A2 is a line A8-4 of 84, the line A8-4 of 84 intersects with the rotating pair at a point P8-3 of 83, and the line A8-4 of 84 intersects with the line A2 of 2 at a point P8-4 of 84; the fourth moving branched chain three-two rotating part 8-5 and the main arm 2 form a rotating pair, and the axis of the rotating pair is a2 line A2; the connecting line of the 82 point P8-2 and the 83 point P8-3 is an 83 line A8-3; the fourth moving branched chain sliding block 8-1 is a moving unit; the fourth motion branched chain two-degree-of-freedom rotation unit 8-2 is a two-degree-of-freedom rotation unit and is a serial joint formed by two rotation pairs with non-parallel axes; the third rotating part 8-4 of the fourth moving branch chain and the third rotating part 8-5 of the fourth moving branch chain are combined to form a three-degree-of-freedom rotating unit which is a serial joint formed by three rotating pairs with non-coplanar axes.

As shown in fig. 6, the fifth moving branch chain includes a fifth moving branch chain slider 6-1, a fifth moving branch chain two-degree-of-freedom rotation unit 6-2, a fifth moving branch chain connecting rod 6-3, a fifth moving branch chain three-rotation part 6-4, and a fifth moving branch chain three-two rotation part 6-5; a second boss 1-3 of the rack and a fifth moving branched chain sliding block 6-1 form a moving pair, and the direction of the moving pair is a13 line A1-3 and points to a far center point 0; the fifth moving branch chain sliding block 6-1 and the fifth moving branch chain two-degree-of-freedom rotating unit 6-2 form a rotating pair; the fifth moving branch chain two-degree-of-freedom rotating unit 6-2 and the fifth moving branch chain connecting rod 6-3 form a rotating pair, the common perpendicular line between the rotating axis and the 13 line A1-3 is a 62 line A6-2, the 62 line A6-2 intersects with the rotating pair at a 62 point P6-2, and the 62 line A6-2 intersects with the 13 line A1-3 at a 61 point P6-1; a fifth moving branch chain connecting rod 6-3 and a fifth moving branch chain three-rotating part 6-4 form a rotating pair; the third rotating part 6-4 of the fifth moving branch chain and the third rotating part 6-5 of the fifth moving branch chain form a rotating pair, the common perpendicular line between the rotating axis of the fifth moving branch chain and the line A2 is a 64-line A6-4, the 64-line A6-4 intersects with the rotating pair at a 63-point P6-3, and the 64-line A6-4 intersects with the line A2 at a 64-point P6-4; the fifth moving branch chain three-two rotating part 6-5 and the main arm 2 form a rotating pair, and the axis of the rotating pair is a2 line A2; the connection line of the point 62P 6-2 and the point 63P 6-3 is a 63-line A6-3; the fifth moving branched chain sliding block 6-1 is a moving unit; the fifth movement branched chain two-degree-of-freedom rotation unit 6-2 is a two-degree-of-freedom rotation unit and is a serial joint formed by two rotation pairs with non-parallel axes; the third rotating component 6-4 of the fifth moving branch chain and the third rotating component 6-5 of the fifth moving branch chain are combined to form a three-degree-of-freedom rotating unit which is a serial joint formed by three rotating pairs with non-coplanar axes.

The three-dimensional space two-degree-of-freedom centrosome motion parallel mechanism has 5 degrees of freedom; each group of motion branched chains is provided with a moving pair and five revolute pairs with 6 degrees of freedom, when a plurality of groups of motion branched chains are connected in parallel, each group of motion branched chains is connected in parallel, the newly added motion branched chain increases 6 degrees of freedom, but the motion branched chains can reduce 6 degrees of freedom when being connected in parallel in the mechanism, so that the three-dimensional space two-degree-of-freedom centrobaric motion parallel mechanism has 6 degrees of freedom; the main arm 2 is connected with all the moving branched chains by the rotating pairs, so that the autorotation freedom degree of the main arm 2 can be regarded as the local freedom degree, and the three-dimensional space two-freedom-degree centrobaric motion parallel mechanism has 5 freedom degrees. The moving pairs between the five groups of moving branched chains and the frame are prime moving parts, the autorotation freedom degree of the main arm 2 is regarded as a local freedom degree, and the three-dimensional space two-freedom-degree centroidal motion parallel mechanism has a determined posture.

As shown in FIG. 7, the size of the first moving branch is scaled up from the size of the second moving branch by an equal ratio, which is expressed by the ratio of the length of line 32A 3-2 to line 42A 4-2, the ratio of the length of line 33A 3-3 to line 43A 4-3, the ratio of the length of line 34A 3-4 to line 44A 4-4 being equal and constant K1; the size of the third moving branch is scaled up from the size of the fourth moving branch by an equal ratio, which is expressed by the ratio of the length of line 72A 7-2 to line 82A 8-2, the ratio of the length of line 73A 7-3 to line 83A 8-3, the ratio of the length of line 74A 7-4 to line 84A 8-4 being equal and constant K2.

The prime mover of the three-dimensional space two-degree-of-freedom centrocentric motion parallel mechanism is a moving pair between five groups of motion branched chains and the frame; the sliding pair is driven by a screw rod nut, a screw rod is respectively arranged on a boss 1-2 of a rack, a boss 1-3 of a rack and a boss 1-4 of a rack, and the nut is respectively arranged on a first moving branched chain sliding block 3-1, a second moving branched chain sliding block 4-1, a third moving branched chain sliding block 7-1, a fourth moving branched chain sliding block 8-1 and a fifth moving branched chain sliding block 6-1; the sliding pair of the first moving branched chain and the sliding pair of the second moving branched chain are driven by the same motor, the motor drives two lead screws with different lead lengths to rotate at the same rotating speed, the ratio of the lead lengths of the two lead screws is K1, namely the ratio of the displacement of the first moving branched chain sliding block 3-1 to the displacement of the second moving branched chain sliding block 4-1 is K1; the sliding pair of the third moving branched chain and the sliding pair of the fourth moving branched chain are driven by the same motor, the motor drives two lead screws with different lead lengths to rotate at the same rotating speed, the ratio of the lead lengths of the two lead screws is K2, namely the ratio of the displacement of the third moving branched chain sliding block 7-1 to the displacement of the fourth moving branched chain sliding block 8-1 is K2; with proper initial position installation, the ratio of the distance from point 31P 3-1 to distal point 0 to the distance from point 41P 4-1 to distal point 0 is K1, and the ratio of the distance from point 71P 7-1 to distal point 0 to the distance from point 81P 8-1 to distal point 0 is K2.

The three-dimensional space two-degree-of-freedom centrosome motion parallel mechanism meeting the relationship has the following solution in a certain space range: the polygon P3-1-0-P3-4-P3-3-P3-2 formed by the first moving branch chain and the main arm 2 is similar to and coplanar with the polygon P4-1-0-P4-4-P4-3-P4-2 formed by the second moving branch chain and the main arm 2, and the similarity ratio is K1; the polygon 0-P7-1-P7-2-P7-3-P7-4 formed by the third moving branch chain and the main arm 2 is similar to and coplanar with the polygon 0-P8-1-P8-2-P8-3-P8-4 formed by the fourth moving branch chain and the main arm 2, and the similarity ratio is K2; line 2A 2 crosses over 0; the polygon similarity adds two constraints to the mechanism, the degree of freedom of the three-dimensional two-degree-of-freedom centrocentric motion parallel mechanism is 3, the number of the prime movers is 3, and the solution is stable.

Since the similarity ratio between the polygon P3-1-0-P3-4-P3-3-P3-2 formed by the first moving branch and the main arm 2 and the polygon P4-1-0-P4-4-P4-3-P4-2 formed by the second moving branch and the main arm 2 is that the distance between K1, 34 point P3-4 and 44 point P4-4 is constant, the distance between 44 point P4-4 and the far center point 0 is constant, and it can be said that the distance between 84 point P8-4 and the far center point 0 is constant, and the distance between the main arm 2 and the far center point 0 is constant.

When the moving branched chains are in the forms of PS 'S, PS' RRR, PUS, PURRR and PRRS, each group of moving branched chains also has 6 degrees of freedom, five groups of branched chains have 6 degrees of freedom after being connected in parallel, and the rotation of the main arm 2 is considered as the local degree of freedom, so that the three-dimensional space two-degree-of-freedom centromere motion parallel mechanism has 5 degrees of freedom. The polygon similarity adds two constraints to the mechanism, the degree of freedom of the three-dimensional two-degree-of-freedom remote center point motion parallel mechanism is 3, the number of the prime movers is 3, and the three-dimensional two-degree-of-freedom remote center point motion parallel mechanism has a determined posture.

If the two-degree-of-freedom rotating unit is a universal joint or a ball-and-pin pair, the length of a 32 line A3-2, a 42 line A4-2, a 62 line A6-2, a 72 line A7-2 and an 82 line A8-2 is zero, a 31 point P3-1 is coincided with a 32 point P3-2, a 41 point P4-1 is coincided with a 42 point P4-2, a 61 point P6-1 is coincided with a 62 point P6-2, a 71 point P7-1 is coincided with a 72 point P7-2, and a 81 point P8-1 is coincided with a 82 point P8-2; if the three-degree-of-freedom rotating unit is a spherical pair, the length of a 34 line A3-4, a 44 line A4-4, a 64 line A6-4, a 74 line A7-4 and an 84 line A8-4 is zero, a 33 point P3-3 is coincided with a 34 point P3-4, a 43 point P4-3 is coincided with a 44 point P4-4, a 63 point P6-3 is coincided with a 64 point P6-4, a 73 point P7-3 is coincided with a 74 point P7-4, and an 83 point P8-3 is coincided with a 84 point P8-4; other parameters such as the size relationship of the mobile branches are consistent with the case where the branches are in the form of PRRRRR.

If the two-degree-of-freedom rotating unit is a universal joint or a ball pin pair, the three-degree-of-freedom rotating unit is a ball pair, a driving link of the three-dimensional space two-degree-of-freedom centrobaric motion parallel mechanism is a moving unit of a moving branched chain, the moving unit enables the moving branched chain and a rack to form a moving pair, and the moving pair direction is consistent with the situation when the moving branched chain is PRRRRR, the moving pair direction of the first moving branched chain and the second moving branched chain is 14 lines A1-4, the moving pair direction of the third moving branched chain and the fourth moving branched chain is 12 lines A1-2, and the moving pair direction of the fifth moving branched chain is 13 lines A1-3; the centre of the spherical pair formed between the kinematic branch and the main arm 2 is on line 2 a2, line 2 a2 pointing towards the apothem 0.

In summary, when the kinematic branches are in the form of PS 'S, PS' RRR, PUS, PURRR, PRRS, and PRRRRR, 2 lines A2 all may be constantly pointing towards 0.

Fig. 8 is a second embodiment of the present disclosure, on the basis of the first embodiment, in order to improve the rigidity and strength of the mechanism and reduce the stress of the moving branch, a sixth moving branch may be added, and the sixth moving branch may be in the form of PS 'S, PS' RRR, PUS, PURRR, PRRS, PRRRRR; taking PRRRRR as an example, the sixth moving branched chain comprises a sixth moving branched chain sliding block 5-1, a sixth moving branched chain two-degree-of-freedom rotating unit 5-2, a sixth moving branched chain connecting rod 5-3, a sixth moving branched chain three-rotating part 5-4 and a sixth moving branched chain three-two rotating part 5-5; a second boss 1-3 of the rack and a sixth moving branch chain sliding block 5-1 form a sliding pair, the sixth moving branch chain sliding block 5-1 and a second degree of freedom rotating unit 5-2 of a sixth moving branch chain form a rotating pair, the second degree of freedom rotating unit 5-2 of the sixth moving branch chain and a sixth moving branch chain connecting rod 5-3 form a rotating pair, the sixth moving branch chain connecting rod 5-3 and a third rotating part 5-4 of the sixth moving branch chain form a rotating pair, the third rotating part 5-4 of the sixth moving branch chain and a third rotating part 5-5 of the sixth moving branch chain form a rotating pair, and the third rotating part 5-5 of the sixth moving branch chain and a main arm 2 form a rotating pair; the sixth motion branched chain two-degree-of-freedom rotation unit 5-2 is a two-degree-of-freedom rotation unit and is a serial joint formed by two rotation pairs with non-parallel axes; the third rotating part 5-4 of the sixth moving branch chain and the third rotating part 5-5 of the sixth moving branch chain are combined into a three-degree-of-freedom rotating unit which is a serial joint formed by three rotating pairs with non-coplanar axes.

Furthermore, in order to simplify the control, the size of the sixth motion branched chain is obtained by amplifying the size of the fifth motion branched chain in equal proportion, a moving pair of the fifth motion branched chain and a moving pair of the sixth motion branched chain are driven by the same motor, the motor drives two lead screws with different leads to rotate at the same rotating speed, and the lead ratio of the two lead screws is the ratio of the distance from the moving pair of the fifth motion branched chain to the far center point 0 to the distance from the moving pair of the sixth motion branched chain to the far center point 0.

The third embodiment disclosed by the invention is based on the first embodiment, in order to control the rotation freedom degree of the main arm 2, a seventh moving branch chain can be added, and the form of the seventh moving branch chain can be PS 'S', PS 'RR, PS' U, PUS ', PURR, PUU, PRRS', PRRU and PRRRR; taking PRRRR as an example, as shown in fig. 9, the seventh moving branch includes a seventh moving branch slider 9-1, a seventh moving branch two-degree-of-freedom rotation unit 9-2, a seventh moving branch link 9-3, a seventh moving branch two-rotation component 9-4, and a seventh moving branch two-rotation component 9-5; a second boss 1-3 of the rack and a seventh moving branch chain sliding block 9-1 form a moving pair, a seventh moving branch chain sliding block 9-1 and a second degree of freedom rotating unit 9-2 of a seventh moving branch chain form a rotating pair, the second degree of freedom rotating unit 9-2 of the seventh moving branch chain and a seventh moving branch chain connecting rod 9-3 form a rotating pair, the seventh moving branch chain connecting rod 9-3 and a second rotating part 9-4 of the seventh moving branch chain form a rotating pair, the second rotating part 9-4 of the seventh moving branch chain and a second rotating part 9-5 of the seventh moving branch chain form a rotating pair, and the second rotating part 9-5 of the seventh moving branch chain is fixedly connected with the main arm 2; the seventh motion branched chain two-degree-of-freedom rotation unit 9-2 is a two-degree-of-freedom rotation unit and is a serial joint formed by two rotation pairs with non-parallel axes; the second rotating part 9-4 of the seventh moving branch chain is a two-degree-of-freedom rotating unit and is a serial joint formed by two rotating pairs with non-parallel axes.

The fourth embodiment disclosed in the present invention is based on the first embodiment, in order to control the rotation degree of freedom of the main arm 2, an eighth moving branch and a ninth moving branch may be added, and have the same form, and the form of the eighth moving branch and the ninth moving branch may be PS 'S, PS' RRR, PUS, PURRR, PRRS, PRRRRR; taking PRRRRR as an example, as shown in fig. 10, the eighth moving branch includes an eighth moving branch slider 10-1, an eighth moving branch two-degree-of-freedom rotation unit 10-2, an eighth moving branch link 10-3, an eighth moving branch tri-rotation component 10-4, and an eighth moving branch tri-rotation component 10-5; the ninth moving branched chain comprises a ninth moving branched chain sliding block 11-1, a ninth moving branched chain two-degree-of-freedom rotating unit 11-2, a ninth moving branched chain connecting rod 11-3, a ninth moving branched chain three-rotating part 11-4 and a ninth moving branched chain three-two-rotating part 11-5.

As shown in fig. 10, a moving pair is formed by the fourth boss 1-6 of the frame and the eighth moving branched chain slider 10-1, and the direction of the moving pair is a 16-line a1-6 pointing to a far center point 0; the eighth moving branch chain sliding block 10-1 and the eighth moving branch chain two-degree-of-freedom rotating unit 10-2 form a rotating pair; the eighth moving branched chain two-degree-of-freedom rotating unit 10-2 and the eighth moving branched chain connecting rod 10-3 form a rotating pair, the common perpendicular line between the rotating axis and the 16 line A1-6 is a 102 line A10-2, the 102 line A10-2 intersects with the rotating pair at a 102 point P10-2, and the 102 line A10-2 intersects with the 16 line A1-6 at a 101 point P10-1; the eighth moving branch connecting rod 10-3 and the eighth moving branch three-rotating part 10-4 form a revolute pair; the eighth moving branch chain three-to-one rotating part 10-4 and the eighth moving branch chain three-to-two rotating part 10-5 form a rotating pair; the eighth moving branch chain three-two rotating component 10-5 and the main arm auxiliary connecting part 2-1 form a rotating pair, the common perpendicular line of the rotating axis of the rotating pair formed by the eighth moving branch chain three-two rotating component 10-4 and the eighth moving branch chain three-two rotating component 10-5 is a 104 line A10-4, the 104 line A10-4 intersects with the former axis at a 104 point P10-4, and the 103 line A10-3 intersects with the latter axis at a 103 point P10-3; the eighth moving branched chain three-two rotating part 10-5 and the main arm auxiliary connecting part 2-1 form a rotating pair, and the axis of the rotating pair is a 105 line A10-5 and points to a far center point 0; the main arm auxiliary connecting part 2-1 and the main arm 2 form fixed connection; the connecting line of the point P10-2 at 102 and the point P10-3 at 103 is a line A10-3; the eighth moving branch two-degree-of-freedom rotation unit 10-2 is a two-degree-of-freedom rotation unit and is a serial joint formed by two rotation pairs with non-parallel axes; the third rotating part 10-4 of the eighth moving branch chain and the third rotating part 10-5 of the eighth moving branch chain are combined to form a three-degree-of-freedom rotating unit which is a serial joint formed by rotating pairs with non-coplanar three axes.

As shown in FIG. 10, a fifth boss 1-5 of the frame and a ninth moving branched chain slider 11-1 form a moving pair, and the direction of the moving pair is a 15 line A1-5 pointing to a far center point 0; the ninth motion branched chain sliding block 11-1 and the ninth motion branched chain two-degree-of-freedom rotation unit 11-2 form a rotation pair; the ninth moving branch two-degree-of-freedom rotating unit 11-2 and the ninth moving branch connecting rod 11-3 form a rotating pair, the common perpendicular line between the rotating axis and the 15 line A1-5 is a 112 line A11-2, the 112 line A11-2 intersects with the rotating pair axis at a 112 point P11-2, and the 112 line A11-2 intersects with the 15 line A1-5 at a 111 point P11-1; a ninth moving branch chain connecting rod 11-3 and a ninth moving branch chain three-rotation part 11-4 form a rotation pair; a revolute pair is formed by the third rotary part 11-4 of the ninth kinematic branch chain and the third rotary part 11-5 of the ninth kinematic branch chain; the ninth moving branch chain three-two rotating part 11-5 and the main arm auxiliary connecting part 2-1 form a rotating pair, the common perpendicular line of the rotating axis of the rotating pair formed by the ninth moving branch chain three-two rotating part 11-4 and the ninth moving branch chain three-two rotating part 11-5 is 114 line A11-4, 114 line A11-4 intersects with the former axis at 114 point P11-4, and 113 line A11-3 intersects with the latter axis at 113 point P11-3; the ninth motion branched chain three-two rotating part 11-5 and the main arm auxiliary connecting part 2-1 form a rotating pair, and the axis of the rotating pair is a 115 line A11-5 and points to a remote center point 0; the connection line of the 112 point P11-2 and the 113 point P11-3 is a 113 line A11-3; the ninth motion branched chain two-degree-of-freedom rotation unit 11-2 is a two-degree-of-freedom rotation unit and is a serial joint formed by two rotation pairs with non-parallel axes; the third rotating component 11-4 of the ninth moving branch chain and the third rotating component 11-5 of the ninth moving branch chain are combined to form a three-degree-of-freedom rotating unit which is a serial joint formed by three rotating pairs with non-coplanar axes.

The driving links of the eighth moving branched chain and the ninth moving branched chain are moving pairs between the eighth moving branched chain and the rack respectively, the moving pairs are driven by lead screw nuts, the lead screw is installed on the rack, and the nuts are installed on the moving branched chains.

As shown in fig. 11, the angle between the eighth moving branch and the ninth moving branch and the direction of the sliding pair formed by the frame is equal to the angle between the eighth moving branch and the ninth moving branch and the direction of the axis of the revolute pair formed by the auxiliary component, which is embodied in that the angle between the 16 line a1-6 and the 15 line a1-5 is equal to the angle between the 105 line a10-5 and the 115 line a11-5, because the angle between the 16 line a1-6 and the 15 line a1-5 is fixed, the distance between the main arm 2 and the apothem 0 is fixed, and the angle between the 105 line a10-5 and the 115 line a11-5 is fixed, this is achieved; the distance from the moving pair formed by the eighth moving branched chain and the rack to the far center point is equal to the distance from the moving pair formed by the ninth moving branched chain and the rack to the far center point, which is specifically represented by the distance from a 101 point P10-1 to the far center point 0 being equal to the distance from a 111 point P11-1 to the far center point 0; the eighth moving branch has the same size as the ninth moving branch, which is represented by the length of line A10-2 being equal to 112 line A11-2, the length of line A10-3 being equal to 113 line A11-3, the length of line A10-4 being equal to 114 line A11-4; the distance from the point 104P 10-4 to the point 0 of remote center is equal to the distance from the point 114P 11-4 to the point 0 of remote center, which is achievable because the distance from the main arm 2 to the point 0 of remote center is fixed and the main arm auxiliary link element 2-1 is fixedly connected to the main arm 2.

The eighth moving branched chain and the ninth moving branched chain which satisfy the above relationship have the following solutions within a certain space range: the polygon 0-P10-1-P10-2-P10-3-P10-4 is totally equal to the polygon 0-P11-1-P11-2-P11-3-P11-4; the quadrangle formed by the point P10-4 at 104, the point P10-1 at 101, the point P11-1 at 111 and the point P11-4 at 114 is an isosceles trapezoid; the line formed by point 104, point P10-4, point 114, point P11-4 is parallel to the line formed by point 101, point P10-1, point 111, point P11-1.

According to the first embodiment, the degree of freedom of rotation of the main arm 2 is uncertain, corresponding to the degree of freedom of the main arm 2 being 1; the eighth moving branch chain has 6 degrees of freedom, and on the basis of the first embodiment, after the eighth moving branch chain is connected in parallel, the degree of freedom of the system is 1; the driving link of the eighth moving branch chain is a moving pair formed by a fourth boss 1-6 of the frame and a sliding block 10-1 of the eighth moving branch chain, so that the autorotation of the main arm 2 is controlled; when the eighth moving branch and the ninth moving branch work together, the distance between the point P10-1 at 101 and the far center point 0 is equal to the distance between the point P11-1 at 111 and the far center point 0, so that the rotation angle of the main arm 2 can be kept unchanged, because the line formed by the points P10-4 at 104 and P11-4 at 114 is parallel to the line formed by the points P10-1 at 101 and P11-1 at 111.

When the eighth moving branch chain and the ninth moving branch chain are in the forms of PS 'S, PS' RRR, PUS, PURRR, PRRS, the eighth moving branch chain and the ninth moving branch chain both have 6 degrees of freedom, and on the basis of the first embodiment, after the eighth moving branch chain is connected in parallel, the eighth moving branch chain can control the degree of freedom of rotation of the main arm 2, and then the ninth moving branch chain is connected in parallel, and the ninth moving branch chain is matched with the movement of the eighth moving branch chain to control the rotation of the main arm 2.

If the two-degree-of-freedom rotating unit is a universal joint or a ball pin pair, the length of a line A10-2 of 102 and a line A11-2 of 112 is zero, a point P10-1 of 101 is coincided with a point P10-2 of 102, and a point P11-1 of 111 is coincided with a point P11-2 of 112; if the three-degree-of-freedom rotating unit is a ball pair, the length of a line A10-4 of 104 and a line A11-4 of 114 is zero, and a point P10-3 of 103 is superposed with a point P10-4 of 104; other parameters such as the size relationship of the mobile branches are consistent with the case where the branches are in the form of PRRRRR.

If the two-degree-of-freedom rotating unit is a universal joint or a ball pin pair, the three-degree-of-freedom rotating unit is a ball pair, the motive power parts of the eighth moving branched chain and the ninth moving branched chain are moving units of the moving branched chains, the moving units enable the moving branched chains and the rack to form moving pairs, the moving pairs are consistent with the situation when the moving branched chain is in a PRRRRR mode, the moving pair direction of the eighth moving branched chain is a 16-line A1-6, and the moving pair direction of the ninth moving branched chain is a 15-line A1-5; the center of the ball pair formed between the eighth moving branch and the main arm auxiliary link part 2-1 is on the line a10-5 105, and the center of the ball pair formed between the ninth moving branch and the main arm auxiliary link part 2-1 is on the line a11-5 115.

In summary, when the eighth and ninth kinematic branches are in the form of PS 'S, PS' RRR, PUS, PURRR, PRRS, PRRRRR, the line formed by points P10-4 at 104 and P11-4 at 114 is parallel to the line formed by points P10-1 at 101 and P11-1 at 111.

The fifth embodiment disclosed by the invention is based on the first embodiment, in order to control the rotation freedom degree of the main arm 2, a twelfth kinematic branch chain can be added, and the form of the twelfth kinematic branch chain can be PS 'RRR, PS' S, PUS, PURRR, PRRS and PRRRRR; taking PRRRRR as an example, as shown in fig. 12, the twelfth moving branch chain includes a twelfth moving branch chain slider 14-1, a twelfth moving branch chain two-degree-of-freedom rotation unit 14-2, a twelfth moving branch chain connecting rod 14-3, a twelfth moving branch chain three-rotation part 14-4, a twelfth moving branch chain three-two rotation part 14-5, and a twelfth moving branch chain auxiliary connecting part 14-6; a second boss 1-3 of the rack and a twelfth motion branch chain sliding block 14-1 form a sliding pair, a twelfth motion branch chain sliding block 14-1 and a twelfth motion branch chain two-degree-of-freedom rotating unit 14-2 form a rotating pair, a twelfth motion branch chain two-degree-of-freedom rotating unit 14-2 and a twelfth motion branch chain connecting rod 14-3 form a rotating pair, a twelfth motion branch chain connecting rod 14-3 and a twelfth motion branch chain three-rotating part 14-4 form a rotating pair, a twelfth motion branch chain three-rotating part 14-4 and a twelfth motion branch chain three-two-rotating part 14-5 form a rotating pair, a twelfth motion branch chain three-two-rotating part 14-5 and a twelfth motion branch chain auxiliary connecting part 14-6 form a rotating pair, and the twelfth motion branch chain auxiliary connecting part 14-6 is fixedly connected with the main arm 2; the twelfth kinematic branched chain two-degree-of-freedom rotation unit 14-2 is a two-degree-of-freedom rotation unit and is a serial joint formed by two rotation pairs with non-parallel axes; the third rotating component 14-4 of the twelfth moving branch chain and the third rotating component 14-5 of the twelfth moving branch chain are combined to form a three-degree-of-freedom rotating unit which is a serial joint formed by three rotating pairs with non-parallel axes.

The sixth embodiment disclosed by the invention is a modification of all the embodiments, the primary driving piece of the three-dimensional space two-degree-of-freedom centrocentric motion parallel mechanism can not be arranged on a moving pair formed by a motion branched chain and a rack, but on a connecting rod of the motion branched chain, the posture of the mechanism is influenced by the length change of the connecting rod; take the form of RRPRRR as an example; as shown in fig. 13, the tenth moving branched chain includes a tenth moving branched chain fixing part 12-1, a tenth moving branched chain two-degree-of-freedom rotating unit 12-2, a tenth moving branched chain front link 12-3, a tenth moving branched chain rear link 12-4, a tenth moving branched chain three-rotating part 12-5, and a tenth moving branched chain three-two-rotating part 12-6; a second boss 1-3 of the rack is fixedly connected with a tenth moving branch fixing part 12-1; the tenth moving branch fixing part 12-1 and the tenth moving branch two-degree-of-freedom rotating unit 12-2 form a rotating pair, and the axis of the rotating pair is a 13-line A1-3 and points to a far center point 0; the tenth motion branch two-degree-of-freedom rotation unit 12-2 and the tenth motion branch front connecting rod 12-3 form a rotation pair, the common perpendicular line between the rotation axis and the line 13A 1-3 is a line 122A 12-2, a line 122A 12-2 intersects with the rotation pair axis at a point 122P 12-2, and a line 122A 12-2 intersects with a line 13A 1-3 at a point 121P 12-1; the tenth moving branch front connecting rod 12-3 and the tenth moving branch rear connecting rod 12-4 form a moving pair; the rear connecting rod 12-4 of the tenth moving branch chain and the third rotating part 12-5 of the tenth moving branch chain form a rotating pair, the third rotating part 12-5 of the tenth moving branch chain and the third rotating part 12-6 of the tenth moving branch chain form a rotating pair, the common perpendicular line of the rotating axis of the rotating pair and the line A2 is a line A12-4 of 124, the line A12-4 of 124 and the rotating pair intersects at a point P12-3 of 123, and the line A12-4 of 124 and the line A2 of 2 intersect at a point P12-4 of 124; the third rotating part 12-6 of the tenth moving branched chain and the main arm 2 form a rotating pair, and the rotating axis of the rotating pair is a 2-line A2; the tenth motion branched chain two-degree-of-freedom rotation unit 12-2 is a two-degree-of-freedom rotation unit and is a serial joint formed by two rotation pairs with non-parallel axes; the third rotating component 12-5 of the tenth moving branch chain and the third rotating component 12-6 of the tenth moving branch chain are combined to form a three-degree-of-freedom rotating unit which is a serial joint formed by rotating pairs with non-coplanar three axes.

As shown in fig. 13, the eleventh moving branched chain includes an eleventh moving branched chain fixing part 13-1, an eleventh moving branched chain two-degree-of-freedom rotating unit 13-2, an eleventh moving branched chain front link 13-3, an eleventh moving branched chain rear link 13-4, an eleventh moving branched chain three-rotating part 13-5, and an eleventh moving branched chain three-two-rotating part 13-6; a second boss 1-3 of the rack is fixedly connected with an eleventh moving branch fixing part 13-1; the eleventh moving branch fixing part 13-1 and the eleventh moving branch two-degree-of-freedom rotating unit 13-2 form a rotating pair, and the axis of the rotating pair is a13 line A1-3 and points to a far center point 0; the eleventh movement branched chain two-degree-of-freedom rotating unit 13-2 and the eleventh movement branched chain front connecting rod 13-3 form a rotating pair, the common perpendicular line between the rotating axis and the line 13A 1-3 is a line 132A 13-2, the line 132A 13-2 intersects with the rotating pair at a point 132P 13-2, and the line 132A 13-2 intersects with the line 13A 1-3 at a point 131P 13-1; the eleventh motion branched chain front connecting rod 13-3 and the eleventh motion branched chain rear connecting rod 13-4 form a moving pair; the eleventh movement branched chain rear connecting rod 13-4 and the eleventh movement branched chain three-rotation part 13-5 form a rotation pair, the eleventh movement branched chain three-rotation part 13-5 and the eleventh movement branched chain three-two rotation part 13-6 form a rotation pair, the common perpendicular line of the rotation axis and the 2 line A2 is a 134 line A13-4, the 134 line A13-4 and the rotation pair axis are intersected at a 133 point P13-3, and the 134 line A13-4 and the 2 line A2 are intersected at a 134 point P13-4; the eleventh moving branched chain three-two rotating part 13-6 and the main arm 2 form a rotating pair, and the rotating axis of the rotating pair is a 2-line A2; the eleventh motion branched chain two-degree-of-freedom rotation unit 13-2 is a two-degree-of-freedom rotation unit and is a serial joint formed by two rotation pairs with non-parallel axes; the eleventh moving branch chain three-rotation part 13-5 and the eleventh moving branch chain three-two-rotation part 13-6 are combined to form a three-degree-of-freedom rotation unit, and the three-degree-of-freedom rotation unit is a serial joint formed by three rotation pairs with non-coplanar axes.

For the first embodiment, when the form of the kinematic chain is converted from PRRRR to RRPRRR, taking the first kinematic chain as an example, the first kinematic chain is replaced by a tenth kinematic chain, and 31 points P3-1, 32 points P3-2, 33 points P3-3 and 34 points P3-4 are replaced by 121 points P12-1, 122 points P12-2, 123 points P12-3 and 124 points P12-4 respectively; the second moving branched chain is replaced by an eleventh moving branched chain, and a point 41P 4-1, a point 42P 4-2, a point 43P 4-3 and a point 44P 4-4 are respectively replaced by a point 131P 13-1, a point 132P 13-2, a point 133P 13-3 and a point 134P 13-4; the dimensional relationships, functions, of the first embodiment are still applicable to this type of moving branch.

For the fourth embodiment, when the form of the kinematic chain is converted from PRRRR to RRPRRR, taking the eighth kinematic chain as an example, the eighth kinematic chain is replaced by the tenth kinematic chain, and the 101 point P10-1, the 102 point P10-2, the 103 point P10-3 and the 104 point P10-4 are respectively replaced by 121 point P12-1, 122 point P12-2, 123 point P12-3 and 124 point P12-4; the dimensional relationships, functions, in the fourth embodiment are still applicable to this type of moving branch.

If the form of the moving branched chain is replaced by S 'PS, S' PRRR, UPS, UPRRR and RRPS, taking a tenth moving branched chain and an eleventh moving branched chain as examples, if the tenth moving branched chain two-degree-of-freedom rotating unit 12-2 is a ball pin pair or a universal joint, the length of a 122 line A12-2 is zero, and a 122 point P12-2 is coincident with a 121 point P12-1; if the eleventh moving branched chain two-degree-of-freedom rotating unit 13-2 is a ball pin pair or a universal joint, the length of the 132 line A13-2 is zero, and the 132 point P13-2 is superposed with the 131 point P13-1; if the three-degree-of-freedom rotation unit of the tenth motion branched chain is a ball pair, the length of a 124 line A12-4 is zero, and a 123 point P12-3 is superposed with a 124 point P12-4; if the three-degree-of-freedom rotating unit of the eleventh moving branched chain is a ball pair, the length of a 134 line A13-4 is zero, and a 133 point P13-3 is superposed with a 134 point P13-4; other parameters such as the size relationship of the moving branches are consistent with those of the branches in the form of PRRRRR, so that the 2-line a2 can always point to 0 as far as the center point when the moving branches are in the form of S 'PS, S' PRRR, UPS, UPRRR, RRPS.

Claims

1. A three-dimensional space two-degree-of-freedom centrosome motion parallel mechanism comprises a frame, a main arm and five groups of motion branched chains; the five groups of moving branched chains comprise a first moving branched chain, a second moving branched chain, a third moving branched chain, a fourth moving branched chain and a fifth moving branched chain; the method is characterized in that: each group of moving branched chains is formed by sequentially connecting a machine frame, a moving unit, a two-degree-of-freedom rotating unit, a connecting rod, a three-degree-of-freedom rotating unit and a main arm (2); through the mobile unit, the mobile unit and the rack can generate one-degree-of-freedom relative movement, through the two-degree-of-freedom rotating unit, the connecting rod and the mobile unit can rotate relatively in two degrees of freedom in a three-dimensional space, and through the three-degree-of-freedom rotating unit, the main arm (2) and the connecting rod can rotate relatively in three degrees of freedom in the three-dimensional space; the two-degree-of-freedom rotating unit can be a ball pin pair, a universal joint and a serial joint formed by two rotating pairs with non-parallel axes, the three-degree-of-freedom rotating unit can be a serial joint formed by a ball pair and a rotating pair with non-coplanar three axes, so that the form of the moving branched chain can be PS 'S, PS' RRR, PUS, PURRR, PRRS and PRRRRR, the first moving branched chain and the second moving branched chain have the same form, and the third moving branched chain and the fourth moving branched chain have the same form; the five groups of motion branched chains and the rack form a moving pair through a moving unit respectively, the direction of the moving pair points to a far center point (0), the moving pair formed by the first motion branched chain and the rack and the moving pair formed by the second motion branched chain and the rack are collinear, and the direction of the moving pair formed by the third motion branched chain and the rack and the moving pair formed by the fourth motion branched chain and the rack are collinear; when the three-degree-of-freedom rotating unit is a serial joint formed by three rotating pairs with non-coplanar axes, the axes of the five groups of moving branched chains and the main arm (2) through the rotating pairs formed by the three-degree-of-freedom rotating unit are collinear with the 2 line (A2); when the three-degree-of-freedom rotating unit is a ball pair, the centers of the ball pairs formed by the five groups of moving branched chains and the main arm (2) are on a line (A2) 2; taking the motion form as PRRRRR for example, the size of the first moving branch is obtained by the equal proportional amplification of the size of the second moving branch, and the first moving branch is represented by the length ratio of 32 line (A3-2) to 42 line (A4-2), the length ratio of 33 line (A3-3) to 43 line (A4-3), the length ratio of 34 line (A3-4) to 44 line (A4-4) being equal and being a constant value K1; the size of the third moving branch is obtained by the size equal-scale enlargement of the fourth moving branch, and is represented by the length ratio of a 72 line (A7-2) to a 82 line (A8-2), the length ratio of a 73 line (A7-3) to an 83 line (A8-3), and the length ratio of a 74 line (A7-4) to an 84 line (A8-4) which are equal and have a constant value of K2; the ratio of the distance from the 31 point (P3-1) to the far center point (0) to the distance from the 41 point (P4-1) to the far center point (0) is K1, and the ratio of the distance from the 71 point (P7-1) to the far center point (0) to the distance from the 81 point (P8-1) to the far center point (0) is K2; if the two-degree-of-freedom rotation unit is a universal joint or a ball-and-pin pair, the lengths of the 32 line (A3-2), the 42 line (A4-2), the 62 line (A6-2), the 72 line (A7-2) and the 82 line (A8-2) are zero, the length of the 31 point (P3-1) coincides with the 32 point (P3-2), the length of the 41 point (P4-1) coincides with the 42 point (P4-2), the length of the 61 point (P6-1) coincides with the 62 point (P6-2), the length of the 71 point (P7-1) coincides with the 72 point (P7-2), the length of the 81 point (P8-1) coincides with the 82 point (P84-2), if the three-degree-of freedom rotation unit is a ball pair, the length of the 34 line (A3-4), the length of the 44 line (A4-4), the 64 line (A6-4), the 74 line (A7-4) and the length of the 84 line (A584) coincides with the length of the P5733-3 point (P584), and the length, When the branched chain motion forms are PS 'S, PS' RRR, PUS, PURRR and PRRS, the size relationship of the moving branched chain is consistent with the size relationship when the moving branched chain form is PRRRRR; the prime mover of the moving branch chain is the length change of a moving pair formed by a moving unit of the moving branch chain and the frame or a connecting rod of the moving branch chain.

2. The three-dimensional space two-degree-of-freedom centrosome motion parallel mechanism according to claim 1, characterized in that: the prime mover of the motion branched chain is a moving pair formed by a moving unit of the motion branched chain and a rack, the moving pair is driven by a screw rod nut, a screw rod is arranged on the rack, the nut is arranged on the motion branched chain, for example, the screw rod is respectively arranged on a third boss (1-2) of the rack, a second boss (1-3) of the rack and a first boss (1-4) of the rack, and the nut is respectively arranged on a first motion branched chain sliding block (3-1), a second motion branched chain sliding block (4-1), a third motion branched chain sliding block (7-1), a fourth motion branched chain sliding block (8-1) and a fifth motion branched chain sliding block (6-1); the sliding pair of the first moving branched chain and the sliding pair of the second moving branched chain are driven by the same motor, the motor drives two lead screws with different lead lengths to rotate at the same rotating speed, the ratio of the lead lengths of the two lead screws is K1, namely the ratio of the displacement of the first moving branched chain sliding block (3-1) to the displacement of the second moving branched chain sliding block (4-1) is K1; the sliding pair of the third moving branched chain and the sliding pair of the fourth moving branched chain are driven by the same motor, the motor drives two lead screws with different lead lengths to rotate at the same rotating speed, the ratio of the lead lengths of the two lead screws is K2, namely the ratio of the displacement of the third moving branched chain sliding block (7-1) to the displacement of the fourth moving branched chain sliding block (8-1) is K2; the ratio of the distance from 31 point (P3-1) to far center point (0) to the distance from 41 point (P4-1) to far center point (0) is K1, and the ratio of the distance from 71 point (P7-1) to far center point (0) to the distance from 81 point (P8-1) to far center point (0) is K2 when installed at a proper initial position; besides, the prime mover can also be arranged on a connecting rod of the moving branch chain, the posture of the mechanism is influenced by the length change of the connecting rod, and the moving branch chain can be in the forms of RRPRRR, S 'PS, S' PRRR, UPS, UPRRR and RRPS.

3. The three-dimensional space two-degree-of-freedom centrosome motion parallel mechanism according to claim 1, characterized in that: an eighth moving branched chain, a ninth moving branched chain and a main arm auxiliary connecting part (2-1) can be added, the eighth moving branched chain and the ninth moving branched chain are formed by sequentially connecting a rack, a moving unit, a two-degree-of-freedom rotating unit, a connecting rod, a three-degree-of-freedom rotating unit and a main arm (2), the eighth moving branched chain and the ninth moving branched chain have the same form, and the form of the eighth moving branched chain and the ninth moving branched chain can be PS 'S, PS' RRR, PUS, PURRR, PRRS and PRRRR; the eighth moving branch chain and the eighth moving branch chain respectively form moving pairs with the rack through moving units, and the directions of the moving pairs point to a far center point (0); when the three-degree-of-freedom rotating unit is a serial joint formed by three rotating pairs with non-coplanar axes, the axes of the five groups of moving branched chains and the main arm (2) through the rotating pairs formed by the three-degree-of-freedom rotating unit are collinear with the 2 line (A2); when the three-degree-of-freedom rotating unit is a ball pair, the centers of the ball pairs formed by the five groups of moving branched chains and the main arm (2) are on a line (A2) 2; taking the motion form as PRRRRR as an example, the included angle between the eighth motion branch chain and the direction of a moving pair formed by the ninth motion branch chain and the machine frame is equal to the included angle between the eighth motion branch chain and the direction of an axis of a rotating pair formed by the ninth motion branch chain and the main arm auxiliary connecting part (2-1), which is represented by the included angle between a line 16 (A1-6) and a line 15 (A1-5) being equal to the included angle between a line 105 (A10-5) and a line 115 (A11-5), the distance from the moving pair formed by the eighth motion branch chain and the machine frame to a far center point (0) being equal to the distance from the moving pair formed by the ninth motion branch chain and the machine frame to a far center point (0), which is represented by the distance from a point 101 (P10-1) to the far center point (0) being equal to the distance from a point 111 (P11-1) to the far center point (0), and the eighth motion branch chain and the ninth motion branch chain have the same size, it is embodied that the length of line 102 (A10-2) is equal to the length of line 112 (A11-2), the length of line 103 (A10-3) is equal to the length of line 113 (A11-3), the length of line 104 (A10-4) is equal to the length of line 114 (A11-4), and the distance from point 104 (P10-4) to the far center point (0) is equal to the distance from point 114 (P11-4) to the far center point (0); when the eighth moving branch chain and the ninth moving branch chain are in the forms of PS 'S, PS' RRR, PUS, PURRR and PRRS, if the two-degree-of-freedom rotating unit is a universal joint or a ball pin pair, the lengths of a 102 line (A10-2) and a 112 line (A11-2) are zero, a 101 point (P10-1) is coincident with a 102 point (P10-2), and a 111 point (P11-1) is coincident with a 112 point (P11-2); if the three-degree-of-freedom rotating unit is a ball pair, the lengths of a line 104 (A10-4) and a line 114 (A11-4) are zero, and a point 103 (P10-3) is superposed with a point 104 (P10-4); other parameters such as the size relation of the moving branched chain are consistent with the condition that the branched chain is in a PRRRRR form, and the size relation of the moving branched chain is consistent with the size relation of the moving branched chain in the PRRRRR form; the prime mover of the moving branch chain is the length change of a moving pair formed by a moving unit of the moving branch chain and the frame or a connecting rod of the moving branch chain.

4. The three-dimensional space two-degree-of-freedom centrosome motion parallel mechanism according to claim 1, characterized in that: a sixth motion branched chain can be added, the sixth motion branched chain is formed by sequentially connecting a rack, a moving unit, a two-degree-of-freedom rotating unit, a connecting rod, a two-degree-of-freedom rotating unit and a main arm (2), and the form of the sixth motion branched chain can be PS 'S, PS' RRR, PUS, PURRR, PRRS and PRRRRR.

5. The three-dimensional space two-degree-of-freedom centrosome motion parallel mechanism according to claim 1, characterized in that: a seventh motion branched chain can be added, the seventh motion branched chain is formed by sequentially connecting a rack, a moving unit, a two-degree-of-freedom rotating unit, a connecting rod, a two-degree-of-freedom rotating unit and a main arm (2), and the seventh motion branched chain can be in the forms of PS 'S', PS 'RR, PS' U, PUS ', PURR, PUU, PRRS', PRRU and PRRRR.

6. The three-dimensional space two-degree-of-freedom centrosome motion parallel mechanism according to claim 1, characterized in that: a twelfth motion branched chain can be added, the twelfth motion branched chain is formed by sequentially connecting a rack, a moving unit, a two-degree-of-freedom rotating unit, a connecting rod, a three-degree-of-freedom rotating unit and a main arm (2), and the twelfth motion branched chain can be in the form of PS 'RRR, PS' S, PUS, PURRR, PRRS and PRRRRR.