Variable stiffness joint driver based on magnetorheological elastomer

Abstract

The utility model relates to the technical field of variable stiffness drivers, and discloses a variable stiffness joint driver based on a magnetorheological elastomer, which comprises a connecting frame used for being connected to a knee joint of a biped robot; the variable stiffness mechanism comprises an electric push rod and a spring-like assembly, the electric push rod is connected to the bottom of the spring-like assembly, the spring-like assembly comprises a magnetorheological fluid opening bottle and a magnetorheological elastic body arranged in the magnetorheological fluid opening bottle, the magnetorheological fluid opening bottle is arranged at the bottom of the connecting frame, and the magnetorheological elastic body is arranged in the magnetorheological fluid opening bottle. The output end of the electric push rod extends out of the first through hole of the magnetorheological elastic body; the excitation assembly comprises a coil framework and an electromagnetic coil wound outside the coil framework, and the coil framework is arranged at the lower end of the magnetorheological fluid opening bottle; and the pressure sensor is arranged between the electric push rod and the magnetorheological fluid open bottle.

Description

Technical Field

[0001] This utility model relates to the field of variable stiffness actuator technology, and in particular to a variable stiffness joint actuator based on a magnetorheological elastomer. Background Technology

[0002] Traditional robots still struggle to maintain stable gait and efficient movement when navigating complex and changing environments. This is because the structure and material properties of the bipedal joints in traditional robots are relatively fixed, making it difficult to adapt to variations in environmental and task requirements. Using variable stiffness actuators typically requires complex mechanical structures to adjust stiffness, such as multi-layered blocking, rotating beam components, or spring plates. This complexity in achieving variable stiffness adjustment through multi-layered blocking, rotating beam components, or spring plates not only increases the difficulty of design and manufacturing but may also lead to higher failure rates and maintenance costs. Utility Model Content

[0003] The technical problem to be solved by this invention is to overcome the shortcomings of the prior art and provide a variable stiffness joint actuator based on magnetorheological elastomer, which improves the flexibility and adaptability of bipedal robots.

[0004] The technical solution of this utility model is as follows: a variable stiffness joint actuator based on a magnetorheological elastomer, comprising a connecting frame for connection to the knee joint of a bipedal robot; a variable stiffness mechanism comprising an electric push rod and a spring-like assembly, the electric push rod being connected to the bottom of the spring-like assembly, the spring-like assembly comprising a magnetorheological fluid open bottle and a magnetorheological elastomer disposed within the magnetorheological fluid open bottle, the magnetorheological fluid open bottle being disposed at the bottom of the connecting frame, and the output end of the electric push rod extending out of the first through hole of the magnetorheological elastomer; an excitation assembly comprising a coil frame and an electromagnetic coil wound around the outside of the coil frame, the coil frame being sleeved on the lower end of the magnetorheological fluid open bottle; and a pressure sensor disposed between the electric push rod and the magnetorheological fluid open bottle, the pressure sensor being electrically connected to the excitation assembly, for measuring the pressure generated by the magnetorheological elastomer under compression, and calculating the required current of the magnetorheological elastomer based on the detected pressure.

[0005] As can be seen from the above scheme, the pressure sensor is used to detect the actual force, and the variable stiffness mechanism is used to change the stiffness. On the one hand, the excitation component generates a magnetic field when the electromagnetic coil is energized, causing the magnetorheological elastomer to undergo a magnetorheological effect, thereby increasing its stiffness along the magnetic field direction. On the other hand, the connecting frame is pushed by the electric push rod, and the force on the connecting frame causes the magnetorheological elastomer to be pre-tightened to different degrees, thereby changing the compression of the spring-like component and thus changing the joint stiffness. This invention uses the pressure sensor to detect the actual force and calculates the current required by the external electromagnetic coil of the magnetorheological elastomer based on the pressure magnitude. This invention can more accurately reflect the actual mechanical requirements, thereby achieving more precise current regulation and improving the control accuracy and adaptability of the device.

[0006] A support plate is provided between the electric push rod and the pressure sensor.

[0007] The magnetorheological elastomer is a fluid-like magnetorheological elastomer.

[0008] The connecting frame includes a base plate and a first side plate and a second side plate disposed opposite to each other on the base plate, with corresponding connecting holes on the first side plate and the second side plate. Therefore, the connecting frame is used for mounting on a bipedal robot.

[0009] The pressure sensor is sleeved on the bottom of the open bottle containing the magnetorheological fluid. Several fixing holes are arranged around the outer wall of the pressure sensor, and fixing pins are inserted into these holes. The end face of the fixing pins contacts the open bottle containing the magnetorheological fluid. The output shaft of the electric push rod passes through the pressure sensor and connects to the magnetorheological elastic body. Therefore, the pressure sensor is fixed to the spring-like assembly via the fixing pins.

[0010] The variable stiffness mechanism is fitted with a mounting housing on its outer side. The mounting housing is provided with limit holes, and the connecting frame is provided with fasteners corresponding to the limit holes. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the structure of this utility model;

[0012] Figure 2 This is a partial structural schematic diagram of the present invention;

[0013] Figure 3 This is another structural schematic diagram of the present invention;

[0014] Figure 4 This is an exploded view of this utility model. Detailed Implementation

[0015] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention.

[0016] like Figures 1 to 4 As shown, this utility model is a variable stiffness joint actuator based on magnetorheological elastomer, including a connecting frame 1 for connecting to the knee joint of a bipedal robot.

[0017] A variable stiffness mechanism includes an electric push rod 2 and a spring-like assembly. The electric push rod 2 is connected to the bottom of the spring-like assembly. The spring-like assembly includes a magnetorheological fluid open bottle 3 and a magnetorheological elastic body 4 disposed inside the magnetorheological fluid open bottle 3. The magnetorheological elastic body 4 is a fluid-like magnetorheological elastic body. The magnetorheological fluid open bottle 3 is disposed at the bottom of the connecting frame 1. The output end of the electric push rod 2 extends out of the first through hole of the magnetorheological elastic body 4 and is connected to the connecting frame 1.

[0018] The excitation assembly includes a coil frame 5 and an electromagnetic coil 6 wound around the outside of the coil frame 5, wherein the coil frame 5 is sleeved on the lower end of the magnetorheological fluid open bottle 3.

[0019] Pressure sensor 7 is disposed between the electric push rod 2 and the magnetorheological fluid open bottle 3. The pressure sensor 7 is electrically connected to the excitation assembly and is used to measure the pressure generated by the magnetorheological elastomer 4 being squeezed. The required current of the magnetorheological elastomer 4 is calculated based on the detected pressure. The current supplied to the electromagnetic coil 6 is adjusted by adjusting the required current to change the magnetic field strength and adjust the stiffness of the actuator joint.

[0020] A support plate 8 is provided between the electric push rod 2 and the pressure sensor 7.

[0021] The connecting frame 1 includes a base plate 11 and a first side plate 12 and a second side plate 13 arranged opposite to each other on the base plate 11. The first side plate 12 and the second side plate 13 are respectively provided with connecting holes 10.

[0022] The pressure sensor 7 is sleeved on the bottom of the magnetorheological fluid open bottle 3. Several fixing holes 71 are arranged around the outer wall of the pressure sensor 7. Fixing pins 8 are inserted into the fixing holes 71. The end face of the fixing pins 8 contacts the magnetorheological fluid open bottle 3. The output shaft of the electric push rod 2 passes through the pressure sensor 7 and is connected to the magnetorheological elastic body 4.

[0023] The variable stiffness mechanism is fitted with a mounting housing 9 on its outer side. The mounting housing 9 is provided with a limiting hole 91. The connecting frame 1 is provided with a fastener 15 corresponding to the limiting hole 91.

[0024] The fluid-like magnetorheological elastomer 4 is a smart material made by mixing and solidifying micron-sized carbonyl iron powder as ferromagnetic particles. The ferromagnetic particles in the magnetorheological elastomer form an ordered chain-like or columnar structure. Under the influence of a magnetic field, the material undergoes a magnetorheological effect, increasing its stiffness along the magnetic field direction. When the magnetic field is removed, the material's stiffness properties return to their state without a magnetic field. The magnetorheological elastomer has the advantages of fast response and good reversibility.

[0025] The shear modulus of the magnetorheological elastic body is ,in, It is the initial shear modulus without an external magnetic field; It is the increase in shear modulus caused by the applied magnetic field.

[0026] Shear modulus increment With the strength of the applied magnetic field The relationship can be represented as ,in, It is a material constant, which is related to the volume fraction of magnetic particles, particle size, and matrix properties; It is an exponential constant, usually between 1 and 2.

[0027] Magnetization of magnetic particles With the strength of the applied magnetic field The relationship can be represented as: ,in is the magnetic susceptibility, which is related to the properties and volume fraction of the magnetic particles.

[0028] Joint stiffness Defined as joint torque With joint angle changes The ratio: So, joint stiffness adjustment is achieved by elastic elements. ,in For the stiffness of the elastic element, The stiffness of the actuator is adjusted by regulating the stiffness of the elastic element. It can achieve dynamic adjustment of joint stiffness.

[0029] As can be seen from the formula for joint stiffness, the compression amount can be changed through a preloaded spring mechanism. Change the current flowing through electromagnetic coil 6 Size affects actuator stiffness Two methods are used to achieve stiffness variation. The variable stiffness actuator based on a magnetorheological elastic body can achieve this by changing the current flowing through the electromagnetic coil 6. The size of the magnetorheological elastomer (MEE) changes the magnetic field strength generated by the electromagnetic coil 6, affecting the stiffness properties of the MEE and thus causing a change in the stiffness of the actuator joint. On the other hand, the force on the connecting frame 1 causes the fluid-like MEE 4 to be pre-tightened to varying degrees, thereby changing the amount of compression. This causes a change in the joint stiffness of the actuator.

[0030] The beneficial effects of this invention are as follows: 1. Due to the variable stiffness of magnetorheological elastomers (MLEs), using MLEs instead of springs in variable stiffness actuators can further expand the range of stiffness variation while retaining the advantages and characteristics of the original variable stiffness actuators, thus meeting the stiffness requirements of more tasks. 2. Due to the millisecond-level stiffness response speed of MLEs, the variable stiffness actuator based on MLEs in this invention has a faster stiffness response speed and can be applied to tasks requiring high-frequency stiffness changes. 3. Compared with traditional actuators that only use pre-tensioned springs to achieve variable stiffness, the introduction of MLEs in this invention expands the methods of variable stiffness, allowing for different stiffness strategies to be adopted when facing different task requirements, reducing energy loss, improving energy efficiency, and reducing the requirement for the maximum output force of the stiffness motor. 4. This invention uses the method of changing the stiffness of the magnetorheological fluid to achieve the change of the equilibrium position, which improves the driving speed compared with the traditional method of using a push rod motor, and can be applied to more task scenarios.

[0031] Finally, it should be emphasized that the above description is not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A variable stiffness joint actuator based on a magnetorheological elastomer, characterized in that, include: A connecting frame (1) is used to connect to the knee joint of the bipedal robot; The variable stiffness mechanism includes an electric push rod (2) and a spring-like assembly. The electric push rod (2) is connected to the bottom of the spring-like assembly. The spring-like assembly includes a magnetorheological fluid open bottle (3) and a magnetorheological elastic body (4) disposed in the magnetorheological fluid open bottle (3). The magnetorheological fluid open bottle (3) is disposed at the bottom of the connecting frame (1). The output end of the electric push rod (2) extends out of the first through hole of the magnetorheological elastic body (4). The excitation assembly includes a coil frame (5) and an electromagnetic coil (6) wound around the outside of the coil frame (5), wherein the coil frame (5) is fitted around the lower end of the magnetorheological fluid open bottle (3). Pressure sensor (7) is disposed between the electric push rod (2) and the magnetorheological fluid open bottle (3). The pressure sensor (7) is electrically connected to the excitation assembly and is used to measure the pressure generated by the magnetorheological elastomer (4) under compression. The required current of the magnetorheological elastomer (4) is calculated based on the detected pressure.

2. The variable stiffness joint actuator based on a magnetorheological elastomer according to claim 1, characterized in that: A support plate (21) is provided between the electric push rod (2) and the pressure sensor (7).

3. The variable stiffness joint actuator based on a magnetorheological elastomer according to claim 1, characterized in that: The magnetorheological elastomer (4) is a fluid-like magnetorheological elastomer.

4. The variable stiffness joint actuator based on a magnetorheological elastomer according to claim 1, characterized in that: The connecting frame (1) includes a base plate (11) and a first side plate (12) and a second side plate (13) arranged opposite to each other on the base plate (11), and the first side plate (12) and the second side plate (13) are respectively provided with connecting holes (10).

5. The variable stiffness joint actuator based on a magnetorheological elastomer according to claim 1, characterized in that: The pressure sensor (7) is sleeved on the bottom of the magnetorheological fluid open bottle (3). Several fixing holes (71) are arranged around the outer wall of the pressure sensor (7). Fixing pins (8) are inserted into the fixing holes (71). The end face of the fixing pins (8) contacts the magnetorheological fluid open bottle (3). The output shaft of the electric push rod (2) passes through the pressure sensor (7) and is connected to the magnetorheological elastic body (4).

6. The variable stiffness joint actuator based on a magnetorheological elastomer according to claim 1, characterized in that: The variable stiffness mechanism is fitted with a mounting housing (9) on the outside. The mounting housing (9) is provided with a limiting hole (91). The connecting frame (1) is provided with a fastener (15) corresponding to the limiting hole (91).

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