Novel spatial three-degree-of-freedom rotational decoupling mechanism

Abstract

This novel three-degree-of-freedom rotational decoupling mechanism belongs to the field of robotics technology. It addresses the insufficient decoupling capability of existing parallel mechanisms. The mechanism includes a moving platform and a fixed platform positioned vertically, connected by three circumferentially arranged branch mechanisms. Each branch mechanism includes a driving link and a driven link, both of which are obliquely arranged arc-shaped rods. The lower end of the driving link is hinged to the fixed platform via a first revolute joint, the upper end of the driving link is hinged to the lower end of the driven link via a second revolute joint, and the upper end of the driven link is hinged to the moving platform via a ball joint. In the three sets of first, second, and ball joints, the axes of any two points to the same point, the rotation center, around which the moving platform rotates. This invention features a simple structure, ease of manufacturing and assembly, motion decoupling, easy control, and good dynamic performance.

Description

Technical Field

[0001] This utility model belongs to the field of robotics technology, and in particular relates to a novel spatial three-degree-of-freedom rotational decoupling mechanism. Background Technology

[0002] Parallel robot mechanisms feature multi-degree-of-freedom, multi-loop closed chains in space. Compared to serial mechanisms, parallel mechanisms offer advantages such as higher stiffness, greater load-bearing capacity, smaller cumulative error, better dynamic characteristics, and a more compact structure. Currently, parallel mechanisms are widely used in various motion simulators, micro-motion control consoles, and other applications.

[0003] The degrees of freedom of parallel mechanisms vary from 2 to 6. Currently, research on 6-DOF parallel mechanisms is relatively comprehensive and in-depth, and they are widely used in industry. However, parallel mechanisms with fewer degrees of freedom have simpler structures and lower manufacturing and control costs. Therefore, they have unique advantages when meeting expected working requirements.

[0004] The prominent issue with parallel mechanisms is their strong coupling, a unique characteristic that distinguishes them from series mechanisms. This includes higher load-bearing capacity, smaller cumulative error, and greater stiffness. However, this very characteristic makes the design, analysis, assembly, and control system development of parallel mechanisms extremely difficult, thus limiting their application range and effectiveness. If parallel mechanisms can achieve complete or partial decoupling of motion, their stiffness and load-bearing capacity remain superior to series mechanisms. Furthermore, their theoretical analysis is simpler, their workspace is larger, their isotropy is better, assembly is easier, and control is simpler, resulting in higher motion accuracy. Utility Model Content

[0005] The purpose of this invention is to provide a novel spatial three-degree-of-freedom rotational decoupling mechanism to solve the problem of insufficient decoupling capability in existing parallel mechanisms. The technical solution adopted by this invention is as follows:

[0006] A novel spatial three-degree-of-freedom rotational decoupling mechanism includes a moving platform and a fixed platform arranged vertically. The fixed platform and the moving platform are connected by three circumferentially arranged branch mechanisms. Each branch mechanism includes a driving rod and a driven rod, both of which are obliquely arranged arc-shaped rods. The lower end of the driving rod is hinged to the fixed platform through a first revolute joint, the upper end of the driving rod is hinged to the lower end of the driven rod through a second revolute joint, and the upper end of the driven rod is hinged to the moving platform through a ball joint.

[0007] Furthermore, both the moving platform and the fixed platform are circular plate-shaped components, with three first revolute joints evenly arranged around the axis of the fixed platform and three spherical joints evenly arranged around the axis of the moving platform.

[0008] Furthermore, the ball seat of the ball joint is connected to the moving platform, the ball joint's club is connected to the driven rod, and the axes of the three clubs, the axes of the three first revolute joints, and the axes of the three second revolute joints intersect at a point.

[0009] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0010] In this invention, any two of the three sets of first revolute joints, second revolute joints, and ball joints have axes pointing to the same point, i.e., the rotation center. The moving platform rotates around this point, and through the rotation of the driving rod, it drives the driven rod, ultimately realizing that the moving platform rotates around the rotation center in three degrees of freedom. This invention has a simple structure, is easy to process and assemble, has decoupled motion, is easy to control, and has good dynamic performance. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the structure of this utility model;

[0012] Figure 2 This is a schematic diagram of the principle model of this utility model.

[0013] In the diagram, 1. Fixed platform, 2. First revolute joint, 3. Second revolute joint, 4. Driving rod, 5. Driven rod, 6. Ball joint, 7. Moving platform. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model is described below with reference to specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the present utility model. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the present utility model.

[0015] The connections mentioned in this utility model are divided into fixed connections and detachable connections. Fixed connections, also known as non-detachable connections, include but are not limited to conventional fixed connection methods such as folded connections, riveted connections, adhesive connections, and welded connections. Detachable connections include but are not limited to conventional disassembly methods such as bolt connections, snap-fit ​​connections, pin connections, and hinge connections. When a specific connection method is not explicitly defined, it is assumed that at least one existing connection method can be found to achieve this function, and those skilled in the art can choose according to their needs. For example, a welded connection can be chosen for a fixed connection, and a bolted connection can be chosen for a detachable connection.

[0016] The present invention will be further described in detail below with reference to the accompanying drawings. The following embodiments are explanations of the present invention, but the present invention is not limited to the following embodiments.

[0017] Example: Figures 1-2As shown, a novel spatial three-degree-of-freedom rotational decoupling mechanism includes a moving platform 7 and a fixed platform 1 arranged vertically. The fixed platform 1 and the moving platform 7 are connected by three circumferentially arranged linkage assemblies. The linkage assembly includes a driving rod 4 and a driven rod 5. Both the driving rod 4 and the driven rod 5 are obliquely arranged arc-shaped rods. The lower end of the driving rod 4 is hinged to the fixed platform 1 through a first revolute joint 2, and the upper end of the driving rod 4 is hinged to the lower end of the driven rod 5 through a second revolute joint 3. The upper end of the driven rod 5 is hinged to the moving platform 7 through a ball joint 6.

[0018] Both the moving platform 7 and the fixed platform 1 are circular plate-shaped components. The three first revolute joints 2 are evenly arranged around the axis of the fixed platform 1, and the three spherical joints 6 are evenly arranged around the axis of the moving platform 7.

[0019] The ball seat of ball joint 6 is connected to the moving platform 7, and the ball stick of ball joint 6 is connected to the driven rod 5. The axes of the three ball sticks, the axes of the three first revolute joints 2, and the axes of the three second revolute joints 3 intersect at a point.

[0020] The novel spatial three-degree-of-freedom rotational decoupling mechanism of this utility model consists of a fixed platform 1, a moving platform 7, and three linkage assemblies connecting the two platforms. This mechanism is a 3-RRS mechanism, where 3 indicates that the mechanism has three linkage assemblies, R indicates a revolute joint, and S indicates a ball joint. The axes of the nine kinematic pairs constituting this mechanism intersect at a single point, which is the rotation center (also called the center of the sphere) of the spherical mechanism. The relative motion between each driving link 4 and driven link 5 is a rotational motion about the axis of this rotation center. The moving platform 7 is connected to the fixed platform 1 through the three linkage assemblies, and the moving platform 7 has three rotational degrees of freedom relative to the fixed platform 1.

[0021] According to the DH rule, establish coordinate system O. ij -X ij Y ij Z ij (i,j=1,2,3), such as Figure 2 As shown, i and j represent the j-th kinematic pair of the i-th link assembly. Since the axes of all nine kinematic pairs in this spherical three-degree-of-freedom parallel mechanism intersect at a single point, the original coordinate system can be simplified to OX. ij Y ij Z ij (i,j=1,2,3), thus, this mechanism has nine link coordinate systems, and the origins of these nine coordinate systems coincide, all being O. When i=1,j=1, the coordinate system is OX. 11 Y 11 Z 11 This indicates that the coordinate system is established on the first revolute joint 2 of the first linkage assembly, and the Z-axis of the coordinate system is... 11 The axis coincides with the axis of the first revolute joint 2 of the first connecting rod assembly, and points outward; due to Z11 With Z 12 Intersecting, according to the DH rule, the X coordinate of the coordinate system 11 The axis is Z 11 and Z 12 The normal direction of the determined plane is: X 11 =±Z 12 ×Z 11 ; Y-axis of the coordinate system 11 The axis is determined by the right-hand screw rule, so: Y 11 =Z 11 ×X 11 Similarly, the coordinate systems for the other eight links are established in the same way.

[0022] A fixed coordinate system {Q}: O-XYZ is established on a fixed platform 1. The Z-axis of the coordinate system {Q} is a vertical axis passing through the center O of the sphere. It passes through the center H of the triangle on the base of the lower pyramid and points upward along HO. The X-axis and Z-axis of the coordinate system {Q} are perpendicular to each other. 11 The determined planes are perpendicular, and the directions are as follows: Figure 2 As shown; the Y-axis of coordinate system {Q} lies on the Z-axis and Z... 11 Within the defined plane, the direction is determined by the right-hand screw rule.

[0023] The moving coordinate system {P}: O-X'Y'Z' is established on the moving platform 7. The Z' axis of the coordinate system {P} is a vertical axis passing through the center O of the sphere. It passes through the center H' of the triangle on the base of the lower pyramid and points upward along OH'. The X' axis of the coordinate system {P} is perpendicular to the Z' axis and the Z... 13 The determined planes are perpendicular, and the directions are as follows: Figure 2 As shown; the Y' axis of coordinate system {P} lies on the Z' axis and Z... 13 Within the defined plane, the direction is determined by the right-hand screw rule.

[0024] The formula for calculating degrees of freedom in Grübler-Kutzbach space is as follows: The number of components is n = 8, including 6 revolute joints and 3 spherical joints. Therefore, the degrees of freedom of this parallel mechanism are F = 6(8-1) - 6(6-1) - 3(6-3) = 3. These three degrees of freedom are about the X-axis, Y-axis, and Z-axis, respectively.

[0025] In this invention, the axes of any two of the three sets of first revolute joints 2, second revolute joints 3, and ball joints 6 point to the same point, i.e., the rotation center, around which the moving platform 7 rotates. Through the rotational motion of the driving rod 4, the driven rod 5 is driven, ultimately enabling the moving platform 7 to rotate around the rotation center in three degrees of freedom. This invention features a simple structure, ease of processing and assembly, motion decoupling, easy control, and good dynamic performance.

[0026] The above embodiments are merely illustrative examples of the present utility model and do not limit its scope of protection. Those skilled in the art can make partial changes to it, as long as they do not exceed the spirit and essence of the present utility model, they are all within the scope of protection of the present utility model.

Claims

1. A novel spatial three-degree-of-freedom rotational decoupling mechanism, characterized in that: It includes a moving platform (7) and a fixed platform (1) arranged vertically. The fixed platform (1) and the moving platform (7) are connected by three circumferentially arranged connecting rod assemblies. The connecting rod assembly includes a driving rod (4) and a driven rod (5). Both the driving rod (4) and the driven rod (5) are obliquely arranged arc-shaped rods. The lower end of the driving rod (4) is hinged to the fixed platform (1) through a first revolute joint (2). The upper end of the driving rod (4) is hinged to the lower end of the driven rod (5) through a second revolute joint (3). The upper end of the driven rod (5) is hinged to the moving platform (7) through a ball joint (6).

2. The novel spatial three-degree-of-freedom rotational decoupling mechanism according to claim 1, characterized in that: Both the moving platform (7) and the fixed platform (1) are circular plate-shaped components. The three first revolute joints (2) are evenly arranged around the axis of the fixed platform (1), and the three spherical joints (6) are evenly arranged around the axis of the moving platform (7).

3. The novel spatial three-degree-of-freedom rotational decoupling mechanism according to claim 2, characterized in that: The ball seat of the ball joint (6) is connected to the moving platform (7), and the ball rod of the ball joint (6) is connected to the driven rod (5). The axes of the three ball rods, the axes of the three first revolute joints (2) and the axes of the three second revolute joints (3) intersect at one point.

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