Four-degree-of-freedom parallel mechanism based on wheel type driving

Abstract

The invention belongs to the technical field of parallel robots, and particularly relates to a four-degree-of-freedom parallel mechanism based on wheel type driving, which comprises a movable platform, parallelogram structures with offset angles are symmetrically arranged on the left side and the right side of the upper surface of the movable platform, and the movable platform is connected with branch chain structures through the parallelogram structures with the offset angles. An output platform is connected below the movable platform; according to the four-degree-of-freedom parallel mechanism provided by the invention, wheel type driving is adopted, so that the four-degree-of-freedom parallel mechanism can realize three-degree-of-freedom movement on a plane, a positioning space is approximate to an environmental space, and the four-degree-of-freedom parallel mechanism has the capability of working in a complex environment through wheel type driving, so that the application range of the mechanism is greatly expanded.

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 based on wheel drive. Background Art

[0002] Traditional 3T1R parallel robots operate for sorting requirements within a fixed range. Limited by the size of the working space, it is difficult to meet the working requirements of long-distance, fast-paced, and synchronous sorting and transportation during multi-station collaborative operations in modern industrial automation. Currently, the general methods for long-distance grasping and transportation operations are difficult to balance the above requirements. The operation method based on a mobile robot + robotic arm has high flexibility and strong collaboration ability, but the working space of the robotic arm is limited, the overall structural stiffness is low, the load is small, and the center of gravity is unstable during the operation process, making it easy to tip over; the operation method based on a conveyor belt + parallel robot has high sorting efficiency, but the working position is fixed, the operation rhythm needs to be synchronized, the end load is small, and the degree of flexible operation is low; the operation method based on forklift handling has a large load capacity and high reliability, but is slow in speed and poor in environmental compatibility, making it difficult to meet the flexible operation requirements. Therefore, it is urgent to liberate the parallel robot from the fixed-position operation mode.

[0003] Among various existing driving methods, wheel drive can face various complex environments and achieve more balanced and flexible operation requirements. At the same time, the wheel structure has strong compatibility with the working environment and large support stiffness. Especially when combined with a symmetric parallel robot, it can reduce the occurrence of special situations such as center-of-gravity offset and instability, and is easier to manufacture and maintain.

[0004] However, the current research on the relevant theories and design methods based on the combination of wheel structure and parallel robot is not yet perfect: on the one hand, most existing parallel robots adopt multi-axis swing rod mechanism design, suspended V-shaped assembly mode, and servo motor drive method, making it difficult to reasonably arrange the wheel structure, and most parallel robots do not have the ability to be compatible with the wheel mechanism in terms of structure; on the other hand, the wheel structure not only plays a transportation role, but also transmits motion to the parallel mechanism through the interaction between the wheels, easily resulting in coupling between the overall motion of the robot and the motion of the end moving platform. Summary of the Invention

[0005] The present invention provides a four-degree-of-freedom parallel mechanism based on wheel drive 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 based on wheel drive, including a moving platform, on the left and right sides of the upper surface of the moving platform, parallelogram structures with offset angles are symmetrically arranged. The moving platform is connected to a chain structure through the parallelogram structures with offset angles, and an output platform is connected below the moving platform; The branched chain structure includes an upper connecting rod, which is fixedly connected to a parallelogram structure with a bias angle. An independent connecting rod is hinged to the front side of the upper connecting rod, and a third connecting rod is hinged to the middle of the upper connecting rod. The lower ends of the independent connecting rod and the third connecting rod are both hinged to the housing of the second hub motor. Moreover, a parallelogram link mechanism is formed among the upper connecting rod, the independent connecting rod, the third connecting rod, and the second hub motor. A harmonic reducer is fixedly installed on the third connecting rod, and a torque motor is fixedly installed on the harmonic reducer. The input end of the harmonic reducer is concentrically and fixedly connected to the output shaft of the torque motor. A fourth connecting rod is fixedly connected to the output shaft of the harmonic reducer, and the output shaft of the harmonic reducer is perpendicular to the fourth connecting rod. The lower end of the fourth connecting rod is hinged to the housing of the first hub motor. A fifth connecting rod is also hinged to the housing of the first hub motor. The upper end of the fifth connecting rod is hinged to the lower end of a sixth connecting rod, and the upper end of the sixth connecting rod is hinged to the rear side of the upper connecting rod. The lengths of the sixth connecting rod, the fifth connecting rod, and the fourth connecting rod are all the same as the distance from the torque motor to the hinged point at the upper end of the third connecting rod. Moreover, the connection line between the hinged point at the lower end of the fourth connecting rod and the hinged point at the lower end of the fifth connecting rod is parallel and equal to the connection line between the hinged point at the upper end of the sixth connecting rod and the hinged point at the upper end of the third connecting rod. Rollers are arranged on the output shafts of the first hub motor and the second hub motor.

[0007] Furthermore, the parallelogram structure with a bias angle includes a rotating shaft rotatably connected to the moving platform. An upper end connecting piece is fixedly connected to the upper end of the rotating shaft. A first connecting rod is hinged to the upper part of the upper end connecting piece. A lower end fixing block is fixed to the lower part of the upper end connecting piece. A second connecting rod is hinged to the lower end fixing block. The other end of the second connecting rod is hinged to the lower part of an upper end connecting member. The other end of the first connecting rod is hinged to an upper end fixing block. The upper end fixing block is fixedly arranged on the upper part of the upper end connecting member. The upper end connecting member is fixedly connected to the upper connecting rod.

[0008] 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 wheel drive, enabling the present invention to achieve three degrees of freedom of movement on a plane, making the positioning space approximate to the environmental space, and enabling the present invention to work in complex environments through wheel drive, greatly expanding the applicable range of the mechanism.

[0009] The present invention introduces an axle distance control function in the branched chain structure. Through the coordinated action of the torque motor and the harmonic reducer arranged on the third connecting rod, a braking torque opposite to the rotation direction of the rotating pair is output to restrict the relative rotation between the third connecting rod and the fourth connecting rod, thereby controlling the axle distance between the front and rear rollers to remain unchanged, realizing partial decoupling of the roller movement and the attitude adjustment of the output platform, and endowing the present invention with excellent end attitude adjustment ability.

[0010] The present invention adopts a unique "4-2-1" structure. Four active moving joints composed of two first hub motors and two second hub motors drive the actions of two chain structures, realizing the three-dimensional translational and one-dimensional rotational motions of the moving platform. 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 an offset angle, which solves the problem of rod interference in the conventional parallelogram mechanism during the motion process. Introducing the offset angle can avoid the local singularity of the parallelogram and increase the pose adjustment space of the moving platform in the third direction.

[0012] The present invention has the advantages of a compact structure, few moving components, low manufacturing cost, few singular configurations, a positioning space approximate to the environmental space, and a large pose adjustment space. It can be widely used for tasks such as explosive disposal, underground crop picking, and other similar operations that require grasping actions in relatively complex ground environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a schematic structural diagram of the present invention; Figure 2 is a schematic structural diagram of the moving platform of the present invention; Figure 3 is a schematic motion diagram of the turning of the present invention; In the figure, the moving platform 1, the parallelogram structure 2 with an offset angle, the chain structure 3, the output platform 4, the planetary housing 101, the planetary gear 102, the sun gear 103, the central shaft 104, the rotating shaft 201, the lower connecting part 202, the first connecting rod 203, the lower fixing block 204, the second connecting rod 205, the upper connecting part 206, the upper fixing block 207, the upper connecting rod 301, the independent connecting rod 302, the third connecting rod 303, the second hub motor 304, the torque motor 305, the harmonic reducer 306, the fourth connecting rod 307, the first hub motor 308, the fifth connecting rod 309, the sixth connecting rod 310, and the roller 311. DETAILED DESCRIPTION OF THE INVENTION

[0014] In order to further elaborate the technical solution of the present invention, the present invention will be further described below through embodiments.

[0015] As Figures 1 to 3 shown, a four-degree-of-freedom parallel mechanism based on wheel drive includes a moving platform 1. On the left and right sides of the upper surface of the moving platform 1, parallelogram structures 2 with an offset angle are symmetrically arranged. The moving platform 1 is connected to the chain structure 3 through the parallelogram structure 2 with an offset angle, and an output platform 4 is connected below the moving platform 1.

[0016] The moving platform 1 includes a planetary housing 101. Inside the planetary housing 101, two planetary gears 102 are provided. The planetary gears 102 are fixedly connected to the lower end of a rotating shaft 201. A sun gear 103 is meshed and connected between the two planetary gears 102. The planetary gears 102 and the sun gear 103 have the same number of teeth. The sun gear 103 is fixedly installed on a central shaft 104. The central shaft 104 is rotatably installed on the planetary housing 101. The lower end of the central shaft 104 extends out of the planetary housing 101 and is fixedly connected to an output platform 4. In the present invention, a planetary gear train is introduced into the moving platform 1, which can realize an angular output of multiple angles for the input rotation angle, thereby increasing the rotation range of the moving platform and greatly improving the pose adjustment space of the present invention.

[0017] The parallelogram structure 2 with an offset angle includes a rotating shaft 201 rotatably connected to the moving platform 1. At the upper end of the rotating shaft 201, a lower end connecting member 202 is fixedly connected. At the upper part of the lower end connecting member 202, a first connecting rod 203 is hinged. At the lower part of the lower end connecting member 202, a lower end fixing block 204 is fixed. At the lower end fixing block 204, a second connecting rod 205 is hinged. The other end of the second connecting rod 205 is hinged to the lower part of an upper end connecting member 206. The other end of the first connecting rod 203 is hinged to an upper end fixing block 207. The upper end fixing block 207 is fixedly arranged at the upper part of the upper end connecting member 206. The upper end connecting member 206 is fixedly connected to an upper end connecting rod 301.

[0018] The branch chain structure 3 includes an upper connecting rod 301. The upper connecting rod 301 is fixedly connected to the parallelogram structure 2 with an offset angle. An independent connecting rod 302 is hinged to the front side of the upper connecting rod 301. A third connecting rod 303 is hinged to the middle of the upper connecting rod 301. The lower ends of the independent connecting rod 302 and the third connecting rod 303 are both hinged to the housing of the second hub motor 304. A parallelogram link mechanism is formed among the upper connecting rod 301, the independent connecting rod 302, the third connecting rod 303, and the second hub motor 304. A harmonic reducer 306 is fixedly installed on the third connecting rod 303. A torque motor 305 is fixedly installed on the harmonic reducer 306. The input end of the harmonic reducer 306 is concentrically and fixedly connected to the output shaft of the torque motor 305. A fourth connecting rod 307 is fixedly connected to the output shaft of the harmonic reducer 306. The output shaft of the harmonic reducer 306 and the fourth connecting rod 307 are arranged perpendicular to each other. The lower end of the fourth connecting rod 307 is hinged to the housing of the first hub motor 308. A fifth connecting rod 309 is also hinged to the housing of the first hub motor 308. The upper end of the fifth connecting rod 309 is hinged to the lower end of a sixth connecting rod 310. The upper end of the sixth connecting rod 310 is hinged to the rear side of the upper connecting rod 301. The lengths of the sixth connecting rod 310, the fifth connecting rod 309, and the fourth connecting rod 307 are the same as the distance from the torque motor 305 to the hinge point at the upper end of the third connecting rod 303. The connection line between the hinge point at the lower end of the fourth connecting rod 307 and the hinge point at the lower end of the fifth connecting rod 309 is parallel and equal to the connection line between the hinge point at the upper end of the sixth connecting rod 310 and the hinge point at the upper end of the third connecting rod 303. Rollers 311 are arranged on the output shafts of both the first hub motor 308 and the second hub motor 304.

[0019] The foregoing has shown and described the main features and advantages of the present invention. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, in any aspect, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, it is intended to embrace all changes within the meaning and scope of the equivalent elements of the claims in the present invention.

[0020] In addition, it should be understood that although this specification is described according to the embodiments, not each embodiment only contains an independent technical solution. This narrative way of the specification is only for 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 embodiments that can be understood by those skilled in the art.

Claims

1. A four-degree-of-freedom parallel mechanism based on wheel drive, characterized in that: It includes a moving platform (1). On the left and right sides of the upper surface of the moving platform (1), parallelogram structures (2) with offset angles are symmetrically arranged. The moving platform (1) is connected to a link structure (3) through the parallelogram structures (2) with offset angles. An output platform (4) is connected below the moving platform (1). The link structure (3) includes an upper connecting rod (301). The upper connecting rod (301) is fixedly connected to the parallelogram structure (2) with an offset angle. An independent connecting rod (302) is hinged to the front side of the upper connecting rod (301). A third connecting rod (303) is hinged to the middle of the upper connecting rod (301). The lower ends of the independent connecting rod (302) and the third connecting rod (303) are both hinged to the housing of a second hub motor (304). And a parallelogram linkage mechanism is formed among the upper connecting rod (301), the independent connecting rod (302), the third connecting rod (303), and the second hub motor (304). A harmonic reducer (306) is fixedly installed on the third connecting rod (303). A torque motor (305) is fixedly installed on the harmonic reducer (306). And the input end of the harmonic reducer (306) is concentrically and fixedly connected to the output shaft of the torque motor (305). A fourth connecting rod (307) is fixedly connected to the output shaft of the harmonic reducer (306). The output shaft of the harmonic reducer (306) is perpendicular to the fourth connecting rod (307). The lower end of the fourth connecting rod (307) is hinged to the housing of a first hub motor (308). A fifth connecting rod (309) is also hinged to the housing of the first hub motor (308). The upper end of the fifth connecting rod (309) is hinged to the lower end of a sixth connecting rod (310). The upper end of the sixth connecting rod (310) is hinged to the rear side of the upper connecting rod (301). The lengths of the sixth connecting rod (310), the fifth connecting rod (309), and the fourth connecting rod (307) are the same as the distance from the torque motor (305) to the hinge point at the upper end of the third connecting rod (303). And the connection line between the hinge point at the lower end of the fourth connecting rod (307) and the hinge point at the lower end of the fifth connecting rod (309) is parallel and equal to the connection line between the hinge point at the upper end of the sixth connecting rod (310) and the hinge point at the upper end of the third connecting rod (303). Rollers (311) are arranged on the output shafts of the first hub motor (308) and the second hub motor (304).

2. The four-degree-of-freedom parallel mechanism based on wheel drive according to claim 1, characterized in that: The parallelogram structure (2) with a bias angle includes a rotating shaft (201) rotatably connected to the moving platform (1). A lower-end connecting member (202) is fixedly connected to the upper end of the rotating shaft (201). A first connecting rod (203) is hinged to the upper part of the lower-end connecting member (202). A lower-end fixing block (204) is fixed to the lower part of the lower-end connecting member (202). A second connecting rod (205) is hinged to the lower-end fixing block (204). The other end of the second connecting rod (205) is hinged to the lower part of an upper-end connecting member (206). The other end of the first connecting rod (203) is hinged to an upper-end fixing block (207). The upper-end fixing block (207) is fixedly arranged on the upper part of the upper-end connecting member (206). The upper-end connecting member (206) is fixedly connected to an upper-end connecting rod (301).

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