Adjustable RCM parallel robot capable of achieving partial decoupling

Abstract

According to the adjustable RCM parallel robot capable of achieving partial decoupling, RCM point adjustment and tail end posture movement are distributed to the first-stage movable platform and the second-stage movable platform to be achieved through function partition design; the first-stage moving platform supports a moving degree of freedom and is used for adjusting the position of a telecentric point, so that the moving telecentric point can move flexibly; the second-stage movable platform can support a two-rotation and one-movement mode and a three-rotation and one-movement mode so as to meet different operation requirements; through the design that the rotating shaft m of the first universal hinge and the rotating shaft m of the third universal hinge are collinear and are perpendicular to the rotating shaft m of the second universal hinge at the same time, a geometric basis is provided for space motion decoupling, then the rotating pair where the rotating shaft m in the second universal hinge is located and the rotating shaft m in the third universal hinge are arranged as driving pairs, and motion control decoupling is directly achieved.

Description

Technical Field

[0001] This invention relates to the field of parallel mechanism and robotics, specifically to an adjustable RCM parallel robot that achieves partial decoupling. Background Technology

[0002] Remote motion center (RCM) parallel robots, with their advantages of high rigidity, high precision, and strong motion stability, have become core execution units in fields such as minimally invasive surgery, precision assembly, and special inspection. They can constrain the end effector's movement around a virtual telecentric point, avoiding additional interference to the work area, and have attracted much attention from scientific research and industry in recent years. Compared with traditional fixed RCM parallel robots, adjustable RCM parallel robots can dynamically adjust the telecentric point position to adapt to the needs of different work scenarios, possessing greater scenario flexibility. Many related technical solutions exist in the prior art, such as patent publication number CN120206484A, which discloses a double parallelogram telecentric movable parallel robot mechanism. However, in practical applications, it has been found that the motion coupling of the branches in this adjustable RCM parallel robot structure is relatively strong. Strong coupling means that the movement of one branch affects the motion state of other branches, making the control algorithm of the entire parallel mechanism very complex. Furthermore, motion coupling amplifies small errors in the system, thus requiring stringent assembly precision and limiting its application in miniaturized equipment such as minimally invasive surgical robots. Summary of the Invention

[0003] To address the issue that the strong motion coupling in existing adjustable RCM parallel robots limits their application scenarios, this invention provides an adjustable RCM parallel robot that achieves partial decoupling. This robot partially decouples RCM point adjustment from end-effector posture motion, thereby improving the robot's adaptability to different scenarios.

[0004] The technical solution of the present invention is as follows: an adjustable RCM parallel robot that achieves partial decoupling, comprising: a fixed base and a moving platform, characterized in that: the moving platform comprises a primary moving platform and a secondary moving platform; the primary moving platform and the secondary moving platform are connected by four branches: a first branch, a second branch, a third branch and a fourth branch; The first branch is a URPc type branch, which includes a universal joint, a sliding joint, a rotating joint and an arc guide rail joint arranged in sequence. The universal joint at one end of the branch is connected to the primary moving platform, and the arc guide rail joint at the other end is connected to the secondary moving platform. The second and third branches have the same structure, which is a URRPc type branch, including a universal joint, two rotating pairs and an arc guide rail pair arranged in sequence. The universal joint at one end of the branch is connected to the first-stage moving platform, and the arc guide rail pair at the other end is connected to the second-stage moving platform. The fourth branch is a PcURRR type branch, which includes a gear arc guide rail pair, a universal joint and three rotating pairs arranged in sequence. The gear arc guide rail pair at one end of the branch is connected to the first-stage moving platform, and the rotating pair at the other end is connected to the second-stage moving platform. The universal joints connecting the first branch, the second branch, and the third branch to the primary moving platform are respectively denoted as: the first universal joint, the second universal joint, and the third universal joint. Each universal joint includes a rotating shaft m and a rotating shaft n that are perpendicular to each other and intersect. Among them, the rotation axes m of the first universal joint and the third universal joint are collinear and perpendicular to the rotation axis m of the second universal joint. The intersection of the rotation axes m of the first universal joint, the second universal joint, and the third universal joint constitutes the centroid of motion of the mechanism. The primary moving platform and the fixed base are connected by a branch chain that supports the adjustment of the telecentric point of displacement by driving the primary moving platform; an instrument connection structure is provided on the secondary moving platform; The sliding joint of the first branch, the rotating joint where the rotating shaft m is located in the second universal joint, the rotating joint where the rotating shaft m is located in the third universal joint, and the gear-arc guide rail joint of the fourth branch are all set as driving joints.

[0005] Its further features are: The telecentric adjustment branch is based on PRR and includes a sliding joint and two rotating joints connected in sequence. The sliding joint at one end of the branch is connected to the fixed base, and the rotating joint at the other end of the branch is connected to the primary moving platform; the rotation axes of the two rotating joints are parallel to each other. Set the moving joint in the branch used for centroid adjustment as the driving joint; The remote center point adjustment chain includes: a remote center point adjustment connecting rod, a lead screw, a nut, and a remote center point adjustment motor; The lead screw is horizontally mounted on the fixed base, and the nut is threadedly connected to the lead screw to form a sliding pair; the nut is connected to one end of the telecentric point adjustment link through a revolute joint, and the other end of the telecentric point adjustment link is connected to the primary moving platform through a revolute joint. The secondary moving platform includes: a secondary platform body, a chain slide groove, and a U-shaped mounting base. The secondary platform body has a barrel-shaped structure. The chain slide groove is formed on the side wall of the secondary platform body and is concentric with the secondary platform body. The U-shaped mounting base is set on the outer wall of the secondary moving platform with its opening facing outward. There are three branch slides, corresponding to the first branch, the second branch, and the third branch respectively; all branch slides have the same height and the same center; the three branch slides form a C-shaped structure, and the U-shaped mounting base is set at the opening of the C-shaped structure; The primary moving platform includes: a primary platform base, a ring rail, an internal gear, a support chain mounting base, and a gear cover plate. The primary platform base has a barrel-shaped structure, with an annular base in the inner cavity at the bottom. The outer circumference of the base is connected to the inner wall of the primary platform base. The ring rail is installed on the inner circle of the annular base, facing the secondary moving platform. The internal gear is installed in the inner cavity of the barrel-shaped primary platform base. The branch mounting base is disposed on the outer circumference of the primary platform base. There are 3 branch mounting bases, which correspond to the preset positions of the first branch, the second branch and the third branch respectively. The gear cover plate is disposed at the top of the primary platform base, and a limiting groove is formed on the gear cover plate, the limiting groove being concentrically arranged with the ring rail; The projection of the center of the ring rail, the internal gear, and the limiting slide groove coincides with the center of the primary platform base; The first branch includes: a first sliding joint, a first slider, and a first universal joint; One end of the first slider is movably inserted into the branch slide groove on the secondary platform body to form an arc guide rail pair; The other end of the first slider is provided with a U-shaped head, and the two open ends of the U-shaped head are provided with through holes; The first moving joint is based on an electric push rod. The output end of the electric push rod is provided with a T-shaped connector. The two ends of the T-shaped connector are respectively inserted into the open end of the U-shaped head of the first slider to form a rotating joint. The rotation axis of the rotating joint in the first branch is parallel to the rotation axis n of the first universal joint. The fixed end of the electric push rod is connected to the branch mounting seat on the first-stage moving platform through the first universal joint. The second branch includes: a second universal joint, an H-shaped connecting rod, an I-shaped connecting rod, and a second slider; One end of the H-shaped connecting rod is connected to the support mounting seat on the primary moving platform via a second universal joint, and the other end forms a revolute joint with one end of the I-shaped connecting rod; the other end of the I-shaped connecting rod forms a revolute joint with one end of the second slider; the other end of the second slider is movably inserted into the support slide groove on the secondary platform body to form an arc guide rail pair; the rotation axes of both revolute joints are parallel to the rotation axis n of the second universal joint; The fourth branch includes: a fourth H-shaped link, a fourth I-shaped link, a T-shaped link, and a fourth universal joint; One end of the H-shaped connecting rod is connected to the gear arc guide pair via the fourth universal joint. The gear arc guide pair is connected to the first-stage moving platform. The other end of the fourth H-shaped connecting rod forms a revolute joint with the crossbar of the fourth I-shaped connecting rod. The other end of the fourth I-shaped connecting rod and one end of the T-shaped connecting rod form a revolute joint. The other end of the T-shaped connecting rod forms a revolute joint with the U-shaped mounting seat on the second-stage platform. The fourth branch also includes: a fourth motor base, a transmission gear, a limiting block, a transmission flange, and a fourth slider; The fourth motor base is connected to the H-shaped link of the fourth branch through the fourth universal joint; the fourth universal joint includes a rotating shaft m and a rotating shaft n that are perpendicular to each other and intersecting, and the projection of the rotating shaft m on the primary moving platform always points to the center of the primary moving platform; the rotating shafts of the three rotating pairs of the fourth branch are all parallel to the rotating shaft n of the fourth universal joint. The drive motor of the fourth branch is mounted on the fourth motor base. The motor output shaft passes sequentially through the limiting grooves of the fourth motor base and the gear cover plate, and is connected to the transmission gear through the transmission flange. The transmission gear is an external gear and meshes with the internal gear of the primary moving platform. The top of the fourth slider is rotatably connected to the bottom end of the transmission gear through a bearing structure. The bottom of the fourth slider is U-shaped and slidably connected to the ring rail. The transmission gear, the internal gear, and the ring rail constitute the gear arc guide rail pair. The bottom of the fourth motor base is provided with a limiting block, the size of which is adapted to the size of the limiting groove, and the limiting block is movably inserted into the limiting groove.

[0006] This application provides an adjustable RCM parallel robot with partial decoupling. Through functional partitioning, it distributes RCM point adjustment and end-effector posture motion to a primary motion platform and a secondary motion platform respectively. The primary motion platform supports one degree of freedom of movement for adjusting the position of the telecentric point, allowing for flexible movement of the telecentric point. The secondary motion platform supports two rotations and one movement, and three rotations and one movement modes to meet different operational needs. By designing the rotation axes m of the first and third universal joints to be collinear and perpendicular to the rotation axis m of the second universal joint, a geometric basis for spatial motion decoupling is provided. Furthermore, by setting the rotational joint containing the rotation axis m of the second universal joint and the rotation axis m of the third universal joint as driving joints, motion control decoupling is directly achieved, effectively solving the core problem of strong motion coupling in existing adjustable RCM parallel robots. This application reduces motion coupling interference and lowers control difficulty through the partial decoupling design of the driving joints. It also reduces redundant interference during motion, improves the accuracy of motion control, and enhances the adaptability of the mechanism to different scenarios. Attached Figure Description

[0007] Figure 1 A schematic diagram of the overall structure of an adjustable RCM parallel robot to achieve partial decoupling; Figure 2 A schematic diagram showing the connection relationship of the kinematic pairs of four branches used to connect the first-stage and second-stage moving platforms; Figure 3 A schematic diagram of the structure of four branches connecting the primary and secondary moving platforms; Figure 4 This is a structural schematic diagram of the primary dynamic platform; Figure 5 A cross-sectional view of the Pc4 gear circular arc guide pair; Figure 6 The diagram shows the structure of the fourth motor base and the fourth slider, where 6a is a schematic diagram of the positional relationship between the fourth motor base and the gear cover plate, and 6b is a schematic diagram of the positional relationship between the fourth motor base and the fourth slider. Figure 7 This is a schematic diagram of the structure of the first slider; Figure 8 This is an example of the general posture of the mechanism in a two-turn-one-shift mode; Figure 9 This is an example of the general posture of the mechanism in the three-turn-one-shift mode. Detailed Implementation

[0008] like Figure 1 As shown, this application includes an adjustable RCM parallel robot with partial decoupling, comprising: a fixed base 6 and a moving platform, the moving platform including a primary moving platform 7 and a secondary moving platform 8; the primary moving platform 7 and the secondary moving platform 8 are connected by four branches: a first branch 1, a second branch 2, a third branch 3, and a fourth branch 4. In the branch structure, U is a universal joint, P is a prismatic joint, R is a revolute joint, and Pc is a circular arc guide rail pair or a gear circular arc guide rail pair.

[0009] The positional relationship between the fixed base 6 and the moving platform, and the spatial relationship between the primary moving platform 7 and the secondary moving platform 8, can be set according to actual needs. The fixed base 6 can be set above, below, or to the side of the moving platform, and the primary moving platform 7 can be set above, below, or to the side of the secondary moving platform 8, as in this embodiment. Figure 1 As shown, in this embodiment, the fixed base 6 has a U-shaped structure and is located at the top. The secondary moving platform 8 is positioned between the primary moving platform 7 and the fixed base 6. A three-jaw chuck 84 is installed on the secondary moving platform 8 to grasp surgical instruments or operating tools, adapting to the needs of different application scenarios.

[0010] The primary moving platform 7 and the fixed base 6 are connected by a telecentric adjustment branch 5 that supports the displacement of the primary moving platform 7. The telecentric adjustment branch 5 can be implemented based on existing structures capable of driving the primary moving platform 7 to achieve displacement, such as electric actuators or electric linear modules. In this embodiment, the fixed base 6 and the primary moving platform 7 are connected by three identical telecentric adjustment branches 5. The telecentric adjustment branch 5 is based on a PRR (Plan-Resistant Joint), and includes a sliding joint and two rotating joints connected in sequence. The sliding joint at one end of the branch connects to the fixed base 6, and the rotating joint at the other end connects to the primary moving platform 7; the rotation axes of the two rotating joints in the PRR branch are parallel to each other.

[0011] Specifically, the sliding joint P in the telecentric adjustment branch 5 is implemented based on a lead screw thread sliding joint. The telecentric adjustment branch 5 includes: a lead screw 51, a nut 52, a telecentric adjustment connecting rod 53, a telecentric adjustment motor 56, and a guide rod 57; the lead screw 51 is horizontally mounted on the fixed base 6, and the guide rod 57 is mounted on the fixed base 6 parallel to the lead screw 51; the nut 52 has two parallel through holes, one of which is a threaded hole and the other serves as a guide hole; the nut 52 is connected to the lead screw 51 based on the threaded hole and is fitted onto the guide rod 57 based on the guide hole; the nut 52 and the lead screw 51 form a sliding joint; the nut 52 is connected to one end of the telecentric adjustment connecting rod 53 through a rotary joint R54, and the other end of the telecentric adjustment connecting rod 53 is connected to the branch mounting seat 74 of the primary moving platform 7 through a rotary joint R55; the rotation axes of the rotary joints R54 and R55 at both ends of the telecentric adjustment connecting rod 53 are parallel to each other. The position of the two moving platforms can be moved by the centroid adjustment motor 56. When using a lead screw thread moving pair as the moving pair P, two centroid adjustment branches 5 set at 180 degrees can be set to change the displacement of the moving platform. In this embodiment, in order to ensure stable movement, three centroid adjustment branches 5 are set. When multiple centroid adjustment branches 5 are set, the centroid adjustment motors 56 in the branches must keep working synchronously.

[0012] The secondary moving platform 8 includes: a secondary platform body 81, a chain slide 82, and a U-shaped mounting base 83. The secondary platform body 81 has a barrel-shaped structure. The chain slide 82 is opened on the side wall of the secondary platform body 81 and is concentric with the secondary platform body 81. The U-shaped mounting base 83 is set on the outer wall of the secondary moving platform 8 with its opening facing outward.

[0013] There are three branch slides 82, all of which have the same height. The arcs of the three circular guide rail pairs are located at the same center, thus ensuring that the secondary moving platform 12 always moves around the same centroid during its movement. In this embodiment, the three branch slides 82 are not interconnected; the three branch slides 82 form a C-shaped structure, and the U-shaped mounting base 83 is located at the opening of the C-shaped structure.

[0014] The primary moving platform 7 includes: a primary platform base 71, an annular rail 72, an internal gear 73, a support chain mounting base 74, and a gear cover plate 75. The primary platform base 71 has a barrel-shaped structure, and the inner cavity at the bottom is provided with an annular base 76. The outer circumference of the base 76 is connected to the inner cavity wall of the primary platform base 71. The annular rail 72 is installed on the inner circle of the annular base, facing the secondary moving platform 8. In this embodiment, the annular rail 72 is perpendicular to the plane where the primary platform base 71 is located. The internal gear 73 is installed in the inner cavity of the barrel-shaped primary platform base 71. The branch mounting base 74 is set on the outer circumference of the first-level platform base 71. There are 3 branch mounting bases 74, which correspond to the preset positions of the first branch 1, the second branch 2 and the third branch 3 respectively. The gear cover plate 75 is located at the top of the primary platform base 71. A limiting groove 751 is provided on the gear cover plate 75, and the limiting groove 751 is concentrically arranged with the ring rail 72. In this embodiment, the gear cover plate 75 is a fan-shaped annular structure, and its position is adapted to the position of the fourth branch 4.

[0015] After the centers of the ring rail 72, internal gear 73 and limiting slide groove 751 are projected onto the primary moving platform 7, the projection coincides with the center of the primary platform base.

[0016] like Figure 2 and Figure 3 As shown, the first branch 1 is a URPc type branch, including a first universal joint U1, a prismatic joint P1, a revolute joint R11, and an arc guide rail joint Pc1 arranged sequentially. The first universal joint at one end of the branch connects to the primary moving platform 7, and the arc guide rail joint Pc1 at the other end connects to the secondary moving platform 8. The first universal joint includes a rotating shaft n1 and a rotating shaft m1 that are perpendicular to each other and intersect.

[0017] like Figure 3 As shown, the URPc type branch corresponding to the first branch 1 includes: a sliding joint P1, a first slider 12, and a first universal joint U1; One end of the first slider 12 is movably inserted into the branch slide groove 82 on the secondary platform body 81 to form an arc guide rail pair Pc. The other end of the first slider 12 is provided with a U-shaped head, and the two open ends of the U-shaped head are provided with through holes; the first sliding pair P1 is based on the electric push rod 11, and the output end of the electric push rod 11 is provided with a T-shaped connector. The two ends of the T-shaped connector are respectively inserted into the open ends of the U-shaped head of the first slider 12 to form a rotating pair R11. The rotation axis of the rotating pair R11 is parallel to the rotation axis n1 of the first universal joint U1; the fixed end of the electric push rod 11 is connected to the support mounting seat 74 on the primary moving platform 7 through the first universal joint U1.

[0018] The first slider 12, the second slider 23, and the third slider 33 have the same structure. The slider structure will be explained using the first slider 12 as an example. Figure 7 As shown, the first slider 12 includes a slider body 121, an insertion part 123, a limiting part 122 and a U-shaped head. The two open ends of the U-shaped head are provided with through holes 124 for connecting the T-shaped connector of the electric push rod 11. The insertion part 123 is movably inserted into the branch slide groove 82 on the secondary platform body 81, and is prevented from falling by the limiting part 121.

[0019] The second branch 2 and the third branch 3 have the same structure and are URRPc type branches.

[0020] like Figure 2 As shown, the second branch 2 includes a second universal joint U2, a revolute joint R21, a revolute joint R22, and an arc guide rail joint Pc2 arranged sequentially. The second universal joint U2 at one end of the branch is connected to the primary moving platform 7, and the arc guide rail joint Pc2 at the other end is connected to the secondary moving platform 8. The second universal joint U2 includes a rotating shaft n2 and a rotating shaft m2 that are perpendicular to each other and intersect.

[0021] The third branch 3 includes a third universal joint U3, a revolute joint R31, a revolute joint R32, and an arc guide rail joint Pc3 arranged sequentially. The second universal joint U3 at one end of the branch is connected to the primary moving platform 7, and the arc guide rail joint Pc3 at the other end is connected to the secondary moving platform 8. The third universal joint U3 includes a rotating shaft n3 and a rotating shaft m3 that are perpendicular to each other and intersect.

[0022] The second branch 2 corresponds to the URRPc type branch, including: the second universal joint U2, the second H-shaped link 21, the second I-shaped link 22, and the second slider 23; the third branch 3 has the same structure as the second branch 2, including: the third universal joint U3, the third H-shaped link 31, the third I-shaped link 32, and the third slider 33.

[0023] Taking the second branch 2 as an example, the structural component connection relationship of the URRPc type branch is explained. One end of the second H-shaped connecting rod 21 is connected to the branch mounting seat 74 on the first-stage moving platform 7 through the second universal joint U2, and the other end forms a rotating pair R21 with one end of the second I-shaped connecting rod 22. The other end of the second I-shaped connecting rod 22 forms a rotating pair R23 with one end of the second slider 23. The rotation axes of the two rotating pairs are parallel to the rotation axis n of the second universal joint U2. The other end of the second slider 23 is movably inserted into the branch slide groove 82 on the second-stage platform body 81 to form an arc guide rail pair Pc2.

[0024] The fourth branch 4 is a PcURRR type branch, which includes a circular arc guide rail pair Pc4, a fourth universal joint U4, a rotary joint R41, a rotary joint R42 and a rotary joint R43 arranged in sequence. The circular arc guide rail pair Pc4 at one end of the branch is connected to the first-stage moving platform 7, and the rotary joint R43 at the other end is connected to the second-stage moving platform 8.

[0025] The PcURRR type branch corresponding to the fourth branch 4 includes: the fourth H-shaped link 41, the fourth I-shaped link 42, the fourth T-shaped link 43, the fourth universal joint U4, the gear arc guide pair Pc4, the fourth motor base 44, the transmission gear 45, the limit block 46, the transmission flange 47, and the fourth slider 48.

[0026] One end of the fourth H-shaped link 41 is connected to the gear arc guide pair Pc4 via the fourth universal joint U4. The gear arc guide pair Pc4 is connected to the first-stage moving platform 7. The other end of the fourth H-shaped link 41 forms a revolute joint R41 with the crossbar of the fourth I-shaped link 42. The crossbar of the other end of the fourth I-shaped link 42 forms a revolute joint R42 with the straight end of the fourth T-shaped link 43. The crossbar of the other end of the fourth T-shaped link 43 forms a revolute joint R43 with the U-shaped mounting seat 83 on the second-stage platform.

[0027] The fourth universal joint U4 is connected to the transmission gear 45 through the fourth motor base 44; the fourth motor base 44 is connected to the fourth H-shaped connecting rod 41 of the fourth branch 4 through the fourth universal joint U4; the fourth universal joint U4 includes mutually perpendicular and intersecting rotation shafts m4 and n4, and the projection of the rotation shaft m4 on the first-stage moving platform 7 always points to the center of the first-stage moving platform 7; the rotation axes of the three rotating pairs of the fourth branch 4: rotating pair R41, rotating pair R42 and rotating pair R43 are all parallel to the rotation shaft n of the fourth universal joint U4.

[0028] like Figure 4 and Figure 5 As shown, the drive motor of the fourth branch 4 is designated as the fourth drive motor 45. The fourth drive motor 45 is mounted on the fourth motor base 44. The output shaft of the fourth drive motor 45 passes sequentially through the mounting hole 441 on the fourth motor base 44 and the limiting groove 751 of the gear cover plate 75, and is connected to the transmission gear 45 via the transmission flange 47. The transmission gear 45 is an external gear and meshes with the internal gear 73 to form a gear pair. The top of the fourth slider 48 is rotatably connected to the bottom end of the transmission gear 45 via a bearing structure. Figure 6 As shown, the bottom of the fourth slider 48 is U-shaped, and the size between the two openings is adapted to the ring rail 72. The fourth slider 48 slides across the ring rail 72 to realize the circumferential movement of the fourth branch 4 relative to the primary moving platform. The transmission gear 45, the ring rail 72, and the internal gear 73 constitute the gear arc guide pair Pc4, thereby achieving high transmission accuracy and load-bearing capacity while ensuring the arc motion constraint.

[0029] When the fourth drive motor 45 starts, the output shaft drives the transmission gear 45 to rotate. The outer teeth of the transmission gear 45 push the teeth of the inner gear 73. Since the position of the inner gear 73 is fixed, the transmission gear 45 will slide along the ring rail 72 with the fourth slider 48 at the bottom, thereby driving the fourth branch chain 4 to move.

[0030] A limiting block 46 is provided at the bottom of the fourth motor base 44. The size of the limiting block 46 is adapted to the size of the limiting slide 751. The limiting block 46 is movably inserted into the limiting slide 751. The fourth motor base 44 is limited by the cooperation of the limiting block 46 and the limiting slide 751.

[0031] The universal joints connecting the first branch 1, the second branch 2, and the third branch 3 to the primary moving platform 7 are respectively denoted as: first universal joint U1, second universal joint U2, and third universal joint U3. Each universal joint includes mutually perpendicular and intersecting rotation axes m and n. These three universal joints are installed at the same height, wherein the rotation axes m1 of the first universal joint and m3 of the third universal joint are collinear and simultaneously perpendicular to the rotation axis m2 of the second universal joint. The intersection of the rotation axes m of the first, second, and third universal joints constitutes the motion telecentric point O of the mechanism. The projection of the motion telecentric point O coincides with the center of the primary moving platform 7; at the same time, the projection of the rotation axis m4 of the universal joint U4 in the fourth branch 4 onto the primary moving platform 7 always points to the center of the primary moving platform 7.

[0032] By setting the positions of the rotation axes m in the first universal joint U1, the second universal joint U2, and the third universal joint U3, a geometric basis for spatial motion decoupling is provided. The x and y axes of the coordinate system are also at a 90° angle. According to the screw theory, when the angle between the rotation axes m in the second universal joint U2 and the third universal joint U3 is 90°, the dot product of the screw vectors of the second branch 2 and the third branch 3 is 0, meaning they do not affect each other and can rotate perfectly along the x and y axes, thus achieving decoupling. If the axis of rotation m is not perpendicular, it cannot rotate perfectly along the x and y axes, leading to motion coupling. By independently controlling the drive pairs in the second and third branches, motion decoupling between corresponding degrees of freedom can be achieved, thereby reducing control complexity and improving the system's operability and stability.

[0033] In this application, the prismatic joint P1 of the first branch 1, the revolute joint containing the rotating shaft m2 in the second universal joint, the revolute joint containing the rotating shaft m3 in the third universal joint, and the gear-arc guide rail joint Pc4 of the fourth branch are all configured as drive joints. Specifically, the prismatic joint P1 of the first branch 1 is implemented based on the electric actuator 11, and the drive device is implemented through the electric actuator 11. The rotating shaft m2 in the second universal joint is connected to the output shaft of the second drive motor 24. The rotating shaft m3 in the third universal joint is connected to the output shaft of the third drive motor 34. The transmission gear 45 in the arc guide rail joint Pc4 is driven based on the fourth drive motor 45. Through the selection and arrangement of drive joints, the parallel robot can achieve multi-degree-of-freedom cooperative drive while ensuring structural compactness.

[0034] This application, through the layout of four branches and the configuration of drive pairs, achieves partial decoupling between RCM point adjustment and end-effector posture motion. In particular, it directly achieves motion control decoupling through the second and third branch drive pairs, effectively solving the core problem of strong motion coupling in existing adjustable RCM parallel robots. This application reduces motion coupling interference and lowers control difficulty through the partial decoupling design of drive pairs. It also reduces redundant interference during motion, improving the accuracy of motion control. The overall structure is compact, the branch layout is simple, and it is easy to modularly manufacture, reducing assembly difficulty and production costs.

[0035] like Figure 1 and Figure 2 As shown, the first branch 1, the second branch 2, and the third branch 3 are connected to the primary moving platform 7 via the first universal joint, the second universal joint, and the third universal joint, respectively, and are connected to the secondary moving platform 8 via the arc guide rail pair. The fourth branch 4 is connected to the primary moving platform 7 via the gear arc guide rail pair Pc4 and is connected to the secondary moving platform 8 via the revolute joint R43. Simultaneously, three PRR-type telecentric adjustment branches 5 are connected to the fixed base 6 via the screw thread sliding pair and to the primary moving platform 7 via the revolute joint, used to drive the primary moving platform 7 to perform translational motion in a predetermined direction.

[0036] This application employs a functional partitioning design, distributing RCM point adjustment and end-effector attitude motion to a primary motion platform and a secondary motion platform respectively. Specifically, the primary motion platform supports one degree of freedom of motion translation; the secondary motion platform supports motion modes including two rotations and one translation, and three rotations and one translation. Figure 8 As shown, when the drive pair gear arc guide pair Pc4 in the fourth branch 4 is not working, the telecentric point is moved up or down through the sliding pair in the telecentric point adjustment branch 5, as shown in the figure. When the telecentric point O is fixed, the secondary moving platform 8 can achieve rotation based on the rotation shafts r1 and r2 through the drive pairs in the first branch 1, the second branch 2, and the third branch 3. Figure 9As shown, after the drive gear arc guide pair Pc4 is working, the secondary moving platform 8 can also achieve rotation based on the rotating shaft r3, on the basis of the rotating shaft r1 and the rotating shaft r2.

[0037] The drive pairs in the second and third branches of the drive pair can achieve motion control decoupling; the intersection of the rotation axes m of the three U-joints (first, second, and third universal joints) is the motion telecentric point O. In this application, the motion telecentric point O can move with the primary moving platform, thereby realizing the adjustable telecentric position. The primary moving platform in this solution supports one degree of freedom of movement, and the secondary moving platform supports commonly used two-rotation-one-transfer and three-rotation-one-transfer modes. The motion telecentric point can move flexibly to adapt to the position requirements of different working scenarios.

[0038] By using the technical solution of this invention, partial decoupling of RCM point adjustment and end-effector posture motion is achieved through functional partitioning design, simplifying control logic and reducing assembly difficulty. Through the movement of the primary moving platform, the spatial position of the intersection point of the rotation axes m of the first, second, and third universal joints changes, thereby forming an RCM motion structure with adjustable telecentric point position. This application achieves decoupling of telecentric point position adjustment and multi-degree-of-freedom motion control without changing the basic branch configuration, which helps reduce mechanism complexity and facilitates control, making it suitable for precision operation applications requiring telecentric motion characteristics. This application achieves continuous adjustment of the telecentric point position while ensuring RCM characteristics, significantly improving the adaptability and application range of parallel robots.

Claims

1. An adjustable RCM parallel robot that achieves partial decoupling, comprising: A fixed base and a moving platform, characterized in that: the moving platform includes a primary moving platform and a secondary moving platform; the primary moving platform and the secondary moving platform are connected by four branches: a first branch, a second branch, a third branch, and a fourth branch; The first branch is a URPc type branch, which includes a universal joint, a sliding joint, a rotating joint and an arc guide rail joint arranged in sequence. The universal joint at one end of the branch is connected to the primary moving platform, and the arc guide rail joint at the other end is connected to the secondary moving platform. The second and third branches have the same structure, which is a URRPc type branch, including a universal joint, two rotating pairs and an arc guide rail pair arranged in sequence. The universal joint at one end of the branch is connected to the first-stage moving platform, and the arc guide rail pair at the other end is connected to the second-stage moving platform. The fourth branch is a PcURRR type branch, which includes a gear arc guide rail pair, a universal joint and three rotating pairs arranged in sequence. The gear arc guide rail pair at one end of the branch is connected to the first-stage moving platform, and the rotating pair at the other end is connected to the second-stage moving platform. The universal joints connecting the first branch, the second branch, and the third branch to the primary moving platform are respectively denoted as: the first universal joint, the second universal joint, and the third universal joint. Each universal joint includes a rotating shaft m and a rotating shaft n that are perpendicular to each other and intersect. Among them, the rotation axes m of the first universal joint and the third universal joint are collinear and perpendicular to the rotation axis m of the second universal joint. The intersection of the rotation axes m of the first universal joint, the second universal joint, and the third universal joint constitutes the centroid of motion of the mechanism. The primary moving platform and the fixed base are connected by a branch chain that supports the adjustment of the telecentric point of displacement by driving the primary moving platform; an instrument connection structure is provided on the secondary moving platform; The sliding joint of the first branch, the rotating joint where the rotating shaft m is located in the second universal joint, the rotating joint where the rotating shaft m is located in the third universal joint, and the gear-arc guide rail joint of the fourth branch are all set as driving joints.

2. The adjustable RCM parallel robot with partial decoupling as described in claim 1, characterized in that: The telecentric adjustment branch is based on PRR and includes a sliding joint and two rotating joints connected in sequence. The sliding joint at one end of the branch is connected to the fixed base, and the rotating joint at the other end of the branch is connected to the primary moving platform; the rotation axes of the two rotating joints are parallel to each other. Set the moving joint in the branch used for centroid adjustment as the driving joint.

3. The adjustable RCM parallel robot with partial decoupling according to claim 2, characterized in that: The remote center point adjustment chain includes: a remote center point adjustment connecting rod, a lead screw, a nut, and a remote center point adjustment motor; The lead screw is horizontally mounted on the fixed base, and the nut is threadedly connected to the lead screw to form a sliding pair; the nut is connected to one end of the telecentric adjustment link through a revolute joint, and the other end of the telecentric adjustment link is connected to the primary moving platform through a revolute joint.

4. The adjustable RCM parallel robot with partial decoupling according to claim 1, characterized in that: The secondary moving platform includes: a secondary platform body, a chain slide groove, and a U-shaped mounting base. The secondary platform body has a barrel-shaped structure. The chain slide groove is formed on the side wall of the secondary platform body and is concentric with the secondary platform body. The U-shaped mounting base is set on the outer wall of the secondary moving platform with its opening facing outward.

5. The adjustable RCM parallel robot with partial decoupling according to claim 4, characterized in that: There are three branch slides, corresponding to the first branch, the second branch and the third branch respectively; all branch slides have the same height and the same center; the three branch slides form a C-shaped structure, and the U-shaped mounting base is set at the opening of the C-shaped structure.

6. The adjustable RCM parallel robot with partial decoupling according to claim 4, characterized in that: The primary moving platform includes: a primary platform base, a ring rail, an internal gear, a support chain mounting base, and a gear cover plate. The primary platform base has a barrel-shaped structure, with an annular base in the inner cavity at the bottom. The outer circumference of the base is connected to the inner wall of the primary platform base. The ring rail is installed on the inner circle of the annular base, facing the secondary moving platform. The internal gear is installed in the inner cavity of the barrel-shaped primary platform base. The branch mounting base is disposed on the outer circumference of the primary platform base. There are 3 branch mounting bases, which correspond to the preset positions of the first branch, the second branch and the third branch respectively. The gear cover plate is disposed at the top of the primary platform base, and a limiting groove is formed on the gear cover plate, the limiting groove being concentrically arranged with the ring rail; The projection of the center of the ring rail, the internal gear, and the limiting slide groove coincides with the center of the primary platform base.

7. The adjustable RCM parallel robot with partial decoupling according to claim 6, characterized in that: The first branch includes: a first sliding joint, a first slider, and a first universal joint; One end of the first slider is movably inserted into the branch slide groove on the secondary platform body to form an arc guide rail pair; The other end of the first slider is provided with a U-shaped head, and the two open ends of the U-shaped head are provided with through holes; The first moving joint is based on an electric push rod. The output end of the electric push rod is provided with a T-shaped connector. The two ends of the T-shaped connector are respectively inserted into the open ends of the U-shaped head of the first slider to form a rotating joint. The rotation axis of the rotating joint in the first branch is parallel to the rotation axis n of the first universal joint. The fixed end of the electric push rod is connected to the branch mounting seat on the first-stage moving platform through the first universal joint.

8. The adjustable RCM parallel robot with partial decoupling according to claim 6, characterized in that: The second branch includes: a second universal joint, an H-shaped connecting rod, an I-shaped connecting rod, and a second slider; One end of the H-shaped connecting rod is connected to the support mounting seat on the primary moving platform via a second universal joint, and the other end forms a revolute joint with one end of the I-shaped connecting rod; the other end of the I-shaped connecting rod forms a revolute joint with one end of the second slider; the other end of the second slider is movably inserted into the support slide groove on the secondary platform body to form an arc guide rail pair; the rotation axes of the two revolute joints are parallel to the rotation axis n of the second universal joint.

9. An adjustable RCM parallel robot with partial decoupling as described in claim 6, characterized in that: The fourth branch includes: a fourth H-shaped link, a fourth I-shaped link, a T-shaped link, and a fourth universal joint; One end of the H-shaped connecting rod is connected to the gear arc guide pair via the fourth universal joint. The gear arc guide pair is connected to the primary moving platform. The other end of the fourth H-shaped connecting rod forms a revolute joint with the crossbar of the fourth I-shaped connecting rod. The other end of the fourth I-shaped connecting rod and one end of the T-shaped connecting rod form a revolute joint. The other end of the T-shaped connecting rod forms a revolute joint with the U-shaped mounting seat on the secondary platform.

10. An adjustable RCM parallel robot with partial decoupling according to claim 9, characterized in that: The fourth branch also includes: a fourth motor base, a transmission gear, a limiting block, a transmission flange, and a fourth slider; The fourth motor base is connected to the H-shaped link of the fourth branch through the fourth universal joint; the fourth universal joint includes a rotating shaft m and a rotating shaft n that are perpendicular to each other and intersecting, and the projection of the rotating shaft m on the primary moving platform always points to the center of the primary moving platform; the rotating shafts of the three rotating pairs of the fourth branch are all parallel to the rotating shaft n of the fourth universal joint. The drive motor of the fourth branch is mounted on the fourth motor base. The motor output shaft passes sequentially through the limiting grooves of the fourth motor base and the gear cover plate, and is connected to the transmission gear through the transmission flange. The transmission gear is an external gear and meshes with the internal gear of the primary moving platform. The top of the fourth slider is rotatably connected to the bottom end of the transmission gear through a bearing structure. The bottom of the fourth slider is U-shaped and slidably connected to the ring rail. The transmission gear, the internal gear, and the ring rail constitute the gear arc guide rail pair. The bottom of the fourth motor base is provided with a limiting block, the size of which is adapted to the size of the limiting groove, and the limiting block is movably inserted into the limiting groove.

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