A tendon-driven mechanical finger capable of adaptive grasping

Abstract

A tendon-driven mechanical finger capable of adaptive gripping, comprising a first phalanx, a second phalanx and a third phalanx from the fingertip to the finger root, the mechanical finger as a whole is hinged on the mounting position through a third joint part, the mechanical finger can be bent from the back of the finger to the finger pulp direction; the first joint part, the second joint part and the third joint part have the same structure, all comprising a rotating shaft, a pulley and an elastic assembly, the pulley is sleeved in the middle part of the rotating shaft and can rotate relative to the rotating shaft, the pulley has limiting grooves on both sides, the elastic assembly comprises two torsional springs respectively sleeved on the rotating shaft on both sides of the pulley, and both ends of the rotating shaft are rotatably mounted on the phalanx; the mechanical finger is driven by a tendon, the tendon is a rigid rope, when the driving tendon is pulled, the three pulleys can be synchronously rotated to the finger pulp direction; the elasticity of the elastic assemblies of the first, second and third joint parts is enhanced in turn, and when the driving tendon is pulled, the first phalanx, the second phalanx and the third phalanx are rotated and bent in turn.

Description

Technical Field

[0001] This invention belongs to the field of robotics, specifically relating to a tendon-driven mechanical finger structure capable of adaptive grasping, used by a robotic hand for grasping objects. Background Technology

[0002] With the continuous development of industrial automation, robotics technology is being applied more and more widely in many fields such as industrial manufacturing, medical and health care, aerospace technology, and military security. As one of the key technologies of robotics, the design and control of robotic arms are also constantly improving and being perfected. As it attracts more and more attention from researchers, the objects that robotic arms can grasp have evolved from single workpieces of specific shapes to a variety of objects with diverse shapes.

[0003] Adaptive grasping allows a robotic hand to adapt to the surface of an object when grasping it, maximizing surface contact and achieving stable grasping without requiring excessive clamping force. Fully actuated robotic hands require multiple actuators for adaptive grasping, resulting in a complex control system and higher operating costs. In contrast, underactuated robotic hands require fewer actuators, adapt well to the shape of the object being grasped, and are easier to control. Tendon actuation, in particular, offers advantages such as simple and compact structure, ease of implementation, long transmission distance, light weight, and a large grasping area. Therefore, proposing a simple, low-cost, tendon-actuated underactuated robotic finger structure is essential. Summary of the Invention

[0004] This invention provides a tendon-driven mechanical finger structure that enables adaptive gripping. It is small in size and uses a single motor to enable the finger to achieve adaptive gripping.

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

[0006] A tendon-driven mechanical finger capable of adaptive grasping includes a first phalanx, a second phalanx, and a third phalanx sequentially from the fingertip to the base. The base of the first phalanx and the tip of the second phalanx are hinged together by a first joint, and the base of the second phalanx and the tip of the third phalanx are hinged together by a second joint. The third phalanx has a third joint. The entire mechanical finger is hinged to a mounting location via the third joint. The first and second phalanxes form a first revolute joint, the second and third phalanxes form a second revolute joint, and the third phalanx and the mounting location of the mechanical finger form a third revolute joint. The motion planes of the three revolute joints are parallel, and the mechanical finger can be bent from the back of the finger to the fingertip.

[0007] The first joint, the second joint, and the third joint have the same structure, each including a rotating shaft, a pulley, and an elastic component. The pulley is rotatably mounted on the middle of the rotating shaft, and the pulley has limiting grooves on both sides. The elastic component includes two torsion springs respectively mounted on the rotating shaft on both sides of the pulley. One end of the torsion spring is embedded in the limiting groove, and the other end is fixed to the inside of the knuckle. The two ends of the rotating shaft are rotatably mounted on the knuckle.

[0008] The mechanical finger is driven by a tendon cord, which is a rigid cord. The tendon cord driving the third phalanx is the active tendon cord, with one end fixed in a pulley groove of the pulley at the third joint and the other end connected to a power source. The tendon cord driving the second phalanx is the second driven tendon cord, with one end fixed in another pulley groove of the pulley at the third joint and the other end fixed in a pulley groove of the pulley at the second joint. One end of the first driven tendon cord is fixed in another pulley groove of the pulley at the second joint and the other end fixed in a pulley groove of the pulley at the first joint. When the active tendon cord is pulled, the three pulleys can rotate synchronously towards the fingertip.

[0009] The first phalanx is a hollow box-shaped body composed of a fingertip ventral plate, a fingertip dorsal plate, and two fingertip side plates. The fingertip ventral plate and the fingertip dorsal plate are located on the fingertip and back of the mechanical finger, respectively. The fingertip ventral plate is a convex curved plate, and the side edge of the fingertip ventral plate is closedly connected to the side edge of the fingertip dorsal plate. The two fingertip side plates are fixed to both sides of the fingertip ventral plate and the fingertip dorsal plate, respectively. The end of the fingertip side plate near the base of the finger has a shaft hole. The second and third phalanxes are hollow box-shaped bodies with the same structure and open ends. Each phalanx includes a phalanx dorsal plate, a phalanx ventral plate, and two fingertip side plates. The phalanx dorsal plate and the phalanx ventral plate are located on the back and fingertip of the phalanx, respectively. The two fingertip side plates are fixed to both sides of the phalanx ventral plate and the fingertip dorsal plate, respectively. Both ends of the fingertip side plates have shaft holes. The two ends of the rotating shaft are inserted into the shaft holes.

[0010] The elasticity of the elastic components at the first, second, and third joints increases sequentially, and when the active tendon is pulled, the first, second, and third phalanges rotate and bend in sequence.

[0011] The tendon-driven mechanical finger capable of adaptive grasping further comprises, in part, double-groove pulleys for the second and third joints.

[0012] In the aforementioned tendon-driven mechanical finger capable of adaptive gripping, a torsion spring is further fixed to the end located on the inner side of the knuckle, with the fixing point on the inner side of the knuckle side plate or the fingertip side plate.

[0013] The tendon-driven mechanical finger capable of adaptive gripping further includes hooks on the outer surfaces of the fingertip back plate and the knuckle back plate. The elastic components of the first joint and the second joint also include elastic telescopic elements, which are installed between the knuckles via hooks. The elastic telescopic elements are tension springs.

[0014] This invention provides the following benefits:

[0015] (1) The mechanical finger provided by the present invention controls each phalanx by tendon rope driven by the same power source, thereby achieving adaptive gripping while reducing the number of actuators and reducing the weight of the gripper;

[0016] (2) The mechanical finger provided by this invention employs a joint comprising an elastic component, a pulley, and a rotating shaft. By selecting torsion springs and tension springs of different specifications, the elasticity of the elastic components in the first, second, and third joints is sequentially enhanced. The torsion spring in the elastic component transmits the rotational torque, which can generate a buffering effect during grasping. This allows the mechanical finger to adaptively adjust the grasping action and force according to the contact position and surface condition of the grasped object during the same grasping action. After the finger completes the grasping of the object, the motor stops driving the tendon rope, and the elastic force of the elastic component generates a reset torque on the finger joint, thereby resetting the finger and facilitating the next grasp.

[0017] (3) In this invention, each finger joint is a revolute joint, which makes it easier to establish an accurate motion model and facilitates precise control.

[0018] (4) The inside of the finger of the present invention is hollow, which can accommodate sensor signal acquisition circuits, such as fingertip force sensors. The wiring can be inside the finger to ensure the safety of the circuit and prevent damage. Attached Figure Description

[0019] Figure 1 This is a three-dimensional view of the mechanical finger described in the embodiment;

[0020] Figure 2 This is a schematic diagram of the overall structure of the mechanical finger described in the embodiment;

[0021] Figure 3 This is a schematic diagram of the first phalanx structure of the mechanical finger described in the embodiment;

[0022] Figure 4 This is a schematic diagram of the second phalanx structure of the mechanical finger described in the embodiment;

[0023] Figure 5 This is a schematic diagram of the grasping state of the mechanical finger mentioned in the embodiment;

[0024] In the diagram, 1-first phalanx, 11-fingertip lateral plate, 12-fingertip dorsal plate, 13-fingertip ventral plate; 2-second phalanx, 21-phalanx lateral plate, 22-phalanx dorsal plate, 23-phalanx ventral plate; 3-third phalanx; 4-rotation shaft, 5-torsion spring, 6-pulley, 61-limiting groove, 7-tendon cord, 70-active tendon cord, 71-first driven tendon cord, 72-second driven tendon cord, 8-tension spring. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0026] This invention provides a tendon-driven mechanical finger capable of adaptive grasping. The mechanical finger comprises a first phalanx 1, a second phalanx 2, and a third phalanx 3, sequentially from the fingertip to the base. The base of the first phalanx and the tip of the second phalanx are hinged together by a first joint, and the base of the second phalanx and the tip of the third phalanx are hinged together by a second joint. The third phalanx has a third joint. The entire mechanical finger is hinged to a mounting location via the third joint. The first and second phalanxes form a first revolute joint, the second and third phalanxes form a second revolute joint, and the third phalanx and the mounting location of the mechanical finger form a third revolute joint. The motion planes of the three revolute joints are parallel, allowing the mechanical finger to bend from the back of the finger towards the fingertip.

[0027] The first, second, and third joints have the same structure, each including a rotating shaft 4, a pulley 6, and an elastic component. The pulley is rotatably mounted on the middle of the rotating shaft, and has limiting grooves 61 on both sides. The elastic component includes two torsion springs 5 ​​respectively mounted on the rotating shaft on both sides of the pulley. One end of the torsion spring is embedded in the limiting groove, and the other end is fixed to the inside of the knuckle. The two ends of the rotating shaft are rotatably mounted on the knuckle. The pulleys of the second and third joints are double-groove pulleys.

[0028] The mechanical finger is driven by a tendon cord 7, which is a rigid cord. The tendon cord driving the third phalanx is the active tendon cord 70, with one end fixed in a pulley groove of the pulley at the third joint and the other end connected to a power source. The tendon cord driving the second phalanx is the second driven tendon cord 72, with one end fixed in another pulley groove of the pulley at the third joint and the other end fixed in a pulley groove of the pulley at the second joint. One end of the first driven tendon cord 71 is fixed in another pulley groove of the pulley at the second joint and the other end fixed in a pulley groove of the pulley at the first joint. When the active tendon cord is pulled, the three pulleys can rotate synchronously towards the fingertip.

[0029] The first phalanx is a hollow box-shaped body composed of a fingertip ventral plate 13, a fingertip dorsal plate 12, and two fingertip side plates 11. The fingertip ventral plate and the fingertip dorsal plate are located on the fingertip and back of the mechanical finger, respectively. The fingertip ventral plate is a convex curved plate, and the side of the fingertip side of the fingertip ventral plate is closedly connected to the side of the fingertip side of the fingertip dorsal plate. The two fingertip side plates are fixed on both sides of the fingertip ventral plate and the fingertip dorsal plate, respectively. The end of the fingertip side plate near the base of the finger has a shaft hole. The second and third phalanxes are hollow box-shaped bodies with the same structure and open at both ends. Each phalanx includes a phalanx dorsal plate 22, a phalanx ventral plate 23, and two fingertip side plates 21. The phalanx dorsal plate and the phalanx ventral plate are located on the back and fingertip of the phalanx, respectively. The two fingertip side plates are fixed on both sides of the phalanx dorsal plate and the phalanx dorsal plate, respectively. The two ends of the fingertip side plates have shaft holes. The two ends of the rotating shaft are inserted into the shaft holes.

[0030] The torsion spring is fixed to the end located on the inside of the knuckle, with the fixing point on the inside of the knuckle side plate or the fingertip side plate.

[0031] The elastic components of the first joint and the second joint also include elastic telescopic elements. The outer surfaces of the fingertip back plate and the knuckle back plate have hooks, and tension springs 8, which serve as elastic telescopic elements, are installed between the first and second knuckles and between the second and third knuckles, respectively, through the hooks.

[0032] The elasticity of the elastic components in the first, second, and third joints increases sequentially, and when the active tendon is pulled, the first, second, and third phalanges rotate and bend in sequence.

[0033] The three-dimensional view of the mechanical finger is as follows: Figure 1 As shown in the diagram, the overall structure is as follows: Figure 2 As shown, a schematic diagram of the first phalanx structure is as follows: Figure 3 As shown; a schematic diagram of the second phalanx structure is shown below. Figure 4 As shown;

[0034] Taking an example, the specific working principle of the mechanical finger provided by the present invention is as follows:

[0035] When an electric motor is used as the power source, the motor is driven to pull the active tendon rope, which drives the pulley of the third joint to rotate. At the same time, the second driven tendon rope drives the pulley of the second joint, and the first driven tendon rope drives the pulley of the first joint to rotate synchronously. The torsion springs of the first, second, and third joints are simultaneously subjected to rotational torque, which is transmitted to the knuckle.

[0036] The elasticity of the elastic components at the first, second, and third joints increases sequentially, and when the active tendon is pulled, the first, second, and third phalanges rotate and bend in sequence.

[0037] During the grasping process, once any phalanx makes initial contact with the object, that phalanx stops moving. However, the three pulleys continue to rotate under the pull of the active and driven tendons. When relative rotation between the phalanges is impossible, the torsional torque generated by the pulley rotation is converted into elastic potential energy through torsion springs, thereby increasing the gripping force of the mechanical finger.

[0038] During the grasping process, if the third knuckle contacts the object first, the remaining knuckles bend sequentially in the order of the first joint causing the first knuckle to bend, the second joint causing the second knuckle to bend, and the third joint causing the third knuckle to rotate and grip the object, thus completing the grasp.

[0039] If the second knuckle touches the object first, the remaining knuckles will bend in sequence according to the order of the first joint driving the first knuckle to bend, the second joint driving the second and third knuckles to rotate relative to each other, and the third joint driving the third knuckle to bend to complete the grasping.

[0040] If the first knuckle contacts the object first, the remaining knuckles bend sequentially in the following order: the first joint drives the first and second knuckles to rotate relative to each other, the second joint drives the second knuckle to rotate, and the third joint drives the third knuckle to rotate, thus completing the grasping motion. A diagram illustrating the grasping state is shown below. Figure 5 As shown

[0041] When the motor stops driving, the elastic component can restore it to its initial straight state, waiting for the next gripping.

[0042] This invention is not limited to the embodiments described above. The above description of specific embodiments is intended to illustrate and explain the technical solutions of this invention. The specific embodiments described above are merely illustrative and not restrictive. Without departing from the spirit and scope of the claims, those skilled in the art can make many specific modifications based on the teachings of this invention, and these modifications all fall within the scope of protection of this invention.

Claims

1. A tendon-driven mechanical finger capable of adaptive grasping, characterized in that: The mechanical finger comprises a first phalanx, a second phalanx, and a third phalanx from the fingertip to the base. The base of the first phalanx and the tip of the second phalanx are hinged together by a first joint. The base of the second phalanx and the tip of the third phalanx are hinged together by a second joint. The third phalanx has a third joint. The entire mechanical finger is hinged to the mounting location via the third joint. The first and second phalanxes form a first revolute joint, the second and third phalanxes form a second revolute joint, and the third phalanx and the mounting location of the mechanical finger form a third revolute joint. The planes of motion of the three revolute joints are parallel, and the mechanical finger can be bent from the back of the finger to the fingertip. The first joint, the second joint, and the third joint have the same structure, each including a rotating shaft, a pulley, and an elastic component. The pulley is rotatably mounted on the middle of the rotating shaft, and the pulley has limiting grooves on both sides. The elastic component includes two torsion springs respectively mounted on the rotating shaft on both sides of the pulley. One end of the torsion spring is embedded in the limiting groove, and the other end is fixed to the inside of the knuckle. The two ends of the rotating shaft are rotatably mounted on the knuckle. The mechanical finger is driven by a tendon cord, which is a rigid cord. The tendon cord driving the third phalanx is the active tendon cord, with one end fixed in a pulley groove of the pulley at the third joint and the other end connected to a power source. The tendon cord driving the second phalanx is the second driven tendon cord, with one end fixed in another pulley groove of the pulley at the third joint and the other end fixed in a pulley groove of the pulley at the second joint. One end of the first driven tendon cord is fixed in another pulley groove of the pulley at the second joint and the other end fixed in a pulley groove of the pulley at the first joint. When the active tendon cord is pulled, the three pulleys can rotate synchronously towards the fingertip. The first phalanx is a hollow box-shaped body composed of a fingertip ventral plate, a fingertip dorsal plate, and two fingertip side plates. The fingertip ventral plate and the fingertip dorsal plate are located on the fingertip and back of the mechanical finger, respectively. The fingertip ventral plate is a convex curved plate, and the side edge of the fingertip ventral plate is closedly connected to the side edge of the fingertip dorsal plate. The two fingertip side plates are fixed to both sides of the fingertip ventral plate and the fingertip dorsal plate, respectively. The end of the fingertip side plate near the base of the finger has a shaft hole. The second and third phalanxes are hollow box-shaped bodies with the same structure and open ends. Each phalanx includes a phalanx dorsal plate, a phalanx ventral plate, and two fingertip side plates. The phalanx dorsal plate and the phalanx ventral plate are located on the back and fingertip of the phalanx, respectively. The two fingertip side plates are fixed to both sides of the phalanx ventral plate and the fingertip dorsal plate, respectively. Both ends of the fingertip side plates have shaft holes. The two ends of the rotating shaft are inserted into the shaft holes. The elasticity of the elastic components at the first, second, and third joints increases sequentially, and when the active tendon is pulled, the first, second, and third phalanges rotate and bend in sequence.

2. The tendon-driven mechanical finger capable of adaptive grasping as described in claim 1, characterized in that, The pulleys of the second and third joints are double-groove pulleys.

3. The tendon-driven mechanical finger capable of adaptive grasping as described in claim 2, characterized in that, The torsion spring is fixed to the end located on the inside of the knuckle, with the fixing point on the inside of the knuckle side plate or the fingertip side plate.

4. A tendon-driven mechanical finger capable of adaptive grasping as described in claim 2 or 3, characterized in that, The outer surfaces of the fingertip backplate and the knuckle backplate have hooks, and the elastic components of the first joint and the second joint also include elastic telescopic elements, which are installed between the knuckles via the hooks.

5. A tendon-driven mechanical finger capable of adaptive grasping as described in claim 4, characterized in that... The elastic extension element is a tension spring.

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