A three-mode parallel robot mechanism based on a reconfigurable platform

Abstract

The present invention provides a three-mode parallel robot mechanism based on a reconfigurable platform, which realizes three different motion modes by adjusting the rotation angles of the six moving platform rotating pairs and controlling whether the axes of the three connecting rotating pairs intersect with each other, namely: three rotations and two movements, two rotations and two movements, and one rotation and two movements; the present application can realize the reconstruction of the motion mode without changing the internal motion pairs of the branch chain, which reduces the complexity of the mode reconstruction, reduces the driving pairs in the branch chain, and thus reduces the moment of inertia during movement; based on the three-mode parallel mechanism in the present application, the mode switching is easy to control, the number of single-degree-of-freedom motion pairs is small, and it does not contain complex motion pairs. The requirements for the stiffness and assembly accuracy of the mechanism components are low, the structure is simple, and it is easy to modularize and process and manufacture. It can be applied to production and assembly tasks that require multiple motion modes.

Description

Technical Field

[0001] The present invention relates to the field of mechanism and robotics technology, and in particular to a three-mode parallel robot mechanism based on a reconfigurable platform. Background Art

[0002] Parallel robots play a crucial role in industrial production. Their advantages include high precision, high stiffness, fast response, and excellent load capacity. They have become a research hotspot in the field of industrial robotics and have been successfully applied in machining, automated production lines, motion simulators, and other fields. Initial industrial robots typically possessed only a single motion mode. However, the increasing complexity of industrial tasks has placed higher demands on the adaptability of industrial robots. Compared to single-mode industrial robots, reconfigurable parallel robots can switch between different motion modes, possessing varying motion capabilities and properties, and adapt to diverse tasks. Consequently, they are gaining increasing attention and favor among researchers.

[0003] Existing patents for reconfigurable parallel robots, such as patent publication number CN115026792A, disclose a reconfigurable parallel mechanism capable of three rotations and three horizontal transformations. However, the mechanism has numerous internal branch kinematic pairs, requiring complex assembly conditions. Furthermore, the kinematic mode changes require internal changes in the branches, placing higher demands on the rigidity and assembly precision of the mechanism components. This limits its application scenarios due to structural complexity and cost. Summary of the Invention

[0004] In order to solve the problems in the prior art of complex assembly conditions of reconfigurable parallel robots and high requirements on the stiffness of mechanism components and assembly accuracy, the present invention provides a three-mode parallel robot mechanism based on a reconfigurable platform, which has a simple structure, a small number of single-degree-of-freedom motion pairs, is easy to process and manufacture, and has simple motion mode switching.

[0005] The technical solution of the present invention is as follows: a three-mode parallel robot mechanism based on a reconfigurable platform, comprising: a fixed base and a reconfigurable moving platform, characterized in that: the fixed base and the reconfigurable moving platform are connected by a first branch chain, a second branch chain, and a third branch chain, and the three branches have the same branch structure, namely, PRRRR branches;

[0006] The reconfigurable moving platform includes six moving platform connecting rods of equal length, and the six moving platform connecting rods are connected end to end via six moving platform revolving pairs; the rotation axes of the moving platform revolving pairs are perpendicular to the plane where the reconfigurable moving platform is located;

[0007] The first branch chain, the second branch chain and the third branch chain are respectively connected to a movable platform connecting rod in a non-adjacent manner through connecting rotating pairs.

[0008] It is further characterized by:

[0009] The branched chain structure includes: a first link, a second link, a third link, and a fourth link, one end of the first link is mounted on the fixed base via a moving pair, the other end of the first link is connected to one end of the second link to form a rotating pair 1, the other end of the second link is connected to one end of the third link via a rotating pair 2; the other end of the third link is connected to one end of the fourth link via a rotating pair 3; the other end of the fourth link is connected to a movable platform link of the reconfigurable movable platform via the connecting rotating pair;

[0010] The moving pair, the first rotating pair, and the second rotating pair form a plane pair, wherein the rotation axes of the first rotating pair and the second rotating pair are always parallel and perpendicular to the movement axis of the moving pair; the plane pair is connected to the third rotating pair and the connecting rotating pair, wherein the rotation axes of the third rotating pair and the connecting rotating pair always intersect at a point;

[0011] The connecting revolute pair is arranged at the midpoint of the connecting rod of the movable platform to which it is connected;

[0012] Among the revolving pairs for the movable platform in the reconfigurable movable platform, three non-adjacent revolving pairs are set as driving pairs to control the configuration change of the reconfigurable movable platform;

[0013] In the first branch chain, the second branch chain and the third branch chain, the motion axes of the three moving pairs are located in the same plane;

[0014] The moving pair in the first branch chain, the moving pair in the second branch chain, the moving pair in the third branch chain, the first rotating pair in the first branch chain, and the third rotating pair in the first branch chain are driving pairs, which are driven by corresponding driving motors;

[0015] In the three-rotation and two-movement motion mode, the angle between two adjacent moving platform links of the reconfigurable moving platform is 120°, and the extended axes of the three connecting revolving pairs intersect at one point.

[0016] In the two-rotation-two-movement motion mode, only the extended lines of the axes of the two connecting revolute pairs intersect at one point;

[0017] In the one-rotation-two-movement motion mode, the extended lines of the axes of the three connecting revolving pairs have no intersection with each other.

[0018] The present invention provides a three-mode parallel robot mechanism based on a reconfigurable platform, which realizes three different motion modes by adjusting the rotation angles of the six moving platform rotating pairs and controlling whether the axes of the three connecting rotating pairs intersect with each other, namely: three rotations and two movements, two rotations and two movements, and one rotation and two movements; the present application can realize the reconstruction of the motion mode without changing the internal motion pairs of the branch chain, which reduces the complexity of the mode reconstruction, reduces the driving pairs in the branch chain, and thus reduces the moment of inertia during movement; based on the three-mode parallel mechanism in the present application, the mode switching is easy to control, the number of single-degree-of-freedom motion pairs is small, and it does not contain complex motion pairs. The requirements for the stiffness and assembly accuracy of the mechanism components are low, the structure is simple, and it is easy to modularize and process and manufacture. It can be applied to production and assembly tasks that require multiple motion modes. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the overall structure of this application;

[0020] Figure 2 This is a schematic diagram of the structure of the first branch;

[0021] Figure 3 It is the general posture of the reconfigurable mobile platform in mode 1;

[0022] Figure 4 is the general posture of the reconfigurable mobile platform in mode 2;

[0023] Figure 5 is the general posture of the reconfigurable mobile platform in mode three;

[0024] Figure 6 It is the general posture of the organization of this application located under the pattern;

[0025] Figure 7 This is the general posture of the institution of this application under Mode 2;

[0026] Figure 8 This is the general posture of the institution of this application under mode three;

[0027] In the figure: 1 first branch chain; 11 first link of first branch chain; 12 second link of first branch chain; 13 third link of first branch chain; 14 fourth link of first branch chain; 2 second branch chain; 21 first link of second branch chain; 22 second link of second branch chain; 23 third link of second branch chain; 24 fourth link of second branch chain; 3 third branch chain; 31 first link of third branch chain; 32 second link of third branch chain; 33 third link of third branch chain; 34 fourth link of third branch chain; 4 reconfigurable mobile platform; 41 first link of mobile platform; 42 second link of mobile platform; 43 third link of mobile platform; 44 fourth link of mobile platform; 45 fifth link of mobile platform; 46 sixth link of mobile platform; 5 fixed base;

[0028] 1-1 first moving pair, 1-2 first rotation pair 1, 1-3 first rotation pair 2, 1-4 first rotation pair 3, 1-5 first connecting rotation pair;

[0029] 2-1 second moving pair, 2-2 second rotation pair 1, 2-3 second rotation pair 2, 2-4 second rotation pair 3, 2-5 second connecting rotation pair;

[0030] 3-1 the third moving pair, 3-2 the third rotational pair 1, 3-3 the third rotational pair 2, 3-4 the third rotational pair 3, 3-5 the third connecting rotational pair;

[0031] The 4-1 moving platform uses the first rotation pair, the 4-2 moving platform uses the second rotation pair, the 4-3 moving platform uses the third rotation pair, the 4-4 moving platform uses the fourth rotation pair, the 4-5 moving platform uses the fifth rotation pair, and the 4-6 moving platform uses the sixth rotation pair. DETAILED DESCRIPTION

[0032] like Figures 1 to 6 As shown, the present invention includes a three-mode parallel robot mechanism based on a reconfigurable platform, comprising: a fixed base 5 and a reconfigurable moving platform 4, connected by a first branch chain 1, a second branch chain 2, and a third branch chain 3. The reconfigurable moving platform 4 includes six equal-length moving platform connecting rods, which are connected end-to-end by six moving platform revolute pairs; the rotation axes of the revolving pairs are perpendicular to the plane of the reconfigurable moving platform 4.

[0033] In the embodiment shown in the accompanying drawings, the reconfigurable moving platform 4 includes: a first moving platform link 41, a second moving platform link 42, a third moving platform link 43, a fourth moving platform link 44, a fifth moving platform link 45 and a sixth moving platform link 46, and the six moving platform rotating pairs are: a moving platform rotating pair 1 4-1, a moving platform rotating pair 2 4-2, a moving platform rotating pair 3 4-3, a moving platform rotating pair 4-4, a moving platform rotating pair 5 4-5 and a moving platform rotating pair 6 4-6.

[0034] Among the reconfigurable moving platform's revolving pairs, three non-adjacent revolving pairs are configured as drive pairs to control the reconfigurable moving platform's configuration. In this embodiment, revolving pair 1 4-1, revolving pair 3 4-3, and revolving pair 5 4-5 are configured as drive pairs to control the reconfigurable moving platform's configuration.

[0035] The first branch chain 1, the second branch chain 2, and the third branch chain 3 are each non-adjacently connected to a movable platform link via a connecting revolute pair. All three branches have the same PRR (RR) branch structure and are symmetrically distributed on the fixed base 5 in their initial configuration. P represents the translation pair, and R represents the revolute pair. The revolute pair 3 of each branch chain, together with the connecting revolute pair, forms a spherical sub-chain (RR).

[0036] The three branch chain structures are the same, and the branch chain structures include: a first link, a second link, a third link and a fourth link. One end of the first link is installed on the fixed base 5 through a movable pair, and the other end of the first link is connected to one end of the second link to form a rotating pair one. The other end of the second link is connected to one end of the third link through a rotating pair two; the other end of the third link is connected to one end of the fourth link through a rotating pair three; the other end of the fourth link is connected to a moving platform link of the reconfigurable moving platform 4 through a connecting rotating pair.

[0037] like Figure 2 As shown, the first branch chain 1 includes four connecting rods and five kinematic pairs, namely: the first branch chain first connecting rod 11, the first branch chain second connecting rod 12, the first branch chain third connecting rod 13, the first branch chain fourth connecting rod 14, the first moving pair 1-1, the first rotating pair 1-2, the first rotating pair 2 1-3, the first rotating pair 3 1-4, and the first connecting rotating pair 1-5.

[0038] One end of the first link 11 of the first branch chain is installed on the fixed base 5 through the movable pair 1-1, the other end of the first link 11 of the first branch chain is connected to one end of the second link 12 of the first branch chain to form a rotating pair 1-2, the other end of the second link 12 of the first branch chain is connected to the third link 13 of the first branch chain through the rotating pair 1-3; the other end of the third link 13 of the first branch chain is connected to the third link 14 of the first branch chain through the rotating pair 1-4; the fourth link of the first branch chain is connected to the first link 41 of the moving platform through the first connecting rotating pair 1-5.

[0039] Among them, the moving pair, the rotating pair 1 and the rotating pair 2 form a plane pair, and the rotation axes of the rotating pair 1 and the rotating pair 2 are always parallel and perpendicular to the movement axis of the moving pair; the plane pair is connected to the rotating pair 3 and the connecting rotating pair, and the rotation axes of the rotating pair 3 and the connecting rotating pair always intersect at one point; the connecting rotating pair is set at the midpoint of the moving platform connecting rod to which it is connected.

[0040] In this embodiment, the first moving pair 1-1, the first rotating pair 1-2 and the first rotating pair 2 1-3 form a plane pair, and the rotation axes of the first rotating pair 1-2 and the first rotating pair 2 1-3 are always parallel and perpendicular to the movement axis of the first moving pair 1-1; the rotation axes of the first rotating pair 3 1-4 and the first connecting rotating pair 1-5 always intersect at one point; the first connecting rotating pair 1-5 is arranged at the midpoint of the first connecting rod 41 of the moving platform.

[0041] Specifically, the intersection of the extension line of the rotation axis of the rotating pair 3 of each branch chain and the connecting rotating pair is located in the direction of the reconfigurable moving platform 4. In mode 1, the intersection is located on the normal passing through the plane perpendicular to the reconfigurable moving platform 4 and through its geometric center point. Figure 3 and Figure 6 In the embodiment, the reconfigurable braking platform 4 is placed horizontally, and the intersection of the extended lines a1 and b1 of the rotational axis of the third revolving pair and the connecting revolving pair can be located above or below the reconfigurable braking platform 4. In this embodiment, the intersection of the rotational axis of the first revolving pair 1-4 and the first connecting revolving pair 1-5 is located below the reconfigurable braking platform 4.

[0042] The second branch chain 2 includes four connecting rods and five kinematic pairs, namely: the second branch chain first connecting rod 21, the second branch chain second connecting rod 22, the second branch chain third connecting rod 23, the second branch chain fourth connecting rod 24, the second moving pair 2-1, the second rotation pair 1 2-2, the second rotation pair 2-3, the second rotation pair 3 2-4, and the second connecting rotation pair 2-5; the specific connection structure is the same as that of the first branch chain 1.

[0043] The third branch chain 3 includes four connecting rods and five kinematic pairs, namely: the third branch chain first connecting rod 31, the third branch chain second connecting rod 32, the third branch chain third connecting rod 33, the third branch chain fourth connecting rod 34, the third moving pair 3-1, the third rotation pair 1 3-2, the third rotation pair 2 3-3, 3-4 the third rotation pair 3 and the third connecting rotation pair 3-5; the specific connection structure is the same as that of the first branch chain 1.

[0044] In this application, in the first branch chain 1, the second branch chain 2 and the third branch chain 3, the motion axes of the three moving pairs installed on the fixed base 5: the first moving pair 1-1, the second moving pair 2-1 and the third moving pair 3-1 are always located in the same plane.

[0045] The first moving pair 1-1 in the first branch chain 1, the second moving pair 2-1 in the second branch chain 2, the third moving pair 3-1 in the third branch chain 3, the first rotating pair 1-2 in the first branch chain 1, and the first rotating pair 1-4 in the first branch chain 1 are driving pairs, which are driven by corresponding driving motors.

[0046] The three non-adjacent moving platform connecting rods of the reconfigurable moving platform 4 are respectively connected to the three branch chains to form a rotating pair; in this embodiment, the first connecting rod 41 of the moving platform and the first branch chain 1 form a first connecting rotating pair 1-5, a second branch chain 2 and a third branch chain 3, the third connecting rod 43 of the moving platform and the second branch chain 2 form a second connecting rotating pair 2-5, and the fifth connecting rod 45 of the moving platform and the third branch chain 3 form a third connecting rotating pair 3-5. By adjusting the angles between the connecting rods in the reconfigurable moving platform 4, the controllable mechanism can enter different motion modes.

[0047] The mechanism of this application supports three different motion modes: three rotations and two movements 3T2R, two rotations and two movements 2T2R, and one rotation and two movements 1T2R.

[0048] The initial state of the mechanism of the present application is a three-rotation and two-movement motion mode. In this mode, among the six movable platform connecting rods of the reconfigurable movable platform 4, the angles between two adjacent movable platform connecting rods on the plane of the movable platform: angle C1 to angle C6 are all 120 degrees. At the same time, the extended axes of the three connecting rotating pairs intersect at one point. Figure 3 and Figure 6 The embodiment shown. Figure 3 In the figure, the six sides of the reconfigurable dynamic platform 4 form a regular hexagon, and the intersection points of the three groups of spherical sub-chains (RR) in the three branch chains intersect at the same point, that is, the rotation axes a1, a2 and a3 of the first connecting rotation pair 1-5, the second connecting rotation pair 2-5 and the third connecting rotation pair 3-5 intersect at the same point. Figure 6 In the figure, the rotation axes of the first rotating pair 1-4 and the first connecting rotating pair 1-5: b1 and a1 always intersect at one point, the rotation axes of the second rotating pair 2-4 and the second connecting rotating pair 2-5: b2 and a2 always intersect at one point, the rotation axes of the third rotating pair 3-4 and the third connecting rotating pair 3-5: b3 and a3 always intersect at one point, and the three intersection points overlap at point O.

[0049] When the angles between the six moving platform connecting rods of the reconfigurable moving platform 4 are fixed, the first moving pair 1-1 in the first branch chain 1, the second moving pair 2-1 in the second branch chain 2, the third moving pair 3-1 in the third branch chain 3, the first rotating pair 1-2 and the first rotating pair 1-4 in the first branch chain 1 serving as the driving pair are driven by corresponding drive motors to realize the three rotations and two movements of the reconfigurable moving platform 4.

[0050] Based on Lie group theory, the motion subgroups of each branch chain are expressed as T2 ( w ) S ( O ), which can also be expressed as G ( w ) S ( O ), this motion subgroup represents three rotations and two translations in space. Figure 3 and Figure 6 In the three branches with the same motion subgroup, if S ( O ) The centers of the spherical motion subgroups intersect at one point, so the intersection of the three branch chain subgroups is T2 ( w ) S (O ), that is, the motion of the moving platform is three rotations and two shifts in space:

[0051] ,

[0052] In the formula, represents the i -th branched chain of the kinematic subgroup.

[0053] In the two-rotation and two-movement motion mode, only the extended lines of the axes of the two connecting revolute pairs intersect at one point. Figure 4 and Figure 7 Example. Figure 4 In the three branches, only two of the three groups of spherical subchains (RR) intersect at one point. There are many ways to achieve this goal in practice, such as Figure 7 As shown, based on the initial three-rotation, two-movement motion mode, the dynamic platform rotational pair 5 4-5 and the dynamic platform rotational pair 3 4-3, acting as the driving pairs, are activated, increasing the angle C5 between the dynamic platform's fifth link 45 and sixth link 46, and the angle C3 between the dynamic platform's third link 43 and fourth link 44. This increases the angle C4 between the dynamic platform's fifth link 45 and fourth link 44, and the angle C6 between the dynamic platform's first link 41 and sixth link 46. Consequently, the intersection O1 of the rotational axes b3 and a3 of the third rotational pair 3-4 and the third connecting rotational pair 3-5 changes position, while the intersections a1 and b1, and a2 and b2, remain at their original positions O2. This creates a two-rotation, two-movement motion mode. With the angles between the six dynamic platform links of the reconfigurable dynamic platform 4 fixed, the two-rotation, two-movement motion of the reconfigurable dynamic platform 4 is achieved through the driving pairs on the branch chains.

[0054] When the center of one of the branches does not intersect with the other two branches:

[0055] ,

[0056] Represents two rotations and two translations in space. S ( O 1) and S ( O 2) Represents point-based O 1 and O 2's spherical three-rotation motion.

[0057] In the one-rotation-two-movement motion mode, the extended lines of the axes of the three connecting revolute pairs have no intersections with each other, such as Figure 5 and Figure 8 The embodiment shown. Figure 5 In the three branches, the intersection points of the three groups of spherical subchains (RR) do not intersect, such as Figure 8As shown, based on the initial three-rotation, two-movement motion pattern, the three drive pairs of the reconfigurable mobile platform 4 are simultaneously activated, increasing angles C3 and C1 while decreasing angle C5. Angle C2 then decreases, while angle C4 increases. Angle C6 remains at 120°. At this point, the intersection points O3' of a1 and b1, O2' of a2 and b2, and O1' of a3 and b3 do not intersect. In other words, the reconfigurable mobile platform 4 enters a one-rotation, two-movement motion pattern. The one-rotation, two-movement motion of the reconfigurable mobile platform 4 is achieved through the drive pairs on the branch chains.

[0058] When the centers of the three branches do not intersect at one point,

[0059] ,

[0060] in, S ( O 1'), S ( O 2') and S ( O 3') respectively represent point-based O 1', O 2' and O 3 'Spherical three-rotation motion.

[0061] After using the technical solution of the present invention, three different motion modes can be realized, namely three rotations and two movements, two rotations and two movements, and one rotation and two movements. It has the advantages of simple structure, high precision, and easy control of mode switching. The structures of the three branches of the mechanism are completely consistent and do not contain complex motion pairs. It is easy to modularize and process and manufacture. It can be applied to production and assembly tasks that require multiple motion modes.

Claims

1. A three-mode parallel robot mechanism based on a reconfigurable platform, comprising: The fixed base and the reconfigurable mobile platform are characterized in that: the fixed base and the reconfigurable mobile platform are connected by a first branch chain, a second branch chain, and a third branch chain, and the three branches have the same branch chain structure, which are all PRRRR branches; the branch chain structure includes a moving pair, a first rotating pair, a second rotating pair, a third rotating pair, and a connecting rotating pair connected in sequence; The reconfigurable moving platform includes six moving platform connecting rods of equal length, and the six moving platform connecting rods are connected end to end via six moving platform revolving pairs; the rotation axes of the moving platform revolving pairs are perpendicular to the plane where the reconfigurable moving platform is located; The first branch chain, the second branch chain and the third branch chain are respectively connected to a movable platform connecting rod via connecting rotating pairs in a non-adjacent manner; Among the rotating pairs for the movable platform in the reconfigurable movable platform, three non-adjacent rotating pairs are set as driving pairs to control the configuration change of the reconfigurable movable platform.

2. The three-mode parallel robot mechanism based on a reconfigurable platform according to claim 1, characterized in that: The branched chain structure includes: a first link, a second link, a third link, and a fourth link, one end of the first link is mounted on the fixed base via a moving pair, the other end of the first link is connected to one end of the second link to form a rotating pair 1, the other end of the second link is connected to one end of the third link via a rotating pair 2; the other end of the third link is connected to one end of the fourth link via a rotating pair 3; the other end of the fourth link is connected to a movable platform link of the reconfigurable movable platform via the connecting rotating pair; The moving pair, the first rotating pair, and the second rotating pair form a plane pair, wherein the rotation axes of the first rotating pair and the second rotating pair are always parallel and perpendicular to the movement axis of the moving pair; the plane pair is connected to the third rotating pair and the connecting rotating pair, wherein the rotation axes of the third rotating pair and the connecting rotating pair always intersect at a point; The connecting revolute pair is arranged at the midpoint of the connecting rod of the moving platform to which it is connected.

3. The three-mode parallel robot mechanism based on a reconfigurable platform according to claim 2, characterized in that: In the first branch chain, the second branch chain and the third branch chain, the motion axes of the three moving pairs are located in the same plane.

4. The three-mode parallel robot mechanism based on a reconfigurable platform according to claim 2, characterized in that: The moving pair in the first branch chain, the moving pair in the second branch chain, the moving pair in the third branch chain, the first rotating pair in the first branch chain, and the third rotating pair in the first branch chain are driving pairs, which are driven by corresponding driving motors.

5. The three-mode parallel robot mechanism based on a reconfigurable platform according to claim 1, characterized in that: In the three-rotation and two-movement motion mode, the angle between two adjacent moving platform connecting rods of the reconfigurable moving platform is 120°, and the extended axes of the three connecting rotating pairs intersect at one point.

6. The three-mode parallel robot mechanism based on a reconfigurable platform according to claim 1, characterized in that: In the two-rotation and two-movement motion mode, only the extended lines of the axes of the two connecting revolute pairs intersect at one point.

7. The three-mode parallel robot mechanism based on a reconfigurable platform according to claim 1, characterized in that: In the one-rotation-two-movement motion mode, the extended lines of the axes of the three connecting revolving pairs have no intersection with each other.

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