Magnetorheological planetary speed reducer with variable stiffness and variable damping characteristics

Abstract

The application discloses a magnetorheological planetary reducer with variable stiffness and variable damping characteristics, which comprises a variable stiffness magnetorheological bearing, a variable damping magnetorheological bearing, a fixed iron plate, an upper cover plate, a variable stiffness coil, a coil framework, a planetary column, a variable damping coil, a spring cover plate, a gear ring, a planetary gear, a sun gear, a spring, an input shaft, an output shaft, an isolation ring and the like, wherein the planetary gear, the planetary column, the variable damping magnetorheological bearing and the variable damping coil form a variable damping structure; and the output shaft, the upper cover plate, the spring cover plate, the variable stiffness magnetorheological bearing, the variable stiffness coil, the isolation ring and the spring form a variable stiffness structure. The variable damping and variable stiffness characteristics are introduced into the planetary reducer, so that the output torque can be controlled in real time, the structure is simple, the stability is good, the system cost is low, and the complexity of the system is reduced. The application is applied to mechanical arm positioning control, reduces overshoot and oscillation time in the positioning process, improves positioning precision and stability, and has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the technical field of achieving precise positioning of robotic arms by reducing overshoot and shortening oscillation time, and specifically to a magnetorheological planetary reducer with variable stiffness and variable damping characteristics. Background Technology

[0002] Robotic arms are typically programmable and function similarly to human arms. They offer advantages such as rapid response, high reliability, and accuracy, improving work efficiency and productivity while helping workers avoid hazards and potential injuries. Therefore, robotic arms are widely used on industrial production lines to perform tasks such as equipment assembly, material handling, picking, welding, and sorting.

[0003] Positioning control performance is crucial for robotic arms because it impacts manufacturing accuracy. When a robotic arm is commanded to move to a desired position, it typically overshoots after passing that position; it then oscillates at the desired position until it eventually stabilizes. Large overshoots and long oscillation times are two common problems that negatively affect the accuracy and efficiency of robotic arms during this process. Furthermore, robotic arms can be subjected to external disturbances, such as unexpected forces or torques. These disturbances can lead to reduced accuracy and stability, and create safety hazards, such as collisions with nearby objects or individuals. Advanced control algorithms can effectively improve the positioning and anti-interference performance of robotic arms; however, this improvement is still limited by the capabilities of the motors driving the robotic arm. When the robotic arm experiences overshoot or disturbance, the controller commands the motors to output maximum torque in the direction of movement to counteract the overshoot or disturbance and pull the robotic arm back to the desired position. However, when the robotic arm is under heavy load or overload, the maximum torque of the motors is often limited. Therefore, the method of integrating additional torque provided by dampers into the robotic arm system has been successfully applied. However, while dampers can improve the positioning performance of robotic arms, their bulky structure significantly increases the complexity and cost of the drive system, which is undesirable in practical applications.

[0004] The drive components of a robotic arm consist of a motor and a planetary gearbox. Since the output torque of the motor is limited, a planetary gearbox is often used to amplify it; therefore, the planetary gearbox is indispensable in the movement of the robotic arm. Thus, the purpose of this work is to develop a gearbox with the ability to modify damping and stiffness, enabling the robotic arm system to achieve better positioning control performance without the need for an additional damper. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention discloses a magnetorheological planetary reducer with variable stiffness and variable damping characteristics. By introducing a variable-damping magnetorheological bearing, the reducer acquires variable damping capability. The variable damping capability of the magnetorheological bearing can be controlled by adjusting the input current, thereby controlling the output torque of the reducer. This makes the entire system more stable when the operating state changes and avoids the drawback of traditional control algorithms that cannot amplify the motor output torque. Simultaneously, this invention introduces variable stiffness characteristics. By controlling the input current, the damping of the magnetorheological bearing can be controlled. The spring is then torsional through the connection between the output shaft and the spring cover plate, giving the reducer variable stiffness capability. This results in faster response characteristics when the system transitions from one operating state to another and avoids the drawback of traditional dampers that increase system complexity. The resulting system is more compact and offers advantages such as high stability, low cost, low power consumption, and high reliability.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A magnetorheological planetary reducer with variable stiffness and variable damping characteristics includes an output shaft, an upper cover plate, a variable stiffness coil, a spring cover plate, a variable stiffness magnetorheological bearing, a spring, a gear ring, planetary gears, a variable damping coil, a variable damping magnetorheological bearing, a planetary column, a sun gear, a coil frame, an isolation ring, an input shaft, and a lower iron plate. The variable damping magnetorheological bearing is the core component providing the variable damping function. The variable damping coil is located at the bottom of the planetary column and provides a magnetic field for the variable damping magnetorheological bearing. The wheel, planetary column, and planetary column root form a magnetic field path, allowing magnetic lines of force to flow through the variable-stiffness magnetorheological bearing to form a closed magnetic circuit. The variable-stiffness magnetorheological bearing is the core component of the variable-stiffness function. The variable-stiffness coil is sleeved on the output shaft and located at the bottom of the upper cover plate and inside the spring cover plate. The bottom of the upper cover plate, the spring cover plate, the isolation ring, and the output shaft provide a magnetic field for the variable-stiffness magnetorheological bearing, allowing magnetic lines of force to flow through the variable-stiffness magnetorheological bearing to form a closed magnetic circuit, and then the variable-stiffness function is achieved through the spring.

[0008] Furthermore, the four sets of variable damping units have identical structures. The variable damping coil has an inner diameter of 5 mm, an outer diameter of 11 mm, a height of 3 mm, a wire diameter of 0.2 mm, and approximately 300 turns. The variable damping coil is fixed to the bottom of the output shaft and the inside of the planetary column with liquid glue. The planetary column adopts a stepped structure, which not only isolates the coil and the variable damping magnetorheological bearing, but also enables bearing positioning and provides a path for the magnetic field.

[0009] Furthermore, the four sets of variable damping coils are connected in parallel in the groove on the inner side of the bottom of the output shaft. This is because the other three can still work when one of the coils wears out. The two leads after connection are connected to the reducer through the output shaft and connected to an external power supply. The coils inside the reducer are all made of enameled wire to prevent short circuits. After being connected to the output shaft, DuPont wires are connected to protect the wires.

[0010] Furthermore, the magnetorheological grease used in this invention is prepared by mixing nano-iron powder and lubricating grease and heating in a water bath. The magnetorheological grease can lubricate the interior of the bearing and provide variable damping characteristics.

[0011] Furthermore, keyed connections are provided on the outer side of the planetary column, the inner and outer sides of the variable damping magnetorheological bearing, and the inner side of the planetary gear to prevent relative sliding between the bearing and the planetary column and planetary gear, which would affect the variable damping performance of the reducer.

[0012] Furthermore, the input shaft is connected to the motor, driving the sun gear to rotate. The planetary gears rotate synchronously through meshing with the sun gear and the ring gear, which in turn drives the output shaft to output torque. When the variable damping coil is energized, the variable damping magnetorheological bearing takes effect within milliseconds, ensuring that there is no relative rotation between the planetary gears and the planetary column. The variable damping magnetorheological bearing provides a damping force opposite to the rotation direction of the planetary gears. The magnitude of the damping force can be controlled by controlling the current, which in turn controls the output torque of the reducer, giving the entire system variable damping characteristics.

[0013] Furthermore, the variable stiffness coil has an inner diameter of 19 mm, an outer diameter of 38 mm, a height of 10 mm, a wire diameter of 0.5 mm, and approximately 300 turns. The variable stiffness coil is wound on a coil frame and fixed to the underside of the upper cover plate with liquid glue. An isolation ring is installed on the output shaft to isolate the variable stiffness magnetorheological bearing from the output shaft and to provide a magnetic field path. Keys are provided on the inner and outer sides of the isolation ring, the outer side of the output shaft, the inner and outer sides of the variable stiffness magnetorheological bearing, and the inner side of the spring cover plate to prevent the variable stiffness magnetorheological bearing from locking up and causing relative sliding between the inner and outer sides.

[0014] Furthermore, small holes are provided on the upper spring cover plate for fixing the spring to the cover plate with wire. Similarly, small holes are also provided on the lower iron plate for fixing the spring. Both the spring cover plate and the lower iron plate are provided with spring seats to fix the first and last turns of the spring. When the variable stiffness coil is energized, the variable stiffness magnetorheological bearing takes effect within milliseconds, so that there is no relative rotation between the output shaft and the spring cover plate. When the reducer is still rotating through the output shaft, the spring cover plate will drive the spring to rotate together. At this time, the spring will generate a torque in the opposite direction to the output torque and store energy in the spring. The spring gives the reducer the variable stiffness characteristic.

[0015] Furthermore, when the variable stiffness magnetorheological bearing is in operation, if the reducer still outputs torque through the output shaft, the output shaft will drive the spring cover plate through the variable stiffness magnetorheological bearing, and then drive the spring to rotate together. At this time, the spring provides reverse torque. That is, the variable stiffness magnetorheological bearing is subjected to the positive torque of the output shaft and the reverse torque of the spring. When the positive torque of the output shaft is large enough, the variable stiffness magnetorheological bearing will no longer be able to maintain the relative stillness between the output shaft and the spring cover plate. At this time, the variable stiffness magnetorheological bearing no longer works, and the energy previously stored in the spring will be completely released.

[0016] According to the above technical solution, the dynamic working process of this invention is as follows: The input shaft of the magnetorheological planetary reducer is connected to the output shaft of the motor, and the input shaft is connected to the sun gear. The output shaft torque is amplified and the rotational speed is reduced through the meshing between the planetary gears, the sun gear, and the ring gear. When the variable damping coils are energized, the four sets of variable damping coils simultaneously generate a magnetic field, causing the magnetic lines of force to flow through the variable damping magnetorheological bearings. At this time, the variable damping magnetorheological bearings play a role within milliseconds, providing a damping force opposite to the rotation direction of the planetary gears. The four magnetorheological bearings simultaneously generate damping forces acting on the output shaft, giving the entire reducer variable damping characteristics. By controlling the magnitude of the current in the variable damping coils, the damping of the entire system is controlled, allowing the system to reach a stable state more quickly. When current flows through the variable stiffness coil, the variable stiffness magnetorheological bearing functions within milliseconds, causing the spring cover and output shaft to remain relatively stationary. The output shaft and spring cover rotate together, which in turn drives the spring to rotate. The spring provides a torque in the opposite direction of rotation and can store energy, thus giving the entire system variable stiffness characteristics. By changing the current in the variable stiffness coil, the stiffness of the system can be controlled, which in turn allows the system to transition from one state to another more quickly.

[0017] The beneficial effects of this invention are:

[0018] (1) This invention is based on magnetorheological technology, which has strong stability, high reliability, simple structure, low maintenance cost, and can provide controllable damping force and variable stiffness without requiring large energy consumption and expensive hardware facilities, thus greatly reducing development costs.

[0019] (2) Compared with traditional speed reducers, the present invention greatly reduces system complexity and has a more compact structure. While amplifying torque, it can change the damping and stiffness of the system without the need for additional equipment, resulting in lower economic cost and better performance.

[0020] (3) By controlling the current flowing into the coil, the present invention can achieve real-time damping and controllable stiffness, which helps to improve the stability of the magnetorheological planetary reducer.

[0021] (4) The introduction of magnetorheological bearings does not consume any energy, has a simple and lightweight structure, strong reliability and flexibility, and a simple activation method, without the need for a complex controller.

[0022] (5) The variable stiffness characteristic makes the time for the reducer to change from one operating state to another when it is applied to the positioning control of the robotic arm shorter, and the variable damping characteristic makes the robotic arm reach a stable state faster during the positioning process.

[0023] Compared to conventional dampers, this invention enables a more compact system while amplifying motor torque. The introduction of variable damping and variable stiffness characteristics saves energy consumed in positioning control and reduces system cost. Furthermore, this invention achieves the effects of mitigating overshoot and shortening oscillation time while ensuring the advantages of high stability, low cost, low power consumption, and high reliability of the semi-active system. Attached Figure Description

[0024] Figure 1 This is a cross-sectional view of a magnetorheological planetary reducer with variable stiffness and variable damping characteristics according to an embodiment of the present invention.

[0025] Among them, 1-output shaft, 2-upper cover plate, 3-variable stiffness coil, 4-spring cover plate, 5-variable stiffness magnetorheological bearing, 6-spring, 7-gear ring, 8-planetary gear, 9-variable damping coil, 10-variable damping magnetorheological bearing, 11-planetary column, 12-sun gear, 13-input shaft, 14-lower iron plate, 15-isolation ring.

[0026] Figure 2 This is a detailed cross-sectional view of the four sets of variable damping structures.

[0027] Figure 3 This is a torque-displacement curve of a magnetorheological planetary reducer under variable damping conditions, with different currents flowing through the variable damping coil.

[0028] Figure 4 This is a torque-displacement curve of a magnetorheological planetary reducer under varying stiffness conditions, with different currents flowing through the variable stiffness coil. Detailed Implementation

[0029] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. However, the following embodiments are only for explaining the present invention, and the scope of protection of the present invention should include all the contents of the claims. Moreover, through the description of the following embodiments, those skilled in the art can fully implement all the contents of the claims of the present invention.

[0030] like Figure 1As shown, a magnetorheological planetary reducer with variable stiffness and variable damping characteristics includes an output shaft 1, an upper cover plate 2, a variable stiffness coil 3, a spring cover plate 4, a variable stiffness magnetorheological bearing 5, a spring 6, a gear ring 7, planetary gears 8, a variable damping coil 9, a variable damping magnetorheological bearing 10, a planetary column 11, a sun gear 12, an input shaft 13, a lower iron plate 14, and an isolation ring 15.

[0031] like Figure 2 As shown, the variable damping structure consists of a variable damping coil 9, a variable damping magnetorheological bearing 10, planetary gears 8, and planetary pillars 11. There are four sets of this variable damping structure, each placed on one of the four planetary pillars 11 at the bottom of the output shaft 1. Preferably, the four variable damping coils have an inner diameter of 5 mm, an outer diameter of 11 mm, a height of 3 mm, a wire diameter of 0.2 mm, and approximately 300 turns. The variable damping coils 9 are fixed to the bottom of the output shaft 1 and the inner side of the planetary pillars 11 with liquid glue, and are connected in parallel at the bottom of the output shaft 1. The leads are connected to an external power supply through the output shaft 1. The planetary pillars 11 adopt a stepped structure, which not only isolates the coils and the variable damping magnetorheological bearing but also positions the bearing and provides a path for the magnetic field.

[0032] The variable stiffness structure consists of an output shaft 1, an upper cover plate 2, a variable stiffness coil 3, a variable stiffness magnetorheological bearing 5, a spring cover plate 4, an isolation ring 15, and a spring 6. Preferably, the variable stiffness coil 3 has an inner diameter of 19 mm, an outer diameter of 38 mm, a height of 10 mm, a wire diameter of 0.5 mm, and approximately 300 turns. The variable stiffness coil 3 is wound on a coil frame and fixed to the lower side of the upper cover plate 2 with liquid glue. An isolation ring 15 is installed on the output shaft 1 to isolate the variable stiffness magnetorheological bearing 5 from the output shaft 1, while also providing a magnetic field path. Keys are provided on the inner and outer sides of the isolation ring 15, the outer side of the output shaft 1, the inner and outer sides of the variable stiffness magnetorheological bearing 5, and the inner side of the spring cover plate 4 to prevent the variable stiffness magnetorheological bearing 5 from locking and causing relative sliding between the inner and outer sides. Small holes are provided on the upper spring cover plate 4 for fixing the spring 6 to the spring cover plate 4 with wire. Small holes are also provided on the lower iron plate 14 for fixing the spring 6. Both the spring cover plate 4 and the lower iron plate 14 are equipped with spring seats to fix the first and last turns of the spring 6.

[0033] The principle of variable damping characteristics lies in the fact that the input shaft 13 of the magnetorheological planetary reducer is connected to the motor, and the input shaft 13 is connected to the sun gear 12. The torque of the output shaft 1 is amplified and the speed is reduced through the meshing between the planetary gear 8, the sun gear 12, and the ring gear 7. When the variable damping coil 9 is energized, the four sets of variable damping coils 9 simultaneously generate a magnetic field, causing the magnetic lines of force to flow through the variable damping magnetorheological bearing 10. At this time, the variable damping magnetorheological bearing 10 plays a role within milliseconds, providing a damping force opposite to the rotation direction of the planetary gear 8. The four variable damping magnetorheological bearings 10 simultaneously generate damping forces acting on the output shaft 1, giving the entire reducer variable damping characteristics. By controlling the magnitude of the current in the variable damping coil 9, the damping of the entire system can be controlled, allowing the entire system to reach a stable state more quickly.

[0034] The principle of variable stiffness characteristics is as follows: when current flows through the variable stiffness coil 3, the variable stiffness magnetorheological bearing 5 takes effect within milliseconds, making the spring cover plate 4 and the output shaft 1 relatively stationary. The output shaft 1 and the spring cover plate 4 rotate together, which in turn drives the spring 6 to rotate. The spring 6 provides a torque in the opposite direction of rotation, and the spring can store energy, thus giving the entire system variable stiffness characteristics. By changing the current of the variable stiffness coil 3, the stiffness of the system can be controlled, and the system can transition from one operating state to another faster.

[0035] The variable stiffness magnetorheological bearing 5 is manufactured as follows: Magnetorheological grease with a concentration of 40% iron powder is added to a conventional bearing to create a magnetorheological bearing. The magnetorheological grease is produced by mixing nano-iron powder and lubricating grease and then heating in a water bath. The magnetorheological grease can lubricate the inner wall of the bearing and provide variable damping characteristics.

[0036] To ensure good magnetic conductivity, the output shaft 1, upper cover plate 2, spring cover plate 4, isolation ring 15, and planetary gear 8 of the variable damping and variable stiffness magnetorheological planetary reducer are all made of low carbon steel. The input shaft 1 is connected to the motor, which drives the sun gear to rotate. The planetary gear 8 rotates synchronously with the sun gear 12 and the gear ring 7 through meshing, which in turn drives the output shaft 1 to output torque.

[0037] In this invention, four sets of variable damping coils 9, variable damping magnetorheological bearings 10, and planetary gears 8 constitute a variable damping unit structure. By controlling the current of the variable damping coils 9, the output torque of the reducer can be changed, thereby changing the damping of the entire system and enabling the system to reach a stable state more quickly. A variable stiffness coil 3, an upper cover plate 2, a spring cover plate 4, a variable stiffness magnetorheological bearing 5, and an output shaft 1 constitute a variable stiffness unit. By controlling the current of the variable stiffness coil 3, the damping magnitude of the variable stiffness magnetorheological bearing can be controlled, thereby controlling the torsion of the spring and changing the stiffness of the entire system, allowing for faster transitions from one operating state to another.

[0038] Without applying a variable stiffness current, different currents are applied to the variable damping coil 9, and the torque-displacement graph of the magnetorheological planetary reducer is as follows. Figure 3 As shown, it can be seen that the area of ​​the torque-displacement curve gradually increases with the increase of the current. This means that the damping of the magnetorheological planetary reducer can be controlled by adjusting the magnitude of the current applied to the variable damping coil 9. When no variable damping current is applied, but only a variable stiffness current is applied, different currents are applied to the variable stiffness coil 3 of the variable stiffness variable damping magnetorheological planetary reducer. The torque-displacement graph of the magnetorheological planetary reducer at this time is as follows: Figure 4 As shown, it can be seen that as the current increases, the slope of torque-displacement also increases continuously. Therefore, the current flowing through the variable stiffness coil 3 can be controlled to achieve controllable stiffness of the planetary reducer, that is, the reverse torque generated by the spring can continuously increase.

[0039] The parts of this invention not described in detail are well-known to those skilled in the art. The embodiments described above are merely preferred embodiments of the invention, and do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Various modifications and improvements to the technical solutions of this invention made by those skilled in the art without departing from the spirit of the invention should fall within the protection scope defined by the claims of this invention.

Claims

1. A magnetorheological planetary reducer with variable stiffness and variable damping characteristics, characterized in that, The components include an output shaft (1), an upper cover plate (2), a variable stiffness coil (3), a spring cover plate (4), a variable stiffness magnetorheological bearing (5), a spring (6), a gear ring (7), planetary gears (8), a variable damping coil (9), a variable damping magnetorheological bearing (10), a planetary column (11), a sun gear (12), an input shaft (13), a lower iron plate (14), and an isolation ring (15). The variable damping magnetorheological bearing (10) provides the core component for variable damping. The variable damping coil (9) is located at the bottom of the planetary column (11) and provides a magnetic field for the variable damping magnetorheological bearing (10). The planetary gears (8), the upper cover plate (2), the variable stiffness coil (3), the spring cover plate (4), the variable stiffness magnetorheological bearing (5), the spring (6), the gear ring (7), the planetary gears (8), the variable damping coil (9), the variable damping magnetorheological bearing (10), the planetary column (11), the sun gear (12), the input shaft (13), the lower iron plate (14), and the isolation ring (15). The roots of the star column (11) and planet column (11) provide a magnetic field path, so that the magnetic lines of force pass through the variable damping magnetorheological bearing (10) to form a closed magnetic circuit; the variable stiffness magnetorheological bearing (5) provides a variable stiffness function, and the variable stiffness coil (3) is sleeved on the output shaft (1), located at the bottom of the upper cover plate (2) and the inner side of the spring cover plate (4). After the coil is energized, the bottom of the upper cover plate (2), the spring cover plate (4), the isolation ring (15) and the output shaft (1) form a magnetic field to form a closed magnetic circuit, so that the magnetic lines of force flow through the variable stiffness magnetorheological bearing (5) and then through the spring (6) to achieve the variable stiffness characteristic; Magnetorheological grease is injected into the bearing inside the planetary gear (8) to give it variable damping characteristics. A variable damping coil (9) is placed at the root of the planetary column (11). The output shaft (1) has four planetary columns (11). The variable damping structure consisting of the variable damping magnetorheological bearing (10), the variable damping coil (9), the planetary gear (8), and the planetary column (11) has four sets. The four variable damping coils (9) are connected together in parallel and then connected to an external power source through a hole at the bottom of the output shaft (1). By energizing the variable damping coil (9) and forming a magnetic field path with the planetary column (11) and the planetary gear (8), the magnetic lines of force flow through the variable damping magnetorheological bearing (10), thereby realizing the variable damping characteristics. The bearing on the output shaft (1) contains magnetorheological grease, which gives it variable stiffness characteristics. A set of variable stiffness coils (3) is placed on the lower side of the upper cover plate (2). By energizing the variable stiffness coils (3), the bottom of the upper cover plate (2), the spring cover plate (4), the isolation ring (15) and the output shaft (1) provide a magnetic field for the variable stiffness magnetorheological bearing, thereby forming a closed magnetic circuit, so that the magnetic lines of force flow through the variable stiffness magnetorheological bearing (5) and then through the spring (6) to achieve the variable stiffness effect. The spring cover plate (4) and the lower iron plate (14) are fitted with spring seats so that the uppermost and lowermost coils of the spring (6) are fixed and will not slide. The spring (6) is fixed to the spring cover plate (4) and the lower iron plate (14) by iron wire so that when the variable stiffness magnetorheological bearing (5) is in operation, the spring cover plate (4) can drive the spring (6) to twist. The variable stiffness coil (3) is wound on the coil frame and fixed to the lower part of the upper cover plate (2). The bottom of the output shaft (1) has a gap for wiring when the four sets of variable damping coils (9) are connected in parallel.

2. The magnetorheological planetary reducer with variable stiffness and variable damping characteristics according to claim 1, characterized in that: Four sets of variable damping coils (9) acting on the variable damping magnetorheological bearing are connected in parallel and then connected to an external power supply. After being energized, the current flowing through the coil generates a magnetic field, and the magnetic lines of force pass through the variable damping magnetorheological bearing (10). Based on the rheological characteristics of magnetorheological grease, the larger the current, the stronger the magnetic field acting on the variable damping magnetorheological bearing (10), the greater the damping force of the variable damping magnetorheological bearing (10), and thus the greater the damping of the reducer, and the smaller the output torque of the reducer. When the current is reduced, the stronger the magnetic field acting on the variable damping magnetorheological bearing, the smaller the damping force of the variable damping magnetorheological bearing (10), and thus the smaller the damping of the reducer, and the greater the output torque of the reducer. Therefore, by controlling the current of the variable damping coils (9), the variable damping characteristics of the reducer can be achieved.

3. A magnetorheological planetary reducer with variable stiffness and variable damping characteristics according to claim 1, characterized in that: The spring (6) is fixed to the spring cover plate (4) and the lower iron plate (14) by iron wire. The variable stiffness coil (3) of the variable stiffness magnetorheological bearing is connected to an external power source. After being energized, the current flowing through the coil generates a magnetic field. The magnetic lines of force pass through the variable stiffness magnetorheological bearing (5). The larger the current, the stronger the magnetic field acting on the variable stiffness magnetorheological bearing (5), and the greater the damping force of the variable stiffness magnetorheological bearing (5). This causes the output shaft (1) to rotate together with the spring cover plate (4) during rotation. The spring cover plate (4) drives the spring to twist, and the stiffness of the reducer is strengthened. The smaller the current, the weaker the magnetic field acting on the variable stiffness magnetorheological bearing (5), the weaker the damping force of the variable stiffness magnetorheological bearing (5), and the smaller the degree of torsion provided by the spring. Consequently, the stiffness of the reducer is smaller. By controlling the current flowing through the variable stiffness coil (3), the variable stiffness characteristic of the planetary reducer is realized.

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