Double-parallelogram telecentric movable parallel robot mechanism

Abstract

According to the double-parallelogram telecentric movable parallel robot mechanism, on the basis that the telecentric point can be adjusted, the overall structure of the mechanism is simple, and the manufacturing and assembling difficulty is lowered. The telecentric point of the movable platform is arranged on the plane where the fixed platform is located, the movable platform and the fixed platform are both achieved based on a multi-rotating-pair branch chain, and each platform comprises N platform rotating pairs with rotating shafts parallel to one another; branched chains of the movable platform and the fixed platform are deformed based on the platform revolute pairs, so that free movement of a telecentric point in a plane where the fixed platform is located can be realized; the first branch chain, the second branch chain and the connecting rods for connecting the two platforms jointly form a first parallelogram, third universal pairs at the two ends of the third branch chain are connected to the first parallelogram through the movable platform and the fixed platform respectively, and the first parallelogram can move in the two directions perpendicular to each other at the same time. And the telecentric point on the third branch chain is driven to move around the telecentric point in two directions with rotational degrees of freedom.

Description

Technical Field

[0001] The present invention relates to the technical field of robotics, and particularly to a double parallelogram telecentric movable parallel robot mechanism. Background Art

[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 telecentric movement. Such movement characteristics have been widely applied in devices such as minimally invasive surgical robots in the medical field. In the operation of a minimally invasive surgical robot, the surgical incision can be regarded as the telecentric point. By controlling and restricting the telecentric movement of the telecentric mechanism, the complex operation of a micro surgical tool is realized to reduce the patient's injury and the operation difficulty.

[0003] Generally, there are two ways to achieve telecentric movement: one is the implementation method based on mechanism design, and the other is the implementation method based on motion control. The implementation method based on motion control realizes telecentric movement by constraining a serial manipulator through a control algorithm. However, this method depends on the accuracy and precision of the control algorithm and is not applicable to all scenarios. In some scenarios, technicians will choose to implement telecentric movement based on the mechanism.

[0004] Currently, most of the telecentric point movable mechanisms are generally serial mechanisms. The errors of serial mechanisms will accumulate step by step. Therefore, most of the telecentric movable parallel robot mechanisms based on serial mechanisms have low precision. The errors of parallel mechanisms are shared by multiple branches. Therefore, the comprehensive error of the moving platform is small and it is suitable for the high-precision medical field. In addition, due to the closed-loop structure of the parallel mechanism, its stiffness characteristics are significantly higher than those of serial mechanisms, and the deformation is smaller under the same load. Currently, only a small number of telecentric movable mechanisms are parallel mechanisms. For example, the patent with the application number CN202311418325.7 discloses a double-platform parallel robot mechanism that supports the movement of the telecentric point in three-dimensional space. However, its structure is relatively complex. In order to realize the three-degree-of-freedom movement of two rotations and one translation of the secondary moving platform driving the instrument arm in space based on the telecentric point, a primary moving platform 5 and a secondary moving platform 10 are set in the mechanism. The primary branch chain is a P-R-Pa-R branch chain and the secondary branch chain is a U-R-R branch chain. Because there are many branch chains and relatively complex kinematic pairs in the mechanism, it is not applicable to all scenarios; at the same time, because the structure is relatively complex, the assembly difficulty of the mechanism is large, and the manufacturing cost is high. Summary of the Invention

[0005] In order to solve the problems that the complex structure of the existing telecentric movable parallel mechanism limits the application scenarios and the assembly difficulty is large, the present invention provides a double parallelogram telecentric movable parallel robot mechanism, which can meet the requirement of adjustable telecentric point, and the overall structure of the mechanism is simple, reducing the manufacturing and assembly difficulty.

[0006] The technical solution of the present invention is as follows: A double parallelogram telecentric movable parallel robot mechanism, which includes: a moving platform and a fixed platform, and the moving platform and the fixed platform are connected by parallel branches; It is characterized in that: the parallel branches include: a first branch, a second branch and a third branch; the structures of the first branch and the second branch are the same, both are realized based on the UU branch, and the third branch is realized based on the URU branch; The UU branch includes two branch universal joints, the branch universal joints are connected based on a connecting rod, and the axes of the two branch universal joints are parallel to each other; the URU branch includes: two third universal joints and a third rotating joint, the third rotating joint is arranged between the two third universal joints, the kinematic pairs are connected by a connecting rod, the axes between the two third universal joints are parallel to each other, and the third rotating joint is parallel to one of the two 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, and 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 realized based on multi-rotating joint branches; Each multi-rotating joint branch includes N platform rotating joints connected in sequence. The first and last platform rotating joints in the multi-rotating joint branch are simultaneously connected to the same platform connecting rod, and another group of adjacent platform rotating joints are simultaneously connected to both ends of an axis of a third universal joint, and the remaining adjacent platform rotating joints are connected based on a connecting rod to form an N-sided polygon; The axes of all the platform rotating joints are parallel to each other and are simultaneously perpendicular to the plane where the fixed platform is located; The fixed platform and the moving platform are respectively connected to a third universal joint and are arranged on the same side of the first parallelogram; the connection line of the rotation centers of the two third universal joints is parallel to the first branch and the second branch; The intersection of the two axes of the third universal joint connected to the fixed platform is set as the telecentric point.

[0007] Its further feature is 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 lengths of the other two branches; In the multi-rotating joint branch, the value of N is greater than or equal to 6; Among all the platform rotating joints connected to the platform connecting rod, one platform rotating joint is selected from each of the upper and lower platform connecting rods and is set as a moving driving joint for controlling the position movement of the telecentric point, and the axis of the moving driving joint is connected to a driving device; Among the branch chain universal joints at both ends of the link for platform connection connected to the fixed platform, select one branch chain universal joint as the driving joint for controlling the rotation of the telecentric point; connect a driving device to each of the two mutually perpendicular rotating shafts of the driving joint for rotation; On the fixed platform, the lengths of the links between adjacent platform rotating joints are the same.

[0008] A dual-parallelogram telecentric movable parallel robot mechanism provided in this application has the telecentric point located on the plane where the fixed platform is located. Both the moving platform and the fixed platform are realized based on multi-rotating-joint branch chains. Each platform includes N platform rotating joints with parallel rotating shafts. Based on the drive of the platform rotating joints, the branch chains of the moving platform and the fixed platform deform, enabling the telecentric point to freely move within the plane where the fixed platform is located. The first branch chain, the second branch chain, and the two links for platform connection together form a first parallelogram. The connection line between the rotation centers of the two third universal joints of the third branch chain is parallel to the first branch chain and the second branch chain. The third universal joints at both ends of the third branch chain are respectively connected to the first parallelogram through the moving platform and the fixed platform. The first parallelogram can move simultaneously in two mutually perpendicular directions based on the first branch chain and the second branch chain, thereby driving the telecentric point on the third branch chain to achieve rotational degrees of freedom in two directions around the telecentric point. The parallel robot mechanism in this application has a simple structure and can achieve rotational degrees of freedom in two directions around the telecentric point only with rotating joints and universal hinges. Therefore, the overall complexity of the mechanism is not high, it is easy to assemble, and the uncertainty of the mechanism in singular configurations is reduced. Description of the Drawings

[0009] Figure 1 It is an overall schematic diagram of the structure of the dual-parallelogram telecentric movable parallel robot mechanism of this application; Figure 2 It is a schematic diagram of the specific structure markings of the structure of the dual-parallelogram telecentric movable parallel robot mechanism of this application; Figure 3 It is a schematic diagram of the structure of the fixed platform; Figure 4 For Figure 1 The enlarged schematic diagram of the structure at point A; Figure 5 For Figure 1 The enlarged schematic diagram of the structure at point B; Figure 6 It is Action Example 1 of the structure of the dual-parallelogram telecentric movable parallel robot mechanism; Figure 7 It is Action Example 2 of the structure of the dual-parallelogram telecentric movable parallel robot mechanism; Figure 8 It is Action Example 3 of the structure of the dual-parallelogram telecentric movable parallel robot mechanism; Figure 9 Schematic diagram of the connection line of the rotation centers of the two rotating shafts of the third universal pair 1 and the third universal pair 2.

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

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

[0012] 6 Remote center point. Detailed implementation manner

[0013] As Figures 1 to 5 shown, the present application includes a double-parallelogram remote-center movable parallel robot mechanism, which includes: a fixed platform 1 and a moving platform 5, and the moving platform 5 and the fixed platform 1 are connected by parallel branch chains. The parallel branch chains include: a first branch chain 2, a second branch chain 3, and a third branch chain 4; the first branch chain 2 and the second branch chain 3 have the same structure and are both realized based on a UU (universal pair-universal pair) branch chain, and the third branch chain 4 is realized based on a URU (universal pair-rotating pair-universal pair) branch chain. The rotating pair and universal pair structures in the present application can all be realized based on existing module products in the prior art.

[0014] The UU branch chain includes two branch universal pairs, and the branch universal pairs are connected based on a connecting rod. Specifically, it includes: the first branch chain 2 includes a first universal pair 21 of the first branch chain and a second universal pair 22 of the first branch chain; the second branch chain 3 includes: a first universal pair 31 of the second branch chain and a second universal pair 32 of the second branch chain.

[0015] The two rotating shafts of each universal pair: the m rotating shaft and the n rotating shaft are perpendicular to each other, forming a cross-shaped structure.

[0016] As Figure 2 In the illustrated embodiment, the first branch chain 2 and the second branch chain 3 are of equal length, and the first fixed-platform link 17 and the first moving-platform link 57 are of equal length. Then: the first branch chain 2, the second branch chain 3, the first fixed-platform link 17, and the first moving-platform link 57 together form a first parallelogram. The first universal pair of the first branch chain 21, the second universal pair of the first branch chain 22, the first universal pair of the second branch chain 31, and the second universal pair of the second branch chain 32 are located at the four vertex positions of the first parallelogram. The m rotating shafts of each universal pair: are parallel to each other and parallel to the plane where the fixed platform is located; based on the m rotating shafts of the four vertex universal pairs, the first parallelogram can deform at various angles within its plane. Among them, the m rotating shafts and n rotating shafts of the four universal pairs are respectively marked as *m and *m in the figure.

[0017] In the first parallelogram, when the universal pairs are connected to each other by links, both ends of each rotating shaft are simultaneously connected to the two branches of the same U-shaped connector, and the closed segments of the U-shaped connector are connected based on the links. As Figure 4 Shown is a detailed structural schematic diagram of the second universal pair of the first branch chain 22. The two ends of the m rotating shaft (marked as 22m in the figure) of the second universal pair of the first branch chain 22 are respectively connected to the first U-shaped connector 2201 of the second universal pair of the first branch chain, and the two ends of the n rotating shaft (marked as 22n in the figure) are respectively connected to the second U-shaped connector 2202 of the second universal pair of the first branch chain; the closed segment of the first U-shaped connector 2201 of the second universal pair of the first branch chain is connected to the second universal pair of the second branch chain 32 through the first moving-platform link 57.

[0018] The URU branch chain includes: two third universal pairs and one third rotating pair. The third rotating pair is arranged between the two third universal pairs, and the kinematic pairs are connected by links. Specifically, the third branch chain 4 includes: the first universal pair of the third branch chain 41, the rotating pair of the third branch chain 42, and the second universal pair of the third branch chain 43 connected in sequence. The two rotating shafts of the first universal pair of the third branch chain 41 and the second universal pair of the third branch chain 43 are respectively parallel to each other, and the third rotating pair 42 of the third branch chain is parallel to one of the rotating shafts of the first universal pair of the third branch chain 41. As Figure 2 Shown, the n rotating shaft (marked as 41n in the figure) of the first universal pair of the third branch chain 41 is parallel to the n rotating shaft (marked as 43n in the figure) of the second universal pair of the third branch chain 43; the m rotating shaft (marked as 41m in the figure) of the first universal pair of the third branch chain 41 is parallel to the m rotating shaft (marked as 43m in the figure) of the second universal pair of the third branch chain 43; the rotating pair 42 of the third branch chain is parallel to the n rotating shaft of the first universal pair of the third branch chain 41, ensuring follow-up motion.

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

[0020] Between the first parallelogram and the third branch chain 4, the connection is realized through the moving platform 5 and the fixed platform 1; that is, two connection endpoints 1701 are provided on the first connecting rod 17 of the fixed platform, which are respectively connected to the first rotating pair 11 and the sixth rotating pair 16 on the fixed platform 1; at the positions symmetrical to the first connecting rod 17 of the fixed platform on the first connecting rod 57 of the moving platform, two connection endpoints are also provided at the same time, which are respectively connected to the first rotating pair 51 and the sixth rotating pair 56 of the moving platform.

[0021] When the first connecting rod 17 of the fixed platform is installed through a mounting bracket (not marked in the figure), when the m-axis and n-axis of the universal joints at the four vertices of the first parallelogram swing at different angles, the first parallelogram can drive the center of the far point 6 at the bottom of the third branch chain 4 to perform a movement with two degrees of rotational freedom around the center of the far point through the fixed platform 1 and the moving platform 5.

[0022] Both the moving platform 5 and the fixed platform 1 are realized based on multi-rotating pair branch chains. Each multi-rotating pair branch chain includes N platform rotating pairs connected in sequence. The moving platform 5 and the fixed platform 1 are arranged in parallel, and the rotating shafts of all the platform rotating pairs in the moving platform 5 and the fixed platform 1 are parallel to each other and are simultaneously perpendicular to the plane where the fixed platform 1 is located. The first and last platform rotating pairs in the multi-rotating pair branch chain are simultaneously connected to the same platform connecting rod, another group of adjacent platform rotating pairs are simultaneously connected to both ends of a rotating shaft of a third universal joint, and the remaining adjacent platform rotating pairs are connected based on connecting rods, and the N platform rotating pairs form an N-sided polygon.

[0023] The fixed platform 1 is connected to the first universal joint 41, the moving platform 5 is connected to the second universal joint 43, and the fixed platform 1 and the moving platform 5 are arranged 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 first universal joint 41 connected to the fixed platform 1 is set as the center of the far point 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 the moving pair of the fixed platform 1 in its plane, thereby driving the change of the position of the telecentric point 6. The range that the position of the telecentric point 6 can reach is related to the side length of the fixed platform 1 and also related to the number of rotating pairs included in the fixed platform 1. However, if the value of N is too small, for example, when N is 3, there will be many positions that the telecentric point 6 cannot reach, that is, there are too many dead points of the telecentric point 6. Therefore, in order to reduce the dead points of the telecentric point 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 pairs for deforming the fixed platform 1 needs to be increased to achieve precise deformation. Therefore, in specific implementation, the size of the side length of the fixed platform 1 and the number of moving pairs need to be selected according to actual needs.

[0025] In this application, through multiple rotating pairs, the fixed platform and the moving platform are designed as a multi-link closed-loop structure, enabling it to achieve a more complex output trajectory, reducing dead points, improving mechanical efficiency, reducing manufacturing and maintenance costs, the position of the telecentric point can be arbitrarily adjusted within the plane, the working space is large, and adjusting the position of the telecentric point is simple and easy to implement.

[0026] This embodiment is designed for a minimally invasive surgical robot. In the multi-rotating pair chain, the value of N is equal to 6. The specific side length of the fixed platform is selected according to the height of the actual operating table. When N is 6, setting a driving pair on each of the fixed platform 1 and the moving platform 5 can meet the actual working needs. Since the structures of the moving platform 5 and the fixed platform 1 are the same, both are 6R chains (6 rotating pairs), and the connection positions with the third chain 4 are also the same. As Figure 3 shown, taking the fixed platform 1 as an example to illustrate the structures of the two platforms. Among the 6 sides of the fixed platform 1, there are four connecting rods with the same length: the second connecting rod 18 of the fixed platform, the third connecting rod 19 of the fixed platform, the fourth connecting rod 110 of the fixed platform, the fifth connecting rod 111 of the fixed platform. The other two sides are respectively between the two connection endpoints 1701 on the first connecting rod 17 of the fixed platform and the m rotating shaft (marked as 41m in the figure) of the first universal pair 41.

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

[0028] The rotating pairs in this application include: a linear rotating shaft and a U-shaped connecting piece. When the two ends of the m-axis of the two universal pairs are respectively connected to the moving pairs, as Figure 5 shown, taking the m-axis of the second universal pair 43 as an example, the specific connection method is described. The third moving-platform rotating pair 53 includes: the rotating shaft 5301 of the third moving-platform rotating pair and the U-shaped connecting piece 5302 of the third moving-platform rotating pair; and the fourth moving-platform rotating pair 54 includes: the rotating shaft 5401 of the fourth moving-platform rotating pair and the U-shaped connecting piece 5402 of the fourth moving-platform rotating pair; the two ends of the n-axis of the second universal pair 43 (marked as 43n in the figure) are respectively connected to the inner sides of the open ends of the U-shaped connecting piece 4301 of the second branch universal pair, and the two ends of the m-axis of the second universal pair 43 (marked as 43m in the figure) are respectively connected to the closed segments of the U-shaped connecting piece 5402 of the fourth moving-platform rotating pair and the U-shaped connecting piece 5302 of the third moving-platform rotating pair.

[0029] The position of the telecentric point is determined by the position constraint relationship provided by the moving platform and the fixed platform. Among all the platform rotating pairs connected to the platform connecting rods, one platform rotating pair is selected from each of the upper and lower platform connecting rods and set as the moving driving pair for controlling the position movement of the telecentric point. A driving motor is set on the rotating shaft of the moving driving pair; as Figure 1 shown, in this embodiment, the first fixed-platform rotating pair 11 and the first moving-platform rotating pair 51 are selected as the moving driving pairs for controlling the position movement of the telecentric point. The rotating shafts of the first fixed-platform rotating pair 11 and the first moving-platform rotating pair 51 are respectively connected to a driving motor to control the synchronous rotation of the first fixed-platform rotating pair 11 and the first moving-platform rotating pair 51 to achieve the position movement of the telecentric point 6. The motor connected to the first fixed-platform rotating pair 11 is denoted as: driving motor E1 ( Figure 1At the connection points marked E1 to E4 between the motor and the driving pair), the motor connected to the first rotating pair 5 of the moving platform is denoted as: driving motor E2. Once the telecentric point 6 moves to the preset position, lock the two driving motors to lock the position of the telecentric point 6.

[0030] Figure 1 The mechanism is in the initial state, that is, 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 the initial position, the telecentric point 6 is located on the left-right symmetry center line of the fixed platform 1. Based on Figure 1 the position, the driving motor E1 and the driving motor E2 rotate clockwise simultaneously to move the position of the telecentric point 6 clockwise to Figure 6 as shown and then lock the two driving motors.

[0031] To ensure balanced force and improve the rigidity of the overall structure, in this embodiment, when the parallel mechanism is in the initial state, a triangle is drawn with the three universal joints of the second chain universal joint two 32, the first chain universal joint two 22, and the third universal joint two 43 as vertices, and the positions of the three universal joints are just at the vertices of an equilateral triangle. Similarly, when the mechanism is in the initial state, the second chain universal joint one 31, the first chain universal joint one 21, and the third universal joint one 41 are also at the vertices of an equilateral triangle.

[0032] The position of the first link 17 of the fixed platform is fixed, and the rotation axes of all platform rotating pairs 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 chain 2 and the second chain 3 are the same, and the length of the third chain 4 is equal to or greater than the other two chains, which can ensure that the plane angle of the fixed platform does not change during the deformation of the fixed platform. When the position of the telecentric point 6 is locked and the first parallelogram deforms, the position and angle of the moving platform 5 change along with the first link 57 of the moving platform. The moving platform 5 and the fixed platform 1 are connected by the third chain 4, and the angle of the telecentric point 6 changes with the deformation of the first parallelogram.

[0033] Among the chain universal joints at both ends of the platform connecting link connected to the fixed platform 1, select one chain universal joint to be set as the rotating driving pair for controlling the rotation of the telecentric point; a driving motor is respectively arranged on two mutually perpendicular rotating shafts of the rotating driving pair. In this embodiment, the first chain universal joint one 21 is selected as the rotating driving pair; the n rotating shaft (marked as 21n in the figure) of the first chain universal joint one 21 is connected to a driving motor, and the motor is denoted as: motor E3; the m rotating shaft (marked as 21m in the figure) of the first chain universal joint one 21 is connected to a driving motor, and the motor is denoted as: motor E4.

[0034] In Figure 6Construct a coordinate system with the telecentric point 6 as the origin of coordinates, and establish a right-handed coordinate system. In the plane where the fixed platform 1 is located, take the straight line where the m-axis of the third-link universal joint is located, and the direction from the telecentric point 6 to the fourth rotating joint of the fixed platform as the positive direction of the Y-axis. Take the direction perpendicular to the plane where the fixed platform is located, passing through the telecentric point 6 and vertically upward as the positive direction of the Z-axis. The established coordinate system is as Figure 6 shown.

[0035] Figure 6 The first parallelogram in Figure 6 is perpendicular to the horizontal plane. On the basis of the position in Figure 7 shown, the motor E3 is started, driving the n-rotating shaft of the first-link universal joint 21 to rotate 30°. Then the motor E3 stops. Then the first parallelogram rotates around the rotating shaft 21n to form an angle of 60° with the horizontal plane, and the moving platform 5 changes in position and angle along with the first link 57 of the moving platform, as

[0036] shown. The moving platform 5 drives the third link 4 to change in angle. At this time, the telecentric point 6 generates a rotation around the rotating shaft 41m; connect the intersection point of the two rotating shafts of the third universal joint 43 with the telecentric point 6 to obtain the connecting line L. The angle of the telecentric point 6 is as shown by the connecting line L. At this time, the included angle between the connecting line L and the XY plane is 60°. Figure 7 On the basis of Figure 8 shown, the motor E4 is started, driving the m-rotating shaft of the first-link universal joint 21 to rotate. When the first link 2 forms an angle of 60° with the horizontal plane, the motor E4 stops. Then the first parallelogram rotates around the rotating shaft 21m and deforms. The moving platform 5 changes in position and angle along with the first link 57 of the moving platform, as

[0037] shown. The moving platform 5 drives the third link 4 to change in angle. At this time, the telecentric point 6 generates a rotation around the rotating shaft 41n; at this time, the included angle between the connecting line L and the ZX plane is 30°.

[0038] Figure 9As shown, the connection line of the rotation centers of the two universal hinges of the third branch chain is parallel to the first branch chain 2 and the second branch chain 3, and the fixed platform 1 is parallel to the moving platform 5. At this time, the connection line L between the center point of the third universal pair one 41 and the center point of the third universal pair two 43 of the third branch chain 4, the plane where the moving platform 5 is located, the plane where the fixed platform 1 is located, and the plane formed by the first branch chain 2 and the second branch chain 3 form a second parallelogram. In this application, two parallelogram structures are designed in the branch chain, so that when the mechanism is in any position, the two parallelogram relationships still exist. Based on the two parallelograms, the telecentric point can be moved arbitrarily within the plane. And the three branch chains of this application have a simple structure and are only composed of rotating pairs and universal pairs. Therefore, the overall complexity of the mechanism is not high, it is easy to assemble, and the uncertainty of the mechanism in the singular configuration is reduced. The three branch chains in this application have a simple structure, reasonable distribution, balanced force, improved stiffness, which is helpful for the modularization and standardization of the design and convenient for manufacturing. The branch chain of this application is a parallel mechanism, and the error is shared by multiple branch chains. Therefore, the comprehensive error of the moving platform is small, which is suitable for the high-precision medical field. The parallel mechanism of this application is composed of 3 independent kinematic chains (branch chains) that jointly connect the moving platform and the static platform. The branch chains, the moving platform, and the fixed platform jointly form a closed-loop structure, and the load is shared by multiple branch chains, with high overall stiffness. The series mechanism in the prior art is an open-chain structure, where the joints and connecting rods are connected in series in sequence, and the end load needs to be transmitted to the base through all joints, resulting in error accumulation and deformation superposition, and weak rigidity. Therefore, the parallel mechanism of this application has a closed-loop structure, making its stiffness characteristics significantly higher than those of traditional series mechanisms, and the deformation is smaller under the same load.

Claims

1. 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 via a parallel branch chain; Characterized in that: the parallel branch chain includes: a first branch chain, a second branch chain and a third branch chain; the first branch chain and the second branch chain have the same structure and are both implemented based on the UU branch chain, and the third branch chain is implemented based on the URU branch chain; The UU branch chain includes two branch chain universal joints, the branch chain universal joints are connected by a connecting rod, and the rotation axes of the two branch chain universal joints are parallel to each other; the URU branch chain includes: two third universal joints and a third rotational joint, the third rotational joint is arranged between the two third universal joints, the kinematic joints are connected by a connecting rod, the rotation axes of the two third universal joints are parallel to each other, and the third rotational joint is parallel to one of the two rotation axes of the third universal joint; The first branch chain and the second branch chain are arranged in parallel, the first branch chain and the second branch chain are connected by two platform connecting rods, and the first branch chain, the second branch chain and the two platform connecting rods together form a first parallelogram; The moving platform and the fixed platform are both realized based on multiple rotating sub-branch chains; Each of the multi-rotational pair branches includes N platform rotational pairs connected in sequence, the first and last two platform rotational pairs in the multi-rotational pair branch are simultaneously connected to the same platform connection connecting rod, another group of adjacent platform rotational pairs are simultaneously connected to the two ends of a rotating shaft of a third universal joint, and the remaining adjacent platform rotational pairs are connected based on connecting rods to form an N-sided polygon; The rotation axes of all the platform rotation pairs are parallel to each other and perpendicular to the plane where the fixed platform is located; The fixed platform and the movable platform are respectively connected to one of the third universal joints and are arranged 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 chain and the second branch chain; The intersection of the two rotating shafts of the third universal joint connected to the fixed platform is set as the telecentric point.

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

3. The double parallelogram telecentric movable parallel robot mechanism according to claim 1, characterized in that: In the multi-rotation sub-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 rotating pairs connected to the platform connecting rod, one platform rotating pair is selected from each of the upper and lower platform connecting rods, and is set as a moving driving pair for controlling the movement of the distal point position, and the rotating shaft of the moving driving pair is connected to the driving device.

5. The double parallelogram telecentric movable parallel robot mechanism according to claim 1, characterized in that: Among the branch chain universal pairs at both ends of the platform connecting rod connected to the fixed platform, one branch chain universal pair is selected as a rotation driving pair for controlling the rotation of the telecentric point; a driving device is respectively connected to two mutually perpendicular rotating shafts of the rotation driving pair.

6. The double parallelogram telecentric movable parallel robot mechanism according to claim 1, characterized in that: On the fixed platform, the lengths of the connecting rods between adjacent platform rotation pairs are the same.

Images