Robot ankle device with passive energy storage and active power assisting functions

Abstract

The invention discloses a robot ankle device with passive energy storage and active power assistance, which belongs to the technical field of humanoid robots and comprises a shank connecting part, a compliance lever part, a foot part, a parallel spring, a series elastic actuator and a state locking mechanism. The top end of the compliance lever part is rotationally connected with the shank connecting part, and the bottom end is hinged with the foot through a joint shaft; the parallel spring is connected between the compliance lever part and the foot part and is used for standing phase early-stage passive energy storage; the series elastic actuator comprises an adjusting mechanism and a joint torque assisting mechanism and is used for adjusting the hinging angle and actively outputting torque in the push-off period. The state locking mechanism is arranged on the foot portion and used for locking the hinge angle of the compliance lever portion and the foot portion. Passive energy storage and active power assisting are combined, efficient energy management and compliant motion control are achieved, and the adaptability and stability of the robot under the complex terrain are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of humanoid robots, and particularly relates to a robot ankle device with passive energy storage and active assistance. BACKGROUND

[0002] At present, robot foot joint devices mainly include passive and active types. The active device can provide the required net positive energy in various scenes such as flat ground, slope and stairs, and makes up for the shortcomings of the passive device, but its actual application still faces the problems of poor energy autonomy and large overall weight.

[0003] In order to reduce the system weight and load, the prior art usually adopts a series elastic actuator (i.e., a motor and a spring are connected in series), which can reduce the peak power of the motor by reasonable adjustment, so that a smaller specification driving motor can be used. Another scheme introduces a parallel spring to passively provide torque, thereby reducing the load of the actuator. Since the motor torque is proportional to the current and the loss is related to the square of the current, reducing the torque demand helps to optimize the motor size, thereby reducing the cost and weight and improving the system safety, and is also conducive to the improvement of transmission design and joint dynamic performance.

[0004] In gait assistance applications, the parallel spring is usually divided into two categories according to the threshold of the joint angle of the trigger torque: one type engages above a fixed angle to avoid interfering with the swing phase motion, but its elastic adjustment range is limited and the terrain adaptability is poor; the other type can dynamically adjust the engagement angle for early energy storage in the standing phase, but needs to disengage in the swing phase, and its adaptive mechanism mostly relies on a complex clutch, resulting in a heavy structure, which is difficult to meet the requirements of robots for lightweight and high dynamic response.

[0005] In addition, the existing device mostly adopts a spring energy storage mechanism, and controls energy release by a state locking mechanism. Such a mechanism only allows energy storage or release at a specific stage of the gait cycle. However, these mechanisms are mostly based on ratchet gear structures, which have obvious disadvantages: limited locking angle and low adjustment precision due to the limitation of discrete engagement between the gear and the pawl; mechanical mutation is easy to occur at the locking moment, affecting the motion stability.

[0006] Therefore, it is necessary to provide a robot ankle device with passive energy storage and active assistance. SUMMARY

[0007] The purpose of this invention is to provide a robotic ankle device with passive energy storage and active assistance to address the lack of flexibility in energy management in existing mechanisms. This mechanism employs a gearless continuous locking mechanism, effectively overcoming the shortcomings of traditional ratchet-type locking methods, such as joint position dispersion, abrupt locking process, and high impact force. The system primarily uses passive energy storage, with active assistance provided only when necessary by the actuator, thereby significantly alleviating the problems of short endurance and excessive system load caused by continuous high energy consumption. Ultimately, this invention aims to comprehensively improve the mechanical performance of the robotic ankle mechanism, achieving reduced power consumption and weight, and providing a continuous and smooth support and movement experience.

[0008] To achieve the above objectives, the present invention provides the following solution: a robotic ankle device with passive energy storage and active assistance, comprising: a lower leg connecting part; a compliant lever part, the top end of which is rotatably connected to the lower leg connecting part; a foot part, which is hinged to the bottom end of the compliant lever part via a joint axis; a parallel spring connected between the compliant lever part and the foot part for passively storing energy in the early standing phase; a series elastic actuator, including an adjustment mechanism and a joint torque assist mechanism connected between the compliant lever part and the foot part for adjusting the hinge angle between the compliant lever part and the foot part, and actively outputting torque during the push-off phase; and a state locking mechanism disposed on the foot part for locking the hinge angle between the compliant lever part and the foot part.

[0009] Furthermore, the state locking mechanism includes a pawl and a ratchet. The ratchet is rotatably connected to the foot, and the pawl is rotatably connected to the foot via a second shaft and asymmetrically engages with the ratchet. A torsion spring is provided between the pawl and the second shaft, and the pawl is also connected to an unlocking mechanism.

[0010] Furthermore, the unlocking mechanism includes a swing arm elastically connected to the pawl, and a second motor that drives the swing arm to swing.

[0011] Furthermore, the adjustment mechanism includes: First elastic rope; The ratchet's central shaft is fixed coaxially with the ratchet. The second and third pulleys are respectively installed on the lever section and the foot. Anchors, fixed to the foot; One end of the first elastic rope is fixed to the central shaft of the ratchet, and the other end is fixed to the anchor after passing through the second and third pulleys to form a closed-loop transmission, which is used to adjust the system stiffness to adapt to different terrains and load requirements.

[0012] Furthermore, the anchor has multiple adjustment holes on the inner side of the foot for manually or automatically adjusting the fixed position of the first elastic rope, thereby achieving discrete or continuous adjustment of stiffness.

[0013] Furthermore, the joint torque assist mechanism includes a second elastic rope, a first pulley, a sliding nut, a slider, a lead screw, and a first motor. The lead screw rotates within the foot and is driven by the first motor. The slider is threadedly engaged with the lead screw and is connected to the sliding nut. The first pulley is installed on the foot. The second elastic rope is connected to the sliding nut and the first pulley and passes around the rear end of the compliant lever to form a transmission.

[0014] Furthermore, the two sliding nuts in the joint torque assist mechanism are symmetrically arranged and form a closed-loop transmission with the two symmetrically arranged first pulleys through the second elastic rope, which is used to move synchronously in opposite directions under the drive of the lead screw, so as to output the joint torque in a balanced manner and reduce the nonlinear error in the transmission process.

[0015] Furthermore, the foot is provided with a groove, and the sliding nut is limited to slide within the groove to ensure that it moves only in a straight line along the groove.

[0016] Furthermore, the first pulley is installed at the foot near the joint axis to shorten the range of change of the lever arm of the second elastic rope and reduce the nonlinear error of the torque output.

[0017] Furthermore, the foot is provided with a hanging shaft on both sides, and the hanging shaft is arranged coaxially with the ratchet, so that the energy storage state of the parallel spring is synchronized with the state locking mechanism.

[0018] As can be seen from the above technical solution, the device of the present invention can retain the impact energy from the ground during the standing phase as elastic potential energy within the mechanism without loss, and release it smoothly as needed during the pushing phase. Simultaneously, through real-time adjustment of stiffness and torque, the joints maintain low-energy, high-response, and virtually impact-free compliant movement under different terrain and load conditions, significantly improving the naturalness, stability, and energy utilization efficiency of the robot's gait. Therefore, with its innovative active locking mechanism and efficient energy management design, the present invention effectively overcomes the limitations of existing technologies in gait simulation, terrain adaptability, and system integration, significantly improving the smoothness and reliability of overall movement. This mechanism provides robots with a more intelligent, safe, and efficient walking solution, making their movement performance closer to the adaptability and energy efficiency levels of natural organisms. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1This is an isometric view of the robot ankle device with passive energy storage and active assistance according to the present invention. Figure 2 This is a front view of the robotic ankle device with passive energy storage and active assistance according to the present invention. Figure 3 This is a schematic diagram of the foot structure in the device of the present invention; Figure 4 This is a front view of the series elastic actuator in the device of the present invention; Figure 5 This is a left view of the series elastic actuator in the device of the present invention; Figure 6 This is a front axonometric view of the series elastic actuator in the device of the present invention; Figure 7 This is a rear view of the series elastic actuators in the device of the present invention; Figure 8 for Figure 7 A magnified view of a section at point A in the middle; Figure 9 This is a rear isometric view of the series elastic actuator in the device of the present invention; Figure 10 for Figure 9 A magnified view of a section at point B.

[0021] In the diagram: 1. Lower leg connection; 2. Alignment lever; 3. Foot; 301. Hanging shaft; 302. Slide groove; 303. First shaft hole; 304. Second shaft hole; 305. Third shaft hole; 306. Fourth shaft hole; 4. Joint shaft; 5. Parallel spring; 6. Adjustment mechanism; 601. First elastic rope; 602. Ratchet central shaft; 603. Second pulley; 604. Third pulley; 605. Anchor; 7. Joint torque assist mechanism; 701. Second elastic rope; 702. First pulley; 703. Sliding nut; 704. Slider; 705. Lead screw; 706. Transmission belt; 707. First motor; 8. State locking mechanism; 801. Second motor; 802. Swing arm; 803. Shaft one; 804. Tension spring; 805. Pawl; 806. Shaft two; 807. Ratchet. Detailed Implementation

[0022] 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.

[0023] To balance high performance, low power consumption, lightweight, high rigidity, and smooth motion, this invention proposes a novel state locking mechanism 8, which, combined with a slider 704 and an activation system, allows for smooth switching between "free movement" and "energy storage" modes. This invention abandons the traditional gear-based state locking mechanism 8, instead providing a novel device comprising a state locking mechanism 8, a slider 704, and an activation system. This device can smoothly switch between free movement and energy storage modes. Its gearless design not only achieves continuous and gentle soft locking, greatly improving comfort and naturalness during joint movement, but also offers greater portability and robustness due to its simplified structure. Furthermore, this design requires no external energy input during most work cycles (such as gait cycles), with the actuator only intervening when additional assistance is needed, significantly improving energy efficiency and making it particularly suitable for robot applications requiring long-term operation.

[0024] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] Reference Figures 1 to 10 As shown, this embodiment of the invention provides a robotic ankle device with passive energy storage and active assistance, including a lower leg connecting part 1, a compliant lever part 2, a foot 3, and a series elastic actuator connected between the compliant lever part 2 and the foot 3. The lower leg connecting part 1 serves as a connecting support component, connecting to the robot's lower leg. One end of the connecting part 1 is connected to the compliant lever part 2 via a pivot. The compliant lever part 2 and the foot 3 are hinged via a joint axis 4, which transmits and adjusts force. The joint axis 4 passes through the compliant lever part 2 and the foot 3, achieving the hinge function for dorsiflexion / plantarflexion movements. The foot 3 serves as an overall support, hinged to the compliant lever part 2 on one hand, and also moving in coordination with the compliant lever part 2 via the series elastic actuator on the other. The series elastic actuator, as the active power source of the system, can output precise torque according to control commands when needed (such as during the "push-off phase" in the gait cycle), providing auxiliary thrust for the plantarflexion movement of the ankle joint, enhancing the robot's propulsion and obstacle-crossing capabilities.

[0026] In this embodiment, a parallel spring 5 is connected between the front end of the lever part 2 and the top of the foot part 3 for passive energy storage in the early standing phase. The parallel spring 5 is a double spring structure and is sleeved on the hanging shaft 301. The hanging shaft 301 is fixed on both sides of the foot 3 and parallel to the joint axis 4.

[0027] In this embodiment, the series elastic actuator is a key component in achieving the efficient, low-consumption, compliant, and controllable motion performance of this embodiment. Specifically, the series elastic actuator includes an adjustment mechanism 6 and a joint torque assist mechanism 7.

[0028] In this embodiment, the foot 3 serves as an integral support structure, and is provided with a hanging shaft 301, a sliding groove 302, a first shaft hole 303, a second shaft hole 304, a third shaft hole 305, and a fourth shaft hole 306. The hanging shaft 301 is used to install a parallel spring 5, which enables elastic linkage between the foot 3 and the compliant lever 2. The sliding groove 302 is located on both sides of the foot 3 to guide the sliding nut 703 to move along a predetermined trajectory. The first shaft hole 303 is used to install a joint shaft 4, enabling hinge connection between the foot 3 and the compliant lever 2. The second shaft hole 304 is used to install the ratchet center shaft 602 of the adjustment mechanism 6, forming the physical basis for the transmission connection. The third shaft hole 305 is used to install the first pulley 702 of the joint torque assist mechanism 7, and the fourth shaft hole 306 is used to install the third pulley 604 of the adjustment mechanism 6.

[0029] The adjustment mechanism 6 includes a first elastic rope 601, a ratchet central shaft 602, a second pulley 603, a third pulley 604, and an anchor 605. One end of the first elastic rope 601 is fixed to the ratchet central shaft 602, and the other end passes sequentially over the second pulley 603 and the third pulley 604 before being fixedly connected to the anchor 605. The anchor 605 is fixed to the inside of the foot 3. By adjusting its position, the effective length of the first elastic rope 601 can be changed, thereby achieving dynamic adjustment of the system stiffness to adapt to the needs of different loads and motion scenarios. The second pulley 603 and the third pulley 604 form a closed-loop transmission structure, effectively optimizing the force transmission path and amplifying the torque.

[0030] The anchor 605 has multiple adjustment holes on the inner side of the foot 3 for manually or automatically adjusting the fixed position of the first elastic rope 601, thereby achieving discrete or continuous adjustment of stiffness.

[0031] The joint torque assist mechanism 7 includes a second elastic rope 701, a first pulley 702, a sliding nut 703, a slider 704, a lead screw 705, a transmission belt 706, and a first motor 707. Two symmetrical grooves 302 are formed on the left and right sides of the foot 3, each containing a sliding nut 703. The first pulleys 702 are symmetrically positioned on the left and right sides of the foot 3 and rotate synchronously via pulley shafts passing through the foot 3. One end of the second elastic rope 701 is attached to the sliding nut 703 on one side of the foot 3, and the other end passes sequentially around the first pulley 702 on that side, the rear end of the lever 2, and the first pulley 702 on the other side before attaching to the sliding nut 703 on the other side of the foot 3. It should be understood that a groove is provided at the rear end of the lever 2 to accommodate the second elastic rope 701. The first motor 707 drives the lead screw 705 to rotate via the transmission belt 706, causing the sliding nut 703 to move linearly along the grooves 302 of the foot 3. The sliding nut 703 is connected to the second elastic rope 701, and converts linear motion into torque output to the joint through the first pulley 702, thereby providing active assistance to the ankle joint. The slider 704 cooperates with the sliding nut 703 to guide and limit the movement, ensuring motion accuracy and reliability.

[0032] The state locking mechanism 8 includes a second motor 801, a swing arm 802, a first shaft 803, a tension spring 804, a pawl 805, a second shaft 806, and a ratchet 807. The second motor 801 drives the swing arm 802 to swing around the first shaft 803, pushing the pawl 805 to engage or disengage with the ratchet 807. A torsion spring is provided between the pawl 805 and the second shaft 806, providing an elastic restoring force opposite to that of the tension spring 804, ensuring that the mechanism can automatically reset under no-load conditions. The ratchet 807 has an asymmetrical tooth profile, with a driving side tilt angle close to 90°, a sliding side tilt angle slightly less than 90°, and a tooth tip tilt angle of approximately 45°, achieving self-locking under load and self-unlocking under no-load conditions, completing a shock-free soft locking and soft unlocking process. It should be understood that in practical applications, the second motor 801 can be a miniature servo motor capable of rotary motion.

[0033] This invention employs a self-locking and self-unlocking locking mechanism 8 based on an asymmetric tooth profile design. This mechanism consists of a ratchet 807 and a pawl 805 with asymmetric teeth. Its drive-side tilt angle is close to 90°, its sliding-side tilt angle is slightly less than 90°, and its tooth tip tilt angle is approximately 45°. It can automatically lock (self-lock) under load and automatically unlock (self-unlock) under no-load conditions. Unlike traditional locking mechanisms that rely on discrete gear meshing (such as the conventional ratchet 807), this invention utilizes a continuous and smooth tooth structure to achieve a shock-free soft locking and soft unlocking process, significantly improving the smoothness of robot joint movement and overall comfort, while reducing the requirements for actuator control precision.

[0034] In terms of the transmission system, this invention is based on a pulley-rope symmetrical transmission structure and an adjustable stiffness mechanism. It employs a symmetrically arranged double pulley system, including lever pulleys and heel pulleys, forming a closed-loop transmission via elastic ropes. This system can dynamically adjust its overall stiffness by adjusting the fixed position of the ropes on the anchoring base, adapting to different robot loads and varying motion scenarios. Compared to traditional rigid linkages or gear transmissions, this design effectively overcomes problems such as high weight, high noise, and fixed stiffness. Through the "flexible rope + symmetrical pulley" configuration, it not only optimizes joint torque amplification and force transmission direction but also possesses actively adjustable stiffness characteristics, significantly enhancing the system's dynamic adaptability under different motion states while achieving lightweight design.

[0035] In terms of energy management, this invention integrates a lockable parallel spring and a series elastic actuator to form a dual-mode energy management system. The lockable parallel spring is used for passive energy storage, while the series elastic actuator is used for active assistance. A microcontroller intelligently switches between the two operating modes, enabling on-demand energy storage and release during the gait cycle. Existing systems often employ purely active or purely passive solutions, making it difficult to balance energy efficiency and assistance performance. This invention, through an electromechanical integration strategy, passively stores energy in the early stages of standing and actively releases energy during the push-off phase, thereby significantly reducing system energy consumption while maintaining rapid response and natural assistance.

[0036] This invention, through the coordinated operation of the above-described structures, achieves efficient energy storage and on-demand release during the gait cycle. The specific working process is as follows: During the preparation phase, the operator presets the system stiffness by adjusting the position of anchor 605 to match the robot's weight and motion pattern. After the system is powered on, the main control unit initializes the sensors and control system.

[0037] After entering the swing phase, the robot's foot 3 lifts up, and the main control unit drives the second motor 801 to unlock the state locking mechanism 8. The parallel spring 5 releases the stored energy to assist the foot 3 in dorsiflexion. The series elastic actuator does not output active torque during this stage, and the tension spring 804 keeps the foot 3 in a neutral posture.

[0038] During the heel strike phase, the heel contacts the ground and begins to bear weight. The parallel spring 5 continues to release energy to provide auxiliary torque. The series elastic actuator begins to work under control. The first motor 707 drives the sliding nut 703 through the joint torque assist mechanism 7 to stretch the second elastic rope 701, providing supplementary thrust for the propulsion action.

[0039] During the full foot support phase, foot 3 is in complete contact with the ground and bears the overall weight. The state locking mechanism 8 enters the locked state under the drive of the second motor 801, allowing the parallel spring 5 to store energy; the series elastic actuator continuously provides adjustable thrust assistance according to gait planning and torque requirements.

[0040] During the push-off phase, the robot's center of gravity shifts forward, preparing to leave the ground. Parallel spring 5 remains locked to store energy, while the series elastic actuator outputs the target torque, assisting in achieving an efficient and stable push-off action.

[0041] The mechanism then enters the oscillating phase again, repeating the aforementioned process. Throughout the walking cycle, the device can adjust the force and torque output in real time based on the movement intention and ground reaction force information, providing appropriate support and propulsion under different terrains, significantly improving the naturalness, stability, and energy efficiency of the gait.

[0042] Compared with the prior art, the embodiments of the present invention disclose at least the following technical effects: This invention organically integrates the lower leg connecting part 1, the compliant lever part 2, the foot part 3, the parallel spring 5, the series elastic actuator and the state locking mechanism 8 into a cooperating whole, enabling the robot to achieve efficient energy management and smooth movement transition directly based on the mechanical properties of the structure itself during walking. Specifically, the hinge structure between the compliant lever 2 and the foot 3 provides a flexible motion basis for the joint, while the passive compression of the parallel spring 5 in the early standing phase directly converts the ground reaction force into elastic potential energy stored inside the structure, avoiding additional energy loss in the transmission chain. When entering the push-off phase, the state locking mechanism 8 instantly locks the relative angle between the foot 3 and the compliant lever 2 through the asymmetrical meshing structure of the ratchet 807 and the pawl 805, so that the stored elastic potential energy is stably maintained and not released prematurely, thus providing a reliable mechanical fulcrum for the subsequent active assistance phase. At the same time, the adjustment mechanism 6 in the series elastic actuator can adjust the fixed position of the rope in real time according to the terrain or load changes through the closed-loop transmission formed by the first elastic rope 601 winding around the second pulley 603 and the third pulley 604, directly changing the system stiffness, so that the structure itself can adapt to different walking environments. An adaptive mechanical response is generated; the joint torque assist mechanism 7 drives the sliding nut 703 to move linearly within the foot 3 groove 302 via the lead screw 705, which in turn drives the second elastic rope 701 to apply a controllable pulling force to the compliant lever part 2 around the first pulley 702, efficiently converting the rotational motion of the motor into joint torque output. Due to the symmetrical arrangement of the sliding nut 703 and the significant compression of the lever arm variation range by the placement of the first pulley 702 close to the joint axis 4, the nonlinear error in the torque transmission process is significantly reduced, thereby achieving smooth and precise assistance to the foot 3 during the push-off phase. In addition, the unlocking mechanism in the state locking mechanism 8, through the cooperation of the swing arm 802 and the second motor 801, can slowly release the pawl 805 in an elastic connection during gait switching, avoiding the mechanical abrupt change at the moment of locking, so that the entire structure always maintains smooth mechanical continuity during energy release and movement transition. Therefore, the entire device does not need to rely on complex control algorithms. It can achieve passive energy storage and locking in the standing phase and active stiffness adjustment and smooth torque output in the pushing phase, thereby directly obtaining a walking assistance effect with low energy consumption, high response and high comfort. It significantly improves the naturalness, stability and energy efficiency of the robot's foot and ankle system in different terrains.

[0043] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0044] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A robotic ankle device with passive energy storage and active assistance, characterized by, The application relates to a compliant leg mechanism, which comprises the following parts: a shank connecting part (1); a compliant lever part (2) rotatably connected with the shank connecting part (1) at the top end; a foot part (3) hingedly connected with the bottom end of the compliant lever part (2) through a joint shaft (4); a parallel spring (5) connected between the compliant lever part (2) and the foot part (3) for passive energy storage in the early stage of a standing phase; a serial elastic actuator comprising an adjusting mechanism (6) and a joint torque assisting mechanism (7) connected between the compliant lever part (2) and the foot part (3), which is used for adjusting the hinging angle of the compliant lever part (2) and the foot part (3) and actively outputting torque in a push-off phase; a state locking mechanism (8) arranged in the foot part (3) and used for locking the hinging angle of the compliant lever part (2) and the foot part (3).

2. The robotic ankle device with passive energy storage and active assistance of claim 1, wherein, The state locking mechanism (8) comprises a pawl (805) and a ratchet wheel (807), the ratchet wheel (807) is rotatably connected with the foot part (3), the pawl (805) is rotatably connected with the foot part (3) through a shaft (806) and asymmetrically engages with the ratchet wheel (807), a torsional spring is arranged between the pawl (805) and the shaft (806), and the pawl (805) is further connected with an unlocking mechanism.

3. The robotic ankle device with passive energy storage and active assistance of claim 2, wherein, The unlocking mechanism comprises a swing arm (802) elastically connected with the pawl (805) and a second motor (801) used for driving the swing arm (802) to swing.

4. The robotic ankle device with passive energy storage and active assistance of claim 2, wherein, The adjusting mechanism (6) comprises the following parts: a first elastic rope (601); a ratchet wheel central shaft (602) coaxially fixed with the ratchet wheel (807); a second pulley (603) and a third pulley (604) respectively arranged in the compliant lever part (2) and the foot part (3); an anchor (605) fixed in the foot part (3); one end of the first elastic rope (601) is fixed to the ratchet wheel central shaft (602), the other end of the first elastic rope (601) is fixed to the anchor (605) after passing through the second pulley (603) and the third pulley (604) to form a closed loop transmission, and the closed loop transmission is used for adjusting the system stiffness to adapt to different terrain and load requirements.

5. The robotic ankle device with passive energy storage and active assistance of claim 4, wherein, The anchor (605) is provided with a plurality of adjusting holes in the inner side of the foot part (3), which are used for manually or automatically adjusting the fixed position of the first elastic rope (601) to realize discrete or continuous adjustment of the stiffness.

6. The robotic ankle device with passive energy storage and active assistance of claim 1, wherein, The joint torque assisting mechanism (7) comprises a second elastic rope (701), a first pulley (702), a sliding nut (703), a sliding block (704), a lead screw (705) and a first motor (707), the lead screw (705) is rotatable in the foot part (3) and is driven by the first motor (707), the sliding block (704) is threadedly matched with the lead screw (705), the sliding block (704) is connected with the sliding nut (703), the first pulley (702) is arranged in the foot part (3), the second elastic rope (701) is connected with the sliding nut (703) and the first pulley (702) and forms a transmission after passing through the rear end of the compliant lever part (2).

7. The robotic ankle device with passive energy storage and active assistance of claim 6, wherein, The two sliding nuts (703) in the joint torque assisting mechanism (7) are symmetrically arranged and form a closed loop transmission with the two symmetrically arranged first pulleys (702) through the second elastic rope (701), for synchronous forward or reverse movement under the drive of the lead screw (705), to balance the output of joint torque and reduce the nonlinear error in the transmission process.

8. The robotic ankle device with passive energy storage and active assistance of claim 7, wherein, The foot (3) is provided with a sliding groove (302), and the sliding nut (703) is limited to slide in the sliding groove (302), so as to ensure that the sliding nut (703) only moves linearly along the sliding groove (302).

9. The robotic ankle device with passive energy storage and active assistance of claim 6, wherein, The first pulley (702) is installed on the foot (3) close to the joint shaft (4), so as to shorten the force arm change range of the second elastic rope (701) and reduce the nonlinear error of torque output.

10. The robotic ankle device with passive energy storage and active assistance of claim 2, wherein, The foot (3) is provided with a hanging shaft (301) on both sides, the hanging shaft (301) is coaxially arranged with the ratchet wheel (807), so that the energy storage state of the parallel spring (5) is synchronized with the state locking mechanism (8).

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