CN112975916B - Two-turn and one-shift parallel mechanism, its end pose determination method and application - Google Patents

Abstract

The invention discloses a two-transition and one-shift parallel mechanism, a method for determining the position and attitude of its end and its application. The two-turn-one-shift parallel mechanism includes a moving platform, a base, and three branch chains. The base includes a static platform, a redundant static platform, and a plurality of connectors connecting the static platform and the redundant static platform. The redundant static platform is located at the Between the moving platform and the static platform, and the redundant static platform is provided with three through holes, three branch chains are connected between the moving platform and the static platform, and each branch chain includes a driving moving pair, a first passive moving pair, a second Two passive moving pairs and spherical pairs, one end of each driving moving pair is movably connected to the static platform through the first passive moving pair, and the opposite end passes through a through hole of the redundant static platform and can be connected to the moving platform through the corresponding spherical pair. are rotatably connected, and the driving moving pair is also movably connected to the redundant static platform through a second passive moving pair. The invention can reduce the distance between the moving platform and the static platform and improve the rigidity of the system.

Description

Two-turn and one-shift parallel mechanism, its end pose determination method and application

technical field

The invention belongs to the technical field of robots, and in particular relates to a two-rotation and one-shift three-degree-of-freedom parallel mechanism and a method for determining the position and posture of its end.

Background technique

Parallel robots and serial robots together constitute an important part of industrial robots. Parallel robots have the advantages of high stiffness, high speed, strong flexibility, and light weight. They are most widely used in light industries such as food, medicine, and electronics. Sorting and other aspects have unparalleled advantages. With the increasing application of parallel robots in the market, it has become a new force for the growth of industrial robot demand.

The parallel robot is different from the series robot. The parallel robot is a closed-loop system composed of a moving platform, a static platform, and two or more independent moving branches connecting the moving platform and the static platform. Compared with the traditional series robot, the parallel robot has no errors. Accumulation, high motion accuracy, the drive can be arranged near the static platform, the motion inertia is small, and the dynamic performance is good.

At present, parallel robots with less than 6 degrees of freedom are the research and application hotspots at home and abroad. Three-degree-of-freedom parallel robots with two rotational degrees of freedom and one moving degree of freedom are also an important category of parallel robots with few degrees of freedom. The 3P P S parallel robot is a typical two-turn and one-shift parallel robot, which can be used in motion simulators, end effectors, vector thrusters, medical equipment and other fields. However, in the process of actually manufacturing the 3P P S parallel robot, due to the long body of the linear drive such as the electric push rod and hydraulic cylinder used to drive the moving pair, the distance between the moving platform and the static platform is large, and the moving platform plays a role in the load. Compared with the static platform, it is easy to deform, and the overall stiffness of the system is poor.

SUMMARY OF THE INVENTION

The main purpose of the present invention is to provide a two-rotation-one-shift parallel mechanism, which reduces the distance between the moving platform and the static platform while improving the rigidity of the system, and also provides a method for determining the end pose of the two-rotation-one-shift parallel mechanism .

In order to achieve the aforementioned purpose of the invention, the technical solution adopted in the present invention includes: a two-turn-one-shift parallel mechanism, wherein the two-turn-one-shift parallel mechanism includes:

mobile platform;

a base, the base includes a static platform, a redundant static platform, and a plurality of connectors connecting the static platform and the redundant static platform, the redundant static platform is located between the dynamic platform and the static platform, and The redundant static platform is provided with three through holes;

Three branched chains are connected between the moving platform and the static platform, each of the branched chains includes a driving moving pair, a first passive moving pair, a second passive moving pair and a spherical pair, and one end of each driving moving pair The first passive moving pair is movably connected to the static platform, the opposite end is rotatably connected to the moving platform through a corresponding spherical pair after passing through a through hole of the redundant static platform, and the driving moving pair is also connected to the moving platform through the second passive moving pair. The mobile pair is movably connected to the redundant static platform.

Preferably, the first passive moving pair includes at least one first sliding rail assembly for guiding and moving the driving moving pair, and the first sliding rail assembly includes a first sliding block and a first sliding block for guiding and moving the first sliding block. A guide rail, the first sliding block is slidably arranged on the first guide rail, any one of the first sliding block and the first guide rail is fixed on the static platform, and the other is connected with the driving moving pair.

Preferably, the second passive moving pair includes at least one second sliding rail assembly for guiding and moving the driving moving pair, and the second sliding rail assembly includes a second sliding block and a first sliding block for guiding and moving the second sliding block. Two guide rails, the second sliding block is slidably arranged on the second guide rail, any one of the second sliding block and the second guide rail is fixed on the redundant static platform, and the other is connected to the driving moving pair.

Preferably, the second slide rail assembly is provided on the redundant static platform and is located between the redundant static platform and the moving platform; or, the second slide rail assembly is provided on the redundant static platform on the platform and between the redundant static platform and the static platform.

Preferably, the second passive moving pair includes two second slide rail assemblies, one of the second slide rail assemblies is provided on both sides of the through hole, and the two second slide rail assemblies are symmetrically arranged.

Preferably, one end of the three branch chains is arranged in an equilateral triangle on the surface of the moving platform, and the opposite ends are arranged in an equilateral triangle on the static platform.

Preferably, the moving platform includes a platform body portion and three lug portions, and the peripheral surface of the platform body portion protrudes outward to form three lug portions, and the adjacent two lug portions have three lug portions. The angle between the center lines is 120 degrees.

Preferably, the static platform includes a first body part and three first extension parts, and the peripheral surface of the first body part protrudes outward to form three first extension parts, and the centers of the adjacent two first extension parts The angle between the lines is 120 degrees.

Preferably, the redundant static platform includes a second body part and three second extension parts, and the peripheral surface of the second body part protrudes outwardly to form three second extension parts, two adjacent second extension parts The centerline angle is 120 degrees.

The present invention also discloses a method for determining the end pose of a two-turn-one-shift parallel mechanism, comprising the following steps:

Obtain the elongation of each branch chain, and calculate the end pose of the two-turn-one-shift parallel mechanism according to the following formula:

、

、

分别为局部坐标系绕全局坐标系x、y、z轴旋转的角度，

为三个球面副的几何中心

、

、

构成的正三角的外接圆的半径，

为正三角形的外接圆的圆心的坐标值。in,

,

,

are the rotation angles of the local coordinate system around the x, y, and z axes of the global coordinate system, respectively,

is the geometric center of the three spherical pairs

,

,

The radius of the circumcircle of the formed regular triangle,

It is the coordinate value of the center of the circumcircle of the equilateral triangle.

The invention also discloses a parallel robot with few degrees of freedom, which includes the two-transition and one-shift parallel mechanism.

Compared with the prior art, the beneficial effects of the present invention are at least as follows:

(1) The present invention forms a double-layer structure by adding a redundant static platform matched with the static platform on the basis of the static platform, so as to carry out double-layer redundant constraints on the driving moving pair in the branch chain, which can effectively reduce the dynamic pressure. The distance between the platform and the static level significantly increases the stiffness of the system.

(2) The present invention adopts a base designed with a double-layer structure, which has a wide range of applications, that is, the design method adopted in the present invention expands the base range of the 3P P S parallel mechanism, making the interface installation of the parallel mechanism and other equipment more flexible , not only can be installed vertically, but also can be installed horizontally using any side.

(3) The present invention also has the advantages of symmetrical and compact structure, high reliability, good dynamic performance, simple control and high precision.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments described in the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

Fig. 1 is the three-dimensional schematic diagram of the two-turn-one-shift parallel mechanism in the first embodiment of the present invention;

Fig. 2 is the three-dimensional schematic diagram of the parallel mechanism of two shifts and one shift in the second embodiment of the present invention;

FIG. 3 is a schematic diagram of a two-rotation and one-shift parallel mechanism in a typical embodiment of the present invention.

Reference numerals: 10, moving platform, 10a, platform body part, 10b, lug part, 20, base, 21, static platform, 21a, first body part, 21b, first extension part, 22, redundant static Platform, 22a, second body part, 22b, second extension part, 221, through hole, 23, connecting piece, 30, branch chain, 31, drive moving pair, 31a, linear drive telescopic rod, 31b, linear drive body, 31c, linear drive base, 32, first passive moving pair, 32a, first sliding block, 32b, first guide rail, 33, second passive moving pair, 33a, second sliding block, 33b, second guide rail, 34, Spherical pair, 40, flange.

Detailed ways

The present invention will be more fully understood from the following detailed description, which should be read in conjunction with the accompanying drawings. Detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and for teaching one skilled in the art to vary in virtually any suitable detailed embodiment. The manner adopts the representative basis of the present invention.

A two-rotation and one-shift parallel mechanism disclosed in the following embodiments of the present invention implements double-layer redundancy constraints on the driving moving pair in the branch chain, that is, on the basis of the static platform, the redundancy matching with the static platform is added. The static platform forms a double-layer structure, which can effectively reduce the distance between the moving platform and the static platform and significantly improve the system rigidity.

The two-transfer-one-shift parallel mechanism of the present invention is described in detail below with two embodiments:

Embodiment 1: As shown in FIG. 1 , a two-turn-one-shift parallel mechanism disclosed in this embodiment is a 3P P S parallel mechanism (P is a moving pair, and P is a driving moving pair. , S is a spherical pair), including a moving platform 10, a base 20 and three branch chains 30. The three branch chains 30 are installed on the base 20 and are connected to the moving platform 10, and the expansion and contraction of the three branch chains 30 are controlled cooperatively. The moving platform 10 can realize the pose transformation of two rotations and one displacement. Specifically, the base 20 includes a static platform 21 , a redundant static platform 22 and a plurality of connectors 23 , the static platform 21 and the redundant static platform 22 are arranged opposite to each other, and the redundant static platform 22 is located between the dynamic platform 10 and the static platform 21 . , and the redundant static platform 22 is provided with three through holes 221, one end of each connecting piece 23 is connected with the static platform 21, and the opposite end is connected with the redundant static platform 22, finally forming a double-layer structure; each branch 30 is connected Between the moving platform 10 and the static platform 21, each branch chain 30 includes a driving moving pair 31, a first passive moving pair 32, a second passive moving pair 33 and a spherical pair 34. One end of the driving moving pair 31 passes through the first passive moving pair 31. The moving pair 32 is movably connected to the static platform 21 , and the opposite end passes through the through hole 221 on the redundant static platform 22 and is rotatably connected to the moving platform 10 through the spherical pair 34 , and the driving moving pair 31 also moves through the second passive movement. The pair 33 is movably connected to the static platform 21 . By adopting the base 20 designed with a double-layer structure, that is, adopting the double-layer structure composed of the static platform 21 and the redundant static platform 22, the double-layer redundant constraint can be applied to the driving moving pair 31 in the branch chain 30, which can reduce the dynamic The distance between the platform 10 and the static platform 21 significantly improves the rigidity of the system, and the distance here refers to the distance between the movable platform 10 and the redundant static platform 22 . The base 20 with the double-layer redundant constraint design is not only suitable for the 3P P S parallel mechanism, but also suitable for other mechanisms using linear drives such as electric push rods and hydraulic cylinders as the driving moving pair 31, and has a wide range of applications.

In this embodiment, the through hole 221 is preferably a rectangular hole. Of course, in other embodiments, the shape of the through hole 221 can also be set according to actual requirements, such as a circle or the like. The three branch chains 30 are arranged in an equilateral triangle around the center of the static platform, that is, one end of the branch chain 30 is arranged in an equilateral triangle on the surface of the moving platform 10, and the opposite end is arranged in an equilateral triangle on the static platform 21. The distances from the ends of the two branches to their respective centers are the same, and the included angle between the two adjacent branch chains 30 is 120 degrees. The driving body 31b and the linear driving base 31c, the linear driving body 31b is connected between the linear driving telescopic rod 31a and the linear driving base 31c, and the linear driving body 31b drives the linear telescopic rod to realize telescopic. When implemented, the linear moving mechanism can choose electric push rod, hydraulic cylinder and so on. The three spherical pairs 34 are arranged in an equilateral triangle on the moving platform 10, and the spherical pairs 34 are preferably ball bearings. The ball bearings have a bearing base and a connecting handle that is connected to the bearing base and can be rotated relative to the bearing base. Of course, in other embodiments, You can choose a mechanism with the same function, such as a joint ball joint.

As shown in FIG. 1 , each first passive moving pair 32 includes at least one first sliding rail assembly disposed on the static platform 21 , and the first sliding rail assembly is used to guide the driving moving pair 31 to move. Specifically, the first sliding rail assembly includes a first sliding block 32a and a first guide rail 32b, the first sliding block 32a is slidably arranged on the first guide rail 32b, and the first sliding block 32a and the linear driving base 31c of the linear moving mechanism are connected by screws In connection, the first guide rails 32b extend along the radial direction of the static platform 21 for guiding and moving the first sliding block 32a.

In this embodiment, among the three first guide rails 32b, the included angle between two adjacent first guide rails 32b is 120 degrees. The sliding block 32 a is arranged on the static platform 21 .

Each second passive moving pair 33 includes at least one second sliding rail assembly disposed on the redundant static platform 22 , and the second sliding rail assembly is used to guide the driving moving pair 31 to move. Specifically, the second sliding rail assembly includes a second sliding block 33a and a second guide rail 33b, the second sliding block 33a is slidably arranged on the second guide rail 33b, and the second sliding block 33a is linearly driven by the flange 40 and the linear moving mechanism The main bodies 31b are connected, and the second guide rails 33b are extended along the radial direction of the redundant static platform 22 for guiding and moving the second sliding block 33a.

In this embodiment, among the three second guide rails 33b, the included angle between two adjacent second guide rails 33b is 120 degrees. The sliding block 33 a is arranged on the redundant static platform 22 . In addition, in this embodiment, each second passive moving pair 33 includes two second slide rail assemblies, two corresponding second slide rail assemblies are provided on both sides of each through hole 221 , and the two second slide rails Components are set symmetrically.

As shown in FIG. 1 , the position of the second sliding rail assembly in the second passive moving pair 33 on the redundant static platform 22 can be set according to actual requirements. Specifically, the redundant static platform 22 has a first end surface and a second end surface disposed opposite to each other, the first end surface faces the moving platform 10 , and the second end surface faces the static platform 21 . In this embodiment, in each second passive moving pair 33 The second slide rail assembly is arranged on the first end surface of the redundant static platform 22 . As shown in the figure, the second sliding rail assembly in each second passive moving pair 33 is disposed on the first end surface of the redundant static platform 22 , that is, the second sliding rail assembly in each second passive moving pair 33 Located between the redundant static platform 22 and the moving platform 10 . By reasonably setting the position of the second passive moving pair 33 , the distance between the moving platform 10 and the static platform 21 can also be correspondingly reduced.

As shown in FIG. 1 , the moving platform 10 includes a platform body portion 10a and three lug portions 10b. The platform body portion 10a is entirely cylindrical, and its peripheral side protrudes outward to form three lug portions 10b, two adjacent to each other. The included angle between the center lines of the lug portions 10b is 120 degrees, that is, the three lug portions 10b are distributed at 120 degrees around the body portion. A spherical pair 34 is installed on each lug portion 10b, and each driving moving pair 31 is fixedly connected to a lug portion 10b through the spherical pair 34. In this embodiment, a ball bearing is installed on each lug portion 10b, and each linear movement mechanism is fixedly connected to a lug portion 10b through the ball bearing. The lugs 10b are fixedly connected, and the connecting handle is connected with the end of the linear driving telescopic rod 31a in the linear moving mechanism by means of screw connection.

As shown in FIG. 1 , the static platform 21 is Y-shaped as a whole, and includes a first body portion 21a and three first extension portions 21b. The peripheral surface of the first body portion 21a protrudes outward to form three first extension portions. 21b, the included angle between the centerlines of the two adjacent first extension parts 21b is 120 degrees, that is, the three first extension parts 21b are distributed around the main body at 120 degrees. A first passive moving pair 32 is mounted on each first extending portion 21b, and each driving moving pair 31 is movably connected to the corresponding first extending portion 21b through the first passive moving pair 32. In this embodiment, a first slide rail assembly is installed on each first extension portion 21b, and the linear drive base 31c in each linear movement mechanism is movably connected to the corresponding first extension portion 21b through the first slide rail assembly, Under the action of the first slide rail assembly, the linear drive base 31c can move relative to the corresponding first extension portion 21b. During implementation, the linear drive base 31c is connected to the first slider 32a in the first slide rail assembly through screws. A guide rail is fixedly connected to the corresponding first extension portion 21b by screws.

As shown in FIG. 1 , the redundant static platform 22 is Y-shaped as a whole, and includes a second body portion 22a and three second extension portions 22b. The peripheral side surface of the second body portion 22a protrudes outward to form three second body portions 22a. In the extension portion 22b, the included angle between the centerlines of two adjacent second extension portions 22b is 120 degrees, that is, the three second extension portions 22b are distributed at 120 degrees around the body portion. A second passive moving pair 33 is mounted on each second extending portion 22b, and each driving moving pair 31 is movably connected to the corresponding second extending portion 22b through the second passive moving pair 33. In this embodiment, each second extension portion 22b is provided with a through hole 221 through which the linear drive body 31b passes, and a second slide rail assembly is provided on both sides of the through hole 221. The linear drive body 31b is movably connected to the corresponding second extension portion 22b through the second slide rail assembly. Under the action of the second slide rail assembly, the linear drive body 31b can move relative to the corresponding second extension portion 22b. , the linear drive body 31b is connected with the second sliding block 33a in the second slide rail assembly through the flange 40, and the second guide rail is fixedly connected with the corresponding second extension part 22b through screws.

In the present invention, the moving platform 10 , the static platform 21 and the redundant static platform 22 are all weight-reducing optimized design structures. Of course, in other embodiments, other shapes and structures, such as circular structures, triangular structures, square structures, etc., can also be used. Wait.

Embodiment 2: As shown in FIG. 2 , a two-transfer and one-shift parallel mechanism disclosed in this embodiment includes a moving platform 10, a base 20 and three branch chains 30, and the three branch chains 30 are installed on the base 20 is connected to the moving platform 10, and the moving platform 10 can realize the pose transformation of two rotations and one displacement by controlling the expansion and contraction of the three branch chains 30 in coordination. Different from the first embodiment, in this embodiment, in each branch chain 30, the second slide rail assembly in each second passive moving pair 33 is arranged on the second end surface of the redundant static platform 22, and also That is, the second sliding rail assembly in each second passive moving pair 33 is located between the static platform 21 and the moving platform 10 .

With reference to FIGS. 1 to 3 , the present invention also discloses the method for determining the end pose of the two-turn-one-shift parallel mechanism provided by the above two embodiments, including the following steps:

Obtain the elongation of each branch chain 30, and calculate the end pose of the two-turn-one-shift parallel mechanism according to the following formula:

、

、

分别为局部坐标系绕全局坐标系x、y、z轴旋转的角度，

为三个球面副34的几何中心

、

、

构成的正三角形的外接圆的半径，

为正三角形的外接圆的圆心的坐标值。in,

,

,

are the rotation angles of the local coordinate system around the x, y, and z axes of the global coordinate system, respectively,

is the geometric center of the three spherical pairs 34

,

,

The radius of the circumcircle of the formed equilateral triangle,

It is the coordinate value of the center of the circumcircle of the equilateral triangle.

、

、

构成一个正三角形，该正三角形的外接圆半径为

，以正三角形

的外接圆圆心P为原点建立局部坐标系

，其中

与

共线且

轴的正方向与

同向，

与

平行且

的正方向与

同向，

的方向根据右手定则确定。以静平台21的几何中心

为原点建立全局坐标系

，全局坐标系坐标轴的方向与局部坐标系一致。该图3中，q1、q2、q3是三个驱动移动副的伸长量，B1、B2、B3是三个驱动移动副与静平台的交点，d1、d2、d3是B1、B2、B3与底部三角形中心的距离，该底部三角形是B1、B2、B3构成的三角形。Specifically, as shown in FIG. 3 , the above formula can be obtained by the following steps: the geometric centers of the three spherical pairs 34

,

,

form an equilateral triangle whose circumcircle radius is

, in an equilateral triangle

The center of the circumcircle P is the origin to establish a local coordinate system

,in

and

collinear and

The positive direction of the axis is the same as

In the same direction,

and

parallel and

positive direction with

In the same direction,

The direction is determined according to the right-hand rule. Taking the geometric center of the static platform 21

Establish a global coordinate system for the origin

, the direction of the global coordinate system coordinate axis is consistent with the local coordinate system. In Fig. 3, q1, q2, q3 are the elongation of the three driving moving pairs, B1, B2, B3 are the intersection points of the three driving moving pairs and the static platform, d1, d2, d3 are B1, B2, B3 and the The distance from the center of the bottom triangle, which is the triangle formed by B1, B2, and B3.

Further, the points in the local coordinate system are transformed to the global coordinate system through the following attitude transformation matrix:

、

、

分别为局部坐标系绕全局坐标系x、y、z轴旋转的角度。in,

,

,

are the rotation angles of the local coordinate system around the x, y, and z axes of the global coordinate system, respectively.

=0，则姿态转换矩阵可简化为：Further, since the 3P P S parallel mechanism has zero twist around the z-axis, so

=0, then the attitude transformation matrix can be simplified as:

、

、

相对于全局坐标系的位置矢量可表示为：Further, the geometric centers of the three spherical pairs 34 on the moving platform 10

,

,

The position vector relative to the global coordinate system can be expressed as:

为

点在局部坐标系的位置矢量，

为P点在全局坐标系的位置矢量。in,

for

the position vector of the point in the local coordinate system,

is the position vector of point P in the global coordinate system.

The expression above is written as a homogeneous transformation as:

，

，

，

；in,

,

,

,

;

只能在

平面内运动，则Further, due to the geometric constraints of the 3P P S parallel mechanism itself,

only in

In-plane motion, then

Combining the above equations, we can obtain:

，

，

,

,

，可得：Further, by

,Available:

In the present invention, a redundant static platform 22 matched with the static platform 21 is added on the basis of the static platform 21 to form a double-layer structure, so as to carry out double-layer redundant constraints on the driving moving pair 31 in the branch chain 30, which can effectively The distance between the moving platform 10 and the static platform 21 is reduced, and the rigidity of the system is significantly improved. In addition, the base 20 designed with a double-layer structure has a wide range of applications, that is, the design method adopted in the present invention expands the range of the base 20 of the 3P P S parallel mechanism, making the interface installation of the parallel mechanism and other equipment more flexible, Not only can it be installed vertically, it can also be installed horizontally using either side. The two-transfer-one-transfer parallel mechanism of the present invention also has the advantages of symmetrical and compact structure, high reliability, good dynamic performance, simple control and high precision.

Further, the present invention also provides a parallel robot with few degrees of freedom, which is a 3P P S parallel robot, and has any of the aforementioned two-turn-one-shift parallel mechanisms.

Although the present invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions and/or additions and the like may be made without departing from the spirit and scope of the invention Effects replace elements of the described embodiments. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Therefore, it is not intended herein to limit the invention to the particular embodiments disclosed for carrying out the invention, but it is intended that this invention include all embodiments falling within the scope of the appended claims.

Claims (9)

1. a two-transfer-one-transfer parallel mechanism is characterized in that: the two-transfer-one-transfer parallel mechanism includes a moving platform, a base and three branch chains; the base includes a static platform, a redundant static platform and a connection place. A plurality of connectors of the static platform and the redundant static platform, the redundant static platform is located between the dynamic platform and the static platform, and the redundant static platform is provided with three through holes; The branch chain is connected between the moving platform and the static platform, and each branch chain includes a driving moving pair, a first passive moving pair, a second passive moving pair and a spherical surface pair, and one end of each driving moving pair passes through the first The passive moving pair is movably connected to the static platform, the opposite end passes through a through hole of the redundant static platform and is rotatably connected to the moving platform through the corresponding spherical pair, and the driving moving pair is also connected to the moving platform through the second passive moving pair. Redundant static platforms are movably connected; The first passive moving pair includes at least one first sliding rail assembly for guiding and moving the driving moving pair, the first sliding rail assembly includes a first sliding block and a first guide rail for guiding and moving the first sliding block, The first sliding block is slidably arranged on the first guide rail, any one of the first sliding block and the first guide rail is fixed on the static platform, and the other is connected with the driving moving pair; The second passive moving pair includes at least one second sliding rail assembly for guiding and moving the driving moving pair, the second sliding rail assembly includes a second sliding block and a second guide rail for guiding and moving the second sliding block, The second sliding block is slidably arranged on the second guide rail, any one of the second sliding block and the second guide rail is fixed on the redundant static platform, and the other is connected with the driving moving pair. 2 . The two-turn-one-shift parallel mechanism according to claim 1 , wherein the second slide rail assembly is arranged on the redundant static platform and is located between the redundant static platform and the moving platform. 3 . ; or, the second slide rail assembly is arranged on the redundant static platform, and is located between the redundant static platform and the static platform. 3 . The parallel mechanism of two rotations and one shift according to claim 1 , wherein the second passive moving pair comprises two second sliding rail assemblies, and one second sliding rail assembly is arranged on both sides of the through hole. 4 . rail assemblies, and the two second slide rail assemblies are symmetrically arranged. 4 . The two-turn-one-shift parallel mechanism according to claim 1 , wherein one end of the three branch chains is arranged in a regular triangle on the surface of the moving platform, and the opposite ends are arranged in a regular triangle on the static platform. 5 . 5 . The parallel mechanism for two rotations and one shift according to claim 1 , wherein the moving platform comprises a platform body portion and three lug portions, and the peripheral surface of the platform body portion protrudes outward to form three lugs. 6 . There are two said lug portions, and the included angle between the center lines of two adjacent said lug portions is 120 degrees. 6 . The two-turn-one-shift parallel mechanism according to claim 1 , wherein the static platform comprises a first body part and three first extension parts, and the peripheral surface of the first body part protrudes outwardly to form an extension. 7 . For the three first extension parts, the included angle between the center lines of two adjacent first extension parts is 120 degrees. 7 . The two-turn-one-shift parallel mechanism according to claim 1 , wherein the redundant static platform comprises a second body part and three second extension parts, and the peripheral surface of the second body part protrudes outward. 8 . Three second extension parts are formed by extension, and the included angle between the center lines of two adjacent second extension parts is 120 degrees. 8. A method for determining the terminal position and orientation of the two-transfer-one-transfer parallel mechanism based on any one of claims 1 to 7, comprising the steps of: Obtain the elongation of each branch chain, and calculate the end pose of the two-turn-one-shift parallel mechanism according to the following formula:

in,

,

,

are the rotation angles of the local coordinate system around the x, y, and z axes of the global coordinate system, respectively,

is the geometric center of the three spherical pairs

,

,

The radius of the circumcircle of the formed regular triangle,

It is the coordinate value of the center of the circumcircle of the equilateral triangle. 9 . A parallel robot with few degrees of freedom, characterized in that it comprises the two-turn-one-shift parallel mechanism according to any one of claims 1 to 7 .

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