Rope-driven robot gripper based on parallel flexible structure

Abstract

The invention discloses a rope-driven robot gripper based on a parallel flexible structure. Comprising a supporting frame, a driving unit fixedly arranged on the supporting frame, a moving pair transmission unit fixedly arranged on the supporting frame and in transmission connection with the driving unit, and two sets of clamping jaw units oppositely and fixedly arranged at the power output ends of the two sides of the moving pair transmission unit. The driving unit drives the two sets of clamping jaw units to be synchronously close to or away from each other through the moving pair transmission unit. Each clamping jaw unit comprises a spherical pair support capable of moving horizontally, a middle hemisphere and at least three tail end hemispheres, wherein the middle hemisphere is spherically hinged in the side face of the spherical pair support and can swing up and down, the tail end hemispheres are spherically hinged in the lateral plane of the middle hemisphere, and all rotating spherical pairs are connected through reset mechanisms. The flexible structure of the parallel spherical pair is composed of rigid components, the structural design is simple, the manufacturing cost is low, self-adaptive enveloping clamping of objects in any shape can be well achieved, and the use requirements in various different scenes are met.

Description

Technical Field

[0001] The present invention belongs to the technical field of robot grippers, and in particular relates to a rope-driven robot gripper based on a parallel flexible structure. Background Art

[0002] In recent years, robots have begun to move from factories into our daily lives, signaling an increasing demand for robots to interact with the world. One crucial performance metric is gripping ability. Early robotic end effectors primarily consisted of simple, single-function gripping tools designed for structured scenarios. They exhibited poor robustness in complex environments, limited precision, and a lack of flexibility. They struggled to adapt to objects of varying shapes and sizes, limiting their application.

[0003] Current robot end effectors mainly include simple grippers, under-actuated grippers, dexterous hands, and flexible material grippers. The advantages of under-actuated grippers are: adaptive grasping, compact structure, and large grasping range. Due to the under-actuated design, the number of actuators is reduced, reducing costs, and it is suitable for various scenarios such as industrial automation, logistics, and scientific research. The disadvantages are: by increasing the redundant degrees of freedom of the mechanism and relying on elastic element constraints, the motion behavior of the connecting rod structure is relatively complex, and a precise mathematical model must be established to achieve precise control. The advantages of dexterous hands are: they have high degrees of freedom, often have multiple fingers and joints, and can perform complex operations. The finger joint design allows for precise grasping of objects of different shapes and sizes, and is widely used in robotic surgery, precision assembly, humanoid robots and other fields. The disadvantages are: they are characterized by complete human imitation and deploy a large number of actuators, which makes the control algorithm difficult and the cost very high. The advantages of flexible material grippers are: they can adapt to objects of different shapes and perform non-destructive grasping; the pressure applied during grasping is extremely low, which is suitable for grasping fragile or soft objects; they are usually pneumatically or hydraulically driven, with a simple structure and easy control, and can be used in food processing, medical care, marine life research and other fields; the disadvantages are: they mainly rely on the conformity of the material to the object being grasped, and can make large-area contact with the object to improve the grasping reliability, but often the grasping force is insufficient, the gripper stiffness is poor, and it relies on the air source. At the same time, it cannot adapt to harsh environments (such as high temperature, acid and alkali conditions).

[0004] Therefore, there is an urgent need to design an under-actuated robotic gripper with a flexible structure composed of rigid components and a simple drive and transmission structure to meet the adaptive enveloping clamping of objects of arbitrary shapes in a variety of different scenarios. Summary of the Invention

[0005] To address the shortcomings of the aforementioned grippers, this paper proposes a cable-driven robotic gripper based on a parallel flexible structure, representing a novel underactuated gripper. This simple parallel flexible structure avoids the complex connecting rod design of conventional underactuated grippers, enabling enveloping gripping of objects of arbitrary shapes. Using common materials, unlike soft grippers, it offers strong adaptability and, with only a single actuator, is significantly less expensive than a dexterous hand. Furthermore, to minimize gripper weight, a two-wire cable drive system is employed for transmission.

[0006] In order to solve the above technical problems, a technical solution adopted by the present invention is:

[0007] A rope-driven robot gripper based on a parallel flexible structure includes a support frame, a drive unit fixedly mounted on the support frame, a mobile sub-transmission unit fixedly mounted on the support frame and transmission-connected to the drive unit, and two sets of gripper units relatively fixedly mounted on power output ends on both sides of the mobile sub-transmission unit. The drive unit drives the two sets of gripper units to synchronously move toward or away from each other through the mobile sub-transmission unit.

[0008] The clamping jaw unit includes a horizontally movable ball support, an intermediate hemisphere that is spherically hinged in the side of the ball support and can swing up and down, and at least three end hemispheres that are spherically hinged in the lateral plane of the intermediate hemisphere. Each end hemisphere is connected to the intermediate hemisphere, and the intermediate hemisphere is connected to the ball support through a reset mechanism.

[0009] Furthermore, a first ball joint concave surface is opened in the side surface of the ball joint support, and at least one ball joint constraint convex strip is provided on the first ball joint concave surface. The side surface of the ball joint constraint convex strip is parallel to the symmetry center plane of the ball joint support. The spherical surface of the middle hemisphere is movably fitted with the first ball joint concave surface, and a limiting groove is provided on the spherical surface of the middle hemisphere to couple and match with the ball joint constraint convex strip.

[0010] Furthermore, a first return spring is connected to the top center of the spherical surface of the middle hemisphere, and the other end of the first return spring is connected to the middle of the ball auxiliary support.

[0011] Furthermore, a second ball joint concave surface is provided in the lateral plane of the middle hemisphere, and the spherical surface of the end hemisphere is movably fitted with the second ball joint concave surface.

[0012] Furthermore, a through hole is provided on the spherical surface of the middle hemisphere and communicates with the concave surface of the second ball joint. A hanging rod is provided in the through hole, and a second return spring is hung on the hanging rod. The other end of the second return spring is connected to the spherical center of the end hemisphere.

[0013] Furthermore, the mobile sub-transmission unit includes an upper guide rail group and a lower guide rail group arranged on the support frame, the two ends of the upper guide rail group are respectively slidably sleeved with a first slider and a second slider, the lower guide rail group is respectively slidably sleeved with a third slider located below the first slider and a fourth slider located below the second slider, the first slider and the fourth slider are connected by a first connecting rod, and the second slider and the third slider are connected by a second connecting rod, and the ball sub-supports of the two groups of clamping units are respectively fixedly connected to the first slider and the second slider.

[0014] Furthermore, the drive unit includes a servo support fixedly mounted on the support frame, a servo fixedly mounted on the servo support, a capstan rotatably mounted in the servo support and transmission-connected to the output shaft end of the servo, and the capstan is wound with two strands of rope with the same rotation direction and a phase difference of °, the two ends of one strand of rope are respectively connected to the first slider and the fourth slider, and the two ends of the other strand of rope are respectively connected to the two ends of the second slider and the third slider.

[0015] Furthermore, both ends of the first connecting rod and the second connecting rod are rotatably provided with lockers, and the four ends of the two twisted ropes are respectively connected to the four lockers.

[0016] Furthermore, a robotic arm adapter is fixedly provided on the side of the servo support.

[0017] Furthermore, positioning detectors are respectively provided at both end portions of the support frame, and detector triggering mechanisms matching the two positioning detectors are respectively provided on the first slider and the fourth slider.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] 1. The present invention adopts a structural form in which the middle hemisphere is hinged in the ball pair support and can swing up and down, and multiple end hemispheres are hinged in the middle hemisphere and can swing in any direction, thereby forming a flexible structure of a parallel ball pair composed of rigid components. The structural design is simple and the manufacturing cost is low. At the same time, it can well realize the adaptive enveloping clamping of objects of arbitrary shapes, meeting the use requirements in various different scenarios.

[0020] 2. The enveloping design of the flexible gripper's gripping end effectively increases the contact area between it and the object being grasped. Through the mutual adaptation and coordination of multiple gripping points, a stable multi-dimensional gripping structure is formed, thereby greatly improving the reliability of gripping.

[0021] 3. By adopting a one-to-two-rope drive transmission method with a winch and a double-strand twisted rope, and coordinating with two sets of moving pairs to achieve synchronous reverse movement of two sets of gripper units, the number of drivers is reduced and the overall weight of the gripper is reduced while ensuring the reliability of drive and transmission, taking into account the optimization needs of cost and benefit.

[0022] 4. The rope-driven robot gripper based on a parallel flexible structure proposed in the present invention has stronger robustness than a simple gripper of the same size; compared with an under-actuated gripper of the same size, it can grasp objects in a wider range of sizes and has a lower design cost; compared with a gripper made of flexible materials, it can adapt to more demanding working environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is one of the three-dimensional structural diagrams of the rope-driven robot gripper based on the parallel flexible structure proposed in the present invention;

[0024] Figure 2 This is the second schematic diagram of the three-dimensional structure of the rope-driven robot gripper based on the parallel flexible structure proposed by the present invention;

[0025] Figure 3 is one of the three-dimensional structural schematic diagrams of the clamping jaw unit;

[0026] Figure 4 The second schematic diagram of the three-dimensional structure of the clamping jaw unit;

[0027] Figure 5 This is one of the three-dimensional structural diagrams of the ball pair bearing;

[0028] Figure 6 The second schematic diagram of the three-dimensional structure of the ball support;

[0029] Figure 7 This is one of the schematic diagrams of the three-dimensional structure of the middle hemisphere;

[0030] Figure 8 The second schematic diagram of the three-dimensional structure of the middle hemisphere;

[0031] Figure 9 A schematic diagram of the three-dimensional structure of the middle hemisphere and the ball support in an assembled state;

[0032] Figure 10 is one of the schematic diagrams of the three-dimensional structure of the terminal hemisphere;

[0033] Figure 11 The second schematic diagram of the three-dimensional structure of the terminal hemisphere;

[0034] Figure 12 is a schematic diagram of the three-dimensional structure of the assembled state of the terminal hemisphere and the middle hemisphere;

[0035] Figure 13 is a schematic diagram of the three-dimensional structure of the moving auxiliary transmission unit;

[0036] Figure 14 Schematic diagram of the three-dimensional structure of one of the moving pairs;

[0037] Figure 15 is a schematic diagram of the three-dimensional structure of the driving unit;

[0038] Figure 16 It is a structural schematic diagram of the connection state between the driving unit and the moving auxiliary transmission unit;

[0039] Figure 17 This is a schematic diagram of the force analysis of the secondary spherical pair structure;

[0040] Figure 18 Schematic diagram of the force analysis of the three-level spherical pair structure.

[0041] In the figure: 1. Support frame; 101. Support base; 102. Guide rail support; 2. Drive unit; 201. Servo support; 202. Servo; 203. Winch; 204. Hitch; 3. Moving auxiliary transmission unit; 301. First slider; 302. Second slider; 303. Third slider; 304. Fourth slider; 305. Upper guide rail assembly; 306. Lower guide rail assembly; 307. First connecting rod; 308. Second connecting rod; 309. Locking device; 3010. First auxiliary slider; 3011. Second auxiliary slider; 4. Gripper unit; 401, ball joint support; 4011, first ball joint concave surface; 4012, ball joint constraint convex strip; 4013, notch; 402, middle hemisphere; 4021, limiting slide groove; 4022, through hole; 4023, second ball joint concave surface; 403, end hemisphere; 4031, sink groove; 404, first return spring; 405, first hanging rod; 406, second return spring; 407, second hanging rod; 408, third hanging rod; 5, positioning detector; 501, detector trigger mechanism; 6, robotic arm adapter. DETAILED DESCRIPTION

[0042] The preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more precise definition of the protection scope of the present invention.

[0043] It should be noted that when a component is referred to as being "mounted on" another component, it may be directly on the other component or there may be a central component. When a component is considered to be "set on" another component, it may be directly set on the other component or there may be a central component. When a component is considered to be "fixed to" another component, it may be directly fixed to the other component or there may be a central component.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "or / and" as used herein includes any and all combinations of one or more of the associated listed items.

[0045] See attached Figure 1 and Figure 2 A rope-driven robot gripper based on a parallel flexible structure includes a support frame 1, a drive unit 2 fixedly arranged on the support frame 1, a mobile sub-transmission unit 3 fixedly arranged on the support frame 1 and transmission-connected to the drive unit 2, and two groups of gripper units 4 relatively fixedly arranged on the power output ends on both sides of the mobile sub-transmission unit 3. The drive unit 2 drives the two groups of gripper units 4 to synchronously approach or move away from each other through the mobile sub-transmission unit 3.

[0046] Specifically, the support frame 1 consists of a horizontal support base 101 and guide rail supports 102 vertically fixed to the top of each end of the support base 101, serving as the mounting base for the entire rope-driven robot gripper. The length of the support base 101 is determined by the gripping range of the rope-driven robot gripper.

[0047] like Figure 3 and Figure 4 As shown, the gripper unit 4 comprises a horizontally movable ball-joint support 401, an intermediate hemisphere 402 spherically hinged within the side of the ball-joint support 401 and capable of swinging up and down, and three terminal hemispheres 403 spherically hinged within the lateral plane of the intermediate hemisphere 402. Thus, the ball-joint support 401, the intermediate hemisphere 402, and the terminal hemispheres 403 form a three-level flexible structure with a ball-joint connection, with the multiple terminal hemispheres 403 forming a parallel ball-joint structure. Because the ball-joint connection allows for rotation around any axis in space, the planar portions of the three terminal hemispheres 403 can arbitrarily envelop the local surface of the object being gripped, achieving adaptive gripping. Simultaneously, the intermediate hemisphere 402 can rotate around a specific axis, allowing the gripper to adapt to the overall contour of the object. Clearly, the greater the number of terminal hemispheres 403, the better the gripper's ability to adapt to the surface of the gripped object, especially for irregular surfaces. However, an increase in the number of the terminal hemispheres 403 will also make the overall structure volume of the clamping unit 4 larger and the manufacturing cost higher. Therefore, in this embodiment, the number of the terminal hemispheres 403 is set to three to take into account the requirements of usage function and production cost.

[0048] Furthermore, Figure 5 and Figure 6As shown, the top of the ball-pair support 401 is a frame structure, which is used to be fixedly connected to the power output end of the mobile transmission unit 3, thereby realizing the horizontal movement of the entire clamping claw unit 4; its bottom is a disc structure, and a first ball joint concave surface 4011 is provided in the side of the disc structure. The first ball joint concave surface 4011 is provided with at least one (two in this embodiment) ball-pair constraint ridge 4012, and the side of the ball-pair constraint ridge 4012 is parallel to the symmetric center plane of the ball-pair support 401, that is, the side of the ball-pair constraint ridge 4012 is located in the vertical plane. Figure 7 and Figure 8 As shown, the middle hemisphere 402 is a hemispherical structure, with one side being spherical and the other being flat. The radius of the spherical surface of the middle hemisphere 402 is the same as the radius of the concave surface of the first spherical joint 4011. Therefore, the spherical surface of the middle hemisphere 402 can flexibly fit with the concave surface of the first spherical joint 4011 to achieve a spherical joint connection. Because the rope-driven robot gripper has two gripper units 4, i.e., a two-claw structure, compared to a three-claw structure, the gripped object is more likely to flip and fall due to center imbalance and other reasons. To prevent the gripped object from accidentally falling, the degrees of freedom of the middle hemisphere 402 must be limited. To this end, a limiting groove 4021 is provided on the spherical surface of the middle hemisphere 402, which is coupled and matched with the ball pair constraint ridge 4011, and the ball pair constraint ridge 4012 is located at the top of the first ball joint concave surface 4011, and the limiting groove 4021 is located in the upper half of the spherical surface of the middle hemisphere 402. Through the sliding cooperation between the limiting groove 4021 and the ball pair constraint ridge 4011, the middle hemisphere 402 can only swing up and down in the vertical plane to adjust its posture, and within the entire swing range, the plane of the middle hemisphere 402 is tilted upward, and when it swings down to the extreme position, the plane of the middle hemisphere 402 can reach a vertical state at most.

[0049] After the clamped object is released, in order to realize the automatic reset of the middle hemisphere 402 in the ball support 401, the middle hemisphere 402 and the ball support 401 are connected by a reset mechanism. In combination with the specific structure, considering the compactness of the structure and the difficulty of ball assembly, in this embodiment, the reset mechanism preferably adopts a spring structure. Specifically, a notch 4013 is provided in the middle position of the symmetrical center plane of the ball support 401, and a first hanging rod 405 is provided at the top of the notch 4013, and a first reset spring 404 is hung on the first hanging rod 405. A second ball joint concave surface 4023 is provided in the lateral plane of the middle hemisphere 402, and three through holes 4022 are provided at the top center of the spherical surface of the middle hemisphere 402, which are connected to the second ball joint concave surface 4023, and a second hanging rod 407 is provided in each through hole 4022. The other end of the first return spring 404 is connected to a second hanging rod 407 in a through hole 4022 at the top of the middle hemisphere 402. Figure 9As shown. Thus, when the middle hemisphere 402 flips downward within the ball support 401 due to an external force, the first return spring 404 is stretched and stores energy. After the external force is removed, the first return spring 404 contracts, pulling the middle hemisphere 402 upward and returning to its original position. Both the first and second hanging rods 405 and 407 utilize bolts. A horizontal bolt connection hole intersecting the top of the notch 4013 is defined in the middle of the sidewall of the ball support 401. A bolt connection hole intersecting the through hole 4022 is also defined on the spherical surface of the middle hemisphere 402. The first and second hanging rods 405 and 407 are respectively secured to the ball support 401 and the middle hemisphere 402 via threaded connections.

[0050] like Figure 10 and Figure 11 As shown, the terminal hemisphere 403 also has a hemispherical structure, that is, one side is a spherical surface and the other side is a circular plane. The radius of the spherical surface of the terminal hemisphere 403 is the same as the radius of the second ball joint concave surface 4023. Therefore, the spherical surface of the terminal hemisphere 403 can be flexibly fitted with the second ball joint concave surface 4023 to achieve a ball-pair connection. After contacting the grasped object, the circular plane of the terminal hemisphere 403 is squeezed and automatically fits with the surface of the grasped object to form a tangent plane. The circular planes of multiple terminal hemispheres 403 simultaneously fit with multiple clamping points of the grasped object, and the two clamping claw units 4 on both sides cooperate to achieve a close clamping of the object. The terminal hemisphere 403 can be arbitrarily rotated and adjusted within the middle hemisphere 402 to adapt to the surface of the grasped object, thereby achieving a high degree of adaptability.

[0051] After the clamped object is released, in order to realize the automatic reset of the end hemisphere 403 in the middle hemisphere 402, the end hemisphere 403 and the middle hemisphere 402 are also connected by a reset mechanism. Similarly, the reset mechanism here also adopts a spring mechanism. Specifically, a sink groove 4031 is provided in the center of the spherical surface of the end hemisphere 403, and a bolt connection hole intersecting with the sink groove 4031 is provided in the spherical surface, and a third hanging rod 408 (also using bolts) is threadedly connected in the bolt connection hole. A second reset spring 406 is hung on the second hanging rod 407 in each through hole 4022, and the other end of the second reset spring 406 is connected to the center of the spherical surface of the corresponding end hemisphere 403, as shown in FIG. Figure 12 Similarly, when the end hemisphere 403 is flipped to one side in the middle hemisphere 402 due to an external force, the second return spring 406 is stretched and stores energy; after the external force is eliminated, the second return spring 406 contracts and pulls the middle hemisphere 402 to flip in the opposite direction and return to its original position.

[0052] The moving pair transmission unit 3 includes two sets of moving pairs, which are used to drive the two sets of clamping jaw units 4 to move closer to or away from each other synchronously to complete the opening and closing action. Figure 13As shown, in this embodiment, the moving sub-transmission unit 3 includes an upper guide rail group 305 and a lower guide rail group 306 arranged on the support frame 1. The upper guide rail group 305 and the lower guide rail group 306 are arranged in parallel and each consists of two cylindrical guide rails. The cylindrical guide rails are arranged horizontally, and the two ends are fixedly connected to the guide rail support 102. For the convenience of description, the four cylindrical guide rails are respectively referred to as the front upper guide rail, the rear upper guide rail, the front lower guide rail and the rear lower guide rail (corresponding to Figure 13 (a, b, c, d in the figure). One set of movable pairs consists of a first slider 301, a fourth slider 304, and a first connecting rod 307. The first slider 301 is movably mounted on the right end of the front upper guide rail via a linear bearing, while the fourth slider 304 is movably mounted on the left ends of the front lower guide rail and the rear lower guide rail via linear bearings, respectively. Articulated seats are provided at the bottom end of the first slider 301 and the top end of the fourth slider 304, respectively. Both ends of the first connecting rod 307 are connected to the articulated seats via bolt assemblies. Since the vertical distance between the upper guide rail group 305 and the lower guide rail group 306 is fixed, the relative positions of the first slider 301 and the fourth slider 304 remain unchanged during the horizontal movement. The first connecting rod 307 is used to hinge the two sliders for easy replacement and assembly. By replacing the first connecting rod 307 of different lengths, the horizontal spacing between the first slider 301 and the fourth slider 304 can be adjusted accordingly, thereby adjusting the overall moving stroke range of the moving pair on the upper guide rail group 305 and the lower guide rail group 306, that is, the horizontal spacing between the sliders increases, the horizontal moving stroke range of the moving pair becomes smaller, and the size range of objects that can be clamped by the two groups of clamping jaw units 4 becomes smaller; conversely, the horizontal spacing between the sliders decreases, the horizontal moving stroke range of the moving pair becomes larger, and the size range of objects that can be clamped by the two groups of clamping jaw units 4 becomes larger.

[0053] The other set of moving pairs consists of a second slider 302, a third slider 303, and a second connecting rod 308. The second slider 302 is movably mounted on the left end of the rear upper guide rail via a linear bearing, while the third slider 303 is movably mounted on the right ends of the front lower guide rail and the rear lower guide rail, respectively, via linear bearings. Articulated seats are provided at the bottom end of the second slider 302 and the top end of the third slider 303, respectively. Both ends of the second connecting rod 308 are connected to the articulated seats via bolt assemblies. In this embodiment, the two moving pairs are centrally symmetrically distributed between the upper guide rail assembly 305 and the lower guide rail assembly 306 when viewed from above.

[0054] Two groups of clamping jaw units 4 are respectively arranged opposite each other on the left and right sides of the support frame 1. Among them, the top frame of the ball-joint support 401 on the left side is sleeved on the outer side of the left end of the support base 101 and the guide rail group, and its side walls are fixedly connected to the side walls of the fourth slider 304 by screws. To improve its operational stability, a first auxiliary slider 3010 is also provided at the left end of the front upper guide rail. The first auxiliary slider 3010 is slidably sleeved on the front upper guide rail through a linear bearing and is located directly above the fourth slider 304. The front side wall of the ball-joint support 401 on the left side is fixedly connected to the side wall of the first auxiliary slider 3010 by screws. Similarly, the top frame of the ball-joint support 401 on the right side is sleeved on the outer side of the right end of the support base 101 and the guide rail group, and its side walls are fixedly connected to the side walls of the third slider 303 by screws. In order to improve its operating stability, a second auxiliary slider 3011 is also provided at the right end of the rear upper guide rail. The second auxiliary slider 3011 is slidably mounted on the rear upper guide rail through a linear bearing and is located directly above the third slider 303. The rear side wall of the right ball joint support 401 is fixedly connected to the side wall of the second auxiliary slider 3011 by screws.

[0055] The drive unit 2 is the power part of the entire rope-driven robot gripper. Figure 15 As shown, the drive unit 2 includes a servo support 201 fixedly mounted on the support frame 1, a servo 202 fixedly mounted on the servo support 201, and a capstan 203 rotatably mounted within the servo support 201 and transmission-connected to the output shaft of the servo 202. The servo support 201 is fixedly mounted in the middle of the top surface of the support base 101, with four guide rails extending through the servo support 201. The servo 202 is fixedly mounted on the top of the servo support 201, ensuring symmetrical mass distribution on the left and right sides of the rope-driven robot gripper. A robotic arm adapter 6 is fixedly mounted on the side of the servo support 201 via screws to facilitate connection to the positioning end of the external robot's actuator structure.

[0056] To simultaneously drive the two sets of movable pairs to move independently and synchronously, the cylindrical surface of the capstan 203 adopts a spiral structure with two heads, around which are wound two strands of rope 204 with the same rotation direction and a phase difference of 180 degrees. The midpoint of the length of each strand of rope 204 is fixedly connected to the axial center position of the outer cylindrical surface of the capstan 203. The two ends of one strand of rope 204 are respectively connected to the first slider 301 and the fourth slider 304, while the two ends of the other strand of rope 204 are respectively connected to the two ends of the second slider 302 and the third slider 303. In this way, the circular motion output by the servo 202 is ultimately converted into the opposite and synchronous linear motion of the two sets of gripper units 4 through the capstan 230 and the movable pairs. There is a kinematic coupling relationship between the two movable pairs. In order to coordinate the movement between the two movable pairs, the strands 204 need to be fixed in a specific order to ensure the centering of the movable pairs on both sides. Therefore, the two ropes 204 are wound around the capstan 203 in the following manner: first, the two ropes 204 are passed through the center hole of the capstan 203, the ropes 204 are folded in half to balance the length of the windings on both sides, and then the single-sided portion of the ropes 204 is wound in a spiral direction, with the two ropes 204 on the same side (upper or lower) of the capstan 203 having a 180° phase difference, and each rope 204 having the same number of turns wound around the upper and lower sides of the center hole of the capstan 203. The two moving pairs are fixed to the extreme positions on both sides to ensure that the two sides are symmetrical. At this time, the ends of the ropes 204 are passed through the corresponding lockers 309, tightened, and fixed.

[0057] Preferably, Figure 16 As shown, to ensure the rope length remains constant during rope actuation, the moving pair features locking devices 309 rotatably mounted on each end of the first and second connecting rods 307 and 308. The four ends of the two strands of rope 204 are connected to corresponding locking devices 309. The locking blocks of these locking devices 309 have a U-shaped cross-section and slide underneath the ends of the first and second connecting rods 307 and 308, facilitating adjustment of their fixed position to ensure that the inclination angle of the rope 204 matches the helical rise angle of the capstan 203, allowing for smooth winding of the rope 204 around the capstan 203. Threaded holes are defined in the sidewalls of the locking blocks, into which set screws are threaded. The locking screws engage the sides of the first and second connecting rods 307 and 308, securing the locking blocks to the connecting rods. The locking block has a through-hole for the end of the rope 204 to pass through. A locking bolt is provided at the bottom of the locking block. The end of the rope 204 passes through the through-hole and is fixedly connected to the nut of the locking bolt (a through-hole is provided here for binding by tying a knot). By rotating the locking bolt, the end of the rope 204 is wrapped around the locking bolt, thereby tightening and fixing the free end of the rope 204. A locking nut is provided on the locking bolt to prevent the locking bolt from loosening.

[0058] Furthermore, to achieve stroke control during the opening and closing of the moving pair and to control the reset position of the gripper, position detectors 5 are respectively installed in the guide rail supports 102 at both ends, and detector trigger mechanisms 501 that match the two position detectors 5 are respectively installed on the first slider 301 and the fourth slider 304. In this embodiment, the position detectors 5 are photoelectric switches, and the detector trigger mechanisms 501 are convex structures supported by metal sheets. Take the motion control of the left gripper unit 4 as an example: when the moving pair drives the left gripper unit 4 to move to the left (corresponding to the opening process of the gripper), the detector trigger mechanism 501 set on the top of the fourth slider 304 reaches the trigger position of the positioning detector 5 at the left end, and the positioning detector 5 controls the servo 202 to stop rotating through the robot control system. At this time, the horizontal distance between the two gripper units 4 is the largest, and the opening degree of the gripper reaches the maximum; when the moving pair drives the left gripper unit 4 to move to the left (corresponding to the opening process of the gripper), the detector trigger mechanism 501 on the top of the fourth slider 304 reaches the trigger position of the positioning detector 5, and the positioning detector 5 controls the servo 202 to stop rotating through the robot control system. At this time, the horizontal distance between the two gripper units 4 is the largest, and the opening degree of the gripper reaches the maximum. When the moving pair drives the left gripper unit 4 to move to the right (corresponding to the clamping process of the gripper), the detector trigger mechanism 501 set on the side of the first slider 301 reaches the trigger position of the positioning detector 5 at the right end, and the positioning detector 5 controls the servo 202 to stop rotating through the robot control system. At this time, the horizontal distance between the two gripper units 4 is the largest, and the opening degree of the gripper reaches the maximum; when the moving pair drives the left gripper unit 4 to move to the left (corresponding to the opening process of the gripper), the detector trigger mechanism 501 set on the top of the fourth slider 304 reaches the trigger position of the positioning detector 5 at the right end, and the positioning detector 5 controls the servo 202 to stop rotating through the robot control system. At this time, the horizontal distance between the two gripper units 4 is the smallest and no collision occurs, and the clamping degree of the gripper reaches the maximum.

[0059] Because the two sets of moving pairs are centrally symmetrically distributed around the axis of the capstan 203 when viewed from above, to enhance the reliability of positioning detection and the structural commonality between components, the second slider 302 adopts the same structure as the first slider 301, and the third slider 303 adopts the same structure as the fourth slider 304. That is, the second and third sliders 302 and 303 are also equipped with the same detector trigger mechanism 501. This allows the positioning detectors 5 on both sides to be triggered simultaneously during the gripper's opening or clamping process, achieving parallel control to stop the servo 202 and ensure control reliability.

[0060] The following is a theoretical calculation of the contact force of the gripper:

[0061] First, take the two-layer structure as an example. Figure 17 As shown, for the convenience of description, the hemispheres of different radius levels are named respectively as the first-level spherical pair (corresponding to the hemisphere with the largest radius) and the second-level spherical pair (corresponding to the three hemispheres with smaller radii).

[0062] The force analysis of the three secondary ball pairs is carried out. Because the equivalent friction coefficient of the ball pair is small enough, in order to simplify the analysis, the friction ball radius is considered to be 0 (ignoring the friction force. In fact, as the ball pair enters the fitting state and the clamping force increases, the dominant force between the ball pairs is the extrusion force). Therefore, Figure 17 As shown: The left reaction force F of the ball pair can be considered L Through the geometric center of the spherical pair, with the direction of the force as the negative direction of the x-axis and the z-axis passing through the geometric center of one of the sub-level spherical pairs, a spatial rectangular coordinate system o-xyz is established for force analysis. are the forces acting on the three secondary ball pair enveloping clamping points, are the vertical distances between the forces acting on the clamping points of the three secondary spherical pairs and the geometric centers of the three secondary spherical pairs, i.e., the origin of the spatial rectangular coordinate system o-xyz. According to the equilibrium conditions of the spatial force system, we have the formula:

[0063]

[0064] Pick The respective unit direction vectors are And let the angles between each direction vector and the x-axis, y-axis and z-axis be defined as β, α, γ respectively, and distinguished by subscripts 1, 2, and 3. The above formula (1) can be changed to:

[0065]

[0066] There are additional conditions:

[0067]

[0068] From equation (2), we can find F R1 、F R2 、F R3 The expressions are:

[0069]

[0070] Where F L It can be measured by sensors (such as adding a potential sensor to measure the pressure in the normal direction of the contact surface). The direction vector of the contact surface of each ball pair can be measured by sensors. The torque balance equation in equation group (2) can be used as a test equation for the error size of the calculation result (4).

[0071] If the envelope effect is to be improved, a method of connecting multiple sets of three-ball pairs in series can be selected, and a set of smaller three-ball pairs can be added to each ball pair to achieve a more subtle envelope of the local area. The advantage of this design layout is that each time the envelope effect is enhanced, the final contact force can be effectively reduced. Similarly, the above solution can be extended to more complex multi-level ball pair combinations. For example, a three-level structure Figure 18 Similarly, the hemispheres are classified according to their radius levels as first-level spherical pairs (corresponding to the hemisphere with the largest radius), second-level spherical pairs (corresponding to the three hemispheres with medium radius), and third-level spherical pairs (corresponding to the nine hemispheres with the smallest radius).

[0072] We can first decouple the secondary ball pair as above and obtain F R1 、F R2 、F R3 , then decouple the three-stage ball pair and deduce the contact force F Rij The calculation formula (5) is used.

[0073]

[0074] Among them, i is the sub-sequence number of the three-level ball group, j is the sub-sequence number of the ball in the group, such as Figure 18 Note: If only the Figure 17 The simple three-ball contact force in the equation (4) can be calculated. Figure 18 The contact force of the three-ball pair in the combination needs to use formulas (4) and (5).

[0075] Estimated envelope shape of the gripper:

[0076] The multi-stage ball-pair flexible gripper mechanism in this paper is based on the mathematical idea of plane fitting surface. The envelope space equation can be deduced from the designed mechanism principle. Figure 18 The specific calculation method is as follows:

[0077] Assume that the position vector of the geometric center position o of the first-level ball pair relative to the geometric center of the gripper is Then the geometric center position vector of the jth contact surface in the i-th group is: This is the contact point position vector; assuming that the normal direction vector of the first-level ball pair is The direction vector of the secondary ball pair relative to the primary ball pair is measured by the sensor The direction vector of the third ball pair relative to the second ball pair Then the normal vector of the j-th contact surface in the i-th group is: This is the direction information of the contact point ( The direction of the force on each ball pair The same direction, such as Figure 18As shown). The spatial equation f(x,y,z) of the contact surface is established based on the position and direction information of the contact point:

[0078]

[0079] According to equation (6), a total of 18 fitting planes can be established, which can be plotted in drawing software and compared with the outline of the grasped object. The advantage of this method is that it can preliminarily determine the approximate outline of the grasped object without the need for a camera, and has good application potential in classification scenarios and places where it is inconvenient to install a camera. If a simple three-ball pair can only fit 6 planes, it cannot well restore the true outline. Therefore, the fitting plane equations of a simple three-ball pair will not be discussed here. As with contact force calculation, as long as the posture information of each ball pair is measured by a sensor, the spatial equation of the plane can be obtained through equation (6). Furthermore, the envelope shape of all fitting planes can be restored in drawing software.

[0080] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0081] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention's description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A rope-driven robot gripper based on a parallel flexible structure, characterized by: The invention comprises a support frame (1), a driving unit (2) fixedly arranged on the support frame (1), a mobile sub-transmission unit (3) fixedly arranged on the support frame (1) and transmission-connected to the driving unit (2), and two groups of clamping claw units (4) relatively fixedly arranged on power output ends on both sides of the mobile sub-transmission unit (3); the driving unit (2) drives the two groups of clamping claw units (4) to move toward or away from each other synchronously through the mobile sub-transmission unit (3); The clamping claw unit (4) comprises a horizontally movable ball support (401), an intermediate hemisphere (402) spherically hinged in the side of the ball support (401) and capable of swinging up and down, and at least three terminal hemispheres (403) spherically hinged in the lateral plane of the intermediate hemisphere (402). Each terminal hemisphere (403) is connected to the intermediate hemisphere (402) and the intermediate hemisphere (402) is connected to the ball support (401) via a reset mechanism.

2. The cable-driven robot gripper based on a parallel flexible structure according to claim 1, characterized in that: A first ball joint concave surface (4011) is provided in the side surface of the ball joint support (401), and at least one ball joint constraint convex strip (4012) is provided on the first ball joint concave surface. The side surface of the ball joint constraint convex strip (4012) is parallel to the symmetry center plane of the ball joint support (401). The spherical surface of the middle hemisphere (402) is movably fitted with the first ball joint concave surface (4011), and a limiting sliding groove (4021) coupled and matched with the ball joint constraint convex strip (4011) is provided on the spherical surface of the middle hemisphere (402).

3. The cable-driven robot gripper based on a parallel flexible structure according to claim 2, characterized in that: The top of the spherical center of the middle hemisphere (402) is connected to a first return spring (404), and the other end of the first return spring (404) is connected to the middle of the ball auxiliary support (401).

4. The cable-driven robot gripper based on a parallel flexible structure according to claim 1, characterized in that: A second ball-joint concave surface (4023) is provided in the side plane of the middle hemisphere (402), and the spherical surface of the end hemisphere (403) is movably fitted with the second ball-joint concave surface (4023).

5. The cable-driven robot gripper based on a parallel flexible structure according to claim 4, characterized in that: A through hole (4022) is provided on the spherical surface of the middle hemisphere (402) and is communicated with the second ball joint concave surface (4023). A hanging rod is provided in the through hole, and a second return spring (406) is hung on the hanging rod. The other end of the second return spring (406) is connected to the spherical center of the end hemisphere (403).

6. The cable-driven robot gripper based on a parallel flexible structure according to any one of claims 1 to 5, characterized in that: The movable sub-transmission unit (3) comprises an upper guide rail group (305) and a lower guide rail group (306) arranged on the support frame (1); a first slider (301) and a second slider (302) are respectively slidably sleeved on both ends of the upper guide rail group (305); a third slider (303) located below the first slider (301) and a fourth slider (304) located below the second slider (302) are respectively slidably sleeved on the lower guide rail group (306); the first slider (301) and the fourth slider (304) are connected via a first connecting rod (307); the second slider (302) and the third slider (303) are connected via a second connecting rod (308); and the ball sub-supports (401) of the two groups of clamping jaw units (4) are respectively fixedly connected to the first slider (301) and the second slider (302).

7. The cable-driven robot gripper based on a parallel flexible structure according to claim 6, characterized in that: The drive unit (2) comprises a steering gear support (201) fixedly arranged on the support frame (1), a steering gear (202) fixedly mounted on the steering gear support (201), and a capstan (203) rotatably mounted in the steering gear support (201) and transmission-connected to the output shaft end of the steering gear (202); two strands of twisted rope (204) with the same rotation direction and a phase difference of 180° are wound around the capstan (203); two ends of one strand of twisted rope (204) are respectively connected to the first slider (301) and the fourth slider (304); and two ends of the other strand of twisted rope (204) are respectively connected to the two ends of the second slider (302) and the third slider (303).

8. The cable-driven robot gripper based on a parallel flexible structure according to claim 7, characterized in that: The two ends of the first connecting rod (307) and the second connecting rod (308) are respectively rotatably provided with lockers (309), and the four ends of the two strands of twisted rope (204) are respectively connected to the four lockers (309).

9. The cable-driven robot gripper based on a parallel flexible structure according to claim 7 or 8, characterized in that: A mechanical arm adapter (6) is fixedly provided on the side of the steering gear support (201).

10. The cable-driven robot gripper based on a parallel flexible structure according to claim 6, characterized in that: Positioning detectors (5) are respectively provided at both end portions of the support frame (1), and detector triggering mechanisms (501) matching the two positioning detectors (5) are respectively provided on the first slider (301) and the fourth slider (304).

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