Variable stiffness biomimetic robotic foot based on low melting point alloy

Abstract

The application discloses a variable stiffness bionic robot foot based on a low-melting-point alloy and belongs to the technical field of robots. The bottom of the bionic robot calf is rotatably arranged at the middle part of the bionic robot foot bottom through a first connecting shaft, two connecting columns are rotatably arranged at the two sides of the middle part of the bionic robot calf through a second connecting shaft, and two variable elastic components are rotatably arranged at the rear end of the bionic robot foot bottom through a third connecting shaft. The variable elastic component comprises a base, a low-melting-point alloy variable stiffness layer, an elastic piece, a top plate and at least two guide columns. The application can effectively realize the simulation work of the human ankle joint, and provides good shock absorption and support for the walking and movement of the robot. The elasticity coefficient of the variable elastic component can be adjusted in real time by controlling the temperature of the low-melting-point alloy variable stiffness layer, so that the demand under different working conditions can be met.

Description

Technical Field

[0001] This invention relates to the field of robotics, and more particularly to a variable stiffness biomimetic robot foot based on a low-melting-point alloy. Background Technology

[0002] In the field of robotics, biomimetic robots have always been a popular research area, especially robots that mimic human movements, which indicate the future direction of robotics technology.

[0003] To better enable robots to simulate human walking movements, researchers have designed many innovative bionic ankle structures for robots to achieve better shock absorption and support. Gradually, researchers have found that bionic ankles with fixed stiffness are not flexible and have poor adaptability when facing different walking environments and load working modes. Therefore, many ankle structures with variable stiffness have emerged.

[0004] Previous variable stiffness bionic robot ankles typically achieved their variable stiffness function through complex mechanical structures, often accompanied by high costs and high failure rates. Therefore, the field needs a new design that is simple in structure and stable in performance. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned shortcomings of the prior art by proposing a variable stiffness biomimetic robot foot based on a low-melting-point alloy.

[0006] The present invention discloses a variable stiffness bionic robot foot based on a low melting point alloy, comprising a bionic robot foot sole, a bionic robot lower leg, and two ankle joint connection mechanisms; the ankle joint connection mechanism includes a connecting post and a variable elastic component disposed at one end of the connecting post; the bottom of the bionic robot lower leg is rotatably disposed in the middle of the bionic robot foot sole via a first connecting shaft, the two connecting posts are rotatably disposed on both sides of the middle of the bionic robot lower leg via a second connecting shaft, and the two variable elastic components are rotatably disposed at the rear end of the bionic robot foot sole via a third connecting shaft;

[0007] The variable elastic component includes a base, a low-melting-point alloy variable stiffness layer, an elastic element, a top plate, and at least two guide posts. The low-melting-point alloy variable stiffness layer is fixed on the base, and at least two guide posts are vertically spaced on the base. The top plate is provided with at least two guide holes, and the top plate is slidably mounted on the guide posts through the guide holes. One side of the elastic element is connected to the upper surface of the low-melting-point alloy variable stiffness layer, and the other side is connected to the top plate.

[0008] Furthermore, the low-melting-point alloy variable stiffness layer includes, from bottom to top, a silicone bottom layer, a low-melting-point alloy block, a silicone interlayer, an electric heating wire, and a silicone top layer, with external power supplies connected to both ends of the electric heating wire.

[0009] Furthermore, the electric heating wire is bent into a vortex shape, with both ends extended and exposed outside the low-melting-point alloy variable stiffness layer to be connected to the power source.

[0010] Furthermore, each of the guide holes is provided with a sliding bearing, and the guide post passes through the sliding bearing.

[0011] Furthermore, the elastic element is a cylindrical helical compression spring.

[0012] Furthermore, the lower surface of the top plate is provided with a cylindrical protrusion with a diameter equal to the inner diameter of the cylindrical helical compression spring, and the cylindrical helical compression spring is sleeved on the cylindrical protrusion.

[0013] Furthermore, the base is a cylinder with a central opening; the base is provided with a groove, and the variable elastic component is disposed in the groove.

[0014] Furthermore, the outer wall of the groove is provided with openings for the two ends of the electric heating wire to extend out.

[0015] Furthermore, the base is provided with at least two mounting holes, and the guide post is disposed in the mounting holes.

[0016] Furthermore, there are three mounting holes, and the line connecting the three mounting holes forms an equilateral triangle.

[0017] In this invention, when the robot takes a step, its lower leg can rotate back and forth relative to the sole of its foot around a first connecting axis, simulating the state of the foot and lower leg when a human takes a step. Simultaneously, the ankle joint connection mechanism and a variable elastic component provide cushioning and support when the robot's foot touches and leaves the ground. By changing the elastic coefficient of the variable elastic component, its cushioning effect and support strength can be altered, thereby changing the stiffness of the robot's ankle joint. This ability to change stiffness allows the robot to adapt to different walking environments and working modes.

[0018] The variable stiffness principle of the variable elastic component is as follows: A low-melting-point alloy block is melted by applying direct current to the heating wire, reducing the stiffness of the variable stiffness layer. After the power is turned off, the low-melting-point alloy block solidifies naturally, restoring the stiffness of the variable stiffness layer. When no power is applied, the low-melting-point alloy variable stiffness layer is in a high-stiffness state. Applying downward pressure to the top plate of the spring compresses the cylindrical helical compression spring, generating elastic force, and the shape of the low-melting-point alloy variable stiffness layer remains unchanged. At this time, the overall elastic coefficient of the variable elastic coefficient spring is equal to that of the cylindrical helical compression spring. After heating, the low-melting-point alloy variable stiffness layer transitions to a low-stiffness state. Applying downward pressure to the top plate compresses the cylindrical helical compression spring, and the center of the low-melting-point alloy variable stiffness layer sinks. This causes the displacement distance of the top plate of the variable elastic coefficient spring to increase under the same pressure. At this point, the overall elastic coefficient of the variable elastic coefficient spring is lower than that of the cylindrical helical compression spring, thus achieving a change in the elastic coefficient. This variable stiffness method does not change the overall structure and working length of the spring, making it easy to model and control robot joints.

[0019] The variable elastic component of this invention achieves controllable switching between solid and liquid states by controlling the temperature of a low-melting-point alloy, thereby enabling dynamic adjustment of the elastic coefficient of the variable elastic component. Simultaneously, the variable elastic coefficient spring based on the low-melting-point alloy exhibits excellent variable stiffness performance and stable properties. Its application in the ankle joint of biomimetic robots can effectively reduce manufacturing and maintenance costs and improve operational stability.

[0020] The beneficial effects of the technical solution provided by the embodiments of the present invention are as follows: The variable stiffness bionic robot foot based on a low-melting-point alloy of the present invention can effectively mimic the human ankle and foot joint, providing good shock absorption and support for robot walking and movement. The core component is a variable elastic component based on a low-melting-point alloy. By controlling the temperature of the variable stiffness layer of the low-melting-point alloy, the elastic coefficient of the variable elastic component can be adjusted in real time to meet the needs under different working conditions. This novel variable elastic coefficient principle changes the spring elastic coefficient without changing the spring's structure and working length. Furthermore, the variable stiffness process does not rely on a motor, further improving the structural stability. Simultaneously, the structure is simple, requiring no complex parts and assembly processes, making it easy to manufacture and maintain. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of a variable stiffness biomimetic robot foot based on a low melting point alloy according to the present invention.

[0022] Figure 2 This is a schematic diagram of the working state of a variable stiffness biomimetic robot foot based on a low melting point alloy according to the present invention.

[0023] Figure 3 This is a schematic diagram of the overall structure of the variable elastic component;

[0024] Figure 4 This is a schematic diagram showing the structural details of the variable elastic component;

[0025] Figure 5 This is a schematic diagram of a variable elastic component under compression in a state of high elasticity coefficient.

[0026] Figure 6 This is a schematic diagram of a variable elastic component under compression at a low elastic coefficient.

[0027] Figure 7 It is the pressure-compression curve of the variable elastic component in two states.

[0028] 1. Bionic robot foot sole; 2. Bionic robot lower leg; 3. Ankle joint connection mechanism; 4. Connecting column; 5. Variable elastic component; 51. Base; 511. Groove; 512. Opening; 513. Mounting hole; 52. Low melting point alloy variable stiffness layer; 521. Silicone bottom layer; 522. Low melting point alloy block; 523. Silicone interlayer; 524. Electric heating wire; 525. Silicone top layer; 53. Elastic element; 54. Top plate; 541. Guide hole; 542. Sliding bearing; 55. Guide column; 6. First connecting shaft; 7. Second connecting shaft; 8. Third connecting shaft. Detailed Implementation

[0029] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0030] Example 1

[0031] like Figure 1 As shown, the present invention discloses a variable stiffness bionic robot foot based on a low melting point alloy, comprising a bionic robot foot sole 1, a bionic robot lower leg 2, and two ankle joint connection mechanisms 3; the ankle joint connection mechanism 3 includes a connecting post 4 and a variable elastic component 5 disposed at one end of the connecting post 4; the bottom of the bionic robot lower leg 2 is rotatably disposed in the middle of the bionic robot foot sole 1 via a first connecting shaft 6, the two connecting posts 4 are rotatably disposed on both sides of the middle of the bionic robot lower leg 2 via a second connecting shaft 7, and the two variable elastic components 5 are rotatably disposed at the rear end of the bionic robot foot sole 1 via a third connecting shaft 8;

[0032] like Figure 3-4As shown, the variable elastic component 5 includes a base 51, a low-melting-point alloy variable stiffness layer 52, an elastic element 53, a top plate 54, and at least two guide posts 55. The low-melting-point alloy variable stiffness layer 52 is fixed on the base 51, and at least two guide posts 55 are vertically spaced on the base 51. The top plate 54 is provided with at least two guide holes 541, and the top plate 54 is slidably mounted on the guide posts 55 through the guide holes 541. One side of the elastic element 53 is connected to the upper surface of the low-melting-point alloy variable stiffness layer 52, and the other side is connected to the top plate 54.

[0033] like Figure 2 As shown, when the robot takes a step, the bionic robot's lower leg 2 can rotate back and forth around the first connecting axis 6 relative to the bionic robot's foot 1, simulating the state of the foot and lower leg when a human takes a step. Simultaneously, the ankle joint connecting mechanism 3 and the variable elastic component 5 provide cushioning and support when the bionic robot's foot 1 touches the ground and leaves the ground. By changing the elastic coefficient of the variable elastic component 5, its cushioning effect and support force can be altered, thereby changing the stiffness of the bionic robot's ankle joint. This ability to change stiffness allows the robot to adapt to different walking environments and working modes.

[0034] This invention discloses a variable stiffness bionic robot foot based on a low-melting-point alloy, which can effectively mimic the human ankle and foot joint, providing good cushioning and support for robot walking and movement. The core component is a variable elastic component 5 based on a low-melting-point alloy. By controlling the temperature of the low-melting-point alloy variable stiffness layer 52, the elastic coefficient of the variable elastic component 5 can be adjusted in real time to meet the needs of different working conditions. This novel variable elastic coefficient principle changes the spring's elastic coefficient without altering its structure or effective length. Furthermore, the variable stiffness process is independent of a motor, further improving structural stability. Simultaneously, the structure is simple, requiring no complex parts or assembly processes, making it easy to manufacture and maintain.

[0035] like Figure 3-4 As shown, the low-melting-point alloy variable stiffness layer 52 can have various structures. In this embodiment, the low-melting-point alloy variable stiffness layer 52 may include, from bottom to top, a silicone base 51, a low-melting-point alloy block 522, a silicone interlayer 523, an electric heating wire 524, and a silicone top layer 525. The electric heating wire 524 is externally connected to a power source at both ends. The electric heating wire 524 is bent into a spiral shape, with both ends extending outwards and exposed outside the low-melting-point alloy variable stiffness layer to be connected to the power source.

[0036] The elastic element 53 can be a cylindrical helical compression spring made of spring steel, with its two ends connected to the upper surface of the low-melting-point alloy variable stiffness layer 52 and the lower surface of the top plate 54, respectively. The lower surface of the top plate 54 has a cylindrical protrusion with a diameter equal to the inner diameter of the cylindrical helical compression spring. The cylindrical helical compression spring is sleeved on the cylindrical protrusion, thus connecting the cylindrical helical compression spring to the lower surface of the top plate 54.

[0037] like Figure 4-7 As shown, the low-melting-point alloy block 522 is melted by heating the electric heating wire 524 with direct current, thereby reducing the stiffness of the low-melting-point alloy variable stiffness layer 52; after the power is turned off, the low-melting-point alloy block 522 can be solidified by natural heat dissipation, thereby restoring the stiffness of the low-melting-point alloy variable stiffness layer 52. When no power is applied, the low-melting-point alloy variable stiffness layer 52 is in a high-stiffness state. At this time, when downward pressure is applied to the top plate 54, the cylindrical helical compression spring is compressed, generating elastic force. The shape of the low-melting-point alloy variable stiffness layer 52 remains unchanged. At this time, the overall elastic coefficient of the variable elastic coefficient spring is equal to the elastic coefficient of the cylindrical helical compression spring. After being heated by electricity, the low-melting-point alloy variable stiffness layer 52 changes to a low-stiffness state. When downward pressure is applied to the top plate 54, the cylindrical helical compression spring is compressed, and the center of the low-melting-point alloy variable stiffness layer 52 sinks. This causes the displacement distance of the top plate 54 to increase when the variable elastic coefficient spring is subjected to the same pressure. At this time, the overall elastic coefficient of the variable elastic coefficient spring is lower than the elastic coefficient of the cylindrical helical compression spring, thus realizing the change of elastic coefficient.

[0038] Alternatively, by replacing the low-melting-point alloy block 522 in the low-melting-point alloy variable stiffness layer 52 with other types of low-melting-point alloys with different melting points, the elastic coefficient can be automatically changed when the temperature of the operating environment reaches the melting point of the low-melting-point alloy.

[0039] Example 2

[0040] like Figure 3 As shown, the guide hole 541 can also be provided with sliding bearings 542, and the guide post 55 passes through the sliding bearing 542. The guide post 55 can be a cylindrical rod made of stainless steel; the top plate 54 slides on the guide post 55 through the sliding bearing 542.

[0041] The base 51 is a cylinder with a central hole; the base 51 has a groove 511, the variable elastic component 5 is disposed in the groove 511, and the outer wall of the groove 511 has openings 512 extending from both ends of the power supply heating wire 524.

[0042] The base 51 may have at least two mounting holes 513. In this embodiment, there are three mounting holes 513, and three guide posts 55 are respectively set in the mounting holes 513. The line connecting the three mounting holes 513 forms an equilateral triangle.

[0043] For any points not covered above, existing technologies shall apply.

[0044] Although specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the direction of the invention or exceeding the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. A variable stiffness biomimetic robot foot based on a low-melting-point alloy, characterized in that: It includes a bionic robot foot (1), a bionic robot lower leg (2), and two ankle joint connecting mechanisms (3); the ankle joint connecting mechanism (3) includes a connecting post (4) and a variable elastic component (5) disposed at one end of the connecting post (4); the bottom of the bionic robot lower leg (2) is rotatably disposed in the middle of the bionic robot foot (1) through a first connecting shaft (6), the two connecting posts (4) are rotatably disposed on both sides of the middle of the bionic robot lower leg (2) through a second connecting shaft (7), and the two variable elastic components (5) are rotatably disposed at the rear end of the bionic robot foot (1) through a third connecting shaft (8); The variable elastic component (5) includes a base (51), a low-melting-point alloy variable stiffness layer (52), an elastic element (53), a top plate (54), and at least two guide posts (55). The low-melting-point alloy variable stiffness layer (52) is fixed on the base (51), and at least two guide posts (55) are vertically spaced on the base (51). The top plate (54) is provided with at least two guide holes (541), and the top plate (54) is slidably disposed on the guide posts (55) through the guide holes (541). One side of the elastic element (53) is connected to the upper surface of the low-melting-point alloy variable stiffness layer (52), and the other side is connected to the top plate (54).

2. The variable stiffness biomimetic robot foot based on a low-melting-point alloy as described in claim 1, characterized in that: The low-melting-point alloy variable stiffness layer (52) includes, from bottom to top, a silicone bottom layer (521), a low-melting-point alloy block (522), a silicone interlayer (523), an electric heating wire (524), and a silicone top layer (525), wherein the electric heating wire (524) is connected to an external power source at both ends.

3. The variable stiffness biomimetic robot foot based on a low-melting-point alloy as described in claim 2, characterized in that: The electric heating wire (524) is bent into a vortex shape, with both ends extended and exposed outside the low-melting-point alloy variable stiffness layer (52) to be connected to the power source.

4. The variable stiffness biomimetic robot foot based on a low-melting-point alloy as described in claim 1, characterized in that: Each of the guide holes (541) is provided with a sliding bearing (542), and the guide post (55) passes through the sliding bearing (542).

5. The variable stiffness biomimetic robot foot based on a low-melting-point alloy as described in claim 1, characterized in that: The elastic element (53) is a cylindrical helical compression spring.

6. The variable stiffness biomimetic robot foot based on a low-melting-point alloy as described in claim 1, characterized in that: The lower surface of the top plate (54) is provided with a cylindrical protrusion with a diameter equal to the inner diameter of the cylindrical helical compression spring, and the cylindrical helical compression spring is sleeved on the cylindrical protrusion.

7. A variable stiffness biomimetic robot foot based on a low-melting-point alloy as described in claim 2, characterized in that: The base (51) is a cylinder with a central opening; the base (51) is provided with a groove (511), and the variable elastic component (5) is disposed in the groove (511).

8. A variable stiffness biomimetic robot foot based on a low-melting-point alloy as described in claim 7, characterized in that: The outer wall of the groove (511) is provided with openings (512) for the two ends of the electric heating wire (524) to extend out.

9. A variable stiffness biomimetic robot foot based on a low-melting-point alloy as described in claim 8, characterized in that: The base (51) is provided with at least two mounting holes (513), and the guide post (55) is disposed in the mounting holes (513).

10. A variable stiffness biomimetic robot foot based on a low-melting-point alloy as described in claim 9, characterized in that: The number of mounting holes (513) is three, and the line connecting the three mounting holes (513) forms an equilateral triangle.

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