Two-degree-of-freedom joint module structure and method for built-in cable leg-foot robot

Abstract

The application discloses a kind of built-in cable leg foot type robot two degrees of freedom joint module structure and method, it is related to robot technical field, solve the problem that built-in cable exists relative swing or influence shaft rigidity in prior art, with the beneficial effect of guaranteeing cable service life, specific scheme is as follows: a kind of built-in cable leg foot type robot two degrees of freedom joint module structure, including motor housing, first cavity is provided with first motor, first motor is connected with first speed reduction mechanism, first speed reduction mechanism is placed in second cavity, the output end of first speed reduction mechanism is connected with first output shaft, first output shaft can be connected with the thigh of robot, first speed reduction mechanism is installed between motor housing and second motor base, second motor base is fixedly connected with motor housing, the output end of second speed reduction mechanism can be connected with the calf of robot, motor housing is provided with wiring groove, second motor cable passes through second motor base and enters the groove and is merged with first motor cable after and is worn out.

Description

Technical Field

[0001] This invention relates to the field of robot joint module technology, and in particular to a two-degree-of-freedom joint module structure and method for a legged robot with built-in cables. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Legged robots possess strong flexibility and adaptability to complex terrain, leading to rapid development in recent years. Many research institutions have developed numerous high-dynamic motor-driven legged robots, such as quadruped robots and humanoid robots. To reduce the rotational inertia of the legs and improve dynamic motion performance, current legged robots often have the knee joint drive module coaxially mounted at the thigh pitch joint. The knee joint motor moves with the thigh pitch joint, resulting in exposed and constantly passively flexing and extending the knee joint motor cable. When a legged robot lies down or collides with the environment, the cable is easily damaged. Prolonged flexion and extension movements also easily cause fatigue damage to the cable, severely affecting the robot's reliability and aesthetics.

[0004] Existing technologies disclose joint structures for motor-driven two-DOF robots, including a first motor assembly, a second motor assembly, and a reduction gear assembly. During operation, the first and second motor assemblies rotate relative to each other. Consequently, the cables of at least one motor assembly are exposed and oscillate back and forth relative to the other motor assembly, making them susceptible to compression and fatigue damage. To avoid exposed cables, another joint assembly solution has been disclosed where the knee joint motor lead wire does not oscillate back and forth with the hip joint movement. However, the output shaft of the outer motor rotor must pass through the inner motor rotor and the reducer, resulting in a slender structure that reduces shaft stiffness and torque transmission capacity. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a two-degree-of-freedom joint module structure for a legged robot with built-in cables, in which there is no relative swing between the two motor cables, thus avoiding cable compression, collision and fatigue damage.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] A two-degree-of-freedom joint module structure for a legged robot with built-in cables includes a motor housing, the interior of which is divided into a first cavity and a second cavity. A first motor is disposed in the first cavity and connected to a first reduction mechanism. The first reduction mechanism is disposed in the second cavity, and its output end is connected to a first output shaft. The first output shaft can be connected to the robot's thigh. The first reduction mechanism is installed between the motor housing and a second motor base. The second motor base is fixedly connected to the motor housing, and the second motor is installed inside the second motor base. The first output shaft is a hollow structure, and the second motor base is disposed inside the first output shaft. The second motor is connected to the second reduction mechanism, and its output end can be connected to the robot's lower leg. The motor housing has a wiring groove, through which the second motor cable passes into the wiring groove and merges with the first motor cable before exiting.

[0008] As described above, in a two-degree-of-freedom joint module structure for a legged robot with built-in cables, the first reduction mechanism is a first planetary gear mechanism, which includes a first gear ring that is rotatable relative to the motor housing. One end of the first output shaft is connected to the first gear ring. The second reduction mechanism is a second planetary gear mechanism, which includes a second gear ring that is connected to the other end of the first output shaft. The second gear ring is also connected to a first output flange, which can be connected to the robot's thigh and is rotatable relative to the motor housing.

[0009] As described above, in a two-degree-of-freedom joint module structure for a legged robot with built-in cables, the first motor includes a first motor stator and a first motor rotor. A first motor magnet is provided between the first motor stator and the first motor rotor. The first motor stator is fixed to the motor housing. The output end of the first motor rotor is connected to a first central gear. The first central gear is connected to the first reduction mechanism. The first motor rotor and the first central gear form a first motor rotor assembly. The first motor rotor assembly is rotatably mounted on the motor housing.

[0010] The motor housing has a wiring groove on the outside of the first cavity, and the wiring groove has a U-shaped structure.

[0011] As described above, in a two-degree-of-freedom joint module structure for a legged robot with built-in cables, a middle partition is provided in the motor housing along the radial direction of the motor housing. The first central gear passes through the middle partition and is connected to the first reduction mechanism. The first reduction mechanism includes a first gear ring, which is rotatably mounted in the second cavity. A first planetary gear is mounted between one side of the middle partition and the second motor base through a first planetary gear shaft. The first planetary gear meshes with the first central gear and the first gear ring simultaneously. One end of the first output shaft is connected to the first gear ring.

[0012] As described above, a two-degree-of-freedom joint module structure for a legged robot with built-in cables is provided at one end of the first cavity, and the motor rear cover is connected to the motor housing. A first drive plate is fixed to the inner wall of the motor rear cover, and the first motor stator is connected to the first drive plate. A first encoder reading plate is also provided on the first drive plate. A first encoder magnetic ring is coaxially installed on one end face of the first motor rotor, and a distance is maintained between the first encoder reading plate and the first encoder magnetic ring.

[0013] As described above, in a two-degree-of-freedom joint module structure for a legged robot with built-in cables, the second motor includes a second motor stator and a second motor rotor. A second motor magnet is disposed between the second motor stator and the second motor rotor. The second motor stator is fixed to the second motor base. The second motor rotor is connected to the second reduction mechanism through a second central gear. The second motor rotor and the second central gear form a second motor rotor assembly. The second motor rotor assembly is rotatable relative to the planetary carrier of the second motor base and the second reduction mechanism.

[0014] The second motor is coaxially mounted with the first motor.

[0015] As described above, in a two-degree-of-freedom joint module structure for a legged robot with an integrated cable, the planetary carrier of the second reduction mechanism includes an inner planetary carrier and a second output flange. The second reduction mechanism also includes a second gear ring. The second planetary gear is mounted between the second output flange and the inner planetary carrier via a second planetary gear shaft. The second output flange can be connected to the robot's lower leg. The second planetary gear meshes simultaneously with the second central gear and the second gear ring. The second output flange is rotatable relative to the first output flange. Both the second output flange and the first output flange are located at the end of the motor housing, and the second output flange and the first output flange are located on the same plane.

[0016] As described above, in a two-degree-of-freedom joint module structure for a legged robot with built-in cables, a second motor cover is provided at the end of the second motor base away from the first cavity. The center of the second motor cover is recessed towards the center of the second motor base. The second motor rotor assembly can rotate relative to both the second motor cover and the inner planetary carrier. One side of the inner planetary carrier is embedded in the recess of the second motor cover, and the inner planetary carrier can rotate relative to the second motor cover.

[0017] As described above, in a two-degree-of-freedom joint module structure for a legged robot with built-in cables, a second encoder magnetic ring is coaxially mounted on the side of the second motor rotor facing the second cavity. A second drive plate is provided inside the second motor base and is connected to the second motor rotor. A second encoder reading plate is installed on the second drive plate, and the second encoder reading plate is set at a distance from the second encoder magnetic ring.

[0018] Secondly, this invention also discloses a method for operating a two-degree-of-freedom joint module structure for a cable-embedded legged robot, comprising the following:

[0019] The first output shaft can be connected to the robot's thigh, and the output end of the second deceleration mechanism can be connected to the robot's lower leg.

[0020] When the first motor is working, it drives the first output shaft to move through the output end of the first reduction mechanism, and the first output shaft drives the robot's thigh to move.

[0021] When the second motor is working, it drives the robot's lower legs to move through the output end of the second reduction mechanism.

[0022] When both the first and second motors are working, the first output shaft and the second reduction mechanism drive the robot's thigh and calf to move respectively.

[0023] The beneficial effects of the present invention are as follows:

[0024] 1) This invention provides a joint module structure, including a motor housing, which is divided into a first cavity and a second cavity. A first motor is placed in the first cavity. The first cavity outputs power through a first reduction mechanism, and then outputs the power to the robot's thigh through a first output shaft. The first reduction mechanism is installed between the motor housing and the second motor base. The second motor base is fixed to the motor housing. When the motor housing remains in a fixed position, the position of the second motor base remains unchanged, providing a fixed support position for the second motor. In this way, the first motor will not drive the second motor to rotate when it rotates, so that the second motor cable will not rotate and will not be fatigued due to rotation. A wiring groove is set in the motor housing. The second motor cable passes through the second motor base into the wiring groove and merges with the first motor cable before exiting. There is no relative swing between the two motor cables, avoiding cable compression, collision and fatigue damage. The overall structure bypasses the first motor, avoiding the impact on the stiffness of the shaft and the transmitted torque.

[0025] 2) The overall structure of this invention is reasonably arranged. The first deceleration mechanism is a first planetary gear mechanism and the first output shaft is a hollow structural component. That is, the robot's thigh is driven through the cylindrical first output shaft. The position of the second deceleration mechanism is reasonably arranged. The second deceleration mechanism is a second planetary gear mechanism, which ensures that the two motors can output a large torque and maintain sufficient rigidity.

[0026] 3) In this invention, a second motor cover is provided at one end of the second motor base. The center of the second motor cover is recessed to facilitate the setting of the inner planetary carrier. The inner planetary carrier and the second output flange support the second planetary gear shaft in the second reduction mechanism, so that the inner planetary carrier and the second output flange are the planetary carriers of the second reduction mechanism. The second motor rotor assembly can rotate relative to the second motor cover and the inner planetary carrier. The inner planetary carrier can rotate relative to the second motor cover. Thus, when the second central gear drives the second planetary gear to rotate, it drives the second output flange to rotate together, thereby driving the robot's lower leg to move. Attached Figure Description

[0027] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0028] Figure 1 This is a cross-sectional view of a two-degree-of-freedom joint module structure of a legged robot with built-in cables, according to one or more embodiments of the present invention.

[0029] Figure 2 This is a schematic diagram of the external structure of a two-degree-of-freedom joint module structure for a cable-driven legged robot according to one or more embodiments of the present invention.

[0030] The diagram exaggerates the spacing or dimensions between parts to show their positions; the diagram is for illustrative purposes only.

[0031] The components are: 1. Motor housing; 2. First motor stator; 3. First motor magnet; 4. First motor rotor; 5. First planetary gear shaft; 6. First wear-resistant gasket; 7. First planetary gear; 8. First bearing; 9. Second bearing; 10. First gear ring; 11. First output shaft; 12. Second drive plate; 13. Second encoder reading plate; 14. Second encoder magnetic ring; 15. Second motor mount; 16. Second motor stator; 17. Second motor magnet; 18. Second motor rotor; 19. Second gear ring; 20. Third bearing; 21. Motor front cover; 22. Second motor cover; 23. Fourth bearing; 24. Second wear-resistant gasket; 25. 26. Second planetary gear shaft, 27. Tenth bearing, 28. Second planetary gear, 29. Second elastic retaining ring, 30. Second center gear, 31. Second pin, 32. Fifth bearing, 33. Sixth bearing, 34. Seventh bearing, 35. Second output flange, 36. First output flange, 37. Cable cover, 38. Main cable, 39. Cable protective sleeve, 40. Second motor cable, 41. First encoder magnetic ring, 42. First pin, 43. First elastic retaining ring, 44. First encoder reading plate, 45. First center gear, 46. Eighth bearing, 47. Ninth bearing, 48. First drive plate, 49. Motor rear cover, 40. Inner planetary carrier. Detailed Implementation

[0032] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0033] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, unless otherwise expressly indicated by the invention, the singular form is also intended to include the plural form. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0034] As described in the background section, in the prior art, exposed cables at robot joints cause wear, while built-in cables can cause relative swaying or affect the stiffness of the shaft. In order to solve the above technical problems, this invention proposes a two-degree-of-freedom joint module structure for a legged robot with built-in cables.

[0035] Example 1

[0036] In a typical embodiment of the present invention, reference is made to Figure 1 and Figure 2 As shown, a two-degree-of-freedom joint module structure for a legged robot with built-in cables includes a motor housing 1, which is internally divided into a first cavity and a second cavity. A first motor is disposed in the first cavity and connected to a first reduction mechanism. The first reduction mechanism is disposed in the second cavity, and its output end is connected to a first output shaft 11. The first output shaft 11 can be connected to the robot's thigh. The first reduction mechanism is installed between the motor housing 1 and a second motor base 15. The second motor base 15 is fixedly connected to the motor housing 1, and the second motor is installed inside the second motor base 15. The first output shaft 11 is a hollow structure, and the second motor base is disposed inside the first output shaft. The second motor is connected to the second reduction mechanism, and its output end can be connected to the robot's lower leg. The motor housing is provided with a wiring groove. The second motor cable 39 passes through the second motor base 15, enters the wiring groove, and merges with the first motor cable to form a total cable 37 that exits from the side of the overall structure.

[0037] Specifically, the first motor includes a motor housing 1, a first motor stator 2, a first motor magnet 3, a first motor rotor 4, and a first drive plate 47. One side of the motor housing 1 is a first cavity, which is a circular cavity, and the other side is a second cavity, which is also a circular cavity. An intermediate partition is provided inside the motor housing 1 along the radial direction of the motor housing 1, and the first central gear passes through the intermediate partition and is connected to the first reduction mechanism.

[0038] The first motor stator 2 is fixedly installed in the first cavity of the motor housing 1. The first motor rotor is placed inside the first motor stator 2. The first motor rotor 4 and the first central gear 44 are rigidly connected coaxially by screws to form the first motor rotor assembly. One end of the first motor rotor 4 and the first central gear 44 are circumferentially fixed by the first pin 41 to transmit torque. The first motor rotor assembly is installed in the seat hole in the middle of the first cavity of the motor housing 1 by the ninth bearing 46 and the eighth bearing 45, and is axially positioned by the first elastic retaining ring 42. The ninth bearing 46 is set close to the motor rear cover 48, and the eighth bearing 45 and the ninth bearing 46 are spaced apart.

[0039] A set of first motor magnets 3 are uniformly fixed on the outer circumference of the first motor rotor 4. A first encoder magnetic ring 40 is coaxially mounted on the left end face of the first motor rotor 4. The motor rear cover 48 encloses the first motor stator 2 and the first motor rotor assembly in the first cavity of the motor housing 1. The first drive plate 47 is fixed on the inner wall of the motor rear cover 48. The winding wires of the first motor stator 2 are connected to the first drive plate 47. A first encoder reading plate 43 is also provided on the first drive plate 47, and the first encoder reading plate 43 maintains an appropriate distance from the first encoder magnetic ring 40. During the rotation of the first motor rotor 4, the first encoder magnetic ring 40 rotates, and the rotation angle of the first motor rotor 4 can be read through the first encoder reading plate 43.

[0040] The first reduction mechanism is a first planetary gear mechanism, including a first ring gear 10 and a first planetary gear 7. The first ring gear 10 is mounted in the second cavity of the motor housing 1 via a first bearing 8, allowing it to rotate relative to the motor housing 1. The first planetary gear 7 is mounted between the right end face of the middle partition plate and the second motor base 15 of the motor housing 1 via a first planetary gear shaft 5 and a second bearing 9. The second motor base 15 is rigidly connected to the motor housing 1 by screws. The first planetary gear 7 meshes simultaneously with the first central gear 44 and the first ring gear 10. The first planetary gear 7 can rotate relative to the motor housing 1 according to the magnitude of the transmitted torque. Multiple planetary gears are symmetrically arranged along the central axis of the housing 1. First wear-resistant pads 6 are installed at both ends of the first planetary gear 7 to reduce friction and wear with the motor housing 1 and the second motor base 15. Lubricant is applied to the meshing points of the first planetary gear 7 with the first central gear 44 and the first gear ring 10 during installation. When the first motor rotor 4 rotates relative to the motor housing 1, it drives the first central gear 44 to rotate. The first central gear 44 drives the first gear ring 10 to rotate through the first planetary gear 7. Since the number of teeth of the first gear ring 10 is much larger than the number of teeth of the first central gear 44, the output torque of the first motor rotor 4 is amplified.

[0041] It should be noted that the first central gear 44 is relatively long. The toothed part of the first central gear meshes with the first planetary gear, and the remaining part of the first central gear is placed in the first cavity of the motor housing 1.

[0042] The second motor includes a second motor stator 16, a second motor magnet 17, a second motor rotor 18, a second drive plate 12, and a second motor cover 22. The second motor is coaxially arranged with the first motor. The second motor stator 16 is fixedly installed in the circular cavity of the second motor base 15. The second motor rotor 18 and the second central gear 29 are rigidly connected coaxially by screws to form a second motor rotor assembly. The second motor rotor 18 and the second central gear 29 are circumferentially fixed by a second pin 30 to transmit torque. The second motor rotor assembly is fixed by a sixth bearing 32 and a fifth bearing 31, and is axially positioned by a second elastic retaining ring 28. The sixth bearing 32 is located close to the second drive plate 12, and the fifth bearing 31 and the sixth bearing 32 are spaced apart. The second motor cover 22 is connected to the second motor base 15. The center of the second motor cover 22 is recessed towards the center of the second motor base and supports the sixth bearing 32.

[0043] It should be explained that a set of second motor magnets 17 are uniformly fixed on the outer circumference of the second motor rotor 18. A second encoder magnetic ring 14 is coaxially mounted on the left end face of the second motor rotor 18. The second motor cover 22 encloses the second motor stator 16 and the second motor rotor assembly within the cavity of the second motor base 15. The second drive plate 12 is fixed to the inner wall of the second motor base 15. A second encoder reading plate 13 is also provided on the second drive plate 12, and the second encoder reading plate 13 maintains an appropriate distance from the second encoder magnetic ring 14. The windings of the second motor stator 16 are connected to the second drive plate 12. The second motor cable 39 originates from the second drive plate 12. 2. The wiring hole at the end of the second motor base 15 and the wiring groove on the wall of the motor housing 1 lead to the direction of the motor rear cover 48. The wiring groove on the wall of the motor housing 1 is U-shaped. The wiring groove bypasses the first motor and is located close to the outside of the overall structure. The two sides of the U-shaped wiring groove bend towards the direction of the first central gear 44. The second motor cable 39 and the first motor cable are merged into a total cable 37. The total cable 37 passes through the motor rear cover 48 and is fixed by the cable protection sleeve 38. Both the second motor cable 39 and the total cable 37 include power lines and communication lines. The wiring groove on the wall of the motor housing 1 is closed by the cable cover 36 to protect the internal second motor cable 39.

[0044] It should be noted that the first motor cable is led out from the side of the first motor stator away from the second motor, and the second motor cable 39 is led out from the side of the second motor stator closer to the first motor.

[0045] It should be noted that both the first drive board and the second drive board are controllers for the corresponding motors.

[0046] The second reduction mechanism is a second planetary gear mechanism, including a second gear ring 19 and a second planetary gear 27. The left end of the first output shaft 11 is fixedly connected to the first gear ring 10 by screws. The first output flange 35 is fixedly connected to the second gear ring by screws. The first output shaft 11 is placed inside the motor housing 1, and the two are spaced apart. Since the second gear ring 19 is connected to the first output shaft, the first output flange 35 is naturally connected to the first output shaft 11. The first output shaft is a hollow structure. The second motor base 15 is located inside the first output shaft 11. When the first motor rotor 4 rotates, the first output shaft 11 is driven to rotate through the first gear ring, and the first output flange 35 is driven to rotate through the first output shaft. The first output flange 35 drives the robot thigh component connected to it to move. The motor front cover 21 is fixedly installed at the front end of the motor housing 1. The first gear ring 10, the first output shaft 11, the second gear ring 19 and the first output flange 35 are rigidly connected together by screws and installed in the second cavity of the motor housing 1 through the first bearing 8 and the third bearing 20.

[0047] It should be noted that the inner planetary carrier 49 and the second output flange 34 are rigidly connected by screws to form the planetary carrier of the second reduction mechanism, and are installed on the second motor cover 22 and the first output flange 35 through the seventh bearing 33 and the fourth bearing 23. The fourth bearing 23 is placed between the first output flange 35 and the second output flange 34. The second output flange 34 is connected to the robot's lower leg through the existing linkage mechanism.

[0048] The second planetary gear 27 is installed between the second output flange 34 and the inner planetary carrier 49 via the second planetary gear shaft 25 and the tenth bearing 26. The second planetary gear 27 meshes simultaneously with the second central gear 29 and the second gear ring 19. The second gear ring 19 is connected to both the first output shaft and the first output flange. Multiple gear rings can be arranged symmetrically relative to the central axis of the second motor according to the magnitude of the transmitted torque. Second wear-resistant gaskets 24 are installed at both ends of the second planetary gear 27 to reduce friction and wear between it and the inner planetary carrier 49 and the second output flange 34. Lubricating grease is applied to the meshing points of the second planetary gear 27 with the second central gear 29 and the second gear ring 19 during installation. When the second motor rotor 18 rotates, the second central gear 29 drives the second gear ring 19 of the second reduction mechanism to rotate through the second planetary gear 27. Since the number of teeth of the second gear ring 19 is much larger than that of the second central gear 29, the output torque of the second motor rotor 18 is amplified.

[0049] Example 2

[0050] This embodiment discloses a working method for a two-degree-of-freedom joint module structure of a legged robot with built-in cables, including the following:

[0051] The first output shaft 11 can be connected to the robot's thigh, and the output end of the second deceleration mechanism can be connected to the robot's lower leg.

[0052] When the first motor is working, it drives the first output shaft 11 to move through the output end of the first reduction mechanism, and the first output shaft 11 drives the robot's thigh to move through the first output flange 35.

[0053] When the second motor is working, it drives the robot's lower legs to move through the second output flange 34 via the output end of the second reduction mechanism.

[0054] When both the first motor and the second motor are working, the first output shaft 11 and the second reduction mechanism drive the robot's thigh and calf to move respectively.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A two-degree-of-freedom joint module structure for a legged robot with built-in cables, characterized in that, The device includes a motor housing, which is internally divided into a first cavity and a second cavity. A first motor is housed in the first cavity and connected to a first reduction mechanism. The first reduction mechanism is located in the second cavity and its output end is connected to a first output shaft. The first output shaft can be connected to the robot's thigh. The first reduction mechanism is installed between the motor housing and a second motor base. The second motor base is fixedly connected to the motor housing and the second motor is installed inside the second motor base. The first output shaft is a hollow structure. The second motor base is located inside the first output shaft. The second motor is connected to the second reduction mechanism, and its output end can be connected to the robot's lower leg. The motor housing has a wiring groove. The second motor cable passes through the second motor base, enters the wiring groove, merges with the first motor cable, and then exits. The first motor includes a first motor stator and a first motor rotor. A first motor magnet is provided between the first motor stator and the first motor rotor. The first motor stator is fixed to the motor housing. The output end of the first motor rotor is connected to a first central gear. The first central gear is connected to the first reduction mechanism. The first motor rotor and the first central gear form a first motor rotor assembly. The first motor rotor assembly is rotatably mounted on the motor housing. An intermediate partition is provided inside the motor housing along the radial direction of the motor housing. The first central gear passes through the intermediate partition and is connected to the first reduction mechanism. The first reduction mechanism includes a first gear ring, which is rotatably mounted in the second cavity. The first planetary gear is mounted between one side of the intermediate partition and the second motor base through a first planetary gear shaft. The first planetary gear meshes with the first central gear and the first gear ring simultaneously. One end of the first output shaft is connected to the first gear ring. The first reduction mechanism is a first planetary gear mechanism, which includes a first gear ring that is rotatable relative to the motor housing. One end of the first output shaft is connected to the first gear ring. The second reduction mechanism is a second planetary gear mechanism, which includes a second gear ring that is connected to the other end of the first output shaft. The second gear ring is connected to a first output flange that can be connected to the robot's thigh and is rotatable relative to the motor housing. The second motor includes a second motor stator and a second motor rotor. A second motor magnet is disposed between the second motor stator and the second motor rotor. The second motor stator is fixed to the second motor base. The second motor rotor is connected to the second reduction mechanism through a second central gear. The second motor rotor and the second central gear form a second motor rotor assembly. The second motor rotor assembly is rotatable relative to the second motor base and the planetary carrier of the second reduction mechanism. The second motor is coaxially arranged with the first motor; The planetary carrier of the second reduction mechanism includes an inner planetary carrier and a second output flange. The second reduction mechanism also includes a second gear ring. The second planetary gear is mounted between the second output flange and the inner planetary carrier through a second planetary gear shaft. The second output flange can be connected to the robot's lower leg. The second planetary gear meshes with the second central gear and the second gear ring simultaneously. The second output flange is rotatable relative to the first output flange. Both the second output flange and the first output flange are located at the end of the motor housing. The second output flange and the first output flange are located on the same plane.

2. The two-degree-of-freedom joint module structure for a legged robot with built-in cables according to claim 1, characterized in that, The motor housing has a wiring groove on the outside of the first cavity, and the wiring groove has a U-shaped structure.

3. The two-degree-of-freedom joint module structure for a legged robot with built-in cables according to claim 1, characterized in that, A motor rear cover is provided at one end of the first cavity. The motor rear cover is connected to the motor housing. A first drive plate is fixed to the inner wall of the motor rear cover. The first motor stator is connected to the first drive plate. A first encoder reading plate is also provided on the first drive plate. A first encoder magnetic ring is coaxially installed on one end face of the first motor rotor. A distance is maintained between the first encoder reading plate and the first encoder magnetic ring.

4. The two-degree-of-freedom joint module structure for a legged robot with built-in cables according to claim 1, characterized in that, A second motor cover is provided at the end of the second motor base away from the first cavity. The center of the second motor cover is recessed towards the center of the second motor base. The second motor rotor assembly can rotate relative to both the second motor cover and the inner planetary carrier. One side of the inner planetary carrier is embedded in the recess of the second motor cover, and the inner planetary carrier can rotate relative to the second motor cover.

5. The two-degree-of-freedom joint module structure for a legged robot with built-in cables according to claim 1, characterized in that, A second encoder magnetic ring is coaxially mounted on the side of the second motor rotor facing the second cavity. A second drive plate is provided inside the second motor base. The second drive plate is connected to the second motor rotor. A second encoder reading plate is installed on the second drive plate. The second encoder reading plate and the second encoder magnetic ring are set at a distance.

6. The working method of the two-degree-of-freedom joint module structure of the built-in cable-driven legged robot according to any one of claims 1-5, characterized in that, Includes the following: The first output shaft can be connected to the robot's thigh, and the output end of the second deceleration mechanism can be connected to the robot's lower leg. When the first motor is working, it drives the first output shaft to move through the output end of the first reduction mechanism, and the first output shaft drives the robot's thigh to move. When the second motor is working, it drives the robot's lower legs to move through the output end of the second reduction mechanism. When both the first and second motors are working, the first output shaft and the second reduction mechanism drive the robot's thigh and calf to move respectively.

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