A four-degree-of-freedom parallel mechanism with offset angle

Abstract

The present invention belongs to the technical field of parallel robots, and specifically relates to a four-degree-of-freedom parallel mechanism with an offset angle, comprising a fixed platform, transmission branches disposed on the left and right sides of the fixed platform, parallelogram structures with offset angles fixedly disposed at the upper ends of the two transmission branches, and a moving platform connected between the two parallelogram structures with offset angles. The four-degree-of-freedom parallel mechanism provided by the present invention adopts a unique "4-2-1" structure, which drives the two transmission branches to move through four active movable joints consisting of two No. 1 sliders and two No. 2 sliders, thereby achieving three-dimensional translation and one-dimensional rotational motion of a moving platform. Its workspace can be infinitely extended along the guide rail direction, and it not only has good motion stability, but also has a compact structure and high rotational flexibility.

Description

Technical Field

[0001] The invention belongs to the technical field of parallel robots, and in particular relates to a four-degree-of-freedom parallel mechanism with an offset angle. Background Art

[0002] Compared to serial robots, parallel robots offer advantages such as greater rigidity, faster speed, higher positioning accuracy, and superior mechanical properties. Targeted at assembly line grasping operations, they can achieve three-dimensional translational motion with three degrees of freedom. Delta robots have a wide range of applications due to their simple configuration, low cost, and high efficiency.

[0003] However, in practice, it was discovered that a Delta robot with only three-dimensional translational motion could not meet the posture adjustment requirements during grasping. Therefore, a four-degree-of-freedom parallel mechanism with three-dimensional translational motion and one-dimensional rotational motion was proposed. By achieving translational motion in the x, y, and z directions and rotation about the z-axis, it can meet the application requirements in fields such as material sorting, food packaging, and parts assembly. Professor Clave first proposed adding an intermediate UPU branch between the moving and fixed platforms of a 3-DOF Delta robot to achieve 1-DOF decoupled rotation, successfully realizing three-dimensional translation and rotation about the z-axis. Furthermore, Pierrot's team subsequently invented mechanisms such as the H4, I4, Heli4, and Par4, each with four kinematic branches and a dual-motion platform structure. Based on the Par4 configuration, they developed the Quattro parallel robot. However, due to the layout constraints of the four-branch structure, parallel mechanisms are prone to mechanical interference and motion singularities, which restrict their workspace. Therefore, researchers have proposed four-degree-of-freedom parallel mechanisms with two kinematic branches and a single-motion platform, but these mechanisms suffer from low stiffness, poor kinematic stability, and a small workspace.

[0004] In summary, the low-DOF parallel robots currently used for high-speed grasping operations are still mostly two-DOF and three-DOF, which often cannot meet the needs of industrial automation. The four-DOF parallel robots have problems such as many moving components, small workspace, and many singular configurations. Summary of the Invention

[0005] In view of the above problems, the present invention provides a four-degree-of-freedom parallel mechanism with an offset angle.

[0006] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions:

[0007] A four-degree-of-freedom parallel mechanism with an offset angle comprises a fixed platform, transmission branches are respectively provided on the left and right sides of the fixed platform, parallelogram structures with an offset angle are fixedly provided at the upper ends of the two transmission branches, and a moving platform is connected between the two parallelogram structures with the offset angle;

[0008] The parallelogram structure with an offset angle includes an upper end connecting member fixedly arranged at the upper end of the transmission branch chain, an upper end fixing block fixedly arranged on the upper part of the upper end connecting member, a seventh connecting rod hinged on the upper end fixing block, an eighth connecting rod hinged on the lower part of the upper end connecting member, the lower end of the seventh connecting rod is hinged to the upper part of the lower end connecting member, the lower end of the eighth connecting rod is hinged to the lower end fixing block, the lower end fixing block is fixedly arranged at the lower part of the lower end connecting member, a rotating shaft is fixedly arranged on the lower end surface of the lower end connecting member, the rotating shaft is rotatably connected to the moving platform, and the seventh connecting rod and the eighth connecting rod are parallel and have the same length.

[0009] The cam is connected to the second sliding member by a spring, and the cam is connected to the first sliding member by a spring, and the cam is connected to the second sliding member by a spring.

[0010] Furthermore, the moving platform includes a planetary housing, the two rotating shafts are symmetrically arranged on both sides of the planetary housing, and are both rotatably connected to the planetary housing, the rotating shaft extends into the interior of the planetary housing and is fixedly connected to the planetary gear, and a sun gear is meshed and connected between the two planetary gears, the sun gear is mounted on the central shaft, the central shaft is rotatably mounted on the planetary housing, and the lower end of the central shaft extends out of the planetary housing and is fixedly connected to the output platform.

[0011] Furthermore, the planetary gears and the sun gear have the same number of teeth.

[0012] Compared with the prior art, the present invention has the following advantages:

[0013] The four-degree-of-freedom parallel mechanism provided by the present invention adopts a unique "4-2-1" structure. Through four active moving joints consisting of two No. 1 sliders and two No. 2 sliders, two transmission branches are driven to move, thereby realizing three-dimensional translation and one-dimensional rotational motion of a moving platform. Its working space can be infinitely extended along the guide rail direction. It not only has good motion stability, but also has a compact structure and high rotation flexibility.

[0014] The present invention adopts a parallelogram structure with an offset angle, which solves the rod interference problem that occurs in the conventional parallelogram mechanism during movement. The introduction of the offset angle can avoid the local singularity of the parallelogram and increase the working space of the moving platform in the third direction.

[0015] The present invention introduces a planetary gear system into the moving platform, which can realize a doubled angle output of the input rotation angle, thereby increasing the rotation working space of the moving platform and greatly improving the application of the present invention in posture adjustment.

[0016] The present invention has the advantages of compact structure, few moving components, low manufacturing cost, few singular configurations, and large working space, and can be widely used in the fields of industrial automation assembly, material picking, packaging and sorting. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of the present invention;

[0018] Figure 2 Schematic diagram of the structure of the parallelogram structure with an offset angle of the present invention;

[0019] Figure 3 is a cross-sectional view of the movable platform of the present invention;

[0020] Figure 4 Schematic diagram of the angle-multiplier output of the dynamic platform of the present invention;

[0021] Figure 5 This is a motion diagram of the present invention moving along the x-axis direction;

[0022] Figure 6 This is a motion diagram of the present invention moving along the Z-axis direction;

[0023] Figure 7 This is a schematic diagram of the motion of the present invention rotating around the Z axis;

[0024] In the figure, fixed platform 1, movable platform 2, guide rail 3, first slider 4, second slider 5, first connecting rod 6, second connecting rod 7, third connecting rod 8, fourth connecting rod 9, horizontal connecting member 10, fifth connecting rod 11, sixth connecting rod 12, upper end connecting member 13, lower end connecting member 14, rotating shaft 15, upper end fixing block 16, seventh connecting rod 17, eighth connecting rod 18, lower end fixing block 19, planetary housing 201, planetary gear 202, sun gear 203, center shaft 204, output platform 205. DETAILED DESCRIPTION

[0025] In order to further illustrate the technical solution of the present invention, the present invention is further described below through examples.

[0026] like Figures 1 to 4As shown, a four-degree-of-freedom parallel mechanism with an offset angle comprises a fixed platform 1, a transmission branch chain is provided on the left and right sides of the fixed platform 1, a parallelogram structure with an offset angle is fixedly provided at the upper end of each of the two transmission branches, and a moving platform 2 is connected between the two parallelogram structures with the offset angle;

[0027] The parallelogram structure with an offset angle includes an upper end connecting member 13 fixedly provided at the upper end of the transmission branch chain, an upper end fixing block 16 fixedly provided on the upper part of the upper end connecting member 13, a seventh connecting rod 17 hinged on the upper end fixing block 16, an eighth connecting rod 18 hinged on the lower part of the upper end connecting member 13, the lower end of the seventh connecting rod 17 is hinged to the upper part of the lower end connecting member 14, the lower end of the eighth connecting rod 18 is hinged to the lower end fixing block 19, the lower end fixing block 19 is fixedly provided at the lower part of the lower end connecting member 14, a rotating shaft 15 is fixedly provided on the lower end surface of the lower end connecting member 14, the rotating shaft 15 is rotatably connected to the moving platform 2, and the seventh connecting rod 17 and the eighth connecting rod 18 are parallel and have the same length.

[0028] The transmission branch chain includes a guide rail 3, which is fixedly connected to a fixed platform 1. A first slider 4 and a second slider 5 are slidably provided on the guide rail 3. A first connecting rod 6 and a second connecting rod 7 are hinged on the first slider 4. A third connecting rod 8 is hinged on the other end of the first connecting rod 6. A fourth connecting rod 9 is hinged on the other end of the second connecting rod 7. The upper ends of the third connecting rod 8 and the fourth connecting rod 9 are both hinged on a horizontal connecting member 10. The first connecting rod 6 is parallel to the fourth connecting rod 9, and the second connecting rod 7 is parallel to the third connecting rod 8. The first connecting rod 6, the second connecting rod 7, the third connecting rod 8, and the fourth connecting rod 9 are all of the same length. The lower end of the third connecting rod 8 is integrally connected to a fifth connecting rod 11, the lower end of which is hinged to the second slider 5. The third connecting rod 8 and the fifth connecting rod 11 together constitute a long connecting rod. A sixth connecting rod 12 is also hinged to the second slider 5, the upper end of which is hinged to a horizontal connecting member 10. The sixth connecting rod 12 is parallel to the long connecting rod and has the same length as the horizontal connecting member 10. The horizontal connecting member 10 is fixedly connected to the upper end connecting member 13. The first slider 4 and the second slider 5 are driven by a linear drive method, such as a linear motor, a rack and pinion, a servo motor and a ball screw, etc.

[0029] The movable platform 2 includes a planetary housing 201, and the two rotating shafts 15 are symmetrically arranged on both sides of the planetary housing 201 and are both rotatably connected to the planetary housing 201. The rotating shafts 15 extend into the interior of the planetary housing 201 and are fixedly connected to the planetary gears 202. A sun gear 203 is meshed and connected between the two planetary gears 202. The sun gear 203 is mounted on a central shaft 204, and the central shaft 204 is rotatably mounted on the planetary housing 201. The lower end of the central shaft 204 extends out of the planetary housing 201 and is fixedly connected to the output platform 205. The planetary gears 202 and the sun gear 203 have the same number of teeth.

[0030] Define a three-dimensional coordinate system, where the axis direction of the guide rail 3 is the y-axis direction, the direction perpendicular to the guide rail 3 and located in the same horizontal plane as the guide rail 3 is the x-axis direction, and the direction perpendicular to the fixed platform 1 is the z-axis direction;

[0031] Under the joint action of the two transmission branches, the moving platform 2 has translational freedom along the x-axis, y-axis, and z-axis directions, and generates rotational freedom around the z-axis through the relative movement of the two transmission branches in the y-axis direction, thereby realizing four degrees of freedom of movement with three translations and one rotation. The specific principle is: when the first slider 4 and the second slider 5 on the two transmission branches move synchronously along the guide rail 3 respectively, if both move forward or backward along the guide rail 3 in the y-axis direction, the moving platform 2 is driven to move forward and backward along the y-axis direction, realizing the translational freedom of the moving platform 2 in the y-axis direction; on the contrary, if they move asynchronously, such as when moving relative to each other along the guide rail 3, specifically, if the first slider 4 and the second slider 5 on one of the transmission branches move forward along the corresponding guide rail 3, and the first slider 4 and the second slider 5 on the other transmission chain move backward along the corresponding guide rail 3, the moving platform 2 is driven to rotate a certain angle around the z-axis direction, realizing the rotational freedom of the moving platform 2 around the z-axis direction, such as Figure 7 When the first slider 4 on the two transmission branches is fixed, the second slider 5 moves forward or backward along the y-axis, and the dynamic platform 2 is driven to move up and down along the z-axis, as shown in FIG. Figure 6 As shown, on the contrary, if the movement is not synchronous, such as relative movement along the guide rail 3, specifically, if the second slider 5 in one transmission branch moves forward along the y-axis direction, and the second slider 5 in the other transmission branch moves backward along the y-axis direction, the movable platform 2 is driven to move left and right along the x-axis direction, realizing the translational freedom of the movable platform 2 in the x-axis direction, as shown in FIG. Figure 5 shown.

[0032] The foregoing shows and describes the principal features and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the present invention is defined by the appended claims, not the foregoing description, and all variations that come within the meaning and range of equivalents of the claims are intended to be embraced therein.

[0033] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A four-degree-of-freedom parallel mechanism with an offset angle, characterized in that: It comprises a fixed platform (1), transmission branches are respectively provided on the left and right sides of the fixed platform (1), parallelogram structures with offset angles are fixedly provided at the upper ends of the two transmission branches, and a moving platform (2) is connected between the two parallelogram structures with offset angles; The parallelogram structure with an offset angle includes an upper end connecting member (13) fixedly arranged at the upper end of the transmission branch chain, an upper end fixing block (16) fixedly arranged on the upper part of the upper end connecting member (13), a seventh connecting rod (17) hinged on the upper end fixing block (16), an eighth connecting rod (18) hinged on the lower part of the upper end connecting member (13), the lower end of the seventh connecting rod (17) is hinged to the upper part of the lower end connecting member (14), the lower end of the eighth connecting rod (18) is hinged to the lower end fixing block (19), the lower end fixing block (19) is fixedly arranged at the lower part of the lower end connecting member (14), a rotating shaft (15) is fixedly arranged on the lower end surface of the lower end connecting member (14), the rotating shaft (15) is rotatably connected to the moving platform (2), and the seventh connecting rod (17) and the eighth connecting rod (18) are parallel and have the same length; The transmission branch chain comprises a guide rail (3), the guide rail (3) is fixedly connected to the fixed platform (1), a first slider (4) and a second slider (5) are slidably provided on the guide rail (3), a first connecting rod (6) and a second connecting rod (7) are hinged on the first slider (4), a third connecting rod (8) is hinged on the other end of the first connecting rod (6), and a fourth connecting rod (9) is hinged on the other end of the second connecting rod (7), the upper ends of the third connecting rod (8) and the fourth connecting rod (9) are hinged on the horizontal connecting member (10), the first connecting rod (6) is parallel to the fourth connecting rod (9), and the second connecting rod (7) is parallel to the third connecting rod (8). The first connecting rod (6), the second connecting rod (7), the third connecting rod (8) and the fourth connecting rod (9) are parallel to each other, and the lengths of the first connecting rod (6), the second connecting rod (7), the third connecting rod (8) and the fourth connecting rod (9) are the same. The lower end of the third connecting rod (8) is integrally connected to the fifth connecting rod (11), and the lower end of the fifth connecting rod (11) is hinged to the second slider (5). The third connecting rod (8) and the fifth connecting rod (11) together constitute a long connecting rod. A sixth connecting rod (12) is also hinged to the second slider (5), and the upper end of the sixth connecting rod (12) is hinged to the horizontal connecting member (10). The sixth connecting rod (12) is parallel to the long connecting rod and has the same length as the long connecting rod. The horizontal connecting member (10) is fixedly connected to the upper end connecting member (13).

2. A four-degree-of-freedom parallel mechanism with an offset angle according to claim 1, characterized in that: The movable platform (2) includes a planetary housing (201), two rotating shafts (15) are symmetrically arranged on both sides of the planetary housing (201), and are both rotatably connected to the planetary housing (201), the rotating shafts (15) extend into the interior of the planetary housing (201) and are fixedly connected to the planetary gears (202), a sun gear (203) is meshed and connected between the two planetary gears (202), the sun gear (203) is mounted on a central shaft (204), the central shaft (204) is rotatably mounted on the planetary housing (201), and the lower end of the central shaft (204) extends out of the planetary housing (201) and is fixedly connected to the output platform (205).

3. The four-degree-of-freedom parallel mechanism with an offset angle according to claim 2, characterized in that: The planetary gear (202) and the sun gear (203) have the same number of teeth.

Images