A double parallelogram telecentric movable parallel robot mechanism

Abstract

The application provides a kind of double parallelogram telecentric movable parallel robot mechanism, which can meet the adjustable basis of telecentric point, the overall structure of the mechanism is simple, and the manufacturing and assembly difficulty is reduced.The telecentric point is arranged on the plane of the fixed platform, and the movable platform and the fixed platform are realized based on the multi-rotating branch chain, each platform includes N rotating shafts parallel platform rotating vice;The branch chain of the platform rotating vice movable platform and fixed platform produces deformation, and the telecentric point can be freely moved in the plane of the fixed platform;The connecting rod connected with the first branch chain, the second branch chain and the two platforms constitutes a first parallelogram, the third universal joint at the two ends of the third branch chain is connected to the first parallelogram through the movable platform and the fixed platform, and the first parallelogram can produce movement in two directions perpendicular to each other at the same time, and the telecentric point on the third branch chain realizes the movement of two directions around the telecentric point.

Description

Technical Field

[0001] This invention relates to the field of robotics, specifically to a dual parallelogram telecentric movable parallel robot mechanism. Background Technology

[0002] A parallel mechanism in which the end effector can move based on a telecentric point is called a telecentric mechanism, and the movement based on the telecentric point is called telecentric motion. This motion characteristic has been widely used in devices such as minimally invasive surgical robots in the medical field. In the operation of minimally invasive surgical robots, the surgical incision can be regarded as the telecentric point. By controlling and restricting the telecentric motion of the telecentric mechanism, complex operations of tiny surgical tools can be controlled, thereby reducing patient injury and simplifying the operation.

[0003] There are generally two ways to achieve telecentric motion: one is based on mechanism design, and the other is based on motion control. The motion control-based method uses control algorithms to constrain the cascaded robotic arm to achieve telecentric motion, but this method relies heavily on the accuracy and precision of the control algorithm and is not suitable for all scenarios. In some situations, engineers will choose to implement telecentric motion based on mechanisms.

[0004] Currently, most telecentric movable mechanisms are serial mechanisms. The errors in serial mechanisms accumulate at each stage, resulting in generally low precision in telecentric movable parallel robot mechanisms. In contrast, the errors in parallel mechanisms are shared by multiple branches, leading to a smaller overall error in the moving platform, making them suitable for high-precision medical applications. Furthermore, the closed-loop structure of parallel mechanisms significantly increases their stiffness compared to serial mechanisms, resulting in less deformation under the same load. Currently, only a small number of telecentric movable mechanisms are parallel mechanisms, such as patent application number CN202311418325.7, which discloses a dual-platform parallel robot mechanism supporting telecentric point movement in three-dimensional space. However, its structure is relatively complex. To achieve the two-rotational-one-translational three-degree-of-freedom motion of the instrument arm based on the telecentric point in space, the mechanism includes a primary moving platform 5 and a secondary moving platform 10, with a primary branch being the PR-Pa-R branch and a secondary branch being the URR branch. Because the mechanism has many branches and relatively complex kinematic pairs, it is not suitable for all scenarios; at the same time, due to its complex structure, the mechanism is difficult to assemble and has high manufacturing costs. Summary of the Invention

[0005] To address the issues of complex structures in existing telecentric movable parallel mechanisms that limit application scenarios and pose significant assembly difficulties, this invention provides a double parallelogram telecentric movable parallel robot mechanism. This mechanism offers adjustable telecentric points while maintaining a simple overall structure, thus reducing manufacturing and assembly challenges.

[0006] The technical solution of the present invention is as follows: a double parallelogram telecentric movable parallel robot mechanism, comprising: a moving platform and a fixed platform, wherein the moving platform and the fixed platform are connected by parallel branches; The feature is that the parallel branch includes a first branch, a second branch, and a third branch; the first branch and the second branch have the same structure and are both implemented based on the UU branch, while the third branch is implemented based on the URU branch; The UU branch chain includes two branch universal joints, which are connected by a linkage, and the rotation axes of the two branch universal joints are parallel to each other; the URU branch chain includes two third universal joints and one third rotary joint, which is disposed between the two third universal joints. The kinematic joints are connected by a linkage, and the rotation axes of the two third universal joints are parallel to each other. The third rotary joint is parallel to one of the two rotation axes of the third universal joint. The first branch and the second branch are arranged in parallel, and the first branch and the second branch are connected by two platform connecting rods. The first branch, the second branch and the two platform connecting rods together form a first parallelogram. Both the moving platform and the fixed platform are implemented based on a multi-rotor joint chain; Each of the multi-rotation joint branches includes N platform rotation joints connected in sequence. The first and last platform rotation joints in the multi-rotation joint branch are simultaneously connected to the same platform connecting rod. Another set of adjacent platform rotation joints are simultaneously connected to both ends of a shaft of a third universal joint. The remaining adjacent platform rotation joints are connected by connecting rods to form an N-sided polygon. The axes of rotation of all the aforementioned platform revolute joints are parallel to each other and simultaneously perpendicular to the plane in which the fixed platform is located; The fixed platform and the moving platform are each connected to a third universal joint and are located on the same side of the first parallelogram; the line connecting the rotation centers of the two third universal joints is parallel to the first branch and the second branch; The intersection of the two rotating shafts of the third universal joint connected to the fixed platform is set as the centroid.

[0007] Its further features are: The first branch and the second branch are of equal length, and the length of the third branch is greater than or equal to the length of the other two branches; In the multi-rotational branch chain, the value of N is greater than or equal to 6; Among all the platform rotary joints connected to the platform connecting rod, one platform rotary joint is selected on each of the upper and lower platform connecting rods and set as a moving drive joint for controlling the movement of the telecentric point position. The rotating shaft of the moving drive joint is connected to the drive device. Among the universal joints at both ends of the connecting rod of the fixed platform, one of the universal joints is selected as a rotation drive joint for controlling the rotation of the distal point; a drive device is connected to each of the two mutually perpendicular rotating shafts of the rotation drive joint. On the fixed platform, the connecting rods between adjacent rotating joints of the platform have the same length.

[0008] This application provides a dual parallelogram-shaped telecentric movable parallel robot mechanism. The telecentric point is set on the plane of the fixed platform. Both the moving platform and the fixed platform are based on multiple revolute joints. Each platform includes N revolute joints with parallel rotating axes. Driven by the platform revolute joints, the branches of the moving platform and the fixed platform deform, enabling the telecentric point to move freely within the plane of the fixed platform. The first branch, the second branch, and the connecting rods of the two platforms together form a first parallelogram. The line connecting the rotation centers of the two third universal joints of the third branch is parallel to the first branch and the second universal joint. The second and third branches have their respective gimbals connected to the first parallelogram via a moving platform and a fixed platform. The first parallelogram can move simultaneously in two mutually perpendicular directions based on the first and second branches, thereby driving the telecentric point on the third branch to achieve rotational degrees of freedom about the telecentric point in two directions. The parallel robot mechanism in this application has a simple structure, and rotational degrees of freedom about the telecentric point can be achieved by only revolute joints and gimbals. Therefore, the overall complexity of the mechanism is not high, it is easy to assemble, and it reduces the uncertainty of the mechanism under singular configurations. Attached Figure Description

[0009] Figure 1 This is an overall schematic diagram of the double parallelogram telecentric movable parallel robot mechanism structure of this application; Figure 2 This is a schematic diagram showing the specific structural markings of the double parallelogram telecentric movable parallel robot mechanism in this application. Figure 3 This is a structural diagram of the platform; Figure 4 for Figure 1 A magnified structural diagram of point A; Figure 5 for Figure 1 A magnified structural diagram of point B; Figure 6 Example 1 of the action of a telecentric movable parallel robot mechanism with double parallelograms; Figure 7 Example 2 of the action of a telecentric movable parallel robot mechanism with double parallelograms; Figure 8 Example 3 of the action of a telecentric movable parallel robot mechanism with double parallelograms; Figure 9 This is a schematic diagram showing the line connecting the rotation centers of the two rotating shafts of the third universal joint 1 and the third universal joint 2.

[0010] In the picture, 1. Fixed platform; 11. First revolute joint of fixed platform; 12. Second revolute joint of fixed platform; 13. Third revolute joint of fixed platform; 14. Fourth revolute joint of fixed platform; 15. Fifth revolute joint of fixed platform; 16. Sixth revolute joint of fixed platform; 17. First connecting rod of fixed platform; 18. Second connecting rod of fixed platform; 19. Third connecting rod of fixed platform; 110. Fourth connecting rod of fixed platform; 111. Fifth connecting rod of fixed platform.

[0011] 2 First branch chain; 21 First branch chain universal joint one; 22 First branch chain universal joint two; 2201 First branch chain universal joint two U-shaped connector one; 2202 First branch chain universal joint two U-shaped connector two; 3. Second branch; 31. Second branch universal joint one; 32. Second branch universal joint two; 4. Third branch; 41. Third universal joint one; 42. Third branch revolute joint; 43. Third universal joint two; 4301. Third branch universal joint two U-shaped connector; 5. Moving platform; 51. First rotating joint of moving platform; 52. Second rotating joint of moving platform; 53. Third rotating joint of moving platform; 5301. Rotating shaft of third rotating joint of moving platform; 5302. U-shaped connector of third rotating joint of moving platform; 54. Fourth rotating joint of moving platform; 5401. Rotating shaft of fourth rotating joint of moving platform; 5402. U-shaped connector of fourth rotating joint of moving platform; 55. Fifth rotating joint of moving platform; 56. Sixth rotating joint of moving platform; 57. First connecting rod of moving platform.

[0012] 6. Telecentric point. Detailed Implementation

[0013] like Figures 1-5 As shown, this application includes a dual parallelogram telecentric movable parallel robot mechanism, comprising: a fixed platform 1 and a moving platform 5, which are connected to the fixed platform 1 via parallel branches. The parallel branches include: a first branch 2, a second branch 3, and a third branch 4; the first branch 2 and the second branch 3 have identical structures, both based on a UU (universal joint-universal joint) branch, while the third branch 4 is based on a URU (universal joint-revolute joint-universal joint) branch. The revolute joint and universal joint structures in this application can be implemented based on existing module products in the prior art.

[0014] The UU branch chain includes two branch universal joints, which are connected by a linkage. Specifically, it includes: the first branch chain 2 includes the first branch universal joint 1 21 and the first branch universal joint 2 22; the second branch chain 3 includes: the second branch universal joint 1 31 and the second branch universal joint 2 32.

[0015] The two axes of each universal joint, m and n, are perpendicular to each other and form a cross-shaped structure.

[0016] like Figure 2 In the illustrated embodiment, the first branch 2 and the second branch 3 are of equal length, and the first connecting rod 17 of the fixed platform and the first connecting rod 57 of the moving platform are of equal length. Therefore, the first branch 2, the second branch 3, the first connecting rod 17 of the fixed platform, and the first connecting rod 57 of the moving platform together constitute a first parallelogram. The first branch universal joint 21, the first branch universal joint 22, the second branch universal joint 31, and the second branch universal joint 32 are located at the four vertices of the first parallelogram. The m-axis of each universal joint is parallel to each other and parallel to the plane of the fixed platform. Based on the m-axis of the four vertex universal joints, the first parallelogram can deform at various angles within its plane. The m-axis and n-axis of the four universal joints are marked as *m and *m respectively in the figure.

[0017] In the first parallelogram, when universal joints are connected to each other via connecting rods, both ends of each shaft are simultaneously connected to two branches of the same U-shaped connector, and the closed segments of the U-shaped connector are connected by connecting rods. For example... Figure 4 The diagram shows a detailed structural schematic of the first branch universal joint 22. The two ends of the m-axis (marked as 22m in the diagram) of the first branch universal joint 22 are connected to the first branch universal joint 2U-shaped connector 2201, and the two ends of the n-axis (marked as 22n in the diagram) are connected to the second branch universal joint 2U-shaped connector 2202. The closed section of the first branch universal joint 2U-shaped connector 2201 is connected to the second branch universal joint 32 through the first connecting rod 57 of the moving platform.

[0018] The URU branch chain includes: two third universal joints and one third revolute joint. The third revolute joint is located between the two third universal joints, and the kinematic joints are connected by a linkage. Specifically, the third branch chain 4 includes: a third universal joint 1 41, a third branch revolute joint 42, and a third universal joint 2 43 connected in sequence. The two axes of rotation of the third universal joint 1 41 and the third universal joint 2 43 are parallel to each other, and the third branch revolute joint 42 is parallel to one of the axes of the third universal joint 1 41. Figure 2 As shown, the n-axis of the third universal joint 41 (marked as 41n in the figure) is parallel to the n-axis of the third universal joint 43 (marked as 43n in the figure); the m-axis of the third universal joint 41 (marked as 41m in the figure) is parallel to the m-axis of the third universal joint 43 (marked as 43m in the figure); the third branch rotary joint 42 is parallel to the n-axis of the third universal joint 41, ensuring follow-up.

[0019] The first branch 2 and the second branch 3 are of equal length and are arranged in parallel; the length of the third branch 4 is greater than or equal to the length of the other two branches; when the length of the third branch 4 is equal to the length of the other two branches, the third branch 4 is parallel to the other two branches. For example... Figure 9 As shown, when the length of the third branch 4 is greater than that of the other two branches, the length of the line connecting the rotation centers of the two rotating shafts of the third universal joint 1 41 and the third universal joint 2 43 of the third branch is equal to the length of the other two branches, and the line L connecting the rotation centers of the two rotating shafts of the third universal joint 1 41 and the third universal joint 2 43 is parallel to the other two branches.

[0020] The first parallelogram and the third branch 4 are connected by the moving platform 5 and the fixed platform 1; that is, two connection endpoints 1701 are provided on the first link 17 of the fixed platform, which are respectively connected to the first rotating joint 11 and the sixth rotating joint 16 of the fixed platform on the fixed platform 1; two connection endpoints are also provided on the first link 57 of the moving platform at the symmetrical position of the first link 17 of the fixed platform, which are respectively connected to the first rotating joint 51 and the sixth rotating joint 56 of the moving platform.

[0021] When the first link 17 of the fixed platform is installed through the mounting bracket (not marked in the figure), and the m-axis and n-axis of the first parallelogram swing at different angles based on the universal joints at the four vertices, the first parallelogram can drive the centroid 6 located at the bottom of the third branch 4 to move in two directions around the centroid through the fixed platform 1 and the moving platform 5.

[0022] Both the moving platform 5 and the fixed platform 1 are implemented based on a multi-revolute chain. Each multi-revolute chain includes N platform revolute joints connected sequentially. The moving platform 5 and the fixed platform 1 are arranged in parallel, and the axes of rotation of all platform revolute joints in the moving platform 5 and the fixed platform 1 are parallel to each other and perpendicular to the plane of the fixed platform 1. The first and last platform revolute joints in the multi-revolute chain are connected to the same platform connecting rod, and another set of adjacent platform revolute joints are connected to both ends of a shaft of a third universal joint. The remaining adjacent platform revolute joints are connected by connecting rods, and the N platform revolute joints form an N-gon.

[0023] Fixed platform 1 is connected to the third universal joint 41, and moving platform 5 is connected to the third universal joint 43. Fixed platform 1 and moving platform 5 are located on the same side of the first parallelogram. The intersection of the m-axis (marked as 41m in the figure) and the n-axis (marked as 41n in the figure) of the third universal joint 41 connected to fixed platform 1 is set as the centroid 6.

[0024] To form a polygon, the minimum value of N is 3. In this application, the shape of the fixed platform 1 is deformed by the rotation of its sliding joints on its plane, thereby changing the position of the centroid 6. The range that the centroid 6 can reach depends on the side length of the fixed platform 1 and the number of sliding joints included in the fixed platform 1. However, if the value of N is too small, such as N=3, many positions of the centroid 6 will be unreachable, i.e., there will be too many dead points for the centroid 6. Therefore, in order to reduce the number of dead points of the centroid 6 within the range of the fixed platform 1, the value of N needs to be increased. However, if the value of N is too large, the number of driving joints used for deformation of the fixed platform 1 needs to be increased in order to achieve accurate deformation. Therefore, in specific implementation, the side length of the fixed platform 1 and the number of sliding joints need to be selected according to actual needs.

[0025] This application uses multiple rotating joints to design the fixed platform and the moving platform as a multi-bar closed-loop structure, which enables them to achieve more complex output trajectories, reduce dead points, improve mechanical efficiency, and reduce manufacturing and maintenance costs. The position of the centroid can be adjusted arbitrarily in the plane, the working space is large, and the adjustment of the centroid position is simple and easy to implement.

[0026] This embodiment is designed for a minimally invasive surgical robot. In the multi-revolute chain, N is set to 6, and the specific side length of the fixed platform is selected based on the actual height of the operating table. When N is 6, one drive joint is sufficient to meet the actual working requirements on both the fixed platform 1 and the moving platform 5. Because the moving platform 5 and the fixed platform 1 have the same structure (6R chains, 6 revolute joints), and their connection positions with the third chain 4 are also the same, such as... Figure 3 As shown, the structure of the two platforms is illustrated using fixed platform 1 as an example. Fixed platform 1 has six sides, including four links of equal length: fixed platform second link 18, fixed platform third link 19, fixed platform fourth link 110, and fixed platform fifth link 111. The other two sides are the two connecting endpoints 1701 on the fixed platform first link 17 and the m-axis (marked as 41m in the figure) of the third universal joint 41.

[0027] The fixed platform 1 comprises six revolute joints: fixed platform first revolute joint 11, fixed platform second revolute joint 12, fixed platform third revolute joint 13, fixed platform fourth revolute joint 14, fixed platform fifth revolute joint 15, and fixed platform sixth revolute joint 16. When fixed platform first revolute joint 11 and fixed platform sixth revolute joint 16 are simultaneously connected to fixed platform first connecting rod 17, the m-axis of the third universal joint 41 can be placed between any two adjacent revolute joints other than those between fixed platform first revolute joint 11 and fixed platform sixth revolute joint 16. In this embodiment, to ensure the accuracy of the telecentric point movement, the m-axis of the third universal joint 41 is set on the opposite side of fixed platform first connecting rod 17, so that the number of connecting rods on both sides of the telecentric point 6 is the same, ensuring more precise control of the telecentric point 6 movement. Similarly, the m-axis of the third universal joint 43 (marked as 43m in the figure) is set between moving platform third revolute joint 53 and moving platform fourth revolute joint 54.

[0028] The revolute joint in this application includes: a straight-line revolute shaft and a U-shaped connector. When the two ends of the m-axis of the two third universal joints are respectively connected to sliding joints, such as... Figure 5 As shown, taking the m-axis of the third universal joint 43 as an example, the specific connection method is explained. The third rotating joint 53 of the moving platform includes: the rotating shaft 5301 of the third rotating joint of the moving platform and the U-shaped connector 5302 of the third rotating joint of the moving platform; and the fourth rotating joint 54 of the moving platform includes: the rotating shaft 5401 of the fourth rotating joint of the moving platform and the U-shaped connector 5402 of the fourth rotating joint of the moving platform; the two ends of the n-axis of the third universal joint 43 (marked as 43n in the figure) are respectively connected to the inner side of the open end of the U-shaped connector 4301 of the third branch universal joint 43, and the two ends of the m-axis of the third universal joint 43 (marked as 43m in the figure) are respectively connected to the closed section of the U-shaped connector 5402 of the fourth rotating joint of the moving platform and the U-shaped connector 5302 of the third rotating joint of the moving platform.

[0029] The position of the telecentric point is determined by the positional constraint relationship provided by the moving platform and the fixed platform. Among all the platform revolute joints connected to the platform connecting rods, one platform revolute joint is selected on each of the upper and lower platform connecting rods and set as a moving drive joint to control the movement of the telecentric point. A drive motor is installed on the rotating shaft of the moving drive joint; for example... Figure 1 As shown, in this embodiment, a moving drive pair is selected to control the movement of the telecentric point by using the fixed platform first rotating joint 11 and the moving platform first rotating joint 51. The rotating shafts of the fixed platform first rotating joint 11 and the moving platform first rotating joint 51 are respectively connected to a drive motor, controlling the synchronous rotation of the fixed platform first rotating joint 11 and the moving platform first rotating joint 51 to achieve the movement of the telecentric point 6. The motor connected to the fixed platform first rotating joint 11 is denoted as: drive motor E1 (…). Figure 1The points marked E1 to E4 are the connection points between the motor and the drive pair. The motor connected to the first rotating pair 5 of the moving platform is designated as drive motor E2. Once the centroid 6 moves to the preset position, both drive motors are locked, thus locking the position of the centroid 6.

[0030] Figure 1 The mechanism is in its initial state, i.e., the first parallelogram is perpendicular to the horizontal plane, and the first parallelogram is a rectangle with an interior angle of 90 degrees. Both the fixed platform 1 and the moving platform 5 are parallel to the horizontal plane. When the fixed platform 1 and the moving platform 5 are in their initial positions, the centroid 6 is located on the left and right symmetrical center line of the fixed platform 1. Based on Figure 1 At the same position, drive motors E1 and E2 rotate clockwise simultaneously, moving the position of the distal point 6 clockwise to... Figure 6 After the above steps are completed, lock the two drive motors.

[0031] To ensure balanced force distribution and improve the overall structural rigidity, in this embodiment, when the parallel mechanism is in its initial state, a triangle is drawn with the three universal joints—the second branch universal joint 32, the first branch universal joint 22, and the third universal joint 43—as vertices. The three universal joints are positioned precisely at the vertices of an equilateral triangle. Similarly, when the mechanism is in its initial state, the second branch universal joint 31, the first branch universal joint 21, and the third universal joint 41 are also positioned at the vertices of an equilateral triangle.

[0032] The position of the first link 17 of the fixed platform is fixed. The rotation axes of all platform rotating joints in the fixed platform 1 are perpendicular to the horizontal plane and also perpendicular to the first link 17 of the fixed platform. The lengths of the first branch 2 and the second branch 3 are the same, and the length of the third branch 4 is equal to or greater than the other two branches, which ensures that the angle of the plane in which the fixed platform is located will not change during the deformation of the fixed platform. When the position of the centroid 6 is locked, when the first parallelogram deforms, the position and angle of the moving platform 5 change with the first link 57 of the moving platform. The moving platform 5 and the fixed platform 1 are connected by the third branch 4, and the angle of the centroid 6 changes with the deformation of the first parallelogram.

[0033] Among the universal joints at both ends of the connecting rod of the fixed platform 1, one universal joint is selected as the rotation drive joint for controlling the rotation of the centroid. A drive motor is respectively installed on the two mutually perpendicular shafts of the rotation drive joint. In this embodiment, the first universal joint 21 is selected as the rotation drive joint; the n shaft (marked as 21n in the figure) of the first universal joint 21 is connected to a drive motor, which is denoted as motor E3; the m shaft (marked as 21m in the figure) of the first universal joint 21 is connected to a drive motor, which is denoted as motor E4.

[0034] exist Figure 6To establish a coordinate system, with the telecentric point 6 as the origin, a right-handed coordinate system is established. Within the plane of the fixed platform 1, the positive Y-axis is defined by the line from the telecentric point 6 to the direction of the fourth revolute joint of the fixed platform, perpendicular to the plane of the fixed platform and passing through the telecentric point 6. The positive Z-axis is defined by the vertically upward direction. The established coordinate system is as follows: Figure 6 As shown.

[0035] Figure 6 The first parallelogram in the diagram is perpendicular to the horizontal plane. Figure 6 Based on the current position, motor E3 starts, driving the n-axis of the first branch universal joint 21 to rotate 30°, and motor E3 stops. Then, the first parallelogram rotates around the axis 21n to an angle of 60° with the horizontal plane. The moving platform 5 changes position and angle along with the first connecting rod 57 of the moving platform, such as... Figure 7 As shown, the moving platform 5 causes the third branch 4 to change angle, at which point the telecentric point 6 rotates around the axis 41m. Connecting the intersection of the two axes of the third universal joint 43 with the telecentric point 6, we obtain line L. The angle of the telecentric point 6 is shown in line L. At this time, the angle between line L and the plane containing XY is 60°.

[0036] exist Figure 7 Based on this, motor E4 starts, driving the m-axis of the first branch universal joint 21 to rotate. When the first branch 2 forms a 60° angle with the horizontal plane, motor E4 stops. The first parallelogram then deforms around the m-axis 21. The moving platform 5 changes position and angle along with the first connecting rod 57 of the moving platform, such as... Figure 8 As shown, the moving platform 5 causes the third branch 4 to change angle, at which point the centroid 6 rotates around the axis 41n; at this time, the angle between the connecting line L and the plane containing ZX is 30°.

[0037] Driven by motors E3 and E4, the distal point 6 rotates around the shafts m and n of the third branch universal joint 41. Simultaneously, due to the structural locking between the fixed platform 1 and the moving platform 5, the distal point 6 will not move during rotation. In practical applications, a sliding pair can be added at the distal point, enabling the parallel structure in this application to achieve a 2-rotation-1-sliding motion.

[0038] Figure 9As shown, the line connecting the rotation centers of the two universal joints of the third branch is parallel to the first branch 2 and the second branch 3. The fixed platform 1 is parallel to the moving platform 5. At this time, the plane formed by the line L connecting the center point of the third universal joint 41 and the center point of the third universal joint 43 of the third branch 4, the plane containing the moving platform 5, the plane containing the fixed platform 1, and the plane formed by the first branch 2 and the second branch 3, forms a second parallelogram. This application designs two parallelogram structures in the branches, so that the relationship between the two parallelograms still exists in any position of the mechanism. Based on the two parallelograms, the centroid can move arbitrarily in the plane. The three branch structures of this application are simple, consisting only of revolute joints and universal joints. Therefore, the overall complexity of the mechanism is not high, it is easy to assemble, and the uncertainty of the mechanism under singular configurations is reduced. The three branch structures in this application are simple and reasonably distributed, with balanced forces and improved stiffness, which helps to modularize and standardize the design and facilitates manufacturing. The branch chain in this application is a parallel mechanism, where the error is shared by multiple branches, resulting in a smaller overall error of the moving platform and making it suitable for high-precision medical applications. The parallel mechanism of this application consists of three independent kinematic chains (branches) connecting the moving and stationary platforms. These branches, along with the moving and stationary platforms, form a closed-loop structure, with the load shared by multiple branches, resulting in high overall stiffness. Existing serial mechanisms are open-chain structures, with joints and links connected sequentially. The end load must be transferred to the base through all joints, leading to error accumulation and deformation superposition, resulting in weaker stiffness. Therefore, the parallel mechanism of this application, due to its closed-loop structure, exhibits significantly higher stiffness characteristics than traditional serial mechanisms, resulting in less deformation under the same load.

Claims

1. A double parallelogram telecentric movable parallel robot mechanism, comprising: A moving platform and a fixed platform are connected to each other via parallel branches; The feature is that the parallel branch includes a first branch, a second branch, and a third branch; the first branch and the second branch have the same structure and are both implemented based on the UU branch, while the third branch is implemented based on the URU branch; The UU branch chain includes two branch universal joints, which are connected by a linkage, and the rotation axes of the two branch universal joints are parallel to each other; the URU branch chain includes two third universal joints and one third rotary joint, which is disposed between the two third universal joints. The kinematic joints are connected by a linkage, and the rotation axes of the two third universal joints are parallel to each other. The third rotary joint is parallel to one of the two rotation axes of the third universal joint. The first branch and the second branch are arranged in parallel, and the first branch and the second branch are connected by two platform connecting rods. The first branch, the second branch and the two platform connecting rods together form a first parallelogram. Both the moving platform and the fixed platform are implemented based on a multi-rotor joint chain; Each of the multi-rotation joint branches includes N platform rotation joints connected in sequence. The first and last platform rotation joints in the multi-rotation joint branch are simultaneously connected to the same platform connecting rod. Another set of adjacent platform rotation joints are simultaneously connected to both ends of a shaft of a third universal joint. The remaining adjacent platform rotation joints are connected by connecting rods to form an N-sided polygon. The axes of rotation of all the aforementioned platform revolute joints are parallel to each other and simultaneously perpendicular to the plane in which the fixed platform is located; The fixed platform and the moving platform are each connected to a third universal joint and are located on the same side of the first parallelogram; the line connecting the rotation centers of the two third universal joints is parallel to the first branch and the second branch; The intersection of the two rotating shafts of the third universal joint connected to the fixed platform is set as the centroid.

2. The double parallelogram telecentric movable parallel robot mechanism according to claim 1, characterized in that: The first branch and the second branch are of equal length, and the length of the third branch is greater than or equal to the length of the other two branches.

3. The double parallelogram telecentric movable parallel robot mechanism according to claim 1, characterized in that: In the multi-rotational branch chain, the value of N is greater than or equal to 6.

4. The double parallelogram telecentric movable parallel robot mechanism according to claim 1, characterized in that: Among all the platform rotary joints connected to the platform connecting rod, one platform rotary joint is selected on each of the upper and lower platform connecting rods and set as a moving drive joint for controlling the movement of the telecentric point position. The rotating shaft of the moving drive joint is connected to the drive device.

5. The double parallelogram telecentric movable parallel robot mechanism according to claim 1, characterized in that: Among the universal joints at both ends of the connecting rod of the fixed platform, one of the universal joints is selected as a rotation drive joint for controlling the rotation of the distal point; a drive device is connected to each of the two mutually perpendicular shafts of the rotation drive joint.

6. The double parallelogram telecentric movable parallel robot mechanism according to claim 1, characterized in that: On the fixed platform, the connecting rods between adjacent rotating joints of the platform have the same length.

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