Four-branch three-degree-of-freedom parallel motion platform

Abstract

A four-branch three-degree-of-freedom parallel motion platform comprises a fixed platform, a movable platform, a first driving branch chain, a second driving branch chain, a third driving branch chain and a just constraint branch chain, the first driving branch chain, the second driving branch chain, the third driving branch chain and the just constraint branch chain are arranged between the fixed platform and the movable platform, and the first driving branch chain and the third driving branch chain have the same structural form and are connected through two connecting rods through cylindrical pairs, rotating pairs and universal hinges. The second driving branch chain is formed by connecting a cylindrical pair and two revolute pairs through two connecting rods, and the right constraint branch chain is formed by connecting a moving pair and the cylindrical pair through a connecting rod. The three driving branch chains respectively and independently control the movement of the movable platform, so that the movable platform can rotate in one direction and move in two directions, complete decoupling of three spatial degrees of freedom is realized, kinematics and dynamics modeling is easy, and the three-degree-of-freedom parallel mechanism has the characteristics of simple structure, easiness in control and the like; the rigidity, the bearing capacity and the stress condition of the mechanism can be obviously improved through the designed just-constrained branched chains, and the mechanism can be applied to the fields of various motion simulators, medical instruments, target tracking and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of robots, and in particular relates to a four-branch three-degree-of-freedom parallel motion platform. Background Art

[0002] Compared with serial mechanisms, parallel mechanisms have many advantages, such as good structural stiffness, small cumulative error, and large load-bearing capacity. Among them, the designed just-constrained branch chain can significantly improve the stiffness, load-bearing capacity, and force condition of the mechanism. Therefore, parallel mechanisms are widely used in the field of robotics, such as various motion simulators, medical devices, target tracking, etc. However, the existence of its strong coupling makes parallel mechanisms difficult in configuration design, mechanism control, and analytical calculation, which limits the application of parallel mechanisms. Summary of the invention

[0003] The purpose of the present invention is to provide a four-branch three-degree-of-freedom parallel motion platform to solve the difficulties in analytical calculation, configuration design and mechanism control caused by the strong coupling of the parallel mechanism existing in the prior art.

[0004] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a four-branch three-degree-of-freedom parallel motion platform, including a fixed platform, a moving platform, three active branches and a just-constrained branch, the three active branches are respectively a first active branch, a second active branch and a third active branch; The first active branch chain comprises a first cylindrical pair, a first rotating pair and a first universal joint connected in sequence by a connecting rod, the first cylindrical pair is connected to the fixed platform, the axis of the first universal joint is divided into a first universal joint inner axis and a first universal joint outer axis, the first universal joint outer axis is connected to the moving platform, the axis of the first cylindrical pair is parallel to the axis of the first rotating pair and the first universal joint inner axis, and is perpendicular to the first universal joint outer axis; The second active branch chain comprises a second cylindrical pair, a second rotating pair and a third rotating pair connected in sequence by a connecting rod, the second cylindrical pair is connected to the fixed platform, the third rotating pair is connected to the movable platform, and the axis of the second cylindrical pair, the axis of the second rotating pair and the axis of the third rotating pair are parallel to each other; The third active branch chain comprises a third cylindrical pair, a fourth rotation pair and a second universal joint connected in sequence by a connecting rod, the third cylindrical pair is connected to the fixed platform, the axis of the second universal joint is divided into a second universal joint inner axis and a second universal joint outer axis, the second universal joint outer axis is connected to the moving platform, the axis of the third cylindrical pair, the axis of the fourth rotation pair and the second universal joint inner axis are parallel to each other and perpendicular to the second universal joint outer axis; The just-constrained branch chain includes a moving pair and a fourth cylindrical pair connected by a connecting rod, the moving pair is connected to the fixed platform, the fourth cylindrical pair is connected to the moving platform, and the moving direction of the moving pair is perpendicular to the axis of the fourth cylindrical pair; The axes of the first cylindrical pair, the second cylindrical pair and the third cylindrical pair are perpendicular to each other, and the moving direction of the moving pair is parallel to the axis of the first cylindrical pair.

[0005] The first cylindrical pair, the second cylindrical pair and the third cylindrical pair are active pairs of corresponding active branch chains, respectively, serving as power input ends and connected one-to-one with corresponding drive motors.

[0006] The moving platform is a rectangular platform.

[0007] The first universal joint outer axis, the axis of the third rotation pair, the second universal joint outer axis and the axis of the fourth cylinder pair are distributed on the same plane and are arranged in parallel.

[0008] The first universal joint, the third rotation pair and the fourth cylindrical pair are distributed on the same side of the moving platform, the second universal joint is distributed on the opposite side of the side of the moving platform, and the fourth cylindrical pair is located between the third rotation pair and the first universal joint.

[0009] The outer axis of the first universal joint, the axis of the fourth cylindrical pair and the axis of the third rotation pair are distributed on the same straight line.

[0010] The connecting rods in the first active branch chain include a first connecting rod and a second connecting rod. The first cylindrical pair is connected to one side of the first rotating pair through the first connecting rod, and the other side of the first rotating pair is connected to the first universal joint through the second connecting rod.

[0011] The connecting rods in the second active branch chain include a third connecting rod and a fourth connecting rod. The second cylindrical pair is connected to one side of the second rotating pair through the third connecting rod, and the other side of the second rotating pair is connected to the third rotating pair through the fourth connecting rod.

[0012] The connecting rods in the third active branch chain include a fifth connecting rod and a sixth connecting rod. The third cylindrical pair is connected to one side of the fourth rotating pair through the fifth connecting rod, and the other side of the fourth rotating pair is connected to the second universal joint through the sixth connecting rod.

[0013] The beneficial effects of the present invention are as follows: in the present invention, when the first cylindrical pair in the first active branch chain is inputted as an active pair alone, the movable platform has one degree of freedom of movement, when the second cylindrical pair in the second active branch chain is inputted as an active pair alone, the movable platform has another degree of freedom of movement, and when the third cylindrical pair of the third active branch chain is inputted as an active pair alone, the movable platform has one degree of freedom of rotation, so that the movable platform of the present invention has rotation in one direction and movement in two directions, that is, three degrees of freedom. At this time, the velocity Jacobian matrix of the mechanism is a diagonal matrix, has completely decoupled kinematic characteristics, and is simple to control and highly practical, which solves the problems of strong coupling of ordinary parallel mechanisms, complex kinematic calculations, and difficult path planning, and has broad application prospects.

[0014] At the same time, the design of the just-constrained branch chain improves the stiffness and load-bearing capacity of the mechanism and improves the stress condition of the mechanism. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 This is a schematic diagram of the structural principle of the four-branch three-degree-of-freedom parallel motion platform of the present invention; Markings in the figure: 100, fixed platform, 200, moving platform; L1, first active branch chain, C11, first cylindrical pair, R12, first revolute pair, U13, first universal joint, U131, first universal joint inner axis, U132, first universal joint outer axis, 1-1, first connecting rod, 1-2, second connecting rod; L2, second active branch chain, C21, second cylindrical pair, R22, second rotation pair, R23, third rotation pair, 2-1, third connecting rod, 2-2, fourth connecting rod; L3, the third active branch chain, C31, the third cylindrical pair, R32, the fourth rotation pair, U33, the second universal joint, U331, the inner axis of the second universal joint, U332, the outer axis of the second universal joint, 3-1, the fifth connecting rod, 3-2, the sixth connecting rod; L4, just constrained branch chain, P41, moving pair, C42, fourth cylindrical pair, 4-1, seventh connecting rod. DETAILED DESCRIPTION

[0017] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments, but they are not intended to limit the invention in any way.

[0018] like Figure 1 As shown, a four-branch three-degree-of-freedom parallel motion platform of the present invention includes a fixed platform 100 and a moving platform 200, and a first active branch chain L1, a second active branch chain L2, a third active branch chain L3 and a just-constrained branch chain L4 arranged between the fixed platform 100 and the moving platform 200.

[0019] The first active branch chain L1 includes a first cylindrical pair C11, a first rotating pair R12 and a first universal joint U13. One end of the first cylindrical pair C11 and the first universal joint U13 are directly connected to the fixed platform 100 and the moving platform 200 respectively. The first rotating pair R12 is connected to the first cylindrical pair C11 and the first universal joint U13 through the first connecting rod 1-1 and the second connecting rod 1-2 respectively. Specifically, the first universal joint U13 has two axes, namely, the first universal joint inner axis U131 and the first universal joint outer axis U132. The first universal joint outer axis U132 is located on one side of the first universal joint U13 for connecting the moving platform 200, and the first universal joint inner axis U131 is located on one side of the first universal joint U13 for connecting the second connecting rod 1-2. Furthermore, the axis of the first cylinder pair C11 is respectively parallel to the axis of the first revolving pair R12 and the first universal joint inner axis U131, and is perpendicular to the first universal joint outer axis U132.

[0020] The second active branch chain L2 includes a second cylindrical pair C21, a second movable rotation pair R22 and a third rotation pair R23. The second cylindrical pair C21 and the third rotation pair R23 are directly connected to the fixed platform 100 and the movable platform 200 respectively, and the second rotation pair R22 is connected to the second cylindrical pair C21 and the third rotation pair R23 through the third connecting rod 2-1 and the fourth connecting rod 2-2 respectively. Among them, the axis of the second cylindrical pair C21 is parallel to the axis of the second rotation pair R22 and the third rotation pair R23 respectively.

[0021] The structure of the third active branch chain L3 is the same as that of the first active branch chain L1, including a third cylindrical pair C31, a fourth rotation pair R32 and a second universal joint U33. The third cylindrical pair C31 and the second universal joint U33 are directly connected to the fixed platform 100 and the moving platform 200 respectively. One side of the fourth rotation pair R32 is connected to the third cylindrical pair C31 through the fifth connecting rod 3-1, and the other side is connected to the second universal joint U33 through the sixth connecting rod 3-2. Specifically, the second universal joint U33 includes two rotation axes, namely, the second universal joint inner axis U331 and the second universal joint outer axis U332. The second universal joint outer axis U332 is located on the side of the second universal joint U33 used to connect to the moving platform 200, and the second universal joint U33 inner axis U331 is located on the side of the second universal joint U33 used to connect to the sixth connecting rod 3-2. Furthermore, the axis of the third cylinder pair C31 is parallel to the fourth rotation pair R32 and the second universal joint inner axis U331, and is perpendicular to the second universal joint outer axis U332.

[0022] The just-constrained branch chain L4 includes a mobile pair P41 and a fourth cylindrical pair C42. One end of the mobile pair P41 and one end of the fourth cylindrical pair are directly connected to the fixed platform 100 and the moving platform 200 respectively, and the mobile pair P41 is connected to the fourth cylindrical pair C42 through the seventh connecting rod 4-1. The moving direction of the mobile pair P41 is perpendicular to the axis of the fourth cylindrical pair C42.

[0023] Furthermore, the axis of the first cylinder pair C11 in the first active branch chain L1, the axis of the second cylinder pair C21 in the second active branch chain L2, and the axis of the third cylinder pair C31 in the third active branch chain L3 are perpendicular to each other, and just constrain the moving direction of the moving pair P41 in the branch chain L4 to be parallel to the axis of the first cylinder pair C11 in the first active branch chain L1.

[0024] Furthermore, the first universal joint outer axis U132 in the first active branch chain L1, the axis of the third rotation pair R23 in the second active branch chain L2, the second universal joint outer axis U332 in the third active branch chain L3, and the axis of the fourth cylindrical pair C42 in the just constraint branch chain L4 are distributed on the same plane and are arranged in parallel. The moving platform 200 adopts a rectangular platform, the first universal joint U13 in the first active branch chain L1, the third rotation pair R23 in the second active branch chain L2, and the fourth cylindrical pair C42 in the just constraint branch chain L4 are distributed on the same side of the moving platform 200, the second universal joint U33 in the third active branch chain L3 is distributed on the opposite side of the side of the moving platform 200, and the first universal joint outer axis U132 in the first active branch chain L1, the axis of the fourth cylindrical pair C42 in the just constraint branch chain L4, and the axis of the third rotation pair R23 in the second active branch chain L2 are arranged in sequence along the length direction of one side of the moving platform and the three are distributed on the same straight line.

[0025] In the parallel mechanism, the first cylinder pair C11, the second cylinder pair C21 and the third cylinder pair C31 respectively connected to the fixed platform 100 in the first active branch chain L1, the second active branch chain L2 and the third active branch chain L3 serve as active pairs and are driven by corresponding servo motors.

[0026] The control principle of the present invention is as follows: the present invention drives the corresponding active pair through the servo motor, and provides power to the moving platform 200 through three active branch chains. The first driving motor drives the first cylindrical pair C11 in the first active branch chain L1, so that the moving platform 200 translates along the axis direction of the first cylindrical pair C11 in the first active branch chain L1; the second driving motor drives the second cylindrical pair C21 in the second active branch chain L2, so that the moving platform 200 translates along the axis direction of the second cylindrical pair C21 in the second active branch chain L2; the third driving motor drives the third cylindrical pair C31 in the third active branch chain L3, so that the moving platform 200 rotates around the axis direction of the fourth cylindrical pair C42 in the just constrained branch chain L4, thereby realizing the parallel mechanism with one rotation and two movements and three degrees of freedom in space.

[0027] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Those skilled in the art should understand that the specific implementation modes of the present invention may be modified or replaced by equivalents with reference to the above embodiments. Any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention are within the scope of protection of the pending claims.

Claims

1. A four-branch three-degree-of-freedom parallel motion platform, characterized in that: It includes a fixed platform (100), a movable platform (200), three active branch chains and a just-constrained branch chain (L4), wherein the three active branch chains are respectively a first active branch chain (L1), a second active branch chain (L2) and a third active branch chain (L3); The first active branch chain (L1) comprises a first cylindrical pair (C11), a first rotation pair (R12) and a first universal joint (U13) connected in sequence by a connecting rod, the first cylindrical pair (C11) is connected to the fixed platform (100), the axis of the first universal joint (U13) is divided into a first universal joint inner axis (U131) and a first universal joint outer axis (U132), the first universal joint outer axis (U132) is connected to the moving platform (200), and the axis of the first cylindrical pair (C11) is parallel to the axis of the first rotation pair (R12) and the first universal joint inner axis (U131), and is perpendicular to the first universal joint outer axis (U132); The second active branch chain (L2) comprises a second cylindrical pair (C21), a second rotation pair (R22) and a third rotation pair (R23) which are connected in sequence by connecting rods, the second cylindrical pair (C21) is connected to the fixed platform (100), the third rotation pair (R23) is connected to the movable platform (200), and the axis of the second cylindrical pair (C21), the axis of the second rotation pair (R22) and the axis of the third rotation pair (R23) are parallel to each other; The third active branch chain (L3) comprises a third cylindrical pair (C31), a fourth rotation pair (R32) and a second universal joint (U33) which are sequentially connected by connecting rods; the third cylindrical pair (C31) is connected to the fixed platform (100); the axis of the second universal joint (U33) is divided into a second universal joint inner axis (U331) and a second universal joint outer axis (U332); the second universal joint outer axis (U332) is connected to the moving platform (200); the axis of the third cylindrical pair (C31), the axis of the fourth rotation pair (R32) and the second universal joint inner axis (U331) are parallel to each other and perpendicular to the second universal joint outer axis (U332); The just-constrained branch chain (L4) comprises a mobile pair (P41) and a fourth cylindrical pair (C42) connected by a connecting rod, the mobile pair (P41) is connected to the fixed platform (100), the fourth cylindrical pair (C42) is connected to the moving platform (200), and the moving direction of the mobile pair (P41) is perpendicular to the axis of the fourth cylindrical pair (C42); The axis of the first cylindrical pair (C11), the axis of the second cylindrical pair (C21) and the axis of the third cylindrical pair (C31) are perpendicular to each other, and the moving direction of the movable pair (P41) is parallel to the axis of the first cylindrical pair (C11).

2. The four-branch three-degree-of-freedom parallel motion platform according to claim 1, characterized in that: The first cylindrical pair (C11), the second cylindrical pair (C21) and the third cylindrical pair (C31) are respectively active pairs of corresponding active branch chains, serving as power input ends and being connected one-to-one with corresponding drive motors.

3. The four-branch three-degree-of-freedom parallel motion platform according to claim 1, characterized in that: The moving platform (200) is a rectangular platform.

4. The four-branch three-degree-of-freedom parallel motion platform according to claim 1 or 3, characterized in that: The first universal joint outer axis (U132), the axis of the third rotation pair (R23), the second universal joint outer axis (U332) and the axis of the fourth cylinder pair (C42) are distributed on the same plane and are arranged in parallel.

5. The four-branch three-degree-of-freedom parallel motion platform according to claim 4, characterized in that: The first universal joint (U13), the third rotational pair (R23) and the fourth cylindrical pair (C42) are distributed on the same side of the moving platform (200), the second universal joint (U33) is distributed on the opposite side of the side of the moving platform (200), and the fourth cylindrical pair (C42) is located between the third rotational pair (R23) and the first universal joint (U13).

6. The four-branch three-degree-of-freedom parallel motion platform according to claim 5, characterized in that: The outer axis (U132) of the first universal joint, the axis of the fourth cylindrical pair (C42) and the axis of the third rotation pair (R23) are distributed on the same straight line.

7. The four-branch three-degree-of-freedom parallel motion platform according to claim 1, characterized in that: The connecting rods in the first active branch chain (L1) include a first connecting rod (1-1) and a second connecting rod (1-2); the first cylindrical pair (C11) is connected to one side of the first rotation pair (R12) through the first connecting rod (1-1); and the other side of the first rotation pair (R12) is connected to the first universal joint (U13) through the second connecting rod (1-2).

8. The four-branch three-degree-of-freedom parallel motion platform according to claim 1, characterized in that: The connecting rods in the second active branch chain (L2) include a third connecting rod (2-1) and a fourth connecting rod (2-2); the second cylindrical pair (C21) is connected to one side of the second rotation pair (R22) through the third connecting rod (2-1); and the other side of the second rotation pair (R22) is connected to the third rotation pair (R23) through the fourth connecting rod (2-2).

9. The four-branch three-degree-of-freedom parallel motion platform according to claim 1, characterized in that: The connecting rods in the third active branch chain (L3) include a fifth connecting rod (3-1) and a sixth connecting rod (3-2); the third cylindrical pair (C31) is connected to one side of the fourth rotation pair (R32) through the fifth connecting rod (3-1); and the other side of the fourth rotation pair (R32) is connected to the second universal joint (U33) through the sixth connecting rod (3-2).

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