A four fingered gripping structure

Abstract

This invention belongs to the technical field of grippers and discloses a four-finger gripping structure, which includes a flexible support structure, a constant stroke gripping mechanism, a variable stroke gripping mechanism, and a fixed mounting mechanism. The constant stroke gripping mechanism and the variable stroke gripping mechanism are respectively connected to the opposite sides of the fixed mounting mechanism. The flexible support structure is disposed on the fixed mounting mechanism and located between the variable stroke gripping mechanism and the constant stroke gripping mechanism. The flexible support structure increases the friction between the four-finger gripping structure and the target object by deformation, thereby improving the stability of gripping smooth and irregularly shaped objects.

Description

Technical Field

[0001] This invention belongs to the technical field of grippers, and more specifically, relates to a four-finger gripping structure. Background Technology

[0002] Underactuated mechanisms are those with fewer actuators than degrees of freedom. These mechanisms possess shape-adaptive capabilities, allowing them to adapt to the shape of objects. In recent years, research on industrial robot grippers has increasingly focused on flexible, multi-degree-of-freedom designs, with the ultimate goal of dexterous manipulation similar to human fingers. Considering the limited space at the robot's end effector and the need to reduce control complexity, underactuated control is a future trend. An underactuated structure is a novel actuation structure where the number of independent actuators is less than the number of degrees of freedom, simplifying control modes while increasing degrees of freedom. Furthermore, current grippers on the market can only effectively grasp specific objects; they cannot reliably grasp or hold irregularly shaped objects.

[0003] Scholars in this field have conducted some research, such as the industrial gripper based on an underdriven differential proposed in patent CN 115319777 B. The differential scheme proposed in this invention results in poor longitudinal space utilization of the gripper. Furthermore, due to the arrangement of this scheme, the palm material is made of steel. When gripping irregularly shaped objects, the palm cannot achieve effective gripping, and there is a risk of slipping, empty gripping, or empty grasping. Summary of the Invention

[0004] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention provides a four-finger gripping structure, which aims to solve the problem of low stability of existing four-finger gripping structures in grasping irregularly shaped objects.

[0005] To achieve the above objectives, according to one aspect of the present invention, a four-finger gripping structure is provided. The four-finger gripping structure includes a flexible support structure, a constant-stroke gripping mechanism, a variable-stroke gripping mechanism, and a fixed mounting mechanism. The constant-stroke gripping mechanism and the variable-stroke gripping mechanism are respectively connected to opposite sides of the fixed mounting mechanism. The flexible support structure is disposed on the fixed mounting mechanism and located between the variable-stroke gripping mechanism and the constant-stroke gripping mechanism. The flexible support structure increases the friction between the four-finger gripping structure and the target object to be gripped by deformation.

[0006] Furthermore, the flexible support structure is made of rubber and has multiple through holes.

[0007] Furthermore, the four-finger gripping structure also includes a gripping motor, a transfer mechanism, and an underdriven gear rack mechanism. The gripping motor is connected to the fixed mounting mechanism through the transfer mechanism, and the transfer mechanism is connected to the underdriven gear rack mechanism. The non-deformable stroke gripping mechanism and the variable stroke gripping mechanism are respectively connected to the underdriven gear rack mechanism.

[0008] Furthermore, the transfer mechanism is equipped with a pulley, which is connected to the variable stroke gripping mechanism via a variable stroke gripper drive belt; the transfer mechanism is used to drive the underdriven gear rack mechanism while simultaneously rotating the pulley.

[0009] Furthermore, the fixed installation mechanism includes a base plate, two trapezoidal support plates, a fixing plate, a flat plate, and a fixed mounting bracket. The two trapezoidal support plates are respectively disposed at opposite ends of the base plate. Each of the two trapezoidal support plates has a groove at its end away from the base plate, and the two ends of the flat plate are respectively disposed within the two grooves. The fixing plate is disposed on the end of the trapezoidal support plate away from the base plate and located on one side of the groove, and is used to support the constant stroke gripping mechanism. The fixed mounting bracket is disposed on the base plate and located between the two trapezoidal support plates, and is used to support the underdriven gear rack mechanism.

[0010] Furthermore, the underdriven gear and rack mechanism includes a coupling, a transmission screw, and a clamping spur gear. The coupling connects the transfer mechanism and one end of the transmission screw, and the other end of the transmission screw is mounted on the fixed mounting bracket via a bearing. The transmission screw is threadedly connected to a connecting block, and a mounting shaft is provided on the connecting block. The clamping spur gear is mounted on the mounting shaft.

[0011] Furthermore, the underdriven gear rack mechanism includes a first transmission rack, a second transmission rack, a first intermediate spur gear, a first bevel gear shaft, a first bevel gear, a first differential, a second intermediate spur gear, a second bevel gear shaft, a second bevel gear, and a second differential. The clamping spur gear meshes with both the first transmission rack and the second transmission rack. The first transmission rack and the second transmission rack mesh with the first intermediate spur gear and the second intermediate spur gear, respectively. The first intermediate gear and the second intermediate spur gear are connected to the first bevel gear and the second bevel gear, respectively, via the first bevel gear shaft and the second bevel gear shaft. The first bevel gear and the second bevel gear are meshed with the first differential and the second differential, respectively.

[0012] Further, the underdriven gear rack mechanism includes a first rectangular shaft, a second rectangular shaft, a first short rectangular shaft, and a second short rectangular shaft. The two ends of the first differential are respectively mounted on a first differential mounting bracket, which is mounted on the base plate. The opposite ends of the first differential are respectively connected to one end of the first rectangular shaft and one end of the second rectangular shaft. The other ends of the first and second rectangular shafts are respectively mounted on two trapezoidal support plates via bearings. The two ends of the second differential are respectively mounted on a second differential mounting bracket, which is mounted on the base plate. The first and second differential mounting brackets are arranged opposite each other. The two ends of the second differential are respectively connected to one end of the first short rectangular shaft and one end of the second short rectangular shaft. The other ends of the first and second short rectangular shafts are respectively connected to the second differential mounting bracket.

[0013] Furthermore, the variable stroke gripping mechanism includes a parallel upper guide rail, a parallel lower guide rail, a variable stroke gripper transmission screw, a first gripper support, a first gripper bracket, a second gripper bracket, and a second gripper support; both ends of the parallel lower guide rail are respectively connected to the two trapezoidal support plates and are located between the two trapezoidal support plates; the first gripper bracket and the second gripper bracket are movably sleeved on the parallel upper guide rail and the parallel lower guide rail; the first gripper support and the second gripper support are respectively disposed on the first gripper bracket and the second gripper bracket; both ends of the variable stroke gripper transmission screw are respectively connected to the two trapezoidal support plates; the first gripper bracket and the second gripper bracket are respectively sleeved on the variable stroke gripper transmission screw and are both threadedly connected to the variable stroke transmission screw; the variable stroke gripper transmission belt connects one end of the variable stroke transmission screw and the pulley.

[0014] Furthermore, the variable stroke gripping mechanism includes a first gripper and a second gripper; the first gripper is connected to a first gripper support; one end of the second gripper is connected to a second gripper support; the variable stroke gripper drive screw has bilaterally symmetrical reverse threads.

[0015] In summary, compared with the prior art, the four-finger gripping structure provided by this invention has the following advantages: 1. The flexible support structure is disposed on the fixed installation mechanism and located between the variable stroke gripping mechanism and the constant stroke gripping mechanism; the flexible support structure increases the friction between the four-finger gripping structure and the target gripping object by deformation, so as to improve the stability of gripping smooth objects and irregularly shaped objects.

[0016] 2. The underdriven gear rack mechanism can complete 12 degrees of freedom of clamping through a clamping motor. When the first differential and the second differential are working, the four jaws can adaptively complete the clamping work according to the time sequence of the jaws contacting the object when they come into contact with objects of different shapes. The principle is that the jaw with less damping performs adaptive envelope clamping, and the jaw with greater damping first makes contact positioning and then assists in clamping. During the clamping process, the grasping force of the four jaws and the elastic force generated by the deformation of the deformable flexible support structure generate a covering frictional force on the object.

[0017] 3. When the underdriven gear rack mechanism moves, if the resistance experienced by the grippers is the same, the clamping spur gear will not rotate, thereby simultaneously driving the first transmission rack and the second transmission rack to move synchronously. If the resistance experienced by the grippers on both sides of the end of the four-finger gripping structure is different, the clamping spur gear will rotate relative to each other and drive the first transmission rack and the second transmission rack to move asynchronously, thereby generating differential movement of the grippers at both ends of the gripper.

[0018] 4. The flexible support structure has small through holes, which allows for sufficient elasticity during deformation while maintaining adequate rigidity. The flexible support structure can undergo significant deformation under irregular pressure, better covering the exterior of irregular objects to provide sufficient friction.

[0019] 5. The variable stroke gripper transmission screw is a double-sided symmetrical reverse screw, which can drive the first gripper and the second gripper to move in opposite directions at the same speed. The radial relative and opposite movements of the first gripper are controlled by controlling the power and direction of the input pulley.

[0020] 6. The first differential and the second differential operate by moving asynchronously based on the resistance difference between the first gripper and the second gripper and the resistance difference between the third gripper and the fourth gripper of the constant stroke gripping mechanism, thereby adaptively gripping objects of different shapes. The four grippers of the four-finger gripping structure can move asynchronously to meet the gripping conditions of different object shapes. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the four-finger clamping structure provided by the present invention; Figure 2 yes Figure 1 A schematic diagram of the underdriven gear and rack mechanism with a four-finger gripping structure. Figure 3 yes Figure 1 A schematic diagram of the constant stroke clamping mechanism of the four-finger clamping structure in the image; Figure 4 yes Figure 1 A schematic diagram of the variable stroke clamping mechanism with a four-finger clamping structure.

[0022] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1-first rectangular shaft, 2-first transmission rack, 3-first differential, 4-first intermediate spur gear, 5-second rectangular shaft, 6-coupling, 7-transfer mechanism, 8-clamping motor, 9-first short rectangular shaft, 10-second differential, 11-second intermediate spur gear, 12-second short rectangular shaft, 13-clamping spur gear, 14-transmission screw, 15-third clamping motor. 16-Third gripper support, 17-Fourth gripper support, 18-Fourth gripper, 19-First gripper, 20-Parallel upper guide rail, 21-Variable stroke gripper transmission screw, 22-First gripper support, 23-First differential mounting bracket, 24-Parallel lower guide rail, 25-First gripper shift fork, 26-Second gripper shift fork, 27-Variable stroke gripper transmission belt, 28-Second gripper bracket, 29-Second gripper, 30-Flexible support structure. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be 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 illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0024] Please see Figure 1 This invention provides a four-finger gripping structure, comprising a gripping motor 8, a transfer mechanism 7, an underdriven gear and rack mechanism, a constant-stroke gripping mechanism, a variable-stroke gripping mechanism, a flexible support structure 30, and a fixed mounting mechanism. The gripping motor 8 is connected to the fixed mounting mechanism via the transfer mechanism 7, which is also connected to the underdriven gear and rack mechanism. The constant-stroke gripping mechanism and the variable-stroke gripping mechanism are respectively connected to opposite sides of the underdriven gear and rack mechanism. The flexible support structure 30 is connected to the fixed mounting mechanism and located between the variable-stroke gripping mechanism and the constant-stroke gripping mechanism.

[0025] Please see Figure 2 , Figure 3 and Figure 4The fixed installation mechanism includes a base plate, two trapezoidal support plates, a fixing plate, a flat plate, and a fixed mounting bracket. The two trapezoidal support plates are respectively disposed at opposite ends of the base plate. Each of the two trapezoidal support plates has a groove at its end away from the base plate, and the two ends of the flat plate are respectively disposed within the two grooves. The fixing plate is disposed on the end of the trapezoidal support plate away from the base plate and located on one side of the groove, and it supports the constant stroke gripping mechanism. The fixed mounting bracket is disposed on the base plate and located between the two trapezoidal support plates, and it supports the underdriven gear and rack mechanism.

[0026] The transfer mechanism 7 has a pulley, which is connected to the variable stroke gripping mechanism via a variable stroke gripper drive belt 27. The output shaft of the gripping motor 8 is connected to the transfer mechanism 7 to drive it. The transfer mechanism 7 drives the underdriven gear rack mechanism while simultaneously rotating the pulley, which in turn drives the variable stroke gripper drive belt 27 to rotate, thereby achieving stroke adjustment of the variable stroke gripping mechanism.

[0027] The underdriven gear and rack mechanism includes a coupling 6, a first intermediate spur gear 4, a transmission screw 14, a clamping spur gear 13, a first transmission rack 2, a first bevel gear shaft, a first bevel gear, a first differential 3, a first rectangular shaft 1, a second rectangular shaft 5, a second transmission rack, a second intermediate spur gear 11, a second bevel gear shaft, a second bevel gear, a second differential 10, a first short rectangular shaft 9, and a second short rectangular shaft 12. The coupling 6 connects the transfer mechanism 7 and one end of the transmission screw 14. The other end of the transmission screw 14 is mounted on the fixed mounting bracket via a bearing. The transmission screw 14 is threadedly connected to a connecting block, and a mounting shaft is provided on the connecting block. The clamping spur gear 13 is mounted on the mounting shaft. The clamping spur gear 13 meshes with both the first transmission rack 2 and the second transmission rack. Meanwhile, the first transmission rack 2 and the second transmission rack mesh with the first intermediate spur gear 4 and the second intermediate spur gear 11 respectively. The first intermediate gear and the second intermediate spur gear 11 are connected to the first bevel gear and the second bevel gear through the first bevel gear shaft and the second bevel gear shaft respectively. The first bevel gear and the second bevel gear are meshed with the first differential 3 and the second differential 10 respectively.

[0028] The two ends of the first differential 3 are respectively mounted on the first differential mounting bracket 23, which is mounted on the base plate. Meanwhile, the opposite ends of the first differential are respectively connected to one end of the first rectangular shaft 1 and one end of the second rectangular shaft 5. The other ends of the first rectangular shaft 1 and the second rectangular shaft 5 are respectively mounted on the two trapezoidal support plates via bearings.

[0029] The two ends of the second differential 10 are respectively mounted on the second differential mounting bracket, which is mounted on the base plate. The first differential mounting bracket 23 is disposed opposite to the second differential mounting bracket. The two ends of the second differential are respectively connected to one end of the first short square shaft 9 and one end of the second short square shaft 12, and the other ends of the first short square shaft 9 and the second short square shaft 12 are respectively connected to the second differential mounting bracket.

[0030] The constant stroke gripping mechanism includes a third gripper 15, a third gripper support 16, a third linkage structure, a fourth gripper 18, a fourth gripper support 17, and a fourth linkage structure. The third gripper 15 is connected to the third gripper support 16, which is mounted on the fixed plate. One end of the third linkage structure is connected to the first short square shaft 9, and the other end is connected to both the third gripper support 16 and the third gripper. The fourth gripper support 17 is mounted on the fixed plate. One end of the fourth gripper is connected to the fourth gripper support 17. One end of the fourth linkage structure is connected to the second short square shaft 12, and the other end is connected to both the fourth gripper and the fourth gripper support 17.

[0031] The variable stroke gripping mechanism includes a parallel upper guide rail 20, a parallel lower guide rail 24, a first gripper 19, a variable stroke gripper transmission screw 21, a first gripper support 22, a first gripper bracket, a first gripper fork 25, a first connecting rod structure, a second gripper 29, a second gripper bracket 28, a second gripper support, a second gripper fork 26, and a second connecting rod structure. The parallel upper guide rail 20 and the parallel lower guide rail 24 are spaced apart, with both ends of the parallel upper guide rail 20 respectively mounted on the two trapezoidal support plates. Both ends of the parallel lower guide rail 24 are connected to the two trapezoidal support plates and are located between the two trapezoidal support plates.

[0032] Both the first gripper bracket and the second gripper bracket 28 are movably sleeved on the parallel upper guide rail 20 and the parallel lower guide rail 24. The first gripper support 22 and the second gripper support are respectively disposed on the first gripper bracket and the second gripper bracket 28. The two ends of the variable stroke gripper transmission screw 21 are respectively connected to the two trapezoidal support plates. The first gripper bracket and the second gripper bracket 28 are respectively sleeved on the variable stroke gripper transmission screw 21, and both are threadedly connected to the variable stroke transmission screw. The variable stroke gripper transmission belt 27 connects one end of the variable stroke transmission screw and the pulley.

[0033] The first gripper is connected to the first gripper support 22. One end of the first connecting rod structure is connected to the first rectangular shaft 1, and the other end is connected to the first gripper support 22 and the first gripper. One end of the first gripper fork 25 is connected to the first gripper support 22, and the other end is connected to the end of the first connecting rod structure connected to the first rectangular shaft 1.

[0034] One end of the second gripper is connected to the second gripper support. One end of the second linkage structure is connected to the second rectangular shaft 5, and the other end is connected to both the second gripper support and the second gripper. One end of the second gripper fork 26 is connected to the second gripper support, and the other end is connected to the end of the second linkage structure connected to the second rectangular shaft 5.

[0035] The first differential and the second differential are respectively connected to the constant stroke gripping mechanism and the variable stroke gripping mechanism to drive the first gripper, the second gripper, the third gripper, and the fourth gripper to clamp the target object. The four-finger gripping structure has two working states: clamping and pinching. Because the fixed mounting mechanism is provided with a deformable flexible support structure 30, it can increase the friction force on the clamped object when the four-finger gripping structure is working, thereby increasing the stability and smoothness of clamping smooth and irregularly shaped objects.

[0036] The underdriven gear rack mechanism can perform 12 degrees of freedom clamping work through a clamping motor 8. When the first differential and the second differential are working, the four jaws can adaptively complete the clamping work according to the time sequence of the jaws contacting the objects when they come into contact with objects of different shapes. The principle is that the jaw with less damping performs adaptive envelope clamping, and the jaw with greater damping first makes contact positioning and then assists in clamping. During the clamping process, the grasping force of the four jaws and the elastic force generated by the deformation of the deformable flexible support structure generate a covering frictional force on the object.

[0037] When the underdriven gear rack mechanism moves, if the resistance experienced by the grippers is the same, the clamping spur gear will not rotate, thereby simultaneously driving the first transmission rack 2 and the second transmission rack to move synchronously. If the resistance experienced by the grippers on both sides of the end of the four-finger gripping structure is different, the clamping spur gear 13 will rotate relative to each other and drive the first transmission rack 2 and the second transmission rack to move asynchronously, thereby generating differential motion of the grippers at both ends of the gripper.

[0038] The flexible support structure 30 is disposed on the flat plate and partially located within the groove, and it has multiple small through holes, which can be strip-shaped holes. In this embodiment, the flexible support structure 30 is a rubber support structure.

[0039] The flexible support structure 30 is an addition to the underdriven gear and rack mechanism, which significantly reduces the size of the transmission mechanism, enhancing the stability and adaptability of the four-finger gripping structure. The flexible support structure 30 has small through holes, allowing for sufficient elasticity during deformation while maintaining adequate rigidity. The flexible support structure 30 can deform significantly under irregular pressure, better covering the exterior of irregular objects to provide sufficient friction. This structure provides sufficient rigidity to the deformable flexible support structure 30, preventing objects from slipping when gripping excessively large or irregular shapes, further improving stability.

[0040] The first differential and the second differential operate by moving asynchronously based on the resistance difference between the first gripper and the second gripper and the resistance difference between the third gripper and the fourth gripper, thereby adaptively gripping objects of different shapes. The four grippers of the four-finger gripping structure can move asynchronously to meet the gripping conditions of different object shapes.

[0041] The variable stroke gripper drive screw 21 is a double-sided symmetrical reverse screw, which can drive the first gripper and the second gripper to move in opposite directions at the same speed. The radial relative and opposite movements of the first gripper are controlled by controlling the power and direction of the input pulley.

[0042] The clamping motor 8 can achieve 12 degrees of freedom of movement for the four grippers with underdrive, and it can also control the movement of the guide rail perpendicular to the clamping direction plane. During the specific clamping process of the four-finger clamping structure, when the four grippers contact objects of different shapes, they can adaptively complete the clamping work according to the order in which the grippers contact the object. The gripper that contacts the object first performs contact positioning, the gripper that contacts the object later performs adaptive envelope clamping similar to a human hand, and then the gripper that performed contact positioning again performs adaptive envelope clamping to assist in clamping. Finally, the four grippers cooperate with a deformable flexible support structure to reliably clamp the object. The first gripper fork 25 and the second gripper fork 26 connect the gripper base to the linkage structure to ensure simultaneous radial movement of the grippers. Meanwhile, for small objects, the guide rail can be used to shorten the distance between the first and second grippers, so that the four grippers are aligned for easy coverage or parallel gripping; for large objects, the guide rail can be used to increase the distance between the grippers, so that the four grippers are not aligned, thus having a larger gripping range to accommodate longer and larger objects.

[0043] In practical applications, multiple four-finger gripping structures can be grouped together to form a gripping system for a long object. In the axial direction of the gripper's slide rail, multiple grippers can work together to grip a very long target object, providing precise and stable adaptive gripping. Multiple four-finger gripping structures can also be grouped together to form a gripping system for an irregularly shaped object (such as a tetrahedral structure). In the longitudinal direction of the four grippers of the four-finger gripping structure, the deformable flexible support structure 30 can undergo significant deformation and provide corresponding stiffness, enabling reliable gripping of the object even when the gripping force of the four grippers is not orthogonal to the surface of the object being gripped.

[0044] Those skilled in the art will readily understand that the above description is merely 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 within the scope of protection of the present invention.

Claims

1. A four-finger gripping structure, characterized in that: The four-finger gripping structure includes a flexible support structure, a constant stroke gripping mechanism, a variable stroke gripping mechanism, and a fixed mounting mechanism. The constant stroke gripping mechanism and the variable stroke gripping mechanism are respectively connected to opposite sides of the fixed mounting mechanism. The flexible support structure is disposed on the fixed mounting mechanism and located between the variable stroke gripping mechanism and the constant stroke gripping mechanism. The flexible support structure increases the friction between the four-finger gripping structure and the target object being gripped by deformation. The flexible support structure is made of rubber and has multiple through holes. The four-finger gripping structure also includes a gripping motor, a transfer mechanism, and an underdriven gear and rack mechanism. The gripping motor is connected to the fixed mounting mechanism through the transfer mechanism, and the transfer mechanism is connected to the underdriven gear and rack mechanism. The constant stroke gripping mechanism and the variable stroke gripping mechanism are respectively connected to the underdriven gear and rack mechanism. The transfer mechanism has a pulley, which is connected to the variable stroke gripping mechanism via a variable stroke gripper drive belt; the transfer mechanism drives the underdriven gear rack mechanism and simultaneously drives the pulley to rotate. The fixed mounting mechanism includes a base plate, two trapezoidal support plates, a fixed plate, a flat plate, and a fixed mounting frame; the underdriven gear rack mechanism includes a coupling, a transmission screw, and a clamping spur gear. The coupling connects the transfer mechanism and one end of the transmission screw, and the other end of the transmission screw is mounted on the fixed mounting frame via a bearing; the transmission screw is threadedly connected to a connecting block, and a mounting shaft is provided on the connecting block, with the clamping spur gear mounted on the mounting shaft; the underdriven gear rack mechanism includes a first transmission rack, a second transmission rack, a first intermediate spur gear, a first bevel gear shaft, and a first bevel gear. The system comprises a first differential, a second intermediate spur gear, a second bevel gear shaft, a second bevel gear, and a second differential. The clamping spur gear simultaneously meshes with the first transmission rack and the second transmission rack. The first transmission rack and the second transmission rack mesh with the first intermediate spur gear and the second intermediate spur gear, respectively. The first intermediate spur gear and the second intermediate spur gear are connected to the first bevel gear and the second bevel gear via the first bevel gear shaft and the second bevel gear shaft, respectively. The first bevel gear and the second bevel gear are respectively meshed with the first differential and the second differential.

2. The four-finger clamping structure as described in claim 1, characterized in that: Two trapezoidal support plates are respectively disposed at opposite ends of the base plate; each of the two trapezoidal support plates has a groove at the end away from the base plate, and the two ends of the flat plate are respectively disposed in the two grooves; the fixing plate is disposed on the end of the trapezoidal support plate away from the base plate and located on one side of the groove, and is used to support the constant stroke gripping mechanism; the fixed mounting bracket is disposed on the base plate and located between the two trapezoidal support plates, and is used to support the underdriven gear rack mechanism.

3. The four-finger clamping structure as described in claim 1, characterized in that: The underdriven gear and rack mechanism includes a first rectangular shaft, a second rectangular shaft, a first short rectangular shaft, and a second short rectangular shaft. The two ends of the first differential are respectively mounted on a first differential mounting bracket, which is mounted on the base plate. The opposite ends of the first differential are respectively connected to one end of the first rectangular shaft and one end of the second rectangular shaft. The other ends of the first and second rectangular shafts are respectively mounted on two trapezoidal support plates via bearings. The two ends of the second differential are respectively mounted on a second differential mounting bracket, which is mounted on the base plate. The first and second differential mounting brackets are positioned opposite each other. The two ends of the second differential are respectively connected to one end of the first short rectangular shaft and one end of the second short rectangular shaft. The other ends of the first and second short rectangular shafts are respectively connected to the second differential mounting bracket.

4. The four-finger clamping structure as described in claim 2, characterized in that: The variable stroke gripping mechanism includes a parallel upper guide rail, a parallel lower guide rail, a variable stroke gripper transmission screw, a first gripper support, a first gripper bracket, a second gripper bracket, and a second gripper support. The two ends of the parallel lower guide rail are respectively connected to two trapezoidal support plates and are located between the two trapezoidal support plates. The first gripper bracket and the second gripper bracket are movably sleeved on the parallel upper guide rail and the parallel lower guide rail. The first gripper support and the second gripper support are respectively disposed on the first gripper bracket and the second gripper bracket. The two ends of the variable stroke gripper transmission screw are respectively connected to the two trapezoidal support plates. The first gripper bracket and the second gripper bracket are respectively sleeved on the variable stroke gripper transmission screw and are threadedly connected to the variable stroke gripper transmission screw. The variable stroke gripper transmission belt connects one end of the variable stroke gripper transmission screw and the pulley.

5. The four-finger clamping structure as described in claim 4, characterized in that: The variable stroke gripping mechanism includes a first gripper and a second gripper; the first gripper is connected to a first gripper support; one end of the second gripper is connected to a second gripper support; the variable stroke gripper drive screw has symmetrical reverse threads on both sides.

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