Three-fingered gripper based on kinematically redundant parallel mechanism

Abstract

The application belongs to the technical field of parallel manipulator, and particularly relates to a three-fingered grabbing manipulator based on a motion-redundant parallel mechanism. The manipulator comprises an upper platform, three five-pole branch chains and a movable platform system with a grabbing degree of freedom; each five-pole branch chain is connected with a corresponding rotary grabber in the movable platform system and operates the rotary grabber to perform a grabbing action. Six driving motors are arranged on the upper platform and correspond to two translational and one rotational degrees of freedom of the whole movable platform system in a plane and three decoupled independent rotational degrees of freedom of the three rotary grabbers, respectively. The layout avoids arranging additional actuators on the motion branch or the movable platform, significantly reduces the motion inertia of the mechanism and improves the high-speed response capability. Meanwhile, when facing objects of different sizes, the rotary grabbers can independently adjust the angle under the premise that the pose of the movable platform remains unchanged, so that the manipulator has stronger task adaptability and operation flexibility.

Description

Technical Field

[0001] This invention relates to the field of parallel manipulator technology, specifically to a three-finger grasping manipulator based on a motion redundancy parallel mechanism. Background Technology

[0002] With the development of industrial technology and the improvement of automation levels, robotic arms are increasingly widely used in intelligent manufacturing, warehousing and logistics, food sorting, and medical assistance. Traditional robotic arms mainly use serial mechanisms to achieve grasping operations, that is, the joints are arranged in series. Although this structure has a large workspace and flexible movement, it also has inherent defects such as large cumulative error, low stiffness, and poor load-bearing capacity. Because the errors of each joint in a serial mechanism will accumulate step by step, the positioning accuracy of the end effector is limited; at the same time, the serial open-chain structure is prone to elastic deformation under heavy loads, and the drive unit is mostly located at the joints, which increases the inertia of the moving parts and is not conducive to high-speed, high-acceleration grasping operations.

[0003] To overcome the aforementioned problems, parallel mechanisms have been gradually introduced into the design of robotic arms. Parallel mechanisms, consisting of multiple kinematic chains connecting the moving and stationary platforms simultaneously, offer advantages such as high rigidity, strong load-bearing capacity, low cumulative error, and fast dynamic response, making them particularly suitable for grasping tasks requiring high precision and speed. However, while traditional parallel robotic arms have significant advantages in rigidity, precision, and dynamic performance, their grasping function typically relies on independent actuators such as suction cups or pneumatic grippers mounted on the moving platform. This "parallel chain + end effector" design, while providing the mechanism with versatility, also introduces certain limitations: independent actuators increase the mass and inertia of the moving platform, weakening the high-speed advantage of parallel mechanisms; and for complex-shaped targets, traditional gripping methods have limited adaptability, making it difficult to fully utilize the high-precision characteristics of parallel mechanisms. To address this issue, this invention proposes a three-finger gripping manipulator based on a motion-redundant parallel mechanism. By introducing motion-redundant degrees of freedom, while maintaining the advantages of high rigidity and high precision of the parallel mechanism, the working performance of the end effector is effectively expanded. This allows the fingers to perform independent decoupled movements when the moving platform has a certain fixed posture. At the same time, the three-finger structure design improves the gripping adaptability and stability, and can meet the reliable gripping requirements of objects of different shapes and sizes under complex working conditions. Summary of the Invention

[0004] To address the limitations of existing technologies, the present invention aims to propose a three-finger grasping manipulator based on a motion redundancy parallel mechanism. Its drive devices are all motors arranged at the base, which have advantages in terms of higher rigidity and precision, and have three independent degrees of freedom for the fingers, enabling it to adapt to more types of grasped objects and meet more practical working conditions.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows.

[0006] The present invention provides a three-finger grasping manipulator based on a motion redundancy parallel mechanism, including an upper platform, a motion platform system containing guide rails and coupled with three rotating grippers, and three five-bar linkages driven by motors mounted on the upper platform and connected to the rotating grippers.

[0007] The moving platform system includes a moving platform frame, a guide rail orthogonal to the moving platform plane, a slider that can move on the guide rail, and a connecting rod; the rotating grippers are respectively connected to the moving platform frame through rotating joints, and the connecting rod connects the slider and the rotating gripper.

[0008] The upper platform includes an upper platform frame and six drive motors arranged on the upper platform frame. The drive motors are arranged in pairs, and each pair of drive motors is responsible for driving the movement of one branch. The axes of rotation output by the six drive motors are all parallel to each other.

[0009] Of the three rotation axes between the rotating gripper and the moving platform frame, the first and second axes are parallel to each other and are also parallel to the axis of the output rotation of the drive motor; the third axis is orthogonal to the first two axes.

[0010] The upper platform and the rotating gripper are connected by three five-bar linkages, each including an upper active bar, a lower active bar, a first passive bar, and a second passive bar. The lower side of the second passive bar of two of the five-bar linkages is connected to the rotating gripper, which has an axis parallel to the other two. The lower side of the second passive bar of the remaining five-bar linkage is connected to the slider via a revolute joint. The rotating gripper, whose rotation axis is orthogonal to the rotation axes of the other two rotating grippers, is connected to the slider via a connecting rod.

[0011] The slider, the connecting rod, and the rotating gripper connected to the connecting rod constitute a PRRR mechanism.

[0012] The rotation axis of the rotating joints at both ends of the connecting rod is orthogonal to the axis of rotation output by the drive motor.

[0013] In the five-bar linkage, one end of the upper driving bar and the lower driving bar are connected to a set of drive motors, and the other end is connected to the first passive bar and the second passive bar, respectively.

[0014] The beneficial effects of this invention compared to the prior art are: The gripping mechanism of this invention combines the high rigidity and high precision characteristics of parallel mechanisms, and arranges all driving elements on the upper platform, without placing the drives in the branches or on the moving platform. This reduces the mechanism's motion inertia, and its motion redundancy helps the robot arm better avoid singular configurations and optimize force transmission performance during tasks. The moving platform in this invention has a planar 2T1R degree of freedom, which can adapt to the gripping task requirements of most industrial production lines. Furthermore, its three rotating grippers have three decoupled rotational degrees of freedom, meaning that when facing objects of different sizes, the rotating grippers can flexibly adjust attitude parameters such as rotation angles, adapting to a wider range of task conditions and performing more flexible operations. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the overall mechanism of a three-finger grasping robot based on a motion redundancy parallel mechanism according to the present invention. Figure 2 This is a schematic diagram of the upper platform of a three-finger grasping robot based on a motion redundancy parallel mechanism according to the present invention. Figure 3 This is a schematic diagram of one of the five-bar linkages of a three-finger grasping robot based on a motion redundancy parallel mechanism according to the present invention. Figure 4 This is a schematic diagram of a five-bar linkage of a three-finger grasping robot based on a motion redundancy parallel mechanism according to the present invention. Figure 5 This is a schematic diagram of the moving platform system of the present invention; in: 1-Upper platform, 2-Five-bar linkage, 3-Moving platform system, 11-Upper platform frame, 12-Drive motor, 21-Upper active rod, 22-Lower active rod, 23-First passive rod, 24-Second passive rod, 31-Moving platform frame, 32-Guide rail, 33-Slider, 34-Connecting rod, 35-Rotating gripper. Detailed Implementation

[0016] To better understand the three-finger grasping robot based on a motion redundancy parallel mechanism provided by this invention, the invention will be described in detail below with reference to the accompanying drawings and examples.

[0017] Figure 1 This invention provides a schematic diagram of the overall structure of a three-finger grasping robot based on a motion redundancy parallel mechanism, including an upper platform 1, a five-bar linkage 2, and a moving platform system 3. The upper platform 1 is connected to the moving platform system 3 via three of the five-bar linkages at different positions.

[0018] Figure 2This invention provides a schematic diagram of the upper platform of a three-finger grasping robot based on a motion redundancy parallel mechanism, including an upper platform frame 11 and drive motors 12. There are six drive motors 12 in total, arranged in pairs and fixed vertically on the moving platform frame.

[0019] Figure 3 This invention provides a schematic diagram of one of the five-bar linkages of a three-finger grasping robot based on a motion redundancy parallel mechanism. The upper side of the five-bar linkage 2 is connected to a set of drive motors 12 in the upper platform 1, and the lower side is connected to a slider 33 on the moving platform system 3. Two sets of linkages of the five-bar linkage 2 are symmetrically arranged on the left and right sides of the mechanism, operating two rotating grippers 35 with parallel axes of rotation. The remaining set of five-bar linkages 2 is arranged in the middle of the mechanism, operating a rotating gripper 35 whose axis is orthogonal to the other rotation axes by operating the slider 33.

[0020] Figure 4 This is a schematic diagram of a five-bar linkage for a three-finger grasping robot based on a motion redundancy parallel mechanism according to the present invention. It includes an upper active bar 21, a lower active bar 22, a first passive bar 23, and a second passive bar 22. The upper active bar 21 and the lower active bar 22 are each connected to a set of drive motors 12 on their upper sides, and the second passive bars 22 are both connected to a moving platform system.

[0021] Figure 5 This is a schematic diagram of the moving platform system of a three-finger grasping robot based on a motion redundancy parallel mechanism according to the present invention. It includes a moving platform frame 31, a guide rail 32, a slider 33, a connecting rod 34, and three rotating grippers 35. Two of the three rotating grippers 35 have parallel rotation axes, and the last rotation axis is orthogonal to the other two. One end of the connecting rod 34 is connected to the slider 33, and the other end is connected to the rotating gripper 35. Its function is to convert the rotational motion of the rotating gripper 35 into the movement motion of the slider 33 on the guide rail 32.

[0022] This invention provides a three-finger gripping robot based on a motion redundancy parallel mechanism, which has six drive motors, i.e., six degrees of freedom. This is reflected in the two rotational and one translational degrees of freedom of the moving platform in the plane, and the three rotational degrees of freedom of the three rotating grippers decoupled. Therefore, this invention can grasp different types of objects by different rotational conditions of the rotating grippers while maintaining the three degrees of freedom gripping motion in the plane. It can also precisely control the position and posture of the moving platform and the opening and closing of the three rotating grippers through the drive motors, providing a reliable solution for the accurate gripping and sorting of complex workpieces.

[0023] The above detailed description further illustrates the purpose, technical solution, and beneficial effects of the invention. The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, or improvements made to the technical solution of the present invention within the spirit and principles of the present invention should be included within the scope of protection defined by the claims of the present invention.

Claims

1. A three-finger grasping manipulator based on a motion redundancy parallel mechanism, characterized in that: It includes an upper platform (1), three five-bar linkages (2) driven by motors mounted on the upper platform and connected to rotating grippers, and a moving platform system (3) containing guide rails and coupled with the three rotating grippers. The upper platform (1) is connected to the moving platform system (3) through three five-bar chains (2), each of the five-bar chains (2) corresponds to a rotating gripper (35) on the moving platform system (3); the upper platform (1) includes six drive motors (12) for driving the chains, which are arranged on the upper platform frame (11).

2. The three-finger grasping manipulator based on a motion redundancy parallel mechanism according to claim 1, characterized in that: The moving platform system includes a moving platform frame (31), a guide rail (32) orthogonal to the moving platform plane, a slider (33) movable on the guide rail, a connecting rod (34), and three rotating grippers (35); the rotating grippers (35) are respectively connected to the moving platform frame (31) through a rotating joint, and the connecting rod (34) connects the slider (33) and the rotating gripper (35).

3. A three-finger grasping manipulator based on a motion redundancy parallel mechanism according to claim 1, characterized in that: The upper platform (1) includes the upper platform frame (11) and six drive motors (12) arranged on the upper platform frame (11). The drive motors (12) are arranged in pairs, and each pair is responsible for driving the movement of one of the five-bar linkages (2). The axes of rotation output by the six drive motors (12) are all parallel to each other.

4. A three-finger grasping manipulator based on a motion redundancy parallel mechanism according to claim 2, characterized in that: Of the three rotation axes between the rotating gripper (35) and the moving platform frame (31), the first axis is parallel to the second axis and is parallel to the axis of the output rotation of the drive motor (12); the third axis is orthogonal to the first two axes.

5. A three-finger grasping manipulator based on a motion redundancy parallel mechanism according to claim 1, characterized in that: The five-bar chain (2) includes an upper active bar (21), a lower active bar (22), a first passive bar (23), and a second passive bar (24); the lower sides of the second passive bars (24) of two of the five-bar chains (2) are respectively connected to the rotating grippers (35) whose axes are parallel to each other, and the lower side of the second passive bar (24) of the remaining five-bar chain (2) is connected to the slider (33) through a rotating joint; the rotating gripper (35) whose rotation axes are orthogonal to the rotation axes of the other two rotating grippers (35) is connected to the slider (33) through the connecting rod (34).

6. A three-finger grasping manipulator based on a motion redundancy parallel mechanism according to claim 5, characterized in that: The slider (33), the connecting rod (34), and the rotating gripper (35) connected to the connecting rod (34) constitute a PRRR mechanism.

7. A three-finger grasping manipulator based on a motion redundancy parallel mechanism according to claim 1, characterized in that: The rotation axis of the rotating pairs at both ends of the connecting rod (34) is orthogonal to the axis of rotation of the drive motor (12).

8. A three-finger grasping manipulator based on a motion redundancy parallel mechanism according to claim 1, characterized in that: In the five-bar chain (2), one end of the upper active rod (21) and the lower active rod (22) are connected to a set of drive motors (35), and the other end is connected to the first passive rod (23) and the second passive rod (24) respectively.

9. A three-finger grasping manipulator based on a motion redundancy parallel mechanism according to claims 1 to 3, characterized in that: The moving platform system (3) as a whole can perform 2T1R (two-shift, one-rotation) motion in the plane, and the three rotating grippers (35) can also perform independent decoupled rotation motion, which can grip items with different shapes and perform operation tasks.

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