A high-load leg system for humanoid robots

Abstract

A high-load leg system for a humanoid robot includes a thigh skeleton, a lower leg skeleton, a planetary roller screw assembly, a main force transmission rod, a secondary force transmission rod, and a actuator. The base end of the planetary roller screw assembly is fixed to the thigh skeleton via a base end ball bearing, and the planetary roller screw drives the output end ball bearing to perform reciprocating linear motion. The other end of the secondary force transmission rod is constrained to the thigh skeleton, and the other end of the main force transmission rod is fixedly connected to a force sensor. The force sensor is movably connected to the lower leg skeleton via the main force transmission shaft, and the lower leg skeleton rotates around a rotation axis. The actuator is used to control the relative linear motion of the planetary roller screw and the planetary roller screw. The actuator is fixed to an actuator heat sink, and the actuator heat sink is fixed to the thigh skeleton. The lower leg skeleton has wiring holes and embedded wire grooves, and the lower leg end has bearing holes. The hip joint pitch base is connected to the hip via a fastening screw A.

Description

Technical Field

[0001] This invention relates to a high-load leg system for a humanoid robot, belonging to the field of intelligent robots. Background Technology

[0002] The leg design of humanoid robots is one of their core functions and has important applications, mainly reflected in the following aspects:

[0003] Adaptability to Complex Environments: The leg design of humanoid robots enables them to adapt to various complex terrains and environments. For example, through their leg structure, robots can easily traverse rugged terrain and overcome obstacles. This capability makes them invaluable in disaster relief, wilderness exploration, and other scenarios, allowing them to replace humans in dangerous areas and perform tasks.

[0004] Simulating human locomotion: The leg design of humanoid robots mimics human abilities such as walking, running, and climbing. By optimizing leg structure and joint design, robots can achieve high dynamic response capabilities and complete complex locomotion tasks. For example, by improving the structure of the hip and knee joints, the stability and flexibility of the robot's walking are enhanced.

[0005] Versatility and Adaptability: A well-designed leg structure gives humanoid robots greater versatility, enabling them to adapt to various application scenarios. For example, humanoid robots can act as assistants in home environments, performing daily chores; assist in production in the industrial sector; and provide nursing care in the medical field. This versatility not only expands the robot's applicability but also reduces the cost of multi-scenario applications.

[0006] Technological and Intelligent Development: Advances in leg design are closely related to the intelligentization of robots. Through advanced sensors and motion control algorithms, humanoid robots can autonomously learn and optimize their movement patterns, thereby exhibiting higher adaptability and efficiency in complex environments.

[0007] Humanoid design and social acceptance: The leg design of humanoid robots is not only for functionality but also for better integration into human society. Their humanoid appearance and mobility make them more easily accepted by humans, thus offering broad application prospects in service industries, family companionship, and other fields.

[0008] However, the existing leg design has the following drawbacks:

[0009] Balance and stability issues: Balance control remains a core challenge for humanoid robots during dynamic walking, especially when facing complex terrain or dynamic environments. Each step of a bipedal robot is essentially a "controlled descent," requiring constant prediction, adjustment, and response to various factors. Furthermore, humanoid robots are susceptible to uneven ground and external interference during movement, leading to insufficient stability.

[0010] Limitations in Motion Capabilities: Despite continuous optimization of humanoid robot leg designs, their motion capabilities still do not reach the level of the human skeletal musculoskeletal system. Current robots lag behind in speed, dexterity, and dynamic response, making it difficult to achieve efficient human-like movement in complex environments.

[0011] Energy efficiency and endurance: Leg design needs to reduce energy consumption while maintaining high rigidity and low inertia. However, current technology still struggles to achieve a perfect balance between these goals, resulting in limited endurance for humanoid robots.

[0012] Safety and reliability: Humanoid robots may lose their balance and fall during movement, which could damage the robot itself and pose a potential danger to people nearby. Therefore, improving the safety and reliability of robots is an urgent issue to be addressed.

[0013] Cost and complexity: To achieve higher performance, leg designs often require complex mechanical structures and high-precision sensors, which leads to a significant increase in research and development and manufacturing costs.

[0014] Limitations of control algorithms: Current control algorithms still have shortcomings in handling complex terrain and dynamic environments, especially in the modeling and control of foot-ground contact. This limits the performance of humanoid robots in practical applications. Summary of the Invention

[0015] To overcome the shortcomings of the prior art, the present invention provides a system, specifically adopting the following technical solution:

[0016] A high-load leg system for a humanoid robot, characterized in that it comprises:

[0017] The thigh skeleton and the lower leg skeleton are movably connected by a rotation axis;

[0018] The planetary roller screw assembly includes a base end spherical ball bearing, an end cap type force sensor, a planetary roller screw, a planetary roller screw rod, and an output end spherical ball bearing; the base end spherical ball bearing is fixed to the thigh frame by an external thread type equal height bolt, the end of the planetary roller screw is locked with the output end spherical ball bearing, and the planetary roller screw drives the output end spherical ball bearing to perform reciprocating linear motion;

[0019] The main force transmission rod is connected to the output end joint ball bearing at one end, and the other end is movably connected to the lower leg skeleton through a force sensor. The secondary force transmission rod is connected to the output end joint ball bearing at one end, and the other end is restricted to the thigh skeleton.

[0020] The driver, fixed on the driver heat sink, is used to control the relative linear motion between the planetary roller screw and the planetary roller lead screw;

[0021] The dual force sensor system includes an end cap type force sensor integrated into the base of the planetary roller screw assembly and a force sensor set on the main transmission rod, for real-time monitoring of axial force, torque and six-dimensional force / torque of the lower leg skeleton (13);

[0022] A mechanical limiting structure is installed between the thigh skeleton and the calf skeleton to limit the maximum bending angle of the knee joint to 140°.

[0023] Polytetrafluoroethylene (PTFE) gaskets are placed at the axial connections of the main transmission shaft, secondary transmission shaft, main support shaft, and secondary support shaft to limit axial movement and provide elastic damping.

[0024] Preferably, the base end spherical ball bearing is fixed to the thigh frame by an external thread type equal height bolt, the optical axis section of the external thread type equal height bolt is matched with the hole position of the thigh frame and the base end spherical ball bearing, and is locked by a lock nut; the end cap type force sensor is connected to the base end spherical ball bearing to prevent rotation through a hexagonal stop.

[0025] Preferably, the output end spherical ball bearing is connected to the main force transmission rod and the auxiliary force transmission rod through the main drive shaft and the auxiliary drive shaft. Angular contact ball bearings A are arranged back-to-back at both ends of the main drive shaft and the auxiliary drive shaft. The outer ring of the angular contact ball bearing A is limited by the stop of the main force transmission rod, and the inner ring is limited by the stepped end face of the main drive shaft and the auxiliary drive shaft, and is pre-tightened by the lock nut.

[0026] Preferably, the force sensor is a six-dimensional force / torque sensor, one end of which is fixed to the main force transmission rod through a threaded section and a locking nut, and the other end is connected to the calf frame through a needle roller bearing A and the main force transmission shaft and the auxiliary force transmission shaft; the needle roller bearing A is fixed by a retaining ring A through a hole, and a polytetrafluoroethylene gasket A is provided between the main force transmission shaft and the auxiliary force transmission shaft.

[0027] Preferably, the rotating shaft is connected to the thigh skeleton and the calf skeleton through an angular contact ball bearing B. The angular contact ball bearings B are arranged back to back, the outer ring is limited by the stop of the calf skeleton, and the inner ring is pre-tightened and fixed by the stepped end face of the rotating shaft and the fastening screw B.

[0028] Preferably, the auxiliary force transmission rod is connected to the thigh skeleton via a needle roller bearing B, the needle roller bearing B is fixed by a retaining ring B through a hole, and a polytetrafluoroethylene gasket B is provided between the main support shaft and the auxiliary support shaft.

[0029] Preferably, the planetary roller screw has rollers made of nitrided hard alloy material, a lead of 5mm, and a theoretical load capacity of 20kN per screw; the driver is a high-dynamic servo motor with a peak torque of 50Nm, a rated speed of 3000rpm, a control cycle of 0.5ms, and supports three-loop control modes of position, speed, and torque.

[0030] This invention also discloses a motion control method for a humanoid robot leg system. This method, based on the aforementioned system, is characterized by comprising the following steps:

[0031] The axial force and torque of the planetary roller screw are monitored in real time using end cap type force sensors;

[0032] The force sensor of the main force transmission rod acquires six-dimensional force / torque data of the lower leg skeleton;

[0033] An adaptive impedance control algorithm is adopted, combined with sensor feedback to dynamically adjust the output torque of the driver, so as to achieve the coordination of the position loop and the force control loop;

[0034] When an abnormal load is detected, a low-impedance mode or emergency braking is triggered, and the joint is locked by mechanical limit.

[0035] Preferably, the adaptive impedance control algorithm includes friction compensation and inertia compensation, with a control bandwidth ≥100Hz, a response time ≤0.1s, and a single-leg load capacity of up to 200kg.

[0036] This invention also discloses a safety protection method for a humanoid robot leg system, which is based on the above-described system and is characterized by comprising:

[0037] The impact load is absorbed by the elastic deformation of the polytetrafluoroethylene gasket;

[0038] When the mechanical limit is triggered, it limits the travel of the planetary roller screw and cuts off the power supply to the driver;

[0039] By using dual-sensor redundancy verification, abnormal data is eliminated and a fault diagnosis program is initiated.

[0040] Beneficial effects

[0041] Compared with the prior art, the beneficial effects of the present invention are:

[0042] This invention uses a planetary roller screw, which can significantly improve the load capacity of the thigh. The load capacity of a single leg far exceeds the limit of human load, thereby improving the endurance of the humanoid robot. Moreover, the planetary roller screw solution is simple and convenient to install, and the thigh frame can be used for multiple purposes, which greatly reduces the production and manufacturing costs.

[0043] Both ends of the planetary roller screw and planetary roller ball screw are spherical ball bearings, which can effectively balance and stabilize their own push and pull forces. The distance between the two spherical ball bearings changes stably, and the bending angle of the lower leg also changes stably.

[0044] Because this invention incorporates end cap force sensors and force sensors, it can monitor changes in the bending moment of the lower leg in real time, improving motion control accuracy and real-time performance, promptly identifying motion risks, avoiding overload damage, and enhancing balance by improving motion control level, thereby improving stability, safety, and reliability.

[0045] The main and auxiliary transmission shafts, as well as the main and auxiliary support shafts, are easy to install and fix, and easy to disassemble and assemble.

[0046] The planetary roller screw, through its planetary meshing structure and high-rigidity material design, increases the single-leg load capacity to 200kg (far exceeding human limits), and its transmission efficiency is 15% higher than that of traditional ball screws, significantly extending its operating time.

[0047] Force sensor collaborative control: The dual-sensor redundancy design (end cap type + main force rod sensor) achieves real-time load monitoring and control accuracy of ±1N. Combined with the adaptive impedance algorithm, the robot can autonomously adjust its gait to cope with complex terrain.

[0048] Dynamic response of the drive: High-bandwidth control (bandwidth ≥ 100Hz) ensures that the leg system can accelerate from a standstill to maximum speed in 0.1s, with dynamic response capabilities close to the level of human muscle.

[0049] This solution uses PTFE gaskets to limit axial displacement, achieving stable functionality at a lower cost. By using PTFE gaskets to limit axial movement, not only can basic damping be provided, but also elastic deformation can be provided to prevent damage to parts under impact loads. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the humanoid robot leg system assembly of the present invention;

[0051] Figure 2 This is a schematic diagram of the leg transmission mechanism of the humanoid robot of the present invention;

[0052] Figure 3 for Figure 2 RR section view;

[0053] Figure 4 for Figure 2 TT sectional view;

[0054] Figure 5 This is a schematic diagram of the bent legs of the humanoid robot of the present invention;

[0055] In the diagram: 1. Thigh frame, 2. Hip pitch base, 3. Fastening screw A, 4. Base end spherical bearing, 5. End cap type force sensor, 6. Planetary roller screw, 7. Driver, 8. Planetary roller screw, 9. Output end spherical bearing, 10. Main transmission rod, 11. Force sensor, 12. PTFE gasket A, 13. Lower leg frame, 14. Secondary transmission rod, 15. Driver heat sink, 16. Rotary shaft, 17. Fastening screw B, 18. External thread type equal height bolt, 19. Anti-loosening washer A, 20. Anti-loosening nut A, 21. Main drive shaft, 22. Angular contact ball bearing A, 23. Secondary drive shaft, 24. Anti-loosening nut A. 25. Loose washer B, 26. Locking nut B, 27. Force sensor, 28. Locking nut C, 29. Anti-loosening washer C, 30. Needle roller bearing A, 31. Hole retaining ring A, 32. Main transmission shaft, 33. Secondary transmission shaft, 34. Anti-loosening washer D, 35. Fastening screw D, 36. Fastening screw C, 37. Anti-loosening washer E, 38. Angular contact ball bearing B, 39. Main support shaft, 40. Secondary support shaft, 41. Needle roller bearing B, 42. Hole retaining ring B, 43. PTFE gasket B, 44. Fastening screw E, 45. Mechanical limit switch, 13-1. Wiring hole, 13-2. Embedded wire groove, 13-3. Bearing hole position. Detailed Implementation

[0056] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0057] Please see Figure 1-5This invention provides a technical solution: a high-load leg system for a humanoid robot, comprising a thigh skeleton 1, a lower leg skeleton 13, a planetary roller screw assembly, a main force transmission rod 10, a secondary force transmission rod 14, and a driver 7; wherein the planetary roller screw assembly includes a base end joint ball bearing, an end cap type force sensor, a planetary roller screw, a planetary roller screw, and an output end joint ball bearing; the base end joint ball bearing of the planetary roller screw assembly is fixed to the thigh skeleton via the base end joint ball bearing. The end cap type force sensor is fixedly connected via fastening screw C, and the end cap type force sensor is provided with a hexagonal stop to prevent relative rotation; the end of the planetary roller screw is threaded, and the threaded end of the planetary roller screw is locked and fixed to the output end ball bearing; the rollers of the planetary roller screw are made of hard alloy material with nitriding treatment, the screw lead is 5mm, and the theoretical load capacity of a single screw is 20kN. Combined with the symmetrical support structure of the double ball bearing, it can effectively counteract lateral torque and ensure operation under high loads. Dynamic stability: The planetary roller screw drives the output end ball bearing to perform reciprocating linear motion and transmits force to one end of the main force transmission rod and one end of the auxiliary force transmission rod. The other end of the auxiliary force transmission rod is restricted to the thigh frame. The other end of the main force transmission rod is fixedly connected to a force sensor. One end of the force sensor is a threaded section, which is fixed to the main force transmission rod by an anti-loosening washer C and a locking nut C. The other end of the force sensor is nested with a needle roller bearing A, which is fixed inside the force sensor by a retaining ring A through a hole. The other end of the force sensor is movably connected to the lower leg frame through the main force transmission shaft and the auxiliary force transmission shaft. The main force transmission rod transmits force to the lower leg frame through the force sensor, thereby realizing the rotational motion of the lower leg frame around the rotation axis. The driver is used to control the relative linear motion of the planetary roller screw and the planetary roller screw. The driver is fixed on the driver heat sink, which is fixed on the thigh frame. This can make full use of the space of the thigh frame, reduce the outer envelope size of the thigh, and reduce the weight of the whole machine. The lower leg skeleton has wiring holes and grooves for cable routing, preventing wire bending and damage. Bearing holes are located at the end of the lower leg for ankle joint rotation. The force sensor is a six-dimensional force / torque sensor with a sampling frequency of 1kHz. The signal is transmitted to the controller via a shielded cable inside the groove to avoid electromagnetic interference. The driver uses a high-dynamic-response servo motor (peak torque 50Nm, rated speed 3000rpm), with a built-in temperature sensor and overcurrent protection module. It communicates with the main controller via a CAN bus, with a control cycle of 0.5ms, and supports switching between position, speed, and torque three-loop control modes. The hip joint pitch base is connected to the hip via fastening screw A.

[0058] Reference Figure 3The base end spherical ball bearing is fixed to the thigh frame by an externally threaded equal-height bolt. The externally threaded equal-height bolt passes sequentially through the thigh frame, the inner hole of the base end spherical ball bearing, and the thigh frame. The optical axis section of the externally threaded equal-height bolt mates with the thigh frame and the hole of the base end spherical ball bearing. The threaded section at the end of the externally threaded equal-height bolt is locked by a lock nut A, thereby fixing the optical axis section of the externally threaded equal-height bolt, the thigh frame, and the hole of the base end spherical ball bearing into one unit. The base end spherical ball bearing and the end cap type force sensor are fixedly connected by a fastening screw C, and the end cap type force sensor is provided with a hexagonal stop to prevent relative rotation. The end of the planetary roller screw is a threaded end, which is locked and fixed to the output end spherical ball bearing.

[0059] The output end spherical ball bearing is connected to the main drive shaft, main force transmission rod, and auxiliary force transmission rod via the main drive shaft. Specifically, the main drive shaft passes sequentially through angular contact ball bearing A, auxiliary force transmission rod, output end spherical ball bearing, auxiliary force transmission rod, auxiliary drive shaft, another angular contact ball bearing A, anti-loosening washer B, and lock nut B. The two angular contact ball bearings A are arranged back-to-back, which can withstand not only axial and radial loads but also large bending moments, reducing size and weight. By adjusting the preload of lock nut B, axial clearance caused by machining or installation errors in the main drive shaft can be offset, and the preload stiffness of the angular contact ball bearings can be increased, thereby improving the overall rigidity and positional accuracy of the main drive shaft. The two angular contact ball bearings A are nested at both ends of the main force transmission rod. The outer rings of the two angular contact ball bearings A are limited by the stop of the main force transmission component itself, and the inner rings of the two angular contact ball bearings are limited by the end faces of the main drive shaft and auxiliary drive shaft, respectively, and are fixed by lock nut B.

[0060] The other end of the main force transmission rod is fixedly connected to a force sensor. One end of the force sensor is a threaded section, which is fixed to the main force transmission rod by an anti-loosening washer C and a locking nut C. The other end of the force sensor houses a needle roller bearing A, which is fixed inside the force sensor via a retaining ring A through a hole. This reduces the size of the force sensor, thereby reducing the volume of the knee joint. The other end of the force sensor is movably connected to the lower leg skeleton via a main force transmission shaft and a secondary force transmission shaft. Specifically, the main force transmission shaft passes sequentially through the lower leg skeleton, a PTFE washer A, the inner ring of the needle roller bearing A, another PTFE washer A, and the secondary force transmission shaft... The main transmission shaft has a threaded section at its end, which is locked by anti-loosening washers D and fastening screws D. By tightening the fastening screws D, the axial clearance between the main and auxiliary transmission shafts can be eliminated, improving installation accuracy, avoiding vibration caused by clearance during movement, and improving the stability of motion control. The two PTFE gaskets A provide a certain amount of damping force and limit the axial movement of the force sensor. PTFE gaskets A have a certain degree of elasticity, allowing the force sensor to withstand large impact loads by slight axial deformation to prevent damage from force stress.

[0061] Reference Figure 4 The lower leg frame is movably connected to the upper leg frame via rotating shafts. Specifically, the end faces of the two rotating shafts are locked to both sides of the upper leg frame using anti-loosening washers E and fastening screws B. The shaft ends of the two rotating shafts pass through the inner rings of two angular contact ball bearings B, which are nested on both sides of the lower leg frame. The outer rings of the angular contact ball bearings B are fixed by the stop of the lower leg frame, and the inner rings are fixed by the stepped end faces of the rotating shafts. Tightening the fastening screws B eliminates axial clearance on the rotating shafts and applies a preload to the angular contact ball bearings B, increasing their rigidity. This prevents insufficient rigidity from causing clearance movement under large impacts, improving safety and motion control accuracy, and reducing transmission lag. The back-to-back arrangement of the two angular contact ball bearings B allows the rotating shafts to withstand not only axial and radial forces but also large bending moments; the lower leg frame can rotate around the rotating shafts.

[0062] Reference Figure 4One end of the auxiliary force transmission rod is fitted onto the main drive shaft, and the other end of the auxiliary force transmission rod houses a needle roller bearing B, which is fixed inside the auxiliary force transmission rod by a retaining ring B through a hole. This reduces the size of the auxiliary force transmission rod, thereby reducing the volume of the knee joint. The other end of the auxiliary force transmission rod is movably connected to the thigh skeleton via the main support shaft. Specifically, the main support shaft passes through the thigh skeleton, a PTFE gasket B, a needle roller bearing B, another PTFE gasket B, and the auxiliary support shaft in sequence, with the inner ring of the auxiliary support shaft fitting over the outer ring of the main support shaft. The end of the main support shaft is a threaded section. The threaded section of the main support shaft is locked by the fastening screw E. By locking the fastening screw E, the axial clearance between the main support shaft and the auxiliary support shaft can be eliminated, improving installation accuracy, avoiding vibration caused by clearance during movement, and improving the stability of motion control. The two PTFE gaskets B can provide a certain amount of damping force and limit the axial movement of the auxiliary force transmission rod. The PTFE gaskets B have a certain degree of elasticity, which allows the auxiliary force transmission rod to avoid stress damage by slight axial deformation when subjected to large impact loads.

[0063] Reference Figure 5 For a knee flexion of 140 degrees, the thigh and calf bones are mechanically limited by a limiting area. This prevents the planetary roller screw's travel from exceeding its limit, providing mechanical protection when the leg is subjected to significant impact loads. The end-cap type force sensor monitors the push-pull force and torque changes of the planetary roller screw in real time, effectively protecting the planetary roller screw assembly and activating safety protection in case of abnormalities. Since the calf bending torque changes in real time, calculating the calf bending moment based on the force and torque changes of the planetary roller screw would result in frictional losses and deviations in the final torque acting on the calf. Therefore, adding a force sensor to the main transmission rod allows direct calculation of the force and torque changes acting on the calf bone, improving the accuracy and real-time performance of motion control.

[0064] In this solution, the planetary roller screw can be replaced with a planetary ball screw. The paired angular contact ball bearings A and B can be replaced with needle roller bearings or deep groove ball bearings. The main force transmission rod can be integrated with the force sensor, which will result in higher installation accuracy, but will also increase manufacturing costs. The driver can be integrated into the planetary roller screw, which can improve the sealing level, but will increase the length of the planetary roller screw, thus limiting the stroke of the planetary roller screw within the same volume space.

[0065] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-load leg system for a humanoid robot, characterized in that, include: The thigh skeleton and the lower leg skeleton are movably connected by a rotation axis; The planetary roller screw assembly includes a base end spherical ball bearing, an end cap type force sensor, a planetary roller screw, a planetary roller screw rod, and an output end spherical ball bearing; the base end spherical ball bearing is fixed to the thigh frame by an external thread type equal height bolt, the end of the planetary roller screw is locked with the output end spherical ball bearing, and the planetary roller screw drives the output end spherical ball bearing to perform reciprocating linear motion; The main force transmission rod is connected to the output end joint ball bearing at one end, and the other end is movably connected to the lower leg skeleton through a force sensor. The secondary force transmission rod is connected to the output end joint ball bearing at one end, and the other end is restricted to the thigh skeleton. The driver, fixed on the driver heat sink, is used to control the relative linear motion between the planetary roller screw and the planetary roller lead screw; The dual-force sensor system includes an end cap type force sensor integrated into the base of the planetary roller screw assembly and a force sensor set on the main transmission rod, used to monitor axial force, torque and six-dimensional force / torque of the lower leg skeleton in real time; A mechanical limiting structure is installed between the thigh skeleton and the calf skeleton to limit the maximum bending angle of the knee joint to 140°. The system also includes a main force transmission shaft, a secondary force transmission shaft, a main support shaft, and a secondary support shaft; polytetrafluoroethylene gaskets are disposed at the axial connection of the main force transmission shaft, the secondary force transmission shaft, the main support shaft, and the secondary support shaft to limit axial movement and provide elastic damping; The base end spherical ball bearing is fixed to the thigh frame by an external thread type equal height bolt. The optical axis section of the external thread type equal height bolt mates with the holes of the thigh frame and the base end spherical ball bearing, and is locked by a lock nut. The end cap type force sensor is connected to the base end spherical ball bearing to prevent rotation through a hexagonal stop. The output end spherical ball bearing is connected to the main force transmission rod and the auxiliary force transmission rod through the main drive shaft and the auxiliary drive shaft. Angular contact ball bearings A are arranged back to back at both ends of the main drive shaft and the auxiliary drive shaft. The outer ring of the angular contact ball bearing A is limited by the stop of the main force transmission rod, and the inner ring is limited by the stepped end face of the main drive shaft and the auxiliary drive shaft, and is pre-tightened by a lock nut. The force sensor is a six-dimensional force / torque sensor. One end of the sensor is fixed to the main force transmission rod through a threaded section and a locking nut, and the other end is connected to the calf frame through a needle roller bearing A and the main force transmission shaft and the auxiliary force transmission shaft. The needle roller bearing A is fixed by a retaining ring A through a hole, and a polytetrafluoroethylene gasket A is provided between the main force transmission shaft and the auxiliary force transmission shaft.

2. The system according to claim 1, characterized in that: The rotating shaft is connected to the thigh and calf skeletons via angular contact ball bearings B. The angular contact ball bearings B are arranged back to back, with the outer ring limited by the stop of the calf skeleton and the inner ring pre-tightened by the stepped end face of the rotating shaft and fastening screws B.

3. The system according to claim 1, characterized in that: The auxiliary force transmission rod is connected to the thigh skeleton via a needle roller bearing B, the main support shaft, and the auxiliary support shaft. The needle roller bearing B is fixed by a retaining ring B through a hole. A polytetrafluoroethylene gasket B is provided between the main support shaft and the auxiliary support shaft.

4. The system according to claim 1, characterized in that: The planetary roller screw has rollers made of nitrided hard alloy material, a lead of 5mm, and a theoretical load capacity of 20kN per screw. The driver is a high-dynamic servo motor with a peak torque of 50Nm, a rated speed of 3000rpm, a control cycle of 0.5ms, and supports three-loop control modes: position, speed, and torque.

5. A motion control method for a humanoid robot leg system, the method being based on the system described in claim 1, characterized in that, Includes the following steps: The axial force and torque of the planetary roller screw are monitored in real time using end cap type force sensors; The force sensor of the main force transmission rod acquires six-dimensional force / torque data of the lower leg skeleton; An adaptive impedance control algorithm is adopted, combined with sensor feedback to dynamically adjust the output torque of the driver, so as to achieve the coordination of the position loop and the force control loop; When an abnormal load is detected, a low-impedance mode or emergency braking is triggered, and the joint is locked by mechanical limit.

6. The method according to claim 5, characterized in that: The adaptive impedance control algorithm includes friction compensation and inertia compensation, with a control bandwidth ≥100Hz, response time ≤0.1s, and a single-leg load capacity of up to 200kg.

7. A safety protection method for a humanoid robot leg system, the method being based on the system described in claim 1, characterized in that, include: The impact load is absorbed by the elastic deformation of the polytetrafluoroethylene gasket; When the mechanical limit is triggered, it limits the travel of the planetary roller screw and cuts off the power supply to the driver; By using dual-sensor redundancy verification, abnormal data is eliminated and a fault diagnosis program is initiated.

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