Foldable leg-type moving structure

Abstract

This invention discloses a foldable legged mobility structure comprising a torso and four leg modules. The four leg modules are respectively mounted on the bottom of the torso and are used to drive the torso's movement. The torso includes a first tetrahedral module, a second tetrahedral module, a third tetrahedral module, a fourth tetrahedral module, a fifth tetrahedral module, a sixth tetrahedral module, and a seventh tetrahedral module. Each leg module includes a first leg unit module, a second leg unit module, a third leg unit module, a fourth leg unit module, and three articulated motors. The first and second leg unit modules, the second and third leg unit modules, and the third and fourth leg unit modules are all connected via articulated motors. This invention features a simple overall structure, and its prone posture more closely resembles that of a real animal, effectively improving safety during task execution.

Description

Technical Field

[0001] This invention belongs to the field of mobile structure technology, and particularly relates to a foldable leg-type mobile structure. Background Technology

[0002] With social development and continuous advancements in science and technology, the robotics industry has also flourished, keeping pace with the times and giving rise to various types of mobile robots to meet societal demands. Quadruped robots, as a type of biomimetic robot, have become a focal point within the robotics industry. By mimicking the movement patterns of quadrupedal animals, they can walk and move on various complex terrains, thus enabling them to replace human labor in some hazardous work environments.

[0003] In existing technologies, quadruped robots typically use long, straight rods for their legs, and rotational drives are the primary method for movement. Furthermore, quadruped robots generally employ a configuration where the leg drive joint axes are parallel, while the hip drive joint axes are perpendicular to the leg drive joint axes; other angular arrangements are rarely used. Additionally, while the prone or kneeling posture is a gait used to demonstrate robot movement, most quadruped robots fail to integrate their legs naturally into their torso like real animals. This makes them easily identifiable during dangerous tasks, leading to mission failure. Summary of the Invention

[0004] To at least partially solve the technical problems existing in the prior art, the present invention provides a foldable leg-type moving structure.

[0005] The foldable leg-type mobility structure of the present invention includes a torso body and four leg modules, wherein the four leg modules are respectively installed at the bottom of the torso body for driving the torso body to move, wherein:

[0006] The main body of the torso includes a first tetrahedral module, a second tetrahedral module, a third tetrahedral module, a fourth tetrahedral module, a fifth tetrahedral module, a sixth tetrahedral module, and a seventh tetrahedral module. The first tetrahedral module is connected to the sixth tetrahedral module and the seventh tetrahedral module, the sixth tetrahedral module is connected to the second tetrahedral module and the third tetrahedral module, and the seventh tetrahedral module is connected to the fourth tetrahedral module and the fifth tetrahedral module.

[0007] The leg module includes a first leg unit module, a second leg unit module, a third leg unit module, a fourth leg unit module, and three joint motors. The first leg unit module is connected to the second leg unit module, the second leg unit module is connected to the third leg unit module, and the third leg unit module is connected to the fourth leg unit module through the joint motors.

[0008] Furthermore, in the above-mentioned foldable leg-type movable structure, the first regular tetrahedron module, the second regular tetrahedron module, the third regular tetrahedron module, the fourth regular tetrahedron module and the fifth regular tetrahedron module have the same structure, and all four sides are arranged in a triangular shape, wherein two adjacent surfaces are provided with first equidistant through holes.

[0009] Furthermore, in the above-mentioned foldable leg-type movable structure, the sixth regular tetrahedral module and the seventh regular tetrahedral module have the same structure, with all four sides arranged in a triangular shape, and three adjacent surfaces are provided with second equidistant through holes.

[0010] Furthermore, in the above-mentioned foldable leg-type movable structure, the second equidistant through hole matches the first equidistant through hole, and there are 6 of each of the first and second equidistant through holes, arranged in a triangular pattern on each surface.

[0011] Furthermore, in the above-mentioned foldable leg-type movable structure, the first equidistant through holes on both sides of the first regular tetrahedral module are respectively connected and fixed to the second equidistant through hole on the front side of the sixth regular tetrahedral module and the second equidistant through hole on the rear side of the seventh regular tetrahedral module by bolts;

[0012] The second equidistant through hole on the right front side of the sixth regular tetrahedron module and the first equidistant through hole on one side of the second regular tetrahedron module are fixed together by bolts; the second equidistant through hole on the left front side of the sixth regular tetrahedron module and the first equidistant through hole on one side of the third regular tetrahedron module are fixed together by bolts.

[0013] The second equidistant through hole on the right rear side of the seventh regular tetrahedron module is connected to the first equidistant through hole on one side of the fourth regular tetrahedron module by bolts, and the second equidistant through hole on the left rear side of the seventh regular tetrahedron module is connected to the first equidistant through hole on one side of the fifth regular tetrahedron module by bolts.

[0014] Furthermore, in the above-mentioned foldable leg-type mobile structure, the top of the first leg unit module is provided with a third equidistant through hole, the third equidistant through hole matching the first equidistant through hole, and the leg module is connected to the first equidistant through hole on the other side of the second regular tetrahedron module, the first equidistant through hole on the other side of the third regular tetrahedron module, the first equidistant through hole on the other side of the fourth regular tetrahedron module, and the first equidistant through hole on one side of the fifth regular tetrahedron module by bolts through the third equidistant through hole.

[0015] Furthermore, in the above-mentioned foldable leg-type mobile structure, the first leg unit module includes a first leg and a first mounting platform. The first mounting platform is welded to the bottom of the first leg. A first clearance groove is provided on one side of the bottom of the first leg to avoid the joint motor. A first connecting hole is provided around the first mounting platform. A first recess is provided in the middle of the first mounting platform. The first joint motor base is embedded in the first recess and connected and fixed to the first connecting hole by bolts.

[0016] Furthermore, in the above-mentioned foldable leg-type mobile structure, the second leg unit module includes a second leg, a first drive shaft connecting platform, and a second mounting platform. The first drive shaft connecting platform is welded to one side of the upper end of the second leg, and the second mounting platform is welded to the bottom of the second leg. The first drive shaft connecting platform is provided with a first connecting shaft hole, and the first joint motor output shaft is connected to the first connecting shaft hole by bolts. The second mounting platform is provided with a second connecting hole around it, and a second recess is provided in the middle of the second mounting platform. The second joint motor base is embedded in the second recess and fixed to the second connecting hole by bolts.

[0017] Furthermore, in the aforementioned foldable leg-type mobile structure, the third leg unit module includes a third leg, a second drive shaft connecting platform, and a third mounting platform. The second drive shaft connecting platform is welded to one side of the upper end of the third leg, and the third mounting platform is welded to the bottom of the third leg. A third recess is provided in the middle of the second drive shaft connecting platform, and a second connecting shaft hole is provided at the bottom of the third recess. The output shaft of the second joint motor is inserted into the third recess and connected to the second connecting shaft hole by bolts. A third connecting hole is provided around the third mounting platform, and the base of the third joint motor is fixed to the third connecting hole by bolts.

[0018] Furthermore, in the above-mentioned foldable leg-type mobile structure, the fourth leg unit module includes a fourth leg and a third drive shaft connecting platform. The second drive shaft connecting platform is welded to one side of the upper end of the third leg. A fourth recess is provided in the middle of the third drive shaft connecting platform. A third connecting shaft hole is provided at the bottom of the fourth recess. The third joint motor output shaft is inserted into the fourth recess and connected to the third connecting shaft hole by bolts. A second clearance groove is provided at the bottom of the fourth leg to avoid the joint motor.

[0019] The foldable leg-type movable structure of the present invention has the following advantages and beneficial effects:

[0020] The overall structure is simple, changing the traditional arrangement of the rotation joint angles of quadruped robots. It uses joint motors to enable walking while also changing the leg modules from an extended state to a folded state, making the prone posture closer to that of a real animal, thereby effectively improving safety when performing tasks. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only for further understanding of the embodiments of the present invention and constitute a part of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings:

[0022] Figure 1 This is a three-dimensional structural diagram of the foldable leg-type movable structure of the present invention;

[0023] Figure 2 This is a schematic diagram of the torso main structure of the foldable leg-type movable structure of the present invention;

[0024] Figure 3 This is a schematic diagram of the first equidistant hole distribution structure of the foldable leg-type movable structure of the present invention.

[0025] Figure 4 This is a schematic diagram of the second equidistant hole distribution structure of the foldable leg-type movable structure of the present invention.

[0026] Figure 5 This is a schematic diagram of the leg module structure of the foldable leg-type movable structure of the present invention;

[0027] Figure 6 This is a schematic diagram of the first leg unit module of the foldable leg-type movable structure of the present invention;

[0028] Figure 7 This is a schematic diagram of the second leg unit module of the foldable leg-type movable structure of the present invention;

[0029] Figure 8 This is a schematic diagram of the third leg unit module of the foldable leg-type movable structure of the present invention;

[0030] Figure 9 This is a schematic diagram of the fourth leg unit module of the foldable leg-type movable structure of the present invention;

[0031] Figure 10 This is a schematic diagram of the folding process of the leg module of the foldable leg-type movable structure of the present invention;

[0032] Figure 11 This is a schematic diagram of the folding structure of the foldable leg-type movable structure of the present invention.

[0033] Explanation of reference numerals in the attached figures:

[0034] 1: Main body of the torso; 11: First regular tetrahedral module; 12: Second regular tetrahedral module;

[0035] 13: Third regular tetrahedron module, 14: Fourth regular tetrahedron module, 15: Fifth regular tetrahedron module, 16: Sixth regular tetrahedron module, 17: Seventh regular tetrahedron module, 18: First equidistant through hole, 19: Second equidistant through hole;

[0036] 2: Leg and foot module;

[0037] 21: First leg unit module; 211: Third equidistant through hole; 212: First leg; 213: First mounting platform; 214: First clearance groove; 215: First connecting hole; 216: First recessed groove;

[0038] 22: Second leg unit module; 221: Second leg; 222: First drive shaft connecting platform; 223: First connecting shaft hole; 224: Second mounting platform; 225: Second connecting hole; 226: Second sinkhole;

[0039] 23: Third leg unit module; 231: Third leg; 232: Second drive shaft connecting platform; 233: Third mounting platform; 234: Third recess; 235: Second connecting shaft hole; 236: Third connecting hole;

[0040] 24: Fourth leg unit module; 241: Fourth leg; 242: Third drive shaft connecting platform; 243: Fourth recess; 244: Third connecting shaft hole; 245: Second clearance groove;

[0041] 25: Joint motor. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0043] like Figures 1 to 9 As shown, the foldable leg-type mobile structure of the present invention includes a torso body and four leg modules. The four leg modules are respectively installed at the bottom of the torso body for driving the torso body to move, wherein:

[0044] The main body of the torso includes a first tetrahedral module, a second tetrahedral module, a third tetrahedral module, a fourth tetrahedral module, a fifth tetrahedral module, a sixth tetrahedral module, and a seventh tetrahedral module. The first tetrahedral module is connected to the sixth tetrahedral module and the seventh tetrahedral module, the sixth tetrahedral module is connected to the second tetrahedral module and the third tetrahedral module, and the seventh tetrahedral module is connected to the fourth tetrahedral module and the fifth tetrahedral module.

[0045] The leg module includes a first leg unit module, a second leg unit module, a third leg unit module, a fourth leg unit module, and three joint motors. The first leg unit module is connected to the second leg unit module, the second leg unit module is connected to the third leg unit module, and the third leg unit module is connected to the fourth leg unit module through joint motors.

[0046] Furthermore, in the foldable leg-type movable structure of the present invention, the first regular tetrahedral module, the second regular tetrahedral module, the third regular tetrahedral module, the fourth regular tetrahedral module and the fifth regular tetrahedral module have the same structure, and all four sides are arranged in a triangular shape, wherein two adjacent surfaces are provided with first equidistant through holes.

[0047] Furthermore, in the foldable leg-type movable structure of the present invention, the sixth regular tetrahedral module and the seventh regular tetrahedral module have the same structure, with all four sides arranged in a triangular shape, and three adjacent surfaces are provided with second equidistant through holes.

[0048] Furthermore, in the foldable leg-type movable structure of the present invention, the second equidistant through hole matches the first equidistant through hole, and the number of the first equidistant through hole and the second equidistant through hole is 6, arranged in a triangular pattern on each surface. For example, the first row has 1 equidistant hole, the second row has 2 equidistant holes, and the third row has 3 equidistant holes.

[0049] Furthermore, in the foldable leg-type movable structure of the present invention, the first equidistant through holes on both sides of the first regular tetrahedral module are respectively connected and fixed to the second equidistant through hole on the front side of the sixth regular tetrahedral module and the second equidistant through hole on the rear side of the seventh regular tetrahedral module by bolts.

[0050] The second equidistant through hole on the right front side of the sixth regular tetrahedron module is fixed to the first equidistant through hole on one side of the second regular tetrahedron module by bolts, and the second equidistant through hole on the left front side of the sixth regular tetrahedron module is fixed to the first equidistant through hole on one side of the third regular tetrahedron module by bolts.

[0051] The second equidistant through hole on the right rear side of the seventh tetrahedron module is connected to the first equidistant through hole on one side of the fourth tetrahedron module by bolts, and the second equidistant through hole on the left rear side of the seventh tetrahedron module is connected to the first equidistant through hole on one side of the fifth tetrahedron module by bolts, thereby ensuring the connection of the torso body.

[0052] Furthermore, in the foldable leg-type mobile structure of the present invention, a third equidistant through hole is provided on the top of the first leg unit module. The third equidistant through hole matches the first equidistant through hole. The leg module is connected to the first equidistant through hole on the other side of the second tetrahedron module, the first equidistant through hole on the other side of the third tetrahedron module, the first equidistant through hole on the other side of the fourth tetrahedron module, and the first equidistant through hole on one side of the fifth tetrahedron module by bolts through the third equidistant through hole, thereby ensuring that the leg module is fixedly connected to the torso body.

[0053] Furthermore, in the foldable leg-type mobile structure of the present invention, the first leg unit module includes a first leg and a first mounting platform. The first mounting platform is welded to the bottom of the first leg. A first clearance groove is provided on one side of the bottom of the first leg to avoid the joint motor. A first connecting hole is provided around the first mounting platform. A first recess is provided in the middle of the first mounting platform. The base of the first joint motor is embedded in the first recess and connected and fixed to the first connecting hole by bolts, thereby ensuring the installation of the joint motor.

[0054] Furthermore, in the foldable leg-type mobile structure of the present invention, the second leg unit module includes a second leg, a first drive shaft connecting platform, and a second mounting platform. The first drive shaft connecting platform is welded to one side of the upper end of the second leg, and the second mounting platform is welded to the bottom of the second leg. The first drive shaft connecting platform is provided with a first connecting shaft hole. The output shaft of the first joint motor is connected to the first connecting shaft hole by bolts, so that when the joint motor rotates, it drives the second leg unit module to fold towards the first leg unit module. The second mounting platform is provided with a second connecting hole around it, and a second recess is provided in the middle of the second mounting platform. The base of the second joint motor is embedded in the second recess and fixed to the second connecting hole by bolts, thereby ensuring the installation of the joint motor.

[0055] Furthermore, in the foldable leg-type mobile structure of the present invention, the third leg unit module includes a third leg, a second drive shaft connecting platform, and a third mounting platform. The second drive shaft connecting platform is welded to one side of the upper end of the third leg, and the third mounting platform is welded to the bottom of the third leg. A third recess is provided in the middle of the second drive shaft connecting platform, and a second connecting shaft hole is provided at the bottom of the third recess. The output shaft of the second joint motor is inserted into the third recess and connected to the second connecting shaft hole by bolts, so that when the joint motor rotates, it drives the third leg unit module to fold towards the second leg unit module. A third connecting hole is provided around the third mounting platform, and the third joint motor base is fixed to the third connecting hole by bolts, thereby ensuring the installation of the joint motor.

[0056] Furthermore, in the foldable leg-type mobile structure of the present invention, the fourth leg unit module includes a fourth leg and a third drive shaft connecting platform. The second drive shaft connecting platform is welded to one side of the upper end of the third leg. A fourth recess is provided in the middle of the third drive shaft connecting platform. A third connecting shaft hole is provided at the bottom of the fourth recess. The output shaft of the third joint motor is inserted into the fourth recess and connected to the third connecting shaft hole by bolts, so that when the joint motor rotates, it drives the fourth leg unit module to fold towards the third leg unit module. A second clearance groove is provided at the bottom of the fourth leg to avoid the joint motor.

[0057] Specifically, during folding, the joint motor between the first and second leg unit modules rotates, causing the second leg unit module to fold towards the first leg unit module; the joint motor between the second and third leg unit modules rotates, causing the third leg unit module to fold towards the second leg unit module; and the joint motor between the third and fourth leg unit modules rotates, causing the fourth leg unit module to fold towards the third leg unit module. Figure 10 As shown, the second leg unit module, the third leg unit module, and the fourth leg unit module are folded from a planar arrangement to an arrangement surrounding the first leg unit module. In this state, the maximum edge length of the leg module is equal to the edge length of the first regular tetrahedron module, the second regular tetrahedron module, the third regular tetrahedron module, the fourth regular tetrahedron module, and the fifth regular tetrahedron module.

[0058] When all four leg modules fold simultaneously, such as Figure 11 As shown, the leg and foot module is folded from a planar arrangement to an arrangement surrounding the first leg and foot unit module. In this state, the transformation from a standing posture to a prone posture can be realized.

[0059] In summary, compared with the prior art, the foldable legged mobile structure of the present invention has the following advantages and beneficial effects: the overall structure is simple, and the connection between the joint motor and the leg unit module effectively changes the arrangement of the rotation joint angle of the traditional quadruped robot. While using the joint motor to achieve walking, the leg module can also change from an extended state to a folded state, and the prone posture is closer to that of a real animal, thereby effectively improving the safety when performing tasks.

[0060] It should be noted that, unless otherwise expressly specified and limited, the term "connection" or its synonyms should be interpreted broadly in this document. For example, "connection" can be a fixed connection or a detachable connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal communication of two elements or the interaction between two elements. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances. Furthermore, expressions such as "first" and "second" are merely used to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Meanwhile, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. In addition, the terms "front," "rear," "left," "right," "upper," and "lower" in this document refer to the placement states shown in the accompanying drawings.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A foldable leg-type mobile structure, characterized in that, The foldable legged mobility structure includes a torso body and four leg modules. The four leg modules are respectively installed at the bottom of the torso body to drive the torso body to move, wherein: The main body of the torso includes a first tetrahedral module, a second tetrahedral module, a third tetrahedral module, a fourth tetrahedral module, a fifth tetrahedral module, a sixth tetrahedral module, and a seventh tetrahedral module. The first tetrahedral module is connected to the sixth tetrahedral module and the seventh tetrahedral module, the sixth tetrahedral module is connected to the second tetrahedral module and the third tetrahedral module, and the seventh tetrahedral module is connected to the fourth tetrahedral module and the fifth tetrahedral module. The leg module includes a first leg unit module, a second leg unit module, a third leg unit module, a fourth leg unit module, and three joint motors. The first leg unit module is connected to the second leg unit module, the second leg unit module is connected to the third leg unit module, and the third leg unit module is connected to the fourth leg unit module through the joint motors. The first regular tetrahedron module, the second regular tetrahedron module, the third regular tetrahedron module, the fourth regular tetrahedron module and the fifth regular tetrahedron module have the same structure, and all four sides are arranged in a triangular shape, with two adjacent surfaces having a first equidistant through hole; The sixth regular tetrahedral module and the seventh regular tetrahedral module have the same structure, with all four sides arranged in a triangular shape, and three adjacent surfaces are provided with second equidistant through holes; The top of the first leg unit module is provided with a third equidistant through hole, which matches the first equidistant through hole. The leg module is connected to the first equidistant through hole on the other side of the second regular tetrahedron module, the first equidistant through hole on the other side of the third regular tetrahedron module, the first equidistant through hole on the other side of the fourth regular tetrahedron module, and the first equidistant through hole on one side of the fifth regular tetrahedron module by bolts through the third equidistant through hole. During folding, the second, third, and fourth leg unit modules are folded from a planar arrangement to an arrangement surrounding the first leg unit module. In this state, the maximum edge length of the leg module is equal to the edge length of the first, second, third, fourth, and fifth regular tetrahedral modules.

2. The foldable leg-type mobile structure according to claim 1, characterized in that, The second equidistant through hole matches the first equidistant through hole, and there are 6 of each of the first and second equidistant through holes, arranged in a triangular pattern on each surface.

3. The foldable leg-type mobile structure according to claim 2, characterized in that, The first equidistant through holes on both sides of the first regular tetrahedral module are respectively connected and fixed to the second equidistant through holes on the front side of the sixth regular tetrahedral module and the second equidistant through holes on the rear side of the seventh regular tetrahedral module by bolts; The second equidistant through hole on the right front side of the sixth regular tetrahedron module and the first equidistant through hole on one side of the second regular tetrahedron module are fixed together by bolts; the second equidistant through hole on the left front side of the sixth regular tetrahedron module and the first equidistant through hole on one side of the third regular tetrahedron module are fixed together by bolts. The second equidistant through hole on the right rear side of the seventh regular tetrahedron module is connected to the first equidistant through hole on one side of the fourth regular tetrahedron module by bolts, and the second equidistant through hole on the left rear side of the seventh regular tetrahedron module is connected to the first equidistant through hole on one side of the fifth regular tetrahedron module by bolts.

4. The foldable leg-type mobile structure according to claim 1, characterized in that, The first leg unit module includes a first leg and a first mounting platform. The first mounting platform is welded to the bottom of the first leg. A first clearance groove is provided on one side of the bottom of the first leg to avoid the joint motor. A first connecting hole is provided around the first mounting platform. A first recess is provided in the middle of the first mounting platform. The first joint motor base is embedded in the first recess and connected and fixed to the first connecting hole by bolts.

5. The foldable leg-type movable structure according to claim 4, characterized in that, The second leg unit module includes a second leg, a first drive shaft connecting platform, and a second mounting platform. The first drive shaft connecting platform is welded to one side of the upper end of the second leg, and the second mounting platform is welded to the bottom of the second leg. The first drive shaft connecting platform is provided with a first connecting shaft hole. The output shaft of the first joint motor is connected to the first connecting shaft hole by bolts. The second mounting platform is provided with a second connecting hole around its perimeter. The second mounting platform is provided with a second recess in the middle. The base of the second joint motor is embedded in the second recess and fixed to the second connecting hole by bolts.

6. The foldable leg-type mobile structure according to claim 5, characterized in that, The third leg unit module includes a third leg, a second drive shaft connecting platform, and a third mounting platform. The second drive shaft connecting platform is welded to one side of the upper end of the third leg, and the third mounting platform is welded to the bottom of the third leg. A third recess is provided in the middle of the second drive shaft connecting platform, and a second connecting shaft hole is provided at the bottom of the third recess. The output shaft of the second joint motor is inserted into the third recess and connected to the second connecting shaft hole by bolts. A third connecting hole is provided around the third mounting platform, and the base of the third joint motor is fixed to the third connecting hole by bolts.

7. The foldable leg-type mobile structure according to claim 6, characterized in that, The fourth leg unit module includes a fourth leg and a third drive shaft connecting platform. The second drive shaft connecting platform is welded to one side of the upper end of the third leg. A fourth recess is provided in the middle of the third drive shaft connecting platform. A third connecting shaft hole is provided at the bottom of the fourth recess. The output shaft of the third joint motor is inserted into the fourth recess and connected to the third connecting shaft hole by bolts. A second clearance groove is provided at the bottom of the fourth leg to avoid the joint motor.

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