A variable stiffness quadruped robot foot structure based on magnetorheological smart materials

Abstract

This invention discloses a variable stiffness quadruped robot foot structure based on magnetically controlled smart materials, belonging to the field of quadruped robot technology. The foot structure includes foot sensors, a foot base, and a first variable stiffness component and a second variable stiffness component fixed within it. The first variable stiffness component includes a first rubber shell filled with magnetically controlled smart materials, a de-energized electromagnet, and its magnetic circuit assembly; the second variable stiffness component includes a second rubber shell filled with magnetically controlled smart materials, an electro-permanent magnet, and its magnetic circuit assembly. By controlling the on / off state of the de-energized electromagnet and the pulsed current charging / demagnetizing of the electro-permanent magnet, the magnetic field strength in the space where the magnetically controlled smart materials are located can be rapidly changed, causing it to instantaneously transition between a liquid and a near-solid state, thereby achieving active and controllable adjustment of the foot stiffness. This invention adopts the above structure, integrating the magnetically controlled smart materials and variable stiffness components in an innovative design. The hybrid magnetic circuit design combines rapid response and low power consumption, effectively buffering the robot's landing impact, reducing vibration, and adapting to the foot stiffness requirements of different motion conditions.

Description

Technical Field

[0001] This invention relates to the field of variable stiffness quadruped robot technology, and in particular to a variable stiffness quadruped robot foot structure based on magnetically controlled smart materials. Background Technology

[0002] Significant progress has been made in the development of quadruped robot leg structures. By mimicking animal gait, quadruped robots exhibit excellent mobility and adaptability in unstructured terrains such as mountains, ruins, and staircases, and have become a research hotspot in the field of robotics in recent years. Typical applications include military reconnaissance, material transportation, disaster relief, planetary exploration, and inspection operations in specific environments.

[0003] Chinese patent CN220721235U discloses a robot foot structure, characterized in that it includes: a main structure, the main structure including a support member and a foot end connecting part, the bottom end of the support member being provided with the foot end connecting part; a detachable foot end structure, the detachable foot end structure including a detachable part and a foot end, the top end of the detachable part being coupled to the inner top end of the foot end connecting part, the inner wall of the detachable part being sleeved with the outer wall of the foot end connecting part and bolted to each other, and the top end of the foot end being welded to the bottom end of the detachable part.

[0004] Chinese patent CN208715328U discloses a robot foot structure, characterized in that it includes an upper connector for connecting to the robot body, a palm top cover, a palm bottom cover, a palm spring, foot toes, and toe springs, wherein there are at least three foot toes and toe springs; the upper connector is movably connected to the palm top cover, and the center of the palm top cover and the center of the palm bottom cover are connected as one piece by the palm spring; the foot toes include a support part and a connecting part for contacting the ground, wherein the support part and the connecting part are integrally formed. The foot end near the connecting part is provided with a connecting groove and a connecting fulcrum in sequence. The connecting groove is located between the connecting fulcrum and the supporting part. A supporting member is provided on the palm cover. The supporting member and the connecting groove are movably connected by a connecting shaft. A rotation fulcrum is formed between the supporting member and the connecting groove, and the foot toe can rotate relative to the supporting member around the rotation fulcrum. One end of the toe spring is connected to the palm cover, and the other end of the toe spring is connected to the connecting fulcrum of the foot toe. The toe spring can play a buffering and shock-absorbing role between the foot toe and the palm cover.

[0005] The foot structures of the robots in the aforementioned patents can effectively solve the stability problem of robots. However, their designs are mostly designed for specific working conditions or regular ground environments. When faced with complex and varied terrain, their adaptability is still limited, and they are easily impacted during movement. Therefore, the requirements for the variable stiffness performance and energy utilization of the feet are becoming increasingly higher. Thus, developing a flexible foot structure that can adjust its stiffness in real time, quickly and efficiently according to the robot's motion state and terrain information is the key to improving the dynamic performance, environmental adaptability and energy efficiency of quadruped robots. It has important research value and application prospects. The variable stiffness scheme based on magnetically controlled smart materials is a cutting-edge solution that has emerged in response to this need. Summary of the Invention

[0006] The problem this invention aims to solve is to provide a variable stiffness quadruped robot foot structure based on magnetically controlled smart materials. By combining magnetically controlled smart materials with innovative magnetic circuit design, the stiffness of the foot can be switched quickly and controllably, thereby effectively buffering the impact of landing, reducing vibration, and adapting to different motion states.

[0007] To achieve the above objectives, the present invention discloses a variable stiffness quadruped robot foot structure based on magnetically controlled smart materials. The variable stiffness foot structure includes a foot base, a foot sensor, a first variable stiffness component, and a second variable stiffness component.

[0008] The bottom of the foot base is threadedly connected to the first and second variable stiffness components; the foot sensor is installed inside the foot base and connected to the mounting bracket via threads; there is one set of the second variable stiffness components, located at the center of the bottom of the foot base; there are three sets of the first variable stiffness components, arranged circumferentially around the second variable stiffness components, with the first set installed directly in front of the second variable stiffness components, and the second and third sets arranged symmetrically to the left and right of the center line, each forming a 45° angle with the center line; the magnetically controlled smart material is filled inside the first and second variable stiffness components.

[0009] The foot base includes a base shell, screws, and bolts. The base shell is connected to the lower legs of the quadruped robot via the screws and to a variable stiffness component via the bolts. The foot base has a cable outlet hole and a variable stiffness component slot inside, with the cable outlet hole connected to one side of the variable stiffness component slot. The inner cavity of the foot base is connected to the cable outlet hole. The top of the base shell has a slot with a threaded hole inside. The first and second variable stiffness components are installed in the variable stiffness component slot.

[0010] The foot sensor includes an accelerometer and a flexible sensor. The accelerometer is rigidly connected to the main structure of the foot base via a dedicated mounting bracket. Its signal line is embedded inside the foot structure through a sleeve and finally connected to the controller, ensuring that there is no relative movement between the sensor and the main body of the foot structure to avoid introducing measurement noise. The flexible sensor is attached to the inner surface of the sole, ensuring that the pressure data transmission path passes directly through the sensor's sensitive element.

[0011] The first and second variable stiffness components are disposed inside the foot base. The first variable stiffness component includes a first rubber shell, a de-energized electromagnet, and a first magnetic circuit assembly. The second variable stiffness component includes a second rubber shell, an electro-permanent magnet, and a second magnetic circuit assembly. The bottoms of the first and second rubber shells constitute the foot contact area, and their internal cavities are filled with magnetically controlled smart material.

[0012] The de-energized electromagnet is positioned above the first rubber shell, with its core extending to the bottom of the first rubber shell. The first magnetic circuit assembly is used to generate a magnetic field within the first rubber shell when the de-energized electromagnet is energized, causing the magnetically controlled smart material therein to be magnetized. The electro-permanent magnet is positioned above the second rubber shell. The second magnetic circuit assembly is used to create an external magnetic field circulation within the second rubber shell after the electro-permanent magnet is pulse-excited, causing the magnetically controlled smart material therein to be magnetized.

[0013] Preferably, the first magnetic circuit assembly includes a first permanent magnet disposed at the end of the core of the de-energized electromagnet and a first coil wound thereon. The magnetic field of the first magnetic circuit assembly is formed by the cancellation of the electromagnetic field generated by the first coil after it is energized and the magnetic field of the first permanent magnet.

[0014] Preferably, the second magnetic circuit assembly includes a magnetic conductor disposed around the electro-permanent magnet and a second coil wound thereon. The magnetic field of the second magnetic circuit assembly is formed by the directional magnetic field generated by the electro-permanent magnet after being pulse-excited by the second coil and the magnetic field of the magnetic conductor.

[0015] Preferably, both the first rubber shell and the second rubber shell are hemispherical elastic shells.

[0016] Preferably, the foot base is provided with a wire outlet hole for the routing of the first coil and the second coil.

[0017] Preferably, both the de-energized electromagnet and the electro-permanent magnet are fixedly installed in the foot base via threaded connections.

[0018] Preferably, the foot base is fixedly installed in the foot base slot with screws to the lower leg of the quadruped robot.

[0019] Preferably, the magnetically controlled smart material is a novel smart material that, under the influence of a magnetic field, can continuously and reversibly transform into a low-flow, high-viscosity fluid within milliseconds, increasing the apparent viscosity by more than two orders of magnitude and acquiring properties similar to a solid. This effect is known as the magnetorheological effect.

[0020] Preferably, the variable stiffness quadruped robot foot structure based on magnetically controlled smart materials is characterized in that the working method of the variable stiffness foot structure includes: First, when the robot is walking normally or needs high rigidity support, the de-energized electromagnet (32) is de-energized so that its core remains magnetic. The magnetically controlled smart material (5) inside the first rubber shell (31) is in a high-viscosity semi-solid state under the magnetic field of the first permanent magnet (33), providing rigid support. At the same time, the electro-permanent magnet (42) is controlled to be in a magnetized state so that the magnetically controlled smart material (5) inside the second rubber shell (41) is in a high-viscosity semi-solid state under the magnetic field. Second, when the robot needs to be cushioned after jumping and landing, the de-energized electromagnet (32) is momentarily energized to cancel the magnetism of its core, so that the magnetically controlled smart material (5) inside the first rubber shell (31) loses the magnetic field and becomes liquid, thus achieving flexible cushioning; the electro-permanent magnet (42) is momentarily demagnetized, so that the magnetically controlled smart material (5) inside the second rubber shell (41) loses the magnetic field and becomes liquid. Third, when the robot climbs, especially when facing complex contact surfaces (such as rough rock walls, irregular steps, or inclined planes) that require both reliable foot adhesion and local compliance, the control method for the variable stiffness foot structure further includes: Based on the feedback information from the quadruped robot's accelerometer and the flexible sensor on the inner surface of its foot, the current climbing stage and contact surface characteristics are determined, and independent or coordinated differentiated control is implemented on the first variable stiffness component (3) and the second variable stiffness component (4): Foot structure entry and initial contact stage A: At the instant the foot structure is about to contact the climbing surface, the de-energized electromagnet (32) is momentarily energized, causing the magnetically controlled smart material (5) inside the first rubber shell (31) to temporarily become liquid. At the same time, the electro-permanent magnet (42) is magnetized, with the neodymium iron boron magnet and the AlNiCo magnet having the same magnetic pole direction, keeping the magnetically controlled smart material (5) inside the second rubber shell (41) semi-solid. In this state, the foot structure exhibits an asymmetrical stiffness characteristic of "one flexible and one rigid". The flexible part (first rubber shell 31) can first conform to the irregular surface, increasing the contact area and absorbing the initial contact impact through deformation; the rigid part (second rubber shell 41) provides initial support and positioning, preventing the foot structure from slipping as a whole. This combination helps the foot structure to "grip" the contact surface smoothly and with low impact.

[0021] Stable attachment and load-bearing stage B: When the foot structure is in full contact and needs to bear the main weight to provide propulsion, the de-energized electromagnet (32) is de-energized, causing its core to regain magnetism. The magnetically controlled smart material (5) inside the first rubber shell (31) quickly returns to a high-viscosity semi-solid state. At the same time, the electro-permanent magnet (42) is kept in a magnetized state. At this time, both variable stiffness units are in high stiffness mode, making the entire foot structure a rigid support platform, which can effectively convert joint torque into propulsion or support force for climbing, and prevent energy loss or instability caused by excessive deformation of the foot structure.

[0022] Terrain Adaptation and Fine-tuning Stage C: During climbing, if sensors detect local unevenness or slight slippage on the contact surface of a single foot structure, local stiffness fine-tuning can be performed. For example, the electro-permanent magnet (42) can be individually controlled to perform instantaneous demagnetization and remagnetization, causing the stiffness of the second rubber shell (41) and its internal magnetically controlled smart material (5) to change dynamically in a short time. This allows for local compliance to adapt to minor terrain undulations or release local stress, while most areas of the entire foot structure (such as the first rubber shell 31) remain rigid to maintain overall stability. This dynamic local adjustment capability enhances the adaptability and adhesion reliability of the foot structure to continuous irregular climbing surfaces.

[0023] The present invention, employing the above-described structure, possesses the following beneficial effects: This invention creatively utilizes the inherent characteristics of both a power-off electromagnet component and an electro-permanent magnet component connected in parallel. The power-off electromagnet component naturally provides a magnetic field when power is off and cancels the magnetic field when power is on, achieving a safe failure mode of "rigid when power is off, flexible when power is on." The electro-permanent magnet component only requires a pulse current to switch and maintain the magnetic state, consuming almost no holding energy and greatly reducing system power consumption. This hybrid magnetic circuit design balances response speed, safety, and energy efficiency.

[0024] This invention seals a magnetically controlled smart material within a rubber shell, achieving integration of a variable stiffness component with the foot structure. The rubber shell itself possesses a certain degree of elasticity and sealing, serving both as part of the magnetic circuit and allowing direct contact with the ground, providing initial flexibility and wear resistance. Under the influence of a magnetic field, the magnetically controlled smart material can rapidly switch between a liquid and a near-solid state, thereby macroscopically altering the overall stiffness and damping characteristics of the foot.

[0025] The dual-component design of this invention provides a flexible control strategy. The stiffness switching function of one or both components can be selectively activated depending on the magnitude of the impact energy. For example, under small impacts, only one component can be switched to achieve a balance between efficient buffering and energy recovery; under large impacts, both components can be switched simultaneously to provide maximum flexibility protection. This design enhances the foot's adaptability to different working conditions. Attached Figure Description

[0026] Figure 1 This is a split structure diagram of the foot structure of a variable stiffness quadruped robot based on magnetically controlled smart materials according to the present invention; Figure 2 This is a bottom structure diagram of the foot structure of a variable stiffness quadruped robot based on magnetically controlled smart materials according to the present invention; Figure 3 This is a cross-sectional view of the foot structure of a variable stiffness quadruped robot based on magnetically controlled smart materials according to the present invention. Figure 4 This is a magnetic field distribution diagram of the first variable stiffness component of the foot structure of a variable stiffness quadruped robot based on magnetically controlled smart materials according to the present invention. Figure 5 This is a magnetic field distribution diagram of the second variable stiffness component of the foot structure of a variable stiffness quadruped robot based on magnetically controlled smart materials according to the present invention. Figure 6 This is a schematic diagram of the climbing gait and foot-end coordinated control of a variable stiffness quadruped robot based on magnetically controlled smart materials according to the present invention. Figure 7 This is a diagram of the foot structure of a variable stiffness quadruped robot based on magnetically controlled smart materials according to the present invention.

[0027] Figure label: 11. Foot base shell; 12. Bolt fastener; 13. Screw; 21. Foot accelerometer; 22. Foot plantar flexibility sensor; 3. First variable stiffness assembly; 31. First rubber shell; 32. De-energized electromagnet; 33. First permanent magnet; 34. First coil; 4. Second variable stiffness assembly; 41. Second rubber shell; 42. Electro-permanent magnet; 43. Magnetic conductor; 44. Second coil; 45. Second permanent magnet; 5. Magnetic control smart material; 6. Lower leg Detailed Implementation The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following description will be provided in conjunction with the accompanying drawings of the embodiments of the present invention. Figures 1 to 6 The technical solutions of the present invention have been clearly and completely described. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0030] In the description of this invention, it should be understood that, in order to more clearly describe the technical content of this invention, different regions, material states, etc. are distinguished by color in order to more intuitively show different features and effects.

[0031] In the description of this invention, it should be understood that the terms "center", "directly in front", "periphery", "upper", "lower", etc., which indicate the direction or location, are limited to simplifying the description of this invention and are not specific locations or directions. The above terms are not intended to limit this invention.

[0032] This invention provides a variable stiffness quadruped robot foot structure based on magnetically controlled smart materials. Its core lies in the precise control of the state of the magnetically controlled smart materials through a hybrid magnetic circuit, thereby achieving rapid and low-power switching of foot stiffness.

[0033] like Figure 1 As shown, the variable stiffness foot structure mainly consists of a foot base 1, a foot sensor 2, a first variable stiffness component 3, and a second variable stiffness component 4. The foot base 1 is fixedly mounted on the lower leg of the quadruped robot with screws, serving as the structural carrier of the entire foot.

[0034] The first variable stiffness assembly 3 includes a first rubber shell 31, a de-energized electromagnet 32, a first permanent magnet 33, and a first coil 34. The first rubber shell 31 is hemispherical and is fixed to a mounting groove at the bottom of the foot base 1 by a threaded connection. Its internal cavity is filled with magnetically controlled smart material 5. The de-energized electromagnet 32 ​​is fixed to the foot base 1 by screws, and the lower end of its iron core extends to the bottom end of the first rubber shell 31. The first permanent magnet 33 (neodymium iron boron permanent magnet) is embedded and fixed to the end of the iron core. The first coil 34 is wound on the iron core of the de-energized electromagnet 32.

[0035] The second variable stiffness component 4 is arranged in parallel with the first component and includes a second rubber shell 41, an electro-permanent magnet 42, a magnetic conductor 43, a second coil 44, and a second permanent magnet 45. Its basic structure is similar to that of the first component. The electro-permanent magnet 42 (AlNiCo permanent magnet) is fixed inside the foot base 1, with its lower end close to the second rubber shell 41. The magnetic conductor 43 is sleeved around the electro-permanent magnet 42 to enhance and guide the magnetic field. The second coil 44 is wound around the electro-permanent magnet 42, and the second permanent magnet 45 (NdFeB permanent magnet) is fixed to the end of the AlNiCo core.

[0036] The foot base 1 has a wire outlet hole for the wires of the first coil 34 and the second coil 44 to be led out and connected to the robot's control system.

[0037] When the robot is in the support phase or requires high rigidity, the control system does not send current to the first coil 34. The core of the de-energized electromagnet 32 ​​remains magnetized under the action of the first permanent magnet 33, forming a strong magnetic field within the first rubber shell 31. This causes the internal magnetically controlled smart material 5 to become a high-viscosity, near-solid state, providing rigid support. Simultaneously, the control system applies a positive pulse current to the electro-permanent magnet 42 through the second coil 44, magnetizing it and forming a strong magnetic field within the second rubber shell 41, similarly causing the internal magnetically controlled smart material 5 to become a near-solid state.

[0038] When the robot detects an impending landing or the need for cushioning, the control system instantaneously applies a reverse current to the first coil 34. The magnetic field generated by this current precisely cancels the magnetic field of the first permanent magnet 33, demagnetizing the core of the de-energized electromagnet 32. The magnetic field within the first rubber shell 31 rapidly disappears, and the magnetically controlled smart material 5 instantly returns to a liquid state, becoming soft to absorb impact energy. Simultaneously, the control system applies a reverse pulse current to the second coil 44, demagnetizing the electro-permanent magnet 42. The magnetic field within the second rubber shell 41 then disappears, and the magnetically controlled smart material 5 becomes liquid again.

[0039] When the robot climbs, especially when facing complex contact surfaces (such as rough rock walls, irregular steps, or inclined planes) that require reliable adhesion and local compliance at the feet, the robot determines the current climbing stage and contact surface characteristics based on feedback information from the quadruped robot's acceleration sensor and the flexible sensor on the inner surface of the foot, and implements independent or coordinated differentiated control on the first variable stiffness component 3 and the second variable stiffness component 4.

[0040] In summary, this invention employs a variable stiffness quadruped robot foot structure based on magnetically controlled smart materials. Through a hybrid magnetic circuit design using de-energized electromagnets and electro-permanent magnets, it achieves rapid and low-power control of the state of the magnetically controlled smart materials. This enables the robot foot to adaptively change its stiffness in real time according to its motion state, effectively solving the problem of high impact on rigid feet.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A variable stiffness quadruped robot foot structure based on magnetically controlled smart materials, characterized in that, The variable stiffness foot structure includes a foot base (1), foot sensors (2), a first variable stiffness component (3), and a second variable stiffness component (4); the foot base (1) serves as the supporting part of the quadruped robot's foot structure; the foot sensors (2) include an acceleration sensor (21) and a flexible sensor (22); the first variable stiffness component (3) includes a first rubber shell (31), a de-energized electromagnet (32), and its magnetic circuit assembly; the second variable stiffness component (4) includes a second rubber shell (41), an electro-permanent magnet (42), and its magnetic circuit assembly; the magnetically controlled smart material (5) is a novel variable stiffness material filled inside the rubber shell; The bottom of the foot base (1) is connected to the first variable stiffness component (3) and the second variable stiffness component (4) by threads; the foot sensor (2) is installed inside the foot base (1) and connected to the mounting bracket by threads; there is one set of the second variable stiffness component (4), which is located at the center of the bottom of the foot base (1); there are three sets of the first variable stiffness component (3), which are arranged at intervals around the second variable stiffness component (4) in the circumferential direction, the first set is installed in front of the second variable stiffness component (4), and the second and third sets are arranged symmetrically on the left and right sides of the center line and at a 45° angle to the center line; the magnetically controlled smart material (5) is filled in the first variable stiffness component (3) and the second variable stiffness component (4). The interior of the variable stiffness component (4); the foot base (1) includes a base shell (11), bolt fasteners (12) and screws (13); the base shell (11) is connected to the outer quadruped robot leg (6) through the bolt fasteners (12) and to the variable stiffness component through the screws (13); the foot base (1) has a cable outlet hole and a variable stiffness component groove inside, and the cable outlet hole is connected to one side of the variable stiffness component groove; the inner cavity of the foot base (1) is connected to the cable outlet hole; the top of the base shell (11) has a slot, and the slot has a threaded hole inside; the first variable stiffness component (3) and the second variable stiffness component (4) are installed in the variable stiffness component groove.

2. The variable stiffness quadruped robot foot structure based on magnetically controlled smart materials according to claim 1, characterized in that, The foot sensor (2) includes an acceleration sensor (21) and a flexible sensor (22). The acceleration sensor (21) is rigidly connected to the main structure of the foot base (1) through a special mounting bracket. Its signal line is embedded in the foot structure through a sleeve and finally connected to the controller. The flexible sensor (22) is attached to the inner surface of the sole to form a tight attachment. Multiple flexible sensors are evenly distributed on the entire inner surface to collect pressure data in real time from multiple angles.

3. The variable stiffness quadruped robot foot structure based on magnetically controlled smart materials according to claim 1, characterized in that, The first variable stiffness component (3) consists of three groups, each group including a first rubber shell (31), a de-energized electromagnet (32) and a first magnetic circuit component; the first rubber shell (31) is a hemispherical elastic shell with the bottom forming the foot contact part, and its internal cavity is filled with magnetically controlled smart material (5); the first rubber shell (31) is located directly below the de-energized electromagnet (32) and the first magnetic circuit component, and is connected to the foot base (1) by threads; the de-energized electromagnet (32) is fixed to the bottom of the foot base (1) by screws; the first magnetic circuit component includes a first permanent magnet (33) and a first coil (34); the magnetic field of the first magnetic circuit component is formed by the cancellation of the electromagnetic field generated by the iron core after the first coil (34) is energized and the magnetic field of the first permanent magnet (33).

4. The variable stiffness quadruped robot foot structure based on magnetically controlled smart materials according to claim 1, characterized in that, The second variable stiffness component (4) consists of a second rubber shell (41), an electro-permanent magnet (42), and a second magnetic circuit component. The second rubber shell (41) is a hemispherical elastic shell with its bottom forming the foot contact part. Its internal cavity is filled with magnetically controlled smart material (5). The second rubber shell (41) is located directly below the electro-permanent magnet (42) and the second magnetic circuit component and is connected to the foot base (1) by threads. The electro-permanent magnet (42) is fixed to the bottom of the foot base (1). The second magnetic circuit component includes a magnetic conductor (43), a second permanent magnet (45) at the end of the electro-permanent magnet (42), and a second coil (44) wound on it. The magnetic field of the second magnetic circuit component is formed by the directional magnetic field generated by the electro-permanent magnet (42) after being pulse-excited by the second coil (44) and the magnetic field of the magnetic conductor (43) and the second permanent magnet (45).

5. The variable stiffness quadruped robot foot structure based on magnetically controlled smart materials according to claim 4, characterized in that, The de-energized electromagnet (32) is located directly above the first rubber shell (31) and inside the bottom of the foot base (1), with its core located at the center of the inner side and extending to the bottom of the first rubber shell (31); the first permanent magnet (33) is embedded in the end of the core of the de-energized electromagnet (32), and the first coil (34) is wound on the core of the de-energized electromagnet (32); the first magnetic circuit assembly is used to form a magnetic field in the first rubber shell (31) when the de-energized electromagnet (32) is discharged, so that the magnetically controlled smart material (5) therein is magnetized.

6. The variable stiffness quadruped robot foot structure based on magnetically controlled smart materials according to claim 5, characterized in that, The electro-permanent magnet (42) is located directly above the second rubber shell (41) and on the bottom inner side of the foot base (1); its iron core is located at the inner center and extends to the bottom of the second rubber shell (41); the magnetic conductor (43) is located around the iron core of the electro-permanent magnet (42); the second permanent magnet (45) is embedded in the end of the iron core of the electro-permanent magnet (42), and the second coil (44) is wound on the iron core of the electro-permanent magnet (42); the second magnetic circuit assembly is used to form an external magnetic field in the second rubber shell (41) after the electro-permanent magnet (42) is pulse-excited, so that the magnetically controlled smart material (5) therein is magnetized.

7. The variable stiffness quadruped robot foot structure based on magnetically controlled smart materials according to claim 1, characterized in that, The de-energized electromagnet (32) and the electro-permanent magnet (42) are both fixedly installed in the foot base (1) by bolt connection.

8. The variable stiffness quadruped robot foot structure based on magnetically controlled smart materials according to claim 1, characterized in that, The foot base (1) is fixedly installed inside the slot by a threaded connection with the outer quadruped robot leg; the foot base (1) is provided with a wire outlet hole for the first coil (34) and the second coil (44) to run.

9. The variable stiffness quadruped robot foot structure based on magnetically controlled smart materials according to claim 1, characterized in that, The magnetically controlled smart material (5) is a new type of smart material. Its main components include carbonyl iron powder, corn starch, water-based silicone oil and silicon dioxide. It has significant magnetorheological effect and variable stiffness function.

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