Heavy-load leg system of humanoid robot

Abstract

A large-load leg system of a humanoid robot comprises a thigh skeleton, a shank skeleton, a planetary roller lead screw assembly, a main dowel bar, an auxiliary dowel bar and a driver. The base end of the planetary roller screw assembly is fixed on the thigh skeleton through a base end joint ball bearing, and a planetary roller screw pushes an output end joint ball bearing to do reciprocating rectilinear motion; the other end of the auxiliary dowel bar is limited on the thigh skeleton, the other end of the main dowel bar is fixedly connected with the force sensor, the force sensor is movably connected with the shank skeleton through the main dowel shaft, and the shank skeleton rotates around the rotating shaft; the driver is used for controlling the relative linear motion of the planetary roller screw rod and the planetary roller screw rod, the driver is fixed on the driver heat dissipation plate, and the driver heat dissipation plate is fixed on the thigh skeleton; the shank skeleton is provided with a wiring hole and a wire embedding groove, and the tail end of the shank is provided with a bearing hole site; the hip joint pitching base is connected with the hip through a fastening screw A;

Description

Technical Field

[0001] The present invention relates to a large-load leg system for a humanoid robot and belongs to the field of intelligent robots. Background Art

[0002] The leg design of a humanoid robot is one of its core functions and has important application backgrounds, mainly reflected in the following aspects:

[0003] Adapting to complex environments: The leg design of a humanoid robot enables it to adapt to various complex terrains and environments. For example, through the leg structure design, the robot can easily cross rough terrains and overcome obstacles. This ability makes it of great value in scenarios such as disaster rescue and field exploration, and it can replace humans to enter dangerous areas and perform tasks.

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

[0005] Versatility and adaptability: A good leg design endows a humanoid robot with stronger versatility, enabling it to adapt to a variety of application scenarios. For example, a humanoid robot can serve as an assistant in a home environment to complete daily housework, assist in production in the industrial field, and assist in nursing in the medical field. This versatility not only expands the applicable range of the robot but also reduces the cost of multi-scenario applications.

[0006] Technology and intelligent development: The progress of leg design is closely related to the intelligent process of the robot. Through advanced sensors and motion control algorithms, a humanoid robot can autonomously learn and optimize its motion patterns, thus showing higher adaptability and efficiency in complex environments.

[0007] Anthropomorphism and social acceptance: The leg design of a humanoid robot is not only for functionality but also for better integration into human society. Its human-like appearance and motion capabilities make it more easily accepted by humans, thus having broad application prospects in the service industry, home companionship, and other fields.

[0008] However, there are drawbacks in the existing leg designs:

[0009] Balance and stability issues: When a humanoid robot is walking dynamically, especially when facing complex terrains or dynamic environments, balance control remains a core problem. Each step of a bipedal robot is essentially in a state of "controlled fall" and requires continuous prediction, adjustment, and response to multiple factors. In addition, a humanoid robot is prone to being affected by factors such as uneven ground and external force interference during movement, resulting in insufficient stability.

[0010] Motion ability limitation: Although the leg design of humanoid robots has been continuously optimized, their motion ability still fails to reach the level of the human skeletal muscle system. Current robots still have gaps in speed, flexibility, and dynamic response ability, making it difficult to achieve efficient human-like motion in complex environments.

[0011] Energy efficiency and endurance: The leg design needs to reduce energy consumption while maintaining high rigidity and low inertia. However, the current technological level still makes it difficult to achieve a perfect balance among these goals, resulting in limited endurance of humanoid robots.

[0012] Safety and reliability: Humanoid robots may fall due to loss of balance during motion, which not only damages the robot itself but also poses potential risks to surrounding personnel. Therefore, improving the safety and reliability of robots is an urgent problem to be solved.

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

[0014] Limitations of control algorithms: Current control algorithms still have deficiencies in dealing with complex terrains 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 deficiencies of the above-mentioned prior art, the present invention provides a system, and specifically adopts the following technical solutions:

[0016] A large-load leg system for a humanoid robot, characterized by comprising:

[0017] A thigh bone frame and a calf bone frame, which are movably connected through a rotating shaft;

[0018] A planetary roller screw assembly, including a base-end spherical joint bearing, an end-cap type force sensor, a planetary roller screw, a planetary roller screw rod, and an output-end spherical joint bearing; the base-end spherical joint bearing is fixed to the thigh bone frame through an externally threaded equal-height bolt, the end of the planetary roller screw rod is locked with the output-end spherical joint bearing, and the planetary roller screw rod pushes the output-end spherical joint bearing to perform reciprocating linear motion;

[0019] A main force transmission rod and a secondary force transmission rod, one end of the main force transmission rod is connected to the output-end spherical joint bearing, and the other end is movably connected to the calf bone frame through a force sensor, one end of the secondary force transmission rod is connected to the output-end spherical joint bearing, and the other end is restricted on the thigh bone frame;

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

[0021] The dual-force sensor system includes an end-cap type force sensor integrated at the base end of the planetary roller screw assembly and a force sensor disposed on the main force transmission rod, and is used to real-time monitor the axial force, torque, and six-dimensional force / moment of the calf skeleton (13);

[0022] The mechanical limit structure is disposed between the thigh skeleton and the calf skeleton to limit the maximum bending angle of the knee joint to 140°;

[0023] The polytetrafluoroethylene gasket is disposed at the axial connection joints of the main force transmission shaft, the secondary force transmission shaft, the main support shaft, and the secondary support shaft, and is used to limit axial movement and provide elastic damping.

[0024] Preferably: The base-end spherical joint bearing is fixed to the thigh skeleton by an externally threaded equal-height bolt. The optical axis section of the externally threaded equal-height bolt is in fit with the hole positions of the thigh skeleton and the base-end spherical joint bearing, and is locked by a locknut; The end-cap type force sensor is anti-rotationally connected to the base-end spherical joint bearing through a hexagonal spigot.

[0025] Preferably: The output-end spherical joint bearing connects the main force transmission rod and the secondary force transmission rod through the main drive shaft and the secondary drive shaft. Angular contact ball bearings A arranged back-to-back are provided at both ends of the main drive shaft and the secondary drive shaft. The outer ring of the angular contact ball bearing A is limited by the spigot of the main force transmission rod, and the inner ring is limited by the stepped end faces of the main drive shaft and the secondary drive shaft, and is preloaded by a locknut.

[0026] Preferably: The force sensor is a six-dimensional force / moment sensor. One end of it is fixed to the main force transmission rod through a threaded section and a locknut, and the other end is connected to the calf skeleton through a needle roller bearing A with the main force transmission shaft and the secondary force transmission shaft; The needle roller bearing A is fixed by a snap ring for hole A, and a polytetrafluoroethylene gasket A is provided between the main force transmission shaft and the secondary force transmission shaft.

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

[0028] Preferably: The secondary force transmission rod is connected to the thigh skeleton through a needle roller bearing B with the main support shaft and the secondary support shaft. The needle roller bearing B is fixed by a snap ring for hole B, and a polytetrafluoroethylene gasket B is provided between the main support shaft and the secondary support shaft.

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

[0030] The present invention also discloses a motion control method for a humanoid robot leg system. Based on the above system, it is characterized by including the following steps:

[0031] Real-time monitor the axial force and torque of the planetary roller screw through an end-cap type force sensor;

[0032] Obtain the six-axis force / moment data of the calf skeleton through the force sensor of the main force transmission rod;

[0033] Adopt an adaptive impedance control algorithm, combine sensor feedback to dynamically adjust the output torque of the driver, and achieve the coordination of the position loop and the force control loop;

[0034] When an abnormal load is detected, trigger the low-impedance mode or emergency braking, and lock the joint through mechanical limit.

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

[0036] The present invention also discloses a safety protection method for a humanoid robot leg system. Based on the above system, it is characterized by including:

[0037] Absorb the impact load through the elastic deformation of the polytetrafluoroethylene gasket;

[0038] When the mechanical limit is triggered, limit the stroke of the planetary roller screw and cut off the power supply of the driver;

[0039] Through dual-sensor redundant verification, eliminate abnormal data and start the fault diagnosis program.

[0040] Beneficial effects

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

[0042] The present invention adopts the form of a planetary roller screw, which can greatly improve the load capacity of the thigh. The single-leg load capacity far exceeds the limit load of humans, thereby improving the endurance of the humanoid robot. Moreover, adopting the planetary roller screw solution, the installation is simple and convenient, and the thigh skeleton can be used for multiple purposes, greatly reducing the production and manufacturing costs.

[0043] Both ends of the planetary roller screw and the planetary roller lead screw are spherical joint bearings, which can well achieve the balance and stability of their own pushing and pulling forces. The distance between the two spherical joint bearings changes stably, and the calf bending angle also changes stably.

[0044] Because of the end cover force sensor and the force sensor in the present invention, the bending moment change of the calf can be monitored in real time, the motion control accuracy and real-time performance can be improved, the motion risk can be identified in time, and the overload damage can be avoided. By improving the motion control level, the balance can be improved, and then the stability, safety and reliability can be improved.

[0045] The installation and fixing methods of the main force transmission shaft and the auxiliary force transmission shaft, and the main support shaft and the auxiliary support shaft are simple and convenient to disassemble and assemble.

[0046] The planetary roller screw is designed with a planetary meshing structure and high-rigidity materials. The single-leg load capacity is increased to 200 kg (far exceeding the human limit), and the transmission efficiency is increased by 15% compared with the traditional ball screw, significantly extending the endurance time;

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

[0048] Driver dynamic response: High-bandwidth control (bandwidth ≥ 100 Hz) ensures that the leg system completes the acceleration from rest to the maximum speed within 0.1 s, and the dynamic response ability is close to the level of human muscles;

[0049] This scheme uses a polytetrafluoroethylene gasket to limit the axial displacement, which can achieve stable functions at a lower cost. The method of using a polytetrafluoroethylene gasket to limit the axial movement can not only provide a certain basic damping, but also provide a certain elastic deformation to avoid the damage of parts after being subjected to impact loads. Description of the Drawings

[0050] Figure 1 It is an assembly schematic diagram of the leg system of the humanoid robot of the present inventor;

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

[0052] Figure 3 It is Figure 2 the R-R cross-sectional view of

[0053] Figure 4 It is Figure 2 the T-T cross-sectional view of

[0054] Figure 5 It is a schematic diagram of the leg bending of the humanoid robot of the present inventor;

[0055] In the figure: 1. thigh bone frame; 2. hip pitching base; 3. fastening screw A; 4. base end joint bearing; 5. end cover type force sensor; 6. planetary roller screw; 7. driver; 8. planetary roller screw; 9. output end joint bearing; 10. main force transmission rod; 11. force sensor; 12. polytetrafluoroethylene gasket A; 13. calf bone frame; 14. auxiliary force transmission rod; 15. driver heat dissipation plate; 16. rotating shaft; 17. fastening screw B; 18. external thread type equal height bolt; 19. lock washer A; 20. lock nut A; 21. main drive shaft; 22. angular contact ball bearing A; 23. auxiliary drive shaft; 24. lock washer B; 25. lock nut B; 26. force sensor; 27. lock nut C; 28. lock washer C; 29. needle roller bearing A; 30. hole retaining ring A; 31. main force transmission shaft; 32. auxiliary force transmission shaft; 33. lock washer D; 34. fastening screw D; 35. fastening screw C; 36. lock washer E; 37. angular contact ball bearing B; 38. main support shaft; 39. auxiliary support shaft; 40. needle roller bearing B; 41. hole retaining ring B; 42. polytetrafluoroethylene gasket B; 43. fastening screw E; 44. mechanical limit; 13-1. wire routing hole; 13-2. wire embedding groove; 13-3. bearing hole position. Specific implementation mode

[0056] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0057] Please refer to Figures 1-5, the present invention provides a technical solution: a large-load leg system for a humanoid robot, including a thigh bone frame 1, a calf bone frame 13, a planetary roller screw assembly, a main force transmission rod 10, an auxiliary force transmission rod 14 and a driver 7; wherein the planetary roller screw assembly includes a base-end spherical joint bearing, an end-cap type force sensor, a planetary roller screw, a planetary roller screw rod, and an output-end spherical joint bearing; the base-end spherical joint of the planetary roller screw assembly is fixed on the thigh bone frame through the base-end spherical joint bearing, the base-end spherical joint bearing and the end-cap type force sensor are fixedly connected through fastening screw C, and a hexagonal counterbore is provided on the end-cap type force sensor to prevent relative rotation; the end of the planetary roller screw rod is a threaded end, and the threaded end of the planetary roller screw rod is locked and fixed with the output-end spherical joint bearing; the rollers of the planetary roller screw are made of cemented carbide material, the surface is nitrided, the lead of the screw is 5mm, the theoretical load capacity of a single screw reaches 20kN, and with the symmetric support structure of the double spherical joint bearings, the lateral torque can be effectively offset to ensure the motion stability under high load; the planetary roller screw rod pushes the output-end spherical joint bearing to make reciprocating linear motion, and transmits the force to one end of the main force transmission rod and one end of the auxiliary force transmission rod, and the other end of the auxiliary force transmission rod is restricted on the thigh bone frame; the other end of the main force transmission rod is fixedly connected with the force sensor, one end of the force sensor is a threaded section, and the threaded section of the force sensor is fixed on the main force transmission rod through a lock washer C and a lock nut C; a needle roller bearing A is nested at the other end of the force sensor, and the needle roller bearing A is fixed in the force sensor through a snap ring A for hole, and the other end of the force sensor is movably connected with the calf bone frame through a main force transmission shaft and an auxiliary force transmission shaft, and the main force transmission rod transmits the force to the calf bone frame through the force sensor, so as to realize the rotational motion of the calf bone 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 rod, the driver is fixed on the driver heat dissipation plate, and the driver heat dissipation plate is fixed on the thigh bone frame, so that the space of the thigh bone frame can be fully utilized for layout, which can reduce the outer envelope size of the thigh and the weight of the whole machine. There are wire routing holes and wire embedding grooves on the calf bone frame for wire routing to avoid damage to the wire harness due to bending. A bearing hole position is provided at the end of the calf for the rotational motion of the ankle joint; the force sensor adopts a six-axis force / torque sensor, the sampling frequency is 1kHz, and the signal is transmitted to the controller through the shielded cable in the wire embedding groove to avoid electromagnetic interference; the driver adopts a high-dynamic-response servo motor (peak torque 50 Nm, rated speed 3000 rpm), with a built-in temperature sensor and an overcurrent protection module, communicates with the main control through the CAN bus, the control period is 0.5 ms, and supports the switching of position, speed, and torque three-loop control modes. The hip joint pitch base is connected to the hip through fastening screw A.

[0058] Refer to Figure 3, The base-end spherical joint bearing is fixed to the thigh bone frame by an externally threaded equal-height bolt. The externally threaded equal-height bolt sequentially passes through the thigh bone frame, the inner hole of the base-end spherical joint bearing, and the thigh bone frame. The smooth shaft section of the externally threaded equal-height bolt is in fit with the thigh bone frame and the hole position of the base-end spherical joint bearing. The threaded section at the end of the externally threaded equal-height bolt is locked by a locknut A, thereby fixing the smooth shaft section of the externally threaded equal-height bolt, the thigh bone frame, and the hole position of the base-end spherical joint bearing as a whole. The base-end spherical joint bearing and the end-cover type force sensor are fixedly connected by a fastening screw C, and a hexagonal spigot is provided on the end-cover type force sensor to prevent relative rotation. The end of the planetary roller screw is a threaded end, and the threaded end of the planetary roller screw is locked and fixed to the output-end spherical joint bearing.

[0059] The output-end spherical joint bearing is connected to the main force transmission rod and the auxiliary force transmission rod through the main drive shaft. The specific connection method is as follows: The main drive shaft sequentially passes through the angular contact ball bearing A, the auxiliary force transmission rod, the output-end spherical joint bearing, the auxiliary force transmission rod, the auxiliary drive shaft, and another angular contact ball bearing A, the lock washer B, and the locknut B. The two angular contact ball bearings A are arranged back-to-back, which can not only bear axial load and radial load, but also bear a large bending moment, reducing the volume and weight. By adjusting the pre-tightening force of the locknut B, the axial clearance caused by machining accuracy or installation error of the main drive shaft can be offset, and the pre-tightening stiffness of the angular contact ball bearing can be improved, thereby improving the stiffness and position accuracy of the entire thigh. The two angular contact ball bearings A are respectively 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 spigot of the main force transmission member itself, and the inner rings of the two angular contact ball bearings are respectively limited by the end faces of the main drive shaft and the auxiliary drive shaft, and are fixed by the locknut B.

[0060] The other end of the main force transfer rod is fixedly connected to the force sensor. One end of the force sensor is a threaded section, and the threaded section of the force sensor is fixed to the main force transfer rod through a lock washer C and a lock nut C. The other end of the force sensor nests a needle roller bearing A, and the needle roller bearing A is fixed in the force sensor through a hole snap ring A, which can reduce the size of the force sensor and thus reduce the volume of the knee joint. The other end of the force sensor is movably connected to the calf skeleton through a main force transfer shaft and a secondary force transfer shaft. The specific connection method is as follows: The main force transfer shaft sequentially passes through the calf skeleton, a polytetrafluoroethylene gasket A, the inner ring of the needle roller bearing A, another polytetrafluoroethylene gasket A, and the secondary force transfer shaft. The end of the main force transfer shaft is a threaded section, and the threaded section of the main force transfer shaft is locked through a lock washer D and a fastening screw D. By tightening the fastening screw D, the axial clearance between the main force transfer shaft and the secondary force transfer shaft can be eliminated, the installation accuracy can be improved, the vibration caused by the clearance during the movement can be avoided, and the stability of the movement control can be improved. The function of the two polytetrafluoroethylene gaskets A is to provide a certain damping force and limit the axial movement of the force sensor. The polytetrafluoroethylene gasket A has a certain elasticity, and when the force sensor is subjected to a large impact load, it allows the polytetrafluoroethylene gasket A to avoid the force sensor being damaged by small axial deformation.

[0061] Refer to Figure 4 , the calf skeleton is movably connected to the thigh skeleton through a rotating shaft. The specific connection method is as follows: The end faces of the two rotating shafts are respectively locked on both sides of the thigh skeleton through a lock washer E and a fastening screw B. The shaft ends of the two rotating shafts respectively pass through the inner rings of two angular contact ball bearings B. The two angular contact ball bearings B are nested on both sides of the calf skeleton. The outer rings of the angular contact ball bearings B are limited and fixed through the stop of the calf skeleton. The inner rings of the angular contact ball bearings B are limited and fixed through the stepped shaft end face of the rotating shaft. By tightening the fastening screw B, the clearance along the axial direction of the rotating shaft can be eliminated, and a certain preload can be applied to the angular contact ball bearings B along the axial direction, improving the stiffness of the bearings, thus avoiding the clearance crosstalk caused by insufficient rigidity when receiving a large impact force, improving the safety and movement control accuracy, and reducing the transmission hysteresis. The two angular contact ball bearings B are arranged back to back, so that the rotating shaft can not only bear axial force and radial force, but also bear a large bending moment; the calf skeleton can rotate around the rotating shaft.

[0062] Refer to Figure 4, one end of the secondary force transmission rod is sleeved on the main drive shaft. A needle roller bearing B is nested at the other end of the secondary force transmission rod, and the needle roller bearing B is fixed in the secondary force transmission rod by a snap ring B for hole use, which can reduce the size of the secondary force transmission rod, thereby reducing the volume of the knee joint. The other end of the secondary force transmission rod is movably connected to the thigh bone frame through the main support shaft. The specific connection method is as follows: the main support shaft sequentially passes through the thigh bone frame, the polytetrafluoroethylene gasket B, the needle roller bearing B, another polytetrafluoroethylene gasket B, the secondary support shaft, and the inner ring of the secondary support shaft sleeving the outer ring of the main support shaft. The end of the main support shaft is a threaded section, and the threaded section of the main support shaft is locked by a fastening screw E. By locking the fastening screw E, the axial clearance between the main support shaft and the secondary support shaft can be eliminated, the installation accuracy can be improved, the vibration caused by the clearance during the movement can be avoided, and the stability of the movement control can be improved. The function of the two polytetrafluoroethylene gaskets B is that they can not only provide a certain damping force but also limit the axial movement of the secondary force transmission rod. The polytetrafluoroethylene gasket B has a certain elasticity and can also allow the polytetrafluoroethylene gasket B to undergo a small axial deformation to avoid the force transmission rod being damaged by jamming when the secondary force transmission rod is subjected to a large impact load.

[0063] Refer to Figure 5 , for the case where the knee joint is bent by 140 degrees, at this time, the thigh bone frame and the calf bone frame will be limited by the mechanical limit area, which can avoid the stroke of the planetary roller screw exceeding the limit range. When the leg is subjected to a large impact load, mechanical limit protection can be provided. The end cap type force sensor can monitor the pushing and pulling force magnitude and torque change of the planetary roller screw in real time, which can well protect the planetary roller screw assembly and start safety protection in case of abnormal conditions. Since the bending moment magnitude of the calf is changing in real time, if the bending moment of the calf is calculated through the force and moment changes of the planetary roller screw, there will be frictional losses, resulting in a deviation in the moment finally acting on the calf. At this time, if a force sensor is installed on the main force transmission rod, the force and moment changes acting on the calf bone frame can be directly calculated, which can improve the accuracy and real-time performance of the movement 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 angular contact ball bearings B can both be replaced with needle roller bearings or deep groove ball bearings. The main force transmission rod can be combined with the force sensor, which will result in higher installation accuracy but also increased 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 and limit the stroke size of the planetary roller screw under 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 perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A large-load leg system for a humanoid robot, characterized in that: include: The thigh frame and the calf frame are movably connected via a rotating axis; The planetary roller screw assembly includes a base end joint ball bearing, an end cover type force sensor, a planetary roller screw, a planetary roller screw, and an output end joint ball bearing; the base end joint 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 joint ball bearing, and the planetary roller screw drives the output end joint ball bearing to perform reciprocating linear motion; A main force transmission rod and a secondary force transmission rod, one end of the main force transmission rod is connected to the output end joint ball bearing, and the other end is movably connected to the calf frame through a force sensor, and one end of the secondary force transmission rod is connected to the output end joint ball bearing, and the other end is restricted on the thigh frame; A driver, fixed on the driver heat sink, is used to control the relative linear motion between the planetary roller screw and the planetary roller screw; A dual force sensor system, comprising an end cap type force sensor integrated at the base end of the planetary roller screw assembly and a force sensor arranged at the main force transmission rod, for real-time monitoring of axial force, torque and six-dimensional force / torque of the calf skeleton (13); The mechanical limit structure is set between the thigh frame and the calf frame to limit the maximum bending angle of the knee joint to 140°; The polytetrafluoroethylene gasket is arranged at the axial connection of the main force transmission shaft, the auxiliary force transmission shaft, the main support shaft and the auxiliary support shaft to limit the axial movement and provide elastic damping.

2. The system according to claim 1, characterized in that: The base-end joint ball bearing is fixed to the thigh frame by an externally threaded contour bolt. The optical axis section of the externally threaded contour bolt cooperates with the hole position of the thigh frame and the base-end joint ball bearing, and is locked by a lock nut. The end cover type force sensor is connected to the base-end joint ball bearing for anti-rotation through a hexagonal stop.

3. The system according to claim 1, characterized in that: Preferably, the output end joint ball bearing connects the main force transmission rod and the auxiliary force transmission rod through the main drive shaft and the auxiliary drive shaft, and angular contact ball bearings A arranged back to back are provided 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 faces of the main drive shaft and the auxiliary drive shaft, and is pre-tightened by a locking nut.

4. The system according to claim 1, characterized in that: 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 bearing A and the main force transmission shaft and the secondary force transmission shaft; the needle bearing A is fixed through a hole with a retaining ring A, and a polytetrafluoroethylene gasket A is arranged between the main force transmission shaft and the secondary force transmission shaft.

5. The system according to claim 1, characterized in that: The rotating shaft is connected to the thigh frame and the calf frame through angular contact ball bearings B. The angular contact ball bearings B are arranged back to back. The outer ring is limited by the stopper of the calf frame, and the inner ring is pre-tightened and fixed by the stepped end face of the rotating shaft and the fastening screws B.

6. The system according to claim 1, characterized in that: The secondary force transmission rod is connected to the thigh frame through a needle bearing B and the main support shaft and the secondary support shaft. The needle bearing B is fixed by a retaining ring B through a hole. A polytetrafluoroethylene gasket B is arranged between the main support shaft and the secondary support shaft.

7. The system according to claim 1, characterized in that: The rollers of the planetary roller screw are made of nitrided carbide material, with a lead of 5mm and a theoretical load capacity of 20kN for a single 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.

8. A motion control method for a humanoid robot leg system, the method being based on the system of claim 1, characterized in that: The following steps are involved: The axial force and torque of the planetary roller screw are monitored in real time through the end cap type force sensor; The six-dimensional force / torque data of the calf skeleton is obtained through the force sensor of the main force transmission rod; Adopting adaptive impedance control algorithm, combined with sensor feedback, dynamically adjusts the output torque of the driver to achieve coordination between the position loop and the force control loop; When abnormal load is detected, low impedance mode or emergency braking is triggered and the joint is locked by mechanical limit stops.

9. The method according to claim 8, characterized in that: The adaptive impedance control algorithm includes friction compensation and inertia compensation, the control bandwidth is ≥100Hz, the response time is ≤0.1s, and the single-leg load capacity is up to 200kg.

10. A safety protection method for a humanoid robot leg system, the method being based on the system of claim 1, characterized in that: include: Absorb shock loads through elastic deformation of PTFE gasket; When the mechanical limit is triggered, the travel of the planetary roller screw is limited and the power supply to the driver is cut off; Through dual sensor redundancy verification, abnormal data is eliminated and the fault diagnosis program is started.

Images