CN112847317B

CN112847317B - Three-dimensional space two-degree-of-freedom telecentric point motion parallel mechanism

Info

Publication number: CN112847317B
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: 2023-05-26
Anticipated expiration: 2041-03-22
Also published as: CN112847317A

Abstract

The invention relates to the technical field of parallel robots, in particular to a parallel mechanism capable of realizing two-degree-of-freedom telecentric point movement in a three-dimensional space, which 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 PS 'S, PS' RRR, PUS, PURRR, PRRS, PRRRRR and the like; wherein five groups of movement branched chains are necessary, the size of the first movement branched chain is amplified by the size of the second movement branched chain in equal proportion, the size of the third movement branched chain is amplified by the size of the fourth movement branched chain in equal proportion, the five groups of movement branched chains have two degrees of freedom, a driving element is arranged on a moving pair formed by the movement branched chains and a frame, and the five groups of movement branched chains can restrict the main arm (2) to constantly point to a telecentric point (0); in addition, some movement branched chains can be added to control the rotation of the main arm (2).

Description

Three-dimensional space two-degree-of-freedom telecentric point 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 telecentric point movement in a three-dimensional space.

Background

Telecentric mechanism refers to a mechanism that enables telecentric motion, which is a widely used motion of the person in minimally invasive surgery, such as laparoscopic surgery. The current method for realizing telecentric point movement mainly comprises the steps of controlling multi-axis linkage by means of an algorithm, utilizing a compound 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 space telecentric point movement, which comprises a base, a movable platform, an instrument and three groups of movable branched chains, wherein a driving part of the mechanism is a moving pair on the three groups of movable branched chains, and the installation relationship of the rotating pair among the movable branched chains, the instrument, the movable platform base and the like in the mechanism ensures that the instrument is always beyond the telecentric point. The mechanism has compact structure, but the rotary joint is likely to be stressed greatly, and the driving part is not suitable for using an electric power element such as a ball screw.

Chinese patent 202010165548.7 discloses a three degrees of freedom series-parallel telecentric mechanism, which comprises a double-parallelogram mechanism, a base, a first linear module, a second linear module and the like, wherein the primary moving part of the mechanism is the first linear module and the second linear module, the first linear module controls the double-parallelogram mechanism to further realize two degrees of freedom telecentric point movement, and the second linear module controls the linear movement of an end effector. A 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 telecentric point movement in a three-dimensional space, which is more convenient to control relative to a multi-axis linkage mode, has higher rigidity relative to a compound 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 telecentric point movement parallel mechanism which comprises a frame, a main arm and five groups of movement branched chains, wherein one ends of the five groups of movement branched chains are respectively connected with the frame, the other ends of the five groups of movement branched chains are respectively connected with the main arm, and a driving element of the mechanism is positioned on the movement branched chains; the mechanism has the functions of restraining the axis of the main arm from constantly pointing to the telecentric point and controlling the main arm to realize two-degree-of-freedom telecentric point movement around the telecentric point.

The three-dimensional space two-degree-of-freedom telecentric point movement parallel mechanism comprises a frame, a main arm and five groups of movement branched chains, wherein the five groups of movement branched chains comprise a first movement branched chain, a second movement branched chain, a third movement branched chain, a fourth movement branched chain and a fifth movement 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 moving 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 movable unit and the frame can relatively move in one degree of freedom, the connecting rod and the movable unit can relatively rotate in two degrees of freedom in a three-dimensional space through the two-degree-of-freedom rotating unit, and the main arm and the connecting rod can relatively rotate in three degrees of freedom in the three-dimensional space through the three-degree-of-freedom rotating unit; the two-degree-of-freedom rotating unit can be a serial joint formed by a ball pin pair, a universal joint and two rotating pairs with non-parallel axes, and the three-degree-of-freedom rotating unit can be a serial joint formed by a ball pair and three rotating pairs with non-coplanar axes, so that the movement branched chain can be in the form of PS 'S, PS' RRR, PUS, PURRR, PRRS, PRRRRR.

The three-dimensional two-degree-of-freedom telecentric point motion parallel mechanism is provided with 5 degrees of freedom, each group of motion branched chains is provided with 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, 6 degrees of freedom are added to the newly added motion branched chains, but 6 degrees of freedom are reduced when the motion branched chains are connected in parallel to the mechanism, so the three-dimensional two-degree-of-freedom telecentric point motion parallel mechanism is provided with 6 degrees of freedom, the rotation degree of freedom of the main arm is regarded as a local degree of freedom, and the three-dimensional two-degree-of-freedom telecentric point motion parallel mechanism is provided with 5 degrees of freedom. Therefore, the moving pair between the five groups of moving branched chains and the rack is a driving element, and the three-dimensional space two-degree-of-freedom telecentric point movement parallel mechanism has a determined gesture.

The five groups of movement branched chains respectively form a moving pair through the moving unit and the frame, and respectively form a ball pair or a rotating pair through the three-degree-of-freedom rotating unit and the main arm; the directions of the five groups of moving branched chains and the moving pair formed by the machine frame are pointed to telecentric points, the directions of the first moving branched chain, the second moving branched chain and the moving pair formed by the machine frame are the same, and the directions of the third moving branched chain, the fourth moving branched chain and the moving pair formed by the machine frame are the same; when the three-degree-of-freedom rotating unit is a ball pair, the center point of the ball pair formed by the five groups of motion branched chains and the main arm is 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 three rotating pairs with non-coplanar axes, the axis directions of the five groups of motion branched chains and the rotating pair formed by the main arm are the same, and the five groups of motion branched chains and the axis directions of the rotating pair formed by the main arm are collinear with the axis of the main arm.

The size of the first moving branched chain is obtained by equal proportion amplification of the size of the second moving branched chain, and the proportion is equal to the proportion of the distance from the moving pair of the first moving branched chain to the telecentric point to the distance from the moving pair of the second moving branched chain to the telecentric point; the size of the third moving branched chain is amplified by 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 telecentric point to the distance from the moving pair of the fourth moving branched chain to the telecentric point.

The three-dimensional space two-degree-of-freedom telecentric point motion parallel mechanism meeting the relation has one solution as follows: when the three-degree-of-freedom rotating unit is a ball pair, the center point of the ball pair formed by the five groups of moving branched chains and the main arm is on the same straight line and passes through the telecentric point, and when the three-degree-of-freedom rotating unit is a serial joint formed by three rotating pairs with non-coplanar axes, the directions of the axes of the five groups of moving branched chains and the rotating pair formed by the main arm are the same and pass through the telecentric point; the first movement branched chain is coplanar with the second movement branched chain, and the third movement branched chain is coplanar with the fourth movement branched chain; the polygon formed by the first moving branched chain and the main arm is similar to the polygon formed by the second moving branched chain and the main arm, the polygon formed by the third moving branched chain and the main arm is similar to the polygon formed by the fourth moving branched chain and the main arm, and the distance between the main arm and the telecentric point is unchanged; the axis of the main arm points to the telecentric point, and the distance between the main arm and the telecentric point is unchanged; because the number of the prime movements of the three-dimensional space two-degree-of-freedom telecentric point motion parallel mechanism is equal to the degree of freedom of the mechanism, the posture of the mechanism is stable when the axis of the main arm is constantly directed to the telecentric point.

The primary moving part of the three-dimensional space two-degree-of-freedom telecentric point movement parallel mechanism is a moving pair between five groups of movement branched chains and the rack; the moving pair is driven by a screw rod nut, the screw rod is arranged on the frame, and the nut is arranged on the moving branched chain; the moving pair of the first moving branched chain and the moving pair of the second moving branched chain are driven by the same motor, the motor drives two lead screws with different leads to rotate at the same rotation speed, and the lead ratio of the two lead screws is the ratio of the distance from the moving pair of the first moving branched chain to the telecentric point to the distance from the moving pair of the second moving branched chain to the telecentric point; the moving pair of the third moving branched chain and the moving pair of the fourth moving 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 third moving branched chain to the telecentric point to the distance from the moving pair of the fourth moving branched chain to the telecentric point; therefore, when the device is installed at a proper initial position, the ratio of the distance from the moving pair of the first moving branched chain to the telecentric point to the distance from the moving pair of the second moving branched chain to the telecentric point is a constant value, and the ratio of the distance from the moving pair of the third moving branched chain to the telecentric point to the distance from the moving pair of the fourth moving branched chain to the telecentric point is a constant value.

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

Further, in order to control the rotation freedom of the main arm, a seventh movement branched chain may be added, which may be in the form of PS 'U, PS' RR, PS 'S', PUS ', PURR, PUU, PRRU, PRRRRU, PRRS'; the seventh movement branched chain and the frame form a moving pair, and form a revolute pair, a ball pin pair or a universal joint with the main arm; the driving part is a moving pair between the seventh moving branched chain and the frame, the moving pair is driven by a screw rod nut, the screw rod is arranged on the frame, and the nut is arranged on the moving branched chain.

Further, in order to control the rotation degree of freedom of the main arm, a method of adding two movement branched chains can be adopted, and an added eighth movement branched chain and a ninth movement branched chain have the same form, and can be PUS, PRRS, PS 'S, PURRR, PRRRRR, PS' RRR; the eighth moving branched chain and the ninth moving branched chain respectively form a moving pair with the frame and are connected with the main arm through auxiliary parts; the direction of a revolute pair formed by the eighth moving branched chain, the ninth moving branched chain and the frame points to a telecentric point, the axial direction of a revolute pair formed by the eighth moving branched chain, the ninth moving branched chain and the auxiliary part points to a telecentric point, and the included angles between the directions of the revolute pair formed by the eighth moving branched chain, the ninth moving branched chain and the frame are equal to the included angles between the axial directions of the revolute pair formed by the eighth moving branched chain, the ninth moving branched chain and the auxiliary part; the distance from the moving pair formed by the eighth moving branched chain and the frame to the telecentric point is equal to the distance from the moving pair formed by the ninth moving branched chain and the frame to the telecentric point; the eighth moving branch has the same size as the ninth moving branch; 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.

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

Furthermore, the driving part of the three-dimensional space two-degree-of-freedom telecentric point movement parallel mechanism can influence the gesture of the mechanism through the length change of the connecting rod on the connecting rod of the movement branched chain instead of the moving pair formed by the movement branched chain and the frame; the movement branched chain and the frame form a revolute pair or a universal joint, and the movement branched chain and the main arm form a revolute pair or a ball pair; the form of the moving branches may be UPS, UPRRR, RRPS, RRPRRR, S 'PS, S' PRRR; all the aforementioned composition, dimensional relationships, functions still apply to such a kinematic chain.

The beneficial effects of the invention are as follows: 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-nut, elements such as a screw, a motor and the like are arranged on the frame, and moving parts such as a moving branched 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 unchanged.

Drawings

Fig. 1 is a three-dimensional view of a mechanism with 5 sets of prrrr moving branches.

Fig. 2 is a three-dimensional view of a first kinematic branching mechanism.

Fig. 3 is a three-dimensional view of a second kinematic branching mechanism.

Fig. 4 is a three-dimensional view of a third kinematic branching mechanism.

Fig. 5 is a three-dimensional view of a fourth kinematic branching mechanism.

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

Fig. 7 is a mechanical dimension diagram with 5 sets of prrrr moving branches.

Fig. 8 is a three-dimensional view of a mechanism with 6 sets of prrrr moving branches.

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

Fig. 10 is a three-dimensional view of an eighth kinematic branched chain and a ninth kinematic branched chain mechanism.

Fig. 11 is a mechanical dimension view of the eighth and ninth moving branches.

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

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

Fig. 14 is a mechanical dimension view of the tenth and eleventh moving branches.

Main symbol description: 1-1 part of the frame base, 1-2 part of the frame third boss, 1-3 part of the frame second boss, 1-4 part of the frame first boss, 1-6 part of the frame fourth boss, 1-5 part of the frame fifth boss, 2 part of the main arm, 2-1 part of the main arm auxiliary connecting part, 3-1 part of the first movement branched chain sliding block, 3-2 part of the first movement branched chain two-freedom rotating unit, 3-3 part of the first movement branched chain connecting rod, 3-4 part of the first movement branched chain three-rotating part, 3-5 part of the first movement branched chain three-rotating part, 4-1 part of the second movement branched chain sliding block, 4-2 part of the second movement branched chain two-freedom rotating unit, 4-3 part of the second movement branched chain connecting rod, 4-4 part of the second movement branched chain three-rotating part, 4-5 part of the second movement branched chain three-rotating part 5-1, 5-2, 5-3, 5-4, 5-5, 6-1, 6-2, 6-3, 6-4, 6-5, 7-1, 7-2, 7-3, 7-4, 7-2, 3, 7-4, and 7-4, 7-5 third moving branch three-two rotating part, 8-1 fourth moving branch sliding block, 8-2 fourth moving branch two-degree-of-freedom rotating unit, 8-3 fourth moving branch connecting rod, 8-4 fourth moving branch three-rotating part, 8-5 fourth moving branch three-rotating part, 9-1 seventh moving branch sliding block, 9-2 seventh moving branch two-degree-of-freedom rotating unit, 9-3 seventh moving branch connecting rod, 9-4 seventh moving branch two-rotating part, 9-5 seventh moving branch two-rotating part, 10-1 eighth moving branch sliding block, 10-2 eighth moving branch two-degree-of-freedom rotating unit, 10-3 eighth moving branch connecting rod, 10-4 eighth moving branch three-rotating part 10-5 eighth moving branch three-rotation part, 11-1 ninth moving branch slide block, 11-2 ninth moving branch three-rotation part, 11-3 ninth moving branch connecting rod, 11-4 ninth moving branch three-rotation part, 11-5 ninth moving branch three-rotation part, 12-1 tenth moving branch fixing part, 12-2 tenth moving branch two-rotation part, 12-3 tenth moving branch front connecting rod, 12-4 tenth moving branch rear connecting rod, 12-5 tenth moving branch three-rotation part, 12-6 tenth moving branch three-rotation part, 13-1 eleventh moving branch fixing part, 13-2 eleventh moving branch two-rotation part, 13-2 tenth moving branch two-rotation part, and third moving branch three-rotation part, 13-3 parts of eleventh movement branched chain front connecting rod, 13-4 parts of eleventh movement branched chain rear connecting rod, 13-5 parts of eleventh movement branched chain three-rotation component, 13-6 parts of eleventh movement branched chain three-rotation component, 14-1 parts of twelfth movement branched chain sliding block, 14-2 parts of twelfth movement branched chain two-degree-of-freedom rotation unit, 14-3 parts of twelfth movement branched chain connecting rod 14-4 twelfth moving branched chain three-rotation component, 14-5 twelfth moving branched chain three-rotation component, 14-6 twelfth moving branched chain auxiliary connecting component, 0 telecentricity 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, A6-4.64 line, A7-2.72 line, A7-3.73 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, A11-2.112 line, A11-3.113 line, A11-4.114 line, A11-5.115 line, A12-2.122 line line A12-3.123, line A12-4.124, line A13-2.132, line A13-3.133, line A13-4.134, point P3-1.31, point P3-2.32, point P3-3.33, point P3-4.34, point P4-1.41, point P4-2.42, point P4-3.43, point P4-4.44, point P6-1.61, point P6-2.62, point P6-3.63, point P6-4.64, point P7-1.71, point P7-2.72, P7-3.73, P7-4.74, P8-1.81, P8-2.82, P8-3.83, 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 describes specific embodiments of the present invention in detail with reference to the drawings.

The two-degree-of-freedom telecentric point motion parallel mechanism in three-dimensional space comprises a frame, a main arm 2, 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; each group of movement branched chains is sequentially connected with 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 movable unit and the frame can relatively move in one degree of freedom, the connecting rod and the movable unit can relatively rotate in two degrees of freedom in a three-dimensional space through the two-degree-of-freedom rotating unit, and the main arm and the connecting rod can relatively rotate in three degrees of freedom in the three-dimensional space through the three-degree-of-freedom rotating unit; the two-degree-of-freedom rotating unit can be a serial joint formed by a ball pin pair, a universal joint and two rotating pairs with non-parallel axes, and the three-degree-of-freedom rotating unit can be a serial joint formed by a ball pair and three rotating pairs with non-coplanar axes, so that the movement branched chain can be in the form of PS 'S, PS' RRR, PUS, PURRR, PRRS, PRRRRR.

FIG. 1 is a first embodiment of the present disclosure, the frame includes a frame base 1-1, a frame No. three boss 1-2, a frame No. two boss 1-3, a frame No. one boss 1-4; the third boss 1-2, the second boss 1-3 and the first boss 1-4 are fixedly connected with the base 1-1 respectively.

Take the form of prrrr as an example of a first, second, third, fourth, and fifth kinematic branched.

As shown in fig. 2, the first movement branched chain comprises a first movement branched chain sliding block 3-1, a first movement branched chain two-degree-of-freedom rotation unit 3-2, a first movement branched chain connecting rod 3-3, a first movement branched chain three-rotation component 3-4 and a first movement branched chain three-two-rotation component 3-5; the first boss 1-4 of the frame and the first moving branched chain sliding block 3-1 form a moving pair, the direction of the moving pair is 14 lines A1-4, and the moving pair points to a telecentric point 0; the first moving branched chain sliding block 3-1 and the first moving branched chain two-degree-of-freedom rotating unit 3-2 form a rotating pair; the first moving branched chain two-degree-of-freedom rotating unit 3-2 and the first moving branched chain connecting rod 3-3 form a rotating pair, a common vertical line between a rotating axis and a 14 line A1-4 is 32 lines A3-2, the 32 lines A3-2 and the rotating pair axis are intersected at a 32 point P3-2, and the 32 lines A3-2 and the 14 line A1-4 are intersected at a 31 point P3-1; the first moving branched chain connecting rod 3-3 and the first moving branched chain three-rotating component 3-4 form a revolute pair; the first moving branched chain three-rotating part 3-4 and the first moving branched chain three-two rotating part 3-5 form a revolute pair, a common vertical line between a rotating axis and A2 line A2 is 34 line A3-4, the 34 line A3-4 and the revolute pair axis are intersected at a 33 point P3-3, and the 34 line A3-4 and the 2 line A2 are intersected at a 34 point P3-4; 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 2 lines A2; the connecting line of the 32 point P3-2 and the 33 point P3-3 is 33 lines A3-3; the first moving branched chain sliding block 3-1 is a moving unit; the first movement branched chain two-degree-of-freedom rotating unit 3-2 is a two-degree-of-freedom rotating unit and is a serial joint formed by two revolute pairs with non-parallel axes; the first moving branched chain three-rotation part 3-4 and the first moving branched chain three-two-rotation part 3-5 are combined into a three-degree-of-freedom rotation unit, and are serial joints formed by three revolute pairs with non-coplanar axes.

As shown in fig. 3, the second movement branched chain comprises a second movement branched chain sliding block 4-1, a second movement branched chain two-degree-of-freedom rotation unit 4-2, a second movement branched chain connecting rod 4-3, a second movement branched chain three-rotation component 4-4 and a second movement branched chain three-two-rotation component 4-5; the first boss 1-4 of the frame and the second moving branched chain sliding block 4-1 form a moving pair, the direction of the moving pair is 14 lines A1-4, and the moving pair points to a telecentric point 0; the second moving branched chain sliding block 4-1 and the second moving branched chain two-degree-of-freedom rotating unit 4-2 form a rotating pair; the second motion branched chain two-degree-of-freedom rotating unit 4-2 and the second motion branched chain connecting rod 4-3 form a rotating pair, a common vertical line between a rotating axis and a 14 line A1-4 is 42 line A4-2, the 42 line A4-2 and the rotating pair axis are intersected at a 42 point P4-2, and the 42 line A4-2 and the 14 line A1-4 are intersected at a 41 point P4-1; the second moving branched chain connecting rod 4-3 and the second moving branched chain three-rotating component 4-4 form a revolute pair; the second moving branched chain three-rotating part 4-4 and the second moving branched chain three-two rotating part 4-5 form a revolute pair, a common vertical line between the rotating axis and the 2 line A2 is 44 line A4-4, the 44 line A4-4 and the revolute pair axis are intersected at a 43 point P4-3, and the 44 line A4-4 and the 2 line A2 are intersected at a 44 point P4-4; the second movement 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 2 lines A2; the connection line between the point 42P 4-2 and the point 43P 4-3 is a 43 line A4-3; the second moving branched chain slide block 4-1 is a moving unit; the second motion branched chain two-degree-of-freedom rotating unit 4-2 is a two-degree-of-freedom rotating unit and is a serial joint formed by two revolute pairs with non-parallel axes; the second moving branched chain three-rotation part 4-4 and the second moving branched chain three-two-rotation part 4-5 are combined into a three-degree-of-freedom rotation unit, and are serial joints formed by three revolute pairs with non-coplanar axes.

As shown in fig. 4, the third moving branch comprises a third moving branch slide block 7-1, a third moving branch two-degree-of-freedom rotation unit 7-2, a third moving branch connecting rod 7-3, a third moving branch three-rotation part 7-4 and a third moving branch three-two-rotation part 7-5; the boss 1-2 of the third frame and the third moving branched chain sliding block 7-1 form a moving pair, the direction of the moving pair is 12 lines A1-2, and the moving pair points to the telecentric point 0; the third moving branched chain sliding block 7-1 and the third moving branched chain two-degree-of-freedom rotating unit 7-2 form a rotating pair; the third movement branched chain two-degree-of-freedom rotating unit 7-2 and the third movement branched chain connecting rod 7-3 form a revolute pair, a common vertical line between a rotating axis and a 12 line A1-2 is 72 line A7-2, the 72 line A7-2 and the revolute pair axis are intersected at a 72 point P7-2, and the 72 line A7-2 and the 12 line A1-2 are intersected at a 71 point P7-1; the third moving branched chain connecting rod 7-3 and the third moving branched chain three rotating parts 7-4 form a revolute pair; the third moving branched chain three-rotating part 7-4 and the third moving branched chain three-two rotating part 7-5 form a revolute pair, a common vertical line between a rotating axis and A2 line A2 is 74 line A7-4, the 74 line A7-4 and the revolute pair axis are intersected at a 73 point P7-3, and the 74 line A7-4 and the 2 line A2 are intersected at a 74 point P7-4; the third moving 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 2 lines A2; the connection line between the 72 point P7-2 and the 73 point P7-3 is 73 line A7-3; the third moving branched chain slide block 7-1 is a moving unit; the third movement branched chain two-degree-of-freedom rotating unit 7-2 is a two-degree-of-freedom rotating unit and is a serial joint formed by two revolute pairs with non-parallel axes; the third moving branched chain three-rotation part 7-4 and the third moving branched chain three-two-rotation part 7-5 are combined into a three-degree-of-freedom rotation unit, and are serial joints formed by three revolute pairs with non-coplanar axes.

As shown in fig. 5, the fourth moving branch comprises a fourth moving branch sliding block 8-1, a fourth moving branch two-degree-of-freedom rotating unit 8-2, a fourth moving branch connecting rod 8-3, a fourth moving branch three-rotating component 8-4 and a fourth moving branch three-two-rotating component 8-5; the boss 1-2 of the third frame and the fourth moving branched chain sliding block 8-1 form a moving pair, the direction of the moving pair is 12 lines A1-2, and the moving pair points to the telecentric point 0; the fourth moving branched chain sliding block 8-1 and the fourth moving branched chain two-degree-of-freedom rotating unit 8-2 form a revolute pair; the fourth movement branched chain two-degree-of-freedom rotating unit 8-2 and the fourth movement branched chain connecting rod 8-3 form a rotating pair, a common vertical line between a rotating axis and a 12 line A1-2 is 82 line A8-2, the 82 line A8-2 and the rotating pair axis are intersected at a 82 point P8-2, and the 82 line A8-2 and the 12 line A1-2 are intersected at a 81 point P8-1; the fourth moving branched chain connecting rod 8-3 and the fourth moving branched chain three-rotating component 8-4 form a revolute pair; the third rotary part 8-4 of the fourth moving branched chain and the third rotary part 8-5 of the fourth moving branched chain form a revolute pair, a common vertical line between the rotary axis and the 2 line A2 is 84 line A8-4, the 84 line A8-4 and the revolute pair axis are intersected at a point P8-3 of 83, and the 84 line A8-4 and the 2 line A2 are intersected at a point P8-4 of 84; the third rotating part 8-5 of the fourth moving branched chain and the main arm 2 form a rotating pair, and the axis of the rotating pair is 2 lines A2; the connection line between the point 82P 8-2 and the point 83P 8-3 is 83 line A8-3; the fourth moving branched chain slide block 8-1 is a moving unit; the fourth movement branched chain two-degree-of-freedom rotating unit 8-2 is a two-degree-of-freedom rotating unit and is a serial joint formed by two revolute pairs with non-parallel axes; the third rotating part 8-4 of the fourth moving branched chain and the third rotating part 8-5 of the fourth moving branched chain are combined into a three-degree-of-freedom rotating unit, and the three-degree-of-freedom rotating unit is a serial joint formed by rotating pairs with three non-coplanar axes.

As shown in fig. 6, the fifth moving branch comprises a fifth moving branch slide block 6-1, a fifth moving branch two-degree-of-freedom rotating unit 6-2, a fifth moving branch connecting rod 6-3, a fifth moving branch three-rotating part 6-4 and a fifth moving branch three-two-rotating part 6-5; the second boss 1-3 of the frame and the fifth moving branched chain sliding block 6-1 form a moving pair, the direction of the moving pair is 13 lines A1-3, and the moving pair points to a telecentric point 0; the fifth moving branched chain sliding block 6-1 and the fifth moving branched chain two-degree-of-freedom rotating unit 6-2 form a rotating pair; the fifth moving branched chain two-degree-of-freedom rotating unit 6-2 and the fifth moving branched chain connecting rod 6-3 form a rotating pair, a common vertical line between the rotating axis and the 13 line A1-3 is 62 line A6-2, the 62 line A6-2 and the rotating pair axis are intersected at a 62 point P6-2, and the 62 line A6-2 and the 13 line A1-3 are intersected at a 61 point P6-1; the fifth moving branched chain connecting rod 6-3 and the fifth moving branched chain three-rotating component 6-4 form a revolute pair; the third rotating part 6-4 of the fifth moving branched chain and the third rotating part 6-5 of the fifth moving branched chain form a revolute pair, a common vertical line between the rotating axis and the 2 line A2 is 64 line A6-4, the 64 line A6-4 and the revolute pair axis are intersected at a 63 point P6-3, and the 64 line A6-4 and the 2 line A2 are intersected at a 64 point P6-4; the fifth moving branched chain three-two rotating part 6-5 and the main arm 2 form a rotating pair, and the axis of the rotating pair is 2 lines A2; the connection line between the 62 point P6-2 and the 63 point P6-3 is 63 line A6-3; the fifth moving branched slider 6-1 is a moving unit; the fifth movement branched chain two-degree-of-freedom rotating unit 6-2 is a two-degree-of-freedom rotating unit and is a serial joint formed by two revolute pairs with non-parallel axes; the third rotating part 6-4 of the fifth moving branched chain and the third rotating part 6-5 of the fifth moving branched chain are combined into a three-degree-of-freedom rotating unit, and the three-degree-of-freedom rotating unit is a serial joint formed by rotating pairs with three non-coplanar axes.

The three-dimensional space two-degree-of-freedom telecentric point movement parallel mechanism has 5 degrees of freedom; each group of motion branched chains is provided with a moving pair and five revolute pairs, 6 degrees of freedom are all provided, when a plurality of groups of motion branched chains are connected in parallel, each group of motion branched chains are connected in parallel, 6 degrees of freedom are increased for the newly added motion branched chains, but 6 degrees of freedom are reduced when the motion branched chains are connected in parallel in the mechanism, so that the three-dimensional space two-degree-of-freedom telecentric point motion parallel mechanism is provided with 6 degrees of freedom; the main arm 2 and all the movement branched chains are connected by rotating pairs, so that the rotation freedom degree of the main arm 2 can be regarded as a local freedom degree, and the three-dimensional space two-freedom-degree telecentric point movement parallel mechanism can be provided with 5 freedom degrees. The moving pairs between the five groups of moving branched chains and the rack are prime moving parts, the rotation freedom degree of the main arm 2 is regarded as a local freedom degree, and the three-dimensional space two-freedom-degree telecentric point movement parallel mechanism has a determined gesture.

As shown in fig. 7, the size of the first moving branch is amplified in equal proportion to the size of the second moving branch, which is represented by the ratio of the lengths of 32 lines A3-2 and 42 lines A4-2, the ratio of the lengths of 33 lines A3-3 and 43 lines A4-3, and the ratio of the lengths of 34 lines A3-4 and 44 lines A4-4 being equal and constant K1; the size of the third movement branched chain is amplified by the size of the fourth movement branched chain in equal proportion, and the size is expressed by the ratio of the lengths of 72 lines A7-2 and 82 lines A8-2, the ratio of the lengths of 73 lines A7-3 and 83 lines A8-3, and the ratio of the lengths of 74 lines A7-4 and 84 lines A8-4 which are equal and have a constant value K2.

The primary moving part of the three-dimensional space two-degree-of-freedom telecentric point movement parallel mechanism is a moving pair between five groups of movement branched chains and the rack; the moving pair is driven by a screw rod nut, the screw rod is respectively arranged on a third boss 1-2 of the frame, a second boss 1-3 of the frame and a first boss 1-4 of the frame, and the nuts are 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 moving pair of the first moving branched chain and the moving pair of the second moving branched chain are driven by the same motor, the motor drives two lead screws with different leads to rotate at the same rotation speed, and the lead ratio 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 moving pair of the third moving branched chain and the moving pair of the fourth moving branched chain are driven by the same motor, the motor drives two lead screws with different leads to rotate at the same rotation speed, the lead ratio 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; under proper initial position installation, the ratio of the distance from the 31 point P3-1 to the telecentric point 0 to the distance from the 41 point P4-1 to the telecentric point 0 is K1, and the ratio of the distance from the 71 point P7-1 to the telecentric point 0 to the distance from the 81 point P8-1 to the telecentric point 0 is K2.

The three-dimensional space two-degree-of-freedom telecentric point motion parallel mechanism meeting the relation has the following solution in a certain space range: the polygon P3-1-0-P3-4-P3-P3-2 formed by the first moving branched chain and the main arm 2 is similar to and coplanar with the polygon P4-1-0-P4-P4-3-P4-2 formed by the second moving branched 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 branched 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 branched chain and the main arm 2, and the similarity ratio is K2; line 2 A2 passes through telecentric point 0; the polygon similarity adds two constraints to the mechanism, the degree of freedom of the three-dimensional two-degree-of-freedom telecentric point motion parallel mechanism is 3, the number of the driving parts is 3, and the solution is stable.

Since the similarity ratio of the polygon P3-1-0-P3-4-P3-P3-2 formed by the first moving branch and the main arm 2 to the polygon P4-1-0-P4-P4-3-P4-2 formed by the second moving branch and the main arm 2 is K1, the distance between the point P3-4 and the point P4-4 at 34 is constant, the distance between the point P4-4 and the point P4-4 at 44 is constant, and the distance between the point P4-4 and the point 0 at 84 is constant, and the distance between the point P8-4 and the point 0 at the center is constant.

When the form of the motion branched chain is PS 'S, PS' RRR, PUS, PURRR, PRRS, each group of motion branched chain has 6 degrees of freedom, and five groups of branched chains have 6 degrees of freedom after being connected in parallel, and the rotation of the main arm 2 is regarded as a local degree of freedom, the three-dimensional two-degree-of-freedom telecentric 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 telecentric point motion parallel mechanism is 3, the number of the driving parts is 3, and the three-dimensional two-degree-of-freedom telecentric point motion parallel mechanism has a determined gesture.

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

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 prime mover of the three-dimensional two-degree-of-freedom telecentric point motion parallel mechanism is a moving unit of a motion branched chain, the moving unit enables the motion branched chain and the frame to form a moving pair, the moving pair direction of the first motion branched chain and the second motion branched chain is 14 lines A1-4, the moving pair direction of the third motion branched chain and the fourth motion branched chain is 12 lines A1-2, and the moving pair direction of the fifth motion branched chain is 13 lines A1-3 in accordance with the condition that the motion branched chain is PRRRR; the center of the ball pair formed between the moving branch and the main arm 2 is on A2-line A2, and the 2-line A2 points to the telecentric point 0.

In summary, when the form of the moving branch is PS 'S, PS' RRR, PUS, PURRR, PRRS, PRRRRR, the 2-line A2 can be constantly directed to the telecentric point 0.

FIG. 8 is a second embodiment of the present disclosure, wherein, based on the first embodiment, in order to improve the rigidity and strength of the mechanism, the stress of the moving branched chain is reduced, a sixth moving branched chain may be added, and the form of the sixth moving branched chain may be PS 'S, PS' RRR, PUS, PURRR, PRRS, PRRRRR; taking PRRRR 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 component 5-4 and a sixth moving branched chain three-two-rotating component 5-5; the second boss 1-3 of the frame and the sixth moving branched chain sliding block 5-1 form a revolute pair, the sixth moving branched chain sliding block 5-1 and the sixth moving branched chain two-degree-of-freedom rotating unit 5-2 form a revolute pair, the sixth moving branched chain two-degree-of-freedom rotating unit 5-2 and the sixth moving branched chain connecting rod 5-3 form a revolute pair, the sixth moving branched chain connecting rod 5-3 and the sixth moving branched chain three-rotating component 5-4 form a revolute pair, the sixth moving branched chain three-rotating component 5-4 and the sixth moving branched chain three-two-rotating component 5-5 form a revolute pair, and the sixth moving branched chain three-two-rotating component 5-5 and the main arm 2 form a revolute pair; the sixth movement branched chain two-degree-of-freedom rotating unit 5-2 is a two-degree-of-freedom rotating unit and is a serial joint formed by two revolute pairs with non-parallel axes; the third rotating part 5-4 of the sixth moving branched chain and the third rotating part 5-5 of the sixth moving branched chain are combined into a three-degree-of-freedom rotating unit, and the three-degree-of-freedom rotating unit is a serial joint formed by rotating pairs with three non-coplanar axes.

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

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

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

As shown in FIG. 10, a boss No. 1-6 of the frame and an eighth moving branched chain sliding block 10-1 form a moving pair, and the direction of the moving pair is 16 lines A1-6 pointing to a telecentric point 0; the eighth moving branched chain sliding block 10-1 and the eighth moving branched 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, a common vertical line between a rotating axis and a 16 line A1-6 is 102 line A10-2, the 102 line A10-2 and the rotating pair axis are intersected at a 102 point P10-2, and the 102 line A10-2 and the 16 line A1-6 are intersected at a 101 point P10-1; the eighth moving branched chain connecting rod 10-3 and the eighth moving branched chain three-rotating component 10-4 form a revolute pair; the eighth moving branch three-rotation part 10-4 and the eighth moving branch three-two rotation part 10-5 form a revolute pair; the rotation axis of the rotation pair formed by the eighth moving branch chain three-two rotation part 10-5 and the main arm auxiliary connection part 2-1 is a 104 line A10-4, the 104 line A10-4 and the axis of the rotation pair formed by the eighth moving branch chain three-rotation part 10-4 and the eighth moving branch chain three-two rotation part 10-5 are intersected at a 104 point P10-4, and the 103 line A10-3 and the axis of the rotation pair are intersected at a 103 point P10-3; the eighth moving branched chain three-two rotating component 10-5 and the main arm auxiliary connecting part 2-1 form a rotating pair, and the axis of the rotating pair is 105 lines A10-5 and points to the telecentric point 0; the main arm auxiliary connecting part 2-1 is fixedly connected with the main arm 2; the connecting line of the 102 point P10-2 and the 103 point P10-3 is 103 line A10-3; the eighth motion branched chain two-degree-of-freedom rotating unit 10-2 is a two-degree-of-freedom rotating unit and is a serial joint formed by two revolute pairs with non-parallel axes; the eighth moving branched chain three-rotation part 10-4 and the eighth moving branched chain three-two-rotation part 10-5 are combined into a three-degree-of-freedom rotation unit, and are serial joints formed by three revolute pairs with non-coplanar axes.

As shown in FIG. 10, a boss No. 1-5 of the frame and a ninth moving branched chain slide block 11-1 form a moving pair, and the direction of the moving pair is 15 lines A1-5 pointing to a telecentric point 0; the ninth moving branched chain sliding block 11-1 and the ninth moving branched chain two-degree-of-freedom rotating unit 11-2 form a rotating pair; the rotation unit 11-2 with two degrees of freedom of the ninth movement branched chain and the connecting rod 11-3 of the ninth movement branched chain form a revolute pair, a common vertical line between the rotation axis and the 15 line A1-5 is 112 line A11-2, the 112 line A11-2 and the revolute pair axis are intersected at 112 point P11-2, and the 112 line A11-2 and the 15 line A1-5 are intersected at 111 point P11-1; the ninth moving branched chain connecting rod 11-3 and the ninth moving branched chain three-rotating component 11-4 form a revolute pair; the ninth moving branched chain three-rotation part 11-4 and the ninth moving branched chain three-rotation part 11-5 form a revolute pair; the rotation axis of the rotation pair formed by the ninth movement branched chain three-rotation part 11-5 and the main arm auxiliary connection part 2-1 is a 114 line A11-4, the 114 line A11-4 and the axis of the rotation pair formed by the ninth movement branched chain three-rotation part 11-4 and the ninth movement branched chain three-rotation part 11-5 are intersected at a 114 point P11-4, and the 113 line A11-3 and the axis of the rotation pair are intersected at a 113 point P11-3; the ninth movement branched chain three-two rotating part 11-5 and the main arm auxiliary connecting part 2-1 form a rotating pair, the axis of the rotating pair is 115 lines A11-5, and the rotating pair points to a telecentric point 0; the connecting line of the 112 point P11-2 and the 113 point P11-3 is a 113 line A11-3; the ninth movement branched chain two-degree-of-freedom rotating unit 11-2 is a two-degree-of-freedom rotating unit and is a serial joint formed by two revolute pairs with non-parallel axes; the ninth moving branched chain three-rotation part 11-4 and the ninth moving branched chain three-two-rotation part 11-5 are combined into a three-degree-of-freedom rotation unit, and are serial joints formed by three revolute pairs with non-coplanar axes.

The driving parts of the eighth moving branched chain and the ninth moving branched chain are respectively a moving pair between the eighth moving branched chain and the frame, the moving pair is driven by a screw rod nut, the screw rod is arranged on the frame, and the nut is arranged on the moving branched chain.

As shown in fig. 11, the included angle between the eighth moving branched chain, the ninth moving branched chain and the direction of the moving pair formed by the frame is equal to the included angle between the eighth moving branched chain, the ninth moving branched chain and the axial direction of the rotating pair formed by the auxiliary part, which is embodied as the included angle between the 16 line A1-6 and the 15 line A1-5 is equal to the included angle between the 105 line a10-5 and the 115 line a11-5, because the included angle between the 16 line A1-6 and the 15 line A1-5 is fixed, the distance between the main arm 2 and the telecentric point 0 is fixed, and the included angle between the 105 line a10-5 and the 115 line a11-5 is fixed, so that is achieved; the distance from the moving pair formed by the eighth moving branched chain and the frame to the telecentric point is equal to the distance from the moving pair formed by the ninth moving branched chain and the frame to the telecentric point, and the distance between the 101 point P10-1 and the telecentric point 0 is equal to the distance between the 111 point P11-1 and the telecentric point 0; the eighth moving branch has the same dimensions as the ninth moving branch, and is embodied by 102 line A10-2 having a length equal to 112 line A11-2, 103 line A10-3 having a length equal to 113 line A11-3, and 104 line A10-4 having a length equal to 114 line A11-4; the distance from point 104P 10-4 to point 0 is equal to the distance from point 114P 11-4 to point 0, which is achievable because the distance from main arm 2 to point 0 is fixed and main arm auxiliary connection element 2-1 is fixedly connected to main arm 2.

The eighth moving branch and the ninth moving branch which satisfy the above relation have one of the following solutions in a certain spatial range: the polygon 0-P10-1-P10-2-P10-3-P10-4 is all equal to the polygon 0-P11-1-P11-2-P11-3-P11-4; the quadrangle formed by 104 points P10-4, 101 points P10-1, 111 points P11-1 and 114 points P11-4 is an isosceles trapezoid; the line formed by points 104P 10-4, 114P 11-4 is parallel to the line formed by points 101P 10-1, 111P 11-1.

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 branched chain has 6 degrees of freedom, and on the basis of the first embodiment, the degree of freedom of the system is 1 after the eighth moving branched chain is connected in parallel; the primary moving part of the eighth moving branched chain is a moving pair formed by a boss 1-6 of a fourth frame and a sliding block 10-1 of the eighth moving branched chain, so that the rotation of the main arm 2 is controlled; when the eighth moving branched chain and the ninth moving branched chain work in a combined mode, the distance between the 101 point P10-1 and the telecentric point 0 is equal to the distance between the 111 point P11-1 and the telecentric point 0, the rotation angle of the main arm 2 can be kept unchanged, and the line formed by the 104 point P10-4 and the 114 point P11-4 is parallel to the line formed by the 101 point P10-1 and the 111 point P11-1.

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

If the two-degree-of-freedom rotation 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, the 101 point P10-1 coincides with the 102 point P10-2, and the 111 point P11-1 coincides with the 112 point P11-2; if the three-degree-of-freedom rotation unit is a ball pair, the lengths of the 104 line A10-4 and the 114 line A11-4 are zero, and the 103 point P10-3 coincides with the 104 point P10-4; other parameters such as the dimensional relationship of the moving branches are consistent with the case where the branch form is prrrr.

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 driving parts of the eighth moving branched chain and the ninth moving branched chain are moving units of the moving branched chain, the moving units enable the moving branched chain to form a moving pair with the frame, the moving pair direction of the eighth moving branched chain is 16 lines A1-6, and the moving pair direction of the ninth moving branched chain is 15 lines A1-5 in accordance with the condition when the moving branched chain is in the form of PRRRR; the center of the ball pair formed between the eighth moving branched chain and the main arm auxiliary connecting part 2-1 is on the line A10-5, and the center of the ball pair formed between the ninth moving branched chain and the main arm auxiliary connecting part 2-1 is on the line A11-5.

In summary, when the eighth and ninth moving branches are in the form of PS 'S, PS' RRR, PUS, PURRR, PRRS, PRRRRR, the line formed by points 104P 10-4 and 114P 11-4 is parallel to the line formed by points 101P 10-1 and 111P 11-1.

A fifth embodiment of the present disclosure is that, on the basis of the first embodiment, in order to control the degree of freedom of rotation of the main arm 2, a twelfth moving branched chain may be added, and the form of the twelfth moving branched chain may be PS 'RRR, PS' S, PUS, PURRR, PRRS, PRRRRR; taking prrrr as an example, as shown in fig. 12, the twelfth moving branched chain includes a twelfth moving branched chain slider 14-1, a twelfth moving branched chain two-degree-of-freedom rotating unit 14-2, a twelfth moving branched chain connecting rod 14-3, a twelfth moving branched chain three-rotating member 14-4, a twelfth moving branched chain three-two-rotating member 14-5, and a twelfth moving branched chain auxiliary connecting piece 14-6; the second boss 1-3 of the frame forms a kinematic pair with the twelfth moving branched chain sliding block 14-1, the twelfth moving branched chain sliding block 14-1 forms a revolute pair with the twelfth moving branched chain two-degree-of-freedom rotating unit 14-2, the twelfth moving branched chain two-degree-of-freedom rotating unit 14-2 forms a revolute pair with the twelfth moving branched chain connecting rod 14-3, the twelfth moving branched chain connecting rod 14-3 forms a revolute pair with the twelfth moving branched chain three-rotating component 14-4, the twelfth moving branched chain three-rotating component 14-4 forms a revolute pair with the twelfth moving branched chain three-two-rotating component 14-5, the twelfth moving branched chain three-rotating component 14-5 forms a revolute pair with the twelfth moving branched chain auxiliary connecting piece 14-6, and the twelfth moving branched chain auxiliary connecting piece 14-6 is fixedly connected with the main arm 2; the twelfth movement branched chain two-degree-of-freedom rotating unit 14-2 is a two-degree-of-freedom rotating unit and is a serial joint formed by two revolute pairs with non-parallel axes; the twelfth moving branch three-rotation part 14-4 and the twelfth moving branch three-two-rotation part 14-5 are combined into a three-degree-of-freedom rotation unit, and are serial joints formed by three revolute pairs with non-parallel axes.

The sixth embodiment disclosed by the invention is a modification of all the above embodiments, wherein the primary moving part of the three-dimensional two-degree-of-freedom telecentric point motion parallel mechanism can influence the gesture of the mechanism through the length change of the connecting rod on the connecting rod of the motion branched chain instead of the moving pair formed by the motion branched chain and the frame; take the form of RRPRRR as an example; as shown in fig. 13, the tenth moving branch includes a tenth moving branch fixing member 12-1, a tenth moving branch two-degree-of-freedom rotation unit 12-2, a tenth moving branch front link 12-3, a tenth moving branch rear link 12-4, a tenth moving branch three-rotation member 12-5, and a tenth moving branch three-two-rotation member 12-6; the second boss 1-3 of the frame is fixedly connected with the tenth movable branched fixing part 12-1; the tenth moving branched chain fixing part 12-1 and the tenth moving branched chain two-degree-of-freedom rotating unit 12-2 form a rotating pair, the axis of the rotating pair is 13 lines A1-3, and the rotating pair points to the telecentric point 0; the rotation unit 12-2 with two degrees of freedom of the tenth movement branched chain and the front connecting rod 12-3 of the tenth movement branched chain form a revolute pair, a common vertical line between the rotation axis and the 13 line A1-3 is 122 line A12-2, the 122 line A12-2 and the revolute pair axis are intersected at a 122 point P12-2, and the 122 line A12-2 and the 13 line A1-3 are intersected at a 121 point P12-1; the tenth movement branched chain front connecting rod 12-3 and the tenth movement branched chain rear connecting rod 12-4 form a moving pair; the rear connecting rod 12-4 of the tenth moving branched chain and the third rotating part 12-5 of the tenth moving branched chain form a rotating pair, the third rotating part 12-5 of the tenth moving branched chain and the third rotating part 12-6 of the tenth moving branched chain form a rotating pair, the common vertical line of the rotating axis and the 2 line A2 is 124 line A12-4, the 124 line A12-4 and the rotating pair are intersected at a point P12-3 of 123, and the 124 line A12-4 and the 2 line A2 are intersected at a point P12-4 of 124; the tenth moving branched chain three-two rotating part 12-6 and the main arm 2 form a rotating pair, and the rotating axis of the rotating pair is 2 lines A2; the tenth movement branched chain two-degree-of-freedom rotating unit 12-2 is a two-degree-of-freedom rotating unit and is a serial joint formed by two revolute pairs with non-parallel axes; the tenth moving branch three-rotation part 12-5 and the tenth moving branch three-two-rotation part 12-6 are combined into a three-degree-of-freedom rotation unit, and are serial joints formed by three revolute pairs with non-coplanar axes.

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

For the first embodiment, when the form of the moving branched chain is converted from prrrr to rrprr, taking the first moving branched chain as an example, the first moving branched chain is replaced by the tenth moving branched chain, and the 31 point P3-1, the 32 point P3-2, the 33 point P3-3 and the 34 point P3-4 are replaced by the 121 point P12-1, the 122 point P12-2, the 123 point P12-3 and the 124 point P12-4 respectively; the second movement branched chain is replaced by the eleventh movement branched chain, and the 41 point P4-1, the 42 point P4-2, the 43 point P4-3 and the 44 point P4-4 are replaced by the 131 point P13-1, the 132 point P13-2, the 133 point P13-3 and the 134 point P13-4 respectively; the dimensional relationships, functions in the first embodiment are still applicable to such moving branches.

For the fourth embodiment, when the form of the moving branched chain is converted from prrrr to rrprr, taking the eighth moving branched chain as an example, the eighth moving branched chain is replaced by the tenth moving branched chain, and the points 101, 102, 10-2, 103, 10-3, and 104 are replaced by the points 121, 12-1, 122, 12-2, 123, 12-3, and 124, 12-4, respectively; the dimensional relationships, functions in the fourth embodiment are still applicable to such a kinematic chain.

Taking a tenth movement branched chain and an eleventh movement branched chain as examples when the movement branched chain is replaced by S 'PS and S' PRRR, UPS, UPRRR, RRPS, if the tenth movement branched chain two-degree-of-freedom rotation 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 overlapped with a 121 point P12-1; if the eleventh motion branched chain two-degree-of-freedom rotation 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 coincides with the 131 point P13-1; if the three-degree-of-freedom rotating unit of the tenth moving branched chain is a ball pair, the length of the 124 line A12-4 is zero, and the 123 point P12-3 is overlapped with the 124 point P12-4; if the three-degree-of-freedom rotation unit of the eleventh motion branched chain is a ball pair, the length of a 134 line A13-4 is zero, and a 133 point P13-3 coincides with a 134 point P13-4; other parameters such as the dimensional relationship of the moving branch are consistent with those in the case of prrrr, so that when the moving branch is S 'PS or S' PRRR, UPS, UPRRR, RRPS, the 2-line A2 can be constantly directed to the telecentric point 0.

Claims

1. A three-dimensional space two-degree-of-freedom telecentric point movement parallel mechanism comprises a frame, a main arm and five groups of movement branched chains; the five groups of movement branched chains comprise a first movement branched chain, a second movement branched chain, a third movement branched chain, a fourth movement branched chain and a fifth movement branched chain; the method is characterized in that: each group of movement branched chains is formed by sequentially connecting 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 movable unit and the frame relatively move in one degree of freedom, the connecting rod and the movable unit relatively rotate in two degrees of freedom in a three-dimensional space through the two-degree-of-freedom rotating unit, and the main arm (2) and the connecting rod relatively rotate in three degrees of freedom in the three-dimensional space through the three-degree-of-freedom rotating unit; the two-degree-of-freedom rotating unit is a ball pin pair, a universal joint or a serial joint formed by two rotating pairs with non-parallel axes, the three-degree-of-freedom rotating unit is a ball pair or a serial joint formed by three rotating pairs with non-coplanar axes, therefore, the form of the moving branched chain is a moving pair, the two-degree-of-freedom rotating unit and the three-degree-of-freedom rotating unit are sequentially connected in series, 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 moving branched chains and the machine frame respectively form a moving pair through a moving unit, the direction of the moving pair points to a telecentric point (0), the moving pair formed by the first moving branched chain and the machine frame is collinear with the moving pair formed by the second moving branched chain and the machine frame, and the direction of the moving pair formed by the third moving branched chain and the machine frame is collinear with the moving pair formed by the fourth moving branched chain and the machine frame; the first movement branched chain and the telecentric point form a polygon, the second movement branched chain and the telecentric point form a polygon, the two polygons are similar, and the ratio between the kinematic dimensions of the first movement branched chain and the second movement branched chain is K1; the third movement branched chain and the telecentric point form a polygon, the fourth movement branched chain and the telecentric point form a polygon, the two polygons are similar, and the ratio between the kinematic dimensions of the third movement branched chain and the fourth movement branched chain is K2; the driving part of the motion branched chain is a moving pair formed by a moving unit of the motion branched chain and the frame, the moving pair is driven by a screw rod nut, the screw rod is arranged on the frame, the nut is arranged on the motion branched chain, the screw rod is respectively arranged on a third boss (1-2) of the frame, a second boss (1-3) of the frame and a first boss (1-4) of the frame, 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 moving pair of the first moving branched chain and the moving pair of the second moving branched chain are driven by the same motor, the motor drives two lead screws with different leads to rotate at the same rotation speed, and the lead ratio of the two lead screws is equal to 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 equal to K1; the moving pair of the third moving branched chain and the moving pair of the fourth moving branched chain are driven by the same motor, the motor drives two lead screws with different leads to rotate at the same rotation speed, and the lead ratio of the two lead screws is equal to K2; in addition, the primary moving part is arranged on the connecting rod of the moving branched chain, the posture of the mechanism is influenced by the length change of the connecting rod, and the moving branched chain is formed by sequentially connecting the certain two-degree-of-freedom rotating unit, the moving pair and the certain three-degree-of-freedom rotating unit in series.

2. The three-dimensional two-degree-of-freedom telecentric point motion parallel mechanism according to claim 1, wherein: the eight movement branched chain, the ninth movement branched chain and the main arm auxiliary connecting part (2-1) are added, the eight movement branched chain and the ninth movement branched chain are formed by sequentially connecting a frame, a moving unit, a two-degree-of-freedom rotating unit, a connecting rod, a three-degree-of-freedom rotating unit, the main arm auxiliary connecting part (2-1) and a main arm (2), the eight movement branched chain and the ninth movement branched chain have the same form, the form of the eight movement branched chain and the ninth movement branched chain is a moving pair, and the certain two-degree-of-freedom rotating unit and the certain three-degree-of-freedom rotating unit are sequentially connected in series; the eighth moving branched chain and the ninth moving branched chain respectively form a moving pair with the frame through the moving unit, and the direction of the moving pair points to a telecentric point (0); the eighth moving branched chain and the ninth moving branched chain respectively form polygons with telecentric points, the polygons are congruent, and the eighth moving branched chain and the ninth moving branched chain have the same kinematic size.

3. The three-dimensional two-degree-of-freedom telecentric point motion parallel mechanism according to claim 1, wherein: and a sixth motion branched chain is added, wherein the sixth motion branched chain is formed by sequentially connecting a frame, 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 sixth motion branched chain is in a form of a moving pair, and the two-degree-of-freedom rotating units are sequentially connected in series.

4. The three-dimensional two-degree-of-freedom telecentric point motion parallel mechanism according to claim 1, wherein: and a seventh motion branched chain is added, wherein the seventh motion branched chain is formed by sequentially connecting a frame, 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 is in a form of a moving pair, and the two-degree-of-freedom rotating units are sequentially connected in series.