Under-actuated manipulator based on hybrid transmission of gear and tendon rope mechanism

Abstract

The invention discloses an under-actuated manipulator based on hybrid transmission of a gear and a tendon rope mechanism, and relates to the technical field of manipulators. One end of the middle connecting mechanism is provided with the floating platform under-actuated mechanism, and the other end of the middle connecting mechanism is provided with three identical finger mechanisms; the floating platform under-actuated mechanism comprises a tendon rope lifting device, a floating platform, a tendon rope winding wheel and a driving motor, a tendon rope penetrates through the lifting device to be connected with the floating platform and then reaches the finger mechanism, and synchronous control over the finger mechanism is achieved; the finger mechanism sequentially comprises a wrist joint, an MP joint and a near-end knuckle and is driven by a single motor to achieve rotary motion. The near-end knuckles are sequentially connected with the DIP joints, the middle knuckles, the PIP joints and the far-end knuckles in series, transmission is achieved through tendon ropes, flexible belts are installed on the inner sides of the near-end knuckles, and self-adaptive grabbing and gripping are achieved. Meanwhile, a torsional spring and a limiting device are arranged at a joint, so that resetting and self-locking functions are realized. The under-actuated manipulator is high in adaptive capacity, high in flexibility and good in stability.

Description

Technical Field

[0001] The present invention relates to the technical field of manipulators, and specifically to an underactuated manipulator based on a hybrid drive of a gear and tendon-cable mechanism. Background Technique

[0002] With the rapid development of modern society and technology, robotics has become a frontier technology that is widely emphasized by countries around the world. It has been widely developed and applied in many fields such as industrial production, ocean development, space development, national defense and military, and life services. As the end effector of a robot, which is the operating tool of the robot, it can provide the robot with more precise and stable grasping ability, expand and extend the application range of the robot. Therefore, its importance has become more prominent with the wide application of robots.

[0003] Generally, the end effectors of robots can be classified into the following two types: special-purpose end effectors and general-purpose end effectors. The special-purpose manipulator is characterized by simple manufacturing, easy control, large grasping force, etc. However, it has a strong pertinence to the grasped object, and its driving method is mostly pneumatic drive, which is suitable for occasions with more hand-opening and hand-closing applications. The general-purpose manipulator mostly has multi-fingered dexterous hands. In this type of manipulator, each joint is usually independently driven and controlled, and the joints mostly adopt a basically series structure. In addition, each degree of freedom of the manipulator is mostly equipped with a driver and a measurement sensor. This method results in a large number of drivers accumulating on the multi-fingered dexterous hand, which further makes the control strategy more complex and the reliability relatively poor. In the further development of multi-fingered dexterous hands, underactuated grippers emerged as the times require. To sum up, with the development of technology and the progress of society, a manipulator that is universal, intelligent, and has strong adaptability to tasks in complex and harsh environments is indispensable. However, the existing special-purpose manipulators are difficult to meet the requirements, while the general-purpose fully-driven multi-fingered dexterous manipulators have disadvantages such as complex control and relatively poor reliability. Therefore, we propose an underactuated manipulator based on a hybrid drive of a gear and tendon-cable mechanism. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the existing defects and provide an underactuated manipulator based on a hybrid drive of a gear and tendon-cable mechanism, which has strong adaptability, good stability, and high flexibility, and breaks through the weaknesses of complex structure, poor reliability, low universality, and poor adaptability to tasks in complex and harsh environments of special-purpose and general-purpose manipulators, and can effectively solve the problems in the background technique.

[0005] To achieve the above object, the present invention provides the following technical solution: An underactuated manipulator based on a hybrid drive of a gear and tendon-cable mechanism, comprising: The intermediate connection mechanism includes an L-shaped fixing frame, base frame 1, base frame 2, and copper posts. Base frame 1 and base frame 2 are fixedly connected by copper posts, and the L-shaped fixing frame is fixedly connected to base frame 1; The underactuated mechanism of the floating platform includes a tendon rope lifting device fixing frame, a tendon rope rising guide tube, a tendon rope winding wheel, a tendon rope driving motor, a floating platform, and copper posts. The tendon rope lifting device fixing frame is installed on base frame 2, and a tendon rope rising guide tube is threadedly connected to its center. The floating platform is sleeved on the tendon rope rising guide tube; A tendon rope driving motor is independently installed on one side of the tendon rope lifting device fixing frame. The lower end of the motor is connected to base frame 2 through a copper post, and the upper end is connected to the tendon rope winding wheel. The tendon rope starts from the tendon rope winding wheel, passes above the tendon rope lifting device fixing frame, passes through the tendon rope rising guide tube, and then is connected to the floating platform; Finger mechanism: It includes a wrist joint, an MP joint, a proximal phalanx, a proximal phalanx fixing frame, a DIP joint, an intermediate phalanx, a PIP joint, and a distal phalanx. One end of the wrist joint is fixed on base frame 1 and is connected to a wrist joint rotation driving motor fixed on base frame 2 through a rotating shaft. The other end of the wrist joint is fixed on the L-shaped bracket. One end of the MP joint is connected to the MP joint driving motor, and the other end is connected to the front end of the proximal phalanx. There is a round shaft near the middle and lower part of the proximal phalanx, and it is fixedly connected to the L-shaped bracket through the round shaft. The end of the proximal phalanx is sequentially connected in series with the PIP joint, the intermediate phalanx, the DIP joint, and the distal phalanx.

[0006] The finger mechanism serves as the main body of the adaptive manipulator for grasping and pinching objects. The wrist joint is equipped with a driving motor to achieve rotational freedom. To achieve the self-locking function, precise pinching, and no-lag response, the proximal phalanx uses a gear transmission as the transmission scheme and utilizes the characteristics of worm and worm gear transmission, and is directly controlled by a motor. To achieve the action process of smoothly switching between the pinching and grasping states, which simulates the freedom and smoothness of the human hand, the intermediate phalanx and the distal phalanx are driven by the contraction of the tendon rope combined with a torsion spring. The torsion spring is installed at the DIP and PIP joints and is provided with a limiting device. A pulley is provided in the middle of the intermediate phalanx to connect the tendon rope, and a straight groove is provided at the distal end. The distal phalanx is connected to the intermediate phalanx through the straight groove, thereby improving the flexibility and adaptability of the distal phalanx. The finger design uses a rigid structure on the outside as the grasping drive and stable support, and a tendon rope and a flexible belt structure on the inside as the grasping interaction, realizing the pinching of the fingertip part and the flexible contact grasping with self-adaptation and uniform pressure distribution on the envelope surface on the inner side of the finger.

[0007] Furthermore, the MP joint includes an MP joint fixed motor, a proximal phalanx bracket, and a bearing. The MP joint of the finger is fixed on the proximal phalanx bracket, and the bracket is further connected to the L-shaped fixing frame. Furthermore, the L-shaped fixing frame is fixedly connected to base frame 1, and this connection part bears the main load instead of the wrist joint rotating shaft.

[0008] Furthermore, the DIP joint includes an arc-shaped adjustable limit device, a torsion spring, and a bearing. The torsion spring enables the finger mechanism to return to its initial position after the grasping task is completed, and the arc-shaped adjustable limit device is used to limit the torsion spring.

[0009] Furthermore, the middle phalanx includes a linear groove design, a limit design, and a tendon pulley design. The distal phalanx is slidably connected to the middle phalanx through the linear groove to achieve flexible conversion between the pinching and grasping states of the manipulator. The limit design includes the back of the phalanx of the distal phalanx and the protrusion at the end of the middle phalanx, and a pulley is installed on the middle phalanx to adjust the direction of the tendon.

[0010] The floating platform underactuated mechanism is beneficial to simplifying the structure of the manipulator. This manipulator contains 3 completely identical fingers. The floating platform is simultaneously connected to the three finger mechanisms through tendons to achieve synchronous control of the finger mechanisms, reduce the number of actuators. At the same time, the floating platform and the tendon rising guide tube protect the tendon, making the manipulator more adaptable to work in complex and extreme environments.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: This underactuated manipulator based on the hybrid drive of the gear and tendon mechanism has the following advantages: 1. High adaptability and flexibility. The finger mechanism of this manipulator designed based on the underactuated principle adopts a hybrid drive method of gears and tendons (mainly tendons), has the interaction ability of outer rigidity and inner flexibility, and realizes stable and rapid adaptive grasping of the object to be clamped. At the same time, the two-degree-of-freedom dexterity design of the distal phalanx enables the manipulator to have the ability to switch between fingertip pinching and envelope grasping.

[0012] 2. High stability. The finger mechanism and the floating platform underactuated mechanism of this manipulator adopt the underactuated method, reduce the number of driving components, and the driving system and the transmission system are installed separately for long-distance transmission. In environments with strong radiation, microgravity, and large temperature differences, such an installation method is beneficial to the shielding and protection of the driving system, enabling the manipulator to work flexibly in complex and extreme environments.

[0013] 3. High reliability. The main execution part of this manipulator adopts a mechanical structure, and the design based on the underactuated principle greatly reduces the driving components, reduces the probability of electronic component failures, and increases the reliability of the manipulator's work. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the overall structure of the underactuated manipulator based on the hybrid drive of the gear and tendon mechanism; Figure 2 It is a schematic diagram of the floating platform underactuated mechanism of the underactuated manipulator based on the hybrid drive of the gear and tendon mechanism; Figure 3Schematic diagram of the intermediate connection mechanism of an underactuated manipulator based on the hybrid drive of a gear and tendon-cable mechanism; Figure 4 Schematic diagram of the finger mechanism of an underactuated manipulator based on the hybrid drive of a gear and tendon-cable mechanism; Figure 5 Schematic diagram of the exploded finger mechanism of an underactuated manipulator based on the hybrid drive of a gear and tendon-cable mechanism; In the figure: 1 floating platform underactuated mechanism, 11 tendon-cable winding wheel, 12 tendon-cable drive motor, 13 copper column, 14 fixed bracket for tendon-cable lifting device, 15 tendon-cable rising conduit, 16 floating platform, 2 intermediate connection mechanism, 21 base frame 1, 22 copper column, 23 base frame 2, 24 L-shaped fixed bracket, 31 wrist joint rotation drive motor, 32 wrist joint rotation shaft, 33 MP joint drive motor, 34 MP joint, 341 proximal phalanx bracket, 342 bearing, 343 rotation shaft, 35 proximal phalanx, 36 limiting device, 361 arc-shaped adjustable limiting device, 362 torsion spring, 37 PIP joint, 371 rolling shaft, 38 middle phalanx, 381 pulley, 39 tendon-cable, 40 DIP joint, 41 distal phalanx. Specific implementation manners

[0015] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0016] Embodiment 1, please refer to Figures 1 to 4 , this embodiment provides a technical solution: an underactuated manipulator based on the hybrid drive of a gear and tendon-cable mechanism, including a floating platform underactuated mechanism 1, an intermediate connection mechanism 2, and a finger mechanism 3.

[0017] The floating platform underactuated mechanism 1 includes a fixed bracket 14 for the tendon-cable lifting device, a tendon-cable rising guide tube 15, a tendon-cable winding wheel 11, a tendon-cable drive motor 12, a floating platform 16, and a copper column 13; the fixed bracket 14 for the tendon-cable lifting device is installed on the base frame 2 by threads, and the tendon-cable rising guide tube 15 is fixedly installed in the middle by threads. The floating platform 15 is sleeved on the guide tube and can slide up and down. The tendon-cable drive motor 12 and the tendon-cable winding wheel 11 are fixedly installed on the base frame 2 by the copper column 13 and are close to the fixed bracket 14 for the tendon-cable lifting device. The tendon-cable winding wheel 11 winds the tendon-cable and guides the tendon-cable to the tendon-cable guide tube 15, and passes through the middle hole of the floating platform 16 through the tendon-cable guide tube 15, so as to realize the control of the up and down movement of the floating platform by the tendon-cable winding wheel 11 through taking in and paying out the tendon-cable.

[0018] The intermediate connection mechanism 2 includes an L-shaped fixing bracket 24, a base bracket 1 21, a base bracket 2 23, and copper columns 22. The base bracket 2 23 is used to connect the upper floating platform underactuated mechanism 1 and provide space for installing the wrist joint rotation drive motor 31. The base bracket 1 21 is threadedly connected to the L-shaped fixing bracket 24 to connect the lower finger mechanism, and the base bracket 1 21 and the base bracket 2 23 are connected and fixed by the copper columns 22.

[0019] There are a total of 3 finger mechanisms arranged in a 120° circle around the base bracket 1, and they include a wrist joint, an MP joint 34, a proximal phalanx 35, a proximal phalanx bracket 341, a DIP joint 40, an intermediate phalanx 38, a PIP joint 37, and a distal phalanx 41.

[0020] The wrist joint includes a wrist joint rotation drive motor 31 and a wrist joint rotation shaft 32. One end of the wrist joint rotation shaft 32 is connected to its independent drive motor 31 through a coupling, and the other end is connected to the proximal phalanx bracket 341. The motor drives the rotation shaft to provide the finger mechanism 3 with the degree of freedom of rotation around the axis.

[0021] The MP joint 33 includes an MP joint drive motor 33, a proximal phalanx bracket 341, and a bearing 342. The MP joint 34 of the finger is fixed on the proximal phalanx bracket. The proximal phalanx bracket 341 is also connected to the L-shaped fixing bracket 24, and further the L-shaped fixing bracket 24 is fixedly connected to the base bracket 1 21. This connection part bears the main load instead of the wrist joint rotation shaft. At the same time, the MP joint 34 is directly controlled by the motor. Thus, it is determined that the proximal phalanx 35 uses gear transmission as the transmission scheme and utilizes the characteristics of the worm and worm gear reducer to achieve the self-locking function, precise pinching, and no lag response.

[0022] For the second implementation case, please refer to Figure 5 , this embodiment provides a technical solution: an underactuated manipulator based on the hybrid drive of a gear and tendon-cable mechanism. This embodiment is a further explanatory description of the structure of the first embodiment.

[0023] The PIP joint 37 of the finger mechanism includes a torsion spring 362, an arc-shaped adjustable limit device 361, and a rotary shaft 343. To ensure that it is in an open state before grasping and returns to its initial position after the grasping task is completed, a torsion spring 362 is installed at its joint. At the same time, a limit device is designed: an arc-shaped adjustable limit device 361; one end of the middle phalanx 38 is connected in series with the PIP joint 37, and a linear groove is designed at one end to be connected in series with the distal phalanx. At the same time, a pulley 381 is designed on the middle phalanx 38 to plan the guiding of the tendon rope 39 and ensure the smooth movement of the tendon rope. The distal phalanx 41 is installed in the linear groove to have two degrees of freedom, namely, rotating around the DIP joint 40 and sliding along the linear groove, so that it can be transformed from a pinching state to a grasping state. At the same time, to ensure that the distal phalanx returns to its initial position after the grasping task is completed, a torsion spring is also designed at the DIP joint 40. At the same time, the limit between the distal phalanx and the middle phalanx is formed by the contact between the back of the phalanx of the distal phalanx and the protrusion at the end of the middle phalanx; the middle phalanx 38 and the distal phalanx 41 are driven by the tendon rope 39. The finger design uses a rigid structure on the outside as the grasping drive and stable support, and has a flexible contact grip on the inside with an adaptive and evenly distributed envelope surface pressure. At the same time, it is assisted by machine vision to judge the shape characteristics of the target object, and then adjust the grasping orientation and posture of the manipulator to automatically adapt to and fit the surface shape of the object to be grasped, realizing a non-destructive and reliable grasp; the tendon ropes 39 of the three finger mechanisms 3 arranged in a 120° circular arrangement pass through the base frame 121 and converge to the floating platform 16, so that the floating platform 16 can simultaneously control the opening and closing of the three finger mechanisms 3, reducing the number of drivers.

[0024] 1. Compared with the prior art, the underactuated manipulator based on the hybrid drive of the gear and tendon rope mechanism breaks through the problems that although the underactuated flexible manipulators at home and abroad can passively adapt to the surface shape of the grasped object, it is difficult to perfectly fit and the grasping force is uneven. An underactuated adaptive manipulator is innovatively designed, which can realize flexible contact and automatically adapt to fit the outer contour shape of the object to be grasped to grasp target objects of different shapes.

[0025] 2. Compared with the prior art, the finger mechanism of the underactuated manipulator of the present invention based on the hybrid drive of the gear and tendon rope mechanism adopts a bionic design, which is composed of a rotary wrist joint, a condylar MP joint, an intermediate PIP joint, and a terminal DIP joint. Driven by a hybrid of gears and tendon ropes, it has the ability to interact between rigidity on the outside and flexibility on the inside, and realizes the work in two states of adaptive envelope grasping and pinching.

[0026] 3. Compared with the prior art, the underactuated manipulator of the present invention based on the hybrid drive of the gear and tendon rope mechanism has a simple structure, few driving elements, and strong reliability, and can better adapt to complex working environments, and can achieve the goal of coordinating with humans to complete various complex and dangerous work tasks.

[0027] The present invention designs an underactuated manipulator based on the hybrid drive of a gear and tendon mechanism, which has the characteristics of a simple manipulator structure, few drive elements, and strong adaptability, aiming to flexibly, stably, and quickly grasp objects of different complex shapes. The underactuated fingers of this adaptive manipulator adopt a bionic design and are composed of a rotary wrist joint, a condylar MP joint, an intermediate PIP joint, and a terminal DIP joint. Driven by a hybrid drive of a gear and tendon, it has the interaction ability of outer rigidity and inner flexibility, and realizes adaptive enveloping grasping and pinching.

[0028] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device.

[0029] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An underactuated manipulator based on the hybrid drive of a gear and tendon-cable mechanism, characterized in that Comprising: An intermediate connection mechanism (1), including an L-shaped fixing bracket (24), a base bracket 1 (21), a base bracket 2 (23) and a copper column (22), wherein the base bracket 1 (21) and the base bracket 2 (23) are fixedly connected through the copper column (22), and the L-shaped fixing bracket (24) is fixedly connected to the base bracket 1 (21); A floating platform underactuated mechanism (2), including a tendon rope lifting device fixing bracket (14), a tendon rope rising guide tube (15), a tendon rope winding wheel (11), a tendon rope driving motor (12), a floating platform (16) and a copper column (15); A finger mechanism (3), including a wrist joint, an MP joint (34), a proximal phalanx (35), a proximal phalanx fixing bracket (34), a DIP joint (40), an intermediate phalanx (38), a PIP joint (37) and a distal phalanx (41).

2. The underactuated manipulator based on the hybrid drive of a gear and tendon-cable mechanism according to claim 1, wherein: The floating platform underactuated mechanism (1) includes a tendon rope lifting device fixing bracket (14), a tendon rope rising guide tube (15), a tendon rope winding wheel (11), a tendon rope driving motor (12), a floating platform (16) and a copper column (13); the tendon rope lifting device fixing bracket (14) is installed on the base bracket 2 through threads, and the tendon rope rising guide tube (15) is fixedly installed in the middle through threads. The floating platform (15) is sleeved on the guide tube and can slide up and down. The tendon rope driving motor (12) and the tendon rope winding wheel (11) are fixedly installed on the base bracket 2 through the copper column (13) and are close to the tendon rope lifting device fixing bracket (14). The tendon rope winding wheel (11) winds the tendon rope and guides the tendon rope to the tendon rope guide tube (15). The tendon rope passes through the middle hole of the floating platform (16) through the tendon rope guide tube (15) to realize the control of the floating platform; three tendon ropes are led out from the rear floating platform and are respectively transmitted to the three finger mechanisms. Pulleys are installed on the intermediate phalanges of the finger mechanisms to transmit the tendon ropes to the distal phalanges, realizing the synchronous control of the three finger mechanisms by the tendon ropes.

3. The under-actuated manipulator based on the hybrid drive of a gear and tendon-cable mechanism according to claim 1, wherein: The intermediate connection mechanism (2) includes an L-shaped fixing bracket (24), a base bracket 1 (21), a base bracket 2 (23) and a copper column (22). The base bracket 2 (23) is used to connect the upper floating platform underactuated mechanism (1) and provide space for installing the wrist joint rotation driving motor (31). The base bracket 1 (21) is threadedly connected to the L-shaped fixing bracket (24) to connect the lower finger mechanism, and the base bracket 1 (21) and the base bracket 2 (23) are connected and fixed through the copper column (22).

4. The underactuated manipulator based on the hybrid drive of the gear and tendon-cable mechanism according to claim 1, characterized in that: There are 3 finger mechanisms in total, arranged in a 120° circular arrangement around the base bracket 1, including a wrist joint, an MP joint (34), a proximal phalanx (35), a proximal phalanx bracket (341), a DIP joint (40), an intermediate phalanx (38), a PIP joint (37) and a distal phalanx (41).

5. The underactuated manipulator based on the hybrid drive of a gear and tendon-cable mechanism according to claim 4, characterized in that: The wrist joint includes a wrist joint rotation driving motor (31) and a wrist joint rotation shaft (32). One end of the wrist joint rotation shaft (32) is connected to its independent driving motor (31) through a coupling, and the other end is connected to the proximal phalanx bracket (341), providing the degree of freedom of rotation around the axis for the finger mechanism (3) by driving the rotation shaft with the motor.

6. The under-actuated manipulator based on the hybrid drive of a gear and tendon-cable mechanism according to claim 1, wherein: The described MP joint (33) includes an MP joint drive motor (33), a proximal phalanx bracket (341), and a bearing (342). The MP joint (34) of the finger is fixed to the proximal phalanx bracket. The proximal phalanx bracket (341) is further connected to the L-shaped fixing bracket (24), and then the L-shaped fixing bracket (24) is fixedly connected to the base frame 1 (21). This connection part replaces the wrist joint rotation axis to bear the main load. At the same time, the MP joint (34) is directly controlled by the motor. Thus, it is determined that the proximal phalanx (35) uses a gear drive as the transmission scheme and utilizes the characteristics of a worm and worm gear reducer to achieve the self-locking function, precise pinching, and non-lagging response.

7. The under-actuated manipulator based on the hybrid drive of a gear and tendon-cable mechanism according to claim 1, wherein: The described PIP joint (37) includes a torsion spring (362), an arc-shaped adjustable limit device (361), and a rotation axis (343). To ensure that it is in an open state before grasping and returns to its initial position after the grasping task is completed, a torsion spring (362) is installed at its joint. At the same time, a limit device is designed: an arc-shaped adjustable limit device (361). One end of the middle phalanx (38) is in series with the PIP joint (37), and the other end is designed with a straight groove in series with the distal phalanx. At the same time, the middle phalanx (38) is designed with a pulley (381) to plan the tendon rope (39) guide and ensure the smooth movement of the tendon rope. The distal phalanx (41) is installed in the straight groove to have two degrees of freedom, namely, rotation around the DIP joint (40) and sliding along the straight groove, so that it can be converted from the pinching state to the grasping state. At the same time, to ensure that the distal phalanx returns to its initial position after the grasping task is completed, a torsion spring is also designed at the DIP joint (40). At the same time, the limit between the distal phalanx and the middle phalanx is formed by the contact between the back of the phalanx of the distal phalanx and the protrusion at the end of the middle phalanx; the transmission between the middle phalanx (38) and the distal phalanx (41) is through the tendon rope (39). The finger design uses a rigid structure on the outside as the grasping drive and stable support, and has an adaptive and evenly distributed envelope surface pressure flexible contact grasping on the inside, and is assisted by machine vision to judge the shape characteristics of the target object, and then adjust the grasping orientation and posture of the manipulator, automatically adapt to and fit the surface shape of the object to be grasped, and achieve non-destructive and reliable grasping; the tendon ropes (39) of the three finger mechanisms (3) arranged in a 120° circular arrangement pass through the base frame 1 (21) and converge to the floating platform (16), so that the floating platform (16) can simultaneously control the opening and closing of the three finger mechanisms (3), reducing the number of drivers.

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