Under-actuated dexterous finger and humanoid robot hand

Abstract

The invention belongs to the technical field related to robots, and discloses an under-actuated dexterous finger and a humanoid robot hand. The finger comprises a far-end phalanx, a connecting rod unit and a finger driving unit, the driving unit comprises a first driving unit and a second driving unit, the connecting rod unit comprises a first connecting rod mechanism and a second connecting rod mechanism, the first driving unit is connected with the first connecting rod mechanism and used for driving the whole finger to swing left and right and rotate around a male shaft, and the second driving unit is connected with the second connecting rod mechanism. The second driving unit is connected with the second connecting rod mechanism and used for driving the fingers to bend. The invention further discloses a robot hand constructed by the finger. By means of the robot dexterous hand, the problem that high flexibility and large output torque of an existing robot dexterous hand are difficult to coexist is solved.

Description

Technical Field

[0001] The present invention belongs to the field of robot-related technologies, and more particularly, relates to an under-actuated dexterous finger and a humanoid robot hand. Background Art

[0002] Humanoid dexterous hands with high degrees of freedom are the most versatile and flexible of all manipulative robots. They are naturally compatible with human operators and can directly adapt to the complex and changing, non-fully structured environments found in various application scenarios, such as military, rescue, production, and service. Furthermore, these highly free-flowing dexterous hands can manipulate various tools used by human operators, replacing them in laborious, tedious, harsh, and dangerous work situations. They can also perform these tasks without fatigue, thus greatly ensuring the safety of human operators while improving work efficiency.

[0003] Most existing dexterous anthropomorphic hands lack the ability to flexibly grasp or manipulate, or they possess some flexibly grasping or manipulating capabilities but struggle to adaptively adjust their behavior based on the environment, which limits functions like pinching. For example, the ILDA Hand establishes a coupled motion relationship between the distal and proximal interphalangeal joints, but this coupling is ensured by a rigid link, lacking the ability to flexibly grasp or manipulate. The Washington Hand uses rope-driven control to mimic muscle tendons. After the proximal interphalangeal joint movement is completely restricted, the distal interphalangeal joint moves again, achieving compliant enveloping grasping. However, due to the weak coupling between the interphalangeal joints, the coupling relationship cannot be adaptively adjusted based on environmental conditions (such as the strength of the fingertip force), resulting in certain limitations when performing hooking and pinching.

[0004] In addition, most existing dexterous hands do not have the ability to fully mobilize their own resources to achieve high gripping force output. In particular, focusing on under-actuated dexterous hands, one motor is usually used to control multiple joints. For example, Shadow Hand controls 24 degrees of freedom through 20 motors. Under-actuation means that under the premise of ensuring the normal operation and function of the mechanical system, a small number of drivers are used to drive more degrees of freedom of movement, that is, the number of driving sources is less than the number of degrees of freedom. Due to the limitations of the transmission structure, when facing heavy load working scenarios, such as the process of strong grasping, the lateral swinging degree of freedom of the fingers is not involved in the movement process, so the corresponding control motor is also in standby state, and cannot fully mobilize all its own resources to output high gripping force. Summary of the Invention

[0005] In response to the above defects or improvement needs of the prior art, the present invention provides an under-actuated dexterous finger and a humanoid robot hand to solve the problem that high flexibility and large output torque are difficult to coexist in existing dexterous robot hands.

[0006] To achieve the above objectives, according to one aspect of the present invention, an underactuated dexterous finger is provided, comprising a distal phalanx, a connecting rod unit, and a finger driving unit, wherein: The driving unit includes a first driving unit and a second driving unit, and the connecting rod unit includes a first connecting rod mechanism and a second connecting rod mechanism. The first driving unit is connected to the first connecting rod mechanism and is used to drive the finger to swing left and right and rotate around the common axis. The second driving unit is connected to the second connecting rod mechanism and is used to drive the finger to bend. The first linkage mechanism includes a proximal phalangeal link and an elastic link, one end of the proximal phalangeal link is fixedly connected to the first drive unit, and the other end is rotatably connected to the elastic link, and the elastic link is rotatably connected to the distal phalange; a spring is provided in the middle of the elastic link, and the expansion and contraction of the spring changes the length of the elastic link; The second linkage mechanism includes a middle phalanx link and a phalanx joint link, one end of the phalanx joint link is connected to the second drive unit, and the other end is rotationally connected to the middle phalanx link, the middle phalanx link is rotationally connected to the distal phalanx, and the middle phalanx link is connected to the proximal phalanx link through a fourth rotation axis.

[0007] Further preferably, the phalangeal joint link includes an end link, a first phalangeal joint link and a second phalangeal joint link, the end link is connected to the second drive unit, the second phalangeal joint is used to connect the first phalangeal joint link and the end link, and the first phalangeal joint link is connected to the middle phalangeal link.

[0008] Further preferably, the end connecting rod is a double-headed ball-end connecting rod, and the second interphalangeal joint connecting rod is L-shaped.

[0009] Further preferably, the elastic link is connected to the distal phalanx via a first rotation axis, the middle phalanx link is connected to the distal phalanx via a second rotation axis, the elastic link is connected to the proximal phalanx link via a third rotation axis, and the middle phalanx link is connected to the first phalanx joint link via a fifth rotation axis.

[0010] Further preferably, the distal phalanx, middle phalanx connecting rod, proximal phalanx connecting rod and elastic connecting rod form a planar four-bar linkage through the first rotation axis, the second rotation axis, the third rotation axis and the fifth rotation axis.

[0011] Further preferably, the first drive unit includes a male shaft, a bevel gear mechanism arranged at both ends of the male shaft, a differential output bevel gear and a metacarpal connecting plate, the metacarpal connecting plate is connected to the proximal phalangeal connecting rod, the differential output bevel gear is fixedly connected to the metacarpal connecting plate, the bevel gear mechanism includes a first bevel gear, a second bevel gear and a third bevel gear, the first bevel gear is connected to the metacarpophalangeal joint drive module, the second bevel gear is meshed with the first bevel gear, the second bevel gear is fixedly connected to the third bevel gear, the third bevel gear is sleeved on the male shaft, and the third bevel gear is meshed with the differential output bevel gear.

[0012] Further preferably, the second drive unit includes a phalangeal joint drive module, a ball screw structure, a slider and a guide rail. The phalangeal joint drive module is connected to the ball screw structure, the ball screw structure is connected to the end connecting rod, the guide rail is vertical in the vertical direction, the slider is connected to the ball screw structure, and the slider drives the end connecting rod to move up and down when it moves up and down on the guide rail.

[0013] Further preferably, the number of the first link mechanisms is 2, and the two first link mechanisms are arranged opposite to each other; the number of the phalangeal joint links is 2, and the two phalangeal joint links are arranged opposite to each other.

[0014] Further preferably, the finger further comprises a middle phalanx shell and a proximal phalanx shell, the middle phalanx shell is connected to the middle phalanx connecting rod, and the proximal phalanx shell is connected to the proximal phalanx connecting rod.

[0015] According to another aspect of the present invention, a humanoid robot hand is provided, wherein the five under-actuated dexterous fingers described above are connected to a finger base to form the robot hand.

[0016] In general, the above technical solutions conceived by the present invention have the following beneficial effects compared with the prior art: 1. The present invention utilizes a combination of a first linkage mechanism, a second linkage mechanism, and an elastic link within the first linkage mechanism. Under the action of a first drive unit and a second drive unit, the curvature of the finger is modified according to the external force acting on the fingertip, thereby achieving kinematic coupling between bending motion and external force-driven motion. While ensuring the pinching function of the finger, the gripper can passively conform to the shape of the object for adaptive grasping. This converts the original active control degree of freedom into a passive degree of freedom, ensuring flexibility, reducing control difficulty, and increasing output torque.

[0017] 2. The first drive unit of the present invention utilizes the principle of a differential to design the metacarpophalangeal joint assembly. Meanwhile, by transforming the traditional differential into a differential output mechanism, on the one hand, the differential mechanism is completely driven by gears, thereby improving the joint strength of the metacarpophalangeal joint. On the other hand, the differential mechanism is provided with joint driving force by two motors during output, and can generate universal joint motion similar to that of the metacarpophalangeal joint, thereby improving the joint output torque while ensuring the flexibility of the joint.

[0018] 3. The interphalangeal joint assembly of the present invention drives the proximal phalangeal joint and the distal phalangeal joint to produce coupled motion through two planar four-bar linkages, and at the same time utilizes a crank slider mechanism to decouple the coupling relationship with the metacarpophalangeal joint, ensuring that the motion of the interphalangeal joint can be independently controlled to improve flexibility. At the same time, the motor of the interphalangeal joint is built into the palm to reduce the inertia of the distal fingers. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic structural diagram of a finger constructed according to a preferred embodiment of the present invention with the outer shell removed; Figure 2 is a side view of a finger constructed in accordance with a preferred embodiment of the present invention with the outer shell removed; Figure 3 is a structural schematic diagram of a second drive unit constructed according to a preferred embodiment of the present invention; Figure 4 is a structural schematic diagram of a first driving unit constructed according to a preferred embodiment of the present invention; Figure 5 is a schematic structural diagram of a bevel gear in a first drive unit constructed according to a preferred embodiment of the present invention; Figure 6 is a schematic structural diagram of a finger constructed according to a preferred embodiment of the present invention; Figure 7 : is a side view of a finger constructed according to a preferred embodiment of the present invention: Figure 8 It is a schematic structural diagram of a robot hand constructed according to a preferred embodiment of the present invention.

[0020] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein: 11-distal phalanx, 12-first rotation axis, 13-second rotation axis, 14-middle phalanx connecting rod, 15-elastic connecting rod, 151-first elastic connecting rod, 152-spring, 153-second elastic connecting rod, 16-third rotation axis, 17-fourth rotation axis, 20-interphalangeal joint assembly, 21-fifth rotation axis, 22-first phalanx joint connecting rod, 23-sixth rotation axis, 24-second phalanx joint connecting rod, 25-proximal phalanx connecting rod, 26-seventh rotation axis, 27-terminal connecting rod, 271-upper ball head, 272-lower Side ball head, 28-ball screw structure, 281-ball screw nut, 282-guide rail, 283-slider, 284-ball screw, 29-phalangeal joint drive module, 30-metacarpal joint assembly, 31-metacarpal connecting plate, 32-second bevel gear, 33-third bevel gear, 34-first bevel gear, 35-metacarpal joint drive module, 351-coupling, 36-end cover, 37-differential output bevel gear, 40-finger base, 41-middle phalanx shell, 42-proximal phalanx shell, 50-palm structure, 51-male shaft. DETAILED DESCRIPTION

[0021] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0022] like Figure 1 and 2 As shown, an underactuated dexterous finger comprises a distal phalanx, a connecting rod unit and a finger driving unit, wherein: The driving unit includes a first driving unit and a second driving unit, and the connecting rod unit includes a first connecting rod mechanism and a second connecting rod mechanism. The first driving unit is connected to the first connecting rod mechanism and is used to drive the finger to swing left and right and rotate around the common axis. The second driving unit is connected to the second connecting rod mechanism and is used to drive the finger to bend. The first linkage mechanism includes a proximal phalangeal link 25 and an elastic link 15. One end of the proximal phalangeal link 25 is fixedly connected to the first drive unit, and the other end is rotatably connected to the elastic link 15. The elastic link is rotatably connected to the distal phalanges. A spring 152 is provided in the middle of the elastic link 15. The expansion and contraction of the spring 152 changes the length of the elastic link. The second linkage mechanism includes a middle phalanx link 14 and a phalanx joint link, one end of the phalanx joint link is connected to the second drive unit, and the other end is rotationally connected to the middle phalanx link 14, the middle phalanx link 14 is rotationally connected to the distal phalanx 11, and at the same time, the middle phalanx link 14 is connected to the proximal phalanx link 25 through a fourth rotation axis.

[0023] The phalangeal joint link includes an end link 27, a first phalangeal joint link 22 and a second phalangeal joint link 24. The end link 27 is connected to the second drive unit. The second phalangeal joint 24 is used to connect the first phalangeal joint 22 link and the end link 27. The first phalangeal joint link 22 is connected to the middle phalangeal link 14.

[0024] The terminal link 27 is a double-ended ball-end link, and the second phalangeal joint link 24 is L-shaped. The elastic link 15 includes a first elastic link 151, a spring 152, and a second elastic link 153. One end of the spring 152 is fixed to the first elastic link 151, and the other end of the spring is fixed to the second elastic link 153. The other end of the first elastic link 151 contacts the other end of the second elastic link 153.

[0025] The fifth rotating shaft 21 connects the middle phalanx link 14 and the first phalanx joint link 22, the first phalanx joint link 22 is connected to the sixth rotating shaft 23, and the sixth rotating shaft 23 is also connected to the second phalanx joint link 24. The second phalanx joint link 24 is an L-shaped link, which is connected to the proximal phalanx link 25 at the turning point and the end is connected to the end link 27. The other end of the end link 27 is connected to the output end of the ball screw structure 28, and the input end of the ball screw structure 28 is connected to the output end of the phalanx joint drive module 29.

[0026] The end connecting rod 27 includes a head ball head 271 and an end ball head 272, and the head ball head 271 and the end ball head 272 are fixed together through a pull rod; the ball screw structure 28 includes a ball screw 284, a ball screw nut 281, a guide rail 282 and a slider 283, the guide rail 282 is fixed on the finger base 40, and the slider 283 can slide freely on the guide rail 282. The input end of the ball screw 284 is connected to the phalangeal joint drive module 29, and the ball screw nut 281 engages with the ball screw 284 to generate movement. At the same time, the ball screw 284 and the slider 283 fix the rotational movement to only generate linear displacement to drive the interphalangeal joint assembly 20.

[0027] The elastic link 15 is connected to the distal phalanx 11 via a first rotation axis 12, the middle phalanx link is connected to the distal phalanx via a second rotation axis 13, the elastic link 15 is connected to the proximal phalanx link 25 via a third rotation axis 16, and the middle phalanx link 14 is connected to the first phalanx joint link 22 via a fifth rotation axis 21. The first rotation axis 12, the second rotation axis 13, the third rotation axis 16, and the fifth rotation axis 21 form a planar four-bar linkage.

[0028] The distal phalanx 11 is connected to the first rotation axis 12, and the first rotation axis 12 is also connected to the elastic link 15. The other end of the elastic link 15 is connected to the third rotation axis 16, and the third rotation axis 16 is installed on the proximal phalanx link 25. The fourth rotation axis 17 is installed on the middle phalanx link 14. The other end of the middle phalanx link 14 is connected to the second rotation axis 13, and the second rotation axis 13 is installed on the distal phalanx 11; a planar four-bar linkage structure is formed by the first rotation axis 12, the second rotation axis 13, the third rotation axis 16 and the fifth rotation axis 21.

[0029] like Figure 4 and 5 As shown, the first drive unit includes a male shaft 51, a bevel gear mechanism arranged at both ends of the male shaft 51, a differential output bevel gear 37 and a metacarpal connecting plate 31, the metacarpal connecting plate is connected to the proximal phalangeal connecting rod 25, the differential output bevel gear 37 is fixedly connected to the metacarpal connecting plate 31, the bevel gear mechanism includes a first bevel gear 34, a second bevel gear 32 and a third bevel gear 33, the first bevel gear 34 is connected to the metacarpophalangeal joint drive module, the second bevel gear 32 is meshed with the first bevel gear 34, the second bevel gear 32 is fixedly connected with the third bevel gear 33, the third bevel gear 33 is sleeved on the male shaft 51, and the third bevel gear 33 is meshed with the differential output bevel gear 37.

[0030] The output end of the metacarpophalangeal joint drive module 35 is connected to the input end of the first bevel gear 34. The first bevel gear 34 is symmetrically distributed on the left and right sides of the sagittal plane of the dexterous hand fingers. The output end of the first bevel gear 34 is engaged with the second bevel gear 32. The second bevel gear 32 is symmetrically distributed on the left and right sides of the sagittal plane of the dexterous hand fingers and the tooth surfaces are opposite. The second group of bevel gears 32 and the third bevel gear 33 are matched with the shaft hole. At the same time, the power transmission is ensured by two symmetrically distributed cylindrical pins. The third bevel gear 33 is symmetrically distributed on the left and right sides of the sagittal plane of the dexterous hand fingers and the tooth surfaces are opposite. Both sides of the third bevel gear 33 are engaged with the differential output bevel gear 37 at the same time.

[0031] like Figure 3As shown, the second drive unit includes a phalangeal joint drive module 29, a ball screw structure, a slider 283 and a guide rail 282. The phalangeal joint drive module 29 is connected to the ball screw structure, the ball screw structure is connected to the end link 27, the guide rail 282 is vertical in the vertical direction, the slider 283 is connected to the ball screw structure, and when the slider moves up and down on the guide rail, it drives the end link to move up and down.

[0032] In some specific embodiments, the fifth rotation axis 21, the sixth rotation axis 23, the seventh rotation axis 26, the first phalangeal joint link 22, the second phalangeal joint link 24, the proximal phalangeal link 25, the terminal link 27, the ball screw structure 28, and the phalangeal joint drive module 29 constitute the interphalangeal joint assembly 20.

[0033] In some specific embodiments, the metacarpal bone 31 , the first set of bevel gears 34 , the second set of bevel gears 32 , the third set of bevel gears 33 , the differential output bevel gear 37 , the metacarpophalangeal joint drive module 35 and the end cover 36 constitute the metacarpophalangeal joint assembly 30 .

[0034] In particular, unlike the traditional differential bevel gear structure, the metacarpophalangeal joint assembly 30 transmits power to the third set of bevel gears 33 through the first set of bevel gears 34 and the second set of bevel gears 32, and then generates a differential output through the differential output bevel gear 37; the traditional differential inputs power to the differential output bevel gear 37 and generates a differential output on the third set of bevel gears 33; although the two have the same structure, the transmission methods are completely opposite, and the metacarpophalangeal joint assembly 30 mainly utilizes the differential output characteristics of the former to generate movement.

[0035] The number of the first link mechanisms is 2, and the two first link mechanisms are arranged opposite to each other. The number of the phalangeal joint links is 2, and the two phalangeal joint links are arranged opposite to each other.

[0036] like Figure 6 and 7 As shown, the finger further includes a middle phalanx shell and a proximal phalanx shell. The middle phalanx shell 41 is connected to the middle phalanx connecting rod 14 , and the proximal phalanx shell 42 is connected to the proximal phalanx connecting rod 25 .

[0037] like Figure 8 As shown, the five fingers are connected to a finger base to form a robot hand.

[0038] The following is a detailed introduction to the movement process of the fingers.

[0039] (1) Left and right swing of fingers, and rotation of fingers around the common axis The output end of the metacarpophalangeal joint drive module 35 is connected to the input end of the first bevel gear 34. The first bevel gear 34 is symmetrically distributed on the left and right sides of the sagittal plane of the dexterous hand fingers. The output end of the first group of bevel gears 34 is meshed with the second bevel gear 32. The second bevel gear 32 is symmetrically distributed on the left and right sides of the sagittal plane of the dexterous hand fingers and the tooth surfaces are opposite. The second bevel gear 32 and the third bevel gear 33 are matched with the shaft hole, and the power transmission is ensured by two symmetrically distributed cylindrical pins. The third group of bevel gears 33 are symmetrically distributed on the left and right sides of the sagittal plane of the dexterous hand fingers and the tooth surfaces are opposite. Both sides of the third group of bevel gears 33 are meshed with the differential output bevel gear 37 at the same time, and the differential output bevel gear 37 is fixed to the metacarpal bone connecting plate 31.

[0040] The metacarpophalangeal joint drive module 35 drives the third bevel gears arranged at both ends of the male shaft 51 to rotate. If the third bevel gears at both ends rotate in opposite directions, the differential output bevel gear 37 drives the finger to rotate around the male shaft 51 through the metacarpal bone connecting plate 31; if the third bevel gears at both ends rotate in the same direction, the differential output bevel gear 37 drives the finger to swing left and right through the metacarpal bone connecting plate 31, and the rotation of the differential output bevel gear 37 corresponds to the left and right swing of the finger.

[0041] (2) Finger bending movement process The planar four-bar linkage structure causes the distal phalanx 11 and the middle phalanx link 14 to move in a coupled manner. The specific process is as follows: the driving force slider 283 of the phalanx joint drive module 29 moves up and down on the guide rail 282, driving the middle phalanx link 14 to rotate around the fourth rotation axis 17 through the terminal link 27, the second phalanx link 24, and the first phalanx link 22. The rotation of the middle phalanx link 14 causes the planar four-bar linkage to rotate, thereby driving the distal phalanx 11 to rotate around the second rotation axis 13, thus achieving the bending of the distal phalanx. (3) Movement process of finger force When the fingers grasp an object, and the object becomes larger, the fingers come into contact with the grasped object, which is equivalent to an external thrust on the fingers. The elastic link 15 is subjected to an external force at the distal phalanx 11. To achieve internal force balance, the spring 152 stretches, causing the overall length of the elastic link 15 to increase. The elastic link 15 is one of the components of the planar four-bar linkage structure. The change in the length of the elastic link 15 changes the kinematic relationship of the planar four-bar linkage structure, thereby changing the coupled kinematic relationship between the middle phalanx link 14 and the distal phalanx 11. The movement stops only when the middle phalanx link 14 and the distal phalanx 11 simultaneously touch the surface of the rigid body. That is, the middle phalanx link 14 rotates until the distal phalanx 11 abuts against the surface of the grasped object. Force balance is achieved within the elastic link 15, thereby dynamically adjusting the coupled kinematic relationship between the proximal interphalangeal joint structure and the distal interphalangeal joint structure, adapting to the enveloping grasp of objects of different sizes.

[0042] The above three motion processes can be coupled arbitrarily without interfering with each other.

[0043] This embodiment is based on existing technology and takes into account the need for humanoid robots to achieve high-demand complex operation tasks, especially some labor-intensive operation scenarios with high loads and heavy weights, to achieve high flexibility of hand movement while providing sufficient driving torque. A feasible technical solution is to achieve multiple motors working simultaneously during the grasping process through structural design, while using elastic elements to flexibly and adaptively perform some grasping and operations. This embodiment proposes a dexterous hand of a humanoid robot with high flexibility and large output torque. The differential output structure ensures that when grasping, the three phalangeal joint drive modules 29 and 35 of a single finger generate output force at the same time to maximize the output torque; the elastic link 15 can change the coupling relationship of the interphalangeal joint movement according to the fingertip force to achieve adaptive grasping or operation, ensuring freedom and flexibility while reducing the number of drive motors, reducing the weight and control difficulty of the dexterous hand.

[0044] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An underactuated dexterous finger, characterized in that: The finger comprises a distal phalanx, a connecting rod unit and a finger drive unit, wherein: The driving unit includes a first driving unit and a second driving unit, and the connecting rod unit includes a first connecting rod mechanism and a second connecting rod mechanism. The first driving unit is connected to the first connecting rod mechanism and is used to drive the finger to swing left and right and rotate around the common axis. The second driving unit is connected to the second connecting rod mechanism and is used to drive the finger to bend. The first link mechanism comprises a proximal phalanx link (25) and an elastic link (15), one end of the proximal phalanx link (25) is fixedly connected to the first drive unit, and the other end is rotationally connected to the elastic link (15), and the elastic link is rotationally connected to the distal phalanx; a spring (152) is provided in the middle of the elastic link (15), and the expansion and contraction change of the spring (152) changes the length of the elastic link; The second link mechanism comprises a middle phalanx link (14) and a phalanx joint link, one end of the phalanx joint link is connected to the second drive unit, and the other end is rotationally connected to the middle phalanx link (14), the middle phalanx link (14) is rotationally connected to the distal phalanx (11), and the middle phalanx link (14) is connected to the proximal phalanx link (25) via a fourth rotation axis.

2. The underactuated dexterous finger according to claim 1 or 2, characterized in that: The phalangeal joint connecting rod comprises an end connecting rod (27), a first phalangeal joint connecting rod (22) and a second phalangeal joint connecting rod (24), wherein the end connecting rod (27) is connected to the second driving unit, the second phalangeal joint (24) is used to connect the first phalangeal joint (22) connecting rod and the end connecting rod (27), and the first phalangeal joint connecting rod (22) is connected to the middle phalangeal connecting rod (14).

3. The underactuated dexterous finger according to claim 2, characterized in that: The end connecting rod (27) is a double-headed ball-end connecting rod, and the second phalangeal joint connecting rod (24) is L-shaped.

4. The underactuated dexterous finger according to claim 3, wherein: The elastic link (15) is connected to the distal phalanx (11) via a first rotation axis (12), the middle phalanx link is connected to the distal phalanx via a second rotation axis (13), the elastic link (15) is connected to the proximal phalanx link (25) via a third rotation axis (16), and the middle phalanx link (14) is connected to the first phalanx joint link (22) via a fifth rotation axis (21).

5. The underactuated dexterous finger according to claim 4, characterized in that: The distal phalanx (11), the middle phalanx connecting rod (14), the proximal phalanx connecting rod (25) and the elastic connecting rod (15) form a planar four-bar linkage via a first rotation axis (12), a second rotation axis (13), a third rotation axis (16) and a fifth rotation axis (21).

6. The underactuated dexterous finger according to claim 1 or 5, characterized in that: The first drive unit includes a male shaft (51), a bevel gear mechanism provided at both ends of the male shaft (51), a differential output bevel gear (37) and a metacarpal connecting plate (31), the metacarpal connecting plate (31) is connected to the proximal phalangeal connecting rod (25), the differential output bevel gear (37) is fixedly connected to the metacarpal connecting plate (31), the bevel gear mechanism includes a first bevel gear (34), a second bevel gear (32) and a third bevel gear (33), the first bevel gear (34) is connected to the metacarpophalangeal joint drive module (35), the second bevel gear (32) is meshed with the first bevel gear (34), the second bevel gear (32) is fixedly connected with the third bevel gear (33), the third bevel gear (33) is sleeved on the male shaft (51), and the third bevel gear (33) is meshed with the differential output bevel gear (37).

7. The under-actuated dexterous finger according to claim 1 or 5, characterized in that: The second drive unit comprises a phalangeal joint drive module (29), a ball screw structure (28), a slider (283) and a guide rail (282), wherein the phalangeal joint drive module is connected to the ball screw structure, the ball screw structure is connected to the end connecting rod (27), the guide rail (282) is placed in a vertical direction, the slider (283) is connected to the ball screw structure, and when the slider moves up and down on the guide rail, it drives the end connecting rod to move up and down.

8. The underactuated dexterous finger according to claim 1 or 5, characterized in that: The number of the first link mechanisms is 2, and the two first link mechanisms are arranged opposite to each other. The number of the phalangeal joint links is 2, and the two phalangeal joint links are arranged opposite to each other.

9. The underactuated dexterous finger according to claim 1 or 5, characterized in that: The finger further comprises a middle phalanx shell and a proximal phalanx shell, wherein the middle phalanx shell (41) is connected to the middle phalanx connecting rod (14), and the proximal phalanx shell (42) is connected to the proximal phalanx connecting rod (25).

10. A humanoid robot hand, characterized in that: Five under-actuated dexterous fingers according to any one of claims 1 to 9 are connected to a finger base to form a robot hand.

Images