A humanoid robot toe joint

Abstract

This invention relates to the field of robotics, specifically to a humanoid robot toe joint, comprising a forefoot plate, a midfoot plate, a rearfoot plate, and a lower leg. The midfoot plate is provided with a mounting base, on which are mounted a front cross-axis support and a rear cross-axis support. A cross-axis body is installed between the front and rear cross-axis supports. The forefoot plate is hinged to the front end of the midfoot plate, and a limit block is provided on the forefoot plate. It also includes a damping buffer assembly, one end of which is hinged to the cross-axis body, and the output end of which is hinged to the forefoot plate. This invention achieves biomimetic flexion and extension movements of the humanoid robot's passive toe joint, absorbing walking impact energy without interfering with the original degrees of freedom of the ankle joint. The damping and preload states can be adjusted, and joint reset and gait propulsion are output through passive energy storage and release.

Description

Technical Field

[0001] This invention relates to the field of robotics, specifically to a toe joint for a humanoid robot. Background Technology

[0002] The toe joints are crucial parts of the human foot, playing a vital role in walking. Biomechanical studies have shown that the rigidity of the toe joints significantly affects ankle strength, center of gravity shift, and propulsive force during walking. The toe joints also coordinate with overall foot deformation to adapt to uneven terrain, maintaining postural stability during standing. Given the important role of the toe joints in gait performance, replicating this biomimetic function in the feet of humanoid robots can help improve the robot's gait biomimetic performance, terrain adaptability, and energy efficiency during walking.

[0003] Currently, various toe joint solutions have been developed in the field of humanoid robots. Some solutions improve the robot's adaptability to complex terrain through flexible arch structures; some solutions use motor-driven methods to achieve active movement output of the toe joints; and some passive joint solutions add elastic components such as torsion springs between the midfoot and toes, relying on elastic components to complete the storage and release of energy, thereby improving the robot's walking performance. All of the above-mentioned solutions can realize the basic biomimetic functions of the toe joint in the corresponding scenarios, but there is still room for further optimization in practical applications. Some structures occupy too much space and the arrangement of components is relatively complex, which puts forward high design requirements for the lower limb control system. In the existing passive toe joints, the buffer element mostly adopts a simple hinge arrangement. When the robot walks and is subjected to ground impact, the buffer component will bear not only the axial force but also a certain radial load. Under long-term reciprocating working conditions, it will have a certain impact on the service life of the buffer component. The limit protection design of many passive joints is relatively simple, and the means of constraining the toe swing stroke are limited. Under the condition of large impact load, the buffer element may overtravel. At the same time, the output stiffness of conventional spring-like elastic elements changes linearly, which is different from the actual nonlinear biomechanical response of the human toe joint. Therefore, we propose a humanoid robot toe joint. Summary of the Invention

[0004] To address the aforementioned technical problems, this application provides a humanoid robot toe joint, comprising a front foot plate, a midfoot plate, a rear foot plate, and a lower leg. The midfoot plate is provided with a mounting base, on which a front cross axis support and a rear cross axis support are mounted. A cross axis body is installed between the front cross axis support and the rear cross axis support. The front foot plate is hinged to the front end of the midfoot plate, and a limit block is provided on the front foot plate. The system also includes a damping buffer assembly, one end of which is hinged to the cross axis body, and the output end of which is hinged to the front foot plate. The rear foot plate contains an elastic reset member, the end of which abuts against a spring cover. The lower leg is connected to the cross axis body via an ankle joint linkage.

[0005] In some embodiments, the damping buffer assembly includes a hydraulic buffer, a hydraulic rod, a hydraulic cap, and a fixed shaft. The hydraulic buffer is hinged to the cross shaft body via the fixed shaft. The end of the hydraulic rod is fitted with a hydraulic cap, which is hinged to the front foot plate. The elastic reset element is a mold spring.

[0006] In some embodiments, the limiting block swings synchronously with the front foot plate.

[0007] In some embodiments, when the front foot plate flexes upward to its limit position, the hydraulic cap abuts against the hydraulic buffer body.

[0008] In some embodiments, a damping regulator is provided at the end of the hydraulic buffer away from the hydraulic rod, and the damping regulator is a rotary valve structure.

[0009] In some embodiments, the fixed shaft is provided with an internal thread, and the fixed shaft is connected to the hydraulic buffer via the thread.

[0010] In some embodiments, the forefoot plate, midfoot plate, damping buffer assembly, and cross shaft body constitute a dual rocker mechanism.

[0011] In some embodiments, the dual rocker mechanism constrains the posture of the hydraulic buffer during toe joint flexion.

[0012] In some embodiments, the cross shaft body transmits the motion torque output by the lower leg via the ankle joint linkage, driving the mounting base, midfoot plate, and rear foot plate to achieve multi-degree-of-freedom movement of the ankle joint, including flexion, extension, adduction, and abduction. The arrangement of the hydraulic buffer passing through the front end support of the cross shaft does not interfere with the multi-degree-of-freedom movement of the ankle joint.

[0013] In some embodiments, the mold spring is arranged along the length of the rear foot plate and the midfoot plate, and the mold spring provides foot preload through the spring stop cover.

[0014] This invention has at least the following beneficial effects: (1) By setting up a cross-axis rotary assembly and an independent mounting base, the present invention realizes the transmission of multi-degree-of-freedom motion between the foot and the ankle joint, ensuring that the original movement of the ankle joint is not interfered with by the toe joint structure, while taking into account the overall strength and lightweight design requirements of the foot by means of the split base structure.

[0015] (2) By setting up a dual rocker mechanism, a hydraulic buffer assembly, a dual limiting structure and an elastic reset component, the present invention realizes the bionic flexion and extension movement of the passive toe joint of the humanoid robot, absorbs the impact energy generated during walking, can adjust the damping and pre-tightening state, and completes joint reset and outputs gait propulsion force by passive energy storage release. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the foot plate structure in this invention; Figure 3 This is a schematic diagram of the front foot plate structure of the present invention; Figure 4 This is a schematic diagram of the limiting block structure of the present invention; Figure 5 This is a schematic diagram of the cross shaft front end support structure of the present invention; Figure 6 This is a schematic diagram of the hydraulic buffer structure of the present invention.

[0017] In the diagram: 1-Forefoot plate; 2-Midfoot plate; 3-Rearfoot plate; 4-Lower leg; 5-Ankle joint link; 6-Rear support of cross shaft; 7-Front support of cross shaft; 8-Cross shaft body; 9-Mounting base; 10-Hydraulic damper; 11-Hydraulic rod; 12-Hydraulic cap; 13-Spring cover; 14-Mold spring; 15-Limit block; 16-Fixed shaft; 17-Damping adjuster. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Example 1: Please refer to Figure 1-6This invention provides a technical solution for a humanoid robot toe joint: a humanoid robot toe joint, including a front foot plate 1, a midfoot plate 2, a rear foot plate 3, a lower leg 4, an ankle joint link 5, a cross shaft rear end support 6, a cross shaft front end support 7, a cross shaft body 8, a mounting base 9, a hydraulic buffer 10, a hydraulic rod 11, a hydraulic cap 12, a spring cover 13, a mold spring 14, a limit block 15, a fixed shaft 16, and a damping adjuster 17.

[0020] The midfoot plate 2 is the central base component of the entire foot. A mounting base 9 is fixedly installed on the midfoot plate 2. The mounting base 9 serves as an independent mounting base for the cross-axis body 8, the rear cross-axis support 6, and the front cross-axis support 7 assembly, bearing the assembly load of the front cross-axis support 7 and the rear cross-axis support 6. The advantage of this split base structure is that the foot plate body can be manufactured using lightweight materials. The installation positions of the front cross-axis support 7 and the rear cross-axis support 6, where stress is concentrated, are locally reinforced by the mounting base 9, eliminating the need to thicken the entire midfoot plate 2, thus balancing structural strength and overall weight reduction. The front cross-axis support 7 and the rear cross-axis support 6 are fixedly mounted on the mounting base 9. The cross-axis body 8 is rotatably mounted between the front cross-axis support 7 and the rear cross-axis support 6, allowing the cross-axis body 8 to rotate relative to these two supports, thereby constructing a multi-degree-of-freedom rotational base for the ankle joint. The lower leg 4 is a lower limb component of the humanoid robot. The lower leg 4 is connected to the cross-axis body 8 via an ankle joint link 5. The swinging torque output by the lower leg 4 is transmitted to the cross-axis body 8 through the ankle joint link 5. The cross-axis body 8 drives the mounting base 9, midfoot plate 2, and rearfoot plate 3 to move synchronously, achieving multi-degree-of-freedom movements of ankle flexion, extension, adduction, and abduction. The combination of the rear cross-axis support 6, the front cross-axis support 7, and the cross-axis body 8 can distribute the torque in various directions of the ankle joint, reducing the concentration of torque on a single hinge axis, lowering the possibility of wear at local hinge points, and improving the overall service life of the ankle joint.

[0021] The forefoot plate 1 is hinged to the front end of the midfoot plate 2. The midfoot plate 2 is equipped with a double-eared hinge support, and the forefoot plate 1 is equipped with a single-eared hinge support at its proximal end. The two are connected by a pin to form a single-degree-of-freedom revolute joint, allowing the forefoot plate 1 to perform flexion, extension, and swinging of the toe joints relative to the midfoot plate 2. The single-degree-of-freedom revolute joint has a simple structure, making it easy to control the movement gap and preventing the introduction of unnecessary swinging degrees of freedom. This allows the toe movement of the forefoot plate 1 to simulate the flexion and extension movements of the human metatarsal joints. A limiting block 15 is fixedly installed at the rear of the forefoot plate 1. The limiting block 15 is integral with the forefoot plate 1 or rigidly connected to it, and the limiting block 15 can swing synchronously with the forefoot plate 1. When the toe joint is in the zero position and the flexion angle is 0°, the limiting block 15 abuts against the support end face of the midfoot plate 2, acting as a zero-position hard limit, restricting the forefoot plate 1 from excessive downward extension. This ensures that the forefoot plate 1, in the zero position, can only flex and swing upward, reducing the possibility of the forefoot plate 1 flipping downward and lowering the risk of instability in the robot's standing posture. When the forefoot plate 1 flexes upward to its maximum limit position, on the one hand, the hydraulic cap 12 directly abuts against the end face of the hydraulic buffer 10 body to achieve a first-level limit; on the other hand, the limiting block 15 again forms a second-level hard limit, constituting a double-limit protection. The benefit of the double-limit setting is that even if the internal components of the hydraulic buffer 10 malfunction, the mechanical limiting block 15 can still constrain the maximum flexion angle of the forefoot plate 1, reducing damage to the hydraulic rod 11 due to overtravel compression, lowering the probability of the internal sealing structure of the hydraulic buffer 10 being crushed, and improving the overall machine's ability to cope with malfunctions.

[0022] The damping buffer assembly specifically consists of a hydraulic buffer 10, a hydraulic rod 11, a hydraulic cap 12, and a fixed shaft 16. The hydraulic buffer 10 is entirely inserted into the space below the front support 7 of the cross shaft. This space is an unused internal space of the ankle joint structure, utilizing the inherent internal space of the foot without the need for an additional outward protrusion of the hydraulic buffer 10 component, thus facilitating a compact overall structural layout. Simultaneously, this insertion arrangement minimizes motion interference between the hydraulic buffer 10 and the front support 7 of the cross shaft or surrounding components during the full range of ankle joint movements (flexion, extension, adduction, and abduction). The ankle joint's original degrees of freedom are not constrained by the toe joint structure. The tail of the hydraulic buffer 10 is hinged to the cross shaft body 8 via the fixed shaft 16. The fixed shaft 16 has internal threads, connecting to the threaded section at the tail of the hydraulic buffer 10. By rotating the fixed shaft 16, the axial position of the hydraulic buffer 10 relative to the fixed shaft 16 can be changed, thereby adjusting the initial pre-compression of the hydraulic rod 11. Adjusting the precompression amount offers several practical benefits: First, it allows for the application of a pre-set preload to the toe joints of the front footplate 1 in a zero-position state, reducing assembly clearance between hinge pins and mitigating vibration and noise in the toe area of ​​the front footplate 1 when the robot stands. Second, it allows for fine-tuning of the initial stroke of the hydraulic rod 11, adjusting the maximum flexion angle of the front footplate 1 to suit different bionic gait adjustments. The hydraulic damper 10 contains a retractable hydraulic rod 11, with a hydraulic cap 12 mounted on its extended end. The hydraulic cap 12 is hinged to the front footplate 1.

[0023] The dual rocker mechanism is composed of four parts: the forefoot plate 1, the midfoot plate 2, the damping buffer assembly, and the cross-axis body 8. Throughout the flexing and swinging process of the forefoot plate 1, the dual rocker mechanism constrains the spatial attitude of the hydraulic buffer 10, ensuring that the force line of the reaction force transmitted from the ground remains collinear with the axis of the hydraulic rod 11. The core benefits of this mechanism are: reducing the radial bending moment load on the hydraulic buffer 10, which primarily bears axial loads; and better adapting the piston rod and seals of the hydraulic rod 11 inside the hydraulic buffer 10 to axial force conditions, as radial bending moments easily cause uneven wear of the piston rod 11 and premature wear and oil leakage of the hydraulic buffer 10 seals. This mechanism alleviates these problems from a kinematic perspective, extending the service life of the hydraulic buffer 10. Simultaneously, most ground impact loads can be absorbed by the hydraulic damping of the hydraulic buffer 10, improving energy absorption performance.

[0024] A damping adjuster 17 is installed at the end of the hydraulic buffer 10 away from the hydraulic rod 11. The damping adjuster 17 is a rotary valve structure. By rotating the damping adjuster 17, the operator can change the flow cross section of the oil inside the hydraulic buffer 10, thereby continuously adjusting the internal damping of the hydraulic buffer 10. This structure brings additional benefits: without replacing parts, it can adapt to various working conditions simply by rotating the damping adjuster 17. When walking on flat ground, the damping can be reduced to obtain a more flexible gait; when walking on uneven ground, the damping can be increased to improve impact resistance. The same hardware can be adapted to humanoid robots of different weights and movement speeds, expanding the applicable scenarios of the hardware.

[0025] A mold spring 14 is arranged inside the rear foot plate 3 along its length. One end of the mold spring 14 abuts against the inner wall of the rear foot plate 3, and the other end abuts against the spring cover 13. The mold spring 14 outputs a preload force through the spring cover 13. Compared with ordinary cylindrical helical springs, the mold spring 14 exhibits more stable stiffness and better fatigue resistance, making it suitable for the robot's repetitive and high-frequency walking conditions. During the robot's landing phase, the front foot plate 1 flexes upward, the hydraulic rod 11 compresses, and the hydraulic buffer 10 stores impact energy. During the lift-off phase, the hydraulic buffer 10 releases the stored energy, and together with the elastic restoring force of the mold spring 14, drives the front foot plate 1 back to its zero position, while simultaneously outputting a forward gait propulsion force. This joint is a purely passive joint, eliminating the need for a drive motor, reducer, and corresponding drive control circuitry. This helps reduce the weight and size of the foot, lowers the computational burden on the lower limb controller, and reduces the workload of developing control algorithms.

[0026] Through the above technical solution: In use, as a preferred embodiment of this application, a hydraulic buffer 10 of model 1412 is selected to adapt to the foot of a humanoid robot with a foot length of 245mm. The total length of the hydraulic buffer 10 is 91mm, the compression stroke of the hydraulic rod 11 is 12mm, and the outer diameter is 14mm. The fixed shaft 16 is adjusted to set the initial pre-compression of the hydraulic rod 11 to 2mm, which controls the swing angle range of the forefoot plate 1 relative to the midfoot plate 2 to 0°-28°. This angle range can be set with reference to the actual flexion and extension angle of the human metatarsal joint to improve the bionic performance.

[0027] This application uses a cross-axis body 8 assembly with an independent mounting base 9. The mounting base 9 locally reinforces the stress-bearing parts of the front support 7 and rear support 6 of the cross-axis. The main body of the midfoot plate 2 can be designed to be lightweight, taking into account the requirements of overall structural strength and weight reduction. The hydraulic buffer 10 is arranged using the internal unused space under the front support 7 of the cross-axis. The whole is highly integrated and compact. It can be mounted on existing cross-axis ankle joint humanoid robots without large-scale modification of the lower leg 4 body. At the same time, it does not easily interfere with the original freedom of movement of ankle joint flexion, extension, adduction and abduction, thus expanding the equipment's adaptability scenarios.

[0028] The dual rocker mechanism is set up to constrain the motion of the hydraulic buffer 10, so that the ground reaction force is input along the axis of the hydraulic rod 11, which reduces the radial bending moment borne by the hydraulic buffer 10, alleviates the wear of the piston rod of the hydraulic rod 11 and the oil leakage failure of the seal of the hydraulic buffer 10, improves the service life of the hydraulic buffer 10, and enhances its performance in absorbing impact energy.

[0029] The limit block 15 is configured to cooperate with the hydraulic buffer 10 body to form a double mechanical limit, which acts on the zero position limit and the maximum flexion angle limit of the toe joint of the front foot plate 1, respectively. The zero position limit reduces the downward flipping of the front foot plate 1 and improves the performance during the standing process. The double limit can protect the mechanism when a fault occurs inside the hydraulic buffer 10, reduce the overtravel damage of the hydraulic rod 11, and improve the equipment's ability to cope with faults.

[0030] The hydraulic damper 10 provides damping force. Compared with the linear stiffness generated by springs in traditional passive toe joints, the hydraulic damper 10 can output nonlinear mechanical characteristics, which is more in line with the biomechanical response of human toes. The rear is equipped with a rotary valve damping adjuster 17, which can continuously adjust the damping size without replacing parts, adapting to various working conditions such as flat ground, uneven ground, and different walking speeds, thus expanding the applicable scenarios of the hardware.

[0031] The fixed shaft 16 with internal thread can be set to adjust the initial pre-compression of the hydraulic rod 11; it can reduce the assembly gap of the articulated joint, alleviate the shaking and abnormal noise during walking, and can also adjust the initial pre-tightening force and swing stroke of the toe joint of the front foot plate 1, which facilitates the debugging of the whole machine.

[0032] The entire structure is a purely passive joint, eliminating the need for drive components such as motors and reducers. This reduces the number, weight, and wiring complexity of foot components such as the front foot plate 1, midfoot plate 2, and rear foot plate 3. When landing, the hydraulic buffer 10 absorbs the impact and stores energy. When lifting the foot, the hydraulic buffer 10 and the mold spring 14 work together to release energy, driving the front foot plate 1 to complete the reset and output gait propulsion force. This reduces the control burden on the lower limb controller and improves the energy utilization performance of the robot during walking.

[0033] The rear foot plate 3 is equipped with a mold spring 14. The mold spring 14 has good fatigue resistance and is suitable for the high-frequency reciprocating walking conditions of the robot. The mold spring 14, together with the spring cover 13 and the hydraulic buffer 10, completes the reset action, speeds up the reset response, and maintains the continuous operation of the gait cycle.

[0034] The motion torque output by the robot's lower leg 4 is transmitted to the cross-axis body 8 via the ankle joint link 5. Supported by the front cross-axis support 7 and the rear cross-axis support 6, the cross-axis body 8 drives the mounting base 9, midfoot plate 2, and rear foot plate 3 to complete ankle flexion, extension, adduction, and abduction movements. When the robot lands, the ground reaction force acts on the front foot plate 1, causing it to flex and swing upwards relative to the midfoot plate 2. The double rocker mechanism composed of the front foot plate 1, midfoot plate 2, hydraulic buffer 10, and cross-axis body 8 constrains the spatial posture of the hydraulic buffer 10, allowing the force to be transmitted axially along the hydraulic rod 11. When the pressure rod 11 is compressed, the hydraulic buffer 10 absorbs and stores the impact energy through its own damping. The limiting block 15 and the body of the hydraulic buffer 10 cooperate to achieve double limiting, which constrains the swing range of the front foot plate 1. During the process of lifting the foot off the ground, the hydraulic buffer 10 releases the stored energy. The mold spring 14 inside the rear foot plate 3 outputs elastic force through the spring cover 13. The two work together to drive the front foot plate 1 back to the zero position. The damping adjuster 17 can change the internal damping of the hydraulic buffer 10 to adapt to different working conditions. The fixed shaft 16 can adjust the initial pre-compression of the hydraulic rod 11, thereby changing the pre-tension state of the joint.

[0035] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0036] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A humanoid robot toe joint, comprising a forefoot plate (1), a midfoot plate (2), a hindfoot plate (3), and a lower leg (4), characterized in that: The midfoot plate (2) is provided with a mounting base (9), on which a cross shaft front end support (7) and a cross shaft rear end support (6) are mounted. A cross shaft body (8) is installed between the cross shaft front end support (7) and the cross shaft rear end support (6). The front foot plate (1) is hinged to the front end of the midfoot plate (2), and a limit block (15) is provided on the front foot plate (1). It also includes a damping buffer assembly, one end of which is hinged to the cross shaft body (8), and the output end of which is hinged to the front foot plate (1). The rear foot plate (3) is provided with an elastic reset member inside, and the end of which abuts against a spring cover (13). The lower leg (4) is connected to the cross shaft body (8) via an ankle joint link (5).

2. The humanoid robot toe joint according to claim 1, characterized in that: The damping buffer assembly includes a hydraulic buffer (10), a hydraulic rod (11), a hydraulic cap (12), and a fixed shaft (16). The hydraulic buffer (10) is hinged to the cross shaft body (8) via the fixed shaft (16). The end of the hydraulic rod (11) is fitted with a hydraulic cap (12), which is hinged to the front foot plate (1). The elastic reset component is a mold spring (14).

3. The humanoid robot toe joint according to claim 2, characterized in that: The limiting block (15) swings synchronously with the front foot plate (1).

4. The humanoid robot toe joint according to claim 3, characterized in that: When the front foot plate (1) flexes upward to its limit position, the hydraulic cap (12) abuts against the body of the hydraulic buffer (10).

5. The humanoid robot toe joint according to claim 4, characterized in that: The hydraulic buffer (10) is provided with a damping regulator (17) at the end away from the hydraulic rod (11), and the damping regulator (17) is a rotary valve structure.

6. The humanoid robot toe joint according to claim 5, characterized in that: The fixed shaft (16) is provided with an internal thread, and the fixed shaft (16) is connected to the hydraulic buffer (10) through the thread.

7. The humanoid robot toe joint according to claim 6, characterized in that: The forefoot plate (1), midfoot plate (2), damping buffer assembly, and cross shaft body (8) constitute a double rocker mechanism.

8. The humanoid robot toe joint according to claim 7, characterized in that: The dual rocker mechanism constrains the posture of the hydraulic buffer (10) during the toe joint flexion movement.

9. The humanoid robot toe joint according to claim 8, characterized in that: The cross shaft body (8) transmits the motion torque output by the lower leg (4) through the ankle joint connecting rod (5), driving the mounting base (9), midfoot plate (2), and rear foot plate (3) to achieve multi-degree-of-freedom movement of ankle joint flexion, extension, adduction and abduction. The arrangement of the hydraulic buffer (10) passing under the front end support (7) of the cross shaft does not interfere with the multi-degree-of-freedom movement of the ankle joint.

10. The humanoid robot toe joint according to claim 2, characterized in that: The mold spring (14) is arranged along the length of the rear foot plate (3) and the midfoot plate (2), and the mold spring (14) provides foot preload through the spring cover (13).

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