Variable stiffness compliant actuator and robot

Abstract

This application discloses a variable stiffness compliant actuator and a robot. The pneumatic muscle assembly has a sealed accommodating cavity, comprising a first assembly section, an adjustment section, and a second assembly section. The second assembly section includes a gas interface seat. A multi-degree-of-freedom deflector is placed within the sealed accommodating cavity and fixedly connected to the second assembly section. The linear drive assembly includes a linear drive motor and an output shaft. The linear drive motor and the adjustment section form a clearance gap. One end of the linear drive motor is movably connected to the multi-degree-of-freedom deflector, and the other end is sealed to the first assembly section. The output shaft is connected to one end of the linear drive motor. Under normal operating conditions, the axis of the linear drive assembly coincides with the axis of the pneumatic muscle assembly. When the pneumatic muscle assembly deforms or is impacted by an external force, the clearance gap provides space for the deflection of the multi-degree-of-freedom deflector and the radial deformation of the pneumatic muscle assembly. This allows the actuator to possess both stiffness and compliance.

Description

Technical Field

[0001] This application relates to the field of biomimetic robotics technology, specifically to a variable stiffness compliant actuator and robot. Background Technology

[0002] The lower limb joints of humanoid robots need to balance high output force, response speed, impact resistance, and the flexibility of simulating human tendons.

[0003] In related technologies, the lower limbs of humanoid robots are mainly driven by purely electric linear joints or pneumatic manual walking, but both solutions have obvious limitations: On the one hand, pure electric linear joints typically exhibit high mechanical stiffness. In scenarios involving foot impact, external disturbances, or human-robot contact, high-stiffness transmission structures are prone to generating large impact forces and transmission reaction forces. This not only hinders the improvement of safety and energy buffering capacity during humanoid robot movement but also fails to realistically simulate the natural compliance characteristics of the human body and tendons.

[0004] On the other hand, although pneumatic artificial muscles have advantages such as light weight, good flexibility, and force distribution similar to human muscles, they have low inherent stiffness and slow dynamic response. Under high load and high frequency dynamic response requirements, they are difficult to serve as independent main actuators to handle the heavy load movements of humanoid robot lower limbs.

[0005] Therefore, how to make the actuator combine the rigidity of an electric linear drive motor with the flexibility of a pneumatic artificial muscle is a technical problem that urgently needs to be solved for the lower limb actuator of a humanoid robot. Summary of the Invention

[0006] Based on the above situation, the main purpose of this application is to provide a variable stiffness compliant actuator, control system and robot to solve the problems of high stiffness and insufficient compliance of pure electric linear joints, and the difficulty of traditional pneumatic muscles to directly bear the main drive of the robot.

[0007] To achieve the above objectives, the technical solution adopted in this application is as follows: A variable stiffness compliant actuator includes a pneumatic muscle assembly, a multi-degree-of-freedom deflector, and a linear drive assembly. The pneumatic muscle assembly has a sealed accommodating cavity inside, and has a first assembly section, an adjustment section and a second assembly section arranged along the axial direction; the second assembly section includes a gas interface seat for filling the sealed accommodating cavity with gas or connecting to an external pressure control device. The multi-degree-of-freedom deflector is placed within the sealed accommodating cavity and fixedly connected to the second assembly section; and... The linear drive assembly includes a linear drive motor and an output shaft; the linear drive motor is located within the sealed accommodating cavity and is radially spaced from the adjusting section to form a clearance; one end of the linear drive motor is movably connected to the multi-degree-of-freedom deflector, and the other end is sealed to the first assembly section; the output shaft is connected to the end of the linear drive motor away from the multi-degree-of-freedom deflector and extends out of the sealed accommodating cavity; In the initial state where no external force is applied, the axis of the linear drive assembly coincides with the axis of the pneumatic muscle assembly. When the pneumatic muscle assembly deforms or is subjected to external impact, the clearance provides clearance space for the deflection of the multi-degree-of-freedom deflector and the radial deformation of the pneumatic muscle assembly.

[0008] Optionally, the first assembly section includes a first flexible tube, a first clamping seat, and a first end cap; The first flexible tube is circumferentially sealed between the first clamping seat and the first end cap; The first clamping seat is fixedly connected to the end face of the linear drive motor away from the multi-degree-of-freedom deflector and is axially sealed to the end face of the linear drive motor; the first end cap is fixedly connected to the first clamping seat. The output shaft passes through the first clamping seat and the first end cap in sequence.

[0009] Optionally, the first clamping seat and the first end cap are respectively provided with matching first conical surfaces, and the first flexible tube body is sealed between the two first conical surfaces; a first sealing element is clamped between the first clamping seat and the opposite end face of the linear drive motor.

[0010] Optionally, the second assembly section includes a second flexible tube, a second end cap, a second clamping seat, and a hollow connecting rod; The second flexible tube is circumferentially sealed between the second end cap and the second clamping seat; The gas interface seat is fixedly connected to the top wall of the second end cover; the hollow connecting rod passes through the second end cover and is inserted into the gas interface seat; the end of the hollow connecting rod away from the gas interface seat is fixedly connected to the multi-degree-of-freedom deflector; the mating points of the gas interface seat, the second end cover, and the hollow connecting rod are sealed. The gas interface seat, the hollow connecting rod, and the multi-degree-of-freedom deflector are respectively provided with a first air passage, a second air passage, and a third air passage. The first air passage, the second air passage, and the third air passage are connected in sequence to form a closed air passage connecting the sealed accommodating cavity.

[0011] Optionally, the inner peripheral wall of the second end cap and the outer peripheral wall of the second clamping seat are respectively provided with matching second conical surfaces, and the second flexible tube body is sealed and clamped between the two second conical surfaces; The gas interface seat has a groove on its end face facing the second end cap; the pneumatic muscle assembly also includes a second sealing element, which is placed in the groove and sleeved on the outer peripheral surface of the hollow connecting rod to seal the assembly gap between the second end cap, the hollow connecting rod and the gas interface seat.

[0012] Optionally, the position of the multi-free biasing element corresponds to that of the adjustment section.

[0013] Optionally, the first flexible tube includes a first flexible inner tube and a first braided mesh covering the outer periphery of the first flexible inner tube; the second flexible tube includes a second flexible inner tube and a second braided mesh covering the outer periphery of the second flexible inner tube; the adjusting section includes a third flexible inner tube and a third braided mesh covering the outer periphery of the third flexible inner tube. The first flexible inner tube, the second flexible inner tube, and the third flexible inner tube are integrally formed to form an elastic core tube; The first woven mesh sleeve, the second woven mesh sleeve, and the third woven mesh sleeve are integrally formed to form a mesh covering; The pneumatic muscle assembly also includes a woven mesh folding guide, wherein the mesh covering passes through the inside of the woven mesh folding guide and folds outward along the end of the woven mesh folding guide to cover and sleeve the outer peripheral surface of the elastic core tube.

[0014] Optionally, the multi-degree-of-freedom biasing member includes a first pivot, a second pivot, and a connecting member; wherein, The first pivot seat is fixedly connected to the hollow connecting rod and is rotatably connected to the connecting member along the first rotation axis; The second pivot seat is movably connected to the linear drive motor and is rotatably connected to the connector along the second rotation axis; the second rotation axis intersects and is orthogonal to the first rotation axis. Optionally, the second pivot is configured to be movable along the axial direction of the linear drive motor and rotatable about the axial direction of the linear drive motor.

[0015] A robot comprising a variable stiffness compliant actuator as described in any of the above embodiments.

[0016] Beneficial effects: This application integrates a linear drive motor within the sealed cavity of the pneumatic muscle assembly, achieving a fusion of electric and pneumatic power. Specifically, this application injects gas into the sealed cavity through the gas interface seat of the second assembly section, allowing the pneumatic muscle assembly to adjust its pneumatic stiffness upon external impact. Combined with the stiffness of the linear drive motor itself, this enables the entire actuator to adjust between stiffness and compliance, effectively solving the problem of traditional actuators having only one stiffness and being unable to balance rigidity and compliance.

[0017] Meanwhile, this application also achieves adaptive buffering and anti-jamming effects through multi-degree-of-freedom deflectors and clearance gaps. Upon external impact, the multi-degree-of-freedom deflectors deflect relative to the linear drive motor, and the pneumatic muscle assembly deforms. At this time, the clearance gap between the linear drive motor and the adjustment section provides ample physical clearance space for both the deflection angle displacement of the multi-degree-of-freedom deflectors and the radial deformation of the pneumatic muscle assembly's adjustment section. In this way, the instantaneous large impact force is converted into the gas compression energy and oscillating clearance displacement of the pneumatic muscle assembly, effectively blocking the direct transmission of lateral impact force to the rigid transmission mechanism of the linear drive motor, preventing motor jamming or structural damage, and greatly improving the mechanical reliability of the actuator under impact conditions. The connection between the multi-degree-of-freedom deflectors and the pneumatic muscle assembly also reasonably constrains the compliance of the pneumatic muscle assembly; its elastic deformation mainly serves axial buffering and variable stiffness control, rather than becoming uncontrolled lateral oscillation.

[0018] Other beneficial effects of this application will be explained in detail through the introduction of specific technical features and technical solutions in the specific embodiments. Those skilled in the art should be able to understand the beneficial technical effects brought about by the technical features and technical solutions through the introduction of these technical features and technical solutions. Attached Figure Description

[0019] The embodiments of this application will now be described with reference to the accompanying drawings. In the drawings: Figure 1 This is a schematic diagram of the overall structure of the variable stiffness compliant actuator of the present invention; Figure 2 This is an exploded view of the variable stiffness compliant actuator of the present invention from a second first-person perspective; Figure 3 This is a schematic diagram of different operating states of the variable stiffness compliant actuator of the present invention; Figure 4 This is an exploded view of the variable stiffness compliant actuator of the present invention from a second perspective. Figure 5 This is a schematic diagram of the linear drive component.

[0020] Figure 6 This is a schematic diagram of the structure of the first end cap in this invention.

[0021] Figure 7 This is a schematic diagram of the structure of the second clamping seat and the hollow connecting rod in this invention.

[0022] Figure 8 This is a cross-sectional view of the variable stiffness compliant actuator of the present invention from a third-angle perspective.

[0023] Figure 9 for Figure 8 Enlarged view of part A in the image. Detailed Implementation

[0024] The present application is described below based on embodiments, but the present application is not limited to these embodiments. In the following detailed description of the present application, some specific details are described in detail, but well-known methods, processes, flows, and elements are not described in detail in order to avoid obscuring the substance of the present application.

[0025] Furthermore, those skilled in the art should understand that the accompanying drawings provided herein are for illustrative purposes only and are not necessarily drawn to scale.

[0026] Unless the context explicitly requires it, the words "comprising," "including," and similar terms throughout the specification and claims should be interpreted as encompassing rather than being exclusive or exhaustive; that is, meaning "including but not limited to."

[0027] In the description of this application, it should be understood that the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, in the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0028] A variable stiffness compliant actuator includes a pneumatic muscle assembly III, a multi-degree-of-freedom deflector II, and a linear drive assembly I. The pneumatic muscle assembly III has a sealed accommodating cavity III-12 internally, comprising a first assembly section III-15, an adjustment section III-14, and a second assembly section III-13 arranged axially. The second assembly section III-13 includes a gas interface seat III-3 for filling the sealed accommodating cavity III-12 with gas or connecting to an external pressure control device. The multi-degree-of-freedom biasing component II is placed inside the sealed accommodating cavity III-12 and is fixedly connected to the second assembly section III-13; The linear drive assembly I includes a linear drive motor I-1 and an output shaft I-2; the linear drive motor I-1 is located in the sealed accommodating cavity III-12 and is radially spaced from the adjusting section III-14 to form a clearance gap; one end of the linear drive motor I-1 is movably connected to the multi-degree-of-freedom biasing member II, and the other end is sealed to the first assembly section III-15; the output shaft I-2 is connected to the end of the linear drive motor I-1 away from the multi-degree-of-freedom biasing member II and extends out of the sealed accommodating cavity III-12; In the initial state where no external force is applied, the axis of the linear drive assembly I coincides with the axis of the pneumatic muscle assembly III. When the pneumatic muscle assembly III deforms or is subjected to external impact, the clearance provides clearance space for the deflection of the multi-degree-of-freedom deflector II and the radial deformation of the pneumatic muscle assembly III.

[0029] The pneumatic muscle assembly III serves as both the flexible housing of the actuator and the stiffness adjustment unit. Its interior forms a sealed accommodating cavity III-12, providing a sealed space for the internal components and forming the basis for the integration of the linear drive assembly I and the multi-degree-of-freedom biasing component II. The pneumatic muscle assembly III includes a mesh covering III-6 and an elastic core tube III-5. The mesh covering III-6 is fitted over the elastic core tube III-5. Since the elastic core tube III-5 tends to expand radially after inflation, without the restraint of the mesh covering III-6, localized bulging, bursting, or uneven expansion can easily occur. The radial constraint of the mesh covering III-6 transforms the internal air pressure into more stable axial elastic support and variable stiffness effect.

[0030] The pneumatic muscle assembly III can be divided into three parts along its axial direction: the first assembly section III-15, the adjustment section III-14, and the second assembly section III-13. The main functions of the first assembly section III-15 and the second assembly section III-13 are to ensure the structural strength and sealing tightness of the actuator joint. Specifically, the gas interface seat III-3 on the second assembly section III-13 is used to connect to an external pressure control device. By filling / draining gas into the sealed accommodating cavity III-12, the internal pressure is changed, thereby dynamically adjusting the equivalent stiffness and compliance of the pneumatic muscle assembly III. The sealed accommodating cavity III-12 can be filled with air or other compressible gases. When the air pressure increases, the radial expansion constraint and axial contraction capacity of the pneumatic muscle assembly III are enhanced, outputting axial traction force, thereby improving the equivalent stiffness of the linear joint drive assembly; when the air pressure decreases, the compliance of the pneumatic muscle assembly III is enhanced, thereby improving cushioning and human-machine interaction safety.

[0031] The multi-degree-of-freedom deflector II connects the linear drive assembly I and the pneumatic muscle assembly III, providing the linear drive motor I-1 with multi-degree-of-freedom decoupling capabilities for tilting, deflection, or slight misalignment. This solves the structural lock-up problem easily caused by the rigid constraints of traditional linear drive joints. The multi-degree-of-freedom deflector II is housed within the sealed accommodating cavity III-12, fixedly connected to the second assembly section III-13, and simultaneously movably connected to the linear drive motor I-1. This allows the drive to undergo slight rotation or deflection via the multi-degree-of-freedom deflector II when subjected to impacts such as lateral, tilting, or bending. This connection method, with one end fixed and the other movably connected, prevents lateral impact forces from being directly applied to the lead screw of the linear drive motor I-1, preventing jamming or permanent mechanical damage to the rigid transmission mechanism. The multi-degree-of-freedom deflector II is located at the end of the electric linear drive assembly to compensate for angular deviations during joint movement, while simultaneously constraining and guiding the pneumatic muscle end, preventing lateral instability due to excessive flexibility. Multi-degree-of-freedom offset component II can be a universal joint, ball joint, etc.

[0032] The linear drive assembly I includes a linear drive motor I-1 and an output shaft I-2. The linear drive motor I-1 provides high-speed, high-thrust linear motion, while the output shaft I-2 passes through the first assembly section III-15 (sealed accommodating cavity III-12) and connects to the external load, ensuring rapid response and high positioning accuracy of the drive under normal operating conditions. The linear drive motor I-1 is sealed to the first assembly section III-15, and the output shaft I-2 extends out of the accommodating cavity through the first assembly section III-15. This forms an end seal of the sealed accommodating cavity III-12, ensuring that the internally mounted axial drive motor does not experience pneumatic discharge, and also enabling transmission between the axial motor body and the external load, ensuring that the shaft thrust is smoothly delivered to the output.

[0033] The linear drive motor I-1 is entirely located inside the sealed accommodating cavity III-12, and is radially spaced from the adjusting section III-14 of the pneumatic muscle assembly III to form a clearance gap. This clearance gap has a dual clearance function. On the one hand, it can play a clearance role during pneumatic deformation. When the air pressure adjustment to the sealed accommodating cavity III-12 causes the adjusting section III-14 to contract inward or expand outward, the clearance gap prevents interference or friction between the inner wall of the artificial muscle and the outer wall of the linear drive motor I-1. On the other hand, it can play a clearance role during deflection motion. When the actuator is subjected to a lateral impact, causing the linear drive motor I-1 to tilt or deflect around the multi-degree-of-freedom deflector II, the clearance gap provides the necessary physical swing space for the multi-degree-of-freedom deflector II and the linear drive motor I-1, preventing them from colliding with the inner wall of the pneumatic muscle assembly III, which would hinder movement or damage the inner wall of the pneumatic muscle assembly III. The linear drive component I can be a linear motor or a linear actuator formed by a rotary motor and a planetary roller screw, ball screw or trapezoidal screw, and there is no limitation here.

[0034] When operating without external force or at a steady speed, the axis of the linear drive component coincides with the axis of the pneumatic muscle assembly III. At this time, the actuator is in a high-rigidity linear drive mode, with a direct and efficient force transmission path, resulting in extremely high transmission efficiency and dynamic response. When the actuator is subjected to an impact, the impact force acts on the output shaft I-2, which is then transmitted to the multi-angle deflector. The multi-degree-of-freedom deflector II deflects relative to the linear drive motor I-1. Simultaneously, due to its fixed connection to the second assembly section III-13 of the pneumatic muscle assembly III, the multi-degree-of-freedom deflector II causes the pneumatic muscle assembly III to deflect and deform, thus mitigating the impact of the external force on the entire actuator.

[0035] This application integrates a linear drive motor I-1 within the sealed cavity III-12 of the pneumatic muscle assembly III, achieving a fusion of electric and pneumatic power. Specifically, this application injects gas into the sealed cavity III-12 through the gas interface seat III-3 of the second assembly section III-13. This allows the pneumatic muscle assembly III to adjust its pneumatic stiffness upon external impact. Combined with the stiffness of the linear drive motor I-1 itself, the entire actuator can be adjusted between stiffness and compliance, effectively solving the problem of traditional actuators having only one stiffness and being unable to balance rigidity and compliance.

[0036] Meanwhile, this application also achieves adaptive buffering and anti-jamming effects through the multi-degree-of-freedom deflector II and the clearance. Upon external impact, the multi-degree-of-freedom deflector II deflects relative to the linear drive motor I-1, and the pneumatic muscle assembly III deforms. At this time, the clearance provided between the linear drive motor I-1 and the adjusting section III-14 provides ample physical clearance space for both the deflection angle displacement of the multi-degree-of-freedom deflector II and the radial deformation of the adjusting section III-14 of the pneumatic muscle assembly III. In this way, the instantaneous large impact force is converted into the gas compression energy and swinging clearance displacement of the pneumatic muscle assembly III, effectively blocking the direct transmission of lateral impact force to the rigid transmission mechanism of the linear drive motor I-1, avoiding motor jamming or structural damage, and greatly improving the mechanical reliability of the actuator under impact conditions. The connection between the multi-degree-of-freedom deflector II and the pneumatic muscle assembly III also reasonably constrains the compliance of the pneumatic muscle assembly III; its elastic deformation mainly serves axial buffering and variable stiffness control, rather than becoming uncontrolled lateral swinging.

[0037] Furthermore, the first assembly section III-15 includes a first flexible tube, a first clamping seat III-4, and a first end cap III-1; the first flexible tube is circumferentially sealed between the first clamping seat III-4 and the first end cap III-1; the first clamping seat III-4 is fixedly connected to the end face of the linear drive motor I-1 away from the multi-degree-of-freedom deflector II, and is axially sealed with the end face of the linear drive motor I-1; the first end cap III-1 is fixedly connected to the first clamping seat III-4; the output shaft I-2 passes through the first clamping seat III-4 and the first end cap III-1 in sequence.

[0038] During the operation of the actuator, the sealed cavity III-12 is filled with high-pressure gas. When the pneumatic muscle assembly III deforms or the output shaft I-2 is subjected to an external lateral impact, the linear drive motor I-1 will tilt or deflect slightly around the multi-degree-of-freedom deflector II within the clearance. If the first assembly section III-15 adopts a traditional fully rigid sealing structure, the deflection of the linear drive motor I-1 will inevitably cause severe interference and jamming between the output shaft I-2 and the end cover, or directly tear and damage the sealing interface.

[0039] In this embodiment, based on the fixed connection between the first clamping seat III-4 and the first end cap III-1, and the fixed connection between the first clamping seat III-4 and the linear drive motor I-1, the axial sealing ensures that no matter how the internal linear drive motor I-1 deflects, the gas in the sealed accommodating cavity III-12 will not leak outward. This ensures that the first assembly section III-15 can maintain extremely high high-pressure airtightness stability and mechanical structural rigidity even under frequent high-pressure charging and venting conditions. It is understood that the first flexible tube includes the corresponding mesh covering III-6 and the elastic core tube III-5.

[0040] The output shaft I-2 is sequentially mounted on the first clamping seat III-4 and the first end cover III-1. After the first clamping seat III-4 and the first end cover III-1 are fixed coaxially, the smoothness of the output shaft I-2 during high-speed linear reciprocating motion is effectively improved.

[0041] The connection between the first end cap III-1 and the first clamping seat III-4 can be made by bolts and flanges, threaded connections, etc., and is not limited here. The first clamping seat III-4 and the end face of the linear drive motor I-1 can be fixed by screws. The axial seal between the first clamping seat III-4 and the end face of the linear drive motor I-1 can be made by O-rings, end face washers, etc.; the circumferential seal between the first flexible tube and the first clamping seat III-4 / first end cap III-1 can be made by conical wedge seals, clamp compression seals, etc.

[0042] Furthermore, the first clamping seat III-4 and the first end cap III-1 are respectively provided with matching first conical surfaces, and the first flexible tube body seal is clamped between the two first conical surfaces; a first sealing element is clamped between the opposite end faces of the first clamping seat III-4 and the linear drive motor I-1.

[0043] In this embodiment, when the first end cap III-1 and the first clamping seat III-4 are tightened relative to each other along the axial direction, the two mating first conical surfaces undergo relative displacement along the axial direction and the gap narrows, causing the first flexible tube sandwiched between them to deform and thus fit tightly between the two first conical surfaces to achieve a sealing effect. In addition, when high-pressure gas is filled into the sealed accommodating cavity III-12 to cause the pneumatic muscle assembly III to expand / contract violently, or when external impact force pulls the first flexible tube along the axial direction, the conical surface will produce a self-locking anti-pull-out effect, so that the more the tube is tightened, the tighter the conical surface bites, effectively preventing the first flexible tube from falling off the first assembly section III-15 or from axially sliding under frequent high-pressure alternating stress.

[0044] A first sealing element is provided between the opposite end faces of the first clamping seat III-4 and the linear drive motor I-1 to prevent gas in the sealed accommodating cavity III-12 from leaking out from the assembly gap between the first clamping seat III-4 and the linear drive motor I-1.

[0045] In one embodiment, the second assembly section III-13 includes a second flexible tube, a second end cap III-9, a second clamping seat III-11, and a hollow connecting rod III-7; The second flexible tube is circumferentially sealed between the second end cap III-9 and the second clamping seat III-11; Gas interface seat III-3 is fixedly connected to the top wall of the second end cover III-9; hollow connecting rod III-7 passes through the second end cover III-9 and is inserted into the gas interface seat III-3; the end of the hollow connecting rod III-7 away from the gas interface seat III-3 is fixedly connected to the multi-degree-of-freedom deflector II; the mating points of the gas interface seat III-3, the second end cover III-9 and the hollow connecting rod III-7 are sealed. Gas interface seat III-3, hollow connecting rod III-7 and multi-degree-of-freedom deflector II are respectively provided with first air passage III-16, second air passage III-17 and third air passage III-18. First air passage III-16, second air passage III-17 and third air passage III-18 are connected in sequence to form a closed air passage for connecting and sealing the accommodating cavity III-12.

[0046] In this embodiment, the high-pressure gas does not need to pass through an external flexible hose, but is directly injected into the sealed receiving cavity III-12 through the gas interface seat III-3, the rigid hollow connecting rod III-7, and the multi-degree-of-freedom deflector II. This avoids the drawback of traditional pneumatic actuators requiring flexible air tubes to be placed outside the moving joint, eliminates the risk of fatigue rupture, air jamming due to bending, or loosening of joints under frequent bending and stretching of external air tubes, and improves the operational stability of the pneumatic artificial muscle.

[0047] Meanwhile, the hollow connecting rod III-7 bears the gas pressure reaction force generated by the gas interface seat III-3 and the load transmitted by the multi-degree-of-freedom deflector II, and evenly distributes it to the second end cap III-9 and the second clamping seat III-11. This prevents high-pressure gas from directly acting on the edge of the sealing mating surface, ensuring that the sealing structure at the mating point will not fail even when the sealing cavity III-12 is under ultra-high pressure or when the multi-degree-of-freedom deflector II is subjected to severe deflection. In some embodiments, the second end cap III-9 is fixedly connected to the second clamping seat III-11.

[0048] Furthermore, the multi-degree-of-freedom deflector is positioned corresponding to the adjustment section III-14. In this embodiment, the third air passage III-18 is opened on the multi-degree-of-freedom deflector II, and its outlet directly faces the center of the sealed accommodating cavity III-12. Gas ejected from the multi-degree-of-freedom deflector II can directly act on the inner wall of the adjustment section III-14 of the pneumatic muscle assembly III, shortening the gas diffusion path in the cavity, improving the dynamic response speed of stiffness adjustment (inflation and degassing), and realizing rapid and precise control of the actuator stiffness.

[0049] Furthermore, the outlet of the third air passage III-18 is positioned towards the linear drive motor I-1. If the outlet of the third air passage III-18 were positioned towards the inner wall of the adjustment section III-14, the high-pressure gas would directly impact the inner wall of the adjustment section III-14, easily causing local stress concentration or uneven gas flow. In this embodiment, however, the outlet of the third air passage III-18 is positioned towards the linear drive motor I-1, so the gas directly impacts the multi-degree-of-freedom deflector or the linear drive motor I-1, then rebounds and fills the entire sealed accommodating cavity III-12. This results in a more uniform force distribution on the pneumatic muscle assembly III and a more stable biomimetic response.

[0050] Furthermore, the inner peripheral wall of the second end cap III-9 and the outer peripheral wall of the second clamping seat III-11 are respectively provided with matching second conical surfaces, and the second flexible tube body is sealed and clamped between the two second conical surfaces. The gas interface seat III-3 has a groove on its end face facing the second end cover III-9; the pneumatic muscle assembly III also includes a second seal, which is placed in the groove and sleeved on the outer peripheral surface of the hollow connecting rod III-7 to seal the assembly gap between the second end cover III-9, the hollow connecting rod III-7 and the gas interface seat III-3.

[0051] In this embodiment, when the second end cap III-9 and the second clamping seat III-11 are axially tightened relative to each other, the two mating second conical surfaces generate axial relative displacement, causing the clamping gap to narrow uniformly in the radial direction. This compensates for assembly tolerances and achieves a sealing effect. Simultaneously, during frequent stiffness adjustments (high-pressure inflation and deflation within the cavity) or when subjected to severe external impacts, the high-pressure gas expansion force and axial tensile force act on the second flexible tube. Due to the inclination angle of the second conical surface, the axial tensile force on the tube is converted into a clamping force along the conical surface, achieving a tightening and densifying effect, avoiding the tube pull-out or slippage problems common with traditional cylindrical interference clamping.

[0052] Simultaneously, this embodiment uses a single second seal to simultaneously seal the end face gap between the gas interface seat III-3 and the second end cap III-9, the radial gap between the gas interface seat III-3 and the hollow connecting rod III-7, and the mating gap between the second end cap III-9 and the hollow connecting rod III-7 under the combined stress of axial compression and radial interference. This simplifies the assembly structure and saves space in the second assembly section III-13.

[0053] Furthermore, the first flexible tube body includes a first flexible inner tube and a first braided mesh sleeve covering the outer circumferential surface of the first flexible inner tube; the second flexible tube body includes a second flexible inner tube and a second braided mesh sleeve covering the outer circumferential surface of the second flexible inner tube; the adjusting section III-14 includes a third flexible inner tube and a third braided mesh sleeve covering the outer circumferential surface of the third flexible inner tube. The first flexible inner tube, the second flexible inner tube, and the third flexible inner tube are integrally arranged to form the elastic core tube III-5; The first woven mesh sleeve, the second woven mesh sleeve, and the third woven mesh sleeve are integrally arranged to form a mesh covering III-6; The pneumatic muscle assembly III also includes a braided mesh folding guide. The mesh covering III-6 passes through the inside of the braided mesh folding guide and folds outward along the end of the braided mesh folding guide to cover the outer peripheral surface of the elastic core tube III-5.

[0054] In this embodiment, the function of the mesh covering III-6 is to limit the disordered radial excessive expansion of the elastic core tube III-5 and to convert the expansion force of the high-pressure gas in the sealed accommodating cavity III-12 into axial contraction force or equivalent elastic support force. The braided mesh folding guide provides continuous and smooth curved surface guidance for the folding of the mesh covering III-6, avoiding shearing damage to the braided mesh when it is pressed and tightened at the end. At the same time, the folding forms multiple interlocking locks to prevent the mesh covering III-6 from being pulled out from the end under high pressure. The braided mesh folding guide can be a circular annular sleeve with a rounded guide angle, a flared sleeve, etc., and is not limited here.

[0055] In one embodiment, the multi-degree-of-freedom biasing element II includes a first pivot seat II-4, a second pivot seat, and a connecting member II-3; wherein, the first pivot seat II-4 is fixedly connected to the hollow connecting rod III-7 and rotatably connected to the connecting member II-3 along the first rotation axis; the second pivot seat is movably connected to the linear drive motor I-1 and rotatably connected to the connecting member II-3 along the second rotation axis; the second rotation axis intersects and is orthogonal to the first rotation axis.

[0056] In traditional linear actuators, if the motor ends are rigidly fixed, the externally applied lateral impact force will be directly converted into a torque acting on the lead screw inside the motor. However, in this embodiment, the lateral impact bending moment is converted into an adjustment of the multi-degree-of-freedom deflector II through the first pivot II-4 and the second pivot, thus avoiding the risk of jamming and damage to the rigid transmission mechanism.

[0057] The first pivot seat II-4 is fixedly connected to the hollow connecting rod III-7, and the second pivot seat is movably connected to the linear drive motor I-1. Under normal operating conditions or without external force, the first pivot seat II-4 and the second pivot seat maintain the linear drive motor I-1 in a coaxial, overlapping state through self-balancing. When an external force impacts the actuator, the first pivot seat II-4 and the second pivot seat deflect through the connecting piece II-3, causing the pneumatic muscle assembly III to undergo traction deformation. After the impact is eliminated, the first pivot seat II-4 and the second pivot seat return to their original positions, and the linear drive motor I-1 and the pneumatic muscle assembly III return to an axially overlapping state. This allows the actuator as a whole to achieve dynamic adaptive adjustment and reset.

[0058] Furthermore, the second pivot is configured to be movable relative to the linear drive motor I-1 along the axial direction of the linear drive motor I-1; and to rotate relative to the linear drive motor I-1 about the axial direction of the linear drive motor I-1.

[0059] In this embodiment, the second pivot seat can move axially relative to the linear drive motor I-1, thereby releasing the rigid distance lock between the second pivot seat and the linear drive motor I-1 in the engagement, allowing the linear drive motor I-1 and the second pivot seat to move at a certain amplitude or in a controlled manner along the axial direction of the linear drive motor I-1.

[0060] Without circumferential rotational freedom, the entire actuator would be in an over-constrained circumferential state when subjected to complex impacts, such as when the robot's feet are closed on the ground. In this embodiment, the second pivot can rotate relative to the linear drive motor I-1 about the axial direction. Thus, when subjected to external impacts, the linear drive motor I-1 can avoid jamming or bending through circumferential rotation.

[0061] If the pneumatic muscle assembly III is connected to the linear drive assembly I, due to the inherent compliance of the pneumatic muscle, problems such as lateral bending, excessive yaw, or uneven end force may occur during robot movement. This embodiment, through the multi-degree-of-freedom deflector II, enables the end of the pneumatic muscle assembly III to not only undergo angle compensation but also to move axially linearly within the guide hole at the end of the linear drive motor I-1, together with the multi-degree-of-freedom deflector II. Thus, the compliance of the pneumatic muscle assembly III is reasonably constrained, and its elastic deformation primarily serves axial buffering and variable stiffness control, rather than becoming uncontrolled lateral oscillation.

[0062] A robot includes the variable stiffness compliant actuator of any of the above embodiments.

[0063] Furthermore, the robot also includes a pressure control device. This device communicates with the gas interface seat III-3 of the pneumatic muscle assembly III, and is used to fill or discharge gas into or from the sealed cavity III-12 of the pneumatic muscle assembly III. Upon receiving a stiffness increase signal, it controls the filling of gas into the sealed cavity III-12 to increase the gas pressure within it; upon receiving a compliance adjustment signal, it controls the discharge of gas from the sealed cavity III-12 to decrease the gas pressure within it.

[0064] During the robot's movement, the controller can adjust the air pressure of the pneumatic muscle assembly III according to the gait phase. For example, during the support phase, the moment of foot landing, or when higher load-bearing capacity is required, the pressure of the sealed air chamber is increased to enhance joint stiffness and impact resistance; during the swing phase, obstacle crossing, or human-robot contact phase, the pressure of the sealed air chamber is decreased to improve compliance and reduce impact force. The linear drive assembly I continues to undertake the main displacement control and power output, while the pneumatic muscle assembly III participates in force-bearing as a biomimetic elastic element with adjustable stiffness.

[0065] This application is applicable to linear joints of the lower limbs of humanoid robots, such as linear actuators for the knee joint. When the actuator is installed between the thigh link and the lower leg link, the electric linear drive component I can provide the main driving force required for knee flexion and extension, and the pneumatic muscle component III can simulate the flexible energy storage and cushioning function of human muscles and tendons, thereby improving stability during rapid walking and foot impact.

[0066] It should be noted that this invention does not require the pneumatic muscle assembly III to completely replace the linear drive assembly I as the main drive source. On the contrary, the key to this invention lies in combining mature electric linear drive capabilities with the adjustable compliance of pneumatic muscles, so that the linear joint, while meeting speed and thrust requirements, has variable stiffness characteristics that can be adjusted by air pressure.

[0067] Those skilled in the art will understand that, without conflict, the above-mentioned preferred solutions can be freely combined and superimposed.

[0068] It should be understood that the above-described embodiments are merely exemplary and not restrictive. Any obvious or equivalent modifications or substitutions made by those skilled in the art regarding the above details without departing from the basic principles of this application shall be included within the scope of the claims of this application.

Claims

1. A variable stiffness compliant actuator, characterized in that, include: The pneumatic muscle assembly (III) has a sealed accommodating cavity (III-12) formed inside, and has a first assembly section (III-15), an adjustment section (III-14), and a second assembly section (III-13) arranged along the axial direction; the second assembly section (III-13) includes a gas interface seat (III-3) for filling the sealed accommodating cavity (III-12) with gas or connecting to an external pressure control device; A multi-degree-of-freedom biasing component (II) is placed within the sealed accommodating cavity (III-12) and fixedly connected to the second assembly section (III-13); and, A linear drive assembly (I) includes a linear drive motor (I-1) and an output shaft (I-2); the linear drive motor (I-1) is located within the sealed accommodating cavity (III-12) and is radially spaced from the adjusting section (III-14) to form a clearance gap; one end of the linear drive motor (I-1) is movably connected to the multi-degree-of-freedom deflector (II), and the other end is sealed to the first assembly section (III-15); the output shaft (I-2) is connected to the end of the linear drive motor (I-1) away from the multi-degree-of-freedom deflector (II) and extends out of the sealed accommodating cavity (III-12); In the initial state where no external force is applied, the axis of the linear drive assembly (I) coincides with the axis of the pneumatic muscle assembly (III). When the pneumatic muscle assembly (III) deforms or is subjected to external impact, the clearance provides clearance space for the deflection of the multi-degree-of-freedom deflector (II) and the radial deformation of the pneumatic muscle assembly (III).

2. The variable stiffness compliant actuator as described in claim 1, characterized in that, The first assembly section (III-15) includes a first flexible tube, a first clamping seat (III-4), and a first end cap (III-1); The first flexible tube is circumferentially sealed between the first clamping seat (III-4) and the first end cap (III-1); The first clamping seat (III-4) is fixedly connected to the end face of the linear drive motor (I-1) away from the multi-degree-of-freedom deflector (II) and is axially sealed to the end face of the linear drive motor (I-1); the first end cover (III-1) is fixedly connected to the first clamping seat (III-4). The output shaft (I-2) is sequentially inserted through the first clamping seat (III-4) and the first end cap (III-1).

3. The variable stiffness compliant actuator as described in claim 2, characterized in that, The first clamping seat (III-4) and the first end cap (III-1) are respectively provided with matching first conical surfaces, and the first flexible tube body is sealed between the two first conical surfaces; a first sealing element (III-3) is clamped between the first clamping seat (III-4) and the opposite end face of the linear drive motor (I-1).

4. The variable stiffness compliant actuator as described in claim 1, characterized in that, The second assembly section (III-13) includes a second flexible tube, a second end cap (III-9), a second clamping seat (III-11), and a hollow connecting rod (III-7); The second flexible tube is circumferentially sealed between the second end cap (III-9) and the second clamping seat (III-11); The gas interface seat (III-3) is fixedly connected to the top wall of the second end cap (III-9); the hollow connecting rod (III-7) passes through the second end cap (III-9) and is inserted into the gas interface seat (III-3); the end of the hollow connecting rod (III-7) away from the gas interface seat (III-3) is fixedly connected to the multi-degree-of-freedom deflector (II); the mating points of the gas interface seat (III-3), the second end cap (III-9), and the hollow connecting rod (III-7) are sealed. The gas interface seat (III-3), the hollow connecting rod (III-7), and the multi-degree-of-freedom deflector (II) are respectively provided with a first air passage (III-16), a second air passage (III-17), and a third air passage (III-18). The first air passage (III-16), the second air passage (III-17), and the third air passage (III-18) are connected in sequence to form a closed air passage connecting the sealed accommodating cavity (III-12).

5. The variable stiffness compliant actuator according to claim 4, characterized in that, The inner peripheral wall of the second end cap (III-9) and the outer peripheral wall of the second clamping seat (III-11) are respectively provided with matching second conical surfaces, and the second flexible tube body is sealed and clamped between the two second conical surfaces; The gas interface seat (III-3) has a groove on its end face facing the second end cap (III-9); the pneumatic muscle assembly (III) also includes a second seal, which is placed in the groove and sleeved on the outer peripheral surface of the hollow connecting rod (III-7) to seal the assembly gap between the second end cap (III-9), the hollow connecting rod (III-7) and the gas interface seat (III-3).

6. The variable stiffness compliant actuator according to claim 5, characterized in that, The position of the multi-degree-of-freedom biasing element (II) corresponds to that of the adjustment section (III-14).

7. The variable stiffness compliant actuator according to claim 5, characterized in that, The first flexible tube includes a first flexible inner tube and a first braided mesh covering the outer circumferential surface of the first flexible inner tube; the second flexible tube includes a second flexible inner tube and a second braided mesh covering the outer circumferential surface of the second flexible inner tube; the adjusting section (III-14) includes a third flexible inner tube and a third braided mesh covering the outer circumferential surface of the third flexible inner tube. The first flexible inner tube, the second flexible inner tube, and the third flexible inner tube are integrally formed to form an elastic core tube (III-5); The first woven mesh sleeve, the second woven mesh sleeve, and the third woven mesh sleeve are integrally formed to form a mesh covering (III-6); The pneumatic muscle assembly (III) further includes a woven mesh folding guide (II-2), the mesh covering (III-6) passing through the inside of the woven mesh folding guide (II-2) and folding outward along the end of the woven mesh folding guide (II-2) to cover and sleeve the outer peripheral surface of the elastic core tube (III-5).

8. The variable stiffness compliant actuator as described in any one of claims 4-6, characterized in that, The multi-degree-of-freedom biasing component (II) includes a first pivot (II-4), a second pivot, and a connecting component (II-3); wherein, The first pivot seat (II-4) is fixedly connected to the hollow connecting rod (III-7) and rotatably connected to the connecting member (II-3) along the first rotation axis; The second pivot seat is movably connected to the linear drive motor (I-1) and rotatably connected to the connector (II-3) along the second rotation axis; the second rotation axis intersects and is orthogonal to the first rotation axis.

9. The variable stiffness compliant actuator as described in claim 8, characterized in that, The second pivot is configured to be movable along the axial direction of the linear drive motor (I-1) and to rotate about the axial direction of the linear drive motor (I-1).

10. A robot, characterized in that, Including the variable stiffness compliant actuator as described in any one of claims 1-8.

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