Four-degree-of-freedom parallel mechanism with offset angle

Abstract

The invention belongs to the technical field of parallel robots, and particularly relates to a four-degree-of-freedom parallel mechanism with an offset angle, which comprises a fixed platform, transmission branch chains are respectively arranged on the left side and the right side of the fixed platform, and parallelogram structures with offset angles are fixedly arranged at the upper ends of the two transmission branch chains; and a movable platform is connected between the two parallelogram structures with the offset angles. According to the four-degree-of-freedom parallel mechanism, a unique 4-2-1 structure is adopted, two driving branch chains are driven to act through four driving moving joints composed of two first sliding blocks and two second sliding blocks, three-dimensional translational motion and one-dimensional rotating motion of one movable platform are achieved, the working space of the four-degree-of-freedom parallel mechanism can extend infinitely in the direction of a guide rail, and the working efficiency of the four-degree-of-freedom parallel mechanism is improved. The device is good in movement stability, compact in structure and high in rotation flexibility.

Description

Technical Field

[0001] The present invention belongs to the technical field of parallel robots, and particularly relates to a four-degree-of-freedom parallel mechanism with a bias angle. Background Art

[0002] Compared with serial robots, parallel robots have the advantages of high stiffness, high speed, high positioning accuracy, and good mechanical properties. For the application requirements of pipeline grasping operations, the three-degree-of-freedom motion of three-dimensional translation can be realized. The Delta robot has a broad application scenario due to its simple configuration, low cost, and high work efficiency.

[0003] However, it is found in actual work that the Delta robot with only three-dimensional translational motion cannot meet the pose adjustment requirements during the grasping process. Therefore, a four-degree-of-freedom parallel mechanism with three-dimensional translation and one-dimensional rotation motion is proposed. By realizing the translation in the x, y, and z directions and the rotation around the z-axis, it can meet the application requirements in the fields of material sorting, food packaging, component assembly, etc. It was first proposed by Professor Clave to add an intermediate UPU chain between the moving platform and the fixed platform of the 3-DOF Delta robot to achieve the decoupled rotation of 1-DOF, successfully realizing the functions of three-dimensional movement and rotation around the z-axis. In addition, the Pierrot team successively invented mechanisms such as H4, I4, Heli4, and Par4 with four motion chains and a double moving platform structure, and developed the Quattro parallel robot based on the Par4 configuration. However, due to the constraints of the four-chain structure layout, the parallel mechanism is prone to mechanical interference and motion singularity, restricting its working space. Therefore, research scholars have proposed a four-degree-of-freedom parallel mechanism with two motion chains and a single moving platform, but all have problems such as low stiffness, poor motion stability, and small working space.

[0004] In summary, currently, the parallel robots with few degrees of freedom for high-speed grasping operations are mostly two-degree-of-freedom and three-degree-of-freedom, often difficult to meet the requirements of industrial automation, while the four-degree-of-freedom parallel robots have problems such as many moving components, small working space, and many singular configurations. Summary of the Invention

[0005] The present invention provides a four-degree-of-freedom parallel mechanism with a bias angle for the above problems.

[0006] To achieve the above object, the present invention adopts the following technical solutions: A four-degree-of-freedom parallel mechanism with a bias angle includes a fixed platform. Transmission chains are respectively arranged on the left and right sides of the fixed platform. Parallelogram structures with a bias angle are fixedly arranged at the upper ends of the two transmission chains. A moving platform is connected between the two parallelogram structures with a bias angle. The parallelogram structure with a bias angle includes an upper-end connecting member fixedly arranged at the upper end of the transmission chain. An upper-end fixing block is fixedly arranged on the upper part of the upper-end connecting member. A seventh connecting rod is hinged on the upper-end fixing block. An eighth connecting rod is 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 a lower-end connecting member. The lower end of the eighth connecting rod is hinged to a lower-end fixing block. The lower-end fixing block is fixedly arranged on 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 rotationally connected to a moving platform. The seventh connecting rod and the eighth connecting rod are parallel and have the same length.

[0007] Further, the transmission chain includes a guide rail fixedly connected to a fixed platform. A first slider and a second slider are slidably arranged on the guide rail. A first connecting rod and a second connecting rod are hinged on the first slider. A third connecting rod is hinged at the other end of the first connecting rod. A fourth connecting rod is hinged at the other end of the second connecting rod. The upper ends of the third connecting rod and the fourth connecting rod are both hinged to a horizontal connecting member. The first connecting rod is parallel to the fourth connecting rod. The second connecting rod is parallel to the third connecting rod. The first connecting rod, the second connecting rod, the third connecting rod, and the fourth connecting rod have the same length. The lower end of the third connecting rod is integrally connected with a fifth connecting rod. The lower end of the fifth connecting rod is hinged to the second slider. The third connecting rod and the fifth connecting rod together form a long connecting rod. A sixth connecting rod is also hinged on the second slider. The upper end of the sixth connecting rod is hinged to the horizontal connecting member. The sixth connecting rod is parallel to the long connecting rod and has the same length. The horizontal connecting member is fixedly connected to the upper-end connecting member.

[0008] Still further, the moving platform includes a planetary housing. The two rotating shafts are symmetrically arranged on both sides of the planetary housing and are both rotationally connected to the planetary housing. The rotating shafts extend into the planetary housing and are fixedly connected to planetary gears. A sun gear is meshingly connected between the two planetary gears. The sun gear is installed on a central shaft. The central shaft is rotatably installed on the planetary housing. The lower end of the central shaft extends out of the planetary housing and is fixedly connected to an output platform.

[0009] Even further, the number of teeth of the planetary gear is the same as that of the sun gear.

[0010] Compared with the prior art, the present invention has the following advantages: The four-degree-of-freedom parallel mechanism provided by the present invention adopts a unique "4-2-1" structure. Through four active moving joints composed of two first sliders and two second sliders, it drives two transmission chains to act, realizing three-dimensional translational and one-dimensional rotational motions of a moving platform. Its working space can extend infinitely along the direction of the guide rail. It not only has good motion stability, but also has a compact structure and high rotational flexibility.

[0011] The present invention adopts a parallelogram structure with a bias angle, which solves the problem of rod interference that occurs in the conventional parallelogram mechanism during movement. Introducing the bias angle can avoid local singularities of the parallelogram and increase the working space of the moving platform in the third direction.

[0012] The present invention introduces a planetary gear train into the moving platform, which can achieve an angular output that is a multiple of the input rotation angle, thereby increasing the rotational working space of the moving platform and greatly enhancing the application of the present invention in pose adjustment.

[0013] The present invention has the advantages of a compact structure, few moving components, low manufacturing cost, few singular configurations, and a large working space, and can be widely applied in fields such as industrial automation assembly, material picking, and packaging sorting. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a schematic structural diagram of the present invention; Figure 2 is a schematic structural diagram of the parallelogram structure with a bias angle of the present invention; Figure 3 is a cross-sectional view of the moving platform of the present invention; Figure 4 is a schematic diagram of the angular output that is a multiple of the moving platform of the present invention; Figure 5 is a schematic diagram of the movement of the present invention moving along the x-axis direction; Figure 6 is a schematic diagram of the movement of the present invention moving along the Z-axis direction; Figure 7 is a schematic diagram of the movement of the present invention rotating around the Z-axis; In the figure, the fixed platform is 1, the moving platform is 2, the guide rail is 3, the first slider is 4, the second slider is 5, the first connecting rod is 6, the second connecting rod is 7, the third connecting rod is 8, the fourth connecting rod is 9, the horizontal connecting member is 10, the fifth connecting rod is 11, the sixth connecting rod is 12, the upper end connecting member is 13, the lower end connecting member is 14, the rotating shaft is 15, the upper end fixing block is 16, the seventh connecting rod is 17, the eighth connecting rod is 18, the lower end fixing block is 19, the planetary housing is 201, the planetary gear is 202, the sun gear is 203, the central shaft is 204, and the output platform is 205. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0015] In order to further elaborate the technical solution of the present invention, the present invention will be further described below through embodiments.

[0016] As Figures 1 to 4 shown, a four-degree-of-freedom parallel mechanism with a bias angle includes a fixed platform 1. Transmission branches are respectively arranged on the left and right sides of the fixed platform 1. Parallelogram structures with a bias angle are fixedly arranged at the upper ends of the two transmission branches. A moving platform 2 is connected between the two parallelogram structures with a bias angle; The parallelogram structure with a bias angle includes an upper connecting member 13 fixedly arranged at the upper end of the transmission chain. An upper fixing block 16 is fixedly arranged on the upper part of the upper connecting member 13. A seventh connecting rod 17 is hinged on the upper fixing block 16. An eighth connecting rod 18 is hinged on the lower part of the upper connecting member 13. The lower end of the seventh connecting rod 17 is hinged to the upper part of a lower connecting member 14. The lower end of the eighth connecting rod 18 is hinged to a lower fixing block 19. The lower fixing block 19 is fixedly arranged on the lower part of the lower connecting member 14. A rotating shaft 15 is fixedly arranged on the lower end face of the lower connecting member 14. The rotating shaft 15 is rotatably connected to a moving platform 2. The seventh connecting rod 17 and the eighth connecting rod 18 are parallel and have the same length.

[0017] The transmission chain includes a guide rail 3 fixedly connected to a fixed platform 1. A first slider 4 and a second slider 5 are slidably arranged on the guide rail 3. A first connecting rod 6 and a second connecting rod 7 are hinged on the first slider 4. The other end of the first connecting rod 6 is hinged to a third connecting rod 8. The other end of the second connecting rod 7 is hinged to a fourth connecting rod 9. The upper ends of the third connecting rod 8 and the fourth connecting rod 9 are both hinged to a horizontal connecting member 10. The first connecting rod 6 is parallel to the fourth connecting rod 9. 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 have 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 the fifth connecting rod 11 is hinged to the second slider 5. The third connecting rod 8 and the fifth connecting rod 11 together form a long connecting rod. A sixth connecting rod 12 is also hinged on the second slider 5. 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. The horizontal connecting member 10 is fixedly connected to the upper connecting member 13. The first slider 4 and the second slider 5 are driven in a linear drive manner, such as by a linear motor, a gear rack, a servo motor plus a ball screw, etc.

[0018] The moving platform 2 includes a planetary housing 201. 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 planetary housing 201 and are fixedly connected to planetary gears 202. A sun gear 203 is meshed and connected between the two planetary gears 202. The sun gear 203 is installed on a central shaft 204. The central shaft 204 is rotatably installed 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 an output platform 205. The planetary gears 202 and the sun gear 203 have the same number of teeth.

[0019] 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; 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.

[0020] 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.

[0021] 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 a bias angle, characterized in that: It includes a fixed platform (1), drive chains are respectively arranged on the left and right sides of the fixed platform (1), parallelogram structures with offset angles are fixedly arranged at the upper ends of the two drive chains, 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 connecting member (13) fixedly arranged at the upper end of the drive chain. An upper fixed block (16) is fixedly arranged on the upper part of the upper connecting member (13). A seventh connecting rod (17) is hinged on the upper fixed block (16). An eighth connecting rod (18) is hinged on the lower part of the upper connecting member (13). The lower end of the seventh connecting rod (17) is hinged to the upper part of a lower connecting member (14). The lower end of the eighth connecting rod (18) is hinged to a lower fixed block (19). The lower fixed block (19) is fixedly arranged on the lower part of the lower connecting member (14). A rotating shaft (15) is fixedly arranged on the lower end surface of the lower connecting member (14). The rotating shaft (15) is rotatably connected to the moving platform (2). The seventh connecting rod (17) and the eighth connecting rod (18) are parallel and have the same length.

2. A four-degree-of-freedom parallel mechanism with a bias angle according to claim 1, characterized in that: The drive chain includes 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 arranged 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 at the other end of the first connecting rod (6). A fourth connecting rod (9) is hinged at 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). 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) have the same length. The lower end of the third connecting rod (8) is integrally connected with a fifth connecting rod (11). 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 form a long connecting rod. A sixth connecting rod (12) is also hinged on the second slider (5). 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. The horizontal connecting member (10) is fixedly connected to the upper connecting member (13).

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

4. A four-degree-of-freedom parallel mechanism with a bias angle according to claim 3, characterized in that: The planetary gear (202) has the same number of teeth as the sun gear (203).

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