Mechanical leg with bionic hydraulic ankle joint and structure of mechanical leg

Abstract

The invention belongs to the technical field of robots, and discloses a mechanical leg with a bionic hydraulic ankle joint and a structure thereof, and the mechanical leg comprises a thigh, a shank oil cylinder, a shank, an achilles tendon oil cylinder and an ankle joint; a traditional mechanism such as a connecting rod speed reducer for achieving inward turning and outward turning movement is simplified into the ankle joint capable of being actively driven through the arc-shaped oil cylinder, and by means of the design, the advantage of large driving force of a hydraulic system is brought into play, and meanwhile the flexibility of the joint is improved; all linear velocities on the long edge of the square piston are kept consistent, and the problem that the oil cylinder is stuck due to rolling of a sealing ring caused by inconsistent linear velocities of all points on the lower round edge of the round section can be avoided; the designed oil cylinder serves as a joint main body to be embedded in the joint, compared with a traditional joint, redundant externally-loaded accessory mechanisms are not needed, the design is more compact, the size is smaller, meanwhile, a buffering mechanism is designed in the dorsal stretching and plantar flexion movement directions, and the bionic kinematics principle is better met.

Description

Technical Field

[0001] This invention belongs to the field of robotics technology, and in particular relates to a mechanical leg with a biomimetic hydraulic ankle joint and its structure. Background Technology

[0002] In humanoid robotics and intelligent prosthetics, the ankle joint is a key component for stable walking and adapting to complex terrain. Traditional ankle joint designs have many limitations. For example, some early designs used multiple drive motors connected in series to drive foot movements. This structure not only resulted in a bulky and redundant ankle joint, but also exhibited a movement pattern that differed significantly from that of human joints, leading to poor biomimicry. Other designs primarily relied on the passive deformation of elastic materials such as carbon fiber. While structurally simple, these designs had limited ability to simulate the active force exertion of a real ankle and adapt to different slopes or uneven surfaces, resulting in a still stiff gait.

[0003] To overcome the aforementioned shortcomings, existing technologies have undergone numerous improvements: one approach is to optimize the drive layout. For example, CN119821540A discloses a leg structure that arranges a pair of drive components on the inner and outer sides of the lower leg, controlling foot rotation through the extension and retraction of these drive components. This design moves the drive source from the ankle joint to the lower leg, effectively reducing the weight and volume of the ankle joint and improving the biomimetic motion effect. Another approach is to integrate active drive and passive damping. For example, CN120645255A discloses a biomimetic foot structure that uses a motor-driven worm gear... By combining planetary gear structures and hydraulic dampers, attempts are made to better match foot rotation through complex electromechanical systems to achieve a more natural gait. One improvement approach is to use high-power-density actuators; for example, CN120402457A discloses a hydraulic humanoid robot using a blade-driven cylinder, which replaces the traditional motor-driven joint to obtain higher driving torque. Another improvement approach is to use energy storage devices; for example, CN118770420A discloses a hydraulically driven joint using a torsion spring, which improves joint flexibility by absorbing and releasing additional energy. These solutions indicate that the ingenious integration of the drive system with the transmission and damping systems is an important development direction for improving ankle joint performance.

[0004] However, most of the aforementioned solutions primarily focus on optimizing ankle plantar flexion and dorsiflexion movements on flat or gently sloping surfaces. They still lack comprehensive active control solutions for adaptability issues related to multi-degree-of-freedom movements such as inversion and eversion, which are crucial in complex terrain. Most designs for multi-degree-of-freedom movements utilize a single, stacked actuator, which, while improving joint flexibility, results in a bulky structure unsuitable for lightweight deployment. To specifically address the issue of poor environmental adaptability, CN117653432A discloses an intelligent foot bionic prosthesis, aiming to solve the problem of passive prostheses being unable to perform dorsiflexion, plantar flexion, inversion, and eversion movements. This solution employs a hybrid actuation strategy: it actively controls the prosthesis's dorsiflexion and plantar flexion movements through an extension / flexion actuator to adapt to various road conditions such as inclines and declines; simultaneously, it passively achieves inversion and eversion movements through an inversion / elevation assembly composed of a hinged shaft and elastic elements. However, the inventors found that the technical solution disclosed in CN117653432A still has the following shortcomings: (1) The inversion and supination movements are passive and have limited adaptability: Its inversion and supination functions rely on the passive compression and rebound of the elastic element, and can only react to the force generated by the ground, but cannot actively output torque to adjust the posture. When the robot or wearer walks on a side-sloping or irregular gravel road, this passive structure cannot actively adjust the foot posture to obtain the maximum support area and stability, which increases the risk of slipping; (2) Multi-axis motion decoupling and poor coordination: This solution will decouple the active dorsiflexion / plantar flexion. The control and passive inversion / outversion functions are separated, and the motion control mechanisms in the two directions are independent of each other. This contradicts the biomechanical principle that the human ankle joint is controlled by multiple muscle groups to achieve complex coupled movements, resulting in insufficient overall motion coordination and low gait biomimicry. (3) The driving potential is not fully utilized: Although the scheme mentions the possibility of using hydraulic cylinders as driving components, it only uses them for active control in a single direction. It fails to build a complete multi-channel active hydraulic system to achieve coordinated and active driving and control of all key degrees of freedom of ankle joint dorsiflexion, plantar flexion, inversion, and eversion.

[0005] Therefore, existing technologies still lack an effective solution to achieve multi-degree-of-freedom coordinated control of the ankle joint by utilizing a unified and active driving method, especially a hydraulic driving method with fast response and high power density, so as to fundamentally solve the problem of adaptability and stability of robots when walking in complex and ever-changing environments.

[0006] Based on the above analysis, the problems and shortcomings of the existing technology are as follows:

[0007] (1) Passive inward and outward turning movements with limited adaptability: Some designs rely on the passive compression and rebound of elastic components for their inward and outward turning functions. They can only react to the forces generated by the ground and cannot actively output torque to adjust their posture. When the robot or wearer walks on a side-sloping or irregular gravel road, this passive structure cannot actively adjust the foot posture to obtain the maximum support area and stability, which increases the risk of slipping.

[0008] (2) Multi-axis motion decoupling and poor coordination: Some schemes separate the active dorsiflexion / plantar flexion control from the passive inversion and eversion function. The motion control mechanisms in the two directions are independent of each other. This is contrary to the biomechanical principle that the human ankle joint is controlled by multiple muscle groups to achieve complex coupled motion, resulting in insufficient overall motion coordination and low gait biomimicry.

[0009] (3) The driving potential is not fully utilized: Although some solutions mention the possibility of using hydraulic cylinders as driving components, they are only used for active control in a single direction. They fail to build a complete multi-channel active hydraulic system to achieve coordinated and active driving and control of all key degrees of freedom of ankle dorsiflexion, plantarflexion, inversion and eversion. Summary of the Invention

[0010] To address the problems existing in the prior art, the present invention provides a mechanical leg with a biomimetic hydraulic ankle joint and its structure.

[0011] This invention is achieved by providing a mechanical leg with a biomimetic hydraulic ankle joint and its structure, comprising:

[0012] Thigh, calf hydraulic cylinder, calf, Achilles tendon hydraulic cylinder, ankle joint;

[0013] The thigh and lower leg are connected together by a lower leg hydraulic cylinder, forming a knee joint degree of freedom; the lower leg and ankle joint are connected together by an Achilles tendon hydraulic cylinder, forming an ankle joint degree of freedom of dorsiflexion and plantar flexion; the ankle joint can provide inversion and eversion degrees of freedom; the entire mechanical leg is driven by three hydraulic cylinders to actively control the three degrees of freedom.

[0014] Furthermore, the ankle joint is mainly composed of two ankle joint cylinder shells spliced ​​together and fastened by cylinder fastening bolts. A piston is installed inside the cylinder shell, and a cylinder cover is installed on the upper end face of the cylinder shell and fastened by bolts. A bearing groove is provided on the upper end face of the cylinder shell for movable connection between the joint axis of the inner frame and the cylinder shell, and a bearing cover is also installed. The cylinder connector is used to supply oil into the cylinder.

[0015] Furthermore, the gyroscope is installed on the lower side of the ankle joint cylinder housing to measure the spatial motion parameters of the ankle joint.

[0016] Furthermore, the X bearing is fixed to the bearing groove on the cylinder housing via the bearing cover, and constitutes a rotational degree of freedom of the joint axis of the inner frame of the joint in the X direction relative to the cylinder housing.

[0017] Furthermore, the Y-bearing is fixed by the joint inner frame fastening bolts through the bearing grooves on the upper and lower parts of the joint inner frame. Since the X and Y directions are orthogonal, the degrees of freedom in the X and Y directions do not interfere with each other. The Y-bearing constitutes a rotational degree of freedom of the joint axis relative to the cylinder housing in the Y direction.

[0018] Furthermore, the joint axis has an internal opening.

[0019] Furthermore, the piston block and piston rod are manufactured using a separate machining technology. A square wedge is provided at the lower end of the piston rod, and a square groove is opened on the upper end face of the piston block. The two fit together and are tightened on opposite sides using piston rod block fixing bolts and piston rod block fixing nuts to form a component. At the same time, a piston sealing ring is provided on the lower end face of the piston block. The two sets of components and their piston sealing rings sandwich a piston spacer and are symmetrically assembled on the left and right using piston block set bolts and piston block set nuts to form a piston.

[0020] Based on the above technical solutions and the technical problems solved, please analyze the advantages and positive effects of the technical solution to be protected by this invention from the following aspects:

[0021] (1) A square cross-section arc cylinder was designed, which simplifies the traditional linkage reducer and other mechanisms that realize inward and outward movement into an ankle joint that can be actively driven by the arc cylinder. This design gives full play to the advantage of the large driving force of the hydraulic system while improving the flexibility of the joint. The square cross-section design facilitates processing and ensures that all linear velocities on the long side of the square piston are consistent, which can avoid the problem of the seal ring rolling and the cylinder jamming caused by the inconsistent linear velocities at various points on the circular edge of the circular cross-section.

[0022] (2) The hydraulic cylinder is embedded inside the joint as the main body. Compared with traditional joints, it does not require extra external load attachments. The design is more compact and smaller in size. At the same time, a buffer mechanism is designed in the direction of dorsiflexion and plantarflexion, which is more in line with the principle of bionic kinematics.

[0023] (3) The invention has a proprietary universal frame. Compared with the traditional mechanical design that decouples the inversion and eversion movements from the dorsiflexion and plantarflexion movements, the invention can couple the inversion and eversion movements with the dorsiflexion and plantarflexion movements under simple reciprocating rotational motion. This reduces the control complexity and improves the system controllability. At the same time, the frame is suspended inside, which provides space for installing sensors and internal space for sensor wiring and oil circuit layout, making it easy to manufacture an integrated device.

[0024] (4) The technical solution of the present invention fills the technical gap in the domestic and foreign industry: The present invention creatively proposes a hydraulically driven ankle joint with a square cross-section arc cylinder, which can directly realize the inversion and eversion movements of the ankle joint without complex mechanisms. At the same time, it is coupled with the dorsiflexion and plantarflexion movements to realize two degrees of freedom of movement. It has the advantages of small size and high flexibility, and fills the technical gap in the domestic and foreign industry. Attached Figure Description

[0025] Figure 1 This is a structural diagram of a mechanical leg with a biomimetic hydraulic ankle joint provided in an embodiment of the present invention.

[0026] Figure 2 This is a diagram of the ankle joint structure provided in an embodiment of the present invention.

[0027] Figure 3 This is an exploded view of the ankle joint structure provided in an embodiment of the present invention.

[0028] Figure 4 This is an exploded view of the internal structure of the ankle joint provided in an embodiment of the present invention.

[0029] Figure 5 This is an exploded view of the piston structure provided in an embodiment of the present invention.

[0030] Figure 6 This is a specific implementation diagram of the hydraulic leg provided in the embodiment of the present invention.

[0031] Figure 7 This is a diagram of an actual ankle inversion movement test provided in an embodiment of the present invention.

[0032] Figure 8 This is a diagram of an actual ankle eversion exercise test provided in an embodiment of the present invention.

[0033] In the diagram: 1. Thigh; 2. Lower leg cylinder; 3. Lower leg; 4. Achilles tendon cylinder; 5. Ankle joint; 101. Thigh plate; 102. Knee joint bearing; 103. Lower leg cylinder hinge; 301. Lower leg plate; 302. Leg plate connecting frame; 303. Achilles tendon cylinder slide rod; 304. Achilles tendon cylinder slider; 305. Rod cylinder spring; 306. Ankle joint connecting plate; 513. Universal hinge; 501. Cylinder cover; 502. Piston; 503. Joint inner frame; 504. Joint axis; 505. Bearing cover; 506. Bolt; 507. Cylinder connector; 508. Ankle joint cylinder outer shell; 509. Hydraulic cylinder fastening bolt; 510. X bearing; 511. Ankle joint hydraulic cylinder oil seal; 512. Y bearing; 5031. Upper part of the joint inner frame; 514. Gyroscope; 5032. Lower part of the joint inner frame; 5033. Joint inner frame fastening bolt; 5034. Piston rod end fixing bolt; 5035. Joint inner frame fastening nut; 5021. Piston block; 5022. Piston rod; 5023. Piston rod block fixing bolt; 5024. Piston block set bolt; 5025. Piston block set nut; 5026. Piston rod block fixing nut; 5027. Piston spacer; 5028. Piston seal ring. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0035] This invention addresses the key technological bottlenecks in the adaptability of current bionic hydraulic robotic legs to complex gaits and terrains. The main technical problems it solves are: the dynamic response lag of hydraulically driven joints and insufficient precision in bionic angle control; the difficulty in coordinated coupling control of the ankle joint under multi-degree-of-freedom complex movements; and the low efficiency of torque transmission and energy feedback in the overall robotic leg. Existing technologies mostly use a single servo motor or linear actuator to drive the joints. While this simplifies the structure, it makes it difficult to simulate the compliance and adaptability of the human ankle joint during gait transitions and impact buffering. This invention, through the collaborative design of a hydraulic system and bionic geometry, redefines the mechanical leg joint's mechanical transmission path, enabling it to maintain compliance and stable support under multi-axis coupling conditions.

[0036] At the system level, the biomimetic hydraulic ankle joint proposed in this invention uses a hydraulic cylinder as the main driving force source, and achieves dynamic adjustment through flow control by a three-way valve and displacement feedback. The X and Y dual-bearing composite structure within the ankle joint allows the joint to rotate independently in two vertical directions, decoupling the movement between inversion / eversion and plantar flexion / dorsiflexion, thereby achieving a biomimetic movement trajectory that approximates the human ankle joint.

[0037] In terms of structural design, the piston and piston rod are machined separately and then locked in a wedge shape to ensure good coaxiality and resistance to lateral displacement under high-pressure cycling conditions. The internal seal uses a rubber sealing ring, which can maintain oil stability during high-frequency reciprocating motion and prevent pressure fluctuations caused by micro-leakage. The joint shaft has a hollow channel inside, which also serves as a signal line and oil return pipe channel, making the entire ankle joint more compact, reducing external interference, and improving overall reliability and protection level.

[0038] In terms of control principle, the gyroscope constitutes the attitude detection unit. By collecting angular velocity and angular acceleration data in real time, the controller processes the data to achieve closed-loop control of the three-degree-of-freedom hydraulic cylinder. The controller can automatically adjust the cylinder flow distribution according to the ground reaction force and gait cycle changes, dynamically correct the ankle joint posture, and enable the robotic leg to adapt to different terrains, slopes, and walking speeds.

[0039] Overall, this robotic leg achieves coordinated control across multiple degrees of freedom while maintaining both mechanical compliance and dynamic stability. Through the deep integration of hydraulic drive and sensor feedback, a force-position hybrid control system, approximating the physiological structure of the human body, has been formed. This provides key technological support for rehabilitation robots, exoskeleton assistive systems, and highly mobile bionic platforms, demonstrating significant potential for industrial application and engineering promotion.

[0040] like Figure 1 As shown, an embodiment of the present invention provides a mechanical leg with a biomimetic hydraulic ankle joint and its structure, comprising:

[0041] 1. Thigh; 2. Calf; 3. Achilles tendon; 4. Ankle; 5.

[0042] The thigh 1 and lower leg 3 are connected together via a lower leg hydraulic cylinder 2, forming a knee joint degree of freedom; the lower leg 3 and ankle joint 5 are connected together via an Achilles tendon hydraulic cylinder 4, forming ankle dorsiflexion and plantarflexion degrees of freedom; ankle joint 5 can provide inversion and eversion degrees of freedom. The entire mechanical leg is driven by three hydraulic cylinders to actively control the three degrees of freedom, overcoming the problems of poor joint environmental adaptability and low degrees of freedom in traditional mechanical legs.

[0043] Combination Figure 2 As shown, the ankle joint 5 is mainly composed of two ankle joint cylinder housings 508 spliced ​​together and fastened by cylinder fastening bolts 509. A piston 502 is installed inside the cylinder housing, and a cylinder cover 501 is installed on the upper surface of the cylinder housing 508 and fastened by bolts 506. A bearing groove is provided on the upper surface of the cylinder housing 508 for movable connection between the joint inner frame 503, the joint axis 504, and the cylinder housing 508, and a bearing cover 505 is also installed thereon. The cylinder connector 507 is used to supply oil to the cylinder.

[0044] Combination Figure 2As shown, the gyroscope 514 is installed on the lower side of the ankle joint cylinder housing 508 and is used to measure the spatial motion parameters of the ankle joint 5.

[0045] Combination Figure 3 As shown, the X-bearing 510 is fixed to the bearing groove on the cylinder housing 508 via the bearing cover 505, forming a rotational degree of freedom in the X direction of the joint axis 504 of the inner frame 503 relative to the cylinder housing 508. This degree of freedom is driven by the ankle joint 5 cylinder, realizing the inversion and eversion functions of the ankle joint. The cylinder driving this degree of freedom is a square-section arc-shaped cylinder. The advantage of this design is that it can ensure that all linear velocities on the long side of the square piston remain consistent during rotational motion, avoiding the problem of cylinder jamming caused by the rolling of the sealing ring due to inconsistent linear velocities at various points on the circular side of the circular cross-section. The cylinder cover 501 is embedded with an ankle joint cylinder oil seal 511 to ensure dynamic sealing when the piston 502 moves. At the same time, the piston rod end is connected to the inner frame 503. This design can enable the piston to be correctly guided in the cylinder while transmitting force to the inner frame 503, thus realizing active control of the degree of freedom in the X direction.

[0046] Combination Figure 4 As shown, the Y-bearing 512 is fixed to the bearing grooves on the upper 5031 and lower 5032 of the joint inner frame using the joint inner frame fastening bolts 5033. Since the X and Y directions are orthogonal, the degrees of freedom in the X and Y directions do not interfere with each other. The Y-bearing 512 constitutes a rotational degree of freedom in the Y direction of the joint axis 504 relative to the cylinder housing 508. This degree of freedom is driven by the Achilles tendon cylinder 4, realizing the dorsiflexion and plantarflexion functions of the ankle joint. At the same time, the piston 502 is fixed to the upper 5031 of the joint inner frame by the piston rod end fixing bolt 5034.

[0047] Combination Figure 4 As shown, the joint axis 504 has an opening inside, which facilitates the introduction of the signal harness of the gyroscope 514 into the joint through the opening, making it easier to manufacture a sensor-integrated ankle joint 5.

[0048] Combination Figure 5 As shown, to further reduce the processing difficulty, the piston block 5021 and piston rod 5022 are manufactured using a split machining technology. A square wedge is provided at the lower end of the piston rod 5022, and a square groove is opened on the upper end face of the piston block 5021. The two are fitted together, and piston rod block fixing bolts 5023 and piston rod block fixing nuts 5026 are tightened on opposite sides to form a component. At the same time, a piston sealing ring 5028 is provided on the lower end face of the piston block 5021. The two components and the piston sealing ring 5028 sandwich a piston spacer 5027, and piston block set bolts 5024 and piston block set nuts 5025 are used to symmetrically assemble the piston 502.

[0049] Combination Figure 6As shown in the figure, thigh 1 is a frame structure formed by two thigh plates 101 connected by a leg plate connecting frame 302. Lower leg 3 is also constructed using lower leg plates 301, and lower leg cylinder hinges 103 are provided on both sides of thigh 1 and lower leg 3. The two ends of lower leg cylinder 2 are connected to the ends of thigh 1 and lower leg 3 via the lower leg cylinder hinges 103. Simultaneously, thigh 1 and lower leg 3 are connected together using knee joint bearings 102 to achieve flexion and extension of the knee joint. It should be ensured that, driven by lower leg cylinder 2, the angle between the thigh 1 and lower leg 3 with the knee joint bearing 102 as the vertex can be between 115° and 180°. Both thigh plates 101 and lower leg plates 301 are made from prefabricated steel plates using CNC laser cutting technology. Lower leg cylinder 2 and lower leg cylinder hinges 103 are commercially available products and are existing technology. The advantage of this design is that it can effectively control the movement range of the lower leg cylinder 2 within the frame structure between the thigh 1 and the lower leg 3, while the frame structure provides ample space for the subsequent wiring harness and pipeline layout.

[0050] Combination Figure 6 and Figure 4 As shown in the figure, the lower leg 3 is connected to the joint axis 504 in the ankle joint 5 by the ankle joint connecting plate 306. An Achilles tendon cylinder slide rod 303 is provided on the lower side of the lower leg. A rod cylinder spring 305 is sleeved on the lower end of the Achilles tendon cylinder slide rod 303. An Achilles tendon cylinder slider 304 is pressed on the upper end of the rod cylinder spring 305. The Achilles tendon cylinder slider 304 can slide freely while being damped by the rod cylinder spring 305. One end of the Achilles tendon cylinder 4 is connected to the Achilles tendon cylinder slider 304 by a universal hinge 513, and the other end is connected to the ankle joint 5 by a universal hinge 513 to realize the dorsiflexion and plantarflexion of the ankle joint. It should ensure that under the drive of the Achilles tendon cylinder 4, the angle between the lower leg 3 and the ankle joint 5 with the Y bearing 512 as the vertex is between 60° and 120°. The Achilles tendon cylinder slide bar 303, Achilles tendon cylinder slider 304, cylinder spring 305, universal hinge 513, and Achilles tendon cylinder 4 are all commercially available products and existing technology. The advantage of this design is that the Achilles tendon cylinder 4, with cylinder spring 305, can be damped during actuation, effectively mitigating the impact force transmitted from the lower leg 3 to the ankle joint 5. Similarly, when the ankle joint 5 is passively actuated, it can mitigate the impact force transmitted from the ankle joint 5 to the lower leg 3.

[0051] Combination Figure 2 and Figure 3As shown in the figure, the main body of the ankle joint is assembled from an ankle joint cylinder housing 508 and corresponding cylinder cover 501 and bearing cover 505. A piston 502 is installed inside the cylinder housing 508. The piston 502 is connected to a movable assembly consisting of an inner joint frame 503 and a joint axis 504, enabling inversion and eversion of the ankle joint. It should ensure that, driven by the piston 502, the movable assembly consisting of the inner joint frame 503 and joint axis 504, and the entire assembly consisting of the ankle joint cylinder housing 508 and corresponding cylinder cover 501 and bearing cover 505, with the X-bearing 510 as the vertex, move at an angle between -62° and 62°. The ankle joint cylinder housing 508, cylinder cover 501, bearing cover 505, and joint axis 504 are manufactured using CNC machining technology. The advantages of this design are: the uniquely designed square cross-section arc-shaped hydraulic cylinder enables rotational motion, and the compact structure allows it to be directly embedded inside the ankle joint 5, realizing active inversion and eversion of the ankle joint, and coordinating motion with the Achilles tendon hydraulic cylinder 4. Compared with the traditional method that requires a large number of linkage mechanisms and deceleration mechanisms to convert linear motion into rotational motion, this greatly simplifies the mechanical structure.

[0052] The ankle joint cylinder consists of two ankle joint cylinder housings 508 assembled by cylinder fastening bolts 509. A sealing groove is formed on the mounting surface of the ankle joint cylinder housing 508, and this groove is filled with silicone rubber adhesive during assembly. The cylinder fastening bolts 509 are pre-tightened first, and after the adhesive has cured, the standard torque corresponding to the bolt size is applied to the cylinder fastening bolts 509. The cylinder connector 507 is threaded onto the cylinder housing 508. The surface roughness of the inner wall of the ankle joint cylinder housing 508 should be controlled to Ra 0.8 and polished. The parallelism of the inner wall should be controlled to tolerance grade 2. Other machining accuracy should comply with grade m in GB-T 1804-2000.

[0053] Combination Figure 3 As shown in the figure, the ankle joint cylinder oil seal 511 is a Y-shaped oil seal. A cavity is provided inside the cylinder cover 501 for the ankle joint cylinder oil seal 511 to be embedded within. During installation, ensure that the opening of the ankle joint cylinder oil seal 511 faces inwards towards the cylinder. When assembling the piston 502, apply appropriate grease to the inner lip of the ankle joint cylinder oil seal 511 for lubrication. The ankle joint cylinder oil seal 511 is a commercially available product. A gyroscope 514, also a commercially available product, is installed on the lower side of the ankle joint cylinder housing 508.

[0054] Combination Figure 4As shown, the inner joint frame 503 is assembled by fastening the upper inner joint frame 5031 and the lower inner joint frame 5032 together with the inner joint frame fastening bolts 5033 and the inner joint frame fastening nuts 5035. Before assembly, Y bearings 512 should be installed on both sides of the joint shaft 504. After assembly, they are placed in the bearing seats of the lower inner joint frame 5032 and the upper inner joint frame 5031, and then the assembly of the inner joint frame 503 is completed. After the assembly of the inner joint frame 503 is completed, X bearings 510 are installed on both sides of the inner joint frame 503, and then it can be assembled with the ankle joint cylinder housing 508 and the bearing cover 505. The upper inner joint frame 5031 and the lower inner joint frame 5032 are manufactured using CNC cutting technology, and the machining accuracy is in accordance with the m-level of GB-T 1804-2000. The X bearings 510 and Y bearings 512 are commercially available products.

[0055] Combination Figure 4 and Figure 5 As shown, piston rod 5022 is tightened to piston block 5021 via piston block set bolt 5024 and piston block set nut 5025. A piston seal ring 5028 is fitted onto the end face of the assembly of the two piston rods 5022 and piston block 5021, with a piston spacer 5027 sandwiched between them. The piston rod 5022 is then assembled into a single unit using piston block set bolt 5024 and piston block set nut 5025. The upper end of piston rod 5022 is fixed to the inner frame 5031 of the joint via piston rod end fixing bolt 5034. The piston block 5021, piston spacer 5027, and piston rod 5022 are first fabricated using 3D metal printing technology, and then precision-machined using CNC cutting technology to achieve the required process surfaces. The piston seal ring 5028 is a Y-shaped oil seal, fabricated using a prototype molding technique, with a hardness of 90HA. The advantages of this design are: the separate processing facilitates the machining of parts; at the same time, the upper end of the piston rod 5022 is fixed to the inner frame of the joint 5031 by the piston rod end fixing bolt 5034, so that the inner frame of the joint 503 plays the role of the guide sleeve in the traditional piston. While effectively preventing the piston 502 from moving eccentrically, it greatly saves the movement space of the piston 502 in the oil cylinder and increases the range of motion of the ankle joint inversion and eversion.

[0056] The biomimetic hydraulic ankle joint designed in this invention, with its high driving force, high flexibility, compact structure, and built-in cushioning, has broad application prospects in several fields with extremely high requirements for lower limb motor performance. Specific application areas include, but are not limited to:

[0057] (1) High-dynamic performance bionic robot field: For bipedal or multi-legged humanoid robots, the instantaneous explosive force and flexibility of the ankle joint are crucial when performing dynamic actions such as running, jumping, and turning. The hydraulic drive used in this invention can output huge torque to meet its high dynamic requirements; the design of highly integrating the drive cylinder into the joint greatly optimizes the leg structure and reduces the end weight, thereby improving the robot's overall motion efficiency and agility, making it move more freely in complex disaster environments.

[0058] (2) In the field of intelligent prostheses: For high-performance intelligent lower limb prostheses, the mechanical leg can bring a near-natural walking experience to lower limb amputees. Its bionic hydraulic ankle joint can not only provide stable dorsiflexion / plantarflexion movements, but also actively adjust the inversion and supination angles when walking on slopes or uneven surfaces, which greatly enhances the safety and comfort of use.

[0059] Figure 7 The figure shows the limit of inversion movement of the ankle joint during the test, with an angle of 62° and a working condition of 3.5 MPa; Figure 8 The figure shows the limit of eversion movement of the ankle joint in the test, with an angle of -62° and a working condition of 3.5 MPa.

[0060] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A bionic hydraulic driven mechanical leg, characterized in that, The thigh, the shank cylinder, the shank, the Achilles tendon cylinder and the ankle joint are included. The thigh and the shank are connected by the shank cylinder to form the knee joint freedom degree, the shank and the ankle joint are connected by the Achilles tendon cylinder to form the ankle joint dorsiflexion and plantar flexion freedom degree, and the ankle joint has the inversion and eversion freedom degree. Three cylinders are independently driven to realize the coordinated control of walking, supporting and posture balance.

2. The bionic hydraulically driven mechanical leg of claim 1, wherein, The thigh and the shank are connected by a hinge, and the hinge center is located at the rotation center of the knee joint, so that the rotation axis of the knee joint is coaxial with the force moment center of the shank cylinder.

3. A bionic hydraulic ankle structure, characterized in that, Two symmetrical oil cylinder housings, piston assemblies, joint inner frames and double bearings are included. The upper end of the oil cylinder housing is provided with a bearing groove, and an X bearing is assembled inside to form the rotation freedom degree of the ankle joint in the X direction. The joint inner frame is provided with a bearing groove, and a Y bearing is assembled inside to form the rotation freedom degree of the ankle joint in the Y direction. The rotation center lines of the X bearing and the Y bearing are perpendicular to each other and intersect at the center point of the ankle joint, forming a double freedom decoupling structure. The piston assembly is driven by hydraulic oil to realize the bionic dorsiflexion and plantar flexion action of the ankle joint.

4. The bionic hydraulic ankle structure of claim 3, wherein, The piston assembly is composed of a piston rod, a piston block, a piston spacer and a piston sealing ring, the lower end of the piston rod is provided with a square wedge part, the upper end of the piston block is provided with a corresponding square groove, and the two are fixed to form a whole through a fastening bolt, then the piston block end part in the two above-mentioned wholes is assembled with the piston sealing ring, and a piston spacer is clamped therebetween and is fastened by a bolt to form a piston whole.

5. The bionic hydraulic ankle structure of claim 3, wherein, A through hole is arranged in the joint shaft center, the hole is used for penetrating a sensing signal line and a hydraulic oil return pipeline, the hole axis is coincided with the joint rotation axis, so as to reduce the motion interference.

6. The bionic hydraulic ankle structure of claim 3, wherein, The oil cylinder housing and the joint inner frame are fixedly connected through a wear-resistant alloy bearing cover, the bearing cover is fastened by a bolt, so as to maintain the stability of the rotation gap and improve the impact resistance.

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